1 /*- 2 * Copyright 2001 Niels Provos <provos@citi.umich.edu> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 * 25 * $OpenBSD: pf_norm.c,v 1.114 2009/01/29 14:11:45 henning Exp $ 26 */ 27 28 #include <sys/cdefs.h> 29 __FBSDID("$FreeBSD$"); 30 31 #include "opt_inet.h" 32 #include "opt_inet6.h" 33 #include "opt_pf.h" 34 35 #include <sys/param.h> 36 #include <sys/kernel.h> 37 #include <sys/lock.h> 38 #include <sys/mbuf.h> 39 #include <sys/mutex.h> 40 #include <sys/refcount.h> 41 #include <sys/rwlock.h> 42 #include <sys/socket.h> 43 44 #include <net/if.h> 45 #include <net/vnet.h> 46 #include <net/pfvar.h> 47 #include <net/if_pflog.h> 48 49 #include <netinet/in.h> 50 #include <netinet/ip.h> 51 #include <netinet/ip_var.h> 52 #include <netinet/tcp.h> 53 #include <netinet/tcp_fsm.h> 54 #include <netinet/tcp_seq.h> 55 56 #ifdef INET6 57 #include <netinet/ip6.h> 58 #endif /* INET6 */ 59 60 struct pf_frent { 61 LIST_ENTRY(pf_frent) fr_next; 62 union { 63 struct { 64 struct ip *_fr_ip; 65 struct mbuf *_fr_m; 66 } _frag; 67 struct { 68 uint16_t _fr_off; 69 uint16_t _fr_end; 70 } _cache; 71 } _u; 72 }; 73 #define fr_ip _u._frag._fr_ip 74 #define fr_m _u._frag._fr_m 75 #define fr_off _u._cache._fr_off 76 #define fr_end _u._cache._fr_end 77 78 struct pf_fragment { 79 RB_ENTRY(pf_fragment) fr_entry; 80 TAILQ_ENTRY(pf_fragment) frag_next; 81 struct in_addr fr_src; 82 struct in_addr fr_dst; 83 u_int8_t fr_p; /* protocol of this fragment */ 84 u_int8_t fr_flags; /* status flags */ 85 #define PFFRAG_SEENLAST 0x0001 /* Seen the last fragment for this */ 86 #define PFFRAG_NOBUFFER 0x0002 /* Non-buffering fragment cache */ 87 #define PFFRAG_DROP 0x0004 /* Drop all fragments */ 88 #define BUFFER_FRAGMENTS(fr) (!((fr)->fr_flags & PFFRAG_NOBUFFER)) 89 u_int16_t fr_id; /* fragment id for reassemble */ 90 u_int16_t fr_max; /* fragment data max */ 91 u_int32_t fr_timeout; 92 LIST_HEAD(, pf_frent) fr_queue; 93 }; 94 95 static struct mtx pf_frag_mtx; 96 MTX_SYSINIT(pf_frag_mtx, &pf_frag_mtx, "pf fragments", MTX_DEF); 97 #define PF_FRAG_LOCK() mtx_lock(&pf_frag_mtx) 98 #define PF_FRAG_UNLOCK() mtx_unlock(&pf_frag_mtx) 99 #define PF_FRAG_ASSERT() mtx_assert(&pf_frag_mtx, MA_OWNED) 100 101 VNET_DEFINE(uma_zone_t, pf_state_scrub_z); /* XXX: shared with pfsync */ 102 103 static VNET_DEFINE(uma_zone_t, pf_frent_z); 104 #define V_pf_frent_z VNET(pf_frent_z) 105 static VNET_DEFINE(uma_zone_t, pf_frag_z); 106 #define V_pf_frag_z VNET(pf_frag_z) 107 108 TAILQ_HEAD(pf_fragqueue, pf_fragment); 109 TAILQ_HEAD(pf_cachequeue, pf_fragment); 110 static VNET_DEFINE(struct pf_fragqueue, pf_fragqueue); 111 #define V_pf_fragqueue VNET(pf_fragqueue) 112 static VNET_DEFINE(struct pf_cachequeue, pf_cachequeue); 113 #define V_pf_cachequeue VNET(pf_cachequeue) 114 RB_HEAD(pf_frag_tree, pf_fragment); 115 static VNET_DEFINE(struct pf_frag_tree, pf_frag_tree); 116 #define V_pf_frag_tree VNET(pf_frag_tree) 117 static VNET_DEFINE(struct pf_frag_tree, pf_cache_tree); 118 #define V_pf_cache_tree VNET(pf_cache_tree) 119 static int pf_frag_compare(struct pf_fragment *, 120 struct pf_fragment *); 121 static RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); 122 static RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); 123 124 /* Private prototypes */ 125 static void pf_free_fragment(struct pf_fragment *); 126 static void pf_remove_fragment(struct pf_fragment *); 127 static int pf_normalize_tcpopt(struct pf_rule *, struct mbuf *, 128 struct tcphdr *, int, sa_family_t); 129 #ifdef INET 130 static void pf_ip2key(struct pf_fragment *, struct ip *); 131 static void pf_scrub_ip(struct mbuf **, u_int32_t, u_int8_t, 132 u_int8_t); 133 static void pf_flush_fragments(void); 134 static struct pf_fragment *pf_find_fragment(struct ip *, struct pf_frag_tree *); 135 static struct mbuf *pf_reassemble(struct mbuf **, struct pf_fragment **, 136 struct pf_frent *, int); 137 static struct mbuf *pf_fragcache(struct mbuf **, struct ip*, 138 struct pf_fragment **, int, int, int *); 139 #endif /* INET */ 140 #ifdef INET6 141 static void pf_scrub_ip6(struct mbuf **, u_int8_t); 142 #endif 143 #define DPFPRINTF(x) do { \ 144 if (V_pf_status.debug >= PF_DEBUG_MISC) { \ 145 printf("%s: ", __func__); \ 146 printf x ; \ 147 } \ 148 } while(0) 149 150 void 151 pf_vnet_normalize_init(void) 152 { 153 154 V_pf_frag_z = uma_zcreate("pf frags", sizeof(struct pf_fragment), 155 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 156 V_pf_frent_z = uma_zcreate("pf frag entries", sizeof(struct pf_frent), 157 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 158 V_pf_state_scrub_z = uma_zcreate("pf state scrubs", 159 sizeof(struct pf_state_scrub), NULL, NULL, NULL, NULL, 160 UMA_ALIGN_PTR, 0); 161 162 V_pf_limits[PF_LIMIT_FRAGS].zone = V_pf_frent_z; 163 V_pf_limits[PF_LIMIT_FRAGS].limit = PFFRAG_FRENT_HIWAT; 164 uma_zone_set_max(V_pf_frent_z, PFFRAG_FRENT_HIWAT); 165 uma_zone_set_warning(V_pf_frent_z, "PF frag entries limit reached"); 166 TAILQ_INIT(&V_pf_fragqueue); 167 TAILQ_INIT(&V_pf_cachequeue); 168 } 169 170 void 171 pf_normalize_cleanup(void) 172 { 173 174 uma_zdestroy(V_pf_state_scrub_z); 175 uma_zdestroy(V_pf_frent_z); 176 uma_zdestroy(V_pf_frag_z); 177 } 178 179 static int 180 pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b) 181 { 182 int diff; 183 184 if ((diff = a->fr_id - b->fr_id)) 185 return (diff); 186 else if ((diff = a->fr_p - b->fr_p)) 187 return (diff); 188 else if (a->fr_src.s_addr < b->fr_src.s_addr) 189 return (-1); 190 else if (a->fr_src.s_addr > b->fr_src.s_addr) 191 return (1); 192 else if (a->fr_dst.s_addr < b->fr_dst.s_addr) 193 return (-1); 194 else if (a->fr_dst.s_addr > b->fr_dst.s_addr) 195 return (1); 196 return (0); 197 } 198 199 void 200 pf_purge_expired_fragments(void) 201 { 202 struct pf_fragment *frag; 203 u_int32_t expire = time_uptime - 204 V_pf_default_rule.timeout[PFTM_FRAG]; 205 206 PF_FRAG_LOCK(); 207 while ((frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue)) != NULL) { 208 KASSERT((BUFFER_FRAGMENTS(frag)), 209 ("BUFFER_FRAGMENTS(frag) == 0: %s", __FUNCTION__)); 210 if (frag->fr_timeout > expire) 211 break; 212 213 DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag)); 214 pf_free_fragment(frag); 215 } 216 217 while ((frag = TAILQ_LAST(&V_pf_cachequeue, pf_cachequeue)) != NULL) { 218 KASSERT((!BUFFER_FRAGMENTS(frag)), 219 ("BUFFER_FRAGMENTS(frag) != 0: %s", __FUNCTION__)); 220 if (frag->fr_timeout > expire) 221 break; 222 223 DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag)); 224 pf_free_fragment(frag); 225 KASSERT((TAILQ_EMPTY(&V_pf_cachequeue) || 226 TAILQ_LAST(&V_pf_cachequeue, pf_cachequeue) != frag), 227 ("!