# Ethernaut CTF Level 0 - Hello Ethernaut

[toc]

## 題目與Setup

https://ethernaut.openzeppelin.com/level/0x7E0f53981657345B31C59aC44e9c21631Ce710c7

<br>

本關算是Setup的一個簡單關卡，目的是認識環境以及Setup
- Setup Metamask
- 選擇Testnet - 我選擇Sepolia
- 先去Faucet要測試Token - https://sepoliafaucet.com/

<br>

設定好後，回到Ethernaut關卡0

按下 `產生新實例` ，進入Dev Console開始遊戲
- 因為是async function, 會需要用 `await`
- `contract.xxx` 是新產生智能合約的實例，我們能夠透過這種方式呼叫合約的function

以下是本題的流程

await contract.info() // "You will find what you need in info1()."

await contract.info1() // 'Try info2(), but with "hello" as a parameter.' 

await contract.info2("hello") // "The property infoNum holds the number of the next info method to call."

await contract.infoNum() // 42

await contract.info42() // "theMethodName is the name of the next method."

await contract.theMethodName() // "The method name is method7123949." 

await contract.method7123949() // "If you know the password, submit it to authenticate()." 

await contract.password() // "ethernaut0" 

await contract.authenticate("ethernaut0") 

最後，按下 `提交新實例` 通過本關卡
<br>

## Source Code

可以看到我們剛剛用了`await contract.xxx`與合約的function做各種互動

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract Instance {

  string public password;
  uint8 public infoNum = 42;
  string public theMethodName = 'The method name is method7123949.';
  bool private cleared = false;

  // constructor
  constructor(string memory _password) {
    password = _password;
  }

  function info() public pure returns (string memory) {
    return 'You will find what you need in info1().';
  }

  function info1() public pure returns (string memory) {
    return 'Try info2(), but with "hello" as a parameter.';
  }

  function info2(string memory param) public pure returns (string memory) {
    if(keccak256(abi.encodePacked(param)) == keccak256(abi.encodePacked('hello'))) {
      return 'The property infoNum holds the number of the next info method to call.';
    }
    return 'Wrong parameter.';
  }

  function info42() public pure returns (string memory) {
    return 'theMethodName is the name of the next method.';
  }

  function method7123949() public pure returns (string memory) {
    return 'If you know the password, submit it to authenticate().';
  }

  function authenticate(string memory passkey) public {
    if(keccak256(abi.encodePacked(passkey)) == keccak256(abi.encodePacked(password))) {
      cleared = true;
    }
  }

  function getCleared() public view returns (bool) {
    return cleared;
  }
}

<br>

## Foundry Test

// SPDX-License-Identifier: UNLICENSED
// forge test -vvvv --match-test testEthernaut00

pragma solidity ^0.8.0;

import "ds-test/test.sol";
import "forge-std/Vm.sol";

interface Instance {
    function authenticate(string memory passkey) external;

    function password() external view returns (string memory);

    function getCleared() external view returns (bool);
}

contract ContractTest is DSTest {
    function setUp() public {
        Vm vm = Vm(address(0x7109709ECfa91a80626fF3989D68f67F5b1DD12D));
        vm.createSelectFork(vm.rpcUrl("sepolia"));
        vm.label(address(this), "Attacker");
        vm.label(
            address(0x6a924cB09C1E2043527e6Af91BaD1fee61acf805),
            "Ethernaut00"
        );
    }

    function testEthernaut00() public {
        Instance contract_lv0 = Instance(
            0x6a924cB09C1E2043527e6Af91BaD1fee61acf805
        );
        // Trigger authenticate
        contract_lv0.authenticate(contract_lv0.password());

        // getCleared
        bool result = contract_lv0.getCleared();
        assert(result == true);
    }
}

###### tags:`Ethernaut` `Smart Contract Audit` `Blockchain`