Merge branch 'bssap'

Author: p1-bmu

pycrate_mobile/TS48006_BSSAP.py

@@ -0,0 +1,107 @@
+# -*- coding: UTF-8 -*-
+#/**
+# * Software Name : pycrate
+# * Version : 0.5
+# *
+# * Copyright 2023. Laurent Ghigonis. P1Sec.
+# *
+# * This library is free software; you can redistribute it and/or
+# * modify it under the terms of the GNU Lesser General Public
+# * License as published by the Free Software Foundation; either
+# * version 2.1 of the License, or (at your option) any later version.
+# *
+# * This library is distributed in the hope that it will be useful,
+# * but WITHOUT ANY WARRANTY; without even the implied warranty of
+# * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# * Lesser General Public License for more details.
+# *
+# * You should have received a copy of the GNU Lesser General Public
+# * License along with this library; if not, write to the Free Software
+# * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, 
+# * MA 02110-1301  USA
+# *
+# *--------------------------------------------------------
+# * File Name : pycrate_mobile/TS48006_BSSAP.py
+# * Created : 2023-01-09
+# * Authors : Laurent Ghigonis
+# *--------------------------------------------------------
+#*/
+
+from enum import IntEnum
+from struct import unpack
+
+from pycrate_core.elt import Envelope, REPR_RAW, REPR_HEX, REPR_BIN
+from pycrate_core.base import *
+from pycrate_core.repr import *
+
+
+#------------------------------------------------------------------------------#
+# BSS Application Part (BSSAP) as defined in 3GPP TS 48.006 and 3GPP TS 49.008
+#------------------------------------------------------------------------------#
+# Implementation notes:
+# * Len has to be set manually in BSSAP_DirectTransfer and BSSAP_Management,
+#   as the layer is an adaption between 2 layers, and does not *include* the upper layer (no setvalauto() in __init__())
+# * procedures : TS49.008 https://www.etsi.org/deliver/etsi_ts/149000_149099/149008/09.00.00_60/ts_149008v090000p.pdf
+# * protocol   : TS48.006 https://www.etsi.org/deliver/etsi_ts/148000_148099/148006/09.00.00_60/ts_148006v090000p.pdf
+# * wireshark implementation : https://github.com/wireshark/wireshark/blob/master/epan/dissectors/packet-bssap.c
+
+
+#------------------------------------------------------------------------------#
+# BSSAP header elements
+#------------------------------------------------------------------------------#
+
+class BSSAPType(IntEnum):
+	BSS_MANAGEMENT  = 0x00
+	DIRECT_TRANSFER = 0x01
+
+
+class DistributionUnit(Envelope):
+	_GEN = (
+		Uint('RadioMessageGroup', bl=7),
+		Uint('Discrimination', bl=1, dic={
+		    BSSAPType.BSS_MANAGEMENT  : 'Not Transparent: BSSMAP',
+		    BSSAPType.DIRECT_TRANSFER : 'Transparent: DTAP'}),
+	)
+
+
+# Service Access Point Identifier, defined in TS44.006
+class BSSAP_SAPI(IntEnum):
+    SIGNALING = 0
+    SMS       = 3
+
+
+BSSAP_SAPI_dict = {
+    BSSAP_SAPI.SIGNALING: 'signaling information',
+    BSSAP_SAPI.SMS:       'SMS',
+    }
+
+
+#------------------------------------------------------------------------------#
+# BSSAP messages
+#------------------------------------------------------------------------------#
+# TS48.006, 9.3.2: Transfer of DTAP messages
+# TS48.006, 9.3.3: Transfer of BSSMAP messages
+
+class BSSAP(Envelope):
+	_GEN = (
+		DistributionUnit('DistributionUnit', val=(0, BSSAPType.DIRECT_TRANSFER)),
+		Envelope('DLCI', GEN=(
+			Uint('ControlChannelIdentification', bl=2, dic={
+			    0: 'no further specified',
+			    1: 'reserved',
+			    2: 'FACCH or SDCCH',
+			    3: 'SACCH'}),
+			Uint('spare', bl=3),
+			Uint('SAPI', bl=3, dic=BSSAP_SAPI_dict)
+			)),
+		Uint8('Len'),
+		Buf('L3', rep=REPR_HEX)
+	    )
+	
+	def __init__(self, *args, **kwargs):
+	    Envelope.__init__(self, *args, **kwargs)
+	    # DLCI only present for DIRECT_TRANSFER
+	    self['DLCI'].set_transauto(lambda: not self['DistributionUnit'].get_val()[1])
+	    self['Len'].set_valauto(lambda: self['L3'].get_len())
+	    self['L3'].set_blauto(lambda: self['Len'].get_val()<<3)
+