1 /* SPDX-License-Identifier: ISC
3 * Copyright (C) 2015-2021 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
4 * Copyright (C) 2019-2021 Matt Dunwoodie <ncon@noconroy.net>
10 #include <sys/param.h>
11 #include <sys/systm.h>
12 #include <sys/kernel.h>
14 #include <sys/mutex.h>
15 #include <sys/rwlock.h>
16 #include <sys/socket.h>
17 #include <crypto/siphash/siphash.h>
18 #include <netinet/in.h>
21 #include "wg_cookie.h"
23 #define COOKIE_MAC1_KEY_LABEL "mac1----"
24 #define COOKIE_COOKIE_KEY_LABEL "cookie--"
25 #define COOKIE_SECRET_MAX_AGE 120
26 #define COOKIE_SECRET_LATENCY 5
28 /* Constants for initiation rate limiting */
29 #define RATELIMIT_SIZE (1 << 13)
30 #define RATELIMIT_MASK (RATELIMIT_SIZE - 1)
31 #define RATELIMIT_SIZE_MAX (RATELIMIT_SIZE * 8)
32 #define INITIATIONS_PER_SECOND 20
33 #define INITIATIONS_BURSTABLE 5
34 #define INITIATION_COST (SBT_1S / INITIATIONS_PER_SECOND)
35 #define TOKEN_MAX (INITIATION_COST * INITIATIONS_BURSTABLE)
36 #define ELEMENT_TIMEOUT 1
37 #define IPV4_MASK_SIZE 4 /* Use all 4 bytes of IPv4 address */
38 #define IPV6_MASK_SIZE 8 /* Use top 8 bytes (/64) of IPv6 address */
40 struct ratelimit_key {
42 uint8_t ip[IPV6_MASK_SIZE];
45 struct ratelimit_entry {
46 LIST_ENTRY(ratelimit_entry) r_entry;
47 struct ratelimit_key r_key;
48 sbintime_t r_last_time; /* sbinuptime */
53 uint8_t rl_secret[SIPHASH_KEY_LENGTH];
56 LIST_HEAD(, ratelimit_entry) rl_table[RATELIMIT_SIZE];
61 static void precompute_key(uint8_t *,
62 const uint8_t[COOKIE_INPUT_SIZE], const char *);
63 static void macs_mac1(struct cookie_macs *, const void *, size_t,
64 const uint8_t[COOKIE_KEY_SIZE]);
65 static void macs_mac2(struct cookie_macs *, const void *, size_t,
66 const uint8_t[COOKIE_COOKIE_SIZE]);
67 static int timer_expired(sbintime_t, uint32_t, uint32_t);
68 static void make_cookie(struct cookie_checker *,
69 uint8_t[COOKIE_COOKIE_SIZE], struct sockaddr *);
70 static void ratelimit_init(struct ratelimit *);
71 static void ratelimit_deinit(struct ratelimit *);
72 static void ratelimit_gc_callout(void *);
73 static void ratelimit_gc_schedule(struct ratelimit *);
74 static void ratelimit_gc(struct ratelimit *, bool);
75 static int ratelimit_allow(struct ratelimit *, struct sockaddr *, struct vnet *);
76 static uint64_t siphash13(const uint8_t [SIPHASH_KEY_LENGTH], const void *, size_t);
78 static struct ratelimit ratelimit_v4;
80 static struct ratelimit ratelimit_v6;
82 static uma_zone_t ratelimit_zone;
84 /* Public Functions */
88 if ((ratelimit_zone = uma_zcreate("wg ratelimit",
89 sizeof(struct ratelimit_entry), NULL, NULL, NULL, NULL, 0, 0)) == NULL)
92 ratelimit_init(&ratelimit_v4);
94 ratelimit_init(&ratelimit_v6);
102 ratelimit_deinit(&ratelimit_v4);
104 ratelimit_deinit(&ratelimit_v6);
106 if (ratelimit_zone != NULL)
107 uma_zdestroy(ratelimit_zone);
111 cookie_checker_init(struct cookie_checker *cc)
113 bzero(cc, sizeof(*cc));
115 rw_init(&cc->cc_key_lock, "cookie_checker_key");
116 mtx_init(&cc->cc_secret_mtx, "cookie_checker_secret", NULL, MTX_DEF);
120 cookie_checker_free(struct cookie_checker *cc)
122 rw_destroy(&cc->cc_key_lock);
123 mtx_destroy(&cc->cc_secret_mtx);
124 explicit_bzero(cc, sizeof(*cc));
128 cookie_checker_update(struct cookie_checker *cc,
129 const uint8_t key[COOKIE_INPUT_SIZE])
