Sky Broadband Router SR101 - Weak WPA-PSK Generation Algorithm

# Exploit Title: Sky Broadband Router – Weak algorithm used to generate WPA-PSK Key
# Google Dork: 
# Date: 08/08/2014
# Author: Matt O'Connor / Planit Computing
# Advisory Link:  http://www.planitcomputing.ie/sky-wifi-attack.pdf 
# Version: 
# Category: Remote
# Tested on: Sky SR101 Router



The SR101 routers supplied by Sky Broadband are vulnerable to an offline dictionary attack if the WPA-PSK handshake is obtained by an attacker.
 
The WPA-PSK pass phrase has the following features:
•	Random
•	A to Z Uppercase only
•	8 characters long
•	208,827,064,576 possible combinations ( AAAAAAAA – ZZZZZZZZ ) 26^8
 
We notified Sky Broadband about the problem in January 2014 yet Sky Broadband are still supplying customers with routers / modems that use this weak algorithm.
At the time, graphics cards were expensive and clustering several machines was not financially viable to the average hacker.

We purchased a used rig in December 2013, comprising off:
•	Windows 7
•	I3 Processor
•	4GB RAM
•	2TB Drive
•	Radeon HD 5850

We generated 26 dictionary files using “mask processor” by ATOM, piping each letter out to its own file, for example:

A:  ./mp32 A?u?u?u?u?u?u?u > A.TXT = AAAAAAAA – AZZZZZZZ
B: ./mp32 B?u?u?u?u?u?u?u > B.TXT = BAAAAAAA – BZZZZZZZ
etc

Each .txt file weighed in at around 60GB’s each.  The 26 files took up about 1.6TB of storage.

We now had the complete key space, partitioned into 26 different files.  This allowed us to distribute the brute force attack amongst multiple computers.  There are other ways with ocl-hashcat but this was the simplest.

Using our Radeon HD5850 on standard settings, we were hitting 80,000 keys per second.  Breakdown below:

•	26^8 = 208,827,064,576 ( 208 billion possible combinations )
•	26^8 / 80,000 keys per second = 2,610,338 seconds
•	2,610,338 / 60 seconds = 43,505 minutes
•	43,505 / 60 minutes = 725 hours
•	725 hours / 24 hours = 30 Days

For €185, we had built a computer that could crack the default Sky Broadband wireless password within 30 days.  The WPA-PSK handshake we used started with the letter S and was cracked within 96 hours.

We ended up getting a second machine for the same price which resulted in our maximum cracking time being reduced to 15 days.

If you’re using the default password on your Sky Broadband connection, we recommend changing it immediately to a more secure password, using a mix of letters, numbers and symbols.