(TAILQ_EMPTY() || TAILQ_LAST() == farg): %s", 228 __FUNCTION__)); 229 } 230 PF_FRAG_UNLOCK(); 231 } 232 233 #ifdef INET 234 /* 235 * Try to flush old fragments to make space for new ones 236 */ 237 static void 238 pf_flush_fragments(void) 239 { 240 struct pf_fragment *frag, *cache; 241 int goal; 242 243 PF_FRAG_ASSERT(); 244 245 goal = uma_zone_get_cur(V_pf_frent_z) * 9 / 10; 246 DPFPRINTF(("trying to free %d frag entriess\n", goal)); 247 while (goal < uma_zone_get_cur(V_pf_frent_z)) { 248 frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue); 249 if (frag) 250 pf_free_fragment(frag); 251 cache = TAILQ_LAST(&V_pf_cachequeue, pf_cachequeue); 252 if (cache) 253 pf_free_fragment(cache); 254 if (frag == NULL && cache == NULL) 255 break; 256 } 257 } 258 #endif /* INET */ 259 260 /* Frees the fragments and all associated entries */ 261 static void 262 pf_free_fragment(struct pf_fragment *frag) 263 { 264 struct pf_frent *frent; 265 266 PF_FRAG_ASSERT(); 267 268 /* Free all fragments */ 269 if (BUFFER_FRAGMENTS(frag)) { 270 for (frent = LIST_FIRST(&frag->fr_queue); frent; 271 frent = LIST_FIRST(&frag->fr_queue)) { 272 LIST_REMOVE(frent, fr_next); 273 274 m_freem(frent->fr_m); 275 uma_zfree(V_pf_frent_z, frent); 276 } 277 } else { 278 for (frent = LIST_FIRST(&frag->fr_queue); frent; 279 frent = LIST_FIRST(&frag->fr_queue)) { 280 LIST_REMOVE(frent, fr_next); 281 282 KASSERT((LIST_EMPTY(&frag->fr_queue) || 283 LIST_FIRST(&frag->fr_queue)->fr_off > 284 frent->fr_end), 285 ("! (LIST_EMPTY() || LIST_FIRST()->fr_off >" 286 " frent->fr_end): %s", __func__)); 287 288 uma_zfree(V_pf_frent_z, frent); 289 } 290 } 291 292 pf_remove_fragment(frag); 293 } 294 295 #ifdef INET 296 static void 297 pf_ip2key(struct pf_fragment *key, struct ip *ip) 298 { 299 key->fr_p = ip->ip_p; 300 key->fr_id = ip->ip_id; 301 key->fr_src.s_addr = ip->ip_src.s_addr; 302 key->fr_dst.s_addr = ip->ip_dst.s_addr; 303 } 304 305 static struct pf_fragment * 306 pf_find_fragment(struct ip *ip, struct pf_frag_tree *tree) 307 { 308 struct pf_fragment key; 309 struct pf_fragment *frag; 310 311 PF_FRAG_ASSERT(); 312 313 pf_ip2key(&key, ip); 314 315 frag = RB_FIND(pf_frag_tree, tree, &key); 316 if (frag != NULL) { 317 /* XXX Are we sure we want to update the timeout? */ 318 frag->fr_timeout = time_uptime; 319 if (BUFFER_FRAGMENTS(frag)) { 320 TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next); 321 TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next); 322 } else { 323 TAILQ_REMOVE(&V_pf_cachequeue, frag, frag_next); 324 TAILQ_INSERT_HEAD(&V_pf_cachequeue, frag, frag_next); 325 } 326 } 327 328 return (frag); 329 } 330 #endif /* INET */ 331 332 /* Removes a fragment from the fragment queue and frees the fragment */ 333 334 static void 335 pf_remove_fragment(struct pf_fragment *frag) 336 { 337 338 PF_FRAG_ASSERT(); 339 340 if (BUFFER_FRAGMENTS(frag)) { 341 RB_REMOVE(pf_frag_tree, &V_pf_frag_tree, frag); 342 TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next); 343 uma_zfree(V_pf_frag_z, frag); 344 } else { 345 RB_REMOVE(pf_frag_tree, &V_pf_cache_tree, frag); 346 TAILQ_REMOVE(&V_pf_cachequeue, frag, frag_next); 347 uma_zfree(V_pf_frag_z, frag); 348 } 349 } 350 351 #ifdef INET 352 #define FR_IP_OFF(fr) ((ntohs((fr)->fr_ip->ip_off) & IP_OFFMASK) << 3) 353 static struct mbuf * 354 pf_reassemble(struct mbuf **m0, struct pf_fragment **frag, 355 struct pf_frent *frent, int mff) 356 { 357 struct mbuf *m = *m0, *m2; 358 struct pf_frent *frea, *next; 359 struct pf_frent *frep = NULL; 360 struct ip *ip = frent->fr_ip; 361 int hlen = ip->ip_hl << 2; 362 u_int16_t off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3; 363 u_int16_t ip_len = ntohs(ip->ip_len) - ip->ip_hl * 4; 364 u_int16_t max = ip_len + off; 365 366 PF_FRAG_ASSERT(); 367 KASSERT((*frag == NULL || BUFFER_FRAGMENTS(*frag)), 368 ("! (*frag == NULL || BUFFER_FRAGMENTS(*frag)): %s", __FUNCTION__)); 369 370 /* Strip off ip header */ 371 m->m_data += hlen; 372 m->m_len -= hlen; 373 374 /* Create a new reassembly queue for this packet */ 375 if (*frag == NULL) { 376 *frag = uma_zalloc(V_pf_frag_z, M_NOWAIT); 377 if (*frag == NULL) { 378 pf_flush_fragments(); 379 *frag = uma_zalloc(V_pf_frag_z, M_NOWAIT); 380 if (*frag == NULL) 381 goto drop_fragment; 382 } 383 384 (*frag)->fr_flags = 0; 385 (*frag)->fr_max = 0; 386 (*frag)->fr_src = frent->fr_ip->ip_src; 387 (*frag)->fr_dst = frent->fr_ip->ip_dst; 388 (*frag)->fr_p = frent->fr_ip->ip_p; 389 (*frag)->fr_id = frent->fr_ip->ip_id; 390 (*frag)->fr_timeout = time_uptime; 391 LIST_INIT(&(*frag)->fr_queue); 392 393 RB_INSERT(pf_frag_tree, &V_pf_frag_tree, *frag); 394 TAILQ_INSERT_HEAD(&V_pf_fragqueue, *frag, frag_next); 395 396 /* We do not have a previous fragment */ 397 frep = NULL; 398 goto insert; 399 } 400 401 /* 402 * Find a fragment after the current one: 403 * - off contains the real shifted offset. 404 */ 405 LIST_FOREACH(frea, &(*frag)->fr_queue, fr_next) { 406 if (FR_IP_OFF(frea) > off) 407 break; 408 frep = frea; 409 } 410 411 KASSERT((frep != NULL || frea != NULL), 412 ("!(frep != NULL || frea != NULL): %s", __FUNCTION__));; 413 414 if (frep != NULL && 415 FR_IP_OFF(frep) + ntohs(frep->fr_ip->ip_len) - frep->fr_ip->ip_hl * 416 4 > off) 417 { 418 u_int16_t precut; 419 420 precut = FR_IP_OFF(frep) + ntohs(frep->fr_ip->ip_len) - 421 frep->fr_ip->ip_hl * 4 - off; 422 if (precut >= ip_len) 423 goto drop_fragment; 424 m_adj(frent->fr_m, precut); 425 DPFPRINTF(("overlap -%d\n", precut)); 426 /* Enforce 8 byte boundaries */ 427 ip->ip_off = htons(ntohs(ip->ip_off) + (precut >> 3)); 428 off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3; 429 ip_len -= precut; 430 ip->ip_len = htons(ip_len); 431 } 432 433 for (; frea != NULL && ip_len + off > FR_IP_OFF(frea); 434 frea = next) 435 { 436 u_int16_t aftercut; 437 438 aftercut = ip_len + off - FR_IP_OFF(frea); 439 DPFPRINTF(("adjust overlap %d\n", aftercut)); 440 if (aftercut < ntohs(frea->fr_ip->ip_len) - frea->fr_ip->ip_hl 441 * 4) 442 { 443 frea->fr_ip->ip_len = 444 htons(ntohs(frea->fr_ip->ip_len) - aftercut); 445 frea->fr_ip->ip_off = htons(ntohs(frea->fr_ip->ip_off) + 446 (aftercut >> 3)); 447 m_adj(frea->fr_m, aftercut); 448 break; 449 } 450 451 /* This fragment is completely overlapped, lose it */ 452 next = LIST_NEXT(frea, fr_next); 453 m_freem(frea->fr_m); 454 LIST_REMOVE(frea, fr_next); 455 uma_zfree(V_pf_frent_z, frea); 456 } 457 458 insert: 459 /* Update maximum data size */ 460 if ((*frag)->fr_max < max) 461 (*frag)->fr_max = max; 462 /* This is the last segment */ 463 if (!mff) 464 (*frag)->fr_flags |= PFFRAG_SEENLAST; 465 466 if (frep == NULL) 467 LIST_INSERT_HEAD(&(*frag)->fr_queue, frent, fr_next); 468 else 469 LIST_INSERT_AFTER(frep, frent, fr_next); 470 471 /* Check if we are completely reassembled */ 472 if (!((*frag)->fr_flags & PFFRAG_SEENLAST)) 473 return (NULL); 474 475 /* Check if we have all the data */ 476 off = 0; 477 for (frep = LIST_FIRST(&(*frag)->fr_queue); frep; frep = next) { 478 next = LIST_NEXT(frep, fr_next); 479 480 off += ntohs(frep->fr_ip->ip_len) - frep->fr_ip->ip_hl * 4; 481 if (off < (*frag)->fr_max && 482 (next == NULL || FR_IP_OFF(next) != off)) 483 { 484 DPFPRINTF(("missing fragment at %d, next %d, max %d\n", 485 off, next == NULL ? -1 : FR_IP_OFF(next), 486 (*frag)->fr_max)); 487 return (NULL); 488 } 489 } 490 DPFPRINTF(("%d < %d?