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/*
* coap.c
*
* Copyright (C) 2016 Sorin Zamfir <sorin.zamfir@yahoo.com>
*
* 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_protocols.h"
#ifdef NDPI_PROTOCOL_COAP
/**
* Entry point when protocol is identified.
*/
static void ndpi_int_coap_add_connection (struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow)
{
// not sure if this is accurate but coap runs on top of udp and should be connectionless
ndpi_set_detected_protocol(ndpi_struct,flow,NDPI_PROTOCOL_COAP,NDPI_PROTOCOL_UNKNOWN);
NDPI_LOG(NDPI_PROTOCOL_COAP, ndpi_struct, NDPI_LOG_DEBUG, "CoAP found.\n");
}
/**
* Dissector function that searches CoAP headers
*/
void ndpi_search_coap (struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow)
{
struct ndpi_packet_struct *packet = &flow->packet;
if (packet->detected_protocol_stack[0] != NDPI_PROTOCOL_UNKNOWN) {
return;
}
NDPI_LOG(NDPI_PROTOCOL_COAP, ndpi_struct, NDPI_LOG_DEBUG, "CoAP detection...\n");
// searching for request
NDPI_LOG(NDPI_PROTOCOL_COAP, ndpi_struct, NDPI_LOG_DEBUG, "====>>>> COAP header: %04x%04x%04x%04x [len: %u]\n",
packet->payload[0], packet->payload[1], packet->payload[2], packet->payload[3], packet->payload_packet_len);
// check if we have version bits
if (packet->payload_packet_len < 4) {
NDPI_LOG(NDPI_PROTOCOL_COAP, ndpi_struct, NDPI_LOG_DEBUG, "Excluding Coap .. mandatory header not found!\n");
NDPI_ADD_PROTOCOL_TO_BITMASK(flow->excluded_protocol_bitmask, NDPI_PROTOCOL_COAP);
return;
}
// since this is always unsigned we could have spared the 0xF0 logical AND
// vt = version and type (version is mandatory 1; type is either 0,1,2,3 )
u_int8_t vt = (u_int8_t) ((packet->payload[0] & 0xF0) >> 4);
if ((vt == 4) || (vt == 5) || (vt == 6) || (vt == 7)) {
NDPI_LOG(NDPI_PROTOCOL_COAP, ndpi_struct, NDPI_LOG_DEBUG, "Continuing Coap detection \n");
// search for values 9 to 15 in the token length
u_int8_t tkl = (u_int8_t) ((packet->payload[0] & 0x0F));
if ((tkl >= 9) && (tkl <= 15)) {
NDPI_LOG(NDPI_PROTOCOL_COAP, ndpi_struct, NDPI_LOG_DEBUG, "Excluding Coap .. invalid token length found!\n");
NDPI_ADD_PROTOCOL_TO_BITMASK(flow->excluded_protocol_bitmask, NDPI_PROTOCOL_COAP);
return;
}
u_int8_t class = (u_int8_t) ((packet->payload[1] & 0xE0) >> 5);
u_int8_t detail = (u_int8_t) ((packet->payload[1] & 0x1F));
if ((class == 0) && (detail == 0) && (tkl == 0) && (packet->payload_packet_len == 4)) {
NDPI_LOG(NDPI_PROTOCOL_COAP, ndpi_struct, NDPI_LOG_DEBUG, "Coap found ... empty message\n");
ndpi_int_coap_add_connection(ndpi_struct,flow);
return;
}
if ((class == 0) && ((detail == 1) || (detail == 2 ) || (detail == 3 ) || (detail == 4 ))) {
// we should probably search for options as well and payload for deeper inspection
NDPI_LOG(NDPI_PROTOCOL_COAP, ndpi_struct, NDPI_LOG_DEBUG, "Coap found ... req message\n");
ndpi_int_coap_add_connection(ndpi_struct,flow);
return;
}
if ((class == 2) || (class == 4) || (class == 5)) {
// we should probably search for options as well and payload for deeper inspection
NDPI_LOG(NDPI_PROTOCOL_COAP, ndpi_struct, NDPI_LOG_DEBUG, "Coap found ... resp message\n");
ndpi_int_coap_add_connection(ndpi_struct,flow);
return;
}
}
NDPI_LOG(NDPI_PROTOCOL_COAP, ndpi_struct, NDPI_LOG_DEBUG, "Excluding Coap ...\n");
NDPI_ADD_PROTOCOL_TO_BITMASK(flow->excluded_protocol_bitmask, NDPI_PROTOCOL_COAP);
return;
}
/**
* Entry point for the ndpi library
*/
void init_coap_dissector (struct ndpi_detection_module_struct *ndpi_struct,
u_int32_t *id, NDPI_PROTOCOL_BITMASK *detection_bitmask)
{
ndpi_set_bitmask_protocol_detection ("COAP", ndpi_struct, detection_bitmask, *id,
NDPI_PROTOCOL_COAP,
ndpi_search_coap,
NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_UDP_WITH_PAYLOAD,
SAVE_DETECTION_BITMASK_AS_UNKNOWN, ADD_TO_DETECTION_BITMASK);
*id +=1;
}
#endif // NDPI_PROTOCOL_COAP
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