ethereum_ecrecover_native_contract.go

ethereum_ecrecover_native_contract.go

// ECRECOVER implemented as a native contract.
type ecrecover struct{}

func (c *ecrecover) RequiredGas(input []byte) uint64 {
  return params.EcrecoverGas
}

func (c *ecrecover) Run(input []byte) ([]byte, error) {
  const ecRecoverInputLength = 128

  input = common.RightPadBytes(input, ecRecoverInputLength)
  // "input" is (hash, v, r, s), each 32 bytes
  // but for ecrecover we want (r, s, v)

  r := new(big.Int).SetBytes(input[64:96])
  s := new(big.Int).SetBytes(input[96:128])
  v := input[63] - 27

  // tighter sig s values input homestead only apply to tx sigs
  if !allZero(input[32:63]) || !crypto.ValidateSignatureValues(v, r, s, false) {
  return nil, nil
  }
  // v needs to be at the end for libsecp256k1
  pubKey, err := crypto.Ecrecover(input[:32], append(input[64:128], v))
  // make sure the public key is a valid one
  if err != nil {
  return nil, nil
  }

  // the first byte of pubkey is bitcoin heritage
  return common.LeftPadBytes(crypto.Keccak256(pubKey[1:])[12:], 32), nil
}