epan/dissectors/packet-lsd.c

   1 /* packet-lsd.c
   2  * Local Service Discovery packet dissector
   3  *
   4  * From http://bittorrent.org/beps/bep_0014.html
   5  *
   6  * Wireshark - Network traffic analyzer
   7  * By Gerald Combs <gerald@wireshark.org>
   8  * Copyright 1998 Gerald Combs
   9  *
  10  * SPDX-License-Identifier: GPL-2.0-or-later
  11  */
  12
  13 #include "config.h"
  14
  15 #include <epan/packet.h>
  16 #include <epan/expert.h>
  17 #include <epan/strutil.h>
  18 #include <wsutil/pint.h>
  19 #include <wsutil/strtoi.h>
  20
  21 void proto_register_lsd(void);
  22 void proto_reg_handoff_lsd(void);
  23
  24 #define LSD_MULTICAST_ADDRESS 0xEFC0988F /* 239.192.152.143 */
  25 #define LSD_PORT 6771
  26
  27 static int proto_lsd;
  28 static int hf_lsd_header;
  29 static int hf_lsd_host;
  30 static int hf_lsd_port;
  31 static int hf_lsd_infohash;
  32 static int hf_lsd_cookie;
  33
  34 static int ett_lsd;
  35
  36 static expert_field ei_lsd_field;
  37
  38 static bool
  39 parse_string_field(proto_tree *tree, int hf, packet_info *pinfo, tvbuff_t *tvb, int offset, int* next_offset, int* linelen)
  40 {
  41   uint8_t *str;
  42   header_field_info* hf_info = proto_registrar_get_nth(hf);
  43   char **field_and_value;
  44   proto_item* ti;
  45   char *p;
  46
  47   *linelen = tvb_find_line_end(tvb, offset, -1, next_offset, false);
  48   if (*linelen < 0)
  49     return false;
  50
  51   str = tvb_get_string_enc(pinfo->pool, tvb, offset, *linelen, ENC_ASCII);
  52   if (g_ascii_strncasecmp(str, hf_info->name, strlen(hf_info->name)) == 0)
  53   {
  54       field_and_value = wmem_strsplit(pinfo->pool, str, ":", 2);
  55       p = field_and_value[1];
  56       if (p) {
  57         while(g_ascii_isspace(*p))
  58           p++;
  59         proto_tree_add_string(tree, hf, tvb, offset, *linelen, p);
  60         return true;
  61       }
  62   }
  63   ti = proto_tree_add_string_format(tree, hf, tvb, offset, *linelen, str, "%s", str);
  64   expert_add_info_format(pinfo, ti, &ei_lsd_field, "%s field malformed", hf_info->name);
  65
  66   return true;
  67 }
  68
  69 static int
  70 dissect_lsd(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
  71 {
  72   proto_item *ti = NULL;
  73   proto_tree *lsd_tree;
  74   int offset = 0, next_offset = 0, linelen;
  75   uint8_t *str;
  76   char **field_and_value;
  77   uint16_t port;
  78   bool valid;
  79
  80   linelen = tvb_find_line_end(tvb, offset, -1, &next_offset, false);
  81   if (linelen < 0)
  82       return 0;
  83
  84   col_set_str(pinfo->cinfo, COL_PROTOCOL, "LSD");
  85   col_clear(pinfo->cinfo, COL_INFO);
  86
  87   /* Create display subtree for the protocol */
  88   ti = proto_tree_add_item(tree, proto_lsd, tvb, 0, -1, ENC_NA);
  89   lsd_tree = proto_item_add_subtree(ti, ett_lsd);
  90
  91   proto_tree_add_item(lsd_tree, hf_lsd_header, tvb, offset, linelen, ENC_ASCII);
  92
  93   offset = next_offset;
  94   if (!parse_string_field(lsd_tree, hf_lsd_host, pinfo, tvb, offset, &next_offset, &linelen))
  95       return offset+linelen;
  96
  97   offset = next_offset;
  98   linelen = tvb_find_line_end(tvb, offset, -1, &next_offset, false);
  99   if (linelen < 0)
 100       return offset+linelen;
 101   str = tvb_get_string_enc(pinfo->pool, tvb, offset, linelen, ENC_ASCII);
 102   if (g_ascii_strncasecmp(str, "Port", strlen("Port")) == 0)
 103   {
 104     field_and_value = wmem_strsplit(pinfo->pool, str, ":", 2);
