1 /* SPDX-License-Identifier: ISC 2 * 3 * Copyright (C) 2015-2021 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. 4 * Copyright (C) 2019-2021 Matt Dunwoodie <ncon@noconroy.net> 5 */ 6 7 #include "opt_inet.h" 8 #include "opt_inet6.h" 9 10 #include <sys/param.h> 11 #include <sys/systm.h> 12 #include <sys/kernel.h> 13 #include <sys/lock.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> 19 #include <vm/uma.h> 20 21 #include "wg_cookie.h" 22 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 27 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 */ 39 40 struct ratelimit_key { 41 struct vnet *vnet; 42 uint8_t ip[IPV6_MASK_SIZE]; 43 }; 44 45 struct ratelimit_entry { 46 LIST_ENTRY(ratelimit_entry) r_entry; 47 struct ratelimit_key r_key; 48 sbintime_t r_last_time; /* sbinuptime */ 49 uint64_t r_tokens; 50 }; 51 52 struct ratelimit { 53 uint8_t rl_secret[SIPHASH_KEY_LENGTH]; 54 struct mtx rl_mtx; 55 struct callout rl_gc; 56 LIST_HEAD(, ratelimit_entry) rl_table[RATELIMIT_SIZE]; 57 size_t rl_table_num; 58 bool rl_initialized; 59 }; 60 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); 77 78 static struct ratelimit ratelimit_v4; 79 #ifdef INET6 80 static struct ratelimit ratelimit_v6; 81 #endif 82 static uma_zone_t ratelimit_zone; 83 84 /* Public Functions */ 85 int 86 cookie_init(void) 87 { 88 ratelimit_zone = uma_zcreate("wg ratelimit", 89 sizeof(struct ratelimit_entry), NULL, NULL, NULL, NULL, 0, 0); 90 91 ratelimit_init(&ratelimit_v4); 92 #ifdef INET6 93 ratelimit_init(&ratelimit_v6); 94 #endif 95 return (0); 96 } 97 98 void 99 cookie_deinit(void) 100 { 101 ratelimit_deinit(&ratelimit_v4); 102 #ifdef INET6 103 ratelimit_deinit(&ratelimit_v6); 104 #endif 105 if (ratelimit_zone != NULL) 106 uma_zdestroy(ratelimit_zone); 107 } 108 109 void 110 cookie_checker_init(struct cookie_checker *cc) 111 { 112 bzero(cc, sizeof(*cc)); 113 114 rw_init(&cc->cc_key_lock, "cookie_checker_key"); 115 mtx_init(&cc->cc_secret_mtx, "cookie_checker_secret", NULL, MTX_DEF); 116 } 117 118 void 119 cookie_checker_free(struct cookie_checker *cc) 120 { 121 rw_destroy(&cc->cc_key_lock); 122 mtx_destroy(&cc->cc_secret_mtx); 123 explicit_bzero(cc, sizeof(*cc)); 124 } 125 126 void 127 cookie_checker_update(struct cookie_checker *cc, 128 const uint8_t key[COOKIE_INPUT_SIZE]) 129 { 130 rw_wlock(&cc->cc_key_lock); 131 if (key) { 132 precompute_key(cc->cc_mac1_key, key, COOKIE_MAC1_KEY_LABEL); 133 precompute_key(cc->cc_cookie_key, key, COOKIE_COOKIE_KEY_LABEL); 134 } else { 135 bzero(cc->cc_mac1_key, sizeof(cc->cc_mac1_key)); 136 bzero(cc->cc_cookie_key, sizeof(cc->cc_cookie_key)); 137 } 138 rw_wunlock(&cc->cc_key_lock); 139 } 140 141 void 142 cookie_checker_create_payload(struct cookie_checker *cc, 143 struct cookie_macs *macs, uint8_t nonce[COOKIE_NONCE_SIZE], 144 uint8_t ecookie[COOKIE_ENCRYPTED_SIZE], struct sockaddr *sa) 145 { 146 uint8_t cookie[COOKIE_COOKIE_SIZE]; 147 148 make_cookie(cc, cookie, sa); 149 arc4random_buf(nonce, COOKIE_NONCE_SIZE); 150 151 rw_rlock(&cc->cc_key_lock); 152 xchacha20poly1305_encrypt(ecookie, cookie, COOKIE_COOKIE_SIZE, 153 macs->mac1, COOKIE_MAC_SIZE, nonce, cc->cc_cookie_key); 154 rw_runlock(&cc->cc_key_lock); 155 156 explicit_bzero(cookie, sizeof(cookie)); 157 } 158 159 void 160 cookie_maker_init(struct cookie_maker *cm, const uint8_t key[COOKIE_INPUT_SIZE]) 161 { 162 bzero(cm, sizeof(*cm)); 