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Malformed packet in the GSM MAP

asked 2018-05-25 06:16:43 +0000

Hanosh gravatar image

Hi,

We couldn't decode some GSM MAP packets in the wireshark.

Kindly check and revert, how to decode it properly in the wireshark.

Thanks, Varghese

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At the very least you would need to provide the capture that has the issue and your OS and Wireshark version details.

grahamb gravatar imagegrahamb ( 2018-05-25 08:50:47 +0000 )edit

Thanks for the response. I couldn't attach the trace here, So I just pasted below and Version 1.2.8 (SVN Rev 32676)

[... snipped for brevity ...]

GSM SMS TPDU (GSM 03.40) SMS-DELIVER
    1... .... = TP-RP: TP Reply Path parameter is set in this SMS SUBMIT/DELIVER
    .1.. .... = TP-UDHI: The beginning of the TP UD field contains a Header in addition to the short message
    ..1. .... = TP-SRI: A status report shall be returned to the SME
    .... .1.. = TP-MMS: No more messages are waiting for the MS in this SC
    .... ..00 = TP-MTI: SMS-DELIVER (0)
    TP-Originating-Address - (919566737288)
    TP-PID: 0
    TP-DCS: 0
        00.. .... = Coding Group Bits: General Data Coding indication (0)
        Special case, GSM 7 bit default alphabet
    TP-Service-Centre-Time-Stamp
        Year 18, Month 05, Day 15
        Hour 09, Minutes 59, Seconds 03
        Timezone: GMT + 5 hours 30 minutes
    TP-User-Data-Length: (6) depends on Data-Coding-Scheme
    TP-User-Data
        User-Data Header
            User Data Header Length (32)
            IE: Reserved for ...
(more)
Hanosh gravatar imageHanosh ( 2018-05-25 10:48:47 +0000 )edit

1.2.8 is a very old version (nearly a decade), any chance of trying a modern one that might have fixed the issue?

grahamb gravatar imagegrahamb ( 2018-05-25 11:54:11 +0000 )edit

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answered 2018-05-25 13:59:06 +0000

Pascal Quantin gravatar image

updated 2018-05-25 13:59:46 +0000

This GSM SMS message really seems to be malformed. It's header indicates that the TP-User-Data-Header is present. So the TP-User-Data 20 58 0E 86 c3 01 starts with a User Data Header. Per 3GPP 23.040 chapter 9.2.3.24, the first byte (here 0x20) is the length of the header. But there are only 5 bytes remaining in the payload and not 32, thus the decoding failure. What was the expected content of the SMS message?

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Asked: 2018-05-25 06:16:43 +0000

Seen: 72 times

Last updated: May 25