/* packet-turnchannel.c

 * Routines for TURN channel dissection (TURN negotiation is handled

 * in the STUN2 dissector

 * Copyright 2008, 8x8 Inc. <petithug@8x8.com>

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

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

 *

 * Please refer to the following specs for protocol detail:

 * - draft-ietf-behave-rfc3489bis-15

 * - draft-ietf-mmusic-ice-19

 * - draft-ietf-behave-nat-behavior-discovery-03

 * - draft-ietf-behave-turn-07

 * - draft-ietf-behave-turn-ipv6-03

 *

 * XXX - these are now:

 * - RFC 5389

 * - RFC 5245

 * - RFC 5780

 * - RFC 5766

 * - RFC 6156

 * - RFC 8656

 *

 * Update as necessary.

 */

#include "config.h"

#include <epan/packet.h>

#include "packet-tcp.h"

void proto_register_turnchannel(void);

void proto_reg_handoff_turnchannel(void);

/* heuristic subdissectors */

static heur_dissector_list_t heur_subdissector_list;

/* Initialize the protocol and registered fields */

static int proto_turnchannel;

static int hf_turnchannel_id;

static int hf_turnchannel_len;

#define TURNCHANNEL_HDR_LEN ((unsigned)4)

#define MS_MULTIPLEX_TURN 0xFF10

/* Initialize the subtree pointers */

static int ett_turnchannel;

static dissector_handle_t turnchannel_tcp_handle;

static dissector_handle_t turnchannel_udp_handle;

/*

 * RFC 5764 defined a demultiplexing scheme to allow TURN is co-exist

 * on the same 5-tuple as STUN, DTLS, RTP/RTCP, and ZTLS by rejecting

 * previous reserved channel numbers, restricting the channel numbers

 * to 0x4000-0x7FFF. RFC 5766 (TURN) did not incorporate the restriction,

 * but RFC 8656 did, further restricting the channel numbers to the

 * range 0x4000-0x4FFF.

 *

 * Reject channel numbers outside 0x4000-0x7FFF (except for the special

 * MS-TURN multiplex channel number), since no implementation has used

 * any value outside that range, and the 0x5000-0x7FFF range is reserved

 * in the multiplexing scheme.

 */

static bool

test_turnchannel_id(uint16_t channel_id)

{

  if ((channel_id & 0x4000) == 0x4000 || channel_id == MS_MULTIPLEX_TURN)

    return true;

  return false;

}

static int

dissect_turnchannel_message(tvbuff_t *tvb, packet_info *pinfo,

          proto_tree *tree, void *data _U_)

{

  unsigned   len;

  uint16_t channel_id;

  uint16_t data_len;

  proto_item *ti;

  proto_tree *turnchannel_tree;

  heur_dtbl_entry_t *hdtbl_entry;

  len = tvb_captured_length(tvb);

  /* First, make sure we have enough data to do the check. */

  if (len < TURNCHANNEL_HDR_LEN) {

      return 0;

  }

  channel_id = tvb_get_ntohs(tvb, 0);

  data_len = tvb_get_ntohs(tvb, 2);

  if (!test_turnchannel_id(channel_id)) {

    return 0;

  }

  if (len != TURNCHANNEL_HDR_LEN + data_len) {

    return 0;

  }

  /* Seems to be a decent TURN channel message */

  col_set_str(pinfo->cinfo, COL_PROTOCOL, "TURN CHANNEL");

  col_add_fstr(pinfo->cinfo, COL_INFO, "Channel Id 0x%x", channel_id);

  ti = proto_tree_add_item(tree, proto_turnchannel, tvb, 0, -1, ENC_NA);

  turnchannel_tree = proto_item_add_subtree(ti, ett_turnchannel);

  proto_tree_add_uint(turnchannel_tree, hf_turnchannel_id, tvb, 0, 2, channel_id);

  proto_tree_add_uint(turnchannel_tree, hf_turnchannel_len, tvb, 2, 2, data_len);

  if (len > TURNCHANNEL_HDR_LEN) {

    tvbuff_t *next_tvb;

    unsigned reported_len;

    reported_len = tvb_reported_length_remaining(tvb,

                   TURNCHANNEL_HDR_LEN);

    if (data_len < reported_len) {

      reported_len = data_len;

