1 /* $NetBSD: pf_norm.c,v 1.27 2013/10/20 21:05:47 christos Exp $ */ 2 /* $OpenBSD: pf_norm.c,v 1.109 2007/05/28 17:16:39 henning Exp $ */ 3 4 /* 5 * Copyright 2001 Niels Provos <provos@citi.umich.edu> 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 #include <sys/cdefs.h> 30 __KERNEL_RCSID(0, "$NetBSD: pf_norm.c,v 1.27 2013/10/20 21:05:47 christos Exp $"); 31 32 #ifdef _KERNEL_OPT 33 #include "opt_inet.h" 34 #endif 35 36 #include "pflog.h" 37 38 #include <sys/param.h> 39 #include <sys/systm.h> 40 #include <sys/mbuf.h> 41 #include <sys/filio.h> 42 #include <sys/fcntl.h> 43 #include <sys/socket.h> 44 #include <sys/kernel.h> 45 #include <sys/time.h> 46 #include <sys/pool.h> 47 48 #ifdef __NetBSD__ 49 #include <sys/rnd.h> 50 #include <sys/cprng.h> 51 #else 52 #include <dev/rndvar.h> 53 #endif /* !__NetBSD__ */ 54 #include <net/if.h> 55 #include <net/if_types.h> 56 #include <net/bpf.h> 57 #include <net/route.h> 58 #include <net/if_pflog.h> 59 60 #include <netinet/in.h> 61 #include <netinet/in_var.h> 62 #include <netinet/in_systm.h> 63 #include <netinet/ip.h> 64 #include <netinet/ip_var.h> 65 #include <netinet/tcp.h> 66 #include <netinet/tcp_seq.h> 67 #include <netinet/udp.h> 68 #include <netinet/ip_icmp.h> 69 70 #ifdef INET6 71 #include <netinet/ip6.h> 72 #endif /* INET6 */ 73 74 #include <net/pfvar.h> 75 76 struct pf_frent { 77 LIST_ENTRY(pf_frent) fr_next; 78 struct ip *fr_ip; 79 struct mbuf *fr_m; 80 }; 81 82 struct pf_frcache { 83 LIST_ENTRY(pf_frcache) fr_next; 84 uint16_t fr_off; 85 uint16_t fr_end; 86 }; 87 88 #define PFFRAG_SEENLAST 0x0001 /* Seen the last fragment for this */ 89 #define PFFRAG_NOBUFFER 0x0002 /* Non-buffering fragment cache */ 90 #define PFFRAG_DROP 0x0004 /* Drop all fragments */ 91 #define BUFFER_FRAGMENTS(fr) (!((fr)->fr_flags & PFFRAG_NOBUFFER)) 92 93 struct pf_fragment { 94 RB_ENTRY(pf_fragment) fr_entry; 95 TAILQ_ENTRY(pf_fragment) frag_next; 96 struct in_addr fr_src; 97 struct in_addr fr_dst; 98 u_int8_t fr_p; /* protocol of this fragment */ 99 u_int8_t fr_flags; /* status flags */ 100 u_int16_t fr_id; /* fragment id for reassemble */ 101 u_int16_t fr_max; /* fragment data max */ 102 u_int32_t fr_timeout; 103 #define fr_queue fr_u.fru_queue 104 #define fr_cache fr_u.fru_cache 105 union { 106 LIST_HEAD(pf_fragq, pf_frent) fru_queue; /* buffering */ 107 LIST_HEAD(pf_cacheq, pf_frcache) fru_cache; /* non-buf */ 108 } fr_u; 109 }; 110 111 TAILQ_HEAD(pf_fragqueue, pf_fragment) pf_fragqueue; 112 TAILQ_HEAD(pf_cachequeue, pf_fragment) pf_cachequeue; 113 114 static __inline int pf_frag_compare(struct pf_fragment *, 115 struct pf_fragment *); 116 RB_HEAD(pf_frag_tree, pf_fragment) pf_frag_tree, pf_cache_tree; 117 RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); 