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triple.go
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triple.go
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/*
Copyright 2016 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 triple generates key-certificate pairs for the
// triple (CA, Server, Client).
package triple
import (
"crypto"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"errors"
"fmt"
"math"
"math/big"
"net"
"time"
certutil "k8s.io/client-go/util/cert"
)
const (
rsaKeySize = 2048
duration365d = time.Hour * 24 * 365
certificateBlockType = "CERTIFICATE"
RSAPrivateKeyBlockType = "RSA PRIVATE KEY"
// ECPrivateKeyBlockType is a possible value for pem.Block.Type.
ECPrivateKeyBlockType = "EC PRIVATE KEY"
PrivateKeyBlockType = "PRIVATE KEY"
CertificateBlockType = "CERTIFICATE"
)
type KeyPair struct {
Key *rsa.PrivateKey
Cert *x509.Certificate
}
func NewCA(name string) (*KeyPair, error) {
key, err := newPrivateKey()
if err != nil {
return nil, fmt.Errorf("unable to create a private key for a new CA: %w", err)
}
config := certutil.Config{
CommonName: name,
}
cert, err := certutil.NewSelfSignedCACert(config, key)
if err != nil {
return nil, fmt.Errorf("unable to create a self-signed certificate for a new CA: %w", err)
}
return &KeyPair{
Key: key,
Cert: cert,
}, nil
}
func NewServerKeyPair(ca *KeyPair, commonName, svcName, svcNamespace, dnsDomain string, ips, hostnames []string) (*KeyPair, error) {
key, err := newPrivateKey()
if err != nil {
return nil, fmt.Errorf("unable to create a server private key: %w", err)
}
namespacedName := fmt.Sprintf("%s.%s", svcName, svcNamespace)
internalAPIServerFQDN := []string{
svcName,
namespacedName,
fmt.Sprintf("%s.svc", namespacedName),
fmt.Sprintf("%s.svc.%s", namespacedName, dnsDomain),
}
altNames := certutil.AltNames{}
for _, ipStr := range ips {
ip := net.ParseIP(ipStr)
if ip != nil {
altNames.IPs = append(altNames.IPs, ip)
}
}
altNames.DNSNames = append(altNames.DNSNames, hostnames...)
altNames.DNSNames = append(altNames.DNSNames, internalAPIServerFQDN...)
config := certutil.Config{
CommonName: commonName,
AltNames: altNames,
Usages: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
}
cert, err := newSignedCert(config, key, ca.Cert, ca.Key)
if err != nil {
return nil, fmt.Errorf("unable to sign the server certificate: %w", err)
}
return &KeyPair{
Key: key,
Cert: cert,
}, nil
}
func NewClientKeyPair(ca *KeyPair, commonName string, organizations []string) (*KeyPair, error) {
key, err := newPrivateKey()
if err != nil {
return nil, fmt.Errorf("unable to create a client private key: %w", err)
}
config := certutil.Config{
CommonName: commonName,
Organization: organizations,
Usages: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
}
cert, err := newSignedCert(config, key, ca.Cert, ca.Key)
if err != nil {
return nil, fmt.Errorf("unable to sign the client certificate: %w", err)
}
return &KeyPair{
Key: key,
Cert: cert,
}, nil
}
// newPrivateKey creates an RSA private key.
func newPrivateKey() (*rsa.PrivateKey, error) {
return rsa.GenerateKey(rand.Reader, rsaKeySize)
}
// newSignedCert creates a signed certificate using the given CA certificate and key.
func newSignedCert(cfg certutil.Config, key crypto.Signer, caCert *x509.Certificate, caKey crypto.Signer) (*x509.Certificate, error) {
serial, err := rand.Int(rand.Reader, new(big.Int).SetInt64(math.MaxInt64))
if err != nil {
return nil, err
}
if len(cfg.CommonName) == 0 {
return nil, errors.New("must specify a CommonName")
}
if len(cfg.Usages) == 0 {
return nil, errors.New("must specify at least one ExtKeyUsage")
}
certTmpl := x509.Certificate{
Subject: pkix.Name{
CommonName: cfg.CommonName,
Organization: cfg.Organization,
},
DNSNames: cfg.AltNames.DNSNames,
IPAddresses: cfg.AltNames.IPs,
SerialNumber: serial,
NotBefore: caCert.NotBefore,
NotAfter: time.Now().Add(duration365d).UTC(),
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
ExtKeyUsage: cfg.Usages,
}
certDERBytes, err := x509.CreateCertificate(rand.Reader, &certTmpl, caCert, key.Public(), caKey)
if err != nil {
return nil, err
}
return x509.ParseCertificate(certDERBytes)
}
func ParseRSAKeyPair(certPEM, keyPEM []byte) (*KeyPair, error) {
certs, err := certutil.ParseCertsPEM(certPEM)
if err != nil {
return nil, fmt.Errorf("certificate is not valid PEM: %w", err)
}
if len(certs) != 1 {
return nil, fmt.Errorf("did not find exactly one but %v certificates", len(certs))
}
key, err := ParsePrivateKeyPEM(keyPEM)
if err != nil {
return nil, fmt.Errorf("private key is not valid PEM: %w", err)
}
rsaKey, isRSAKey := key.(*rsa.PrivateKey)
if !isRSAKey {
return nil, errors.New("private key is not a RSA key")
}
return &KeyPair{Cert: certs[0], Key: rsaKey}, nil
}
// EncodeCertPEM returns PEM-endcoded certificate data.
