CSAW CTF 2014 - Networking 100: "Big Data"

This is the only networking problem, and it is only 100 points, so it turned out to be very easy.

The problem starts with the following text:

Something, something, data, something, something, big

Written by HockeyInJune


Inspecting the Wireshark File

The file extension .pcapng correspond to files for packet capture. They usually contain a dump of data packets captured over a network. This type of files holds blocks or data, and they can be used to rebuild captured packets into recognizable data.

We can open this file with Wireshark, which is an open-source packet analyzer, or using chaosreader, a freeware tool to trace TCP and UDP sessions. We choose the first. There are several things that we could explore and look for in this file:

    - We could search for all the the interesting protocols inside and analyze them.

    - We could go to *Statistics*-> *Protocol Hierarchy* and look at the traffic patterns.

    - We could search in packet bytes, looking for specific strings such as login or password.

    - We could try to find something interesting in *Conversations*.

Searching for the String Password

It turned out that all we need was to look for the string password. To do this we followed these steps in Wireshark:

     1. Go to *Edit*

     2. Go to *Find Packet*

     3. Search for **password** choosing the options *string* and *packet bytes*.

Yay! We found something over a telnet protocol:

Following the TCP Stream

Now, all we need to do is to right-click in the line and choose Follow TCP Stream. This returns:

..... .....'...........%..&..... ..#..'..$..%..&..#..............$.. .....'.............P...... .38400,38400....'.......XTERM.......".....!.....".....!............
Linux 3.13.0-32-generic (ubuntu) (pts/0)

..ubuntu login: j.ju.ul.li.ia.an.n
..Password: flag{bigdataisaproblemnotasolution}
Login incorrect
..ubuntu login:

And we find our flag: bigdataisaproblemnotasolution!

Hack all the things!

Edited: If you had decided to use chaosreader to process the pcapng file instead, the solution from this write-up is also cool:

for f in pcap.pcapng-chaosreader/*.html; do cat "${f}" | w3m -dump -T text/html "${f}"; done | egrep "flag{"