Mauvaise baleine

Description

This year, the FCSC tech team is testing a new way to store flags in Docker challenges, so that they can be changed quickly.

The challenges are built on “basic” Docker images, which contain: the flag, a secret and a change_flag script that allows you to change change the flag if you know the secret.

We have developed a small service that allows to change the flag in challenge images, by running the images, then committing the containers with the new flag.

Unfortunately, the service got exposed on the internet by mistake due to a bad firewall configuration.

To run locally :

$ ./start.sh
$ nc localhost 2053
Entrer "help" pour le message d'aide

> change_flag V3ryS3cr3t FCSC{NewFlag}
flag: FCSC{ThisIsTheFl4g}
> change_flag V3ryS3cr3t FCSC{NewNewFlag}
flag: FCSC{NewFlag}
> exit
> À la prochaine !

Note:

• You will be automatically disconnected after 2 minutes.
• The challenge should be solved on an Ubuntu 22.04 machine, with the latest version of Docker (23.0.4).