\n", off, (*frag)->fr_max)); 491 if (off < (*frag)->fr_max) 492 return (NULL); 493 494 /* We have all the data */ 495 frent = LIST_FIRST(&(*frag)->fr_queue); 496 KASSERT((frent != NULL), ("frent == NULL: %s", __FUNCTION__)); 497 if ((frent->fr_ip->ip_hl << 2) + off > IP_MAXPACKET) { 498 DPFPRINTF(("drop: too big: %d\n", off)); 499 pf_free_fragment(*frag); 500 *frag = NULL; 501 return (NULL); 502 } 503 next = LIST_NEXT(frent, fr_next); 504 505 /* Magic from ip_input */ 506 ip = frent->fr_ip; 507 m = frent->fr_m; 508 m2 = m->m_next; 509 m->m_next = NULL; 510 m_cat(m, m2); 511 uma_zfree(V_pf_frent_z, frent); 512 for (frent = next; frent != NULL; frent = next) { 513 next = LIST_NEXT(frent, fr_next); 514 515 m2 = frent->fr_m; 516 uma_zfree(V_pf_frent_z, frent); 517 m->m_pkthdr.csum_flags &= m2->m_pkthdr.csum_flags; 518 m->m_pkthdr.csum_data += m2->m_pkthdr.csum_data; 519 m_cat(m, m2); 520 } 521 522 while (m->m_pkthdr.csum_data & 0xffff0000) 523 m->m_pkthdr.csum_data = (m->m_pkthdr.csum_data & 0xffff) + 524 (m->m_pkthdr.csum_data >> 16); 525 ip->ip_src = (*frag)->fr_src; 526 ip->ip_dst = (*frag)->fr_dst; 527 528 /* Remove from fragment queue */ 529 pf_remove_fragment(*frag); 530 *frag = NULL; 531 532 hlen = ip->ip_hl << 2; 533 ip->ip_len = htons(off + hlen); 534 m->m_len += hlen; 535 m->m_data -= hlen; 536 537 /* some debugging cruft by sklower, below, will go away soon */ 538 /* XXX this should be done elsewhere */ 539 if (m->m_flags & M_PKTHDR) { 540 int plen = 0; 541 for (m2 = m; m2; m2 = m2->m_next) 542 plen += m2->m_len; 543 m->m_pkthdr.len = plen; 544 } 545 546 DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip->ip_len))); 547 return (m); 548 549 drop_fragment: 550 /* Oops - fail safe - drop packet */ 551 uma_zfree(V_pf_frent_z, frent); 552 m_freem(m); 553 return (NULL); 554 } 555 556 static struct mbuf * 557 pf_fragcache(struct mbuf **m0, struct ip *h, struct pf_fragment **frag, int mff, 558 int drop, int *nomem) 559 { 560 struct mbuf *m = *m0; 561 struct pf_frent *frp, *fra, *cur = NULL; 562 int ip_len = ntohs(h->ip_len) - (h->ip_hl << 2); 563 u_int16_t off = ntohs(h->ip_off) << 3; 564 u_int16_t max = ip_len + off; 565 int hosed = 0; 566 567 PF_FRAG_ASSERT(); 568 KASSERT((*frag == NULL || !BUFFER_FRAGMENTS(*frag)), 569 ("!(*frag == NULL || !BUFFER_FRAGMENTS(*frag)): %s", __FUNCTION__)); 570 571 /* Create a new range queue for this packet */ 572 if (*frag == NULL) { 573 *frag = uma_zalloc(V_pf_frag_z, M_NOWAIT); 574 if (*frag == NULL) { 575 pf_flush_fragments(); 576 *frag = uma_zalloc(V_pf_frag_z, M_NOWAIT); 577 if (*frag == NULL) 578 goto no_mem; 579 } 580 581 /* Get an entry for the queue */ 582 cur = uma_zalloc(V_pf_frent_z, M_NOWAIT); 583 if (cur == NULL) { 584 uma_zfree(V_pf_frag_z, *frag); 585 *frag = NULL; 586 goto no_mem; 587 } 588 589 (*frag)->fr_flags = PFFRAG_NOBUFFER; 590 (*frag)->fr_max = 0; 591 (*frag)->fr_src = h->ip_src; 592 (*frag)->fr_dst = h->ip_dst; 593 (*frag)->fr_p = h->ip_p; 594 (*frag)->fr_id = h->ip_id; 595 (*frag)->fr_timeout = time_uptime; 596 597 cur->fr_off = off; 598 cur->fr_end = max; 599 LIST_INIT(&(*frag)->fr_queue); 600 LIST_INSERT_HEAD(&(*frag)->fr_queue, cur, fr_next); 601 602 RB_INSERT(pf_frag_tree, &V_pf_cache_tree, *frag); 603 TAILQ_INSERT_HEAD(&V_pf_cachequeue, *frag, frag_next); 604 605 DPFPRINTF(("fragcache[%d]: new %d-%d\n", h->ip_id, off, max)); 606 607 goto pass; 608 } 609 610 /* 611 * Find a fragment after the current one: 612 * - off contains the real shifted offset. 613 */ 614 frp = NULL; 615 LIST_FOREACH(fra, &(*frag)->fr_queue, fr_next) { 616 if (fra->fr_off > off) 617 break; 618 frp = fra; 619 } 620 621 KASSERT((frp != NULL || fra != NULL), 622 ("!(frp != NULL || fra != NULL): %s", __FUNCTION__)); 623 624 if (frp != NULL) { 625 int precut; 626 627 precut = frp->fr_end - off; 628 if (precut >= ip_len) { 629 /* Fragment is entirely a duplicate */ 630 DPFPRINTF(("fragcache[%d]: dead (%d-%d) %d-%d\n", 631 h->ip_id, frp->fr_off, frp->fr_end, off, max)); 632 goto drop_fragment; 633 } 634 if (precut == 0) { 635 /* They are adjacent. Fixup cache entry */ 636 DPFPRINTF(("fragcache[%d]: adjacent (%d-%d) %d-%d\n", 637 h->ip_id, frp->fr_off, frp->fr_end, off, max)); 638 frp->fr_end = max; 639 } else if (precut > 0) { 640 /* The first part of this payload overlaps with a 641 * fragment that has already been passed. 642 * Need to trim off the first part of the payload. 643 * But to do so easily, we need to create another 644 * mbuf to throw the original header into. 645 */ 646 647 DPFPRINTF(("fragcache[%d]: chop %d (%d-%d) %d-%d\n", 648 h->ip_id, precut, frp->fr_off, frp->fr_end, off, 649 max)); 650 651 off += precut; 652 max -= precut; 653 /* Update the previous frag to encompass this one */ 654 frp->fr_end = max; 655 656 if (!drop) { 657 /* XXX Optimization opportunity 658 * This is a very heavy way to trim the payload. 659 * we could do it much faster by diddling mbuf 660 * internals but that would be even less legible 661 * than this mbuf magic. For my next trick, 662 * I'll pull a rabbit out of my laptop. 663 */ 664 *m0 = m_dup(m, M_NOWAIT); 665 if (*m0 == NULL) 666 goto no_mem; 667 /* From KAME Project : We have missed this! */ 668 m_adj(*m0, (h->ip_hl << 2) - 669 (*m0)->m_pkthdr.len); 670 671 KASSERT(((*m0)->m_next == NULL), 672 ("(*m0)->m_next != NULL: %s", 673 __FUNCTION__)); 674 m_adj(m, precut + (h->ip_hl << 2)); 675 m_cat(*m0, m); 676 m = *m0; 677 if (m->m_flags & M_PKTHDR) { 678 int plen = 0; 679 struct mbuf *t; 680 for (t = m; t; t = t->m_next) 681 plen += t->m_len; 682 m->m_pkthdr.len = plen; 683 } 684 685 686 h = mtod(m, struct ip *); 687 688 KASSERT(((int)m->m_len == 689 ntohs(h->ip_len) - precut), 690 ("m->m_len != ntohs(h->ip_len) - precut: %s", 691 __FUNCTION__)); 692 h->ip_off = htons(ntohs(h->ip_off) + 693 (precut >> 3)); 694 h->ip_len = htons(ntohs(h->ip_len) - precut); 695 } else { 696 hosed++; 697 } 698 } else { 699 /* There is a gap between fragments */ 700 701 DPFPRINTF(("fragcache[%d]: gap %d (%d-%d) %d-%d\n", 702 h->ip_id, -precut, frp->fr_off, frp->fr_end, off, 703 max)); 704 705 cur = uma_zalloc(V_pf_frent_z, M_NOWAIT); 706 if (cur == NULL) 707 goto no_mem; 708 709 cur->fr_off = off; 710 cur->fr_end = max; 711 LIST_INSERT_AFTER(frp, cur, fr_next); 712 } 713 } 714 715 if (fra != NULL) { 716 int aftercut; 717 int merge = 0; 718 719 aftercut = max - fra->fr_off; 720 if (aftercut == 0) { 721 /* Adjacent fragments */ 722 DPFPRINTF(("fragcache[%d]: adjacent %d-%d (%d-%d)\n", 723 h->ip_id, off, max, fra->fr_off, fra->fr_end)); 724 fra->fr_off = off; 725 merge = 1; 726 } else if (aftercut > 0) { 727 /* Need to chop off the tail of this fragment */ 728 DPFPRINTF(("fragcache[%d]: chop %d %d-%d (%d-%d)\n", 729 h->ip_id, aftercut, off, max, fra->fr_off, 730 fra->fr_end)); 731 fra->fr_off = off; 732 max -= aftercut; 733 734 merge = 1; 735 736 if (!drop) { 737 m_adj(m, -aftercut); 738 if (m->m_flags & M_PKTHDR) { 739 int plen = 0; 740 struct mbuf *t; 741 for (t = m; t; t = t->m_next) 742 plen += t->m_len; 743 m->m_pkthdr.len = plen; 744 } 745 h = mtod(m, struct ip *); 746 KASSERT(((int)m->m_len == ntohs(h->ip_len) - aftercut), 747 ("m->m_len != ntohs(h->ip_len) - aftercut: %s", 748 __FUNCTION__)); 749 h->ip_len = htons(ntohs(h->ip_len) - aftercut); 750 } else { 751 hosed++; 752 } 753 } else if (frp == NULL) { 754 /* There is a gap between fragments */ 755 DPFPRINTF(("fragcache[%d]: gap %d %d-%d (%d-%d)\n", 756 h->ip_id, -aftercut, off, max, fra->fr_off, 757 fra->fr_end)); 758 759 cur = uma_zalloc(V_pf_frent_z, M_NOWAIT); 760 if (cur == NULL) 761 goto no_mem; 762 763 cur->fr_off = off; 764 cur->fr_end = max; 765 LIST_INSERT_BEFORE(fra, cur, fr_next); 766 } 767 768 769 /* Need to glue together two separate fragment descriptors */ 770 if (merge) { 771 if (cur && fra->fr_off <= cur->fr_end) { 772 /* Need to merge in a previous 'cur' */ 773 DPFPRINTF(("fragcache[%d]: adjacent(merge " 774 "%d-%d) %d-%d (%d-%d)\n", 775 h->ip_id, cur->fr_off, cur->fr_end, off, 776 