SECUINSIDE CTF Quals 2014 – Reversing 100 yayaya

2014-06-05T14:26:00+02:00

The task

This task contains an SWF file with Crossbridge embedded. Additionally there is an ELF file inside that SWF. At the first look I thought that this is really an RE job. But I was wrong (thanks to nurfed — it's his solution). There is no RE, and even a Flash decompiler was not needed. The entire work comprises capturing Flash movie frames with random color blocks.

Some random frame from the Flash movie:

Capturing frames

These color blocks appeared at some interval, and the solution was to capture these frames and then combine them together. For screen capture I chose pyscreenshot:

import pyscreenshot as ImageGrab
import time

print 'z'
for z in range(2000):
    im = ImageGrab.grab(bbox=(269, 100, 469, 300))
    im.save('e:\\sc\\im_{}.png'.format(z))
    time.sleep(0.1)

Combining the frames

I decided to use PIL to combine screenshots, but nurfed (thanks again) chose an easier way — ImageMagick. So simple:

convert -evaluate-sequence add "e:\sc\im_*.png" out.png

The flag

And we get the final image:

Flag is GANADAHAAH.

ASIS CTF Quals 2014: Trivia 50

2014-05-12T14:28:00+02:00

The challenge

This challenge was fun. It was a NES ROM image that contains the famous game — Battle City. After quick examining the ROM in a hex editor we did not find anything useful, so we decided to run it. Emulator used: FCE Ultra v0.98.13.

Booting the ROM

Startup screen:

Finding the flag

When we played it we tried to dump ROM memory (trying to find out the flag, but not succeeded). And when the 1st level was done we got the flag:

There is a little bit of brute-forcing in the answer because the flag 8 bit rules was not the correct submission. After trying different versions we landed on the flag: 8BIT_RULEZ.

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