131 rw_wlock(&cc->cc_key_lock);
133 precompute_key(cc->cc_mac1_key, key, COOKIE_MAC1_KEY_LABEL);
134 precompute_key(cc->cc_cookie_key, key, COOKIE_COOKIE_KEY_LABEL);
136 bzero(cc->cc_mac1_key, sizeof(cc->cc_mac1_key));
137 bzero(cc->cc_cookie_key, sizeof(cc->cc_cookie_key));
139 rw_wunlock(&cc->cc_key_lock);
143 cookie_checker_create_payload(struct cookie_checker *cc,
144 struct cookie_macs *macs, uint8_t nonce[COOKIE_NONCE_SIZE],
145 uint8_t ecookie[COOKIE_ENCRYPTED_SIZE], struct sockaddr *sa)
147 uint8_t cookie[COOKIE_COOKIE_SIZE];
149 make_cookie(cc, cookie, sa);
150 arc4random_buf(nonce, COOKIE_NONCE_SIZE);
152 rw_rlock(&cc->cc_key_lock);
153 xchacha20poly1305_encrypt(ecookie, cookie, COOKIE_COOKIE_SIZE,
154 macs->mac1, COOKIE_MAC_SIZE, nonce, cc->cc_cookie_key);
155 rw_runlock(&cc->cc_key_lock);
157 explicit_bzero(cookie, sizeof(cookie));
161 cookie_maker_init(struct cookie_maker *cm, const uint8_t key[COOKIE_INPUT_SIZE])
163 bzero(cm, sizeof(*cm));
164 precompute_key(cm->cm_mac1_key, key, COOKIE_MAC1_KEY_LABEL);
165 precompute_key(cm->cm_cookie_key, key, COOKIE_COOKIE_KEY_LABEL);
166 rw_init(&cm->cm_lock, "cookie_maker");
170 cookie_maker_free(struct cookie_maker *cm)
172 rw_destroy(&cm->cm_lock);
173 explicit_bzero(cm, sizeof(*cm));
177 cookie_maker_consume_payload(struct cookie_maker *cm,
178 uint8_t nonce[COOKIE_NONCE_SIZE], uint8_t ecookie[COOKIE_ENCRYPTED_SIZE])
180 uint8_t cookie[COOKIE_COOKIE_SIZE];
183 rw_rlock(&cm->cm_lock);
184 if (!cm->cm_mac1_sent) {
189 if (!xchacha20poly1305_decrypt(cookie, ecookie, COOKIE_ENCRYPTED_SIZE,
190 cm->cm_mac1_last, COOKIE_MAC_SIZE, nonce, cm->cm_cookie_key)) {
194 rw_runlock(&cm->cm_lock);
196 rw_wlock(&cm->cm_lock);
197 memcpy(cm->cm_cookie, cookie, COOKIE_COOKIE_SIZE);
198 cm->cm_cookie_birthdate = getsbinuptime();
199 cm->cm_cookie_valid = true;
200 cm->cm_mac1_sent = false;
201 rw_wunlock(&cm->cm_lock);
205 rw_runlock(&cm->cm_lock);
210 cookie_maker_mac(struct cookie_maker *cm, struct cookie_macs *macs, void *buf,
213 rw_wlock(&cm->cm_lock);
214 macs_mac1(macs, buf, len, cm->cm_mac1_key);
215 memcpy(cm->cm_mac1_last, macs->mac1, COOKIE_MAC_SIZE);
216 cm->cm_mac1_sent = true;
218 if (cm->cm_cookie_valid &&
219 !timer_expired(cm->cm_cookie_birthdate,
220 COOKIE_SECRET_MAX_AGE - COOKIE_SECRET_LATENCY, 0)) {
221 macs_mac2(macs, buf, len, cm->cm_cookie);
223 bzero(macs->mac2, COOKIE_MAC_SIZE);
224 cm->cm_cookie_valid = false;
226 rw_wunlock(&cm->cm_lock);
230 cookie_checker_validate_macs(struct cookie_checker *cc, struct cookie_macs *macs,
231 void *buf, size_t len, bool check_cookie, struct sockaddr *sa, struct vnet *vnet)
233 struct cookie_macs our_macs;
234 uint8_t cookie[COOKIE_COOKIE_SIZE];
236 /* Validate incoming MACs */
237 rw_rlock(&cc->cc_key_lock);
238 macs_mac1(&our_macs, buf, len, cc->cc_mac1_key);
239 rw_runlock(&cc->cc_key_lock);
241 /* If mac1 is invald, we want to drop the packet */
242 if (timingsafe_bcmp(our_macs.mac1, macs->mac1, COOKIE_MAC_SIZE) != 0)
246 make_cookie(cc, cookie, sa);
247 macs_mac2(&our_macs, buf, len, cookie);
249 /* If the mac2 is invalid, we want to send a cookie response */
250 if (timingsafe_bcmp(our_macs.mac2, macs->mac2, COOKIE_MAC_SIZE) != 0)
253 /* If the mac2 is valid, we may want rate limit the peer.