max, fra->fr_off, fra->fr_end)); 777 fra->fr_off = cur->fr_off; 778 LIST_REMOVE(cur, fr_next); 779 uma_zfree(V_pf_frent_z, cur); 780 cur = NULL; 781 782 } else if (frp && fra->fr_off <= frp->fr_end) { 783 /* Need to merge in a modified 'frp' */ 784 KASSERT((cur == NULL), ("cur != NULL: %s", 785 __FUNCTION__)); 786 DPFPRINTF(("fragcache[%d]: adjacent(merge " 787 "%d-%d) %d-%d (%d-%d)\n", 788 h->ip_id, frp->fr_off, frp->fr_end, off, 789 max, fra->fr_off, fra->fr_end)); 790 fra->fr_off = frp->fr_off; 791 LIST_REMOVE(frp, fr_next); 792 uma_zfree(V_pf_frent_z, frp); 793 frp = NULL; 794 795 } 796 } 797 } 798 799 if (hosed) { 800 /* 801 * We must keep tracking the overall fragment even when 802 * we're going to drop it anyway so that we know when to 803 * free the overall descriptor. Thus we drop the frag late. 804 */ 805 goto drop_fragment; 806 } 807 808 809 pass: 810 /* Update maximum data size */ 811 if ((*frag)->fr_max < max) 812 (*frag)->fr_max = max; 813 814 /* This is the last segment */ 815 if (!mff) 816 (*frag)->fr_flags |= PFFRAG_SEENLAST; 817 818 /* Check if we are completely reassembled */ 819 if (((*frag)->fr_flags & PFFRAG_SEENLAST) && 820 LIST_FIRST(&(*frag)->fr_queue)->fr_off == 0 && 821 LIST_FIRST(&(*frag)->fr_queue)->fr_end == (*frag)->fr_max) { 822 /* Remove from fragment queue */ 823 DPFPRINTF(("fragcache[%d]: done 0-%d\n", h->ip_id, 824 (*frag)->fr_max)); 825 pf_free_fragment(*frag); 826 *frag = NULL; 827 } 828 829 return (m); 830 831 no_mem: 832 *nomem = 1; 833 834 /* Still need to pay attention to !IP_MF */ 835 if (!mff && *frag != NULL) 836 (*frag)->fr_flags |= PFFRAG_SEENLAST; 837 838 m_freem(m); 839 return (NULL); 840 841 drop_fragment: 842 843 /* Still need to pay attention to !IP_MF */ 844 if (!mff && *frag != NULL) 845 (*frag)->fr_flags |= PFFRAG_SEENLAST; 846 847 if (drop) { 848 /* This fragment has been deemed bad. Don't reass */ 849 if (((*frag)->fr_flags & PFFRAG_DROP) == 0) 850 DPFPRINTF(("fragcache[%d]: dropping overall fragment\n", 851 h->ip_id)); 852 (*frag)->fr_flags |= PFFRAG_DROP; 853 } 854 855 m_freem(m); 856 return (NULL); 857 } 858 859 int 860 pf_normalize_ip(struct mbuf **m0, int dir, struct pfi_kif *kif, u_short *reason, 861 struct pf_pdesc *pd) 862 { 863 struct mbuf *m = *m0; 864 struct pf_rule *r; 865 struct pf_frent *frent; 866 struct pf_fragment *frag = NULL; 867 struct ip *h = mtod(m, struct ip *); 868 int mff = (ntohs(h->ip_off) & IP_MF); 869 int hlen = h->ip_hl << 2; 870 u_int16_t fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3; 871 u_int16_t max; 872 int ip_len; 873 int ip_off; 874 int tag = -1; 875 876 PF_RULES_RASSERT(); 877 878 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 879 while (r != NULL) { 880 r->evaluations++; 881 if (pfi_kif_match(r->kif, kif) == r->ifnot) 882 r = r->skip[PF_SKIP_IFP].ptr; 883 else if (r->direction && r->direction != dir) 884 r = r->skip[PF_SKIP_DIR].ptr; 885 else if (r->af && r->af != AF_INET) 886 r = r->skip[PF_SKIP_AF].ptr; 887 else if (r->proto && r->proto != h->ip_p) 888 r = r->skip[PF_SKIP_PROTO].ptr; 889 else if (PF_MISMATCHAW(&r->src.addr, 890 (struct pf_addr *)&h->ip_src.s_addr, AF_INET, 891 r->src.neg, kif, M_GETFIB(m))) 892 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 893 else if (PF_MISMATCHAW(&r->dst.addr, 894 (struct pf_addr *)&h->ip_dst.s_addr, AF_INET, 895 r->dst.neg, NULL, M_GETFIB(m))) 896 r = r->skip[PF_SKIP_DST_ADDR].ptr; 897 else if (r->match_tag && !pf_match_tag(m, r, &tag, 898 pd->pf_mtag ? pd->pf_mtag->tag : 0)) 899 r = TAILQ_NEXT(r, entries); 900 else 901 break; 902 } 903 904 if (r == NULL || r->action == PF_NOSCRUB) 905 return (PF_PASS); 906 else { 907 r->packets[dir == PF_OUT]++; 908 r->bytes[dir == PF_OUT] += pd->tot_len; 909 } 910 911 /* Check for illegal packets */ 912 if (hlen < (int)sizeof(struct ip)) 913 goto drop; 914 915 if (hlen > ntohs(h->ip_len)) 916 goto drop; 917 918 /* Clear IP_DF if the rule uses the no-df option */ 919 if (r->rule_flag & PFRULE_NODF && h->ip_off & htons(IP_DF)) { 920 u_int16_t ip_off = h->ip_off; 921 922 h->ip_off &= htons(~IP_DF); 923 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0); 924 } 925 926 /* We will need other tests here */ 927 if (!fragoff && !mff) 928 goto no_fragment; 929 930 /* We're dealing with a fragment now. Don't allow fragments 931 * with IP_DF to enter the cache. If the flag was cleared by 932 * no-df above, fine. Otherwise drop it. 933 */ 934 if (h->ip_off & htons(IP_DF)) { 935 DPFPRINTF(("IP_DF\n")); 936 goto bad; 937 } 938 939 ip_len = ntohs(h->ip_len) - hlen; 940 ip_off = (ntohs(h->ip_off) & IP_OFFMASK) << 3; 941 942 /* All fragments are 8 byte aligned */ 943 if (mff && (ip_len & 0x7)) { 944 DPFPRINTF(("mff and %d\n", ip_len)); 945 goto bad; 946 } 947 948 /* Respect maximum length */ 949 if (fragoff + ip_len > IP_MAXPACKET) { 950 DPFPRINTF(("max packet %d\n", fragoff + ip_len)); 951 goto bad; 952 } 953 max = fragoff + ip_len; 954 955 if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0) { 956 957 /* Fully buffer all of the fragments */ 958 PF_FRAG_LOCK(); 959 frag = pf_find_fragment(h, &V_pf_frag_tree); 960 961 /* Check if we saw the last fragment already */ 962 if (frag != NULL && (frag->fr_flags & PFFRAG_SEENLAST) && 963 max > frag->fr_max) 964 goto bad; 965 966 /* Get an entry for the fragment queue */ 967 frent = uma_zalloc(V_pf_frent_z, M_NOWAIT); 968 if (frent == NULL) { 969 PF_FRAG_UNLOCK(); 970 REASON_SET(reason, PFRES_MEMORY); 971 return (PF_DROP); 972 } 973 frent->fr_ip = h; 974 frent->fr_m = m; 975 976 /* Might return a completely reassembled mbuf, or NULL */ 977 DPFPRINTF(("reass frag %d @ %d-%d\n", h->ip_id, fragoff, max)); 978 *m0 = m = pf_reassemble(m0, &frag, frent, mff); 979 PF_FRAG_UNLOCK(); 980 981 if (m == NULL) 982 return (PF_DROP); 983 984 if (frag != NULL && (frag->fr_flags & PFFRAG_DROP)) 985 goto drop; 986 987 h = mtod(m, struct ip *); 988 } else { 989 /* non-buffering fragment cache (drops or masks overlaps) */ 990 int nomem = 0; 991 992 if (dir == PF_OUT && pd->pf_mtag && 993 pd->pf_mtag->flags & PF_TAG_FRAGCACHE) { 994 /* 995 * Already passed the fragment cache in the 996 * input direction. If we continued, it would 997 * appear to be a dup and would be dropped. 998 */ 999 goto fragment_pass; 1000 } 1001 1002 PF_FRAG_LOCK(); 1003 frag = pf_find_fragment(h, &V_pf_cache_tree); 1004 1005 /* Check if we saw the last fragment already */ 1006 if (frag != NULL && (frag->fr_flags & PFFRAG_SEENLAST) && 1007 max > frag->fr_max) { 1008 if (r->rule_flag & PFRULE_FRAGDROP) 1009 frag->fr_flags |= PFFRAG_DROP; 1010 goto bad; 1011 } 1012 1013 *m0 = m = pf_fragcache(m0, h, &frag, mff, 1014 (r->rule_flag & PFRULE_FRAGDROP) ? 