So, among all the binaries Plaidctf also followed the tradition in CTF to hide a stego as a forensics challenge. We had a challenge with this description:
“Meow meow mw mw m.
In the cat.rar file we found two files:
The biggest event of the robot year is happening this week! Robot invitations are cool in that they are just a password that validates at the door. We acquired the validator to be used. Can you find an invitation for us in time?
In this challenge we’re given an ELF binary which asks for a password. Disassembly in IDA quickly shows what the mess is all about – function pointers, lots of them.
Robots enjoy some strange games and we just can’t quite figure this one out.
Maybe you will have better luck than us.
Title: The Game (100)
The challenge consisted of a game we could play by connecting to a service running on port 6969.
The game provided two hex strings, and our job was to find out which one was the biggest.
To get the key, we had to win 75 runs in a row.
We recently intercepted a plethora of robot transmissions but they are all encrypted with some strange scheme we just can’t quite figure out. Can you crack it?
200 points, Password Guessing, 6 teams solved this
A very cool and surprisingly easy crypto challenge: all you have to do is break 4096-bit RSA!
Of course, there are some special circumstances which make solving this possible at all. We have two files, one is the encrypted data (presumably, it is named enc.dat and looks like random data) and the other is a RSA public key in PEM format. Let’s list the details of this public key:
Robots are running secret service that aims to mill down diamonds into fairy dust, and use it to take over our world! Help us please!
300 points, Pwnables, 18 teams solved this
This is one of those challenges where just playing around with it turned out to be faster than actually figuring out what was going on.
This was a remote exploit challenge. The service in question allows you to create “chests” (or data stores) which can hold a certain amount of data. If you add more data, the chest is deleted (“blows up”). You can also destroy a chest yourself. It is possible to access a chest from more than one connection at a time, leading us to suspect a synchronization issue.
Format is exactly what you’d expect: a remote format string exploit. To get to the format string takes a little bit of reversing first, but it’s not too hard.
Robot hackers, like their human counter parts, have a largely unmet need to dump large amounts of text to their peers. We recently got access to one of their servers and are providing you with the files. What have they been talking about?
Title: Paste (100)
Category: Practical Packets
This challenge is a webapplication, a pastebin for robot hackers. Luckily the humans got the source code. It contains an admin cookie employing the well known ‘security by obscurity’ method, a questionable
preg_replace statement using eval mode and an unchecked
require. What can we do with those?
It turns out that robots, like humans, are cheap and do not like paying for their movies and music. We were able to intercept some torrent downloads but are unsure what the file being downloaded was. Can you figure it out?
We recently gained access to a log of a robot operative interacting with computer. We are unsure what he was up to but we know it is of the upmost importance to figure it out.
Opening the file it contains key logging of a session with user interacting with a number of editors. We first cleaned up this file in readable key combinations:
We saw two robots dressed in sweater dresses, leggings and press on nails and decided we had to listen in. But, these robots were speaking an unintelligible language. Can you figure out what they were saying?
Title: 80s Thinking (250)
Category: Practical Packets
In this challenge we received an audio file (80s.wav). Listening to the audio file we got the idea it might be a modem or fax connection, this also fits in with the challenge description.