8dfb47b69015cbc665ae7d9f7b8a08a73e2e72ae
[strongswan.git] / src / libcharon / network / receiver.c
1 /*
2 * Copyright (C) 2008-2012 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 <hydra.h>
24 #include <daemon.h>
25 #include <network/socket.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 #include <threading/mutex.h>
31 #include <networking/packet.h>
32
33 /** lifetime of a cookie, in seconds */
34 #define COOKIE_LIFETIME 10
35 /** time we wait before disabling cookies */
36 #define COOKIE_CALMDOWN_DELAY 10
37 /** how many times to reuse the secret */
38 #define COOKIE_REUSE 10000
39 /** default value for private_receiver_t.cookie_threshold */
40 #define COOKIE_THRESHOLD_DEFAULT 10
41 /** default value for private_receiver_t.block_threshold */
42 #define BLOCK_THRESHOLD_DEFAULT 5
43 /** length of the secret to use for cookie calculation */
44 #define SECRET_LENGTH 16
45 /** Length of a notify payload header */
46 #define NOTIFY_PAYLOAD_HEADER_LENGTH 8
47
48 typedef struct private_receiver_t private_receiver_t;
49
50 /**
51 * Private data of a receiver_t object.
52 */
53 struct private_receiver_t {
54 /**
55 * Public part of a receiver_t object.
56 */
57 receiver_t public;
58
59 /**
60 * Registered callback for ESP packets
61 */
62 struct {
63 receiver_esp_cb_t cb;
64 void *data;
65 } esp_cb;
66
67 /**
68 * Mutex for ESP callback
69 */
70 mutex_t *esp_cb_mutex;
71
72 /**
73 * current secret to use for cookie calculation
74 */
75 char secret[SECRET_LENGTH];
76
77 /**
78 * previous secret used to verify older cookies
79 */
80 char secret_old[SECRET_LENGTH];
81
82 /**
83 * how many times we have used "secret" so far
84 */
85 u_int32_t secret_used;
86
87 /**
88 * time we did the cookie switch
89 */
90 u_int32_t secret_switch;
91
92 /**
93 * time offset to use, hides our system time
94 */
95 u_int32_t secret_offset;
96
97 /**
98 * the RNG to use for secret generation
99 */
100 rng_t *rng;
101
102 /**
103 * hasher to use for cookie calculation
104 */
105 hasher_t *hasher;
106
107 /**
108 * require cookies after this many half open IKE_SAs
109 */
110 u_int32_t cookie_threshold;
111
112 /**
113 * timestamp of last cookie requested
114 */
115 time_t last_cookie;
116
117 /**
118 * how many half open IKE_SAs per peer before blocking
119 */
120 u_int32_t block_threshold;
121
122 /**
123 * Drop IKE_SA_INIT requests if processor job load exceeds this limit
124 */
125 u_int init_limit_job_load;
126
127 /**
128 * Drop IKE_SA_INIT requests if half open IKE_SA count exceeds this limit
129 */
130 u_int init_limit_half_open;
131
132 /**
133 * Delay for receiving incoming packets, to simulate larger RTT
134 */
135 int receive_delay;
136
137 /**
138 * Specific message type to delay, 0 for any
139 */
140 int receive_delay_type;
141
142 /**
143 * Delay request messages?
144 */
145 bool receive_delay_request;
146
147 /**
148 * Delay response messages?
