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wireshark/epan/dissectors/packet-git.c

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/* 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>
#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 = -1;
static expert_field ei_git_bad_pkt_len = EI_INIT;
static expert_field ei_git_malformed = EI_INIT;
static gint ett_git = -1;
static gint hf_git_protocol_version = -1;
static gint hf_git_packet_type = -1;
static gint hf_git_packet_len = -1;
static gint hf_git_packet_data = -1;
static gint hf_git_sideband_control_code = -1;
static gint hf_git_upload_pack_adv = -1;
static gint hf_git_upload_pack_req = -1;
static gint hf_git_upload_pack_res = -1;
#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 gboolean git_desegment = TRUE;
static gboolean get_packet_length(tvbuff_t *tvb, int offset,
guint16 *length)
{
guint8 *lenstr;
lenstr = tvb_get_string_enc(wmem_packet_scope(), tvb, offset, 4, ENC_ASCII);
return (sscanf(lenstr, "%hx", length) == 1);
}
static guint
get_git_pdu_len(packet_info *pinfo _U_, tvbuff_t *tvb, int offset, void *data _U_)
{
guint16 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 gboolean
dissect_pkt_line(tvbuff_t *tvb, packet_info *pinfo, proto_tree *git_tree,
int *offset)
{
guint16 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_guint8(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 gint *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:
*/
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