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Source file src/pkg/crypto/tls/generate_cert.go

     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			return
    47		}
    48	
    49		var notBefore time.Time
    50		if len(*validFrom) == 0 {
    51			notBefore = time.Now()
    52		} else {
    53			notBefore, err = time.Parse("Jan 2 15:04:05 2006", *validFrom)
    54			if err != nil {
    55				fmt.Fprintf(os.Stderr, "Failed to parse creation date: %s\n", err)
    56				os.Exit(1)
    57			}
    58		}
    59	
    60		notAfter := notBefore.Add(*validFor)
    61	
    62		// end of ASN.1 time
    63		endOfTime := time.Date(2049, 12, 31, 23, 59, 59, 0, time.UTC)
    64		if notAfter.After(endOfTime) {
    65			notAfter = endOfTime
    66		}
    67	
    68		template := x509.Certificate{
    69			SerialNumber: new(big.Int).SetInt64(0),
    70			Subject: pkix.Name{
    71				Organization: []string{"Acme Co"},
    72			},
    73			NotBefore: notBefore,
    74			NotAfter:  notAfter,
    75	
    76			KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
    77			ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
    78			BasicConstraintsValid: true,
    79		}
    80	
    81		hosts := strings.Split(*host, ",")
    82		for _, h := range hosts {
    83			if ip := net.ParseIP(h); ip != nil {
    84				template.IPAddresses = append(template.IPAddresses, ip)
    85			} else {
    86				template.DNSNames = append(template.DNSNames, h)
    87			}
    88		}
    89	
    90		if *isCA {
    91			template.IsCA = true
    92			template.KeyUsage |= x509.KeyUsageCertSign
    93		}
    94	
    95		derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &priv.PublicKey, priv)
    96		if err != nil {
    97			log.Fatalf("Failed to create certificate: %s", err)
    98			return
    99		}
   100	
   101		certOut, err := os.Create("cert.pem")
   102		if err != nil {
   103			log.Fatalf("failed to open cert.pem for writing: %s", err)
   104			return
   105		}
   106		pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes})
   107		certOut.Close()
   108		log.Print("written cert.pem\n")
   109	
   110		keyOut, err := os.OpenFile("key.pem", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
   111		if err != nil {
   112			log.Print("failed to open key.pem for writing:", err)
   113			return
   114		}
   115		pem.Encode(keyOut, &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(priv)})
   116		keyOut.Close()
   117		log.Print("written key.pem\n")
   118	}

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