selfsigned.go

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2023 Oracle and/or its affiliates.
 * Copyright (c) 2024 Damian Peckett <damian@pecke.tt>.
 *
 * tlshd-go 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; version 2.
 *
 * 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

package util

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

	"github.com/dpeckett/ktls/tls"
)

// GenerateSelfSignedCert generates a self-signed certificate for use in testing.
func GenerateSelfSignedCert() (tls.Certificate, error) {
	privKey, err := rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		return tls.Certificate{}, err
	}

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

	certTemplate := x509.Certificate{
		SerialNumber: serialNumber,
		Subject: pkix.Name{
			Organization: []string{"Test"},
		},
		NotBefore:             time.Now(),
		NotAfter:              time.Now().Add(time.Hour),
		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
		BasicConstraintsValid: true,
		DNSNames:              []string{"localhost"},
	}

	certBytes, err := x509.CreateCertificate(rand.Reader, &certTemplate, &certTemplate, &privKey.PublicKey, privKey)
	if err != nil {
		return tls.Certificate{}, err
	}

	certPEM := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: certBytes})
	privKeyPEM := pem.EncodeToMemory(&pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(privKey)})

	return tls.X509KeyPair(certPEM, privKeyPEM)
}