epan/dissectors/packet-git.c

   1 /* packet-git.c
   2  * Routines for git packet dissection
   3  * Copyright 2010, Jelmer Vernooij <jelmer@samba.org>
   4  *
   5  * Wireshark - Network traffic analyzer
   6  * By Gerald Combs <gerald@wireshark.org>
   7  * Copyright 1998 Gerald Combs
   8  *
   9  * Copied from packet-pop.c
  10  *
  11  * SPDX-License-Identifier: GPL-2.0-or-later
  12  *
  13  * Current testing suite 'case_dissect_git' can be found at
  14  * test/suite_dissection.py
  15  */
  16
  17 #include "config.h"
  18
  19 #include <stdio.h>    /* for sscanf() */
  20
  21 #include <epan/packet.h>
  22 #include <epan/expert.h>
  23 #include <epan/prefs.h>
  24 #include "packet-tcp.h"
  25
  26 void proto_register_git(void);
  27 void proto_reg_handoff_git(void);
  28
  29 static dissector_handle_t git_handle;
  30
  31 static int proto_git;
  32 static expert_field ei_git_bad_pkt_len;
  33 static expert_field ei_git_malformed;
  34
  35 static int ett_git;
  36
  37 static int hf_git_protocol_version;
  38 static int hf_git_packet_type;
  39 static int hf_git_packet_len;
  40 static int hf_git_packet_data;
  41 static int hf_git_sideband_control_code;
  42 static int hf_git_upload_pack_adv;
  43 static int hf_git_upload_pack_req;
  44 static int hf_git_upload_pack_res;
  45
  46 #define PNAME  "Git Smart Protocol"
  47 #define PSNAME "Git"
  48 #define PFNAME "git"
  49
  50 #define TCP_PORT_GIT    9418
  51
  52 static const value_string packet_type_vals[] = {
  53   { 0, "Flush" },
  54   { 1, "Delimiter" },
  55   { 2, "Response end" },
  56   { 0, NULL }
  57 };
  58
  59 static const value_string version_vals[] = {
  60   { '1', "Git protocol version 1" },
  61   { '2', "Git protocol version 2" },
  62   { 0, NULL }
  63 };
  64
  65 #define SIDEBAND_PACKFILE_DATA 0x01
  66 #define SIDEBAND_PROGRESS_INFO 0x02
  67 #define SIDEBAND_ERROR_INFO 0x03
  68 static const value_string sideband_vals[] = {
  69   { SIDEBAND_PACKFILE_DATA, "Git packfile data" },
  70   { SIDEBAND_PROGRESS_INFO, "Git progress data" },
  71   { SIDEBAND_ERROR_INFO, "Git error data" },
  72   { 0, NULL }
  73 };
  74
  75 /* desegmentation of Git over TCP */
  76 static bool git_desegment = true;
  77
  78 static bool get_packet_length(tvbuff_t *tvb, int offset,
  79                                   uint16_t *length)
  80 {
  81   uint8_t *lenstr;
  82
  83   lenstr = tvb_get_string_enc(wmem_packet_scope(), tvb, offset, 4, ENC_ASCII);
  84
  85   return (sscanf(lenstr, "%hx", length) == 1);
  86 }
  87
  88 static unsigned
  89 get_git_pdu_len(packet_info *pinfo _U_, tvbuff_t *tvb, int offset, void *data _U_)
  90 {
  91   uint16_t plen;
  92
  93   if (!get_packet_length(tvb, offset, &plen))
  94     return 0; /* No idea what this is */
  95
  96   return plen < 4
  97       ? 4   // Special packet (e.g., flush-pkt)
  98       : plen;
  99 }
 100
 101 /* Parse pkt-lines one-by-one
 102  *
 103  * @param  tvb       The buffer to dissect.
 104  * @param  pinfo     Packet info associated to this buffer.
 105  * @param  git_tree  The git protocol subtree.
 106  * @param  offset    The offset at which to start the dissection.
 107  * @return bool      After successful/unsuccessful parsing.
 108  *
 109  * This new helper takes the contents of the tvbuffer, updates the
 110  * offset, and returns to the caller for subsequent processing of the
 111  * remainder of the data.
 112 */
 113 static bool
 114 dissect_pkt_line(tvbuff_t *tvb, packet_info *pinfo, proto_tree *git_tree,
 115                  int *offset)
 116 {
 117   uint16_t plen;
 118
 119   // what type of pkt-line is it?
 120   if (!get_packet_length(tvb, *offset, &plen))
 121     return false;
 122   if (plen < 4) {   // a special packet (e.g., flush-pkt)
 123     proto_item *ti =
 124         proto_tree_add_uint(git_tree, hf_git_packet_type, tvb,
 125                             *offset, 4, plen);
 126     *offset += 4;
 127
 128     if (!try_val_to_str(plen, packet_type_vals))
 129       expert_add_info(pinfo, ti, &ei_git_bad_pkt_len);
 130     return true;
 131   }
 132
 133   proto_tree_add_uint(git_tree, hf_git_packet_len, tvb, *offset, 4, plen);
 134   *offset += 4;
 135   plen -= 4;
 136
 137   /*
 138    * Parse out the version of the Git Protocol
 139    *
 140    * The initial server response contains the version of the Git Protocol in use;
 141    * 1 or 2. Parsing out this information helps identify the capabilities and
 142    * information that can be used with the protocol.