254 * ratelimit_allow will return either 0 or ECONNREFUSED,
255 * implying there is no ratelimiting, or we should ratelimit
256 * (refuse) respectively. */
257 if (sa->sa_family == AF_INET)
258 return ratelimit_allow(&ratelimit_v4, sa, vnet);
260 else if (sa->sa_family == AF_INET6)
261 return ratelimit_allow(&ratelimit_v6, sa, vnet);
270 /* Private functions */
272 precompute_key(uint8_t *key, const uint8_t input[COOKIE_INPUT_SIZE],
275 struct blake2s_state blake;
276 blake2s_init(&blake, COOKIE_KEY_SIZE);
277 blake2s_update(&blake, label, strlen(label));
278 blake2s_update(&blake, input, COOKIE_INPUT_SIZE);
279 blake2s_final(&blake, key);
283 macs_mac1(struct cookie_macs *macs, const void *buf, size_t len,
284 const uint8_t key[COOKIE_KEY_SIZE])
286 struct blake2s_state state;
287 blake2s_init_key(&state, COOKIE_MAC_SIZE, key, COOKIE_KEY_SIZE);
288 blake2s_update(&state, buf, len);
289 blake2s_final(&state, macs->mac1);
293 macs_mac2(struct cookie_macs *macs, const void *buf, size_t len,
294 const uint8_t key[COOKIE_COOKIE_SIZE])
296 struct blake2s_state state;
297 blake2s_init_key(&state, COOKIE_MAC_SIZE, key, COOKIE_COOKIE_SIZE);
298 blake2s_update(&state, buf, len);
299 blake2s_update(&state, macs->mac1, COOKIE_MAC_SIZE);
300 blake2s_final(&state, macs->mac2);
304 timer_expired(sbintime_t timer, uint32_t sec, uint32_t nsec)
306 sbintime_t now = getsbinuptime();
307 return (now > (timer + sec * SBT_1S + nstosbt(nsec))) ? ETIMEDOUT : 0;
311 make_cookie(struct cookie_checker *cc, uint8_t cookie[COOKIE_COOKIE_SIZE],
314 struct blake2s_state state;
316 mtx_lock(&cc->cc_secret_mtx);
317 if (timer_expired(cc->cc_secret_birthdate,
318 COOKIE_SECRET_MAX_AGE, 0)) {
319 arc4random_buf(cc->cc_secret, COOKIE_SECRET_SIZE);
320 cc->cc_secret_birthdate = getsbinuptime();
322 blake2s_init_key(&state, COOKIE_COOKIE_SIZE, cc->cc_secret,
324 mtx_unlock(&cc->cc_secret_mtx);
326 if (sa->sa_family == AF_INET) {
327 blake2s_update(&state, (uint8_t *)&satosin(sa)->sin_addr,
328 sizeof(struct in_addr));
329 blake2s_update(&state, (uint8_t *)&satosin(sa)->sin_port,
331 blake2s_final(&state, cookie);
333 } else if (sa->sa_family == AF_INET6) {
334 blake2s_update(&state, (uint8_t *)&satosin6(sa)->sin6_addr,
335 sizeof(struct in6_addr));
336 blake2s_update(&state, (uint8_t *)&satosin6(sa)->sin6_port,
338 blake2s_final(&state, cookie);
341 arc4random_buf(cookie, COOKIE_COOKIE_SIZE);
346 ratelimit_init(struct ratelimit *rl)
349 mtx_init(&rl->rl_mtx, "ratelimit_lock", NULL, MTX_DEF);
350 callout_init_mtx(&rl->rl_gc, &rl->rl_mtx, 0);
351 arc4random_buf(rl->rl_secret, sizeof(rl->rl_secret));
352 for (i = 0; i < RATELIMIT_SIZE; i++)
353 LIST_INIT(&rl->rl_table[i]);
354 rl->rl_table_num = 0;
355 rl->rl_initialized = true;
359 ratelimit_deinit(struct ratelimit *rl)
361 if (!rl->rl_initialized)
363 mtx_lock(&rl->rl_mtx);
364 callout_stop(&rl->rl_gc);
365 ratelimit_gc(rl, true);
366 mtx_unlock(&rl->rl_mtx);
367 mtx_destroy(&rl->rl_mtx);
369 rl->rl_initialized = false;
373 ratelimit_gc_callout(void *_rl)
375 /* callout will lock rl_mtx for us */
376 ratelimit_gc(_rl, false);
380 ratelimit_gc_schedule(struct ratelimit *rl)
382 /* Trigger another GC if needed. There is no point calling GC if there
383 * are no entries in the table. We also want to ensure that GC occurs
384 * on a regular interval, so don't override a currently pending GC.
