Scenario: "Alexandria": The Vanishing Backups

Level: Easy

Type: Fix

Access: Email

Description: A critical backup cron job has silently stopped working 3 days ago. The backup script is located at /opt/backup/backup.sh and should create daily backups in /var/backups/daily/, but no new backups have been created recently.

Looking at the backup directory, you can see old backup files from a few days ago, proving the system used to work. However, there are no error emails, no obvious error logs, and the cron service appears to be running normally.

Fix ALL issues preventing the backups from running, so that backups are created successfully and reliably.

Test directory: /var/backups/daily/
Backup script: /opt/backup/backup.sh

Test: The solution will be validated by checking if a backup file has been created in the last 10 minutes.

The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.

Time to Solve: 5 minutes.

Scenario: "Kortenberg": Can't touch this!

Level: Easy

Type: Fix

Access: Email

Description: Is "All I want for Christmas is you" already everywhere?. A bit unrelated, someone messed up the permissions in this server, the admin user can't list new directories and can't write into new files. Fix the issue.
NOTE: Besides solving the problem in your current admin shell session, you need to fix it permanently, as in a new login shell for user "admin" (like the one initiated by the scenario checker) should have the problem fixed as well.

Test: The admin user in a separate Bash login session should be able to create a new directory in your /home/admin directory, as well as being able to create a file into this new directory and add text into the new file.

The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.

Time to Solve: 15 minutes.

Scenario: "Solanea": ClickHouse mad house

Level: Medium

Type: Do

Access: Email

Description: You have a ClickHouse installation CHI running on a Kubernetes cluster and a set of requests (located at ~/data/requests.csv) that you must populate into the http_requests table in the monitoring database (table may not exist in all pod instances).
Do this insert in all pod instances of the database.
The user and password to connect to the database are default.
The keeper pods provide clickhouse replication services.

Test: You are able to query the database and see the data:

clickhouse-client -h --password default -q 'SELECT COUNT(*) FROM monitoring.http_requests'

The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.

Time to Solve: 20 minutes.

Scenario: "Tunis": Redis Replication Problem

Level: Medium

Type: Fix

Access: Email

Description: A Redis master-replica setup is running on this server, with the master on port 6379 and the replica on port 6380. Both instances show as "connected" when you check their status, but data synchronization has silently broken.

Recent writes to the master don't appear on the replica, even though there are no obvious errors in the logs and both Redis instances appear healthy.

Fix the replication issues so that data written to the master (port 6379) immediately appears on the replica (port 6380) without data loss.

Master: localhost:6379
Replica: localhost:6380
Password: masterpass123

A helper test script is available at /home/admin/test_replication.sh

Test: The solution will be validated by writing a test key to the master and verifying it appears on the replica within 2 seconds.

The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.

Time to Solve: 20 minutes.

Scenario: "Toulon": Denied Lamp

Level: Medium

Type: Fix

Access: Business

Description: The security team has asked again Mary and John to implemente more security measures. Unfortunately, this time they have broken the LAMP stack (Apache with PHP) so the frontend is unable get an answer upstream, thus, they need your help again to fix it.

The fixed application should be able to serve the content from the webserver, the problem is a network connectivity, although the logs have valuable informatiion, it has nothing to do with the configuration of the apache server.

Test: curl localhost | head -n1 returns SadServers - LAMP Stack

The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.

Time to Solve: 15 minutes.

Scenario: "Bermuda": Command not found

Level: Medium

Type: Fix

Access: Business

Description: While working with a distro with a very small footprint, we just found out that there are some basic commands not present, this was supposed to be a security feature, after all this is just a small server, however, the web content was not deployed. Your task is to decompress the file /home/admin/web.zip and move the file home.html in it to /var/www/html/index.html

Test: The service must return the string "Homepage". You can check with the command curl -s localhost

The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.

Time to Solve: 10 minutes.

Scenario: "Auderghem": Containers miscommunication

Level: Medium

Type: Fix

Access: Email

Description: There is an nginx Docker container that listens on port 80, the purpose of which is to redirect the traffic to two other containers statichtml1 and statichtml2 but this redirection is not working.
Fix the problem.

IMPORTANT. You can restart all containers, but don't stop or remove them.

Test: The nginx container must redirect the traffic to the statichtml1 and statichtml2 containers:

curl http://localhost returns the Welcome to nginx default page
curl http://localhost/1 returns HelloWorld;1
curl http://localhost/2 returns HelloWorld;2

The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.

Time to Solve: 15 minutes.

Scenario: "Marseille": Rocky security

Level: Medium

Type: Fix

Access: Email

Description: As the Christmas shopping season approaches, the security team has asked Mary and John to implemente more security measures. Unfortunately, this time they have broken the LAMP stack; the frontend is unable get an answer from upstream, thus they need your help again to fix it.

The application should be able to serve the content from the webserver.

Note for Pro users: direct SSH access is not avaiable (yet) for this scenario.

Test: curl localhost | head -n1 returns SadServers - LAMP Stack

The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.

Time to Solve: 15 minutes.

Scenario: "Woluwe": Too many images

Level: Medium

Type: Fix

Access: Email

Description: A pipeline created a lot of Docker images locally for a web app. All these images except for one contain a typo introduced by a developer: there's an incorrect image instruction to pipe "HelloWorld" to "index.htmlz" instead of using the correct "index.html"
Find which image doesn't have the typo (and uses the correct "index.html"), tag this correct image as "prod" (rather than fixing the current prod image) and then deploy it with docker run -d --name prod -p 3000:3000 prod so it responds correctly to HTTP requests on port :3000 instead of "404 Not Found".

Test: curl http://localhost:3000 should respond with HelloWorld;529

The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.

Time to Solve: 15 minutes.

Scenario: "La Rinconada": Elevating privileges

Level: Medium

Type: Hack

Access: Email

Description: You are logged in as the user "admin" without general "sudo" privileges.
The system administrator has granted you limited "sudo" access; this was intended to allow you to read log files.

Your mission is to find a way to exploit this limited sudo permission to gain a full root shell and read the secret file at /var/log/secret.txt
Copy the content of /root/secret.txt into the /home/admin/solution.txt file, for example: cat /root/secret.txt > /home/admin/solution.txt (the "admin" user must be able to read the file).

Test: As the user "admin", md5sum /home/admin/solution.txt returns 52a55258e4d530489ffe0cc4cf02030c (we also accept the hash of the same secret string without an ending newline).

The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.

Time to Solve: 15 minutes.