BreizhCTF 2019: Werizchacha

Challenge details

Event	Challenge	Category	Points	Solves
BreizhCTF 2019	Werizchacha	Reverse	25	?

Challenge: werizchacha md5sum : fdee16febd35909b93ccd22147d60df4

TL;DR

Easy reverse, break at strcmp :)

Methodology

Recon with Ltrace

First launch the binary with ltrace :

# ltrace ./werizchacha aa
strlen("AQDHYGBSEzj2x^G0c0mf^hm^O030m^Rh"...)                                                                                       = 36
strcmp("BREIZHCTF{k3y_H1d1ng_in_P141n_Si"..., "aaa")                                                                                = -31
puts("That's not the flag."That's not the flag.
)                                                                                                        = 21
+++ exited (status 1) ++++

There is some string that look alike a flag but it’s truncated.

GDB time

gdb ./werizchacha

We search strcmp in the main function : disass main

break at main+220 where strcmp is called : b *main+220 then run : r aaaa

Got an easy flag :smile:

Flag

BREIZHCTF{k3y_H1d1ng_in_P141n_SiGhT}

@Areizen