certificate.go

/*
Copyright 2022 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package kubernetes

import (
	"bytes"
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"fmt"
	"io"
	"math/big"
	"net"
	"testing"
	"time"

	"github.com/stretchr/testify/require"
	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
)

const (
	rsaBits  = 2048
	validFor = 365 * 24 * time.Hour
)

// MustCreateSelfSignedCertSecret creates a self-signed SSL certificate and stores it in a secret
func MustCreateSelfSignedCertSecret(t *testing.T, namespace, secretName string, hosts []string) *corev1.Secret {
	require.NotEmpty(t, hosts, "require a non-empty hosts for Subject Alternate Name values")

	var serverKey, serverCert bytes.Buffer

	require.NoError(t, generateRSACert(hosts, &serverKey, &serverCert), "failed to generate RSA certificate")

	data := map[string][]byte{
		corev1.TLSCertKey:       serverCert.Bytes(),
		corev1.TLSPrivateKeyKey: serverKey.Bytes(),
	}

	newSecret := &corev1.Secret{
		ObjectMeta: metav1.ObjectMeta{
			Namespace: namespace,
			Name:      secretName,
		},
		Type: corev1.SecretTypeTLS,
		Data: data,
	}

	return newSecret
}

// generateRSACert generates a basic self-signed certificate valid for a year
func generateRSACert(hosts []string, keyOut, certOut io.Writer) error {
	priv, err := rsa.GenerateKey(rand.Reader, rsaBits)
	if err != nil {
		return fmt.Errorf("failed to generate key: %w", err)
	}
	notBefore := time.Now()
	notAfter := notBefore.Add(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: %w", err)
	}

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

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

	for _, h := range hosts {
		if ip := net.ParseIP(h); ip != nil {
			template.IPAddresses = append(template.IPAddresses, ip)
		} else {
			template.DNSNames = append(template.DNSNames, h)
		}
	}

	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &priv.PublicKey, priv)
	if err != nil {
		return fmt.Errorf("failed to create certificate: %w", err)
	}

	if err := pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes}); err != nil {
		return fmt.Errorf("failed creating cert: %w", err)
	}

	if err := pem.Encode(keyOut, &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(priv)}); err != nil {
		return fmt.Errorf("failed creating key: %w", err)
	}

	return nil
}