163 precompute_key(cm->cm_mac1_key, key, COOKIE_MAC1_KEY_LABEL); 164 precompute_key(cm->cm_cookie_key, key, COOKIE_COOKIE_KEY_LABEL); 165 rw_init(&cm->cm_lock, "cookie_maker"); 166 } 167 168 void 169 cookie_maker_free(struct cookie_maker *cm) 170 { 171 rw_destroy(&cm->cm_lock); 172 explicit_bzero(cm, sizeof(*cm)); 173 } 174 175 int 176 cookie_maker_consume_payload(struct cookie_maker *cm, 177 uint8_t nonce[COOKIE_NONCE_SIZE], uint8_t ecookie[COOKIE_ENCRYPTED_SIZE]) 178 { 179 uint8_t cookie[COOKIE_COOKIE_SIZE]; 180 int ret; 181 182 rw_rlock(&cm->cm_lock); 183 if (!cm->cm_mac1_sent) { 184 ret = ETIMEDOUT; 185 goto error; 186 } 187 188 if (!xchacha20poly1305_decrypt(cookie, ecookie, COOKIE_ENCRYPTED_SIZE, 189 cm->cm_mac1_last, COOKIE_MAC_SIZE, nonce, cm->cm_cookie_key)) { 190 ret = EINVAL; 191 goto error; 192 } 193 rw_runlock(&cm->cm_lock); 194 195 rw_wlock(&cm->cm_lock); 196 memcpy(cm->cm_cookie, cookie, COOKIE_COOKIE_SIZE); 197 cm->cm_cookie_birthdate = getsbinuptime(); 198 cm->cm_cookie_valid = true; 199 cm->cm_mac1_sent = false; 200 rw_wunlock(&cm->cm_lock); 201 202 return 0; 203 error: 204 rw_runlock(&cm->cm_lock); 205 return ret; 206 } 207 208 void 209 cookie_maker_mac(struct cookie_maker *cm, struct cookie_macs *macs, void *buf, 210 size_t len) 211 { 212 rw_wlock(&cm->cm_lock); 213 macs_mac1(macs, buf, len, cm->cm_mac1_key); 214 memcpy(cm->cm_mac1_last, macs->mac1, COOKIE_MAC_SIZE); 215 cm->cm_mac1_sent = true; 216 217 if (cm->cm_cookie_valid && 218 !timer_expired(cm->cm_cookie_birthdate, 219 COOKIE_SECRET_MAX_AGE - COOKIE_SECRET_LATENCY, 0)) { 220 macs_mac2(macs, buf, len, cm->cm_cookie); 221 } else { 222 bzero(macs->mac2, COOKIE_MAC_SIZE); 223 cm->cm_cookie_valid = false; 224 } 225 rw_wunlock(&cm->cm_lock); 226 } 227 228 int 229 cookie_checker_validate_macs(struct cookie_checker *cc, struct cookie_macs *macs, 230 void *buf, size_t len, bool check_cookie, struct sockaddr *sa, struct vnet *vnet) 231 { 232 struct cookie_macs our_macs; 233 uint8_t cookie[COOKIE_COOKIE_SIZE]; 234 235 /* Validate incoming MACs */ 236 rw_rlock(&cc->cc_key_lock); 237 macs_mac1(&our_macs, buf, len, cc->cc_mac1_key); 238 rw_runlock(&cc->cc_key_lock); 239 240 /* If mac1 is invald, we want to drop the packet */ 241 if (timingsafe_bcmp(our_macs.mac1, macs->mac1, COOKIE_MAC_SIZE) != 0) 242 return EINVAL; 243 244 if (check_cookie) { 245 make_cookie(cc, cookie, sa); 246 macs_mac2(&our_macs, buf, len, cookie); 247 248 /* If the mac2 is invalid, we want to send a cookie response */ 249 if (timingsafe_bcmp(our_macs.mac2, macs->mac2, COOKIE_MAC_SIZE) != 0) 250 return EAGAIN; 251 252 /* If the mac2 is valid, we may want rate limit the peer. 253 * ratelimit_allow will return either 0 or ECONNREFUSED, 254 * implying there is no ratelimiting, or we should ratelimit 255 * (refuse) respectively. */ 256 if (sa->sa_family == AF_INET) 257 return ratelimit_allow(&ratelimit_v4, sa, vnet); 258 #ifdef INET6 259 else if (sa->sa_family == AF_INET6) 260 return ratelimit_allow(&ratelimit_v6, sa, vnet); 261 #endif 262 else 263 return EAFNOSUPPORT; 264 } 265 266 return 0; 267 } 268 269 /* Private functions */ 270 static void 271 precompute_key(uint8_t *key, const uint8_t input[COOKIE_INPUT_SIZE], 272 const char *label) 273 { 274 struct blake2s_state blake; 275 blake2s_init(&blake, COOKIE_KEY_SIZE); 276 blake2s_update(&blake, label, strlen(label)); 