1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
|
/*
* mdns.c
*
* Copyright (C) 2016-20 - 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_MDNS
#include "ndpi_api.h"
#define NDPI_MAX_MDNS_REQUESTS 128
PACK_ON
struct mdns_header {
u_int16_t transaction_id, flags, questions, answers, authority_rr, additional_rr;
} PACK_OFF;
/**
MDNS header is similar to dns header
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ID = 0x0000 |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| FLAGS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QDCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ANCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| NSCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ARCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
*/
static void ndpi_int_mdns_add_connection(struct ndpi_detection_module_struct
*ndpi_struct, struct ndpi_flow_struct *flow) {
ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_MDNS, NDPI_PROTOCOL_UNKNOWN);
}
static int ndpi_int_check_mdns_payload(struct ndpi_detection_module_struct
*ndpi_struct, struct ndpi_flow_struct *flow) {
struct ndpi_packet_struct *packet = &flow->packet;
struct mdns_header *h = (struct mdns_header*)packet->payload;
u_int16_t questions = ntohs(h->questions), answers = ntohs(h->answers);
if((questions > NDPI_MAX_MDNS_REQUESTS)
|| (answers > NDPI_MAX_MDNS_REQUESTS))
return(0);
if((packet->payload[2] & 0x80) == 0) {
NDPI_LOG_INFO(ndpi_struct, "found MDNS with question query\n");
return 1;
} else if((packet->payload[2] & 0x80) != 0) {
char answer[256];
int i, j, len;
for(i=13, j=0; (i < packet->payload_packet_len) && (i < (sizeof(answer)-1)) && (packet->payload[i] != 0); i++)
answer[j++] = (packet->payload[i] < 13) ? '.' : packet->payload[i];
answer[j] = '\0';
/* printf("==> [%d] %s\n", j, answer); */
len = ndpi_min(sizeof(flow->protos.mdns.answer)-1, j);
strncpy(flow->protos.mdns.answer, (const char *)answer, len);
flow->protos.mdns.answer[len] = '\0';
NDPI_LOG_INFO(ndpi_struct, "found MDNS with answer query\n");
return 1;
}
return 0;
}
void ndpi_search_mdns(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)
{
struct ndpi_packet_struct *packet = &flow->packet;
NDPI_LOG_DBG(ndpi_struct, "search MDNS\n");
/**
information from http://www.it-administrator.de/lexikon/multicast-dns.html
*/
/* check if UDP packet */
if(packet->udp != NULL) {
/* read destination port */
u_int16_t sport = ntohs(packet->udp->source);
u_int16_t dport = ntohs(packet->udp->dest);
/* check standard MDNS ON port 5353 */
if(((dport == 5353) || (sport == 5353))
&& (packet->payload_packet_len >= 12)) {
if(packet->iph != NULL) {
if(ndpi_int_check_mdns_payload(ndpi_struct, flow) == 1) {
ndpi_int_mdns_add_connection(ndpi_struct, flow);
return;
}
}
#ifdef NDPI_DETECTION_SUPPORT_IPV6
if(packet->iphv6 != NULL) {
u_int32_t daddr_0 = packet->iphv6->ip6_dst.u6_addr.u6_addr32[0];
if(daddr_0 == htonl(0xff020000) /* && daddr[1] == 0 && daddr[2] == 0 && daddr[3] == htonl(0xfb) */) {
NDPI_LOG_INFO(ndpi_struct, "found MDNS with destination address ff02::fb\n");
if(ndpi_int_check_mdns_payload(ndpi_struct, flow) == 1) {
ndpi_int_mdns_add_connection(ndpi_struct, flow);
return;
}
}
}
#endif
}
}
NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
}
void init_mdns_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id, NDPI_PROTOCOL_BITMASK *detection_bitmask)
{
ndpi_set_bitmask_protocol_detection("MDNS", ndpi_struct, detection_bitmask, *id,
NDPI_PROTOCOL_MDNS,
ndpi_search_mdns,
NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_UDP_WITH_PAYLOAD,
SAVE_DETECTION_BITMASK_AS_UNKNOWN,
ADD_TO_DETECTION_BITMASK);
*id += 1;
}
|