CTF Gameserver

This is a gameserver for attack-defense (IT security) CTFs. It was originally written for FAUST CTF 2015, but is designed to be re-usable for other competitions.

What's included

The gameserver consists of multiple components. They may be deployed separately of each other as their only means of communication is a shared database.

• Web: A Django-based web application for team registration and scoreboards. It also contains the model files, which define the database structure.
• Controller: Coordinates the progress of the competition, e.g. the current tick and flags to be placed.
• Checker: Offers an interface for checker scripts, which place and retrieve flags and test the status of services.
• Submission: Server to submit captured flags to.
• Lib: Some code that is shared between the components.

For deployment instructions and details on the implementations, see the READMEs of the individual components.

Related projects

There are several alternatives out there, although none of them could really convince us. Your mileage may vary at this point.

• ucsb-seclab/ictf-framework from the team behind iCTF, one of the most well-known attack-defense CTFs. In addition to a gameserver, it includes utilities for VM creation and network setup. We had trouble to get it running and documentation is generally rather rare.
• HackerDom/checksystem is the gameserver powering the RuCTF. The first impression wasn't too bad, but it didn't look quite feature-complete to us. However, we didn't really grasp the Perl code, so we might have overlooked something.
• isislab/CTFd appears to be de-facto standard for jeopardy-based CTFs. It is, however, not suitable for an attack-defense CTF.

Another factor for the creation of our own system was that we didn't want to build a large CTF on top of a system which we don't entirely understand.

Design principles

The software will probably only be used once a year for severals hours, but it has to work reliably then. It will hopefully continue to be used by future generations. These requirements led to the incorporation of some principles:

• Non-complex solutions: Keep the amount of code low and chose the less fancy path. That's why we use the built-in Django admin interface instead of writing a custom admin dashboard – it'll be good enough for the few people using it.
• Few external dependencies: Of course one shouldn't re-invent the wheel all over again, but every external dependency means another moving part. Some libraries you always have to keep up with, others will become unmaintained. We therefore focus on few, mature, well-chosen external dependencies. That's why we use a plain old Makefile instead of Bower for JavaScript dependencies and Django's built-in PBKDF2 instead of fancy bcrypt for password hashing.
• Extensive documentation: This should be a no-brainer for any project, although it is easier said than done.
• Re-usability: The gameserver should be adjustable to your needs with some additional lines of code. An example for such customizations can be found in the faustctf-2015 branch of this repository.
• Scalability: We couldn't really estimate the load beforehand, nor could we easily do realistic load-testing. That's why the components are loosely coupled and can be run on different machines.

Licensing

The whole gameserver is released under the MIT (expat) license. Contributions are welcome!