Adding upstream version 1.18.10.upstream/1.18.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

38 files changed, 15693 insertions, 0 deletions

diff --git a/src/crypto/x509/cert_pool.go b/src/crypto/x509/cert_pool.go
new file mode 100644
index 0000000..873ffee
--- /dev/null
+++ b/src/crypto/x509/cert_pool.go
@@ -0,0 +1,251 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/pem"
+	"sync"
+)
+
+type sum224 [sha256.Size224]byte
+
+// CertPool is a set of certificates.
+type CertPool struct {
+	byName map[string][]int // cert.RawSubject => index into lazyCerts
+
+	// lazyCerts contains funcs that return a certificate,
+	// lazily parsing/decompressing it as needed.
+	lazyCerts []lazyCert
+
+	// haveSum maps from sum224(cert.Raw) to true. It's used only
+	// for AddCert duplicate detection, to avoid CertPool.contains
+	// calls in the AddCert path (because the contains method can
+	// call getCert and otherwise negate savings from lazy getCert
+	// funcs).
+	haveSum map[sum224]bool
+
+	// systemPool indicates whether this is a special pool derived from the
+	// system roots. If it includes additional roots, it requires doing two
+	// verifications, one using the roots provided by the caller, and one using
+	// the system platform verifier.
+	systemPool bool
+}
+
+// lazyCert is minimal metadata about a Cert and a func to retrieve it
+// in its normal expanded *Certificate form.
+type lazyCert struct {
+	// rawSubject is the Certificate.RawSubject value.
+	// It's the same as the CertPool.byName key, but in []byte
+	// form to make CertPool.Subjects (as used by crypto/tls) do
+	// fewer allocations.
+	rawSubject []byte
+
+	// getCert returns the certificate.
+	//
+	// It is not meant to do network operations or anything else
+	// where a failure is likely; the func is meant to lazily
+	// parse/decompress data that is already known to be good. The
+	// error in the signature primarily is meant for use in the
+	// case where a cert file existed on local disk when the program
+	// started up is deleted later before it's read.
+	getCert func() (*Certificate, error)
+}
+
+// NewCertPool returns a new, empty CertPool.
+func NewCertPool() *CertPool {
+	return &CertPool{
+		byName:  make(map[string][]int),
+		haveSum: make(map[sum224]bool),
+	}
+}
+
+// len returns the number of certs in the set.
+// A nil set is a valid empty set.
+func (s *CertPool) len() int {
+	if s == nil {
+		return 0
+	}
+	return len(s.lazyCerts)
+}
+
+// cert returns cert index n in s.
+func (s *CertPool) cert(n int) (*Certificate, error) {
+	return s.lazyCerts[n].getCert()
+}
+
+func (s *CertPool) copy() *CertPool {
+	p := &CertPool{
+		byName:     make(map[string][]int, len(s.byName)),
+		lazyCerts:  make([]lazyCert, len(s.lazyCerts)),
+		haveSum:    make(map[sum224]bool, len(s.haveSum)),
+		systemPool: s.systemPool,
+	}
+	for k, v := range s.byName {
+		indexes := make([]int, len(v))
+		copy(indexes, v)
+		p.byName[k] = indexes
+	}
+	for k := range s.haveSum {
+		p.haveSum[k] = true
+	}
+	copy(p.lazyCerts, s.lazyCerts)
+	return p
+}
+
+// SystemCertPool returns a copy of the system cert pool.
+//
+// On Unix systems other than macOS the environment variables SSL_CERT_FILE and
+// SSL_CERT_DIR can be used to override the system default locations for the SSL
+// certificate file and SSL certificate files directory, respectively. The
+// latter can be a colon-separated list.
+//
+// Any mutations to the returned pool are not written to disk and do not affect
+// any other pool returned by SystemCertPool.
+//
+// New changes in the system cert pool might not be reflected in subsequent calls.
+func SystemCertPool() (*CertPool, error) {
+	if sysRoots := systemRootsPool(); sysRoots != nil {
+		return sysRoots.copy(), nil
+	}
+
+	return loadSystemRoots()
+}
+
+// findPotentialParents returns the indexes of certificates in s which might
+// have signed cert.
+func (s *CertPool) findPotentialParents(cert *Certificate) []*Certificate {
+	if s == nil {
+		return nil
+	}
+
+	// consider all candidates where cert.Issuer matches cert.Subject.
+	// when picking possible candidates the list is built in the order
+	// of match plausibility as to save cycles in buildChains:
+	//   AKID and SKID match
+	//   AKID present, SKID missing / AKID missing, SKID present
+	//   AKID and SKID don't match
+	var matchingKeyID, oneKeyID, mismatchKeyID []*Certificate
+	for _, c := range s.byName[string(cert.RawIssuer)] {
+		candidate, err := s.cert(c)
+		if err != nil {
+			continue
+		}
+		kidMatch := bytes.Equal(candidate.SubjectKeyId, cert.AuthorityKeyId)
+		switch {
+		case kidMatch:
+			matchingKeyID = append(matchingKeyID, candidate)
+		case (len(candidate.SubjectKeyId) == 0 && len(cert.AuthorityKeyId) > 0) ||
+			(len(candidate.SubjectKeyId) > 0 && len(cert.AuthorityKeyId) == 0):
+			oneKeyID = append(oneKeyID, candidate)
+		default:
+			mismatchKeyID = append(mismatchKeyID, candidate)
+		}
+	}
+
+	found := len(matchingKeyID) + len(oneKeyID) + len(mismatchKeyID)
+	if found == 0 {
+		return nil
+	}
+	candidates := make([]*Certificate, 0, found)
+	candidates = append(candidates, matchingKeyID...)
+	candidates = append(candidates, oneKeyID...)
+	candidates = append(candidates, mismatchKeyID...)
+	return candidates
+}
+
+func (s *CertPool) contains(cert *Certificate) bool {
+	if s == nil {
+		return false
+	}
+	return s.haveSum[sha256.Sum224(cert.Raw)]
+}
+
+// AddCert adds a certificate to a pool.
+func (s *CertPool) AddCert(cert *Certificate) {
+	if cert == nil {
+		panic("adding nil Certificate to CertPool")
+	}
+	s.addCertFunc(sha256.Sum224(cert.Raw), string(cert.RawSubject), func() (*Certificate, error) {
+		return cert, nil
+	})
+}
+
+// addCertFunc adds metadata about a certificate to a pool, along with
+// a func to fetch that certificate later when needed.
+//
+// The rawSubject is Certificate.RawSubject and must be non-empty.
+// The getCert func may be called 0 or more times.
+func (s *CertPool) addCertFunc(rawSum224 sum224, rawSubject string, getCert func() (*Certificate, error)) {
+	if getCert == nil {
+		panic("getCert can't be nil")
+	}
+
+	// Check that the certificate isn't being added twice.
+	if s.haveSum[rawSum224] {
+		return
+	}
+
+	s.haveSum[rawSum224] = true
+	s.lazyCerts = append(s.lazyCerts, lazyCert{
+		rawSubject: []byte(rawSubject),
+		getCert:    getCert,
+	})
+	s.byName[rawSubject] = append(s.byName[rawSubject], len(s.lazyCerts)-1)
+}
+
+// AppendCertsFromPEM attempts to parse a series of PEM encoded certificates.
+// It appends any certificates found to s and reports whether any certificates
+// were successfully parsed.
+//
+// On many Linux systems, /etc/ssl/cert.pem will contain the system wide set
+// of root CAs in a format suitable for this function.
+func (s *CertPool) AppendCertsFromPEM(pemCerts []byte) (ok bool) {
+	for len(pemCerts) > 0 {
+		var block *pem.Block
+		block, pemCerts = pem.Decode(pemCerts)
+		if block == nil {
+			break
+		}
+		if block.Type != "CERTIFICATE" || len(block.Headers) != 0 {
+			continue
+		}
+
+		certBytes := block.Bytes
+		cert, err := ParseCertificate(certBytes)
+		if err != nil {
+			continue
+		}
+		var lazyCert struct {
+			sync.Once
+			v *Certificate
+		}
+		s.addCertFunc(sha256.Sum224(cert.Raw), string(cert.RawSubject), func() (*Certificate, error) {
+			lazyCert.Do(func() {
+				// This can't fail, as the same bytes already parsed above.
+				lazyCert.v, _ = ParseCertificate(certBytes)
+				certBytes = nil
+			})
+			return lazyCert.v, nil
+		})
+		ok = true
+	}
+
+	return ok
+}
+
+// Subjects returns a list of the DER-encoded subjects of
+// all of the certificates in the pool.
+//
+// Deprecated: if s was returned by SystemCertPool, Subjects
+// will not include the system roots.
+func (s *CertPool) Subjects() [][]byte {
+	res := make([][]byte, s.len())
+	for i, lc := range s.lazyCerts {
+		res[i] = lc.rawSubject
+	}
+	return res
+}
diff --git a/src/crypto/x509/example_test.go b/src/crypto/x509/example_test.go
new file mode 100644
index 0000000..19d249a
--- /dev/null
+++ b/src/crypto/x509/example_test.go
@@ -0,0 +1,137 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509_test
+
+import (
+	"crypto/dsa"
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+)
+
+func ExampleCertificate_Verify() {
+	// Verifying with a custom list of root certificates.
+
+	const rootPEM = `
+-----BEGIN CERTIFICATE-----
+MIIEBDCCAuygAwIBAgIDAjppMA0GCSqGSIb3DQEBBQUAMEIxCzAJBgNVBAYTAlVT
+MRYwFAYDVQQKEw1HZW9UcnVzdCBJbmMuMRswGQYDVQQDExJHZW9UcnVzdCBHbG9i
+YWwgQ0EwHhcNMTMwNDA1MTUxNTU1WhcNMTUwNDA0MTUxNTU1WjBJMQswCQYDVQQG
+EwJVUzETMBEGA1UEChMKR29vZ2xlIEluYzElMCMGA1UEAxMcR29vZ2xlIEludGVy
+bmV0IEF1dGhvcml0eSBHMjCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEB
+AJwqBHdc2FCROgajguDYUEi8iT/xGXAaiEZ+4I/F8YnOIe5a/mENtzJEiaB0C1NP
+VaTOgmKV7utZX8bhBYASxF6UP7xbSDj0U/ck5vuR6RXEz/RTDfRK/J9U3n2+oGtv
+h8DQUB8oMANA2ghzUWx//zo8pzcGjr1LEQTrfSTe5vn8MXH7lNVg8y5Kr0LSy+rE
+ahqyzFPdFUuLH8gZYR/Nnag+YyuENWllhMgZxUYi+FOVvuOAShDGKuy6lyARxzmZ
+EASg8GF6lSWMTlJ14rbtCMoU/M4iarNOz0YDl5cDfsCx3nuvRTPPuj5xt970JSXC
+DTWJnZ37DhF5iR43xa+OcmkCAwEAAaOB+zCB+DAfBgNVHSMEGDAWgBTAephojYn7
+qwVkDBF9qn1luMrMTjAdBgNVHQ4EFgQUSt0GFhu89mi1dvWBtrtiGrpagS8wEgYD
+VR0TAQH/BAgwBgEB/wIBADAOBgNVHQ8BAf8EBAMCAQYwOgYDVR0fBDMwMTAvoC2g
+K4YpaHR0cDovL2NybC5nZW90cnVzdC5jb20vY3Jscy9ndGdsb2JhbC5jcmwwPQYI
+KwYBBQUHAQEEMTAvMC0GCCsGAQUFBzABhiFodHRwOi8vZ3RnbG9iYWwtb2NzcC5n
+ZW90cnVzdC5jb20wFwYDVR0gBBAwDjAMBgorBgEEAdZ5AgUBMA0GCSqGSIb3DQEB
+BQUAA4IBAQA21waAESetKhSbOHezI6B1WLuxfoNCunLaHtiONgaX4PCVOzf9G0JY
+/iLIa704XtE7JW4S615ndkZAkNoUyHgN7ZVm2o6Gb4ChulYylYbc3GrKBIxbf/a/
+zG+FA1jDaFETzf3I93k9mTXwVqO94FntT0QJo544evZG0R0SnU++0ED8Vf4GXjza
+HFa9llF7b1cq26KqltyMdMKVvvBulRP/F/A8rLIQjcxz++iPAsbw+zOzlTvjwsto
+WHPbqCRiOwY1nQ2pM714A5AuTHhdUDqB1O6gyHA43LL5Z/qHQF1hwFGPa4NrzQU6
+yuGnBXj8ytqU0CwIPX4WecigUCAkVDNx
+-----END CERTIFICATE-----`
+
+	const certPEM = `
+-----BEGIN CERTIFICATE-----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==
+-----END CERTIFICATE-----`
+
+	// First, create the set of root certificates. For this example we only
+	// have one. It's also possible to omit this in order to use the
+	// default root set of the current operating system.
+	roots := x509.NewCertPool()
+	ok := roots.AppendCertsFromPEM([]byte(rootPEM))
+	if !ok {
+		panic("failed to parse root certificate")
+	}
+
+	block, _ := pem.Decode([]byte(certPEM))
+	if block == nil {
+		panic("failed to parse certificate PEM")
+	}
+	cert, err := x509.ParseCertificate(block.Bytes)
+	if err != nil {
+		panic("failed to parse certificate: " + err.Error())
+	}
+
+	opts := x509.VerifyOptions{
+		DNSName: "mail.google.com",
+		Roots:   roots,
+	}
+
+	if _, err := cert.Verify(opts); err != nil {
+		panic("failed to verify certificate: " + err.Error())
+	}
+}
+
+func ExampleParsePKIXPublicKey() {
+	const pubPEM = `
+-----BEGIN PUBLIC KEY-----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+-----END PUBLIC KEY-----`
+
+	block, _ := pem.Decode([]byte(pubPEM))
+	if block == nil {
+		panic("failed to parse PEM block containing the public key")
+	}
+
+	pub, err := x509.ParsePKIXPublicKey(block.Bytes)
+	if err != nil {
+		panic("failed to parse DER encoded public key: " + err.Error())
+	}
+
+	switch pub := pub.(type) {
+	case *rsa.PublicKey:
+		fmt.Println("pub is of type RSA:", pub)
+	case *dsa.PublicKey:
+		fmt.Println("pub is of type DSA:", pub)
+	case *ecdsa.PublicKey:
+		fmt.Println("pub is of type ECDSA:", pub)
+	case ed25519.PublicKey:
+		fmt.Println("pub is of type Ed25519:", pub)
+	default:
+		panic("unknown type of public key")
+	}
+}
diff --git a/src/crypto/x509/hybrid_pool_test.go b/src/crypto/x509/hybrid_pool_test.go
new file mode 100644
index 0000000..d4dd9d5
--- /dev/null
+++ b/src/crypto/x509/hybrid_pool_test.go
@@ -0,0 +1,95 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509_test
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"internal/testenv"
+	"math/big"
+	"runtime"
+	"testing"
+	"time"
+)
+
+func TestHybridPool(t *testing.T) {
+	if !(runtime.GOOS == "windows" || runtime.GOOS == "darwin" || runtime.GOOS == "ios") {
+		t.Skipf("platform verifier not available on %s", runtime.GOOS)
+	}
+	if !testenv.HasExternalNetwork() {
+		t.Skip()
+	}
+
+	// Get the google.com chain, which should be valid on all platforms we
+	// are testing
+	c, err := tls.Dial("tcp", "google.com:443", &tls.Config{InsecureSkipVerify: true})
+	if err != nil {
+		t.Fatalf("tls connection failed: %s", err)
+	}
+	googChain := c.ConnectionState().PeerCertificates
+
+	rootTmpl := &x509.Certificate{
+		SerialNumber:          big.NewInt(1),
+		Subject:               pkix.Name{CommonName: "Go test root"},
+		IsCA:                  true,
+		BasicConstraintsValid: true,
+		NotBefore:             time.Now().Add(-time.Hour),
+		NotAfter:              time.Now().Add(time.Hour * 10),
+	}
+	k, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatalf("failed to generate test key: %s", err)
+	}
+	rootDER, err := x509.CreateCertificate(rand.Reader, rootTmpl, rootTmpl, k.Public(), k)
+	if err != nil {
+		t.Fatalf("failed to create test cert: %s", err)
+	}
+	root, err := x509.ParseCertificate(rootDER)
+	if err != nil {
+		t.Fatalf("failed to parse test cert: %s", err)
+	}
+
+	pool, err := x509.SystemCertPool()
+	if err != nil {
+		t.Fatalf("SystemCertPool failed: %s", err)
+	}
+	opts := x509.VerifyOptions{Roots: pool}
+
+	_, err = googChain[0].Verify(opts)
+	if err != nil {
+		t.Fatalf("verification failed for google.com chain (empty pool): %s", err)
+	}
+
+	pool.AddCert(root)
+
+	_, err = googChain[0].Verify(opts)
+	if err != nil {
+		t.Fatalf("verification failed for google.com chain (hybrid pool): %s", err)
+	}
+
+	certTmpl := &x509.Certificate{
+		SerialNumber: big.NewInt(1),
+		NotBefore:    time.Now().Add(-time.Hour),
+		NotAfter:     time.Now().Add(time.Hour * 10),
+		DNSNames:     []string{"example.com"},
+	}
+	certDER, err := x509.CreateCertificate(rand.Reader, certTmpl, rootTmpl, k.Public(), k)
+	if err != nil {
+		t.Fatalf("failed to create test cert: %s", err)
+	}
+	cert, err := x509.ParseCertificate(certDER)
+	if err != nil {
+		t.Fatalf("failed to parse test cert: %s", err)
+	}
+
+	_, err = cert.Verify(opts)
+	if err != nil {
+		t.Fatalf("verification failed for custom chain (hybrid pool): %s", err)
+	}
+}
diff --git a/src/crypto/x509/internal/macos/corefoundation.go b/src/crypto/x509/internal/macos/corefoundation.go
new file mode 100644
index 0000000..2b20b52
--- /dev/null
+++ b/src/crypto/x509/internal/macos/corefoundation.go
@@ -0,0 +1,214 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build darwin
+
+// Package macOS provides cgo-less wrappers for Core Foundation and
+// Security.framework, similarly to how package syscall provides access to
+// libSystem.dylib.
+package macOS
+
+import (
+	"errors"
+	"internal/abi"
+	"reflect"
+	"runtime"
+	"time"
+	"unsafe"
+)
+
+// Core Foundation linker flags for the external linker. See Issue 42459.
+//go:cgo_ldflag "-framework"
+//go:cgo_ldflag "CoreFoundation"
+
+// CFRef is an opaque reference to a Core Foundation object. It is a pointer,
+// but to memory not owned by Go, so not an unsafe.Pointer.
+type CFRef uintptr
+
+// CFDataToSlice returns a copy of the contents of data as a bytes slice.
+func CFDataToSlice(data CFRef) []byte {
+	length := CFDataGetLength(data)
+	ptr := CFDataGetBytePtr(data)
+	src := (*[1 << 20]byte)(unsafe.Pointer(ptr))[:length:length]
+	out := make([]byte, length)
+	copy(out, src)
+	return out
+}
+
+// CFStringToString returns a Go string representation of the passed
+// in CFString.
+func CFStringToString(ref CFRef) string {
+	data := CFStringCreateExternalRepresentation(ref)
+	b := CFDataToSlice(data)
+	CFRelease(data)
+	return string(b)
+}
+
+// TimeToCFDateRef converts a time.Time into an apple CFDateRef
+func TimeToCFDateRef(t time.Time) CFRef {
+	secs := t.Sub(time.Date(2001, 1, 1, 0, 0, 0, 0, time.UTC)).Seconds()
+	ref := CFDateCreate(secs)
+	return ref
+}
+
+type CFString CFRef
+
+const kCFAllocatorDefault = 0
+const kCFStringEncodingUTF8 = 0x08000100
+
+//go:cgo_import_dynamic x509_CFDataCreate CFDataCreate "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func BytesToCFData(b []byte) CFRef {
+	p := unsafe.Pointer((*reflect.SliceHeader)(unsafe.Pointer(&b)).Data)
+	ret := syscall(abi.FuncPCABI0(x509_CFDataCreate_trampoline), kCFAllocatorDefault, uintptr(p), uintptr(len(b)), 0, 0, 0)
+	runtime.KeepAlive(p)
+	return CFRef(ret)
+}
+func x509_CFDataCreate_trampoline()
+
+//go:cgo_import_dynamic x509_CFStringCreateWithBytes CFStringCreateWithBytes "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+// StringToCFString returns a copy of the UTF-8 contents of s as a new CFString.
+func StringToCFString(s string) CFString {
+	p := unsafe.Pointer((*reflect.StringHeader)(unsafe.Pointer(&s)).Data)
+	ret := syscall(abi.FuncPCABI0(x509_CFStringCreateWithBytes_trampoline), kCFAllocatorDefault, uintptr(p),
+		uintptr(len(s)), uintptr(kCFStringEncodingUTF8), 0 /* isExternalRepresentation */, 0)
+	runtime.KeepAlive(p)
+	return CFString(ret)
+}
+func x509_CFStringCreateWithBytes_trampoline()
+
+//go:cgo_import_dynamic x509_CFDictionaryGetValueIfPresent CFDictionaryGetValueIfPresent "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func CFDictionaryGetValueIfPresent(dict CFRef, key CFString) (value CFRef, ok bool) {
+	ret := syscall(abi.FuncPCABI0(x509_CFDictionaryGetValueIfPresent_trampoline), uintptr(dict), uintptr(key),
+		uintptr(unsafe.Pointer(&value)), 0, 0, 0)
+	if ret == 0 {
+		return 0, false
+	}
+	return value, true
+}
+func x509_CFDictionaryGetValueIfPresent_trampoline()
+
+const kCFNumberSInt32Type = 3
+
+//go:cgo_import_dynamic x509_CFNumberGetValue CFNumberGetValue "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func CFNumberGetValue(num CFRef) (int32, error) {
+	var value int32
+	ret := syscall(abi.FuncPCABI0(x509_CFNumberGetValue_trampoline), uintptr(num), uintptr(kCFNumberSInt32Type),
+		uintptr(unsafe.Pointer(&value)), 0, 0, 0)
+	if ret == 0 {
+		return 0, errors.New("CFNumberGetValue call failed")
+	}
+	return value, nil
+}
+func x509_CFNumberGetValue_trampoline()
+
+//go:cgo_import_dynamic x509_CFDataGetLength CFDataGetLength "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func CFDataGetLength(data CFRef) int {
+	ret := syscall(abi.FuncPCABI0(x509_CFDataGetLength_trampoline), uintptr(data), 0, 0, 0, 0, 0)
+	return int(ret)
+}
+func x509_CFDataGetLength_trampoline()
+
+//go:cgo_import_dynamic x509_CFDataGetBytePtr CFDataGetBytePtr "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func CFDataGetBytePtr(data CFRef) uintptr {
+	ret := syscall(abi.FuncPCABI0(x509_CFDataGetBytePtr_trampoline), uintptr(data), 0, 0, 0, 0, 0)
+	return ret
+}
+func x509_CFDataGetBytePtr_trampoline()
+
+//go:cgo_import_dynamic x509_CFArrayGetCount CFArrayGetCount "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func CFArrayGetCount(array CFRef) int {
+	ret := syscall(abi.FuncPCABI0(x509_CFArrayGetCount_trampoline), uintptr(array), 0, 0, 0, 0, 0)
+	return int(ret)
+}
+func x509_CFArrayGetCount_trampoline()
+
+//go:cgo_import_dynamic x509_CFArrayGetValueAtIndex CFArrayGetValueAtIndex "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func CFArrayGetValueAtIndex(array CFRef, index int) CFRef {
+	ret := syscall(abi.FuncPCABI0(x509_CFArrayGetValueAtIndex_trampoline), uintptr(array), uintptr(index), 0, 0, 0, 0)
+	return CFRef(ret)
+}
+func x509_CFArrayGetValueAtIndex_trampoline()
+
+//go:cgo_import_dynamic x509_CFEqual CFEqual "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func CFEqual(a, b CFRef) bool {
+	ret := syscall(abi.FuncPCABI0(x509_CFEqual_trampoline), uintptr(a), uintptr(b), 0, 0, 0, 0)
+	return ret == 1
+}
+func x509_CFEqual_trampoline()
+
+//go:cgo_import_dynamic x509_CFRelease CFRelease "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func CFRelease(ref CFRef) {
+	syscall(abi.FuncPCABI0(x509_CFRelease_trampoline), uintptr(ref), 0, 0, 0, 0, 0)
+}
+func x509_CFRelease_trampoline()
+
+//go:cgo_import_dynamic x509_CFArrayCreateMutable CFArrayCreateMutable "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func CFArrayCreateMutable() CFRef {
+	ret := syscall(abi.FuncPCABI0(x509_CFArrayCreateMutable_trampoline), kCFAllocatorDefault, 0, 0 /* kCFTypeArrayCallBacks */, 0, 0, 0)
+	return CFRef(ret)
+}
+func x509_CFArrayCreateMutable_trampoline()
+
+//go:cgo_import_dynamic x509_CFArrayAppendValue CFArrayAppendValue "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func CFArrayAppendValue(array CFRef, val CFRef) {
+	syscall(abi.FuncPCABI0(x509_CFArrayAppendValue_trampoline), uintptr(array), uintptr(val), 0, 0, 0, 0)
+}
+func x509_CFArrayAppendValue_trampoline()
+
+//go:cgo_import_dynamic x509_CFDateCreate CFDateCreate "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func CFDateCreate(seconds float64) CFRef {
+	ret := syscall(abi.FuncPCABI0(x509_CFDateCreate_trampoline), kCFAllocatorDefault, 0, 0, 0, 0, seconds)
+	return CFRef(ret)
+}
+func x509_CFDateCreate_trampoline()
+
+//go:cgo_import_dynamic x509_CFErrorCopyDescription CFErrorCopyDescription "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func CFErrorCopyDescription(errRef CFRef) CFRef {
+	ret := syscall(abi.FuncPCABI0(x509_CFErrorCopyDescription_trampoline), uintptr(errRef), 0, 0, 0, 0, 0)
+	return CFRef(ret)
+}
+func x509_CFErrorCopyDescription_trampoline()
+
+//go:cgo_import_dynamic x509_CFErrorGetCode CFErrorGetCode "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func CFErrorGetCode(errRef CFRef) int {
+	return int(syscall(abi.FuncPCABI0(x509_CFErrorGetCode_trampoline), uintptr(errRef), 0, 0, 0, 0, 0))
+}
+func x509_CFErrorGetCode_trampoline()
+
+//go:cgo_import_dynamic x509_CFStringCreateExternalRepresentation CFStringCreateExternalRepresentation "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+
+func CFStringCreateExternalRepresentation(strRef CFRef) CFRef {
+	ret := syscall(abi.FuncPCABI0(x509_CFStringCreateExternalRepresentation_trampoline), kCFAllocatorDefault, uintptr(strRef), kCFStringEncodingUTF8, 0, 0, 0)
+	return CFRef(ret)
+}
+func x509_CFStringCreateExternalRepresentation_trampoline()
+
+// syscall is implemented in the runtime package (runtime/sys_darwin.go)
+func syscall(fn, a1, a2, a3, a4, a5 uintptr, f1 float64) uintptr
+
+// ReleaseCFArray iterates through an array, releasing its contents, and then
+// releases the array itself. This is necessary because we cannot, easily, set the
+// CFArrayCallBacks argument when creating CFArrays.
+func ReleaseCFArray(array CFRef) {
+	for i := 0; i < CFArrayGetCount(array); i++ {
+		ref := CFArrayGetValueAtIndex(array, i)
+		CFRelease(ref)
+	}
+	CFRelease(array)
+}
diff --git a/src/crypto/x509/internal/macos/corefoundation.s b/src/crypto/x509/internal/macos/corefoundation.s
new file mode 100644
index 0000000..49cd084
--- /dev/null
+++ b/src/crypto/x509/internal/macos/corefoundation.s
@@ -0,0 +1,43 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build darwin
+
+#include "textflag.h"
+
+// The trampolines are ABIInternal as they are address-taken in
+// Go code.
+
+TEXT ·x509_CFArrayGetCount_trampoline(SB),NOSPLIT,$0-0
+	JMP	x509_CFArrayGetCount(SB)
+TEXT ·x509_CFArrayGetValueAtIndex_trampoline(SB),NOSPLIT,$0-0
+	JMP	x509_CFArrayGetValueAtIndex(SB)
+TEXT ·x509_CFDataGetBytePtr_trampoline(SB),NOSPLIT,$0-0
+	JMP	x509_CFDataGetBytePtr(SB)
+TEXT ·x509_CFDataGetLength_trampoline(SB),NOSPLIT,$0-0
+	JMP	x509_CFDataGetLength(SB)
+TEXT ·x509_CFStringCreateWithBytes_trampoline(SB),NOSPLIT,$0-0
+	JMP	x509_CFStringCreateWithBytes(SB)
+TEXT ·x509_CFRelease_trampoline(SB),NOSPLIT,$0-0
+	JMP	x509_CFRelease(SB)
+TEXT ·x509_CFDictionaryGetValueIfPresent_trampoline(SB),NOSPLIT,$0-0
+	JMP	x509_CFDictionaryGetValueIfPresent(SB)
+TEXT ·x509_CFNumberGetValue_trampoline(SB),NOSPLIT,$0-0
+	JMP	x509_CFNumberGetValue(SB)
+TEXT ·x509_CFEqual_trampoline(SB),NOSPLIT,$0-0
+	JMP	x509_CFEqual(SB)
+TEXT ·x509_CFArrayCreateMutable_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_CFArrayCreateMutable(SB)
+TEXT ·x509_CFArrayAppendValue_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_CFArrayAppendValue(SB)
+TEXT ·x509_CFDateCreate_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_CFDateCreate(SB)
+TEXT ·x509_CFDataCreate_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_CFDataCreate(SB)
+TEXT ·x509_CFErrorCopyDescription_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_CFErrorCopyDescription(SB)
+TEXT ·x509_CFErrorGetCode_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_CFErrorGetCode(SB)
+TEXT ·x509_CFStringCreateExternalRepresentation_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_CFStringCreateExternalRepresentation(SB)
diff --git a/src/crypto/x509/internal/macos/security.go b/src/crypto/x509/internal/macos/security.go
new file mode 100644
index 0000000..0b7958e
--- /dev/null
+++ b/src/crypto/x509/internal/macos/security.go
@@ -0,0 +1,243 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build darwin
+
+package macOS
+
+import (
+	"errors"
+	"internal/abi"
+	"strconv"
+	"unsafe"
+)
+
+// Security.framework linker flags for the external linker. See Issue 42459.
+//go:cgo_ldflag "-framework"
+//go:cgo_ldflag "Security"
+
+// Based on https://opensource.apple.com/source/Security/Security-59306.41.2/base/Security.h
+
+type SecTrustSettingsResult int32
+
+const (
+	SecTrustSettingsResultInvalid SecTrustSettingsResult = iota
+	SecTrustSettingsResultTrustRoot
+	SecTrustSettingsResultTrustAsRoot
+	SecTrustSettingsResultDeny
+	SecTrustSettingsResultUnspecified
+)
+
+type SecTrustResultType int32
+
+const (
+	SecTrustResultInvalid SecTrustResultType = iota
+	SecTrustResultProceed
+	SecTrustResultConfirm // deprecated
+	SecTrustResultDeny
+	SecTrustResultUnspecified
+	SecTrustResultRecoverableTrustFailure
+	SecTrustResultFatalTrustFailure
+	SecTrustResultOtherError
+)
+
+type SecTrustSettingsDomain int32
+
+const (
+	SecTrustSettingsDomainUser SecTrustSettingsDomain = iota
+	SecTrustSettingsDomainAdmin
+	SecTrustSettingsDomainSystem
+)
+
+const (
+	// various macOS error codes that can be returned from
+	// SecTrustEvaluateWithError that we can map to Go cert
+	// verification error types.
+	ErrSecCertificateExpired = -67818
+	ErrSecHostNameMismatch   = -67602
+	ErrSecNotTrusted         = -67843
+)
+
+type OSStatus struct {
+	call   string
+	status int32
+}
+
+func (s OSStatus) Error() string {
+	return s.call + " error: " + strconv.Itoa(int(s.status))
+}
+
+// Dictionary keys are defined as build-time strings with CFSTR, but the Go
+// linker's internal linking mode can't handle CFSTR relocations. Create our
+// own dynamic strings instead and just never release them.
+//
+// Note that this might be the only thing that can break over time if
+// these values change, as the ABI arguably requires using the strings
+// pointed to by the symbols, not values that happen to be equal to them.
+
+var SecTrustSettingsResultKey = StringToCFString("kSecTrustSettingsResult")
+var SecTrustSettingsPolicy = StringToCFString("kSecTrustSettingsPolicy")
+var SecTrustSettingsPolicyString = StringToCFString("kSecTrustSettingsPolicyString")
+var SecPolicyOid = StringToCFString("SecPolicyOid")
+var SecPolicyAppleSSL = StringToCFString("1.2.840.113635.100.1.3") // defined by POLICYMACRO
+
+var ErrNoTrustSettings = errors.New("no trust settings found")
+
+const errSecNoTrustSettings = -25263
+
+//go:cgo_import_dynamic x509_SecTrustSettingsCopyCertificates SecTrustSettingsCopyCertificates "/System/Library/Frameworks/Security.framework/Versions/A/Security"
+
+func SecTrustSettingsCopyCertificates(domain SecTrustSettingsDomain) (certArray CFRef, err error) {
+	ret := syscall(abi.FuncPCABI0(x509_SecTrustSettingsCopyCertificates_trampoline), uintptr(domain),
+		uintptr(unsafe.Pointer(&certArray)), 0, 0, 0, 0)
+	if int32(ret) == errSecNoTrustSettings {
+		return 0, ErrNoTrustSettings
+	} else if ret != 0 {
+		return 0, OSStatus{"SecTrustSettingsCopyCertificates", int32(ret)}
+	}
+	return certArray, nil
+}
+func x509_SecTrustSettingsCopyCertificates_trampoline()
+
+const errSecItemNotFound = -25300
+
+//go:cgo_import_dynamic x509_SecTrustSettingsCopyTrustSettings SecTrustSettingsCopyTrustSettings "/System/Library/Frameworks/Security.framework/Versions/A/Security"
+
+func SecTrustSettingsCopyTrustSettings(cert CFRef, domain SecTrustSettingsDomain) (trustSettings CFRef, err error) {
+	ret := syscall(abi.FuncPCABI0(x509_SecTrustSettingsCopyTrustSettings_trampoline), uintptr(cert), uintptr(domain),
+		uintptr(unsafe.Pointer(&trustSettings)), 0, 0, 0)
+	if int32(ret) == errSecItemNotFound {
+		return 0, ErrNoTrustSettings
+	} else if ret != 0 {
+		return 0, OSStatus{"SecTrustSettingsCopyTrustSettings", int32(ret)}
+	}
+	return trustSettings, nil
+}
+func x509_SecTrustSettingsCopyTrustSettings_trampoline()
+
+//go:cgo_import_dynamic x509_SecPolicyCopyProperties SecPolicyCopyProperties "/System/Library/Frameworks/Security.framework/Versions/A/Security"
+
+func SecPolicyCopyProperties(policy CFRef) CFRef {
+	ret := syscall(abi.FuncPCABI0(x509_SecPolicyCopyProperties_trampoline), uintptr(policy), 0, 0, 0, 0, 0)
+	return CFRef(ret)
+}
+func x509_SecPolicyCopyProperties_trampoline()
+
+//go:cgo_import_dynamic x509_SecTrustCreateWithCertificates SecTrustCreateWithCertificates "/System/Library/Frameworks/Security.framework/Versions/A/Security"
+
+func SecTrustCreateWithCertificates(certs CFRef, policies CFRef) (CFRef, error) {
+	var trustObj CFRef
+	ret := syscall(abi.FuncPCABI0(x509_SecTrustCreateWithCertificates_trampoline), uintptr(certs), uintptr(policies),
+		uintptr(unsafe.Pointer(&trustObj)), 0, 0, 0)
+	if int32(ret) != 0 {
+		return 0, OSStatus{"SecTrustCreateWithCertificates", int32(ret)}
+	}
+	return trustObj, nil
+}
+func x509_SecTrustCreateWithCertificates_trampoline()
+
+//go:cgo_import_dynamic x509_SecCertificateCreateWithData SecCertificateCreateWithData "/System/Library/Frameworks/Security.framework/Versions/A/Security"
+
+func SecCertificateCreateWithData(b []byte) CFRef {
+	data := BytesToCFData(b)
+	ret := syscall(abi.FuncPCABI0(x509_SecCertificateCreateWithData_trampoline), kCFAllocatorDefault, uintptr(data), 0, 0, 0, 0)
+	CFRelease(data)
+	return CFRef(ret)
+}
+func x509_SecCertificateCreateWithData_trampoline()
+
+//go:cgo_import_dynamic x509_SecPolicyCreateSSL SecPolicyCreateSSL "/System/Library/Frameworks/Security.framework/Versions/A/Security"
+
+func SecPolicyCreateSSL(name string) CFRef {
+	var hostname CFString
+	if name != "" {
+		hostname = StringToCFString(name)
+		defer CFRelease(CFRef(hostname))
+	}
+	ret := syscall(abi.FuncPCABI0(x509_SecPolicyCreateSSL_trampoline), 1 /* true */, uintptr(hostname), 0, 0, 0, 0)
+	return CFRef(ret)
+}
+func x509_SecPolicyCreateSSL_trampoline()
+
+//go:cgo_import_dynamic x509_SecTrustSetVerifyDate SecTrustSetVerifyDate "/System/Library/Frameworks/Security.framework/Versions/A/Security"
+
+func SecTrustSetVerifyDate(trustObj CFRef, dateRef CFRef) error {
+	ret := syscall(abi.FuncPCABI0(x509_SecTrustSetVerifyDate_trampoline), uintptr(trustObj), uintptr(dateRef), 0, 0, 0, 0)
+	if int32(ret) != 0 {
+		return OSStatus{"SecTrustSetVerifyDate", int32(ret)}
+	}
+	return nil
+}
+func x509_SecTrustSetVerifyDate_trampoline()
+
+//go:cgo_import_dynamic x509_SecTrustEvaluate SecTrustEvaluate "/System/Library/Frameworks/Security.framework/Versions/A/Security"
+
+func SecTrustEvaluate(trustObj CFRef) (CFRef, error) {
+	var result CFRef
+	ret := syscall(abi.FuncPCABI0(x509_SecTrustEvaluate_trampoline), uintptr(trustObj), uintptr(unsafe.Pointer(&result)), 0, 0, 0, 0)
+	if int32(ret) != 0 {
+		return 0, OSStatus{"SecTrustEvaluate", int32(ret)}
+	}
+	return CFRef(result), nil
+}
+func x509_SecTrustEvaluate_trampoline()
+
+//go:cgo_import_dynamic x509_SecTrustGetResult SecTrustGetResult "/System/Library/Frameworks/Security.framework/Versions/A/Security"
+
+func SecTrustGetResult(trustObj CFRef, result CFRef) (CFRef, CFRef, error) {
+	var chain, info CFRef
+	ret := syscall(abi.FuncPCABI0(x509_SecTrustGetResult_trampoline), uintptr(trustObj), uintptr(unsafe.Pointer(&result)),
+		uintptr(unsafe.Pointer(&chain)), uintptr(unsafe.Pointer(&info)), 0, 0)
+	if int32(ret) != 0 {
+		return 0, 0, OSStatus{"SecTrustGetResult", int32(ret)}
+	}
+	return chain, info, nil
+}
+func x509_SecTrustGetResult_trampoline()
+
+//go:cgo_import_dynamic x509_SecTrustEvaluateWithError SecTrustEvaluateWithError "/System/Library/Frameworks/Security.framework/Versions/A/Security"
+
+func SecTrustEvaluateWithError(trustObj CFRef) (int, error) {
+	var errRef CFRef
+	ret := syscall(abi.FuncPCABI0(x509_SecTrustEvaluateWithError_trampoline), uintptr(trustObj), uintptr(unsafe.Pointer(&errRef)), 0, 0, 0, 0)
+	if int32(ret) != 1 {
+		errStr := CFErrorCopyDescription(errRef)
+		err := errors.New(CFStringToString(errStr))
+		errCode := CFErrorGetCode(errRef)
+		CFRelease(errRef)
+		CFRelease(errStr)
+		return errCode, err
+	}
+	return 0, nil
+}
+func x509_SecTrustEvaluateWithError_trampoline()
+
+//go:cgo_import_dynamic x509_SecTrustGetCertificateCount SecTrustGetCertificateCount "/System/Library/Frameworks/Security.framework/Versions/A/Security"
+
+func SecTrustGetCertificateCount(trustObj CFRef) int {
+	ret := syscall(abi.FuncPCABI0(x509_SecTrustGetCertificateCount_trampoline), uintptr(trustObj), 0, 0, 0, 0, 0)
+	return int(ret)
+}
+func x509_SecTrustGetCertificateCount_trampoline()
+
+//go:cgo_import_dynamic x509_SecTrustGetCertificateAtIndex SecTrustGetCertificateAtIndex "/System/Library/Frameworks/Security.framework/Versions/A/Security"
+
+func SecTrustGetCertificateAtIndex(trustObj CFRef, i int) CFRef {
+	ret := syscall(abi.FuncPCABI0(x509_SecTrustGetCertificateAtIndex_trampoline), uintptr(trustObj), uintptr(i), 0, 0, 0, 0)
+	return CFRef(ret)
+}
+func x509_SecTrustGetCertificateAtIndex_trampoline()
+
+//go:cgo_import_dynamic x509_SecCertificateCopyData SecCertificateCopyData "/System/Library/Frameworks/Security.framework/Versions/A/Security"
+
+func SecCertificateCopyData(cert CFRef) ([]byte, error) {
+	ret := syscall(abi.FuncPCABI0(x509_SecCertificateCopyData_trampoline), uintptr(cert), 0, 0, 0, 0, 0)
+	if ret == 0 {
+		return nil, errors.New("x509: invalid certificate object")
+	}
+	b := CFDataToSlice(CFRef(ret))
+	CFRelease(CFRef(ret))
+	return b, nil
+}
+func x509_SecCertificateCopyData_trampoline()
diff --git a/src/crypto/x509/internal/macos/security.s b/src/crypto/x509/internal/macos/security.s
new file mode 100644
index 0000000..36f814f
--- /dev/null
+++ b/src/crypto/x509/internal/macos/security.s
@@ -0,0 +1,37 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build darwin
+
+#include "textflag.h"
+
+// The trampolines are ABIInternal as they are address-taken in
+// Go code.
+
+TEXT ·x509_SecTrustSettingsCopyCertificates_trampoline(SB),NOSPLIT,$0-0
+	JMP	x509_SecTrustSettingsCopyCertificates(SB)
+TEXT ·x509_SecTrustSettingsCopyTrustSettings_trampoline(SB),NOSPLIT,$0-0
+	JMP	x509_SecTrustSettingsCopyTrustSettings(SB)
+TEXT ·x509_SecPolicyCopyProperties_trampoline(SB),NOSPLIT,$0-0
+	JMP	x509_SecPolicyCopyProperties(SB)
+TEXT ·x509_SecTrustCreateWithCertificates_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_SecTrustCreateWithCertificates(SB)
+TEXT ·x509_SecCertificateCreateWithData_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_SecCertificateCreateWithData(SB)
+TEXT ·x509_SecPolicyCreateSSL_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_SecPolicyCreateSSL(SB)
+TEXT ·x509_SecTrustSetVerifyDate_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_SecTrustSetVerifyDate(SB)
+TEXT ·x509_SecTrustEvaluate_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_SecTrustEvaluate(SB)
+TEXT ·x509_SecTrustGetResult_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_SecTrustGetResult(SB)
+TEXT ·x509_SecTrustEvaluateWithError_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_SecTrustEvaluateWithError(SB)
+TEXT ·x509_SecTrustGetCertificateCount_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_SecTrustGetCertificateCount(SB)
+TEXT ·x509_SecTrustGetCertificateAtIndex_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_SecTrustGetCertificateAtIndex(SB)
+TEXT ·x509_SecCertificateCopyData_trampoline(SB),NOSPLIT,$0-0
+	JMP x509_SecCertificateCopyData(SB)
diff --git a/src/crypto/x509/name_constraints_test.go b/src/crypto/x509/name_constraints_test.go
new file mode 100644
index 0000000..04c1e7a
--- /dev/null
+++ b/src/crypto/x509/name_constraints_test.go
@@ -0,0 +1,2164 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	"bytes"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"encoding/hex"
+	"encoding/pem"
+	"fmt"
+	"math/big"
+	"net"
+	"net/url"
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+const (
+	// testNameConstraintsAgainstOpenSSL can be set to true to run tests
+	// against the system OpenSSL. This is disabled by default because Go
+	// cannot depend on having OpenSSL installed at testing time.
+	testNameConstraintsAgainstOpenSSL = false
+
+	// debugOpenSSLFailure can be set to true, when
+	// testNameConstraintsAgainstOpenSSL is also true, to cause
+	// intermediate files to be preserved for debugging.
+	debugOpenSSLFailure = false
+)
+
+type nameConstraintsTest struct {
+	roots         []constraintsSpec
+	intermediates [][]constraintsSpec
+	leaf          leafSpec
+	requestedEKUs []ExtKeyUsage
+	expectedError string
+	noOpenSSL     bool
+	ignoreCN      bool
+}
+
+type constraintsSpec struct {
+	ok   []string
+	bad  []string
+	ekus []string
+}
+
+type leafSpec struct {
+	sans []string
+	ekus []string
+	cn   string
+}
+
+var nameConstraintsTests = []nameConstraintsTest{
+	// #0: dummy test for the certificate generation process itself.
+	{
+		roots: make([]constraintsSpec, 1),
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+	},
+
+	// #1: dummy test for the certificate generation process itself: single
+	// level of intermediate.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+	},
+
+	// #2: dummy test for the certificate generation process itself: two
+	// levels of intermediates.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+	},
+
+	// #3: matching DNS constraint in root
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+	},
+
+	// #4: matching DNS constraint in intermediate.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ok: []string{"dns:example.com"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+	},
+
+	// #5: .example.com only matches subdomains.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:.example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+		expectedError: "\"example.com\" is not permitted",
+	},
+
+	// #6: .example.com matches subdomains.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ok: []string{"dns:.example.com"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:foo.example.com"},
+		},
+	},
+
+	// #7: .example.com matches multiple levels of subdomains
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:.example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:foo.bar.example.com"},
+		},
+	},
+
+	// #8: specifying a permitted list of names does not exclude other name
+	// types
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:.example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"ip:10.1.1.1"},
+		},
+	},
+
+	// #9: specifying a permitted list of names does not exclude other name
+	// types
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"ip:10.0.0.0/8"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+	},
+
+	// #10: intermediates can try to permit other names, which isn't
+	// forbidden if the leaf doesn't mention them. I.e. name constraints
+	// apply to names, not constraints themselves.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ok: []string{"dns:example.com", "dns:foo.com"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+	},
+
+	// #11: intermediates cannot add permitted names that the root doesn't
+	// grant them.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ok: []string{"dns:example.com", "dns:foo.com"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:foo.com"},
+		},
+		expectedError: "\"foo.com\" is not permitted",
+	},
+
+	// #12: intermediates can further limit their scope if they wish.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:.example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ok: []string{"dns:.bar.example.com"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:foo.bar.example.com"},
+		},
+	},
+
+	// #13: intermediates can further limit their scope and that limitation
+	// is effective
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:.example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ok: []string{"dns:.bar.example.com"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:foo.notbar.example.com"},
+		},
+		expectedError: "\"foo.notbar.example.com\" is not permitted",
+	},
+
+	// #14: roots can exclude subtrees and that doesn't affect other names.
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"dns:.example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:foo.com"},
+		},
+	},
+
+	// #15: roots exclusions are effective.
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"dns:.example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:foo.example.com"},
+		},
+		expectedError: "\"foo.example.com\" is excluded",
+	},
+
+	// #16: intermediates can also exclude names and that doesn't affect
+	// other names.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					bad: []string{"dns:.example.com"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:foo.com"},
+		},
+	},
+
+	// #17: intermediate exclusions are effective.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					bad: []string{"dns:.example.com"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:foo.example.com"},
+		},
+		expectedError: "\"foo.example.com\" is excluded",
+	},
+
+	// #18: having an exclusion doesn't prohibit other types of names.
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"dns:.example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:foo.com", "ip:10.1.1.1"},
+		},
+	},
+
+	// #19: IP-based exclusions are permitted and don't affect unrelated IP
+	// addresses.
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"ip:10.0.0.0/8"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"ip:192.168.1.1"},
+		},
+	},
+
+	// #20: IP-based exclusions are effective
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"ip:10.0.0.0/8"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"ip:10.0.0.1"},
+		},
+		expectedError: "\"10.0.0.1\" is excluded",
+	},
+
+	// #21: intermediates can further constrain IP ranges.
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"ip:0.0.0.0/1"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					bad: []string{"ip:11.0.0.0/8"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"ip:11.0.0.1"},
+		},
+		expectedError: "\"11.0.0.1\" is excluded",
+	},
+
+	// #22: when multiple intermediates are present, chain building can
+	// avoid intermediates with incompatible constraints.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ok: []string{"dns:.foo.com"},
+				},
+				{
+					ok: []string{"dns:.example.com"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:foo.example.com"},
+		},
+		noOpenSSL: true, // OpenSSL's chain building is not informed by constraints.
+	},
+
+	// #23: (same as the previous test, but in the other order in ensure
+	// that we don't pass it by luck.)
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ok: []string{"dns:.example.com"},
+				},
+				{
+					ok: []string{"dns:.foo.com"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:foo.example.com"},
+		},
+		noOpenSSL: true, // OpenSSL's chain building is not informed by constraints.
+	},
+
+	// #24: when multiple roots are valid, chain building can avoid roots
+	// with incompatible constraints.
+	{
+		roots: []constraintsSpec{
+			{},
+			{
+				ok: []string{"dns:foo.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+		noOpenSSL: true, // OpenSSL's chain building is not informed by constraints.
+	},
+
+	// #25: (same as the previous test, but in the other order in ensure
+	// that we don't pass it by luck.)
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:foo.com"},
+			},
+			{},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+		noOpenSSL: true, // OpenSSL's chain building is not informed by constraints.
+	},
+
+	// #26: chain building can find a valid path even with multiple levels
+	// of alternative intermediates and alternative roots.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:foo.com"},
+			},
+			{
+				ok: []string{"dns:example.com"},
+			},
+			{},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+				{
+					ok: []string{"dns:foo.com"},
+				},
+			},
+			{
+				{},
+				{
+					ok: []string{"dns:foo.com"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:bar.com"},
+		},
+		noOpenSSL: true, // OpenSSL's chain building is not informed by constraints.
+	},
+
+	// #27: chain building doesn't get stuck when there is no valid path.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:foo.com"},
+			},
+			{
+				ok: []string{"dns:example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+				{
+					ok: []string{"dns:foo.com"},
+				},
+			},
+			{
+				{
+					ok: []string{"dns:bar.com"},
+				},
+				{
+					ok: []string{"dns:foo.com"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:bar.com"},
+		},
+		expectedError: "\"bar.com\" is not permitted",
+	},
+
+	// #28: unknown name types don't cause a problem without constraints.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"unknown:"},
+		},
+	},
+
+	// #29: unknown name types are allowed even in constrained chains.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:foo.com", "dns:.foo.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"unknown:"},
+		},
+	},
+
+	// #30: without SANs, a certificate with a CN is still accepted in a
+	// constrained chain, since we ignore the CN in VerifyHostname.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:foo.com", "dns:.foo.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{},
+			cn:   "foo.com",
+		},
+	},
+
+	// #31: IPv6 addresses work in constraints: roots can permit them as
+	// expected.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"ip:2000:abcd::/32"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"ip:2000:abcd:1234::"},
+		},
+	},
+
+	// #32: IPv6 addresses work in constraints: root restrictions are
+	// effective.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"ip:2000:abcd::/32"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"ip:2000:1234:abcd::"},
+		},
+		expectedError: "\"2000:1234:abcd::\" is not permitted",
+	},
+
+	// #33: An IPv6 permitted subtree doesn't affect DNS names.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"ip:2000:abcd::/32"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"ip:2000:abcd::", "dns:foo.com"},
+		},
+	},
+
+	// #34: IPv6 exclusions don't affect unrelated addresses.
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"ip:2000:abcd::/32"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"ip:2000:1234::"},
+		},
+	},
+
+	// #35: IPv6 exclusions are effective.
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"ip:2000:abcd::/32"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"ip:2000:abcd::"},
+		},
+		expectedError: "\"2000:abcd::\" is excluded",
+	},
+
+	// #36: IPv6 constraints do not permit IPv4 addresses.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"ip:2000:abcd::/32"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"ip:10.0.0.1"},
+		},
+		expectedError: "\"10.0.0.1\" is not permitted",
+	},
+
+	// #37: IPv4 constraints do not permit IPv6 addresses.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"ip:10.0.0.0/8"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"ip:2000:abcd::"},
+		},
+		expectedError: "\"2000:abcd::\" is not permitted",
+	},
+
+	// #38: an exclusion of an unknown type doesn't affect other names.
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"unknown:"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+	},
+
+	// #39: a permitted subtree of an unknown type doesn't affect other
+	// name types.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"unknown:"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+	},
+
+	// #40: exact email constraints work
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"email:foo@example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"email:foo@example.com"},
+		},
+	},
+
+	// #41: exact email constraints are effective
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"email:foo@example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"email:bar@example.com"},
+		},
+		expectedError: "\"bar@example.com\" is not permitted",
+	},
+
+	// #42: email canonicalisation works.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"email:foo@example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"email:\"\\f\\o\\o\"@example.com"},
+		},
+		noOpenSSL: true, // OpenSSL doesn't canonicalise email addresses before matching
+	},
+
+	// #43: limiting email addresses to a host works.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"email:example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"email:foo@example.com"},
+		},
+	},
+
+	// #44: a leading dot matches hosts one level deep
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"email:.example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"email:foo@sub.example.com"},
+		},
+	},
+
+	// #45: a leading dot does not match the host itself
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"email:.example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"email:foo@example.com"},
+		},
+		expectedError: "\"foo@example.com\" is not permitted",
+	},
+
+	// #46: a leading dot also matches two (or more) levels deep.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"email:.example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"email:foo@sub.sub.example.com"},
+		},
+	},
+
+	// #47: the local part of an email is case-sensitive
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"email:foo@example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"email:Foo@example.com"},
+		},
+		expectedError: "\"Foo@example.com\" is not permitted",
+	},
+
+	// #48: the domain part of an email is not case-sensitive
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"email:foo@EXAMPLE.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"email:foo@example.com"},
+		},
+	},
+
+	// #49: the domain part of a DNS constraint is also not case-sensitive.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:EXAMPLE.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+	},
+
+	// #50: URI constraints only cover the host part of the URI
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"uri:example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{
+				"uri:http://example.com/bar",
+				"uri:http://example.com:8080/",
+				"uri:https://example.com/wibble#bar",
+			},
+		},
+	},
+
+	// #51: URIs with IPs are rejected
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"uri:example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"uri:http://1.2.3.4/"},
+		},
+		expectedError: "URI with IP",
+	},
+
+	// #52: URIs with IPs and ports are rejected
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"uri:example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"uri:http://1.2.3.4:43/"},
+		},
+		expectedError: "URI with IP",
+	},
+
+	// #53: URIs with IPv6 addresses are also rejected
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"uri:example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"uri:http://[2006:abcd::1]/"},
+		},
+		expectedError: "URI with IP",
+	},
+
+	// #54: URIs with IPv6 addresses with ports are also rejected
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"uri:example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"uri:http://[2006:abcd::1]:16/"},
+		},
+		expectedError: "URI with IP",
+	},
+
+	// #55: URI constraints are effective
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"uri:example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"uri:http://bar.com/"},
+		},
+		expectedError: "\"http://bar.com/\" is not permitted",
+	},
+
+	// #56: URI constraints are effective
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"uri:foo.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"uri:http://foo.com/"},
+		},
+		expectedError: "\"http://foo.com/\" is excluded",
+	},
+
+	// #57: URI constraints can allow subdomains
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"uri:.foo.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"uri:http://www.foo.com/"},
+		},
+	},
+
+	// #58: excluding an IPv4-mapped-IPv6 address doesn't affect the IPv4
+	// version of that address.
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"ip:::ffff:1.2.3.4/128"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"ip:1.2.3.4"},
+		},
+	},
+
+	// #59: a URI constraint isn't matched by a URN.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"uri:example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"uri:urn:example"},
+		},
+		expectedError: "URI with empty host",
+	},
+
+	// #60: excluding all IPv6 addresses doesn't exclude all IPv4 addresses
+	// too, even though IPv4 is mapped into the IPv6 range.
+	{
+		roots: []constraintsSpec{
+			{
+				ok:  []string{"ip:1.2.3.0/24"},
+				bad: []string{"ip:::0/0"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"ip:1.2.3.4"},
+		},
+	},
+
+	// #61: omitting extended key usage in a CA certificate implies that
+	// any usage is ok.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+			ekus: []string{"serverAuth", "other"},
+		},
+	},
+
+	// #62: The “any” EKU also means that any usage is ok.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ekus: []string{"any"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+			ekus: []string{"serverAuth", "other"},
+		},
+	},
+
+	// #63: An intermediate with enumerated EKUs causes a failure if we
+	// test for an EKU not in that set. (ServerAuth is required by
+	// default.)
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ekus: []string{"email"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+			ekus: []string{"serverAuth"},
+		},
+		expectedError: "incompatible key usage",
+	},
+
+	// #64: an unknown EKU in the leaf doesn't break anything, even if it's not
+	// correctly nested.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ekus: []string{"email"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+			ekus: []string{"other"},
+		},
+		requestedEKUs: []ExtKeyUsage{ExtKeyUsageAny},
+	},
+
+	// #65: trying to add extra permitted key usages in an intermediate
+	// (after a limitation in the root) is acceptable so long as the leaf
+	// certificate doesn't use them.
+	{
+		roots: []constraintsSpec{
+			{
+				ekus: []string{"serverAuth"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ekus: []string{"serverAuth", "email"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+			ekus: []string{"serverAuth"},
+		},
+	},
+
+	// #66: EKUs in roots are not ignored.
+	{
+		roots: []constraintsSpec{
+			{
+				ekus: []string{"email"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ekus: []string{"serverAuth"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+			ekus: []string{"serverAuth"},
+		},
+		expectedError: "incompatible key usage",
+	},
+
+	// #67: SGC key usages used to permit serverAuth and clientAuth,
+	// but don't anymore.
+	{
+		roots: []constraintsSpec{
+			{},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ekus: []string{"netscapeSGC"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+			ekus: []string{"serverAuth", "clientAuth"},
+		},
+		expectedError: "incompatible key usage",
+	},
+
+	// #68: SGC key usages used to permit serverAuth and clientAuth,
+	// but don't anymore.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ekus: []string{"msSGC"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+			ekus: []string{"serverAuth", "clientAuth"},
+		},
+		expectedError: "incompatible key usage",
+	},
+
+	// #69: an empty DNS constraint should allow anything.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+	},
+
+	// #70: an empty DNS constraint should also reject everything.
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"dns:"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+		},
+		expectedError: "\"example.com\" is excluded",
+	},
+
+	// #71: an empty email constraint should allow anything
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"email:"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"email:foo@example.com"},
+		},
+	},
+
+	// #72: an empty email constraint should also reject everything.
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"email:"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"email:foo@example.com"},
+		},
+		expectedError: "\"foo@example.com\" is excluded",
+	},
+
+	// #73: an empty URI constraint should allow anything
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"uri:"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"uri:https://example.com/test"},
+		},
+	},
+
+	// #74: an empty URI constraint should also reject everything.
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"uri:"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"uri:https://example.com/test"},
+		},
+		expectedError: "\"https://example.com/test\" is excluded",
+	},
+
+	// #75: serverAuth in a leaf shouldn't permit clientAuth when requested in
+	// VerifyOptions.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+			ekus: []string{"serverAuth"},
+		},
+		requestedEKUs: []ExtKeyUsage{ExtKeyUsageClientAuth},
+		expectedError: "incompatible key usage",
+	},
+
+	// #76: MSSGC in a leaf used to match a request for serverAuth, but doesn't
+	// anymore.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+			ekus: []string{"msSGC"},
+		},
+		requestedEKUs: []ExtKeyUsage{ExtKeyUsageServerAuth},
+		expectedError: "incompatible key usage",
+	},
+
+	// An invalid DNS SAN should be detected only at validation time so
+	// that we can process CA certificates in the wild that have invalid SANs.
+	// See https://github.com/golang/go/issues/23995
+
+	// #77: an invalid DNS or mail SAN will not be detected if name constraint
+	// checking is not triggered.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:this is invalid", "email:this @ is invalid"},
+		},
+	},
+
+	// #78: an invalid DNS SAN will be detected if any name constraint checking
+	// is triggered.
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"uri:"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:this is invalid"},
+		},
+		expectedError: "cannot parse dnsName",
+	},
+
+	// #79: an invalid email SAN will be detected if any name constraint
+	// checking is triggered.
+	{
+		roots: []constraintsSpec{
+			{
+				bad: []string{"uri:"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"email:this @ is invalid"},
+		},
+		expectedError: "cannot parse rfc822Name",
+	},
+
+	// #80: if several EKUs are requested, satisfying any of them is sufficient.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+			ekus: []string{"email"},
+		},
+		requestedEKUs: []ExtKeyUsage{ExtKeyUsageClientAuth, ExtKeyUsageEmailProtection},
+	},
+
+	// #81: EKUs that are not asserted in VerifyOpts are not required to be
+	// nested.
+	{
+		roots: make([]constraintsSpec, 1),
+		intermediates: [][]constraintsSpec{
+			{
+				{
+					ekus: []string{"serverAuth"},
+				},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:example.com"},
+			// There's no email EKU in the intermediate. This would be rejected if
+			// full nesting was required.
+			ekus: []string{"email", "serverAuth"},
+		},
+	},
+
+	// #82: a certificate without SANs and CN is accepted in a constrained chain.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:foo.com", "dns:.foo.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{},
+		},
+	},
+
+	// #83: a certificate without SANs and with a CN that does not parse as a
+	// hostname is accepted in a constrained chain.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:foo.com", "dns:.foo.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{},
+			cn:   "foo,bar",
+		},
+	},
+
+	// #84: a certificate with SANs and CN is accepted in a constrained chain.
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"dns:foo.com", "dns:.foo.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"dns:foo.com"},
+			cn:   "foo.bar",
+		},
+	},
+}
+
+func makeConstraintsCACert(constraints constraintsSpec, name string, key *ecdsa.PrivateKey, parent *Certificate, parentKey *ecdsa.PrivateKey) (*Certificate, error) {
+	var serialBytes [16]byte
+	rand.Read(serialBytes[:])
+
+	template := &Certificate{
+		SerialNumber: new(big.Int).SetBytes(serialBytes[:]),
+		Subject: pkix.Name{
+			CommonName: name,
+		},
+		NotBefore:             time.Unix(1000, 0),
+		NotAfter:              time.Unix(2000, 0),
+		KeyUsage:              KeyUsageCertSign,
+		BasicConstraintsValid: true,
+		IsCA:                  true,
+	}
+
+	if err := addConstraintsToTemplate(constraints, template); err != nil {
+		return nil, err
+	}
+
+	if parent == nil {
+		parent = template
+	}
+	derBytes, err := CreateCertificate(rand.Reader, template, parent, &key.PublicKey, parentKey)
+	if err != nil {
+		return nil, err
+	}
+
+	caCert, err := ParseCertificate(derBytes)
+	if err != nil {
+		return nil, err
+	}
+
+	return caCert, nil
+}
+
+func makeConstraintsLeafCert(leaf leafSpec, key *ecdsa.PrivateKey, parent *Certificate, parentKey *ecdsa.PrivateKey) (*Certificate, error) {
+	var serialBytes [16]byte
+	rand.Read(serialBytes[:])
+
+	template := &Certificate{
+		SerialNumber: new(big.Int).SetBytes(serialBytes[:]),
+		Subject: pkix.Name{
+			OrganizationalUnit: []string{"Leaf"},
+			CommonName:         leaf.cn,
+		},
+		NotBefore:             time.Unix(1000, 0),
+		NotAfter:              time.Unix(2000, 0),
+		KeyUsage:              KeyUsageDigitalSignature,
+		BasicConstraintsValid: true,
+		IsCA:                  false,
+	}
+
+	for _, name := range leaf.sans {
+		switch {
+		case strings.HasPrefix(name, "dns:"):
+			template.DNSNames = append(template.DNSNames, name[4:])
+
+		case strings.HasPrefix(name, "ip:"):
+			ip := net.ParseIP(name[3:])
+			if ip == nil {
+				return nil, fmt.Errorf("cannot parse IP %q", name[3:])
+			}
+			template.IPAddresses = append(template.IPAddresses, ip)
+
+		case strings.HasPrefix(name, "invalidip:"):
+			ipBytes, err := hex.DecodeString(name[10:])
+			if err != nil {
+				return nil, fmt.Errorf("cannot parse invalid IP: %s", err)
+			}
+			template.IPAddresses = append(template.IPAddresses, net.IP(ipBytes))
+
+		case strings.HasPrefix(name, "email:"):
+			template.EmailAddresses = append(template.EmailAddresses, name[6:])
+
+		case strings.HasPrefix(name, "uri:"):
+			uri, err := url.Parse(name[4:])
+			if err != nil {
+				return nil, fmt.Errorf("cannot parse URI %q: %s", name[4:], err)
+			}
+			template.URIs = append(template.URIs, uri)
+
+		case strings.HasPrefix(name, "unknown:"):
+			// This is a special case for testing unknown
+			// name types. A custom SAN extension is
+			// injected into the certificate.
+			if len(leaf.sans) != 1 {
+				panic("when using unknown name types, it must be the sole name")
+			}
+
+			template.ExtraExtensions = append(template.ExtraExtensions, pkix.Extension{
+				Id: []int{2, 5, 29, 17},
+				Value: []byte{
+					0x30, // SEQUENCE
+					3,    // three bytes
+					9,    // undefined GeneralName type 9
+					1,
+					1,
+				},
+			})
+
+		default:
+			return nil, fmt.Errorf("unknown name type %q", name)
+		}
+	}
+
+	var err error
+	if template.ExtKeyUsage, template.UnknownExtKeyUsage, err = parseEKUs(leaf.ekus); err != nil {
+		return nil, err
+	}
+
+	if parent == nil {
+		parent = template
+	}
+
+	derBytes, err := CreateCertificate(rand.Reader, template, parent, &key.PublicKey, parentKey)
+	if err != nil {
+		return nil, err
+	}
+
+	return ParseCertificate(derBytes)
+}
+
+func customConstraintsExtension(typeNum int, constraint []byte, isExcluded bool) pkix.Extension {
+	appendConstraint := func(contents []byte, tag uint8) []byte {
+		contents = append(contents, tag|32 /* constructed */ |0x80 /* context-specific */)
+		contents = append(contents, byte(4+len(constraint)) /* length */)
+		contents = append(contents, 0x30 /* SEQUENCE */)
+		contents = append(contents, byte(2+len(constraint)) /* length */)
+		contents = append(contents, byte(typeNum) /* GeneralName type */)
+		contents = append(contents, byte(len(constraint)))
+		return append(contents, constraint...)
+	}
+
+	var contents []byte
+	if !isExcluded {
+		contents = appendConstraint(contents, 0 /* tag 0 for permitted */)
+	} else {
+		contents = appendConstraint(contents, 1 /* tag 1 for excluded */)
+	}
+
+	var value []byte
+	value = append(value, 0x30 /* SEQUENCE */)
+	value = append(value, byte(len(contents)))
+	value = append(value, contents...)
