Checksystem

It's a scalable competition platform for attack-defense CTF.

It's written in Perl with Mojolicious framework.

Architecture

• cs-manager: a component that is responsible for the beginning and ending of the game, for managing breaks, for generating rounds. After the start of the round it puts tasks in the queue for launching checkers and also puts the task in the queue for calculating the scoreboard for the past rounds.

• cs-watcher: an optional component which periodically (several times per round) checks the availability of the TCP port for each service and team and skips launching the checkers if the port is not available.

• postgres: the database which used to store all the data required for the checksystem. It's also used as a backend for the Minion job queue.

• cs-worker: the minion workers which runs the checkers for teams and services.

• cs-web: the hypnotoad which serves checksystem's web components: scoreboars, API, flags.

Useful URLs

• /board: a built-in scoreboard with simple html table with teams, services and scores.
• /admin: an admin page for the game which allows to view checker's logs.
• /admin/info: an admin page with useful game statistics.
• /admin/minion: an admin page with jobs statistics.
• /ctftime/scoreboard.json: a scoreboard in CTFtime format.

HTTP API

For scoreboard

For teams

API between checkers and checksystem

Checker is an executable file that get input from the checksystem via args and STDIN and return output via exit code and STDOUT/STDERR.

Checksystem runs checkers with that format: /path/to/checker mode host id flag

Modes

INFO

Cheker must return 101 exit code and print to STDOUT lines with key: value format. Supported keys:

• public_flag_description: description of flag in the service for teams.
• vulns: number of vulns in the service, must be set to 1.

CHECK

The checker must check the general functionality of the service at host.

PUT

The checker must put the flag to the service at host by id. If exit code is 101 then checker should print to STDOUT a JSON object with public_flag_id field wich will be accessible to the teams. You can add any additional fields to the object. This JSON object will be passed to the GET mode in the future.

GET

The checker must try to get flag from the service at host by id.

Exit codes

• 101 OK.
• 102 CORRUPT: The service works fine, but there is no requested flag (only in get mode)
• 103 MUMBLE: The service works incorrect
• 104 DOWN: The service doesn't work.
• 110 CHECKER ERROR: Internal error of checker.