BIC 2023 WINTER CTF

Description: This is a CTF hosted by Blacks In Cybersecurity

It was a fun challenge which I focused only on solving all pwn challenges but sadly they only brought one pwn challenge. I was able to solve the pwn challenge with an easy reverse engineering chall. Lets get straight to it

Reverse Engineering

Firstly i’ll do the easy reverse engineering challenge

Basic file checks

┌──(mark㉿haxor)-[~/Desktop/CTF/WinterCon/rev]
└─$ file chall       
chall: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, BuildID[sha1]=32b061e72f3608b65f0649e1f97e7d5d5b049b87, for GNU/Linux 3.2.0, stripped

From the file check we know that its a x64 binary and its statically linked (meaning that all libraries that the executable needs are integrated inside) and also is stripped ( meaning that we won’t be able to see the function names)

Lets run it to know what it does

┌──(mark㉿haxor)-[~/Desktop/CTF/WinterCon/rev]
└─$ ./chall       
/===========================================================================\
|               Welcome to BIC Winter CTF \0/                               |
+===========================================================================+
[ERROR] Login information missing
Usage: ./chall <username> <password>

It requires passing two parameters which are username and password

Since i don’t know it lets decompile the binary using ghidra

After decompiling