epan/dissectors/packet-ipsec-tcp.c

   1 /*
   2  * Routines for the disassembly of the proprietary Cisco IPSEC in
   3  * TCP encapsulation protocol
   4  *
   5  * $Id$
   6  *
   7  * Copyright 2007 Joerg Mayer (see AUTHORS file)
   8  *
   9  * Wireshark - Network traffic analyzer
  10  * By Gerald Combs <gerald@wireshark.org>
  11  * Copyright 1998 Gerald Combs
  12  *
  13  * This program is free software; you can redistribute it and/or
  14  * modify it under the terms of the GNU General Public License
  15  * as published by the Free Software Foundation; either version 2
  16  * of the License, or (at your option) any later version.
  17  *
  18  * This program is distributed in the hope that it will be useful,
  19  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21  * GNU General Public License for more details.
  22  *
  23  * You should have received a copy of the GNU General Public License
  24  * along with this program; if not, write to the Free Software
  25  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  26  */
  27
  28 /* TODO:
  29  * - Find out the meaning of the (unknown) trailer
  30  * - UDP checksum is wrong
  31  * - Currently doesn't handle AH (lack of sample trace)
  32  */
  33
  34 #include "config.h"
  35
  36 #include <glib.h>
  37 #include <epan/packet.h>
  38 #include <epan/prefs.h>
  39 #include "packet-ndmp.h"
  40
  41 static int hf_tcpencap_unknown = -1;
  42 static int hf_tcpencap_zero = -1;
  43 static int hf_tcpencap_seq = -1;
  44 static int hf_tcpencap_ike_direction = -1;
  45 static int hf_tcpencap_esp_zero = -1;
  46 static int hf_tcpencap_magic = -1;
  47 static int hf_tcpencap_proto = -1;
  48 static int hf_tcpencap_magic2 = -1;
  49
  50 static int proto_tcpencap = -1;
  51 static gint ett_tcpencap = -1;
  52 static gint ett_tcpencap_unknown = -1;
  53
  54 static const value_string tcpencap_ikedir_vals[] = {
  55         { 0x0000,       "Server to client" },
  56         { 0x4000,       "Client to server" },
  57
  58         { 0,    NULL }
  59 };
  60
  61 static const value_string tcpencap_proto_vals[] = {
  62         { 0x11, "ISAKMP" },
  63         { 0x32, "ESP" },
  64
  65         { 0,    NULL }
  66 };
  67
  68 #define TRAILERLENGTH 16
  69 #define TCP_CISCO_IPSEC 10000
  70 /* Another case of several companies creating protocols and
  71    choosing an easy-to-remember port. Playing tonight: Cisco vs NDMP.
  72    Since NDMP has officially registered port 10000 with IANA, it should be the default
  73 */
  74 static guint global_tcpencap_tcp_port = 0;
  75
  76 static dissector_handle_t esp_handle;
  77 static dissector_handle_t udp_handle;
  78
  79 #define TCP_ENCAP_P_ESP 1
  80 #define TCP_ENCAP_P_UDP 2
  81
  82
  83 static int
  84 packet_is_tcpencap(tvbuff_t *tvb, packet_info *pinfo, guint32 offset)
  85 {
  86         if (    /* Must be zero */
  87                 tvb_get_ntohl(tvb, offset + 0) != 0 ||
  88                 /* Lower 12 bits must be zero */
  89                 (tvb_get_ntohs(tvb, offset + 6) & 0xfff) != 0 ||
  90                 /* Protocol must be UDP or ESP */
  91                 (tvb_get_guint8(tvb, offset + 13) != 17 &&
  92                  tvb_get_guint8(tvb, offset + 13) != 50)
  93         ) {
  94                 return FALSE;
  95         }
  96
  97         if(check_if_ndmp(tvb, pinfo)){
  98                 return FALSE;
  99         }
 100
 101         return TRUE;
 102 }
 103
 104 /*
 105  * TCP Encapsulation of IPsec Packets
 106  * as supported by the cisco vpn3000 concentrator series
 107  */
 108 static int
 109 dissect_tcpencap(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
