// Verify does the actual check.
func (v ECDSAVerifier) Verify(key data.Key, sig []byte, msg []byte) error {
algorithm := key.Algorithm()
var pubKey crypto.PublicKey
switch algorithm {
case data.ECDSAx509Key:
pemCert, _ := pem.Decode([]byte(key.Public()))
if pemCert == nil {
logrus.Infof("failed to decode PEM-encoded x509 certificate for keyID: %s", key.ID())
logrus.Debugf("certificate bytes: %s", string(key.Public()))
return ErrInvalid
}
cert, err := x509.ParseCertificate(pemCert.Bytes)
if err != nil {
logrus.Infof("failed to parse x509 certificate: %s\n", err)
return ErrInvalid
}
pubKey = cert.PublicKey
case data.ECDSAKey:
var err error
pubKey, err = x509.ParsePKIXPublicKey(key.Public())
if err != nil {
logrus.Infof("Failed to parse private key for keyID: %s, %s\n", key.ID(), err)
return ErrInvalid
}
default:
logrus.Infof("invalid key type for ECDSA verifier: %s", algorithm)
return ErrInvalid
}
ecdsaPubKey, ok := pubKey.(*ecdsa.PublicKey)
if !ok {
logrus.Infof("value isn't an ECDSA public key")
return ErrInvalid
}
sigLength := len(sig)
expectedOctetLength := 2 * ((ecdsaPubKey.Params().BitSize + 7) >> 3)
if sigLength != expectedOctetLength {
logrus.Infof("signature had an unexpected length")
return ErrInvalid
}
rBytes, sBytes := sig[:sigLength/2], sig[sigLength/2:]
r := new(big.Int).SetBytes(rBytes)
s := new(big.Int).SetBytes(sBytes)
digest := sha256.Sum256(msg)
if !ecdsa.Verify(ecdsaPubKey, digest[:], r, s) {
logrus.Infof("failed ECDSA signature validation")
return ErrInvalid
}
return nil
}
