/*

 * dcerpc.c

 *

 * Copyright (C) 2011-18 by ntop.org

 *

 * This file is part of nDPI, an open source deep packet inspection

 * library based on the OpenDPI and PACE technology by ipoque GmbH

 *

 * nDPI is free software: you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * nDPI is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with nDPI.  If not, see <http://www.gnu.org/licenses/>.

 *

 */

#include "ndpi_protocol_ids.h"

#define NDPI_CURRENT_PROTO NDPI_PROTOCOL_DCERPC

#include "ndpi_api.h"

#include "ndpi_private.h"

#include <stdbool.h>

static void ndpi_int_dcerpc_add_connection(struct ndpi_detection_module_struct

               *ndpi_struct, struct ndpi_flow_struct *flow)

{

  ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_DCERPC, NDPI_PROTOCOL_UNKNOWN, NDPI_CONFIDENCE_DPI);

}

static bool is_connection_oriented_dcerpc(struct ndpi_packet_struct *packet)

{

  if((packet->tcp != NULL)

     && (packet->payload_packet_len >= 64)

     && (packet->payload[0] == 0x05) /* version 5 */

     && (packet->payload[2] < 16) /* Packet type */

     && (((packet->payload[9]<<8) | packet->payload[8]) == packet->payload_packet_len) /* Packet Length */

     ) {

    return true;

  }

  return false;

}

static bool is_connectionless_dcerpc(struct ndpi_packet_struct *packet)

{

  u_int16_t fragment_len;

  if (packet->udp == NULL)

    return false;

  if (packet->payload_packet_len < 80)

    return false;

  if (packet->payload[0] != 0x04) /* type must be equal to 4 */

    return false;

  if (packet->payload[1] > 10) /* must be <= CANCEL ACK or it's not connectionless DCE/RPC */

    return false;

  if (packet->payload[3] & 0xFC) /* flags2: bit 3:8 are reserved for future use and must be set to 0 */

    return false;

  if (packet->payload[4] & 0xEE) /* neither big endian nor little endian */

    return false;

  if (packet->payload[5] > 3) /* invalid floating point type */

    return false;

  if(packet->payload[4] == 0x10)

    fragment_len = (packet->payload[75] << 8) + packet->payload[74]; /* Big endian */

  else

    fragment_len = (packet->payload[74] << 8) + packet->payload[75]; /* Little endian */

  if(packet->payload_packet_len != (fragment_len+76 /* offset */ + 4 /* rest of the packet */))

    return false; /* Too short or too long, bot RPC */

  return true;

}

static void ndpi_search_dcerpc(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)

{

  struct ndpi_packet_struct *packet = &ndpi_struct->packet;

  NDPI_LOG_DBG(ndpi_struct, "search DCERPC\n");

  if (is_connection_oriented_dcerpc(packet) || is_connectionless_dcerpc(packet)) {

    NDPI_LOG_INFO(ndpi_struct, "found DCERPC\n");

    ndpi_int_dcerpc_add_connection(ndpi_struct, flow);

    return;

  }

  if(packet->payload_packet_len>1)

    NDPI_EXCLUDE_DISSECTOR(ndpi_struct, flow);

}

void init_dcerpc_dissector(struct ndpi_detection_module_struct *ndpi_struct)

{

  register_dissector("DCERPC", ndpi_struct,

                     ndpi_search_dcerpc,

                     NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_TCP_OR_UDP_WITH_PAYLOAD_WITHOUT_RETRANSMISSION,

                     1, NDPI_PROTOCOL_DCERPC);

}