+
+	return pkix.Extension{
+		Id:    []int{2, 5, 29, 30},
+		Value: value,
+	}
+}
+
+func addConstraintsToTemplate(constraints constraintsSpec, template *Certificate) error {
+	parse := func(constraints []string) (dnsNames []string, ips []*net.IPNet, emailAddrs []string, uriDomains []string, err error) {
+		for _, constraint := range constraints {
+			switch {
+			case strings.HasPrefix(constraint, "dns:"):
+				dnsNames = append(dnsNames, constraint[4:])
+
+			case strings.HasPrefix(constraint, "ip:"):
+				_, ipNet, err := net.ParseCIDR(constraint[3:])
+				if err != nil {
+					return nil, nil, nil, nil, err
+				}
+				ips = append(ips, ipNet)
+
+			case strings.HasPrefix(constraint, "email:"):
+				emailAddrs = append(emailAddrs, constraint[6:])
+
+			case strings.HasPrefix(constraint, "uri:"):
+				uriDomains = append(uriDomains, constraint[4:])
+
+			default:
+				return nil, nil, nil, nil, fmt.Errorf("unknown constraint %q", constraint)
+			}
+		}
+
+		return dnsNames, ips, emailAddrs, uriDomains, err
+	}
+
+	handleSpecialConstraint := func(constraint string, isExcluded bool) bool {
+		switch {
+		case constraint == "unknown:":
+			template.ExtraExtensions = append(template.ExtraExtensions, customConstraintsExtension(9 /* undefined GeneralName type */, []byte{1}, isExcluded))
+
+		default:
+			return false
+		}
+
+		return true
+	}
+
+	if len(constraints.ok) == 1 && len(constraints.bad) == 0 {
+		if handleSpecialConstraint(constraints.ok[0], false) {
+			return nil
+		}
+	}
+
+	if len(constraints.bad) == 1 && len(constraints.ok) == 0 {
+		if handleSpecialConstraint(constraints.bad[0], true) {
+			return nil
+		}
+	}
+
+	var err error
+	template.PermittedDNSDomains, template.PermittedIPRanges, template.PermittedEmailAddresses, template.PermittedURIDomains, err = parse(constraints.ok)
+	if err != nil {
+		return err
+	}
+
+	template.ExcludedDNSDomains, template.ExcludedIPRanges, template.ExcludedEmailAddresses, template.ExcludedURIDomains, err = parse(constraints.bad)
+	if err != nil {
+		return err
+	}
+
+	if template.ExtKeyUsage, template.UnknownExtKeyUsage, err = parseEKUs(constraints.ekus); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func parseEKUs(ekuStrs []string) (ekus []ExtKeyUsage, unknowns []asn1.ObjectIdentifier, err error) {
+	for _, s := range ekuStrs {
+		switch s {
+		case "serverAuth":
+			ekus = append(ekus, ExtKeyUsageServerAuth)
+		case "clientAuth":
+			ekus = append(ekus, ExtKeyUsageClientAuth)
+		case "email":
+			ekus = append(ekus, ExtKeyUsageEmailProtection)
+		case "netscapeSGC":
+			ekus = append(ekus, ExtKeyUsageNetscapeServerGatedCrypto)
+		case "msSGC":
+			ekus = append(ekus, ExtKeyUsageMicrosoftServerGatedCrypto)
+		case "any":
+			ekus = append(ekus, ExtKeyUsageAny)
+		case "other":
+			unknowns = append(unknowns, asn1.ObjectIdentifier{2, 4, 1, 2, 3})
+		default:
+			return nil, nil, fmt.Errorf("unknown EKU %q", s)
+		}
+	}
+
+	return
+}
+
+func TestConstraintCases(t *testing.T) {
+	privateKeys := sync.Pool{
+		New: func() any {
+			priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+			if err != nil {
+				panic(err)
+			}
+			return priv
+		},
+	}
+
+	for i, test := range nameConstraintsTests {
+		rootPool := NewCertPool()
+		rootKey := privateKeys.Get().(*ecdsa.PrivateKey)
+		rootName := "Root " + strconv.Itoa(i)
+
+		// keys keeps track of all the private keys used in a given
+		// test and puts them back in the privateKeys pool at the end.
+		keys := []*ecdsa.PrivateKey{rootKey}
+
+		// At each level (root, intermediate(s), leaf), parent points to
+		// an example parent certificate and parentKey the key for the
+		// parent level. Since all certificates at a given level have
+		// the same name and public key, any parent certificate is
+		// sufficient to get the correct issuer name and authority
+		// key ID.
+		var parent *Certificate
+		parentKey := rootKey
+
+		for _, root := range test.roots {
+			rootCert, err := makeConstraintsCACert(root, rootName, rootKey, nil, rootKey)
+			if err != nil {
+				t.Fatalf("#%d: failed to create root: %s", i, err)
+			}
+
+			parent = rootCert
+			rootPool.AddCert(rootCert)
+		}
+
+		intermediatePool := NewCertPool()
+
+		for level, intermediates := range test.intermediates {
+			levelKey := privateKeys.Get().(*ecdsa.PrivateKey)
+			keys = append(keys, levelKey)
+			levelName := "Intermediate level " + strconv.Itoa(level)
+			var last *Certificate
+
+			for _, intermediate := range intermediates {
+				caCert, err := makeConstraintsCACert(intermediate, levelName, levelKey, parent, parentKey)
+				if err != nil {
+					t.Fatalf("#%d: failed to create %q: %s", i, levelName, err)
+				}
+
+				last = caCert
+				intermediatePool.AddCert(caCert)
+			}
+
+			parent = last
+			parentKey = levelKey
+		}
+
+		leafKey := privateKeys.Get().(*ecdsa.PrivateKey)
+		keys = append(keys, leafKey)
+
+		leafCert, err := makeConstraintsLeafCert(test.leaf, leafKey, parent, parentKey)
+		if err != nil {
+			t.Fatalf("#%d: cannot create leaf: %s", i, err)
+		}
+
+		// Skip tests with CommonName set because OpenSSL will try to match it
+		// against name constraints, while we ignore it when it's not hostname-looking.
+		if !test.noOpenSSL && testNameConstraintsAgainstOpenSSL && test.leaf.cn == "" {
+			output, err := testChainAgainstOpenSSL(t, leafCert, intermediatePool, rootPool)
+			if err == nil && len(test.expectedError) > 0 {
+				t.Errorf("#%d: unexpectedly succeeded against OpenSSL", i)
+				if debugOpenSSLFailure {
+					return
+				}
+			}
+
+			if err != nil {
+				if _, ok := err.(*exec.ExitError); !ok {
+					t.Errorf("#%d: OpenSSL failed to run: %s", i, err)
+				} else if len(test.expectedError) == 0 {
+					t.Errorf("#%d: OpenSSL unexpectedly failed: %v", i, output)
+					if debugOpenSSLFailure {
+						return
+					}
+				}
+			}
+		}
+
+		verifyOpts := VerifyOptions{
+			Roots:         rootPool,
+			Intermediates: intermediatePool,
+			CurrentTime:   time.Unix(1500, 0),
+			KeyUsages:     test.requestedEKUs,
+		}
+		_, err = leafCert.Verify(verifyOpts)
+
+		logInfo := true
+		if len(test.expectedError) == 0 {
+			if err != nil {
+				t.Errorf("#%d: unexpected failure: %s", i, err)
+			} else {
+				logInfo = false
+			}
+		} else {
+			if err == nil {
+				t.Errorf("#%d: unexpected success", i)
+			} else if !strings.Contains(err.Error(), test.expectedError) {
+				t.Errorf("#%d: expected error containing %q, but got: %s", i, test.expectedError, err)
+			} else {
+				logInfo = false
+			}
+		}
+
+		if logInfo {
+			certAsPEM := func(cert *Certificate) string {
+				var buf bytes.Buffer
+				pem.Encode(&buf, &pem.Block{Type: "CERTIFICATE", Bytes: cert.Raw})
+				return buf.String()
+			}
+			t.Errorf("#%d: root:\n%s", i, certAsPEM(rootPool.mustCert(t, 0)))
+			t.Errorf("#%d: leaf:\n%s", i, certAsPEM(leafCert))
+		}
+
+		for _, key := range keys {
+			privateKeys.Put(key)
+		}
+	}
+}
+
+func writePEMsToTempFile(certs []*Certificate) *os.File {
+	file, err := os.CreateTemp("", "name_constraints_test")
+	if err != nil {
+		panic("cannot create tempfile")
+	}
+
+	pemBlock := &pem.Block{Type: "CERTIFICATE"}
+	for _, cert := range certs {
+		pemBlock.Bytes = cert.Raw
+		pem.Encode(file, pemBlock)
+	}
+
+	return file
+}
+
+func testChainAgainstOpenSSL(t *testing.T, leaf *Certificate, intermediates, roots *CertPool) (string, error) {
+	args := []string{"verify", "-no_check_time"}
+
+	rootsFile := writePEMsToTempFile(allCerts(t, roots))
+	if debugOpenSSLFailure {
+		println("roots file:", rootsFile.Name())
+	} else {
+		defer os.Remove(rootsFile.Name())
+	}
+	args = append(args, "-CAfile", rootsFile.Name())
+
+	if intermediates.len() > 0 {
+		intermediatesFile := writePEMsToTempFile(allCerts(t, intermediates))
+		if debugOpenSSLFailure {
+			println("intermediates file:", intermediatesFile.Name())
+		} else {
+			defer os.Remove(intermediatesFile.Name())
+		}
+		args = append(args, "-untrusted", intermediatesFile.Name())
+	}
+
+	leafFile := writePEMsToTempFile([]*Certificate{leaf})
+	if debugOpenSSLFailure {
+		println("leaf file:", leafFile.Name())
+	} else {
+		defer os.Remove(leafFile.Name())
+	}
+	args = append(args, leafFile.Name())
+
+	var output bytes.Buffer
+	cmd := exec.Command("openssl", args...)
+	cmd.Stdout = &output
+	cmd.Stderr = &output
+
+	err := cmd.Run()
+	return output.String(), err
+}
+
+var rfc2821Tests = []struct {
+	in                string
+	localPart, domain string
+}{
+	{"foo@example.com", "foo", "example.com"},
+	{"@example.com", "", ""},
+	{"\"@example.com", "", ""},
+	{"\"\"@example.com", "", "example.com"},
+	{"\"a\"@example.com", "a", "example.com"},
+	{"\"\\a\"@example.com", "a", "example.com"},
+	{"a\"@example.com", "", ""},
+	{"foo..bar@example.com", "", ""},
+	{".foo.bar@example.com", "", ""},
+	{"foo.bar.@example.com", "", ""},
+	{"|{}?'@example.com", "|{}?'", "example.com"},
+
+	// Examples from RFC 3696
+	{"Abc\\@def@example.com", "Abc@def", "example.com"},
+	{"Fred\\ Bloggs@example.com", "Fred Bloggs", "example.com"},
+	{"Joe.\\\\Blow@example.com", "Joe.\\Blow", "example.com"},
+	{"\"Abc@def\"@example.com", "Abc@def", "example.com"},
+	{"\"Fred Bloggs\"@example.com", "Fred Bloggs", "example.com"},
+	{"customer/department=shipping@example.com", "customer/department=shipping", "example.com"},
+	{"$A12345@example.com", "$A12345", "example.com"},
+	{"!def!xyz%abc@example.com", "!def!xyz%abc", "example.com"},
+	{"_somename@example.com", "_somename", "example.com"},
+}
+
+func TestRFC2821Parsing(t *testing.T) {
+	for i, test := range rfc2821Tests {
+		mailbox, ok := parseRFC2821Mailbox(test.in)
+		expectedFailure := len(test.localPart) == 0 && len(test.domain) == 0
+
+		if ok && expectedFailure {
+			t.Errorf("#%d: %q unexpectedly parsed as (%q, %q)", i, test.in, mailbox.local, mailbox.domain)
+			continue
+		}
+
+		if !ok && !expectedFailure {
+			t.Errorf("#%d: unexpected failure for %q", i, test.in)
+			continue
+		}
+
+		if !ok {
+			continue
+		}
+
+		if mailbox.local != test.localPart || mailbox.domain != test.domain {
+			t.Errorf("#%d: %q parsed as (%q, %q), but wanted (%q, %q)", i, test.in, mailbox.local, mailbox.domain, test.localPart, test.domain)
+		}
+	}
+}
+
+func TestBadNamesInConstraints(t *testing.T) {
+	constraintParseError := func(err error) bool {
+		str := err.Error()
+		return strings.Contains(str, "failed to parse ") && strings.Contains(str, "constraint")
+	}
+
+	encodingError := func(err error) bool {
+		return strings.Contains(err.Error(), "cannot be encoded as an IA5String")
+	}
+
+	// Bad names in constraints should not parse.
+	badNames := []struct {
+		name    string
+		matcher func(error) bool
+	}{
+		{"dns:foo.com.", constraintParseError},
+		{"email:abc@foo.com.", constraintParseError},
+		{"email:foo.com.", constraintParseError},
+		{"uri:example.com.", constraintParseError},
+		{"uri:1.2.3.4", constraintParseError},
+		{"uri:ffff::1", constraintParseError},
+		{"dns:not–hyphen.com", encodingError},
+		{"email:foo@not–hyphen.com", encodingError},
+		{"uri:not–hyphen.com", encodingError},
+	}
+
+	priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		panic(err)
+	}
+
+	for _, test := range badNames {
+		_, err := makeConstraintsCACert(constraintsSpec{
+			ok: []string{test.name},
+		}, "TestAbsoluteNamesInConstraints", priv, nil, priv)
+
+		if err == nil {
+			t.Errorf("bad name %q unexpectedly accepted in name constraint", test.name)
+			continue
+		} else {
+			if !test.matcher(err) {
+				t.Errorf("bad name %q triggered unrecognised error: %s", test.name, err)
+			}
+		}
+	}
+}
+
+func TestBadNamesInSANs(t *testing.T) {
+	// Bad names in URI and IP SANs should not parse. Bad DNS and email SANs
+	// will parse and are tested in name constraint tests at the top of this
+	// file.
+	badNames := []string{
+		"uri:https://example.com./dsf",
+		"invalidip:0102",
+		"invalidip:0102030405",
+	}
+
+	priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		panic(err)
+	}
+
+	for _, badName := range badNames {
+		_, err := makeConstraintsLeafCert(leafSpec{sans: []string{badName}}, priv, nil, priv)
+
+		if err == nil {
+			t.Errorf("bad name %q unexpectedly accepted in SAN", badName)
+			continue
+		}
+
+		if str := err.Error(); !strings.Contains(str, "cannot parse ") {
+			t.Errorf("bad name %q triggered unrecognised error: %s", badName, str)
+		}
+	}
+}
diff --git a/src/crypto/x509/parser.go b/src/crypto/x509/parser.go
new file mode 100644
index 0000000..2cb1ad2
--- /dev/null
+++ b/src/crypto/x509/parser.go
@@ -0,0 +1,1013 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+package x509
+
+import (
+	"bytes"
+	"crypto/dsa"
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/elliptic"
+	"crypto/rsa"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"errors"
+	"fmt"
+	"math/big"
+	"net"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+	"unicode/utf16"
+	"unicode/utf8"
+
+	"golang.org/x/crypto/cryptobyte"
+	cryptobyte_asn1 "golang.org/x/crypto/cryptobyte/asn1"
+)
+
+// isPrintable reports whether the given b is in the ASN.1 PrintableString set.
+// This is a simplified version of encoding/asn1.isPrintable.
+func isPrintable(b byte) bool {
+	return 'a' <= b && b <= 'z' ||
+		'A' <= b && b <= 'Z' ||
+		'0' <= b && b <= '9' ||
+		'\'' <= b && b <= ')' ||
+		'+' <= b && b <= '/' ||
+		b == ' ' ||
+		b == ':' ||
+		b == '=' ||
+		b == '?' ||
+		// This is technically not allowed in a PrintableString.
+		// However, x509 certificates with wildcard strings don't
+		// always use the correct string type so we permit it.
+		b == '*' ||
+		// This is not technically allowed either. However, not
+		// only is it relatively common, but there are also a
+		// handful of CA certificates that contain it. At least
+		// one of which will not expire until 2027.
+		b == '&'
+}
+
+// parseASN1String parses the ASN.1 string types T61String, PrintableString,
+// UTF8String, BMPString, IA5String, and NumericString. This is mostly copied
+// from the respective encoding/asn1.parse... methods, rather than just
+// increasing the API surface of that package.
+func parseASN1String(tag cryptobyte_asn1.Tag, value []byte) (string, error) {
+	switch tag {
+	case cryptobyte_asn1.T61String:
+		return string(value), nil
+	case cryptobyte_asn1.PrintableString:
+		for _, b := range value {
+			if !isPrintable(b) {
+				return "", errors.New("invalid PrintableString")
+			}
+		}
+		return string(value), nil
+	case cryptobyte_asn1.UTF8String:
+		if !utf8.Valid(value) {
+			return "", errors.New("invalid UTF-8 string")
+		}
+		return string(value), nil
+	case cryptobyte_asn1.Tag(asn1.TagBMPString):
+		if len(value)%2 != 0 {
+			return "", errors.New("invalid BMPString")
+		}
+
+		// Strip terminator if present.
+		if l := len(value); l >= 2 && value[l-1] == 0 && value[l-2] == 0 {
+			value = value[:l-2]
+		}
+
+		s := make([]uint16, 0, len(value)/2)
+		for len(value) > 0 {
+			s = append(s, uint16(value[0])<<8+uint16(value[1]))
+			value = value[2:]
+		}
+
+		return string(utf16.Decode(s)), nil
+	case cryptobyte_asn1.IA5String:
+		s := string(value)
+		if isIA5String(s) != nil {
+			return "", errors.New("invalid IA5String")
+		}
+		return s, nil
+	case cryptobyte_asn1.Tag(asn1.TagNumericString):
+		for _, b := range value {
+			if !('0' <= b && b <= '9' || b == ' ') {
+				return "", errors.New("invalid NumericString")
+			}
+		}
+		return string(value), nil
+	}
+	return "", fmt.Errorf("unsupported string type: %v", tag)
+}
+
+// parseName parses a DER encoded Name as defined in RFC 5280. We may
+// want to export this function in the future for use in crypto/tls.
+func parseName(raw cryptobyte.String) (*pkix.RDNSequence, error) {
+	if !raw.ReadASN1(&raw, cryptobyte_asn1.SEQUENCE) {
+		return nil, errors.New("x509: invalid RDNSequence")
+	}
+
+	var rdnSeq pkix.RDNSequence
+	for !raw.Empty() {
+		var rdnSet pkix.RelativeDistinguishedNameSET
+		var set cryptobyte.String
+		if !raw.ReadASN1(&set, cryptobyte_asn1.SET) {
+			return nil, errors.New("x509: invalid RDNSequence")
+		}
+		for !set.Empty() {
+			var atav cryptobyte.String
+			if !set.ReadASN1(&atav, cryptobyte_asn1.SEQUENCE) {
+				return nil, errors.New("x509: invalid RDNSequence: invalid attribute")
+			}
+			var attr pkix.AttributeTypeAndValue
+			if !atav.ReadASN1ObjectIdentifier(&attr.Type) {
+				return nil, errors.New("x509: invalid RDNSequence: invalid attribute type")
+			}
+			var rawValue cryptobyte.String
+			var valueTag cryptobyte_asn1.Tag
+			if !atav.ReadAnyASN1(&rawValue, &valueTag) {
+				return nil, errors.New("x509: invalid RDNSequence: invalid attribute value")
+			}
+			var err error
+			attr.Value, err = parseASN1String(valueTag, rawValue)
+			if err != nil {
+				return nil, fmt.Errorf("x509: invalid RDNSequence: invalid attribute value: %s", err)
+			}
+			rdnSet = append(rdnSet, attr)
+		}
+
+		rdnSeq = append(rdnSeq, rdnSet)
+	}
+
+	return &rdnSeq, nil
+}
+
+func parseAI(der cryptobyte.String) (pkix.AlgorithmIdentifier, error) {
+	ai := pkix.AlgorithmIdentifier{}
+	if !der.ReadASN1ObjectIdentifier(&ai.Algorithm) {
+		return ai, errors.New("x509: malformed OID")
+	}
+	if der.Empty() {
+		return ai, nil
+	}
+	var params cryptobyte.String
+	var tag cryptobyte_asn1.Tag
+	if !der.ReadAnyASN1Element(&params, &tag) {
+		return ai, errors.New("x509: malformed parameters")
+	}
+	ai.Parameters.Tag = int(tag)
+	ai.Parameters.FullBytes = params
+	return ai, nil
+}
+
+func parseValidity(der cryptobyte.String) (time.Time, time.Time, error) {
+	extract := func() (time.Time, error) {
+		var t time.Time
+		switch {
+		case der.PeekASN1Tag(cryptobyte_asn1.UTCTime):
+			// TODO(rolandshoemaker): once #45411 is fixed, the following code
+			// should be replaced with a call to der.ReadASN1UTCTime.
+			var utc cryptobyte.String
+			if !der.ReadASN1(&utc, cryptobyte_asn1.UTCTime) {
+				return t, errors.New("x509: malformed UTCTime")
+			}
+			s := string(utc)
+
+			formatStr := "0601021504Z0700"
+			var err error
+			t, err = time.Parse(formatStr, s)
+			if err != nil {
+				formatStr = "060102150405Z0700"
+				t, err = time.Parse(formatStr, s)
+			}
+			if err != nil {
+				return t, err
+			}
+
+			if serialized := t.Format(formatStr); serialized != s {
+				return t, errors.New("x509: malformed UTCTime")
+			}
+
+			if t.Year() >= 2050 {
+				// UTCTime only encodes times prior to 2050. See https://tools.ietf.org/html/rfc5280#section-4.1.2.5.1
+				t = t.AddDate(-100, 0, 0)
+			}
+		case der.PeekASN1Tag(cryptobyte_asn1.GeneralizedTime):
+			if !der.ReadASN1GeneralizedTime(&t) {
+				return t, errors.New("x509: malformed GeneralizedTime")
+			}
+		default:
+			return t, errors.New("x509: unsupported time format")
+		}
+		return t, nil
+	}
+
+	notBefore, err := extract()
+	if err != nil {
+		return time.Time{}, time.Time{}, err
+	}
+	notAfter, err := extract()
+	if err != nil {
+		return time.Time{}, time.Time{}, err
+	}
+
+	return notBefore, notAfter, nil
+}
+
+func parseExtension(der cryptobyte.String) (pkix.Extension, error) {
+	var ext pkix.Extension
+	if !der.ReadASN1ObjectIdentifier(&ext.Id) {
+		return ext, errors.New("x509: malformed extension OID field")
+	}
+	if der.PeekASN1Tag(cryptobyte_asn1.BOOLEAN) {
+		if !der.ReadASN1Boolean(&ext.Critical) {
+			return ext, errors.New("x509: malformed extension critical field")
+		}
+	}
+	var val cryptobyte.String
+	if !der.ReadASN1(&val, cryptobyte_asn1.OCTET_STRING) {
+		return ext, errors.New("x509: malformed extension value field")
+	}
+	ext.Value = val
+	return ext, nil
+}
+
+func parsePublicKey(algo PublicKeyAlgorithm, keyData *publicKeyInfo) (any, error) {
+	der := cryptobyte.String(keyData.PublicKey.RightAlign())
+	switch algo {
+	case RSA:
+		// RSA public keys must have a NULL in the parameters.
+		// See RFC 3279, Section 2.3.1.
+		if !bytes.Equal(keyData.Algorithm.Parameters.FullBytes, asn1.NullBytes) {
+			return nil, errors.New("x509: RSA key missing NULL parameters")
+		}
+
+		p := &pkcs1PublicKey{N: new(big.Int)}
+		if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {
+			return nil, errors.New("x509: invalid RSA public key")
+		}
+		if !der.ReadASN1Integer(p.N) {
+			return nil, errors.New("x509: invalid RSA modulus")
+		}
+		if !der.ReadASN1Integer(&p.E) {
+			return nil, errors.New("x509: invalid RSA public exponent")
+		}
+
+		if p.N.Sign() <= 0 {
+			return nil, errors.New("x509: RSA modulus is not a positive number")
+		}
+		if p.E <= 0 {
+			return nil, errors.New("x509: RSA public exponent is not a positive number")
+		}
+
+		pub := &rsa.PublicKey{
+			E: p.E,
+			N: p.N,
+		}
+		return pub, nil
+	case ECDSA:
+		paramsDer := cryptobyte.String(keyData.Algorithm.Parameters.FullBytes)
+		namedCurveOID := new(asn1.ObjectIdentifier)
+		if !paramsDer.ReadASN1ObjectIdentifier(namedCurveOID) {
+			return nil, errors.New("x509: invalid ECDSA parameters")
+		}
+		namedCurve := namedCurveFromOID(*namedCurveOID)
+		if namedCurve == nil {
+			return nil, errors.New("x509: unsupported elliptic curve")
+		}
+		x, y := elliptic.Unmarshal(namedCurve, der)
+		if x == nil {
+			return nil, errors.New("x509: failed to unmarshal elliptic curve point")
+		}
+		pub := &ecdsa.PublicKey{
+			Curve: namedCurve,
+			X:     x,
+			Y:     y,
+		}
+		return pub, nil
+	case Ed25519:
+		// RFC 8410, Section 3
+		// > For all of the OIDs, the parameters MUST be absent.
+		if len(keyData.Algorithm.Parameters.FullBytes) != 0 {
+			return nil, errors.New("x509: Ed25519 key encoded with illegal parameters")
+		}
+		if len(der) != ed25519.PublicKeySize {
+			return nil, errors.New("x509: wrong Ed25519 public key size")
+		}
+		return ed25519.PublicKey(der), nil
+	case DSA:
+		y := new(big.Int)
+		if !der.ReadASN1Integer(y) {
+			return nil, errors.New("x509: invalid DSA public key")
+		}
+		pub := &dsa.PublicKey{
+			Y: y,
+			Parameters: dsa.Parameters{
+				P: new(big.Int),
+				Q: new(big.Int),
+				G: new(big.Int),
+			},
+		}
+		paramsDer := cryptobyte.String(keyData.Algorithm.Parameters.FullBytes)
+		if !paramsDer.ReadASN1(&paramsDer, cryptobyte_asn1.SEQUENCE) ||
+			!paramsDer.ReadASN1Integer(pub.Parameters.P) ||
+			!paramsDer.ReadASN1Integer(pub.Parameters.Q) ||
+			!paramsDer.ReadASN1Integer(pub.Parameters.G) {
+			return nil, errors.New("x509: invalid DSA parameters")
+		}
+		if pub.Y.Sign() <= 0 || pub.Parameters.P.Sign() <= 0 ||
+			pub.Parameters.Q.Sign() <= 0 || pub.Parameters.G.Sign() <= 0 {
+			return nil, errors.New("x509: zero or negative DSA parameter")
+		}
+		return pub, nil
+	default:
+		return nil, nil
+	}
+}
+
+func parseKeyUsageExtension(der cryptobyte.String) (KeyUsage, error) {
+	var usageBits asn1.BitString
+	if !der.ReadASN1BitString(&usageBits) {
+		return 0, errors.New("x509: invalid key usage")
+	}
+
+	var usage int
+	for i := 0; i < 9; i++ {
+		if usageBits.At(i) != 0 {
+			usage |= 1 << uint(i)
+		}
+	}
+	return KeyUsage(usage), nil
+}
+
+func parseBasicConstraintsExtension(der cryptobyte.String) (bool, int, error) {
+	var isCA bool
+	if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {
+		return false, 0, errors.New("x509: invalid basic constraints a")
+	}
+	if der.PeekASN1Tag(cryptobyte_asn1.BOOLEAN) {
+		if !der.ReadASN1Boolean(&isCA) {
+			return false, 0, errors.New("x509: invalid basic constraints b")
+		}
+	}
+	maxPathLen := -1
+	if !der.Empty() && der.PeekASN1Tag(cryptobyte_asn1.INTEGER) {
+		if !der.ReadASN1Integer(&maxPathLen) {
+			return false, 0, errors.New("x509: invalid basic constraints c")
+		}
+	}
+
+	// TODO: map out.MaxPathLen to 0 if it has the -1 default value? (Issue 19285)
+	return isCA, maxPathLen, nil
+}
+
+func forEachSAN(der cryptobyte.String, callback func(tag int, data []byte) error) error {
+	if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {
+		return errors.New("x509: invalid subject alternative names")
+	}
+	for !der.Empty() {
+		var san cryptobyte.String
+		var tag cryptobyte_asn1.Tag
+		if !der.ReadAnyASN1(&san, &tag) {
+			return errors.New("x509: invalid subject alternative name")
+		}
+		if err := callback(int(tag^0x80), san); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func parseSANExtension(der cryptobyte.String) (dnsNames, emailAddresses []string, ipAddresses []net.IP, uris []*url.URL, err error) {
+	err = forEachSAN(der, func(tag int, data []byte) error {
+		switch tag {
+		case nameTypeEmail:
+			email := string(data)
+			if err := isIA5String(email); err != nil {
+				return errors.New("x509: SAN rfc822Name is malformed")
+			}
+			emailAddresses = append(emailAddresses, email)
+		case nameTypeDNS:
+			name := string(data)
+			if err := isIA5String(name); err != nil {
+				return errors.New("x509: SAN dNSName is malformed")
+			}
+			dnsNames = append(dnsNames, string(name))
+		case nameTypeURI:
+			uriStr := string(data)
+			if err := isIA5String(uriStr); err != nil {
+				return errors.New("x509: SAN uniformResourceIdentifier is malformed")
+			}
+			uri, err := url.Parse(uriStr)
+			if err != nil {
+				return fmt.Errorf("x509: cannot parse URI %q: %s", uriStr, err)
+			}
+			if len(uri.Host) > 0 {
+				if _, ok := domainToReverseLabels(uri.Host); !ok {
+					return fmt.Errorf("x509: cannot parse URI %q: invalid domain", uriStr)
+				}
+			}
+			uris = append(uris, uri)
+		case nameTypeIP:
+			switch len(data) {
+			case net.IPv4len, net.IPv6len:
+				ipAddresses = append(ipAddresses, data)
+			default:
+				return errors.New("x509: cannot parse IP address of length " + strconv.Itoa(len(data)))
+			}
+		}
+
+		return nil
+	})
+
+	return
+}
+
+func parseExtKeyUsageExtension(der cryptobyte.String) ([]ExtKeyUsage, []asn1.ObjectIdentifier, error) {
+	var extKeyUsages []ExtKeyUsage
+	var unknownUsages []asn1.ObjectIdentifier
+	if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {
+		return nil, nil, errors.New("x509: invalid extended key usages")
+	}
+	for !der.Empty() {
+		var eku asn1.ObjectIdentifier
+		if !der.ReadASN1ObjectIdentifier(&eku) {
+			return nil, nil, errors.New("x509: invalid extended key usages")
+		}
+		if extKeyUsage, ok := extKeyUsageFromOID(eku); ok {
+			extKeyUsages = append(extKeyUsages, extKeyUsage)
+		} else {
+			unknownUsages = append(unknownUsages, eku)
+		}
+	}
+	return extKeyUsages, unknownUsages, nil
+}
+
+func parseCertificatePoliciesExtension(der cryptobyte.String) ([]asn1.ObjectIdentifier, error) {
+	var oids []asn1.ObjectIdentifier
+	if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {
+		return nil, errors.New("x509: invalid certificate policies")
+	}
+	for !der.Empty() {
+		var cp cryptobyte.String
+		if !der.ReadASN1(&cp, cryptobyte_asn1.SEQUENCE) {
+			return nil, errors.New("x509: invalid certificate policies")
+		}
+		var oid asn1.ObjectIdentifier
+		if !cp.ReadASN1ObjectIdentifier(&oid) {
+			return nil, errors.New("x509: invalid certificate policies")
+		}
+		oids = append(oids, oid)
+	}
+
+	return oids, nil
+}
+
+// isValidIPMask reports whether mask consists of zero or more 1 bits, followed by zero bits.
+func isValidIPMask(mask []byte) bool {
+	seenZero := false
+
+	for _, b := range mask {
+		if seenZero {
+			if b != 0 {
+				return false
+			}
+
+			continue
+		}
+
+		switch b {
+		case 0x00, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe:
+			seenZero = true
+		case 0xff:
+		default:
+			return false
+		}
+	}
+
+	return true
+}
+
+func parseNameConstraintsExtension(out *Certificate, e pkix.Extension) (unhandled bool, err error) {
+	// RFC 5280, 4.2.1.10
+
+	// NameConstraints ::= SEQUENCE {
+	//      permittedSubtrees       [0]     GeneralSubtrees OPTIONAL,
+	//      excludedSubtrees        [1]     GeneralSubtrees OPTIONAL }
+	//
+	// GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
+	//
+	// GeneralSubtree ::= SEQUENCE {
+	//      base                    GeneralName,
+	//      minimum         [0]     BaseDistance DEFAULT 0,
+	//      maximum         [1]     BaseDistance OPTIONAL }
+	//
+	// BaseDistance ::= INTEGER (0..MAX)
+
+	outer := cryptobyte.String(e.Value)
+	var toplevel, permitted, excluded cryptobyte.String
+	var havePermitted, haveExcluded bool
+	if !outer.ReadASN1(&toplevel, cryptobyte_asn1.SEQUENCE) ||
+		!outer.Empty() ||
+		!toplevel.ReadOptionalASN1(&permitted, &havePermitted, cryptobyte_asn1.Tag(0).ContextSpecific().Constructed()) ||
+		!toplevel.ReadOptionalASN1(&excluded, &haveExcluded, cryptobyte_asn1.Tag(1).ContextSpecific().Constructed()) ||
+		!toplevel.Empty() {
+		return false, errors.New("x509: invalid NameConstraints extension")
+	}
+
+	if !havePermitted && !haveExcluded || len(permitted) == 0 && len(excluded) == 0 {
+		// From RFC 5280, Section 4.2.1.10:
+		//   “either the permittedSubtrees field
+		//   or the excludedSubtrees MUST be
+		//   present”
+		return false, errors.New("x509: empty name constraints extension")
+	}
+
+	getValues := func(subtrees cryptobyte.String) (dnsNames []string, ips []*net.IPNet, emails, uriDomains []string, err error) {
+		for !subtrees.Empty() {
+			var seq, value cryptobyte.String
+			var tag cryptobyte_asn1.Tag
+			if !subtrees.ReadASN1(&seq, cryptobyte_asn1.SEQUENCE) ||
+				!seq.ReadAnyASN1(&value, &tag) {
+				return nil, nil, nil, nil, fmt.Errorf("x509: invalid NameConstraints extension")
+			}
+
+			var (
+				dnsTag   = cryptobyte_asn1.Tag(2).ContextSpecific()
+				emailTag = cryptobyte_asn1.Tag(1).ContextSpecific()
+				ipTag    = cryptobyte_asn1.Tag(7).ContextSpecific()
+				uriTag   = cryptobyte_asn1.Tag(6).ContextSpecific()
+			)
+
+			switch tag {
+			case dnsTag:
+				domain := string(value)
+				if err := isIA5String(domain); err != nil {
+					return nil, nil, nil, nil, errors.New("x509: invalid constraint value: " + err.Error())
+				}
+
+				trimmedDomain := domain
+				if len(trimmedDomain) > 0 && trimmedDomain[0] == '.' {
+					// constraints can have a leading
+					// period to exclude the domain
+					// itself, but that's not valid in a
+					// normal domain name.
+					trimmedDomain = trimmedDomain[1:]
+				}
+				if _, ok := domainToReverseLabels(trimmedDomain); !ok {
+					return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse dnsName constraint %q", domain)
+				}
+				dnsNames = append(dnsNames, domain)
+
+			case ipTag:
+				l := len(value)
+				var ip, mask []byte
+
+				switch l {
+				case 8:
+					ip = value[:4]
+					mask = value[4:]
+
+				case 32:
+					ip = value[:16]
+					mask = value[16:]
+
+				default:
+					return nil, nil, nil, nil, fmt.Errorf("x509: IP constraint contained value of length %d", l)
+				}
+
+				if !isValidIPMask(mask) {
+					return nil, nil, nil, nil, fmt.Errorf("x509: IP constraint contained invalid mask %x", mask)
+				}
+
+				ips = append(ips, &net.IPNet{IP: net.IP(ip), Mask: net.IPMask(mask)})
+
+			case emailTag:
+				constraint := string(value)
+				if err := isIA5String(constraint); err != nil {
+					return nil, nil, nil, nil, errors.New("x509: invalid constraint value: " + err.Error())
+				}
+
+				// If the constraint contains an @ then
+				// it specifies an exact mailbox name.
+				if strings.Contains(constraint, "@") {
+					if _, ok := parseRFC2821Mailbox(constraint); !ok {
+						return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse rfc822Name constraint %q", constraint)
+					}
+				} else {
+					// Otherwise it's a domain name.
+					domain := constraint
+					if len(domain) > 0 && domain[0] == '.' {
+						domain = domain[1:]
+					}
+					if _, ok := domainToReverseLabels(domain); !ok {
+						return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse rfc822Name constraint %q", constraint)
+					}
+				}
+				emails = append(emails, constraint)
+
+			case uriTag:
+				domain := string(value)
+				if err := isIA5String(domain); err != nil {
+					return nil, nil, nil, nil, errors.New("x509: invalid constraint value: " + err.Error())
+				}
+
+				if net.ParseIP(domain) != nil {
+					return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse URI constraint %q: cannot be IP address", domain)
+				}
+
+				trimmedDomain := domain
+				if len(trimmedDomain) > 0 && trimmedDomain[0] == '.' {
+					// constraints can have a leading
+					// period to exclude the domain itself,
+					// but that's not valid in a normal
+					// domain name.
+					trimmedDomain = trimmedDomain[1:]
+				}
+				if _, ok := domainToReverseLabels(trimmedDomain); !ok {
+					return nil, nil, nil, nil, fmt.Errorf("x509: failed to parse URI constraint %q", domain)
+				}
+				uriDomains = append(uriDomains, domain)
+
+			default:
+				unhandled = true
+			}
+		}
+
+		return dnsNames, ips, emails, uriDomains, nil
+	}
+
+	if out.PermittedDNSDomains, out.PermittedIPRanges, out.PermittedEmailAddresses, out.PermittedURIDomains, err = getValues(permitted); err != nil {
+		return false, err
+	}
+	if out.ExcludedDNSDomains, out.ExcludedIPRanges, out.ExcludedEmailAddresses, out.ExcludedURIDomains, err = getValues(excluded); err != nil {
+		return false, err
+	}
+	out.PermittedDNSDomainsCritical = e.Critical
+
+	return unhandled, nil
+}
+
+func processExtensions(out *Certificate) error {
+	var err error
+	for _, e := range out.Extensions {
+		unhandled := false
+
+		if len(e.Id) == 4 && e.Id[0] == 2 && e.Id[1] == 5 && e.Id[2] == 29 {
+			switch e.Id[3] {
+			case 15:
+				out.KeyUsage, err = parseKeyUsageExtension(e.Value)
+				if err != nil {
+					return err
+				}
+			case 19:
+				out.IsCA, out.MaxPathLen, err = parseBasicConstraintsExtension(e.Value)
+				if err != nil {
+					return err
+				}
+				out.BasicConstraintsValid = true
+				out.MaxPathLenZero = out.MaxPathLen == 0
+			case 17:
+				out.DNSNames, out.EmailAddresses, out.IPAddresses, out.URIs, err = parseSANExtension(e.Value)
+				if err != nil {
+					return err
+				}
+
+				if len(out.DNSNames) == 0 && len(out.EmailAddresses) == 0 && len(out.IPAddresses) == 0 && len(out.URIs) == 0 {
+					// If we didn't parse anything then we do the critical check, below.
+					unhandled = true
+				}
+
+			case 30:
+				unhandled, err = parseNameConstraintsExtension(out, e)
+				if err != nil {
+					return err
+				}
+
+			case 31:
+				// RFC 5280, 4.2.1.13
+
+				// CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint
+				//
+				// DistributionPoint ::= SEQUENCE {
+				//     distributionPoint       [0]     DistributionPointName OPTIONAL,
+				//     reasons                 [1]     ReasonFlags OPTIONAL,
+				//     cRLIssuer               [2]     GeneralNames OPTIONAL }
+				//
+				// DistributionPointName ::= CHOICE {
+				//     fullName                [0]     GeneralNames,
+				//     nameRelativeToCRLIssuer [1]     RelativeDistinguishedName }
+				val := cryptobyte.String(e.Value)
+				if !val.ReadASN1(&val, cryptobyte_asn1.SEQUENCE) {
+					return errors.New("x509: invalid CRL distribution points")
+				}
+				for !val.Empty() {
+					var dpDER cryptobyte.String
+					if !val.ReadASN1(&dpDER, cryptobyte_asn1.SEQUENCE) {
+						return errors.New("x509: invalid CRL distribution point")
+					}
+					var dpNameDER cryptobyte.String
+					var dpNamePresent bool
+					if !dpDER.ReadOptionalASN1(&dpNameDER, &dpNamePresent, cryptobyte_asn1.Tag(0).Constructed().ContextSpecific()) {
+						return errors.New("x509: invalid CRL distribution point")
+					}
+					if !dpNamePresent {
+						continue
+					}
+					if !dpNameDER.ReadASN1(&dpNameDER, cryptobyte_asn1.Tag(0).Constructed().ContextSpecific()) {
+						return errors.New("x509: invalid CRL distribution point")
+					}
+					for !dpNameDER.Empty() {
+						if !dpNameDER.PeekASN1Tag(cryptobyte_asn1.Tag(6).ContextSpecific()) {
+							break
+						}
+						var uri cryptobyte.String
+						if !dpNameDER.ReadASN1(&uri, cryptobyte_asn1.Tag(6).ContextSpecific()) {
+							return errors.New("x509: invalid CRL distribution point")
+						}
+						out.CRLDistributionPoints = append(out.CRLDistributionPoints, string(uri))
+					}
+				}
+
+			case 35:
+				// RFC 5280, 4.2.1.1
+				val := cryptobyte.String(e.Value)
+				var akid cryptobyte.String
+				if !val.ReadASN1(&akid, cryptobyte_asn1.SEQUENCE) {
+					return errors.New("x509: invalid authority key identifier")
+				}
+				if akid.PeekASN1Tag(cryptobyte_asn1.Tag(0).ContextSpecific()) {
+					if !akid.ReadASN1(&akid, cryptobyte_asn1.Tag(0).ContextSpecific()) {
+						return errors.New("x509: invalid authority key identifier")
+					}
+					out.AuthorityKeyId = akid
+				}
+			case 37:
+				out.ExtKeyUsage, out.UnknownExtKeyUsage, err = parseExtKeyUsageExtension(e.Value)
+				if err != nil {
+					return err
+				}
+			case 14:
+				// RFC 5280, 4.2.1.2
+				val := cryptobyte.String(e.Value)
+				var skid cryptobyte.String
+				if !val.ReadASN1(&skid, cryptobyte_asn1.OCTET_STRING) {
+					return errors.New("x509: invalid subject key identifier")
+				}
+				out.SubjectKeyId = skid
+			case 32:
+				out.PolicyIdentifiers, err = parseCertificatePoliciesExtension(e.Value)
+				if err != nil {
+					return err
+				}
+			default:
+				// Unknown extensions are recorded if critical.
+				unhandled = true
+			}
+		} else if e.Id.Equal(oidExtensionAuthorityInfoAccess) {
+			// RFC 5280 4.2.2.1: Authority Information Access
+			val := cryptobyte.String(e.Value)
+			if !val.ReadASN1(&val, cryptobyte_asn1.SEQUENCE) {
+				return errors.New("x509: invalid authority info access")
+			}
+			for !val.Empty() {
+				var aiaDER cryptobyte.String
+				if !val.ReadASN1(&aiaDER, cryptobyte_asn1.SEQUENCE) {
+					return errors.New("x509: invalid authority info access")
+				}
+				var method asn1.ObjectIdentifier
+				if !aiaDER.ReadASN1ObjectIdentifier(&method) {
+					return errors.New("x509: invalid authority info access")
+				}
+				if !aiaDER.PeekASN1Tag(cryptobyte_asn1.Tag(6).ContextSpecific()) {
+					continue
+				}
+				if !aiaDER.ReadASN1(&aiaDER, cryptobyte_asn1.Tag(6).ContextSpecific()) {
+					return errors.New("x509: invalid authority info access")
+				}
+				switch {
+				case method.Equal(oidAuthorityInfoAccessOcsp):
+					out.OCSPServer = append(out.OCSPServer, string(aiaDER))
+				case method.Equal(oidAuthorityInfoAccessIssuers):
+					out.IssuingCertificateURL = append(out.IssuingCertificateURL, string(aiaDER))
+				}
+			}
+		} else {
+			// Unknown extensions are recorded if critical.
+			unhandled = true
+		}
+
+		if e.Critical && unhandled {
+			out.UnhandledCriticalExtensions = append(out.UnhandledCriticalExtensions, e.Id)
+		}
+	}
+
+	return nil
+}
+
+func parseCertificate(der []byte) (*Certificate, error) {
+	cert := &Certificate{}
+
+	input := cryptobyte.String(der)
+	// we read the SEQUENCE including length and tag bytes so that
+	// we can populate Certificate.Raw, before unwrapping the
+	// SEQUENCE so it can be operated on
+	if !input.ReadASN1Element(&input, cryptobyte_asn1.SEQUENCE) {
+		return nil, errors.New("x509: malformed certificate")
+	}
+	cert.Raw = input
+	if !input.ReadASN1(&input, cryptobyte_asn1.SEQUENCE) {
+		return nil, errors.New("x509: malformed certificate")
+	}
+
+	var tbs cryptobyte.String
+	// do the same trick again as above to extract the raw
+	// bytes for Certificate.RawTBSCertificate
+	if !input.ReadASN1Element(&tbs, cryptobyte_asn1.SEQUENCE) {
+		return nil, errors.New("x509: malformed tbs certificate")
+	}
+	cert.RawTBSCertificate = tbs
+	if !tbs.ReadASN1(&tbs, cryptobyte_asn1.SEQUENCE) {
+		return nil, errors.New("x509: malformed tbs certificate")
+	}
+
+	if !tbs.ReadOptionalASN1Integer(&cert.Version, cryptobyte_asn1.Tag(0).Constructed().ContextSpecific(), 0) {
+		return nil, errors.New("x509: malformed version")
+	}
+	if cert.Version < 0 {
+		return nil, errors.New("x509: malformed version")
+	}
+	// for backwards compat reasons Version is one-indexed,
+	// rather than zero-indexed as defined in 5280
+	cert.Version++
+	if cert.Version > 3 {
+		return nil, errors.New("x509: invalid version")
+	}
+
+	serial := new(big.Int)
+	if !tbs.ReadASN1Integer(serial) {
+		return nil, errors.New("x509: malformed serial number")
+	}
+	// we ignore the presence of negative serial numbers because
+	// of their prevalence, despite them being invalid
+	// TODO(rolandshoemaker): revist this decision, there are currently
+	// only 10 trusted certificates with negative serial numbers
+	// according to censys.io.
+	cert.SerialNumber = serial
+
+	var sigAISeq cryptobyte.String
+	if !tbs.ReadASN1(&sigAISeq, cryptobyte_asn1.SEQUENCE) {
+		return nil, errors.New("x509: malformed signature algorithm identifier")
+	}
+	// Before parsing the inner algorithm identifier, extract
+	// the outer algorithm identifier and make sure that they
+	// match.
+	var outerSigAISeq cryptobyte.String
+	if !input.ReadASN1(&outerSigAISeq, cryptobyte_asn1.SEQUENCE) {
+		return nil, errors.New("x509: malformed algorithm identifier")
+	}
+	if !bytes.Equal(outerSigAISeq, sigAISeq) {
+		return nil, errors.New("x509: inner and outer signature algorithm identifiers don't match")
+	}
+	sigAI, err := parseAI(sigAISeq)
+	if err != nil {
+		return nil, err
+	}
+	cert.SignatureAlgorithm = getSignatureAlgorithmFromAI(sigAI)
+
+	var issuerSeq cryptobyte.String
+	if !tbs.ReadASN1Element(&issuerSeq, cryptobyte_asn1.SEQUENCE) {
+		return nil, errors.New("x509: malformed issuer")
+	}
+	cert.RawIssuer = issuerSeq
+	issuerRDNs, err := parseName(issuerSeq)
+	if err != nil {
+		return nil, err
+	}
+	cert.Issuer.FillFromRDNSequence(issuerRDNs)
+
+	var validity cryptobyte.String
+	if !tbs.ReadASN1(&validity, cryptobyte_asn1.SEQUENCE) {
+		return nil, errors.New("x509: malformed validity")
+	}
+	cert.NotBefore, cert.NotAfter, err = parseValidity(validity)
+	if err != nil {
+		return nil, err
+	}
+
+	var subjectSeq cryptobyte.String
+	if !tbs.ReadASN1Element(&subjectSeq, cryptobyte_asn1.SEQUENCE) {
+		return nil, errors.New("x509: malformed issuer")
+	}
+	cert.RawSubject = subjectSeq
+	subjectRDNs, err := parseName(subjectSeq)
+	if err != nil {
+		return nil, err
+	}
+	cert.Subject.FillFromRDNSequence(subjectRDNs)
+
+	var spki cryptobyte.String
+	if !tbs.ReadASN1Element(&spki, cryptobyte_asn1.SEQUENCE) {
+		return nil, errors.New("x509: malformed spki")
+	}
+	cert.RawSubjectPublicKeyInfo = spki
+	if !spki.ReadASN1(&spki, cryptobyte_asn1.SEQUENCE) {
+		return nil, errors.New("x509: malformed spki")
+	}
+	var pkAISeq cryptobyte.String
+	if !spki.ReadASN1(&pkAISeq, cryptobyte_asn1.SEQUENCE) {
+		return nil, errors.New("x509: malformed public key algorithm identifier")
+	}
+	pkAI, err := parseAI(pkAISeq)
+	if err != nil {
+		return nil, err
+	}
+	cert.PublicKeyAlgorithm = getPublicKeyAlgorithmFromOID(pkAI.Algorithm)
+	var spk asn1.BitString
+	if !spki.ReadASN1BitString(&spk) {
+		return nil, errors.New("x509: malformed subjectPublicKey")
+	}
+	cert.PublicKey, err = parsePublicKey(cert.PublicKeyAlgorithm, &publicKeyInfo{
+		Algorithm: pkAI,
+		PublicKey: spk,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	if cert.Version > 1 {
+		if !tbs.SkipOptionalASN1(cryptobyte_asn1.Tag(1).ContextSpecific()) {
+			return nil, errors.New("x509: malformed issuerUniqueID")
+		}
+		if !tbs.SkipOptionalASN1(cryptobyte_asn1.Tag(2).ContextSpecific()) {
+			return nil, errors.New("x509: malformed subjectUniqueID")
+		}
+		if cert.Version == 3 {
+			var extensions cryptobyte.String
+			var present bool
+			if !tbs.ReadOptionalASN1(&extensions, &present, cryptobyte_asn1.Tag(3).Constructed().ContextSpecific()) {
+				return nil, errors.New("x509: malformed extensions")
+			}
+			if present {
+				if !extensions.ReadASN1(&extensions, cryptobyte_asn1.SEQUENCE) {
+					return nil, errors.New("x509: malformed extensions")
+				}
+				for !extensions.Empty() {
+					var extension cryptobyte.String
+					if !extensions.ReadASN1(&extension, cryptobyte_asn1.SEQUENCE) {
+						return nil, errors.New("x509: malformed extension")
+					}
+					ext, err := parseExtension(extension)
+					if err != nil {
+						return nil, err
+					}
+					cert.Extensions = append(cert.Extensions, ext)
+				}
+				err = processExtensions(cert)
+				if err != nil {
+					return nil, err
+				}
+			}
+		}
+	}
+
+	var signature asn1.BitString
+	if !input.ReadASN1BitString(&signature) {
+		return nil, errors.New("x509: malformed signature")
+	}
+	cert.Signature = signature.RightAlign()
+
+	return cert, nil
+}
+
+// ParseCertificate parses a single certificate from the given ASN.1 DER data.
+func ParseCertificate(der []byte) (*Certificate, error) {
+	cert, err := parseCertificate(der)
+	if err != nil {
+		return nil, err
+	}
+	if len(der) != len(cert.Raw) {
+		return nil, errors.New("x509: trailing data")
+	}
+	return cert, err
+}
+
+// ParseCertificates parses one or more certificates from the given ASN.1 DER
+// data. The certificates must be concatenated with no intermediate padding.
+func ParseCertificates(der []byte) ([]*Certificate, error) {
+	var certs []*Certificate
+	for len(der) > 0 {
+		cert, err := parseCertificate(der)
+		if err != nil {
+			return nil, err
+		}
+		certs = append(certs, cert)
+		der = der[len(cert.Raw):]
+	}
+	return certs, nil
+}
diff --git a/src/crypto/x509/parser_test.go b/src/crypto/x509/parser_test.go
new file mode 100644
index 0000000..d7cf7ea
--- /dev/null
+++ b/src/crypto/x509/parser_test.go
@@ -0,0 +1,102 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+package x509
+
+import (
+	"encoding/asn1"
+	"testing"
+
+	cryptobyte_asn1 "golang.org/x/crypto/cryptobyte/asn1"
+)
+
+func TestParseASN1String(t *testing.T) {
+	tests := []struct {
+		name        string
+		tag         cryptobyte_asn1.Tag
+		value       []byte
+		expected    string
+		expectedErr string
+	}{
+		{
+			name:     "T61String",
+			tag:      cryptobyte_asn1.T61String,
+			value:    []byte{80, 81, 82},
+			expected: string("PQR"),
+		},
+		{
+			name:     "PrintableString",
+			tag:      cryptobyte_asn1.PrintableString,
+			value:    []byte{80, 81, 82},
+			expected: string("PQR"),
+		},
+		{
+			name:        "PrintableString (invalid)",
+			tag:         cryptobyte_asn1.PrintableString,
+			value:       []byte{1, 2, 3},
+			expectedErr: "invalid PrintableString",
+		},
+		{
+			name:     "UTF8String",
+			tag:      cryptobyte_asn1.UTF8String,
+			value:    []byte{80, 81, 82},
+			expected: string("PQR"),
+		},
+		{
+			name:        "UTF8String (invalid)",
+			tag:         cryptobyte_asn1.UTF8String,
+			value:       []byte{255},
+			expectedErr: "invalid UTF-8 string",
+		},
+		{
+			name:     "BMPString",
+			tag:      cryptobyte_asn1.Tag(asn1.TagBMPString),
+			value:    []byte{80, 81},
+			expected: string("偑"),
+		},
+		{
+			name:        "BMPString (invalid length)",
+			tag:         cryptobyte_asn1.Tag(asn1.TagBMPString),
+			value:       []byte{255},
+			expectedErr: "invalid BMPString",
+		},
+		{
+			name:     "IA5String",
+			tag:      cryptobyte_asn1.IA5String,
+			value:    []byte{80, 81},
+			expected: string("PQ"),
+		},
+		{
+			name:        "IA5String (invalid)",
+			tag:         cryptobyte_asn1.IA5String,
+			value:       []byte{255},
+			expectedErr: "invalid IA5String",
+		},
+		{
+			name:     "NumericString",
+			tag:      cryptobyte_asn1.Tag(asn1.TagNumericString),
+			value:    []byte{49, 50},
+			expected: string("12"),
+		},
+		{
+			name:        "NumericString (invalid)",
+			tag:         cryptobyte_asn1.Tag(asn1.TagNumericString),
+			value:       []byte{80},
+			expectedErr: "invalid NumericString",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			out, err := parseASN1String(tc.tag, tc.value)
+			if err != nil && err.Error() != tc.expectedErr {
+				t.Fatalf("parseASN1String returned unexpected error: got %q, want %q", err, tc.expectedErr)
+			} else if err == nil && tc.expectedErr != "" {
+				t.Fatalf("parseASN1String didn't fail, expected: %s", tc.expectedErr)
+			}
+			if out != tc.expected {
+				t.Fatalf("parseASN1String returned unexpected value: got %q, want %q", out, tc.expected)
+			}
+		})
+	}
+}
diff --git a/src/crypto/x509/pem_decrypt.go b/src/crypto/x509/pem_decrypt.go
new file mode 100644
index 0000000..682923a
--- /dev/null
+++ b/src/crypto/x509/pem_decrypt.go
@@ -0,0 +1,252 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+// RFC 1423 describes the encryption of PEM blocks. The algorithm used to
+// generate a key from the password was derived by looking at the OpenSSL
+// implementation.
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/des"
+	"crypto/md5"
+	"encoding/hex"
+	"encoding/pem"
+	"errors"
+	"io"
+	"strings"
+)
+
+type PEMCipher int
+
+// Possible values for the EncryptPEMBlock encryption algorithm.
+const (
+	_ PEMCipher = iota
+	PEMCipherDES
+	PEMCipher3DES
+	PEMCipherAES128
+	PEMCipherAES192
+	PEMCipherAES256
+)
+
+// rfc1423Algo holds a method for enciphering a PEM block.
+type rfc1423Algo struct {
+	cipher     PEMCipher
+	name       string
+	cipherFunc func(key []byte) (cipher.Block, error)
+	keySize    int
+	blockSize  int
+}
+
+// rfc1423Algos holds a slice of the possible ways to encrypt a PEM
+// block. The ivSize numbers were taken from the OpenSSL source.
+var rfc1423Algos = []rfc1423Algo{{
+	cipher:     PEMCipherDES,
+	name:       "DES-CBC",
+	cipherFunc: des.NewCipher,
+	keySize:    8,
+	blockSize:  des.BlockSize,
+}, {
+	cipher:     PEMCipher3DES,
+	name:       "DES-EDE3-CBC",
+	cipherFunc: des.NewTripleDESCipher,
+	keySize:    24,
+	blockSize:  des.BlockSize,
+}, {
+	cipher:     PEMCipherAES128,
+	name:       "AES-128-CBC",
+	cipherFunc: aes.NewCipher,
+	keySize:    16,
+	blockSize:  aes.BlockSize,
+}, {
+	cipher:     PEMCipherAES192,
+	name:       "AES-192-CBC",
+	cipherFunc: aes.NewCipher,
+	keySize:    24,
+	blockSize:  aes.BlockSize,
+}, {
+	cipher:     PEMCipherAES256,
+	name:       "AES-256-CBC",
+	cipherFunc: aes.NewCipher,
+	keySize:    32,
+	blockSize:  aes.BlockSize,
+},
+}
+
+// deriveKey uses a key derivation function to stretch the password into a key
+// with the number of bits our cipher requires. This algorithm was derived from
+// the OpenSSL source.
+func (c rfc1423Algo) deriveKey(password, salt []byte) []byte {
+	hash := md5.New()
+	out := make([]byte, c.keySize)
+	var digest []byte
+
+	for i := 0; i < len(out); i += len(digest) {
+		hash.Reset()
+		hash.Write(digest)
+		hash.Write(password)
+		hash.Write(salt)
+		digest = hash.Sum(digest[:0])
+		copy(out[i:], digest)
+	}
+	return out
+}
+
+// IsEncryptedPEMBlock returns whether the PEM block is password encrypted
+// according to RFC 1423.
+//
+// Deprecated: Legacy PEM encryption as specified in RFC 1423 is insecure by
+// design. Since it does not authenticate the ciphertext, it is vulnerable to
+// padding oracle attacks that can let an attacker recover the plaintext.
+func IsEncryptedPEMBlock(b *pem.Block) bool {
+	_, ok := b.Headers["DEK-Info"]
+	return ok
+}
+
+// IncorrectPasswordError is returned when an incorrect password is detected.
+var IncorrectPasswordError = errors.New("x509: decryption password incorrect")
+
+// DecryptPEMBlock takes a PEM block encrypted according to RFC 1423 and the
+// password used to encrypt it and returns a slice of decrypted DER encoded
+// bytes. It inspects the DEK-Info header to determine the algorithm used for
+// decryption. If no DEK-Info header is present, an error is returned. If an
+// incorrect password is detected an IncorrectPasswordError is returned. Because
+// of deficiencies in the format, it's not always possible to detect an
+// incorrect password. In these cases no error will be returned but the
+// decrypted DER bytes will be random noise.
+//
+// Deprecated: Legacy PEM encryption as specified in RFC 1423 is insecure by
+// design. Since it does not authenticate the ciphertext, it is vulnerable to
+// padding oracle attacks that can let an attacker recover the plaintext.
+func DecryptPEMBlock(b *pem.Block, password []byte) ([]byte, error) {
+	dek, ok := b.Headers["DEK-Info"]
+	if !ok {
+		return nil, errors.New("x509: no DEK-Info header in block")
+	}
+
+	mode, hexIV, ok := strings.Cut(dek, ",")
+	if !ok {
+		return nil, errors.New("x509: malformed DEK-Info header")
+	}
+
+	ciph := cipherByName(mode)
+	if ciph == nil {
+		return nil, errors.New("x509: unknown encryption mode")
+	}
+	iv, err := hex.DecodeString(hexIV)
+	if err != nil {
+		return nil, err
+	}
+	if len(iv) != ciph.blockSize {
+		return nil, errors.New("x509: incorrect IV size")
+	}
+
+	// Based on the OpenSSL implementation. The salt is the first 8 bytes
+	// of the initialization vector.
+	key := ciph.deriveKey(password, iv[:8])
+	block, err := ciph.cipherFunc(key)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(b.Bytes)%block.BlockSize() != 0 {
+		return nil, errors.New("x509: encrypted PEM data is not a multiple of the block size")
+	}
+
+	data := make([]byte, len(b.Bytes))
+	dec := cipher.NewCBCDecrypter(block, iv)
+	dec.CryptBlocks(data, b.Bytes)
+
+	// Blocks are padded using a scheme where the last n bytes of padding are all
+	// equal to n. It can pad from 1 to blocksize bytes inclusive. See RFC 1423.
+	// For example:
+	//	[x y z 2 2]
+	//	[x y 7 7 7 7 7 7 7]
+	// If we detect a bad padding, we assume it is an invalid password.
+	dlen := len(data)
+	if dlen == 0 || dlen%ciph.blockSize != 0 {
+		return nil, errors.New("x509: invalid padding")
+	}
+	last := int(data[dlen-1])
+	if dlen < last {
+		return nil, IncorrectPasswordError
+	}
+	if last == 0 || last > ciph.blockSize {
+		return nil, IncorrectPasswordError
+	}
+	for _, val := range data[dlen-last:] {
+		if int(val) != last {
+			return nil, IncorrectPasswordError
+		}
+	}
+	return data[:dlen-last], nil
+}
+
+// EncryptPEMBlock returns a PEM block of the specified type holding the
+// given DER encoded data encrypted with the specified algorithm and
+// password according to RFC 1423.
+//
+// Deprecated: Legacy PEM encryption as specified in RFC 1423 is insecure by
+// design. Since it does not authenticate the ciphertext, it is vulnerable to
+// padding oracle attacks that can let an attacker recover the plaintext.
+func EncryptPEMBlock(rand io.Reader, blockType string, data, password []byte, alg PEMCipher) (*pem.Block, error) {
+	ciph := cipherByKey(alg)
+	if ciph == nil {
+		return nil, errors.New("x509: unknown encryption mode")
+	}
+	iv := make([]byte, ciph.blockSize)
+	if _, err := io.ReadFull(rand, iv); err != nil {
+		return nil, errors.New("x509: cannot generate IV: " + err.Error())
+	}
+	// The salt is the first 8 bytes of the initialization vector,
+	// matching the key derivation in DecryptPEMBlock.
+	key := ciph.deriveKey(password, iv[:8])
+	block, err := ciph.cipherFunc(key)
+	if err != nil {
+		return nil, err
+	}
+	enc := cipher.NewCBCEncrypter(block, iv)
+	pad := ciph.blockSize - len(data)%ciph.blockSize
+	encrypted := make([]byte, len(data), len(data)+pad)
+	// We could save this copy by encrypting all the whole blocks in
+	// the data separately, but it doesn't seem worth the additional
+	// code.
+	copy(encrypted, data)
+	// See RFC 1423, Section 1.1.