149 */
150 bool receive_delay_response;
151
152 /**
153 * Endpoint is allowed to act as an initiator only
154 */
155 bool initiator_only;
156
157 };
158
159 /**
160 * send a notify back to the sender
161 */
162 static void send_notify(message_t *request, int major, exchange_type_t exchange,
163 notify_type_t type, chunk_t data)
164 {
165 ike_sa_id_t *ike_sa_id;
166 message_t *response;
167 host_t *src, *dst;
168 packet_t *packet;
169
170 response = message_create(major, 0);
171 response->set_exchange_type(response, exchange);
172 response->add_notify(response, FALSE, type, data);
173 dst = request->get_source(request);
174 src = request->get_destination(request);
175 response->set_source(response, src->clone(src));
176 response->set_destination(response, dst->clone(dst));
177 if (major == IKEV2_MAJOR_VERSION)
178 {
179 response->set_request(response, FALSE);
180 }
181 response->set_message_id(response, 0);
182 ike_sa_id = request->get_ike_sa_id(request);
183 ike_sa_id->switch_initiator(ike_sa_id);
184 response->set_ike_sa_id(response, ike_sa_id);
185 if (response->generate(response, NULL, &packet) == SUCCESS)
186 {
187 charon->sender->send(charon->sender, packet);
188 }
189 response->destroy(response);
190 }
191
192 /**
193 * build a cookie
194 */
195 static bool cookie_build(private_receiver_t *this, message_t *message,
196 u_int32_t t, chunk_t secret, chunk_t *cookie)
197 {
198 u_int64_t spi = message->get_initiator_spi(message);
199 host_t *ip = message->get_source(message);
200 chunk_t input, hash;
201
202 /* COOKIE = t | sha1( IPi | SPIi | t | secret ) */
203 input = chunk_cata("cccc", ip->get_address(ip), chunk_from_thing(spi),
204 chunk_from_thing(t), secret);
205 hash = chunk_alloca(this->hasher->get_hash_size(this->hasher));
206 if (!this->hasher->get_hash(this->hasher, input, hash.ptr))
207 {
208 return FALSE;
209 }
210 *cookie = chunk_cat("cc", chunk_from_thing(t), hash);
211 return TRUE;
212 }
213
214 /**
215 * verify a received cookie
216 */
217 static bool cookie_verify(private_receiver_t *this, message_t *message,
218 chunk_t cookie)
219 {
220 u_int32_t t, now;
221 chunk_t reference;
222 chunk_t secret;
223
224 now = time_monotonic(NULL);
225 t = *(u_int32_t*)cookie.ptr;
226
227 if (cookie.len != sizeof(u_int32_t) +
228 this->hasher->get_hash_size(this->hasher) ||
229 t < now - this->secret_offset - COOKIE_LIFETIME)
230 {
231 DBG2(DBG_NET, "received cookie lifetime expired, rejecting");
232 return FALSE;
233 }
234
235 /* check if cookie is derived from old_secret */
236 if (t + this->secret_offset > this->secret_switch)
237 {
238 secret = chunk_from_thing(this->secret);
239 }
240 else
241 {
242 secret = chunk_from_thing(this->secret_old);
243 }
244
245 /* compare own calculation against received */
246 if (!cookie_build(this, message, t, secret, &reference))
247 {
248 return FALSE;
249 }
250 if (chunk_equals(reference, cookie))
251 {
252 chunk_free(&reference);
253 return TRUE;
254 }
255 chunk_free(&reference);
256 return FALSE;
257 }
258
259 /**
260 * Check if a valid cookie found
261 */
262 static bool check_cookie(private_receiver_t *this, message_t *message)
263 {
264 chunk_t data;
265
266 /* check for a cookie. We don't use our parser here and do it
267 * quick and dirty for performance reasons.
