Challenge · capture the flag

Mini-CTF

Ten challenges are hidden in this portfolio: web, Linux, crypto, network, forensics, reverse… Every flag looks like TLG{…}. Find them, submit them here or in the terminal (Ctrl + K), and climb to the Root rank.

Everything runs in your browser: nothing is sent anywhere and your progress stays on your device. No need to attack the server — every flag can be found by exploring the site.

Flag validation requires JavaScript.

WebEasy50

Source code

Developers sometimes leave things behind in the HTML. The home page has a secret to tell you.

Hint

View the home page source (Ctrl + U) and look for a comment.

WebEasy50

Robots

Some files aren't meant for humans but for search engines. What does this site tell them?

Hint

A well-known text file at the site root: /robots.txt.

LinuxEasy50

Hidden file

The site's terminal hides a file. You still need to know how to list it… and read it.

Hint

Open the terminal, type ls -a, then cat the file. Its content is encoded: base64 -d is your friend.

ReconEasy50

Recon

Explore the interactive demo of my multi-site network: what is the name of my LAN's VTP domain? The flag is TLG{DOMAIN_NAME}.

Hint

Click the core switch that acts as the VTP server.

CryptoEasy50

Tired Caesar

A colleague "encrypted" this message and thinks it's safe:

GYT{p3f4e_3fg_s4g1th3}

Hint

Every letter was shifted by the same amount and the digits didn't move. Does 13 ring a bell?

NetworkMedium100

Packet capture

An admin logged into a switch's web interface over plain HTTP. Here is an excerpt of the Wireshark capture. Their password is the flag.

POST /login HTTP/1.1
Host: 10.242.15.2
User-Agent: Mozilla/5.0
Authorization: Basic YWRtaW46VExHe2I0czFjXzR1dGhfM25fY2w0MXJ9
Content-Length: 0

Hint

"Basic" isn't encryption, just encoding. Decode what follows it, in the user:password format.

CryptoMedium100

Weak password

This MD5 hash leaked from an old database:

23206deb7eba65b3fbc80a2ffbc53c28

Recover the password. The flag is TLG{password}.

Hint

Unsalted MD5 + a common password: it's almost certainly in an online hash database, or in rockyou.txt.

ForensicsMedium100

Talkative diagram

Here is the diagram of my very first enterprise network. The image says more than it seems.

↓ plan-reseau.png

Hint

Files have metadata. Try exiftool, strings or an online EXIF viewer.

CryptoHard200

Single-byte XOR

This flag was encrypted with XOR using a single-byte key. Here it is in hexadecimal:

0e161d21226a2805376a346a056a392e692e05396e29296927

Hint

You know how the plaintext starts: TLG{. The first encrypted byte XOR the code of "T" gives you the key.

ReverseHard250

The vault

This vault checks the access code right in your browser. Bad idea… Find the code and the vault will hand you the flag.

Hint

The check lives in ctf.js. Read the vault function, then reverse it character by character.