tls.go

package main

// A library version of https://golang.org/src/crypto/tls/generate_cert.go

import (
	"crypto/ecdsa"
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"math/big"
	"os"
	"time"
)

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)}
	default:
		return nil
	}
}

// MakeSelfSignedCert creates a cert for the local shim
func MakeSelfSignedCert() {
	var priv interface{}
	var err error

	priv, err = rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		panic(err)
	}

	notBefore := time.Now()
	notAfter := notBefore.Add(365 * 24 * time.Hour)

	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
	if err != nil {
		panic(err)
	}

	template := x509.Certificate{
		SerialNumber: serialNumber,
		Subject: pkix.Name{
			Organization: []string{"Talexmpp"},
		},
		NotBefore: notBefore,
		NotAfter:  notAfter,

		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
		BasicConstraintsValid: true,
	}

	template.DNSNames = append(template.DNSNames, "localhost")

	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, publicKey(priv), priv)
	if err != nil {
		panic(err)
	}

	certOut, err := os.Create("cert.pem")
	if err != nil {
		panic(err)
	}
	pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes})
	certOut.Close()

	keyOut, err := os.OpenFile("key.pem", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
	if err != nil {
		panic(err)
	}
	pem.Encode(keyOut, pemBlockForKey(priv))
	keyOut.Close()
}