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crypto.go
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crypto.go
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// Copyright 2022 Clastix Labs
// SPDX-License-Identifier: Apache-2.0
package crypto
import (
"bytes"
cryptorand "crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"fmt"
"math/big"
mathrand "math/rand"
"time"
"github.com/pkg/errors"
)
// CheckPublicAndPrivateKeyValidity checks if the given bytes for the private and public keys are valid.
func CheckPublicAndPrivateKeyValidity(publicKey []byte, privateKey []byte) (bool, error) {
if len(publicKey) == 0 || len(privateKey) == 0 {
return false, nil
}
pubKey, err := ParsePublicKeyBytes(publicKey)
if err != nil {
return false, err
}
privKey, err := ParsePrivateKeyBytes(privateKey)
if err != nil {
return false, err
}
return checkPublicKeys(privKey.PublicKey, *pubKey), nil
}
// CheckCertificateAndPrivateKeyPairValidity checks if the certificate and private key pair are valid.
func CheckCertificateAndPrivateKeyPairValidity(certificate []byte, privateKey []byte) (bool, error) {
switch {
case len(certificate) == 0, len(privateKey) == 0:
return false, nil
default:
return IsValidCertificateKeyPairBytes(certificate, privateKey)
}
}
// GenerateCertificatePrivateKeyPair starts from the Certificate Authority bytes a certificate using the provided
// template, returning the bytes both for the certificate and its key.
func GenerateCertificatePrivateKeyPair(template *x509.Certificate, caCertificate []byte, caPrivateKey []byte) (*bytes.Buffer, *bytes.Buffer, error) {
caCertBytes, err := ParseCertificateBytes(caCertificate)
if err != nil {
return nil, nil, err
}
caPrivKeyBytes, err := ParsePrivateKeyBytes(caPrivateKey)
if err != nil {
return nil, nil, errors.Wrap(err, "provided CA private key for certificate generation cannot be parsed")
}
return generateCertificateKeyPairBytes(template, caCertBytes, caPrivKeyBytes)
}
// ParseCertificateBytes takes the certificate bytes returning a x509 certificate by parsing it.
func ParseCertificateBytes(content []byte) (*x509.Certificate, error) {
pemContent, _ := pem.Decode(content)
if pemContent == nil {
return nil, fmt.Errorf("no right PEM block")
}
crt, err := x509.ParseCertificate(pemContent.Bytes)
if err != nil {
return nil, errors.Wrap(err, "cannot parse x509 Certificate")
}
return crt, nil
}
// ParsePrivateKeyBytes takes the private key bytes returning an RSA private key by parsing it.
func ParsePrivateKeyBytes(content []byte) (*rsa.PrivateKey, error) {
pemContent, _ := pem.Decode(content)
if pemContent == nil {
return nil, fmt.Errorf("no right PEM block")
}
privateKey, err := x509.ParsePKCS1PrivateKey(pemContent.Bytes)
if err != nil {
return nil, errors.Wrap(err, "cannot parse PKCS1 Private Key")
}
return privateKey, nil
}
// ParsePublicKeyBytes takes the public key bytes returning an RSA public key by parsing it.
func ParsePublicKeyBytes(content []byte) (*rsa.PublicKey, error) {
pemContent, _ := pem.Decode(content)
if pemContent == nil {
return nil, fmt.Errorf("no right PEM block")
}
publicKey, err := x509.ParsePKIXPublicKey(pemContent.Bytes)
if err != nil {
return nil, err
}
rsaPublicKey, ok := publicKey.(*rsa.PublicKey)
if !ok {
return nil, fmt.Errorf("expected *rsa.PublicKey, got %T", rsaPublicKey)
}
return rsaPublicKey, nil
}
// IsValidCertificateKeyPairBytes checks if the certificate matches the private key bounded to it.
func IsValidCertificateKeyPairBytes(certificateBytes []byte, privateKeyBytes []byte) (bool, error) {
crt, err := ParseCertificateBytes(certificateBytes)
if err != nil {
return false, err
}
key, err := ParsePrivateKeyBytes(privateKeyBytes)
if err != nil {
return false, err
}
switch {
case !checkCertificateValidity(*crt):
return false, nil
case !checkPublicKeys(*crt.PublicKey.(*rsa.PublicKey), key.PublicKey): //nolint:forcetypeassert
return false, nil
default:
return true, nil
}
}
func VerifyCertificate(cert, ca []byte, usages ...x509.ExtKeyUsage) (bool, error) {
if len(usages) == 0 {
return false, fmt.Errorf("missing usages for certificate verification")
}
crt, err := ParseCertificateBytes(cert)
if err != nil {
return false, err
}
caCrt, err := ParseCertificateBytes(ca)
if err != nil {
return false, err
}
roots := x509.NewCertPool()
roots.AddCert(caCrt)
chains, err := crt.Verify(x509.VerifyOptions{
Roots: roots,
KeyUsages: usages,
})
return len(chains) > 0, err
}
func generateCertificateKeyPairBytes(template *x509.Certificate, caCert *x509.Certificate, caKey *rsa.PrivateKey) (*bytes.Buffer, *bytes.Buffer, error) {
certPrivKey, err := rsa.GenerateKey(cryptorand.Reader, 2048)
if err != nil {
return nil, nil, errors.Wrap(err, "cannot generate an RSA key")
}
certBytes, err := x509.CreateCertificate(cryptorand.Reader, template, caCert, &certPrivKey.PublicKey, caKey)
if err != nil {
return nil, nil, errors.Wrap(err, "cannot create the certificate")
}
certPEM := &bytes.Buffer{}
if err = pem.Encode(certPEM, &pem.Block{
Type: "CERTIFICATE",
Headers: nil,
Bytes: certBytes,
}); err != nil {
return nil, nil, errors.Wrap(err, "cannot encode the generate certificate bytes")
}
certPrivKeyPEM := &bytes.Buffer{}
if err = pem.Encode(certPrivKeyPEM, &pem.Block{
Type: "RSA PRIVATE KEY",
Headers: nil,
Bytes: x509.MarshalPKCS1PrivateKey(certPrivKey),
}); err != nil {
return nil, nil, errors.Wrap(err, "cannot encode private key")
}
return certPEM, certPrivKeyPEM, nil
}
func checkCertificateValidity(cert x509.Certificate) bool {
now := time.Now()
return now.Before(cert.NotAfter) && now.After(cert.NotBefore)
}
func checkPublicKeys(a rsa.PublicKey, b rsa.PublicKey) bool {
isN := a.N.Cmp(b.N) == 0
isE := a.E == b.E
return isN && isE
}
// NewCertificateTemplate returns the template that must be used to generate a certificate,
// used to perform the authentication against the DataStore.
func NewCertificateTemplate(commonName string) *x509.Certificate {
return &x509.Certificate{
PublicKeyAlgorithm: x509.RSA,
SerialNumber: big.NewInt(mathrand.Int63()),
Subject: pkix.Name{
CommonName: commonName,
Organization: []string{"system:masters"},
},
NotBefore: time.Now(),
NotAfter: time.Now().AddDate(10, 0, 0),
SubjectKeyId: []byte{1, 2, 3, 4, 6},
ExtKeyUsage: []x509.ExtKeyUsage{
x509.ExtKeyUsageClientAuth,
x509.ExtKeyUsageServerAuth,
x509.ExtKeyUsageCodeSigning,
},
KeyUsage: x509.KeyUsageDigitalSignature,
}
}