    }

    next_tvb = tvb_new_subset_length(tvb, TURNCHANNEL_HDR_LEN, reported_len);

    if (!dissector_try_heuristic(heur_subdissector_list,

               next_tvb, pinfo, tree, &hdtbl_entry, NULL)) {

      call_data_dissector(next_tvb, pinfo, tree);

    }

  }

  return tvb_captured_length(tvb);

}

static unsigned

get_turnchannel_message_len(packet_info *pinfo _U_, tvbuff_t *tvb,

                            int offset, void *data _U_)

{

  uint16_t channel_id;

  channel_id = tvb_get_ntohs(tvb, 0);

  /* If the channel number is outside the range, either we missed

         * a TCP segment or this is STUN, DTLS, RTP, etc. multiplexed on

         * the same 5-tuple. Report the length as the rest of the packet

         * and dissect_turnchannel_message will reject it, rather than

         * using a bogus PDU length and messing up the dissection of

         * future TURN packets.

         */

  if (!test_turnchannel_id(channel_id)) {

    return tvb_reported_length(tvb);

  }

  return (unsigned)tvb_get_ntohs(tvb, offset+2) + TURNCHANNEL_HDR_LEN;

}

static int

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

{

  tcp_dissect_pdus(tvb, pinfo, tree, true, TURNCHANNEL_HDR_LEN,

      get_turnchannel_message_len, dissect_turnchannel_message, data);

  return tvb_captured_length(tvb);

}

void

proto_register_turnchannel(void)

{

  static hf_register_info hf[] = {

    { &hf_turnchannel_id,

      { "TURN Channel ID",  "turnchannel.id", FT_UINT16,

      BASE_HEX, NULL, 0x0,  NULL, HFILL }

    },

    { &hf_turnchannel_len,

      { "Data Length",  "turnchannel.length", FT_UINT16,

      BASE_DEC, NULL, 0x0,  NULL, HFILL }

    },

  };

/* Setup protocol subtree array */

  static int *ett[] = {

    &ett_turnchannel,

  };

/* Register the protocol name and description */

  proto_turnchannel = proto_register_protocol("TURN Channel", "TURNCHANNEL", "turnchannel");

  turnchannel_tcp_handle = register_dissector("turnchannel-tcp", dissect_turnchannel_tcp, proto_turnchannel);

  turnchannel_udp_handle = register_dissector("turnchannel", dissect_turnchannel_message, proto_turnchannel);

/* subdissectors */

  /* XXX: Nothing actually registers to this list. All dissectors register

         * to the heuristic subdissector list for STUN, since the STUN dissector

         * doesn't actually call this dissector but uses its own implementation

         * of TURN Channel messages.

         */

  heur_subdissector_list = register_heur_dissector_list_with_description("turnchannel", "TURN Channel message", proto_turnchannel);

/* Required function calls to register the header fields and subtrees used */

  proto_register_field_array(proto_turnchannel, hf, array_length(hf));

  proto_register_subtree_array(ett, array_length(ett));

}

void

proto_reg_handoff_turnchannel(void)

{

  /* Register for "Decode As" in case STUN negotiation isn't captured */

  dissector_add_for_decode_as_with_preference("tcp.port", turnchannel_tcp_handle);

  dissector_add_for_decode_as_with_preference("udp.port", turnchannel_udp_handle);

  /*

   * SSL/TLS and DTLS Application-Layer Protocol Negotiation (ALPN)

   * protocol ID.

   */

  dissector_add_string("tls.alpn", "stun.turn", turnchannel_tcp_handle);

  dissector_add_string("dtls.alpn", "stun.turn", turnchannel_udp_handle);

}

/*

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

 *

 * Local variables:

 * c-basic-offset: 8

 * tab-width: 8

 * indent-tabs-mode: t

 * End:

 *

 * vi: set shiftwidth=8 tabstop=8 noexpandtab:

 * :indentSize=8:tabSize=8:noTabs=false:

 */