path: root/vm/address.go

package vm

import (
    "math/big"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/crypto"
)

type Address interface {
    Call(in []byte) []byte
}

type PrecompiledAccount struct {
    Gas func(l int) *big.Int
    fn  func(in []byte) []byte
}

func (self PrecompiledAccount) Call(in []byte) []byte {
    return self.fn(in)
}

var Precompiled = PrecompiledContracts()

// XXX Could set directly. Testing requires resetting and setting of pre compiled contracts.
func PrecompiledContracts() map[string]*PrecompiledAccount {
    return map[string]*PrecompiledAccount{
        // ECRECOVER
        string(common.LeftPadBytes([]byte{1}, 20)): &PrecompiledAccount{func(l int) *big.Int {
            return GasEcrecover
        }, ecrecoverFunc},

        // SHA256
        string(common.LeftPadBytes([]byte{2}, 20)): &PrecompiledAccount{func(l int) *big.Int {
            n := big.NewInt(int64(l+31) / 32)
            n.Mul(n, GasSha256Word)
            return n.Add(n, GasSha256Base)
        }, sha256Func},

        // RIPEMD160
        string(common.LeftPadBytes([]byte{3}, 20)): &PrecompiledAccount{func(l int) *big.Int {
            n := big.NewInt(int64(l+31) / 32)
            n.Mul(n, GasRipemdWord)
            return n.Add(n, GasRipemdBase)
        }, ripemd160Func},

        string(common.LeftPadBytes([]byte{4}, 20)): &PrecompiledAccount{func(l int) *big.Int {
            n := big.NewInt(int64(l+31) / 32)
            n.Mul(n, GasIdentityWord)

            return n.Add(n, GasIdentityBase)
        }, memCpy},
    }
}

func sha256Func(in []byte) []byte {
    return crypto.Sha256(in)
}

func ripemd160Func(in []byte) []byte {
    return common.LeftPadBytes(crypto.Ripemd160(in), 32)
}

const EcRecoverInputLength = 128

func ecrecoverFunc(in []byte) []byte {
    // "in" is (hash, v, r, s), each 32 bytes
    // but for ecrecover we want (r, s, v)
    if len(in) < EcRecoverInputLength {
        return nil
    }
    hash := in[:32]
    // v is only a bit, but comes as 32 bytes from vm. We only need least significant byte
    encodedV := in[32:64]
    v := encodedV[31] - 27
    if !(v == 0 || v == 1) {
        return nil
    }
    sig := append(in[64:], v)
    pubKey := crypto.Ecrecover(append(hash, sig...))
    // secp256.go returns either nil or 65 bytes
    if pubKey == nil || len(pubKey) != 65 {
        return nil
    }
    // the first byte of pubkey is bitcoin heritage
    return common.LeftPadBytes(crypto.Sha3(pubKey[1:])[12:], 32)
}

func memCpy(in []byte) []byte {
    return in
}