examples: tls: Add a simple TLS example
Was useful for testing things...
This commit is contained in:
James Shubin
203
examples/tls/tls.go
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203
examples/tls/tls.go
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// Modified from: golang/src/crypto/tls/generate_cert.go
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package main
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import (
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"crypto/ecdsa"
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"crypto/ed25519"
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"crypto/elliptic"
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"crypto/rand"
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"crypto/rsa"
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"crypto/x509"
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"crypto/x509/pkix"
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"encoding/pem"
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"fmt"
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"log"
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"math/big"
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"net"
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"net/http"
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"os"
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"strings"
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"time"
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)
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// NewTLS builds a new TLS struct with some defaults.
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func NewTLS() *TLS {
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return &TLS{
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ValidFor: 365 * 24 * time.Hour,
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RsaBits: 2048,
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}
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}
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// TLS handles all of the TLS building.
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type TLS struct {
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Host string // Comma-separated hostnames and IPs to generate a certificate for
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ValidFrom string // Creation date formatted as Jan 1 15:04:05 2011
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ValidFor time.Duration // Duration that certificate is valid for
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IsCA bool // Whether this cert should be its own Certificate Authority
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RsaBits int // Size of RSA key to generate. Ignored if EcdsaCurve is set
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EcdsaCurve string // ECDSA curve to use to generate a key. Valid values are P224, P256 (recommended), P384, P521
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Ed25519Key bool // Generate an Ed25519 key
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}
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// Generate writes out the two files. Usually keyPemFile is key.pem and
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// certPemFile is cert.pem which go into http.ListenAndServeTLS.
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func (obj *TLS) Generate(keyPemFile, certPemFile string) error {
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if len(obj.Host) == 0 {
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return fmt.Errorf("missing required Host parameter")
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}
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var priv any
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var err error
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switch obj.EcdsaCurve {
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case "":
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if obj.Ed25519Key {
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_, priv, err = ed25519.GenerateKey(rand.Reader)
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} else {
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priv, err = rsa.GenerateKey(rand.Reader, obj.RsaBits)
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}
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case "P224":
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priv, err = ecdsa.GenerateKey(elliptic.P224(), rand.Reader)
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case "P256":
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priv, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
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case "P384":
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priv, err = ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
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case "P521":
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priv, err = ecdsa.GenerateKey(elliptic.P521(), rand.Reader)
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default:
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return fmt.Errorf("unrecognized elliptic curve: %q", obj.EcdsaCurve)
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}
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if err != nil {
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return fmt.Errorf("failed to generate private key: %v", err)
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}
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// ECDSA, ED25519 and RSA subject keys should have the DigitalSignature
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// KeyUsage bits set in the x509.Certificate template
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keyUsage := x509.KeyUsageDigitalSignature
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// Only RSA subject keys should have the KeyEncipherment KeyUsage bits set. In
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// the context of TLS this KeyUsage is particular to RSA key exchange and
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// authentication.
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if _, isRSA := priv.(*rsa.PrivateKey); isRSA {
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keyUsage |= x509.KeyUsageKeyEncipherment
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}
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var notBefore time.Time
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if len(obj.ValidFrom) == 0 {
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notBefore = time.Now()
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} else {
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notBefore, err = time.Parse("Jan 2 15:04:05 2006", obj.ValidFrom)
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if err != nil {
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return fmt.Errorf("failed to parse creation date: %v", err)
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}
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}
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notAfter := notBefore.Add(obj.ValidFor)
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serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
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serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
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if err != nil {
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return fmt.Errorf("failed to generate serial number: %v", err)
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}
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template := x509.Certificate{
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SerialNumber: serialNumber,
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Subject: pkix.Name{
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Organization: []string{"Whatever Corp"}, // XXX: change me...
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},
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NotBefore: notBefore,
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NotAfter: notAfter,
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KeyUsage: keyUsage,
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ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
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BasicConstraintsValid: true,
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}
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hosts := strings.Split(obj.Host, ",")
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for _, h := range hosts {
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if ip := net.ParseIP(h); ip != nil {
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template.IPAddresses = append(template.IPAddresses, ip)
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} else {
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template.DNSNames = append(template.DNSNames, h)
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}
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}
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if obj.IsCA {
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template.IsCA = true
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template.KeyUsage |= x509.KeyUsageCertSign
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}
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derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, publicKey(priv), priv)
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if err != nil {
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return fmt.Errorf("failed to create certificate: %v", err)
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}
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certOut, err := os.Create(certPemFile)
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if err != nil {
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return fmt.Errorf("failed to open %s for writing: %v", certPemFile, err)
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}
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if err := pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes}); err != nil {
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return fmt.Errorf("failed to write data to %s: %v", certPemFile, err)
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}
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if err := certOut.Close(); err != nil {
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return fmt.Errorf("error closing %s: %v", certPemFile, err)
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}
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log.Printf("wrote %s", certPemFile)
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keyOut, err := os.OpenFile(keyPemFile, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
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if err != nil {
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return fmt.Errorf("failed to open %s for writing: %v", keyPemFile, err)
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}
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privBytes, err := x509.MarshalPKCS8PrivateKey(priv)
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if err != nil {
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return fmt.Errorf("unable to marshal private key: %v", err)
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}
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if err := pem.Encode(keyOut, &pem.Block{Type: "PRIVATE KEY", Bytes: privBytes}); err != nil {
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return fmt.Errorf("failed to write data to %s: %v", keyPemFile, err)
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}
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if err := keyOut.Close(); err != nil {
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return fmt.Errorf("error closing %s: %v", keyPemFile, err)
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}
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log.Printf("wrote %s", keyPemFile)
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return nil
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}
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// HelloServer is a simple handler.
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func HelloServer(w http.ResponseWriter, req *http.Request) {
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fmt.Printf("req: %+v\n", req)
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w.Header().Set("Content-Type", "text/plain")
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w.Write([]byte("This is hello world!\n"))
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}
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func publicKey(priv any) any {
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switch k := priv.(type) {
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case *rsa.PrivateKey:
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return &k.PublicKey
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case *ecdsa.PrivateKey:
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return &k.PublicKey
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case ed25519.PrivateKey:
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return k.Public().(ed25519.PublicKey)
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default:
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return nil
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}
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}
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func main() {
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// wget --no-check-certificate https://127.0.0.1:1443/hello -O -
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tls := NewTLS()
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tls.Host = "localhost" // TODO: choose something
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keyPemFile := "/tmp/key.pem"
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certPemFile := "/tmp/cert.pem"
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if err := tls.Generate(keyPemFile, certPemFile); err != nil {
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fmt.Printf("error: %v\n", err)
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return
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}
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http.HandleFunc("/hello", HelloServer)
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if err := http.ListenAndServeTLS(":1443", certPemFile, keyPemFile, nil); err != nil {
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log.Fatal("ListenAndServe: ", err)
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}
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}
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