IAX2 encryption: calls end abrutly due to normal packet loss

[François Marier]

Binary package hint: asterisk

As described upstream, IAX2 encryption is broken in the Jaunty version of asterisk:

  If an iax channel is encrypted, and a retransmit frame is sent, that packet's iseqno
  is updated while it is encrypted. This causes the entire frame to be corrupted. When
  the corrupted frame is sent, the other side decrypts it and sends a VNAK back because
  the decrypted frame doesn't make any sense. When we get the VNAK, we look through the
  sent queue and send the same corrupted frame causing a loop. To fix this, encrypted
  frames requiring retransmission are decrypted, updated, then re-encrypted. Since
  key-rotation may change the key held by the pvt struct, the keys used for
  encryption/decryption are held within the iax_frame to guarantee they remain correct.

This makes it practically impossible to turn IAX2 encryption in most of my calls
because the connection constantly cuts off. So it's a very serious bug for anybody using
encryption with Asterisk.

I have attached a debdiff which applies the upstream patch on the current Jaunty version.

[François Marier (fmarier)]

I have also uploaded a fixed package to my PPA:

  deb http://ppa.launchpad.net/fmarier/ppa/ubuntu jaunty main

[Jon Charge (seropith)]

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François Marier wrote:
> Public bug reported:
>
> Binary package hint: asterisk
>
> As described upstream, IAX2 encryption is broken in the Jaunty
> version of asterisk:
>
> If an iax channel is encrypted, and a retransmit frame is sent,
> that packet's iseqno is updated while it is encrypted. This causes
> the entire frame to be corrupted. When the corrupted frame is sent,
> the other side decrypts it and sends a VNAK back because the
> decrypted frame doesn't make any sense. When we get the VNAK, we
> look through the sent queue and send the same corrupted frame
> causing a loop. To fix this, encrypted frames requiring
> retransmission are decrypted, updated, then re-encrypted. Since
> key-rotation may change the key held by the pvt struct, the keys
> used for encryption/decryption are held within the iax_frame to
> guarantee they remain correct.
>
> This makes it practically impossible to turn IAX2 encryption in
> most of my calls because the connection constantly cuts off. So
> it's a very serious bug for anybody using encryption with Asterisk.
>
>
> I have attached a debdiff which applies the upstream patch on the
> current Jaunty version.
>
> ** Affects: asterisk Importance: Unknown Status: Unknown
>
> ** Affects: asterisk (Ubuntu) Importance: Undecided Status: New
>
> ** Affects: asterisk (Debian) Importance: Unknown Status: Unknown
>

status confirmed
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[Scott Kitterman (kitterman)]

Ack conditional on the sponsor goes to upstream svn and double checks this is the upstream fix.

[Iain Lane (laney)]

Uploaded, thanks for your work. Double thanks for forwarding back to Debian. I just added LP: #xxx in the changelog to close this bug.

[François Marier (fmarier)]

Here is how to extract the patch from the upstream svn repo (their svn web interface doesn't work):

  svn checkout http://svn.digium.com/svn/asterisk/branches/1.4 asterisk-1.4
  cd asterisk-1.4
  svn log -r 181340
  svn diff -r 181339:181340

(The revision number is from the upstream bug linked to above)

[Launchpad Janitor (janitor)]

This bug was fixed in the package asterisk - 1:1.4.21.2~dfsg-3ubuntu2

---------------
asterisk (1:1.4.21.2~dfsg-3ubuntu2) jaunty; urgency=low

  * Fix for IAX2 encrypted channels dropping out due to normal packet loss
    (LP: #350732)

 -- Francois Marier <email address hidden> Sun, 29 Mar 2009 17:45:27 +1300