util: Add a TLS helper

Make it easier to build TLS stuff in pure golang.
purpleidea · Nov 1, 2024 · 3fb492f · 3fb492f
1 parent e4f062b
commit 3fb492f
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Showing 2 changed files with 227 additions and 169 deletions.
diff --git a/examples/tls/tls.go b/examples/tls/tls.go
@@ -3,165 +3,12 @@
 package main
 
 import (
-	"crypto/ecdsa"
-	"crypto/ed25519"
-	"crypto/elliptic"
-	"crypto/rand"
-	"crypto/rsa"
-	"crypto/x509"
-	"crypto/x509/pkix"
-	"encoding/pem"
 	"fmt"
 	"log"
-	"math/big"
-	"net"
 	"net/http"
-	"os"
-	"strings"
-	"time"
-)
-
-// NewTLS builds a new TLS struct with some defaults.
-func NewTLS() *TLS {
-	return &TLS{
-		ValidFor: 365 * 24 * time.Hour,
-		RsaBits:  2048,
-	}
-}
-
-// TLS handles all of the TLS building.
-type TLS struct {
-	Host       string        // Comma-separated hostnames and IPs to generate a certificate for
-	ValidFrom  string        // Creation date formatted as Jan 1 15:04:05 2011
-	ValidFor   time.Duration // Duration that certificate is valid for
-	IsCA       bool          // Whether this cert should be its own Certificate Authority
-	RsaBits    int           // Size of RSA key to generate. Ignored if EcdsaCurve is set
-	EcdsaCurve string        // ECDSA curve to use to generate a key. Valid values are P224, P256 (recommended), P384, P521
-	Ed25519Key bool          // Generate an Ed25519 key
-}
-
-// Generate writes out the two files. Usually keyPemFile is key.pem and
-// certPemFile is cert.pem which go into http.ListenAndServeTLS.
-func (obj *TLS) Generate(keyPemFile, certPemFile string) error {
-
-	if len(obj.Host) == 0 {
-		return fmt.Errorf("missing required Host parameter")
-	}
-
-	var priv any
-	var err error
-	switch obj.EcdsaCurve {
-	case "":
-		if obj.Ed25519Key {
-			_, priv, err = ed25519.GenerateKey(rand.Reader)
-		} else {
-			priv, err = rsa.GenerateKey(rand.Reader, obj.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:
-		return fmt.Errorf("unrecognized elliptic curve: %q", obj.EcdsaCurve)
-	}
-	if err != nil {
-		return fmt.Errorf("failed to generate private key: %v", err)
-	}
-
-	// ECDSA, ED25519 and RSA subject keys should have the DigitalSignature
-	// KeyUsage bits set in the x509.Certificate template
-	keyUsage := x509.KeyUsageDigitalSignature
-	// Only RSA subject keys should have the KeyEncipherment KeyUsage bits set. In
-	// the context of TLS this KeyUsage is particular to RSA key exchange and
-	// authentication.
-	if _, isRSA := priv.(*rsa.PrivateKey); isRSA {
-		keyUsage |= x509.KeyUsageKeyEncipherment
-	}
-
-	var notBefore time.Time
-	if len(obj.ValidFrom) == 0 {
-		notBefore = time.Now()
-	} else {
-		notBefore, err = time.Parse("Jan 2 15:04:05 2006", obj.ValidFrom)
-		if err != nil {
-			return fmt.Errorf("failed to parse creation date: %v", err)
-		}
-	}
-
-	notAfter := notBefore.Add(obj.ValidFor)
-
-	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
-	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
-	if err != nil {
-		return fmt.Errorf("failed to generate serial number: %v", err)
-	}
-
-	template := x509.Certificate{
-		SerialNumber: serialNumber,
-		Subject: pkix.Name{
-			Organization: []string{"Whatever Corp"}, // XXX: change me...
-		},
-		NotBefore: notBefore,
-		NotAfter:  notAfter,
-
-		KeyUsage:              keyUsage,
-		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
-		BasicConstraintsValid: true,
-	}
-
-	hosts := strings.Split(obj.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 obj.IsCA {
-		template.IsCA = true
-		template.KeyUsage |= x509.KeyUsageCertSign
-	}
-
-	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, publicKey(priv), priv)
-	if err != nil {
-		return fmt.Errorf("failed to create certificate: %v", err)
-	}
-
-	certOut, err := os.Create(certPemFile)
-	if err != nil {
-		return fmt.Errorf("failed to open %s for writing: %v", certPemFile, err)
-	}
-	if err := pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes}); err != nil {
-		return fmt.Errorf("failed to write data to %s: %v", certPemFile, err)
-	}
-	if err := certOut.Close(); err != nil {
-		return fmt.Errorf("error closing %s: %v", certPemFile, err)
-	}
-	log.Printf("wrote %s", certPemFile)
 
-	keyOut, err := os.OpenFile(keyPemFile, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
-	if err != nil {
-		return fmt.Errorf("failed to open %s for writing: %v", keyPemFile, err)
-	}
-	privBytes, err := x509.MarshalPKCS8PrivateKey(priv)
-	if err != nil {
-		return fmt.Errorf("unable to marshal private key: %v", err)
-	}
-	if err := pem.Encode(keyOut, &pem.Block{Type: "PRIVATE KEY", Bytes: privBytes}); err != nil {
-		return fmt.Errorf("failed to write data to %s: %v", keyPemFile, err)
-	}
-	if err := keyOut.Close(); err != nil {
-		return fmt.Errorf("error closing %s: %v", keyPemFile, err)
-	}
-	log.Printf("wrote %s", keyPemFile)
-
-	return nil
-}
+	"github.com/purpleidea/mgmt/util"
+)
 
 // HelloServer is a simple handler.
 func HelloServer(w http.ResponseWriter, req *http.Request) {
@@ -170,23 +17,10 @@ func HelloServer(w http.ResponseWriter, req *http.Request) {
 	w.Write([]byte("This is hello world!\n"))
 }
 
-func publicKey(priv any) any {
-	switch k := priv.(type) {
-	case *rsa.PrivateKey:
-		return &k.PublicKey
-	case *ecdsa.PrivateKey:
-		return &k.PublicKey
-	case ed25519.PrivateKey:
-		return k.Public().(ed25519.PublicKey)
-	default:
-		return nil
-	}
-}
-
 func main() {
 	// wget --no-check-certificate https://127.0.0.1:1443/hello -O -
 
-	tls := NewTLS()
+	tls := util.NewTLS()
 	tls.Host = "localhost" // TODO: choose something
 	keyPemFile := "/tmp/key.pem"
 	certPemFile := "/tmp/cert.pem"