+	for i := 0; i < pad; i++ {
+		encrypted = append(encrypted, byte(pad))
+	}
+	enc.CryptBlocks(encrypted, encrypted)
+
+	return &pem.Block{
+		Type: blockType,
+		Headers: map[string]string{
+			"Proc-Type": "4,ENCRYPTED",
+			"DEK-Info":  ciph.name + "," + hex.EncodeToString(iv),
+		},
+		Bytes: encrypted,
+	}, nil
+}
+
+func cipherByName(name string) *rfc1423Algo {
+	for i := range rfc1423Algos {
+		alg := &rfc1423Algos[i]
+		if alg.name == name {
+			return alg
+		}
+	}
+	return nil
+}
+
+func cipherByKey(key PEMCipher) *rfc1423Algo {
+	for i := range rfc1423Algos {
+		alg := &rfc1423Algos[i]
+		if alg.cipher == key {
+			return alg
+		}
+	}
+	return nil
+}
diff --git a/src/crypto/x509/pem_decrypt_test.go b/src/crypto/x509/pem_decrypt_test.go
new file mode 100644
index 0000000..dacef8b
--- /dev/null
+++ b/src/crypto/x509/pem_decrypt_test.go
@@ -0,0 +1,249 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/base64"
+	"encoding/pem"
+	"strings"
+	"testing"
+)
+
+func TestDecrypt(t *testing.T) {
+	for i, data := range testData {
+		t.Logf("test %v. %v", i, data.kind)
+		block, rest := pem.Decode(data.pemData)
+		if len(rest) > 0 {
+			t.Error("extra data")
+		}
+		der, err := DecryptPEMBlock(block, data.password)
+		if err != nil {
+			t.Error("decrypt failed: ", err)
+			continue
+		}
+		if _, err := ParsePKCS1PrivateKey(der); err != nil {
+			t.Error("invalid private key: ", err)
+		}
+		plainDER, err := base64.StdEncoding.DecodeString(data.plainDER)
+		if err != nil {
+			t.Fatal("cannot decode test DER data: ", err)
+		}
+		if !bytes.Equal(der, plainDER) {
+			t.Error("data mismatch")
+		}
+	}
+}
+
+func TestEncrypt(t *testing.T) {
+	for i, data := range testData {
+		t.Logf("test %v. %v", i, data.kind)
+		plainDER, err := base64.StdEncoding.DecodeString(data.plainDER)
+		if err != nil {
+			t.Fatal("cannot decode test DER data: ", err)
+		}
+		password := []byte("kremvax1")
+		block, err := EncryptPEMBlock(rand.Reader, "RSA PRIVATE KEY", plainDER, password, data.kind)
+		if err != nil {
+			t.Error("encrypt: ", err)
+			continue
+		}
+		if !IsEncryptedPEMBlock(block) {
+			t.Error("PEM block does not appear to be encrypted")
+		}
+		if block.Type != "RSA PRIVATE KEY" {
+			t.Errorf("unexpected block type; got %q want %q", block.Type, "RSA PRIVATE KEY")
+		}
+		if block.Headers["Proc-Type"] != "4,ENCRYPTED" {
+			t.Errorf("block does not have correct Proc-Type header")
+		}
+		der, err := DecryptPEMBlock(block, password)
+		if err != nil {
+			t.Error("decrypt: ", err)
+			continue
+		}
+		if !bytes.Equal(der, plainDER) {
+			t.Errorf("data mismatch")
+		}
+	}
+}
+
+var testData = []struct {
+	kind     PEMCipher
+	password []byte
+	pemData  []byte
+	plainDER string
+}{
+	{
+		kind:     PEMCipherDES,
+		password: []byte("asdf"),
+		pemData: []byte(testingKey(`
+-----BEGIN RSA TESTING KEY-----
+Proc-Type: 4,ENCRYPTED
+DEK-Info: DES-CBC,34F09A4FC8DE22B5
+
+WXxy8kbZdiZvANtKvhmPBLV7eVFj2A5z6oAxvI9KGyhG0ZK0skfnt00C24vfU7m5
+ICXeoqP67lzJ18xCzQfHjDaBNs53DSDT+Iz4e8QUep1xQ30+8QKX2NA2coee3nwc
+6oM1cuvhNUDemBH2i3dKgMVkfaga0zQiiOq6HJyGSncCMSruQ7F9iWEfRbFcxFCx
+qtHb1kirfGKEtgWTF+ynyco6+2gMXNu70L7nJcnxnV/RLFkHt7AUU1yrclxz7eZz
+XOH9VfTjb52q/I8Suozq9coVQwg4tXfIoYUdT//O+mB7zJb9HI9Ps77b9TxDE6Gm
+4C9brwZ3zg2vqXcwwV6QRZMtyll9rOpxkbw6NPlpfBqkc3xS51bbxivbO/Nve4KD
+r12ymjFNF4stXCfJnNqKoZ50BHmEEUDu5Wb0fpVn82XrGw7CYc4iug==
+-----END RSA TESTING KEY-----`)),
+		plainDER: `
+MIIBPAIBAAJBAPASZe+tCPU6p80AjHhDkVsLYa51D35e/YGa8QcZyooeZM8EHozo
+KD0fNiKI+53bHdy07N+81VQ8/ejPcRoXPlsCAwEAAQJBAMTxIuSq27VpR+zZ7WJf
+c6fvv1OBvpMZ0/d1pxL/KnOAgq2rD5hDtk9b0LGhTPgQAmrrMTKuSeGoIuYE+gKQ
+QvkCIQD+GC1m+/do+QRurr0uo46Kx1LzLeSCrjBk34wiOp2+dwIhAPHfTLRXS2fv
+7rljm0bYa4+eDZpz+E8RcXEgzhhvcQQ9AiAI5eHZJGOyml3MXnQjiPi55WcDOw0w
+glcRgT6QCEtz2wIhANSyqaFtosIkHKqrDUGfz/bb5tqMYTAnBruVPaf/WEOBAiEA
+9xORWeRG1tRpso4+dYy4KdDkuLPIO01KY6neYGm3BCM=`,
+	},
+	{
+		kind:     PEMCipher3DES,
+		password: []byte("asdf"),
+		pemData: []byte(testingKey(`
+-----BEGIN RSA TESTING KEY-----
+Proc-Type: 4,ENCRYPTED
+DEK-Info: DES-EDE3-CBC,C1F4A6A03682C2C7
+
+0JqVdBEH6iqM7drTkj+e2W/bE3LqakaiWhb9WUVonFkhyu8ca/QzebY3b5gCvAZQ
+YwBvDcT/GHospKqPx+cxDHJNsUASDZws6bz8ZXWJGwZGExKzr0+Qx5fgXn44Ms3x
+8g1ENFuTXtxo+KoNK0zuAMAqp66Llcds3Fjl4XR18QaD0CrVNAfOdgATWZm5GJxk
+Fgx5f84nT+/ovvreG+xeOzWgvtKo0UUZVrhGOgfKLpa57adumcJ6SkUuBtEFpZFB
+ldw5w7WC7d13x2LsRkwo8ZrDKgIV+Y9GNvhuCCkTzNP0V3gNeJpd201HZHR+9n3w
+3z0VjR/MGqsfcy1ziEWMNOO53At3zlG6zP05aHMnMcZoVXadEK6L1gz++inSSDCq
+gI0UJP4e3JVB7AkgYymYAwiYALAkoEIuanxoc50njJk=
+-----END RSA TESTING KEY-----`)),
+		plainDER: `
+MIIBOwIBAAJBANOCXKdoNS/iP/MAbl9cf1/SF3P+Ns7ZeNL27CfmDh0O6Zduaax5
+NBiumd2PmjkaCu7lQ5JOibHfWn+xJsc3kw0CAwEAAQJANX/W8d1Q/sCqzkuAn4xl
+B5a7qfJWaLHndu1QRLNTRJPn0Ee7OKJ4H0QKOhQM6vpjRrz+P2u9thn6wUxoPsef
+QQIhAP/jCkfejFcy4v15beqKzwz08/tslVjF+Yq41eJGejmxAiEA05pMoqfkyjcx
+fyvGhpoOyoCp71vSGUfR2I9CR65oKh0CIC1Msjs66LlfJtQctRq6bCEtFCxEcsP+
+eEjYo/Sk6WphAiEAxpgWPMJeU/shFT28gS+tmhjPZLpEoT1qkVlC14u0b3ECIQDX
+tZZZxCtPAm7shftEib0VU77Lk8MsXJcx2C4voRsjEw==`,
+	},
+	{
+		kind:     PEMCipherAES128,
+		password: []byte("asdf"),
+		pemData: []byte(testingKey(`
+-----BEGIN RSA TESTING KEY-----
+Proc-Type: 4,ENCRYPTED
+DEK-Info: AES-128-CBC,D4492E793FC835CC038A728ED174F78A
+
+EyfQSzXSjv6BaNH+NHdXRlkHdimpF9izWlugVJAPApgXrq5YldPe2aGIOFXyJ+QE
+ZIG20DYqaPzJRjTEbPNZ6Es0S2JJ5yCpKxwJuDkgJZKtF39Q2i36JeGbSZQIuWJE
+GZbBpf1jDH/pr0iGonuAdl2PCCZUiy+8eLsD2tyviHUkFLOB+ykYoJ5t8ngZ/B6D
+33U43LLb7+9zD4y3Q9OVHqBFGyHcxCY9+9Qh4ZnFp7DTf6RY5TNEvE3s4g6aDpBs
+3NbvRVvYTgs8K9EPk4K+5R+P2kD8J8KvEIGxVa1vz8QoCJ/jr7Ka2rvNgPCex5/E
+080LzLHPCrXKdlr/f50yhNWq08ZxMWQFkui+FDHPDUaEELKAXV8/5PDxw80Rtybo
+AVYoCVIbZXZCuCO81op8UcOgEpTtyU5Lgh3Mw5scQL0=
+-----END RSA TESTING KEY-----`)),
+		plainDER: `
+MIIBOgIBAAJBAMBlj5FxYtqbcy8wY89d/S7n0+r5MzD9F63BA/Lpl78vQKtdJ5dT
+cDGh/rBt1ufRrNp0WihcmZi7Mpl/3jHjiWECAwEAAQJABNOHYnKhtDIqFYj1OAJ3
+k3GlU0OlERmIOoeY/cL2V4lgwllPBEs7r134AY4wMmZSBUj8UR/O4SNO668ElKPE
+cQIhAOuqY7/115x5KCdGDMWi+jNaMxIvI4ETGwV40ykGzqlzAiEA0P9oEC3m9tHB
+kbpjSTxaNkrXxDgdEOZz8X0uOUUwHNsCIAwzcSCiGLyYJTULUmP1ESERfW1mlV78
+XzzESaJpIM/zAiBQkSTcl9VhcJreQqvjn5BnPZLP4ZHS4gPwJAGdsj5J4QIhAOVR
+B3WlRNTXR2WsJ5JdByezg9xzdXzULqmga0OE339a`,
+	},
+	{
+		kind:     PEMCipherAES192,
+		password: []byte("asdf"),
+		pemData: []byte(testingKey(`
+-----BEGIN RSA TESTING KEY-----
+Proc-Type: 4,ENCRYPTED
+DEK-Info: AES-192-CBC,E2C9FB02BCA23ADE1829F8D8BC5F5369
+
+cqVslvHqDDM6qwU6YjezCRifXmKsrgEev7ng6Qs7UmDJOpHDgJQZI9fwMFUhIyn5
+FbCu1SHkLMW52Ld3CuEqMnzWMlhPrW8tFvUOrMWPYSisv7nNq88HobZEJcUNL2MM
+Y15XmHW6IJwPqhKyLHpWXyOCVEh4ODND2nV15PCoi18oTa475baxSk7+1qH7GuIs
+Rb7tshNTMqHbCpyo9Rn3UxeFIf9efdl8YLiMoIqc7J8E5e9VlbeQSdLMQOgDAQJG
+ReUtTw8exmKsY4gsSjhkg5uiw7/ZB1Ihto0qnfQJgjGc680qGkT1d6JfvOfeYAk6
+xn5RqS/h8rYAYm64KnepfC9vIujo4NqpaREDmaLdX5MJPQ+SlytITQvgUsUq3q/t
+Ss85xjQEZH3hzwjQqdJvmA4hYP6SUjxYpBM+02xZ1Xw=
+-----END RSA TESTING KEY-----`)),
+		plainDER: `
+MIIBOwIBAAJBAMGcRrZiNNmtF20zyS6MQ7pdGx17aFDl+lTl+qnLuJRUCMUG05xs
+OmxmL/O1Qlf+bnqR8Bgg65SfKg21SYuLhiMCAwEAAQJBAL94uuHyO4wux2VC+qpj
+IzPykjdU7XRcDHbbvksf4xokSeUFjjD3PB0Qa83M94y89ZfdILIqS9x5EgSB4/lX
+qNkCIQD6cCIqLfzq/lYbZbQgAAjpBXeQVYsbvVtJrPrXJAlVVQIhAMXpDKMeFPMn
+J0g2rbx1gngx0qOa5r5iMU5w/noN4W2XAiBjf+WzCG5yFvazD+dOx3TC0A8+4x3P
+uZ3pWbaXf5PNuQIgAcdXarvhelH2w2piY1g3BPeFqhzBSCK/yLGxR82KIh8CIQDD
++qGKsd09NhQ/G27y/DARzOYtml1NvdmCQAgsDIIOLA==`,
+	},
+	{
+		kind:     PEMCipherAES256,
+		password: []byte("asdf"),
+		pemData: []byte(testingKey(`
+-----BEGIN RSA TESTING KEY-----
+Proc-Type: 4,ENCRYPTED
+DEK-Info: AES-256-CBC,8E7ED5CD731902CE938957A886A5FFBD
+
+4Mxr+KIzRVwoOP0wwq6caSkvW0iS+GE2h2Ov/u+n9ZTMwL83PRnmjfjzBgfRZLVf
+JFPXxUK26kMNpIdssNnqGOds+DhB+oSrsNKoxgxSl5OBoYv9eJTVYm7qOyAFIsjr
+DRKAcjYCmzfesr7PVTowwy0RtHmYwyXMGDlAzzZrEvaiySFFmMyKKvtoavwaFoc7
+Pz3RZScwIuubzTGJ1x8EzdffYOsdCa9Mtgpp3L136+23dOd6L/qK2EG2fzrJSHs/
+2XugkleBFSMKzEp9mxXKRfa++uidQvMZTFLDK9w5YjrRvMBo/l2BoZIsq0jAIE1N
+sv5Z/KwlX+3MDEpPQpUwGPlGGdLnjI3UZ+cjgqBcoMiNc6HfgbBgYJSU6aDSHuCk
+clCwByxWkBNgJ2GrkwNrF26v+bGJJJNR4SKouY1jQf0=
+-----END RSA TESTING KEY-----`)),
+		plainDER: `
+MIIBOgIBAAJBAKy3GFkstoCHIEeUU/qO8207m8WSrjksR+p9B4tf1w5k+2O1V/GY
+AQ5WFCApItcOkQe/I0yZZJk/PmCqMzSxrc8CAwEAAQJAOCAz0F7AW9oNelVQSP8F
+Sfzx7O1yom+qWyAQQJF/gFR11gpf9xpVnnyu1WxIRnDUh1LZwUsjwlDYb7MB74id
+oQIhANPcOiLwOPT4sIUpRM5HG6BF1BI7L77VpyGVk8xNP7X/AiEA0LMHZtk4I+lJ
+nClgYp4Yh2JZ1Znbu7IoQMCEJCjwKDECIGd8Dzm5tViTkUW6Hs3Tlf73nNs65duF
+aRnSglss8I3pAiEAonEnKruawgD8RavDFR+fUgmQiPz4FnGGeVgfwpGG1JECIBYq
+PXHYtPqxQIbD2pScR5qum7iGUh11lEUPkmt+2uqS`,
+	},
+	{
+		// generated with:
+		// openssl genrsa -aes128 -passout pass:asdf -out server.orig.key 128
+		kind:     PEMCipherAES128,
+		password: []byte("asdf"),
+		pemData: []byte(testingKey(`
+-----BEGIN RSA TESTING KEY-----
+Proc-Type: 4,ENCRYPTED
+DEK-Info: AES-128-CBC,74611ABC2571AF11B1BF9B69E62C89E7
+
+6ei/MlytjE0FFgZOGQ+jrwomKfpl8kdefeE0NSt/DMRrw8OacHAzBNi3pPEa0eX3
+eND9l7C9meCirWovjj9QWVHrXyugFuDIqgdhQ8iHTgCfF3lrmcttVrbIfMDw+smD
+hTP8O1mS/MHl92NE0nhv0w==
+-----END RSA TESTING KEY-----`)),
+		plainDER: `
+MGMCAQACEQC6ssxmYuauuHGOCDAI54RdAgMBAAECEQCWIn6Yv2O+kBcDF7STctKB
+AgkA8SEfu/2i3g0CCQDGNlXbBHX7kQIIK3Ww5o0cYbECCQDCimPb0dYGsQIIeQ7A
+jryIst8=`,
+	},
+}
+
+var incompleteBlockPEM = testingKey(`
+-----BEGIN RSA TESTING KEY-----
+Proc-Type: 4,ENCRYPTED
+DEK-Info: AES-128-CBC,74611ABC2571AF11B1BF9B69E62C89E7
+
+6L8yXK2MTQUWBk4ZD6OvCiYp+mXyR1594TQ1K38MxGvDw5pwcDME2Lek8RrR5fd40P2XsL2Z4KKt
+ai+OP1BZUetfK6AW4MiqB2FDyIdOAJ8XeWuZy21Wtsh8wPD6yYOFM/w7WZL8weX3Y0TSeG/T
+-----END RSA TESTING KEY-----`)
+
+func TestIncompleteBlock(t *testing.T) {
+	// incompleteBlockPEM contains ciphertext that is not a multiple of the
+	// block size. This previously panicked. See #11215.
+	block, _ := pem.Decode([]byte(incompleteBlockPEM))
+	_, err := DecryptPEMBlock(block, []byte("foo"))
+	if err == nil {
+		t.Fatal("Bad PEM data decrypted successfully")
+	}
+	const expectedSubstr = "block size"
+	if e := err.Error(); !strings.Contains(e, expectedSubstr) {
+		t.Fatalf("Expected error containing %q but got: %q", expectedSubstr, e)
+	}
+}
+
+func testingKey(s string) string { return strings.ReplaceAll(s, "TESTING KEY", "PRIVATE KEY") }
diff --git a/src/crypto/x509/pkcs1.go b/src/crypto/x509/pkcs1.go
new file mode 100644
index 0000000..f9d3840
--- /dev/null
+++ b/src/crypto/x509/pkcs1.go
@@ -0,0 +1,173 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	"crypto/rsa"
+	"encoding/asn1"
+	"errors"
+	"math/big"
+)
+
+// pkcs1PrivateKey is a structure which mirrors the PKCS #1 ASN.1 for an RSA private key.
+type pkcs1PrivateKey struct {
+	Version int
+	N       *big.Int
+	E       int
+	D       *big.Int
+	P       *big.Int
+	Q       *big.Int
+	// We ignore these values, if present, because rsa will calculate them.
+	Dp   *big.Int `asn1:"optional"`
+	Dq   *big.Int `asn1:"optional"`
+	Qinv *big.Int `asn1:"optional"`
+
+	AdditionalPrimes []pkcs1AdditionalRSAPrime `asn1:"optional,omitempty"`
+}
+
+type pkcs1AdditionalRSAPrime struct {
+	Prime *big.Int
+
+	// We ignore these values because rsa will calculate them.
+	Exp   *big.Int
+	Coeff *big.Int
+}
+
+// pkcs1PublicKey reflects the ASN.1 structure of a PKCS #1 public key.
+type pkcs1PublicKey struct {
+	N *big.Int
+	E int
+}
+
+// ParsePKCS1PrivateKey parses an RSA private key in PKCS #1, ASN.1 DER form.
+//
+// This kind of key is commonly encoded in PEM blocks of type "RSA PRIVATE KEY".
+func ParsePKCS1PrivateKey(der []byte) (*rsa.PrivateKey, error) {
+	var priv pkcs1PrivateKey
+	rest, err := asn1.Unmarshal(der, &priv)
+	if len(rest) > 0 {
+		return nil, asn1.SyntaxError{Msg: "trailing data"}
+	}
+	if err != nil {
+		if _, err := asn1.Unmarshal(der, &ecPrivateKey{}); err == nil {
+			return nil, errors.New("x509: failed to parse private key (use ParseECPrivateKey instead for this key format)")
+		}
+		if _, err := asn1.Unmarshal(der, &pkcs8{}); err == nil {
+			return nil, errors.New("x509: failed to parse private key (use ParsePKCS8PrivateKey instead for this key format)")
+		}
+		return nil, err
+	}
+
+	if priv.Version > 1 {
+		return nil, errors.New("x509: unsupported private key version")
+	}
+
+	if priv.N.Sign() <= 0 || priv.D.Sign() <= 0 || priv.P.Sign() <= 0 || priv.Q.Sign() <= 0 {
+		return nil, errors.New("x509: private key contains zero or negative value")
+	}
+
+	key := new(rsa.PrivateKey)
+	key.PublicKey = rsa.PublicKey{
+		E: priv.E,
+		N: priv.N,
+	}
+
+	key.D = priv.D
+	key.Primes = make([]*big.Int, 2+len(priv.AdditionalPrimes))
+	key.Primes[0] = priv.P
+	key.Primes[1] = priv.Q
+	for i, a := range priv.AdditionalPrimes {
+		if a.Prime.Sign() <= 0 {
+			return nil, errors.New("x509: private key contains zero or negative prime")
+		}
+		key.Primes[i+2] = a.Prime
+		// We ignore the other two values because rsa will calculate
+		// them as needed.
+	}
+
+	err = key.Validate()
+	if err != nil {
+		return nil, err
+	}
+	key.Precompute()
+
+	return key, nil
+}
+
+// MarshalPKCS1PrivateKey converts an RSA private key to PKCS #1, ASN.1 DER form.
+//
+// This kind of key is commonly encoded in PEM blocks of type "RSA PRIVATE KEY".
+// For a more flexible key format which is not RSA specific, use
+// MarshalPKCS8PrivateKey.
+func MarshalPKCS1PrivateKey(key *rsa.PrivateKey) []byte {
+	key.Precompute()
+
+	version := 0
+	if len(key.Primes) > 2 {
+		version = 1
+	}
+
+	priv := pkcs1PrivateKey{
+		Version: version,
+		N:       key.N,
+		E:       key.PublicKey.E,
+		D:       key.D,
+		P:       key.Primes[0],
+		Q:       key.Primes[1],
+		Dp:      key.Precomputed.Dp,
+		Dq:      key.Precomputed.Dq,
+		Qinv:    key.Precomputed.Qinv,
+	}
+
+	priv.AdditionalPrimes = make([]pkcs1AdditionalRSAPrime, len(key.Precomputed.CRTValues))
+	for i, values := range key.Precomputed.CRTValues {
+		priv.AdditionalPrimes[i].Prime = key.Primes[2+i]
+		priv.AdditionalPrimes[i].Exp = values.Exp
+		priv.AdditionalPrimes[i].Coeff = values.Coeff
+	}
+
+	b, _ := asn1.Marshal(priv)
+	return b
+}
+
+// ParsePKCS1PublicKey parses an RSA public key in PKCS #1, ASN.1 DER form.
+//
+// This kind of key is commonly encoded in PEM blocks of type "RSA PUBLIC KEY".
+func ParsePKCS1PublicKey(der []byte) (*rsa.PublicKey, error) {
+	var pub pkcs1PublicKey
+	rest, err := asn1.Unmarshal(der, &pub)
+	if err != nil {
+		if _, err := asn1.Unmarshal(der, &publicKeyInfo{}); err == nil {
+			return nil, errors.New("x509: failed to parse public key (use ParsePKIXPublicKey instead for this key format)")
+		}
+		return nil, err
+	}
+	if len(rest) > 0 {
+		return nil, asn1.SyntaxError{Msg: "trailing data"}
+	}
+
+	if pub.N.Sign() <= 0 || pub.E <= 0 {
+		return nil, errors.New("x509: public key contains zero or negative value")
+	}
+	if pub.E > 1<<31-1 {
+		return nil, errors.New("x509: public key contains large public exponent")
+	}
+
+	return &rsa.PublicKey{
+		E: pub.E,
+		N: pub.N,
+	}, nil
+}
+
+// MarshalPKCS1PublicKey converts an RSA public key to PKCS #1, ASN.1 DER form.
+//
+// This kind of key is commonly encoded in PEM blocks of type "RSA PUBLIC KEY".
+func MarshalPKCS1PublicKey(key *rsa.PublicKey) []byte {
+	derBytes, _ := asn1.Marshal(pkcs1PublicKey{
+		N: key.N,
+		E: key.E,
+	})
+	return derBytes
+}
diff --git a/src/crypto/x509/pkcs8.go b/src/crypto/x509/pkcs8.go
new file mode 100644
index 0000000..d77efa3
--- /dev/null
+++ b/src/crypto/x509/pkcs8.go
@@ -0,0 +1,136 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/rsa"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"errors"
+	"fmt"
+)
+
+// pkcs8 reflects an ASN.1, PKCS #8 PrivateKey. See
+// ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-8/pkcs-8v1_2.asn
+// and RFC 5208.
+type pkcs8 struct {
+	Version    int
+	Algo       pkix.AlgorithmIdentifier
+	PrivateKey []byte
+	// optional attributes omitted.
+}
+
+// ParsePKCS8PrivateKey parses an unencrypted private key in PKCS #8, ASN.1 DER form.
+//
+// It returns a *rsa.PrivateKey, a *ecdsa.PrivateKey, or a ed25519.PrivateKey.
+// More types might be supported in the future.
+//
+// This kind of key is commonly encoded in PEM blocks of type "PRIVATE KEY".
+func ParsePKCS8PrivateKey(der []byte) (key any, err error) {
+	var privKey pkcs8
+	if _, err := asn1.Unmarshal(der, &privKey); err != nil {
+		if _, err := asn1.Unmarshal(der, &ecPrivateKey{}); err == nil {
+			return nil, errors.New("x509: failed to parse private key (use ParseECPrivateKey instead for this key format)")
+		}
+		if _, err := asn1.Unmarshal(der, &pkcs1PrivateKey{}); err == nil {
+			return nil, errors.New("x509: failed to parse private key (use ParsePKCS1PrivateKey instead for this key format)")
+		}
+		return nil, err
+	}
+	switch {
+	case privKey.Algo.Algorithm.Equal(oidPublicKeyRSA):
+		key, err = ParsePKCS1PrivateKey(privKey.PrivateKey)
+		if err != nil {
+			return nil, errors.New("x509: failed to parse RSA private key embedded in PKCS#8: " + err.Error())
+		}
+		return key, nil
+
+	case privKey.Algo.Algorithm.Equal(oidPublicKeyECDSA):
+		bytes := privKey.Algo.Parameters.FullBytes
+		namedCurveOID := new(asn1.ObjectIdentifier)
+		if _, err := asn1.Unmarshal(bytes, namedCurveOID); err != nil {
+			namedCurveOID = nil
+		}
+		key, err = parseECPrivateKey(namedCurveOID, privKey.PrivateKey)
+		if err != nil {
+			return nil, errors.New("x509: failed to parse EC private key embedded in PKCS#8: " + err.Error())
+		}
+		return key, nil
+
+	case privKey.Algo.Algorithm.Equal(oidPublicKeyEd25519):
+		if l := len(privKey.Algo.Parameters.FullBytes); l != 0 {
+			return nil, errors.New("x509: invalid Ed25519 private key parameters")
+		}
+		var curvePrivateKey []byte
+		if _, err := asn1.Unmarshal(privKey.PrivateKey, &curvePrivateKey); err != nil {
+			return nil, fmt.Errorf("x509: invalid Ed25519 private key: %v", err)
+		}
+		if l := len(curvePrivateKey); l != ed25519.SeedSize {
+			return nil, fmt.Errorf("x509: invalid Ed25519 private key length: %d", l)
+		}
+		return ed25519.NewKeyFromSeed(curvePrivateKey), nil
+
+	default:
+		return nil, fmt.Errorf("x509: PKCS#8 wrapping contained private key with unknown algorithm: %v", privKey.Algo.Algorithm)
+	}
+}
+
+// MarshalPKCS8PrivateKey converts a private key to PKCS #8, ASN.1 DER form.
+//
+// The following key types are currently supported: *rsa.PrivateKey, *ecdsa.PrivateKey
+// and ed25519.PrivateKey. Unsupported key types result in an error.
+//
+// This kind of key is commonly encoded in PEM blocks of type "PRIVATE KEY".
+func MarshalPKCS8PrivateKey(key any) ([]byte, error) {
+	var privKey pkcs8
+
+	switch k := key.(type) {
+	case *rsa.PrivateKey:
+		privKey.Algo = pkix.AlgorithmIdentifier{
+			Algorithm:  oidPublicKeyRSA,
+			Parameters: asn1.NullRawValue,
+		}
+		privKey.PrivateKey = MarshalPKCS1PrivateKey(k)
+
+	case *ecdsa.PrivateKey:
+		oid, ok := oidFromNamedCurve(k.Curve)
+		if !ok {
+			return nil, errors.New("x509: unknown curve while marshaling to PKCS#8")
+		}
+
+		oidBytes, err := asn1.Marshal(oid)
+		if err != nil {
+			return nil, errors.New("x509: failed to marshal curve OID: " + err.Error())
+		}
+
+		privKey.Algo = pkix.AlgorithmIdentifier{
+			Algorithm: oidPublicKeyECDSA,
+			Parameters: asn1.RawValue{
+				FullBytes: oidBytes,
+			},
+		}
+
+		if privKey.PrivateKey, err = marshalECPrivateKeyWithOID(k, nil); err != nil {
+			return nil, errors.New("x509: failed to marshal EC private key while building PKCS#8: " + err.Error())
+		}
+
+	case ed25519.PrivateKey:
+		privKey.Algo = pkix.AlgorithmIdentifier{
+			Algorithm: oidPublicKeyEd25519,
+		}
+		curvePrivateKey, err := asn1.Marshal(k.Seed())
+		if err != nil {
+			return nil, fmt.Errorf("x509: failed to marshal private key: %v", err)
+		}
+		privKey.PrivateKey = curvePrivateKey
+
+	default:
+		return nil, fmt.Errorf("x509: unknown key type while marshaling PKCS#8: %T", key)
+	}
+
+	return asn1.Marshal(privKey)
+}
diff --git a/src/crypto/x509/pkcs8_test.go b/src/crypto/x509/pkcs8_test.go
new file mode 100644
index 0000000..cb7ee4c
--- /dev/null
+++ b/src/crypto/x509/pkcs8_test.go
@@ -0,0 +1,140 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	"bytes"
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/elliptic"
+	"crypto/rsa"
+	"encoding/hex"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// Generated using:
+//   openssl genrsa 1024 | openssl pkcs8 -topk8 -nocrypt
+var pkcs8RSAPrivateKeyHex = `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`
+
+// Generated using:
+//   openssl ecparam -genkey -name secp224r1 | openssl pkcs8 -topk8 -nocrypt
+var pkcs8P224PrivateKeyHex = `3078020100301006072a8648ce3d020106052b810400210461305f020101041cca3d72b3e88fed2684576dad9b80a9180363a5424986900e3abcab3fa13c033a0004f8f2a6372872a4e61263ed893afb919576a4cacfecd6c081a2cbc76873cf4ba8530703c6042b3a00e2205087e87d2435d2e339e25702fae1`
+
+// Generated using:
+//   openssl ecparam -genkey -name secp256r1 | openssl pkcs8 -topk8 -nocrypt
+var pkcs8P256PrivateKeyHex = `308187020100301306072a8648ce3d020106082a8648ce3d030107046d306b0201010420dad6b2f49ca774c36d8ae9517e935226f667c929498f0343d2424d0b9b591b43a14403420004b9c9b90095476afe7b860d8bd43568cab7bcb2eed7b8bf2fa0ce1762dd20b04193f859d2d782b1e4cbfd48492f1f533113a6804903f292258513837f07fda735`
+
+// Generated using:
+//   openssl ecparam -genkey -name secp384r1 | openssl pkcs8 -topk8 -nocrypt
+var pkcs8P384PrivateKeyHex = `3081b6020100301006072a8648ce3d020106052b8104002204819e30819b02010104309bf832f6aaaeacb78ce47ffb15e6fd0fd48683ae79df6eca39bfb8e33829ac94aa29d08911568684c2264a08a4ceb679a164036200049070ad4ed993c7770d700e9f6dc2baa83f63dd165b5507f98e8ff29b5d2e78ccbe05c8ddc955dbf0f7497e8222cfa49314fe4e269459f8e880147f70d785e530f2939e4bf9f838325bb1a80ad4cf59272ae0e5efe9a9dc33d874492596304bd3`
+
+// Generated using:
+//   openssl ecparam -genkey -name secp521r1 | openssl pkcs8 -topk8 -nocrypt
+//
+// Note that OpenSSL will truncate the private key if it can (i.e. it emits it
+// like an integer, even though it's an OCTET STRING field). Thus if you
+// regenerate this you may, randomly, find that it's a byte shorter than
+// expected and the Go test will fail to recreate it exactly.
+var pkcs8P521PrivateKeyHex = `3081ee020100301006072a8648ce3d020106052b810400230481d63081d3020101044200cfe0b87113a205cf291bb9a8cd1a74ac6c7b2ebb8199aaa9a5010d8b8012276fa3c22ac913369fa61beec2a3b8b4516bc049bde4fb3b745ac11b56ab23ac52e361a1818903818600040138f75acdd03fbafa4f047a8e4b272ba9d555c667962b76f6f232911a5786a0964e5edea6bd21a6f8725720958de049c6e3e6661c1c91b227cebee916c0319ed6ca003db0a3206d372229baf9dd25d868bf81140a518114803ce40c1855074d68c4e9dab9e65efba7064c703b400f1767f217dac82715ac1f6d88c74baf47a7971de4ea`
+
+// From RFC 8410, Section 7.
+var pkcs8Ed25519PrivateKeyHex = `302e020100300506032b657004220420d4ee72dbf913584ad5b6d8f1f769f8ad3afe7c28cbf1d4fbe097a88f44755842`
+
+func TestPKCS8(t *testing.T) {
+	tests := []struct {
+		name    string
+		keyHex  string
+		keyType reflect.Type
+		curve   elliptic.Curve
+	}{
+		{
+			name:    "RSA private key",
+			keyHex:  pkcs8RSAPrivateKeyHex,
+			keyType: reflect.TypeOf(&rsa.PrivateKey{}),
+		},
+		{
+			name:    "P-224 private key",
+			keyHex:  pkcs8P224PrivateKeyHex,
+			keyType: reflect.TypeOf(&ecdsa.PrivateKey{}),
+			curve:   elliptic.P224(),
+		},
+		{
+			name:    "P-256 private key",
+			keyHex:  pkcs8P256PrivateKeyHex,
+			keyType: reflect.TypeOf(&ecdsa.PrivateKey{}),
+			curve:   elliptic.P256(),
+		},
+		{
+			name:    "P-384 private key",
+			keyHex:  pkcs8P384PrivateKeyHex,
+			keyType: reflect.TypeOf(&ecdsa.PrivateKey{}),
+			curve:   elliptic.P384(),
+		},
+		{
+			name:    "P-521 private key",
+			keyHex:  pkcs8P521PrivateKeyHex,
+			keyType: reflect.TypeOf(&ecdsa.PrivateKey{}),
+			curve:   elliptic.P521(),
+		},
+		{
+			name:    "Ed25519 private key",
+			keyHex:  pkcs8Ed25519PrivateKeyHex,
+			keyType: reflect.TypeOf(ed25519.PrivateKey{}),
+		},
+	}
+
+	for _, test := range tests {
+		derBytes, err := hex.DecodeString(test.keyHex)
+		if err != nil {
+			t.Errorf("%s: failed to decode hex: %s", test.name, err)
+			continue
+		}
+		privKey, err := ParsePKCS8PrivateKey(derBytes)
+		if err != nil {
+			t.Errorf("%s: failed to decode PKCS#8: %s", test.name, err)
+			continue
+		}
+		if reflect.TypeOf(privKey) != test.keyType {
+			t.Errorf("%s: decoded PKCS#8 returned unexpected key type: %T", test.name, privKey)
+			continue
+		}
+		if ecKey, isEC := privKey.(*ecdsa.PrivateKey); isEC && ecKey.Curve != test.curve {
+			t.Errorf("%s: decoded PKCS#8 returned unexpected curve %#v", test.name, ecKey.Curve)
+			continue
+		}
+		reserialised, err := MarshalPKCS8PrivateKey(privKey)
+		if err != nil {
+			t.Errorf("%s: failed to marshal into PKCS#8: %s", test.name, err)
+			continue
+		}
+		if !bytes.Equal(derBytes, reserialised) {
+			t.Errorf("%s: marshaled PKCS#8 didn't match original: got %x, want %x", test.name, reserialised, derBytes)
+			continue
+		}
+	}
+}
+
+const hexPKCS8TestPKCS1Key = "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"
+const hexPKCS8TestECKey = "3081a40201010430bdb9839c08ee793d1157886a7a758a3c8b2a17a4df48f17ace57c72c56b4723cf21dcda21d4e1ad57ff034f19fcfd98ea00706052b81040022a16403620004feea808b5ee2429cfcce13c32160e1c960990bd050bb0fdf7222f3decd0a55008e32a6aa3c9062051c4cba92a7a3b178b24567412d43cdd2f882fa5addddd726fe3e208d2c26d733a773a597abb749714df7256ead5105fa6e7b3650de236b50"
+
+var pkcs8MismatchKeyTests = []struct {
+	hexKey        string
+	errorContains string
+}{
+	{hexKey: hexPKCS8TestECKey, errorContains: "use ParseECPrivateKey instead"},
+	{hexKey: hexPKCS8TestPKCS1Key, errorContains: "use ParsePKCS1PrivateKey instead"},
+}
+
+func TestPKCS8MismatchKeyFormat(t *testing.T) {
+	for i, test := range pkcs8MismatchKeyTests {
+		derBytes, _ := hex.DecodeString(test.hexKey)
+		_, err := ParsePKCS8PrivateKey(derBytes)
+		if !strings.Contains(err.Error(), test.errorContains) {
+			t.Errorf("#%d: expected error containing %q, got %s", i, test.errorContains, err)
+		}
+	}
+}
diff --git a/src/crypto/x509/pkix/pkix.go b/src/crypto/x509/pkix/pkix.go
new file mode 100644
index 0000000..e9179ed
--- /dev/null
+++ b/src/crypto/x509/pkix/pkix.go
@@ -0,0 +1,316 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package pkix contains shared, low level structures used for ASN.1 parsing
+// and serialization of X.509 certificates, CRL and OCSP.
+package pkix
+
+import (
+	"encoding/asn1"
+	"encoding/hex"
+	"fmt"
+	"math/big"
+	"time"
+)
+
+// AlgorithmIdentifier represents the ASN.1 structure of the same name. See RFC
+// 5280, section 4.1.1.2.
+type AlgorithmIdentifier struct {
+	Algorithm  asn1.ObjectIdentifier
+	Parameters asn1.RawValue `asn1:"optional"`
+}
+
+type RDNSequence []RelativeDistinguishedNameSET
+
+var attributeTypeNames = map[string]string{
+	"2.5.4.6":  "C",
+	"2.5.4.10": "O",
+	"2.5.4.11": "OU",
+	"2.5.4.3":  "CN",
+	"2.5.4.5":  "SERIALNUMBER",
+	"2.5.4.7":  "L",
+	"2.5.4.8":  "ST",
+	"2.5.4.9":  "STREET",
+	"2.5.4.17": "POSTALCODE",
+}
+
+// String returns a string representation of the sequence r,
+// roughly following the RFC 2253 Distinguished Names syntax.
+func (r RDNSequence) String() string {
+	s := ""
+	for i := 0; i < len(r); i++ {
+		rdn := r[len(r)-1-i]
+		if i > 0 {
+			s += ","
+		}
+		for j, tv := range rdn {
+			if j > 0 {
+				s += "+"
+			}
+
+			oidString := tv.Type.String()
+			typeName, ok := attributeTypeNames[oidString]
+			if !ok {
+				derBytes, err := asn1.Marshal(tv.Value)
+				if err == nil {
+					s += oidString + "=#" + hex.EncodeToString(derBytes)
+					continue // No value escaping necessary.
+				}
+
+				typeName = oidString
+			}
+
+			valueString := fmt.Sprint(tv.Value)
+			escaped := make([]rune, 0, len(valueString))
+
+			for k, c := range valueString {
+				escape := false
+
+				switch c {
+				case ',', '+', '"', '\\', '<', '>', ';':
+					escape = true
+
+				case ' ':
+					escape = k == 0 || k == len(valueString)-1
+
+				case '#':
+					escape = k == 0
+				}
+
+				if escape {
+					escaped = append(escaped, '\\', c)
+				} else {
+					escaped = append(escaped, c)
+				}
+			}
+
+			s += typeName + "=" + string(escaped)
+		}
+	}
+
+	return s
+}
+
+type RelativeDistinguishedNameSET []AttributeTypeAndValue
+
+// AttributeTypeAndValue mirrors the ASN.1 structure of the same name in
+// RFC 5280, Section 4.1.2.4.
+type AttributeTypeAndValue struct {
+	Type  asn1.ObjectIdentifier
+	Value any
+}
+
+// AttributeTypeAndValueSET represents a set of ASN.1 sequences of
+// AttributeTypeAndValue sequences from RFC 2986 (PKCS #10).
+type AttributeTypeAndValueSET struct {
+	Type  asn1.ObjectIdentifier
+	Value [][]AttributeTypeAndValue `asn1:"set"`
+}
+
+// Extension represents the ASN.1 structure of the same name. See RFC
+// 5280, section 4.2.
+type Extension struct {
+	Id       asn1.ObjectIdentifier
+	Critical bool `asn1:"optional"`
+	Value    []byte
+}
+
+// Name represents an X.509 distinguished name. This only includes the common
+// elements of a DN. Note that Name is only an approximation of the X.509
+// structure. If an accurate representation is needed, asn1.Unmarshal the raw
+// subject or issuer as an RDNSequence.
+type Name struct {
+	Country, Organization, OrganizationalUnit []string
+	Locality, Province                        []string
+	StreetAddress, PostalCode                 []string
+	SerialNumber, CommonName                  string
+
+	// Names contains all parsed attributes. When parsing distinguished names,
+	// this can be used to extract non-standard attributes that are not parsed
+	// by this package. When marshaling to RDNSequences, the Names field is
+	// ignored, see ExtraNames.
+	Names []AttributeTypeAndValue
+
+	// ExtraNames contains attributes to be copied, raw, into any marshaled
+	// distinguished names. Values override any attributes with the same OID.
+	// The ExtraNames field is not populated when parsing, see Names.
+	ExtraNames []AttributeTypeAndValue
+}
+
+// FillFromRDNSequence populates n from the provided RDNSequence.
+// Multi-entry RDNs are flattened, all entries are added to the
+// relevant n fields, and the grouping is not preserved.
+func (n *Name) FillFromRDNSequence(rdns *RDNSequence) {
+	for _, rdn := range *rdns {
+		if len(rdn) == 0 {
+			continue
+		}
+
+		for _, atv := range rdn {
+			n.Names = append(n.Names, atv)
+			value, ok := atv.Value.(string)
+			if !ok {
+				continue
+			}
+
+			t := atv.Type
+			if len(t) == 4 && t[0] == 2 && t[1] == 5 && t[2] == 4 {
+				switch t[3] {
+				case 3:
+					n.CommonName = value
+				case 5:
+					n.SerialNumber = value
+				case 6:
+					n.Country = append(n.Country, value)
+				case 7:
+					n.Locality = append(n.Locality, value)
+				case 8:
+					n.Province = append(n.Province, value)
+				case 9:
+					n.StreetAddress = append(n.StreetAddress, value)
+				case 10:
+					n.Organization = append(n.Organization, value)
+				case 11:
+					n.OrganizationalUnit = append(n.OrganizationalUnit, value)
+				case 17:
+					n.PostalCode = append(n.PostalCode, value)
+				}
+			}
+		}
+	}
+}
+
+var (
+	oidCountry            = []int{2, 5, 4, 6}
+	oidOrganization       = []int{2, 5, 4, 10}
+	oidOrganizationalUnit = []int{2, 5, 4, 11}
+	oidCommonName         = []int{2, 5, 4, 3}
+	oidSerialNumber       = []int{2, 5, 4, 5}
+	oidLocality           = []int{2, 5, 4, 7}
+	oidProvince           = []int{2, 5, 4, 8}
+	oidStreetAddress      = []int{2, 5, 4, 9}
+	oidPostalCode         = []int{2, 5, 4, 17}
+)
+
+// appendRDNs appends a relativeDistinguishedNameSET to the given RDNSequence
+// and returns the new value. The relativeDistinguishedNameSET contains an
+// attributeTypeAndValue for each of the given values. See RFC 5280, A.1, and
+// search for AttributeTypeAndValue.
+func (n Name) appendRDNs(in RDNSequence, values []string, oid asn1.ObjectIdentifier) RDNSequence {
+	if len(values) == 0 || oidInAttributeTypeAndValue(oid, n.ExtraNames) {
+		return in
+	}
+
+	s := make([]AttributeTypeAndValue, len(values))
+	for i, value := range values {
+		s[i].Type = oid
+		s[i].Value = value
+	}
+
+	return append(in, s)
+}
+
+// ToRDNSequence converts n into a single RDNSequence. The following
+// attributes are encoded as multi-value RDNs:
+//
+//  - Country
+//  - Organization
+//  - OrganizationalUnit
+//  - Locality
+//  - Province
+//  - StreetAddress
+//  - PostalCode
+//
+// Each ExtraNames entry is encoded as an individual RDN.
+func (n Name) ToRDNSequence() (ret RDNSequence) {
+	ret = n.appendRDNs(ret, n.Country, oidCountry)
+	ret = n.appendRDNs(ret, n.Province, oidProvince)
+	ret = n.appendRDNs(ret, n.Locality, oidLocality)
+	ret = n.appendRDNs(ret, n.StreetAddress, oidStreetAddress)
+	ret = n.appendRDNs(ret, n.PostalCode, oidPostalCode)
+	ret = n.appendRDNs(ret, n.Organization, oidOrganization)
+	ret = n.appendRDNs(ret, n.OrganizationalUnit, oidOrganizationalUnit)
+	if len(n.CommonName) > 0 {
+		ret = n.appendRDNs(ret, []string{n.CommonName}, oidCommonName)
+	}
+	if len(n.SerialNumber) > 0 {
+		ret = n.appendRDNs(ret, []string{n.SerialNumber}, oidSerialNumber)
+	}
+	for _, atv := range n.ExtraNames {
+		ret = append(ret, []AttributeTypeAndValue{atv})
+	}
+
+	return ret
+}
+
+// String returns the string form of n, roughly following
+// the RFC 2253 Distinguished Names syntax.
+func (n Name) String() string {
+	var rdns RDNSequence
+	// If there are no ExtraNames, surface the parsed value (all entries in
+	// Names) instead.
+	if n.ExtraNames == nil {
+		for _, atv := range n.Names {
+			t := atv.Type
+			if len(t) == 4 && t[0] == 2 && t[1] == 5 && t[2] == 4 {
+				switch t[3] {
+				case 3, 5, 6, 7, 8, 9, 10, 11, 17:
+					// These attributes were already parsed into named fields.
+					continue
+				}
+			}
+			// Place non-standard parsed values at the beginning of the sequence
+			// so they will be at the end of the string. See Issue 39924.
+			rdns = append(rdns, []AttributeTypeAndValue{atv})
+		}
+	}
+	rdns = append(rdns, n.ToRDNSequence()...)
+	return rdns.String()
+}
+
+// oidInAttributeTypeAndValue reports whether a type with the given OID exists
+// in atv.
+func oidInAttributeTypeAndValue(oid asn1.ObjectIdentifier, atv []AttributeTypeAndValue) bool {
+	for _, a := range atv {
+		if a.Type.Equal(oid) {
+			return true
+		}
+	}
+	return false
+}
+
+// CertificateList represents the ASN.1 structure of the same name. See RFC
+// 5280, section 5.1. Use Certificate.CheckCRLSignature to verify the
+// signature.
+type CertificateList struct {
+	TBSCertList        TBSCertificateList
+	SignatureAlgorithm AlgorithmIdentifier
+	SignatureValue     asn1.BitString
+}
+
+// HasExpired reports whether certList should have been updated by now.
+func (certList *CertificateList) HasExpired(now time.Time) bool {
+	return !now.Before(certList.TBSCertList.NextUpdate)
+}
+
+// TBSCertificateList represents the ASN.1 structure of the same name. See RFC
+// 5280, section 5.1.
+type TBSCertificateList struct {
+	Raw                 asn1.RawContent
+	Version             int `asn1:"optional,default:0"`
+	Signature           AlgorithmIdentifier
+	Issuer              RDNSequence
+	ThisUpdate          time.Time
+	NextUpdate          time.Time            `asn1:"optional"`
+	RevokedCertificates []RevokedCertificate `asn1:"optional"`
+	Extensions          []Extension          `asn1:"tag:0,optional,explicit"`
+}
+
+// RevokedCertificate represents the ASN.1 structure of the same name. See RFC
+// 5280, section 5.1.
+type RevokedCertificate struct {
+	SerialNumber   *big.Int
+	RevocationTime time.Time
+	Extensions     []Extension `asn1:"optional"`
+}
diff --git a/src/crypto/x509/root.go b/src/crypto/x509/root.go
new file mode 100644
index 0000000..eef9c04
--- /dev/null
+++ b/src/crypto/x509/root.go
@@ -0,0 +1,31 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+// To update the embedded iOS root store, update the -version
+// argument to the latest security_certificates version from
+// https://opensource.apple.com/source/security_certificates/
+// and run "go generate". See https://golang.org/issue/38843.
+//go:generate go run root_ios_gen.go -version 55188.120.1.0.1
+
+import "sync"
+
+var (
+	once           sync.Once
+	systemRoots    *CertPool
+	systemRootsErr error
+)
+
+func systemRootsPool() *CertPool {
+	once.Do(initSystemRoots)
+	return systemRoots
+}
+
+func initSystemRoots() {
+	systemRoots, systemRootsErr = loadSystemRoots()
+	if systemRootsErr != nil {
+		systemRoots = nil
+	}
+}
diff --git a/src/crypto/x509/root_aix.go b/src/crypto/x509/root_aix.go
new file mode 100644
index 0000000..99b7463
--- /dev/null
+++ b/src/crypto/x509/root_aix.go
@@ -0,0 +1,15 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+// Possible certificate files; stop after finding one.
+var certFiles = []string{
+	"/var/ssl/certs/ca-bundle.crt",
+}
+
+// Possible directories with certificate files; all will be read.
+var certDirectories = []string{
+	"/var/ssl/certs",
+}
diff --git a/src/crypto/x509/root_bsd.go b/src/crypto/x509/root_bsd.go
new file mode 100644
index 0000000..a76aef8
--- /dev/null
+++ b/src/crypto/x509/root_bsd.go
@@ -0,0 +1,22 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build dragonfly || freebsd || netbsd || openbsd
+
+package x509
+
+// Possible certificate files; stop after finding one.
+var certFiles = []string{
+	"/usr/local/etc/ssl/cert.pem",            // FreeBSD
+	"/etc/ssl/cert.pem",                      // OpenBSD
+	"/usr/local/share/certs/ca-root-nss.crt", // DragonFly
+	"/etc/openssl/certs/ca-certificates.crt", // NetBSD
+}
+
+// Possible directories with certificate files; all will be read.
+var certDirectories = []string{
+	"/etc/ssl/certs",         // FreeBSD 12.2+
+	"/usr/local/share/certs", // FreeBSD
+	"/etc/openssl/certs",     // NetBSD
+}
diff --git a/src/crypto/x509/root_darwin.go b/src/crypto/x509/root_darwin.go
new file mode 100644
index 0000000..c35885a
--- /dev/null
+++ b/src/crypto/x509/root_darwin.go
@@ -0,0 +1,123 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	macOS "crypto/x509/internal/macos"
+	"errors"
+	"fmt"
+)
+
+func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate, err error) {
+	certs := macOS.CFArrayCreateMutable()
+	defer macOS.ReleaseCFArray(certs)
+	leaf := macOS.SecCertificateCreateWithData(c.Raw)
+	if leaf == 0 {
+		return nil, errors.New("invalid leaf certificate")
+	}
+	macOS.CFArrayAppendValue(certs, leaf)
+	if opts.Intermediates != nil {
+		for _, lc := range opts.Intermediates.lazyCerts {
+			c, err := lc.getCert()
+			if err != nil {
+				return nil, err
+			}
+			sc := macOS.SecCertificateCreateWithData(c.Raw)
+			if sc != 0 {
+				macOS.CFArrayAppendValue(certs, sc)
+			}
+		}
+	}
+
+	policies := macOS.CFArrayCreateMutable()
+	defer macOS.ReleaseCFArray(policies)
+	sslPolicy := macOS.SecPolicyCreateSSL(opts.DNSName)
+	macOS.CFArrayAppendValue(policies, sslPolicy)
+
+	trustObj, err := macOS.SecTrustCreateWithCertificates(certs, policies)
+	if err != nil {
+		return nil, err
+	}
+	defer macOS.CFRelease(trustObj)
+
+	if !opts.CurrentTime.IsZero() {
+		dateRef := macOS.TimeToCFDateRef(opts.CurrentTime)
+		defer macOS.CFRelease(dateRef)
+		if err := macOS.SecTrustSetVerifyDate(trustObj, dateRef); err != nil {
+			return nil, err
+		}
+	}
+
+	// TODO(roland): we may want to allow passing in SCTs via VerifyOptions and
+	// set them via SecTrustSetSignedCertificateTimestamps, since Apple will
+	// always enforce its SCT requirements, and there are still _some_ people
+	// using TLS or OCSP for that.
+
+	if ret, err := macOS.SecTrustEvaluateWithError(trustObj); err != nil {
+		switch ret {
+		case macOS.ErrSecCertificateExpired:
+			return nil, CertificateInvalidError{c, Expired, err.Error()}
+		case macOS.ErrSecHostNameMismatch:
+			return nil, HostnameError{c, opts.DNSName}
+		case macOS.ErrSecNotTrusted:
+			return nil, UnknownAuthorityError{Cert: c}
+		default:
+			return nil, fmt.Errorf("x509: %s", err)
+		}
+	}
+
+	chain := [][]*Certificate{{}}
+	numCerts := macOS.SecTrustGetCertificateCount(trustObj)
+	for i := 0; i < numCerts; i++ {
+		certRef := macOS.SecTrustGetCertificateAtIndex(trustObj, i)
+		cert, err := exportCertificate(certRef)
+		if err != nil {
+			return nil, err
+		}
+		chain[0] = append(chain[0], cert)
+	}
+	if len(chain[0]) == 0 {
+		// This should _never_ happen, but to be safe
+		return nil, errors.New("x509: macOS certificate verification internal error")
+	}
+
+	if opts.DNSName != "" {
+		// If we have a DNS name, apply our own name verification
+		if err := chain[0][0].VerifyHostname(opts.DNSName); err != nil {
+			return nil, err
+		}
+	}
+
+	keyUsages := opts.KeyUsages
+	if len(keyUsages) == 0 {
+		keyUsages = []ExtKeyUsage{ExtKeyUsageServerAuth}
+	}
+
+	// If any key usage is acceptable then we're done.
+	for _, usage := range keyUsages {
+		if usage == ExtKeyUsageAny {
+			return chain, nil
+		}
+	}
+
+	if !checkChainForKeyUsage(chain[0], keyUsages) {
+		return nil, CertificateInvalidError{c, IncompatibleUsage, ""}
+	}
+
+	return chain, nil
+}
+
+// exportCertificate returns a *Certificate for a SecCertificateRef.
+func exportCertificate(cert macOS.CFRef) (*Certificate, error) {
+	data, err := macOS.SecCertificateCopyData(cert)
+	if err != nil {
+		return nil, err
+	}
+	return ParseCertificate(data)
+}
+
+func loadSystemRoots() (*CertPool, error) {
+	return &CertPool{systemPool: true}, nil
+}
diff --git a/src/crypto/x509/root_darwin_test.go b/src/crypto/x509/root_darwin_test.go
new file mode 100644
index 0000000..299cecf
--- /dev/null
+++ b/src/crypto/x509/root_darwin_test.go
@@ -0,0 +1,122 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509_test
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"internal/testenv"
+	"testing"
+	"time"
+)
+
+func TestPlatformVerifier(t *testing.T) {
+	if !testenv.HasExternalNetwork() {
+		t.Skip()
+	}
+
+	getChain := func(host string) []*x509.Certificate {
+		t.Helper()
+		c, err := tls.Dial("tcp", host+":443", &tls.Config{InsecureSkipVerify: true})
+		if err != nil {
+			t.Fatalf("tls connection failed: %s", err)
+		}
+		return c.ConnectionState().PeerCertificates
+	}
+
+	tests := []struct {
+		name        string
+		host        string
+		verifyName  string
+		verifyTime  time.Time
+		verifyEKU   []x509.ExtKeyUsage
+		expectedErr string
+	}{
+		{
+			// whatever google.com serves should, hopefully, be trusted
+			name: "valid chain",
+			host: "google.com",
+		},
+		{
+			name:        "expired leaf",
+			host:        "expired.badssl.com",
+			expectedErr: "x509: certificate has expired or is not yet valid: “*.badssl.com” certificate is expired",
+		},
+		{
+			name:        "wrong host for leaf",
+			host:        "wrong.host.badssl.com",
+			verifyName:  "wrong.host.badssl.com",
+			expectedErr: "x509: certificate is valid for *.badssl.com, badssl.com, not wrong.host.badssl.com",
+		},
+		{
+			name:        "self-signed leaf",
+			host:        "self-signed.badssl.com",
+			expectedErr: "x509: certificate signed by unknown authority",
+		},
+		{
+			name:        "untrusted root",
+			host:        "untrusted-root.badssl.com",
+			expectedErr: "x509: certificate signed by unknown authority",
+		},
+		{
+			name:        "revoked leaf",
+			host:        "revoked.badssl.com",
+			expectedErr: "x509: “revoked.badssl.com” certificate is revoked",
+		},
+		{
+			name:        "leaf missing SCTs",
+			host:        "no-sct.badssl.com",
+			expectedErr: "x509: “no-sct.badssl.com” certificate is not standards compliant",
+		},
+		{
+			name:        "expired leaf (custom time)",
+			host:        "google.com",
+			verifyTime:  time.Time{}.Add(time.Hour),
+			expectedErr: "x509: certificate has expired or is not yet valid: “*.google.com” certificate is expired",
+		},
+		{
+			name:       "valid chain (custom time)",
+			host:       "google.com",
+			verifyTime: time.Now(),
+		},
+		{
+			name:        "leaf doesn't have acceptable ExtKeyUsage",
+			host:        "google.com",
+			expectedErr: "x509: certificate specifies an incompatible key usage",
+			verifyEKU:   []x509.ExtKeyUsage{x509.ExtKeyUsageEmailProtection},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			chain := getChain(tc.host)
+			var opts x509.VerifyOptions
+			if len(chain) > 1 {
+				opts.Intermediates = x509.NewCertPool()
+				for _, c := range chain[1:] {
+					opts.Intermediates.AddCert(c)
+				}
+			}
+			if tc.verifyName != "" {
+				opts.DNSName = tc.verifyName
+			}
+			if !tc.verifyTime.IsZero() {
+				opts.CurrentTime = tc.verifyTime
+			}
+			if len(tc.verifyEKU) > 0 {
+				opts.KeyUsages = tc.verifyEKU
+			}
+
+			_, err := chain[0].Verify(opts)
+			if err != nil && tc.expectedErr == "" {
+				t.Errorf("unexpected verification error: %s", err)
+			} else if err != nil && err.Error() != tc.expectedErr {
+				t.Errorf("unexpected verification error: got %q, want %q", err.Error(), tc.expectedErr)
+			} else if err == nil && tc.expectedErr != "" {
+				t.Errorf("unexpected verification success: want %q", tc.expectedErr)
+			}
+		})
+	}
+}
diff --git a/src/crypto/x509/root_js.go b/src/crypto/x509/root_js.go
new file mode 100644
index 0000000..7b3f1e4
--- /dev/null
+++ b/src/crypto/x509/root_js.go
@@ -0,0 +1,13 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build js && wasm
+
+package x509
+
+// Possible certificate files; stop after finding one.
+var certFiles = []string{}
+
+// Possible directories with certificate files; all will be read.
+var certDirectories = []string{}
diff --git a/src/crypto/x509/root_linux.go b/src/crypto/x509/root_linux.go
new file mode 100644
index 0000000..e32989b
--- /dev/null
+++ b/src/crypto/x509/root_linux.go
@@ -0,0 +1,22 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+// Possible certificate files; stop after finding one.
+var certFiles = []string{
+	"/etc/ssl/certs/ca-certificates.crt",                // Debian/Ubuntu/Gentoo etc.
+	"/etc/pki/tls/certs/ca-bundle.crt",                  // Fedora/RHEL 6
+	"/etc/ssl/ca-bundle.pem",                            // OpenSUSE
+	"/etc/pki/tls/cacert.pem",                           // OpenELEC
+	"/etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem", // CentOS/RHEL 7
+	"/etc/ssl/cert.pem",                                 // Alpine Linux
+}
+
+// Possible directories with certificate files; all will be read.
+var certDirectories = []string{
+	"/etc/ssl/certs",               // SLES10/SLES11, https://golang.org/issue/12139
+	"/etc/pki/tls/certs",           // Fedora/RHEL
+	"/system/etc/security/cacerts", // Android
+}
diff --git a/src/crypto/x509/root_plan9.go b/src/crypto/x509/root_plan9.go
new file mode 100644
index 0000000..3bd06fe
--- /dev/null
+++ b/src/crypto/x509/root_plan9.go
@@ -0,0 +1,39 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build plan9
+
+package x509
+
+import (
+	"os"
+)
+
+// Possible certificate files; stop after finding one.
+var certFiles = []string{
+	"/sys/lib/tls/ca.pem",
+}
+
+func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate, err error) {
+	return nil, nil
+}
+
+func loadSystemRoots() (*CertPool, error) {
+	roots := NewCertPool()
+	var bestErr error
+	for _, file := range certFiles {
+		data, err := os.ReadFile(file)
+		if err == nil {
+			roots.AppendCertsFromPEM(data)
+			return roots, nil
+		}
+		if bestErr == nil || (os.IsNotExist(bestErr) && !os.IsNotExist(err)) {
+			bestErr = err
+		}
+	}
+	if bestErr == nil {
+		return roots, nil
+	}
+	return nil, bestErr
+}
diff --git a/src/crypto/x509/root_solaris.go b/src/crypto/x509/root_solaris.go
new file mode 100644
index 0000000..617f269
--- /dev/null
+++ b/src/crypto/x509/root_solaris.go
@@ -0,0 +1,17 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+// Possible certificate files; stop after finding one.
+var certFiles = []string{
+	"/etc/certs/ca-certificates.crt",     // Solaris 11.2+
+	"/etc/ssl/certs/ca-certificates.crt", // Joyent SmartOS
+	"/etc/ssl/cacert.pem",                // OmniOS
+}
+
+// Possible directories with certificate files; all will be read.
+var certDirectories = []string{
+	"/etc/certs/CA",
+}
diff --git a/src/crypto/x509/root_unix.go b/src/crypto/x509/root_unix.go
new file mode 100644
index 0000000..aa54f89
--- /dev/null
+++ b/src/crypto/x509/root_unix.go
@@ -0,0 +1,108 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build aix || dragonfly || freebsd || (js && wasm) || linux || netbsd || openbsd || solaris
+
+package x509
+
+import (
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+const (
+	// certFileEnv is the environment variable which identifies where to locate
+	// the SSL certificate file. If set this overrides the system default.
+	certFileEnv = "SSL_CERT_FILE"
+
+	// certDirEnv is the environment variable which identifies which directory
+	// to check for SSL certificate files. If set this overrides the system default.
+	// It is a colon separated list of directories.
+	// See https://www.openssl.org/docs/man1.0.2/man1/c_rehash.html.
+	certDirEnv = "SSL_CERT_DIR"
+)
+
+func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate, err error) {
+	return nil, nil
+}
+
+func loadSystemRoots() (*CertPool, error) {
+	roots := NewCertPool()
+
+	files := certFiles
+	if f := os.Getenv(certFileEnv); f != "" {
+		files = []string{f}
+	}
+
+	var firstErr error
+	for _, file := range files {
+		data, err := os.ReadFile(file)
+		if err == nil {
+			roots.AppendCertsFromPEM(data)
+			break
+		}
+		if firstErr == nil && !os.IsNotExist(err) {
+			firstErr = err
+		}
+	}
+
+	dirs := certDirectories
+	if d := os.Getenv(certDirEnv); d != "" {
+		// OpenSSL and BoringSSL both use ":" as the SSL_CERT_DIR separator.
+		// See:
+		//  * https://golang.org/issue/35325
+		//  * https://www.openssl.org/docs/man1.0.2/man1/c_rehash.html
+		dirs = strings.Split(d, ":")
+	}
+
+	for _, directory := range dirs {
+		fis, err := readUniqueDirectoryEntries(directory)
+		if err != nil {
+			if firstErr == nil && !os.IsNotExist(err) {
+				firstErr = err
+			}
+			continue
+		}
+		for _, fi := range fis {
+			data, err := os.ReadFile(directory + "/" + fi.Name())
+			if err == nil {
+				roots.AppendCertsFromPEM(data)
+			}
+		}
+	}
+
+	if roots.len() > 0 || firstErr == nil {
+		return roots, nil
+	}
+
+	return nil, firstErr
+}
+
+// readUniqueDirectoryEntries is like os.ReadDir but omits
+// symlinks that point within the directory.
+func readUniqueDirectoryEntries(dir string) ([]fs.DirEntry, error) {
+	files, err := os.ReadDir(dir)
+	if err != nil {
+		return nil, err
+	}
+	uniq := files[:0]
+	for _, f := range files {
+		if !isSameDirSymlink(f, dir) {
+			uniq = append(uniq, f)
+		}
+	}
+	return uniq, nil
+}
+
+// isSameDirSymlink reports whether fi in dir is a symlink with a
+// target not containing a slash.
+func isSameDirSymlink(f fs.DirEntry, dir string) bool {
+	if f.Type()&fs.ModeSymlink == 0 {
+		return false
+	}
+	target, err := os.Readlink(filepath.Join(dir, f.Name()))
+	return err == nil && !strings.Contains(target, "/")
+}
diff --git a/src/crypto/x509/root_unix_test.go b/src/crypto/x509/root_unix_test.go
new file mode 100644
index 0000000..7197a0d
--- /dev/null
+++ b/src/crypto/x509/root_unix_test.go
@@ -0,0 +1,228 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build dragonfly || freebsd || linux || netbsd || openbsd || solaris
+
+package x509
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+const (
+	testDir     = "testdata"
+	testDirCN   = "test-dir"
+	testFile    = "test-file.crt"
+	testFileCN  = "test-file"
+	testMissing = "missing"
+)
+
+func TestEnvVars(t *testing.T) {
+	testCases := []struct {
+		name    string
+		fileEnv string
+		dirEnv  string
+		files   []string
+		dirs    []string
+		cns     []string
+	}{
+		{
+			// Environment variables override the default locations preventing fall through.
+			name:    "override-defaults",
+			fileEnv: testMissing,
+			dirEnv:  testMissing,
+			files:   []string{testFile},
+			dirs:    []string{testDir},
+			cns:     nil,
+		},
+		{
+			// File environment overrides default file locations.
+			name:    "file",
+			fileEnv: testFile,
+			dirEnv:  "",
+			files:   nil,
+			dirs:    nil,
+			cns:     []string{testFileCN},
+		},
+		{
+			// Directory environment overrides default directory locations.
+			name:    "dir",
+			fileEnv: "",
+			dirEnv:  testDir,
+			files:   nil,
+			dirs:    nil,
+			cns:     []string{testDirCN},
+		},
+		{
+			// File & directory environment overrides both default locations.
+			name:    "file+dir",
+			fileEnv: testFile,
+			dirEnv:  testDir,
+			files:   nil,
+			dirs:    nil,
+			cns:     []string{testFileCN, testDirCN},
+		},
+		{
+			// Environment variable empty / unset uses default locations.
+			name:    "empty-fall-through",
+			fileEnv: "",
+			dirEnv:  "",
+			files:   []string{testFile},
+			dirs:    []string{testDir},
+			cns:     []string{testFileCN, testDirCN},
+		},
+	}
+
+	// Save old settings so we can restore before the test ends.
+	origCertFiles, origCertDirectories := certFiles, certDirectories
+	origFile, origDir := os.Getenv(certFileEnv), os.Getenv(certDirEnv)
+	defer func() {
+		certFiles = origCertFiles
+		certDirectories = origCertDirectories
+		os.Setenv(certFileEnv, origFile)
+		os.Setenv(certDirEnv, origDir)
+	}()
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			if err := os.Setenv(certFileEnv, tc.fileEnv); err != nil {
+				t.Fatalf("setenv %q failed: %v", certFileEnv, err)
+			}
+			if err := os.Setenv(certDirEnv, tc.dirEnv); err != nil {
+				t.Fatalf("setenv %q failed: %v", certDirEnv, err)
+			}
+
+			certFiles, certDirectories = tc.files, tc.dirs
+
+			r, err := loadSystemRoots()
+			if err != nil {
+				t.Fatal("unexpected failure:", err)
+			}
+
+			if r == nil {
+				t.Fatal("nil roots")
+			}
+
+			// Verify that the returned certs match, otherwise report where the mismatch is.
+			for i, cn := range tc.cns {
+				if i >= r.len() {
+					t.Errorf("missing cert %v @ %v", cn, i)
+				} else if r.mustCert(t, i).Subject.CommonName != cn {
+					fmt.Printf("%#v\n", r.mustCert(t, 0).Subject)
+					t.Errorf("unexpected cert common name %q, want %q", r.mustCert(t, i).Subject.CommonName, cn)
+				}
+			}
+			if r.len() > len(tc.cns) {
+				t.Errorf("got %v certs, which is more than %v wanted", r.len(), len(tc.cns))
+			}
+		})
+	}
+}
+
+// Ensure that "SSL_CERT_DIR" when used as the environment
+// variable delimited by colons, allows loadSystemRoots to
+// load all the roots from the respective directories.
+// See https://golang.org/issue/35325.
+func TestLoadSystemCertsLoadColonSeparatedDirs(t *testing.T) {
+	origFile, origDir := os.Getenv(certFileEnv), os.Getenv(certDirEnv)
+	origCertFiles := certFiles[:]
+
+	// To prevent any other certs from being loaded in
+	// through "SSL_CERT_FILE" or from known "certFiles",
+	// clear them all, and they'll be reverting on defer.
+	certFiles = certFiles[:0]
+	os.Setenv(certFileEnv, "")
+
+	defer func() {
+		certFiles = origCertFiles[:]
+		os.Setenv(certDirEnv, origDir)
+		os.Setenv(certFileEnv, origFile)
+	}()
+
+	tmpDir := t.TempDir()
+
+	rootPEMs := []string{
+		geoTrustRoot,
+		googleLeaf,
+		startComRoot,
+	}
+
+	var certDirs []string
+	for i, certPEM := range rootPEMs {
+		certDir := filepath.Join(tmpDir, fmt.Sprintf("cert-%d", i))
+		if err := os.MkdirAll(certDir, 0755); err != nil {
+			t.Fatalf("Failed to create certificate dir: %v", err)
+		}
+		certOutFile := filepath.Join(certDir, "cert.crt")
+		if err := os.WriteFile(certOutFile, []byte(certPEM), 0655); err != nil {
+			t.Fatalf("Failed to write certificate to file: %v", err)
+		}
+		certDirs = append(certDirs, certDir)
+	}
+
+	// Sanity check: the number of certDirs should be equal to the number of roots.
+	if g, w := len(certDirs), len(rootPEMs); g != w {
+		t.Fatalf("Failed sanity check: len(certsDir)=%d is not equal to len(rootsPEMS)=%d", g, w)
+	}
+
+	// Now finally concatenate them with a colon.
+	colonConcatCertDirs := strings.Join(certDirs, ":")
+	os.Setenv(certDirEnv, colonConcatCertDirs)
+	gotPool, err := loadSystemRoots()
+	if err != nil {
+		t.Fatalf("Failed to load system roots: %v", err)
+	}
+	subjects := gotPool.Subjects()
+	// We expect exactly len(rootPEMs) subjects back.