 105     valid = ws_strtou16(field_and_value[1], NULL, &port);
 106     ti = proto_tree_add_uint(lsd_tree, hf_lsd_port, tvb, offset, linelen, port);
 107     if (!valid)
 108     {
 109       expert_add_info_format(pinfo, ti, &ei_lsd_field, "Port value malformed");
 110     }
 111   }
 112   else
 113   {
 114     ti = proto_tree_add_uint(lsd_tree, hf_lsd_port, tvb, offset, 0, 0xFFFF);
 115     expert_add_info_format(pinfo, ti, &ei_lsd_field, "Port field malformed");
 116   }
 117   proto_item_set_len(ti, linelen);
 118
 119   offset = next_offset;
 120   if (!parse_string_field(lsd_tree, hf_lsd_infohash, pinfo, tvb, offset, &next_offset, &linelen))
 121       return offset+linelen;
 122
 123   offset = next_offset;
 124   linelen = tvb_find_line_end(tvb, offset, -1, &next_offset, false);
 125   if (linelen < 0)
 126       return offset+linelen;
 127   /* Cookie is optional */
 128   if (tvb_strncaseeql(tvb, offset, "cookie", strlen("cookie")) == 0)
 129   {
 130     if (!parse_string_field(lsd_tree, hf_lsd_cookie, pinfo, tvb, offset, &next_offset, &linelen))
 131       return offset+linelen;
 132   }
 133
 134   return tvb_captured_length(tvb);
 135 }
 136
 137 static bool
 138 dissect_lsd_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
 139 {
 140   if (pinfo->dst.type == AT_IPv4 && pntoh32(pinfo->dst.data) == LSD_MULTICAST_ADDRESS && pinfo->destport == LSD_PORT)
 141       return (dissect_lsd(tvb, pinfo, tree, data) != 0);
 142
 143   if (pinfo->dst.type == AT_IPv6 && pinfo->destport == LSD_PORT)
 144       return (dissect_lsd(tvb, pinfo, tree, data) != 0);
 145
 146   return false;
 147 }
 148
 149 void
 150 proto_register_lsd(void)
 151 {
 152   static hf_register_info hf[] = {
 153     { &hf_lsd_header,
 154       { "Header", "lsd.header",
 155         FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }
 156     },
 157     { &hf_lsd_host,
 158       { "Host", "lsd.host",
 159         FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }
 160     },
 161     { &hf_lsd_port,
 162       { "Port", "lsd.port",
 163         FT_UINT32, BASE_DEC, NULL, 0, NULL, HFILL }
 164     },
 165     { &hf_lsd_infohash,
 166       { "Infohash", "lsd.infohash",
 167         FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }
 168     },
 169     { &hf_lsd_cookie,
 170       { "cookie", "lsd.cookie",
 171         FT_STRING, BASE_NONE, NULL, 0, NULL, HFILL }
 172     },
 173   };
 174
 175   static int *ett[] = {
 176     &ett_lsd,
 177   };
 178
 179   static ei_register_info ei[] = {
 180     { &ei_lsd_field, { "lsd.malformed_field", PI_MALFORMED, PI_ERROR, "Malformed LDS field", EXPFILL }},
 181   };
 182
 183   expert_module_t* expert_lsd;
 184
 185   proto_lsd = proto_register_protocol("Local Service Discovery", "LSD", "lsd");
 186
 187   proto_register_field_array(proto_lsd, hf, array_length(hf));
 188   proto_register_subtree_array(ett, array_length(ett));
 189   expert_lsd = expert_register_protocol(proto_lsd);
 190   expert_register_field_array(expert_lsd, ei, array_length(ei));
 191 }
 192
 193 void
 194 proto_reg_handoff_lsd(void)
 195 {
 196     heur_dissector_add( "udp", dissect_lsd_heur, "LSD over UDP", "lsd_udp", proto_lsd, HEURISTIC_ENABLE);
 197 }
 198
 199 /*
 200  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 201  *
 202  * Local Variables:
 203  * c-basic-offset: 2
 204  * tab-width: 8
 205  * indent-tabs-mode: nil
 206  * End:
 207  *
 208  * ex: set shiftwidth=2 tabstop=8 expandtab:
 209  * :indentSize=2:tabSize=8:noTabs=true:
 210  */