/* packet-git.c

 * Routines for git packet dissection

 * Copyright 2010, Jelmer Vernooij <jelmer@samba.org>

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

 * Copied from packet-pop.c

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 *

 * Current testing suite 'case_dissect_git' can be found at

 * test/suite_dissection.py

 */

#include "config.h"

#include <stdio.h>    /* for sscanf() */

#include <epan/packet.h>

#include <epan/expert.h>

#include <epan/prefs.h>

#include "packet-tcp.h"

void proto_register_git(void);

void proto_reg_handoff_git(void);

static dissector_handle_t git_handle;

static int proto_git;

static expert_field ei_git_bad_pkt_len;

static expert_field ei_git_malformed;

static int ett_git;

static int hf_git_protocol_version;

static int hf_git_packet_type;

static int hf_git_packet_len;

static int hf_git_packet_data;

static int hf_git_sideband_control_code;

static int hf_git_upload_pack_adv;

static int hf_git_upload_pack_req;

static int hf_git_upload_pack_res;

#define PNAME  "Git Smart Protocol"

#define PSNAME "Git"

#define PFNAME "git"

#define TCP_PORT_GIT    9418

static const value_string packet_type_vals[] = {

  { 0, "Flush" },

  { 1, "Delimiter" },

  { 2, "Response end" },

  { 0, NULL }

};

static const value_string version_vals[] = {

  { '1', "Git protocol version 1" },

  { '2', "Git protocol version 2" },

  { 0, NULL }

};

#define SIDEBAND_PACKFILE_DATA 0x01

#define SIDEBAND_PROGRESS_INFO 0x02

#define SIDEBAND_ERROR_INFO 0x03

static const value_string sideband_vals[] = {

  { SIDEBAND_PACKFILE_DATA, "Git packfile data" },

  { SIDEBAND_PROGRESS_INFO, "Git progress data" },

  { SIDEBAND_ERROR_INFO, "Git error data" },

  { 0, NULL }

};

/* desegmentation of Git over TCP */

static bool git_desegment = true;

static bool get_packet_length(tvbuff_t *tvb, int offset,

                                  uint16_t *length)

{

  uint8_t *lenstr;

  lenstr = tvb_get_string_enc(wmem_packet_scope(), tvb, offset, 4, ENC_ASCII);

  return (sscanf(lenstr, "%hx", length) == 1);

}

static unsigned

get_git_pdu_len(packet_info *pinfo _U_, tvbuff_t *tvb, int offset, void *data _U_)

{

  uint16_t plen;

  if (!get_packet_length(tvb, offset, &plen))

    return 0; /* No idea what this is */

  return plen < 4

      ? 4   // Special packet (e.g., flush-pkt)

      : plen;

}

/* Parse pkt-lines one-by-one

 *

 * @param  tvb       The buffer to dissect.

 * @param  pinfo     Packet info associated to this buffer.

 * @param  git_tree  The git protocol subtree.

 * @param  offset    The offset at which to start the dissection.

 * @return bool      After successful/unsuccessful parsing.

 *

 * This new helper takes the contents of the tvbuffer, updates the

 * offset, and returns to the caller for subsequent processing of the

 * remainder of the data.

*/

static bool

dissect_pkt_line(tvbuff_t *tvb, packet_info *pinfo, proto_tree *git_tree,

                 int *offset)

{

  uint16_t plen;

  // what type of pkt-line is it?

  if (!get_packet_length(tvb, *offset, &plen))

    return false;

  if (plen < 4) {   // a special packet (e.g., flush-pkt)

    proto_item *ti =

        proto_tree_add_uint(git_tree, hf_git_packet_type, tvb,

                            *offset, 4, plen);

    *offset += 4;

    if (!try_val_to_str(plen, packet_type_vals))

      expert_add_info(pinfo, ti, &ei_git_bad_pkt_len);

    return true;

  }

  proto_tree_add_uint(git_tree, hf_git_packet_len, tvb, *offset, 4, plen);

  *offset += 4;

  plen -= 4;

  /*

   * Parse out the version of the Git Protocol

   *

   * The initial server response contains the version of the Git Protocol in use;

   * 1 or 2. Parsing out this information helps identify the capabilities and

   * information that can be used with the protocol.