+	if g, w := len(subjects), len(rootPEMs); g != w {
+		t.Fatalf("Invalid number of subjects: got %d want %d", g, w)
+	}
+
+	wantPool := NewCertPool()
+	for _, certPEM := range rootPEMs {
+		wantPool.AppendCertsFromPEM([]byte(certPEM))
+	}
+	strCertPool := func(p *CertPool) string {
+		return string(bytes.Join(p.Subjects(), []byte("\n")))
+	}
+
+	if !certPoolEqual(gotPool, wantPool) {
+		g, w := strCertPool(gotPool), strCertPool(wantPool)
+		t.Fatalf("Mismatched certPools\nGot:\n%s\n\nWant:\n%s", g, w)
+	}
+}
+
+func TestReadUniqueDirectoryEntries(t *testing.T) {
+	tmp := t.TempDir()
+	temp := func(base string) string { return filepath.Join(tmp, base) }
+	if f, err := os.Create(temp("file")); err != nil {
+		t.Fatal(err)
+	} else {
+		f.Close()
+	}
+	if err := os.Symlink("target-in", temp("link-in")); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Symlink("../target-out", temp("link-out")); err != nil {
+		t.Fatal(err)
+	}
+	got, err := readUniqueDirectoryEntries(tmp)
+	if err != nil {
+		t.Fatal(err)
+	}
+	gotNames := []string{}
+	for _, fi := range got {
+		gotNames = append(gotNames, fi.Name())
+	}
+	wantNames := []string{"file", "link-out"}
+	if !reflect.DeepEqual(gotNames, wantNames) {
+		t.Errorf("got %q; want %q", gotNames, wantNames)
+	}
+}
diff --git a/src/crypto/x509/root_windows.go b/src/crypto/x509/root_windows.go
new file mode 100644
index 0000000..d65d876
--- /dev/null
+++ b/src/crypto/x509/root_windows.go
@@ -0,0 +1,277 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	"errors"
+	"syscall"
+	"unsafe"
+)
+
+func loadSystemRoots() (*CertPool, error) {
+	return &CertPool{systemPool: true}, nil
+}
+
+// Creates a new *syscall.CertContext representing the leaf certificate in an in-memory
+// certificate store containing itself and all of the intermediate certificates specified
+// in the opts.Intermediates CertPool.
+//
+// A pointer to the in-memory store is available in the returned CertContext's Store field.
+// The store is automatically freed when the CertContext is freed using
+// syscall.CertFreeCertificateContext.
+func createStoreContext(leaf *Certificate, opts *VerifyOptions) (*syscall.CertContext, error) {
+	var storeCtx *syscall.CertContext
+
+	leafCtx, err := syscall.CertCreateCertificateContext(syscall.X509_ASN_ENCODING|syscall.PKCS_7_ASN_ENCODING, &leaf.Raw[0], uint32(len(leaf.Raw)))
+	if err != nil {
+		return nil, err
+	}
+	defer syscall.CertFreeCertificateContext(leafCtx)
+
+	handle, err := syscall.CertOpenStore(syscall.CERT_STORE_PROV_MEMORY, 0, 0, syscall.CERT_STORE_DEFER_CLOSE_UNTIL_LAST_FREE_FLAG, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer syscall.CertCloseStore(handle, 0)
+
+	err = syscall.CertAddCertificateContextToStore(handle, leafCtx, syscall.CERT_STORE_ADD_ALWAYS, &storeCtx)
+	if err != nil {
+		return nil, err
+	}
+
+	if opts.Intermediates != nil {
+		for i := 0; i < opts.Intermediates.len(); i++ {
+			intermediate, err := opts.Intermediates.cert(i)
+			if err != nil {
+				return nil, err
+			}
+			ctx, err := syscall.CertCreateCertificateContext(syscall.X509_ASN_ENCODING|syscall.PKCS_7_ASN_ENCODING, &intermediate.Raw[0], uint32(len(intermediate.Raw)))
+			if err != nil {
+				return nil, err
+			}
+
+			err = syscall.CertAddCertificateContextToStore(handle, ctx, syscall.CERT_STORE_ADD_ALWAYS, nil)
+			syscall.CertFreeCertificateContext(ctx)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	return storeCtx, nil
+}
+
+// extractSimpleChain extracts the final certificate chain from a CertSimpleChain.
+func extractSimpleChain(simpleChain **syscall.CertSimpleChain, count int) (chain []*Certificate, err error) {
+	if simpleChain == nil || count == 0 {
+		return nil, errors.New("x509: invalid simple chain")
+	}
+
+	simpleChains := (*[1 << 20]*syscall.CertSimpleChain)(unsafe.Pointer(simpleChain))[:count:count]
+	lastChain := simpleChains[count-1]
+	elements := (*[1 << 20]*syscall.CertChainElement)(unsafe.Pointer(lastChain.Elements))[:lastChain.NumElements:lastChain.NumElements]
+	for i := 0; i < int(lastChain.NumElements); i++ {
+		// Copy the buf, since ParseCertificate does not create its own copy.
+		cert := elements[i].CertContext
+		encodedCert := (*[1 << 20]byte)(unsafe.Pointer(cert.EncodedCert))[:cert.Length:cert.Length]
+		buf := make([]byte, cert.Length)
+		copy(buf, encodedCert)
+		parsedCert, err := ParseCertificate(buf)
+		if err != nil {
+			return nil, err
+		}
+		chain = append(chain, parsedCert)
+	}
+
+	return chain, nil
+}
+
+// checkChainTrustStatus checks the trust status of the certificate chain, translating
+// any errors it finds into Go errors in the process.
+func checkChainTrustStatus(c *Certificate, chainCtx *syscall.CertChainContext) error {
+	if chainCtx.TrustStatus.ErrorStatus != syscall.CERT_TRUST_NO_ERROR {
+		status := chainCtx.TrustStatus.ErrorStatus
+		switch status {
+		case syscall.CERT_TRUST_IS_NOT_TIME_VALID:
+			return CertificateInvalidError{c, Expired, ""}
+		case syscall.CERT_TRUST_IS_NOT_VALID_FOR_USAGE:
+			return CertificateInvalidError{c, IncompatibleUsage, ""}
+		// TODO(filippo): surface more error statuses.
+		default:
+			return UnknownAuthorityError{c, nil, nil}
+		}
+	}
+	return nil
+}
+
+// checkChainSSLServerPolicy checks that the certificate chain in chainCtx is valid for
+// use as a certificate chain for a SSL/TLS server.
+func checkChainSSLServerPolicy(c *Certificate, chainCtx *syscall.CertChainContext, opts *VerifyOptions) error {
+	servernamep, err := syscall.UTF16PtrFromString(opts.DNSName)
+	if err != nil {
+		return err
+	}
+	sslPara := &syscall.SSLExtraCertChainPolicyPara{
+		AuthType:   syscall.AUTHTYPE_SERVER,
+		ServerName: servernamep,
+	}
+	sslPara.Size = uint32(unsafe.Sizeof(*sslPara))
+
+	para := &syscall.CertChainPolicyPara{
+		ExtraPolicyPara: (syscall.Pointer)(unsafe.Pointer(sslPara)),
+	}
+	para.Size = uint32(unsafe.Sizeof(*para))
+
+	status := syscall.CertChainPolicyStatus{}
+	err = syscall.CertVerifyCertificateChainPolicy(syscall.CERT_CHAIN_POLICY_SSL, chainCtx, para, &status)
+	if err != nil {
+		return err
+	}
+
+	// TODO(mkrautz): use the lChainIndex and lElementIndex fields
+	// of the CertChainPolicyStatus to provide proper context, instead
+	// using c.
+	if status.Error != 0 {
+		switch status.Error {
+		case syscall.CERT_E_EXPIRED:
+			return CertificateInvalidError{c, Expired, ""}
+		case syscall.CERT_E_CN_NO_MATCH:
+			return HostnameError{c, opts.DNSName}
+		case syscall.CERT_E_UNTRUSTEDROOT:
+			return UnknownAuthorityError{c, nil, nil}
+		default:
+			return UnknownAuthorityError{c, nil, nil}
+		}
+	}
+
+	return nil
+}
+
+// windowsExtKeyUsageOIDs are the C NUL-terminated string representations of the
+// OIDs for use with the Windows API.
+var windowsExtKeyUsageOIDs = make(map[ExtKeyUsage][]byte, len(extKeyUsageOIDs))
+
+func init() {
+	for _, eku := range extKeyUsageOIDs {
+		windowsExtKeyUsageOIDs[eku.extKeyUsage] = []byte(eku.oid.String() + "\x00")
+	}
+}
+
+func verifyChain(c *Certificate, chainCtx *syscall.CertChainContext, opts *VerifyOptions) (chain []*Certificate, err error) {
+	err = checkChainTrustStatus(c, chainCtx)
+	if err != nil {
+		return nil, err
+	}
+
+	if opts != nil && len(opts.DNSName) > 0 {
+		err = checkChainSSLServerPolicy(c, chainCtx, opts)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	chain, err = extractSimpleChain(chainCtx.Chains, int(chainCtx.ChainCount))
+	if err != nil {
+		return nil, err
+	}
+	if len(chain) == 0 {
+		return nil, errors.New("x509: internal error: system verifier returned an empty chain")
+	}
+
+	// Mitigate CVE-2020-0601, where the Windows system verifier might be
+	// tricked into using custom curve parameters for a trusted root, by
+	// double-checking all ECDSA signatures. If the system was tricked into
+	// using spoofed parameters, the signature will be invalid for the correct
+	// ones we parsed. (We don't support custom curves ourselves.)
+	for i, parent := range chain[1:] {
+		if parent.PublicKeyAlgorithm != ECDSA {
+			continue
+		}
+		if err := parent.CheckSignature(chain[i].SignatureAlgorithm,
+			chain[i].RawTBSCertificate, chain[i].Signature); err != nil {
+			return nil, err
+		}
+	}
+	return chain, nil
+}
+
+// systemVerify is like Verify, except that it uses CryptoAPI calls
+// to build certificate chains and verify them.
+func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate, err error) {
+	storeCtx, err := createStoreContext(c, opts)
+	if err != nil {
+		return nil, err
+	}
+	defer syscall.CertFreeCertificateContext(storeCtx)
+
+	para := new(syscall.CertChainPara)
+	para.Size = uint32(unsafe.Sizeof(*para))
+
+	keyUsages := opts.KeyUsages
+	if len(keyUsages) == 0 {
+		keyUsages = []ExtKeyUsage{ExtKeyUsageServerAuth}
+	}
+	oids := make([]*byte, 0, len(keyUsages))
+	for _, eku := range keyUsages {
+		if eku == ExtKeyUsageAny {
+			oids = nil
+			break
+		}
+		if oid, ok := windowsExtKeyUsageOIDs[eku]; ok {
+			oids = append(oids, &oid[0])
+		}
+	}
+	if oids != nil {
+		para.RequestedUsage.Type = syscall.USAGE_MATCH_TYPE_OR
+		para.RequestedUsage.Usage.Length = uint32(len(oids))
+		para.RequestedUsage.Usage.UsageIdentifiers = &oids[0]
+	} else {
+		para.RequestedUsage.Type = syscall.USAGE_MATCH_TYPE_AND
+		para.RequestedUsage.Usage.Length = 0
+		para.RequestedUsage.Usage.UsageIdentifiers = nil
+	}
+
+	var verifyTime *syscall.Filetime
+	if opts != nil && !opts.CurrentTime.IsZero() {
+		ft := syscall.NsecToFiletime(opts.CurrentTime.UnixNano())
+		verifyTime = &ft
+	}
+
+	// The default is to return only the highest quality chain,
+	// setting this flag will add additional lower quality contexts.
+	// These are returned in the LowerQualityChains field.
+	const CERT_CHAIN_RETURN_LOWER_QUALITY_CONTEXTS = 0x00000080
+
+	// CertGetCertificateChain will traverse Windows's root stores in an attempt to build a verified certificate chain
+	var topCtx *syscall.CertChainContext
+	err = syscall.CertGetCertificateChain(syscall.Handle(0), storeCtx, verifyTime, storeCtx.Store, para, CERT_CHAIN_RETURN_LOWER_QUALITY_CONTEXTS, 0, &topCtx)
+	if err != nil {
+		return nil, err
+	}
+	defer syscall.CertFreeCertificateChain(topCtx)
+
+	chain, topErr := verifyChain(c, topCtx, opts)
+	if topErr == nil {
+		chains = append(chains, chain)
+	}
+
+	if lqCtxCount := topCtx.LowerQualityChainCount; lqCtxCount > 0 {
+		lqCtxs := (*[1 << 20]*syscall.CertChainContext)(unsafe.Pointer(topCtx.LowerQualityChains))[:lqCtxCount:lqCtxCount]
+
+		for _, ctx := range lqCtxs {
+			chain, err := verifyChain(c, ctx, opts)
+			if err == nil {
+				chains = append(chains, chain)
+			}
+		}
+	}
+
+	if len(chains) == 0 {
+		// Return the error from the highest quality context.
+		return nil, topErr
+	}
+
+	return chains, nil
+}
diff --git a/src/crypto/x509/root_windows_test.go b/src/crypto/x509/root_windows_test.go
new file mode 100644
index 0000000..f6dafe4
--- /dev/null
+++ b/src/crypto/x509/root_windows_test.go
@@ -0,0 +1,115 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509_test
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"errors"
+	"internal/testenv"
+	"net"
+	"strings"
+	"syscall"
+	"testing"
+	"time"
+)
+
+func TestPlatformVerifier(t *testing.T) {
+	if !testenv.HasExternalNetwork() {
+		t.Skip()
+	}
+
+	getChain := func(t *testing.T, host string) []*x509.Certificate {
+		t.Helper()
+		c, err := tls.Dial("tcp", host+":443", &tls.Config{InsecureSkipVerify: true})
+		if err != nil {
+			// From https://docs.microsoft.com/en-us/windows/win32/winsock/windows-sockets-error-codes-2,
+			// matching the error string observed in https://go.dev/issue/52094.
+			const WSATRY_AGAIN syscall.Errno = 11002
+			var errDNS *net.DNSError
+			if strings.HasSuffix(host, ".badssl.com") && errors.As(err, &errDNS) && strings.HasSuffix(errDNS.Err, WSATRY_AGAIN.Error()) {
+				t.Log(err)
+				testenv.SkipFlaky(t, 52094)
+			}
+
+			t.Fatalf("tls connection failed: %s", err)
+		}
+		return c.ConnectionState().PeerCertificates
+	}
+
+	tests := []struct {
+		name        string
+		host        string
+		verifyName  string
+		verifyTime  time.Time
+		expectedErr string
+	}{
+		{
+			// whatever google.com serves should, hopefully, be trusted
+			name: "valid chain",
+			host: "google.com",
+		},
+		{
+			name:        "expired leaf",
+			host:        "expired.badssl.com",
+			expectedErr: "x509: certificate has expired or is not yet valid: ",
+		},
+		{
+			name:        "wrong host for leaf",
+			host:        "wrong.host.badssl.com",
+			verifyName:  "wrong.host.badssl.com",
+			expectedErr: "x509: certificate is valid for *.badssl.com, badssl.com, not wrong.host.badssl.com",
+		},
+		{
+			name:        "self-signed leaf",
+			host:        "self-signed.badssl.com",
+			expectedErr: "x509: certificate signed by unknown authority",
+		},
+		{
+			name:        "untrusted root",
+			host:        "untrusted-root.badssl.com",
+			expectedErr: "x509: certificate signed by unknown authority",
+		},
+		{
+			name:        "expired leaf (custom time)",
+			host:        "google.com",
+			verifyTime:  time.Time{}.Add(time.Hour),
+			expectedErr: "x509: certificate has expired or is not yet valid: ",
+		},
+		{
+			name:       "valid chain (custom time)",
+			host:       "google.com",
+			verifyTime: time.Now(),
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			chain := getChain(t, tc.host)
+			var opts x509.VerifyOptions
+			if len(chain) > 1 {
+				opts.Intermediates = x509.NewCertPool()
+				for _, c := range chain[1:] {
+					opts.Intermediates.AddCert(c)
+				}
+			}
+			if tc.verifyName != "" {
+				opts.DNSName = tc.verifyName
+			}
+			if !tc.verifyTime.IsZero() {
+				opts.CurrentTime = tc.verifyTime
+			}
+
+			_, err := chain[0].Verify(opts)
+			if err != nil && tc.expectedErr == "" {
+				t.Errorf("unexpected verification error: %s", err)
+			} else if err != nil && err.Error() != tc.expectedErr {
+				t.Errorf("unexpected verification error: got %q, want %q", err.Error(), tc.expectedErr)
+			} else if err == nil && tc.expectedErr != "" {
+				t.Errorf("unexpected verification success: want %q", tc.expectedErr)
+			}
+		})
+	}
+}
diff --git a/src/crypto/x509/sec1.go b/src/crypto/x509/sec1.go
new file mode 100644
index 0000000..52c108f
--- /dev/null
+++ b/src/crypto/x509/sec1.go
@@ -0,0 +1,120 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"encoding/asn1"
+	"errors"
+	"fmt"
+	"math/big"
+)
+
+const ecPrivKeyVersion = 1
+
+// ecPrivateKey reflects an ASN.1 Elliptic Curve Private Key Structure.
+// References:
+//   RFC 5915
+//   SEC1 - http://www.secg.org/sec1-v2.pdf
+// Per RFC 5915 the NamedCurveOID is marked as ASN.1 OPTIONAL, however in
+// most cases it is not.
+type ecPrivateKey struct {
+	Version       int
+	PrivateKey    []byte
+	NamedCurveOID asn1.ObjectIdentifier `asn1:"optional,explicit,tag:0"`
+	PublicKey     asn1.BitString        `asn1:"optional,explicit,tag:1"`
+}
+
+// ParseECPrivateKey parses an EC private key in SEC 1, ASN.1 DER form.
+//
+// This kind of key is commonly encoded in PEM blocks of type "EC PRIVATE KEY".
+func ParseECPrivateKey(der []byte) (*ecdsa.PrivateKey, error) {
+	return parseECPrivateKey(nil, der)
+}
+
+// MarshalECPrivateKey converts an EC private key to SEC 1, ASN.1 DER form.
+//
+// This kind of key is commonly encoded in PEM blocks of type "EC PRIVATE KEY".
+// For a more flexible key format which is not EC specific, use
+// MarshalPKCS8PrivateKey.
+func MarshalECPrivateKey(key *ecdsa.PrivateKey) ([]byte, error) {
+	oid, ok := oidFromNamedCurve(key.Curve)
+	if !ok {
+		return nil, errors.New("x509: unknown elliptic curve")
+	}
+
+	return marshalECPrivateKeyWithOID(key, oid)
+}
+
+// marshalECPrivateKey marshals an EC private key into ASN.1, DER format and
+// sets the curve ID to the given OID, or omits it if OID is nil.
+func marshalECPrivateKeyWithOID(key *ecdsa.PrivateKey, oid asn1.ObjectIdentifier) ([]byte, error) {
+	privateKey := make([]byte, (key.Curve.Params().N.BitLen()+7)/8)
+	return asn1.Marshal(ecPrivateKey{
+		Version:       1,
+		PrivateKey:    key.D.FillBytes(privateKey),
+		NamedCurveOID: oid,
+		PublicKey:     asn1.BitString{Bytes: elliptic.Marshal(key.Curve, key.X, key.Y)},
+	})
+}
+
+// parseECPrivateKey parses an ASN.1 Elliptic Curve Private Key Structure.
+// The OID for the named curve may be provided from another source (such as
+// the PKCS8 container) - if it is provided then use this instead of the OID
+// that may exist in the EC private key structure.
+func parseECPrivateKey(namedCurveOID *asn1.ObjectIdentifier, der []byte) (key *ecdsa.PrivateKey, err error) {
+	var privKey ecPrivateKey
+	if _, err := asn1.Unmarshal(der, &privKey); err != nil {
+		if _, err := asn1.Unmarshal(der, &pkcs8{}); err == nil {
+			return nil, errors.New("x509: failed to parse private key (use ParsePKCS8PrivateKey instead for this key format)")
+		}
+		if _, err := asn1.Unmarshal(der, &pkcs1PrivateKey{}); err == nil {
+			return nil, errors.New("x509: failed to parse private key (use ParsePKCS1PrivateKey instead for this key format)")
+		}
+		return nil, errors.New("x509: failed to parse EC private key: " + err.Error())
+	}
+	if privKey.Version != ecPrivKeyVersion {
+		return nil, fmt.Errorf("x509: unknown EC private key version %d", privKey.Version)
+	}
+
+	var curve elliptic.Curve
+	if namedCurveOID != nil {
+		curve = namedCurveFromOID(*namedCurveOID)
+	} else {
+		curve = namedCurveFromOID(privKey.NamedCurveOID)
+	}
+	if curve == nil {
+		return nil, errors.New("x509: unknown elliptic curve")
+	}
+
+	k := new(big.Int).SetBytes(privKey.PrivateKey)
+	curveOrder := curve.Params().N
+	if k.Cmp(curveOrder) >= 0 {
+		return nil, errors.New("x509: invalid elliptic curve private key value")
+	}
+	priv := new(ecdsa.PrivateKey)
+	priv.Curve = curve
+	priv.D = k
+
+	privateKey := make([]byte, (curveOrder.BitLen()+7)/8)
+
+	// Some private keys have leading zero padding. This is invalid
+	// according to [SEC1], but this code will ignore it.
+	for len(privKey.PrivateKey) > len(privateKey) {
+		if privKey.PrivateKey[0] != 0 {
+			return nil, errors.New("x509: invalid private key length")
+		}
+		privKey.PrivateKey = privKey.PrivateKey[1:]
+	}
+
+	// Some private keys remove all leading zeros, this is also invalid
+	// according to [SEC1] but since OpenSSL used to do this, we ignore
+	// this too.
+	copy(privateKey[len(privateKey)-len(privKey.PrivateKey):], privKey.PrivateKey)
+	priv.X, priv.Y = curve.ScalarBaseMult(privateKey)
+
+	return priv, nil
+}
diff --git a/src/crypto/x509/sec1_test.go b/src/crypto/x509/sec1_test.go
new file mode 100644
index 0000000..9ac2518
--- /dev/null
+++ b/src/crypto/x509/sec1_test.go
@@ -0,0 +1,66 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	"bytes"
+	"encoding/hex"
+	"strings"
+	"testing"
+)
+
+var ecKeyTests = []struct {
+	derHex            string
+	shouldReserialize bool
+}{
+	// Generated using:
+	//   openssl ecparam -genkey -name secp384r1 -outform PEM
+	{"3081a40201010430bdb9839c08ee793d1157886a7a758a3c8b2a17a4df48f17ace57c72c56b4723cf21dcda21d4e1ad57ff034f19fcfd98ea00706052b81040022a16403620004feea808b5ee2429cfcce13c32160e1c960990bd050bb0fdf7222f3decd0a55008e32a6aa3c9062051c4cba92a7a3b178b24567412d43cdd2f882fa5addddd726fe3e208d2c26d733a773a597abb749714df7256ead5105fa6e7b3650de236b50", true},
+	// This key was generated by GnuTLS and has illegal zero-padding of the
+	// private key. See https://golang.org/issues/13699.
+	{"3078020101042100f9f43a04b9bdc3ab01f53be6df80e7a7bc3eaf7b87fc24e630a4a0aa97633645a00a06082a8648ce3d030107a1440342000441a51bc318461b4c39a45048a16d4fc2a935b1ea7fe86e8c1fa219d6f2438f7c7fd62957d3442efb94b6a23eb0ea66dda663dc42f379cda6630b21b7888a5d3d", false},
+	// This was generated using an old version of OpenSSL and is missing a
+	// leading zero byte in the private key that should be present.
+	{"3081db0201010441607b4f985774ac21e633999794542e09312073480baa69550914d6d43d8414441e61b36650567901da714f94dffb3ce0e2575c31928a0997d51df5c440e983ca17a00706052b81040023a181890381860004001661557afedd7ac8d6b70e038e576558c626eb62edda36d29c3a1310277c11f67a8c6f949e5430a37dcfb95d902c1b5b5379c389873b9dd17be3bdb088a4774a7401072f830fb9a08d93bfa50a03dd3292ea07928724ddb915d831917a338f6b0aecfbc3cf5352c4a1295d356890c41c34116d29eeb93779aab9d9d78e2613437740f6", false},
+}
+
+func TestParseECPrivateKey(t *testing.T) {
+	for i, test := range ecKeyTests {
+		derBytes, _ := hex.DecodeString(test.derHex)
+		key, err := ParseECPrivateKey(derBytes)
+		if err != nil {
+			t.Fatalf("#%d: failed to decode EC private key: %s", i, err)
+		}
+		serialized, err := MarshalECPrivateKey(key)
+		if err != nil {
+			t.Fatalf("#%d: failed to encode EC private key: %s", i, err)
+		}
+		matches := bytes.Equal(serialized, derBytes)
+		if matches != test.shouldReserialize {
+			t.Fatalf("#%d: when serializing key: matches=%t, should match=%t: original %x, reserialized %x", i, matches, test.shouldReserialize, serialized, derBytes)
+		}
+	}
+}
+
+const hexECTestPKCS1Key = "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"
+const hexECTestPKCS8Key = "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"
+
+var ecMismatchKeyTests = []struct {
+	hexKey        string
+	errorContains string
+}{
+	{hexKey: hexECTestPKCS8Key, errorContains: "use ParsePKCS8PrivateKey instead"},
+	{hexKey: hexECTestPKCS1Key, errorContains: "use ParsePKCS1PrivateKey instead"},
+}
+
+func TestECMismatchKeyFormat(t *testing.T) {
+	for i, test := range ecMismatchKeyTests {
+		derBytes, _ := hex.DecodeString(test.hexKey)
+		_, err := ParseECPrivateKey(derBytes)
+		if !strings.Contains(err.Error(), test.errorContains) {
+			t.Errorf("#%d: expected error containing %q, got %s", i, test.errorContains, err)
+		}
+	}
+}
diff --git a/src/crypto/x509/test-file.crt b/src/crypto/x509/test-file.crt
new file mode 100644
index 0000000..caa83b9
--- /dev/null
+++ b/src/crypto/x509/test-file.crt
@@ -0,0 +1,32 @@
+-----BEGIN CERTIFICATE-----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+CSqGSIb3DQEBCwUAA4ICAQB3sCntCcQwhMgRPPyvOCMyTcQ/Iv+cpfxz2Ck14nlx
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+r05pE3PdHn9JrCl4iWdVlgtiI9BoPtQyDfa/OEFaScE8KYR8LxaAgdgp3zYncWls
+BpwQ6Y/A2wIkhlD9eEp5Ib2hz7isXOs9UwjdriKqrBXqcIAE5M+YIk3+KAQKxAtd
+4YsK3CSJ010uphr12YKqlScj4vuKFjuOtd5RyyMIxUG3lrrhAu2AzCeKCLdVgA8+
+75FrYMApUdvcjp4uzbBoED4XRQlx9kdFHVbYgmE/+yddBYJM8u4YlgAL0hW2/D8p
+z9JWIfxVmjJnBnXaKGBuiUyZ864A3PJndP6EMMo7TzS2CDnfCYuJjvI0KvDjFNmc
+rQA04+qfMSEz3nmKhbbZu4eYLzlADhfH8tT4GMtXf71WLA5AUHGf2Y4+HIHTsmHG
+vQ==
+-----END CERTIFICATE-----
diff --git a/src/crypto/x509/testdata/test-dir.crt b/src/crypto/x509/testdata/test-dir.crt
new file mode 100644
index 0000000..b7fc9c5
--- /dev/null
+++ b/src/crypto/x509/testdata/test-dir.crt
@@ -0,0 +1,31 @@
+-----BEGIN CERTIFICATE-----
+MIIFazCCA1OgAwIBAgIJAL8a/lsnspOqMA0GCSqGSIb3DQEBCwUAMEwxCzAJBgNV
+BAYTAlVLMRMwEQYDVQQIDApUZXN0LVN0YXRlMRUwEwYDVQQKDAxHb2xhbmcgVGVz
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+Xlxc/qijM8set/nOqp7hVd5J0uG6qdwLRILUddZ6OpXd7ZNi1EXg+Bpc7ehzGsDt
+3UFGzYXDjxYnK2frQfjLS8stOQIqSrGthW6x0fdkVx0y8BByvd5J6+JmZl4UZfzA
+m99VxXSt4B9x6BvnY7ktzcFDOjtuLc4B/7yg9fv1eQuStA4cHGGAttsCg1X/Kx8W
+PvkkeH0UWDZ9vhH9K36703z89da6MWF+bz92B0+4HoOmlVaXRkvblsNaynJnL0LC
+Ayry7QBxuh5cMnDdRwJB3AVJIiJ1GVpb7aGvBOnx+s2lwRv9HWtghb+cbwwktx1M
+JHyBf3GZNSWTpKY7cD8V+NnBv3UuioOVVo+XAU4LF/bYUjdRpxWADJizNtZrtFo=
+-----END CERTIFICATE-----
diff --git a/src/crypto/x509/verify.go b/src/crypto/x509/verify.go
new file mode 100644
index 0000000..4be4eb6
--- /dev/null
+++ b/src/crypto/x509/verify.go
@@ -0,0 +1,1114 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"net"
+	"net/url"
+	"reflect"
+	"runtime"
+	"strings"
+	"time"
+	"unicode/utf8"
+)
+
+type InvalidReason int
+
+const (
+	// NotAuthorizedToSign results when a certificate is signed by another
+	// which isn't marked as a CA certificate.
+	NotAuthorizedToSign InvalidReason = iota
+	// Expired results when a certificate has expired, based on the time
+	// given in the VerifyOptions.
+	Expired
+	// CANotAuthorizedForThisName results when an intermediate or root
+	// certificate has a name constraint which doesn't permit a DNS or
+	// other name (including IP address) in the leaf certificate.
+	CANotAuthorizedForThisName
+	// TooManyIntermediates results when a path length constraint is
+	// violated.
+	TooManyIntermediates
+	// IncompatibleUsage results when the certificate's key usage indicates
+	// that it may only be used for a different purpose.
+	IncompatibleUsage
+	// NameMismatch results when the subject name of a parent certificate
+	// does not match the issuer name in the child.
+	NameMismatch
+	// NameConstraintsWithoutSANs is a legacy error and is no longer returned.
+	NameConstraintsWithoutSANs
+	// UnconstrainedName results when a CA certificate contains permitted
+	// name constraints, but leaf certificate contains a name of an
+	// unsupported or unconstrained type.
+	UnconstrainedName
+	// TooManyConstraints results when the number of comparison operations
+	// needed to check a certificate exceeds the limit set by
+	// VerifyOptions.MaxConstraintComparisions. This limit exists to
+	// prevent pathological certificates can consuming excessive amounts of
+	// CPU time to verify.
+	TooManyConstraints
+	// CANotAuthorizedForExtKeyUsage results when an intermediate or root
+	// certificate does not permit a requested extended key usage.
+	CANotAuthorizedForExtKeyUsage
+)
+
+// CertificateInvalidError results when an odd error occurs. Users of this
+// library probably want to handle all these errors uniformly.
+type CertificateInvalidError struct {
+	Cert   *Certificate
+	Reason InvalidReason
+	Detail string
+}
+
+func (e CertificateInvalidError) Error() string {
+	switch e.Reason {
+	case NotAuthorizedToSign:
+		return "x509: certificate is not authorized to sign other certificates"
+	case Expired:
+		return "x509: certificate has expired or is not yet valid: " + e.Detail
+	case CANotAuthorizedForThisName:
+		return "x509: a root or intermediate certificate is not authorized to sign for this name: " + e.Detail
+	case CANotAuthorizedForExtKeyUsage:
+		return "x509: a root or intermediate certificate is not authorized for an extended key usage: " + e.Detail
+	case TooManyIntermediates:
+		return "x509: too many intermediates for path length constraint"
+	case IncompatibleUsage:
+		return "x509: certificate specifies an incompatible key usage"
+	case NameMismatch:
+		return "x509: issuer name does not match subject from issuing certificate"
+	case NameConstraintsWithoutSANs:
+		return "x509: issuer has name constraints but leaf doesn't have a SAN extension"
+	case UnconstrainedName:
+		return "x509: issuer has name constraints but leaf contains unknown or unconstrained name: " + e.Detail
+	}
+	return "x509: unknown error"
+}
+
+// HostnameError results when the set of authorized names doesn't match the
+// requested name.
+type HostnameError struct {
+	Certificate *Certificate
+	Host        string
+}
+
+func (h HostnameError) Error() string {
+	c := h.Certificate
+
+	if !c.hasSANExtension() && matchHostnames(c.Subject.CommonName, h.Host) {
+		return "x509: certificate relies on legacy Common Name field, use SANs instead"
+	}
+
+	var valid string
+	if ip := net.ParseIP(h.Host); ip != nil {
+		// Trying to validate an IP
+		if len(c.IPAddresses) == 0 {
+			return "x509: cannot validate certificate for " + h.Host + " because it doesn't contain any IP SANs"
+		}
+		for _, san := range c.IPAddresses {
+			if len(valid) > 0 {
+				valid += ", "
+			}
+			valid += san.String()
+		}
+	} else {
+		valid = strings.Join(c.DNSNames, ", ")
+	}
+
+	if len(valid) == 0 {
+		return "x509: certificate is not valid for any names, but wanted to match " + h.Host
+	}
+	return "x509: certificate is valid for " + valid + ", not " + h.Host
+}
+
+// UnknownAuthorityError results when the certificate issuer is unknown
+type UnknownAuthorityError struct {
+	Cert *Certificate
+	// hintErr contains an error that may be helpful in determining why an
+	// authority wasn't found.
+	hintErr error
+	// hintCert contains a possible authority certificate that was rejected
+	// because of the error in hintErr.
+	hintCert *Certificate
+}
+
+func (e UnknownAuthorityError) Error() string {
+	s := "x509: certificate signed by unknown authority"
+	if e.hintErr != nil {
+		certName := e.hintCert.Subject.CommonName
+		if len(certName) == 0 {
+			if len(e.hintCert.Subject.Organization) > 0 {
+				certName = e.hintCert.Subject.Organization[0]
+			} else {
+				certName = "serial:" + e.hintCert.SerialNumber.String()
+			}
+		}
+		s += fmt.Sprintf(" (possibly because of %q while trying to verify candidate authority certificate %q)", e.hintErr, certName)
+	}
+	return s
+}
+
+// SystemRootsError results when we fail to load the system root certificates.
+type SystemRootsError struct {
+	Err error
+}
+
+func (se SystemRootsError) Error() string {
+	msg := "x509: failed to load system roots and no roots provided"
+	if se.Err != nil {
+		return msg + "; " + se.Err.Error()
+	}
+	return msg
+}
+
+func (se SystemRootsError) Unwrap() error { return se.Err }
+
+// errNotParsed is returned when a certificate without ASN.1 contents is
+// verified. Platform-specific verification needs the ASN.1 contents.
+var errNotParsed = errors.New("x509: missing ASN.1 contents; use ParseCertificate")
+
+// VerifyOptions contains parameters for Certificate.Verify.
+type VerifyOptions struct {
+	// DNSName, if set, is checked against the leaf certificate with
+	// Certificate.VerifyHostname or the platform verifier.
+	DNSName string
+
+	// Intermediates is an optional pool of certificates that are not trust
+	// anchors, but can be used to form a chain from the leaf certificate to a
+	// root certificate.
+	Intermediates *CertPool
+	// Roots is the set of trusted root certificates the leaf certificate needs
+	// to chain up to. If nil, the system roots or the platform verifier are used.
+	Roots *CertPool
+
+	// CurrentTime is used to check the validity of all certificates in the
+	// chain. If zero, the current time is used.
+	CurrentTime time.Time
+
+	// KeyUsages specifies which Extended Key Usage values are acceptable. A
+	// chain is accepted if it allows any of the listed values. An empty list
+	// means ExtKeyUsageServerAuth. To accept any key usage, include ExtKeyUsageAny.
+	KeyUsages []ExtKeyUsage
+
+	// MaxConstraintComparisions is the maximum number of comparisons to
+	// perform when checking a given certificate's name constraints. If
+	// zero, a sensible default is used. This limit prevents pathological
+	// certificates from consuming excessive amounts of CPU time when
+	// validating. It does not apply to the platform verifier.
+	MaxConstraintComparisions int
+}
+
+const (
+	leafCertificate = iota
+	intermediateCertificate
+	rootCertificate
+)
+
+// rfc2821Mailbox represents a “mailbox” (which is an email address to most
+// people) by breaking it into the “local” (i.e. before the '@') and “domain”
+// parts.
+type rfc2821Mailbox struct {
+	local, domain string
+}
+
+// parseRFC2821Mailbox parses an email address into local and domain parts,
+// based on the ABNF for a “Mailbox” from RFC 2821. According to RFC 5280,
+// Section 4.2.1.6 that's correct for an rfc822Name from a certificate: “The
+// format of an rfc822Name is a "Mailbox" as defined in RFC 2821, Section 4.1.2”.
+func parseRFC2821Mailbox(in string) (mailbox rfc2821Mailbox, ok bool) {
+	if len(in) == 0 {
+		return mailbox, false
+	}
+
+	localPartBytes := make([]byte, 0, len(in)/2)
+
+	if in[0] == '"' {
+		// Quoted-string = DQUOTE *qcontent DQUOTE
+		// non-whitespace-control = %d1-8 / %d11 / %d12 / %d14-31 / %d127
+		// qcontent = qtext / quoted-pair
+		// qtext = non-whitespace-control /
+		//         %d33 / %d35-91 / %d93-126
+		// quoted-pair = ("\" text) / obs-qp
+		// text = %d1-9 / %d11 / %d12 / %d14-127 / obs-text
+		//
+		// (Names beginning with “obs-” are the obsolete syntax from RFC 2822,
+		// Section 4. Since it has been 16 years, we no longer accept that.)
+		in = in[1:]
+	QuotedString:
+		for {
+			if len(in) == 0 {
+				return mailbox, false
+			}
+			c := in[0]
+			in = in[1:]
+
+			switch {
+			case c == '"':
+				break QuotedString
+
+			case c == '\\':
+				// quoted-pair
+				if len(in) == 0 {
+					return mailbox, false
+				}
+				if in[0] == 11 ||
+					in[0] == 12 ||
+					(1 <= in[0] && in[0] <= 9) ||
+					(14 <= in[0] && in[0] <= 127) {
+					localPartBytes = append(localPartBytes, in[0])
+					in = in[1:]
+				} else {
+					return mailbox, false
+				}
+
+			case c == 11 ||
+				c == 12 ||
+				// Space (char 32) is not allowed based on the
+				// BNF, but RFC 3696 gives an example that
+				// assumes that it is. Several “verified”
+				// errata continue to argue about this point.
+				// We choose to accept it.
+				c == 32 ||
+				c == 33 ||
+				c == 127 ||
+				(1 <= c && c <= 8) ||
+				(14 <= c && c <= 31) ||
+				(35 <= c && c <= 91) ||
+				(93 <= c && c <= 126):
+				// qtext
+				localPartBytes = append(localPartBytes, c)
+
+			default:
+				return mailbox, false
+			}
+		}
+	} else {
+		// Atom ("." Atom)*
+	NextChar:
+		for len(in) > 0 {
+			// atext from RFC 2822, Section 3.2.4
+			c := in[0]
+
+			switch {
+			case c == '\\':
+				// Examples given in RFC 3696 suggest that
+				// escaped characters can appear outside of a
+				// quoted string. Several “verified” errata
+				// continue to argue the point. We choose to
+				// accept it.
+				in = in[1:]
+				if len(in) == 0 {
+					return mailbox, false
+				}
+				fallthrough
+
+			case ('0' <= c && c <= '9') ||
+				('a' <= c && c <= 'z') ||
+				('A' <= c && c <= 'Z') ||
+				c == '!' || c == '#' || c == '$' || c == '%' ||
+				c == '&' || c == '\'' || c == '*' || c == '+' ||
+				c == '-' || c == '/' || c == '=' || c == '?' ||
+				c == '^' || c == '_' || c == '`' || c == '{' ||
+				c == '|' || c == '}' || c == '~' || c == '.':
+				localPartBytes = append(localPartBytes, in[0])
+				in = in[1:]
+
+			default:
+				break NextChar
+			}
+		}
+
+		if len(localPartBytes) == 0 {
+			return mailbox, false
+		}
+
+		// From RFC 3696, Section 3:
+		// “period (".") may also appear, but may not be used to start
+		// or end the local part, nor may two or more consecutive
+		// periods appear.”
+		twoDots := []byte{'.', '.'}
+		if localPartBytes[0] == '.' ||
+			localPartBytes[len(localPartBytes)-1] == '.' ||
+			bytes.Contains(localPartBytes, twoDots) {
+			return mailbox, false
+		}
+	}
+
+	if len(in) == 0 || in[0] != '@' {
+		return mailbox, false
+	}
+	in = in[1:]
+
+	// The RFC species a format for domains, but that's known to be
+	// violated in practice so we accept that anything after an '@' is the
+	// domain part.
+	if _, ok := domainToReverseLabels(in); !ok {
+		return mailbox, false
+	}
+
+	mailbox.local = string(localPartBytes)
+	mailbox.domain = in
+	return mailbox, true
+}
+
+// domainToReverseLabels converts a textual domain name like foo.example.com to
+// the list of labels in reverse order, e.g. ["com", "example", "foo"].
+func domainToReverseLabels(domain string) (reverseLabels []string, ok bool) {
+	for len(domain) > 0 {
+		if i := strings.LastIndexByte(domain, '.'); i == -1 {
+			reverseLabels = append(reverseLabels, domain)
+			domain = ""
+		} else {
+			reverseLabels = append(reverseLabels, domain[i+1:])
+			domain = domain[:i]
+		}
+	}
+
+	if len(reverseLabels) > 0 && len(reverseLabels[0]) == 0 {
+		// An empty label at the end indicates an absolute value.
+		return nil, false
+	}
+
+	for _, label := range reverseLabels {
+		if len(label) == 0 {
+			// Empty labels are otherwise invalid.
+			return nil, false
+		}
+
+		for _, c := range label {
+			if c < 33 || c > 126 {
+				// Invalid character.
+				return nil, false
+			}
+		}
+	}
+
+	return reverseLabels, true
+}
+
+func matchEmailConstraint(mailbox rfc2821Mailbox, constraint string) (bool, error) {
+	// If the constraint contains an @, then it specifies an exact mailbox
+	// name.
+	if strings.Contains(constraint, "@") {
+		constraintMailbox, ok := parseRFC2821Mailbox(constraint)
+		if !ok {
+			return false, fmt.Errorf("x509: internal error: cannot parse constraint %q", constraint)
+		}
+		return mailbox.local == constraintMailbox.local && strings.EqualFold(mailbox.domain, constraintMailbox.domain), nil
+	}
+
+	// Otherwise the constraint is like a DNS constraint of the domain part
+	// of the mailbox.
+	return matchDomainConstraint(mailbox.domain, constraint)
+}
+
+func matchURIConstraint(uri *url.URL, constraint string) (bool, error) {
+	// From RFC 5280, Section 4.2.1.10:
+	// “a uniformResourceIdentifier that does not include an authority
+	// component with a host name specified as a fully qualified domain
+	// name (e.g., if the URI either does not include an authority
+	// component or includes an authority component in which the host name
+	// is specified as an IP address), then the application MUST reject the
+	// certificate.”
+
+	host := uri.Host
+	if len(host) == 0 {
+		return false, fmt.Errorf("URI with empty host (%q) cannot be matched against constraints", uri.String())
+	}
+
+	if strings.Contains(host, ":") && !strings.HasSuffix(host, "]") {
+		var err error
+		host, _, err = net.SplitHostPort(uri.Host)
+		if err != nil {
+			return false, err
+		}
+	}
+
+	if strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]") ||
+		net.ParseIP(host) != nil {
+		return false, fmt.Errorf("URI with IP (%q) cannot be matched against constraints", uri.String())
+	}
+
+	return matchDomainConstraint(host, constraint)
+}
+
+func matchIPConstraint(ip net.IP, constraint *net.IPNet) (bool, error) {
+	if len(ip) != len(constraint.IP) {
+		return false, nil
+	}
+
+	for i := range ip {
+		if mask := constraint.Mask[i]; ip[i]&mask != constraint.IP[i]&mask {
+			return false, nil
+		}
+	}
+
+	return true, nil
+}
+
+func matchDomainConstraint(domain, constraint string) (bool, error) {
+	// The meaning of zero length constraints is not specified, but this
+	// code follows NSS and accepts them as matching everything.
+	if len(constraint) == 0 {
+		return true, nil
+	}
+
+	domainLabels, ok := domainToReverseLabels(domain)
+	if !ok {
+		return false, fmt.Errorf("x509: internal error: cannot parse domain %q", domain)
+	}
+
+	// RFC 5280 says that a leading period in a domain name means that at
+	// least one label must be prepended, but only for URI and email
+	// constraints, not DNS constraints. The code also supports that
+	// behaviour for DNS constraints.
+
+	mustHaveSubdomains := false
+	if constraint[0] == '.' {
+		mustHaveSubdomains = true
+		constraint = constraint[1:]
+	}
+
+	constraintLabels, ok := domainToReverseLabels(constraint)
+	if !ok {
+		return false, fmt.Errorf("x509: internal error: cannot parse domain %q", constraint)
+	}
+
+	if len(domainLabels) < len(constraintLabels) ||
+		(mustHaveSubdomains && len(domainLabels) == len(constraintLabels)) {
+		return false, nil
+	}
+
+	for i, constraintLabel := range constraintLabels {
+		if !strings.EqualFold(constraintLabel, domainLabels[i]) {
+			return false, nil
+		}
+	}
+
+	return true, nil
+}
+
+// checkNameConstraints checks that c permits a child certificate to claim the
+// given name, of type nameType. The argument parsedName contains the parsed
+// form of name, suitable for passing to the match function. The total number
+// of comparisons is tracked in the given count and should not exceed the given
+// limit.
+func (c *Certificate) checkNameConstraints(count *int,
+	maxConstraintComparisons int,
+	nameType string,
+	name string,
+	parsedName any,
+	match func(parsedName, constraint any) (match bool, err error),
+	permitted, excluded any) error {
+
+	excludedValue := reflect.ValueOf(excluded)
+
+	*count += excludedValue.Len()
+	if *count > maxConstraintComparisons {
+		return CertificateInvalidError{c, TooManyConstraints, ""}
+	}
+
+	for i := 0; i < excludedValue.Len(); i++ {
+		constraint := excludedValue.Index(i).Interface()
+		match, err := match(parsedName, constraint)
+		if err != nil {
+			return CertificateInvalidError{c, CANotAuthorizedForThisName, err.Error()}
+		}
+
+		if match {
+			return CertificateInvalidError{c, CANotAuthorizedForThisName, fmt.Sprintf("%s %q is excluded by constraint %q", nameType, name, constraint)}
+		}
+	}
+
+	permittedValue := reflect.ValueOf(permitted)
+
+	*count += permittedValue.Len()
+	if *count > maxConstraintComparisons {
+		return CertificateInvalidError{c, TooManyConstraints, ""}
+	}
+
+	ok := true
+	for i := 0; i < permittedValue.Len(); i++ {
+		constraint := permittedValue.Index(i).Interface()
+
+		var err error
+		if ok, err = match(parsedName, constraint); err != nil {
+			return CertificateInvalidError{c, CANotAuthorizedForThisName, err.Error()}
+		}
+
+		if ok {
+			break
+		}
+	}
+
+	if !ok {
+		return CertificateInvalidError{c, CANotAuthorizedForThisName, fmt.Sprintf("%s %q is not permitted by any constraint", nameType, name)}
+	}
+
+	return nil
+}
+
+// isValid performs validity checks on c given that it is a candidate to append
+// to the chain in currentChain.
+func (c *Certificate) isValid(certType int, currentChain []*Certificate, opts *VerifyOptions) error {
+	if len(c.UnhandledCriticalExtensions) > 0 {
+		return UnhandledCriticalExtension{}
+	}
+
+	if len(currentChain) > 0 {
+		child := currentChain[len(currentChain)-1]
+		if !bytes.Equal(child.RawIssuer, c.RawSubject) {
+			return CertificateInvalidError{c, NameMismatch, ""}
+		}
+	}
+
+	now := opts.CurrentTime
+	if now.IsZero() {
+		now = time.Now()
+	}
+	if now.Before(c.NotBefore) {
+		return CertificateInvalidError{
+			Cert:   c,
+			Reason: Expired,
+			Detail: fmt.Sprintf("current time %s is before %s", now.Format(time.RFC3339), c.NotBefore.Format(time.RFC3339)),
+		}
+	} else if now.After(c.NotAfter) {
+		return CertificateInvalidError{
+			Cert:   c,
+			Reason: Expired,
+			Detail: fmt.Sprintf("current time %s is after %s", now.Format(time.RFC3339), c.NotAfter.Format(time.RFC3339)),
+		}
+	}
+
+	maxConstraintComparisons := opts.MaxConstraintComparisions
+	if maxConstraintComparisons == 0 {
+		maxConstraintComparisons = 250000
+	}
+	comparisonCount := 0
+
+	var leaf *Certificate
+	if certType == intermediateCertificate || certType == rootCertificate {
+		if len(currentChain) == 0 {
+			return errors.New("x509: internal error: empty chain when appending CA cert")
+		}
+		leaf = currentChain[0]
+	}
+
+	if (certType == intermediateCertificate || certType == rootCertificate) &&
+		c.hasNameConstraints() && leaf.hasSANExtension() {
+		err := forEachSAN(leaf.getSANExtension(), func(tag int, data []byte) error {
+			switch tag {
+			case nameTypeEmail:
+				name := string(data)
+				mailbox, ok := parseRFC2821Mailbox(name)
+				if !ok {
+					return fmt.Errorf("x509: cannot parse rfc822Name %q", mailbox)
+				}
+
+				if err := c.checkNameConstraints(&comparisonCount, maxConstraintComparisons, "email address", name, mailbox,
+					func(parsedName, constraint any) (bool, error) {
+						return matchEmailConstraint(parsedName.(rfc2821Mailbox), constraint.(string))
+					}, c.PermittedEmailAddresses, c.ExcludedEmailAddresses); err != nil {
+					return err
+				}
+
+			case nameTypeDNS:
+				name := string(data)
+				if _, ok := domainToReverseLabels(name); !ok {
+					return fmt.Errorf("x509: cannot parse dnsName %q", name)
+				}
+
+				if err := c.checkNameConstraints(&comparisonCount, maxConstraintComparisons, "DNS name", name, name,
+					func(parsedName, constraint any) (bool, error) {
+						return matchDomainConstraint(parsedName.(string), constraint.(string))
+					}, c.PermittedDNSDomains, c.ExcludedDNSDomains); err != nil {
+					return err
+				}
+
+			case nameTypeURI:
+				name := string(data)
+				uri, err := url.Parse(name)
+				if err != nil {
+					return fmt.Errorf("x509: internal error: URI SAN %q failed to parse", name)
+				}
+
+				if err := c.checkNameConstraints(&comparisonCount, maxConstraintComparisons, "URI", name, uri,
+					func(parsedName, constraint any) (bool, error) {
+						return matchURIConstraint(parsedName.(*url.URL), constraint.(string))
+					}, c.PermittedURIDomains, c.ExcludedURIDomains); err != nil {
+					return err
+				}
+
+			case nameTypeIP:
+				ip := net.IP(data)
+				if l := len(ip); l != net.IPv4len && l != net.IPv6len {
+					return fmt.Errorf("x509: internal error: IP SAN %x failed to parse", data)
+				}
+
+				if err := c.checkNameConstraints(&comparisonCount, maxConstraintComparisons, "IP address", ip.String(), ip,
+					func(parsedName, constraint any) (bool, error) {
+						return matchIPConstraint(parsedName.(net.IP), constraint.(*net.IPNet))
+					}, c.PermittedIPRanges, c.ExcludedIPRanges); err != nil {
+					return err
+				}
+
+			default:
+				// Unknown SAN types are ignored.
+			}
+
+			return nil
+		})
+
+		if err != nil {
+			return err
+		}
+	}
+
+	// KeyUsage status flags are ignored. From Engineering Security, Peter
+	// Gutmann: A European government CA marked its signing certificates as
+	// being valid for encryption only, but no-one noticed. Another
+	// European CA marked its signature keys as not being valid for
+	// signatures. A different CA marked its own trusted root certificate
+	// as being invalid for certificate signing. Another national CA
+	// distributed a certificate to be used to encrypt data for the
+	// country’s tax authority that was marked as only being usable for
+	// digital signatures but not for encryption. Yet another CA reversed
+	// the order of the bit flags in the keyUsage due to confusion over
+	// encoding endianness, essentially setting a random keyUsage in
+	// certificates that it issued. Another CA created a self-invalidating
+	// certificate by adding a certificate policy statement stipulating
+	// that the certificate had to be used strictly as specified in the
+	// keyUsage, and a keyUsage containing a flag indicating that the RSA
+	// encryption key could only be used for Diffie-Hellman key agreement.
+
+	if certType == intermediateCertificate && (!c.BasicConstraintsValid || !c.IsCA) {
+		return CertificateInvalidError{c, NotAuthorizedToSign, ""}
+	}
+
+	if c.BasicConstraintsValid && c.MaxPathLen >= 0 {
+		numIntermediates := len(currentChain) - 1
+		if numIntermediates > c.MaxPathLen {
+			return CertificateInvalidError{c, TooManyIntermediates, ""}
+		}
+	}
+
+	return nil
+}
+
+// Verify attempts to verify c by building one or more chains from c to a
+// certificate in opts.Roots, using certificates in opts.Intermediates if
+// needed. If successful, it returns one or more chains where the first
+// element of the chain is c and the last element is from opts.Roots.
+//
+// If opts.Roots is nil, the platform verifier might be used, and
+// verification details might differ from what is described below. If system
+// roots are unavailable the returned error will be of type SystemRootsError.
+//
+// Name constraints in the intermediates will be applied to all names claimed
+// in the chain, not just opts.DNSName. Thus it is invalid for a leaf to claim
+// example.com if an intermediate doesn't permit it, even if example.com is not
+// the name being validated. Note that DirectoryName constraints are not
+// supported.
+//
+// Name constraint validation follows the rules from RFC 5280, with the
+// addition that DNS name constraints may use the leading period format
+// defined for emails and URIs. When a constraint has a leading period
+// it indicates that at least one additional label must be prepended to
+// the constrained name to be considered valid.
+//
+// Extended Key Usage values are enforced nested down a chain, so an intermediate
+// or root that enumerates EKUs prevents a leaf from asserting an EKU not in that
+// list. (While this is not specified, it is common practice in order to limit
+// the types of certificates a CA can issue.)
+//
+// Certificates that use SHA1WithRSA and ECDSAWithSHA1 signatures are not supported,
+// and will not be used to build chains.
+//
+// WARNING: this function doesn't do any revocation checking.
+func (c *Certificate) Verify(opts VerifyOptions) (chains [][]*Certificate, err error) {
+	// Platform-specific verification needs the ASN.1 contents so
+	// this makes the behavior consistent across platforms.
+	if len(c.Raw) == 0 {
+		return nil, errNotParsed
+	}
+	for i := 0; i < opts.Intermediates.len(); i++ {
+		c, err := opts.Intermediates.cert(i)
+		if err != nil {
+			return nil, fmt.Errorf("crypto/x509: error fetching intermediate: %w", err)
+		}
+		if len(c.Raw) == 0 {
+			return nil, errNotParsed
+		}
+	}
+
+	// Use platform verifiers, where available, if Roots is from SystemCertPool.
+	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
+		if opts.Roots == nil {
+			return c.systemVerify(&opts)
+		}
+		if opts.Roots != nil && opts.Roots.systemPool {
+			platformChains, err := c.systemVerify(&opts)
+			// If the platform verifier succeeded, or there are no additional
+			// roots, return the platform verifier result. Otherwise, continue
+			// with the Go verifier.
+			if err == nil || opts.Roots.len() == 0 {
+				return platformChains, err
+			}
+		}
+	}
+
+	if opts.Roots == nil {
+		opts.Roots = systemRootsPool()
+		if opts.Roots == nil {
+			return nil, SystemRootsError{systemRootsErr}
+		}
+	}
+
+	err = c.isValid(leafCertificate, nil, &opts)
+	if err != nil {
+		return
+	}
+
+	if len(opts.DNSName) > 0 {
+		err = c.VerifyHostname(opts.DNSName)
+		if err != nil {
+			return
+		}
+	}
+
+	var candidateChains [][]*Certificate
+	if opts.Roots.contains(c) {
+		candidateChains = append(candidateChains, []*Certificate{c})
+	} else {
+		if candidateChains, err = c.buildChains(nil, []*Certificate{c}, nil, &opts); err != nil {
+			return nil, err
+		}
+	}
+
+	keyUsages := opts.KeyUsages
+	if len(keyUsages) == 0 {
+		keyUsages = []ExtKeyUsage{ExtKeyUsageServerAuth}
+	}
+
+	// If any key usage is acceptable then we're done.
+	for _, usage := range keyUsages {
+		if usage == ExtKeyUsageAny {
+			return candidateChains, nil
+		}
+	}
+
+	for _, candidate := range candidateChains {
+		if checkChainForKeyUsage(candidate, keyUsages) {
+			chains = append(chains, candidate)
+		}
+	}
+
+	if len(chains) == 0 {
+		return nil, CertificateInvalidError{c, IncompatibleUsage, ""}
+	}
+
+	return chains, nil
+}
+
+func appendToFreshChain(chain []*Certificate, cert *Certificate) []*Certificate {
+	n := make([]*Certificate, len(chain)+1)
+	copy(n, chain)
+	n[len(chain)] = cert
+	return n
+}
+
+// maxChainSignatureChecks is the maximum number of CheckSignatureFrom calls
+// that an invocation of buildChains will (transitively) make. Most chains are
+// less than 15 certificates long, so this leaves space for multiple chains and
+// for failed checks due to different intermediates having the same Subject.
+const maxChainSignatureChecks = 100
+
+func (c *Certificate) buildChains(cache map[*Certificate][][]*Certificate, currentChain []*Certificate, sigChecks *int, opts *VerifyOptions) (chains [][]*Certificate, err error) {
+	var (
+		hintErr  error
+		hintCert *Certificate
+	)
+
+	considerCandidate := func(certType int, candidate *Certificate) {
+		for _, cert := range currentChain {
+			if cert.Equal(candidate) {
+				return
+			}
+		}
+
+		if sigChecks == nil {
+			sigChecks = new(int)
+		}
+		*sigChecks++
+		if *sigChecks > maxChainSignatureChecks {
+			err = errors.New("x509: signature check attempts limit reached while verifying certificate chain")
+			return
+		}
+
+		if err := c.CheckSignatureFrom(candidate); err != nil {
+			if hintErr == nil {
+				hintErr = err
+				hintCert = candidate
+			}
+			return
+		}
+
+		err = candidate.isValid(certType, currentChain, opts)
+		if err != nil {
+			return
+		}
+
+		switch certType {
+		case rootCertificate:
+			chains = append(chains, appendToFreshChain(currentChain, candidate))
+		case intermediateCertificate:
+			if cache == nil {
+				cache = make(map[*Certificate][][]*Certificate)
+			}
+			childChains, ok := cache[candidate]
+			if !ok {
+				childChains, err = candidate.buildChains(cache, appendToFreshChain(currentChain, candidate), sigChecks, opts)
+				cache[candidate] = childChains
+			}
+			chains = append(chains, childChains...)
+		}
+	}
+
+	for _, root := range opts.Roots.findPotentialParents(c) {
+		considerCandidate(rootCertificate, root)
+	}
+	for _, intermediate := range opts.Intermediates.findPotentialParents(c) {
+		considerCandidate(intermediateCertificate, intermediate)
+	}
+
+	if len(chains) > 0 {
+		err = nil
+	}
+	if len(chains) == 0 && err == nil {
+		err = UnknownAuthorityError{c, hintErr, hintCert}
+	}
+
+	return
+}
+
+func validHostnamePattern(host string) bool { return validHostname(host, true) }
+func validHostnameInput(host string) bool   { return validHostname(host, false) }
+
+// validHostname reports whether host is a valid hostname that can be matched or
+// matched against according to RFC 6125 2.2, with some leniency to accommodate
+// legacy values.
+func validHostname(host string, isPattern bool) bool {
+	if !isPattern {
+		host = strings.TrimSuffix(host, ".")
+	}
+	if len(host) == 0 {
+		return false
+	}
+
+	for i, part := range strings.Split(host, ".") {
+		if part == "" {
+			// Empty label.
+			return false
+		}
+		if isPattern && i == 0 && part == "*" {
+			// Only allow full left-most wildcards, as those are the only ones
+			// we match, and matching literal '*' characters is probably never
+			// the expected behavior.
+			continue
+		}
+		for j, c := range part {
+			if 'a' <= c && c <= 'z' {
+				continue
+			}
+			if '0' <= c && c <= '9' {
+				continue
+			}
+			if 'A' <= c && c <= 'Z' {
+				continue
+			}
+			if c == '-' && j != 0 {
+				continue
+			}
+			if c == '_' {
+				// Not a valid character in hostnames, but commonly
+				// found in deployments outside the WebPKI.
+				continue
+			}
+			return false
+		}
+	}
+
+	return true
+}
+
+func matchExactly(hostA, hostB string) bool {
+	if hostA == "" || hostA == "." || hostB == "" || hostB == "." {
+		return false
+	}
+	return toLowerCaseASCII(hostA) == toLowerCaseASCII(hostB)
+}
+
+func matchHostnames(pattern, host string) bool {
+	pattern = toLowerCaseASCII(pattern)
+	host = toLowerCaseASCII(strings.TrimSuffix(host, "."))
+
+	if len(pattern) == 0 || len(host) == 0 {
+		return false
+	}
+
+	patternParts := strings.Split(pattern, ".")
+	hostParts := strings.Split(host, ".")
+
+	if len(patternParts) != len(hostParts) {
+		return false
+	}
+
+	for i, patternPart := range patternParts {
+		if i == 0 && patternPart == "*" {
+			continue
+		}
+		if patternPart != hostParts[i] {
+			return false
+		}
+	}
+
+	return true
+}
+
+// toLowerCaseASCII returns a lower-case version of in. See RFC 6125 6.4.1. We use
+// an explicitly ASCII function to avoid any sharp corners resulting from
+// performing Unicode operations on DNS labels.
+func toLowerCaseASCII(in string) string {
+	// If the string is already lower-case then there's nothing to do.
+	isAlreadyLowerCase := true
+	for _, c := range in {
+		if c == utf8.RuneError {
+			// If we get a UTF-8 error then there might be
+			// upper-case ASCII bytes in the invalid sequence.
+			isAlreadyLowerCase = false
+			break
+		}
+		if 'A' <= c && c <= 'Z' {
+			isAlreadyLowerCase = false
+			break
+		}
+	}
+
+	if isAlreadyLowerCase {
+		return in
+	}
+
+	out := []byte(in)
+	for i, c := range out {
+		if 'A' <= c && c <= 'Z' {
+			out[i] += 'a' - 'A'
+		}
+	}
+	return string(out)
+}
+
+// VerifyHostname returns nil if c is a valid certificate for the named host.
+// Otherwise it returns an error describing the mismatch.
+//
+// IP addresses can be optionally enclosed in square brackets and are checked
+// against the IPAddresses field. Other names are checked case insensitively
+// against the DNSNames field. If the names are valid hostnames, the certificate
+// fields can have a wildcard as the left-most label.
+//
+// Note that the legacy Common Name field is ignored.
+func (c *Certificate) VerifyHostname(h string) error {
+	// IP addresses may be written in [ ].
+	candidateIP := h
+	if len(h) >= 3 && h[0] == '[' && h[len(h)-1] == ']' {
+		candidateIP = h[1 : len(h)-1]
+	}
+	if ip := net.ParseIP(candidateIP); ip != nil {
+		// We only match IP addresses against IP SANs.
+		// See RFC 6125, Appendix B.2.
+		for _, candidate := range c.IPAddresses {
+			if ip.Equal(candidate) {
+				return nil
+			}
+		}
+		return HostnameError{c, candidateIP}
+	}
+
+	candidateName := toLowerCaseASCII(h) // Save allocations inside the loop.
+	validCandidateName := validHostnameInput(candidateName)
+
+	for _, match := range c.DNSNames {
+		// Ideally, we'd only match valid hostnames according to RFC 6125 like
+		// browsers (more or less) do, but in practice Go is used in a wider
+		// array of contexts and can't even assume DNS resolution. Instead,
+		// always allow perfect matches, and only apply wildcard and trailing
+		// dot processing to valid hostnames.
+		if validCandidateName && validHostnamePattern(match) {
+			if matchHostnames(match, candidateName) {
+				return nil
+			}
+		} else {
+			if matchExactly(match, candidateName) {
+				return nil
+			}
+		}
+	}
+
+	return HostnameError{c, h}
+}
+
+func checkChainForKeyUsage(chain []*Certificate, keyUsages []ExtKeyUsage) bool {
+	usages := make([]ExtKeyUsage, len(keyUsages))
+	copy(usages, keyUsages)
+
+	if len(chain) == 0 {
+		return false
+	}
+
+	usagesRemaining := len(usages)
+
+	// We walk down the list and cross out any usages that aren't supported
+	// by each certificate. If we cross out all the usages, then the chain
+	// is unacceptable.
+
+NextCert:
+	for i := len(chain) - 1; i >= 0; i-- {
+		cert := chain[i]
+		if len(cert.ExtKeyUsage) == 0 && len(cert.UnknownExtKeyUsage) == 0 {
+			// The certificate doesn't have any extended key usage specified.
+			continue
+		}
+
+		for _, usage := range cert.ExtKeyUsage {
+			if usage == ExtKeyUsageAny {
+				// The certificate is explicitly good for any usage.
+				continue NextCert
+			}
+		}
+
+		const invalidUsage ExtKeyUsage = -1
+
+	NextRequestedUsage:
+		for i, requestedUsage := range usages {
+			if requestedUsage == invalidUsage {
+				continue
+			}
+
+			for _, usage := range cert.ExtKeyUsage {
+				if requestedUsage == usage {
+					continue NextRequestedUsage
+				}
+			}
+
+			usages[i] = invalidUsage
+			usagesRemaining--
+			if usagesRemaining == 0 {
+				return false
+			}
+		}
+	}
+
+	return true
+}
diff --git a/src/crypto/x509/verify_test.go b/src/crypto/x509/verify_test.go
new file mode 100644
index 0000000..c3ef503
--- /dev/null
+++ b/src/crypto/x509/verify_test.go
@@ -0,0 +1,1912 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"internal/testenv"
+	"math/big"
+	"runtime"
+	"strings"
+	"testing"
+	"time"
+)
+
+type verifyTest struct {
+	name          string
+	leaf          string
+	intermediates []string
+	roots         []string
+	currentTime   int64
+	dnsName       string
+	systemSkip    bool
+	systemLax     bool
+	keyUsages     []ExtKeyUsage
+
+	errorCallback  func(*testing.T, error)
+	expectedChains [][]string
+}
+
+var verifyTests = []verifyTest{
+	{
+		name:          "Valid",
+		leaf:          googleLeaf,
+		intermediates: []string{giag2Intermediate},
+		roots:         []string{geoTrustRoot},
+		currentTime:   1395785200,
+		dnsName:       "www.google.com",
+
+		expectedChains: [][]string{
+			{"Google", "Google Internet Authority", "GeoTrust"},
+		},
+	},
+	{
+		name:          "MixedCase",
+		leaf:          googleLeaf,
+		intermediates: []string{giag2Intermediate},
+		roots:         []string{geoTrustRoot},
+		currentTime:   1395785200,
+		dnsName:       "WwW.GooGLE.coM",
+
+		expectedChains: [][]string{
+			{"Google", "Google Internet Authority", "GeoTrust"},
+		},
+	},
+	{
+		name:          "HostnameMismatch",
+		leaf:          googleLeaf,
+		intermediates: []string{giag2Intermediate},
+		roots:         []string{geoTrustRoot},
+		currentTime:   1395785200,
+		dnsName:       "www.example.com",
+
+		errorCallback: expectHostnameError("certificate is valid for"),
+	},
+	{
+		name:          "IPMissing",
+		leaf:          googleLeaf,
+		intermediates: []string{giag2Intermediate},
+		roots:         []string{geoTrustRoot},
+		currentTime:   1395785200,
+		dnsName:       "1.2.3.4",
+
+		errorCallback: expectHostnameError("doesn't contain any IP SANs"),
+	},
+	{
+		name:          "Expired",
+		leaf:          googleLeaf,
+		intermediates: []string{giag2Intermediate},
+		roots:         []string{geoTrustRoot},
+		currentTime:   1,
+		dnsName:       "www.example.com",
+
+		errorCallback: expectExpired,
+	},
+	{
+		name:        "MissingIntermediate",
+		leaf:        googleLeaf,
+		roots:       []string{geoTrustRoot},
+		currentTime: 1395785200,
+		dnsName:     "www.google.com",
+
+		// Skip when using systemVerify, since Windows
+		// *will* find the missing intermediate cert.
