CTF

Imaginary CTF is not your classical weekend CTF. Instead, they have been publishing fun challenges almost every day since April 2021 – pretty impressive. I’ve been solving some of their challenges here and there. This one, from last month, was especially fun. Also I wanted to try a jupyter notebook style write-up. Let me know if this helps comprehension or maybe too much mixing of code and text. The challenge states:

This post is about turning a photo of a cat into a photo of a goldfish by changing only one pixel, at least according to resnet50. With Organizers we participated in RCTF during the close race at the end 2022 to be #1 on CTFtime. This literally meant to participate in every high rated CTF and solving every challenge, including the miscy of the misc. The challenge catspy appeared at around 2am in the misc category and the description states:

With KITCTF we participated in the bo01lers CTF and finished 6th. There were some quite fun challenges. Including the resnet challenge, which is a machine learning challenge. I hope to see more machine learning challenges in the future. Challenge description: A naive AI startup released a new visual password system based on State-of-the-Art Neural Network technology. Wanting to save on costs they reuse the popular Resnet model to create embeddings which input password images are checked against hoping to leverage the feature extraction capabilities of Resnet.

Read more writeups at kitctf.de Challenge description: Our lab administrator has just passed out from a strange virus. Please help us find the password to his messaging app so we can identify what he was working on and save his life. We are given an apk (Android Package) starting it, it asks for username and password to enter. It does not require any network connection, so it is a classical CrackMe.

Read more writeups at kitctf.de Challenge description: Please use my shitty blog 🤎! We are given a docker container running php. The only notable things about it, is that there is a readflag binary on the server and that the webroot is /var/www/html. Other than that only index.php is interesting: <?php // TODO: fully implement multi-user / guest feature :( $secret = 'SECRET_PLACEHOLDER'; $salt = '$6$'.substr(hash_hmac('md5', $_SERVER['REMOTE_ADDR'], $secret), 16).'$'; if(! isset($_COOKIE['session'])){ $id = random_int(1, PHP_INT_MAX); $mac = substr(crypt(hash_hmac('md5', $id, $secret, true), $salt), 20); } else { $session = explode('|', $_COOKIE['session']); if( !

Tenbagger # Challenge description: I think I took it too far and made some trades and lost everything. My only chance to fix my account balance is a tenbagger. We are given a pcap and open in Wireshark. It contains a lot of what looks like normal web browsing. But somewhere in there are a few FIX messages. FIX is the Financial Information eXchange protocol. First, I thought that we need to get the credentials from the FIX login, but there are no such packages.

These are writeups for the first CTF I participated in during a weekend. Before that I only solved some picoctf and Google Beginners quest challenges after the events. I played with KITCTF the CTF team of the Karlsruhe Institute of Technology. Factory # Challenge description In the simplest terms, factory misco-graphy is the ratio of output to input! The challenge file is only one pdf. Opening the only shows the text “Real-World Misco-graphy”.