The last post described some of the background details of how the new CCMP-attack works. Using this feature in Pyrit is quite easy:

As the Temporal Key is not used during the authentication but only in the following data-stream, Pyrit needs more than just the fourway-handshake. The ‘analyze‘-command from now on indicates if an encrypted packet can be associated with an authentication and sufficiently constrained to actually “belong” to this authentication (encrypted with the Temporal Key from that authentication). A simply asterisk shows that:

>pyrit -r wpa2psk-linksys.dump.gz analyze

Pyrit 0.4.1-dev (svn r304) (C) 2008-2011 Lukas Lueg http://pyrit.googlecode.com

This code is distributed under the GNU General Public License v3+ Parsing file ‘wpa2psk-linksys.dump.gz’ (1/1)…

Parsed 499 packets (499 802.11-packets), got 1 AP(s) #1: AccessPoint 00:0b:86:c2:a4:85 (‘linksys’):

#1: Station 00:13:ce:55:98:ef, 3 handshake(s):

#1: HMAC_SHA1_AES, good*, spread 1

#2: HMAC_SHA1_AES, good*, spread 1

#3: HMAC_SHA1_AES, good*, spread 1

All “attack“-commands from now on understand the new switch “–aes“. This switch tells Pyrit to attack an authentication using the new CCMP-approach if possible. You can, in fact, apply this switch all the time. Pyrit will figure out if the CCMP-path is actually possible. The switch will be removed (or reversed) in the future.

>pyrit -r wpa2psk-linksys.dump.gz -i dict.gz –aes attack_passthrough

Pyrit 0.4.1-dev (svn r304) (C) 2008-2011 Lukas Lueg http://pyrit.googlecode.com

This code is distributed under the GNU General Public License v3+ Parsing file ‘wpa2psk-linksys.dump.gz’ (1/1)…

Parsed 499 packets (499 802.11-packets), got 1 AP(s) Picked AccessPoint 00:0b:86:c2:a4:85 (‘linksys’) automatically.

Tried 4094 PMKs so far; 1049 PMKs per second. The password is ‘dictionary’.

Pyrit can use the new AES-NI instruction-set found in recent processors (e.g. Intel Sandy Bridge) to boost performance. The “list-cores“-command shows if the local processor supports this instruction-set:

> pyrit list_cores

Pyrit 0.4.1-dev (svn r304) (C) 2008-2011 Lukas Lueg http://pyrit.googlecode.com

This code is distributed under the GNU General Public License v3+ The following cores seem available…

#1: ‘CPU-Core (SSE2/AES)’

#2: ‘CPU-Core (SSE2/AES)’

#3: ‘CPU-Core (SSE2/AES)’

#4: ‘CPU-Core (SSE2/AES)’

Note that a recent version of GCC 4.4+ is required to compile the intrinsics for the new AES-NI instructions. Pyrit‘s module will not be able to use the hardware-based AES-acceleration if it was compiled with a previous version of GCC.

Please also note that this feature is currently only the the svn-codebase and not found in a released stable version. Your help is required to make this process faster. Please submit cases where Pyrit is able to successfully attack a handshake using the original approach but fails to do so when the –aes switch is applied. Such regressions need to be sorted out before we can make the new CCMP-approach a default and get a new stable version 0.4.1 out onto the road. Please open a bug on Pyrit’s bugtracker for these cases (including all necessary information).

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April 19, 2011

Categories: Uncategorized . . Author: ebfe

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