Moving charon to libcharon.
[strongswan.git] / src / libcharon / network / receiver.c
1 /*
2 * Copyright (C) 2008 Tobias Brunner
3 * Copyright (C) 2005-2006 Martin Willi
4 * Copyright (C) 2005 Jan Hutter
5 * Hochschule fuer Technik Rapperswil
6 *
7 * This program is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License as published by the
9 * Free Software Foundation; either version 2 of the License, or (at your
10 * option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
11 *
12 * This program is distributed in the hope that it will be useful, but
13 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * for more details.
16 */
17
18 #include <stdlib.h>
19 #include <unistd.h>
20
21 #include "receiver.h"
22
23 #include <daemon.h>
24 #include <network/socket.h>
25 #include <network/packet.h>
26 #include <processing/jobs/job.h>
27 #include <processing/jobs/process_message_job.h>
28 #include <processing/jobs/callback_job.h>
29 #include <crypto/hashers/hasher.h>
30
31 /** lifetime of a cookie, in seconds */
32 #define COOKIE_LIFETIME 10
33 /** how many times to reuse the secret */
34 #define COOKIE_REUSE 10000
35 /** default value for private_receiver_t.cookie_threshold */
36 #define COOKIE_THRESHOLD_DEFAULT 10
37 /** default value for private_receiver_t.block_threshold */
38 #define BLOCK_THRESHOLD_DEFAULT 5
39 /** length of the secret to use for cookie calculation */
40 #define SECRET_LENGTH 16
41
42 typedef struct private_receiver_t private_receiver_t;
43
44 /**
45 * Private data of a receiver_t object.
46 */
47 struct private_receiver_t {
48 /**
49 * Public part of a receiver_t object.
50 */
51 receiver_t public;
52
53 /**
54 * Threads job receiving packets
55 */
56 callback_job_t *job;
57
58 /**
59 * current secret to use for cookie calculation
60 */
61 char secret[SECRET_LENGTH];
62
63 /**
64 * previous secret used to verify older cookies
65 */
66 char secret_old[SECRET_LENGTH];
67
68 /**
69 * how many times we have used "secret" so far
70 */
71 u_int32_t secret_used;
72
73 /**
74 * time we did the cookie switch
75 */
76 u_int32_t secret_switch;
77
78 /**
79 * time offset to use, hides our system time
80 */
81 u_int32_t secret_offset;
82
83 /**
84 * the RNG to use for secret generation
85 */
86 rng_t *rng;
87
88 /**
89 * hasher to use for cookie calculation
90 */
91 hasher_t *hasher;
92
93 /**
94 * require cookies after this many half open IKE_SAs
95 */
96 u_int32_t cookie_threshold;
97
98 /**
99 * how many half open IKE_SAs per peer before blocking
100 */
101 u_int32_t block_threshold;
102
103 /**
104 * Delay for receiving incoming packets, to simulate larger RTT
105 */
106 u_int receive_delay;
107 };
108
109 /**
110 * send a notify back to the sender
111 */
112 static void send_notify(message_t *request, notify_type_t type, chunk_t data)
113 {
114 if (request->get_request(request) &&
115 request->get_exchange_type(request) == IKE_SA_INIT)
116 {
117 message_t *response;
118 host_t *src, *dst;
119 packet_t *packet;
120 ike_sa_id_t *ike_sa_id;
121
122 response = message_create();
123 dst = request->get_source(request);
124 src = request->get_destination(request);
125 response->set_source(response, src->clone(src));
126 response->set_destination(response, dst->clone(dst));
127 response->set_exchange_type(response, request->get_exchange_type(request));
128 response->set_request(response, FALSE);
129 response->set_message_id(response, 0);
130 ike_sa_id = request->get_ike_sa_id(request);
131 ike_sa_id->switch_initiator(ike_sa_id);
132 response->set_ike_sa_id(response, ike_sa_id);
133 response->add_notify(response, FALSE, type, data);
134 if (response->generate(response, NULL, NULL, &packet) == SUCCESS)
135 {
136 charon->sender->send(charon->sender, packet);
137 response->destroy(response);
138 }
139 }
140 }
141
142 /**
143 * build a cookie
144 */
145 static chunk_t cookie_build(private_receiver_t *this, message_t *message,