+		systemSkip:    true,
+		errorCallback: expectAuthorityUnknown,
+	},
+	{
+		name:          "RootInIntermediates",
+		leaf:          googleLeaf,
+		intermediates: []string{geoTrustRoot, giag2Intermediate},
+		roots:         []string{geoTrustRoot},
+		currentTime:   1395785200,
+		dnsName:       "www.google.com",
+
+		expectedChains: [][]string{
+			{"Google", "Google Internet Authority", "GeoTrust"},
+		},
+		// CAPI doesn't build the chain with the duplicated GeoTrust
+		// entry so the results don't match.
+		systemLax: true,
+	},
+	{
+		name:          "dnssec-exp",
+		leaf:          dnssecExpLeaf,
+		intermediates: []string{startComIntermediate},
+		roots:         []string{startComRoot},
+		currentTime:   1302726541,
+
+		// The StartCom root is not trusted by Windows when the default
+		// ServerAuth EKU is requested.
+		systemSkip: true,
+
+		expectedChains: [][]string{
+			{"dnssec-exp", "StartCom Class 1", "StartCom Certification Authority"},
+		},
+	},
+	{
+		name:          "dnssec-exp/AnyEKU",
+		leaf:          dnssecExpLeaf,
+		intermediates: []string{startComIntermediate},
+		roots:         []string{startComRoot},
+		currentTime:   1302726541,
+		keyUsages:     []ExtKeyUsage{ExtKeyUsageAny},
+
+		expectedChains: [][]string{
+			{"dnssec-exp", "StartCom Class 1", "StartCom Certification Authority"},
+		},
+	},
+	{
+		name:          "dnssec-exp/RootInIntermediates",
+		leaf:          dnssecExpLeaf,
+		intermediates: []string{startComIntermediate, startComRoot},
+		roots:         []string{startComRoot},
+		currentTime:   1302726541,
+		systemSkip:    true, // see dnssec-exp test
+
+		expectedChains: [][]string{
+			{"dnssec-exp", "StartCom Class 1", "StartCom Certification Authority"},
+		},
+	},
+	{
+		name:          "InvalidHash",
+		leaf:          googleLeafWithInvalidHash,
+		intermediates: []string{giag2Intermediate},
+		roots:         []string{geoTrustRoot},
+		currentTime:   1395785200,
+		dnsName:       "www.google.com",
+
+		// The specific error message may not occur when using system
+		// verification.
+		systemLax:     true,
+		errorCallback: expectHashError,
+	},
+	// EKULeaf tests use an unconstrained chain leading to a leaf certificate
+	// with an E-mail Protection EKU but not a Server Auth one, checking that
+	// the EKUs on the leaf are enforced.
+	{
+		name:          "EKULeaf",
+		leaf:          smimeLeaf,
+		intermediates: []string{smimeIntermediate},
+		roots:         []string{smimeRoot},
+		currentTime:   1594673418,
+
+		errorCallback: expectUsageError,
+	},
+	{
+		name:          "EKULeafExplicit",
+		leaf:          smimeLeaf,
+		intermediates: []string{smimeIntermediate},
+		roots:         []string{smimeRoot},
+		currentTime:   1594673418,
+		keyUsages:     []ExtKeyUsage{ExtKeyUsageServerAuth},
+
+		errorCallback: expectUsageError,
+	},
+	{
+		name:          "EKULeafValid",
+		leaf:          smimeLeaf,
+		intermediates: []string{smimeIntermediate},
+		roots:         []string{smimeRoot},
+		currentTime:   1594673418,
+		keyUsages:     []ExtKeyUsage{ExtKeyUsageEmailProtection},
+
+		expectedChains: [][]string{
+			{"CORPORATIVO FICTICIO ACTIVO", "EAEko Herri Administrazioen CA - CA AAPP Vascas (2)", "IZENPE S.A."},
+		},
+	},
+	{
+		// Check that a name constrained intermediate works even when
+		// it lists multiple constraints.
+		name:          "MultipleConstraints",
+		leaf:          nameConstraintsLeaf,
+		intermediates: []string{nameConstraintsIntermediate1, nameConstraintsIntermediate2},
+		roots:         []string{globalSignRoot},
+		currentTime:   1382387896,
+		dnsName:       "secure.iddl.vt.edu",
+
+		expectedChains: [][]string{
+			{
+				"Technology-enhanced Learning and Online Strategies",
+				"Virginia Tech Global Qualified Server CA",
+				"Trusted Root CA G2",
+				"GlobalSign Root CA",
+			},
+		},
+	},
+	{
+		// Check that SHA-384 intermediates (which are popping up)
+		// work.
+		name:          "SHA-384",
+		leaf:          moipLeafCert,
+		intermediates: []string{comodoIntermediateSHA384, comodoRSAAuthority},
+		roots:         []string{addTrustRoot},
+		currentTime:   1397502195,
+		dnsName:       "api.moip.com.br",
+
+		// CryptoAPI can find alternative validation paths.
+		systemLax: true,
+
+		expectedChains: [][]string{
+			{
+				"api.moip.com.br",
+				"COMODO RSA Extended Validation Secure Server CA",
+				"COMODO RSA Certification Authority",
+				"AddTrust External CA Root",
+			},
+		},
+	},
+	{
+		// Putting a certificate as a root directly should work as a
+		// way of saying “exactly this”.
+		name:        "LeafInRoots",
+		leaf:        selfSigned,
+		roots:       []string{selfSigned},
+		currentTime: 1471624472,
+		dnsName:     "foo.example",
+		systemSkip:  true, // does not chain to a system root
+
+		expectedChains: [][]string{
+			{"Acme Co"},
+		},
+	},
+	{
+		// Putting a certificate as a root directly should not skip
+		// other checks however.
+		name:        "LeafInRootsInvalid",
+		leaf:        selfSigned,
+		roots:       []string{selfSigned},
+		currentTime: 1471624472,
+		dnsName:     "notfoo.example",
+		systemSkip:  true, // does not chain to a system root
+
+		errorCallback: expectHostnameError("certificate is valid for"),
+	},
+	{
+		// An X.509 v1 certificate should not be accepted as an
+		// intermediate.
+		name:          "X509v1Intermediate",
+		leaf:          x509v1TestLeaf,
+		intermediates: []string{x509v1TestIntermediate},
+		roots:         []string{x509v1TestRoot},
+		currentTime:   1481753183,
+		systemSkip:    true, // does not chain to a system root
+
+		errorCallback: expectNotAuthorizedError,
+	},
+	{
+		name:        "IgnoreCNWithSANs",
+		leaf:        ignoreCNWithSANLeaf,
+		dnsName:     "foo.example.com",
+		roots:       []string{ignoreCNWithSANRoot},
+		currentTime: 1486684488,
+		systemSkip:  true, // does not chain to a system root
+
+		errorCallback: expectHostnameError("certificate is not valid for any names"),
+	},
+	{
+		// Test that excluded names are respected.
+		name:          "ExcludedNames",
+		leaf:          excludedNamesLeaf,
+		dnsName:       "bender.local",
+		intermediates: []string{excludedNamesIntermediate},
+		roots:         []string{excludedNamesRoot},
+		currentTime:   1486684488,
+		systemSkip:    true, // does not chain to a system root
+
+		errorCallback: expectNameConstraintsError,
+	},
+	{
+		// Test that unknown critical extensions in a leaf cause a
+		// verify error.
+		name:          "CriticalExtLeaf",
+		leaf:          criticalExtLeafWithExt,
+		intermediates: []string{criticalExtIntermediate},
+		roots:         []string{criticalExtRoot},
+		currentTime:   1486684488,
+		systemSkip:    true, // does not chain to a system root
+
+		errorCallback: expectUnhandledCriticalExtension,
+	},
+	{
+		// Test that unknown critical extensions in an intermediate
+		// cause a verify error.
+		name:          "CriticalExtIntermediate",
+		leaf:          criticalExtLeaf,
+		intermediates: []string{criticalExtIntermediateWithExt},
+		roots:         []string{criticalExtRoot},
+		currentTime:   1486684488,
+		systemSkip:    true, // does not chain to a system root
+
+		errorCallback: expectUnhandledCriticalExtension,
+	},
+	{
+		name:        "ValidCN",
+		leaf:        validCNWithoutSAN,
+		dnsName:     "foo.example.com",
+		roots:       []string{invalidCNRoot},
+		currentTime: 1540000000,
+		systemSkip:  true, // does not chain to a system root
+
+		errorCallback: expectHostnameError("certificate relies on legacy Common Name field"),
+	},
+	{
+		// A certificate with an AKID should still chain to a parent without SKID.
+		// See Issue 30079.
+		name:        "AKIDNoSKID",
+		leaf:        leafWithAKID,
+		roots:       []string{rootWithoutSKID},
+		currentTime: 1550000000,
+		dnsName:     "example",
+		systemSkip:  true, // does not chain to a system root
+
+		expectedChains: [][]string{
+			{"Acme LLC", "Acme Co"},
+		},
+	},
+	{
+		// When there are two parents, one with a incorrect subject but matching SKID
+		// and one with a correct subject but missing SKID, the latter should be
+		// considered as a possible parent.
+		leaf:        leafMatchingAKIDMatchingIssuer,
+		roots:       []string{rootMatchingSKIDMismatchingSubject, rootMismatchingSKIDMatchingSubject},
+		currentTime: 1550000000,
+		dnsName:     "example",
+		systemSkip:  true,
+
+		expectedChains: [][]string{
+			{"Leaf", "Root B"},
+		},
+	},
+}
+
+func expectHostnameError(msg string) func(*testing.T, error) {
+	return func(t *testing.T, err error) {
+		if _, ok := err.(HostnameError); !ok {
+			t.Fatalf("error was not a HostnameError: %v", err)
+		}
+		if !strings.Contains(err.Error(), msg) {
+			t.Fatalf("HostnameError did not contain %q: %v", msg, err)
+		}
+	}
+}
+
+func expectExpired(t *testing.T, err error) {
+	if inval, ok := err.(CertificateInvalidError); !ok || inval.Reason != Expired {
+		t.Fatalf("error was not Expired: %v", err)
+	}
+}
+
+func expectUsageError(t *testing.T, err error) {
+	if inval, ok := err.(CertificateInvalidError); !ok || inval.Reason != IncompatibleUsage {
+		t.Fatalf("error was not IncompatibleUsage: %v", err)
+	}
+}
+
+func expectAuthorityUnknown(t *testing.T, err error) {
+	e, ok := err.(UnknownAuthorityError)
+	if !ok {
+		t.Fatalf("error was not UnknownAuthorityError: %v", err)
+	}
+	if e.Cert == nil {
+		t.Fatalf("error was UnknownAuthorityError, but missing Cert: %v", err)
+	}
+}
+
+func expectHashError(t *testing.T, err error) {
+	if err == nil {
+		t.Fatalf("no error resulted from invalid hash")
+	}
+	if expected := "algorithm unimplemented"; !strings.Contains(err.Error(), expected) {
+		t.Fatalf("error resulting from invalid hash didn't contain '%s', rather it was: %v", expected, err)
+	}
+}
+
+func expectNameConstraintsError(t *testing.T, err error) {
+	if inval, ok := err.(CertificateInvalidError); !ok || inval.Reason != CANotAuthorizedForThisName {
+		t.Fatalf("error was not a CANotAuthorizedForThisName: %v", err)
+	}
+}
+
+func expectNotAuthorizedError(t *testing.T, err error) {
+	if inval, ok := err.(CertificateInvalidError); !ok || inval.Reason != NotAuthorizedToSign {
+		t.Fatalf("error was not a NotAuthorizedToSign: %v", err)
+	}
+}
+
+func expectUnhandledCriticalExtension(t *testing.T, err error) {
+	if _, ok := err.(UnhandledCriticalExtension); !ok {
+		t.Fatalf("error was not an UnhandledCriticalExtension: %v", err)
+	}
+}
+
+func certificateFromPEM(pemBytes string) (*Certificate, error) {
+	block, _ := pem.Decode([]byte(pemBytes))
+	if block == nil {
+		return nil, errors.New("failed to decode PEM")
+	}
+	return ParseCertificate(block.Bytes)
+}
+
+func testVerify(t *testing.T, test verifyTest, useSystemRoots bool) {
+	opts := VerifyOptions{
+		Intermediates: NewCertPool(),
+		DNSName:       test.dnsName,
+		CurrentTime:   time.Unix(test.currentTime, 0),
+		KeyUsages:     test.keyUsages,
+	}
+
+	if !useSystemRoots {
+		opts.Roots = NewCertPool()
+		for j, root := range test.roots {
+			ok := opts.Roots.AppendCertsFromPEM([]byte(root))
+			if !ok {
+				t.Fatalf("failed to parse root #%d", j)
+			}
+		}
+	}
+
+	for j, intermediate := range test.intermediates {
+		ok := opts.Intermediates.AppendCertsFromPEM([]byte(intermediate))
+		if !ok {
+			t.Fatalf("failed to parse intermediate #%d", j)
+		}
+	}
+
+	leaf, err := certificateFromPEM(test.leaf)
+	if err != nil {
+		t.Fatalf("failed to parse leaf: %v", err)
+	}
+
+	chains, err := leaf.Verify(opts)
+
+	if test.errorCallback == nil && err != nil {
+		if runtime.GOOS == "windows" && strings.HasSuffix(testenv.Builder(), "-2008") && err.Error() == "x509: certificate signed by unknown authority" {
+			testenv.SkipFlaky(t, 19564)
+		}
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if test.errorCallback != nil {
+		if useSystemRoots && test.systemLax {
+			if err == nil {
+				t.Fatalf("expected error")
+			}
+		} else {
+			test.errorCallback(t, err)
+		}
+	}
+
+	doesMatch := func(expectedChain []string, chain []*Certificate) bool {
+		if len(chain) != len(expectedChain) {
+			return false
+		}
+
+		for k, cert := range chain {
+			if !strings.Contains(nameToKey(&cert.Subject), expectedChain[k]) {
+				return false
+			}
+		}
+		return true
+	}
+
+	// Every expected chain should match 1 returned chain
+	for _, expectedChain := range test.expectedChains {
+		nChainMatched := 0
+		for _, chain := range chains {
+			if doesMatch(expectedChain, chain) {
+				nChainMatched++
+			}
+		}
+
+		if nChainMatched != 1 {
+			t.Errorf("Got %v matches instead of %v for expected chain %v", nChainMatched, 1, expectedChain)
+			for _, chain := range chains {
+				if doesMatch(expectedChain, chain) {
+					t.Errorf("\t matched %v", chainToDebugString(chain))
+				}
+			}
+		}
+	}
+
+	// Every returned chain should match 1 expected chain (or <2 if testing against the system)
+	for _, chain := range chains {
+		nMatched := 0
+		for _, expectedChain := range test.expectedChains {
+			if doesMatch(expectedChain, chain) {
+				nMatched++
+			}
+		}
+		// Allow additional unknown chains if systemLax is set
+		if nMatched == 0 && test.systemLax == false || nMatched > 1 {
+			t.Errorf("Got %v matches for chain %v", nMatched, chainToDebugString(chain))
+			for _, expectedChain := range test.expectedChains {
+				if doesMatch(expectedChain, chain) {
+					t.Errorf("\t matched %v", expectedChain)
+				}
+			}
+		}
+	}
+}
+
+func TestGoVerify(t *testing.T) {
+	// Temporarily enable SHA-1 verification since a number of test chains
+	// require it. TODO(filippo): regenerate test chains.
+	t.Setenv("GODEBUG", "x509sha1=1")
+
+	for _, test := range verifyTests {
+		t.Run(test.name, func(t *testing.T) {
+			testVerify(t, test, false)
+		})
+	}
+}
+
+func TestSystemVerify(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		t.Skipf("skipping verify test using system APIs on %q", runtime.GOOS)
+	}
+
+	for _, test := range verifyTests {
+		t.Run(test.name, func(t *testing.T) {
+			if test.systemSkip {
+				t.SkipNow()
+			}
+			testVerify(t, test, true)
+		})
+	}
+}
+
+func chainToDebugString(chain []*Certificate) string {
+	var chainStr string
+	for _, cert := range chain {
+		if len(chainStr) > 0 {
+			chainStr += " -> "
+		}
+		chainStr += nameToKey(&cert.Subject)
+	}
+	return chainStr
+}
+
+func nameToKey(name *pkix.Name) string {
+	return strings.Join(name.Country, ",") + "/" + strings.Join(name.Organization, ",") + "/" + strings.Join(name.OrganizationalUnit, ",") + "/" + name.CommonName
+}
+
+const geoTrustRoot = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const giag2Intermediate = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const googleLeaf = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+// googleLeafWithInvalidHash is the same as googleLeaf, but the signature
+// algorithm in the certificate contains a nonsense OID.
+const googleLeafWithInvalidHash = `-----BEGIN CERTIFICATE-----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+Kom08eUK8skxAzfDDijZPh10VtJ66uBoiDPdT+uCBehcBIcmSTrKjFGX
+-----END CERTIFICATE-----`
+
+const dnssecExpLeaf = `-----BEGIN CERTIFICATE-----
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++b+/a3RVjxmkV5OCcGVBxsXNDn54Q6wsdw0TBMcjwoEndzpLS7yWgFbbkq5ZiGpw
+Qibb2+CfKuQ+WFV1GkVQmVA=
+-----END CERTIFICATE-----`
+
+const startComIntermediate = `-----BEGIN CERTIFICATE-----
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+0q6Dp6jOW6c=
+-----END CERTIFICATE-----`
+
+const startComRoot = `-----BEGIN CERTIFICATE-----
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+NOsF/5oirpt9P/FlUQqmMGqz9IgcgA38corog14=
+-----END CERTIFICATE-----`
+
+const smimeLeaf = `-----BEGIN CERTIFICATE-----
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+mYust+gxVtOZs1gk2MUCgJ1V1X+g7r/Cg7viIn6TLkLrpS1kS1hvMqkl9M+7XqPo
+Qd95nJKOkusQpy99X4dF/lfbYAQnnjnqh3DLD2gvYObXFaAYFaiBKTiMTV2X72F+
+-----END CERTIFICATE-----`
+
+const smimeIntermediate = `-----BEGIN CERTIFICATE-----
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+k+lzD44wofy8paAy9uC9Owae0zMEzhcsyRm7
+-----END CERTIFICATE-----`
+
+const smimeRoot = `-----BEGIN CERTIFICATE-----
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+QyYBNWNgVYkDOnXYukrZVP/u3oDYLdE41V4tC5h9Pmzb/CaIxw==
+-----END CERTIFICATE-----`
+
+var nameConstraintsLeaf = `-----BEGIN CERTIFICATE-----
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+GBUwDrQNTb+gsXsDkjd5lcYxNx6l
+-----END CERTIFICATE-----`
+
+var nameConstraintsIntermediate1 = `-----BEGIN CERTIFICATE-----
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+jUY+v9vLQXmaVwI0AYL7g9LN
+-----END CERTIFICATE-----`
+
+var nameConstraintsIntermediate2 = `-----BEGIN CERTIFICATE-----
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+hcC8roQwkHT7HvfYBoc74FM=
+-----END CERTIFICATE-----`
+
+var globalSignRoot = `-----BEGIN CERTIFICATE-----
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+HMUfpIBvFSDJ3gyICh3WZlXi/EjJKSZp4A==
+-----END CERTIFICATE-----`
+
+var moipLeafCert = `-----BEGIN CERTIFICATE-----
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+jhuy8PqqZS9OuLilTeLu4a8z2JI=
+-----END CERTIFICATE-----`
+
+var comodoIntermediateSHA384 = `-----BEGIN CERTIFICATE-----
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+pLwltum95OmYdBbxN4SBB7SC
+-----END CERTIFICATE-----`
+
+const comodoRSAAuthority = `-----BEGIN CERTIFICATE-----
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+Jw5dhHk3QBN39bSsHNA7qxcS1u80GH4r6XnTq1dFDK8o+tDb5VCViLvfhVdpfZLY
+Uspzgb8c8+a4bmYRBbMelC1/kZWSWfFMzqORcUx8Rww7Cxn2obFshj5cqsQugsv5
+B5a6SE2Q8pTIqXOi6wZ7I53eovNNVZ96YUWYGGjHXkBrI/V5eu+MtWuLt29G9Hvx
+PUsE2JOAWVrgQSQdso8VYFhH2+9uRv0V9dlfmrPb2LjkQLPNlzmuhbsdjrzch5vR
+pu/xO28QOG8=
+-----END CERTIFICATE-----`
+
+const addTrustRoot = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const selfSigned = `-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----`
+
+const issuerSubjectMatchRoot = `-----BEGIN CERTIFICATE-----
+MIICIDCCAYmgAwIBAgIIAj5CwoHlWuYwDQYJKoZIhvcNAQELBQAwIzEPMA0GA1UE
+ChMGR29sYW5nMRAwDgYDVQQDEwdSb290IGNhMB4XDTE1MDEwMTAwMDAwMFoXDTI1
+MDEwMTAwMDAwMFowIzEPMA0GA1UEChMGR29sYW5nMRAwDgYDVQQDEwdSb290IGNh
+MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDpDn8RDOZa5oaDcPZRBy4CeBH1
+siSSOO4mYgLHlPE+oXdqwI/VImi2XeJM2uCFETXCknJJjYG0iJdrt/yyRFvZTQZw
++QzGj+mz36NqhGxDWb6dstB2m8PX+plZw7jl81MDvUnWs8yiQ/6twgu5AbhWKZQD
+JKcNKCEpqa6UW0r5nwIDAQABo10wWzAOBgNVHQ8BAf8EBAMCAgQwHQYDVR0lBBYw
+FAYIKwYBBQUHAwEGCCsGAQUFBwMCMA8GA1UdEwEB/wQFMAMBAf8wGQYDVR0OBBIE
+EEA31wH7QC+4HH5UBCeMWQEwDQYJKoZIhvcNAQELBQADgYEAb4TfSeCZ1HFmHTKG
+VsvqWmsOAGrRWm4fBiMH/8vRGnTkJEMLqiqgc3Ulgry/P6n4SIis7TqUOw3TiMhn
+RGEz33Fsxa/tFoy/gvlJu+MqB1M2NyV33pGkdwl/b7KRWMQFieqO+uE7Ge/49pS3
+eyfm5ITdK/WT9TzYhsU4AVZcn20=
+-----END CERTIFICATE-----`
+
+const issuerSubjectMatchLeaf = `-----BEGIN CERTIFICATE-----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=
+-----END CERTIFICATE-----`
+
+const x509v1TestRoot = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const x509v1TestIntermediate = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const x509v1TestLeaf = `-----BEGIN CERTIFICATE-----
+MIICMzCCAZygAwIBAgIJAPo99mqJJrpJMA0GCSqGSIb3DQEBCwUAMDAxDzANBgNV
+BAoTBkdvbGFuZzEdMBsGA1UEAxMUWC41MDl2MSBpbnRlcm1lZGlhdGUwHhcNMTUw
+MTAxMDAwMDAwWhcNMjUwMTAxMDAwMDAwWjArMQ8wDQYDVQQKEwZHb2xhbmcxGDAW
+BgNVBAMTD2Zvby5leGFtcGxlLmNvbTCBnzANBgkqhkiG9w0BAQEFAAOBjQAwgYkC
+gYEApUh60Z+a5/oKJxG//Dn8CihSo2CJHNIIO3zEJZ1EeNSMZCynaIR6D3IPZEIR
++RG2oGt+f5EEukAPYxwasp6VeZEezoQWJ+97nPCT6DpwLlWp3i2MF8piK2R9vxkG
+Z5n0+HzYk1VM8epIrZFUXSMGTX8w1y041PX/yYLxbdEifdcCAwEAAaNaMFgwDgYD
+VR0PAQH/BAQDAgWgMB0GA1UdJQQWMBQGCCsGAQUFBwMBBggrBgEFBQcDAjAMBgNV
+HRMBAf8EAjAAMBkGA1UdDgQSBBBFozXe0SnzAmjy+1U6M/cvMA0GCSqGSIb3DQEB
+CwUAA4GBADYzYUvaToO/ucBskPdqXV16AaakIhhSENswYVSl97/sODaxsjishKq9
+5R7siu+JnIFotA7IbBe633p75xEnLN88X626N/XRFG9iScLzpj0o0PWXBUiB+fxL
+/jt8qszOXCv2vYdUTPNuPqufXLWMoirpuXrr1liJDmedCcAHepY/
+-----END CERTIFICATE-----`
+
+const ignoreCNWithSANRoot = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const ignoreCNWithSANLeaf = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const excludedNamesLeaf = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const excludedNamesIntermediate = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const excludedNamesRoot = `-----BEGIN CERTIFICATE-----
+MIIEGTCCAwGgAwIBAgIHDUSFpInn/zANBgkqhkiG9w0BAQsFADCBozELMAkGA1UE
+BhMCVVMxEzARBgNVBAgMCkNhbGlmb3JuaWExEjAQBgNVBAcMCUxvcyBHYXRvczEU
+MBIGA1UECgwLTmV0ZmxpeCBJbmMxLTArBgNVBAsMJFBsYXRmb3JtIFNlY3VyaXR5
+ICgzNzMxNTA5NDM3NDYyNDg1KTEmMCQGA1UEAwwdTmFtZSBDb25zdHJhaW50cyBU
+ZXN0IFJvb3QgQ0EwHhcNMTcwMjA4MjExNTA0WhcNMTgwMjA4MjAyNDU4WjCBmTEL
+MAkGA1UEBhMCVVMxEzARBgNVBAgMCkNhbGlmb3JuaWExEjAQBgNVBAcMCUxvcyBH
+YXRvczEUMBIGA1UECgwLTmV0ZmxpeCBJbmMxLTArBgNVBAsMJFBsYXRmb3JtIFNl
+Y3VyaXR5ICgzNzM0NTE1NDc5MDY0NjAyKTEcMBoGA1UEAwwTTG9jYWwgUm9vdCBm
+b3IgMzM5MjCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAJymcnX29ekc
+7+MLyr8QuAzoHWznmGdDd2sITwWRjM89/21cdlHCGKSpULUNdFp9HDLWvYECtxt+
+8TuzKiQz7qAerzGUT1zI5McIjHy0e/i4xIkfiBiNeTCuB/N9QRbZlcfM80ErkaA4
+gCAFK8qZAcWkHIl6e+KaQFMPLKk9kckgAnVDHEJe8oLNCogCJ15558b65g05p9eb
+5Lg+E98hoPRTQaDwlz3CZPfTTA2EiEZInSi8qzodFCbTpJUVTbiVUH/JtVjlibbb
+smdcx5PORK+8ZJkhLEh54AjaWOX4tB/7Tkk8stg2VBmrIARt/j4UVj7cTrIWU3bV
+m8TwHJG+YgsCAwEAAaNaMFgwDwYDVR0TAQH/BAUwAwEB/zBFBgNVHR4EPjA8oBww
+CocICgEAAP//AAAwDoIMYmVuZGVyLmxvY2FsoRwwCocICgEAAP//AAAwDoIMYmVu
+ZGVyLmxvY2FsMA0GCSqGSIb3DQEBCwUAA4IBAQAMjbheffPxtSKSv9NySW+8qmHs
+n7Mb5GGyCFu+cMZSoSaabstbml+zHEFJvWz6/1E95K4F8jKhAcu/CwDf4IZrSD2+
+Hee0DolVSQhZpnHgPyj7ZATz48e3aJaQPUlhCEOh0wwF4Y0N4FV0t7R6woLylYRZ
+yU1yRHUqUYpN0DWFpsPbBqgM6uUAVO2ayBFhPgWUaqkmSbZ/Nq7isGvknaTmcIwT
+6mOAFN0qFb4RGzfGJW7x6z7KCULS7qVDp6fU3tRoScHFEgRubks6jzQ1W5ooSm4o
++NQCZDd5eFeU8PpNX7rgaYE4GPq+EEmLVCBYmdctr8QVdqJ//8Xu3+1phjDy
+-----END CERTIFICATE-----`
+
+const invalidCNRoot = `-----BEGIN CERTIFICATE-----
+MIIBFjCBvgIJAIsu4r+jb70UMAoGCCqGSM49BAMCMBQxEjAQBgNVBAsMCVRlc3Qg
+cm9vdDAeFw0xODA3MTExODMyMzVaFw0yODA3MDgxODMyMzVaMBQxEjAQBgNVBAsM
+CVRlc3Qgcm9vdDBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABF6oDgMg0LV6YhPj
+QXaPXYCc2cIyCdqp0ROUksRz0pOLTc5iY2nraUheRUD1vRRneq7GeXOVNn7uXONg
+oCGMjNwwCgYIKoZIzj0EAwIDRwAwRAIgDSiwgIn8g1lpruYH0QD1GYeoWVunfmrI
+XzZZl0eW/ugCICgOfXeZ2GGy3wIC0352BaC3a8r5AAb2XSGNe+e9wNN6
+-----END CERTIFICATE-----`
+
+const validCNWithoutSAN = `-----BEGIN CERTIFICATE-----
+MIIBJzCBzwIUB7q8t9mrDAL+UB1OFaMN5BEWFKQwCgYIKoZIzj0EAwIwFDESMBAG
+A1UECwwJVGVzdCByb290MB4XDTE4MDcxMTE4NDcyNFoXDTI4MDcwODE4NDcyNFow
+GjEYMBYGA1UEAwwPZm9vLmV4YW1wbGUuY29tMFkwEwYHKoZIzj0CAQYIKoZIzj0D
+AQcDQgAEp6Z8IjOnR38Iky1fYTUu2kVndvKXcxiwARJKGtW3b0E8uwVp9AZd/+sr
+p4ULTPdFToFAeqnGHbu62bkms8pQkDAKBggqhkjOPQQDAgNHADBEAiBTbNe3WWFR
+cqUYo0sNUuoV+tCTMDJUS+0PWIW4qBqCOwIgFHdLDn5PCk9kJpfc0O2qZx03hdq0
+h7olHCpY9yMRiz0=
+-----END CERTIFICATE-----`
+
+const rootWithoutSKID = `-----BEGIN CERTIFICATE-----
+MIIBbzCCARSgAwIBAgIQeCkq3C8SOX/JM5PqYTl9cDAKBggqhkjOPQQDAjASMRAw
+DgYDVQQKEwdBY21lIENvMB4XDTE5MDIwNDIyNTYzNFoXDTI5MDIwMTIyNTYzNFow
+EjEQMA4GA1UEChMHQWNtZSBDbzBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABISm
+jGlTr4dLOWT+BCTm2PzWRjk1DpLcSAh+Al8eB1Nc2eBWxYIH9qPirfatvqBOA4c5
+ZwycRpFoaw6O+EmXnVujTDBKMA4GA1UdDwEB/wQEAwICpDATBgNVHSUEDDAKBggr
+BgEFBQcDATAPBgNVHRMBAf8EBTADAQH/MBIGA1UdEQQLMAmCB2V4YW1wbGUwCgYI
+KoZIzj0EAwIDSQAwRgIhAMaBYWFCjTfn0MNyQ0QXvYT/iIFompkIqzw6wB7qjLrA
+AiEA3sn65V7G4tsjZEOpN0Jykn9uiTjqniqn/S/qmv8gIec=
+-----END CERTIFICATE-----`
+
+const leafWithAKID = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const rootMatchingSKIDMismatchingSubject = `-----BEGIN CERTIFICATE-----
+MIIBQjCB6aADAgECAgEAMAoGCCqGSM49BAMCMBExDzANBgNVBAMTBlJvb3QgQTAe
+Fw0wOTExMTAyMzAwMDBaFw0xOTExMDgyMzAwMDBaMBExDzANBgNVBAMTBlJvb3Qg
+QTBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABPK4p1uXq2aAeDtKDHIokg2rTcPM
+2gq3N9Y96wiW6/7puBK1+INEW//cO9x6FpzkcsHw/TriAqy4sck/iDAvf9WjMjAw
+MA8GA1UdJQQIMAYGBFUdJQAwDwYDVR0TAQH/BAUwAwEB/zAMBgNVHQ4EBQQDAQID
+MAoGCCqGSM49BAMCA0gAMEUCIQDgtAp7iVHxMnKxZPaLQPC+Tv2r7+DJc88k2SKH
+MPs/wQIgFjjNvBoQEl7vSHTcRGCCcFMdlN4l0Dqc9YwGa9fyrQs=
+-----END CERTIFICATE-----`
+
+const rootMismatchingSKIDMatchingSubject = `-----BEGIN CERTIFICATE-----
+MIIBNDCB26ADAgECAgEAMAoGCCqGSM49BAMCMBExDzANBgNVBAMTBlJvb3QgQjAe
+Fw0wOTExMTAyMzAwMDBaFw0xOTExMDgyMzAwMDBaMBExDzANBgNVBAMTBlJvb3Qg
+QjBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABI1YRFcIlkWzm9BdEVrIsEQJ2dT6
+qiW8/WV9GoIhmDtX9SEDHospc0Cgm+TeD2QYW2iMrS5mvNe4GSw0Jezg/bOjJDAi
+MA8GA1UdJQQIMAYGBFUdJQAwDwYDVR0TAQH/BAUwAwEB/zAKBggqhkjOPQQDAgNI
+ADBFAiEAukWOiuellx8bugRiwCS5XQ6IOJ1SZcjuZxj76WojwxkCIHqa71qNw8FM
+DtA5yoL9M2pDFF6ovFWnaCe+KlzSwAW/
+-----END CERTIFICATE-----`
+
+const leafMatchingAKIDMatchingIssuer = `-----BEGIN CERTIFICATE-----
+MIIBNTCB26ADAgECAgEAMAoGCCqGSM49BAMCMBExDzANBgNVBAMTBlJvb3QgQjAe
+Fw0wOTExMTAyMzAwMDBaFw0xOTExMDgyMzAwMDBaMA8xDTALBgNVBAMTBExlYWYw
+WTATBgcqhkjOPQIBBggqhkjOPQMBBwNCAASNWERXCJZFs5vQXRFayLBECdnU+qol
+vP1lfRqCIZg7V/UhAx6LKXNAoJvk3g9kGFtojK0uZrzXuBksNCXs4P2zoyYwJDAO
+BgNVHSMEBzAFgAMBAgMwEgYDVR0RBAswCYIHZXhhbXBsZTAKBggqhkjOPQQDAgNJ
+ADBGAiEAnV9XV7a4h0nfJB8pWv+pBUXRlRFA2uZz3mXEpee8NYACIQCWa+wL70GL
+ePBQCV1F9sE2q4ZrnsT9TZoNrSe/bMDjzA==
+-----END CERTIFICATE-----`
+
+var unknownAuthorityErrorTests = []struct {
+	cert     string
+	expected string
+}{
+	{selfSignedWithCommonName, "x509: certificate signed by unknown authority (possibly because of \"empty\" while trying to verify candidate authority certificate \"test\")"},
+	{selfSignedNoCommonNameWithOrgName, "x509: certificate signed by unknown authority (possibly because of \"empty\" while trying to verify candidate authority certificate \"ca\")"},
+	{selfSignedNoCommonNameNoOrgName, "x509: certificate signed by unknown authority (possibly because of \"empty\" while trying to verify candidate authority certificate \"serial:0\")"},
+}
+
+func TestUnknownAuthorityError(t *testing.T) {
+	for i, tt := range unknownAuthorityErrorTests {
+		der, _ := pem.Decode([]byte(tt.cert))
+		if der == nil {
+			t.Errorf("#%d: Unable to decode PEM block", i)
+		}
+		c, err := ParseCertificate(der.Bytes)
+		if err != nil {
+			t.Errorf("#%d: Unable to parse certificate -> %v", i, err)
+		}
+		uae := &UnknownAuthorityError{
+			Cert:     c,
+			hintErr:  fmt.Errorf("empty"),
+			hintCert: c,
+		}
+		actual := uae.Error()
+		if actual != tt.expected {
+			t.Errorf("#%d: UnknownAuthorityError.Error() response invalid actual: %s expected: %s", i, actual, tt.expected)
+		}
+	}
+}
+
+var nameConstraintTests = []struct {
+	constraint, domain string
+	expectError        bool
+	shouldMatch        bool
+}{
+	{"", "anything.com", false, true},
+	{"example.com", "example.com", false, true},
+	{"example.com.", "example.com", true, false},
+	{"example.com", "example.com.", true, false},
+	{"example.com", "ExAmPle.coM", false, true},
+	{"example.com", "exampl1.com", false, false},
+	{"example.com", "www.ExAmPle.coM", false, true},
+	{"example.com", "sub.www.ExAmPle.coM", false, true},
+	{"example.com", "notexample.com", false, false},
+	{".example.com", "example.com", false, false},
+	{".example.com", "www.example.com", false, true},
+	{".example.com", "www..example.com", true, false},
+}
+
+func TestNameConstraints(t *testing.T) {
+	for i, test := range nameConstraintTests {
+		result, err := matchDomainConstraint(test.domain, test.constraint)
+
+		if err != nil && !test.expectError {
+			t.Errorf("unexpected error for test #%d: domain=%s, constraint=%s, err=%s", i, test.domain, test.constraint, err)
+			continue
+		}
+
+		if err == nil && test.expectError {
+			t.Errorf("unexpected success for test #%d: domain=%s, constraint=%s", i, test.domain, test.constraint)
+			continue
+		}
+
+		if result != test.shouldMatch {
+			t.Errorf("unexpected result for test #%d: domain=%s, constraint=%s, result=%t", i, test.domain, test.constraint, result)
+		}
+	}
+}
+
+const selfSignedWithCommonName = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+const selfSignedNoCommonNameWithOrgName = `-----BEGIN CERTIFICATE-----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=
+-----END CERTIFICATE-----`
+const selfSignedNoCommonNameNoOrgName = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const criticalExtRoot = `-----BEGIN CERTIFICATE-----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=
+-----END CERTIFICATE-----`
+
+const criticalExtIntermediate = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const criticalExtLeafWithExt = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const criticalExtIntermediateWithExt = `-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----`
+
+const criticalExtLeaf = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+func TestValidHostname(t *testing.T) {
+	tests := []struct {
+		host                     string
+		validInput, validPattern bool
+	}{
+		{host: "example.com", validInput: true, validPattern: true},
+		{host: "eXample123-.com", validInput: true, validPattern: true},
+		{host: "-eXample123-.com"},
+		{host: ""},
+		{host: "."},
+		{host: "example..com"},
+		{host: ".example.com"},
+		{host: "example.com.", validInput: true},
+		{host: "*.example.com."},
+		{host: "*.example.com", validPattern: true},
+		{host: "*foo.example.com"},
+		{host: "foo.*.example.com"},
+		{host: "exa_mple.com", validInput: true, validPattern: true},
+		{host: "foo,bar"},
+		{host: "project-dev:us-central1:main"},
+	}
+	for _, tt := range tests {
+		if got := validHostnamePattern(tt.host); got != tt.validPattern {
+			t.Errorf("validHostnamePattern(%q) = %v, want %v", tt.host, got, tt.validPattern)
+		}
+		if got := validHostnameInput(tt.host); got != tt.validInput {
+			t.Errorf("validHostnameInput(%q) = %v, want %v", tt.host, got, tt.validInput)
+		}
+	}
+}
+
+func generateCert(cn string, isCA bool, issuer *Certificate, issuerKey crypto.PrivateKey) (*Certificate, crypto.PrivateKey, error) {
+	priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
+	serialNumber, _ := rand.Int(rand.Reader, serialNumberLimit)
+
+	template := &Certificate{
+		SerialNumber: serialNumber,
+		Subject:      pkix.Name{CommonName: cn},
+		NotBefore:    time.Now().Add(-1 * time.Hour),
+		NotAfter:     time.Now().Add(24 * time.Hour),
+
+		KeyUsage:              KeyUsageKeyEncipherment | KeyUsageDigitalSignature | KeyUsageCertSign,
+		ExtKeyUsage:           []ExtKeyUsage{ExtKeyUsageServerAuth},
+		BasicConstraintsValid: true,
+		IsCA:                  isCA,
+	}
+	if issuer == nil {
+		issuer = template
+		issuerKey = priv
+	}
+
+	derBytes, err := CreateCertificate(rand.Reader, template, issuer, priv.Public(), issuerKey)
+	if err != nil {
+		return nil, nil, err
+	}
+	cert, err := ParseCertificate(derBytes)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return cert, priv, nil
+}
+
+func TestPathologicalChain(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping generation of a long chain of certificates in short mode")
+	}
+
+	// Build a chain where all intermediates share the same subject, to hit the
+	// path building worst behavior.
+	roots, intermediates := NewCertPool(), NewCertPool()
+
+	parent, parentKey, err := generateCert("Root CA", true, nil, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	roots.AddCert(parent)
+
+	for i := 1; i < 100; i++ {
+		parent, parentKey, err = generateCert("Intermediate CA", true, parent, parentKey)
+		if err != nil {
+			t.Fatal(err)
+		}
+		intermediates.AddCert(parent)
+	}
+
+	leaf, _, err := generateCert("Leaf", false, parent, parentKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	start := time.Now()
+	_, err = leaf.Verify(VerifyOptions{
+		Roots:         roots,
+		Intermediates: intermediates,
+	})
+	t.Logf("verification took %v", time.Since(start))
+
+	if err == nil || !strings.Contains(err.Error(), "signature check attempts limit") {
+		t.Errorf("expected verification to fail with a signature checks limit error; got %v", err)
+	}
+}
+
+func TestLongChain(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping generation of a long chain of certificates in short mode")
+	}
+
+	roots, intermediates := NewCertPool(), NewCertPool()
+
+	parent, parentKey, err := generateCert("Root CA", true, nil, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	roots.AddCert(parent)
+
+	for i := 1; i < 15; i++ {
+		name := fmt.Sprintf("Intermediate CA #%d", i)
+		parent, parentKey, err = generateCert(name, true, parent, parentKey)
+		if err != nil {
+			t.Fatal(err)
+		}
+		intermediates.AddCert(parent)
+	}
+
+	leaf, _, err := generateCert("Leaf", false, parent, parentKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	start := time.Now()
+	if _, err := leaf.Verify(VerifyOptions{
+		Roots:         roots,
+		Intermediates: intermediates,
+	}); err != nil {
+		t.Error(err)
+	}
+	t.Logf("verification took %v", time.Since(start))
+}
+
+func TestSystemRootsError(t *testing.T) {
+	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
+		t.Skip("Windows and darwin do not use (or support) systemRoots")
+	}
+
+	defer func(oldSystemRoots *CertPool) { systemRoots = oldSystemRoots }(systemRootsPool())
+
+	opts := VerifyOptions{
+		Intermediates: NewCertPool(),
+		DNSName:       "www.google.com",
+		CurrentTime:   time.Unix(1395785200, 0),
+	}
+
+	if ok := opts.Intermediates.AppendCertsFromPEM([]byte(giag2Intermediate)); !ok {
+		t.Fatalf("failed to parse intermediate")
+	}
+
+	leaf, err := certificateFromPEM(googleLeaf)
+	if err != nil {
+		t.Fatalf("failed to parse leaf: %v", err)
+	}
+
+	systemRoots = nil
+
+	_, err = leaf.Verify(opts)
+	if _, ok := err.(SystemRootsError); !ok {
+		t.Errorf("error was not SystemRootsError: %v", err)
+	}
+}
+
+func TestSystemRootsErrorUnwrap(t *testing.T) {
+	var err1 = errors.New("err1")
+	err := SystemRootsError{Err: err1}
+	if !errors.Is(err, err1) {
+		t.Error("errors.Is failed, wanted success")
+	}
+}
+
+func TestIssue51759(t *testing.T) {
+	// badCertData contains a cert that we parse as valid
+	// but that macOS SecCertificateCreateWithData rejects.
+	const badCertData = "0\x82\x01U0\x82\x01\a\xa0\x03\x02\x01\x02\x02\x01\x020\x05\x06\x03+ep0R1P0N\x06\x03U\x04\x03\x13Gderpkey8dc58100b2493614ee1692831a461f3f4dd3f9b3b088e244f887f81b4906ac260\x1e\x17\r220112235755Z\x17\r220313235755Z0R1P0N\x06\x03U\x04\x03\x13Gderpkey8dc58100b2493614ee1692831a461f3f4dd3f9b3b088e244f887f81b4906ac260*0\x05\x06\x03+ep\x03!\x00bA\xd8e\xadW\xcb\xefZ\x89\xb5\"\x1eR\x9d\xba\x0e:\x1042Q@\u007f\xbd\xfb{ks\x04\xd1£\x020\x000\x05\x06\x03+ep\x03A\x00[\xa7\x06y\x86(\x94\x97\x9eLwA\x00\x01x\xaa\xbc\xbd Ê]\n(΅!ف0\xf5\x9a%I\x19<\xffo\xf1\xeaaf@\xb1\xa7\xaf\xfd\xe9R\xc7\x0f\x8d&\xd5\xfc\x0f;Ϙ\x82\x84a\xbc\r"
+	badCert, err := ParseCertificate([]byte(badCertData))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	t.Run("leaf", func(t *testing.T) {
+		opts := VerifyOptions{}
+		_, err = badCert.Verify(opts)
+		if err == nil {
+			t.Fatal("expected error")
+		}
+	})
+
+	goodCert, err := certificateFromPEM(googleLeaf)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	t.Run("intermediate", func(t *testing.T) {
+		opts := VerifyOptions{
+			Intermediates: NewCertPool(),
+		}
+		opts.Intermediates.AddCert(badCert)
+		_, err = goodCert.Verify(opts)
+		if err == nil {
+			t.Fatal("expected error")
+		}
+	})
+}
diff --git a/src/crypto/x509/x509.go b/src/crypto/x509/x509.go
new file mode 100644
index 0000000..dc470f5
--- /dev/null
+++ b/src/crypto/x509/x509.go
@@ -0,0 +1,2222 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package x509 parses X.509-encoded keys and certificates.
+package x509
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/elliptic"
+	"crypto/rsa"
+	"crypto/sha1"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"internal/godebug"
+	"io"
+	"math/big"
+	"net"
+	"net/url"
+	"strconv"
+	"time"
+	"unicode"
+
+	// Explicitly import these for their crypto.RegisterHash init side-effects.
+	// Keep these as blank imports, even if they're imported above.
+	_ "crypto/sha1"
+	_ "crypto/sha256"
+	_ "crypto/sha512"
+
+	"golang.org/x/crypto/cryptobyte"
+	cryptobyte_asn1 "golang.org/x/crypto/cryptobyte/asn1"
+)
+
+// pkixPublicKey reflects a PKIX public key structure. See SubjectPublicKeyInfo
+// in RFC 3280.
+type pkixPublicKey struct {
+	Algo      pkix.AlgorithmIdentifier
+	BitString asn1.BitString
+}
+
+// ParsePKIXPublicKey parses a public key in PKIX, ASN.1 DER form.
+// The encoded public key is a SubjectPublicKeyInfo structure
+// (see RFC 5280, Section 4.1).
+//
+// It returns a *rsa.PublicKey, *dsa.PublicKey, *ecdsa.PublicKey, or
+// ed25519.PublicKey. More types might be supported in the future.
+//
+// This kind of key is commonly encoded in PEM blocks of type "PUBLIC KEY".
+func ParsePKIXPublicKey(derBytes []byte) (pub any, err error) {
+	var pki publicKeyInfo
+	if rest, err := asn1.Unmarshal(derBytes, &pki); err != nil {
+		if _, err := asn1.Unmarshal(derBytes, &pkcs1PublicKey{}); err == nil {
+			return nil, errors.New("x509: failed to parse public key (use ParsePKCS1PublicKey instead for this key format)")
+		}
+		return nil, err
+	} else if len(rest) != 0 {
+		return nil, errors.New("x509: trailing data after ASN.1 of public-key")
+	}
+	algo := getPublicKeyAlgorithmFromOID(pki.Algorithm.Algorithm)
+	if algo == UnknownPublicKeyAlgorithm {
+		return nil, errors.New("x509: unknown public key algorithm")
+	}
+	return parsePublicKey(algo, &pki)
+}
+
+func marshalPublicKey(pub any) (publicKeyBytes []byte, publicKeyAlgorithm pkix.AlgorithmIdentifier, err error) {
+	switch pub := pub.(type) {
+	case *rsa.PublicKey:
+		publicKeyBytes, err = asn1.Marshal(pkcs1PublicKey{
+			N: pub.N,
+			E: pub.E,
+		})
+		if err != nil {
+			return nil, pkix.AlgorithmIdentifier{}, err
+		}
+		publicKeyAlgorithm.Algorithm = oidPublicKeyRSA
+		// This is a NULL parameters value which is required by
+		// RFC 3279, Section 2.3.1.
+		publicKeyAlgorithm.Parameters = asn1.NullRawValue
+	case *ecdsa.PublicKey:
+		publicKeyBytes = elliptic.Marshal(pub.Curve, pub.X, pub.Y)
+		oid, ok := oidFromNamedCurve(pub.Curve)
+		if !ok {
+			return nil, pkix.AlgorithmIdentifier{}, errors.New("x509: unsupported elliptic curve")
+		}
+		publicKeyAlgorithm.Algorithm = oidPublicKeyECDSA
+		var paramBytes []byte
+		paramBytes, err = asn1.Marshal(oid)
+		if err != nil {
+			return
+		}
+		publicKeyAlgorithm.Parameters.FullBytes = paramBytes
+	case ed25519.PublicKey:
+		publicKeyBytes = pub
+		publicKeyAlgorithm.Algorithm = oidPublicKeyEd25519
+	default:
+		return nil, pkix.AlgorithmIdentifier{}, fmt.Errorf("x509: unsupported public key type: %T", pub)
+	}
+
+	return publicKeyBytes, publicKeyAlgorithm, nil
+}
+
+// MarshalPKIXPublicKey converts a public key to PKIX, ASN.1 DER form.
+// The encoded public key is a SubjectPublicKeyInfo structure
+// (see RFC 5280, Section 4.1).
+//
+// The following key types are currently supported: *rsa.PublicKey, *ecdsa.PublicKey
+// and ed25519.PublicKey. Unsupported key types result in an error.
+//
+// This kind of key is commonly encoded in PEM blocks of type "PUBLIC KEY".
+func MarshalPKIXPublicKey(pub any) ([]byte, error) {
+	var publicKeyBytes []byte
+	var publicKeyAlgorithm pkix.AlgorithmIdentifier
+	var err error
+
+	if publicKeyBytes, publicKeyAlgorithm, err = marshalPublicKey(pub); err != nil {
+		return nil, err
+	}
+
+	pkix := pkixPublicKey{
+		Algo: publicKeyAlgorithm,
+		BitString: asn1.BitString{
+			Bytes:     publicKeyBytes,
+			BitLength: 8 * len(publicKeyBytes),
+		},
+	}
+
+	ret, _ := asn1.Marshal(pkix)
+	return ret, nil
+}
+
+// These structures reflect the ASN.1 structure of X.509 certificates.:
+
+type certificate struct {
+	Raw                asn1.RawContent
+	TBSCertificate     tbsCertificate
+	SignatureAlgorithm pkix.AlgorithmIdentifier
+	SignatureValue     asn1.BitString
+}
+
+type tbsCertificate struct {
+	Raw                asn1.RawContent
+	Version            int `asn1:"optional,explicit,default:0,tag:0"`
+	SerialNumber       *big.Int
+	SignatureAlgorithm pkix.AlgorithmIdentifier
+	Issuer             asn1.RawValue
+	Validity           validity
+	Subject            asn1.RawValue
+	PublicKey          publicKeyInfo
+	UniqueId           asn1.BitString   `asn1:"optional,tag:1"`
+	SubjectUniqueId    asn1.BitString   `asn1:"optional,tag:2"`
+	Extensions         []pkix.Extension `asn1:"optional,explicit,tag:3"`
+}
+
+type dsaAlgorithmParameters struct {
+	P, Q, G *big.Int
+}
+
+type validity struct {
+	NotBefore, NotAfter time.Time
+}
+
+type publicKeyInfo struct {
+	Raw       asn1.RawContent
+	Algorithm pkix.AlgorithmIdentifier
+	PublicKey asn1.BitString
+}
+
+// RFC 5280,  4.2.1.1
+type authKeyId struct {
+	Id []byte `asn1:"optional,tag:0"`
+}
+
+type SignatureAlgorithm int
+
+const (
+	UnknownSignatureAlgorithm SignatureAlgorithm = iota
+
+	MD2WithRSA  // Unsupported.
+	MD5WithRSA  // Only supported for signing, not verification.
+	SHA1WithRSA // Only supported for signing, and verification of CRLs, CSRs, and OCSP responses.
+	SHA256WithRSA
+	SHA384WithRSA
+	SHA512WithRSA
+	DSAWithSHA1   // Unsupported.
+	DSAWithSHA256 // Unsupported.
+	ECDSAWithSHA1 // Only supported for signing, and verification of CRLs, CSRs, and OCSP responses.
+	ECDSAWithSHA256
+	ECDSAWithSHA384
+	ECDSAWithSHA512
+	SHA256WithRSAPSS
+	SHA384WithRSAPSS
+	SHA512WithRSAPSS
+	PureEd25519
+)
+
+func (algo SignatureAlgorithm) isRSAPSS() bool {
+	switch algo {
+	case SHA256WithRSAPSS, SHA384WithRSAPSS, SHA512WithRSAPSS:
+		return true
+	default:
+		return false
+	}
+}
+
+func (algo SignatureAlgorithm) String() string {
+	for _, details := range signatureAlgorithmDetails {
+		if details.algo == algo {
+			return details.name
+		}
+	}
+	return strconv.Itoa(int(algo))
+}
+
+type PublicKeyAlgorithm int
+
+const (
+	UnknownPublicKeyAlgorithm PublicKeyAlgorithm = iota
+	RSA
+	DSA // Unsupported.
+	ECDSA
+	Ed25519
+)
+
+var publicKeyAlgoName = [...]string{
+	RSA:     "RSA",
+	DSA:     "DSA",
+	ECDSA:   "ECDSA",
+	Ed25519: "Ed25519",
+}
+
+func (algo PublicKeyAlgorithm) String() string {
+	if 0 < algo && int(algo) < len(publicKeyAlgoName) {
+		return publicKeyAlgoName[algo]
+	}
+	return strconv.Itoa(int(algo))
+}
+
+// OIDs for signature algorithms
+//
+// pkcs-1 OBJECT IDENTIFIER ::= {
+//    iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 1 }
+//
+//
+// RFC 3279 2.2.1 RSA Signature Algorithms
+//
+// md2WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 2 }
+//
+// md5WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 4 }
+//
+// sha-1WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 5 }
+//
+// dsaWithSha1 OBJECT IDENTIFIER ::= {
+//    iso(1) member-body(2) us(840) x9-57(10040) x9cm(4) 3 }
+//
+// RFC 3279 2.2.3 ECDSA Signature Algorithm
+//
+// ecdsa-with-SHA1 OBJECT IDENTIFIER ::= {
+// 	  iso(1) member-body(2) us(840) ansi-x962(10045)
+//    signatures(4) ecdsa-with-SHA1(1)}
+//
+//
+// RFC 4055 5 PKCS #1 Version 1.5
+//
+// sha256WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 11 }
+//
+// sha384WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 12 }
+//
+// sha512WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 13 }
+//
+//
+// RFC 5758 3.1 DSA Signature Algorithms
+//
+// dsaWithSha256 OBJECT IDENTIFIER ::= {
+//    joint-iso-ccitt(2) country(16) us(840) organization(1) gov(101)
+//    csor(3) algorithms(4) id-dsa-with-sha2(3) 2}
+//
+// RFC 5758 3.2 ECDSA Signature Algorithm
+//
+// ecdsa-with-SHA256 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
+//    us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 2 }
+//
+// ecdsa-with-SHA384 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
+//    us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 3 }
+//
+// ecdsa-with-SHA512 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
+//    us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 4 }
+//
+//
+// RFC 8410 3 Curve25519 and Curve448 Algorithm Identifiers
+//
+// id-Ed25519   OBJECT IDENTIFIER ::= { 1 3 101 112 }
+
+var (
+	oidSignatureMD2WithRSA      = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 2}
+	oidSignatureMD5WithRSA      = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 4}
+	oidSignatureSHA1WithRSA     = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 5}
+	oidSignatureSHA256WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 11}
+	oidSignatureSHA384WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 12}
+	oidSignatureSHA512WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 13}
+	oidSignatureRSAPSS          = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 10}
+	oidSignatureDSAWithSHA1     = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 3}
+	oidSignatureDSAWithSHA256   = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 3, 2}
+	oidSignatureECDSAWithSHA1   = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 1}
+	oidSignatureECDSAWithSHA256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 2}
+	oidSignatureECDSAWithSHA384 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 3}
+	oidSignatureECDSAWithSHA512 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 4}
+	oidSignatureEd25519         = asn1.ObjectIdentifier{1, 3, 101, 112}
+
+	oidSHA256 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 1}
+	oidSHA384 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 2}
+	oidSHA512 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 3}
+
+	oidMGF1 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 8}
+
+	// oidISOSignatureSHA1WithRSA means the same as oidSignatureSHA1WithRSA
+	// but it's specified by ISO. Microsoft's makecert.exe has been known
+	// to produce certificates with this OID.
+	oidISOSignatureSHA1WithRSA = asn1.ObjectIdentifier{1, 3, 14, 3, 2, 29}
+)
+
+var signatureAlgorithmDetails = []struct {
+	algo       SignatureAlgorithm
+	name       string
+	oid        asn1.ObjectIdentifier
+	pubKeyAlgo PublicKeyAlgorithm
+	hash       crypto.Hash
+}{
+	{MD2WithRSA, "MD2-RSA", oidSignatureMD2WithRSA, RSA, crypto.Hash(0) /* no value for MD2 */},
+	{MD5WithRSA, "MD5-RSA", oidSignatureMD5WithRSA, RSA, crypto.MD5},
+	{SHA1WithRSA, "SHA1-RSA", oidSignatureSHA1WithRSA, RSA, crypto.SHA1},
+	{SHA1WithRSA, "SHA1-RSA", oidISOSignatureSHA1WithRSA, RSA, crypto.SHA1},
+	{SHA256WithRSA, "SHA256-RSA", oidSignatureSHA256WithRSA, RSA, crypto.SHA256},
+	{SHA384WithRSA, "SHA384-RSA", oidSignatureSHA384WithRSA, RSA, crypto.SHA384},
+	{SHA512WithRSA, "SHA512-RSA", oidSignatureSHA512WithRSA, RSA, crypto.SHA512},
+	{SHA256WithRSAPSS, "SHA256-RSAPSS", oidSignatureRSAPSS, RSA, crypto.SHA256},
+	{SHA384WithRSAPSS, "SHA384-RSAPSS", oidSignatureRSAPSS, RSA, crypto.SHA384},
+	{SHA512WithRSAPSS, "SHA512-RSAPSS", oidSignatureRSAPSS, RSA, crypto.SHA512},
+	{DSAWithSHA1, "DSA-SHA1", oidSignatureDSAWithSHA1, DSA, crypto.SHA1},
+	{DSAWithSHA256, "DSA-SHA256", oidSignatureDSAWithSHA256, DSA, crypto.SHA256},
+	{ECDSAWithSHA1, "ECDSA-SHA1", oidSignatureECDSAWithSHA1, ECDSA, crypto.SHA1},
+	{ECDSAWithSHA256, "ECDSA-SHA256", oidSignatureECDSAWithSHA256, ECDSA, crypto.SHA256},
+	{ECDSAWithSHA384, "ECDSA-SHA384", oidSignatureECDSAWithSHA384, ECDSA, crypto.SHA384},
+	{ECDSAWithSHA512, "ECDSA-SHA512", oidSignatureECDSAWithSHA512, ECDSA, crypto.SHA512},
+	{PureEd25519, "Ed25519", oidSignatureEd25519, Ed25519, crypto.Hash(0) /* no pre-hashing */},
+}
+
+// hashToPSSParameters contains the DER encoded RSA PSS parameters for the
+// SHA256, SHA384, and SHA512 hashes as defined in RFC 3447, Appendix A.2.3.
+// The parameters contain the following values:
+//   * hashAlgorithm contains the associated hash identifier with NULL parameters
+//   * maskGenAlgorithm always contains the default mgf1SHA1 identifier
+//   * saltLength contains the length of the associated hash
+//   * trailerField always contains the default trailerFieldBC value
+var hashToPSSParameters = map[crypto.Hash]asn1.RawValue{
+	crypto.SHA256: asn1.RawValue{FullBytes: []byte{48, 52, 160, 15, 48, 13, 6, 9, 96, 134, 72, 1, 101, 3, 4, 2, 1, 5, 0, 161, 28, 48, 26, 6, 9, 42, 134, 72, 134, 247, 13, 1, 1, 8, 48, 13, 6, 9, 96, 134, 72, 1, 101, 3, 4, 2, 1, 5, 0, 162, 3, 2, 1, 32}},
+	crypto.SHA384: asn1.RawValue{FullBytes: []byte{48, 52, 160, 15, 48, 13, 6, 9, 96, 134, 72, 1, 101, 3, 4, 2, 2, 5, 0, 161, 28, 48, 26, 6, 9, 42, 134, 72, 134, 247, 13, 1, 1, 8, 48, 13, 6, 9, 96, 134, 72, 1, 101, 3, 4, 2, 2, 5, 0, 162, 3, 2, 1, 48}},
+	crypto.SHA512: asn1.RawValue{FullBytes: []byte{48, 52, 160, 15, 48, 13, 6, 9, 96, 134, 72, 1, 101, 3, 4, 2, 3, 5, 0, 161, 28, 48, 26, 6, 9, 42, 134, 72, 134, 247, 13, 1, 1, 8, 48, 13, 6, 9, 96, 134, 72, 1, 101, 3, 4, 2, 3, 5, 0, 162, 3, 2, 1, 64}},
+}
+
+// pssParameters reflects the parameters in an AlgorithmIdentifier that
+// specifies RSA PSS. See RFC 3447, Appendix A.2.3.
+type pssParameters struct {
+	// The following three fields are not marked as
+	// optional because the default values specify SHA-1,
+	// which is no longer suitable for use in signatures.
+	Hash         pkix.AlgorithmIdentifier `asn1:"explicit,tag:0"`
+	MGF          pkix.AlgorithmIdentifier `asn1:"explicit,tag:1"`
+	SaltLength   int                      `asn1:"explicit,tag:2"`
+	TrailerField int                      `asn1:"optional,explicit,tag:3,default:1"`
+}
+
+func getSignatureAlgorithmFromAI(ai pkix.AlgorithmIdentifier) SignatureAlgorithm {
+	if ai.Algorithm.Equal(oidSignatureEd25519) {
+		// RFC 8410, Section 3
+		// > For all of the OIDs, the parameters MUST be absent.
+		if len(ai.Parameters.FullBytes) != 0 {
+			return UnknownSignatureAlgorithm
+		}
+	}
+
+	if !ai.Algorithm.Equal(oidSignatureRSAPSS) {
+		for _, details := range signatureAlgorithmDetails {
+			if ai.Algorithm.Equal(details.oid) {
+				return details.algo
+			}
+		}
+		return UnknownSignatureAlgorithm
+	}
+
+	// RSA PSS is special because it encodes important parameters
+	// in the Parameters.
+
+	var params pssParameters
+	if _, err := asn1.Unmarshal(ai.Parameters.FullBytes, &params); err != nil {
+		return UnknownSignatureAlgorithm
+	}
+
+	var mgf1HashFunc pkix.AlgorithmIdentifier
+	if _, err := asn1.Unmarshal(params.MGF.Parameters.FullBytes, &mgf1HashFunc); err != nil {
+		return UnknownSignatureAlgorithm
+	}
+
+	// PSS is greatly overburdened with options. This code forces them into
+	// three buckets by requiring that the MGF1 hash function always match the
+	// message hash function (as recommended in RFC 3447, Section 8.1), that the
+	// salt length matches the hash length, and that the trailer field has the
+	// default value.
+	if (len(params.Hash.Parameters.FullBytes) != 0 && !bytes.Equal(params.Hash.Parameters.FullBytes, asn1.NullBytes)) ||
+		!params.MGF.Algorithm.Equal(oidMGF1) ||
+		!mgf1HashFunc.Algorithm.Equal(params.Hash.Algorithm) ||
+		(len(mgf1HashFunc.Parameters.FullBytes) != 0 && !bytes.Equal(mgf1HashFunc.Parameters.FullBytes, asn1.NullBytes)) ||
+		params.TrailerField != 1 {
+		return UnknownSignatureAlgorithm
+	}
+
+	switch {
+	case params.Hash.Algorithm.Equal(oidSHA256) && params.SaltLength == 32:
+		return SHA256WithRSAPSS
+	case params.Hash.Algorithm.Equal(oidSHA384) && params.SaltLength == 48:
+		return SHA384WithRSAPSS
+	case params.Hash.Algorithm.Equal(oidSHA512) && params.SaltLength == 64:
+		return SHA512WithRSAPSS
+	}
+
+	return UnknownSignatureAlgorithm
+}
+
+// RFC 3279, 2.3 Public Key Algorithms
+//
+// pkcs-1 OBJECT IDENTIFIER ::== { iso(1) member-body(2) us(840)
+//    rsadsi(113549) pkcs(1) 1 }
+//
+// rsaEncryption OBJECT IDENTIFIER ::== { pkcs1-1 1 }
+//
+// id-dsa OBJECT IDENTIFIER ::== { iso(1) member-body(2) us(840)
+//    x9-57(10040) x9cm(4) 1 }
+//
+// RFC 5480, 2.1.1 Unrestricted Algorithm Identifier and Parameters
+//
+// id-ecPublicKey OBJECT IDENTIFIER ::= {
+//       iso(1) member-body(2) us(840) ansi-X9-62(10045) keyType(2) 1 }
+var (
+	oidPublicKeyRSA     = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 1}
+	oidPublicKeyDSA     = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 1}
+	oidPublicKeyECDSA   = asn1.ObjectIdentifier{1, 2, 840, 10045, 2, 1}
+	oidPublicKeyEd25519 = oidSignatureEd25519
+)
+
+func getPublicKeyAlgorithmFromOID(oid asn1.ObjectIdentifier) PublicKeyAlgorithm {
+	switch {
+	case oid.Equal(oidPublicKeyRSA):
+		return RSA
+	case oid.Equal(oidPublicKeyDSA):
+		return DSA
+	case oid.Equal(oidPublicKeyECDSA):
+		return ECDSA
+	case oid.Equal(oidPublicKeyEd25519):
+		return Ed25519
+	}
+	return UnknownPublicKeyAlgorithm
+}
+
+// RFC 5480, 2.1.1.1. Named Curve
+//
+// secp224r1 OBJECT IDENTIFIER ::= {
+//   iso(1) identified-organization(3) certicom(132) curve(0) 33 }
+//
+// secp256r1 OBJECT IDENTIFIER ::= {
+//   iso(1) member-body(2) us(840) ansi-X9-62(10045) curves(3)
+//   prime(1) 7 }
+//
+// secp384r1 OBJECT IDENTIFIER ::= {
+//   iso(1) identified-organization(3) certicom(132) curve(0) 34 }
+//
+// secp521r1 OBJECT IDENTIFIER ::= {
+//   iso(1) identified-organization(3) certicom(132) curve(0) 35 }
+//
+// NB: secp256r1 is equivalent to prime256v1
+var (
+	oidNamedCurveP224 = asn1.ObjectIdentifier{1, 3, 132, 0, 33}
+	oidNamedCurveP256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 3, 1, 7}
+	oidNamedCurveP384 = asn1.ObjectIdentifier{1, 3, 132, 0, 34}
+	oidNamedCurveP521 = asn1.ObjectIdentifier{1, 3, 132, 0, 35}
+)
+
+func namedCurveFromOID(oid asn1.ObjectIdentifier) elliptic.Curve {
+	switch {
+	case oid.Equal(oidNamedCurveP224):
+		return elliptic.P224()
+	case oid.Equal(oidNamedCurveP256):
+		return elliptic.P256()
+	case oid.Equal(oidNamedCurveP384):
+		return elliptic.P384()
+	case oid.Equal(oidNamedCurveP521):
+		return elliptic.P521()
+	}
+	return nil
+}
+
+func oidFromNamedCurve(curve elliptic.Curve) (asn1.ObjectIdentifier, bool) {
+	switch curve {
+	case elliptic.P224():
+		return oidNamedCurveP224, true
+	case elliptic.P256():
+		return oidNamedCurveP256, true
+	case elliptic.P384():
+		return oidNamedCurveP384, true
+	case elliptic.P521():
+		return oidNamedCurveP521, true
+	}
+
+	return nil, false
+}
+
+// KeyUsage represents the set of actions that are valid for a given key. It's
+// a bitmap of the KeyUsage* constants.