268 * we assume the cookie is the first payload (which is a MUST), and
269 * the cookie's SPI length is zero. */
270 data = message->get_packet_data(message);
271 if (data.len <
272 IKE_HEADER_LENGTH + NOTIFY_PAYLOAD_HEADER_LENGTH +
273 sizeof(u_int32_t) + this->hasher->get_hash_size(this->hasher) ||
274 *(data.ptr + 16) != NOTIFY ||
275 *(u_int16_t*)(data.ptr + IKE_HEADER_LENGTH + 6) != htons(COOKIE))
276 {
277 /* no cookie found */
278 return FALSE;
279 }
280 data.ptr += IKE_HEADER_LENGTH + NOTIFY_PAYLOAD_HEADER_LENGTH;
281 data.len = sizeof(u_int32_t) + this->hasher->get_hash_size(this->hasher);
282 if (!cookie_verify(this, message, data))
283 {
284 DBG2(DBG_NET, "found cookie, but content invalid");
285 return FALSE;
286 }
287 return TRUE;
288 }
289
290 /**
291 * Check if we currently require cookies
292 */
293 static bool cookie_required(private_receiver_t *this,
294 u_int half_open, u_int32_t now)
295 {
296 if (this->cookie_threshold && half_open >= this->cookie_threshold)
297 {
298 this->last_cookie = now;
299 return TRUE;
300 }
301 if (this->last_cookie && now < this->last_cookie + COOKIE_CALMDOWN_DELAY)
302 {
303 /* We don't disable cookies unless we haven't seen IKE_SA_INITs
304 * for COOKIE_CALMDOWN_DELAY seconds. This avoids jittering between
305 * cookie on / cookie off states, which is problematic. Consider the
306 * following: A legitimiate initiator sends a IKE_SA_INIT while we
307 * are under a DoS attack. If we toggle our cookie behavior,
308 * multiple retransmits of this IKE_SA_INIT might get answered with
309 * and without cookies. The initiator goes on and retries with
310 * a cookie, but it can't know if the completing IKE_SA_INIT response
311 * is to its IKE_SA_INIT request with or without cookies. This is
312 * problematic, as the cookie is part of AUTH payload data.
313 */
314 this->last_cookie = now;
315 return TRUE;
316 }
317 return FALSE;
318 }
319
320 /**
321 * Check if we should drop IKE_SA_INIT because of cookie/overload checking
322 */
323 static bool drop_ike_sa_init(private_receiver_t *this, message_t *message)
324 {
325 u_int half_open;
326 u_int32_t now;
327
328 now = time_monotonic(NULL);
329 half_open = charon->ike_sa_manager->get_half_open_count(
330 charon->ike_sa_manager, NULL);
331
332 /* check for cookies in IKEv2 */
333 if (message->get_major_version(message) == IKEV2_MAJOR_VERSION &&
334 cookie_required(this, half_open, now) && !check_cookie(this, message))
335 {
336 chunk_t cookie;
337
338 DBG2(DBG_NET, "received packet from: %#H to %#H",
339 message->get_source(message),
340 message->get_destination(message));
341 if (!cookie_build(this, message, now - this->secret_offset,
342 chunk_from_thing(this->secret), &cookie))
343 {
344 return TRUE;
345 }
346 DBG2(DBG_NET, "sending COOKIE notify to %H",
347 message->get_source(message));
348 send_notify(message, IKEV2_MAJOR_VERSION, IKE_SA_INIT, COOKIE, cookie);
349 chunk_free(&cookie);
350 if (++this->secret_used > COOKIE_REUSE)
351 {
352 char secret[SECRET_LENGTH];
353
354 DBG1(DBG_NET, "generating new cookie secret after %d uses",
355 this->secret_used);
356 if (this->rng->get_bytes(this->rng, SECRET_LENGTH, secret))
357 {
358 memcpy(this->secret_old, this->secret, SECRET_LENGTH);
359 memcpy(this->secret, secret, SECRET_LENGTH);
360 memwipe(secret, SECRET_LENGTH);
361 this->secret_switch = now;
362 this->secret_used = 0;
363 }
364 else
365 {
366 DBG1(DBG_NET, "failed to allocated cookie secret, keeping old");
367 }
368 }
369 return TRUE;
370 }
371
372 /* check if peer has too many IKE_SAs half open */
373 if (this->block_threshold &&