1 : 0, &nomem); 1015 PF_FRAG_UNLOCK(); 1016 if (m == NULL) { 1017 if (nomem) 1018 goto no_mem; 1019 goto drop; 1020 } 1021 1022 if (dir == PF_IN) { 1023 /* Use mtag from copied and trimmed mbuf chain. */ 1024 pd->pf_mtag = pf_get_mtag(m); 1025 if (pd->pf_mtag == NULL) { 1026 m_freem(m); 1027 *m0 = NULL; 1028 goto no_mem; 1029 } 1030 pd->pf_mtag->flags |= PF_TAG_FRAGCACHE; 1031 } 1032 1033 if (frag != NULL && (frag->fr_flags & PFFRAG_DROP)) 1034 goto drop; 1035 goto fragment_pass; 1036 } 1037 1038 no_fragment: 1039 /* At this point, only IP_DF is allowed in ip_off */ 1040 if (h->ip_off & ~htons(IP_DF)) { 1041 u_int16_t ip_off = h->ip_off; 1042 1043 h->ip_off &= htons(IP_DF); 1044 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0); 1045 } 1046 1047 /* not missing a return here */ 1048 1049 fragment_pass: 1050 pf_scrub_ip(&m, r->rule_flag, r->min_ttl, r->set_tos); 1051 1052 if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0) 1053 pd->flags |= PFDESC_IP_REAS; 1054 return (PF_PASS); 1055 1056 no_mem: 1057 REASON_SET(reason, PFRES_MEMORY); 1058 if (r != NULL && r->log) 1059 PFLOG_PACKET(kif, m, AF_INET, dir, *reason, r, NULL, NULL, pd, 1060 1); 1061 return (PF_DROP); 1062 1063 drop: 1064 REASON_SET(reason, PFRES_NORM); 1065 if (r != NULL && r->log) 1066 PFLOG_PACKET(kif, m, AF_INET, dir, *reason, r, NULL, NULL, pd, 1067 1); 1068 return (PF_DROP); 1069 1070 bad: 1071 DPFPRINTF(("dropping bad fragment\n")); 1072 1073 /* Free associated fragments */ 1074 if (frag != NULL) { 1075 pf_free_fragment(frag); 1076 PF_FRAG_UNLOCK(); 1077 } 1078 1079 REASON_SET(reason, PFRES_FRAG); 1080 if (r != NULL && r->log) 1081 PFLOG_PACKET(kif, m, AF_INET, dir, *reason, r, NULL, NULL, pd, 1082 1); 1083 1084 return (PF_DROP); 1085 } 1086 #endif 1087 1088 #ifdef INET6 1089 int 1090 pf_normalize_ip6(struct mbuf **m0, int dir, struct pfi_kif *kif, 1091 u_short *reason, struct pf_pdesc *pd) 1092 { 1093 struct mbuf *m = *m0; 1094 struct pf_rule *r; 1095 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1096 int off; 1097 struct ip6_ext ext; 1098 struct ip6_opt opt; 1099 struct ip6_opt_jumbo jumbo; 1100 struct ip6_frag frag; 1101 u_int32_t jumbolen = 0, plen; 1102 u_int16_t fragoff = 0; 1103 int optend; 1104 int ooff; 1105 u_int8_t proto; 1106 int terminal; 1107 1108 PF_RULES_RASSERT(); 1109 1110 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 1111 while (r != NULL) { 1112 r->evaluations++; 1113 if (pfi_kif_match(r->kif, kif) == r->ifnot) 1114 r = r->skip[PF_SKIP_IFP].ptr; 1115 else if (r->direction && r->direction != dir) 1116 r = r->skip[PF_SKIP_DIR].ptr; 1117 else if (r->af && r->af != AF_INET6) 1118 r = r->skip[PF_SKIP_AF].ptr; 1119 #if 0 /* header chain! */ 1120 else if (r->proto && r->proto != h->ip6_nxt) 1121 r = r->skip[PF_SKIP_PROTO].ptr; 1122 #endif 1123 else if (PF_MISMATCHAW(&r->src.addr, 1124 (struct pf_addr *)&h->ip6_src, AF_INET6, 1125 r->src.neg, kif, M_GETFIB(m))) 1126 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 1127 else if (PF_MISMATCHAW(&r->dst.addr, 1128 (struct pf_addr *)&h->ip6_dst, AF_INET6, 1129 r->dst.neg, NULL, M_GETFIB(m))) 1130 r = r->skip[PF_SKIP_DST_ADDR].ptr; 1131 else 1132 break; 1133 } 1134 1135 if (r == NULL || r->action == PF_NOSCRUB) 1136 return (PF_PASS); 1137 else { 1138 r->packets[dir == PF_OUT]++; 1139 r->bytes[dir == PF_OUT] += pd->tot_len; 1140 } 1141 1142 /* Check for illegal packets */ 1143 if (sizeof(struct ip6_hdr) + IPV6_MAXPACKET < m->m_pkthdr.len) 1144 goto drop; 1145 1146 off = sizeof(struct ip6_hdr); 1147 proto = h->ip6_nxt; 1148 terminal = 0; 1149 do { 1150 switch (proto) { 1151 case IPPROTO_FRAGMENT: 1152 goto fragment; 1153 break; 1154 case IPPROTO_AH: 1155 case IPPROTO_ROUTING: 1156 case IPPROTO_DSTOPTS: 1157 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL, 1158 NULL, AF_INET6)) 1159 goto shortpkt; 1160 if (proto == IPPROTO_AH) 1161 off += (ext.ip6e_len + 2) * 4; 1162 else 1163 off += (ext.ip6e_len + 1) * 8; 1164 proto = ext.ip6e_nxt; 1165 break; 1166 case IPPROTO_HOPOPTS: 1167 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL, 1168 NULL, AF_INET6)) 1169 goto shortpkt; 1170 optend = off + (ext.ip6e_len + 1) * 8; 1171 ooff = off + sizeof(ext); 1172 do { 1173 if (!pf_pull_hdr(m, ooff, &opt.ip6o_type, 1174 sizeof(opt.ip6o_type), NULL, NULL, 1175 AF_INET6)) 1176 goto shortpkt; 1177 if (opt.ip6o_type == IP6OPT_PAD1) { 1178 ooff++; 1179 continue; 1180 } 1181 if (!pf_pull_hdr(m, ooff, &opt, sizeof(opt), 1182 NULL, NULL, AF_INET6)) 1183 goto shortpkt; 1184 if (ooff + sizeof(opt) + opt.ip6o_len > optend) 1185 goto drop; 1186 switch (opt.ip6o_type) { 1187 case IP6OPT_JUMBO: 1188 if (h->ip6_plen != 0) 1189 goto drop; 1190 if (!pf_pull_hdr(m, ooff, &jumbo, 1191 sizeof(jumbo), NULL, NULL, 1192 AF_INET6)) 1193 goto shortpkt; 1194 memcpy(&jumbolen, jumbo.ip6oj_jumbo_len, 1195 sizeof(jumbolen)); 1196 jumbolen = ntohl(jumbolen); 1197 if (jumbolen <= IPV6_MAXPACKET) 1198 goto drop; 1199 if (sizeof(struct ip6_hdr) + jumbolen != 1200 m->m_pkthdr.len) 1201 goto drop; 1202 break; 1203 default: 1204 break; 1205 } 1206 ooff += sizeof(opt) + opt.ip6o_len; 1207 } while (ooff < optend); 1208 1209 off = optend; 1210 proto = ext.ip6e_nxt; 1211 break; 1212 default: 1213 terminal = 1; 1214 break; 1215 } 1216 } while (!terminal); 1217 1218 /* jumbo payload option must be present, or plen > 0 */ 1219 if (ntohs(h->ip6_plen) == 0) 1220 plen = jumbolen; 1221 else 1222 plen = ntohs(h->ip6_plen); 1223 if (plen == 0) 1224 goto drop; 1225 if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len) 1226 goto shortpkt; 1227 1228 pf_scrub_ip6(&m, r->min_ttl); 1229 1230 return (PF_PASS); 1231 1232 fragment: 1233 if (ntohs(h->ip6_plen) == 0 || jumbolen) 1234 goto drop; 1235 plen = ntohs(h->ip6_plen); 1236 1237 if (!pf_pull_hdr(m, off, &frag, sizeof(frag), NULL, NULL, AF_INET6)) 1238 goto shortpkt; 1239 fragoff = ntohs(frag.ip6f_offlg & IP6F_OFF_MASK); 1240 if (fragoff + (plen - off - sizeof(frag)) > IPV6_MAXPACKET) 1241 goto badfrag; 1242 1243 /* do something about it */ 1244 /* remember to set pd->flags |= PFDESC_IP_REAS */ 1245 return (PF_PASS); 1246 1247 shortpkt: 1248 REASON_SET(reason, PFRES_SHORT); 1249 if (r != NULL && r->log) 1250 PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd, 1251 1); 1252 return (PF_DROP); 1253 1254 drop: 1255 REASON_SET(reason, PFRES_NORM); 1256 if (r != NULL && r->log) 1257 PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd, 1258 1); 1259 return (PF_DROP); 1260 1261 badfrag: 1262 REASON_SET(reason, PFRES_FRAG); 1263 if (r != NULL && r->log) 1264 PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd, 1265 1); 1266 return (PF_DROP); 1267 } 1268 #endif /* INET6 */ 1269 1270 int 1271 pf_normalize_tcp(int dir, struct pfi_kif *kif, struct mbuf *m, int ipoff, 1272 int off, void *h, struct pf_pdesc *pd) 1273 { 1274 struct pf_rule *r, *rm = NULL; 1275 struct tcphdr *th = pd->hdr.tcp; 1276 int rewrite = 0; 1277 u_short reason; 1278 u_int8_t flags; 1279 sa_family_t af = pd->af; 1280 1281 PF_RULES_RASSERT(); 1282 1283 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 1284 while (r != NULL) { 1285 r->evaluations++; 1286 if (pfi_kif_match(r->kif, kif) == r->ifnot) 1287 r = r->skip[PF_SKIP_IFP].ptr; 1288 else if (r->direction && r->direction != dir) 1289 r = r->skip[PF_SKIP_DIR].ptr; 1290 else if (r->af && r->af != af) 1291 r = r->skip[PF_SKIP_AF].ptr; 1292 else if (r->proto && r->proto != pd->proto) 1293 r = r->skip[PF_SKIP_PROTO].ptr; 1294 else if (PF_MISMATCHAW(&r->src.addr, pd->src, af, 1295 r->src.neg, kif, M_GETFIB(m))) 1296 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 1297 else if (r->src.port_op && !pf_match_port(r->src.port_op, 1298 r->src.port[0], r->src.port[1], th->th_sport)) 1299 r = r->skip[PF_SKIP_SRC_PORT].ptr; 1300 else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af, 1301 r->dst.neg, NULL, M_GETFIB(m))) 1302 r = r->skip[PF_SKIP_DST_ADDR].ptr; 1303 else if (r->dst.port_op && !pf_match_port(r->dst.port_op, 1304 r->dst.port[0], r->dst.port[1], th->th_dport)) 1305 r = r->skip[PF_SKIP_DST_PORT].ptr; 1306 else if (r->os_fingerprint != PF_OSFP_ANY && !pf_osfp_match( 1307 pf_osfp_fingerprint(pd, m, off, th), 1308 r->os_fingerprint)) 1309 r = TAILQ_NEXT(r, entries); 1310 else { 1311 rm = r; 1312 break; 1313 } 1314 } 1315 1316 if (rm == NULL || rm->action == PF_NOSCRUB) 1317 return (PF_PASS); 1318 else { 1319 r->packets[dir == PF_OUT]++; 1320 r->bytes[dir == PF_OUT] += pd->tot_len; 1321 } 1322 1323 if (rm->rule_flag & PFRULE_REASSEMBLE_TCP) 1324 pd->flags |= PFDESC_TCP_NORM; 1325 1326 flags = th->th_flags; 1327 if (flags & TH_SYN) { 1328 /* Illegal packet */ 1329 if (flags & TH_RST) 1330 goto tcp_drop; 1331 1332 if (flags & TH_FIN) 1333 flags &= ~TH_FIN; 1334 } else { 1335 /* Illegal packet */ 1336 if (!