 110 {
 111         proto_tree *tcpencap_tree = NULL;
 112         proto_tree *tcpencap_unknown_tree = NULL;
 113
 114         proto_item *tree_item = NULL;
 115         proto_item *unknown_item = NULL;
 116         tvbuff_t *next_tvb;
 117         guint32 reported_length = tvb_reported_length(tvb);
 118         guint32 offset;
 119         guint8  protocol;
 120
 121         col_set_str(pinfo->cinfo, COL_PROTOCOL, "TCPENCAP");
 122         col_clear(pinfo->cinfo, COL_INFO);
 123
 124         /* If the first 4 bytes are 0x01f401f4 (udp src and dst port = 500)
 125            we most likely have UDP (isakmp) traffic */
 126
 127         if (tvb_get_ntohl(tvb, 0) == 0x01f401f4) { /* UDP means ISAKMP */
 128                 protocol = TCP_ENCAP_P_UDP;
 129         } else { /* Hopefully ESP */
 130                 protocol = TCP_ENCAP_P_ESP;
 131         }
 132
 133         if (tree) {
 134                 tree_item = proto_tree_add_item(tree, proto_tcpencap, tvb, 0, -1, ENC_NA);
 135                 tcpencap_tree = proto_item_add_subtree(tree_item, ett_tcpencap);
 136
 137                 /* Dissect the trailer following the encapsulated IPSEC/ISAKMP packet */
 138                 offset = reported_length - TRAILERLENGTH;
 139                 unknown_item = proto_tree_add_item(tcpencap_tree, hf_tcpencap_unknown, tvb,
 140                         offset, TRAILERLENGTH, ENC_NA);
 141                 /* Try to guess the contents of the trailer */
 142                 tcpencap_unknown_tree = proto_item_add_subtree(unknown_item, ett_tcpencap_unknown);
 143                 proto_tree_add_item(tcpencap_unknown_tree, hf_tcpencap_zero, tvb, offset + 0, 4, ENC_NA);
 144                 proto_tree_add_item(tcpencap_unknown_tree, hf_tcpencap_seq, tvb, offset + 4, 2, ENC_BIG_ENDIAN);
 145                 if (protocol == TCP_ENCAP_P_UDP) {
 146                         proto_tree_add_item(tcpencap_unknown_tree, hf_tcpencap_ike_direction, tvb, offset + 6, 2, ENC_BIG_ENDIAN);
 147                 } else {
 148                         proto_tree_add_item(tcpencap_unknown_tree, hf_tcpencap_esp_zero, tvb, offset + 6, 2, ENC_BIG_ENDIAN);
 149                 }
 150                 proto_tree_add_item(tcpencap_unknown_tree, hf_tcpencap_magic, tvb, offset + 8, 5, ENC_NA);
 151                 proto_tree_add_item(tcpencap_unknown_tree, hf_tcpencap_proto, tvb, offset + 13, 1, ENC_BIG_ENDIAN);
 152                 proto_tree_add_item(tcpencap_unknown_tree, hf_tcpencap_magic2, tvb, offset + 14, 2, ENC_NA);
 153         }
 154
 155         /* Create the tvbuffer for the next dissector */
 156         next_tvb = tvb_new_subset(tvb, 0, reported_length - TRAILERLENGTH , -1);
 157         if (protocol == TCP_ENCAP_P_UDP) {
 158                 call_dissector(udp_handle, next_tvb, pinfo, tree);
 159         } else { /* Hopefully ESP */
 160                 call_dissector(esp_handle, next_tvb, pinfo, tree);
 161         }
 162
 163         return tvb_length(tvb);
 164 }
 165
 166 static gboolean
 167 dissect_tcpencap_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
 168 {
 169         guint32 reported_length = tvb_reported_length(tvb);
 170         guint32 length = tvb_length(tvb);
 171
 172         if (reported_length <= TRAILERLENGTH + 8 ||
 173                 /* Ensure we have enough bytes for packet_is_tcpencap analysis */
 174                 (reported_length - length) > (TRAILERLENGTH - 13) ||
 175                 !packet_is_tcpencap(tvb, pinfo, reported_length - TRAILERLENGTH) ) {
 176                 return FALSE;
 177         }
 178
 179         dissect_tcpencap(tvb, pinfo, tree, data);
 180         return TRUE;
