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
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
|
/* Copyright (C) 2012-2021 Open Information Security Foundation
*
* You can copy, redistribute or modify this Program under the terms of
* the GNU General Public License version 2 as published by the Free
* Software Foundation.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* version 2 along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*/
/**
* \ingroup decode
*
* @{
*/
/**
* \file
*
* \author Eric Leblond <eric@regit.org>
*
* Decode Teredo Tunneling protocol.
*
* This implementation is based upon RFC 4380: http://www.ietf.org/rfc/rfc4380.txt
*/
#include "suricata-common.h"
#include "decode.h"
#include "decode-ipv6.h"
#include "decode-teredo.h"
#include "util-validate.h"
#include "util-debug.h"
#include "conf.h"
#include "detect.h"
#include "detect-engine-port.h"
#define TEREDO_ORIG_INDICATION_LENGTH 8
#define TEREDO_MAX_PORTS 4
#define TEREDO_UNSET_PORT -1
static bool g_teredo_enabled = true;
static bool g_teredo_ports_any = true;
static int g_teredo_ports_cnt = 0;
static int g_teredo_ports[TEREDO_MAX_PORTS] = { TEREDO_UNSET_PORT, TEREDO_UNSET_PORT,
TEREDO_UNSET_PORT, TEREDO_UNSET_PORT };
bool DecodeTeredoEnabledForPort(const uint16_t sp, const uint16_t dp)
{
SCLogDebug("ports %u->%u ports %d %d %d %d", sp, dp, g_teredo_ports[0], g_teredo_ports[1],
g_teredo_ports[2], g_teredo_ports[3]);
if (g_teredo_enabled) {
/* no port config means we are enabled for all ports */
if (g_teredo_ports_any) {
return true;
}
for (int i = 0; i < g_teredo_ports_cnt; i++) {
if (g_teredo_ports[i] == TEREDO_UNSET_PORT)
return false;
const int port = g_teredo_ports[i];
if (port == (const int)sp || port == (const int)dp)
return true;
}
}
return false;
}
static void DecodeTeredoConfigPorts(const char *pstr)
{
SCLogDebug("parsing \'%s\'", pstr);
if (strcmp(pstr, "any") == 0) {
g_teredo_ports_any = true;
return;
}
DetectPort *head = NULL;
DetectPortParse(NULL, &head, pstr);
g_teredo_ports_any = false;
g_teredo_ports_cnt = 0;
for (DetectPort *p = head; p != NULL; p = p->next) {
if (g_teredo_ports_cnt >= TEREDO_MAX_PORTS) {
SCLogWarning("only %d Teredo ports can be defined", TEREDO_MAX_PORTS);
break;
}
g_teredo_ports[g_teredo_ports_cnt++] = (int)p->port;
}
DetectPortCleanupList(NULL, head);
}
void DecodeTeredoConfig(void)
{
int enabled = 0;
if (ConfGetBool("decoder.teredo.enabled", &enabled) == 1) {
if (enabled) {
g_teredo_enabled = true;
} else {
g_teredo_enabled = false;
}
}
if (g_teredo_enabled) {
ConfNode *node = ConfGetNode("decoder.teredo.ports");
if (node && node->val) {
DecodeTeredoConfigPorts(node->val);
}
}
}
/**
* \brief Function to decode Teredo packets
*
* \retval TM_ECODE_FAILED if packet is not a Teredo packet, TM_ECODE_OK if it is
*/
int DecodeTeredo(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
const uint8_t *pkt, uint16_t len)
{
DEBUG_VALIDATE_BUG_ON(pkt == NULL);
if (!g_teredo_enabled)
return TM_ECODE_FAILED;
const uint8_t *start = pkt;
/* Is this packet to short to contain an IPv6 packet ? */
if (len < IPV6_HEADER_LEN)
return TM_ECODE_FAILED;
/* Teredo encapsulate IPv6 in UDP and can add some custom message
* part before the IPv6 packet. In our case, we just want to get
* over an ORIGIN indication. So we just make one offset if needed. */
if (start[0] == 0x0) {
/* origin indication: compatible with tunnel */
if (start[1] == 0x0) {
/* offset is not coherent with len and presence of an IPv6 header */
if (len < TEREDO_ORIG_INDICATION_LENGTH + IPV6_HEADER_LEN)
return TM_ECODE_FAILED;
start += TEREDO_ORIG_INDICATION_LENGTH;
/* either authentication negotiation not real tunnel or invalid second byte */
} else {
return TM_ECODE_FAILED;
}
}
/* There is no specific field that we can check to prove that the packet
* is a Teredo packet. We've zapped here all the possible Teredo header
* and we should have an IPv6 packet at the start pointer.
* We then can only do a few checks before sending the encapsulated packets
* to decoding:
* - The packet has a protocol version which is IPv6.
* - The IPv6 length of the packet matches what remains in buffer.
* - HLIM is 0. This would technically be valid, but still weird.
* - NH 0 (HOP) and not enough data.
*
* If all these conditions are met, the tunnel decoder will be called.
* If the packet gets an invalid event set, it will still be rejected.
*/
if (IP_GET_RAW_VER(start) == 6) {
IPV6Hdr *thdr = (IPV6Hdr *)start;
/* ignore hoplimit 0 packets, most likely an artifact of bad detection */
if (IPV6_GET_RAW_HLIM(thdr) == 0)
return TM_ECODE_FAILED;
/* if nh is 0 (HOP) with little data we have a bogus packet */
if (IPV6_GET_RAW_NH(thdr) == 0 && IPV6_GET_RAW_PLEN(thdr) < 8)
return TM_ECODE_FAILED;
if (len == IPV6_HEADER_LEN +
IPV6_GET_RAW_PLEN(thdr) + (start - pkt)) {
int blen = len - (start - pkt);
/* spawn off tunnel packet */
Packet *tp = PacketTunnelPktSetup(tv, dtv, p, start, blen,
DECODE_TUNNEL_IPV6_TEREDO);
if (tp != NULL) {
PKT_SET_SRC(tp, PKT_SRC_DECODER_TEREDO);
/* add the tp to the packet queue. */
PacketEnqueueNoLock(&tv->decode_pq,tp);
StatsIncr(tv, dtv->counter_teredo);
return TM_ECODE_OK;
}
}
return TM_ECODE_FAILED;
}
return TM_ECODE_FAILED;
}
/**
* @}
*/
|
