Re: [Linphone-developers] ZRTP error 0x70 during negotiation between Lin

Dear Werner Dittmann,

Yes, this issue used to occur every time when I called my friend. However, when
I called my friend with another computer which has an Ubuntu 12.04 installation,
I was very surprised to see that the ZRTP negotiation was successful.
Afterwards, I did the same with a Debian Sid based virtual machine with a set-up
similar to my physical installation, and the ZRTP negotiation was also successful.

Afterwards, it occurred to me that this problem could be with something related
to my Linphone settings, which were specific to my friend.

I tried recreating my configuration file, but that did not help. However, then I
realized/remembered that the ".linphone-zidcache" file contains contact-specific
persistent data for ZRTP. As a last resort, I deleted this file. ZRTP
negotiations started working again when I called my friend afterwards.

All in all, it looks like the problem was caused by a corrupted
".linphone-zidcache" file. In hindsight, I wish I had kept a copy of the
corrupted file in case you wanted to look at it, but I didn't think of this
possibility during my debugging.

I realize I caused some inconvenience to you with this spurious bug report. I
hope that you will accept my sincere thanks for offering your help.

Thank you,

M. Vefa Bicakci

On 09/04/13 02:25 AM, Werner Dittmann wrote:

Does it happen for every call when Linphone Mac OS X is involved?

Yes, the error code 0x70 if a failure on the confirm HMAC check. This

may happen if the data was modified while traveling on the network

(not very plausible :-) ) or some of the crypto functions don't work

correctly on the Mac.

The Confirm packet exchange in ZRTP confirms that the computed DH and

derived keys are correct. Thus my first rough guess is that the DH

functions have some problems. I don't know the Linphone integration/build

scripts. Can you check which crypto library Linphone on Linux and Mac OS X

uses?

ZRTP supports openSSL to perform big integer, HMAC, AES functions and it

also supports/contains stand-alone crypto/big integer functions that do

not require openSSL.

Werner

Am 08.04.2013 23:27, schrieb M. Vefa Bicakci:

Hello,

A friend of mine is using the official distribution of Linphone 3.5.2 with ZRTP enabled on Mac OS X 10.7.5, and I am using Linphone 3.5.2 with ZRTP enabled on Debian Sid. (I compiled Linphone from sources, and confirmed that ZRTP works.)

The problem is, when I call my friend, or when my friend calls me, ZRTP negotiation fails with "error 0x70", which I believe is an HMAC verification error, based on the libzrtpcpp2 source code. The call, however, goes through properly, and we are able to talk without ZRTP. I have verified this issue with sip2sip.info and sip.linphone.org accounts.

Below, under my signature, I am quoting the relevant part of the logs from the Linux side of a ZRTP negotiation attempt.

Because Linphone/Linux to Linphone/Linux calls work for me with ZRTP, I think the ZRTP negotiation failure has to do running Linphone and/or libzrtpcpp2 on Mac OS X.

Is there any information I can provide to help in fixing this problem? I wrote a few MacPorts port files to compile Linphone with ZRTP support under Mac OS X, so I can test patches for Linphone (or libzrtpcpp2) if needed.

Thank you in advance,

M. Vefa Bicakci

=-=-=-=

Log excerpt from Linux-side of a ZRTP negotiation.

[snip]

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From:	‏bader Albader
Subject:	Re: [Linphone-developers] ZRTP error 0x70 during negotiation between Linphone on Linux and Linphone on Mac OS X.
Date:	Thu, 11 Apr 2013 10:38:34 +0300