+type KeyUsage int
+
+const (
+	KeyUsageDigitalSignature KeyUsage = 1 << iota
+	KeyUsageContentCommitment
+	KeyUsageKeyEncipherment
+	KeyUsageDataEncipherment
+	KeyUsageKeyAgreement
+	KeyUsageCertSign
+	KeyUsageCRLSign
+	KeyUsageEncipherOnly
+	KeyUsageDecipherOnly
+)
+
+// RFC 5280, 4.2.1.12  Extended Key Usage
+//
+// anyExtendedKeyUsage OBJECT IDENTIFIER ::= { id-ce-extKeyUsage 0 }
+//
+// id-kp OBJECT IDENTIFIER ::= { id-pkix 3 }
+//
+// id-kp-serverAuth             OBJECT IDENTIFIER ::= { id-kp 1 }
+// id-kp-clientAuth             OBJECT IDENTIFIER ::= { id-kp 2 }
+// id-kp-codeSigning            OBJECT IDENTIFIER ::= { id-kp 3 }
+// id-kp-emailProtection        OBJECT IDENTIFIER ::= { id-kp 4 }
+// id-kp-timeStamping           OBJECT IDENTIFIER ::= { id-kp 8 }
+// id-kp-OCSPSigning            OBJECT IDENTIFIER ::= { id-kp 9 }
+var (
+	oidExtKeyUsageAny                            = asn1.ObjectIdentifier{2, 5, 29, 37, 0}
+	oidExtKeyUsageServerAuth                     = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 1}
+	oidExtKeyUsageClientAuth                     = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 2}
+	oidExtKeyUsageCodeSigning                    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 3}
+	oidExtKeyUsageEmailProtection                = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 4}
+	oidExtKeyUsageIPSECEndSystem                 = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 5}
+	oidExtKeyUsageIPSECTunnel                    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 6}
+	oidExtKeyUsageIPSECUser                      = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 7}
+	oidExtKeyUsageTimeStamping                   = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 8}
+	oidExtKeyUsageOCSPSigning                    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 9}
+	oidExtKeyUsageMicrosoftServerGatedCrypto     = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 311, 10, 3, 3}
+	oidExtKeyUsageNetscapeServerGatedCrypto      = asn1.ObjectIdentifier{2, 16, 840, 1, 113730, 4, 1}
+	oidExtKeyUsageMicrosoftCommercialCodeSigning = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 311, 2, 1, 22}
+	oidExtKeyUsageMicrosoftKernelCodeSigning     = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 311, 61, 1, 1}
+)
+
+// ExtKeyUsage represents an extended set of actions that are valid for a given key.
+// Each of the ExtKeyUsage* constants define a unique action.
+type ExtKeyUsage int
+
+const (
+	ExtKeyUsageAny ExtKeyUsage = iota
+	ExtKeyUsageServerAuth
+	ExtKeyUsageClientAuth
+	ExtKeyUsageCodeSigning
+	ExtKeyUsageEmailProtection
+	ExtKeyUsageIPSECEndSystem
+	ExtKeyUsageIPSECTunnel
+	ExtKeyUsageIPSECUser
+	ExtKeyUsageTimeStamping
+	ExtKeyUsageOCSPSigning
+	ExtKeyUsageMicrosoftServerGatedCrypto
+	ExtKeyUsageNetscapeServerGatedCrypto
+	ExtKeyUsageMicrosoftCommercialCodeSigning
+	ExtKeyUsageMicrosoftKernelCodeSigning
+)
+
+// extKeyUsageOIDs contains the mapping between an ExtKeyUsage and its OID.
+var extKeyUsageOIDs = []struct {
+	extKeyUsage ExtKeyUsage
+	oid         asn1.ObjectIdentifier
+}{
+	{ExtKeyUsageAny, oidExtKeyUsageAny},
+	{ExtKeyUsageServerAuth, oidExtKeyUsageServerAuth},
+	{ExtKeyUsageClientAuth, oidExtKeyUsageClientAuth},
+	{ExtKeyUsageCodeSigning, oidExtKeyUsageCodeSigning},
+	{ExtKeyUsageEmailProtection, oidExtKeyUsageEmailProtection},
+	{ExtKeyUsageIPSECEndSystem, oidExtKeyUsageIPSECEndSystem},
+	{ExtKeyUsageIPSECTunnel, oidExtKeyUsageIPSECTunnel},
+	{ExtKeyUsageIPSECUser, oidExtKeyUsageIPSECUser},
+	{ExtKeyUsageTimeStamping, oidExtKeyUsageTimeStamping},
+	{ExtKeyUsageOCSPSigning, oidExtKeyUsageOCSPSigning},
+	{ExtKeyUsageMicrosoftServerGatedCrypto, oidExtKeyUsageMicrosoftServerGatedCrypto},
+	{ExtKeyUsageNetscapeServerGatedCrypto, oidExtKeyUsageNetscapeServerGatedCrypto},
+	{ExtKeyUsageMicrosoftCommercialCodeSigning, oidExtKeyUsageMicrosoftCommercialCodeSigning},
+	{ExtKeyUsageMicrosoftKernelCodeSigning, oidExtKeyUsageMicrosoftKernelCodeSigning},
+}
+
+func extKeyUsageFromOID(oid asn1.ObjectIdentifier) (eku ExtKeyUsage, ok bool) {
+	for _, pair := range extKeyUsageOIDs {
+		if oid.Equal(pair.oid) {
+			return pair.extKeyUsage, true
+		}
+	}
+	return
+}
+
+func oidFromExtKeyUsage(eku ExtKeyUsage) (oid asn1.ObjectIdentifier, ok bool) {
+	for _, pair := range extKeyUsageOIDs {
+		if eku == pair.extKeyUsage {
+			return pair.oid, true
+		}
+	}
+	return
+}
+
+// A Certificate represents an X.509 certificate.
+type Certificate struct {
+	Raw                     []byte // Complete ASN.1 DER content (certificate, signature algorithm and signature).
+	RawTBSCertificate       []byte // Certificate part of raw ASN.1 DER content.
+	RawSubjectPublicKeyInfo []byte // DER encoded SubjectPublicKeyInfo.
+	RawSubject              []byte // DER encoded Subject
+	RawIssuer               []byte // DER encoded Issuer
+
+	Signature          []byte
+	SignatureAlgorithm SignatureAlgorithm
+
+	PublicKeyAlgorithm PublicKeyAlgorithm
+	PublicKey          any
+
+	Version             int
+	SerialNumber        *big.Int
+	Issuer              pkix.Name
+	Subject             pkix.Name
+	NotBefore, NotAfter time.Time // Validity bounds.
+	KeyUsage            KeyUsage
+
+	// Extensions contains raw X.509 extensions. When parsing certificates,
+	// this can be used to extract non-critical extensions that are not
+	// parsed by this package. When marshaling certificates, the Extensions
+	// field is ignored, see ExtraExtensions.
+	Extensions []pkix.Extension
+
+	// ExtraExtensions contains extensions to be copied, raw, into any
+	// marshaled certificates. Values override any extensions that would
+	// otherwise be produced based on the other fields. The ExtraExtensions
+	// field is not populated when parsing certificates, see Extensions.
+	ExtraExtensions []pkix.Extension
+
+	// UnhandledCriticalExtensions contains a list of extension IDs that
+	// were not (fully) processed when parsing. Verify will fail if this
+	// slice is non-empty, unless verification is delegated to an OS
+	// library which understands all the critical extensions.
+	//
+	// Users can access these extensions using Extensions and can remove
+	// elements from this slice if they believe that they have been
+	// handled.
+	UnhandledCriticalExtensions []asn1.ObjectIdentifier
+
+	ExtKeyUsage        []ExtKeyUsage           // Sequence of extended key usages.
+	UnknownExtKeyUsage []asn1.ObjectIdentifier // Encountered extended key usages unknown to this package.
+
+	// BasicConstraintsValid indicates whether IsCA, MaxPathLen,
+	// and MaxPathLenZero are valid.
+	BasicConstraintsValid bool
+	IsCA                  bool
+
+	// MaxPathLen and MaxPathLenZero indicate the presence and
+	// value of the BasicConstraints' "pathLenConstraint".
+	//
+	// When parsing a certificate, a positive non-zero MaxPathLen
+	// means that the field was specified, -1 means it was unset,
+	// and MaxPathLenZero being true mean that the field was
+	// explicitly set to zero. The case of MaxPathLen==0 with MaxPathLenZero==false
+	// should be treated equivalent to -1 (unset).
+	//
+	// When generating a certificate, an unset pathLenConstraint
+	// can be requested with either MaxPathLen == -1 or using the
+	// zero value for both MaxPathLen and MaxPathLenZero.
+	MaxPathLen int
+	// MaxPathLenZero indicates that BasicConstraintsValid==true
+	// and MaxPathLen==0 should be interpreted as an actual
+	// maximum path length of zero. Otherwise, that combination is
+	// interpreted as MaxPathLen not being set.
+	MaxPathLenZero bool
+
+	SubjectKeyId   []byte
+	AuthorityKeyId []byte
+
+	// RFC 5280, 4.2.2.1 (Authority Information Access)
+	OCSPServer            []string
+	IssuingCertificateURL []string
+
+	// Subject Alternate Name values. (Note that these values may not be valid
+	// if invalid values were contained within a parsed certificate. For
+	// example, an element of DNSNames may not be a valid DNS domain name.)
+	DNSNames       []string
+	EmailAddresses []string
+	IPAddresses    []net.IP
+	URIs           []*url.URL
+
+	// Name constraints
+	PermittedDNSDomainsCritical bool // if true then the name constraints are marked critical.
+	PermittedDNSDomains         []string
+	ExcludedDNSDomains          []string
+	PermittedIPRanges           []*net.IPNet
+	ExcludedIPRanges            []*net.IPNet
+	PermittedEmailAddresses     []string
+	ExcludedEmailAddresses      []string
+	PermittedURIDomains         []string
+	ExcludedURIDomains          []string
+
+	// CRL Distribution Points
+	CRLDistributionPoints []string
+
+	PolicyIdentifiers []asn1.ObjectIdentifier
+}
+
+// ErrUnsupportedAlgorithm results from attempting to perform an operation that
+// involves algorithms that are not currently implemented.
+var ErrUnsupportedAlgorithm = errors.New("x509: cannot verify signature: algorithm unimplemented")
+
+// An InsecureAlgorithmError indicates that the SignatureAlgorithm used to
+// generate the signature is not secure, and the signature has been rejected.
+//
+// To temporarily restore support for SHA-1 signatures, include the value
+// "x509sha1=1" in the GODEBUG environment variable. Note that this option will
+// be removed in Go 1.19.
+type InsecureAlgorithmError SignatureAlgorithm
+
+func (e InsecureAlgorithmError) Error() string {
+	var override string
+	if SignatureAlgorithm(e) == SHA1WithRSA || SignatureAlgorithm(e) == ECDSAWithSHA1 {
+		override = " (temporarily override with GODEBUG=x509sha1=1)"
+	}
+	return fmt.Sprintf("x509: cannot verify signature: insecure algorithm %v", SignatureAlgorithm(e)) + override
+}
+
+// ConstraintViolationError results when a requested usage is not permitted by
+// a certificate. For example: checking a signature when the public key isn't a
+// certificate signing key.
+type ConstraintViolationError struct{}
+
+func (ConstraintViolationError) Error() string {
+	return "x509: invalid signature: parent certificate cannot sign this kind of certificate"
+}
+
+func (c *Certificate) Equal(other *Certificate) bool {
+	if c == nil || other == nil {
+		return c == other
+	}
+	return bytes.Equal(c.Raw, other.Raw)
+}
+
+func (c *Certificate) hasSANExtension() bool {
+	return oidInExtensions(oidExtensionSubjectAltName, c.Extensions)
+}
+
+// CheckSignatureFrom verifies that the signature on c is a valid signature
+// from parent. SHA1WithRSA and ECDSAWithSHA1 signatures are not supported.
+func (c *Certificate) CheckSignatureFrom(parent *Certificate) error {
+	// RFC 5280, 4.2.1.9:
+	// "If the basic constraints extension is not present in a version 3
+	// certificate, or the extension is present but the cA boolean is not
+	// asserted, then the certified public key MUST NOT be used to verify
+	// certificate signatures."
+	if parent.Version == 3 && !parent.BasicConstraintsValid ||
+		parent.BasicConstraintsValid && !parent.IsCA {
+		return ConstraintViolationError{}
+	}
+
+	if parent.KeyUsage != 0 && parent.KeyUsage&KeyUsageCertSign == 0 {
+		return ConstraintViolationError{}
+	}
+
+	if parent.PublicKeyAlgorithm == UnknownPublicKeyAlgorithm {
+		return ErrUnsupportedAlgorithm
+	}
+
+	// TODO(agl): don't ignore the path length constraint.
+
+	return checkSignature(c.SignatureAlgorithm, c.RawTBSCertificate, c.Signature, parent.PublicKey, false)
+}
+
+// CheckSignature verifies that signature is a valid signature over signed from
+// c's public key.
+func (c *Certificate) CheckSignature(algo SignatureAlgorithm, signed, signature []byte) error {
+	return checkSignature(algo, signed, signature, c.PublicKey, true)
+}
+
+func (c *Certificate) hasNameConstraints() bool {
+	return oidInExtensions(oidExtensionNameConstraints, c.Extensions)
+}
+
+func (c *Certificate) getSANExtension() []byte {
+	for _, e := range c.Extensions {
+		if e.Id.Equal(oidExtensionSubjectAltName) {
+			return e.Value
+		}
+	}
+	return nil
+}
+
+func signaturePublicKeyAlgoMismatchError(expectedPubKeyAlgo PublicKeyAlgorithm, pubKey any) error {
+	return fmt.Errorf("x509: signature algorithm specifies an %s public key, but have public key of type %T", expectedPubKeyAlgo.String(), pubKey)
+}
+
+// checkSignature verifies that signature is a valid signature over signed from
+// a crypto.PublicKey.
+func checkSignature(algo SignatureAlgorithm, signed, signature []byte, publicKey crypto.PublicKey, allowSHA1 bool) (err error) {
+	var hashType crypto.Hash
+	var pubKeyAlgo PublicKeyAlgorithm
+
+	for _, details := range signatureAlgorithmDetails {
+		if details.algo == algo {
+			hashType = details.hash
+			pubKeyAlgo = details.pubKeyAlgo
+		}
+	}
+
+	switch hashType {
+	case crypto.Hash(0):
+		if pubKeyAlgo != Ed25519 {
+			return ErrUnsupportedAlgorithm
+		}
+	case crypto.MD5:
+		return InsecureAlgorithmError(algo)
+	case crypto.SHA1:
+		// SHA-1 signatures are mostly disabled. See go.dev/issue/41682.
+		if !allowSHA1 && godebug.Get("x509sha1") != "1" {
+			return InsecureAlgorithmError(algo)
+		}
+		fallthrough
+	default:
+		if !hashType.Available() {
+			return ErrUnsupportedAlgorithm
+		}
+		h := hashType.New()
+		h.Write(signed)
+		signed = h.Sum(nil)
+	}
+
+	switch pub := publicKey.(type) {
+	case *rsa.PublicKey:
+		if pubKeyAlgo != RSA {
+			return signaturePublicKeyAlgoMismatchError(pubKeyAlgo, pub)
+		}
+		if algo.isRSAPSS() {
+			return rsa.VerifyPSS(pub, hashType, signed, signature, &rsa.PSSOptions{SaltLength: rsa.PSSSaltLengthEqualsHash})
+		} else {
+			return rsa.VerifyPKCS1v15(pub, hashType, signed, signature)
+		}
+	case *ecdsa.PublicKey:
+		if pubKeyAlgo != ECDSA {
+			return signaturePublicKeyAlgoMismatchError(pubKeyAlgo, pub)
+		}
+		if !ecdsa.VerifyASN1(pub, signed, signature) {
+			return errors.New("x509: ECDSA verification failure")
+		}
+		return
+	case ed25519.PublicKey:
+		if pubKeyAlgo != Ed25519 {
+			return signaturePublicKeyAlgoMismatchError(pubKeyAlgo, pub)
+		}
+		if !ed25519.Verify(pub, signed, signature) {
+			return errors.New("x509: Ed25519 verification failure")
+		}
+		return
+	}
+	return ErrUnsupportedAlgorithm
+}
+
+// CheckCRLSignature checks that the signature in crl is from c.
+func (c *Certificate) CheckCRLSignature(crl *pkix.CertificateList) error {
+	algo := getSignatureAlgorithmFromAI(crl.SignatureAlgorithm)
+	return c.CheckSignature(algo, crl.TBSCertList.Raw, crl.SignatureValue.RightAlign())
+}
+
+type UnhandledCriticalExtension struct{}
+
+func (h UnhandledCriticalExtension) Error() string {
+	return "x509: unhandled critical extension"
+}
+
+type basicConstraints struct {
+	IsCA       bool `asn1:"optional"`
+	MaxPathLen int  `asn1:"optional,default:-1"`
+}
+
+// RFC 5280 4.2.1.4
+type policyInformation struct {
+	Policy asn1.ObjectIdentifier
+	// policyQualifiers omitted
+}
+
+const (
+	nameTypeEmail = 1
+	nameTypeDNS   = 2
+	nameTypeURI   = 6
+	nameTypeIP    = 7
+)
+
+// RFC 5280, 4.2.2.1
+type authorityInfoAccess struct {
+	Method   asn1.ObjectIdentifier
+	Location asn1.RawValue
+}
+
+// RFC 5280, 4.2.1.14
+type distributionPoint struct {
+	DistributionPoint distributionPointName `asn1:"optional,tag:0"`
+	Reason            asn1.BitString        `asn1:"optional,tag:1"`
+	CRLIssuer         asn1.RawValue         `asn1:"optional,tag:2"`
+}
+
+type distributionPointName struct {
+	FullName     []asn1.RawValue  `asn1:"optional,tag:0"`
+	RelativeName pkix.RDNSequence `asn1:"optional,tag:1"`
+}
+
+func reverseBitsInAByte(in byte) byte {
+	b1 := in>>4 | in<<4
+	b2 := b1>>2&0x33 | b1<<2&0xcc
+	b3 := b2>>1&0x55 | b2<<1&0xaa
+	return b3
+}
+
+// asn1BitLength returns the bit-length of bitString by considering the
+// most-significant bit in a byte to be the "first" bit. This convention
+// matches ASN.1, but differs from almost everything else.
+func asn1BitLength(bitString []byte) int {
+	bitLen := len(bitString) * 8
+
+	for i := range bitString {
+		b := bitString[len(bitString)-i-1]
+
+		for bit := uint(0); bit < 8; bit++ {
+			if (b>>bit)&1 == 1 {
+				return bitLen
+			}
+			bitLen--
+		}
+	}
+
+	return 0
+}
+
+var (
+	oidExtensionSubjectKeyId          = []int{2, 5, 29, 14}
+	oidExtensionKeyUsage              = []int{2, 5, 29, 15}
+	oidExtensionExtendedKeyUsage      = []int{2, 5, 29, 37}
+	oidExtensionAuthorityKeyId        = []int{2, 5, 29, 35}
+	oidExtensionBasicConstraints      = []int{2, 5, 29, 19}
+	oidExtensionSubjectAltName        = []int{2, 5, 29, 17}
+	oidExtensionCertificatePolicies   = []int{2, 5, 29, 32}
+	oidExtensionNameConstraints       = []int{2, 5, 29, 30}
+	oidExtensionCRLDistributionPoints = []int{2, 5, 29, 31}
+	oidExtensionAuthorityInfoAccess   = []int{1, 3, 6, 1, 5, 5, 7, 1, 1}
+	oidExtensionCRLNumber             = []int{2, 5, 29, 20}
+)
+
+var (
+	oidAuthorityInfoAccessOcsp    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 48, 1}
+	oidAuthorityInfoAccessIssuers = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 48, 2}
+)
+
+// oidNotInExtensions reports whether an extension with the given oid exists in
+// extensions.
+func oidInExtensions(oid asn1.ObjectIdentifier, extensions []pkix.Extension) bool {
+	for _, e := range extensions {
+		if e.Id.Equal(oid) {
+			return true
+		}
+	}
+	return false
+}
+
+// marshalSANs marshals a list of addresses into a the contents of an X.509
+// SubjectAlternativeName extension.
+func marshalSANs(dnsNames, emailAddresses []string, ipAddresses []net.IP, uris []*url.URL) (derBytes []byte, err error) {
+	var rawValues []asn1.RawValue
+	for _, name := range dnsNames {
+		if err := isIA5String(name); err != nil {
+			return nil, err
+		}
+		rawValues = append(rawValues, asn1.RawValue{Tag: nameTypeDNS, Class: 2, Bytes: []byte(name)})
+	}
+	for _, email := range emailAddresses {
+		if err := isIA5String(email); err != nil {
+			return nil, err
+		}
+		rawValues = append(rawValues, asn1.RawValue{Tag: nameTypeEmail, Class: 2, Bytes: []byte(email)})
+	}
+	for _, rawIP := range ipAddresses {
+		// If possible, we always want to encode IPv4 addresses in 4 bytes.
+		ip := rawIP.To4()
+		if ip == nil {
+			ip = rawIP
+		}
+		rawValues = append(rawValues, asn1.RawValue{Tag: nameTypeIP, Class: 2, Bytes: ip})
+	}
+	for _, uri := range uris {
+		uriStr := uri.String()
+		if err := isIA5String(uriStr); err != nil {
+			return nil, err
+		}
+		rawValues = append(rawValues, asn1.RawValue{Tag: nameTypeURI, Class: 2, Bytes: []byte(uriStr)})
+	}
+	return asn1.Marshal(rawValues)
+}
+
+func isIA5String(s string) error {
+	for _, r := range s {
+		// Per RFC5280 "IA5String is limited to the set of ASCII characters"
+		if r > unicode.MaxASCII {
+			return fmt.Errorf("x509: %q cannot be encoded as an IA5String", s)
+		}
+	}
+
+	return nil
+}
+
+func buildCertExtensions(template *Certificate, subjectIsEmpty bool, authorityKeyId []byte, subjectKeyId []byte) (ret []pkix.Extension, err error) {
+	ret = make([]pkix.Extension, 10 /* maximum number of elements. */)
+	n := 0
+
+	if template.KeyUsage != 0 &&
+		!oidInExtensions(oidExtensionKeyUsage, template.ExtraExtensions) {
+		ret[n], err = marshalKeyUsage(template.KeyUsage)
+		if err != nil {
+			return nil, err
+		}
+		n++
+	}
+
+	if (len(template.ExtKeyUsage) > 0 || len(template.UnknownExtKeyUsage) > 0) &&
+		!oidInExtensions(oidExtensionExtendedKeyUsage, template.ExtraExtensions) {
+		ret[n], err = marshalExtKeyUsage(template.ExtKeyUsage, template.UnknownExtKeyUsage)
+		if err != nil {
+			return nil, err
+		}
+		n++
+	}
+
+	if template.BasicConstraintsValid && !oidInExtensions(oidExtensionBasicConstraints, template.ExtraExtensions) {
+		ret[n], err = marshalBasicConstraints(template.IsCA, template.MaxPathLen, template.MaxPathLenZero)
+		if err != nil {
+			return nil, err
+		}
+		n++
+	}
+
+	if len(subjectKeyId) > 0 && !oidInExtensions(oidExtensionSubjectKeyId, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionSubjectKeyId
+		ret[n].Value, err = asn1.Marshal(subjectKeyId)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if len(authorityKeyId) > 0 && !oidInExtensions(oidExtensionAuthorityKeyId, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionAuthorityKeyId
+		ret[n].Value, err = asn1.Marshal(authKeyId{authorityKeyId})
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if (len(template.OCSPServer) > 0 || len(template.IssuingCertificateURL) > 0) &&
+		!oidInExtensions(oidExtensionAuthorityInfoAccess, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionAuthorityInfoAccess
+		var aiaValues []authorityInfoAccess
+		for _, name := range template.OCSPServer {
+			aiaValues = append(aiaValues, authorityInfoAccess{
+				Method:   oidAuthorityInfoAccessOcsp,
+				Location: asn1.RawValue{Tag: 6, Class: 2, Bytes: []byte(name)},
+			})
+		}
+		for _, name := range template.IssuingCertificateURL {
+			aiaValues = append(aiaValues, authorityInfoAccess{
+				Method:   oidAuthorityInfoAccessIssuers,
+				Location: asn1.RawValue{Tag: 6, Class: 2, Bytes: []byte(name)},
+			})
+		}
+		ret[n].Value, err = asn1.Marshal(aiaValues)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if (len(template.DNSNames) > 0 || len(template.EmailAddresses) > 0 || len(template.IPAddresses) > 0 || len(template.URIs) > 0) &&
+		!oidInExtensions(oidExtensionSubjectAltName, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionSubjectAltName
+		// From RFC 5280, Section 4.2.1.6:
+		// “If the subject field contains an empty sequence ... then
+		// subjectAltName extension ... is marked as critical”
+		ret[n].Critical = subjectIsEmpty
+		ret[n].Value, err = marshalSANs(template.DNSNames, template.EmailAddresses, template.IPAddresses, template.URIs)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if len(template.PolicyIdentifiers) > 0 &&
+		!oidInExtensions(oidExtensionCertificatePolicies, template.ExtraExtensions) {
+		ret[n], err = marshalCertificatePolicies(template.PolicyIdentifiers)
+		if err != nil {
+			return nil, err
+		}
+		n++
+	}
+
+	if (len(template.PermittedDNSDomains) > 0 || len(template.ExcludedDNSDomains) > 0 ||
+		len(template.PermittedIPRanges) > 0 || len(template.ExcludedIPRanges) > 0 ||
+		len(template.PermittedEmailAddresses) > 0 || len(template.ExcludedEmailAddresses) > 0 ||
+		len(template.PermittedURIDomains) > 0 || len(template.ExcludedURIDomains) > 0) &&
+		!oidInExtensions(oidExtensionNameConstraints, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionNameConstraints
+		ret[n].Critical = template.PermittedDNSDomainsCritical
+
+		ipAndMask := func(ipNet *net.IPNet) []byte {
+			maskedIP := ipNet.IP.Mask(ipNet.Mask)
+			ipAndMask := make([]byte, 0, len(maskedIP)+len(ipNet.Mask))
+			ipAndMask = append(ipAndMask, maskedIP...)
+			ipAndMask = append(ipAndMask, ipNet.Mask...)
+			return ipAndMask
+		}
+
+		serialiseConstraints := func(dns []string, ips []*net.IPNet, emails []string, uriDomains []string) (der []byte, err error) {
+			var b cryptobyte.Builder
+
+			for _, name := range dns {
+				if err = isIA5String(name); err != nil {
+					return nil, err
+				}
+
+				b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
+					b.AddASN1(cryptobyte_asn1.Tag(2).ContextSpecific(), func(b *cryptobyte.Builder) {
+						b.AddBytes([]byte(name))
+					})
+				})
+			}
+
+			for _, ipNet := range ips {
+				b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
+					b.AddASN1(cryptobyte_asn1.Tag(7).ContextSpecific(), func(b *cryptobyte.Builder) {
+						b.AddBytes(ipAndMask(ipNet))
+					})
+				})
+			}
+
+			for _, email := range emails {
+				if err = isIA5String(email); err != nil {
+					return nil, err
+				}
+
+				b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
+					b.AddASN1(cryptobyte_asn1.Tag(1).ContextSpecific(), func(b *cryptobyte.Builder) {
+						b.AddBytes([]byte(email))
+					})
+				})
+			}
+
+			for _, uriDomain := range uriDomains {
+				if err = isIA5String(uriDomain); err != nil {
+					return nil, err
+				}
+
+				b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
+					b.AddASN1(cryptobyte_asn1.Tag(6).ContextSpecific(), func(b *cryptobyte.Builder) {
+						b.AddBytes([]byte(uriDomain))
+					})
+				})
+			}
+
+			return b.Bytes()
+		}
+
+		permitted, err := serialiseConstraints(template.PermittedDNSDomains, template.PermittedIPRanges, template.PermittedEmailAddresses, template.PermittedURIDomains)
+		if err != nil {
+			return nil, err
+		}
+
+		excluded, err := serialiseConstraints(template.ExcludedDNSDomains, template.ExcludedIPRanges, template.ExcludedEmailAddresses, template.ExcludedURIDomains)
+		if err != nil {
+			return nil, err
+		}
+
+		var b cryptobyte.Builder
+		b.AddASN1(cryptobyte_asn1.SEQUENCE, func(b *cryptobyte.Builder) {
+			if len(permitted) > 0 {
+				b.AddASN1(cryptobyte_asn1.Tag(0).ContextSpecific().Constructed(), func(b *cryptobyte.Builder) {
+					b.AddBytes(permitted)
+				})
+			}
+
+			if len(excluded) > 0 {
+				b.AddASN1(cryptobyte_asn1.Tag(1).ContextSpecific().Constructed(), func(b *cryptobyte.Builder) {
+					b.AddBytes(excluded)
+				})
+			}
+		})
+
+		ret[n].Value, err = b.Bytes()
+		if err != nil {
+			return nil, err
+		}
+		n++
+	}
+
+	if len(template.CRLDistributionPoints) > 0 &&
+		!oidInExtensions(oidExtensionCRLDistributionPoints, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionCRLDistributionPoints
+
+		var crlDp []distributionPoint
+		for _, name := range template.CRLDistributionPoints {
+			dp := distributionPoint{
+				DistributionPoint: distributionPointName{
+					FullName: []asn1.RawValue{
+						{Tag: 6, Class: 2, Bytes: []byte(name)},
+					},
+				},
+			}
+			crlDp = append(crlDp, dp)
+		}
+
+		ret[n].Value, err = asn1.Marshal(crlDp)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	// Adding another extension here? Remember to update the maximum number
+	// of elements in the make() at the top of the function and the list of
+	// template fields used in CreateCertificate documentation.
+
+	return append(ret[:n], template.ExtraExtensions...), nil
+}
+
+func marshalKeyUsage(ku KeyUsage) (pkix.Extension, error) {
+	ext := pkix.Extension{Id: oidExtensionKeyUsage, Critical: true}
+
+	var a [2]byte
+	a[0] = reverseBitsInAByte(byte(ku))
+	a[1] = reverseBitsInAByte(byte(ku >> 8))
+
+	l := 1
+	if a[1] != 0 {
+		l = 2
+	}
+
+	bitString := a[:l]
+	var err error
+	ext.Value, err = asn1.Marshal(asn1.BitString{Bytes: bitString, BitLength: asn1BitLength(bitString)})
+	if err != nil {
+		return ext, err
+	}
+	return ext, nil
+}
+
+func marshalExtKeyUsage(extUsages []ExtKeyUsage, unknownUsages []asn1.ObjectIdentifier) (pkix.Extension, error) {
+	ext := pkix.Extension{Id: oidExtensionExtendedKeyUsage}
+
+	oids := make([]asn1.ObjectIdentifier, len(extUsages)+len(unknownUsages))
+	for i, u := range extUsages {
+		if oid, ok := oidFromExtKeyUsage(u); ok {
+			oids[i] = oid
+		} else {
+			return ext, errors.New("x509: unknown extended key usage")
+		}
+	}
+
+	copy(oids[len(extUsages):], unknownUsages)
+
+	var err error
+	ext.Value, err = asn1.Marshal(oids)
+	if err != nil {
+		return ext, err
+	}
+	return ext, nil
+}
+
+func marshalBasicConstraints(isCA bool, maxPathLen int, maxPathLenZero bool) (pkix.Extension, error) {
+	ext := pkix.Extension{Id: oidExtensionBasicConstraints, Critical: true}
+	// Leaving MaxPathLen as zero indicates that no maximum path
+	// length is desired, unless MaxPathLenZero is set. A value of
+	// -1 causes encoding/asn1 to omit the value as desired.
+	if maxPathLen == 0 && !maxPathLenZero {
+		maxPathLen = -1
+	}
+	var err error
+	ext.Value, err = asn1.Marshal(basicConstraints{isCA, maxPathLen})
+	if err != nil {
+		return ext, nil
+	}
+	return ext, nil
+}
+
+func marshalCertificatePolicies(policyIdentifiers []asn1.ObjectIdentifier) (pkix.Extension, error) {
+	ext := pkix.Extension{Id: oidExtensionCertificatePolicies}
+	policies := make([]policyInformation, len(policyIdentifiers))
+	for i, policy := range policyIdentifiers {
+		policies[i].Policy = policy
+	}
+	var err error
+	ext.Value, err = asn1.Marshal(policies)
+	if err != nil {
+		return ext, err
+	}
+	return ext, nil
+}
+
+func buildCSRExtensions(template *CertificateRequest) ([]pkix.Extension, error) {
+	var ret []pkix.Extension
+
+	if (len(template.DNSNames) > 0 || len(template.EmailAddresses) > 0 || len(template.IPAddresses) > 0 || len(template.URIs) > 0) &&
+		!oidInExtensions(oidExtensionSubjectAltName, template.ExtraExtensions) {
+		sanBytes, err := marshalSANs(template.DNSNames, template.EmailAddresses, template.IPAddresses, template.URIs)
+		if err != nil {
+			return nil, err
+		}
+
+		ret = append(ret, pkix.Extension{
+			Id:    oidExtensionSubjectAltName,
+			Value: sanBytes,
+		})
+	}
+
+	return append(ret, template.ExtraExtensions...), nil
+}
+
+func subjectBytes(cert *Certificate) ([]byte, error) {
+	if len(cert.RawSubject) > 0 {
+		return cert.RawSubject, nil
+	}
+
+	return asn1.Marshal(cert.Subject.ToRDNSequence())
+}
+
+// signingParamsForPublicKey returns the parameters to use for signing with
+// priv. If requestedSigAlgo is not zero then it overrides the default
+// signature algorithm.
+func signingParamsForPublicKey(pub any, requestedSigAlgo SignatureAlgorithm) (hashFunc crypto.Hash, sigAlgo pkix.AlgorithmIdentifier, err error) {
+	var pubType PublicKeyAlgorithm
+
+	switch pub := pub.(type) {
+	case *rsa.PublicKey:
+		pubType = RSA
+		hashFunc = crypto.SHA256
+		sigAlgo.Algorithm = oidSignatureSHA256WithRSA
+		sigAlgo.Parameters = asn1.NullRawValue
+
+	case *ecdsa.PublicKey:
+		pubType = ECDSA
+
+		switch pub.Curve {
+		case elliptic.P224(), elliptic.P256():
+			hashFunc = crypto.SHA256
+			sigAlgo.Algorithm = oidSignatureECDSAWithSHA256
+		case elliptic.P384():
+			hashFunc = crypto.SHA384
+			sigAlgo.Algorithm = oidSignatureECDSAWithSHA384
+		case elliptic.P521():
+			hashFunc = crypto.SHA512
+			sigAlgo.Algorithm = oidSignatureECDSAWithSHA512
+		default:
+			err = errors.New("x509: unknown elliptic curve")
+		}
+
+	case ed25519.PublicKey:
+		pubType = Ed25519
+		sigAlgo.Algorithm = oidSignatureEd25519
+
+	default:
+		err = errors.New("x509: only RSA, ECDSA and Ed25519 keys supported")
+	}
+
+	if err != nil {
+		return
+	}
+
+	if requestedSigAlgo == 0 {
+		return
+	}
+
+	found := false
+	for _, details := range signatureAlgorithmDetails {
+		if details.algo == requestedSigAlgo {
+			if details.pubKeyAlgo != pubType {
+				err = errors.New("x509: requested SignatureAlgorithm does not match private key type")
+				return
+			}
+			sigAlgo.Algorithm, hashFunc = details.oid, details.hash
+			if hashFunc == 0 && pubType != Ed25519 {
+				err = errors.New("x509: cannot sign with hash function requested")
+				return
+			}
+			if requestedSigAlgo.isRSAPSS() {
+				sigAlgo.Parameters = hashToPSSParameters[hashFunc]
+			}
+			found = true
+			break
+		}
+	}
+
+	if !found {
+		err = errors.New("x509: unknown SignatureAlgorithm")
+	}
+
+	return
+}
+
+// emptyASN1Subject is the ASN.1 DER encoding of an empty Subject, which is
+// just an empty SEQUENCE.
+var emptyASN1Subject = []byte{0x30, 0}
+
+// CreateCertificate creates a new X.509 v3 certificate based on a template.
+// The following members of template are currently used:
+//
+//  - AuthorityKeyId
+//  - BasicConstraintsValid
+//  - CRLDistributionPoints
+//  - DNSNames
+//  - EmailAddresses
+//  - ExcludedDNSDomains
+//  - ExcludedEmailAddresses
+//  - ExcludedIPRanges
+//  - ExcludedURIDomains
+//  - ExtKeyUsage
+//  - ExtraExtensions
+//  - IPAddresses
+//  - IsCA
+//  - IssuingCertificateURL
+//  - KeyUsage
+//  - MaxPathLen
+//  - MaxPathLenZero
+//  - NotAfter
+//  - NotBefore
+//  - OCSPServer
+//  - PermittedDNSDomains
+//  - PermittedDNSDomainsCritical
+//  - PermittedEmailAddresses
+//  - PermittedIPRanges
+//  - PermittedURIDomains
+//  - PolicyIdentifiers
+//  - SerialNumber
+//  - SignatureAlgorithm
+//  - Subject
+//  - SubjectKeyId
+//  - URIs
+//  - UnknownExtKeyUsage
+//
+// The certificate is signed by parent. If parent is equal to template then the
+// certificate is self-signed. The parameter pub is the public key of the
+// certificate to be generated and priv is the private key of the signer.
+//
+// The returned slice is the certificate in DER encoding.
+//
+// The currently supported key types are *rsa.PublicKey, *ecdsa.PublicKey and
+// ed25519.PublicKey. pub must be a supported key type, and priv must be a
+// crypto.Signer with a supported public key.
+//
+// The AuthorityKeyId will be taken from the SubjectKeyId of parent, if any,
+// unless the resulting certificate is self-signed. Otherwise the value from
+// template will be used.
+//
+// If SubjectKeyId from template is empty and the template is a CA, SubjectKeyId
+// will be generated from the hash of the public key.
+func CreateCertificate(rand io.Reader, template, parent *Certificate, pub, priv any) ([]byte, error) {
+	key, ok := priv.(crypto.Signer)
+	if !ok {
+		return nil, errors.New("x509: certificate private key does not implement crypto.Signer")
+	}
+
+	if template.SerialNumber == nil {
+		return nil, errors.New("x509: no SerialNumber given")
+	}
+
+	if template.BasicConstraintsValid && !template.IsCA && template.MaxPathLen != -1 && (template.MaxPathLen != 0 || template.MaxPathLenZero) {
+		return nil, errors.New("x509: only CAs are allowed to specify MaxPathLen")
+	}
+
+	hashFunc, signatureAlgorithm, err := signingParamsForPublicKey(key.Public(), template.SignatureAlgorithm)
+	if err != nil {
+		return nil, err
+	}
+
+	publicKeyBytes, publicKeyAlgorithm, err := marshalPublicKey(pub)
+	if err != nil {
+		return nil, err
+	}
+
+	asn1Issuer, err := subjectBytes(parent)
+	if err != nil {
+		return nil, err
+	}
+
+	asn1Subject, err := subjectBytes(template)
+	if err != nil {
+		return nil, err
+	}
+
+	authorityKeyId := template.AuthorityKeyId
+	if !bytes.Equal(asn1Issuer, asn1Subject) && len(parent.SubjectKeyId) > 0 {
+		authorityKeyId = parent.SubjectKeyId
+	}
+
+	subjectKeyId := template.SubjectKeyId
+	if len(subjectKeyId) == 0 && template.IsCA {
+		// SubjectKeyId generated using method 1 in RFC 5280, Section 4.2.1.2:
+		//   (1) The keyIdentifier is composed of the 160-bit SHA-1 hash of the
+		//   value of the BIT STRING subjectPublicKey (excluding the tag,
+		//   length, and number of unused bits).
+		h := sha1.Sum(publicKeyBytes)
+		subjectKeyId = h[:]
+	}
+
+	// Check that the signer's public key matches the private key, if available.
+	type privateKey interface {
+		Equal(crypto.PublicKey) bool
+	}
+	if privPub, ok := key.Public().(privateKey); !ok {
+		return nil, errors.New("x509: internal error: supported public key does not implement Equal")
+	} else if parent.PublicKey != nil && !privPub.Equal(parent.PublicKey) {
+		return nil, errors.New("x509: provided PrivateKey doesn't match parent's PublicKey")
+	}
+
+	extensions, err := buildCertExtensions(template, bytes.Equal(asn1Subject, emptyASN1Subject), authorityKeyId, subjectKeyId)
+	if err != nil {
+		return nil, err
+	}
+
+	encodedPublicKey := asn1.BitString{BitLength: len(publicKeyBytes) * 8, Bytes: publicKeyBytes}
+	c := tbsCertificate{
+		Version:            2,
+		SerialNumber:       template.SerialNumber,
+		SignatureAlgorithm: signatureAlgorithm,
+		Issuer:             asn1.RawValue{FullBytes: asn1Issuer},
+		Validity:           validity{template.NotBefore.UTC(), template.NotAfter.UTC()},
+		Subject:            asn1.RawValue{FullBytes: asn1Subject},
+		PublicKey:          publicKeyInfo{nil, publicKeyAlgorithm, encodedPublicKey},
+		Extensions:         extensions,
+	}
+
+	tbsCertContents, err := asn1.Marshal(c)
+	if err != nil {
+		return nil, err
+	}
+	c.Raw = tbsCertContents
+
+	signed := tbsCertContents
+	if hashFunc != 0 {
+		h := hashFunc.New()
+		h.Write(signed)
+		signed = h.Sum(nil)
+	}
+
+	var signerOpts crypto.SignerOpts = hashFunc
+	if template.SignatureAlgorithm != 0 && template.SignatureAlgorithm.isRSAPSS() {
+		signerOpts = &rsa.PSSOptions{
+			SaltLength: rsa.PSSSaltLengthEqualsHash,
+			Hash:       hashFunc,
+		}
+	}
+
+	var signature []byte
+	signature, err = key.Sign(rand, signed, signerOpts)
+	if err != nil {
+		return nil, err
+	}
+
+	signedCert, err := asn1.Marshal(certificate{
+		nil,
+		c,
+		signatureAlgorithm,
+		asn1.BitString{Bytes: signature, BitLength: len(signature) * 8},
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	// Check the signature to ensure the crypto.Signer behaved correctly.
+	sigAlg := getSignatureAlgorithmFromAI(signatureAlgorithm)
+	switch sigAlg {
+	case MD5WithRSA:
+		// We skip the check if the signature algorithm is only supported for
+		// signing, not verification.
+	default:
+		if err := checkSignature(sigAlg, c.Raw, signature, key.Public(), true); err != nil {
+			return nil, fmt.Errorf("x509: signature over certificate returned by signer is invalid: %w", err)
+		}
+	}
+
+	return signedCert, nil
+}
+
+// pemCRLPrefix is the magic string that indicates that we have a PEM encoded
+// CRL.
+var pemCRLPrefix = []byte("-----BEGIN X509 CRL")
+
+// pemType is the type of a PEM encoded CRL.
+var pemType = "X509 CRL"
+
+// ParseCRL parses a CRL from the given bytes. It's often the case that PEM
+// encoded CRLs will appear where they should be DER encoded, so this function
+// will transparently handle PEM encoding as long as there isn't any leading
+// garbage.
+func ParseCRL(crlBytes []byte) (*pkix.CertificateList, error) {
+	if bytes.HasPrefix(crlBytes, pemCRLPrefix) {
+		block, _ := pem.Decode(crlBytes)
+		if block != nil && block.Type == pemType {
+			crlBytes = block.Bytes
+		}
+	}
+	return ParseDERCRL(crlBytes)
+}
+
+// ParseDERCRL parses a DER encoded CRL from the given bytes.
+func ParseDERCRL(derBytes []byte) (*pkix.CertificateList, error) {
+	certList := new(pkix.CertificateList)
+	if rest, err := asn1.Unmarshal(derBytes, certList); err != nil {
+		return nil, err
+	} else if len(rest) != 0 {
+		return nil, errors.New("x509: trailing data after CRL")
+	}
+	return certList, nil
+}
+
+// CreateCRL returns a DER encoded CRL, signed by this Certificate, that
+// contains the given list of revoked certificates.
+//
+// Note: this method does not generate an RFC 5280 conformant X.509 v2 CRL.
+// To generate a standards compliant CRL, use CreateRevocationList instead.
+func (c *Certificate) CreateCRL(rand io.Reader, priv any, revokedCerts []pkix.RevokedCertificate, now, expiry time.Time) (crlBytes []byte, err error) {
+	key, ok := priv.(crypto.Signer)
+	if !ok {
+		return nil, errors.New("x509: certificate private key does not implement crypto.Signer")
+	}
+
+	hashFunc, signatureAlgorithm, err := signingParamsForPublicKey(key.Public(), 0)
+	if err != nil {
+		return nil, err
+	}
+
+	// Force revocation times to UTC per RFC 5280.
+	revokedCertsUTC := make([]pkix.RevokedCertificate, len(revokedCerts))
+	for i, rc := range revokedCerts {
+		rc.RevocationTime = rc.RevocationTime.UTC()
+		revokedCertsUTC[i] = rc
+	}
+
+	tbsCertList := pkix.TBSCertificateList{
+		Version:             1,
+		Signature:           signatureAlgorithm,
+		Issuer:              c.Subject.ToRDNSequence(),
+		ThisUpdate:          now.UTC(),
+		NextUpdate:          expiry.UTC(),
+		RevokedCertificates: revokedCertsUTC,
+	}
+
+	// Authority Key Id
+	if len(c.SubjectKeyId) > 0 {
+		var aki pkix.Extension
+		aki.Id = oidExtensionAuthorityKeyId
+		aki.Value, err = asn1.Marshal(authKeyId{Id: c.SubjectKeyId})
+		if err != nil {
+			return
+		}
+		tbsCertList.Extensions = append(tbsCertList.Extensions, aki)
+	}
+
+	tbsCertListContents, err := asn1.Marshal(tbsCertList)
+	if err != nil {
+		return
+	}
+
+	signed := tbsCertListContents
+	if hashFunc != 0 {
+		h := hashFunc.New()
+		h.Write(signed)
+		signed = h.Sum(nil)
+	}
+
+	var signature []byte
+	signature, err = key.Sign(rand, signed, hashFunc)
+	if err != nil {
+		return
+	}
+
+	return asn1.Marshal(pkix.CertificateList{
+		TBSCertList:        tbsCertList,
+		SignatureAlgorithm: signatureAlgorithm,
+		SignatureValue:     asn1.BitString{Bytes: signature, BitLength: len(signature) * 8},
+	})
+}
+
+// CertificateRequest represents a PKCS #10, certificate signature request.
+type CertificateRequest struct {
+	Raw                      []byte // Complete ASN.1 DER content (CSR, signature algorithm and signature).
+	RawTBSCertificateRequest []byte // Certificate request info part of raw ASN.1 DER content.
+	RawSubjectPublicKeyInfo  []byte // DER encoded SubjectPublicKeyInfo.
+	RawSubject               []byte // DER encoded Subject.
+
+	Version            int
+	Signature          []byte
+	SignatureAlgorithm SignatureAlgorithm
+
+	PublicKeyAlgorithm PublicKeyAlgorithm
+	PublicKey          any
+
+	Subject pkix.Name
+
+	// Attributes contains the CSR attributes that can parse as
+	// pkix.AttributeTypeAndValueSET.
+	//
+	// Deprecated: Use Extensions and ExtraExtensions instead for parsing and
+	// generating the requestedExtensions attribute.
+	Attributes []pkix.AttributeTypeAndValueSET
+
+	// Extensions contains all requested extensions, in raw form. When parsing
+	// CSRs, this can be used to extract extensions that are not parsed by this
+	// package.
+	Extensions []pkix.Extension
+
+	// ExtraExtensions contains extensions to be copied, raw, into any CSR
+	// marshaled by CreateCertificateRequest. Values override any extensions
+	// that would otherwise be produced based on the other fields but are
+	// overridden by any extensions specified in Attributes.
+	//
+	// The ExtraExtensions field is not populated by ParseCertificateRequest,
+	// see Extensions instead.
+	ExtraExtensions []pkix.Extension
+
+	// Subject Alternate Name values.
+	DNSNames       []string
+	EmailAddresses []string
+	IPAddresses    []net.IP
+	URIs           []*url.URL
+}
+
+// These structures reflect the ASN.1 structure of X.509 certificate
+// signature requests (see RFC 2986):
+
+type tbsCertificateRequest struct {
+	Raw           asn1.RawContent
+	Version       int
+	Subject       asn1.RawValue
+	PublicKey     publicKeyInfo
+	RawAttributes []asn1.RawValue `asn1:"tag:0"`
+}
+
+type certificateRequest struct {
+	Raw                asn1.RawContent
+	TBSCSR             tbsCertificateRequest
+	SignatureAlgorithm pkix.AlgorithmIdentifier
+	SignatureValue     asn1.BitString
+}
+
+// oidExtensionRequest is a PKCS #9 OBJECT IDENTIFIER that indicates requested
+// extensions in a CSR.
+var oidExtensionRequest = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 14}
+
+// newRawAttributes converts AttributeTypeAndValueSETs from a template
+// CertificateRequest's Attributes into tbsCertificateRequest RawAttributes.
+func newRawAttributes(attributes []pkix.AttributeTypeAndValueSET) ([]asn1.RawValue, error) {
+	var rawAttributes []asn1.RawValue
+	b, err := asn1.Marshal(attributes)
+	if err != nil {
+		return nil, err
+	}
+	rest, err := asn1.Unmarshal(b, &rawAttributes)
+	if err != nil {
+		return nil, err
+	}
+	if len(rest) != 0 {
+		return nil, errors.New("x509: failed to unmarshal raw CSR Attributes")
+	}
+	return rawAttributes, nil
+}
+
+// parseRawAttributes Unmarshals RawAttributes into AttributeTypeAndValueSETs.
+func parseRawAttributes(rawAttributes []asn1.RawValue) []pkix.AttributeTypeAndValueSET {
+	var attributes []pkix.AttributeTypeAndValueSET
+	for _, rawAttr := range rawAttributes {
+		var attr pkix.AttributeTypeAndValueSET
+		rest, err := asn1.Unmarshal(rawAttr.FullBytes, &attr)
+		// Ignore attributes that don't parse into pkix.AttributeTypeAndValueSET
+		// (i.e.: challengePassword or unstructuredName).
+		if err == nil && len(rest) == 0 {
+			attributes = append(attributes, attr)
+		}
+	}
+	return attributes
+}
+
+// parseCSRExtensions parses the attributes from a CSR and extracts any
+// requested extensions.
+func parseCSRExtensions(rawAttributes []asn1.RawValue) ([]pkix.Extension, error) {
+	// pkcs10Attribute reflects the Attribute structure from RFC 2986, Section 4.1.
+	type pkcs10Attribute struct {
+		Id     asn1.ObjectIdentifier
+		Values []asn1.RawValue `asn1:"set"`
+	}
+
+	var ret []pkix.Extension
+	for _, rawAttr := range rawAttributes {
+		var attr pkcs10Attribute
+		if rest, err := asn1.Unmarshal(rawAttr.FullBytes, &attr); err != nil || len(rest) != 0 || len(attr.Values) == 0 {
+			// Ignore attributes that don't parse.
+			continue
+		}
+
+		if !attr.Id.Equal(oidExtensionRequest) {
+			continue
+		}
+
+		var extensions []pkix.Extension
+		if _, err := asn1.Unmarshal(attr.Values[0].FullBytes, &extensions); err != nil {
+			return nil, err
+		}
+		ret = append(ret, extensions...)
+	}
+
+	return ret, nil
+}
+
+// CreateCertificateRequest creates a new certificate request based on a
+// template. The following members of template are used:
+//
+//  - SignatureAlgorithm
+//  - Subject
+//  - DNSNames
+//  - EmailAddresses
+//  - IPAddresses
+//  - URIs
+//  - ExtraExtensions
+//  - Attributes (deprecated)
+//
+// priv is the private key to sign the CSR with, and the corresponding public
+// key will be included in the CSR. It must implement crypto.Signer and its
+// Public() method must return a *rsa.PublicKey or a *ecdsa.PublicKey or a
+// ed25519.PublicKey. (A *rsa.PrivateKey, *ecdsa.PrivateKey or
+// ed25519.PrivateKey satisfies this.)
+//
+// The returned slice is the certificate request in DER encoding.
+func CreateCertificateRequest(rand io.Reader, template *CertificateRequest, priv any) (csr []byte, err error) {
+	key, ok := priv.(crypto.Signer)
+	if !ok {
+		return nil, errors.New("x509: certificate private key does not implement crypto.Signer")
+	}
+
+	var hashFunc crypto.Hash
+	var sigAlgo pkix.AlgorithmIdentifier
+	hashFunc, sigAlgo, err = signingParamsForPublicKey(key.Public(), template.SignatureAlgorithm)
+	if err != nil {
+		return nil, err
+	}
+
+	var publicKeyBytes []byte
+	var publicKeyAlgorithm pkix.AlgorithmIdentifier
+	publicKeyBytes, publicKeyAlgorithm, err = marshalPublicKey(key.Public())
+	if err != nil {
+		return nil, err
+	}
+
+	extensions, err := buildCSRExtensions(template)
+	if err != nil {
+		return nil, err
+	}
+
+	// Make a copy of template.Attributes because we may alter it below.
+	attributes := make([]pkix.AttributeTypeAndValueSET, 0, len(template.Attributes))
+	for _, attr := range template.Attributes {
+		values := make([][]pkix.AttributeTypeAndValue, len(attr.Value))
+		copy(values, attr.Value)
+		attributes = append(attributes, pkix.AttributeTypeAndValueSET{
+			Type:  attr.Type,
+			Value: values,
+		})
+	}
+
+	extensionsAppended := false
+	if len(extensions) > 0 {
+		// Append the extensions to an existing attribute if possible.
+		for _, atvSet := range attributes {
+			if !atvSet.Type.Equal(oidExtensionRequest) || len(atvSet.Value) == 0 {
+				continue
+			}
+
+			// specifiedExtensions contains all the extensions that we
+			// found specified via template.Attributes.
+			specifiedExtensions := make(map[string]bool)
+
+			for _, atvs := range atvSet.Value {
+				for _, atv := range atvs {
+					specifiedExtensions[atv.Type.String()] = true
+				}
+			}
+
+			newValue := make([]pkix.AttributeTypeAndValue, 0, len(atvSet.Value[0])+len(extensions))
+			newValue = append(newValue, atvSet.Value[0]...)
+
+			for _, e := range extensions {
+				if specifiedExtensions[e.Id.String()] {
+					// Attributes already contained a value for
+					// this extension and it takes priority.
+					continue
+				}
+
+				newValue = append(newValue, pkix.AttributeTypeAndValue{
+					// There is no place for the critical
+					// flag in an AttributeTypeAndValue.
+					Type:  e.Id,
+					Value: e.Value,
+				})
+			}
+
+			atvSet.Value[0] = newValue
+			extensionsAppended = true
+			break
+		}
+	}
+
+	rawAttributes, err := newRawAttributes(attributes)
+	if err != nil {
+		return
+	}
+
+	// If not included in attributes, add a new attribute for the
+	// extensions.
+	if len(extensions) > 0 && !extensionsAppended {
+		attr := struct {
+			Type  asn1.ObjectIdentifier
+			Value [][]pkix.Extension `asn1:"set"`
+		}{
+			Type:  oidExtensionRequest,
+			Value: [][]pkix.Extension{extensions},
+		}
+
+		b, err := asn1.Marshal(attr)
+		if err != nil {
+			return nil, errors.New("x509: failed to serialise extensions attribute: " + err.Error())
+		}
+
+		var rawValue asn1.RawValue
+		if _, err := asn1.Unmarshal(b, &rawValue); err != nil {
+			return nil, err
+		}
+
+		rawAttributes = append(rawAttributes, rawValue)
+	}
+
+	asn1Subject := template.RawSubject
+	if len(asn1Subject) == 0 {
+		asn1Subject, err = asn1.Marshal(template.Subject.ToRDNSequence())
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	tbsCSR := tbsCertificateRequest{
+		Version: 0, // PKCS #10, RFC 2986
+		Subject: asn1.RawValue{FullBytes: asn1Subject},
+		PublicKey: publicKeyInfo{
+			Algorithm: publicKeyAlgorithm,
+			PublicKey: asn1.BitString{
+				Bytes:     publicKeyBytes,
+				BitLength: len(publicKeyBytes) * 8,
+			},
+		},
+		RawAttributes: rawAttributes,
+	}
+
+	tbsCSRContents, err := asn1.Marshal(tbsCSR)
+	if err != nil {
+		return
+	}
+	tbsCSR.Raw = tbsCSRContents
+
+	signed := tbsCSRContents
+	if hashFunc != 0 {
+		h := hashFunc.New()
+		h.Write(signed)
+		signed = h.Sum(nil)
+	}
+
+	var signature []byte
+	signature, err = key.Sign(rand, signed, hashFunc)
+	if err != nil {
+		return
+	}
+
+	return asn1.Marshal(certificateRequest{
+		TBSCSR:             tbsCSR,
+		SignatureAlgorithm: sigAlgo,
+		SignatureValue: asn1.BitString{
+			Bytes:     signature,
+			BitLength: len(signature) * 8,
+		},
+	})
+}
+
+// ParseCertificateRequest parses a single certificate request from the
+// given ASN.1 DER data.
+func ParseCertificateRequest(asn1Data []byte) (*CertificateRequest, error) {
+	var csr certificateRequest
+
+	rest, err := asn1.Unmarshal(asn1Data, &csr)
+	if err != nil {
+		return nil, err
+	} else if len(rest) != 0 {
+		return nil, asn1.SyntaxError{Msg: "trailing data"}
+	}
+
+	return parseCertificateRequest(&csr)
+}
+
+func parseCertificateRequest(in *certificateRequest) (*CertificateRequest, error) {
+	out := &CertificateRequest{
+		Raw:                      in.Raw,
+		RawTBSCertificateRequest: in.TBSCSR.Raw,
+		RawSubjectPublicKeyInfo:  in.TBSCSR.PublicKey.Raw,
+		RawSubject:               in.TBSCSR.Subject.FullBytes,
+
+		Signature:          in.SignatureValue.RightAlign(),
+		SignatureAlgorithm: getSignatureAlgorithmFromAI(in.SignatureAlgorithm),
+
+		PublicKeyAlgorithm: getPublicKeyAlgorithmFromOID(in.TBSCSR.PublicKey.Algorithm.Algorithm),
+
+		Version:    in.TBSCSR.Version,
+		Attributes: parseRawAttributes(in.TBSCSR.RawAttributes),
+	}
+
+	var err error
+	out.PublicKey, err = parsePublicKey(out.PublicKeyAlgorithm, &in.TBSCSR.PublicKey)
+	if err != nil {
+		return nil, err
+	}
+
+	var subject pkix.RDNSequence
+	if rest, err := asn1.Unmarshal(in.TBSCSR.Subject.FullBytes, &subject); err != nil {
+		return nil, err
+	} else if len(rest) != 0 {
+		return nil, errors.New("x509: trailing data after X.509 Subject")
+	}
+
+	out.Subject.FillFromRDNSequence(&subject)
+
+	if out.Extensions, err = parseCSRExtensions(in.TBSCSR.RawAttributes); err != nil {
+		return nil, err
+	}
+
+	for _, extension := range out.Extensions {
+		switch {
+		case extension.Id.Equal(oidExtensionSubjectAltName):
+			out.DNSNames, out.EmailAddresses, out.IPAddresses, out.URIs, err = parseSANExtension(extension.Value)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	return out, nil
+}
+
+// CheckSignature reports whether the signature on c is valid.
+func (c *CertificateRequest) CheckSignature() error {
+	return checkSignature(c.SignatureAlgorithm, c.RawTBSCertificateRequest, c.Signature, c.PublicKey, true)
+}
+
+// RevocationList contains the fields used to create an X.509 v2 Certificate
+// Revocation list with CreateRevocationList.
+type RevocationList struct {
+	// SignatureAlgorithm is used to determine the signature algorithm to be
+	// used when signing the CRL. If 0 the default algorithm for the signing
+	// key will be used.
+	SignatureAlgorithm SignatureAlgorithm
+
+	// RevokedCertificates is used to populate the revokedCertificates
+	// sequence in the CRL, it may be empty. RevokedCertificates may be nil,
+	// in which case an empty CRL will be created.
+	RevokedCertificates []pkix.RevokedCertificate
+
+	// Number is used to populate the X.509 v2 cRLNumber extension in the CRL,
+	// which should be a monotonically increasing sequence number for a given
+	// CRL scope and CRL issuer.
+	Number *big.Int
+	// ThisUpdate is used to populate the thisUpdate field in the CRL, which
+	// indicates the issuance date of the CRL.
+	ThisUpdate time.Time
+	// NextUpdate is used to populate the nextUpdate field in the CRL, which
+	// indicates the date by which the next CRL will be issued. NextUpdate
+	// must be greater than ThisUpdate.
+	NextUpdate time.Time
+	// ExtraExtensions contains any additional extensions to add directly to
+	// the CRL.
+	ExtraExtensions []pkix.Extension
+}
+
+// CreateRevocationList creates a new X.509 v2 Certificate Revocation List,
+// according to RFC 5280, based on template.
+//
+// The CRL is signed by priv which should be the private key associated with
+// the public key in the issuer certificate.
+//
+// The issuer may not be nil, and the crlSign bit must be set in KeyUsage in
+// order to use it as a CRL issuer.
+//
+// The issuer distinguished name CRL field and authority key identifier
+// extension are populated using the issuer certificate. issuer must have
+// SubjectKeyId set.
+func CreateRevocationList(rand io.Reader, template *RevocationList, issuer *Certificate, priv crypto.Signer) ([]byte, error) {
+	if template == nil {
+		return nil, errors.New("x509: template can not be nil")
+	}
+	if issuer == nil {
+		return nil, errors.New("x509: issuer can not be nil")
+	}
+	if (issuer.KeyUsage & KeyUsageCRLSign) == 0 {
+		return nil, errors.New("x509: issuer must have the crlSign key usage bit set")
+	}
+	if len(issuer.SubjectKeyId) == 0 {
+		return nil, errors.New("x509: issuer certificate doesn't contain a subject key identifier")
+	}
+	if template.NextUpdate.Before(template.ThisUpdate) {
+		return nil, errors.New("x509: template.ThisUpdate is after template.NextUpdate")
+	}
+	if template.Number == nil {
+		return nil, errors.New("x509: template contains nil Number field")
+	}
+
+	hashFunc, signatureAlgorithm, err := signingParamsForPublicKey(priv.Public(), template.SignatureAlgorithm)
+	if err != nil {
+		return nil, err
+	}
+
+	// Force revocation times to UTC per RFC 5280.
+	revokedCertsUTC := make([]pkix.RevokedCertificate, len(template.RevokedCertificates))
+	for i, rc := range template.RevokedCertificates {
+		rc.RevocationTime = rc.RevocationTime.UTC()
+		revokedCertsUTC[i] = rc
+	}
+
+	aki, err := asn1.Marshal(authKeyId{Id: issuer.SubjectKeyId})
+	if err != nil {
+		return nil, err
+	}
+	crlNum, err := asn1.Marshal(template.Number)
+	if err != nil {
+		return nil, err
+	}
+
+	tbsCertList := pkix.TBSCertificateList{
+		Version:    1, // v2
+		Signature:  signatureAlgorithm,
+		Issuer:     issuer.Subject.ToRDNSequence(),
+		ThisUpdate: template.ThisUpdate.UTC(),
+		NextUpdate: template.NextUpdate.UTC(),
+		Extensions: []pkix.Extension{
+			{
+				Id:    oidExtensionAuthorityKeyId,
+				Value: aki,
+			},
+			{
+				Id:    oidExtensionCRLNumber,
+				Value: crlNum,
+			},
+		},
+	}
+	if len(revokedCertsUTC) > 0 {
+		tbsCertList.RevokedCertificates = revokedCertsUTC
+	}
+
+	if len(template.ExtraExtensions) > 0 {
+		tbsCertList.Extensions = append(tbsCertList.Extensions, template.ExtraExtensions...)
+	}
+
+	tbsCertListContents, err := asn1.Marshal(tbsCertList)
+	if err != nil {
+		return nil, err
+	}
+
+	input := tbsCertListContents
+	if hashFunc != 0 {
+		h := hashFunc.New()
+		h.Write(tbsCertListContents)
+		input = h.Sum(nil)
+	}
+	var signerOpts crypto.SignerOpts = hashFunc
+	if template.SignatureAlgorithm.isRSAPSS() {
+		signerOpts = &rsa.PSSOptions{
+			SaltLength: rsa.PSSSaltLengthEqualsHash,
+			Hash:       hashFunc,
+		}
+	}
+
+	signature, err := priv.Sign(rand, input, signerOpts)
+	if err != nil {
+		return nil, err
+	}
+
+	return asn1.Marshal(pkix.CertificateList{
+		TBSCertList:        tbsCertList,
+		SignatureAlgorithm: signatureAlgorithm,
+		SignatureValue:     asn1.BitString{Bytes: signature, BitLength: len(signature) * 8},
+	})
+}
diff --git a/src/crypto/x509/x509_test.go b/src/crypto/x509/x509_test.go
new file mode 100644
index 0000000..48a8640
--- /dev/null
+++ b/src/crypto/x509/x509_test.go
@@ -0,0 +1,3443 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/dsa"
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/rsa"
+	_ "crypto/sha256"
+	_ "crypto/sha512"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"encoding/base64"
+	"encoding/hex"
+	"encoding/pem"
+	"fmt"
+	"internal/testenv"
+	"io"
+	"math/big"
+	"net"
+	"net/url"
+	"os/exec"
+	"reflect"
+	"runtime"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestParsePKCS1PrivateKey(t *testing.T) {
+	block, _ := pem.Decode([]byte(pemPrivateKey))
+	priv, err := ParsePKCS1PrivateKey(block.Bytes)
+	if err != nil {
+		t.Errorf("Failed to parse private key: %s", err)
+		return
+	}
+	if priv.PublicKey.N.Cmp(rsaPrivateKey.PublicKey.N) != 0 ||
+		priv.PublicKey.E != rsaPrivateKey.PublicKey.E ||
+		priv.D.Cmp(rsaPrivateKey.D) != 0 ||
+		priv.Primes[0].Cmp(rsaPrivateKey.Primes[0]) != 0 ||
+		priv.Primes[1].Cmp(rsaPrivateKey.Primes[1]) != 0 {
+		t.Errorf("got:%+v want:%+v", priv, rsaPrivateKey)
+	}
+
+	// This private key includes an invalid prime that
+	// rsa.PrivateKey.Validate should reject.
