/
gogencerts.go
executable file
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/
gogencerts.go
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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Generate a self-signed X.509 certificate for a TLS server. Outputs to
// 'cert.pem' and 'key.pem' and will overwrite existing files.
// troyxmccall mods - note don't use this shit in prod - probably better to reverse proxy with a let's encrypt cert over nginx to a non-secure go web server.
package gogencerts
import (
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"fmt"
"log"
"math/big"
"net"
"os"
"strings"
"time"
)
var (
validFrom = ""
validFor = 365 * 24 * time.Hour
isCA = true
rsaBits = 2048
ecdsaCurve = ""
)
func publicKey(priv interface{}) interface{} {
switch k := priv.(type) {
case *rsa.PrivateKey:
return &k.PublicKey
case *ecdsa.PrivateKey:
return &k.PublicKey
default:
return nil
}
}
func pemBlockForKey(priv interface{}) *pem.Block {
switch k := priv.(type) {
case *rsa.PrivateKey:
return &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(k)}
case *ecdsa.PrivateKey:
b, err := x509.MarshalECPrivateKey(k)
if err != nil {
fmt.Fprintf(os.Stderr, "Unable to marshal ECDSA private key: %v", err)
os.Exit(2)
}
return &pem.Block{Type: "EC PRIVATE KEY", Bytes: b}
default:
return nil
}
}
func Check(certPath string, keyPath string) error {
if _, err := os.Stat(certPath); os.IsNotExist(err) {
return err
} else if _, err := os.Stat(keyPath); os.IsNotExist(err) {
return err
}
return nil
}
func Generate(certPath string, keyPath string, host string) error {
var priv interface{}
var err error
switch ecdsaCurve {
case "":
priv, err = rsa.GenerateKey(rand.Reader, rsaBits)
case "P224":
priv, err = ecdsa.GenerateKey(elliptic.P224(), rand.Reader)
case "P256":
priv, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
case "P384":
priv, err = ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
case "P521":
priv, err = ecdsa.GenerateKey(elliptic.P521(), rand.Reader)
default:
fmt.Fprintf(os.Stderr, "Unrecognized elliptic curve: %q", ecdsaCurve)
os.Exit(1)
}
if err != nil {
log.Printf("failed to generate private key: %s", err)
return err
}
var notBefore time.Time
if len(validFrom) == 0 {
notBefore = time.Now()
} else {
notBefore, err = time.Parse("Jan 2 15:04:05 2006", validFrom)
if err != nil {
fmt.Fprintf(os.Stderr, "Failed to parse creation date: %s\n", err)
return err
}
}
notAfter := notBefore.Add(validFor)
serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
if err != nil {
log.Printf("failed to generate serial number: %s", err)
return err
}
template := x509.Certificate{
SerialNumber: serialNumber,
Subject: pkix.Name{
Organization: []string{"Acme Co"},
},
NotBefore: notBefore,
NotAfter: notAfter,
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
BasicConstraintsValid: true,
}
hosts := strings.Split(host, ",")
for _, h := range hosts {
if ip := net.ParseIP(h); ip != nil {
template.IPAddresses = append(template.IPAddresses, ip)
} else {
template.DNSNames = append(template.DNSNames, h)
}
}
if isCA {
template.IsCA = true
template.KeyUsage |= x509.KeyUsageCertSign
}
derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, publicKey(priv), priv)
if err != nil {
log.Printf("Failed to create certificate: %s", err)
return err
}
certOut, err := os.Create(certPath)
if err != nil {
log.Printf("failed to open "+certPath+" for writing: %s", err)
return err
}
pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes})
certOut.Close()
log.Print("written cert.pem\n")
keyOut, err := os.OpenFile(keyPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
if err != nil {
log.Print("failed to open "+keyPath+" for writing:", err)
return err
}
pem.Encode(keyOut, pemBlockForKey(priv))
keyOut.Close()
log.Print("written key.pem\n")
return nil
}