 143   */
 144   if (plen >= 9 && !tvb_strneql(tvb, *offset, "version ", 8)) {
 145     proto_tree_add_item(git_tree, hf_git_protocol_version, tvb, *offset + 8,
 146                         1, ENC_NA);
 147   }
 148
 149   /*
 150    * Parse out the sideband control code.
 151    *
 152    * Not all pkt-lines have a sideband control code. With more context from the rest of
 153    * the request or response, we would be able to tell whether sideband is expected here;
 154    * lacking that, let's assume for now that all pkt-lines starting with \1, \2, or \3
 155    * are using sideband.
 156    */
 157   int sideband_code = tvb_get_uint8(tvb, *offset);
 158
 159   if (1 <= sideband_code && sideband_code <= 3) {
 160     proto_tree_add_uint(git_tree, hf_git_sideband_control_code, tvb, *offset, 1,
 161                         sideband_code);
 162     (*offset)++;
 163     plen--;
 164   }
 165
 166   proto_tree_add_item(git_tree, hf_git_packet_data, tvb, *offset, plen, ENC_NA);
 167   *offset += plen;
 168   return true;
 169 }
 170
 171 static int
 172 dissect_git_pdu(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
 173 {
 174   proto_tree             *git_tree;
 175   proto_item             *ti;
 176   int offset = 0;
 177
 178   col_set_str(pinfo->cinfo, COL_PROTOCOL, PSNAME);
 179
 180   col_set_str(pinfo->cinfo, COL_INFO, PNAME);
 181
 182   ti = proto_tree_add_item(tree, proto_git, tvb, offset, -1, ENC_NA);
 183   git_tree = proto_item_add_subtree(ti, ett_git);
 184
 185   if (!dissect_pkt_line(tvb, pinfo, git_tree, &offset))
 186     return 0;
 187
 188   return tvb_captured_length(tvb);
 189 }
 190
 191 /* Parse http packs
 192  *
 193  * @param  tvb        The buffer to dissect.
 194  * @param  pinfo      The Packet Info.
 195  * @param  tree       The protocol tree.
 196  * @param  hfindex    The type of http pack.
 197  * @return tvb_length The amount of captured data in the buffer,
 198  *                    returns 0 if parsing failed.
 199  *
 200  * This new helper takes the contents of the tvbuffer sent by http
 201  * dissectors, adds the packs to the git subtree and returns the amount
 202  * of consumed bytes in the tvb buffer.
 203 */
 204 static int
 205 dissect_http_pkt_lines(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int hfindex)
 206 {
 207   proto_tree             *git_tree;
 208   proto_item             *ti;
 209   int offset = 0;
 210   int total_len = 0;
 211
 212   col_set_str(pinfo->cinfo, COL_PROTOCOL, PSNAME);
 213
 214   col_set_str(pinfo->cinfo, COL_INFO, PNAME);
 215
 216   ti = proto_tree_add_item(tree, proto_git, tvb, offset, -1, ENC_NA);
 217   git_tree = proto_item_add_subtree(ti, ett_git);
 218
 219   proto_tree_add_item(git_tree, hfindex, tvb, offset,
 220                       tvb_captured_length(tvb), ENC_NA);
 221
 222   total_len = tvb_reported_length(tvb);
 223   while (offset < total_len) {
 224     /* Add expert info if there is trouble parsing part-way through */
 225     if (!dissect_pkt_line(tvb, pinfo, git_tree, &offset)) {
 226       proto_tree_add_expert(git_tree, pinfo, &ei_git_malformed, tvb, offset, -1);
 227       break;
 228     }
 229   }
 230
 231   return tvb_captured_length(tvb);
 232 }
 233
 234 static int
 235 dissect_git_upload_pack_adv(tvbuff_t *tvb, packet_info *pinfo,
 236                             proto_tree *tree, void *data _U_)
 237 {
 238   return dissect_http_pkt_lines(tvb, pinfo, tree, hf_git_upload_pack_adv);
 239 }
 240
 241 static int
 242 dissect_git_upload_pack_req(tvbuff_t *tvb, packet_info *pinfo,
 243                             proto_tree *tree, void *data _U_)
 244 {
 245   return dissect_http_pkt_lines(tvb, pinfo, tree, hf_git_upload_pack_req);
 246 }
 247
 248 static int
 249 dissect_git_upload_pack_res(tvbuff_t *tvb, packet_info *pinfo,
 250                             proto_tree *tree, void *data _U_)
 251 {
 252   return dissect_http_pkt_lines(tvb, pinfo, tree, hf_git_upload_pack_res);
 253 }
 254
 255 static int
 256 dissect_git(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data)
 257 {
 258   tcp_dissect_pdus(tvb, pinfo, tree, git_desegment, 4, get_git_pdu_len,
 259                    dissect_git_pdu, data);
 260   return tvb_captured_length(tvb);
 261 }
 262
 263 void
 264 proto_register_git(void)
 265 {
 266   static hf_register_info hf[] = {
 267     { &hf_git_protocol_version,
 268       { "Git Protocol Version", "git.version", FT_UINT8, BASE_NONE, VALS(version_vals),
