Wireshark-dev: [Wireshark-dev] Decoding error SS7 SMS-MO (ok) vs SMPP Deliver SM (malformed)

From: Andreas Fink <afink@xxxxxxxxxxxxx>
Date: Tue, 6 Jul 2021 18:11:29 +0200
Hello,

I run into a decoding error in SMPP

I have a GSM SMS payload which comes in as SMS-MO into a SMSC.

the GSM-SMS TPDU SMS-submit -> TP-UserData section contains the bytes:
    027100001412000001897d3623d52eaea27bb6dad9e9c37cfa

Wireshark decodes this correctly as having a UDH header of 0x71 which is a (U)SIM Tooling Security Header and some raw binary data.



This same Payload is now packed by the SMSC into a SMPP Deliver SM.
The bytes are exactly the same. but now Wireshark can't decode it anymore



So I presume the SMPP branch doesn't know the same User Data Headers as the SS7 branch of Wireshark.
Even worse, it does not skip over a unknown UDH header but assumes everything is wrong.


I think this needs fixing.
I can probably find it in the right spot in the source but I don't have a wireshark build environment set up as I used it mainly on a Mac (which has quite some complex dependencies). So if someone has an easy way to fix this, it would be greatly apprechiated.




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