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/*
* skype.c
*
* Copyright (C) 2017 - 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_api.h"
#ifdef NDPI_PROTOCOL_SKYPE
static u_int8_t is_skype_host(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t host) {
struct in_addr pin;
pin.s_addr = host;
return((ndpi_network_ptree_match(ndpi_struct, &pin) == NDPI_PROTOCOL_SKYPE) ? 1 : 0);
}
u_int8_t is_skype_flow(struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow) {
struct ndpi_packet_struct *packet = &flow->packet;
if(packet->iph) {
/*
Skype connections are identified by some SSL-like communications
without SSL certificate being exchanged
*/
if(is_skype_host(ndpi_struct, packet->iph->saddr)
|| is_skype_host(ndpi_struct, packet->iph->daddr)) {
return(1);
}
}
return(0);
}
static void ndpi_check_skype(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)
{
struct ndpi_packet_struct *packet = &flow->packet;
// const u_int8_t *packet_payload = packet->payload;
u_int32_t payload_len = packet->payload_packet_len;
if(flow->host_server_name[0] != '\0')
return;
if(is_skype_flow(ndpi_struct, flow)) {
ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_SKYPE, NDPI_PROTOCOL_UNKNOWN);
return;
}
// UDP check
if(packet->udp != NULL) {
flow->l4.udp.skype_packet_id++;
if(flow->l4.udp.skype_packet_id < 5) {
u_int16_t dport = ntohs(packet->udp->dest);
/* skype-to-skype */
if(dport != 1119) /* It can be confused with battle.net */ {
if(((payload_len == 3) && ((packet->payload[2] & 0x0F)== 0x0d)) ||
((payload_len >= 16)
&& (packet->payload[0] != 0x30) /* Avoid invalid SNMP detection */
&& (packet->payload[2] == 0x02))) {
NDPI_LOG(NDPI_PROTOCOL_SKYPE, ndpi_struct, NDPI_LOG_DEBUG, "Found skype.\n");
ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_SKYPE, NDPI_PROTOCOL_UNKNOWN);
}
}
return;
}
NDPI_ADD_PROTOCOL_TO_BITMASK(flow->excluded_protocol_bitmask, NDPI_PROTOCOL_SKYPE);
return;
// TCP check
} else if(packet->tcp != NULL) {
flow->l4.tcp.skype_packet_id++;
if(flow->l4.tcp.skype_packet_id < 3) {
; /* Too early */
} else if((flow->l4.tcp.skype_packet_id == 3)
/* We have seen the 3-way handshake */
&& flow->l4.tcp.seen_syn
&& flow->l4.tcp.seen_syn_ack
&& flow->l4.tcp.seen_ack) {
if((payload_len == 8) || (payload_len == 3)) {
//printf("[SKYPE] %u/%u\n", ntohs(packet->tcp->source), ntohs(packet->tcp->dest));
NDPI_LOG(NDPI_PROTOCOL_SKYPE, ndpi_struct, NDPI_LOG_DEBUG, "Found skype.\n");
ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_SKYPE, NDPI_PROTOCOL_UNKNOWN);
}
/* printf("[SKYPE] [id: %u][len: %d]\n", flow->l4.tcp.skype_packet_id, payload_len); */
} else
NDPI_ADD_PROTOCOL_TO_BITMASK(flow->excluded_protocol_bitmask, NDPI_PROTOCOL_SKYPE);
return;
}
}
void ndpi_search_skype(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)
{
struct ndpi_packet_struct *packet = &flow->packet;
NDPI_LOG(NDPI_PROTOCOL_SKYPE, ndpi_struct, NDPI_LOG_DEBUG, "skype detection...\n");
/* skip marked packets */
if(packet->detected_protocol_stack[0] != NDPI_PROTOCOL_SKYPE)
ndpi_check_skype(ndpi_struct, flow);
}
void init_skype_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id, NDPI_PROTOCOL_BITMASK *detection_bitmask)
{
ndpi_set_bitmask_protocol_detection("Skype", ndpi_struct, detection_bitmask, *id,
NDPI_PROTOCOL_SKYPE,
ndpi_search_skype,
NDPI_SELECTION_BITMASK_PROTOCOL_TCP_OR_UDP_WITH_PAYLOAD,
SAVE_DETECTION_BITMASK_AS_UNKNOWN,
ADD_TO_DETECTION_BITMASK);
*id += 1;
}
#endif
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