  */

  if (plen >= 9 && !tvb_strneql(tvb, *offset, "version ", 8)) {

    proto_tree_add_item(git_tree, hf_git_protocol_version, tvb, *offset + 8,

                        1, ENC_NA);

  }

  /*

   * Parse out the sideband control code.

   *

   * Not all pkt-lines have a sideband control code. With more context from the rest of

   * the request or response, we would be able to tell whether sideband is expected here;

   * lacking that, let's assume for now that all pkt-lines starting with \1, \2, or \3

   * are using sideband.

   */

  int sideband_code = tvb_get_uint8(tvb, *offset);

  if (1 <= sideband_code && sideband_code <= 3) {

    proto_tree_add_uint(git_tree, hf_git_sideband_control_code, tvb, *offset, 1,

                        sideband_code);

    (*offset)++;

    plen--;

  }

  proto_tree_add_item(git_tree, hf_git_packet_data, tvb, *offset, plen, ENC_NA);

  *offset += plen;

  return true;

}

static int

dissect_git_pdu(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)

{

  proto_tree             *git_tree;

  proto_item             *ti;

  int offset = 0;

  col_set_str(pinfo->cinfo, COL_PROTOCOL, PSNAME);

  col_set_str(pinfo->cinfo, COL_INFO, PNAME);

  ti = proto_tree_add_item(tree, proto_git, tvb, offset, -1, ENC_NA);

  git_tree = proto_item_add_subtree(ti, ett_git);

  if (!dissect_pkt_line(tvb, pinfo, git_tree, &offset))

    return 0;

  return tvb_captured_length(tvb);

}

/* Parse http packs

 *

 * @param  tvb        The buffer to dissect.

 * @param  pinfo      The Packet Info.

 * @param  tree       The protocol tree.

 * @param  hfindex    The type of http pack.

 * @return tvb_length The amount of captured data in the buffer,

 *                    returns 0 if parsing failed.

 *

 * This new helper takes the contents of the tvbuffer sent by http

 * dissectors, adds the packs to the git subtree and returns the amount

 * of consumed bytes in the tvb buffer.

*/

static int

dissect_http_pkt_lines(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int hfindex)

{

  proto_tree             *git_tree;

  proto_item             *ti;

  int offset = 0;

  int total_len = 0;

  col_set_str(pinfo->cinfo, COL_PROTOCOL, PSNAME);

  col_set_str(pinfo->cinfo, COL_INFO, PNAME);

  ti = proto_tree_add_item(tree, proto_git, tvb, offset, -1, ENC_NA);

  git_tree = proto_item_add_subtree(ti, ett_git);

  proto_tree_add_item(git_tree, hfindex, tvb, offset,

                      tvb_captured_length(tvb), ENC_NA);

  total_len = tvb_reported_length(tvb);

  while (offset < total_len) {

    /* Add expert info if there is trouble parsing part-way through */

    if (!dissect_pkt_line(tvb, pinfo, git_tree, &offset)) {

      proto_tree_add_expert(git_tree, pinfo, &ei_git_malformed, tvb, offset, -1);

      break;

    }

  }

  return tvb_captured_length(tvb);

}

static int

dissect_git_upload_pack_adv(tvbuff_t *tvb, packet_info *pinfo,

                            proto_tree *tree, void *data _U_)

{

  return dissect_http_pkt_lines(tvb, pinfo, tree, hf_git_upload_pack_adv);

}

static int

dissect_git_upload_pack_req(tvbuff_t *tvb, packet_info *pinfo,

                            proto_tree *tree, void *data _U_)

{

  return dissect_http_pkt_lines(tvb, pinfo, tree, hf_git_upload_pack_req);

}

static int

dissect_git_upload_pack_res(tvbuff_t *tvb, packet_info *pinfo,

                            proto_tree *tree, void *data _U_)

{

  return dissect_http_pkt_lines(tvb, pinfo, tree, hf_git_upload_pack_res);

}

static int

dissect_git(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data)

{

  tcp_dissect_pdus(tvb, pinfo, tree, git_desegment, 4, get_git_pdu_len,

                   dissect_git_pdu, data);

  return tvb_captured_length(tvb);

