epan/dissectors/packet-gsm_sms_ud.c

   1 /* packet-gsm_sms_ud.c
   2  * Routines for GSM SMS TP-UD (GSM 03.40) dissection
   3  *
   4  * Refer to the AUTHORS file or the AUTHORS section in the man page
   5  * for contacting the author(s) of this file.
   6  *
   7  * Separated from the SMPP dissector by Chris Wilson.
   8  *
   9  * UDH and WSP dissection of SMS message, Short Message reassembly,
  10  * "Decode Short Message with Port Number UDH as CL-WSP" preference,
  11  * "Always try subdissection of 1st fragment" preference,
  12  * provided by Olivier Biot.
  13  *
  14  * Note on SMS Message reassembly
  15  * ------------------------------
  16  *   The current Short Message reassembly is possible thanks to the
  17  *   message identifier (8 or 16 bit identifier). It is able to reassemble
  18  *   short messages that are sent over either the same SMPP connection or
  19  *   distinct SMPP connections. Normally the reassembly code is able to deal
  20  *   with duplicate message identifiers since the fragment_add_seq_check()
  21  *   call is used.
  22  *
  23  *   The SMS TP-UD preference "always try subdissection of 1st fragment" allows
  24  *   a subdissector to be called for the first Short Message fragment,
  25  *   even if reassembly is not possible. This way partial dissection
  26  *   is still possible. This preference is switched off by default.
  27  *
  28  * Note on Short Message decoding as CL-WSP
  29  * ----------------------------------------
  30  *    The SMS TP-UD preference "port_number_udh_means_wsp" is switched off
  31  *    by default. If it is enabled, then any Short Message with a Port Number
  32  *    UDH will be decoded as CL-WSP if:
  33  *    -  The Short Message is not segmented
  34  *    -  The entire segmented Short Message is reassembled
  35  *    -  It is the 1st segment of an unreassembled Short Message (if the
  36  *       "always try subdissection of 1st fragment" preference is enabled)
  37  *
  38  * Wireshark - Network traffic analyzer
  39  * By Gerald Combs <gerald@wireshark.org>
  40  * Copyright 1998 Gerald Combs
  41  *
  42  * SPDX-License-Identifier: GPL-2.0-or-later
  43  */
  44
  45 #include "config.h"
  46
  47 #include <epan/packet.h>
  48
  49 #include <epan/prefs.h>
  50 #include <epan/reassemble.h>
  51 #include "packet-gsm_sms.h"
  52 #include "packet-smpp.h"
  53
  54 void proto_register_gsm_sms_ud(void);
  55 void proto_reg_handoff_gsm_sms_ud(void);
  56
  57 static int proto_gsm_sms_ud;
  58
  59 /*
  60  * Short Message fragment handling
  61  */
  62 static int hf_gsm_sms_ud_fragments;
  63 static int hf_gsm_sms_ud_fragment;
  64 static int hf_gsm_sms_ud_fragment_overlap;
  65 static int hf_gsm_sms_ud_fragment_overlap_conflicts;
  66 static int hf_gsm_sms_ud_fragment_multiple_tails;
  67 static int hf_gsm_sms_ud_fragment_too_long_fragment;
  68 static int hf_gsm_sms_ud_fragment_error;
  69 static int hf_gsm_sms_ud_fragment_count;
  70 static int hf_gsm_sms_ud_reassembled_in;
  71 static int hf_gsm_sms_ud_reassembled_length;
  72 static int hf_gsm_sms_ud_short_msg;
  73
  74 static int ett_gsm_sms;
  75 static int ett_gsm_sms_ud_fragment;
  76 static int ett_gsm_sms_ud_fragments;
  77
  78 /* Subdissector declarations */
  79 static dissector_table_t gsm_sms_dissector_table;
  80
  81 /* Short Message reassembly */
  82 static reassembly_table sm_reassembly_table;
  83
  84 static const fragment_items sm_frag_items = {
