util: Add a TLS helper

Make it easier to build TLS stuff in pure golang.

examples/tls/tls.go

@@ -3,166 +3,13 @@
 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"
+	"github.com/purpleidea/mgmt/util"
-	"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
-}
-
 // HelloServer is a simple handler.
 func HelloServer(w http.ResponseWriter, req *http.Request) {
 	fmt.Printf("req: %+v\n", req)
@@ -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"

util/tls.go

@@ -0,0 +1,224 @@
+// Mgmt
+// Copyright (C) 2013-2024+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+//
+// Additional permission under GNU GPL version 3 section 7
+//
+// If you modify this program, or any covered work, by linking or combining it
+// with embedded mcl code and modules (and that the embedded mcl code and
+// modules which link with this program, contain a copy of their source code in
+// the authoritative form) containing parts covered by the terms of any other
+// license, the licensors of this program grant you additional permission to
+// convey the resulting work. Furthermore, the licensors of this program grant
+// the original author, James Shubin, additional permission to update this
+// additional permission if he deems it necessary to achieve the goals of this
+// additional permission.
+
+// Modified from: golang/src/crypto/tls/generate_cert.go
+
+package util
+
+import (
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"fmt"
+	"log"
+	"math/big"
+	"net"
+	"os"
+	"strings"
+	"time"
+)
+
+// NewTLS builds a new TLS struct with some defaults.
+func NewTLS() *TLS {
+	return &TLS{
+		ValidFor:     365 * 24 * time.Hour,
+		RsaBits:      2048,
+		Organization: "Example Corp",
+	}
+}
+
+// TLS handles all of the TLS building.
+type TLS struct {
+	// Host is comma-separated hostnames and IPs to generate a certificate
+	// for.
+	Host string
+
+	// ValidFrom is the creation date formatted as Jan 1 15:04:05 2011.
+	ValidFrom string
+
+	// ValidFor is the duration that certificate is valid for.
+	ValidFor time.Duration
+
+	// IsCA is Whether this cert should be its own Certificate Authority.
+	IsCA bool
+
+	// RsaBits is the size of RSA key to generate. Ignored if EcdsaCurve is
+	// set.
+	RsaBits int
+
+	// EcdsaCurve is the ECDSA curve to use to generate a key. Valid values
+	// are P224, P256 (recommended), P384, P521.
+	EcdsaCurve string
+
+	// Ed25519Key is true to generate an Ed25519 key.
+	Ed25519Key bool
+
+	// Organization is the name of the organization to store in the cert.
+	Organization string
+}
+
+// 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{obj.Organization},
+		},
+		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, obj.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
+}
+
+func (obj *TLS) 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
+	}
+}