possible bug in ZRTP implementation - SRTP replay check failed!

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Hi Werner,

Thanks for replying. It's quite an honor after all you've done to get ZRTP
into the mainstream.

I'm using the latest CSip nightly build, and I've also experimented with
Regie's fullOpenSSLbuild too. Both give these results.
I've uploaded a full log here <http://pastebin.com/bgQiiuaU>. I don't see
any other ZRTP messages. On the clients, usually everything works ok (ie
SAS pops up, gets verified,etc) and audio flows both ways before the crash.

I stand corrected on attributing the issue to PJSIP. Obviously I'm no
expert on these issues, all I know is what I've reported.
And I've been using CSip's ZRTP since it first came along (a year or 2
ago?). Although it was never easy to get it working, I have used it
successfully with your PJSIP  ZRTP implementation. The crashes I mention
are fairly recent. Can't really say when they started since I haven't used
CS in quite some time. If it helps any, I think that ZRTP worked fine last
time I used it last December.

I think I also mentioned that I tested the same setup with (SDES) "classic"
SRTP, and there were no issues then. On both ZRTP and SDES SRTP tests, I
always use TLS (v1) transport. Calls lasted well over 10 minutes without
any problems with SDES. Maybe its a bug in the SRTP stack. I really don't
know but I hope smarter people like you can figure it out.

Let me know if there's any other tests I can do or help in any other way
with my limited knowledge.

And thanks again for your contributions to ZRTP. Many people appreciate
your work.


On Tue, Jun 4, 2013 at 6:55 AM, Werner Dittmann <Werner.Dittmann at t-online.de
> wrote:

> Am 03.06.2013 20:33, schrieb Privus 007:
> > Hello list,
> >
> > I've researched this issue quite a bit before posting it here, so I'm now
> > fairly confident this bug/issue is with PJSIP's implementation of ZRTP
> and
> > not an Android or CSipSimple issue.
> >
> > In a nutshell, as I reported in CSipSimple's issue tracker here
> > http://code.google.com/p/csipsimple/issues/detail?id=2378 , all my ZRTP
> > enabled calls crash after a few seconds with the log full of these error
> > messages:
> >
> > "zrtp_android.c !ZRTP warning message: Dropping packet because SRTP
> > replay check failed!"
>
> Actually this message occurs _after_ ZRTP has setup the SRTP crypto
> context.
> Do you see any other ZRTP message before the replay message on one of the
> clients?
>
> >
> > I don't see anyone reporting the issue here, and I believe CSip
> > basically uses PJSIP's code for its ZRTP and SRTP implementation, so I
> > think the root of the problem lies in PJSIP.
>
> Not really PJSIP. It could be in the handling of the SRTP packets. Replay
> error
> means that the SRTP crypto stack thinks the packet was already received,
> i.e.
> a duplicate sequence number. This can have several reasons: the packet was
> given
> twice to the SRTP stack or some data was overwritten or the SRTP stack has
> a bug
>
> >
> > I've experimented with different phones (Samsung S3 LTE running 4.2.2
> > as well as Sony Xperia running stock 4.0.4) and the crashes always
> > occur with ZRTP. Plain old (SDES based) SRTP calls are fine though.
>
> Which version of CSipSimple do you use? Nightly? I need to check which
> version of the ZRTP/SRTP stack CSIpSImple uses. I did some small fixes in
> SRTP some time ago that solves a "border case problem" with replay
> handling,
> however your report does not indicate this border case.
>
> >
> > Let me know if there's anything I can do to help or if you need more
> > logs and/or info.
> >
> > Thanks,
> >
> > Privus
> >
> >
> >
> > _______________________________________________
> > Visit our blog: http://blog.pjsip.org
> >
> > pjsip mailing list
> > pjsip at lists.pjsip.org
> > http://lists.pjsip.org/mailman/listinfo/pjsip_lists.pjsip.org
> >
>
>
> --
> ----------------------------------------------
> Werner Dittmann    Werner.Dittmann at t-online.de
> Tel +49 173 44 37 659
> PGP key: 82EF5E8B
>
> _______________________________________________
> Visit our blog: http://blog.pjsip.org
>
> pjsip mailing list
> pjsip at lists.pjsip.org
> http://lists.pjsip.org/mailman/listinfo/pjsip_lists.pjsip.org
>
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