// VerifySignatureV3 returns nil iff sig is a valid signature, made by this
// public key, of the data hashed into signed. signed is mutated by this call.
func (pk *PublicKeyV3) VerifySignatureV3(signed hash.Hash, sig *SignatureV3) (err error) {
if !pk.CanSign() {
return errors.InvalidArgumentError("public key cannot generate signatures")
}
suffix := make([]byte, 5)
suffix[0] = byte(sig.SigType)
binary.BigEndian.PutUint32(suffix[1:], uint32(sig.CreationTime.Unix()))
signed.Write(suffix)
hashBytes := signed.Sum(nil)
if hashBytes[0] != sig.HashTag[0] || hashBytes[1] != sig.HashTag[1] {
return errors.SignatureError("hash tag doesn't match")
}
if pk.PubKeyAlgo != sig.PubKeyAlgo {
return errors.InvalidArgumentError("public key and signature use different algorithms")
}
switch pk.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
if err = rsa.VerifyPKCS1v15(pk.PublicKey, sig.Hash, hashBytes, sig.RSASignature.bytes); err != nil {
return errors.SignatureError("RSA verification failure")
}
return
default:
// V3 public keys only support RSA.
panic("shouldn't happen")
}
panic("unreachable")
}
// VerifySignature returns nil iff sig is a valid signature, made by this
// public key, of the data hashed into signed. signed is mutated by this call.
func (pk *PublicKey) VerifySignature(signed hash.Hash, sig *Signature) (err error) {
if !pk.CanSign() {
return errors.InvalidArgumentError("public key cannot generate signatures")
}
signed.Write(sig.HashSuffix)
hashBytes := signed.Sum(nil)
// NOTE(maxtaco) 2016-08-22
//
// We used to do this:
//
// if hashBytes[0] != sig.HashTag[0] || hashBytes[1] != sig.HashTag[1] {
// return errors.SignatureError("hash tag doesn't match")
// }
//
// But don't do anything in this case. Some GPGs generate bad
// 2-byte hash prefixes, but GPG also doesn't seem to care on
// import. See BrentMaxwell's key. I think it's safe to disable
// this check!
if pk.PubKeyAlgo != sig.PubKeyAlgo {
return errors.InvalidArgumentError("public key and signature use different algorithms")
}
switch pk.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
rsaPublicKey, _ := pk.PublicKey.(*rsa.PublicKey)
err = rsa.VerifyPKCS1v15(rsaPublicKey, sig.Hash, hashBytes, sig.RSASignature.bytes)
if err != nil {
return errors.SignatureError("RSA verification failure")
}
return nil
case PubKeyAlgoDSA:
dsaPublicKey, _ := pk.PublicKey.(*dsa.PublicKey)
// Need to truncate hashBytes to match FIPS 186-3 section 4.6.
subgroupSize := (dsaPublicKey.Q.BitLen() + 7) / 8
if len(hashBytes) > subgroupSize {
hashBytes = hashBytes[:subgroupSize]
}
if !dsa.Verify(dsaPublicKey, hashBytes, new(big.Int).SetBytes(sig.DSASigR.bytes), new(big.Int).SetBytes(sig.DSASigS.bytes)) {
return errors.SignatureError("DSA verification failure")
}
return nil
case PubKeyAlgoECDSA:
ecdsaPublicKey := pk.PublicKey.(*ecdsa.PublicKey)
if !ecdsa.Verify(ecdsaPublicKey, hashBytes, new(big.Int).SetBytes(sig.ECDSASigR.bytes), new(big.Int).SetBytes(sig.ECDSASigS.bytes)) {
return errors.SignatureError("ECDSA verification failure")
}
return nil
case PubKeyAlgoEdDSA:
if !pk.edk.Verify(hashBytes, sig.EdDSASigR, sig.EdDSASigS) {
return errors.SignatureError("EdDSA verification failure")
}
return nil
default:
return errors.SignatureError("Unsupported public key algorithm used in signature")
}
panic("unreachable")
}
// VerifySignature returns nil iff sig is a valid signature, made by this
// public key, of the data hashed into signed. signed is mutated by this call.
