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certificategen.go
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certificategen.go
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package crypto
import (
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"fmt"
"math/big"
"net"
"time"
)
type certificategenerator struct{}
type CertificateGenerator interface {
GenerateIamAuthSelfSignCertKeyPair() ([]byte, []byte, error)
}
func NewCertificateGenerator() CertificateGenerator {
return &certificategenerator{}
}
func (cg *certificategenerator) GenerateIamAuthSelfSignCertKeyPair() ([]byte, []byte, error) {
bitSize := 2048
privateKey, err := cg.generatePrivateKey(bitSize)
if err != nil || privateKey == nil {
return nil, nil, fmt.Errorf("failed to generate private key for self sign cert: %v", err)
}
notBefore, notAfter := cg.getCertLifeTime()
serialNumber, err := cg.generateCertSerialNumber()
if err != nil {
return nil, nil, fmt.Errorf("failed to generate serial number for self sign cert: %v", err)
}
template := cg.generateAwsIamAuthCertTemplate(serialNumber, notBefore, notAfter)
certBytes, err := cg.generateSelfSignCertificate(template, privateKey)
if err != nil {
return nil, nil, fmt.Errorf("failed to generate certificate for self sign cert: %v", err)
}
keyBytes := cg.encodePrivateKey(privateKey)
return cg.encodeToPEM(certBytes, "CERTIFICATE"), cg.encodeToPEM(keyBytes, "RSA PRIVATE KEY"), nil
}
func (cg *certificategenerator) generatePrivateKey(bitSize int) (*rsa.PrivateKey, error) {
// Private Key generation
privateKey, err := rsa.GenerateKey(rand.Reader, bitSize)
if err != nil {
return nil, err
}
// Validate Private Key
err = privateKey.Validate()
if err != nil {
return nil, err
}
return privateKey, nil
}
func (cg *certificategenerator) getCertLifeTime() (time.Time, time.Time) {
// lifetime of the CA certificate
lifeTime := time.Hour * 24 * 365 * 100
lifeTimeStart := time.Now()
lifeTimeEnd := lifeTimeStart.Add(lifeTime)
return lifeTimeStart, lifeTimeEnd
}
func (cg *certificategenerator) generateCertSerialNumber() (*big.Int, error) {
// choose a random 128 bit serial number
serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
if err != nil {
return nil, err
}
return serialNumber, nil
}
func (cg *certificategenerator) generateAwsIamAuthCertTemplate(serialNumber *big.Int, notBefore, notAfter time.Time) x509.Certificate {
template := x509.Certificate{
SerialNumber: serialNumber,
Subject: pkix.Name{
CommonName: "aws-iam-authenticator",
},
NotBefore: notBefore,
NotAfter: notAfter,
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
BasicConstraintsValid: true,
IsCA: true,
IPAddresses: []net.IP{net.ParseIP("127.0.0.1")},
DNSNames: []string{"localhost"},
}
return template
}
func (cg *certificategenerator) generateSelfSignCertificate(template x509.Certificate, privateKey *rsa.PrivateKey) ([]byte, error) {
certBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &privateKey.PublicKey, privateKey)
if err != nil {
return nil, err
}
return certBytes, nil
}
func (cg *certificategenerator) encodePrivateKey(privateKey *rsa.PrivateKey) []byte {
// ASN.1 DER format
return x509.MarshalPKCS1PrivateKey(privateKey)
}
func (cg *certificategenerator) encodeToPEM(bytes []byte, blockType string) []byte {
block := pem.Block{
Type: blockType,
Headers: nil,
Bytes: bytes,
}
return pem.EncodeToMemory(&block)
}