ASIS Cyber Security Contest Quals 2014: Image

Category: Trivia Points: 50 Description:

Download the attached file and find the flag file No need to calculate MD5 or appending ASIS_.

We are given the file joy_50_25b927e48a23a4b41f215303ca988a01 without any extensions so the first thing we do is to run file command which gives us:

$ file joy_50_25b927e48a23a4b41f215303ca988a01
joy_50_25b927e48a23a4b41f215303ca988a01: xz compressed data

We can decompress it by running the tar command with the following arguments:

$ tar -xv --xz -f joy_50_25b927e48a23a4b41f215303ca988a01
1
x joy_a653520127e5147e0f9cc489ea9d1cf6

Running the file command again on extracted file gives us

joy_a653520127e5147e0f9cc489ea9d1cf6: iNES ROM dump, 1x16k PRG, 1x8k CHR, [Horiz.]

So we can rename it to add a proper extension.

$ mv joy_a653520127e5147e0f9cc489ea9d1cf6 joy_a653520127e5147e0f9cc489ea9d1cf6.nes

Look like we need to find ourselves a SNES emulator. There are plenty of those available on the Internet for various OSes. A good place to start for finding tools to play with ROMs is romhacking.net, on Ubuntu though we can install bsnes which is available via Ubuntu Software Center.

After loading the ROM file we are presented with an old game of Namco - Tank Battalion with some minor tweaks.

By playing a game and going through the first level we are shown with a map for level two.

Thus the flag should be: 8BIT RULES, but it did not work.

Later (2014-05-10 01:31) during the competition the image file was updated. Repeating the steps as described above gives us:

The flag is 8BIT_RULES.

We do not need to play the game to get to second (or in that matter to any) level. On the level selection screen we can press X (bind to A button on SNES pad) to change level to 2.

Other write-ups and resources

• http://nickthefrost.com/2014/05/10/asis-ctf-quals-2014-image/