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/*
* skype.c
*
* Copyright (C) 2017-22 - ntop.org
*
* 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_SKYPE_TEAMS
#include "ndpi_api.h"
#include "ndpi_private.h"
static int is_port(u_int16_t a, u_int16_t b, u_int16_t c) {
return(((a == c) || (b == c)) ? 1 : 0);
}
static void ndpi_check_skype(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow) {
struct ndpi_packet_struct *packet = &ndpi_struct->packet;
u_int32_t payload_len = packet->payload_packet_len;
/* No need to do ntohl() with 0xFFFFFFFF */
if(packet->iph
&& ((packet->iph->daddr == 0xFFFFFFFF /* 255.255.255.255 */)
|| ((ntohl(packet->iph->daddr) & 0xFFFFFF00) == 0xE0000000 /* multicast */)
)) {
NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
return;
}
if(flow->host_server_name[0] != '\0')
return;
if(flow->packet_counter < 5) {
u_int16_t sport = ntohs(packet->udp->source);
u_int16_t dport = ntohs(packet->udp->dest);
/* skype-to-skype */
if(is_port(sport, dport, 1119) /* It can be confused with battle.net */
|| is_port(sport, dport, 80) /* No HTTP-like protocols UDP/80 */
) {
;
} else {
/* Too many false positives */
if(((payload_len == 3) && ((packet->payload[2] & 0x0F)== 0x0d))
||
((payload_len >= 16)
&& (((packet->payload[0] & 0xC0) >> 6) == 0x02 /* RTPv2 */
|| (((packet->payload[0] & 0xF0) >> 4) == 0 /* Zoom */)
|| (((packet->payload[0] & 0xF0) >> 4) == 0x07 /* Skype */)
)
&& (packet->payload[0] != 0x30) /* Avoid invalid SNMP detection */
&& (packet->payload[0] != 0x00) /* Avoid invalid CAPWAP detection */
&& (packet->payload[0] != 0x80) /* Avoid invalid FINS detection */
&& (packet->payload[0] != 0xC0) /* Avoid invalid FINS detection */
&& (packet->payload[0] != 0xC1) /* Avoid invalid FINS detection */
&& (packet->payload[2] == 0x02))) {
if(is_port(sport, dport, 8801)) {
NDPI_LOG_INFO(ndpi_struct, "found ZOOM (in SKYPE_TEAMS code)\n");
ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_ZOOM, NDPI_PROTOCOL_UNKNOWN, NDPI_CONFIDENCE_DPI);
} else if((payload_len >= 16)
&& (packet->payload[0] != 0x01) /* Avoid invalid Cisco HSRP detection / RADIUS */
&& (sport != dport) /* Avoid matching simple OT protocols such as CIP that have src and dst port alike */
) {
NDPI_LOG_INFO(ndpi_struct, "found SKYPE_TEAMS\n");
ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_SKYPE_TEAMS_CALL, NDPI_PROTOCOL_SKYPE_TEAMS, NDPI_CONFIDENCE_DPI);
}
}
if (flow->detected_protocol_stack[0] == NDPI_PROTOCOL_UNKNOWN) {
const uint8_t id_flags_iv_crc_len = 11;
const uint8_t crc_len = sizeof(flow->l4.udp.skype_crc);
const uint8_t crc_offset = id_flags_iv_crc_len - crc_len;
/* Look for two pkts with the same crc */
if((payload_len >= id_flags_iv_crc_len) &&
(packet->payload[2] == 0x02 /* Payload flag */ )) {
if(flow->packet_counter == 1) {
memcpy(flow->l4.udp.skype_crc, &packet->payload[crc_offset], crc_len);
} else {
if(memcmp(flow->l4.udp.skype_crc, &packet->payload[crc_offset], crc_len) == 0) {
NDPI_LOG_INFO(ndpi_struct, "found SKYPE_TEAMS\n");
/* As there is some heuristic we need to double check before detecting the protocol */
if((flow->guessed_protocol_id_by_ip == NDPI_PROTOCOL_MICROSOFT_AZURE)
|| (flow->guessed_protocol_id_by_ip == NDPI_PROTOCOL_SKYPE_TEAMS)) {
ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_SKYPE_TEAMS, NDPI_PROTOCOL_UNKNOWN, NDPI_CONFIDENCE_DPI);
return;
}
}
}
/* No idea if the two pkts need to be consecutive; in doubt wait for some more pkts */
return;
}
}
}
NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
return;
}
}
static void ndpi_search_skype(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)
{
NDPI_LOG_DBG(ndpi_struct, "search skype\n");
ndpi_check_skype(ndpi_struct, flow);
}
void init_skype_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id)
{
ndpi_set_bitmask_protocol_detection("Skype_Teams", ndpi_struct, *id,
NDPI_PROTOCOL_SKYPE_TEAMS,
ndpi_search_skype,
NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_UDP_WITH_PAYLOAD,
SAVE_DETECTION_BITMASK_AS_UNKNOWN,
ADD_TO_DETECTION_BITMASK);
*id += 1;
}
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