146 u_int32_t t, chunk_t secret)
147 {
148 u_int64_t spi = message->get_initiator_spi(message);
149 host_t *ip = message->get_source(message);
150 chunk_t input, hash;
151
152 /* COOKIE = t | sha1( IPi | SPIi | t | secret ) */
153 input = chunk_cata("cccc", ip->get_address(ip), chunk_from_thing(spi),
154 chunk_from_thing(t), secret);
155 hash = chunk_alloca(this->hasher->get_hash_size(this->hasher));
156 this->hasher->get_hash(this->hasher, input, hash.ptr);
157 return chunk_cat("cc", chunk_from_thing(t), hash);
158 }
159
160 /**
161 * verify a received cookie
162 */
163 static bool cookie_verify(private_receiver_t *this, message_t *message,
164 chunk_t cookie)
165 {
166 u_int32_t t, now;
167 chunk_t reference;
168 chunk_t secret;
169
170 now = time_monotonic(NULL);
171 t = *(u_int32_t*)cookie.ptr;
172
173 if (cookie.len != sizeof(u_int32_t) +
174 this->hasher->get_hash_size(this->hasher) ||
175 t < now - this->secret_offset - COOKIE_LIFETIME)
176 {
177 DBG2(DBG_NET, "received cookie lifetime expired, rejecting");
178 return FALSE;
179 }
180
181 /* check if cookie is derived from old_secret */
182 if (t + this->secret_offset > this->secret_switch)
183 {
184 secret = chunk_from_thing(this->secret);
185 }
186 else
187 {
188 secret = chunk_from_thing(this->secret_old);
189 }
190
191 /* compare own calculation against received */
192 reference = cookie_build(this, message, t, secret);
193 if (chunk_equals(reference, cookie))
194 {
195 chunk_free(&reference);
196 return TRUE;
197 }
198 chunk_free(&reference);
199 return FALSE;
200 }
201
202 /**
203 * check if cookies are required, and if so, a valid cookie is included
204 */
205 static bool cookie_required(private_receiver_t *this, message_t *message)
206 {
207 bool failed = FALSE;
208
209 if (charon->ike_sa_manager->get_half_open_count(charon->ike_sa_manager,
210 NULL) >= this->cookie_threshold)
211 {
212 /* check for a cookie. We don't use our parser here and do it
213 * quick and dirty for performance reasons.
214 * we assume the cookie is the first payload (which is a MUST), and
215 * the cookie's SPI length is zero. */
216 packet_t *packet = message->get_packet(message);
217 chunk_t data = packet->get_data(packet);
218 if (data.len <
219 IKE_HEADER_LENGTH + NOTIFY_PAYLOAD_HEADER_LENGTH +
220 sizeof(u_int32_t) + this->hasher->get_hash_size(this->hasher) ||
221 *(data.ptr + 16) != NOTIFY ||
222 *(u_int16_t*)(data.ptr + IKE_HEADER_LENGTH + 6) != htons(COOKIE))
223 {
224 /* no cookie found */
225 failed = TRUE;
226 }
227 else
228 {
229 data.ptr += IKE_HEADER_LENGTH + NOTIFY_PAYLOAD_HEADER_LENGTH;
230 data.len = sizeof(u_int32_t) + this->hasher->get_hash_size(this->hasher);
231 if (!cookie_verify(this, message, data))
232 {
233 DBG2(DBG_NET, "found cookie, but content invalid");
234 failed = TRUE;
235 }
236 }
237 packet->destroy(packet);
238 }
239 return failed;
240 }
241
242 /**
243 * check if peer has to many half open IKE_SAs
244 */
245 static bool peer_to_aggressive(private_receiver_t *this, message_t *message)
246 {
247 if (charon->ike_sa_manager->get_half_open_count(charon->ike_sa_manager,
248 message->get_source(message)) >= this->block_threshold)
249 {
250 return TRUE;
251 }
252 return FALSE;
253 }
254
255 /**
256 * Job callback to receive packets
257 */
258 static job_requeue_t receive_packets(private_receiver_t *this)
259 {
260 packet_t *packet;
261 message_t *message;
262 job_t *job;
263
264 /* read in a packet */
265 if (charon->socket->receive(charon->socket, &packet) != SUCCESS)
266 {
267 DBG2(DBG_NET, "receiving from socket failed!");
268 return JOB_REQUEUE_FAIR;
269 }
270
271 /* parse message header */
272 message = message_create_from_packet(packet);
273 if (message->parse_header(message) != SUCCESS)
274 {
275 DBG1(DBG_NET, "received invalid IKE header from %H - ignored",
276 packet->get_source(packet));
277 message->destroy(message);
278 return JOB_REQUEUE_DIRECT;
