HackVent 2023 - [HV23.04] Bowser

Difficulty: Easy

Categories: Reverse Engineering

Author: veganjay

Santa has heard that some kids appreciate a video game as a christmas gift. He would rather have the kids solve some CTF challenges, so he took some inspiration and turned it into a challenge. Can you save the princess?

Opening the binary in binary ninja reveals the following:

Just running ./bowser mario doesn’t work though, we only get a message:

Sorry, your flag is in another castle.

So, let’s look at the algorithm; &str seems to contain the flag, “encrypted” with bitwise NOT. It looks like the loop is terminated early due to a NULL byte though. The easiest way for me was to just use CyberChef with the string and use the NOT operation:

The flag is: HV23{You_Have_Saved_the_Princess}