Wireshark · Wireshark-bugs: [Wireshark-bugs] [Bug 9622] sendRoutingInfoForSMResp Phase 1 decode problem (GSM MAP)

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Comment # 3 on bug 9622 from Luke Mewburn

I think you're right about the schema.

The ASN.1 for RoutingInfoForSM-Arg and RoutingInfoForSM-Res was changed in a
non-backwards-compatible manner between version 1 and subsequent versions.

E.g. from ETS 300 599: December 2000 (GSM 09.02 version 4.19.1)

--v--
RoutingInfoForSM-Res::= SEQUENCE {
        imsi                    IMSI,
        locationInfoWithLMSI            [0] LocationInfoWithLMSI,
        mwd-Set         [2] BOOLEAN     OPTIONAL,
        -- mwd-Set must be absent in version greater 1
        ...}

LocationInfoWithLMSI ::= SEQUENCE {
                locationInfo    LocationInfo,
                lmsi            LMSI                    OPTIONAL,
        ...}
--^--


>From 3GPP TS 29.002 V12.3.0 (2013-12) (in Wireshark as MAP-SM-DataTypes.asn)

--v--
RoutingInfoForSM-Res ::= SEQUENCE {
        imsi                    IMSI,
        locationInfoWithLMSI    [0] LocationInfoWithLMSI,
        extensionContainer      [4] ExtensionContainer  OPTIONAL,
        ...,
        ip-sm-gwGuidance        [5] IP-SM-GW-Guidance   OPTIONAL }

LocationInfoWithLMSI ::= SEQUENCE {
        networkNode-Number      [1] ISDN-AddressString,
        lmsi                    LMSI                    OPTIONAL,
        extensionContainer      ExtensionContainer      OPTIONAL,
        ...,
        gprsNodeIndicator       [5]     NULL            OPTIONAL,
        -- gprsNodeIndicator is set only if the SGSN number is sent as the
        -- Network Node Number
-- [ .. etc ...]

--^--


As you can see, the structure of LocationInfoWithLMSI differs in what I think
is incompatible between the v1 and v3 versions.


Wireshark appears to have a workaround for v1 RoutingInfoForSM-Arg in
asn1/gsm_map/GSMMAP.asn as RoutingInfoForSM-ArgV1.


I think the fix would be to extend GSMMAP.asn to have v1 definitions for
RoutingInfoForSM-Res and LocationInfoWithLMSI, and modify
packet-gsm_map-template.c dissect_returnResultData() handling for case 45 to be
similar to dissect_invokeData()'s version-specific handling.

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