Re: Capturing Wifi traffic on MacOS Lion

[frank cui <frankcui24 () gmail com>]

Hi Marco,

I have done some more search on this, and yes, the 802.11 data payload is
encrypted according to 802.11i standard.
[http://www.cwnp.com/bbpress/topic.php?id=2267]

I haven't got an answer, but here are two examples that might be very
related to our problems:

[1] After joining a wpa2-personal-psk network, i have telnet'ed to a
server, and captured all the telnet traffic with a filter. Then i followed
the tcp stream in those traffic, the username and password are all in plain
text without any encryption. And wireshark perceive those packets as
ether\ip\tcp.

[2] There is a wiki page explaining the usage of decrypting 802.11i
traffic. [http://wiki.wireshark.org/HowToDecrypt802.11]
. And a sample dump can be found at the bottom of the page. Wireshark
perceive those packets as 802.11 beacon frames.

So obviously this two kinds of traffic are different from the perspective
of wireshark. I'm also not a expert on wireless, but i guess in the first
case, the OS has already decrypted the traffic for us since we are in the
wifi network. You are also in the first case because you are capturing all
the traffic directed to you. In the second case, it's in monitoring mode
and the pre-requisite is that you are not in the wifi network.

however this is only my speculation, hope some wireless networkers could
give some ideas on this problem.

thanks
frank

2011/11/11 Marco Zuppone <msz () msz it>

> Hello Frank,
>
> I'm using a WPN824v2 Netgear with WPA2-PSK[AES] key.
> In my opinion the paylod should be encrypted as well…but I'm not an expert
> of the subject.
> If they payload is not encrypted what is the  wpa-pwd:myPassword setting
> for??
>  Kind regards,
> Marco - StockTrader
> On 11 Nov 2011, at 07:33, Frank Cui wrote:
>
> > Hi Marco,
> >
> > Is your wifi network using a common wpa/wpa2 pre-shared key
> configuration? If so, then I believe there is no symmetric encryption
> algorithm applied to the payload. The key is primarily used to prevent
> unknown users joining your network.
> > Thanks
> > Frank
> >
> > Sent from my iPad
> >
> > On 2011-11-12, at 12:53 AM, Marco Zuppone <msz () msz it> wrote:
> >
> > > Hello,
> > >
> > >
> > > I'm studying for the certification and so I was trying to capture some
> Wifi traffic but I have some questions about it:
> > > In the IEEE 802.11 protocol configuration I added the key in the format
> wpa-pwd:myPassword
> > > Then I started to capture the traffic with the default options: Monitor
> mode + promisquous mode + 802.11 plus radio tap header
> > > I used this capture filter: wlan host 00:26:08:dc:e1:55  to capture
> only the communication directed to my pc (I know that I could disable the
> monitor mode in this case…)
> > > I started the capture and browsed to an Internet site for some minutes,
> I applied the display filter wlan.fc.type_subtype == 0x20 && !llc to get
> only the data frames and I was able to see some HTTP requests in cleartext
> in the payload.
> > > So far so good but now I have the question:
> > >
> > > I modified the password using deliberatly a wrong one, applied, even
> closed and reopened WireShark and repeated the process.
> > > I can still see the cleartext….
> > > So how come I can see the decrypted cleartext using a password that is
> wrong? Is this because is the OS driver that decrypts for me??
> > > Kind regards & Thanks
> > > Marco - StockTrader
> ___________________________________________________________________________
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