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certs.go
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certs.go
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// most of the code was copied from https://github.com/knative/pkg
package cert
import (
"bufio"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"errors"
"fmt"
"io"
"math/big"
"os"
"strings"
"sync"
"time"
logf "sigs.k8s.io/controller-runtime/pkg/log"
)
const (
organization = "redhat.com"
resolverFileName = "/etc/resolv.conf"
defaultDomainName = "cluster.local"
)
var (
domainName = defaultDomainName
once sync.Once
log = logf.Log.WithName("certificate_manager")
)
// Create the common parts of the cert. These don't change between
// the root/CA cert and the server cert.
func createCertTemplate(name, namespace string, notAfter time.Time) (*x509.Certificate, error) {
serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
if err != nil {
return nil, errors.New("failed to generate serial number: " + err.Error())
}
serviceName := name + "." + namespace
commonName := serviceName + ".svc"
serviceHostname := fmt.Sprintf("%s.%s.svc.%s", name, namespace, getClusterDomainName())
serviceNames := []string{
name,
serviceName,
commonName,
serviceHostname,
}
tmpl := x509.Certificate{
SerialNumber: serialNumber,
Subject: pkix.Name{
Organization: []string{organization},
CommonName: commonName,
},
SignatureAlgorithm: x509.SHA256WithRSA,
NotBefore: time.Now(),
NotAfter: notAfter,
BasicConstraintsValid: true,
DNSNames: serviceNames,
}
return &tmpl, nil
}
// Create cert template suitable for CA and hence signing
func createCACertTemplate(name, namespace string, notAfter time.Time) (*x509.Certificate, error) {
rootCert, err := createCertTemplate(name, namespace, notAfter)
if err != nil {
return nil, err
}
// Make it into a CA cert and change it so we can use it to sign certs
rootCert.IsCA = true
rootCert.KeyUsage = x509.KeyUsageCertSign | x509.KeyUsageDigitalSignature
rootCert.ExtKeyUsage = []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageClientAuth}
return rootCert, nil
}
// Create cert template that we can use on the server for TLS
func createServerCertTemplate(name, namespace string, notAfter time.Time) (*x509.Certificate, error) {
serverCert, err := createCertTemplate(name, namespace, notAfter)
if err != nil {
return nil, err
}
serverCert.KeyUsage = x509.KeyUsageDigitalSignature
serverCert.ExtKeyUsage = []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth}
return serverCert, err
}
// Actually sign the cert and return things in a form that we can use later on
func createCert(template, parent *x509.Certificate, pub, parentPriv interface{}) (
cert *x509.Certificate, certPEM []byte, err error) {
certDER, err := x509.CreateCertificate(rand.Reader, template, parent, pub, parentPriv)
if err != nil {
return
}
cert, err = x509.ParseCertificate(certDER)
if err != nil {
return
}
b := pem.Block{Type: "CERTIFICATE", Bytes: certDER}
certPEM = pem.EncodeToMemory(&b)
return
}
func createCA(name, namespace string, notAfter time.Time) (*rsa.PrivateKey, *x509.Certificate, []byte, error) {
rootKey, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil {
log.Error(err, "error generating random key")
return nil, nil, nil, err
}
rootCertTmpl, err := createCACertTemplate(name, namespace, notAfter)
if err != nil {
log.Error(err, "error generating CA cert")
return nil, nil, nil, err
}
rootCert, rootCertPEM, err := createCert(rootCertTmpl, rootCertTmpl, &rootKey.PublicKey, rootKey)
if err != nil {
log.Error(err, "error signing the CA cert")
return nil, nil, nil, err
}
return rootKey, rootCert, rootCertPEM, nil
}
// CreateCerts creates and returns a CA certificate and certificate and
// key for the server. serverKey and serverCert are used by the server
// to establish trust for clients, CA certificate is used by the
// client to verify the server authentication chain. notAfter specifies
// the expiration date.
func CreateCerts(name, namespace string, notAfter time.Time) (serverKey, serverCert, caCert []byte, err error) {
// First create a CA certificate and private key
caKey, caCertificate, caCertificatePEM, err := createCA(name, namespace, notAfter)
if err != nil {
return nil, nil, nil, err
}
// Then create the private key for the serving cert
servKey, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil {
log.Error(err, "error generating random key")
return nil, nil, nil, err
}
servCertTemplate, err := createServerCertTemplate(name, namespace, notAfter)
if err != nil {
log.Error(err, "failed to create the server certificate template")
return nil, nil, nil, err
}
// create a certificate which wraps the server's public key, sign it with the CA private key
_, servCertPEM, err := createCert(servCertTemplate, caCertificate, &servKey.PublicKey, caKey)
if err != nil {
log.Error(err, "error signing server certificate template")
return nil, nil, nil, err
}
servKeyPEM := pem.EncodeToMemory(&pem.Block{
Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(servKey),
})
return servKeyPEM, servCertPEM, caCertificatePEM, nil
}
// getClusterDomainName returns cluster's domain name or an error
// Closes issue: https://github.com/knative/eventing/issues/714
func getClusterDomainName() string {
once.Do(func() {
f, err := os.Open(resolverFileName)
if err != nil {
return
}
defer func() {
if err := f.Close(); err != nil {
log.Error(err, "unable to close", "file", resolverFileName)
}
}()
domainName = getDomainName(f)
})
return domainName
}
func getDomainName(r io.Reader) string {
for scanner := bufio.NewScanner(r); scanner.Scan(); {
elements := strings.Split(scanner.Text(), " ")
if elements[0] != "search" {
continue
}
for _, e := range elements[1:] {
if strings.HasPrefix(e, "svc.") {
return strings.TrimSuffix(e[4:], ".")
}
}
}
// For all abnormal cases return default domain name.
return defaultDomainName
}