Sunday, 4 November 2018

Note For Ethernaut#1 - Fallback

Note For Ethernaut#1 - Fallback

Solidity

pragma solidity ^0.4.18;

import 'zeppelin-solidity/contracts/ownership/Ownable.sol';

contract Fallback is Ownable {

  mapping(address => uint) public contributions;

  function Fallback() public {
    contributions[msg.sender] = 1000 * (1 ether);
  }

  function contribute() public payable {
    require(msg.value < 0.001 ether);
    contributions[msg.sender] += msg.value;
    if(contributions[msg.sender] > contributions[owner]) {
      owner = msg.sender;
    }
  }

  function getContribution() public view returns (uint) {
    return contributions[msg.sender];
  }

  function withdraw() public onlyOwner {
    owner.transfer(this.balance);
  }

  function() payable public {
    require(msg.value > 0 && contributions[msg.sender] > 0);
    owner = msg.sender;
  }
}

What I learned From It

Fallback Function

每個合約裡最多能有一個未命名的公開 funtion,沒有參數、回傳值。
在幾種情況下會執行:
  1. 呼叫合約的函式不在 abi 裡。
  2. 對合約轉帳 (不帶 data 參數)。
只有 payable 的 Function 才能接收 Ether.

Reference:

tags: ethernaut solidity

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