Re-entrancy

Goal

Drain the Reentrance contract's ETH balance.

Your task

Read Reentrance.sol, then complete Exploit.s.sol.

:~/targets/ethernaut-reentrance$

// SPDX-License-Identifier: MIT
pragma solidity ^0.6.12;

import "openzeppelin-contracts-06/math/SafeMath.sol";

contract Reentrance {
    using SafeMath for uint256;
    mapping(address => uint256) public balances;

    function donate(address _to) public payable {
        balances[_to] = balances[_to].add(msg.value);
    }

    function withdraw(uint256 _amount) public {
        if (balances[msg.sender] >= _amount) {
            (bool result,) = msg.sender.call{value: _amount}("");
            if (result) {
                _amount;
            }
            balances[msg.sender] -= _amount;
        }
    }

    receive() external payable {}
}

Starter exploit

Exploit.s.sol

Read-only

// Already wired up for you - do NOT add imports or a contract wrapper:
//   reentranceInstance -> the deployed Reentrance contract
//   PLAYER_PRIVATE_KEY / PLAYER_ADDRESS -> your key and address
// Write only the code below.

contract HelperContract {
    // TODO: implement the exploit.
}

function run() external {
    vm.startBroadcast(PLAYER_PRIVATE_KEY);

    // TODO: implement the exploit.

    vm.stopBroadcast();
}

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Re-entrancy

Goal

Your task

Re-entrancy

Exploit.s.sol

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