Decoding error on NAS: 5GS tracking area identity list with more than one element

[bjoern-r]

Issue Description

Corescope fails parsing the "5GS tracking area identity list" form the NAS-PDU inside a Registration accept message when the list contains more than one TAC.

5GS tracking area identity list
    Element ID: 0x54
    Length: 43
    Partial tracking area list  1
        .00. .... = Type of list: list of TACs belonging to one PLMN or SNPN, with non-consecutive TAC values (0)
        ...0 1100 = Number of elements: 13 elements (12)
        Mobile Country Code (MCC): Unknown (1)
        Mobile Network Code (MNC): Unknown (01)
        TAC: 1
        TAC: 2
        TAC: 3
        TAC: 81
        TAC: 111
        TAC: 112
        TAC: 117
        TAC: 121
        TAC: 122
        TAC: 123
        TAC: 141
        TAC: 151
        TAC: 152

Setup Details

git rev a7fd328
Running corescope against an instance of Open5Gcore from Fraunhofer FOKUS.
The AMF has configured support for a total number of 13 TAC.

Expected Behavior

2022-01-19T15:15:09.111703 [NGAP ] [I] Tx NGAP SDU, UplinkNASTransport, rnti=0xb
2022-01-19T15:15:09.113997 [NGAP ] [I] Tx NGAP SDU, InitialContextSetupResponse, rnti=0xb
2022-01-19T15:15:09.114006 [RRC ] [D] Incoming data from NGAP, writing to UE RRC. RNTI=0xb, 70 Bytes.

Actual Behaviour

2022-01-19T15:05:04.949000 [NGAP ] [I] Tx NGAP SDU, UplinkNASTransport, rnti=0xc
2022-01-19T15:05:04.951365 [NGAP ] [I] Tx NGAP SDU, InitialContextSetupResponse, rnti=0xc
2022-01-19T15:05:04.951388 [ASN1 ] [E] [ 0] Decoding Failed (5GS tracking area identity list): Length (43) does not equal expected length 7
2022-01-19T15:05:04.951389 [ASN1 ] [E] [ 0] [/home/o5gc/src/srs/corescope/srsRAN/lib/src/asn1/nas_5g_msg.cc][524] Decoding failure.
2022-01-19T15:05:04.951389 [ASN1 ] [E] [ 0] [/home/o5gc/src/srs/corescope/srsRAN/lib/src/asn1/nas_5g_msg.cc][3929] Decoding failure.
2022-01-19T15:05:04.951389 [ASN1 ] [E] [ 0] [/home/o5gc/src/srs/corescope/srsRAN/lib/src/asn1/nas_5g_msg.cc][3905] Decoding failure.

Steps to reproduce the problem

Confige an AMF to send a Registration Accept message with a "5GS tracking area identity list" that contians more than one TAC entry.

Additional Information

[Any additional information, configuration or data that might be necessary to reproduce the issue]