func ecrecoverFunc(in []byte) []byte {
in = common.RightPadBytes(in, 128)
// "in" is (hash, v, r, s), each 32 bytes
// but for ecrecover we want (r, s, v)
r := common.BytesToBig(in[64:96])
s := common.BytesToBig(in[96:128])
// Treat V as a 256bit integer
vbig := common.Bytes2Big(in[32:64])
v := byte(vbig.Uint64())
if !crypto.ValidateSignatureValues(v, r, s) {
glog.V(logger.Debug).Infof("EC RECOVER FAIL: v, r or s value invalid")
return nil
}
// v needs to be at the end and normalized for libsecp256k1
vbignormal := new(big.Int).Sub(vbig, big.NewInt(27))
vnormal := byte(vbignormal.Uint64())
rsv := append(in[64:128], vnormal)
pubKey, err := crypto.Ecrecover(in[:32], rsv)
// make sure the public key is a valid one
if err != nil {
glog.V(logger.Error).Infof("EC RECOVER FAIL: ", err)
return nil
}
// the first byte of pubkey is bitcoin heritage
return common.LeftPadBytes(crypto.Sha3(pubKey[1:])[12:], 32)
}
func (tx *Transaction) publicKey() ([]byte, error) {
if !crypto.ValidateSignatureValues(tx.data.V, tx.data.R, tx.data.S) {
return nil, ErrInvalidSig
}
// encode the signature in uncompressed format
r, s := tx.data.R.Bytes(), tx.data.S.Bytes()
sig := make([]byte, 65)
copy(sig[32-len(r):32], r)
copy(sig[64-len(s):64], s)
sig[64] = tx.data.V - 27
// recover the public key from the signature
hash := tx.SigHash()
pub, err := crypto.Ecrecover(hash[:], sig)
if err != nil {
glog.V(logger.Error).Infof("Could not get pubkey from signature: ", err)
return nil, err
}
if len(pub) == 0 || pub[0] != 4 {
return nil, errors.New("invalid public key")
}
return pub, nil
}