374 charon->ike_sa_manager->get_half_open_count(charon->ike_sa_manager,
375 message->get_source(message)) >= this->block_threshold)
376 {
377 DBG1(DBG_NET, "ignoring IKE_SA setup from %H, "
378 "peer too aggressive", message->get_source(message));
379 return TRUE;
380 }
381
382 /* check if global half open IKE_SA limit reached */
383 if (this->init_limit_half_open &&
384 half_open >= this->init_limit_half_open)
385 {
386 DBG1(DBG_NET, "ignoring IKE_SA setup from %H, half open IKE_SA "
387 "count of %d exceeds limit of %d", message->get_source(message),
388 half_open, this->init_limit_half_open);
389 return TRUE;
390 }
391
392 /* check if job load acceptable */
393 if (this->init_limit_job_load)
394 {
395 u_int jobs = 0, i;
396
397 for (i = 0; i < JOB_PRIO_MAX; i++)
398 {
399 jobs += lib->processor->get_job_load(lib->processor, i);
400 }
401 if (jobs > this->init_limit_job_load)
402 {
403 DBG1(DBG_NET, "ignoring IKE_SA setup from %H, job load of %d "
404 "exceeds limit of %d", message->get_source(message),
405 jobs, this->init_limit_job_load);
406 return TRUE;
407 }
408 }
409 return FALSE;
410 }
411
412 /**
413 * Job callback to receive packets
414 */
415 static job_requeue_t receive_packets(private_receiver_t *this)
416 {
417 ike_sa_id_t *id;
418 packet_t *packet;
419 message_t *message;
420 host_t *src, *dst;
421 status_t status;
422 bool supported = TRUE;
423 chunk_t data, marker = chunk_from_chars(0x00, 0x00, 0x00, 0x00);
424
425 /* read in a packet */
426 status = charon->socket->receive(charon->socket, &packet);
427 if (status == NOT_SUPPORTED)
428 {
429 return JOB_REQUEUE_NONE;
430 }
431 else if (status != SUCCESS)
432 {
433 DBG2(DBG_NET, "receiving from socket failed!");
434 return JOB_REQUEUE_FAIR;
435 }
436
437 data = packet->get_data(packet);
438 if (data.len == 1 && data.ptr[0] == 0xFF)
439 { /* silently drop NAT-T keepalives */
440 packet->destroy(packet);
441 return JOB_REQUEUE_DIRECT;
442 }
443 else if (data.len < marker.len)
444 { /* drop packets that are too small */
445 DBG3(DBG_NET, "received packet is too short (%d bytes)", data.len);
446 packet->destroy(packet);
447 return JOB_REQUEUE_DIRECT;
448 }
449
450 dst = packet->get_destination(packet);
451 src = packet->get_source(packet);
452 if (!hydra->kernel_interface->all_interfaces_usable(hydra->kernel_interface)
453 && !hydra->kernel_interface->get_interface(hydra->kernel_interface,
454 dst, NULL))
455 {
456 DBG3(DBG_NET, "received packet from %#H to %#H on ignored interface",
457 src, dst);
458 packet->destroy(packet);
459 return JOB_REQUEUE_DIRECT;
460 }
461
462 /* if neither source nor destination port is 500 we assume an IKE packet
463 * with Non-ESP marker or an ESP packet */
464 if (dst->get_port(dst) != IKEV2_UDP_PORT &&
465 src->get_port(src) != IKEV2_UDP_PORT)
466 {
467 if (memeq(data.ptr, marker.ptr, marker.len))
468 { /* remove Non-ESP marker */
469 packet->skip_bytes(packet, marker.len);
470 }
471 else
472 { /* this seems to be an ESP packet */
473 this->esp_cb_mutex->lock(this->esp_cb_mutex);
474 if (this->esp_cb.cb)
475 {
476 this->esp_cb.cb(this->esp_cb.data, packet);
477 }
478 else
479 {
480 packet->destroy(packet);
481 }
482 this->esp_cb_mutex->unlock(this->esp_cb_mutex);
483 return JOB_REQUEUE_DIRECT;
484 }
485 }
486
487 /* parse message header */
488 message = message_create_from_packet(packet);
489 if (message->parse_header(message) != SUCCESS)
490 {
491 DBG1(DBG_NET, "received invalid IKE header from %H - ignored",
492 packet->get_source(packet));
493 charon->bus->alert(charon->bus, ALERT_PARSE_ERROR_HEADER, message);
494 message->destroy(message);
495 return JOB_REQUEUE_DIRECT;