+	data := []byte("0\x16\x02\x00\x02\x02\u007f\x00\x02\x0200\x02\x0200\x02\x02\x00\x01\x02\x02\u007f\x00")
+	if _, err := ParsePKCS1PrivateKey(data); err == nil {
+		t.Errorf("parsing invalid private key did not result in an error")
+	}
+}
+
+func TestPKCS1MismatchPublicKeyFormat(t *testing.T) {
+
+	const pkixPublicKey = "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"
+	const errorContains = "use ParsePKIXPublicKey instead"
+	derBytes, _ := hex.DecodeString(pkixPublicKey)
+	_, err := ParsePKCS1PublicKey(derBytes)
+	if !strings.Contains(err.Error(), errorContains) {
+		t.Errorf("expected error containing %q, got %s", errorContains, err)
+	}
+}
+
+func testParsePKIXPublicKey(t *testing.T, pemBytes string) (pub any) {
+	block, _ := pem.Decode([]byte(pemBytes))
+	pub, err := ParsePKIXPublicKey(block.Bytes)
+	if err != nil {
+		t.Fatalf("Failed to parse public key: %s", err)
+	}
+
+	pubBytes2, err := MarshalPKIXPublicKey(pub)
+	if err != nil {
+		t.Errorf("Failed to marshal public key for the second time: %s", err)
+		return
+	}
+	if !bytes.Equal(pubBytes2, block.Bytes) {
+		t.Errorf("Reserialization of public key didn't match. got %x, want %x", pubBytes2, block.Bytes)
+	}
+	return
+}
+
+func TestParsePKIXPublicKey(t *testing.T) {
+	t.Run("RSA", func(t *testing.T) {
+		pub := testParsePKIXPublicKey(t, pemPublicKey)
+		_, ok := pub.(*rsa.PublicKey)
+		if !ok {
+			t.Errorf("Value returned from ParsePKIXPublicKey was not an RSA public key")
+		}
+	})
+	t.Run("Ed25519", func(t *testing.T) {
+		pub := testParsePKIXPublicKey(t, pemEd25519Key)
+		_, ok := pub.(ed25519.PublicKey)
+		if !ok {
+			t.Errorf("Value returned from ParsePKIXPublicKey was not an Ed25519 public key")
+		}
+	})
+}
+
+var pemPublicKey = `-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA3VoPN9PKUjKFLMwOge6+
+wnDi8sbETGIx2FKXGgqtAKpzmem53kRGEQg8WeqRmp12wgp74TGpkEXsGae7RS1k
+enJCnma4fii+noGH7R0qKgHvPrI2Bwa9hzsH8tHxpyM3qrXslOmD45EH9SxIDUBJ
+FehNdaPbLP1gFyahKMsdfxFJLUvbUycuZSJ2ZnIgeVxwm4qbSvZInL9Iu4FzuPtg
+fINKcbbovy1qq4KvPIrXzhbY3PWDc6btxCf3SE0JdE1MCPThntB62/bLMSQ7xdDR
+FF53oIpvxe/SCOymfWq/LW849Ytv3Xwod0+wzAP8STXG4HSELS4UedPYeHJJJYcZ
++QIDAQAB
+-----END PUBLIC KEY-----
+`
+
+var pemPrivateKey = testingKey(`
+-----BEGIN RSA TESTING KEY-----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+-----END RSA TESTING KEY-----
+`)
+
+// pemEd25519Key is the example from RFC 8410, Secrion 4.
+var pemEd25519Key = `
+-----BEGIN PUBLIC KEY-----
+MCowBQYDK2VwAyEAGb9ECWmEzf6FQbrBZ9w7lshQhqowtrbLDFw4rXAxZuE=
+-----END PUBLIC KEY-----
+`
+
+func TestPKIXMismatchPublicKeyFormat(t *testing.T) {
+
+	const pkcs1PublicKey = "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"
+	const errorContains = "use ParsePKCS1PublicKey instead"
+	derBytes, _ := hex.DecodeString(pkcs1PublicKey)
+	_, err := ParsePKIXPublicKey(derBytes)
+	if !strings.Contains(err.Error(), errorContains) {
+		t.Errorf("expected error containing %q, got %s", errorContains, err)
+	}
+}
+
+var testPrivateKey *rsa.PrivateKey
+
+func init() {
+	block, _ := pem.Decode([]byte(pemPrivateKey))
+
+	var err error
+	if testPrivateKey, err = ParsePKCS1PrivateKey(block.Bytes); err != nil {
+		panic("Failed to parse private key: " + err.Error())
+	}
+}
+
+func bigFromString(s string) *big.Int {
+	ret := new(big.Int)
+	ret.SetString(s, 10)
+	return ret
+}
+
+func fromBase10(base10 string) *big.Int {
+	i := new(big.Int)
+	i.SetString(base10, 10)
+	return i
+}
+
+func bigFromHexString(s string) *big.Int {
+	ret := new(big.Int)
+	ret.SetString(s, 16)
+	return ret
+}
+
+var rsaPrivateKey = &rsa.PrivateKey{
+	PublicKey: rsa.PublicKey{
+		N: bigFromString("124737666279038955318614287965056875799409043964547386061640914307192830334599556034328900586693254156136128122194531292927142396093148164407300419162827624945636708870992355233833321488652786796134504707628792159725681555822420087112284637501705261187690946267527866880072856272532711620639179596808018872997"),
+		E: 65537,
+	},
+	D: bigFromString("69322600686866301945688231018559005300304807960033948687567105312977055197015197977971637657636780793670599180105424702854759606794705928621125408040473426339714144598640466128488132656829419518221592374964225347786430566310906679585739468938549035854760501049443920822523780156843263434219450229353270690889"),
+	Primes: []*big.Int{
+		bigFromString("11405025354575369741595561190164746858706645478381139288033759331174478411254205003127028642766986913445391069745480057674348716675323735886284176682955723"),
+		bigFromString("10937079261204603443118731009201819560867324167189758120988909645641782263430128449826989846631183550578761324239709121189827307416350485191350050332642639"),
+	},
+}
+
+func TestMarshalRSAPrivateKey(t *testing.T) {
+	priv := &rsa.PrivateKey{
+		PublicKey: rsa.PublicKey{
+			N: fromBase10("16346378922382193400538269749936049106320265317511766357599732575277382844051791096569333808598921852351577762718529818072849191122419410612033592401403764925096136759934497687765453905884149505175426053037420486697072448609022753683683718057795566811401938833367954642951433473337066311978821180526439641496973296037000052546108507805269279414789035461158073156772151892452251106173507240488993608650881929629163465099476849643165682709047462010581308719577053905787496296934240246311806555924593059995202856826239801816771116902778517096212527979497399966526283516447337775509777558018145573127308919204297111496233"),
+			E: 3,
+		},
+		D: fromBase10("10897585948254795600358846499957366070880176878341177571733155050184921896034527397712889205732614568234385175145686545381899460748279607074689061600935843283397424506622998458510302603922766336783617368686090042765718290914099334449154829375179958369993407724946186243249568928237086215759259909861748642124071874879861299389874230489928271621259294894142840428407196932444474088857746123104978617098858619445675532587787023228852383149557470077802718705420275739737958953794088728369933811184572620857678792001136676902250566845618813972833750098806496641114644760255910789397593428910198080271317419213080834885003"),
+		Primes: []*big.Int{
+			fromBase10("1025363189502892836833747188838978207017355117492483312747347695538428729137306368764177201532277413433182799108299960196606011786562992097313508180436744488171474690412562218914213688661311117337381958560443"),
+			fromBase10("3467903426626310123395340254094941045497208049900750380025518552334536945536837294961497712862519984786362199788654739924501424784631315081391467293694361474867825728031147665777546570788493758372218019373"),
+			fromBase10("4597024781409332673052708605078359346966325141767460991205742124888960305710298765592730135879076084498363772408626791576005136245060321874472727132746643162385746062759369754202494417496879741537284589047"),
+		},
+	}
+
+	derBytes := MarshalPKCS1PrivateKey(priv)
+
+	priv2, err := ParsePKCS1PrivateKey(derBytes)
+	if err != nil {
+		t.Errorf("error parsing serialized key: %s", err)
+		return
+	}
+	if priv.PublicKey.N.Cmp(priv2.PublicKey.N) != 0 ||
+		priv.PublicKey.E != priv2.PublicKey.E ||
+		priv.D.Cmp(priv2.D) != 0 ||
+		len(priv2.Primes) != 3 ||
+		priv.Primes[0].Cmp(priv2.Primes[0]) != 0 ||
+		priv.Primes[1].Cmp(priv2.Primes[1]) != 0 ||
+		priv.Primes[2].Cmp(priv2.Primes[2]) != 0 {
+		t.Errorf("got:%+v want:%+v", priv, priv2)
+	}
+}
+
+func TestMarshalRSAPublicKey(t *testing.T) {
+	pub := &rsa.PublicKey{
+		N: fromBase10("16346378922382193400538269749936049106320265317511766357599732575277382844051791096569333808598921852351577762718529818072849191122419410612033592401403764925096136759934497687765453905884149505175426053037420486697072448609022753683683718057795566811401938833367954642951433473337066311978821180526439641496973296037000052546108507805269279414789035461158073156772151892452251106173507240488993608650881929629163465099476849643165682709047462010581308719577053905787496296934240246311806555924593059995202856826239801816771116902778517096212527979497399966526283516447337775509777558018145573127308919204297111496233"),
+		E: 3,
+	}
+	derBytes := MarshalPKCS1PublicKey(pub)
+	pub2, err := ParsePKCS1PublicKey(derBytes)
+	if err != nil {
+		t.Errorf("ParsePKCS1PublicKey: %s", err)
+	}
+	if pub.N.Cmp(pub2.N) != 0 || pub.E != pub2.E {
+		t.Errorf("ParsePKCS1PublicKey = %+v, want %+v", pub, pub2)
+	}
+
+	// It's never been documented that asn1.Marshal/Unmarshal on rsa.PublicKey works,
+	// but it does, and we know of code that depends on it.
+	// Lock that in, even though we'd prefer that people use MarshalPKCS1PublicKey and ParsePKCS1PublicKey.
+	derBytes2, err := asn1.Marshal(*pub)
+	if err != nil {
+		t.Errorf("Marshal(rsa.PublicKey): %v", err)
+	} else if !bytes.Equal(derBytes, derBytes2) {
+		t.Errorf("Marshal(rsa.PublicKey) = %x, want %x", derBytes2, derBytes)
+	}
+	pub3 := new(rsa.PublicKey)
+	rest, err := asn1.Unmarshal(derBytes, pub3)
+	if err != nil {
+		t.Errorf("Unmarshal(rsa.PublicKey): %v", err)
+	}
+	if len(rest) != 0 || pub.N.Cmp(pub3.N) != 0 || pub.E != pub3.E {
+		t.Errorf("Unmarshal(rsa.PublicKey) = %+v, %q want %+v, %q", pub, rest, pub2, []byte(nil))
+	}
+
+	publicKeys := []struct {
+		derBytes          []byte
+		expectedErrSubstr string
+	}{
+		{
+			derBytes: []byte{
+				0x30, 6, // SEQUENCE, 6 bytes
+				0x02, 1, // INTEGER, 1 byte
+				17,
+				0x02, 1, // INTEGER, 1 byte
+				3, // 3
+			},
+		}, {
+			derBytes: []byte{
+				0x30, 6, // SEQUENCE
+				0x02, 1, // INTEGER, 1 byte
+				0xff,    // -1
+				0x02, 1, // INTEGER, 1 byte
+				3,
+			},
+			expectedErrSubstr: "zero or negative",
+		}, {
+			derBytes: []byte{
+				0x30, 6, // SEQUENCE
+				0x02, 1, // INTEGER, 1 byte
+				17,
+				0x02, 1, // INTEGER, 1 byte
+				0xff, // -1
+			},
+			expectedErrSubstr: "zero or negative",
+		}, {
+			derBytes: []byte{
+				0x30, 6, // SEQUENCE
+				0x02, 1, // INTEGER, 1 byte
+				17,
+				0x02, 1, // INTEGER, 1 byte
+				3,
+				1,
+			},
+			expectedErrSubstr: "trailing data",
+		}, {
+			derBytes: []byte{
+				0x30, 9, // SEQUENCE
+				0x02, 1, // INTEGER, 1 byte
+				17,
+				0x02, 4, // INTEGER, 4 bytes
+				0x7f, 0xff, 0xff, 0xff,
+			},
+		}, {
+			derBytes: []byte{
+				0x30, 10, // SEQUENCE
+				0x02, 1, // INTEGER, 1 byte
+				17,
+				0x02, 5, // INTEGER, 5 bytes
+				0x00, 0x80, 0x00, 0x00, 0x00,
+			},
+			// On 64-bit systems, encoding/asn1 will accept the
+			// public exponent, but ParsePKCS1PublicKey will return
+			// an error. On 32-bit systems, encoding/asn1 will
+			// return the error. The common substring of both error
+			// is the word “large”.
+			expectedErrSubstr: "large",
+		},
+	}
+
+	for i, test := range publicKeys {
+		shouldFail := len(test.expectedErrSubstr) > 0
+		pub, err := ParsePKCS1PublicKey(test.derBytes)
+		if shouldFail {
+			if err == nil {
+				t.Errorf("#%d: unexpected success, got %#v", i, pub)
+			} else if !strings.Contains(err.Error(), test.expectedErrSubstr) {
+				t.Errorf("#%d: expected error containing %q, got %s", i, test.expectedErrSubstr, err)
+			}
+		} else {
+			if err != nil {
+				t.Errorf("#%d: unexpected failure: %s", i, err)
+				continue
+			}
+			reserialized := MarshalPKCS1PublicKey(pub)
+			if !bytes.Equal(reserialized, test.derBytes) {
+				t.Errorf("#%d: failed to reserialize: got %x, expected %x", i, reserialized, test.derBytes)
+			}
+		}
+	}
+}
+
+type matchHostnamesTest struct {
+	pattern, host string
+	ok            bool
+}
+
+var matchHostnamesTests = []matchHostnamesTest{
+	{"a.b.c", "a.b.c", true},
+	{"a.b.c", "b.b.c", false},
+	{"", "b.b.c", false},
+	{"a.b.c", "", false},
+	{"example.com", "example.com", true},
+	{"example.com", "www.example.com", false},
+	{"*.example.com", "example.com", false},
+	{"*.example.com", "www.example.com", true},
+	{"*.example.com", "www.example.com.", true},
+	{"*.example.com", "xyz.www.example.com", false},
+	{"*.example.com", "https://www.example.com", false}, // Issue 27591
+	{"*.example..com", "www.example..com", false},
+	{"www.example..com", "www.example..com", true},
+	{"*.*.example.com", "xyz.www.example.com", false},
+	{"*.www.*.com", "xyz.www.example.com", false},
+	{"*bar.example.com", "foobar.example.com", false},
+	{"f*.example.com", "foobar.example.com", false},
+	{"www.example.com", "*.example.com", false},
+	{"", ".", false},
+	{".", "", false},
+	{".", ".", false},
+	{"example.com", "example.com.", true},
+	{"example.com.", "example.com", false},
+	{"example.com.", "example.com.", true}, // perfect matches allow trailing dots in patterns
+	{"*.com.", "example.com.", false},
+	{"*.com.", "example.com", false},
+	{"*.com", "example.com", true},
+	{"*.com", "example.com.", true},
+	{"foo:bar", "foo:bar", true},
+	{"*.foo:bar", "xxx.foo:bar", false},
+	{"*.2.3.4", "1.2.3.4", false},
+	{"*.2.3.4", "[1.2.3.4]", false},
+	{"*:4860:4860::8888", "2001:4860:4860::8888", false},
+	{"*:4860:4860::8888", "[2001:4860:4860::8888]", false},
+	{"2001:4860:4860::8888", "2001:4860:4860::8888", false},
+	{"2001:4860:4860::8888", "[2001:4860:4860::8888]", false},
+	{"[2001:4860:4860::8888]", "2001:4860:4860::8888", false},
+	{"[2001:4860:4860::8888]", "[2001:4860:4860::8888]", false},
+}
+
+func TestMatchHostnames(t *testing.T) {
+	for i, test := range matchHostnamesTests {
+		c := &Certificate{DNSNames: []string{test.pattern}}
+		r := c.VerifyHostname(test.host) == nil
+		if r != test.ok {
+			t.Errorf("#%d mismatch got: %t want: %t when matching '%s' against '%s'", i, r, test.ok, test.host, test.pattern)
+		}
+	}
+}
+
+func TestMatchIP(t *testing.T) {
+	// Check that pattern matching is working.
+	c := &Certificate{
+		DNSNames: []string{"*.foo.bar.baz"},
+		Subject: pkix.Name{
+			CommonName: "*.foo.bar.baz",
+		},
+	}
+	err := c.VerifyHostname("quux.foo.bar.baz")
+	if err != nil {
+		t.Fatalf("VerifyHostname(quux.foo.bar.baz): %v", err)
+	}
+
+	// But check that if we change it to be matching against an IP address,
+	// it is rejected.
+	c = &Certificate{
+		DNSNames: []string{"*.2.3.4"},
+		Subject: pkix.Name{
+			CommonName: "*.2.3.4",
+		},
+	}
+	err = c.VerifyHostname("1.2.3.4")
+	if err == nil {
+		t.Fatalf("VerifyHostname(1.2.3.4) should have failed, did not")
+	}
+
+	c = &Certificate{
+		IPAddresses: []net.IP{net.ParseIP("127.0.0.1"), net.ParseIP("::1")},
+	}
+	err = c.VerifyHostname("127.0.0.1")
+	if err != nil {
+		t.Fatalf("VerifyHostname(127.0.0.1): %v", err)
+	}
+	err = c.VerifyHostname("::1")
+	if err != nil {
+		t.Fatalf("VerifyHostname(::1): %v", err)
+	}
+	err = c.VerifyHostname("[::1]")
+	if err != nil {
+		t.Fatalf("VerifyHostname([::1]): %v", err)
+	}
+}
+
+func TestCertificateParse(t *testing.T) {
+	s, _ := base64.StdEncoding.DecodeString(certBytes)
+	certs, err := ParseCertificates(s)
+	if err != nil {
+		t.Error(err)
+	}
+	if len(certs) != 2 {
+		t.Errorf("Wrong number of certs: got %d want 2", len(certs))
+		return
+	}
+
+	err = certs[0].CheckSignatureFrom(certs[1])
+	if err != nil {
+		t.Error(err)
+	}
+
+	if err := certs[0].VerifyHostname("mail.google.com"); err != nil {
+		t.Error(err)
+	}
+
+	const expectedExtensions = 10
+	if n := len(certs[0].Extensions); n != expectedExtensions {
+		t.Errorf("want %d extensions, got %d", expectedExtensions, n)
+	}
+}
+
+func TestCertificateEqualOnNil(t *testing.T) {
+	cNonNil := new(Certificate)
+	var cNil1, cNil2 *Certificate
+	if !cNil1.Equal(cNil2) {
+		t.Error("Nil certificates: cNil1 is not equal to cNil2")
+	}
+	if !cNil2.Equal(cNil1) {
+		t.Error("Nil certificates: cNil2 is not equal to cNil1")
+	}
+	if cNil1.Equal(cNonNil) {
+		t.Error("Unexpectedly cNil1 is equal to cNonNil")
+	}
+	if cNonNil.Equal(cNil1) {
+		t.Error("Unexpectedly cNonNil is equal to cNil1")
+	}
+}
+
+func TestMismatchedSignatureAlgorithm(t *testing.T) {
+	der, _ := pem.Decode([]byte(rsaPSSSelfSignedPEM))
+	if der == nil {
+		t.Fatal("Failed to find PEM block")
+	}
+
+	cert, err := ParseCertificate(der.Bytes)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err = cert.CheckSignature(ECDSAWithSHA256, nil, nil); err == nil {
+		t.Fatal("CheckSignature unexpectedly return no error")
+	}
+
+	const expectedSubstring = " but have public key of type "
+	if !strings.Contains(err.Error(), expectedSubstring) {
+		t.Errorf("Expected error containing %q, but got %q", expectedSubstring, err)
+	}
+}
+
+var certBytes = "MIIE0jCCA7qgAwIBAgIQWcvS+TTB3GwCAAAAAGEAWzANBgkqhkiG9w0BAQsFADBCMQswCQYD" +
+	"VQQGEwJVUzEeMBwGA1UEChMVR29vZ2xlIFRydXN0IFNlcnZpY2VzMRMwEQYDVQQDEwpHVFMg" +
+	"Q0EgMU8xMB4XDTIwMDQwMTEyNTg1NloXDTIwMDYyNDEyNTg1NlowaTELMAkGA1UEBhMCVVMx" +
+	"EzARBgNVBAgTCkNhbGlmb3JuaWExFjAUBgNVBAcTDU1vdW50YWluIFZpZXcxEzARBgNVBAoT" +
+	"Ckdvb2dsZSBMTEMxGDAWBgNVBAMTD21haWwuZ29vZ2xlLmNvbTBZMBMGByqGSM49AgEGCCqG" +
+	"SM49AwEHA0IABO+dYiPnkFl+cZVf6mrWeNp0RhQcJSBGH+sEJxjvc+cYlW3QJCnm57qlpFdd" +
+	"pz3MPyVejvXQdM6iI1mEWP4C2OujggJmMIICYjAOBgNVHQ8BAf8EBAMCB4AwEwYDVR0lBAww" +
+	"CgYIKwYBBQUHAwEwDAYDVR0TAQH/BAIwADAdBgNVHQ4EFgQUI6pZhnQ/lQgmPDwSKR2A54G7" +
+	"AS4wHwYDVR0jBBgwFoAUmNH4bhDrz5vsYJ8YkBug630J/SswZAYIKwYBBQUHAQEEWDBWMCcG" +
+	"CCsGAQUFBzABhhtodHRwOi8vb2NzcC5wa2kuZ29vZy9ndHMxbzEwKwYIKwYBBQUHMAKGH2h0" +
+	"dHA6Ly9wa2kuZ29vZy9nc3IyL0dUUzFPMS5jcnQwLAYDVR0RBCUwI4IPbWFpbC5nb29nbGUu" +
+	"Y29tghBpbmJveC5nb29nbGUuY29tMCEGA1UdIAQaMBgwCAYGZ4EMAQICMAwGCisGAQQB1nkC" +
+	"BQMwLwYDVR0fBCgwJjAkoCKgIIYeaHR0cDovL2NybC5wa2kuZ29vZy9HVFMxTzEuY3JsMIIB" +
+	"AwYKKwYBBAHWeQIEAgSB9ASB8QDvAHYAsh4FzIuizYogTodm+Su5iiUgZ2va+nDnsklTLe+L" +
+	"kF4AAAFxNgmxKgAABAMARzBFAiEA12/OHdTGXQ3qHHC3NvYCyB8aEz/+ZFOLCAI7lhqj28sC" +
+	"IG2/7Yz2zK6S6ai+dH7cTMZmoFGo39gtaTqtZAqEQX7nAHUAXqdz+d9WwOe1Nkh90EngMnqR" +
+	"mgyEoRIShBh1loFxRVgAAAFxNgmxTAAABAMARjBEAiA7PNq+MFfv6O9mBkxFViS2TfU66yRB" +
+	"/njcebWglLQjZQIgOyRKhxlEizncFRml7yn4Bg48ktXKGjo+uiw6zXEINb0wDQYJKoZIhvcN" +
+	"AQELBQADggEBADM2Rh306Q10PScsolYMxH1B/K4Nb2WICvpY0yDPJFdnGjqCYym196TjiEvs" +
+	"R6etfeHdyzlZj6nh82B4TVyHjiWM02dQgPalOuWQcuSy0OvLh7F1E7CeHzKlczdFPBTOTdM1" +
+	"RDTxlvw1bAqc0zueM8QIAyEy3opd7FxAcGQd5WRIJhzLBL+dbbMOW/LTeW7cm/Xzq8cgCybN" +
+	"BSZAvhjseJ1L29OlCTZL97IfnX0IlFQzWuvvHy7V2B0E3DHlzM0kjwkkCKDUUp/wajv2NZKC" +
+	"TkhEyERacZRKc9U0ADxwsAzHrdz5+5zfD2usEV/MQ5V6d8swLXs+ko0X6swrd4YCiB8wggRK" +
+	"MIIDMqADAgECAg0B47SaoY2KqYElaVC4MA0GCSqGSIb3DQEBCwUAMEwxIDAeBgNVBAsTF0ds" +
+	"b2JhbFNpZ24gUm9vdCBDQSAtIFIyMRMwEQYDVQQKEwpHbG9iYWxTaWduMRMwEQYDVQQDEwpH" +
+	"bG9iYWxTaWduMB4XDTE3MDYxNTAwMDA0MloXDTIxMTIxNTAwMDA0MlowQjELMAkGA1UEBhMC" +
+	"VVMxHjAcBgNVBAoTFUdvb2dsZSBUcnVzdCBTZXJ2aWNlczETMBEGA1UEAxMKR1RTIENBIDFP" +
+	"MTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBANAYz0XUi83TnORA73603WkhG8nP" +
+	"PI5MdbkPMRmEPZ48Ke9QDRCTbwWAgJ8qoL0SSwLhPZ9YFiT+MJ8LdHdVkx1L903hkoIQ9lGs" +
+	"DMOyIpQPNGuYEEnnC52DOd0gxhwt79EYYWXnI4MgqCMS/9Ikf9Qv50RqW03XUGawr55CYwX7" +
+	"4BzEY2Gvn2oz/2KXvUjZ03wUZ9x13C5p6PhteGnQtxAFuPExwjsk/RozdPgj4OxrGYoWxuPN" +
+	"pM0L27OkWWA4iDutHbnGjKdTG/y82aSrvN08YdeTFZjugb2P4mRHIEAGTtesl+i5wFkSoUkl" +
+	"I+TtcDQspbRjfPmjPYPRzW0krAcCAwEAAaOCATMwggEvMA4GA1UdDwEB/wQEAwIBhjAdBgNV" +
+	"HSUEFjAUBggrBgEFBQcDAQYIKwYBBQUHAwIwEgYDVR0TAQH/BAgwBgEB/wIBADAdBgNVHQ4E" +
+	"FgQUmNH4bhDrz5vsYJ8YkBug630J/SswHwYDVR0jBBgwFoAUm+IHV2ccHsBqBt5ZtJot39wZ" +
+	"hi4wNQYIKwYBBQUHAQEEKTAnMCUGCCsGAQUFBzABhhlodHRwOi8vb2NzcC5wa2kuZ29vZy9n" +
+	"c3IyMDIGA1UdHwQrMCkwJ6AloCOGIWh0dHA6Ly9jcmwucGtpLmdvb2cvZ3NyMi9nc3IyLmNy" +
+	"bDA/BgNVHSAEODA2MDQGBmeBDAECAjAqMCgGCCsGAQUFBwIBFhxodHRwczovL3BraS5nb29n" +
+	"L3JlcG9zaXRvcnkvMA0GCSqGSIb3DQEBCwUAA4IBAQAagD42efvzLqlGN31eVBY1rsdOCJn+" +
+	"vdE0aSZSZgc9CrpJy2L08RqO/BFPaJZMdCvTZ96yo6oFjYRNTCBlD6WW2g0W+Gw7228EI4hr" +
+	"OmzBYL1on3GO7i1YNAfw1VTphln9e14NIZT1jMmo+NjyrcwPGvOap6kEJ/mjybD/AnhrYbrH" +
+	"NSvoVvpPwxwM7bY8tEvq7czhPOzcDYzWPpvKQliLzBYhF0C8otZm79rEFVvNiaqbCSbnMtIN" +
+	"bmcgAlsQsJAJnAwfnq3YO+qh/GzoEFwIUhlRKnG7rHq13RXtK8kIKiyKtKYhq2P/11JJUNCJ" +
+	"t63yr/tQri/hlQ3zRq2dnPXK"
+
+func parseCIDR(s string) *net.IPNet {
+	_, net, err := net.ParseCIDR(s)
+	if err != nil {
+		panic(err)
+	}
+	return net
+}
+
+func parseURI(s string) *url.URL {
+	uri, err := url.Parse(s)
+	if err != nil {
+		panic(err)
+	}
+	return uri
+}
+
+func TestCreateSelfSignedCertificate(t *testing.T) {
+	random := rand.Reader
+
+	ecdsaPriv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatalf("Failed to generate ECDSA key: %s", err)
+	}
+
+	ed25519Pub, ed25519Priv, err := ed25519.GenerateKey(random)
+	if err != nil {
+		t.Fatalf("Failed to generate Ed25519 key: %s", err)
+	}
+
+	tests := []struct {
+		name      string
+		pub, priv any
+		checkSig  bool
+		sigAlgo   SignatureAlgorithm
+	}{
+		{"RSA/RSA", &testPrivateKey.PublicKey, testPrivateKey, true, SHA384WithRSA},
+		{"RSA/ECDSA", &testPrivateKey.PublicKey, ecdsaPriv, false, ECDSAWithSHA384},
+		{"ECDSA/RSA", &ecdsaPriv.PublicKey, testPrivateKey, false, SHA256WithRSA},
+		{"ECDSA/ECDSA", &ecdsaPriv.PublicKey, ecdsaPriv, true, ECDSAWithSHA256},
+		{"RSAPSS/RSAPSS", &testPrivateKey.PublicKey, testPrivateKey, true, SHA256WithRSAPSS},
+		{"ECDSA/RSAPSS", &ecdsaPriv.PublicKey, testPrivateKey, false, SHA256WithRSAPSS},
+		{"RSAPSS/ECDSA", &testPrivateKey.PublicKey, ecdsaPriv, false, ECDSAWithSHA384},
+		{"Ed25519", ed25519Pub, ed25519Priv, true, PureEd25519},
+	}
+
+	testExtKeyUsage := []ExtKeyUsage{ExtKeyUsageClientAuth, ExtKeyUsageServerAuth}
+	testUnknownExtKeyUsage := []asn1.ObjectIdentifier{[]int{1, 2, 3}, []int{2, 59, 1}}
+	extraExtensionData := []byte("extra extension")
+
+	for _, test := range tests {
+		commonName := "test.example.com"
+		template := Certificate{
+			// SerialNumber is negative to ensure that negative
+			// values are parsed. This is due to the prevalence of
+			// buggy code that produces certificates with negative
+			// serial numbers.
+			SerialNumber: big.NewInt(-1),
+			Subject: pkix.Name{
+				CommonName:   commonName,
+				Organization: []string{"Σ Acme Co"},
+				Country:      []string{"US"},
+				ExtraNames: []pkix.AttributeTypeAndValue{
+					{
+						Type:  []int{2, 5, 4, 42},
+						Value: "Gopher",
+					},
+					// This should override the Country, above.
+					{
+						Type:  []int{2, 5, 4, 6},
+						Value: "NL",
+					},
+				},
+			},
+			NotBefore: time.Unix(1000, 0),
+			NotAfter:  time.Unix(100000, 0),
+
+			SignatureAlgorithm: test.sigAlgo,
+
+			SubjectKeyId: []byte{1, 2, 3, 4},
+			KeyUsage:     KeyUsageCertSign,
+
+			ExtKeyUsage:        testExtKeyUsage,
+			UnknownExtKeyUsage: testUnknownExtKeyUsage,
+
+			BasicConstraintsValid: true,
+			IsCA:                  true,
+
+			OCSPServer:            []string{"http://ocsp.example.com"},
+			IssuingCertificateURL: []string{"http://crt.example.com/ca1.crt"},
+
+			DNSNames:       []string{"test.example.com"},
+			EmailAddresses: []string{"gopher@golang.org"},
+			IPAddresses:    []net.IP{net.IPv4(127, 0, 0, 1).To4(), net.ParseIP("2001:4860:0:2001::68")},
+			URIs:           []*url.URL{parseURI("https://foo.com/wibble#foo")},
+
+			PolicyIdentifiers:       []asn1.ObjectIdentifier{[]int{1, 2, 3}},
+			PermittedDNSDomains:     []string{".example.com", "example.com"},
+			ExcludedDNSDomains:      []string{"bar.example.com"},
+			PermittedIPRanges:       []*net.IPNet{parseCIDR("192.168.1.1/16"), parseCIDR("1.2.3.4/8")},
+			ExcludedIPRanges:        []*net.IPNet{parseCIDR("2001:db8::/48")},
+			PermittedEmailAddresses: []string{"foo@example.com"},
+			ExcludedEmailAddresses:  []string{".example.com", "example.com"},
+			PermittedURIDomains:     []string{".bar.com", "bar.com"},
+			ExcludedURIDomains:      []string{".bar2.com", "bar2.com"},
+
+			CRLDistributionPoints: []string{"http://crl1.example.com/ca1.crl", "http://crl2.example.com/ca1.crl"},
+
+			ExtraExtensions: []pkix.Extension{
+				{
+					Id:    []int{1, 2, 3, 4},
+					Value: extraExtensionData,
+				},
+				// This extension should override the SubjectKeyId, above.
+				{
+					Id:       oidExtensionSubjectKeyId,
+					Critical: false,
+					Value:    []byte{0x04, 0x04, 4, 3, 2, 1},
+				},
+			},
+		}
+
+		derBytes, err := CreateCertificate(random, &template, &template, test.pub, test.priv)
+		if err != nil {
+			t.Errorf("%s: failed to create certificate: %s", test.name, err)
+			continue
+		}
+
+		cert, err := ParseCertificate(derBytes)
+		if err != nil {
+			t.Errorf("%s: failed to parse certificate: %s", test.name, err)
+			continue
+		}
+
+		if len(cert.PolicyIdentifiers) != 1 || !cert.PolicyIdentifiers[0].Equal(template.PolicyIdentifiers[0]) {
+			t.Errorf("%s: failed to parse policy identifiers: got:%#v want:%#v", test.name, cert.PolicyIdentifiers, template.PolicyIdentifiers)
+		}
+
+		if len(cert.PermittedDNSDomains) != 2 || cert.PermittedDNSDomains[0] != ".example.com" || cert.PermittedDNSDomains[1] != "example.com" {
+			t.Errorf("%s: failed to parse name constraints: %#v", test.name, cert.PermittedDNSDomains)
+		}
+
+		if len(cert.ExcludedDNSDomains) != 1 || cert.ExcludedDNSDomains[0] != "bar.example.com" {
+			t.Errorf("%s: failed to parse name constraint exclusions: %#v", test.name, cert.ExcludedDNSDomains)
+		}
+
+		if len(cert.PermittedIPRanges) != 2 || cert.PermittedIPRanges[0].String() != "192.168.0.0/16" || cert.PermittedIPRanges[1].String() != "1.0.0.0/8" {
+			t.Errorf("%s: failed to parse IP constraints: %#v", test.name, cert.PermittedIPRanges)
+		}
+
+		if len(cert.ExcludedIPRanges) != 1 || cert.ExcludedIPRanges[0].String() != "2001:db8::/48" {
+			t.Errorf("%s: failed to parse IP constraint exclusions: %#v", test.name, cert.ExcludedIPRanges)
+		}
+
+		if len(cert.PermittedEmailAddresses) != 1 || cert.PermittedEmailAddresses[0] != "foo@example.com" {
+			t.Errorf("%s: failed to parse permitted email addreses: %#v", test.name, cert.PermittedEmailAddresses)
+		}
+
+		if len(cert.ExcludedEmailAddresses) != 2 || cert.ExcludedEmailAddresses[0] != ".example.com" || cert.ExcludedEmailAddresses[1] != "example.com" {
+			t.Errorf("%s: failed to parse excluded email addreses: %#v", test.name, cert.ExcludedEmailAddresses)
+		}
+
+		if len(cert.PermittedURIDomains) != 2 || cert.PermittedURIDomains[0] != ".bar.com" || cert.PermittedURIDomains[1] != "bar.com" {
+			t.Errorf("%s: failed to parse permitted URIs: %#v", test.name, cert.PermittedURIDomains)
+		}
+
+		if len(cert.ExcludedURIDomains) != 2 || cert.ExcludedURIDomains[0] != ".bar2.com" || cert.ExcludedURIDomains[1] != "bar2.com" {
+			t.Errorf("%s: failed to parse excluded URIs: %#v", test.name, cert.ExcludedURIDomains)
+		}
+
+		if cert.Subject.CommonName != commonName {
+			t.Errorf("%s: subject wasn't correctly copied from the template. Got %s, want %s", test.name, cert.Subject.CommonName, commonName)
+		}
+
+		if len(cert.Subject.Country) != 1 || cert.Subject.Country[0] != "NL" {
+			t.Errorf("%s: ExtraNames didn't override Country", test.name)
+		}
+
+		for _, ext := range cert.Extensions {
+			if ext.Id.Equal(oidExtensionSubjectAltName) {
+				if ext.Critical {
+					t.Fatal("SAN extension is marked critical")
+				}
+			}
+		}
+
+		found := false
+		for _, atv := range cert.Subject.Names {
+			if atv.Type.Equal([]int{2, 5, 4, 42}) {
+				found = true
+				break
+			}
+		}
+		if !found {
+			t.Errorf("%s: Names didn't contain oid 2.5.4.42 from ExtraNames", test.name)
+		}
+
+		if cert.Issuer.CommonName != commonName {
+			t.Errorf("%s: issuer wasn't correctly copied from the template. Got %s, want %s", test.name, cert.Issuer.CommonName, commonName)
+		}
+
+		if cert.SignatureAlgorithm != test.sigAlgo {
+			t.Errorf("%s: SignatureAlgorithm wasn't copied from template. Got %v, want %v", test.name, cert.SignatureAlgorithm, test.sigAlgo)
+		}
+
+		if !reflect.DeepEqual(cert.ExtKeyUsage, testExtKeyUsage) {
+			t.Errorf("%s: extkeyusage wasn't correctly copied from the template. Got %v, want %v", test.name, cert.ExtKeyUsage, testExtKeyUsage)
+		}
+
+		if !reflect.DeepEqual(cert.UnknownExtKeyUsage, testUnknownExtKeyUsage) {
+			t.Errorf("%s: unknown extkeyusage wasn't correctly copied from the template. Got %v, want %v", test.name, cert.UnknownExtKeyUsage, testUnknownExtKeyUsage)
+		}
+
+		if !reflect.DeepEqual(cert.OCSPServer, template.OCSPServer) {
+			t.Errorf("%s: OCSP servers differ from template. Got %v, want %v", test.name, cert.OCSPServer, template.OCSPServer)
+		}
+
+		if !reflect.DeepEqual(cert.IssuingCertificateURL, template.IssuingCertificateURL) {
+			t.Errorf("%s: Issuing certificate URLs differ from template. Got %v, want %v", test.name, cert.IssuingCertificateURL, template.IssuingCertificateURL)
+		}
+
+		if !reflect.DeepEqual(cert.DNSNames, template.DNSNames) {
+			t.Errorf("%s: SAN DNS names differ from template. Got %v, want %v", test.name, cert.DNSNames, template.DNSNames)
+		}
+
+		if !reflect.DeepEqual(cert.EmailAddresses, template.EmailAddresses) {
+			t.Errorf("%s: SAN emails differ from template. Got %v, want %v", test.name, cert.EmailAddresses, template.EmailAddresses)
+		}
+
+		if len(cert.URIs) != 1 || cert.URIs[0].String() != "https://foo.com/wibble#foo" {
+			t.Errorf("%s: URIs differ from template. Got %v, want %v", test.name, cert.URIs, template.URIs)
+		}
+
+		if !reflect.DeepEqual(cert.IPAddresses, template.IPAddresses) {
+			t.Errorf("%s: SAN IPs differ from template. Got %v, want %v", test.name, cert.IPAddresses, template.IPAddresses)
+		}
+
+		if !reflect.DeepEqual(cert.CRLDistributionPoints, template.CRLDistributionPoints) {
+			t.Errorf("%s: CRL distribution points differ from template. Got %v, want %v", test.name, cert.CRLDistributionPoints, template.CRLDistributionPoints)
+		}
+
+		if !bytes.Equal(cert.SubjectKeyId, []byte{4, 3, 2, 1}) {
+			t.Errorf("%s: ExtraExtensions didn't override SubjectKeyId", test.name)
+		}
+
+		if !bytes.Contains(derBytes, extraExtensionData) {
+			t.Errorf("%s: didn't find extra extension in DER output", test.name)
+		}
+
+		if test.checkSig {
+			err = cert.CheckSignatureFrom(cert)
+			if err != nil {
+				t.Errorf("%s: signature verification failed: %s", test.name, err)
+			}
+		}
+	}
+}
+
+// Self-signed certificate using ECDSA with SHA1 & secp256r1
+var ecdsaSHA1CertPem = `
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+`
+
+// Self-signed certificate using ECDSA with SHA256 & secp256r1
+var ecdsaSHA256p256CertPem = `
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+`
+
+// Self-signed certificate using ECDSA with SHA256 & secp384r1
+var ecdsaSHA256p384CertPem = `
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+`
+
+// Self-signed certificate using ECDSA with SHA384 & secp521r1
+var ecdsaSHA384p521CertPem = `
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+`
+
+var ecdsaTests = []struct {
+	sigAlgo SignatureAlgorithm
+	pemCert string
+}{
+	{ECDSAWithSHA256, ecdsaSHA256p256CertPem},
+	{ECDSAWithSHA256, ecdsaSHA256p384CertPem},
+	{ECDSAWithSHA384, ecdsaSHA384p521CertPem},
+}
+
+func TestECDSA(t *testing.T) {
+	for i, test := range ecdsaTests {
+		pemBlock, _ := pem.Decode([]byte(test.pemCert))
+		cert, err := ParseCertificate(pemBlock.Bytes)
+		if err != nil {
+			t.Errorf("%d: failed to parse certificate: %s", i, err)
+			continue
+		}
+		if sa := cert.SignatureAlgorithm; sa != test.sigAlgo {
+			t.Errorf("%d: signature algorithm is %v, want %v", i, sa, test.sigAlgo)
+		}
+		if parsedKey, ok := cert.PublicKey.(*ecdsa.PublicKey); !ok {
+			t.Errorf("%d: wanted an ECDSA public key but found: %#v", i, parsedKey)
+		}
+		if pka := cert.PublicKeyAlgorithm; pka != ECDSA {
+			t.Errorf("%d: public key algorithm is %v, want ECDSA", i, pka)
+		}
+		if err = cert.CheckSignatureFrom(cert); err != nil {
+			t.Errorf("%d: certificate verification failed: %s", i, err)
+		}
+	}
+}
+
+// Self-signed certificate using DSA with SHA1
+var dsaCertPem = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+`
+
+func TestParseCertificateWithDsaPublicKey(t *testing.T) {
+	expectedKey := &dsa.PublicKey{
+		Parameters: dsa.Parameters{
+			P: bigFromHexString("00BC84B52743B169158BB85974E3E832AF5EFCFC42B264349095313A4A013EEE069A1B937D92E51ACF297A1C77880DF25C8607D8204B4DC45651305EF4A63B40C7D8C42D91EDA397D8F51CBC9D0A531FE2C6F1E55E9357D205C39D395358968CBEDAC11320C607BE16CB9DB492B6E78163305A34DD99CE43C64927D13A0040EB97"),
+			Q: bigFromHexString("009A67067F66A323F5D4EC7902C73FE5D9E36FA74F"),
+			G: bigFromHexString("009147778295BF5893542BC41BA806898A29E43261DBC85441C37D92E97ED80D323D44825FDDE8374D0FF15877798812682599B216BBCC31B9DCCAD527465FEAFFD7FC2A193612E575E34E7A98AF4D10339FE47390A518CB9975B3160B1D0285D1418D0977C52994F43C29A053E3D685834104C9FAFDC221E38BE9F3989D7A8E42"),
+		},
+		Y: bigFromHexString("59A27C269FCDE45AA2160A5C980C19211A820095091AB9C5DC8309AB7EC1B3A48C2E267C6D35FEE9B71BCBB92F16AC8E559129347FB5C00BEEDD10BA8915C90698755CA965735A32DC7575BED806E1E38F768FFBC24E41123DC73F1C6E9E4D0C9E692128853AFE29DC665FA993DCA9C903B7BF00B6442B9A76A5DADC6186317A"),
+	}
+	pemBlock, _ := pem.Decode([]byte(dsaCertPem))
+	cert, err := ParseCertificate(pemBlock.Bytes)
+	if err != nil {
+		t.Fatalf("Failed to parse certificate: %s", err)
+	}
+	if cert.PublicKeyAlgorithm != DSA {
+		t.Errorf("Parsed key algorithm was not DSA")
+	}
+	parsedKey, ok := cert.PublicKey.(*dsa.PublicKey)
+	if !ok {
+		t.Fatalf("Parsed key was not a DSA key: %s", err)
+	}
+	if expectedKey.Y.Cmp(parsedKey.Y) != 0 ||
+		expectedKey.P.Cmp(parsedKey.P) != 0 ||
+		expectedKey.Q.Cmp(parsedKey.Q) != 0 ||
+		expectedKey.G.Cmp(parsedKey.G) != 0 {
+		t.Fatal("Parsed key differs from expected key")
+	}
+}
+
+func TestParseCertificateWithDSASignatureAlgorithm(t *testing.T) {
+	pemBlock, _ := pem.Decode([]byte(dsaCertPem))
+	cert, err := ParseCertificate(pemBlock.Bytes)
+	if err != nil {
+		t.Fatalf("Failed to parse certificate: %s", err)
+	}
+	if cert.SignatureAlgorithm != DSAWithSHA1 {
+		t.Errorf("Parsed signature algorithm was not DSAWithSHA1")
+	}
+}
+
+func TestVerifyCertificateWithDSASignature(t *testing.T) {
+	pemBlock, _ := pem.Decode([]byte(dsaCertPem))
+	cert, err := ParseCertificate(pemBlock.Bytes)
+	if err != nil {
+		t.Fatalf("Failed to parse certificate: %s", err)
+	}
+	// test cert is self-signed
+	if err = cert.CheckSignatureFrom(cert); err == nil {
+		t.Fatalf("Expected error verifying DSA certificate")
+	}
+}
+
+var rsaPSSSelfSignedPEM = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+// openssl req -newkey rsa:2048 -keyout test.key -sha256 -sigopt \
+// rsa_padding_mode:pss -sigopt rsa_pss_saltlen:32 -sigopt rsa_mgf1_md:sha256 \
+// -x509 -days 3650 -nodes -subj '/C=US/ST=CA/L=SF/O=Test/CN=Test' -out \
+// test.pem
+var rsaPSSSelfSignedOpenSSL110PEM = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+func TestRSAPSSSelfSigned(t *testing.T) {
+	for i, pemBlock := range []string{rsaPSSSelfSignedPEM, rsaPSSSelfSignedOpenSSL110PEM} {
+		der, _ := pem.Decode([]byte(pemBlock))
+		if der == nil {
+			t.Errorf("#%d: failed to find PEM block", i)
+			continue
+		}
+
+		cert, err := ParseCertificate(der.Bytes)
+		if err != nil {
+			t.Errorf("#%d: failed to parse: %s", i, err)
+			continue
+		}
+
+		if err = cert.CheckSignatureFrom(cert); err != nil {
+			t.Errorf("#%d: signature check failed: %s", i, err)
+			continue
+		}
+	}
+}
+
+const ed25519Certificate = `
+Certificate:
+    Data:
+        Version: 3 (0x2)
+        Serial Number:
+            0c:83:d8:21:2b:82:cb:23:98:23:63:e2:f7:97:8a:43:5b:f3:bd:92
+        Signature Algorithm: ED25519
+        Issuer: CN = Ed25519 test certificate
+        Validity
+            Not Before: May  6 17:27:16 2019 GMT
+            Not After : Jun  5 17:27:16 2019 GMT
+        Subject: CN = Ed25519 test certificate
+        Subject Public Key Info:
+            Public Key Algorithm: ED25519
+                ED25519 Public-Key:
+                pub:
+                    36:29:c5:6c:0d:4f:14:6c:81:d0:ff:75:d3:6a:70:
+                    5f:69:cd:0f:4d:66:d5:da:98:7e:82:49:89:a3:8a:
+                    3c:fa
+        X509v3 extensions:
+            X509v3 Subject Key Identifier:
+                09:3B:3A:9D:4A:29:D8:95:FF:68:BE:7B:43:54:72:E0:AD:A2:E3:AE
+            X509v3 Authority Key Identifier:
+                keyid:09:3B:3A:9D:4A:29:D8:95:FF:68:BE:7B:43:54:72:E0:AD:A2:E3:AE
+
+            X509v3 Basic Constraints: critical
+                CA:TRUE
+    Signature Algorithm: ED25519
+         53:a5:58:1c:2c:3b:2a:9e:ac:9d:4e:a5:1d:5f:5d:6d:a6:b5:
+         08:de:12:82:f3:97:20:ae:fa:d8:98:f4:1a:83:32:6b:91:f5:
+         24:1d:c4:20:7f:2c:e2:4d:da:13:3b:6d:54:1a:d2:a8:28:dc:
+         60:b9:d4:f4:78:4b:3c:1c:91:00
+-----BEGIN CERTIFICATE-----
+MIIBWzCCAQ2gAwIBAgIUDIPYISuCyyOYI2Pi95eKQ1vzvZIwBQYDK2VwMCMxITAf
+BgNVBAMMGEVkMjU1MTkgdGVzdCBjZXJ0aWZpY2F0ZTAeFw0xOTA1MDYxNzI3MTZa
+Fw0xOTA2MDUxNzI3MTZaMCMxITAfBgNVBAMMGEVkMjU1MTkgdGVzdCBjZXJ0aWZp
+Y2F0ZTAqMAUGAytlcAMhADYpxWwNTxRsgdD/ddNqcF9pzQ9NZtXamH6CSYmjijz6
+o1MwUTAdBgNVHQ4EFgQUCTs6nUop2JX/aL57Q1Ry4K2i464wHwYDVR0jBBgwFoAU
+CTs6nUop2JX/aL57Q1Ry4K2i464wDwYDVR0TAQH/BAUwAwEB/zAFBgMrZXADQQBT
+pVgcLDsqnqydTqUdX11tprUI3hKC85cgrvrYmPQagzJrkfUkHcQgfyziTdoTO21U
+GtKoKNxgudT0eEs8HJEA
+-----END CERTIFICATE-----`
+
+func TestEd25519SelfSigned(t *testing.T) {
+	der, _ := pem.Decode([]byte(ed25519Certificate))
+	if der == nil {
+		t.Fatalf("Failed to find PEM block")
+	}
+
+	cert, err := ParseCertificate(der.Bytes)
+	if err != nil {
+		t.Fatalf("Failed to parse: %s", err)
+	}
+
+	if cert.PublicKeyAlgorithm != Ed25519 {
+		t.Fatalf("Parsed key algorithm was not Ed25519")
+	}
+	parsedKey, ok := cert.PublicKey.(ed25519.PublicKey)
+	if !ok {
+		t.Fatalf("Parsed key was not an Ed25519 key: %s", err)
+	}
+	if len(parsedKey) != ed25519.PublicKeySize {
+		t.Fatalf("Invalid Ed25519 key")
+	}
+
+	if err = cert.CheckSignatureFrom(cert); err != nil {
+		t.Fatalf("Signature check failed: %s", err)
+	}
+}
+
+const pemCertificate = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const ed25519CRLCertificate = `
+Certificate:
+Data:
+	Version: 3 (0x2)
+	Serial Number:
+		7a:07:a0:9d:14:04:16:fc:1f:d8:e5:fe:d1:1d:1f:8d
+	Signature Algorithm: ED25519
+	Issuer: CN = Ed25519 CRL Test CA
+	Validity
+		Not Before: Oct 30 01:20:20 2019 GMT
+		Not After : Dec 31 23:59:59 9999 GMT
+	Subject: CN = Ed25519 CRL Test CA
+	Subject Public Key Info:
+		Public Key Algorithm: ED25519
+			ED25519 Public-Key:
+			pub:
+				95:73:3b:b0:06:2a:31:5a:b6:a7:a6:6e:ef:71:df:
+				ac:6f:6b:39:03:85:5e:63:4b:f8:a6:0f:68:c6:6f:
+				75:21
+	X509v3 extensions:
+		X509v3 Key Usage: critical
+			Digital Signature, Certificate Sign, CRL Sign
+		X509v3 Extended Key Usage: 
+			TLS Web Client Authentication, TLS Web Server Authentication, OCSP Signing
+		X509v3 Basic Constraints: critical
+			CA:TRUE
+		X509v3 Subject Key Identifier: 
+			B7:17:DA:16:EA:C5:ED:1F:18:49:44:D3:D2:E3:A0:35:0A:81:93:60
+		X509v3 Authority Key Identifier: 
+			keyid:B7:17:DA:16:EA:C5:ED:1F:18:49:44:D3:D2:E3:A0:35:0A:81:93:60
+
+Signature Algorithm: ED25519
+	 fc:3e:14:ea:bb:70:c2:6f:38:34:70:bc:c8:a7:f4:7c:0d:1e:
+	 28:d7:2a:9f:22:8a:45:e8:02:76:84:1e:2d:64:2d:1e:09:b5:
+	 29:71:1f:95:8a:4e:79:87:51:60:9a:e7:86:40:f6:60:c7:d1:
+	 ee:68:76:17:1d:90:cc:92:93:07
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+var ed25519CRLKey = testingKey(`-----BEGIN TEST KEY-----
+MC4CAQAwBQYDK2VwBCIEINdKh2096vUBYu4EIFpjShsUSh3vimKya1sQ1YTT4RZG
+-----END TEST KEY-----`)
+
+func TestCRLCreation(t *testing.T) {
+	block, _ := pem.Decode([]byte(pemPrivateKey))
+	privRSA, _ := ParsePKCS1PrivateKey(block.Bytes)
+	block, _ = pem.Decode([]byte(pemCertificate))
+	certRSA, _ := ParseCertificate(block.Bytes)
+
+	block, _ = pem.Decode([]byte(ed25519CRLKey))
+	privEd25519, _ := ParsePKCS8PrivateKey(block.Bytes)
+	block, _ = pem.Decode([]byte(ed25519CRLCertificate))
+	certEd25519, _ := ParseCertificate(block.Bytes)
+
+	tests := []struct {
+		name string
+		priv any
+		cert *Certificate
+	}{
+		{"RSA CA", privRSA, certRSA},
+		{"Ed25519 CA", privEd25519, certEd25519},
+	}
+
+	loc := time.FixedZone("Oz/Atlantis", int((2 * time.Hour).Seconds()))
+
+	now := time.Unix(1000, 0).In(loc)
+	nowUTC := now.UTC()
+	expiry := time.Unix(10000, 0)
+
+	revokedCerts := []pkix.RevokedCertificate{
+		{
+			SerialNumber:   big.NewInt(1),
+			RevocationTime: nowUTC,
+		},
+		{
+			SerialNumber: big.NewInt(42),
+			// RevocationTime should be converted to UTC before marshaling.
+			RevocationTime: now,
+		},
+	}
+	expectedCerts := []pkix.RevokedCertificate{
+		{
+			SerialNumber:   big.NewInt(1),
+			RevocationTime: nowUTC,
+		},
+		{
+			SerialNumber:   big.NewInt(42),
+			RevocationTime: nowUTC,
+		},
+	}
+
+	for _, test := range tests {
+		crlBytes, err := test.cert.CreateCRL(rand.Reader, test.priv, revokedCerts, now, expiry)
+		if err != nil {
+			t.Errorf("%s: error creating CRL: %s", test.name, err)
+		}
+
+		parsedCRL, err := ParseDERCRL(crlBytes)
+		if err != nil {
+			t.Errorf("%s: error reparsing CRL: %s", test.name, err)
+		}
+		if !reflect.DeepEqual(parsedCRL.TBSCertList.RevokedCertificates, expectedCerts) {
+			t.Errorf("%s: RevokedCertificates mismatch: got %v; want %v.", test.name,
+				parsedCRL.TBSCertList.RevokedCertificates, expectedCerts)
+		}
+	}
+}
+
+func fromBase64(in string) []byte {
+	out := make([]byte, base64.StdEncoding.DecodedLen(len(in)))
+	n, err := base64.StdEncoding.Decode(out, []byte(in))
+	if err != nil {
+		panic("failed to base64 decode")
+	}
+	return out[:n]
+}
+
+func TestParseDERCRL(t *testing.T) {
+	derBytes := fromBase64(derCRLBase64)
+	certList, err := ParseDERCRL(derBytes)
+	if err != nil {
+		t.Errorf("error parsing: %s", err)
+		return
+	}
+	numCerts := len(certList.TBSCertList.RevokedCertificates)
+	expected := 88
+	if numCerts != expected {
+		t.Errorf("bad number of revoked certificates. got: %d want: %d", numCerts, expected)
+	}
+
+	if certList.HasExpired(time.Unix(1302517272, 0)) {
+		t.Errorf("CRL has expired (but shouldn't have)")
+	}
+
+	// Can't check the signature here without a package cycle.
+}
+
+func TestCRLWithoutExpiry(t *testing.T) {
+	derBytes := fromBase64("MIHYMIGZMAkGByqGSM44BAMwEjEQMA4GA1UEAxMHQ2FybERTUxcNOTkwODI3MDcwMDAwWjBpMBMCAgDIFw05OTA4MjIwNzAwMDBaMBMCAgDJFw05OTA4MjIwNzAwMDBaMBMCAgDTFw05OTA4MjIwNzAwMDBaMBMCAgDSFw05OTA4MjIwNzAwMDBaMBMCAgDUFw05OTA4MjQwNzAwMDBaMAkGByqGSM44BAMDLwAwLAIUfmVSdjP+NHMX0feW+aDU2G1cfT0CFAJ6W7fVWxjBz4fvftok8yqDnDWh")
+	certList, err := ParseDERCRL(derBytes)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !certList.TBSCertList.NextUpdate.IsZero() {
+		t.Errorf("NextUpdate is not the zero value")
+	}
+}
+
+func TestParsePEMCRL(t *testing.T) {
+	pemBytes := fromBase64(pemCRLBase64)
+	certList, err := ParseCRL(pemBytes)
+	if err != nil {
+		t.Errorf("error parsing: %s", err)
+		return
+	}
+	numCerts := len(certList.TBSCertList.RevokedCertificates)
+	expected := 2
+	if numCerts != expected {
+		t.Errorf("bad number of revoked certificates. got: %d want: %d", numCerts, expected)
+	}
+
+	if certList.HasExpired(time.Unix(1302517272, 0)) {
+		t.Errorf("CRL has expired (but shouldn't have)")
+	}
+
+	// Can't check the signature here without a package cycle.
+}
+
+func TestImports(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping in -short mode")
+	}
+	testenv.MustHaveGoRun(t)
+
+	if out, err := exec.Command(testenv.GoToolPath(t), "run", "x509_test_import.go").CombinedOutput(); err != nil {
+		t.Errorf("failed to run x509_test_import.go: %s\n%s", err, out)
+	}
+}
+
+const derCRLBase64 = "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"
+
+const pemCRLBase64 = "LS0tLS1CRUdJTiBYNTA5IENSTC0tLS0tDQpNSUlCOWpDQ0FWOENBUUV3RFFZSktvWklodmNOQVFFRkJRQXdiREVhTUJnR0ExVUVDaE1SVWxOQklGTmxZM1Z5DQphWFI1SUVsdVl5NHhIakFjQmdOVkJBTVRGVkpUUVNCUWRXSnNhV01nVW05dmRDQkRRU0IyTVRFdU1Dd0dDU3FHDQpTSWIzRFFFSkFSWWZjbk5oYTJWdmJuSnZiM1J6YVdkdVFISnpZWE5sWTNWeWFYUjVMbU52YlJjTk1URXdNakl6DQpNVGt5T0RNd1doY05NVEV3T0RJeU1Ua3lPRE13V2pDQmpEQktBaEVBckRxb2g5RkhKSFhUN09QZ3V1bjQrQmNODQpNRGt4TVRBeU1UUXlOekE1V2pBbU1Bb0dBMVVkRlFRRENnRUpNQmdHQTFVZEdBUVJHQTh5TURBNU1URXdNakUwDQpNalExTlZvd1BnSVJBTEd6blowOTVQQjVhQU9MUGc1N2ZNTVhEVEF5TVRBeU16RTBOVEF4TkZvd0dqQVlCZ05WDQpIUmdFRVJnUE1qQXdNakV3TWpNeE5EVXdNVFJhb0RBd0xqQWZCZ05WSFNNRUdEQVdnQlQxVERGNlVRTS9MTmVMDQpsNWx2cUhHUXEzZzltekFMQmdOVkhSUUVCQUlDQUlRd0RRWUpLb1pJaHZjTkFRRUZCUUFEZ1lFQUZVNUFzNk16DQpxNVBSc2lmYW9iUVBHaDFhSkx5QytNczVBZ2MwYld5QTNHQWR4dXI1U3BQWmVSV0NCamlQL01FSEJXSkNsQkhQDQpHUmNxNXlJZDNFakRrYUV5eFJhK2k2N0x6dmhJNmMyOUVlNks5cFNZd2ppLzdSVWhtbW5Qclh0VHhsTDBsckxyDQptUVFKNnhoRFJhNUczUUE0Q21VZHNITnZicnpnbUNZcHZWRT0NCi0tLS0tRU5EIFg1MDkgQ1JMLS0tLS0NCg0K"
+
+func TestCreateCertificateRequest(t *testing.T) {
+	random := rand.Reader
+
+	ecdsa256Priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatalf("Failed to generate ECDSA key: %s", err)
+	}
+
+	ecdsa384Priv, err := ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
+	if err != nil {
+		t.Fatalf("Failed to generate ECDSA key: %s", err)
+	}
+
+	ecdsa521Priv, err := ecdsa.GenerateKey(elliptic.P521(), rand.Reader)
+	if err != nil {
+		t.Fatalf("Failed to generate ECDSA key: %s", err)
+	}
+
+	_, ed25519Priv, err := ed25519.GenerateKey(random)
+	if err != nil {
+		t.Fatalf("Failed to generate Ed25519 key: %s", err)
+	}
+
+	tests := []struct {
+		name    string
+		priv    any
+		sigAlgo SignatureAlgorithm
+	}{
+		{"RSA", testPrivateKey, SHA256WithRSA},
+		{"ECDSA-256", ecdsa256Priv, ECDSAWithSHA256},
+		{"ECDSA-384", ecdsa384Priv, ECDSAWithSHA256},
+		{"ECDSA-521", ecdsa521Priv, ECDSAWithSHA256},
+		{"Ed25519", ed25519Priv, PureEd25519},
+	}
+
+	for _, test := range tests {
+		template := CertificateRequest{
+			Subject: pkix.Name{
+				CommonName:   "test.example.com",
+				Organization: []string{"Σ Acme Co"},
+			},
+			SignatureAlgorithm: test.sigAlgo,
+			DNSNames:           []string{"test.example.com"},
+			EmailAddresses:     []string{"gopher@golang.org"},
+			IPAddresses:        []net.IP{net.IPv4(127, 0, 0, 1).To4(), net.ParseIP("2001:4860:0:2001::68")},
+		}
+
+		derBytes, err := CreateCertificateRequest(random, &template, test.priv)
+		if err != nil {
+			t.Errorf("%s: failed to create certificate request: %s", test.name, err)
+			continue
+		}
+
+		out, err := ParseCertificateRequest(derBytes)
+		if err != nil {
+			t.Errorf("%s: failed to create certificate request: %s", test.name, err)
+			continue
+		}
+
+		err = out.CheckSignature()
+		if err != nil {
+			t.Errorf("%s: failed to check certificate request signature: %s", test.name, err)
+			continue
+		}
+
+		if out.Subject.CommonName != template.Subject.CommonName {
+			t.Errorf("%s: output subject common name and template subject common name don't match", test.name)
+		} else if len(out.Subject.Organization) != len(template.Subject.Organization) {
+			t.Errorf("%s: output subject organisation and template subject organisation don't match", test.name)
+		} else if len(out.DNSNames) != len(template.DNSNames) {
+			t.Errorf("%s: output DNS names and template DNS names don't match", test.name)
+		} else if len(out.EmailAddresses) != len(template.EmailAddresses) {
+			t.Errorf("%s: output email addresses and template email addresses don't match", test.name)
+		} else if len(out.IPAddresses) != len(template.IPAddresses) {
+			t.Errorf("%s: output IP addresses and template IP addresses names don't match", test.name)
+		}
+	}
+}
+
+func marshalAndParseCSR(t *testing.T, template *CertificateRequest) *CertificateRequest {
+	derBytes, err := CreateCertificateRequest(rand.Reader, template, testPrivateKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	csr, err := ParseCertificateRequest(derBytes)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	return csr
+}
+
+func TestCertificateRequestOverrides(t *testing.T) {
+	sanContents, err := marshalSANs([]string{"foo.example.com"}, nil, nil, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	template := CertificateRequest{
+		Subject: pkix.Name{
+			CommonName:   "test.example.com",
+			Organization: []string{"Σ Acme Co"},
+		},
+		DNSNames: []string{"test.example.com"},
+
+		// An explicit extension should override the DNSNames from the
+		// template.
+		ExtraExtensions: []pkix.Extension{
+			{
+				Id:       oidExtensionSubjectAltName,
+				Value:    sanContents,
+				Critical: true,
+			},
+		},
+	}
+
+	csr := marshalAndParseCSR(t, &template)
+
+	if len(csr.DNSNames) != 1 || csr.DNSNames[0] != "foo.example.com" {
+		t.Errorf("Extension did not override template. Got %v\n", csr.DNSNames)
+	}
+
+	if len(csr.Extensions) != 1 || !csr.Extensions[0].Id.Equal(oidExtensionSubjectAltName) || !csr.Extensions[0].Critical {
+		t.Errorf("SAN extension was not faithfully copied, got %#v", csr.Extensions)
+	}
+
+	// If there is already an attribute with X.509 extensions then the
+	// extra extensions should be added to it rather than creating a CSR
+	// with two extension attributes.
+
+	template.Attributes = []pkix.AttributeTypeAndValueSET{
+		{
+			Type: oidExtensionRequest,
+			Value: [][]pkix.AttributeTypeAndValue{
+				{
+					{
+						Type:  oidExtensionAuthorityInfoAccess,
+						Value: []byte("foo"),
+					},
+				},
+			},
+		},
+	}
+
+	csr = marshalAndParseCSR(t, &template)
+	if l := len(csr.Attributes); l != 1 {
+		t.Errorf("incorrect number of attributes: %d\n", l)
+	}
+
+	if !csr.Attributes[0].Type.Equal(oidExtensionRequest) ||
+		len(csr.Attributes[0].Value) != 1 ||
+		len(csr.Attributes[0].Value[0]) != 2 {
+		t.Errorf("bad attributes: %#v\n", csr.Attributes)
+	}
+
+	sanContents2, err := marshalSANs([]string{"foo2.example.com"}, nil, nil, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Extensions in Attributes should override those in ExtraExtensions.
+	template.Attributes[0].Value[0] = append(template.Attributes[0].Value[0], pkix.AttributeTypeAndValue{
+		Type:  oidExtensionSubjectAltName,
+		Value: sanContents2,
+	})
+
+	csr = marshalAndParseCSR(t, &template)
+
+	if len(csr.DNSNames) != 1 || csr.DNSNames[0] != "foo2.example.com" {
+		t.Errorf("Attributes did not override ExtraExtensions. Got %v\n", csr.DNSNames)
+	}
+}
+
+func TestParseCertificateRequest(t *testing.T) {
+	for _, csrBase64 := range csrBase64Array {
+		csrBytes := fromBase64(csrBase64)
+		csr, err := ParseCertificateRequest(csrBytes)
+		if err != nil {
+			t.Fatalf("failed to parse CSR: %s", err)
+		}
+
+		if len(csr.EmailAddresses) != 1 || csr.EmailAddresses[0] != "gopher@golang.org" {
+			t.Errorf("incorrect email addresses found: %v", csr.EmailAddresses)
+		}
+
+		if len(csr.DNSNames) != 1 || csr.DNSNames[0] != "test.example.com" {
+			t.Errorf("incorrect DNS names found: %v", csr.DNSNames)
+		}
+
+		if len(csr.Subject.Country) != 1 || csr.Subject.Country[0] != "AU" {
+			t.Errorf("incorrect Subject name: %v", csr.Subject)
+		}
+
+		found := false
+		for _, e := range csr.Extensions {
+			if e.Id.Equal(oidExtensionBasicConstraints) {
+				found = true
+				break
+			}
+		}
+		if !found {
+			t.Errorf("basic constraints extension not found in CSR")
+		}
+	}
+}
+
+func TestCriticalFlagInCSRRequestedExtensions(t *testing.T) {
+	// This CSR contains an extension request where the extensions have a
+	// critical flag in them. In the past we failed to handle this.