func (pk *PublicKey) VerifySignature(signed hash.Hash, sig *Signature) (err error) {
if !pk.CanSign() {
return errors.InvalidArgumentError("public key cannot generate signatures")
}
signed.Write(sig.HashSuffix)
hashBytes := signed.Sum(nil)
if hashBytes[0] != sig.HashTag[0] || hashBytes[1] != sig.HashTag[1] {
return errors.SignatureError("hash tag doesn't match")
}
if pk.PubKeyAlgo != sig.PubKeyAlgo {
return errors.InvalidArgumentError("public key and signature use different algorithms")
}
switch pk.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
rsaPublicKey, _ := pk.PublicKey.(*rsa.PublicKey)
err = rsa.VerifyPKCS1v15(rsaPublicKey, sig.Hash, hashBytes, sig.RSASignature.bytes)
if err != nil {
return errors.SignatureError("RSA verification failure")
}
return nil
case PubKeyAlgoDSA:
dsaPublicKey, _ := pk.PublicKey.(*dsa.PublicKey)
// Need to truncate hashBytes to match FIPS 186-3 section 4.6.
subgroupSize := (dsaPublicKey.Q.BitLen() + 7) / 8
if len(hashBytes) > subgroupSize {
hashBytes = hashBytes[:subgroupSize]
}
if !dsa.Verify(dsaPublicKey, hashBytes, new(big.Int).SetBytes(sig.DSASigR.bytes), new(big.Int).SetBytes(sig.DSASigS.bytes)) {
return errors.SignatureError("DSA verification failure")
}
return nil
case PubKeyAlgoECDSA:
ecdsaPublicKey := pk.PublicKey.(*ecdsa.PublicKey)
if !ecdsa.Verify(ecdsaPublicKey, hashBytes, new(big.Int).SetBytes(sig.ECDSASigR.bytes), new(big.Int).SetBytes(sig.ECDSASigS.bytes)) {
return errors.SignatureError("ECDSA verification failure")
}
return nil
case PubKeyAlgoEdDSA:
if !pk.edk.Verify(hashBytes, sig.EdDSASigR, sig.EdDSASigS) {
return errors.SignatureError("EdDSA verification failure")
}
return nil
default:
return errors.SignatureError("Unsupported public key algorithm used in signature")
}
panic("unreachable")
}
// VerifySignatureV3 returns nil iff sig is a valid signature, made by this
// public key, of the data hashed into signed. signed is mutated by this call.
func (pk *PublicKey) VerifySignatureV3(signed hash.Hash, sig *SignatureV3) (err error) {
if !pk.CanSign() {
return errors.InvalidArgumentError("public key cannot generate signatures")
}
suffix := make([]byte, 5)
suffix[0] = byte(sig.SigType)
binary.BigEndian.PutUint32(suffix[1:], uint32(sig.CreationTime.Unix()))
signed.Write(suffix)
hashBytes := signed.Sum(nil)
if hashBytes[0] != sig.HashTag[0] || hashBytes[1] != sig.HashTag[1] {
return errors.SignatureError("hash tag doesn't match")
}
if pk.PubKeyAlgo != sig.PubKeyAlgo {
return errors.InvalidArgumentError("public key and signature use different algorithms")
}
switch pk.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
rsaPublicKey := pk.PublicKey.(*rsa.PublicKey)
if err = rsa.VerifyPKCS1v15(rsaPublicKey, sig.Hash, hashBytes, sig.RSASignature.bytes); err != nil {
return errors.SignatureError("RSA verification failure")
}
return
case PubKeyAlgoDSA:
dsaPublicKey := pk.PublicKey.(*dsa.PublicKey)
// Need to truncate hashBytes to match FIPS 186-3 section 4.6.
subgroupSize := (dsaPublicKey.Q.BitLen() + 7) / 8
if len(hashBytes) > subgroupSize {
hashBytes = hashBytes[:subgroupSize]
}
if !dsa.Verify(dsaPublicKey, hashBytes, new(big.Int).SetBytes(sig.DSASigR.bytes), new(big.Int).SetBytes(sig.DSASigS.bytes)) {
return errors.SignatureError("DSA verification failure")
}
return nil
default:
panic("shouldn't happen")
}
panic("unreachable")
}