(flags & (TH_ACK|TH_RST))) 1337 goto tcp_drop; 1338 } 1339 1340 if (!(flags & TH_ACK)) { 1341 /* These flags are only valid if ACK is set */ 1342 if ((flags & TH_FIN) || (flags & TH_PUSH) || (flags & TH_URG)) 1343 goto tcp_drop; 1344 } 1345 1346 /* Check for illegal header length */ 1347 if (th->th_off < (sizeof(struct tcphdr) >> 2)) 1348 goto tcp_drop; 1349 1350 /* If flags changed, or reserved data set, then adjust */ 1351 if (flags != th->th_flags || th->th_x2 != 0) { 1352 u_int16_t ov, nv; 1353 1354 ov = *(u_int16_t *)(&th->th_ack + 1); 1355 th->th_flags = flags; 1356 th->th_x2 = 0; 1357 nv = *(u_int16_t *)(&th->th_ack + 1); 1358 1359 th->th_sum = pf_cksum_fixup(th->th_sum, ov, nv, 0); 1360 rewrite = 1; 1361 } 1362 1363 /* Remove urgent pointer, if TH_URG is not set */ 1364 if (!(flags & TH_URG) && th->th_urp) { 1365 th->th_sum = pf_cksum_fixup(th->th_sum, th->th_urp, 0, 0); 1366 th->th_urp = 0; 1367 rewrite = 1; 1368 } 1369 1370 /* Process options */ 1371 if (r->max_mss && pf_normalize_tcpopt(r, m, th, off, pd->af)) 1372 rewrite = 1; 1373 1374 /* copy back packet headers if we sanitized */ 1375 if (rewrite) 1376 m_copyback(m, off, sizeof(*th), (caddr_t)th); 1377 1378 return (PF_PASS); 1379 1380 tcp_drop: 1381 REASON_SET(&reason, PFRES_NORM); 1382 if (rm != NULL && r->log) 1383 PFLOG_PACKET(kif, m, AF_INET, dir, reason, r, NULL, NULL, pd, 1384 1); 1385 return (PF_DROP); 1386 } 1387 1388 int 1389 pf_normalize_tcp_init(struct mbuf *m, int off, struct pf_pdesc *pd, 1390 struct tcphdr *th, struct pf_state_peer *src, struct pf_state_peer *dst) 1391 { 1392 u_int32_t tsval, tsecr; 1393 u_int8_t hdr[60]; 1394 u_int8_t *opt; 1395 1396 KASSERT((src->scrub == NULL), 1397 ("pf_normalize_tcp_init: src->scrub != NULL")); 1398 1399 src->scrub = uma_zalloc(V_pf_state_scrub_z, M_ZERO | M_NOWAIT); 1400 if (src->scrub == NULL) 1401 return (1); 1402 1403 switch (pd->af) { 1404 #ifdef INET 1405 case AF_INET: { 1406 struct ip *h = mtod(m, struct ip *); 1407 src->scrub->pfss_ttl = h->ip_ttl; 1408 break; 1409 } 1410 #endif /* INET */ 1411 #ifdef INET6 1412 case AF_INET6: { 1413 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1414 src->scrub->pfss_ttl = h->ip6_hlim; 1415 break; 1416 } 1417 #endif /* INET6 */ 1418 } 1419 1420 1421 /* 1422 * All normalizations below are only begun if we see the start of 1423 * the connections. They must all set an enabled bit in pfss_flags 1424 */ 1425 if ((th->th_flags & TH_SYN) == 0) 1426 return (0); 1427 1428 1429 if (th->th_off > (sizeof(struct tcphdr) >> 2) && src->scrub && 1430 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) { 1431 /* Diddle with TCP options */ 1432 int hlen; 1433 opt = hdr + sizeof(struct tcphdr); 1434 hlen = (th->th_off << 2) - sizeof(struct tcphdr); 1435 while (hlen >= TCPOLEN_TIMESTAMP) { 1436 switch (*opt) { 1437 case TCPOPT_EOL: /* FALLTHROUGH */ 1438 case TCPOPT_NOP: 1439 opt++; 1440 hlen--; 1441 break; 1442 case TCPOPT_TIMESTAMP: 1443 if (opt[1] >= TCPOLEN_TIMESTAMP) { 1444 src->scrub->pfss_flags |= 1445 PFSS_TIMESTAMP; 1446 src->scrub->pfss_ts_mod = 1447 htonl(arc4random()); 1448 1449 /* note PFSS_PAWS not set yet */ 1450 memcpy(&tsval, &opt[2], 1451 sizeof(u_int32_t)); 1452 memcpy(&tsecr, &opt[6], 1453 sizeof(u_int32_t)); 1454 src->scrub->pfss_tsval0 = ntohl(tsval); 1455 src->scrub->pfss_tsval = ntohl(tsval); 1456 src->scrub->pfss_tsecr = ntohl(tsecr); 1457 getmicrouptime(&src->scrub->pfss_last); 1458 } 1459 /* FALLTHROUGH */ 1460 default: 1461 hlen -= MAX(opt[1], 2); 1462 opt += MAX(opt[1], 2); 1463 break; 1464 } 1465 } 1466 } 1467 1468 return (0); 1469 } 1470 1471 void 1472 pf_normalize_tcp_cleanup(struct pf_state *state) 1473 { 1474 if (state->src.scrub) 1475 uma_zfree(V_pf_state_scrub_z, state->src.scrub); 1476 if (state->dst.scrub) 1477 uma_zfree(V_pf_state_scrub_z, state->dst.scrub); 1478 1479 /* Someday... flush the TCP segment reassembly descriptors. */ 1480 } 1481 1482 int 1483 pf_normalize_tcp_stateful(struct mbuf *m, int off, struct pf_pdesc *pd, 1484 u_short *reason, struct tcphdr *th, struct pf_state *state, 1485 struct pf_state_peer *src, struct pf_state_peer *dst, int *writeback) 1486 { 1487 struct timeval uptime; 1488 u_int32_t tsval, tsecr; 1489 u_int tsval_from_last; 1490 u_int8_t hdr[60]; 1491 u_int8_t *opt; 1492 int copyback = 0; 1493 int got_ts = 0; 1494 1495 KASSERT((src->scrub || dst->scrub), 1496 ("%s: src->scrub && dst->scrub!", __func__)); 1497 1498 /* 1499 * Enforce the minimum TTL seen for this connection. Negate a common 1500 * technique to evade an intrusion detection system and confuse 1501 * firewall state code. 1502 */ 1503 switch (pd->af) { 1504 #ifdef INET 1505 case AF_INET: { 1506 if (src->scrub) { 1507 struct ip *h = mtod(m, struct ip *); 1508 if (h->ip_ttl > src->scrub->pfss_ttl) 1509 src->scrub->pfss_ttl = h->ip_ttl; 1510 h->ip_ttl = src->scrub->pfss_ttl; 1511 } 1512 break; 1513 } 1514 #endif /* INET */ 1515 #ifdef INET6 1516 case AF_INET6: { 1517 if (src->scrub) { 1518 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1519 if (h->ip6_hlim > src->scrub->pfss_ttl) 1520 src->scrub->pfss_ttl = h->ip6_hlim; 1521 h->ip6_hlim = src->scrub->pfss_ttl; 1522 } 1523 break; 1524 } 1525 #endif /* INET6 */ 1526 } 1527 1528 if (th->th_off > (sizeof(struct tcphdr) >> 2) && 1529 ((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) || 1530 (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) && 1531 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) { 1532 /* Diddle with TCP options */ 1533 int hlen; 1534 opt = hdr + sizeof(struct tcphdr); 1535 hlen = (th->th_off << 2) - sizeof(struct tcphdr); 1536 while (hlen >= TCPOLEN_TIMESTAMP) { 1537 switch (*opt) { 1538 case TCPOPT_EOL: /* FALLTHROUGH */ 1539 case TCPOPT_NOP: 1540 opt++; 1541 hlen--; 1542 break; 1543 case TCPOPT_TIMESTAMP: 1544 /* Modulate the timestamps. Can be used for 1545 * NAT detection, OS uptime determination or 1546 * reboot detection. 