Hack-a-Sat 2 Qualifier

This repository contains the open source release for the Hack-a-Sat 2 qualifier from 2021.

Released artifacts include:

• Source code for all challenges
• Source code for all challenge solutions
• Infrastructure to build all challenges and their solutions
• Notes on how to build and solve challenges

Released artifacts do not include:

• Infrastructure used to host and run the game
• Source code for the score board
• Source code for the "ticket taker" or "lifecycle manager" (used to host randomized challenges within the live game infrastructure)
• Source code for the "sat solver" (used to test challenges before deployment)

Repository Structure

The infrastructure for Hack-a-Sat 2021 deployed challenges from self-contained Docker images. Each challenge has an internal name that is used to refer to that challenge's containers. These names are not necessarily the same as the name that was used on the scoreboard. Folders within this repository are named according to each challenge's internal name, rather than its external one.

The following is a mapping of all names by category:

The generator-base folder is included to build the base image for all challenges that use a generator (see below).

Building and Deploying Challenges

For instructions on how to build each challenge's Docker images, please refer to each folder's README.md. Each challenge may have up to 3 separate images:

• generator - Used to generate any static files necessary to give to teams.
• challenge - Used to host the actual challenge on the game infrastructure.
• solver - Used to ensure the challenge would be solvable for a given team.

Missing Infrastructure

This repository does not contain the ticket-taker, lifecycle-manager, or sat-solver programs (or their source code).

During the live Hack-a-Sat 2 qualifier, challenges were deployed with a program called ticket-taker. This program would take a supplied ticket and use it to generate a seed value and flag specific to that ticket. It would then launch an instance of the challenge container, passing any options necessary via environment variables.

Using ticket-taker posed a problem for certain challenges: External tools we expected players to use, like Google Maps, don't understand "tickets". A second program called lifecycle-manager was used for these challenges. ticket-taker would launch an instance of lifecycle-manager to "manage" the connection between the player and the challenge after the player authenticated with their ticket.

The commands below are from our internal test tool (called sat-solver), that was capable of testing the solver against a specific seed in a managed environment without ticket-taker or lifecycle-manager. These commands should be sufficient for anyone using this repository to quickly host challenges locally for testing.

This file can be used as a "decoder ring" for turning tickets from the live event into seed values that allow you to run the same copy of the challenge your team got in the 2020 qualifier.

Generators

These were run in a job queue prior to the release of a challenge to generate the unique status files for each team's challenge seed:

docker run -t --rm -v <dir>:/out -e SEED=<seed> -e FLAG=<flag> <container>:generator

• dir is the output directory on the host where you want generated files to be stored.
• seed is the random seed you want files to be generated for.
• flag is the flag you expect the team to submit to the scoreboard.
• container is the internal name of the challenge (see above).

Generators were typically built off of the generator-base Docker image. As a result, you'll need to build the image in the generator-base folder before building any generator images.

Challenges

These were run on hardened AWS VMs that were provisioned by a central Puppet Master. Every VM only hosted a single challenge. Multiple VMs were used with a round-robin DNS loadbalancer to spread connections across all VMs provisioned for that challenge.

Puppet would install xinetd, which would open up a single port for incoming connections for ticket-taker. ticket-taker would be responsible for executing one of the commands below based on a configuration file after the player's ticket was verified:

# use this if the challenge only needs basic options
docker run --rm -i -e SEED=<seed> -e FLAG=<flag> <container>:challenge

# use this if the challenge needs generated files to run
docker run --rm -i -e DIR=/mnt -v <dir>:/mnt -e SEED=<seed> -e FLAG=<flag> <container>:challenge

# use this if the challenge is required to have its connections managed
docker run --rm -i -e SERVICE_HOST=<host> -e SERVICE_PORT=<port> -e SEED=<seed> -e FLAG=<flag> <container>:challenge

# use this if the challenge needs both generated files and a managed connection
docker run --rm -i -e DIR=/mnt -v <dir>:/mnt -e SERVICE_HOST=<host> -e SERVICE_PORT=<port> -e SEED=<seed> -e FLAG=<flag> <container>:challenge

• seed is the random seed to use when running the challenge.
• flag is the flag you expect the team to submit to the scoreboard.
• container is the internal name of the challenge (see above).
• host is the IP or address of the host this container is running on.
• port is the additional port the challenge should open.
• dir is the directory on the host where generated files are stored.

To re-host these challenges without xinetd, you can use socat like so:

# remember to escape any colons (":") in the commands above with backslashes!
socat -v tcp-listen:<port>,reuseaddr "exec:<command from above>"

Solvers

These were run in batches on a server with tons of cores to ensure every team would be able to solve their randomized version of each challenge. They were also run any time a team wanted verification that a challenge was working as intended during the live game.

# use this if the solver only needs basic options
docker run -it --rm -e HOST=<host> -e PORT=<port> <container>:solver

# use this if the solver needs generated files to run
docker run -it --rm -e HOST=<host> -e PORT=<port> -e DIR=/mnt -v <dir>:/mnt <container>:solver

# use this if you want to solve with a specific ticket
docker run -it --rm -e HOST=<host> -e PORT=<port> -e TICKET=<ticket> <container>:solver

# use this if you want to solve with a specific ticket and need generated files
docker run -it --rm -e HOST=<host> -e PORT=<port> -e DIR=/mnt -v <dir>:/mnt -e TICKET=<ticket> <container>:solver

• seed is the random seed of the challenge you're trying to solve.
• ticket is the ticket for your team.
• container is the internal name of the challenge (see above).
• host is the IP or address of the challenge host.
• port is the port on the challenge host for this challenge.
• dir is the directory on the host where generated files are stored.

It should be noted that these solvers implement a solution for their challenge, not the solution. Many challenges had alternative ways of solving them (some easier, some harder) that were not tested by (and, in some cases, not intended by) the organizers.

License

Challenges in this repository are provided as-is under the MIT license. See LICENSE.md for more details.

Contact

Questions, comments, or concerns can be sent to hackasat[at]cromulence.com.