496 }
497
498 /* check IKE major version */
499 switch (message->get_major_version(message))
500 {
501 case IKEV2_MAJOR_VERSION:
502 #ifndef USE_IKEV2
503 if (message->get_exchange_type(message) == IKE_SA_INIT &&
504 message->get_request(message))
505 {
506 send_notify(message, IKEV1_MAJOR_VERSION, INFORMATIONAL_V1,
507 INVALID_MAJOR_VERSION, chunk_empty);
508 supported = FALSE;
509 }
510 #endif /* USE_IKEV2 */
511 break;
512 case IKEV1_MAJOR_VERSION:
513 #ifndef USE_IKEV1
514 if (message->get_exchange_type(message) == ID_PROT ||
515 message->get_exchange_type(message) == AGGRESSIVE)
516 {
517 send_notify(message, IKEV2_MAJOR_VERSION, INFORMATIONAL,
518 INVALID_MAJOR_VERSION, chunk_empty);
519 supported = FALSE;
520 }
521 #endif /* USE_IKEV1 */
522 break;
523 default:
524 #ifdef USE_IKEV2
525 send_notify(message, IKEV2_MAJOR_VERSION, INFORMATIONAL,
526 INVALID_MAJOR_VERSION, chunk_empty);
527 #endif /* USE_IKEV2 */
528 #ifdef USE_IKEV1
529 send_notify(message, IKEV1_MAJOR_VERSION, INFORMATIONAL_V1,
530 INVALID_MAJOR_VERSION, chunk_empty);
531 #endif /* USE_IKEV1 */
532 supported = FALSE;
533 break;
534 }
535 if (!supported)
536 {
537 DBG1(DBG_NET, "received unsupported IKE version %d.%d from %H, sending "
538 "INVALID_MAJOR_VERSION", message->get_major_version(message),
539 message->get_minor_version(message), packet->get_source(packet));
540 message->destroy(message);
541 return JOB_REQUEUE_DIRECT;
542 }
543 if (message->get_request(message) &&
544 message->get_exchange_type(message) == IKE_SA_INIT)
545 {
546 if (this->initiator_only || drop_ike_sa_init(this, message))
547 {
548 message->destroy(message);
549 return JOB_REQUEUE_DIRECT;
550 }
551 }
552 if (message->get_exchange_type(message) == ID_PROT ||
553 message->get_exchange_type(message) == AGGRESSIVE)
554 {
555 id = message->get_ike_sa_id(message);
556 if (id->get_responder_spi(id) == 0 &&
557 (this->initiator_only || drop_ike_sa_init(this, message)))
558 {
559 message->destroy(message);
560 return JOB_REQUEUE_DIRECT;
561 }
562 }
563
564 if (this->receive_delay)
565 {
566 if (this->receive_delay_type == 0 ||
567 this->receive_delay_type == message->get_exchange_type(message))
568 {
569 if ((message->get_request(message) && this->receive_delay_request) ||
570 (!message->get_request(message) && this->receive_delay_response))
571 {
572 DBG1(DBG_NET, "using receive delay: %dms",
573 this->receive_delay);
574 lib->scheduler->schedule_job_ms(lib->scheduler,
575 (job_t*)process_message_job_create(message),
576 this->receive_delay);
577 return JOB_REQUEUE_DIRECT;
578 }
579 }
580 }
581 lib->processor->queue_job(lib->processor,
582 (job_t*)process_message_job_create(message));
583 return JOB_REQUEUE_DIRECT;
584 }
585
586 METHOD(receiver_t, add_esp_cb, void,
587 private_receiver_t *this, receiver_esp_cb_t callback, void *data)
588 {
589 this->esp_cb_mutex->lock(this->esp_cb_mutex);
590 this->esp_cb.cb = callback;
591 this->esp_cb.data = data;
592 this->esp_cb_mutex->unlock(this->esp_cb_mutex);
593 }
594
595 METHOD(receiver_t, del_esp_cb, void,
596 private_receiver_t *this, receiver_esp_cb_t callback)
597 {
598 this->esp_cb_mutex->lock(this->esp_cb_mutex);
599 if (this->esp_cb.cb == callback)
600 {
601 this->esp_cb.cb = NULL;
602 this->esp_cb.data = NULL;
603 }
604 this->esp_cb_mutex->unlock(this->esp_cb_mutex);
605 }
606
607 METHOD(receiver_t, destroy, void,
608 private_receiver_t *this)
609 {
610 this->rng->destroy(this->rng);
611 this->hasher->destroy(this->hasher);
612 this->esp_cb_mutex->destroy(this->esp_cb_mutex);
613 free(this);
614 }
615
616 /*
617 * Described in header.
