ec30fca619bbd2ca7f7e16d48085a14f449cd5f1
[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 * Drop IKE_SA_INIT requests if processor job load exceeds this limit
105 */
106 u_int init_limit_job_load;
107
108 /**
109 * Drop IKE_SA_INIT requests if half open IKE_SA count exceeds this limit
110 */
111 u_int init_limit_half_open;
112
113 /**
114 * Delay for receiving incoming packets, to simulate larger RTT
115 */
116 int receive_delay;
117
118 /**
119 * Specific message type to delay, 0 for any
120 */
121 int receive_delay_type;
122
123 /**
124 * Delay request messages?
125 */
126 bool receive_delay_request;
127
128 /**
129 * Delay response messages?
130 */
131 bool receive_delay_response;
132 };
133
134 /**
135 * send a notify back to the sender
136 */
137 static void send_notify(message_t *request, notify_type_t type, chunk_t data)
138 {
139 if (request->get_request(request) &&
140 request->get_exchange_type(request) == IKE_SA_INIT)
141 {
142 message_t *response;
143 host_t *src, *dst;
144 packet_t *packet;
145 ike_sa_id_t *ike_sa_id;
146
147 response = message_create();
148 dst = request->get_source(request);
149 src = request->get_destination(request);
150 response->set_source(response, src->clone(src));
151 response->set_destination(response, dst->clone(dst));
152 response->set_exchange_type(response, request->get_exchange_type(request));
153 response->set_request(response, FALSE);
154 response->set_message_id(response, 0);
155 ike_sa_id = request->get_ike_sa_id(request);
156 ike_sa_id->switch_initiator(ike_sa_id);
157 response->set_ike_sa_id(response, ike_sa_id);
158 response->add_notify(response, FALSE, type, data);
159 if (response->generate(response, NULL, &packet) == SUCCESS)
160 {
161 charon->sender->send(charon->sender, packet);
162 response->destroy(response);
163 }
164 }
165 }
166
167 /**
168 * build a cookie
169 */
170 static chunk_t cookie_build(private_receiver_t *this, message_t *message,
171 u_int32_t t, chunk_t secret)
172 {
173 u_int64_t spi = message->get_initiator_spi(message);
174 host_t *ip = message->get_source(message);
175 chunk_t input, hash;
176
177 /* COOKIE = t | sha1( IPi | SPIi | t | secret ) */
178 input = chunk_cata("cccc", ip->get_address(ip), chunk_from_thing(spi),
179 chunk_from_thing(t), secret);
180 hash = chunk_alloca(this->hasher->get_hash_size(this->hasher));
181 this->hasher->get_hash(this->hasher, input, hash.ptr);
182 return chunk_cat("cc", chunk_from_thing(t), hash);
183 }
184
185 /**
186 * verify a received cookie
187 */
188 static bool cookie_verify(private_receiver_t *this, message_t *message,
189 chunk_t cookie)
190 {
191 u_int32_t t, now;
192 chunk_t reference;
193 chunk_t secret;
194
195 now = time_monotonic(NULL);
196 t = *(u_int32_t*)cookie.ptr;
197
198 if (cookie.len != sizeof(u_int32_t) +
199 this->hasher->get_hash_size(this->hasher) ||
200 t < now - this->secret_offset - COOKIE_LIFETIME)
201 {
202 DBG2(DBG_NET, "received cookie lifetime expired, rejecting");
203 return FALSE;
204 }
205
206 /* check if cookie is derived from old_secret */
207 if (t + this->secret_offset > this->secret_switch)
208 {
209 secret = chunk_from_thing(this->secret);
210 }
211 else
212 {
213 secret = chunk_from_thing(this->secret_old);
214 }
215
216 /* compare own calculation against received */
217 reference = cookie_build(this, message, t, secret);
218 if (chunk_equals(reference, cookie))
219 {
220 chunk_free(&reference);
221 return TRUE;
222 }
223 chunk_free(&reference);
224 return FALSE;
225 }
226
227 /**
228 * Check if a valid cookie found
229 */
230 static bool check_cookie(private_receiver_t *this, message_t *message)
231 {
232 packet_t *packet;
233 chunk_t data;
234
235 /* check for a cookie. We don't use our parser here and do it
236 * quick and dirty for performance reasons.