1547 */ 1548 1549 if (got_ts) { 1550 /* Huh? Multiple timestamps!? */ 1551 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1552 DPFPRINTF(("multiple TS??")); 1553 pf_print_state(state); 1554 printf("\n"); 1555 } 1556 REASON_SET(reason, PFRES_TS); 1557 return (PF_DROP); 1558 } 1559 if (opt[1] >= TCPOLEN_TIMESTAMP) { 1560 memcpy(&tsval, &opt[2], 1561 sizeof(u_int32_t)); 1562 if (tsval && src->scrub && 1563 (src->scrub->pfss_flags & 1564 PFSS_TIMESTAMP)) { 1565 tsval = ntohl(tsval); 1566 pf_change_a(&opt[2], 1567 &th->th_sum, 1568 htonl(tsval + 1569 src->scrub->pfss_ts_mod), 1570 0); 1571 copyback = 1; 1572 } 1573 1574 /* Modulate TS reply iff valid (!0) */ 1575 memcpy(&tsecr, &opt[6], 1576 sizeof(u_int32_t)); 1577 if (tsecr && dst->scrub && 1578 (dst->scrub->pfss_flags & 1579 PFSS_TIMESTAMP)) { 1580 tsecr = ntohl(tsecr) 1581 - dst->scrub->pfss_ts_mod; 1582 pf_change_a(&opt[6], 1583 &th->th_sum, htonl(tsecr), 1584 0); 1585 copyback = 1; 1586 } 1587 got_ts = 1; 1588 } 1589 /* FALLTHROUGH */ 1590 default: 1591 hlen -= MAX(opt[1], 2); 1592 opt += MAX(opt[1], 2); 1593 break; 1594 } 1595 } 1596 if (copyback) { 1597 /* Copyback the options, caller copys back header */ 1598 *writeback = 1; 1599 m_copyback(m, off + sizeof(struct tcphdr), 1600 (th->th_off << 2) - sizeof(struct tcphdr), hdr + 1601 sizeof(struct tcphdr)); 1602 } 1603 } 1604 1605 1606 /* 1607 * Must invalidate PAWS checks on connections idle for too long. 1608 * The fastest allowed timestamp clock is 1ms. That turns out to 1609 * be about 24 days before it wraps. XXX Right now our lowerbound 1610 * TS echo check only works for the first 12 days of a connection 1611 * when the TS has exhausted half its 32bit space 1612 */ 1613 #define TS_MAX_IDLE (24*24*60*60) 1614 #define TS_MAX_CONN (12*24*60*60) /* XXX remove when better tsecr check */ 1615 1616 getmicrouptime(&uptime); 1617 if (src->scrub && (src->scrub->pfss_flags & PFSS_PAWS) && 1618 (uptime.tv_sec - src->scrub->pfss_last.tv_sec > TS_MAX_IDLE || 1619 time_uptime - state->creation > TS_MAX_CONN)) { 1620 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1621 DPFPRINTF(("src idled out of PAWS\n")); 1622 pf_print_state(state); 1623 printf("\n"); 1624 } 1625 src->scrub->pfss_flags = (src->scrub->pfss_flags & ~PFSS_PAWS) 1626 | PFSS_PAWS_IDLED; 1627 } 1628 if (dst->scrub && (dst->scrub->pfss_flags & PFSS_PAWS) && 1629 uptime.tv_sec - dst->scrub->pfss_last.tv_sec > TS_MAX_IDLE) { 1630 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1631 DPFPRINTF(("dst idled out of PAWS\n")); 1632 pf_print_state(state); 1633 printf("\n"); 1634 } 1635 dst->scrub->pfss_flags = (dst->scrub->pfss_flags & ~PFSS_PAWS) 1636 | PFSS_PAWS_IDLED; 1637 } 1638 1639 if (got_ts && src->scrub && dst->scrub && 1640 (src->scrub->pfss_flags & PFSS_PAWS) && 1641 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1642 /* Validate that the timestamps are "in-window". 1643 * RFC1323 describes TCP Timestamp options that allow 1644 * measurement of RTT (round trip time) and PAWS 1645 * (protection against wrapped sequence numbers). PAWS 1646 * gives us a set of rules for rejecting packets on 1647 * long fat pipes (packets that were somehow delayed 1648 * in transit longer than the time it took to send the 1649 * full TCP sequence space of 4Gb). We can use these 1650 * rules and infer a few others that will let us treat 1651 * the 32bit timestamp and the 32bit echoed timestamp 1652 * as sequence numbers to prevent a blind attacker from 1653 * inserting packets into a connection. 1654 * 1655 * RFC1323 tells us: 1656 * - The timestamp on this packet must be greater than 1657 * or equal to the last value echoed by the other 1658 * endpoint. The RFC says those will be discarded 1659 * since it is a dup that has already been acked. 1660 * This gives us a lowerbound on the timestamp. 1661 * timestamp >= other last echoed timestamp 1662 * - The timestamp will be less than or equal to 1663 * the last timestamp plus the time between the 1664 * last packet and now. The RFC defines the max 1665 * clock rate as 1ms. We will allow clocks to be 1666 * up to 10% fast and will allow a total difference 1667 * or 30 seconds due to a route change. And this 1668 * gives us an upperbound on the timestamp. 1669 * timestamp <= last timestamp + max ticks 1670 * We have to be careful here. Windows will send an 1671 * initial timestamp of zero and then initialize it 1672 * to a random value after the 3whs; presumably to 1673 * avoid a DoS by having to call an expensive RNG 1674 * during a SYN flood. Proof MS has at least one 1675 * good security geek. 1676 * 1677 * - The TCP timestamp option must also echo the other 1678 * endpoints timestamp. The timestamp echoed is the 1679 * one carried on the earliest unacknowledged segment 1680 * on the left edge of the sequence window. The RFC 1681 * states that the host will reject any echoed 1682 * timestamps that were larger than any ever sent. 1683 * This gives us an upperbound on the TS echo. 1684 * tescr <= largest_tsval 1685 * - The lowerbound on the TS echo is a little more 1686 * tricky to determine. The other endpoint's echoed 1687 * values will not decrease. But there may be 1688 * network conditions that re-order packets and 1689 * cause our view of them to decrease. For now the 1690 * only lowerbound we can safely determine is that 1691 * the TS echo will never be less than the original 1692 * TS. XXX There is probably a better lowerbound. 1693 * Remove TS_MAX_CONN with better lowerbound check. 1694 * tescr >= other original TS 1695 * 1696 * It is also important to note that the fastest 1697 * timestamp clock of 1ms will wrap its 32bit space in 1698 * 24 days. So we just disable TS checking after 24 1699 * days of idle time. We actually must use a 12d 1700 * connection limit until we can come up with a better 1701 * lowerbound to the TS echo check. 1702 */ 1703 struct timeval delta_ts; 1704 int ts_fudge; 1705 1706 1707 /* 1708 * PFTM_TS_DIFF is how many seconds of leeway to allow 1709 * a host's timestamp. This can happen if the previous 1710 * packet got delayed in transit for much longer than 1711 * this packet. 1712 */ 1713 if ((ts_fudge = state->rule.ptr->timeout[PFTM_TS_DIFF]) == 0) 1714 ts_fudge = V_pf_default_rule.timeout[PFTM_TS_DIFF]; 1715 1716 /* Calculate max ticks since the last timestamp */ 1717 #define TS_MAXFREQ 1100 /* RFC max TS freq of 1Khz + 10% skew */ 1718 #define TS_MICROSECS 1000000 /* microseconds per second */ 1719 delta_ts = uptime; 1720 timevalsub(&delta_ts, &src->scrub->pfss_last); 1721 tsval_from_last = (delta_ts.tv_sec + ts_fudge) * TS_MAXFREQ; 1722 tsval_from_last += delta_ts.tv_usec / (TS_MICROSECS/TS_MAXFREQ); 1723 1724 if ((src->state >= TCPS_ESTABLISHED && 1725 dst->state >= TCPS_ESTABLISHED) && 1726 (SEQ_LT(tsval, dst->scrub->pfss_tsecr) || 1727 SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) || 1728 (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) || 1729 SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) { 1730 /* Bad RFC1323 implementation or an insertion attack. 1731 * 1732 * - Solaris 2.6 and 2.7 are known to send another ACK 1733 * after the FIN,FIN|ACK,ACK closing that carries 1734 * an old timestamp. 