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/* packet-lsd.c
* Local Service Discovery packet dissector
*
* From http://bittorrent.org/beps/bep_0014.html
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/expert.h>
#include <epan/strutil.h>
#include <wsutil/pint.h>
#include <wsutil/strtoi.h>
void proto_register_lsd(void);
void proto_reg_handoff_lsd(void);
#define LSD_MULTICAST_ADDRESS 0xEFC0988F /* 239.192.152.143 */
#define LSD_PORT 6771
static int proto_lsd;
static int hf_lsd_header;
static int hf_lsd_host;
static int hf_lsd_port;
static int hf_lsd_infohash;
static int hf_lsd_cookie;
static int ett_lsd;
static expert_field ei_lsd_field;
static bool
parse_string_field(proto_tree *tree, int hf, packet_info *pinfo, tvbuff_t *tvb, int offset, int* next_offset, int* linelen)
{
uint8_t *str;
header_field_info* hf_info = proto_registrar_get_nth(hf);
char **field_and_value;
proto_item* ti;
char *p;
*linelen = tvb_find_line_end(tvb, offset, -1, next_offset, false);
if (*linelen < 0)
return false;
str = tvb_get_string_enc(pinfo->pool, tvb, offset, *linelen, ENC_ASCII);
if (g_ascii_strncasecmp(str, hf_info->name, strlen(hf_info->name)) == 0)
{
field_and_value = wmem_strsplit(pinfo->pool, str, ":", 2);
p = field_and_value[1];
if (p) {
while(g_ascii_isspace(*p))
p++;
proto_tree_add_string(tree, hf, tvb, offset, *linelen, p);
return true;
}
}
ti = proto_tree_add_string_format(tree, hf, tvb, offset, *linelen, str, "%s", str);
expert_add_info_format(pinfo, ti, &ei_lsd_field, "%s field malformed", hf_info->name);
return true;
}
static int
dissect_lsd(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
{
proto_item *ti = NULL;
proto_tree *lsd_tree;
int offset = 0, next_offset = 0, linelen;
uint8_t *str;
char **field_and_value;
uint16_t port;
bool valid;
linelen = tvb_find_line_end(tvb, offset, -1, &next_offset, false);
if (linelen < 0)
return 0;
col_set_str(pinfo->cinfo, COL_PROTOCOL, "LSD");
col_clear(pinfo->cinfo, COL_INFO);
/* Create display subtree for the protocol */
ti = proto_tree_add_item(tree, proto_lsd, tvb, 0, -1, ENC_NA);
lsd_tree = proto_item_add_subtree(ti, ett_lsd);
proto_tree_add_item(lsd_tree, hf_lsd_header, tvb, offset, linelen, ENC_ASCII);
offset = next_offset;
if (!parse_string_field(lsd_tree, hf_lsd_host, pinfo, tvb, offset, &next_offset, &linelen))
return offset+linelen;
offset = next_offset;
linelen = tvb_find_line_end(tvb, offset, -1, &next_offset, false);
if (linelen < 0)
return offset+linelen;
str = tvb_get_string_enc(pinfo->pool, tvb, offset, linelen, ENC_ASCII);
if (g_ascii_strncasecmp(str, "Port", strlen("Port")) == 0)
{
field_and_value = wmem_strsplit(pinfo->pool, str, ":", 2);
valid = ws_strtou16(field_and_value[1], NULL, &port);
ti = proto_tree_add_uint(lsd_tree, hf_lsd_port, tvb, offset, linelen, port);
if (!valid)
{
expert_add_info_format(pinfo, ti, &ei_lsd_field, "Port value malformed");
}
}
else
{
ti = proto_tree_add_uint(lsd_tree, hf_lsd_port, tvb, offset, 0, 0xFFFF);
expert_add_info_format(pinfo, ti, &ei_lsd_field, "Port field malformed");
}
proto_item_set_len(ti, linelen);
offset = next_offset;
if (!parse_string_field(lsd_tree, hf_lsd_infohash, pinfo, tvb, offset, &next_offset, &linelen))
return offset+linelen;
offset = next_offset;
linelen = tvb_find_line_end(tvb, offset, -1, &next_offset, false);
if (linelen < 0)
return offset+linelen;
/* Cookie is optional */
if (tvb_strncaseeql(tvb, offset, "cookie", strlen("cookie")) == 0)
{
if (!parse_string_field(lsd_tree, hf_lsd_cookie, pinfo, tvb, offset, &next_offset, &linelen))
return offset+linelen;
}
return tvb_captured_length(tvb);
}
static bool
dissect_lsd_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
{
if (pinfo->dst.type == AT_IPv4 && pntoh32(pinfo->dst.data) == LSD_MULTICAST_ADDRESS && pinfo->destport == LSD_PORT)
return (dissect_lsd(tvb, pinfo, tree, data) != 0);
if (pinfo->dst.type == AT_IPv6 && pinfo->destport == LSD_PORT)
return (dissect_lsd(tvb, pinfo, tree, data) != 0);
return false;
}
void
proto_register_lsd(void)
{
static hf_register_info hf[] = {
{ &hf_lsd_header,
{ "Header", "lsd.header",
FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }
},
{ &hf_lsd_host,
{ "Host", "lsd.host",
FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }
},
{ &hf_lsd_port,
{ "Port", "lsd.port",
FT_UINT32, BASE_DEC, NULL, 0, NULL, HFILL }
},
{ &hf_lsd_infohash,
{ "Infohash", "lsd.infohash",
FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }
},
{ &hf_lsd_cookie,
{ "cookie", "lsd.cookie",
FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }
},
};
static int *ett[] = {
&ett_lsd,
};
static ei_register_info ei[] = {
{ &ei_lsd_field, { "lsd.malformed_field", PI_MALFORMED, PI_ERROR, "Malformed LDS field", EXPFILL }},
};
expert_module_t* expert_lsd;
proto_lsd = proto_register_protocol("Local Service Discovery", "LSD", "lsd");
proto_register_field_array(proto_lsd, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
expert_lsd = expert_register_protocol(proto_lsd);
expert_register_field_array(expert_lsd, ei, array_length(ei));
}
void
proto_reg_handoff_lsd(void)
{
heur_dissector_add( "udp", dissect_lsd_heur, "LSD over UDP", "lsd_udp", proto_lsd, HEURISTIC_ENABLE);
}
/*
* 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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