237 * we assume the cookie is the first payload (which is a MUST), and
238 * the cookie's SPI length is zero. */
239 packet = message->get_packet(message);
240 data = packet->get_data(packet);
241 if (data.len <
242 IKE_HEADER_LENGTH + NOTIFY_PAYLOAD_HEADER_LENGTH +
243 sizeof(u_int32_t) + this->hasher->get_hash_size(this->hasher) ||
244 *(data.ptr + 16) != NOTIFY ||
245 *(u_int16_t*)(data.ptr + IKE_HEADER_LENGTH + 6) != htons(COOKIE))
246 {
247 /* no cookie found */
248 packet->destroy(packet);
249 return FALSE;
250 }
251 data.ptr += IKE_HEADER_LENGTH + NOTIFY_PAYLOAD_HEADER_LENGTH;
252 data.len = sizeof(u_int32_t) + this->hasher->get_hash_size(this->hasher);
253 if (!cookie_verify(this, message, data))
254 {
255 DBG2(DBG_NET, "found cookie, but content invalid");
256 packet->destroy(packet);
257 return FALSE;
258 }
259 return TRUE;
260 }
261
262 /**
263 * Check if we should drop IKE_SA_INIT because of cookie/overload checking
264 */
265 static bool drop_ike_sa_init(private_receiver_t *this, message_t *message)
266 {
267 u_int half_open;
268
269 half_open = charon->ike_sa_manager->get_half_open_count(
270 charon->ike_sa_manager, NULL);
271
272 /* check for cookies */
273 if (this->cookie_threshold && half_open >= this->cookie_threshold &&
274 !check_cookie(this, message))
275 {
276 u_int32_t now = time_monotonic(NULL);
277 chunk_t cookie = cookie_build(this, message, now - this->secret_offset,
278 chunk_from_thing(this->secret));
279
280 DBG2(DBG_NET, "received packet from: %#H to %#H",
281 message->get_source(message),
282 message->get_destination(message));
283 DBG2(DBG_NET, "sending COOKIE notify to %H",
284 message->get_source(message));
285 send_notify(message, COOKIE, cookie);
286 chunk_free(&cookie);
287 if (++this->secret_used > COOKIE_REUSE)
288 {
289 /* create new cookie */
290 DBG1(DBG_NET, "generating new cookie secret after %d uses",
291 this->secret_used);
292 memcpy(this->secret_old, this->secret, SECRET_LENGTH);
293 this->rng->get_bytes(this->rng, SECRET_LENGTH, this->secret);
294 this->secret_switch = now;
295 this->secret_used = 0;
296 }
297 return TRUE;
298 }
299
300 /* check if peer has too many IKE_SAs half open */
301 if (this->block_threshold &&
302 charon->ike_sa_manager->get_half_open_count(charon->ike_sa_manager,
303 message->get_source(message)) >= this->block_threshold)
304 {
305 DBG1(DBG_NET, "ignoring IKE_SA setup from %H, "
306 "peer too aggressive", message->get_source(message));
307 return TRUE;
308 }
309
310 /* check if global half open IKE_SA limit reached */
311 if (this->init_limit_half_open &&
312 half_open >= this->init_limit_half_open)
313 {
314 DBG1(DBG_NET, "ignoring IKE_SA setup from %H, half open IKE_SA "
315 "count of %d exceeds limit of %d", message->get_source(message),
316 half_open, this->init_limit_half_open);
317 return TRUE;
318 }
319
320 /* check if job load acceptable */
321 if (this->init_limit_job_load)
322 {
323 u_int jobs = 0, i;
324
325 for (i = 0; i < JOB_PRIO_MAX; i++)
326 {
327 jobs += lib->processor->get_job_load(lib->processor, i);
328 }
329 if (jobs > this->init_limit_job_load)
330 {
331 DBG1(DBG_NET, "ignoring IKE_SA setup from %H, job load of %d "
332 "exceeds limit of %d", message->get_source(message),
333 jobs, this->init_limit_job_load);
334 return TRUE;
335 }
336 }
337 return FALSE;
338 }
339
340 /**
341 * Job callback to receive packets
342 */
343 static job_requeue_t receive_packets(private_receiver_t *this)
344 {
345 packet_t *packet;
346 message_t *message;
347 status_t status;
348
349 /* read in a packet */
350 status = charon->socket->receive(charon->socket, &packet);
351 if (status == NOT_SUPPORTED)
352 {
353 /* the processor destroys this job */
354 this->job = NULL;
355 return JOB_REQUEUE_NONE;
356 }
357 else if (status != SUCCESS)
358 {
359 DBG2(DBG_NET, "receiving from socket failed!");
360 return JOB_REQUEUE_FAIR;
361 }
362
363 /* parse message header */
364 message = message_create_from_packet(packet);