386 * In the case of a forced ratelimit_gc, there will be no entries left
387 * so we will will not schedule another GC. */
388 if (rl->rl_table_num > 0 && !callout_pending(&rl->rl_gc))
389 callout_reset(&rl->rl_gc, ELEMENT_TIMEOUT * hz,
390 ratelimit_gc_callout, rl);
394 ratelimit_gc(struct ratelimit *rl, bool force)
397 struct ratelimit_entry *r, *tr;
400 mtx_assert(&rl->rl_mtx, MA_OWNED);
402 if (rl->rl_table_num == 0)
405 expiry = getsbinuptime() - ELEMENT_TIMEOUT * SBT_1S;
407 for (i = 0; i < RATELIMIT_SIZE; i++) {
408 LIST_FOREACH_SAFE(r, &rl->rl_table[i], r_entry, tr) {
409 if (r->r_last_time < expiry || force) {
411 LIST_REMOVE(r, r_entry);
412 uma_zfree(ratelimit_zone, r);
417 ratelimit_gc_schedule(rl);
421 ratelimit_allow(struct ratelimit *rl, struct sockaddr *sa, struct vnet *vnet)
423 uint64_t bucket, tokens;
424 sbintime_t diff, now;
425 struct ratelimit_entry *r;
426 int ret = ECONNREFUSED;
427 struct ratelimit_key key = { .vnet = vnet };
428 size_t len = sizeof(key);
430 if (sa->sa_family == AF_INET) {
431 memcpy(key.ip, &satosin(sa)->sin_addr, IPV4_MASK_SIZE);
432 len -= IPV6_MASK_SIZE - IPV4_MASK_SIZE;
435 else if (sa->sa_family == AF_INET6)
436 memcpy(key.ip, &satosin6(sa)->sin6_addr, IPV6_MASK_SIZE);
441 bucket = siphash13(rl->rl_secret, &key, len) & RATELIMIT_MASK;
442 mtx_lock(&rl->rl_mtx);
444 LIST_FOREACH(r, &rl->rl_table[bucket], r_entry) {
445 if (bcmp(&r->r_key, &key, len) != 0)
448 /* If we get to here, we've found an entry for the endpoint.
449 * We apply standard token bucket, by calculating the time
450 * lapsed since our last_time, adding that, ensuring that we
451 * cap the tokens at TOKEN_MAX. If the endpoint has no tokens
452 * left (that is tokens <= INITIATION_COST) then we block the
453 * request, otherwise we subtract the INITITIATION_COST and
455 now = getsbinuptime();
456 diff = now - r->r_last_time;
457 r->r_last_time = now;
459 tokens = r->r_tokens + diff;
461 if (tokens > TOKEN_MAX)
464 if (tokens >= INITIATION_COST) {
465 r->r_tokens = tokens - INITIATION_COST;
468 r->r_tokens = tokens;
473 /* If we get to here, we didn't have an entry for the endpoint, let's
474 * add one if we have space. */
475 if (rl->rl_table_num >= RATELIMIT_SIZE_MAX)
478 /* Goto error if out of memory */
479 if ((r = uma_zalloc(ratelimit_zone, M_NOWAIT | M_ZERO)) == NULL)
484 /* Insert entry into the hashtable and ensure it's initialised */
485 LIST_INSERT_HEAD(&rl->rl_table[bucket], r, r_entry);
487 r->r_last_time = getsbinuptime();
488 r->r_tokens = TOKEN_MAX - INITIATION_COST;
490 /* If we've added a new entry, let's trigger GC. */
491 ratelimit_gc_schedule(rl);
495 mtx_unlock(&rl->rl_mtx);
499 static uint64_t siphash13(const uint8_t key[SIPHASH_KEY_LENGTH], const void *src, size_t len)
502 return (SipHashX(&ctx, 1, 3, key, src, len));
506 #include "selftest/cookie.c"
507 #endif /* SELFTESTS */