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Source file src/crypto/tls/generate_cert.go

  // 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.
  
  // +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/elliptic"
  	"crypto/rand"
  	"crypto/rsa"
  	"crypto/x509"
  	"crypto/x509/pkix"
  	"encoding/pem"
  	"flag"
  	"fmt"
  	"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, P384, P521")
  )
  
  func publicKey(priv interface{}) interface{} {
  	switch k := priv.(type) {
  	case *rsa.PrivateKey:
  		return &k.PublicKey
  	case *ecdsa.PrivateKey:
  		return &k.PublicKey
  	default:
  		return nil
  	}
  }
  
  func pemBlockForKey(priv interface{}) *pem.Block {
  	switch k := priv.(type) {
  	case *rsa.PrivateKey:
  		return &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(k)}
  	case *ecdsa.PrivateKey:
  		b, err := x509.MarshalECPrivateKey(k)
  		if err != nil {
  			fmt.Fprintf(os.Stderr, "Unable to marshal ECDSA private key: %v", err)
  			os.Exit(2)
  		}
  		return &pem.Block{Type: "EC PRIVATE KEY", Bytes: b}
  	default:
  		return nil
  	}
  }
  
  func main() {
  	flag.Parse()
  
  	if len(*host) == 0 {
  		log.Fatalf("Missing required --host parameter")
  	}
  
  	var priv interface{}
  	var err error
  	switch *ecdsaCurve {
  	case "":
  		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:
  		fmt.Fprintf(os.Stderr, "Unrecognized elliptic curve: %q", *ecdsaCurve)
  		os.Exit(1)
  	}
  	if err != nil {
  		log.Fatalf("failed to generate private key: %s", err)
  	}
  
  	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 {
  			fmt.Fprintf(os.Stderr, "Failed to parse creation date: %s\n", err)
  			os.Exit(1)
  		}
  	}
  
  	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: %s", err)
  	}
  
  	template := x509.Certificate{
  		SerialNumber: serialNumber,
  		Subject: pkix.Name{
  			Organization: []string{"Acme Co"},
  		},
  		NotBefore: notBefore,
  		NotAfter:  notAfter,
  
  		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
  		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: %s", err)
  	}
  
  	certOut, err := os.Create("cert.pem")
  	if err != nil {
  		log.Fatalf("failed to open cert.pem for writing: %s", err)
  	}
  	pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes})
  	certOut.Close()
  	log.Print("written cert.pem\n")
  
  	keyOut, err := os.OpenFile("key.pem", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
  	if err != nil {
  		log.Print("failed to open key.pem for writing:", err)
  		return
  	}
  	pem.Encode(keyOut, pemBlockForKey(priv))
  	keyOut.Close()
  	log.Print("written key.pem\n")
  }
  

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