[pkg-wpa-devel] Bug#579297: Re: Bug#579297: wpasupplicant: Recompiling with gnutls fixes (or workarounds) the problem

[Balint Reczey]

tags 579297 patch
severity 579297 important
thanks

On 11/03/2012 12:33 AM, Stefan Lippers-Hollmann wrote:
> Control: forcemerge 668612 -1
>
> Hi
>
> On Friday 02 November 2012, Klaus Knopper wrote:
>> Package: wpasupplicant
>> Version: 1.0-3
>> Severity: normal
>>
>>
>> In an eduroam environment (which is basically WPA-Enterprise), I can
>> confirm disconnects without the possibility to reconnect when using
>> wpa_supplicant wit network-manager. Killing and restarting
>> wpa_supplicant allows a temporary reconnect.
> This is
> 	http://w1.fi/bugz/show_bug.cgi?id=447
> respectively
> 	http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=668612
> 	http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=561081
> 	http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=574714
> 	http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=579297
> 	http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=667706
>
>> When researching the problem, I found this posting:
>> https://bugs.launchpad.net/ubuntu/+source/wpasupplicant/+bug/429370/comments/19
>>
>> It states that the problem may be actually an openssl bug which lets the rekeying
>> process fail permamently, and recommended recompiling with gnutls instead of
>> openssl. I did this:
> […]
>
> The problem with this suggestion and the according patch, is that it
> switches from one (known) set of bugs to another (unknown) one. While
> linking to gnutls is supported upstream, none of the major
> distributions (not even Ubuntu) actually does so, which makes it pretty
> much untested in practice. Even if we wanted to switch to gnutls, doing
> so simply isn't possible at this stage of Debian's release process and
> in freeze*.
>
> *)	However technically speaking, we can't switch to gnutls anytime
> 	soon, because gnutls doesn't provide an udeb, which is needed for
> 	using wpa_supplicant by the Debian installer (d-i). While your
> 	package build against gnutls succeeded, you have most likely ended
> 	with an unsatisfiable (in the d-i/ udeb context) dependency on
> 	libgnutls26-udeb for wpasupplicant-udeb_*.udeb (dpkg-gensymbols
> 	employs very crude heuristics to construct the dependencies for
> 	udeb packages without actually having access to a udeb context).
>
> […]
>> and have been testing the modified package for about a month now, the
>> frequent disconnects have completely disappeared.
>>
>> The right place for a real fix would probably be openssl, but the
>> problem does not seem to be addressed or sufficiently researched there,
>> so the workaround by using gnutls instead of openssl gnutls seems to be
>> the best option for now.
> […]
>
> At this moment it is not obvious to me if wpa_supplicant is broken, or
> if some popular commercial wlan installations used for eduroam
> institutions are to blame. While, given the ubiquity and prevalence of
> this issue in academic environments, it might be possible that
> wpa_supplicant may need to work around the problem, however this would
> best be fixed at wpa_supplicant's upstream. Unfortunately none of the
> current wpa maintainers for Debian has access to an affected wlan setup
> in order to try to reproduce the problem, nor has enough information to
> recreate an affected EAP/ PAP setup for debugging, which significantly
> reduces our abilities to help. Therefore it's probably best to engage
> with wpa_supplicant upstream to get this fixed once and for all.
>
> Regards
> 	Stefan Lippers-Hollmann
Hi,

Please see the attached patch fixing the problem while not breaking 
other use cases.

The fix turns off listing the SessionTicket TLS extension in every 
second hello packet allowing broken servers to accept the connection.

Log:
1 0.000000000 Apple_ee:ee:ee -> Procurve_aa:aa:aa EAP 30 Response, Identity
3 0.060381000 Procurve_aa:aa:aa -> Apple_ee:ee:ee EAP 60 Request, 
Protected EAP (EAP-PEAP)
4 0.060918000 Apple_ee:ee:ee -> Procurve_aa:aa:aa SSL 249 Client Hello
5 0.111778000 Procurve_aa:aa:aa -> Apple_ee:ee:ee TLSv1 60 Alert (Level: 
Fatal, Description: Bad Certificate)
6 0.112140000 Apple_ee:ee:ee -> Procurve_aa:aa:aa EAP 24 Response, 
Protected EAP (EAP-PEAP)
7 0.163244000 Procurve_aa:aa:aa -> Apple_ee:ee:ee EAP 60 Failure
8 0.745350000 Procurve_aa:aa:ab -> Apple_ee:ee:ee EAP 60 Request, Identity
9 0.745615000 Apple_ee:ee:ee -> Procurve_aa:aa:ab EAP 30 Response, Identity
10 0.809622000 Procurve_aa:aa:ab -> Apple_ee:ee:ee EAP 60 Request, 
Protected EAP (EAP-PEAP)
11 0.810101000 Apple_ee:ee:ee -> Procurve_aa:aa:ab SSL 245 Client Hello
12 0.901729000 Procurve_aa:aa:ab -> Apple_ee:ee:ee EAP 918 Request, 
Protected EAP (EAP-PEAP)
13 0.901942000 Apple_ee:ee:ee -> Procurve_aa:aa:ab EAP 24 Response, 
Protected EAP (EAP-PEAP)


As you can see the first hello is longer due to the extension and has 
been rejected by the buggy server.
The second connection attempt has not listed the extension and has been 
accepted by the buggy server - which happens to run on a different host.

Please forward the patch upstream as well, I did not want to register to 
their bugzilla for this single patch.

IMO this fix is needed in Wheezy, but I did not want to push the 
priority higher on my own.

Cheers,
Balint
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