618 */
619 receiver_t *receiver_create()
620 {
621 private_receiver_t *this;
622 u_int32_t now = time_monotonic(NULL);
623
624 INIT(this,
625 .public = {
626 .add_esp_cb = _add_esp_cb,
627 .del_esp_cb = _del_esp_cb,
628 .destroy = _destroy,
629 },
630 .esp_cb_mutex = mutex_create(MUTEX_TYPE_DEFAULT),
631 .secret_switch = now,
632 .secret_offset = random() % now,
633 );
634
635 if (lib->settings->get_bool(lib->settings,
636 "%s.dos_protection", TRUE, lib->ns))
637 {
638 this->cookie_threshold = lib->settings->get_int(lib->settings,
639 "%s.cookie_threshold", COOKIE_THRESHOLD_DEFAULT, lib->ns);
640 this->block_threshold = lib->settings->get_int(lib->settings,
641 "%s.block_threshold", BLOCK_THRESHOLD_DEFAULT, lib->ns);
642 }
643 this->init_limit_job_load = lib->settings->get_int(lib->settings,
644 "%s.init_limit_job_load", 0, lib->ns);
645 this->init_limit_half_open = lib->settings->get_int(lib->settings,
646 "%s.init_limit_half_open", 0, lib->ns);
647 this->receive_delay = lib->settings->get_int(lib->settings,
648 "%s.receive_delay", 0, lib->ns);
649 this->receive_delay_type = lib->settings->get_int(lib->settings,
650 "%s.receive_delay_type", 0, lib->ns),
651 this->receive_delay_request = lib->settings->get_bool(lib->settings,
652 "%s.receive_delay_request", TRUE, lib->ns),
653 this->receive_delay_response = lib->settings->get_bool(lib->settings,
654 "%s.receive_delay_response", TRUE, lib->ns),
655 this->initiator_only = lib->settings->get_bool(lib->settings,
656 "%s.initiator_only", FALSE, lib->ns),
657
658 this->hasher = lib->crypto->create_hasher(lib->crypto, HASH_SHA1);
659 if (!this->hasher)
660 {
661 DBG1(DBG_NET, "creating cookie hasher failed, no hashers supported");
662 free(this);
663 return NULL;
664 }
665 this->rng = lib->crypto->create_rng(lib->crypto, RNG_STRONG);
666 if (!this->rng)
667 {
668 DBG1(DBG_NET, "creating cookie RNG failed, no RNG supported");
669 this->hasher->destroy(this->hasher);
670 free(this);
671 return NULL;
672 }
673 if (!this->rng->get_bytes(this->rng, SECRET_LENGTH, this->secret))
674 {
675 DBG1(DBG_NET, "creating cookie secret failed");
676 destroy(this);
677 return NULL;
678 }
679 memcpy(this->secret_old, this->secret, SECRET_LENGTH);
680
681 lib->processor->queue_job(lib->processor,
682 (job_t*)callback_job_create_with_prio((callback_job_cb_t)receive_packets,
683 this, NULL, (callback_job_cancel_t)return_false, JOB_PRIO_CRITICAL));
684
685 return &this->public;
686 }
687