bg-ctf

Challenge 6: Meet all the conditions

In this challenge, you need to satisfy multiple conditions including contract interface requirements and precise gas control!

Contract Overview

The contract requires:

A correct code based on the current count
Your contract must implement name() returning a specific string
The remaining gas must be within a specific range (190,000-200,000)

Hints

Hint 1

The code is calculated by shifting the count left by 8 bits (count << 8)

Hint 2

Your contract needs to implement the IContract6Solution interface with the exact name string

Hint 3

You can control initial gas by specifying it in the function call

Solution

Click to reveal solution

1. Create a contract implementing the interface:


contract Solution is IContract6Solution {
    function name() external pure returns (string memory) {
        return "BG CTF Challenge 6 Solution";
    }

    function attack(Challenge6 challenge6) external {
        uint256 code = challenge6.count() << 8;
        challenge6.mintFlag{ gas: 200_000 }(code);
    }
}

2. The solution works because: - We implement the required interface - We calculate the correct code - We specify exact gas amount in the call Congratulations! You've mastered interface implementation and gas control! 🎉

Remember: Gas control is a crucial aspect of Ethereum development, affecting both security and optimization. Understanding how to manipulate and control gas usage is an essential skill!