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main.go
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main.go
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// Copyright 2016 Google, Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import (
"crypto/rand"
"crypto/rsa"
"crypto/sha1"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"flag"
"fmt"
"log"
"math/big"
"net"
"os"
"strings"
"time"
)
var (
notBefore, notAfter time.Time
serialNumberLimit *big.Int
rsaBits = 2048
host string
)
var serverSubjectAlternateNames = []string{
"*.example.com",
"localhost",
"127.0.0.1",
}
type certificateConfig struct {
isCA bool
caCert *x509.Certificate
caKey *rsa.PrivateKey
hosts []string
keyUsage x509.KeyUsage
extKeyUsage []x509.ExtKeyUsage
}
func init() {
notBefore = time.Now().Add(-5 * time.Minute).UTC()
notAfter = notBefore.Add(365 * 24 * time.Hour).UTC()
serialNumberLimit = new(big.Int).Lsh(big.NewInt(1), 128)
flag.StringVar(&host, "host", "", "Comma-separated hostnames and IPs to generate a certificate for")
}
func main() {
flag.Parse()
// Generate CA
caCert, caKey, err := generateCertificate(certificateConfig{
isCA: true,
hosts: []string{""},
keyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
extKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
})
if err != nil {
log.Fatal(err)
}
err = writeCert("ca", caCert, caKey)
if err != nil {
log.Fatal(err)
}
caParsedCertificates, err := x509.ParseCertificates(caCert)
if err != nil {
log.Fatal(err)
}
// Generate Server Certificates
hosts := make([]string, 0)
for _, h := range strings.Split(host, ",") {
if h == "" {
continue
}
hosts = append(hosts, h)
}
hosts = append(hosts, serverSubjectAlternateNames...)
serverCert, serverKey, err := generateCertificate(certificateConfig{
caCert: caParsedCertificates[0],
caKey: caKey,
hosts: hosts,
keyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
extKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
})
if err != nil {
log.Fatal(err)
}
err = writeCert("server", serverCert, serverKey)
if err != nil {
log.Fatal(err)
}
}
func writeCert(name string, cert []byte, key *rsa.PrivateKey) error {
certFilename := fmt.Sprintf("%s.pem", name)
keyFilename := fmt.Sprintf("%s-key.pem", name)
certFile, err := os.Create(certFilename)
if err != nil {
return err
}
pem.Encode(certFile, &pem.Block{Type: "CERTIFICATE", Bytes: cert})
certFile.Close()
fmt.Printf("wrote %s\n", certFilename)
keyFile, err := os.OpenFile(keyFilename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
if err != nil {
return err
}
pem.Encode(keyFile, &pem.Block{
Type: "RSA PRIVATE KEY",
Bytes: x509.MarshalPKCS1PrivateKey(key),
})
keyFile.Close()
fmt.Printf("wrote %s\n", keyFilename)
return nil
}
func generateCertificate(c certificateConfig) ([]byte, *rsa.PrivateKey, error) {
serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
if err != nil {
return nil, nil, err
}
key, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil {
return nil, nil, err
}
// Generate the subject key ID
derEncodedPubKey, err := x509.MarshalPKIXPublicKey(&key.PublicKey)
if err != nil {
return nil, nil, err
}
pubKeyHash := sha1.New()
pubKeyHash.Write(derEncodedPubKey)
template := x509.Certificate{
SerialNumber: serialNumber,
Subject: pkix.Name{
Organization: []string{"Kubernetes"},
},
NotBefore: notBefore,
NotAfter: notAfter,
IsCA: c.isCA,
KeyUsage: c.keyUsage,
ExtKeyUsage: c.extKeyUsage,
BasicConstraintsValid: true,
SubjectKeyId: pubKeyHash.Sum(nil),
}
if c.hosts[0] != "" {
template.Subject.CommonName = c.hosts[0]
}
if c.isCA {
c.caCert = &template
c.caKey = key
}
for _, h := range c.hosts {
if ip := net.ParseIP(h); ip != nil {
template.IPAddresses = append(template.IPAddresses, ip)
} else {
template.DNSNames = append(template.DNSNames, h)
}
}
derBytes, err := x509.CreateCertificate(rand.Reader, &template, c.caCert, &key.PublicKey, c.caKey)
if err != nil {
return nil, nil, err
}
return derBytes, key, nil
}