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Re: Re: MAC Spoofing Prevention in Wireless
From: Jamie Ivanov <jamie.ivanov () gmail com>
Date: Thu, 14 Jul 2011 18:55:32 -0500

The DHCP server would be helpful but a static IP would render that
form of detection useless (unless there is some form of encrypted
dhcp, no idea of that technology exists). Using a combination of time
of association and which AP the host is on and whether it is actively
associated will be the best I can come up with off the top of my head.

Say Client1 associated with WAP1 and is still connected, Client2
spoofed Client1's MAC (even with a static IP) and associated sometime
after. What are the odds that in a multi-wap environment that both
clients will be on the same WAP? If Client1 is STILL associated on
WAP1 and Client2 tries to connect on WAP7, the controller will be like
"fuck no, someone with that mac is already auth'd on another WAP". The
more waps you have the more true that would become.

My only other suggestion is an additional transport protocol that can
tag packets in a specific fashion to determine the true/original
client vs. a spoofed interface. I doubt client isolation would be
beneficial here.

But because this is rather hard to do, it would be wise to have
additional security measures in place to prevent this scenario from
occurring. While I have experience in *some* cisco wireless equipment
in standalone, I can imagine that cisco has some specific enhancements
that could do something similar without you having to generate a
custom solution.

I've been up for 3 days with less than 5 hours of sleep, be gentle...

On Thu, Jul 14, 2011 at 12:53 PM, David Gillett <gillettdavid () fhda edu> wrote:
 And what are they going to tell you?

 IF you're very lucky, you might see the same MAC address trying to renew
more than one IP address -- but that can only happen if one of the clients
got its lease from somewhere else.  You'll probably just see some address
requests from MACs that the server thinks already have valid leases -- and
THAT happens all the time, perfectly legitimately.

 Finding out what MAC addresses are on your network IS straightforward.
Detecting that one or more of them are not unique, though, is NOT -- unless
you can see that they are on different physical ports, or associating to
different APs, or generating both associated and non-associated wireless
control traffic.  And none of those things is going to be visible to or
logged by your DHCP server....

 Any obvious/straightforward method of detecting duplicate MAC addresses
has to presume some OTHER mechanism for identifying distinct clients.  Since
in the standard/portable case, distinct MAC addresses ARE the mechanism for
making that distinction, a working solution, if one exists, is going to
depend on something non-standard or non-portable or with an otherwise
strange definition of "straightforward".

David Gillett

________________________________

From: Brent Jesmer [mailto:BJesmer () platformsolutions com]
Sent: Wednesday, July 13, 2011 14:56
To: David Gillett; security-basics () securityfocus com
Subject: RE: Re: MAC Spoofing Prevention in Wireless


So checking the dhcp logs or dhcp client tables isn't straight forward?

Brent Jesmer
Platform Solutions Inc.
Sr. Security Consultant
Sent via DROID. Please excuse any mis spelling.


-----Original message-----


       From: David Gillett <gillettdavid () fhda edu>
       To: Brent Jesmer <BJesmer () PlatformSolutions com>,
"security-basics () securityfocus com" <security-basics () securityfocus com>
       Sent: Wed, Jul 13, 2011 21:53:31 GMT+00:00
       Subject: RE: Re: MAC Spoofing Prevention in Wireless


                  It's not "straightforward" at all.  How do you tell that
there are two
       MACs the same on the network?

         On a wired network with STP enabled, you know there's *something*
strange
       going on if you see packets with the same source MAC address from
more than
       one wired interface.  But that simply doesn't translate to wireless.

       (HINT:  MAC addresses are supposed to be unique on a subnet/segment.
If
       they're not, your network is out of spec and unlikely to work
properly; any
       communications that happen to work are just good luck and may not be
       reproducible.)

       David Gillett


       -----Original Message-----
       From: bjesmer () platformsolutions com
[mailto:bjesmer () platformsolutions com]
       Sent: Friday, July 08, 2011 12:31
       To: security-basics () securityfocus com
       Subject: Re: Re: MAC Spoofing Prevention in Wireless

       The concept is fairly straight forward. The AP looks to see if there
are 2
       MACs of the same on the network and disallows the second one on the
network.
       Not having worked with the Aruba yet, i would try a deauth attack
against
       the mac you are going to spoof and then try to get on. If you can
deauth
       that client and get on before it, you might be able to get in.


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-- 
Jamie Ivanov / KC9LFD
m.608.399.4252
http://www.linkedin.com/in/jamieivanov
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