[asterisk-bugs] [Asterisk 0019202]: [patch] switching From-address mid-register breaks channel variables

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=19202 
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Reported By:                wdoekes
Assigned To:                
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Project:                    Asterisk
Issue ID:                   19202
Category:                   Channels/chan_sip/General
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     ready for review
Asterisk Version:           1.4.41 
JIRA:                       SWP-3397 
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2011-04-29 05:12 CDT
Last Modified:              2011-05-06 15:01 CDT
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Summary:                    [patch] switching From-address mid-register breaks
channel variables
Description: 
Hi,

I'm using a inbound proxy before my asterisk which guesses which account
someone is using based on message headers and IP addresses. This is not
reliable until I get a Digest username. When I get the digest username I
am certain which user it is, and I replace the From-address accordingly.

In this scenario, the following can happen:

(1) INVITE from CLIENT to PROXY
(2) PROXY replaces From: with "Joe" and sends to ASTERISK
(3) ASTERISK challenges the INVITE with a 40[17]

(4) INVITE from CLIENT TO PROXY using Digest username "Lucy"
(5) PROXY replaces From: with "Lucy" and sends to ASTERISK
(6) ASTERISK handles INVITE fine...

... except for the fact that the channel variables are now duplicated
(and in the wrong order).


sip.conf:

[JoeUser]
setvar=username=Joe
accountcode=JoeAccount
...
[LucyUser]
setvar=username=Lucy
accountcode=LucyAccount
...

Now, in my dialplan:
- ${CDR(accountcode)} equals "LucyAccount"
and 
- ${username} equals "Joe"

Why is that? Because the channel variables set during the first INVITE
are not destroyed. And, due to the linked-list nature of chanvars, they
are in the "wrong" order, containing first username=Lucy and then
username=Joe.

When copying the chanvars to the dialplan context using
pbx_builtin_setvar_helper Joe overwrites Lucy, hence the inconsistency.


The attached patch should fix it.


Regards,
Walter Doekes
OSSO B.V.


P.S. I'm expecting someone to reply that switching From: mid-INVITE is
not legal, SIP-wise. As a pre-emptive response to that:
(1) I couldn't find the relevant RFC-part that states so and,
(2) asterisk is inconsistent in it's behaviour because it *does* accept
    the switch, apart from this bug.
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---------------------------------------------------------------------- 
 (0134597) svnbot (reporter) - 2011-05-06 15:01
 https://issues.asterisk.org/view.php?id=19202#c134597 
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Repository: asterisk
Revision: 317867

U   branches/1.8/channels/chan_sip.c

------------------------------------------------------------------------
r317867 | russell | 2011-05-06 15:01:17 -0500 (Fri, 06 May 2011) | 10
lines

chan_sip: Destroy variables on a sip_pvt before copying vars from the
sip_peer.

Don't duplicate variables on the sip_pvt.  Just reset the variable list
each
time.

(closes issue https://issues.asterisk.org/view.php?id=19202)
Reported by: wdoekes
Patches:
      issue19202_destroy_challenged_invite_chanvars.patch uploaded by
wdoekes (license 717)

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http://svn.digium.com/view/asterisk?view=rev&revision=317867 

Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2011-05-06 15:01 svnbot         Checkin                                      
2011-05-06 15:01 svnbot         Note Added: 0134597                          
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