+	const csrBase64 = "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"
+
+	csrBytes := fromBase64(csrBase64)
+	csr, err := ParseCertificateRequest(csrBytes)
+	if err != nil {
+		t.Fatalf("failed to parse CSR: %s", err)
+	}
+
+	expected := []struct {
+		Id    asn1.ObjectIdentifier
+		Value []byte
+	}{
+		{oidExtensionBasicConstraints, fromBase64("MAYBAf8CAQA=")},
+		{oidExtensionKeyUsage, fromBase64("AwIChA==")},
+	}
+
+	if n := len(csr.Extensions); n != len(expected) {
+		t.Fatalf("expected to find %d extensions but found %d", len(expected), n)
+	}
+
+	for i, extension := range csr.Extensions {
+		if !extension.Id.Equal(expected[i].Id) {
+			t.Fatalf("extension #%d has unexpected type %v (expected %v)", i, extension.Id, expected[i].Id)
+		}
+
+		if !bytes.Equal(extension.Value, expected[i].Value) {
+			t.Fatalf("extension #%d has unexpected contents %x (expected %x)", i, extension.Value, expected[i].Value)
+		}
+	}
+}
+
+// serialiseAndParse generates a self-signed certificate from template and
+// returns a parsed version of it.
+func serialiseAndParse(t *testing.T, template *Certificate) *Certificate {
+	derBytes, err := CreateCertificate(rand.Reader, template, template, &testPrivateKey.PublicKey, testPrivateKey)
+	if err != nil {
+		t.Fatalf("failed to create certificate: %s", err)
+		return nil
+	}
+
+	cert, err := ParseCertificate(derBytes)
+	if err != nil {
+		t.Fatalf("failed to parse certificate: %s", err)
+		return nil
+	}
+
+	return cert
+}
+
+func TestMaxPathLenNotCA(t *testing.T) {
+	template := &Certificate{
+		SerialNumber: big.NewInt(1),
+		Subject: pkix.Name{
+			CommonName: "Σ Acme Co",
+		},
+		NotBefore: time.Unix(1000, 0),
+		NotAfter:  time.Unix(100000, 0),
+
+		BasicConstraintsValid: true,
+		IsCA:                  false,
+	}
+	if m := serialiseAndParse(t, template).MaxPathLen; m != -1 {
+		t.Errorf("MaxPathLen should be -1 when IsCa is false, got %d", m)
+	}
+
+	template.MaxPathLen = -1
+	if m := serialiseAndParse(t, template).MaxPathLen; m != -1 {
+		t.Errorf("MaxPathLen should be -1 when IsCa is false and MaxPathLen set to -1, got %d", m)
+	}
+
+	template.MaxPathLen = 5
+	if _, err := CreateCertificate(rand.Reader, template, template, &testPrivateKey.PublicKey, testPrivateKey); err == nil {
+		t.Error("specifying a MaxPathLen when IsCA is false should fail")
+	}
+
+	template.MaxPathLen = 0
+	template.MaxPathLenZero = true
+	if _, err := CreateCertificate(rand.Reader, template, template, &testPrivateKey.PublicKey, testPrivateKey); err == nil {
+		t.Error("setting MaxPathLenZero when IsCA is false should fail")
+	}
+
+	template.BasicConstraintsValid = false
+	if m := serialiseAndParse(t, template).MaxPathLen; m != 0 {
+		t.Errorf("Bad MaxPathLen should be ignored if BasicConstraintsValid is false, got %d", m)
+	}
+}
+
+func TestMaxPathLen(t *testing.T) {
+	template := &Certificate{
+		SerialNumber: big.NewInt(1),
+		Subject: pkix.Name{
+			CommonName: "Σ Acme Co",
+		},
+		NotBefore: time.Unix(1000, 0),
+		NotAfter:  time.Unix(100000, 0),
+
+		BasicConstraintsValid: true,
+		IsCA:                  true,
+	}
+
+	cert1 := serialiseAndParse(t, template)
+	if m := cert1.MaxPathLen; m != -1 {
+		t.Errorf("Omitting MaxPathLen didn't turn into -1, got %d", m)
+	}
+	if cert1.MaxPathLenZero {
+		t.Errorf("Omitting MaxPathLen resulted in MaxPathLenZero")
+	}
+
+	template.MaxPathLen = 1
+	cert2 := serialiseAndParse(t, template)
+	if m := cert2.MaxPathLen; m != 1 {
+		t.Errorf("Setting MaxPathLen didn't work. Got %d but set 1", m)
+	}
+	if cert2.MaxPathLenZero {
+		t.Errorf("Setting MaxPathLen resulted in MaxPathLenZero")
+	}
+
+	template.MaxPathLen = 0
+	template.MaxPathLenZero = true
+	cert3 := serialiseAndParse(t, template)
+	if m := cert3.MaxPathLen; m != 0 {
+		t.Errorf("Setting MaxPathLenZero didn't work, got %d", m)
+	}
+	if !cert3.MaxPathLenZero {
+		t.Errorf("Setting MaxPathLen to zero didn't result in MaxPathLenZero")
+	}
+}
+
+func TestNoAuthorityKeyIdInSelfSignedCert(t *testing.T) {
+	template := &Certificate{
+		SerialNumber: big.NewInt(1),
+		Subject: pkix.Name{
+			CommonName: "Σ Acme Co",
+		},
+		NotBefore: time.Unix(1000, 0),
+		NotAfter:  time.Unix(100000, 0),
+
+		BasicConstraintsValid: true,
+		IsCA:                  true,
+		SubjectKeyId:          []byte{1, 2, 3, 4},
+	}
+
+	if cert := serialiseAndParse(t, template); len(cert.AuthorityKeyId) != 0 {
+		t.Fatalf("self-signed certificate contained default authority key id")
+	}
+
+	template.AuthorityKeyId = []byte{1, 2, 3, 4}
+	if cert := serialiseAndParse(t, template); len(cert.AuthorityKeyId) == 0 {
+		t.Fatalf("self-signed certificate erased explicit authority key id")
+	}
+}
+
+func TestNoSubjectKeyIdInCert(t *testing.T) {
+	template := &Certificate{
+		SerialNumber: big.NewInt(1),
+		Subject: pkix.Name{
+			CommonName: "Σ Acme Co",
+		},
+		NotBefore: time.Unix(1000, 0),
+		NotAfter:  time.Unix(100000, 0),
+
+		BasicConstraintsValid: true,
+		IsCA:                  true,
+	}
+	if cert := serialiseAndParse(t, template); len(cert.SubjectKeyId) == 0 {
+		t.Fatalf("self-signed certificate did not generate subject key id using the public key")
+	}
+
+	template.IsCA = false
+	if cert := serialiseAndParse(t, template); len(cert.SubjectKeyId) != 0 {
+		t.Fatalf("self-signed certificate generated subject key id when it isn't a CA")
+	}
+
+	template.SubjectKeyId = []byte{1, 2, 3, 4}
+	if cert := serialiseAndParse(t, template); len(cert.SubjectKeyId) == 0 {
+		t.Fatalf("self-signed certificate erased explicit subject key id")
+	}
+}
+
+func TestASN1BitLength(t *testing.T) {
+	tests := []struct {
+		bytes  []byte
+		bitLen int
+	}{
+		{nil, 0},
+		{[]byte{0x00}, 0},
+		{[]byte{0x00, 0x00}, 0},
+		{[]byte{0xf0}, 4},
+		{[]byte{0x88}, 5},
+		{[]byte{0xff}, 8},
+		{[]byte{0xff, 0x80}, 9},
+		{[]byte{0xff, 0x81}, 16},
+	}
+
+	for i, test := range tests {
+		if got := asn1BitLength(test.bytes); got != test.bitLen {
+			t.Errorf("#%d: calculated bit-length of %d for %x, wanted %d", i, got, test.bytes, test.bitLen)
+		}
+	}
+}
+
+func TestVerifyEmptyCertificate(t *testing.T) {
+	if _, err := new(Certificate).Verify(VerifyOptions{}); err != errNotParsed {
+		t.Errorf("Verifying empty certificate resulted in unexpected error: %q (wanted %q)", err, errNotParsed)
+	}
+}
+
+func TestInsecureAlgorithmErrorString(t *testing.T) {
+	tests := []struct {
+		sa   SignatureAlgorithm
+		want string
+	}{
+		{MD5WithRSA, "x509: cannot verify signature: insecure algorithm MD5-RSA"},
+		{SHA1WithRSA, "x509: cannot verify signature: insecure algorithm SHA1-RSA (temporarily override with GODEBUG=x509sha1=1)"},
+		{ECDSAWithSHA1, "x509: cannot verify signature: insecure algorithm ECDSA-SHA1 (temporarily override with GODEBUG=x509sha1=1)"},
+		{MD2WithRSA, "x509: cannot verify signature: insecure algorithm MD2-RSA"},
+		{-1, "x509: cannot verify signature: insecure algorithm -1"},
+		{0, "x509: cannot verify signature: insecure algorithm 0"},
+		{9999, "x509: cannot verify signature: insecure algorithm 9999"},
+	}
+	for i, tt := range tests {
+		if got := fmt.Sprint(InsecureAlgorithmError(tt.sa)); got != tt.want {
+			t.Errorf("%d. mismatch.\n got: %s\nwant: %s\n", i, got, tt.want)
+		}
+	}
+}
+
+// These CSR was generated with OpenSSL:
+//  openssl req -out CSR.csr -new -sha256 -nodes -keyout privateKey.key -config openssl.cnf
+//
+// With openssl.cnf containing the following sections:
+//   [ v3_req ]
+//   basicConstraints = CA:FALSE
+//   keyUsage = nonRepudiation, digitalSignature, keyEncipherment
+//   subjectAltName = email:gopher@golang.org,DNS:test.example.com
+//   [ req_attributes ]
+//   challengePassword = ignored challenge
+//   unstructuredName  = ignored unstructured name
+var csrBase64Array = [...]string{
+	// Just [ v3_req ]
+	"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",
+	// Both [ v3_req ] and [ req_attributes ]
+	"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",
+}
+
+var md5cert = `
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+`
+
+func TestMD5(t *testing.T) {
+	pemBlock, _ := pem.Decode([]byte(md5cert))
+	cert, err := ParseCertificate(pemBlock.Bytes)
+	if err != nil {
+		t.Fatalf("failed to parse certificate: %s", err)
+	}
+	if sa := cert.SignatureAlgorithm; sa != MD5WithRSA {
+		t.Errorf("signature algorithm is %v, want %v", sa, MD5WithRSA)
+	}
+	if err = cert.CheckSignatureFrom(cert); err == nil {
+		t.Fatalf("certificate verification succeeded incorrectly")
+	}
+	if _, ok := err.(InsecureAlgorithmError); !ok {
+		t.Fatalf("certificate verification returned %v (%T), wanted InsecureAlgorithmError", err, err)
+	}
+}
+
+func TestSHA1(t *testing.T) {
+	pemBlock, _ := pem.Decode([]byte(ecdsaSHA1CertPem))
+	cert, err := ParseCertificate(pemBlock.Bytes)
+	if err != nil {
+		t.Fatalf("failed to parse certificate: %s", err)
+	}
+	if sa := cert.SignatureAlgorithm; sa != ECDSAWithSHA1 {
+		t.Errorf("signature algorithm is %v, want %v", sa, ECDSAWithSHA1)
+	}
+	if err = cert.CheckSignatureFrom(cert); err == nil {
+		t.Fatalf("certificate verification succeeded incorrectly")
+	}
+	if _, ok := err.(InsecureAlgorithmError); !ok {
+		t.Fatalf("certificate verification returned %v (%T), wanted InsecureAlgorithmError", err, err)
+	}
+
+	t.Setenv("GODEBUG", "x509sha1=1")
+	if err = cert.CheckSignatureFrom(cert); err != nil {
+		t.Fatalf("SHA-1 certificate did not verify with GODEBUG=x509sha1=1: %v", err)
+	}
+}
+
+// certMissingRSANULL contains an RSA public key where the AlgorithmIdentifier
+// parameters are omitted rather than being an ASN.1 NULL.
+const certMissingRSANULL = `
+-----BEGIN CERTIFICATE-----
+MIIB7TCCAVigAwIBAgIBADALBgkqhkiG9w0BAQUwJjEQMA4GA1UEChMHQWNtZSBD
+bzESMBAGA1UEAxMJMTI3LjAuMC4xMB4XDTExMTIwODA3NTUxMloXDTEyMTIwNzA4
+MDAxMlowJjEQMA4GA1UEChMHQWNtZSBDbzESMBAGA1UEAxMJMTI3LjAuMC4xMIGc
+MAsGCSqGSIb3DQEBAQOBjAAwgYgCgYBO0Hsx44Jk2VnAwoekXh6LczPHY1PfZpIG
+hPZk1Y/kNqcdK+izIDZFI7Xjla7t4PUgnI2V339aEu+H5Fto5OkOdOwEin/ekyfE
+ARl6vfLcPRSr0FTKIQzQTW6HLlzF0rtNS0/Otiz3fojsfNcCkXSmHgwa2uNKWi7e
+E5xMQIhZkwIDAQABozIwMDAOBgNVHQ8BAf8EBAMCAKAwDQYDVR0OBAYEBAECAwQw
+DwYDVR0jBAgwBoAEAQIDBDALBgkqhkiG9w0BAQUDgYEANh+zegx1yW43RmEr1b3A
+p0vMRpqBWHyFeSnIyMZn3TJWRSt1tukkqVCavh9a+hoV2cxVlXIWg7nCto/9iIw4
+hB2rXZIxE0/9gzvGnfERYraL7KtnvshksBFQRlgXa5kc0x38BvEO5ZaoDPl4ILdE
+GFGNEH5PlGffo05wc46QkYU=
+-----END CERTIFICATE-----`
+
+func TestRSAMissingNULLParameters(t *testing.T) {
+	block, _ := pem.Decode([]byte(certMissingRSANULL))
+	if _, err := ParseCertificate(block.Bytes); err == nil {
+		t.Error("unexpected success when parsing certificate with missing RSA NULL parameter")
+	} else if !strings.Contains(err.Error(), "missing NULL") {
+		t.Errorf("unrecognised error when parsing certificate with missing RSA NULL parameter: %s", err)
+	}
+}
+
+const certISOOID = `
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+func TestISOOIDInCertificate(t *testing.T) {
+	block, _ := pem.Decode([]byte(certISOOID))
+	if cert, err := ParseCertificate(block.Bytes); err != nil {
+		t.Errorf("certificate with ISO OID failed to parse: %s", err)
+	} else if cert.SignatureAlgorithm == UnknownSignatureAlgorithm {
+		t.Errorf("ISO OID not recognised in certificate")
+	}
+}
+
+// certMultipleRDN contains a RelativeDistinguishedName with two elements (the
+// common name and serial number). This particular certificate was the first
+// such certificate in the “Pilot” Certificate Transparency log.
+const certMultipleRDN = `
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+func TestMultipleRDN(t *testing.T) {
+	block, _ := pem.Decode([]byte(certMultipleRDN))
+	cert, err := ParseCertificate(block.Bytes)
+	if err != nil {
+		t.Fatalf("certificate with two elements in an RDN failed to parse: %v", err)
+	}
+
+	if want := "eportal.mss.edus.si"; cert.Subject.CommonName != want {
+		t.Errorf("got common name of %q, but want %q", cert.Subject.CommonName, want)
+	}
+
+	if want := "1236484010010"; cert.Subject.SerialNumber != want {
+		t.Errorf("got serial number of %q, but want %q", cert.Subject.SerialNumber, want)
+	}
+}
+
+func TestSystemCertPool(t *testing.T) {
+	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
+		t.Skip("not implemented on Windows (Issue 16736, 18609) or darwin (Issue 46287)")
+	}
+	a, err := SystemCertPool()
+	if err != nil {
+		t.Fatal(err)
+	}
+	b, err := SystemCertPool()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !certPoolEqual(a, b) {
+		t.Fatal("two calls to SystemCertPool had different results")
+	}
+	if ok := b.AppendCertsFromPEM([]byte(`
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+	`)); !ok {
+		t.Fatal("AppendCertsFromPEM failed")
+	}
+	if reflect.DeepEqual(a, b) {
+		t.Fatal("changing one pool modified the other")
+	}
+}
+
+const emptyNameConstraintsPEM = `
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+func TestEmptyNameConstraints(t *testing.T) {
+	block, _ := pem.Decode([]byte(emptyNameConstraintsPEM))
+	_, err := ParseCertificate(block.Bytes)
+	if err == nil {
+		t.Fatal("unexpected success")
+	}
+
+	const expected = "empty name constraints"
+	if str := err.Error(); !strings.Contains(str, expected) {
+		t.Errorf("expected %q in error but got %q", expected, str)
+	}
+}
+
+func TestPKIXNameString(t *testing.T) {
+	der, err := base64.StdEncoding.DecodeString(certBytes)
+	if err != nil {
+		t.Fatal(err)
+	}
+	certs, err := ParseCertificates(der)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Check that parsed non-standard attributes are printed.
+	rdns := pkix.Name{
+		Locality: []string{"Gophertown"},
+		ExtraNames: []pkix.AttributeTypeAndValue{
+			{Type: asn1.ObjectIdentifier([]int{1, 2, 3, 4, 5}), Value: "golang.org"}},
+	}.ToRDNSequence()
+	nn := pkix.Name{}
+	nn.FillFromRDNSequence(&rdns)
+
+	// Check that zero-length non-nil ExtraNames hide Names.
+	extra := []pkix.AttributeTypeAndValue{
+		{Type: asn1.ObjectIdentifier([]int{1, 2, 3, 4, 5}), Value: "backing array"}}
+	extraNotNil := pkix.Name{
+		Locality:   []string{"Gophertown"},
+		ExtraNames: extra[:0],
+		Names: []pkix.AttributeTypeAndValue{
+			{Type: asn1.ObjectIdentifier([]int{1, 2, 3, 4, 5}), Value: "golang.org"}},
+	}
+
+	tests := []struct {
+		dn   pkix.Name
+		want string
+	}{
+		{nn, "L=Gophertown,1.2.3.4.5=#130a676f6c616e672e6f7267"},
+		{extraNotNil, "L=Gophertown"},
+		{pkix.Name{
+			CommonName:         "Steve Kille",
+			Organization:       []string{"Isode Limited"},
+			OrganizationalUnit: []string{"RFCs"},
+			Locality:           []string{"Richmond"},
+			Province:           []string{"Surrey"},
+			StreetAddress:      []string{"The Square"},
+			PostalCode:         []string{"TW9 1DT"},
+			SerialNumber:       "RFC 2253",
+			Country:            []string{"GB"},
+		}, "SERIALNUMBER=RFC 2253,CN=Steve Kille,OU=RFCs,O=Isode Limited,POSTALCODE=TW9 1DT,STREET=The Square,L=Richmond,ST=Surrey,C=GB"},
+		{certs[0].Subject,
+			"CN=mail.google.com,O=Google LLC,L=Mountain View,ST=California,C=US"},
+		{pkix.Name{
+			Organization: []string{"#Google, Inc. \n-> 'Alphabet\" "},
+			Country:      []string{"US"},
+		}, "O=\\#Google\\, Inc. \n-\\> 'Alphabet\\\"\\ ,C=US"},
+		{pkix.Name{
+			CommonName:   "foo.com",
+			Organization: []string{"Gopher Industries"},
+			ExtraNames: []pkix.AttributeTypeAndValue{
+				{Type: asn1.ObjectIdentifier([]int{2, 5, 4, 3}), Value: "bar.com"}},
+		}, "CN=bar.com,O=Gopher Industries"},
+		{pkix.Name{
+			Locality: []string{"Gophertown"},
+			ExtraNames: []pkix.AttributeTypeAndValue{
+				{Type: asn1.ObjectIdentifier([]int{1, 2, 3, 4, 5}), Value: "golang.org"}},
+		}, "1.2.3.4.5=#130a676f6c616e672e6f7267,L=Gophertown"},
+		// If there are no ExtraNames, the Names are printed instead.
+		{pkix.Name{
+			Locality: []string{"Gophertown"},
+			Names: []pkix.AttributeTypeAndValue{
+				{Type: asn1.ObjectIdentifier([]int{1, 2, 3, 4, 5}), Value: "golang.org"}},
+		}, "L=Gophertown,1.2.3.4.5=#130a676f6c616e672e6f7267"},
+		// If there are both, print only the ExtraNames.
+		{pkix.Name{
+			Locality: []string{"Gophertown"},
+			ExtraNames: []pkix.AttributeTypeAndValue{
+				{Type: asn1.ObjectIdentifier([]int{1, 2, 3, 4, 5}), Value: "golang.org"}},
+			Names: []pkix.AttributeTypeAndValue{
+				{Type: asn1.ObjectIdentifier([]int{1, 2, 3, 4, 6}), Value: "example.com"}},
+		}, "1.2.3.4.5=#130a676f6c616e672e6f7267,L=Gophertown"},
+	}
+
+	for i, test := range tests {
+		if got := test.dn.String(); got != test.want {
+			t.Errorf("#%d: String() = \n%s\n, want \n%s", i, got, test.want)
+		}
+	}
+
+	if extra[0].Value != "backing array" {
+		t.Errorf("the backing array of an empty ExtraNames got modified by String")
+	}
+}
+
+func TestRDNSequenceString(t *testing.T) {
+	// Test some extra cases that get lost in pkix.Name conversions such as
+	// multi-valued attributes.
+
+	var (
+		oidCountry            = []int{2, 5, 4, 6}
+		oidOrganization       = []int{2, 5, 4, 10}
+		oidOrganizationalUnit = []int{2, 5, 4, 11}
+		oidCommonName         = []int{2, 5, 4, 3}
+	)
+
+	tests := []struct {
+		seq  pkix.RDNSequence
+		want string
+	}{
+		{
+			seq: pkix.RDNSequence{
+				pkix.RelativeDistinguishedNameSET{
+					pkix.AttributeTypeAndValue{Type: oidCountry, Value: "US"},
+				},
+				pkix.RelativeDistinguishedNameSET{
+					pkix.AttributeTypeAndValue{Type: oidOrganization, Value: "Widget Inc."},
+				},
+				pkix.RelativeDistinguishedNameSET{
+					pkix.AttributeTypeAndValue{Type: oidOrganizationalUnit, Value: "Sales"},
+					pkix.AttributeTypeAndValue{Type: oidCommonName, Value: "J. Smith"},
+				},
+			},
+			want: "OU=Sales+CN=J. Smith,O=Widget Inc.,C=US",
+		},
+	}
+
+	for i, test := range tests {
+		if got := test.seq.String(); got != test.want {
+			t.Errorf("#%d: String() = \n%s\n, want \n%s", i, got, test.want)
+		}
+	}
+}
+
+const criticalNameConstraintWithUnknownTypePEM = `
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+func TestCriticalNameConstraintWithUnknownType(t *testing.T) {
+	block, _ := pem.Decode([]byte(criticalNameConstraintWithUnknownTypePEM))
+	cert, err := ParseCertificate(block.Bytes)
+	if err != nil {
+		t.Fatalf("unexpected parsing failure: %s", err)
+	}
+
+	if l := len(cert.UnhandledCriticalExtensions); l != 1 {
+		t.Fatalf("expected one unhandled critical extension, but found %d", l)
+	}
+}
+
+const badIPMaskPEM = `
+-----BEGIN CERTIFICATE-----
+MIICzzCCAbegAwIBAgICEjQwDQYJKoZIhvcNAQELBQAwHTEbMBkGA1UEAxMSQmFk
+IElQIG1hc2sgaXNzdWVyMB4XDTEzMDIwMTAwMDAwMFoXDTIwMDUzMDEwNDgzOFow
+FjEUMBIGA1UEAxMLQmFkIElQIG1hc2swggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAw
+ggEKAoIBAQDCuISVQi3csKqYk5uz7IOhY8MXkiqBaTqagihtiM997G1mJhTojcR+
+8DCg3E8OQ3ZajByhxRkwlsR4Srl5sGSwWfF/XaAHGUhWIhjBkDO7toW+EMzI8pAj
+cLwIbRlIL0AFnUTe6Z0DcIS5406Y/9MKE2oKXbf4EbVBv88mSkA74Z+lZJWFNxXn
+cx/9wq8UdyMY2vHN1Kir1/JbtrqB9wYRBjQtWSbAVZR8nTBPyRp4uvQTS2jOQh+j
+TUo1Y3O/o1xg/zRA4FEOUCla704OYRUkc8NuXHiPNNDcktr7gO8E06NVQ6n6aBGa
+OJbSst2vHA7Eiog7A2PB4wKn+GDFf+FNAgMBAAGjIDAeMBwGA1UdHgEB/wQSMBCg
+DDAKhwgBAgME//8BAKEAMA0GCSqGSIb3DQEBCwUAA4IBAQBYb7/NQwdCE/y40K2B
+IfKKb++HvCaKfAC9aAwrGWQsEWezqdl5Cqw5XWUAFjtTRm6iprVnmdvov6IlrgSV
+EQk6L96stz24vAF0MIBHSFRMoPtrqLiihLf0NOV7ztxSePQxbUJRroe/lKy+lhb7
+VeV5gmT9rFA45NzLgSznd2+dmyNcfQQD9AeeftRX4maUTeu1XFxinowtg+ZGFOKh
+E4D92uCGJxGSK72HF0/LGRhLXozmDdmPfSN2b6T/oLo942031iY46BqcI5LIVh8a
+Go4A1jOma5X6gh50Cw+kht8jM3yeNhSzXOKj7Uigjijx10z2wJu09Tyj5ahjoiwI
+pdX+
+-----END CERTIFICATE-----`
+
+func TestBadIPMask(t *testing.T) {
+	block, _ := pem.Decode([]byte(badIPMaskPEM))
+	_, err := ParseCertificate(block.Bytes)
+	if err == nil {
+		t.Fatalf("unexpected success")
+	}
+
+	const expected = "contained invalid mask"
+	if !strings.Contains(err.Error(), expected) {
+		t.Fatalf("expected %q in error but got: %s", expected, err)
+	}
+}
+
+const additionalGeneralSubtreePEM = `
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+func TestAdditionFieldsInGeneralSubtree(t *testing.T) {
+	// Very rarely, certificates can include additional fields in the
+	// GeneralSubtree structure. This tests that such certificates can be
+	// parsed.
+	block, _ := pem.Decode([]byte(additionalGeneralSubtreePEM))
+	if _, err := ParseCertificate(block.Bytes); err != nil {
+		t.Fatalf("failed to parse certificate: %s", err)
+	}
+}
+
+func TestEmptySubject(t *testing.T) {
+	template := Certificate{
+		SerialNumber: big.NewInt(1),
+		DNSNames:     []string{"example.com"},
+	}
+
+	derBytes, err := CreateCertificate(rand.Reader, &template, &template, &testPrivateKey.PublicKey, testPrivateKey)
+	if err != nil {
+		t.Fatalf("failed to create certificate: %s", err)
+	}
+
+	cert, err := ParseCertificate(derBytes)
+	if err != nil {
+		t.Fatalf("failed to parse certificate: %s", err)
+	}
+
+	for _, ext := range cert.Extensions {
+		if ext.Id.Equal(oidExtensionSubjectAltName) {
+			if !ext.Critical {
+				t.Fatal("SAN extension is not critical")
+			}
+			return
+		}
+	}
+
+	t.Fatal("SAN extension is missing")
+}
+
+// multipleURLsInCRLDPPEM contains two URLs in a single CRL DistributionPoint
+// structure. It is taken from https://crt.sh/?id=12721534.
+const multipleURLsInCRLDPPEM = `
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+`
+
+func TestMultipleURLsInCRLDP(t *testing.T) {
+	block, _ := pem.Decode([]byte(multipleURLsInCRLDPPEM))
+	cert, err := ParseCertificate(block.Bytes)
+	if err != nil {
+		t.Fatalf("failed to parse certificate: %s", err)
+	}
+
+	want := []string{
+		"http://epscd.catcert.net/crl/ec-acc.crl",
+		"http://epscd2.catcert.net/crl/ec-acc.crl",
+	}
+	if got := cert.CRLDistributionPoints; !reflect.DeepEqual(got, want) {
+		t.Errorf("CRL distribution points = %#v, want #%v", got, want)
+	}
+}
+
+const hexPKCS1TestPKCS8Key = "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"
+const hexPKCS1TestECKey = "3081a40201010430bdb9839c08ee793d1157886a7a758a3c8b2a17a4df48f17ace57c72c56b4723cf21dcda21d4e1ad57ff034f19fcfd98ea00706052b81040022a16403620004feea808b5ee2429cfcce13c32160e1c960990bd050bb0fdf7222f3decd0a55008e32a6aa3c9062051c4cba92a7a3b178b24567412d43cdd2f882fa5addddd726fe3e208d2c26d733a773a597abb749714df7256ead5105fa6e7b3650de236b50"
+
+var pkcs1MismatchKeyTests = []struct {
+	hexKey        string
+	errorContains string
+}{
+	{hexKey: hexPKCS1TestPKCS8Key, errorContains: "use ParsePKCS8PrivateKey instead"},
+	{hexKey: hexPKCS1TestECKey, errorContains: "use ParseECPrivateKey instead"},
+}
+
+func TestPKCS1MismatchKeyFormat(t *testing.T) {
+	for i, test := range pkcs1MismatchKeyTests {
+		derBytes, _ := hex.DecodeString(test.hexKey)
+		_, err := ParsePKCS1PrivateKey(derBytes)
+		if !strings.Contains(err.Error(), test.errorContains) {
+			t.Errorf("#%d: expected error containing %q, got %s", i, test.errorContains, err)
+		}
+	}
+}
+
+func TestCreateRevocationList(t *testing.T) {
+	ec256Priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatalf("Failed to generate ECDSA P256 key: %s", err)
+	}
+	_, ed25519Priv, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		t.Fatalf("Failed to generate Ed25519 key: %s", err)
+	}
+	tests := []struct {
+		name          string
+		key           crypto.Signer
+		issuer        *Certificate
+		template      *RevocationList
+		expectedError string
+	}{
+		{
+			name:          "nil template",
+			key:           ec256Priv,
+			issuer:        nil,
+			template:      nil,
+			expectedError: "x509: template can not be nil",
+		},
+		{
+			name:          "nil issuer",
+			key:           ec256Priv,
+			issuer:        nil,
+			template:      &RevocationList{},
+			expectedError: "x509: issuer can not be nil",
+		},
+		{
+			name: "issuer doesn't have crlSign key usage bit set",
+			key:  ec256Priv,
+			issuer: &Certificate{
+				KeyUsage: KeyUsageCertSign,
+			},
+			template:      &RevocationList{},
+			expectedError: "x509: issuer must have the crlSign key usage bit set",
+		},
+		{
+			name: "issuer missing SubjectKeyId",
+			key:  ec256Priv,
+			issuer: &Certificate{
+				KeyUsage: KeyUsageCRLSign,
+			},
+			template:      &RevocationList{},
+			expectedError: "x509: issuer certificate doesn't contain a subject key identifier",
+		},
+		{
+			name: "nextUpdate before thisUpdate",
+			key:  ec256Priv,
+			issuer: &Certificate{
+				KeyUsage: KeyUsageCRLSign,
+				Subject: pkix.Name{
+					CommonName: "testing",
+				},
+				SubjectKeyId: []byte{1, 2, 3},
+			},
+			template: &RevocationList{
+				ThisUpdate: time.Time{}.Add(time.Hour),
+				NextUpdate: time.Time{},
+			},
+			expectedError: "x509: template.ThisUpdate is after template.NextUpdate",
+		},
+		{
+			name: "nil Number",
+			key:  ec256Priv,
+			issuer: &Certificate{
+				KeyUsage: KeyUsageCRLSign,
+				Subject: pkix.Name{
+					CommonName: "testing",
+				},
+				SubjectKeyId: []byte{1, 2, 3},
+			},
+			template: &RevocationList{
+				ThisUpdate: time.Time{}.Add(time.Hour * 24),
+				NextUpdate: time.Time{}.Add(time.Hour * 48),
+			},
+			expectedError: "x509: template contains nil Number field",
+		},
+		{
+			name: "invalid signature algorithm",
+			key:  ec256Priv,
+			issuer: &Certificate{
+				KeyUsage: KeyUsageCRLSign,
+				Subject: pkix.Name{
+					CommonName: "testing",
+				},
+				SubjectKeyId: []byte{1, 2, 3},
+			},
+			template: &RevocationList{
+				SignatureAlgorithm: SHA256WithRSA,
+				RevokedCertificates: []pkix.RevokedCertificate{
+					{
+						SerialNumber:   big.NewInt(2),
+						RevocationTime: time.Time{}.Add(time.Hour),
+					},
+				},
+				Number:     big.NewInt(5),
+				ThisUpdate: time.Time{}.Add(time.Hour * 24),
+				NextUpdate: time.Time{}.Add(time.Hour * 48),
+			},
+			expectedError: "x509: requested SignatureAlgorithm does not match private key type",
+		},
+		{
+			name: "valid",
+			key:  ec256Priv,
+			issuer: &Certificate{
+				KeyUsage: KeyUsageCRLSign,
+				Subject: pkix.Name{
+					CommonName: "testing",
+				},
+				SubjectKeyId: []byte{1, 2, 3},
+			},
+			template: &RevocationList{
+				RevokedCertificates: []pkix.RevokedCertificate{
+					{
+						SerialNumber:   big.NewInt(2),
+						RevocationTime: time.Time{}.Add(time.Hour),
+					},
+				},
+				Number:     big.NewInt(5),
+				ThisUpdate: time.Time{}.Add(time.Hour * 24),
+				NextUpdate: time.Time{}.Add(time.Hour * 48),
+			},
+		},
+		{
+			name: "valid, Ed25519 key",
+			key:  ed25519Priv,
+			issuer: &Certificate{
+				KeyUsage: KeyUsageCRLSign,
+				Subject: pkix.Name{
+					CommonName: "testing",
+				},
+				SubjectKeyId: []byte{1, 2, 3},
+			},
+			template: &RevocationList{
+				RevokedCertificates: []pkix.RevokedCertificate{
+					{
+						SerialNumber:   big.NewInt(2),
+						RevocationTime: time.Time{}.Add(time.Hour),
+					},
+				},
+				Number:     big.NewInt(5),
+				ThisUpdate: time.Time{}.Add(time.Hour * 24),
+				NextUpdate: time.Time{}.Add(time.Hour * 48),
+			},
+		},
+		{
+			name: "valid, non-default signature algorithm",
+			key:  ec256Priv,
+			issuer: &Certificate{
+				KeyUsage: KeyUsageCRLSign,
+				Subject: pkix.Name{
+					CommonName: "testing",
+				},
+				SubjectKeyId: []byte{1, 2, 3},
+			},
+			template: &RevocationList{
+				SignatureAlgorithm: ECDSAWithSHA512,
+				RevokedCertificates: []pkix.RevokedCertificate{
+					{
+						SerialNumber:   big.NewInt(2),
+						RevocationTime: time.Time{}.Add(time.Hour),
+					},
+				},
+				Number:     big.NewInt(5),
+				ThisUpdate: time.Time{}.Add(time.Hour * 24),
+				NextUpdate: time.Time{}.Add(time.Hour * 48),
+			},
+		},
+		{
+			name: "valid, extra extension",
+			key:  ec256Priv,
+			issuer: &Certificate{
+				KeyUsage: KeyUsageCRLSign,
+				Subject: pkix.Name{
+					CommonName: "testing",
+				},
+				SubjectKeyId: []byte{1, 2, 3},
+			},
+			template: &RevocationList{
+				RevokedCertificates: []pkix.RevokedCertificate{
+					{
+						SerialNumber:   big.NewInt(2),
+						RevocationTime: time.Time{}.Add(time.Hour),
+					},
+				},
+				Number:     big.NewInt(5),
+				ThisUpdate: time.Time{}.Add(time.Hour * 24),
+				NextUpdate: time.Time{}.Add(time.Hour * 48),
+				ExtraExtensions: []pkix.Extension{
+					{
+						Id:    []int{2, 5, 29, 99},
+						Value: []byte{5, 0},
+					},
+				},
+			},
+		},
+		{
+			name: "valid, empty list",
+			key:  ec256Priv,
+			issuer: &Certificate{
+				KeyUsage: KeyUsageCRLSign,
+				Subject: pkix.Name{
+					CommonName: "testing",
+				},
+				SubjectKeyId: []byte{1, 2, 3},
+			},
+			template: &RevocationList{
+				Number:     big.NewInt(5),
+				ThisUpdate: time.Time{}.Add(time.Hour * 24),
+				NextUpdate: time.Time{}.Add(time.Hour * 48),
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			crl, err := CreateRevocationList(rand.Reader, tc.template, tc.issuer, tc.key)
+			if err != nil && tc.expectedError == "" {
+				t.Fatalf("CreateRevocationList failed unexpectedly: %s", err)
+			} else if err != nil && tc.expectedError != err.Error() {
+				t.Fatalf("CreateRevocationList failed unexpectedly, wanted: %s, got: %s", tc.expectedError, err)
+			} else if err == nil && tc.expectedError != "" {
+				t.Fatalf("CreateRevocationList didn't fail, expected: %s", tc.expectedError)
+			}
+			if tc.expectedError != "" {
+				return
+			}
+
+			parsedCRL, err := ParseDERCRL(crl)
+			if err != nil {
+				t.Fatalf("Failed to parse generated CRL: %s", err)
+			}
+
+			if tc.template.SignatureAlgorithm != UnknownSignatureAlgorithm &&
+				parsedCRL.SignatureAlgorithm.Algorithm.Equal(signatureAlgorithmDetails[tc.template.SignatureAlgorithm].oid) {
+				t.Fatalf("SignatureAlgorithm mismatch: got %v; want %v.", parsedCRL.SignatureAlgorithm,
+					tc.template.SignatureAlgorithm)
+			}
+
+			if !reflect.DeepEqual(parsedCRL.TBSCertList.RevokedCertificates, tc.template.RevokedCertificates) {
+				t.Fatalf("RevokedCertificates mismatch: got %v; want %v.",
+					parsedCRL.TBSCertList.RevokedCertificates, tc.template.RevokedCertificates)
+			}
+
+			if len(parsedCRL.TBSCertList.Extensions) != 2+len(tc.template.ExtraExtensions) {
+				t.Fatalf("Generated CRL has wrong number of extensions, wanted: %d, got: %d", 2+len(tc.template.ExtraExtensions), len(parsedCRL.TBSCertList.Extensions))
+			}
+			expectedAKI, err := asn1.Marshal(authKeyId{Id: tc.issuer.SubjectKeyId})
+			if err != nil {
+				t.Fatalf("asn1.Marshal failed: %s", err)
+			}
+			akiExt := pkix.Extension{
+				Id:    oidExtensionAuthorityKeyId,
+				Value: expectedAKI,
+			}
+			if !reflect.DeepEqual(parsedCRL.TBSCertList.Extensions[0], akiExt) {
+				t.Fatalf("Unexpected first extension: got %v, want %v",
+					parsedCRL.TBSCertList.Extensions[0], akiExt)
+			}
+			expectedNum, err := asn1.Marshal(tc.template.Number)
+			if err != nil {
+				t.Fatalf("asn1.Marshal failed: %s", err)
+			}
+			crlExt := pkix.Extension{
+				Id:    oidExtensionCRLNumber,
+				Value: expectedNum,
+			}
+			if !reflect.DeepEqual(parsedCRL.TBSCertList.Extensions[1], crlExt) {
+				t.Fatalf("Unexpected second extension: got %v, want %v",
+					parsedCRL.TBSCertList.Extensions[1], crlExt)
+			}
+			if len(parsedCRL.TBSCertList.Extensions[2:]) == 0 && len(tc.template.ExtraExtensions) == 0 {
+				// If we don't have anything to check return early so we don't
+				// hit a [] != nil false positive below.
+				return
+			}
+			if !reflect.DeepEqual(parsedCRL.TBSCertList.Extensions[2:], tc.template.ExtraExtensions) {
+				t.Fatalf("Extensions mismatch: got %v; want %v.",
+					parsedCRL.TBSCertList.Extensions[2:], tc.template.ExtraExtensions)
+			}
+		})
+	}
+}
+
+func TestRSAPSAParameters(t *testing.T) {
+	generateParams := func(hashFunc crypto.Hash) []byte {
+		var hashOID asn1.ObjectIdentifier
+
+		switch hashFunc {
+		case crypto.SHA256:
+			hashOID = oidSHA256
+		case crypto.SHA384:
+			hashOID = oidSHA384
+		case crypto.SHA512:
+			hashOID = oidSHA512
+		}
+
+		params := pssParameters{
+			Hash: pkix.AlgorithmIdentifier{
+				Algorithm:  hashOID,
+				Parameters: asn1.NullRawValue,
+			},
+			MGF: pkix.AlgorithmIdentifier{
+				Algorithm: oidMGF1,
+			},
+			SaltLength:   hashFunc.Size(),
+			TrailerField: 1,
+		}
+
+		mgf1Params := pkix.AlgorithmIdentifier{
+			Algorithm:  hashOID,
+			Parameters: asn1.NullRawValue,
+		}
+
+		var err error
+		params.MGF.Parameters.FullBytes, err = asn1.Marshal(mgf1Params)
+		if err != nil {
+			t.Fatalf("failed to marshal MGF parameters: %s", err)
+		}
+
+		serialized, err := asn1.Marshal(params)
+		if err != nil {
+			t.Fatalf("failed to marshal parameters: %s", err)
+		}
+
+		return serialized
+	}
+
+	for h, params := range hashToPSSParameters {
+		generated := generateParams(h)
+		if !bytes.Equal(params.FullBytes, generated) {
+			t.Errorf("hardcoded parameters for %s didn't match generated parameters: got (generated) %x, wanted (hardcoded) %x", h, generated, params.FullBytes)
+		}
+	}
+}
+
+func TestUnknownExtKey(t *testing.T) {
+	const errorContains = "unknown extended key usage"
+
+	template := &Certificate{
+		SerialNumber: big.NewInt(10),
+		DNSNames:     []string{"foo"},
+		ExtKeyUsage:  []ExtKeyUsage{ExtKeyUsage(-1)},
+	}
+	signer, err := rsa.GenerateKey(rand.Reader, 1024)
+	if err != nil {
+		t.Errorf("failed to generate key for TestUnknownExtKey")
+	}
+
+	_, err = CreateCertificate(rand.Reader, template, template, signer.Public(), signer)
+	if !strings.Contains(err.Error(), errorContains) {
+		t.Errorf("expected error containing %q, got %s", errorContains, err)
+	}
+}
+
+func TestIA5SANEnforcement(t *testing.T) {
+	k, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatalf("ecdsa.GenerateKey failed: %s", err)
+	}
+
+	testURL, err := url.Parse("https://example.com/")
+	if err != nil {
+		t.Fatalf("url.Parse failed: %s", err)
+	}
+	testURL.RawQuery = "∞"
+
+	marshalTests := []struct {
+		name          string
+		template      *Certificate
+		expectedError string
+	}{
+		{
+			name: "marshal: unicode dNSName",
+			template: &Certificate{
+				SerialNumber: big.NewInt(0),
+				DNSNames:     []string{"∞"},
+			},
+			expectedError: "x509: \"∞\" cannot be encoded as an IA5String",
+		},
+		{
+			name: "marshal: unicode rfc822Name",
+			template: &Certificate{
+				SerialNumber:   big.NewInt(0),
+				EmailAddresses: []string{"∞"},
+			},
+			expectedError: "x509: \"∞\" cannot be encoded as an IA5String",
+		},
+		{
+			name: "marshal: unicode uniformResourceIdentifier",
+			template: &Certificate{
+				SerialNumber: big.NewInt(0),
+				URIs:         []*url.URL{testURL},
+			},
+			expectedError: "x509: \"https://example.com/?∞\" cannot be encoded as an IA5String",
+		},
+	}
+
+	for _, tc := range marshalTests {
+		t.Run(tc.name, func(t *testing.T) {
+			_, err := CreateCertificate(rand.Reader, tc.template, tc.template, k.Public(), k)
+			if err == nil {
+				t.Errorf("expected CreateCertificate to fail with template: %v", tc.template)
+			} else if err.Error() != tc.expectedError {
+				t.Errorf("unexpected error: got %q, want %q", err.Error(), tc.expectedError)
+			}
+		})
+	}
+
+	unmarshalTests := []struct {
+		name          string
+		cert          string
+		expectedError string
+	}{
+		{
+			name:          "unmarshal: unicode dNSName",
+			cert:          "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",
+			expectedError: "x509: SAN dNSName is malformed",
+		},
+		{
+			name:          "unmarshal: unicode rfc822Name",
+			cert:          "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",
+			expectedError: "x509: SAN rfc822Name is malformed",
+		},
+		{
+			name:          "unmarshal: unicode uniformResourceIdentifier",
+			cert:          "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",
+			expectedError: "x509: SAN uniformResourceIdentifier is malformed",
+		},
+	}
+
+	for _, tc := range unmarshalTests {
+		der, err := hex.DecodeString(tc.cert)
+		if err != nil {
+			t.Fatalf("failed to decode test cert: %s", err)
+		}
+		_, err = ParseCertificate(der)
+		if err == nil {
+			t.Error("expected CreateCertificate to fail")
+		} else if err.Error() != tc.expectedError {
+			t.Errorf("unexpected error: got %q, want %q", err.Error(), tc.expectedError)
+		}
+	}
+}
+
+func BenchmarkCreateCertificate(b *testing.B) {
+	template := &Certificate{
+		SerialNumber: big.NewInt(10),
+		DNSNames:     []string{"example.com"},
+	}
+	tests := []struct {
+		name string
+		gen  func() crypto.Signer
+	}{
+		{
+			name: "RSA 2048",
+			gen: func() crypto.Signer {
+				k, err := rsa.GenerateKey(rand.Reader, 2048)
+				if err != nil {
+					b.Fatalf("failed to generate test key: %s", err)
+				}
+				return k
+			},
+		},
+		{
+			name: "ECDSA P256",
+			gen: func() crypto.Signer {
+				k, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+				if err != nil {
+					b.Fatalf("failed to generate test key: %s", err)
+				}
+				return k
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		k := tc.gen()
+		b.ResetTimer()
+		b.Run(tc.name, func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				_, err := CreateCertificate(rand.Reader, template, template, k.Public(), k)
+				if err != nil {
+					b.Fatalf("failed to create certificate: %s", err)
+				}
+			}
+		})
+	}
+}
+
+type brokenSigner struct {
+	pub crypto.PublicKey
+}
+
+func (bs *brokenSigner) Public() crypto.PublicKey {
+	return bs.pub
+}
+
+func (bs *brokenSigner) Sign(_ io.Reader, _ []byte, _ crypto.SignerOpts) ([]byte, error) {
+	return []byte{1, 2, 3}, nil
+}
+
+func TestCreateCertificateBrokenSigner(t *testing.T) {
+	template := &Certificate{
+		SerialNumber: big.NewInt(10),
+		DNSNames:     []string{"example.com"},
+	}
+	k, err := rsa.GenerateKey(rand.Reader, 1024)
+	if err != nil {
+		t.Fatalf("failed to generate test key: %s", err)
+	}
+	expectedErr := "x509: signature over certificate returned by signer is invalid: crypto/rsa: verification error"
+	_, err = CreateCertificate(rand.Reader, template, template, k.Public(), &brokenSigner{k.Public()})
+	if err == nil {
+		t.Fatal("expected CreateCertificate to fail with a broken signer")
+	} else if err.Error() != expectedErr {
+		t.Fatalf("CreateCertificate returned an unexpected error: got %q, want %q", err, expectedErr)
+	}
+}
+
+func TestCreateCertificateLegacy(t *testing.T) {
+	sigAlg := MD5WithRSA
+	template := &Certificate{
+		SerialNumber:       big.NewInt(10),
+		DNSNames:           []string{"example.com"},
+		SignatureAlgorithm: sigAlg,
+	}
+	_, err := CreateCertificate(rand.Reader, template, template, testPrivateKey.Public(), &brokenSigner{testPrivateKey.Public()})
+	if err != nil {
+		t.Fatalf("CreateCertificate failed when SignatureAlgorithm = %v: %s", sigAlg, err)
+	}
+}
+
+func (s *CertPool) mustCert(t *testing.T, n int) *Certificate {
+	c, err := s.lazyCerts[n].getCert()
+	if err != nil {
+		t.Fatalf("failed to load cert %d: %v", n, err)
+	}
+	return c
+}
+
+func allCerts(t *testing.T, p *CertPool) []*Certificate {
+	all := make([]*Certificate, p.len())
+	for i := range all {
+		all[i] = p.mustCert(t, i)
+	}
+	return all
+}
+
+// certPoolEqual reports whether a and b are equal, except for the
+// function pointers.
+func certPoolEqual(a, b *CertPool) bool {
+	if (a != nil) != (b != nil) {
+		return false
+	}
+	if a == nil {
+		return true
+	}
+	if !reflect.DeepEqual(a.byName, b.byName) ||
+		len(a.lazyCerts) != len(b.lazyCerts) {
+		return false
+	}
+	for i := range a.lazyCerts {
+		la, lb := a.lazyCerts[i], b.lazyCerts[i]
+		if !bytes.Equal(la.rawSubject, lb.rawSubject) {
+			return false
+		}
+		ca, err := la.getCert()
+		if err != nil {
+			panic(err)
+		}
+		cb, err := la.getCert()
+		if err != nil {
+			panic(err)
+		}
+		if !ca.Equal(cb) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func TestCertificateRequestRoundtripFields(t *testing.T) {
+	urlA, err := url.Parse("https://example.com/_")
+	if err != nil {
+		t.Fatal(err)
+	}
+	urlB, err := url.Parse("https://example.org/_")
+	if err != nil {
+		t.Fatal(err)
+	}
+	in := &CertificateRequest{
+		DNSNames:       []string{"example.com", "example.org"},
+		EmailAddresses: []string{"a@example.com", "b@example.com"},
+		IPAddresses:    []net.IP{net.IPv4(192, 0, 2, 0), net.IPv6loopback},
+		URIs:           []*url.URL{urlA, urlB},
+	}
+	out := marshalAndParseCSR(t, in)
+
+	if !reflect.DeepEqual(in.DNSNames, out.DNSNames) {
+		t.Fatalf("Unexpected DNSNames: got %v, want %v", out.DNSNames, in.DNSNames)
+	}
+	if !reflect.DeepEqual(in.EmailAddresses, out.EmailAddresses) {
+		t.Fatalf("Unexpected EmailAddresses: got %v, want %v", out.EmailAddresses, in.EmailAddresses)
+	}
+	if len(in.IPAddresses) != len(out.IPAddresses) ||
+		!in.IPAddresses[0].Equal(out.IPAddresses[0]) ||
+		!in.IPAddresses[1].Equal(out.IPAddresses[1]) {
+		t.Fatalf("Unexpected IPAddresses: got %v, want %v", out.IPAddresses, in.IPAddresses)
+	}
+	if !reflect.DeepEqual(in.URIs, out.URIs) {
+		t.Fatalf("Unexpected URIs: got %v, want %v", out.URIs, in.URIs)
+	}
+}
+
+func BenchmarkParseCertificate(b *testing.B) {
+	cases := []struct {
+		name string
+		pem  string
+	}{
+		{
+			name: "ecdsa leaf",
+			pem: `-----BEGIN CERTIFICATE-----
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+-----END CERTIFICATE-----`,
+		},
+		{
+			name: "rsa leaf",
+			pem: `-----BEGIN CERTIFICATE-----
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+ZS5jboIKdXJjaGluLmNvbYIKd3d3Lmdvby5nbIIIeW91dHUuYmWCC3lvdXR1YmUu
+Y29tghR5b3V0dWJlZWR1Y2F0aW9uLmNvbYIPeW91dHViZWtpZHMuY29tggV5dC5i
+ZTAhBgNVHSAEGjAYMAgGBmeBDAECAjAMBgorBgEEAdZ5AgUDMDMGA1UdHwQsMCow
+KKAmoCSGImh0dHA6Ly9jcmwucGtpLmdvb2cvR1RTMU8xY29yZS5jcmwwEwYKKwYB
+BAHWeQIEAwEB/wQCBQAwDQYJKoZIhvcNAQELBQADggEBAHh9/ozYUGRd+W5akWlM
+4WvX808TK2oUISnagbxCCFZ2trpg2oi03CJf4o4o3Je5Qzzz10s22oQY6gPHAR0B
+QHzrpqAveQw9D5vd8xjgtQ/SAujPzPKNQee5511rS7/EKW9I83ccd5XhhoEyx8A1
+/65RTS+2hKpJKTMkr0yHBPJV7kUW+n/KIef5YaSOA9VYK7hyH0niDpvm9EmoqvWS
+U5xAFAe/Xrrq3sxTuDJPQA8alk6h/ql5Klkw6dL53csiPka/MevDqdifWkzuT/6n
+YK/ePeJzPD17FA9V+N1rcuF3Wk29AZvCOSasdIkIuE82vGr3dfNrsrn9E9lWIbCr
+Qc4=
+-----END CERTIFICATE-----`,
+		},
+	}
+	for _, c := range cases {
+		b.Run(c.name, func(b *testing.B) {
+			pemBlock, _ := pem.Decode([]byte(c.pem))
+			b.ReportAllocs()
+			b.ResetTimer()
+			for i := 0; i < b.N; i++ {
+				_, err := ParseCertificate(pemBlock.Bytes)
+				if err != nil {
+					b.Fatal(err)
+				}
+			}
+		})
+	}
+}
+
+func TestParseCertificateRawEquals(t *testing.T) {
+	p, _ := pem.Decode([]byte(pemCertificate))
+	cert, err := ParseCertificate(p.Bytes)
+	if err != nil {
+		t.Fatalf("failed to parse certificate: %s", err)
+	}
+	if !bytes.Equal(p.Bytes, cert.Raw) {
+		t.Fatalf("unexpected Certificate.Raw\ngot: %x\nwant: %x\n", cert.Raw, p.Bytes)
+	}
+}
+
+// mismatchingSigAlgIDPEM contains a certificate where the Certificate
+// signatureAlgorithm and the TBSCertificate signature contain
+// mismatching OIDs
+const mismatchingSigAlgIDPEM = `-----BEGIN CERTIFICATE-----
+MIIBBzCBrqADAgECAgEAMAoGCCqGSM49BAMCMAAwIhgPMDAwMTAxMDEwMDAwMDBa
+GA8wMDAxMDEwMTAwMDAwMFowADBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABOqV
+EDuVXxwZgIU3+dOwv1SsMu0xuV48hf7xmK8n7sAMYgllB+96DnPqBeboJj4snYnx
+0AcE0PDVQ1l4Z3YXsQWjFTATMBEGA1UdEQEB/wQHMAWCA2FzZDAKBggqhkjOPQQD
+AwNIADBFAiBi1jz/T2HT5nAfrD7zsgR+68qh7Erc6Q4qlxYBOgKG4QIhAOtjIn+Q
+tA+bq+55P3ntxTOVRq0nv1mwnkjwt9cQR9Fn
+-----END CERTIFICATE-----`
+
+// mismatchingSigAlgParamPEM contains a certificate where the Certificate
+// signatureAlgorithm and the TBSCertificate signature contain
+// mismatching parameters
+const mismatchingSigAlgParamPEM = `-----BEGIN CERTIFICATE-----
+MIIBCTCBrqADAgECAgEAMAoGCCqGSM49BAMCMAAwIhgPMDAwMTAxMDEwMDAwMDBa
+GA8wMDAxMDEwMTAwMDAwMFowADBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABOqV
+EDuVXxwZgIU3+dOwv1SsMu0xuV48hf7xmK8n7sAMYgllB+96DnPqBeboJj4snYnx
+0AcE0PDVQ1l4Z3YXsQWjFTATMBEGA1UdEQEB/wQHMAWCA2FzZDAMBggqhkjOPQQD
+AgUAA0gAMEUCIGLWPP9PYdPmcB+sPvOyBH7ryqHsStzpDiqXFgE6AobhAiEA62Mi
+f5C0D5ur7nk/ee3FM5VGrSe/WbCeSPC31xBH0Wc=
+-----END CERTIFICATE-----`
+
+func TestSigAlgMismatch(t *testing.T) {
+	for _, certPEM := range []string{mismatchingSigAlgIDPEM, mismatchingSigAlgParamPEM} {
+		b, _ := pem.Decode([]byte(certPEM))
+		if b == nil {
+			t.Fatalf("couldn't decode test certificate")
+		}
+		_, err := ParseCertificate(b.Bytes)
+		if err == nil {
+			t.Fatalf("expected ParseCertificate to fail")
+		}
+		expected := "x509: inner and outer signature algorithm identifiers don't match"
+		if err.Error() != expected {
+			t.Errorf("unexpected error from ParseCertificate: got %q, want %q", err.Error(), expected)
+		}
+	}
+}
+
+const optionalAuthKeyIDPEM = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+func TestAuthKeyIdOptional(t *testing.T) {
+	b, _ := pem.Decode([]byte(optionalAuthKeyIDPEM))
+	if b == nil {
+		t.Fatalf("couldn't decode test certificate")
+	}
+	_, err := ParseCertificate(b.Bytes)
+	if err != nil {
+		t.Fatalf("ParseCertificate to failed to parse certificate with optional authority key identifier fields: %s", err)
+	}
+}
+
+const largeOIDPEM = `
+Certificate:
+    Data:
+        Version: 3 (0x2)
+        Serial Number:
+            da:ba:53:19:1b:09:4b:82:b2:89:26:7d:c7:6f:a0:02
+        Signature Algorithm: sha256WithRSAEncryption
+        Issuer: O = Acme Co
+        Validity
+            Not Before: Dec 21 16:59:27 2021 GMT
+            Not After : Dec 21 16:59:27 2022 GMT
+        Subject: O = Acme Co
+        Subject Public Key Info:
+            Public Key Algorithm: rsaEncryption
+                RSA Public-Key: (2048 bit)
+                Modulus:
+                    00:bf:17:16:d8:bc:29:9c:16:e5:76:b4:93:15:78:
+                    ad:6e:45:c5:4a:63:46:a1:b2:76:71:65:51:9c:14:
+                    c4:ea:74:13:e4:34:df:2f:2c:65:11:e8:56:52:69:
+                    11:f9:0e:fc:77:bb:63:a8:7c:1a:c6:a1:7b:6e:6c:
+                    e7:18:25:25:c9:e8:fb:06:7f:a2:a9:98:fe:2a:bc:
+                    8a:b3:75:b6:b8:7d:b6:c9:6b:29:08:32:22:10:cb:
+                    8d:d6:60:c8:83:ad:f5:58:91:d6:11:e8:55:56:fb:
+                    8f:a3:a2:9f:48:cb:79:e4:65:4a:8c:a6:52:64:9f:
+                    99:38:35:d4:d5:ac:6f:cf:a0:cb:42:8c:07:eb:21:
+                    17:31:3a:eb:91:7b:62:43:a4:75:5f:ef:a7:2f:94:
+                    f8:69:0b:d4:ec:09:e6:00:c0:8c:dd:07:63:0b:e4:
+                    77:aa:60:18:3c:a0:e0:ae:0a:ea:0e:52:3b:b4:fa:
+                    6a:30:1b:50:62:21:73:53:33:01:60:a1:6b:99:58:
+                    00:f3:77:c6:0f:46:19:ca:c2:5d:cd:f5:e2:52:4d:
+                    84:94:23:d3:32:2f:ae:5f:da:43:a1:19:95:d2:17:
+                    dd:49:14:b4:d9:48:1c:08:13:93:8e:d5:09:43:21:
+                    b6:ce:52:e8:87:bb:d2:60:0d:c6:4e:bf:c5:93:6a:
+                    c6:bf
+                Exponent: 65537 (0x10001)
+        X509v3 extensions:
+            X509v3 Key Usage: critical
+                Digital Signature, Key Encipherment
+            X509v3 Extended Key Usage:
+                TLS Web Server Authentication
+            X509v3 Basic Constraints: critical
+                CA:FALSE
+            X509v3 Subject Alternative Name:
+                DNS:longOID.example
+            X509v3 Certificate Policies:
+                Policy: 1.3.6.1.4.1.311.21.8.1492336001
+
+    Signature Algorithm: sha256WithRSAEncryption
+         72:77:8b:de:48:fb:6d:9a:94:b1:be:d4:90:7d:4c:e6:d3:79:
+         fa:fb:fc:3e:d5:3d:e9:a0:ce:28:2b:2f:94:77:3f:87:f8:9c:
+         9f:91:1c:f3:f6:58:91:15:6b:24:b9:ca:ae:9f:ee:ca:c8:31:
+         db:1a:3d:bb:6b:83:6d:bc:81:8b:a1:79:d5:3e:bb:dd:93:fe:
+         35:3e:b7:99:e0:d6:eb:58:0c:fd:42:73:dc:49:da:e2:b7:ae:
+         15:ee:e6:cc:aa:ef:91:41:9a:18:46:8d:4a:39:65:a2:85:3c:
+         7f:0c:41:f8:0b:9c:e8:1f:35:36:60:8d:8c:e0:8e:18:b1:06:
+         57:d0:4e:c4:c3:cd:8f:6f:e7:76:02:52:da:03:43:61:2b:b3:
+         bf:19:fd:73:0d:6a:0b:b4:b6:cb:a9:6f:70:4e:53:2a:54:07:
+         b3:74:fd:85:49:57:5b:23:8d:8c:6b:53:2b:09:e8:41:a5:80:
+         3f:69:1b:11:d1:6b:13:35:2e:f9:d6:50:15:d9:91:38:42:43:
+         e9:17:af:67:d9:96:a4:d1:6a:4f:cc:b4:a7:8e:48:1f:00:72:
+         69:de:4d:f1:73:a4:47:12:67:e9:f9:07:3e:79:75:90:42:b8:
+         d4:b5:fd:d1:7e:35:04:f7:00:04:cf:f1:36:be:0f:27:81:1f:
+         a6:ba:88:6c
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+func TestLargeOID(t *testing.T) {
+	// See Issue 49678.
+	b, _ := pem.Decode([]byte(largeOIDPEM))
+	if b == nil {
+		t.Fatalf("couldn't decode test certificate")
+	}
+	_, err := ParseCertificate(b.Bytes)
+	if err != nil {
+		t.Fatalf("ParseCertificate to failed to parse certificate with large OID: %s", err)
+	}
+}
+
+func TestDisableSHA1ForCertOnly(t *testing.T) {
+	t.Setenv("GODEBUG", "")
+
+	tmpl := &Certificate{
+		SerialNumber:          big.NewInt(1),
+		NotBefore:             time.Now().Add(-time.Hour),
+		NotAfter:              time.Now().Add(time.Hour),
+		SignatureAlgorithm:    SHA1WithRSA,
+		BasicConstraintsValid: true,
+		IsCA:                  true,
+		KeyUsage:              KeyUsageCertSign | KeyUsageCRLSign,
+	}
+	certDER, err := CreateCertificate(rand.Reader, tmpl, tmpl, rsaPrivateKey.Public(), rsaPrivateKey)
+	if err != nil {
+		t.Fatalf("failed to generate test cert: %s", err)
+	}
+	cert, err := ParseCertificate(certDER)
+	if err != nil {
+		t.Fatalf("failed to parse test cert: %s", err)
+	}
+
+	err = cert.CheckSignatureFrom(cert)
+	if err == nil {
+		t.Error("expected CheckSignatureFrom to fail")
+	} else if _, ok := err.(InsecureAlgorithmError); !ok {
+		t.Errorf("expected InsecureAlgorithmError error, got %T", err)
+	}
+
+	crlDER, err := CreateRevocationList(rand.Reader, &RevocationList{
+		SignatureAlgorithm: SHA1WithRSA,
+		Number:             big.NewInt(1),
+		ThisUpdate:         time.Now().Add(-time.Hour),
+		NextUpdate:         time.Now().Add(time.Hour),
+	}, cert, rsaPrivateKey)
+	if err != nil {
+		t.Fatalf("failed to generate test CRL: %s", err)
+	}
+	// TODO(rolandshoemaker): this should be ParseRevocationList once it lands
+	crl, err := ParseCRL(crlDER)
+	if err != nil {
+		t.Fatalf("failed to parse test CRL: %s", err)
+	}
+
+	if err = cert.CheckCRLSignature(crl); err != nil {
+		t.Errorf("unexpected error: %s", err)
+	}
+
+	// This is an unrelated OCSP response, which will fail signature verification
+	// but shouldn't return a InsecureAlgorithmError, since SHA1 should be allowed
+	// for OCSP.
+	ocspTBSHex := "30819fa2160414884451ff502a695e2d88f421bad90cf2cecbea7c180f32303133303631383037323434335a30743072304a300906052b0e03021a0500041448b60d38238df8456e4ee5843ea394111802979f0414884451ff502a695e2d88f421bad90cf2cecbea7c021100f78b13b946fc9635d8ab49de9d2148218000180f32303133303631383037323434335aa011180f32303133303632323037323434335a"
+	ocspTBS, err := hex.DecodeString(ocspTBSHex)
+	if err != nil {
+		t.Fatalf("failed to decode OCSP response TBS hex: %s", err)
+	}
+
+	err = cert.CheckSignature(SHA1WithRSA, ocspTBS, nil)
+	if err != rsa.ErrVerification {
+		t.Errorf("unexpected error: %s", err)
+	}
+}
+
+const uniqueIDPEM = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+func TestParseUniqueID(t *testing.T) {
+	b, _ := pem.Decode([]byte(uniqueIDPEM))
+	if b == nil {
+		t.Fatalf("couldn't decode test certificate")
+	}
+	cert, err := ParseCertificate(b.Bytes)
+	if err != nil {
+		t.Fatalf("ParseCertificate to failed to parse certificate with unique identifier id: %s", err)
+	}
+	if len(cert.Extensions) != 7 {
+		t.Fatalf("unexpected number of extensions (probably because the extension section was not parsed): got %d, want 7", len(cert.Extensions))
+	}
+}
diff --git a/src/crypto/x509/x509_test_import.go b/src/crypto/x509/x509_test_import.go
new file mode 100644
index 0000000..2474e3d
--- /dev/null
+++ b/src/crypto/x509/x509_test_import.go
@@ -0,0 +1,56 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build ignore
+
+// This file is run by the x509 tests to ensure that a program with minimal
+// imports can sign certificates without errors resulting from missing hash
+// functions.
+package main
+
+import (
+	"crypto/rand"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"math/big"
+	"strings"
+	"time"
+)
+
+func main() {
+	block, _ := pem.Decode([]byte(pemPrivateKey))
+	rsaPriv, err := x509.ParsePKCS1PrivateKey(block.Bytes)
+	if err != nil {
+		panic("Failed to parse private key: " + err.Error())
+	}
+
+	template := x509.Certificate{
+		SerialNumber: big.NewInt(1),
+		Subject: pkix.Name{
+			CommonName:   "test",
+			Organization: []string{"Σ Acme Co"},
+		},
+		NotBefore: time.Unix(1000, 0),
+		NotAfter:  time.Unix(100000, 0),
+		KeyUsage:  x509.KeyUsageCertSign,
+	}
+
+	if _, err = x509.CreateCertificate(rand.Reader, &template, &template, &rsaPriv.PublicKey, rsaPriv); err != nil {
+		panic("failed to create certificate with basic imports: " + err.Error())
+	}
+}
+
+var pemPrivateKey = testingKey(`-----BEGIN RSA TESTING KEY-----
+MIIBOgIBAAJBALKZD0nEffqM1ACuak0bijtqE2QrI/KLADv7l3kK3ppMyCuLKoF0
+fd7Ai2KW5ToIwzFofvJcS/STa6HA5gQenRUCAwEAAQJBAIq9amn00aS0h/CrjXqu
+/ThglAXJmZhOMPVn4eiu7/ROixi9sex436MaVeMqSNf7Ex9a8fRNfWss7Sqd9eWu
+RTUCIQDasvGASLqmjeffBNLTXV2A5g4t+kLVCpsEIZAycV5GswIhANEPLmax0ME/
+EO+ZJ79TJKN5yiGBRsv5yvx5UiHxajEXAiAhAol5N4EUyq6I9w1rYdhPMGpLfk7A
+IU2snfRJ6Nq2CQIgFrPsWRCkV+gOYcajD17rEqmuLrdIRexpg8N1DOSXoJ8CIGlS
+tAboUGBxTDq3ZroNism3DaMIbKPyYrAqhKov1h5V
+-----END RSA TESTING KEY-----
+`)
+
+func testingKey(s string) string { return strings.ReplaceAll(s, "TESTING KEY", "PRIVATE KEY") }