diff options
Diffstat (limited to 'src/service/nat/gnunet-service-nat_stun.c')
-rw-r--r-- | src/service/nat/gnunet-service-nat_stun.c | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/src/service/nat/gnunet-service-nat_stun.c b/src/service/nat/gnunet-service-nat_stun.c new file mode 100644 index 000000000..203728ebf --- /dev/null +++ b/src/service/nat/gnunet-service-nat_stun.c | |||
@@ -0,0 +1,215 @@ | |||
1 | /* | ||
2 | This file is part of GNUnet. | ||
3 | Copyright (C) 2009, 2015, 2016 GNUnet e.V. | ||
4 | |||
5 | GNUnet is free software: you can redistribute it and/or modify it | ||
6 | under the terms of the GNU Affero General Public License as published | ||
7 | by the Free Software Foundation, either version 3 of the License, | ||
8 | or (at your option) any later version. | ||
9 | |||
10 | GNUnet is distributed in the hope that it will be useful, but | ||
11 | WITHOUT ANY WARRANTY; without even the implied warranty of | ||
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
13 | Affero General Public License for more details. | ||
14 | |||
15 | You should have received a copy of the GNU Affero General Public License | ||
16 | along with this program. If not, see <http://www.gnu.org/licenses/>. | ||
17 | |||
18 | SPDX-License-Identifier: AGPL3.0-or-later | ||
19 | */ | ||
20 | /** | ||
21 | * This code provides some support for doing STUN transactions. We | ||
22 | * receive the simplest possible packet as the STUN server and try | ||
23 | * to respond properly. | ||
24 | * | ||
25 | * All STUN packets start with a simple header made of a type, | ||
26 | * length (excluding the header) and a 16-byte random transaction id. | ||
27 | * Following the header we may have zero or more attributes, each | ||
28 | * structured as a type, length and a value (whose format depends | ||
29 | * on the type, but often contains addresses). | ||
30 | * Of course all fields are in network format. | ||
31 | * | ||
32 | * This code was based on ministun.c. | ||
33 | * | ||
34 | * @file nat/gnunet-service-nat_stun.c | ||
35 | * @brief Functions for STUN functionality | ||
36 | * @author Bruno Souza Cabral | ||
37 | */ | ||
38 | |||
39 | #include "platform.h" | ||
40 | #include "gnunet_util_lib.h" | ||
41 | #include "nat_stun.h" | ||
42 | |||
43 | #define LOG(kind, ...) GNUNET_log_from (kind, "stun", __VA_ARGS__) | ||
44 | |||
45 | |||
46 | /** | ||
47 | * Context for #stun_get_mapped(). | ||
48 | * Used to store state across processing attributes. | ||
49 | */ | ||
50 | struct StunState | ||
51 | { | ||
52 | uint16_t attr; | ||
53 | }; | ||
54 | |||
55 | |||
56 | /** | ||
57 | * Extract the STUN_MAPPED_ADDRESS from the stun response. | ||
58 | * This is used as a callback for stun_handle_response | ||
59 | * when called from stun_request. | ||
60 | * | ||
61 | * @param[out] st pointer where we will set the type | ||
62 | * @param attr received stun attribute | ||
63 | * @param magic Magic cookie | ||
64 | * @param[out] arg pointer to a sockaddr_in where we will set the reported IP and port | ||
65 | * @return #GNUNET_OK if @a arg was initialized | ||
66 | */ | ||
67 | static int | ||
68 | stun_get_mapped (struct StunState *st, | ||
69 | const struct stun_attr *attr, | ||
70 | uint32_t magic, | ||
71 | struct sockaddr_in *arg) | ||
72 | { | ||
73 | const struct stun_addr *returned_addr; | ||
74 | struct sockaddr_in *sa = (struct sockaddr_in *) arg; | ||
75 | uint16_t type = ntohs (attr->attr); | ||
76 | |||
77 | switch (type) | ||
78 | { | ||
79 | case STUN_MAPPED_ADDRESS: | ||
80 | if ((st->attr == STUN_XOR_MAPPED_ADDRESS) || | ||
81 | (st->attr == STUN_MS_XOR_MAPPED_ADDRESS)) | ||
82 | return GNUNET_NO; | ||
83 | magic = 0; | ||
84 | break; | ||
85 | |||
86 | case STUN_MS_XOR_MAPPED_ADDRESS: | ||
87 | if (st->attr == STUN_XOR_MAPPED_ADDRESS) | ||
88 | return GNUNET_NO; | ||
89 | break; | ||
90 | |||
91 | case STUN_XOR_MAPPED_ADDRESS: | ||
92 | break; | ||
93 | |||
94 | default: | ||
95 | return GNUNET_NO; | ||
96 | } | ||
97 | |||
98 | if (ntohs (attr->len) < sizeof(struct stun_addr)) | ||
99 | return GNUNET_NO; | ||
100 | returned_addr = (const struct stun_addr *) (attr + 1); | ||