277 blake2s_update(&blake, input, COOKIE_INPUT_SIZE); 278 blake2s_final(&blake, key); 279 } 280 281 static void 282 macs_mac1(struct cookie_macs *macs, const void *buf, size_t len, 283 const uint8_t key[COOKIE_KEY_SIZE]) 284 { 285 struct blake2s_state state; 286 blake2s_init_key(&state, COOKIE_MAC_SIZE, key, COOKIE_KEY_SIZE); 287 blake2s_update(&state, buf, len); 288 blake2s_final(&state, macs->mac1); 289 } 290 291 static void 292 macs_mac2(struct cookie_macs *macs, const void *buf, size_t len, 293 const uint8_t key[COOKIE_COOKIE_SIZE]) 294 { 295 struct blake2s_state state; 296 blake2s_init_key(&state, COOKIE_MAC_SIZE, key, COOKIE_COOKIE_SIZE); 297 blake2s_update(&state, buf, len); 298 blake2s_update(&state, macs->mac1, COOKIE_MAC_SIZE); 299 blake2s_final(&state, macs->mac2); 300 } 301 302 static __inline int 303 timer_expired(sbintime_t timer, uint32_t sec, uint32_t nsec) 304 { 305 sbintime_t now = getsbinuptime(); 306 return (now > (timer + sec * SBT_1S + nstosbt(nsec))) ? ETIMEDOUT : 0; 307 } 308 309 static void 310 make_cookie(struct cookie_checker *cc, uint8_t cookie[COOKIE_COOKIE_SIZE], 311 struct sockaddr *sa) 312 { 313 struct blake2s_state state; 314 315 mtx_lock(&cc->cc_secret_mtx); 316 if (timer_expired(cc->cc_secret_birthdate, 317 COOKIE_SECRET_MAX_AGE, 0)) { 318 arc4random_buf(cc->cc_secret, COOKIE_SECRET_SIZE); 319 cc->cc_secret_birthdate = getsbinuptime(); 320 } 321 blake2s_init_key(&state, COOKIE_COOKIE_SIZE, cc->cc_secret, 322 COOKIE_SECRET_SIZE); 323 mtx_unlock(&cc->cc_secret_mtx); 324 325 if (sa->sa_family == AF_INET) { 326 blake2s_update(&state, (uint8_t *)&satosin(sa)->sin_addr, 327 sizeof(struct in_addr)); 328 blake2s_update(&state, (uint8_t *)&satosin(sa)->sin_port, 329 sizeof(in_port_t)); 330 blake2s_final(&state, cookie); 331 #ifdef INET6 332 } else if (sa->sa_family == AF_INET6) { 333 blake2s_update(&state, (uint8_t *)&satosin6(sa)->sin6_addr, 334 sizeof(struct in6_addr)); 335 blake2s_update(&state, (uint8_t *)&satosin6(sa)->sin6_port, 336 sizeof(in_port_t)); 337 blake2s_final(&state, cookie); 338 #endif 339 } else { 340 arc4random_buf(cookie, COOKIE_COOKIE_SIZE); 341 } 342 } 343 344 static void 345 ratelimit_init(struct ratelimit *rl) 346 { 347 size_t i; 348 mtx_init(&rl->rl_mtx, "ratelimit_lock", NULL, MTX_DEF); 349 callout_init_mtx(&rl->rl_gc, &rl->rl_mtx, 0); 350 arc4random_buf(rl->rl_secret, sizeof(rl->rl_secret)); 351 for (i = 0; i < RATELIMIT_SIZE; i++) 352 LIST_INIT(&rl->rl_table[i]); 353 rl->rl_table_num = 0; 354 rl->rl_initialized = true; 355 } 356 357 static void 358 ratelimit_deinit(struct ratelimit *rl) 359 { 360 if (!rl->rl_initialized) 361 return; 362 mtx_lock(&rl->rl_mtx); 363 callout_stop(&rl->rl_gc); 364 ratelimit_gc(rl, true); 365 mtx_unlock(&rl->rl_mtx); 366 mtx_destroy(&rl->rl_mtx); 367 368 rl->rl_initialized = false; 369 } 370 371 static void 372 ratelimit_gc_callout(void *_rl) 373 { 374 /* callout will lock rl_mtx for us */ 375 ratelimit_gc(_rl, false); 376 } 377 378 static void 379 ratelimit_gc_schedule(struct ratelimit *rl) 380 { 381 /* Trigger another GC if needed. There is no point calling GC if there 382 * are no entries in the table. We also want to ensure that GC occurs 383 * on a regular interval, so don't override a currently pending GC. 384 * 385 * In the case of a forced ratelimit_gc, there will be no entries left 386 * so we will will