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self_sign_certificate.go
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self_sign_certificate.go
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package selfsigned
import (
"context"
"crypto"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"fmt"
"math/big"
"time"
"open-cluster-management.io/cluster-proxy/pkg/common"
openshiftcrypto "github.com/openshift/library-go/pkg/crypto"
"github.com/pkg/errors"
apierrors "k8s.io/apimachinery/pkg/api/errors"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/util/cert"
)
var (
rsaKeySize = 2048 // a decent number, as of 2019
bigOne = big.NewInt(1)
)
type CertRotation interface {
EnsureTargetCertKeyPair(signingCertKeyPair *openshiftcrypto.CA, caBundleCerts []*x509.Certificate, fns ...openshiftcrypto.CertificateExtensionFunc) error
}
type SelfSigner interface {
Sign(cfg cert.Config, expiry time.Duration) (CertPair, error)
CAData() []byte
GetSigner() crypto.Signer
CA() *openshiftcrypto.CA
}
var _ SelfSigner = &selfSigner{}
type selfSigner struct {
caCert *x509.Certificate
caKey crypto.Signer
nextSerial *big.Int
}
func NewSelfSignerFromSecretOrGenerate(c kubernetes.Interface, secretNamespace, secretName string) (SelfSigner, error) {
shouldGenerate := false
caSecret, err := c.CoreV1().Secrets(secretNamespace).Get(context.TODO(), secretName, metav1.GetOptions{})
if err != nil {
if !apierrors.IsNotFound(err) {
return nil, errors.Wrapf(err, "failed to read ca from secret %v/%v", secretNamespace, secretName)
}
shouldGenerate = true
}
if !shouldGenerate {
return NewSelfSignerWithCAData(caSecret.Data[TLSCACert], caSecret.Data[TLSCAKey])
}
generatedSigner, err := NewGeneratedSelfSigner()
if err != nil {
return nil, errors.Wrapf(err, "failed to generate new self-signer")
}
rawKeyData, err := x509.MarshalPKCS8PrivateKey(generatedSigner.GetSigner())
if err != nil {
return nil, err
}
caKeyData := pem.EncodeToMemory(&pem.Block{
Type: "PRIVATE KEY",
Bytes: rawKeyData,
})
isAlreadyExists, err := DumpCASecret(c,
secretNamespace, secretName,
generatedSigner.CAData(), caKeyData)
if err != nil {
return nil, errors.Wrapf(err, "failed to dump generated ca secret %v/%v", secretNamespace, secretName)
}
if isAlreadyExists {
return NewSelfSignerFromSecretOrGenerate(c, secretNamespace, secretName)
}
return generatedSigner, nil
}
func NewGeneratedSelfSigner() (SelfSigner, error) {
privateKey, err := rsa.GenerateKey(rand.Reader, rsaKeySize)
if err != nil {
return nil, err
}
caCert, err := cert.NewSelfSignedCACert(cert.Config{
CommonName: common.AddonFullName,
}, privateKey)
if err != nil {
return nil, err
}
return NewSelfSignerWithCA(caCert, privateKey, big.NewInt(1))
}
func NewSelfSignerWithCAData(caCertData, caKeyData []byte) (SelfSigner, error) {
certBlock, _ := pem.Decode(caCertData)
caCert, err := x509.ParseCertificate(certBlock.Bytes)
if err != nil {
return nil, errors.Wrapf(err, "failed to parse ca certificate")
}
keyBlock, _ := pem.Decode(caKeyData)
caKey, err := x509.ParsePKCS8PrivateKey(keyBlock.Bytes)
if err != nil {
return nil, errors.Wrapf(err, "failed to parse ca key")
}
next := big.NewInt(0)
next.Add(caCert.SerialNumber, big.NewInt(1))
return NewSelfSignerWithCA(caCert, caKey.(*rsa.PrivateKey), next)
}
func NewSelfSignerWithCA(caCert *x509.Certificate, caKey *rsa.PrivateKey, nextSerial *big.Int) (SelfSigner, error) {
return &selfSigner{
caCert: caCert,
caKey: caKey,
nextSerial: nextSerial,
}, nil
}
func (s selfSigner) Sign(cfg cert.Config, expiry time.Duration) (CertPair, error) {
now := time.Now()
key, err := rsa.GenerateKey(rand.Reader, rsaKeySize)
if err != nil {
return CertPair{}, fmt.Errorf("unable to create private key: %v", err)
}
serial := new(big.Int).Set(s.nextSerial)
s.nextSerial.Add(s.nextSerial, bigOne)
template := x509.Certificate{
Subject: pkix.Name{CommonName: cfg.CommonName, Organization: cfg.Organization},
DNSNames: cfg.AltNames.DNSNames,
IPAddresses: cfg.AltNames.IPs,
SerialNumber: serial,
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
ExtKeyUsage: cfg.Usages,
NotBefore: now.UTC(),
NotAfter: now.Add(expiry).UTC(),
}
certRaw, err := x509.CreateCertificate(rand.Reader, &template, s.caCert, key.Public(), s.caKey)
if err != nil {
return CertPair{}, fmt.Errorf("unable to create certificate: %v", err)
}
certificate, err := x509.ParseCertificate(certRaw)
if err != nil {
return CertPair{}, fmt.Errorf("generated invalid certificate, could not parse: %v", err)
}
return CertPair{
Key: key,
Cert: certificate,
}, nil
}
func (s selfSigner) CAData() []byte {
return pem.EncodeToMemory(&pem.Block{
Type: "CERTIFICATE",
Bytes: s.caCert.Raw,
})
}
func (s selfSigner) GetSigner() crypto.Signer {
return s.caKey
}
func (s selfSigner) CA() *openshiftcrypto.CA {
return &openshiftcrypto.CA{
Config: &openshiftcrypto.TLSCertificateConfig{
Certs: []*x509.Certificate{s.caCert},
Key: s.caKey,
},
SerialGenerator: &openshiftcrypto.RandomSerialGenerator{},
}
}
type CertPair struct {
Key crypto.Signer
Cert *x509.Certificate
}
func (k CertPair) CertBytes() []byte {
return pem.EncodeToMemory(&pem.Block{
Type: "CERTIFICATE",
Bytes: k.Cert.Raw,
})
}
func (k CertPair) AsBytes() (cert []byte, key []byte, err error) {
cert = k.CertBytes()
rawKeyData, err := x509.MarshalPKCS8PrivateKey(k.Key)
if err != nil {
return nil, nil, fmt.Errorf("unable to encode private key: %v", err)
}
key = pem.EncodeToMemory(&pem.Block{
Type: "PRIVATE KEY",
Bytes: rawKeyData,
})
return cert, key, nil
}