279 }
280
281 /* check IKE major version */
282 if (message->get_major_version(message) != IKE_MAJOR_VERSION)
283 {
284 DBG1(DBG_NET, "received unsupported IKE version %d.%d from %H, "
285 "sending INVALID_MAJOR_VERSION", message->get_major_version(message),
286 message->get_minor_version(message), packet->get_source(packet));
287 send_notify(message, INVALID_MAJOR_VERSION, chunk_empty);
288 message->destroy(message);
289 return JOB_REQUEUE_DIRECT;
290 }
291
292 if (message->get_request(message) &&
293 message->get_exchange_type(message) == IKE_SA_INIT)
294 {
295 /* check for cookies */
296 if (this->cookie_threshold && cookie_required(this, message))
297 {
298 u_int32_t now = time_monotonic(NULL);
299 chunk_t cookie = cookie_build(this, message, now - this->secret_offset,
300 chunk_from_thing(this->secret));
301
302 DBG2(DBG_NET, "received packet from: %#H to %#H",
303 message->get_source(message),
304 message->get_destination(message));
305 DBG2(DBG_NET, "sending COOKIE notify to %H",
306 message->get_source(message));
307 send_notify(message, COOKIE, cookie);
308 chunk_free(&cookie);
309 if (++this->secret_used > COOKIE_REUSE)
310 {
311 /* create new cookie */
312 DBG1(DBG_NET, "generating new cookie secret after %d uses",
313 this->secret_used);
314 memcpy(this->secret_old, this->secret, SECRET_LENGTH);
315 this->rng->get_bytes(this->rng, SECRET_LENGTH, this->secret);
316 this->secret_switch = now;
317 this->secret_used = 0;
318 }
319 message->destroy(message);
320 return JOB_REQUEUE_DIRECT;
321 }
322
323 /* check if peer has not too many IKE_SAs half open */
324 if (this->block_threshold && peer_to_aggressive(this, message))
325 {
326 DBG1(DBG_NET, "ignoring IKE_SA setup from %H, "
327 "peer too aggressive", message->get_source(message));
328 message->destroy(message);
329 return JOB_REQUEUE_DIRECT;
330 }
331 }
332 job = (job_t*)process_message_job_create(message);
333 if (this->receive_delay)
334 {
335 charon->scheduler->schedule_job_ms(charon->scheduler,
336 job, this->receive_delay);
337 }
338 else
339 {
340 charon->processor->queue_job(charon->processor, job);
341 }
342 return JOB_REQUEUE_DIRECT;
343 }
344
345 METHOD(receiver_t, destroy, void,
346 private_receiver_t *this)
347 {
348 this->job->cancel(this->job);
349 this->rng->destroy(this->rng);
350 this->hasher->destroy(this->hasher);
351 free(this);
352 }
353
354 /*
355 * Described in header.
356 */
357 receiver_t *receiver_create()
358 {
359 private_receiver_t *this;
360 u_int32_t now = time_monotonic(NULL);
361
362 INIT(this,
363 .public.destroy = _destroy,
364 .secret_switch = now,
365 .secret_offset = random() % now,
366 );
367
368 if (lib->settings->get_bool(lib->settings, "charon.dos_protection", TRUE))
369 {
370 this->cookie_threshold = lib->settings->get_int(lib->settings,
371 "charon.cookie_threshold", COOKIE_THRESHOLD_DEFAULT);
372 this->block_threshold = lib->settings->get_int(lib->settings,
373 "charon.block_threshold", BLOCK_THRESHOLD_DEFAULT);
374 }
375 this->receive_delay = lib->settings->get_int(lib->settings,
376 "charon.receive_delay", 0);
377
378 this->hasher = lib->crypto->create_hasher(lib->crypto, HASH_PREFERRED);
379 if (this->hasher == NULL)
380 {
381 DBG1(DBG_NET, "creating cookie hasher failed, no hashers supported");
382 free(this);
383 return NULL;
384 }
385 this->rng = lib->crypto->create_rng(lib->crypto, RNG_STRONG);
386 if (this->rng == NULL)
387 {
388 DBG1(DBG_NET, "creating cookie RNG failed, no RNG supported");
389 this->hasher->destroy(this->hasher);
390 free(this);
391 return NULL;
392 }
393 this->rng->get_bytes(this->rng, SECRET_LENGTH, this->secret);
394 memcpy(this->secret_old, this->secret, SECRET_LENGTH);
395
396 this->job = callback_job_create((callback_job_cb_t)receive_packets,
397 this, NULL, NULL);
398 charon->processor->queue_job(charon->processor, (job_t*)this->job);
399
400 return &this->public;
401 }
402