1 files changed, 277 insertions, 0 deletions
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
+}