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https://github.com/starknet-edu/starknet-cc-ctf-challenges


https://github.com/starknet-edu/starknet-cc-ctf-challenges

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README 

        
# StarkNet-CC CTF 2022 Challenges



The repository hosts challenges given at the StarkNet-CC CTF, held on Nov 1st 2022 in Lisbon.

The infra is based on the [Paradigm CTF]("https://github.com/paradigmxyz/paradigm-ctf-2022") infrastructure.

Each challenge is a separate directory containing the following



- Contracts in Cairo

- Deployment script using [starknet.py]("https://github.com/software-mansion/starknet.py")



## Versions



The challenges are targeting the following versions:



```

cairo-lang==0.10.0

starknet-devnet==0.3.3

starknet-py==0.5.2a0

```



## Installing



### Prerequisites



- Docker

- Python 3



### Configuration



You'll need to set the following environment variables:



- `PYTHONPATH` to point to mpwn

- You can source the existing `envs.sh` file: `source envs.sh`



It's recommended that you run everything from a `venv`:



```bash

python3 -m venv venv

. ./venv/bin/activate

```



Install the requirements in the requirements file if you are running the first time.

Requirements match those in the development environment



```bash

pip install -r requirements.txt

```



You'll also need to install the following:



- `pip install pyyaml ecdsa pysha3 web3`



## Usage



### Build everything



```bash

./local-build.sh

```



### Run a challenge



Running a challenge will open a port which users will `nc` to.

Challenge name is the same as its directory.



```

./local-run.sh solve-me 31337 5050

```



On another terminal:



```

nc localhost 31337

```



When prompted for the ticket, use any value



```

$ 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

```



### Running the autosolver



All challenges come with a solution in the private directory (avoid if you do not want spoilers). To run the solution, start the challenge as explained above. _DO NOT_ run `nc`.

Comment out all but the challenge you want to solve in the `solve.sh` file.



Run:



```bash

./solve.sh

```



## Create new Challenge



To create a new challenge, please create a new PR, following a similar structure to the existing examples.

The new directory should contain:



- A `public` dir (this will be made public to the contesters)

- A `private` dir (this will remain private for testing and internal use)

- A `info.yaml` file, with the authors name, and a short description of the challenge



### The public dir



The public dir should have the following structure:



- `./public/contracts`

- `./public/deploy`



The contracts dir should have all the contract needed to setup the sandbox environment on the deployed devnet.

The deploy dir should have a file called `chal.py`, in charge of setting up the contracts and checking results



The public dir should also have the `Dockerfile` that will later be used during the event, and for local testing.



#### The structure of chal.py



- The script should have a `deploy` function which deploys the contracts, and gives some information on the deployment process

- The script should have a `check` function running the final check on the state, to make sure the challenges was solved correctly



### The private dir



The private dir should have a solution to the challenge, that we can easily run and test that all challenges are working well. The solution file should be called `solve.py`



## Checking challenge packaging with docker



The best way to make sure the challenge and the solution works is to build a local docker image, and to test it with the existing infra. Here are the instructions on how to do this:



1. Copy the same structure of the example challenges: `public`, `private`, `chal.py`, `Dockerfile`, etc. The infra expects the filenames in this format. The names `chal.py`, `solve.py` should be kept and only their content should be updated.

2. Update `Dockerfile` with the current contract names and the order in which they should be compiled (see examples)

3. Update the `chal.py` script for the correct contract names in your `public/contracts`

4. Update the `solve.py` to call and execute the correct sequence of calls. No need to setup new accounts etc.



Next are instructions to create a local image and test it



1. Inside the `public` directory of the challenge, which contains the file `Dockerfile`, run a docker build command:



```

docker build -t   .

```



2. Update the `local-build.sh` file with the name of the challenge dir. (add it to the list of existing challenges)



3. Run the challenge with `./local-run.sh  31337 5050`



4. Update the `solver.sh` file to include the challenge name, and comment out all other challenges



5. Run the solver file `./solver.sh`



The result of the run should be the template flag name



**NOTICE** first, check you can create a new instance by running the server with the  try to `nc` to it as described. To test the `solve.py` script, run the sever again \_without* running `nc`. Only run `solve.py` with on  uncommented.



## Running solutions manually



The dir `./manual-solutions` has the example for the solution as it should be written by the contesters.

You can write and run a similar solution as well.



1. Run the `run.sh` script as before

2. `nc` to the port and select create new instance (as before)

3. Update the `node_url`, `private_key`, `contract`, `player_address` variables after running `nc` and creating a new instance

4. Write the solution to the challenge

5. Run the script bring the state to the desired conditions

6. Run `nc` again and ask for the flag



### Questions



- Following the structure of the examples should solve most of the issues.



- For any question, please feel free to open an issue on this repo