365 if (message->parse_header(message) != SUCCESS)
366 {
367 DBG1(DBG_NET, "received invalid IKE header from %H - ignored",
368 packet->get_source(packet));
369 message->destroy(message);
370 return JOB_REQUEUE_DIRECT;
371 }
372
373 /* check IKE major version */
374 if (message->get_major_version(message) != IKEV2_MAJOR_VERSION)
375 {
376 DBG1(DBG_NET, "received unsupported IKE version %d.%d from %H, "
377 "sending INVALID_MAJOR_VERSION", message->get_major_version(message),
378 message->get_minor_version(message), packet->get_source(packet));
379 send_notify(message, INVALID_MAJOR_VERSION, chunk_empty);
380 message->destroy(message);
381 return JOB_REQUEUE_DIRECT;
382 }
383
384 if (message->get_request(message) &&
385 message->get_exchange_type(message) == IKE_SA_INIT)
386 {
387 if (drop_ike_sa_init(this, message))
388 {
389 message->destroy(message);
390 return JOB_REQUEUE_DIRECT;
391 }
392 }
393 if (this->receive_delay)
394 {
395 if (this->receive_delay_type == 0 ||
396 this->receive_delay_type == message->get_exchange_type(message))
397 {
398 if ((message->get_request(message) && this->receive_delay_request) ||
399 (!message->get_request(message) && this->receive_delay_response))
400 {
401 DBG1(DBG_NET, "using receive delay: %dms",
402 this->receive_delay);
403 lib->scheduler->schedule_job_ms(lib->scheduler,
404 (job_t*)process_message_job_create(message),
405 this->receive_delay);
406 return JOB_REQUEUE_DIRECT;
407 }
408 }
409 }
410 lib->processor->queue_job(lib->processor,
411 (job_t*)process_message_job_create(message));
412 return JOB_REQUEUE_DIRECT;
413 }
414
415 METHOD(receiver_t, destroy, void,
416 private_receiver_t *this)
417 {
418 if (this->job)
419 {
420 this->job->cancel(this->job);
421 }
422 this->rng->destroy(this->rng);
423 this->hasher->destroy(this->hasher);
424 free(this);
425 }
426
427 /*
428 * Described in header.
429 */
430 receiver_t *receiver_create()
431 {
432 private_receiver_t *this;
433 u_int32_t now = time_monotonic(NULL);
434
435 INIT(this,
436 .public = {
437 .destroy = _destroy,
438 },
439 .secret_switch = now,
440 .secret_offset = random() % now,
441 );
442
443 if (lib->settings->get_bool(lib->settings, "charon.dos_protection", TRUE))
444 {
445 this->cookie_threshold = lib->settings->get_int(lib->settings,
446 "charon.cookie_threshold", COOKIE_THRESHOLD_DEFAULT);
447 this->block_threshold = lib->settings->get_int(lib->settings,
448 "charon.block_threshold", BLOCK_THRESHOLD_DEFAULT);
449 }
450 this->init_limit_job_load = lib->settings->get_int(lib->settings,
451 "charon.init_limit_job_load", 0);
452 this->init_limit_half_open = lib->settings->get_int(lib->settings,
453 "charon.init_limit_half_open", 0);
454 this->receive_delay = lib->settings->get_int(lib->settings,
455 "charon.receive_delay", 0);
456 this->receive_delay_type = lib->settings->get_int(lib->settings,
457 "charon.receive_delay_type", 0),
458 this->receive_delay_request = lib->settings->get_bool(lib->settings,
459 "charon.receive_delay_request", TRUE),
460 this->receive_delay_response = lib->settings->get_int(lib->settings,
461 "charon.receive_delay_response", TRUE),
462
463 this->hasher = lib->crypto->create_hasher(lib->crypto, HASH_PREFERRED);
464 if (this->hasher == NULL)
465 {
466 DBG1(DBG_NET, "creating cookie hasher failed, no hashers supported");
467 free(this);
468 return NULL;
469 }
470 this->rng = lib->crypto->create_rng(lib->crypto, RNG_STRONG);
471 if (this->rng == NULL)
472 {
473 DBG1(DBG_NET, "creating cookie RNG failed, no RNG supported");
474 this->hasher->destroy(this->hasher);
475 free(this);
476 return NULL;
477 }
478 this->rng->get_bytes(this->rng, SECRET_LENGTH, this->secret);
479 memcpy(this->secret_old, this->secret, SECRET_LENGTH);
480
481 this->job = callback_job_create_with_prio((callback_job_cb_t)receive_packets,
482 this, NULL, NULL, JOB_PRIO_CRITICAL);
483 lib->processor->queue_job(lib->processor, (job_t*)this->job);
484
485 return &this->public;
486 }
487