[OpenSIPS-Users] UAC module causing malformed CANCEL

[Ben Newlin]

Hello,

I have found an issue with using the UAC module to replace the From/To headers. When one of these headers is the last header in a SIP INVITE, the UAC module is injecting an extra line break in subsequent CANCEL requests causing an invalid request. This happens when either of these headers are the last header in the originally received INVITE, but also if they become the last header due to modifications made to the original INVITE, e.g. if the last 2 headers were To followed by P-Asserted-Identity and the script processing calls remove_hf(“P-Asserted-Identity”) thus making the To header last.

I have only seen this happen on a CANCEL request. Other sequential requests like BYE or re-INVITE are not malformed.

A tcpdump capture of the message sequence can be found here: https://pastebin.com/myDVU5Jz. Note the extra whitespace line in the second CANCEL message forwarded from OpenSIPS (203.0.113.3).

Ben Newlin
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