I was sniffing some web traffic for a while, I think i finally got something interesting. Help me find flag through all these packets.
net_756d631588cb0a400cc16d1848a5f0fb.pcap

This was a 100 point challenge. Overall it was pretty fun. First thing to do with the pcap is strings it and look for an easy win. While we didn't get an easy win here, we did get a nice reference point:

 

$ strings net_756d631588cb0a400cc16d1848a5f0fb.pcap | grep -i flag
FLAG = 'flag{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}'
        print encode(FLAG, cnt=?)

Precision was an exploit challenge worth 100 points. We're given a binary, and a server that it's running on, and told to exploit it. Let's take a look at the binary.

 

$ file precision 
precision: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.24, BuildID[sha1]=929fc6f283d6f6c3c039ee19bc846e927103ebcd, not stripped

 

As you can see, it's a 32-bit elf binary using shared libs. Also, it's not stripped, which is nice because it means that named symbols will still be present in the binary (to make reversing easier). Seeing as the goal here is to exploit it, let's take a look at the security controls baked in.

ones_and_zer0es (50 points)

eps1.1_ones-and-zer0es_c4368e65e1883044f3917485ec928173.mpeg

 

This was a warm-up "challenge". I'm including it as a writeup primarily because I have never posted previously about how to binary translate things like this. The file you download ends in .mpeg, but it's not an mpeg. In fact, the first thing I do with any challenge is to run the Linux "file" command on it.

I'm adding this writeup primarily because so many people were complaining about this challenge. I think this is an example of a challenge that will turn people away from CTFs as it only minimally has to do with crypto and has more to do with guessing what the challenge author wants. This challenge was worth 100 points.

 

All we are given is a link to http://52.7.208.12/. This web page has an entry field, and will give an error if you enter too few characters (i think it was 5 or something) and complain that "Your note isn't long enough so it's not security". This would lead you to believe that the solution has something to do with the length of the input string.