Setting up a CTFd instance

This guide will teach you how to set up a CTFd instance using Docker and Docker Compose.

Step 1: Set up a server

The first step is to set up a server to host the actual CTFd instance. This can be done on any cloud platform that supports Docker and Docker Compose. For this guide, I will be using DigitalOcean.

If you are using a different cloud platform, the exact steps to set up a server will not be covered. However, after accessing the server through ssh, you can continue with the rest of the guide from here.

Step 2: Clone the CTFd repository

At this point, you should have a cloud server that you can access. ssh into the server as root using the private key you saved earlier.

ssh -i /path/to/private/key root@<server_ip>

You should now be in the server. Install Docker and Docker Compose using the following commands: (From the official Docker documentation)

sudo apt-get update
sudo apt-get install \
    ca-certificates \
    curl \
    gnupg \
    lsb-release
sudo mkdir -p /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \
  $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-compose-plugin

We will be working in /app for this guide. Create the directory and change into it.

mkdir /app
cd /app

After Docker and Docker Compose are installed, clone the CTFd repository using the following command:

git clone https://github.com/CTFd/CTFd.git
cd CTFd

Step 3: Configure the CTFd instance

Now that we have the CTFd repository cloned, we need to configure the CTFd instance. This can be done by editing the docker-compose.yml file. Open the file using your favorite text editor.

nano docker-compose.yml

Modify the SECRET_KEY to a random, secret string.

Now build the images and run the containers. This might take a while.

docker compose up -d --build

When all is said and done, you should be able to access the CTFd instance at http://<server_ip>:80. You can also access the admin panel at http://<server_ip>:80/admin.

To check that your CTFd instance is running, run the following command, and you should see all 4 containers running.

docker ps

Access your CTFd instance at http://<server_ip>:80. You should see a setup page. Fill out the form (everything can be edited later).

Step 4: Done!

Now that you have a CTFd instance running, there a few things to do before fully launching the CTF.

• Set up SSL/TLS (Requires a domain name)
  • https://dev.to/roeeyn/how-to-setup-your-ctfd-platform-with-https-and-ssl-3fda
• Configure email
• Set up challenges

But for now, you have a working CTFd instance. Congratulations!

Step 5: Bonus: Setting up individual challenges

If you want a quick and lazy hack to set up small challenges on the same server as the CTFd instance, this section is for you!

Note that this is not recommended at all for any challenge that will experience major load or access during the contest. Use this ONLY for challenges you are sure will not impact the performance of the CTFd instance in any way.

mkdir /app/chal
cd /app/chal
scp -r /path/to/challenge/files root@<server_ip>:/app/chal

FROM ubuntu:20.04
 
RUN apt-get update && apt-get install -y python3 python3-pip socat
COPY . /app # contains server.py and flag.txt
WORKDIR /app
 
RUN chmod 444 flag.txt
ENTRYPOINT ["socat", "-T60", "TCP-LISTEN:1337,reuseaddr,fork", "EXEC:'python3 server.py',pty,stderr,echo=0"]

version: '2'
 
services:
  challenge:
    container_name: challenge
    build: .
    ports:
      - "1337:1337"

docker-compose up -d --build