github.com/ader1990/go@v0.0.0-20140630135419-8c24447fa791/src/pkg/crypto/tls/generate_cert.go (about)

     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/rand"
    14  	"crypto/rsa"
    15  	"crypto/x509"
    16  	"crypto/x509/pkix"
    17  	"encoding/pem"
    18  	"flag"
    19  	"fmt"
    20  	"log"
    21  	"math/big"
    22  	"net"
    23  	"os"
    24  	"strings"
    25  	"time"
    26  )
    27  
    28  var (
    29  	host      = flag.String("host", "", "Comma-separated hostnames and IPs to generate a certificate for")
    30  	validFrom = flag.String("start-date", "", "Creation date formatted as Jan 1 15:04:05 2011")
    31  	validFor  = flag.Duration("duration", 365*24*time.Hour, "Duration that certificate is valid for")
    32  	isCA      = flag.Bool("ca", false, "whether this cert should be its own Certificate Authority")
    33  	rsaBits   = flag.Int("rsa-bits", 2048, "Size of RSA key to generate")
    34  )
    35  
    36  func main() {
    37  	flag.Parse()
    38  
    39  	if len(*host) == 0 {
    40  		log.Fatalf("Missing required --host parameter")
    41  	}
    42  
    43  	priv, err := rsa.GenerateKey(rand.Reader, *rsaBits)
    44  	if err != nil {
    45  		log.Fatalf("failed to generate private key: %s", err)
    46  	}
    47  
    48  	var notBefore time.Time
    49  	if len(*validFrom) == 0 {
    50  		notBefore = time.Now()
    51  	} else {
    52  		notBefore, err = time.Parse("Jan 2 15:04:05 2006", *validFrom)
    53  		if err != nil {
    54  			fmt.Fprintf(os.Stderr, "Failed to parse creation date: %s\n", err)
    55  			os.Exit(1)
    56  		}
    57  	}
    58  
    59  	notAfter := notBefore.Add(*validFor)
    60  
    61  	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
    62  	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
    63  	if err != nil {
    64  		log.Fatalf("failed to generate serial number: %s", err)
    65  	}
    66  
    67  	template := x509.Certificate{
    68  		SerialNumber: serialNumber,
    69  		Subject: pkix.Name{
    70  			Organization: []string{"Acme Co"},
    71  		},
    72  		NotBefore: notBefore,
    73  		NotAfter:  notAfter,
    74  
    75  		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
    76  		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
    77  		BasicConstraintsValid: true,
    78  	}
    79  
    80  	hosts := strings.Split(*host, ",")
    81  	for _, h := range hosts {
    82  		if ip := net.ParseIP(h); ip != nil {
    83  			template.IPAddresses = append(template.IPAddresses, ip)
    84  		} else {
    85  			template.DNSNames = append(template.DNSNames, h)
    86  		}
    87  	}
    88  
    89  	if *isCA {
    90  		template.IsCA = true
    91  		template.KeyUsage |= x509.KeyUsageCertSign
    92  	}
    93  
    94  	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &priv.PublicKey, priv)
    95  	if err != nil {
    96  		log.Fatalf("Failed to create certificate: %s", err)
    97  	}
    98  
    99  	certOut, err := os.Create("cert.pem")
   100  	if err != nil {
   101  		log.Fatalf("failed to open cert.pem for writing: %s", err)
   102  	}
   103  	pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes})
   104  	certOut.Close()
   105  	log.Print("written cert.pem\n")
   106  
   107  	keyOut, err := os.OpenFile("key.pem", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
   108  	if err != nil {
   109  		log.Print("failed to open key.pem for writing:", err)
   110  		return
   111  	}
   112  	pem.Encode(keyOut, &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(priv)})
   113  	keyOut.Close()
   114  	log.Print("written key.pem\n")
   115  }