  85     /* Fragment subtrees */
  86     &ett_gsm_sms_ud_fragment,
  87     &ett_gsm_sms_ud_fragments,
  88     /* Fragment fields */
  89     &hf_gsm_sms_ud_fragments,
  90     &hf_gsm_sms_ud_fragment,
  91     &hf_gsm_sms_ud_fragment_overlap,
  92     &hf_gsm_sms_ud_fragment_overlap_conflicts,
  93     &hf_gsm_sms_ud_fragment_multiple_tails,
  94     &hf_gsm_sms_ud_fragment_too_long_fragment,
  95     &hf_gsm_sms_ud_fragment_error,
  96     &hf_gsm_sms_ud_fragment_count,
  97     /* Reassembled in field */
  98     &hf_gsm_sms_ud_reassembled_in,
  99     /* Reassembled length field */
 100     &hf_gsm_sms_ud_reassembled_length,
 101     /* Reassembled data field */
 102     NULL,
 103     /* Tag */
 104     "Short Message fragments"
 105 };
 106
 107 /* Dissect all SM data as WSP if the UDH contains a Port Number IE */
 108 static bool port_number_udh_means_wsp;
 109
 110 /* Always try dissecting the 1st fragment of a SM,
 111  * even if it is not reassembled */
 112 static bool try_dissect_1st_frag;
 113
 114 /* Prevent subdissectors changing column data */
 115 static bool prevent_subdissectors_changing_columns;
 116
 117 static dissector_handle_t wsp_handle;
 118
 119 /* Parse Short Message. This function is only called from the SMPP
 120  * dissector if the UDH present, or if the UDH fields were obtained
 121  * elsewhere in SMPP TLVs.
 122  * Call WSP dissector if port matches WSP traffic.
 123  */
 124 static void
 125 parse_gsm_sms_ud_message(proto_tree *sm_tree, tvbuff_t *tvb, packet_info *pinfo, smpp_data_t *smpp_data)
 126 {
 127     tvbuff_t      *sm_tvb                    = NULL;
 128     proto_tree    *top_tree;
 129     unsigned       sm_len                    = tvb_reported_length(tvb);
 130     uint32_t       i                         = 0;
 131     /* Multiple Messages UDH */
 132     bool           is_fragmented             = false;
 133     fragment_head *fd_sm                     = NULL;
 134     bool           save_fragmented           = false;
 135     bool           try_gsm_sms_ud_reassemble = false;
 136     /* SMS Message reassembly */
 137     bool           reassembled               = false;
 138     uint32_t       reassembled_in            = 0;
 139
 140     gsm_sms_udh_fields_t *udh_fields = NULL;
 141     if (smpp_data) {
 142         udh_fields = smpp_data->udh_fields;
 143     }
 144
 145     top_tree = proto_tree_get_parent_tree(sm_tree);
 146
 147     if (!udh_fields) {
 148         udh_fields = wmem_new0(pinfo->pool, gsm_sms_udh_fields_t);
 149     }
 150
 151     if (smpp_data && smpp_data->udhi) {
 152         /* XXX: We don't handle different encodings in this dissector yet,
 153          * so just treat everything as 8-bit binary encoding. */
 154         uint8_t fill_bits = 0;
 155         uint8_t udl = sm_len;
 156         dis_field_udh(tvb, pinfo, sm_tree, &i, &sm_len, &udl, OTHER, &fill_bits, udh_fields);
 157     }
 158
 159     if (tvb_reported_length_remaining(tvb, i) <= 0)
 160         return; /* No more data */
 161
 162     if (udh_fields->frags > 1) {
 163         is_fragmented = true;
 164     }
 165
 166     /*
 167      * Try reassembling the packets.
 168      * XXX - fragment numbers are 1-origin, but the fragment number
 169      * field could be 0.
 170      * Should we flag a fragmented message with a fragment number field
 171      * of 0?
 172      * What if the fragment count is 0?  Should we flag that as well?
