1 files changed, 171 insertions, 0 deletions
diff --git a/src/crypto/tls/generate_cert.go b/src/crypto/tls/generate_cert.go
new file mode 100644
index 0000000..cd4bfc5
--- /dev/null
+++ b/src/crypto/tls/generate_cert.go
@@ -0,0 +1,171 @@
+// 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.
+
+//go:build ignore
+
+// Generate a self-signed X.509 certificate for a TLS server. Outputs to
+// 'cert.pem' and 'key.pem' and will overwrite existing files.
+
+package main
+
+import (
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"flag"
+	"log"
+	"math/big"
+	"net"
+	"os"
+	"strings"
+	"time"
+)
+
+var (
+	host       = flag.String("host", "", "Comma-separated hostnames and IPs to generate a certificate for")
+	validFrom  = flag.String("start-date", "", "Creation date formatted as Jan 1 15:04:05 2011")
+	validFor   = flag.Duration("duration", 365*24*time.Hour, "Duration that certificate is valid for")
+	isCA       = flag.Bool("ca", false, "whether this cert should be its own Certificate Authority")
+	rsaBits    = flag.Int("rsa-bits", 2048, "Size of RSA key to generate. Ignored if --ecdsa-curve is set")
+	ecdsaCurve = flag.String("ecdsa-curve", "", "ECDSA curve to use to generate a key. Valid values are P224, P256 (recommended), P384, P521")
+	ed25519Key = flag.Bool("ed25519", false, "Generate an Ed25519 key")
+)
+
+func publicKey(priv any) any {
+	switch k := priv.(type) {
+	case *rsa.PrivateKey:
+		return &k.PublicKey
+	case *ecdsa.PrivateKey:
+		return &k.PublicKey
+	case ed25519.PrivateKey:
+		return k.Public().(ed25519.PublicKey)
+	default:
+		return nil
+	}
+}
+
+func main() {
+	flag.Parse()
+
+	if len(*host) == 0 {
+		log.Fatalf("Missing required --host parameter")
+	}
+
+	var priv any
+	var err error
+	switch *ecdsaCurve {
+	case "":
+		if *ed25519Key {
+			_, priv, err = ed25519.GenerateKey(rand.Reader)
+		} else {
+			priv, err = rsa.GenerateKey(rand.Reader, *rsaBits)
+		}
+	case "P224":
+		priv, err = ecdsa.GenerateKey(elliptic.P224(), rand.Reader)
+	case "P256":
+		priv, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	case "P384":
+		priv, err = ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
+	case "P521":
+		priv, err = ecdsa.GenerateKey(elliptic.P521(), rand.Reader)
+	default:
+		log.Fatalf("Unrecognized elliptic curve: %q", *ecdsaCurve)
+	}
+	if err != nil {
+		log.Fatalf("Failed to generate private key: %v", err)
+	}
+
+	// ECDSA, ED25519 and RSA subject keys should have the DigitalSignature
+	// KeyUsage bits set in the x509.Certificate template
+	keyUsage := x509.KeyUsageDigitalSignature
+	// Only RSA subject keys should have the KeyEncipherment KeyUsage bits set. In
+	// the context of TLS this KeyUsage is particular to RSA key exchange and
+	// authentication.
+	if _, isRSA := priv.(*rsa.PrivateKey); isRSA {
+		keyUsage |= x509.KeyUsageKeyEncipherment
+	}
+
+	var notBefore time.Time
+	if len(*validFrom) == 0 {
+		notBefore = time.Now()
+	} else {
+		notBefore, err = time.Parse("Jan 2 15:04:05 2006", *validFrom)
+		if err != nil {
+			log.Fatalf("Failed to parse creation date: %v", err)
+		}
+	}
+
+	notAfter := notBefore.Add(*validFor)
+
+	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
+	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
+	if err != nil {
+		log.Fatalf("Failed to generate serial number: %v", err)
+	}
+
+	template := x509.Certificate{
+		SerialNumber: serialNumber,
+		Subject: pkix.Name{
+			Organization: []string{"Acme Co"},
+		},
+		NotBefore: notBefore,
+		NotAfter:  notAfter,
+
+		KeyUsage:              keyUsage,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		BasicConstraintsValid: true,
+	}
+
+	hosts := strings.Split(*host, ",")
+	for _, h := range hosts {
+		if ip := net.ParseIP(h); ip != nil {
+			template.IPAddresses = append(template.IPAddresses, ip)
+		} else {
+			template.DNSNames = append(template.DNSNames, h)
+		}
+	}
+
+	if *isCA {
+		template.IsCA = true
+		template.KeyUsage |= x509.KeyUsageCertSign
+	}
+
+	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, publicKey(priv), priv)
+	if err != nil {
+		log.Fatalf("Failed to create certificate: %v", err)
+	}
+
+	certOut, err := os.Create("cert.pem")
+	if err != nil {
+		log.Fatalf("Failed to open cert.pem for writing: %v", err)
+	}
+	if err := pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes}); err != nil {
+		log.Fatalf("Failed to write data to cert.pem: %v", err)
+	}
+	if err := certOut.Close(); err != nil {
+		log.Fatalf("Error closing cert.pem: %v", err)
+	}
+	log.Print("wrote cert.pem\n")
+
+	keyOut, err := os.OpenFile("key.pem", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		log.Fatalf("Failed to open key.pem for writing: %v", err)
+	}
+	privBytes, err := x509.MarshalPKCS8PrivateKey(priv)
+	if err != nil {
+		log.Fatalf("Unable to marshal private key: %v", err)
+	}
+	if err := pem.Encode(keyOut, &pem.Block{Type: "PRIVATE KEY", Bytes: privBytes}); err != nil {
+		log.Fatalf("Failed to write data to key.pem: %v", err)
+	}
+	if err := keyOut.Close(); err != nil {
+		log.Fatalf("Error closing key.pem: %v", err)
+	}
+	log.Print("wrote key.pem\n")
+}