1735 */ 1736 1737 DPFPRINTF(("Timestamp failed %c%c%c%c\n", 1738 SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '0' : ' ', 1739 SEQ_GT(tsval, src->scrub->pfss_tsval + 1740 tsval_from_last) ? '1' : ' ', 1741 SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ', 1742 SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' ')); 1743 DPFPRINTF((" tsval: %u tsecr: %u +ticks: %u " 1744 "idle: %jus %lums\n", 1745 tsval, tsecr, tsval_from_last, 1746 (uintmax_t)delta_ts.tv_sec, 1747 delta_ts.tv_usec / 1000)); 1748 DPFPRINTF((" src->tsval: %u tsecr: %u\n", 1749 src->scrub->pfss_tsval, src->scrub->pfss_tsecr)); 1750 DPFPRINTF((" dst->tsval: %u tsecr: %u tsval0: %u" 1751 "\n", dst->scrub->pfss_tsval, 1752 dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0)); 1753 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1754 pf_print_state(state); 1755 pf_print_flags(th->th_flags); 1756 printf("\n"); 1757 } 1758 REASON_SET(reason, PFRES_TS); 1759 return (PF_DROP); 1760 } 1761 1762 /* XXX I'd really like to require tsecr but it's optional */ 1763 1764 } else if (!got_ts && (th->th_flags & TH_RST) == 0 && 1765 ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED) 1766 || pd->p_len > 0 || (th->th_flags & TH_SYN)) && 1767 src->scrub && dst->scrub && 1768 (src->scrub->pfss_flags & PFSS_PAWS) && 1769 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1770 /* Didn't send a timestamp. Timestamps aren't really useful 1771 * when: 1772 * - connection opening or closing (often not even sent). 1773 * but we must not let an attacker to put a FIN on a 1774 * data packet to sneak it through our ESTABLISHED check. 1775 * - on a TCP reset. RFC suggests not even looking at TS. 1776 * - on an empty ACK. The TS will not be echoed so it will 1777 * probably not help keep the RTT calculation in sync and 1778 * there isn't as much danger when the sequence numbers 1779 * got wrapped. So some stacks don't include TS on empty 1780 * ACKs :-( 1781 * 1782 * To minimize the disruption to mostly RFC1323 conformant 1783 * stacks, we will only require timestamps on data packets. 1784 * 1785 * And what do ya know, we cannot require timestamps on data 1786 * packets. There appear to be devices that do legitimate 1787 * TCP connection hijacking. There are HTTP devices that allow 1788 * a 3whs (with timestamps) and then buffer the HTTP request. 1789 * If the intermediate device has the HTTP response cache, it 1790 * will spoof the response but not bother timestamping its 1791 * packets. So we can look for the presence of a timestamp in 1792 * the first data packet and if there, require it in all future 1793 * packets. 1794 */ 1795 1796 if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) { 1797 /* 1798 * Hey! Someone tried to sneak a packet in. Or the 1799 * stack changed its RFC1323 behavior?!?! 1800 */ 1801 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1802 DPFPRINTF(("Did not receive expected RFC1323 " 1803 "timestamp\n")); 1804 pf_print_state(state); 1805 pf_print_flags(th->th_flags); 1806 printf("\n"); 1807 } 1808 REASON_SET(reason, PFRES_TS); 1809 return (PF_DROP); 1810 } 1811 } 1812 1813 1814 /* 1815 * We will note if a host sends his data packets with or without 1816 * timestamps. And require all data packets to contain a timestamp 1817 * if the first does. PAWS implicitly requires that all data packets be 1818 * timestamped. But I think there are middle-man devices that hijack 1819 * TCP streams immediately after the 3whs and don't timestamp their 1820 * packets (seen in a WWW accelerator or cache). 1821 */ 1822 if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags & 1823 (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) { 1824 if (got_ts) 1825 src->scrub->pfss_flags |= PFSS_DATA_TS; 1826 else { 1827 src->scrub->pfss_flags |= PFSS_DATA_NOTS; 1828 if (V_pf_status.debug >= PF_DEBUG_MISC && dst->scrub && 1829 (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) { 1830 /* Don't warn if other host rejected RFC1323 */ 1831 DPFPRINTF(("Broken RFC1323 stack did not " 1832 "timestamp data packet. Disabled PAWS " 1833 "security.\n")); 1834 pf_print_state(state); 1835 pf_print_flags(th->th_flags); 1836 printf("\n"); 1837 } 1838 } 1839 } 1840 1841 1842 /* 1843 * Update PAWS values 1844 */ 1845 if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags & 1846 (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) { 1847 getmicrouptime(&src->scrub->pfss_last); 1848 if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) || 1849 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1850 src->scrub->pfss_tsval = tsval; 1851 1852 if (tsecr) { 1853 if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) || 1854 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1855 src->scrub->pfss_tsecr = tsecr; 1856 1857 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 && 1858 (SEQ_LT(tsval, src->scrub->pfss_tsval0) || 1859 src->scrub->pfss_tsval0 == 0)) { 1860 /* tsval0 MUST be the lowest timestamp */ 1861 src->scrub->pfss_tsval0 = tsval; 1862 } 1863 1864 /* Only fully initialized after a TS gets echoed */ 1865 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0) 1866 src->scrub->pfss_flags |= PFSS_PAWS; 1867 } 1868 } 1869 1870 /* I have a dream.... TCP segment reassembly.... */ 1871 return (0); 1872 } 1873 1874 static int 1875 pf_normalize_tcpopt(struct pf_rule *r, struct mbuf *m, struct tcphdr *th, 1876 int off, sa_family_t af) 1877 { 1878 u_int16_t *mss; 1879 int thoff; 1880 int opt, cnt, optlen = 0; 1881 int rewrite = 0; 1882 u_char opts[TCP_MAXOLEN]; 1883 u_char *optp = opts; 1884 1885 thoff = th->th_off << 2; 1886 cnt = thoff - sizeof(struct tcphdr); 1887 1888 if (cnt > 0 && !pf_pull_hdr(m, off + sizeof(*th), opts, cnt, 1889 NULL, NULL, af)) 1890 return (rewrite); 1891 1892 for (; cnt > 0; cnt -= optlen, optp += optlen) { 1893 opt = optp[0]; 1894 if (opt == TCPOPT_EOL) 1895 break; 1896 if (opt == TCPOPT_NOP) 1897 optlen = 1; 1898 else { 1899 if (cnt < 2) 1900 break; 1901 optlen = optp[1]; 1902 if (optlen < 2 || optlen > cnt) 1903 break; 1904 } 1905 switch (opt) { 1906 case TCPOPT_MAXSEG: 1907 mss = (u_int16_t *)(optp + 2); 1908 if ((ntohs(*mss)) > r->max_mss) { 1909 th->th_sum = pf_cksum_fixup(th->th_sum, 1910 *mss, htons(r->max_mss), 0); 1911 *mss = htons(r->max_mss); 1912 rewrite = 1; 1913 } 1914 break; 1915 default: 1916 break; 1917 } 1918 } 1919 1920 if (rewrite) 1921 m_copyback(m, off + sizeof(*th), thoff - sizeof(*th), opts); 1922 1923 return (rewrite); 1924 } 1925 1926 #ifdef INET 1927 static void 1928 pf_scrub_ip(struct mbuf **m0, u_int32_t flags, u_int8_t min_ttl, u_int8_t tos) 1929 { 1930 struct mbuf *m = *m0; 1931 struct ip *h = mtod(m, struct ip *); 1932 1933 /* Clear IP_DF if no-df was requested */ 1934 if (flags & PFRULE_NODF && h->ip_off & htons(IP_DF)) { 1935 u_int16_t ip_off = h->ip_off; 1936 1937 h->ip_off &= htons(~IP_DF); 1938 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0); 1939 } 1940 1941 /* Enforce a minimum ttl, may cause endless packet loops */ 1942 if (min_ttl && h->ip_ttl < min_ttl) { 1943 u_int16_t ip_ttl = h->ip_ttl; 1944 1945 h->ip_ttl = min_ttl; 1946 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0); 1947 } 1948 1949 /* Enforce tos */ 1950 if (flags & PFRULE_SET_TOS) { 1951 u_int16_t ov, nv; 1952 1953 ov = *(u_int16_t *)h; 1954 h->ip_tos = tos; 1955 nv = *(u_int16_t *)h; 1956 1957 h->ip_sum = pf_cksum_fixup(h->ip_sum, ov, nv, 0); 1958 } 1959 1960 /* random-id, but not for fragments */ 1961 if (flags & PFRULE_RANDOMID && !(h->ip_off & ~htons(IP_DF))) { 1962 u_int16_t ip_id = h->ip_id; 1963 1964 h->ip_id = ip_randomid(); 1965 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_id, h->ip_id, 0); 1966 } 1967 } 1968 #endif /* INET */ 1969 1970 #ifdef INET6 1971 static void 1972 pf_scrub_ip6(struct mbuf **m0, u_int8_t min_ttl) 1973 { 1974 struct mbuf *m = *m0; 1975 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1976 1977 /* Enforce a minimum ttl, may cause endless packet loops */ 1978 if (min_ttl && h->ip6_hlim < min_ttl) 1979 h->ip6_hlim = min_ttl; 1980 } 1981 #endif 1982