# 26. DoubleEntryPoint

By [xwal](https://paragraph.com/@xwave) · 2022-05-07

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Difficulty: 4/10

Level: [https://ethernaut.openzeppelin.com/level/0x128BA32Ec698610f2fF8f010A7b74f9985a6D17c](https://ethernaut.openzeppelin.com/level/0x128BA32Ec698610f2fF8f010A7b74f9985a6D17c)

先看通关介绍：

该合约具有 Forta 合约，任何用户都可以在其中注册自己的检测机器人合约。 Forta 是一个去中心化的、基于社区的监控网络，用于尽快检测 DeFi、NFT、治理、桥梁和其他 Web3 系统上的威胁和异常。您的工作是实施检测机器人并将其注册到 Forta 合同中。机器人的实施将需要发出正确的警报，以防止潜在的攻击或漏洞利用。

按 Get new instance 开始闯关。MetaMask 会弹出交易请求，确认以部署关卡合约，关卡正式开始。

创建 Bot 合约
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1.  打开 Remix IDE: [https://remix.ethereum.org/](https://www.youtube.com/redirect?event=video_description&redir_token=QUFFLUhqbWdtMTk1UGRpRnRGMUN3Tm1EX1ZWallTTXVmZ3xBQ3Jtc0trUWlwMnQxbzRkZUlSTVdzbVZsaHQwRkp4cmJtSnAtMmpLY3RtcHUtNXBEWDYxNFRkdDVvWGNwU2hjd3JzbVc3b3Z2MkF5TW9xLWl4OFdJd1RsTTZ4Zm1PY00taDFtTFNGbGJ6Y2wzTFpvODV5Rm5VVQ&q=https%3A%2F%2Fremix.ethereum.org%2F&v=M7Sv7I9hF70) 创建 workspace。
    
2.  新建 `Bot.sol` 文件
    
3.  拷贝代码到 `Bot.sol`
    
        pragma solidity 0.8.7;
        
        interface IDetectionBot {
            function handleTransaction(address user, bytes calldata msgData) external;
        }
        
        interface IForta {
            function setDetectionBot(address detectionBotAddress) external;
            function notify(address user, bytes calldata msgData) external;
            function raiseAlert(address user) external;
        }
        
        contract Bot is IDetectionBot {
        
            address fortaContract = 0xD386F824FabC0bB1e85a2AD1D24642C9BaAa231A; // 通过 await contract.forta() 获得
        
            function handleTransaction(address user, bytes calldata msgData) override external {
                require(msg.sender == fortaContract);
                IForta(fortaContract).raiseAlert(user);
            }
        
        }
        
    
4.  编译，部署。
    
    1.  在 `Solidity compiler` 中选择 `Compile Bot.sol`
        
    2.  在 `DEPLOY & RUN TRANSACTIONS` 中 `ENVIRONMENT` 中选择 `Injected Web3` ，选择 `CONTRACT` 为 `Bot.sol`。
        
    3.  部署完成后，会在下方显示 `Deployed Contracts`。
        

交互 Forta 合约
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1.  新建 `Forta.sol` 文件
    
2.  拷贝代码到 `Forta.sol`
    
        pragma solidity 0.8.7;
        
        interface IDetectionBot {
            function handleTransaction(address user, bytes calldata msgData) external;
        }
        
        interface IForta {
            function setDetectionBot(address detectionBotAddress) external;
            function notify(address user, bytes calldata msgData) external;
            function raiseAlert(address user) external;
        }
        
        contract Forta is IForta {
          mapping(address => IDetectionBot) public usersDetectionBots;
          mapping(address => uint256) public botRaisedAlerts;
        
          function setDetectionBot(address detectionBotAddress) external override {
              require(address(usersDetectionBots[msg.sender]) == address(0), "DetectionBot already set");
              usersDetectionBots[msg.sender] = IDetectionBot(detectionBotAddress);
          }
        
          function notify(address user, bytes calldata msgData) external override {
            if(address(usersDetectionBots[user]) == address(0)) return;
            try usersDetectionBots[user].handleTransaction(user, msgData) {
                return;
            } catch {}
          }
        
          function raiseAlert(address user) external override {
              if(address(usersDetectionBots[user]) != msg.sender) return;
              botRaisedAlerts[msg.sender] += 1;
          } 
        }
        
    
3.  编译 `Forta.sol`
    
4.  在 `DEPLOY & RUN TRANSACTIONS` 中 `CONTRACT` 选择 `Forta.sol` ；在 `At Address` 中填入 `0xD386F824FabC0bB1e85a2AD1D24642C9BaAa231A` ；展开下方的 `Deployed Contracts`。
    

![](https://storage.googleapis.com/papyrus_images/c46967ee84c683bb25af900eb5e9e8c9780a164b9c56a7b7171ae0aeb6260a06.png)

5.  点开 `setDetectionBot` ，传入上一步部署 bot 合约的地址，点击 `transct` 。
    

![](https://storage.googleapis.com/papyrus_images/423480580c1f8e81fe4fdda1f96d378551ee918365a4337acce54c3b0e248785.png)

点击提交，本关完成。

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*Originally published on [xwal](https://paragraph.com/@xwave/26-doubleentrypoint)*