}

void

proto_register_git(void)

{

  static hf_register_info hf[] = {

    { &hf_git_protocol_version,

      { "Git Protocol Version", "git.version", FT_UINT8, BASE_NONE, VALS(version_vals),

      0, NULL, HFILL },

    },

    { &hf_git_packet_type,

      { "Git Packet Type", "git.packet_type", FT_UINT8, BASE_NONE, VALS(packet_type_vals),

      0, NULL, HFILL },

    },

    { &hf_git_packet_len,

      { "Packet length", "git.length", FT_UINT16, BASE_HEX, NULL, 0x0, NULL, HFILL },

    },

    { &hf_git_packet_data,

      { "Packet data", "git.data", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL },

    },

    { &hf_git_sideband_control_code,

      { "Sideband control code", "git.sideband_control_code", FT_UINT8,

      BASE_HEX, VALS(sideband_vals), 0, NULL, HFILL },

    },

    { &hf_git_upload_pack_adv,

      { "Upload Pack Advertisement", "git.upload_pack_advertisement",

      FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL },

    },

    { &hf_git_upload_pack_req,

      { "Upload Pack Request", "git.upload_pack_request",

      FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL },

    },

    { &hf_git_upload_pack_res,

      { "Upload Pack Result", "git.upload_pack_result",

      FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL },

    },

  };

  static int *ett[] = {

    &ett_git,

  };

  static ei_register_info ei[] = {

    { &ei_git_bad_pkt_len,

      { "git.bad_pkt_len", PI_PROTOCOL, PI_ERROR,

        "unrecognized special pkt-len value", EXPFILL }

    },

    { &ei_git_malformed,

      { "git.malformed", PI_MALFORMED, PI_ERROR,

        "malformed packet", EXPFILL }

    },

  };

  module_t *git_module;

  expert_module_t *expert_git;

  proto_git = proto_register_protocol(PNAME, PSNAME, PFNAME);

  proto_register_field_array(proto_git, hf, array_length(hf));

  proto_register_subtree_array(ett, array_length(ett));

  expert_git = expert_register_protocol(proto_git);

  expert_register_field_array(expert_git, ei, array_length(ei));

  git_handle = register_dissector(PFNAME, dissect_git, proto_git);

  git_module = prefs_register_protocol(proto_git, NULL);

  prefs_register_bool_preference(git_module, "desegment",

                                 "Reassemble GIT messages spanning multiple TCP segments",

                                 "Whether the GIT dissector should reassemble messages spanning multiple TCP segments."

                                 " To use this option, you must also enable \"Allow subdissectors to reassemble TCP streams\" in the TCP protocol settings.",

                                 &git_desegment);

}

void

proto_reg_handoff_git(void)

{

  /*

   * Add the dissectors for GIT over HTTP

   *

   * Reference documentation at

   * https://www.kernel.org/pub/software/scm/git/docs//technical/http-protocol.txt

   */

  dissector_handle_t git_upload_pack_adv_handle;

  dissector_handle_t git_upload_pack_req_handle;

  dissector_handle_t git_upload_pack_res_handle;

  git_upload_pack_adv_handle = create_dissector_handle(dissect_git_upload_pack_adv,

                        proto_git);

  git_upload_pack_req_handle = create_dissector_handle(dissect_git_upload_pack_req,

                        proto_git);

  git_upload_pack_res_handle = create_dissector_handle(dissect_git_upload_pack_res,

                        proto_git);

  dissector_add_string("media_type",

                        "application/x-git-upload-pack-advertisement",

                        git_upload_pack_adv_handle);

  dissector_add_string("media_type",

                        "application/x-git-upload-pack-request",

                        git_upload_pack_req_handle);

  dissector_add_string("media_type",

                        "application/x-git-upload-pack-result",

                        git_upload_pack_res_handle);

  dissector_add_uint_with_preference("tcp.port", TCP_PORT_GIT, git_handle);

}

/*

 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html

 *

 * Local Variables:

 * c-basic-offset: 2

 * tab-width: 8

 * indent-tabs-mode: nil

 * End:

 *

 * ex: set shiftwidth=2 tabstop=8 expandtab:

 * :indentSize=2:tabSize=8:noTabs=true:

 */