github.com/myafeier/go-ethereum@v1.6.8-0.20170719123245-3e0dbe0eaa72/core/vm/contracts.go (about)

     1  // Copyright 2014 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package vm
    18  
    19  import (
    20  	"crypto/sha256"
    21  	"errors"
    22  	"math/big"
    23  
    24  	"github.com/ethereum/go-ethereum/common"
    25  	"github.com/ethereum/go-ethereum/crypto"
    26  	"github.com/ethereum/go-ethereum/params"
    27  	"golang.org/x/crypto/ripemd160"
    28  )
    29  
    30  var errBadPrecompileInput = errors.New("bad pre compile input")
    31  
    32  // Precompiled contract is the basic interface for native Go contracts. The implementation
    33  // requires a deterministic gas count based on the input size of the Run method of the
    34  // contract.
    35  type PrecompiledContract interface {
    36  	RequiredGas(input []byte) uint64  // RequiredPrice calculates the contract gas use
    37  	Run(input []byte) ([]byte, error) // Run runs the precompiled contract
    38  }
    39  
    40  // PrecompiledContracts contains the default set of ethereum contracts
    41  var PrecompiledContracts = map[common.Address]PrecompiledContract{
    42  	common.BytesToAddress([]byte{1}): &ecrecover{},
    43  	common.BytesToAddress([]byte{2}): &sha256hash{},
    44  	common.BytesToAddress([]byte{3}): &ripemd160hash{},
    45  	common.BytesToAddress([]byte{4}): &dataCopy{},
    46  }
    47  
    48  // RunPrecompile runs and evaluate the output of a precompiled contract defined in contracts.go
    49  func RunPrecompiledContract(p PrecompiledContract, input []byte, contract *Contract) (ret []byte, err error) {
    50  	gas := p.RequiredGas(input)
    51  	if contract.UseGas(gas) {
    52  		return p.Run(input)
    53  	} else {
    54  		return nil, ErrOutOfGas
    55  	}
    56  }
    57  
    58  // ECRECOVER implemented as a native contract
    59  type ecrecover struct{}
    60  
    61  func (c *ecrecover) RequiredGas(input []byte) uint64 {
    62  	return params.EcrecoverGas
    63  }
    64  
    65  func (c *ecrecover) Run(in []byte) ([]byte, error) {
    66  	const ecRecoverInputLength = 128
    67  
    68  	in = common.RightPadBytes(in, ecRecoverInputLength)
    69  	// "in" is (hash, v, r, s), each 32 bytes
    70  	// but for ecrecover we want (r, s, v)
    71  
    72  	r := new(big.Int).SetBytes(in[64:96])
    73  	s := new(big.Int).SetBytes(in[96:128])
    74  	v := in[63] - 27
    75  
    76  	// tighter sig s values in homestead only apply to tx sigs
    77  	if !allZero(in[32:63]) || !crypto.ValidateSignatureValues(v, r, s, false) {
    78  		return nil, nil
    79  	}
    80  	// v needs to be at the end for libsecp256k1
    81  	pubKey, err := crypto.Ecrecover(in[:32], append(in[64:128], v))
    82  	// make sure the public key is a valid one
    83  	if err != nil {
    84  		return nil, nil
    85  	}
    86  
    87  	// the first byte of pubkey is bitcoin heritage
    88  	return common.LeftPadBytes(crypto.Keccak256(pubKey[1:])[12:], 32), nil
    89  }
    90  
    91  // SHA256 implemented as a native contract
    92  type sha256hash struct{}
    93  
    94  // RequiredGas returns the gas required to execute the pre-compiled contract.
    95  //
    96  // This method does not require any overflow checking as the input size gas costs
    97  // required for anything significant is so high it's impossible to pay for.
    98  func (c *sha256hash) RequiredGas(input []byte) uint64 {
    99  	return uint64(len(input)+31)/32*params.Sha256WordGas + params.Sha256Gas
   100  }
   101  func (c *sha256hash) Run(in []byte) ([]byte, error) {
   102  	h := sha256.Sum256(in)
   103  	return h[:], nil
   104  }
   105  
   106  // RIPMED160 implemented as a native contract
   107  type ripemd160hash struct{}
   108  
   109  // RequiredGas returns the gas required to execute the pre-compiled contract.
   110  //
   111  // This method does not require any overflow checking as the input size gas costs
   112  // required for anything significant is so high it's impossible to pay for.
   113  func (c *ripemd160hash) RequiredGas(input []byte) uint64 {
   114  	return uint64(len(input)+31)/32*params.Ripemd160WordGas + params.Ripemd160Gas
   115  }
   116  func (c *ripemd160hash) Run(in []byte) ([]byte, error) {
   117  	ripemd := ripemd160.New()
   118  	ripemd.Write(in)
   119  	return common.LeftPadBytes(ripemd.Sum(nil), 32), nil
   120  }
   121  
   122  // data copy implemented as a native contract
   123  type dataCopy struct{}
   124  
   125  // RequiredGas returns the gas required to execute the pre-compiled contract.
   126  //
   127  // This method does not require any overflow checking as the input size gas costs
   128  // required for anything significant is so high it's impossible to pay for.
   129  func (c *dataCopy) RequiredGas(input []byte) uint64 {
   130  	return uint64(len(input)+31)/32*params.IdentityWordGas + params.IdentityGas
   131  }
   132  func (c *dataCopy) Run(in []byte) ([]byte, error) {
   133  	return in, nil
   134  }