CTf Small Template — Quickstart

Minimal CTF web challenge template (Flask) ready to build locally and deploy.

Files included

• Dockerfile — builds a small production image with Gunicorn.
• app.py — minimal Flask app and the starting point to the backend.
• requirements.txt — dependencies.
• .dockerignore — keep images small.

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1) Build & run locally with Docker (quick test)

# build (tag the image)
docker build -t ctf-template:latest .

# run (map host 8000 -> container 8000)
docker run --rm -p 8000:8000 ctf-template:latest

Open: http://localhost:8000 — you should see the flag.

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2) Prepare GitHub repo & push (one-time per student)

# local steps (run inside repo folder)
git init
git add .
git commit -m "Initial CTF template"
# create a GitHub repo on github.com (name: cyberus-ctf-xx) then:
git remote add origin https://github.com/<username>/<repo>.git
git branch -M main
git push -u origin main

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3) Deploy to Railway

1. Sign up / sign in to Railway: https://railway.app
2. Create a new project → choose Deploy from GitHub and select your repo.
3. Railway will detect the Dockerfile and build the image.
4. After build, In settings go to networking section, choose a domain and the gunicorn port. Railway will then give you a public domain you can use.

Note: For private repos, make sure to authorize Railway to access them otherwise they won't appear in the search:

1. Go to Railway Account Integrations → GitHub → Install & configure repository access.
2. This ensures Railway can see your private repo during deployment.

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4) Add your challenge to the main CTFd scoreboard

• On CTFd, create a new challenge that links to the Railway URL.

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Happy (and hopefully error-free) CTF setting! 🙂