 269       0, NULL, HFILL },
 270     },
 271     { &hf_git_packet_type,
 272       { "Git Packet Type", "git.packet_type", FT_UINT8, BASE_NONE, VALS(packet_type_vals),
 273       0, NULL, HFILL },
 274     },
 275     { &hf_git_packet_len,
 276       { "Packet length", "git.length", FT_UINT16, BASE_HEX, NULL, 0x0, NULL, HFILL },
 277     },
 278     { &hf_git_packet_data,
 279       { "Packet data", "git.data", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL },
 280     },
 281     { &hf_git_sideband_control_code,
 282       { "Sideband control code", "git.sideband_control_code", FT_UINT8,
 283       BASE_HEX, VALS(sideband_vals), 0, NULL, HFILL },
 284     },
 285     { &hf_git_upload_pack_adv,
 286       { "Upload Pack Advertisement", "git.upload_pack_advertisement",
 287       FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL },
 288     },
 289     { &hf_git_upload_pack_req,
 290       { "Upload Pack Request", "git.upload_pack_request",
 291       FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL },
 292     },
 293     { &hf_git_upload_pack_res,
 294       { "Upload Pack Result", "git.upload_pack_result",
 295       FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL },
 296     },
 297   };
 298
 299   static int *ett[] = {
 300     &ett_git,
 301   };
 302
 303   static ei_register_info ei[] = {
 304     { &ei_git_bad_pkt_len,
 305       { "git.bad_pkt_len", PI_PROTOCOL, PI_ERROR,
 306         "unrecognized special pkt-len value", EXPFILL }
 307     },
 308     { &ei_git_malformed,
 309       { "git.malformed", PI_MALFORMED, PI_ERROR,
 310         "malformed packet", EXPFILL }
 311     },
 312   };
 313
 314   module_t *git_module;
 315   expert_module_t *expert_git;
 316
 317   proto_git = proto_register_protocol(PNAME, PSNAME, PFNAME);
 318   proto_register_field_array(proto_git, hf, array_length(hf));
 319   proto_register_subtree_array(ett, array_length(ett));
 320
 321   expert_git = expert_register_protocol(proto_git);
 322   expert_register_field_array(expert_git, ei, array_length(ei));
 323
 324   git_handle = register_dissector(PFNAME, dissect_git, proto_git);
 325
 326   git_module = prefs_register_protocol(proto_git, NULL);
 327
 328   prefs_register_bool_preference(git_module, "desegment",
 329                                  "Reassemble GIT messages spanning multiple TCP segments",
 330                                  "Whether the GIT dissector should reassemble messages spanning multiple TCP segments."
 331                                  " To use this option, you must also enable \"Allow subdissectors to reassemble TCP streams\" in the TCP protocol settings.",
 332                                  &git_desegment);
 333 }
 334
 335 void
 336 proto_reg_handoff_git(void)
 337 {
 338   /*
 339    * Add the dissectors for GIT over HTTP
 340    *
 341    * Reference documentation at
 342    * https://www.kernel.org/pub/software/scm/git/docs//technical/http-protocol.txt
 343    */
 344   dissector_handle_t git_upload_pack_adv_handle;
 345   dissector_handle_t git_upload_pack_req_handle;
 346   dissector_handle_t git_upload_pack_res_handle;
 347
 348   git_upload_pack_adv_handle = create_dissector_handle(dissect_git_upload_pack_adv,
 349                         proto_git);
 350
 351   git_upload_pack_req_handle = create_dissector_handle(dissect_git_upload_pack_req,
 352                         proto_git);
 353
 354   git_upload_pack_res_handle = create_dissector_handle(dissect_git_upload_pack_res,
 355                         proto_git);
 356
 357   dissector_add_string("media_type",
 358                         "application/x-git-upload-pack-advertisement",
 359                         git_upload_pack_adv_handle);
 360   dissector_add_string("media_type",
 361                         "application/x-git-upload-pack-request",
 362                         git_upload_pack_req_handle);
 363   dissector_add_string("media_type",
 364                         "application/x-git-upload-pack-result",
 365                         git_upload_pack_res_handle);
 366
 367   dissector_add_uint_with_preference("tcp.port", TCP_PORT_GIT, git_handle);
 368 }
 369
 370 /*
 371  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 372  *
 373  * Local Variables:
 374  * c-basic-offset: 2
 375  * tab-width: 8
 376  * indent-tabs-mode: nil
 377  * End:
 378  *
 379  * ex: set shiftwidth=2 tabstop=8 expandtab:
 380  * :indentSize=2:tabSize=8:noTabs=true:
 381  */