gmh5225 / blockchain-example-ctf-challenge

A self-contained example Ethereum challenge using Paradigm's CTF framework

Example Ethereum CTF challenge

This challenge uses the Ethereum ctf challenge framework developed by samczsun at Paradigm. It was originally written for CSAW CTF 2022.

We've made this challenge public so as to provide a self-contained example on how to use Paradigm's CTF framework.

See this blog post for more information. Pull requests welcome!

Installing

Prerequisites

• Docker
• mpwn
• Python 3

Configuration

You'll need to set the following environment variables:

• ETH_RPC_URL to a valid Ethereum JSON-RPC endpoint
• PYTHONPATH to point to mpwn

You'll also need to manually install the following:

• pip install yaml ecdsa pysha3 web3

Usage

Build everything

docker buildx build --platform linux/amd64 -t mytag .

Run a challenge

Running a challenge will open a port which users will nc to. For Ethereum/Starknet related challenges, an additional port must be supplied so that users can connect to the Ethereum/Starknet node

./run.sh mytag 31337 8545

On another terminal:

nc localhost 31337

When prompted for the ticket, they will need to solve a PoW. This ticket should NOT be shared between teams, it's a secret.

$ nc localhost 31337
1 - launch new instance
2 - kill instance
3 - get flag
action? 1
ticket please: ticket

your private blockchain has been deployed
it will automatically terminate in 30 minutes
here's some useful information

How to solve it

See solve.sh, basically just deploy Exploit.sol contract and run it. Constructor expects 100 eth and parameter is setup contract address