[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:              2011-05-05 07:49 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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---------------------------------------------------------------------- 
 (0134480) Marquis (developer) - 2011-05-05 07:49
 https://issues.asterisk.org/view.php?id=19202#c134480 
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Aside from any RFC issues, I think the desired behaviour would be that the
authenticated INVITE would be the source of the channel variables.  So my
opinion is that this patch should be committed. 

Issue History 
Date Modified    Username       Field                    Change               
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2011-05-05 07:49 Marquis        Note Added: 0134480                          
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