github.com/zmap/zcrypto@v0.0.0-20240512203510-0fef58d9a9db/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  //go:build ignore
     6  // +build ignore
     7  
     8  // Generate a self-signed X.509 certificate for a TLS server. Outputs to
     9  // 'cert.pem' and 'key.pem' and will overwrite existing files.
    10  
    11  package main
    12  
    13  import (
    14  	"crypto/rand"
    15  	"crypto/rsa"
    16  
    17  	"github.com/zmap/zcrypto/x509"
    18  	"github.com/zmap/zcrypto/x509/pkix"
    19  
    20  	"encoding/pem"
    21  	"flag"
    22  	"fmt"
    23  	"log"
    24  	"math/big"
    25  	"net"
    26  	"os"
    27  	"strings"
    28  	"time"
    29  )
    30  
    31  var (
    32  	host      = flag.String("host", "", "Comma-separated hostnames and IPs to generate a certificate for")
    33  	validFrom = flag.String("start-date", "", "Creation date formatted as Jan 1 15:04:05 2011")
    34  	validFor  = flag.Duration("duration", 365*24*time.Hour, "Duration that certificate is valid for")
    35  	isCA      = flag.Bool("ca", false, "whether this cert should be its own Certificate Authority")
    36  	rsaBits   = flag.Int("rsa-bits", 2048, "Size of RSA key to generate")
    37  )
    38  
    39  func main() {
    40  	flag.Parse()
    41  
    42  	if len(*host) == 0 {
    43  		log.Fatalf("Missing required --host parameter")
    44  	}
    45  
    46  	priv, err := rsa.GenerateKey(rand.Reader, *rsaBits)
    47  	if err != nil {
    48  		log.Fatalf("failed to generate private key: %s", err)
    49  	}
    50  
    51  	var notBefore time.Time
    52  	if len(*validFrom) == 0 {
    53  		notBefore = time.Now()
    54  	} else {
    55  		notBefore, err = time.Parse("Jan 2 15:04:05 2006", *validFrom)
    56  		if err != nil {
    57  			fmt.Fprintf(os.Stderr, "Failed to parse creation date: %s\n", err)
    58  			os.Exit(1)
    59  		}
    60  	}
    61  
    62  	notAfter := notBefore.Add(*validFor)
    63  
    64  	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
    65  	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
    66  	if err != nil {
    67  		log.Fatalf("failed to generate serial number: %s", err)
    68  	}
    69  
    70  	template := x509.Certificate{
    71  		SerialNumber: serialNumber,
    72  		Subject: pkix.Name{
    73  			Organization: []string{"Acme Co"},
    74  		},
    75  		NotBefore: notBefore,
    76  		NotAfter:  notAfter,
    77  
    78  		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
    79  		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
    80  		BasicConstraintsValid: true,
    81  	}
    82  
    83  	hosts := strings.Split(*host, ",")
    84  	for _, h := range hosts {
    85  		if ip := net.ParseIP(h); ip != nil {
    86  			template.IPAddresses = append(template.IPAddresses, ip)
    87  		} else {
    88  			template.DNSNames = append(template.DNSNames, h)
    89  		}
    90  	}
    91  
    92  	if *isCA {
    93  		template.IsCA = true
    94  		template.KeyUsage |= x509.KeyUsageCertSign
    95  	}
    96  
    97  	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &priv.PublicKey, priv)
    98  	if err != nil {
    99  		log.Fatalf("Failed to create certificate: %s", err)
   100  	}
   101  
   102  	certOut, err := os.Create("cert.pem")
   103  	if err != nil {
   104  		log.Fatalf("failed to open cert.pem for writing: %s", err)
   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  }