101 | if (AF_INET != returned_addr->family) | ||
102 | return GNUNET_NO; | ||
103 | st->attr = type; | ||
104 | sa->sin_family = AF_INET; | ||
105 | sa->sin_port = returned_addr->port ^ htons (ntohl (magic) >> 16); | ||
106 | sa->sin_addr.s_addr = returned_addr->addr ^ magic; | ||
107 | return GNUNET_OK; | ||
108 | } | ||
109 | |||
110 | |||
111 | /** | ||
112 | * Handle an incoming STUN response. Do some basic sanity checks on | ||
113 | * packet size and content, try to extract information. | ||
114 | * At the moment this only processes BIND requests, | ||
115 | * and returns the externally visible address of the original | ||
116 | * request. | ||
117 | * | ||
118 | * @param data the packet | ||
119 | * @param len the length of the packet in @a data | ||
120 | * @param[out] arg sockaddr_in where we will set our discovered address | ||
121 | * @return #GNUNET_OK on success, | ||
122 | * #GNUNET_NO if the packet is invalid (not a stun packet) | ||
123 | */ | ||
124 | int | ||
125 | GNUNET_NAT_stun_handle_packet_ (const void *data, | ||
126 | size_t len, | ||
127 | struct sockaddr_in *arg) | ||
128 | { | ||
129 | const struct stun_header *hdr; | ||
130 | const struct stun_attr *attr; | ||
131 | struct StunState st; | ||
132 | uint32_t advertised_message_size; | ||
133 | uint32_t message_magic_cookie; | ||
134 | int ret = GNUNET_SYSERR; | ||
135 | |||
136 | /* On entry, 'len' is the length of the UDP payload. After the | ||
137 | * initial checks it becomes the size of unprocessed options, | ||
138 | * while 'data' is advanced accordingly. | ||
139 | */ | ||
140 | if (len < sizeof(struct stun_header)) | ||
141 | { | ||
142 | LOG (GNUNET_ERROR_TYPE_DEBUG, | ||
143 | "Packet too short to be a STUN packet\n"); | ||
144 | return GNUNET_NO; | ||
145 | } | ||
146 | hdr = data; | ||
147 | /* Skip header as it is already in hdr */ | ||
148 | len -= sizeof(struct stun_header); | ||
149 | data += sizeof(struct stun_header); | ||
150 | |||
151 | /* len as advertised in the message */ | ||
152 | advertised_message_size = ntohs (hdr->msglen); | ||
153 | message_magic_cookie = ntohl (hdr->magic); | ||
154 | /* Compare if the cookie match */ | ||
155 | if (STUN_MAGIC_COOKIE != message_magic_cookie) | ||
156 | { | ||
157 | LOG (GNUNET_ERROR_TYPE_DEBUG, | ||
158 | "Invalid magic cookie for STUN packet\n"); | ||
159 | return GNUNET_NO; | ||
160 | } | ||
161 | |||
162 | LOG (GNUNET_ERROR_TYPE_INFO, | ||
163 | "STUN Packet, msg %s (%04x), length: %d\n", | ||
164 | stun_msg2str (ntohs (hdr->msgtype)), | ||
165 | ntohs (hdr->msgtype), | ||
166 | advertised_message_size); | ||
167 | if (advertised_message_size > len) | ||
168 | { | ||
169 | LOG (GNUNET_ERROR_TYPE_INFO, | ||
170 | "Scrambled STUN packet length (got %d, expecting %d)\n", | ||
171 | advertised_message_size, | ||
172 | (int) len); | ||
173 | return GNUNET_NO; | ||
174 | } | ||
175 | len = advertised_message_size; | ||
176 | memset (&st, 0, sizeof(st)); | ||
177 | |||
178 | while (len > 0) | ||
179 | { | ||
180 | if (len < sizeof(struct stun_attr)) | ||
181 | { | ||
182 | LOG (GNUNET_ERROR_TYPE_INFO, | ||
183 | "Attribute too short (got %d, expecting %d)\n", | ||
184 | (int) len, | ||
185 | (int) sizeof(struct stun_attr)); | ||
186 | break; | ||
187 | } | ||
188 | attr = (const struct stun_attr *) data; | ||
189 | |||
190 | /* compute total attribute length */ | ||
191 | advertised_message_size = ntohs (attr->len) + sizeof(struct stun_attr); | ||
192 | |||
193 | /* Check if we still have space in our buffer */ | ||
194 | if (advertised_message_size > len) | ||
195 | { | ||
196 | LOG (GNUNET_ERROR_TYPE_INFO, | ||
197 | "Inconsistent attribute (length %d exceeds remaining msg len %d)\n", | ||
198 | advertised_message_size, | ||
199 | (int) len); | ||
200 | break; | ||
201 | } | ||
202 | if (GNUNET_OK == | ||
203 | stun_get_mapped (&st, | ||
204 | attr, | ||
205 | hdr->magic, | ||
206 | arg)) | ||
207 | ret = GNUNET_OK; | ||
208 | data += advertised_message_size; | ||
209 | len -= advertised_message_size; | ||
210 | } | ||
211 | return ret; | ||
212 | } | ||
213 | |||
214 | |||
215 | /* end of gnunet-service-nat_stun.c */ | ||