not schedule another GC. */ 387 if (rl->rl_table_num > 0 && !callout_pending(&rl->rl_gc)) 388 callout_reset(&rl->rl_gc, ELEMENT_TIMEOUT * hz, 389 ratelimit_gc_callout, rl); 390 } 391 392 static void 393 ratelimit_gc(struct ratelimit *rl, bool force) 394 { 395 size_t i; 396 struct ratelimit_entry *r, *tr; 397 sbintime_t expiry; 398 399 mtx_assert(&rl->rl_mtx, MA_OWNED); 400 401 if (rl->rl_table_num == 0) 402 return; 403 404 expiry = getsbinuptime() - ELEMENT_TIMEOUT * SBT_1S; 405 406 for (i = 0; i < RATELIMIT_SIZE; i++) { 407 LIST_FOREACH_SAFE(r, &rl->rl_table[i], r_entry, tr) { 408 if (r->r_last_time < expiry || force) { 409 rl->rl_table_num--; 410 LIST_REMOVE(r, r_entry); 411 uma_zfree(ratelimit_zone, r); 412 } 413 } 414 } 415 416 ratelimit_gc_schedule(rl); 417 } 418 419 static int 420 ratelimit_allow(struct ratelimit *rl, struct sockaddr *sa, struct vnet *vnet) 421 { 422 uint64_t bucket, tokens; 423 sbintime_t diff, now; 424 struct ratelimit_entry *r; 425 int ret = ECONNREFUSED; 426 struct ratelimit_key key = { .vnet = vnet }; 427 size_t len = sizeof(key); 428 429 if (sa->sa_family == AF_INET) { 430 memcpy(key.ip, &satosin(sa)->sin_addr, IPV4_MASK_SIZE); 431 len -= IPV6_MASK_SIZE - IPV4_MASK_SIZE; 432 } 433 #ifdef INET6 434 else if (sa->sa_family == AF_INET6) 435 memcpy(key.ip, &satosin6(sa)->sin6_addr, IPV6_MASK_SIZE); 436 #endif 437 else 438 return ret; 439 440 bucket = siphash13(rl->rl_secret, &key, len) & RATELIMIT_MASK; 441 mtx_lock(&rl->rl_mtx); 442 443 LIST_FOREACH(r, &rl->rl_table[bucket], r_entry) { 444 if (bcmp(&r->r_key, &key, len) != 0) 445 continue; 446 447 /* If we get to here, we've found an entry for the endpoint. 448 * We apply standard token bucket, by calculating the time 449 * lapsed since our last_time, adding that, ensuring that we 450 * cap the tokens at TOKEN_MAX. If the endpoint has no tokens 451 * left (that is tokens <= INITIATION_COST) then we block the 452 * request, otherwise we subtract the INITITIATION_COST and 453 * return OK. */ 454 now = getsbinuptime(); 455 diff = now - r->r_last_time; 456 r->r_last_time = now; 457 458 tokens = r->r_tokens + diff; 459 460 if (tokens > TOKEN_MAX) 461 tokens = TOKEN_MAX; 462 463 if (tokens >= INITIATION_COST) { 464 r->r_tokens = tokens - INITIATION_COST; 465 goto ok; 466 } else { 467 r->r_tokens = tokens; 468 goto error; 469 } 470 } 471 472 /* If we get to here, we didn't have an entry for the endpoint, let's 473 * add one if we have space. */ 474 if (rl->rl_table_num >= RATELIMIT_SIZE_MAX) 475 goto error; 476 477 /* Goto error if out of memory */ 478 if ((r = uma_zalloc(ratelimit_zone, M_NOWAIT | M_ZERO)) == NULL) 479 goto error; 480 481 rl->rl_table_num++; 482 483 /* Insert entry into the hashtable and ensure it's initialised */ 484 LIST_INSERT_HEAD(&rl->rl_table[bucket], r, r_entry); 485 r->r_key = key; 486 r->r_last_time = getsbinuptime(); 487 r->r_tokens = TOKEN_MAX - INITIATION_COST; 488 489 /* If we've added a new entry, let's trigger GC. */ 490 ratelimit_gc_schedule(rl); 491 ok: 492 ret = 0; 493 error: 494 mtx_unlock(&rl->rl_mtx); 495 return ret; 496 } 497 498 static uint64_t siphash13(const uint8_t key[SIPHASH_KEY_LENGTH], const void *src, size_t len) 499 { 500 SIPHASH_CTX ctx; 501 return (SipHashX(&ctx, 1, 3, key, src, len)); 502 } 503 504 #ifdef SELFTESTS 505 #include "selftest/cookie.c" 506 #endif /* SELFTESTS */ 507