 181 }
 182
 183 void
 184 proto_register_tcpencap(void)
 185 {
 186         static hf_register_info hf[] = {
 187
 188                 { &hf_tcpencap_unknown,
 189                 { "Unknown trailer",      "tcpencap.unknown", FT_BYTES, BASE_NONE, NULL,
 190                         0x0, NULL, HFILL }},
 191
 192                 { &hf_tcpencap_zero,
 193                 { "All zero",      "tcpencap.zero", FT_BYTES, BASE_NONE, NULL,
 194                         0x0, NULL, HFILL }},
 195
 196                 { &hf_tcpencap_seq,
 197                 { "Sequence number",      "tcpencap.seq", FT_UINT16, BASE_HEX, NULL,
 198                         0x0, NULL, HFILL }},
 199
 200                 { &hf_tcpencap_esp_zero,
 201                 { "ESP zero",      "tcpencap.espzero", FT_UINT16, BASE_HEX, NULL,
 202                         0x0, NULL, HFILL }},
 203
 204                 { &hf_tcpencap_ike_direction,
 205                 { "ISAKMP traffic direction",      "tcpencap.ikedirection", FT_UINT16, BASE_HEX, VALS(tcpencap_ikedir_vals),
 206                         0x0, NULL, HFILL }},
 207
 208                 { &hf_tcpencap_magic,
 209                 { "Magic number",      "tcpencap.magic", FT_BYTES, BASE_NONE, NULL,
 210                         0x0, NULL, HFILL }},
 211
 212                 { &hf_tcpencap_proto,
 213                 { "Protocol",      "tcpencap.proto", FT_UINT8, BASE_HEX, VALS(tcpencap_proto_vals),
 214                         0x0, NULL, HFILL }},
 215
 216                 { &hf_tcpencap_magic2,
 217                 { "Magic 2",      "tcpencap.magic2", FT_BYTES, BASE_NONE, NULL,
 218                         0x0, NULL, HFILL }},
 219
 220         };
 221
 222         static gint *ett[] = {
 223                 &ett_tcpencap,
 224                 &ett_tcpencap_unknown,
 225         };
 226
 227         module_t *tcpencap_module;
 228
 229         void proto_reg_handoff_tcpencap(void);
 230
 231         proto_tcpencap = proto_register_protocol(
 232                 "TCP Encapsulation of IPsec Packets", "TCPENCAP", "tcpencap");
 233         proto_register_field_array(proto_tcpencap, hf, array_length(hf));
 234         proto_register_subtree_array(ett, array_length(ett));
 235         tcpencap_module = prefs_register_protocol(proto_tcpencap, proto_reg_handoff_tcpencap);
 236         prefs_register_uint_preference(tcpencap_module, "tcp.port", "IPSEC TCP Port",
 237                 "Set the port for IPSEC/ISAKMP messages (typically 10000)",
 238                 10, &global_tcpencap_tcp_port);
 239 }
 240
 241 void
 242 proto_reg_handoff_tcpencap(void)
 243 {
 244         static dissector_handle_t tcpencap_handle;
 245         static gboolean initialized = FALSE;
 246         static guint tcpencap_tcp_port = 0;
 247
 248         if (!initialized) {
 249                 tcpencap_handle = new_create_dissector_handle(dissect_tcpencap, proto_tcpencap);
 250                 esp_handle = find_dissector("esp");
 251                 udp_handle = find_dissector("udp");
 252
 253                 heur_dissector_add("tcp", dissect_tcpencap_heur, proto_tcpencap);
 254
 255                 initialized = TRUE;
 256         }
 257
 258         /* Register TCP port for dissection */
 259         if(tcpencap_tcp_port != 0 && tcpencap_tcp_port != global_tcpencap_tcp_port){
 260                 dissector_delete_uint("tcp.port", tcpencap_tcp_port, tcpencap_handle);
 261         }
 262
 263         if(global_tcpencap_tcp_port != 0 && tcpencap_tcp_port != global_tcpencap_tcp_port) {
 264                 dissector_add_uint("tcp.port", global_tcpencap_tcp_port, tcpencap_handle);
 265         }
 266 }
 267