 173      */
 174     if (is_fragmented && udh_fields->frag != 0 && udh_fields->frags != 0 &&
 175         tvb_bytes_exist(tvb, i, sm_len)) {
 176         try_gsm_sms_ud_reassemble = true;
 177         save_fragmented = pinfo->fragmented;
 178         pinfo->fragmented = true;
 179         fd_sm = fragment_add_seq_check(&sm_reassembly_table,
 180                 tvb, i,
 181                 pinfo,
 182                 udh_fields->sm_id,    /* uint32_t ID for fragments belonging together */
 183                 NULL,
 184                 udh_fields->frag-1,   /* uint32_t fragment sequence number */
 185                 sm_len,               /* uint32_t fragment length */
 186                 (udh_fields->frag != udh_fields->frags));     /* More fragments? */
 187         if (fd_sm) {
 188             reassembled    = true;
 189             reassembled_in = fd_sm->reassembled_in;
 190         }
 191         sm_tvb = process_reassembled_data(tvb, i, pinfo,
 192             "Reassembled Short Message", fd_sm, &sm_frag_items,
 193             NULL, sm_tree);
 194         if (reassembled) { /* Reassembled */
 195             col_append_str(pinfo->cinfo, COL_INFO,
 196                         " (Short Message Reassembled)");
 197         } else {
 198             /* Not last packet of reassembled Short Message */
 199             col_append_fstr(pinfo->cinfo, COL_INFO,
 200                     " (Short Message fragment %u of %u)", udh_fields->frag, udh_fields->frags);
 201         }
 202     } /* Else: not fragmented */
 203
 204     if (! sm_tvb) /* One single Short Message, or not reassembled */
 205         sm_tvb = tvb_new_subset_remaining(tvb, i);
 206     /* Try calling a subdissector */
 207     if (sm_tvb) {
 208         if ((reassembled && pinfo->num == reassembled_in)
 209             || udh_fields->frag==0 || (udh_fields->frag==1 && try_dissect_1st_frag)) {
 210             /* Try calling a subdissector only if:
 211              *  - the Short Message is reassembled in this very packet,
 212              *  - the Short Message consists of only one "fragment",
 213              *  - the preference "Always Try Dissection for 1st SM fragment"
 214              *    is switched on, and this is the SM's 1st fragment. */
 215             if (udh_fields->port_src || udh_fields->port_dst) {
 216                 bool disallow_write = false; /* true if we changed writability
 217                                     of the columns of the summary */
 218                 if (prevent_subdissectors_changing_columns && col_get_writable(pinfo->cinfo, -1)) {
 219                     disallow_write = true;
 220                     col_set_writable(pinfo->cinfo, -1, false);
 221                 }
 222
 223                 if (port_number_udh_means_wsp) {
 224                     call_dissector(wsp_handle, sm_tvb, pinfo, top_tree);
 225                 } else {
 226                     if (! dissector_try_uint(gsm_sms_dissector_table, udh_fields->port_src,
 227                                 sm_tvb, pinfo, top_tree)) {
 228                         if (! dissector_try_uint(gsm_sms_dissector_table, udh_fields->port_dst,
 229                                     sm_tvb, pinfo, top_tree)) {
 230                             if (sm_tree) { /* Only display if needed */
 231                                 proto_tree_add_item(sm_tree, hf_gsm_sms_ud_short_msg, sm_tvb, 0, -1, ENC_NA);
 232                             }
 233                         }
 234                     }
 235                 }
 236
 237                 if (disallow_write)
 238                     col_set_writable(pinfo->cinfo, -1, true);
 239             } else { /* No ports IE */
 240                 proto_tree_add_item(sm_tree, hf_gsm_sms_ud_short_msg, sm_tvb, 0, -1, ENC_NA);
 241             }
 242         } else {
 243             /* The packet is not reassembled,
 244              * or it is reassembled in another packet */
