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MEVBriber.sol
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//SPDX-License-Identifier: MIT
pragma solidity ^0.7.3;
pragma experimental ABIEncoderV2;
import "./FlashbotsCheckAndSend.sol";
import "./interface/IWETH.sol";
import "@openzeppelin/contracts/utils/Counters.sol";
import "@openzeppelin/contracts/cryptography/ECDSA.sol";
import "@openzeppelin/contracts/drafts/EIP712.sol";
/*
Copyright 2021 Kendrick Tan (kendricktrh@gmail.com).
This contract is an extension of flashbot's FlashbotsCheckAndSend.sol
This contract takes in WETH instead of ETH so that transactions can be signed via a browser.
But needs to be approved beforehand.
*/
contract MEVBriber is FlashbotsCheckAndSend, EIP712 {
using Counters for Counters.Counter;
constructor() EIP712("MEVBriber", "1") {}
IWETH public constant WETH =
IWETH(0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2);
event Bribed(address indexed briber, address indexed miner, uint256 amount);
bytes32 public constant PERMIT_TYPEHASH =
keccak256(
"Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"
);
mapping(address => Counters.Counter) private _nonces;
receive() external payable {}
function check32BytesAndSendWETH(
address _owner,
address _spender,
uint256 _value,
uint256 _deadline,
uint8 _v,
bytes32 _r,
bytes32 _s,
address _target,
bytes memory _payload,
bytes32 _resultMatch
) external {
briberPermitted(_owner, _spender, _value, _deadline, _v, _r, _s);
_check32Bytes(_target, _payload, _resultMatch);
WETH.transferFrom(_owner, address(this), _value);
WETH.withdraw(_value);
block.coinbase.transfer(_value);
emit Bribed(_owner, block.coinbase, _value);
}
function check32BytesAndSendMultiWETH(
address _owner,
address _spender,
uint256 _value,
uint256 _deadline,
uint8 _v,
bytes32 _r,
bytes32 _s,
address[] memory _targets,
bytes[] memory _payloads,
bytes32[] memory _resultMatches
) external {
require(_targets.length == _payloads.length);
require(_targets.length == _resultMatches.length);
briberPermitted(_owner, _spender, _value, _deadline, _v, _r, _s);
for (uint256 i = 0; i < _targets.length; i++) {
_check32Bytes(_targets[i], _payloads[i], _resultMatches[i]);
}
WETH.transferFrom(_owner, address(this), _value);
WETH.withdraw(_value);
block.coinbase.transfer(_value);
emit Bribed(_owner, block.coinbase, _value);
}
function checkBytesAndSendWETH(
address _owner,
address _spender,
uint256 _value,
uint256 _deadline,
uint8 _v,
bytes32 _r,
bytes32 _s,
address _target,
bytes memory _payload,
bytes memory _resultMatch
) external {
briberPermitted(_owner, _spender, _value, _deadline, _v, _r, _s);
_checkBytes(_target, _payload, _resultMatch);
WETH.transferFrom(_owner, address(this), _value);
WETH.withdraw(_value);
block.coinbase.transfer(_value);
emit Bribed(_owner, block.coinbase, _value);
}
function checkBytesAndSendMultiWETH(
address _owner,
address _spender,
uint256 _value,
uint256 _deadline,
uint8 _v,
bytes32 _r,
bytes32 _s,
address[] memory _targets,
bytes[] memory _payloads,
bytes[] memory _resultMatches
) external {
require(_targets.length == _payloads.length);
require(_targets.length == _resultMatches.length);
briberPermitted(_owner, _spender, _value, _deadline, _v, _r, _s);
for (uint256 i = 0; i < _targets.length; i++) {
_checkBytes(_targets[i], _payloads[i], _resultMatches[i]);
}
WETH.transferFrom(_owner, address(this), _value);
WETH.withdraw(_value);
block.coinbase.transfer(_value);
emit Bribed(_owner, block.coinbase, _value);
}
// Briber permit functionality
function briberPermitted(
address owner,
address spender,
uint256 value,
uint256 deadline,
uint8 v,
bytes32 r,
bytes32 s
) public {
// solhint-disable-next-line not-rely-on-time
require(block.timestamp <= deadline, "ERC20Permit: expired deadline");
bytes32 structHash =
keccak256(
abi.encode(
PERMIT_TYPEHASH,
owner,
spender,
value,
_nonces[owner].current(),
deadline
)
);
bytes32 hash = _hashTypedDataV4(structHash);
address signer = ECDSA.recover(hash, v, r, s);
require(signer == owner, "ERC20Permit: invalid signature");
require(spender == address(this), "ERC20Permit: invalid signature");
_nonces[owner].increment();
}
// **** Helpers ****
function nonces(address owner) public view virtual returns (uint256) {
return _nonces[owner].current();
}
}