func EncodeCertPEM(cert *x509.Certificate) []byte {
block := pem.Block{
Type: certificateBlockType,
Bytes: cert.Raw,
}
return pem.EncodeToMemory(&block)
}
// EncodePrivateKeyPEM returns PEM-encoded private key data.
func EncodePrivateKeyPEM(key *rsa.PrivateKey) []byte {
block := pem.Block{
Type: RSAPrivateKeyBlockType,
Bytes: x509.MarshalPKCS1PrivateKey(key),
}
return pem.EncodeToMemory(&block)
}
// ParsePrivateKeyPEM returns a private key parsed from a PEM block in the supplied data.
// Recognizes PEM blocks for "EC PRIVATE KEY", "RSA PRIVATE KEY", or "PRIVATE KEY".
func ParsePrivateKeyPEM(keyData []byte) (interface{}, error) {
var privateKeyPemBlock *pem.Block
for {
privateKeyPemBlock, keyData = pem.Decode(keyData)
if privateKeyPemBlock == nil {
break
}
switch privateKeyPemBlock.Type {
case ECPrivateKeyBlockType:
// ECDSA Private Key in ASN.1 format
if key, err := x509.ParseECPrivateKey(privateKeyPemBlock.Bytes); err == nil {
return key, nil
}
case RSAPrivateKeyBlockType:
// RSA Private Key in PKCS#1 format
if key, err := x509.ParsePKCS1PrivateKey(privateKeyPemBlock.Bytes); err == nil {
return key, nil
}
case PrivateKeyBlockType:
// RSA or ECDSA Private Key in unencrypted PKCS#8 format
if key, err := x509.ParsePKCS8PrivateKey(privateKeyPemBlock.Bytes); err == nil {
return key, nil
}
}
// tolerate non-key PEM blocks for compatibility with things like "EC PARAMETERS" blocks
// originally, only the first PEM block was parsed and expected to be a key block
}
// we read all the PEM blocks and didn't recognize one
return nil, fmt.Errorf("data does not contain a valid RSA or ECDSA private key")
}
// ParseCertsPEM returns the x509.Certificates contained in the given PEM-encoded byte array
// Returns an error if a certificate could not be parsed, or if the data does not contain any certificates.
func ParseCertsPEM(pemCerts []byte) ([]*x509.Certificate, error) {
ok := false
certs := []*x509.Certificate{}
for len(pemCerts) > 0 {
var block *pem.Block
block, pemCerts = pem.Decode(pemCerts)
if block == nil {
break
}
// Only use PEM "CERTIFICATE" blocks without extra headers
if block.Type != CertificateBlockType || len(block.Headers) != 0 {
continue
}
cert, err := x509.ParseCertificate(block.Bytes)
if err != nil {
return certs, err
}
certs = append(certs, cert)
ok = true
}
if !ok {
return certs, errors.New("data does not contain any valid RSA or ECDSA certificates")
}
return certs, nil
}
// NewPrivateKey creates an RSA private key.
func NewPrivateKey() (*rsa.PrivateKey, error) {
return rsa.GenerateKey(rand.Reader, rsaKeySize)
}
// NewSignedCert creates a signed certificate using the given CA certificate and key.
func NewSignedCert(cfg certutil.Config, key crypto.Signer, caCert *x509.Certificate, caKey crypto.Signer) (*x509.Certificate, error) {
serial, err := rand.Int(rand.Reader, new(big.Int).SetInt64(math.MaxInt64))
if err != nil {
return nil, err
}
if len(cfg.CommonName) == 0 {
return nil, errors.New("must specify a CommonName")
}
if len(cfg.Usages) == 0 {
return nil, errors.New("must specify at least one ExtKeyUsage")
}
certTmpl := x509.Certificate{
Subject: pkix.Name{
CommonName: cfg.CommonName,
Organization: cfg.Organization,
},
DNSNames: cfg.AltNames.DNSNames,
IPAddresses: cfg.AltNames.IPs,
SerialNumber: serial,
NotBefore: caCert.NotBefore,
NotAfter: time.Now().Add(duration365d).UTC(),
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
ExtKeyUsage: cfg.Usages,
}
certDERBytes, err := x509.CreateCertificate(rand.Reader, &certTmpl, caCert, key.Public(), caKey)
if err != nil {
return nil, err
}
return x509.ParseCertificate(certDERBytes)
}