 245             proto_tree_add_bytes_format(sm_tree, hf_gsm_sms_ud_short_msg, sm_tvb, 0, -1,
 246                     NULL, "Unreassembled Short Message fragment %u of %u",
 247                     udh_fields->frag, udh_fields->frags);
 248         }
 249     }
 250
 251     if (try_gsm_sms_ud_reassemble) /* Clean up defragmentation */
 252         pinfo->fragmented = save_fragmented;
 253     return;
 254 }
 255
 256 static int
 257 dissect_gsm_sms_ud(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data)
 258 {
 259     proto_item *ti;
 260     proto_tree *subtree;
 261     smpp_data_t *smpp_data = NULL;
 262
 263     if (data) {
 264         smpp_data = (smpp_data_t*)data;
 265     }
 266
 267     ti      = proto_tree_add_item(tree, proto_gsm_sms_ud, tvb, 0, -1, ENC_NA);
 268     subtree = proto_item_add_subtree(ti, ett_gsm_sms);
 269     parse_gsm_sms_ud_message(subtree, tvb, pinfo, smpp_data);
 270     return tvb_captured_length(tvb);
 271 }
 272
 273 /* Register the protocol with Wireshark */
 274 void
 275 proto_register_gsm_sms_ud(void)
 276 {
 277     module_t *gsm_sms_ud_module; /* Preferences for GSM SMS UD */
 278
 279     /* Setup list of header fields  */
 280     static hf_register_info hf[] = {
 281         /*
 282          * Short Message fragment reassembly
 283          */
 284         {   &hf_gsm_sms_ud_fragments,
 285             {   "Short Message fragments", "gsm_sms_ud.fragments",
 286                 FT_NONE, BASE_NONE, NULL, 0x00,
 287                 "GSM Short Message fragments",
 288                 HFILL
 289             }
 290         },
 291         {   &hf_gsm_sms_ud_fragment,
 292             {   "Short Message fragment", "gsm_sms_ud.fragment",
 293                 FT_FRAMENUM, BASE_NONE, NULL, 0x00,
 294                 "GSM Short Message fragment",
 295                 HFILL
 296             }
 297         },
 298         {   &hf_gsm_sms_ud_fragment_overlap,
 299             {   "Short Message fragment overlap", "gsm_sms_ud.fragment.overlap",
 300                 FT_BOOLEAN, BASE_NONE, NULL, 0x0,
 301                 "GSM Short Message fragment overlaps with other fragment(s)",
 302                 HFILL
 303             }
 304         },
 305         {   &hf_gsm_sms_ud_fragment_overlap_conflicts,
 306             {   "Short Message fragment overlapping with conflicting data",
 307                 "gsm_sms_ud.fragment.overlap.conflicts",
 308                 FT_BOOLEAN, BASE_NONE, NULL, 0x0,
 309                 "GSM Short Message fragment overlaps with conflicting data",
 310                 HFILL
 311             }
 312         },
 313         {   &hf_gsm_sms_ud_fragment_multiple_tails,
 314             {   "Short Message has multiple tail fragments",
 315                 "gsm_sms_ud.fragment.multiple_tails",
 316                 FT_BOOLEAN, BASE_NONE, NULL, 0x0,
 317                 "GSM Short Message fragment has multiple tail fragments",
 318                 HFILL
 319             }
 320         },
 321         {   &hf_gsm_sms_ud_fragment_too_long_fragment,
 322             {   "Short Message fragment too long",
 323                 "gsm_sms_ud.fragment.too_long_fragment",
 324                 FT_BOOLEAN, BASE_NONE, NULL, 0x0,
 325                 "GSM Short Message fragment data goes beyond the packet end",
 326                 HFILL
 327             }
 328         },
 329         {   &hf_gsm_sms_ud_fragment_error,
 330             {   "Short Message defragmentation error", "gsm_sms_ud.fragment.error",
 331                 FT_FRAMENUM, BASE_NONE, NULL, 0x00,
 332                 "GSM Short Message defragmentation error due to illegal fragments",
 333                 HFILL
 334             }
 335         },
 336         {   &hf_gsm_sms_ud_fragment_count,
 337             {   "Short Message fragment count", "gsm_sms_ud.fragment.count",
 338                 FT_UINT32, BASE_DEC, NULL, 0x00,
 339                 NULL,
