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Source file src/crypto/tls/generate_cert.go

Documentation: crypto/tls

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // +build ignore
     6  
     7  // Generate a self-signed X.509 certificate for a TLS server. Outputs to
     8  // 'cert.pem' and 'key.pem' and will overwrite existing files.
     9  
    10  package main
    11  
    12  import (
    13  	"crypto/ecdsa"
    14  	"crypto/elliptic"
    15  	"crypto/rand"
    16  	"crypto/rsa"
    17  	"crypto/x509"
    18  	"crypto/x509/pkix"
    19  	"encoding/pem"
    20  	"flag"
    21  	"fmt"
    22  	"log"
    23  	"math/big"
    24  	"net"
    25  	"os"
    26  	"strings"
    27  	"time"
    28  )
    29  
    30  var (
    31  	host       = flag.String("host", "", "Comma-separated hostnames and IPs to generate a certificate for")
    32  	validFrom  = flag.String("start-date", "", "Creation date formatted as Jan 1 15:04:05 2011")
    33  	validFor   = flag.Duration("duration", 365*24*time.Hour, "Duration that certificate is valid for")
    34  	isCA       = flag.Bool("ca", false, "whether this cert should be its own Certificate Authority")
    35  	rsaBits    = flag.Int("rsa-bits", 2048, "Size of RSA key to generate. Ignored if --ecdsa-curve is set")
    36  	ecdsaCurve = flag.String("ecdsa-curve", "", "ECDSA curve to use to generate a key. Valid values are P224, P256 (recommended), P384, P521")
    37  )
    38  
    39  func publicKey(priv interface{}) interface{} {
    40  	switch k := priv.(type) {
    41  	case *rsa.PrivateKey:
    42  		return &k.PublicKey
    43  	case *ecdsa.PrivateKey:
    44  		return &k.PublicKey
    45  	default:
    46  		return nil
    47  	}
    48  }
    49  
    50  func pemBlockForKey(priv interface{}) *pem.Block {
    51  	switch k := priv.(type) {
    52  	case *rsa.PrivateKey:
    53  		return &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(k)}
    54  	case *ecdsa.PrivateKey:
    55  		b, err := x509.MarshalECPrivateKey(k)
    56  		if err != nil {
    57  			fmt.Fprintf(os.Stderr, "Unable to marshal ECDSA private key: %v", err)
    58  			os.Exit(2)
    59  		}
    60  		return &pem.Block{Type: "EC PRIVATE KEY", Bytes: b}
    61  	default:
    62  		return nil
    63  	}
    64  }
    65  
    66  func main() {
    67  	flag.Parse()
    68  
    69  	if len(*host) == 0 {
    70  		log.Fatalf("Missing required --host parameter")
    71  	}
    72  
    73  	var priv interface{}
    74  	var err error
    75  	switch *ecdsaCurve {
    76  	case "":
    77  		priv, err = rsa.GenerateKey(rand.Reader, *rsaBits)
    78  	case "P224":
    79  		priv, err = ecdsa.GenerateKey(elliptic.P224(), rand.Reader)
    80  	case "P256":
    81  		priv, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
    82  	case "P384":
    83  		priv, err = ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
    84  	case "P521":
    85  		priv, err = ecdsa.GenerateKey(elliptic.P521(), rand.Reader)
    86  	default:
    87  		fmt.Fprintf(os.Stderr, "Unrecognized elliptic curve: %q", *ecdsaCurve)
    88  		os.Exit(1)
    89  	}
    90  	if err != nil {
    91  		log.Fatalf("failed to generate private key: %s", err)
    92  	}
    93  
    94  	var notBefore time.Time
    95  	if len(*validFrom) == 0 {
    96  		notBefore = time.Now()
    97  	} else {
    98  		notBefore, err = time.Parse("Jan 2 15:04:05 2006", *validFrom)
    99  		if err != nil {
   100  			fmt.Fprintf(os.Stderr, "Failed to parse creation date: %s\n", err)
   101  			os.Exit(1)
   102  		}
   103  	}
   104  
   105  	notAfter := notBefore.Add(*validFor)
   106  
   107  	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
   108  	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
   109  	if err != nil {
   110  		log.Fatalf("failed to generate serial number: %s", err)
   111  	}
   112  
   113  	template := x509.Certificate{
   114  		SerialNumber: serialNumber,
   115  		Subject: pkix.Name{
   116  			Organization: []string{"Acme Co"},
   117  		},
   118  		NotBefore: notBefore,
   119  		NotAfter:  notAfter,
   120  
   121  		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
   122  		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
   123  		BasicConstraintsValid: true,
   124  	}
   125  
   126  	hosts := strings.Split(*host, ",")
   127  	for _, h := range hosts {
   128  		if ip := net.ParseIP(h); ip != nil {
   129  			template.IPAddresses = append(template.IPAddresses, ip)
   130  		} else {
   131  			template.DNSNames = append(template.DNSNames, h)
   132  		}
   133  	}
   134  
   135  	if *isCA {
   136  		template.IsCA = true
   137  		template.KeyUsage |= x509.KeyUsageCertSign
   138  	}
   139  
   140  	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, publicKey(priv), priv)
   141  	if err != nil {
   142  		log.Fatalf("Failed to create certificate: %s", err)
   143  	}
   144  
   145  	certOut, err := os.Create("cert.pem")
   146  	if err != nil {
   147  		log.Fatalf("failed to open cert.pem for writing: %s", err)
   148  	}
   149  	if err := pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes}); err != nil {
   150  		log.Fatalf("failed to write data to cert.pem: %s", err)
   151  	}
   152  	if err := certOut.Close(); err != nil {
   153  		log.Fatalf("error closing cert.pem: %s", err)
   154  	}
   155  	log.Print("wrote cert.pem\n")
   156  
   157  	keyOut, err := os.OpenFile("key.pem", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
   158  	if err != nil {
   159  		log.Print("failed to open key.pem for writing:", err)
   160  		return
   161  	}
   162  	if err := pem.Encode(keyOut, pemBlockForKey(priv)); err != nil {
   163  		log.Fatalf("failed to write data to key.pem: %s", err)
   164  	}
   165  	if err := keyOut.Close(); err != nil {
   166  		log.Fatalf("error closing key.pem: %s", err)
   167  	}
   168  	log.Print("wrote key.pem\n")
   169  }
   170  

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