5Charlie CTF - Myste-RE

less than 1 minute read

A write-up of the “Myste-RE” reverse-engineering challenge from 5Charlie CTF.

Myste-RE 1

Myste-RE 1 - Challenge

Somebody made this to do something, but what?

Note: Flag format is flag(*).

Attachments: flag - Binary

Myste-RE 1 - Solution

This one took a hot minute to figure out. Our team played around with various architectures and eventually agreed that 16-bit x86 made the most sense. We were able to create environment and read through using radare2 and the commands e asm.arch=x86 and e asm.bits=16.

We had some trouble getting an environment running but eventually decided to package it up as a DOSBox package and upload it to an online javascript-based DOSBox emulator: https://caiiiycuk.github.io/dosify/

DOSify Input

We give it a run…

DOSify Output

Now we start seeing a bunch of dots being printed to the screen. It turns out that triple-dots are dashes, the single dots are dots, and the long breaks are character delimiters- morse code! And then I copied that by hand into CyberChef.



Whoever made this enjoys suffering.