 340                 HFILL
 341             }
 342         },
 343         {   &hf_gsm_sms_ud_reassembled_in,
 344             {   "Reassembled in",
 345                 "gsm_sms_ud.reassembled.in",
 346                 FT_FRAMENUM, BASE_NONE, NULL, 0x00,
 347                 "GSM Short Message has been reassembled in this packet.",
 348                 HFILL
 349             }
 350         },
 351         {   &hf_gsm_sms_ud_reassembled_length,
 352             {   "Reassembled Short Message length",
 353                 "gsm_sms_ud.reassembled.length",
 354                 FT_UINT32, BASE_DEC, NULL, 0x00,
 355                 "The total length of the reassembled payload",
 356                 HFILL
 357             }
 358         },
 359         {   &hf_gsm_sms_ud_short_msg,
 360             {   "Short Message body",
 361                 "gsm_sms_ud.short_msg",
 362                 FT_BYTES, BASE_NONE, NULL, 0x00, NULL, HFILL
 363             }
 364         },
 365     };
 366
 367     static int *ett[] = {
 368     &ett_gsm_sms,
 369     &ett_gsm_sms_ud_fragment,
 370     &ett_gsm_sms_ud_fragments,
 371     };
 372     /* Register the protocol name and description */
 373     proto_gsm_sms_ud = proto_register_protocol("GSM Short Message Service User Data", "GSM SMS UD", "gsm_sms_ud");
 374
 375     /* Required function calls to register header fields and subtrees used */
 376     proto_register_field_array(proto_gsm_sms_ud, hf, array_length(hf));
 377     proto_register_subtree_array(ett, array_length(ett));
 378
 379     /* Subdissector code */
 380     gsm_sms_dissector_table = register_dissector_table("gsm_sms_ud.udh.port",
 381         "GSM SMS port IE in UDH", proto_gsm_sms_ud, FT_UINT16, BASE_DEC);
 382
 383     /* Preferences for GSM SMS UD */
 384     gsm_sms_ud_module = prefs_register_protocol(proto_gsm_sms_ud, NULL);
 385     /* For reading older preference files with "smpp-gsm-sms." preferences */
 386     prefs_register_module_alias("smpp-gsm-sms", gsm_sms_ud_module);
 387     prefs_register_bool_preference(gsm_sms_ud_module,
 388         "port_number_udh_means_wsp",
 389         "Port Number IE in UDH always triggers CL-WSP dissection",
 390         "Always decode a GSM Short Message as Connectionless WSP "
 391         "if a Port Number Information Element is present "
 392         "in the SMS User Data Header.",
 393         &port_number_udh_means_wsp);
 394     prefs_register_bool_preference(gsm_sms_ud_module, "try_dissect_1st_fragment",
 395         "Always try subdissection of 1st Short Message fragment",
 396         "Always try subdissection of the 1st fragment of a fragmented "
 397         "GSM Short Message. If reassembly is possible, the Short Message "
 398         "may be dissected twice (once as a short frame, once in its "
 399         "entirety).",
 400         &try_dissect_1st_frag);
 401     prefs_register_bool_preference(gsm_sms_ud_module, "prevent_dissectors_chg_cols",
 402             "Prevent sub-dissectors from changing column data",
 403         "Prevent sub-dissectors from replacing column data with their "
 404         "own. Eg. Prevent WSP dissector overwriting SMPP information.",
 405         &prevent_subdissectors_changing_columns);
 406
 407     register_dissector("gsm_sms_ud", dissect_gsm_sms_ud, proto_gsm_sms_ud);
 408
 409     reassembly_table_register(&sm_reassembly_table,
 410                           &addresses_reassembly_table_functions);
 411 }
 412
 413 void
 414 proto_reg_handoff_gsm_sms_ud(void)
 415 {
 416     wsp_handle = find_dissector_add_dependency("wsp-cl", proto_gsm_sms_ud);
 417     DISSECTOR_ASSERT(wsp_handle);
 418 }
 419
 420 /*
 421  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 422  *
 423  * Local variables:
 424  * c-basic-offset: 4
 425  * tab-width: 8
 426  * indent-tabs-mode: nil
 427  * End:
 428  *
 429  * vi: set shiftwidth=4 tabstop=8 expandtab:
 430  * :indentSize=4:tabSize=8:noTabs=true:
 431  */