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)
}
// getData returns a slice from the data based on the start and size and pads
// up to size with zero's. This function is overflow safe.
func getData(data []byte, start, size *big.Int) []byte {
dlen := big.NewInt(int64(len(data)))
s := common.BigMin(start, dlen)
e := common.BigMin(new(big.Int).Add(s, size), dlen)
return common.RightPadBytes(data[s.Uint64():e.Uint64()], int(size.Uint64()))
}