118 RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); 119 120 /* Private prototypes */ 121 void pf_ip2key(struct pf_fragment *, struct ip *); 122 void pf_remove_fragment(struct pf_fragment *); 123 void pf_flush_fragments(void); 124 void pf_free_fragment(struct pf_fragment *); 125 struct pf_fragment *pf_find_fragment(struct ip *, struct pf_frag_tree *); 126 struct mbuf *pf_reassemble(struct mbuf **, struct pf_fragment **, 127 struct pf_frent *, int); 128 struct mbuf *pf_fragcache(struct mbuf **, struct ip*, 129 struct pf_fragment **, int, int, int *); 130 int pf_normalize_tcpopt(struct pf_rule *, struct mbuf *, 131 struct tcphdr *, int); 132 133 #define DPFPRINTF(x) do { \ 134 if (pf_status.debug >= PF_DEBUG_MISC) { \ 135 printf("%s: ", __func__); \ 136 printf x ; \ 137 } \ 138 } while(0) 139 140 /* Globals */ 141 struct pool pf_frent_pl, pf_frag_pl, pf_cache_pl, pf_cent_pl; 142 struct pool pf_state_scrub_pl; 143 int pf_nfrents, pf_ncache; 144 145 void 146 pf_normalize_init(void) 147 { 148 #ifdef __NetBSD__ 149 pool_init(&pf_frent_pl, sizeof(struct pf_frent), 0, 0, 0, "pffrent", 150 NULL, IPL_SOFTNET); 151 pool_init(&pf_frag_pl, sizeof(struct pf_fragment), 0, 0, 0, "pffrag", 152 NULL, IPL_SOFTNET); 153 pool_init(&pf_cache_pl, sizeof(struct pf_fragment), 0, 0, 0, 154 "pffrcache", NULL, IPL_SOFTNET); 155 pool_init(&pf_cent_pl, sizeof(struct pf_frcache), 0, 0, 0, "pffrcent", 156 NULL, IPL_SOFTNET); 157 pool_init(&pf_state_scrub_pl, sizeof(struct pf_state_scrub), 0, 0, 0, 158 "pfstscr", NULL, IPL_SOFTNET); 159 #else 160 pool_init(&pf_frent_pl, sizeof(struct pf_frent), 0, 0, 0, "pffrent", 161 NULL); 162 pool_init(&pf_frag_pl, sizeof(struct pf_fragment), 0, 0, 0, "pffrag", 163 NULL); 164 pool_init(&pf_cache_pl, sizeof(struct pf_fragment), 0, 0, 0, 165 "pffrcache", NULL); 166 pool_init(&pf_cent_pl, sizeof(struct pf_frcache), 0, 0, 0, "pffrcent", 167 NULL); 168 pool_init(&pf_state_scrub_pl, sizeof(struct pf_state_scrub), 0, 0, 0, 169 "pfstscr", NULL); 170 #endif /* !__NetBSD__ */ 171 172 pool_sethiwat(&pf_frag_pl, PFFRAG_FRAG_HIWAT); 173 pool_sethardlimit(&pf_frent_pl, PFFRAG_FRENT_HIWAT, NULL, 0); 174 pool_sethardlimit(&pf_cache_pl, PFFRAG_FRCACHE_HIWAT, NULL, 0); 175 pool_sethardlimit(&pf_cent_pl, PFFRAG_FRCENT_HIWAT, NULL, 0); 176 177 TAILQ_INIT(&pf_fragqueue); 178 TAILQ_INIT(&pf_cachequeue); 179 } 180 181 #ifdef _MODULE 182 void 183 pf_normalize_destroy(void) 184 { 185 pool_destroy(&pf_state_scrub_pl); 186 pool_destroy(&pf_cent_pl); 187 pool_destroy(&pf_cache_pl); 188 pool_destroy(&pf_frag_pl); 189 pool_destroy(&pf_frent_pl); 190 } 191 #endif /* _MODULE */ 192 193 static __inline int 194 pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b) 195 { 196 int diff; 197 198 if ((diff = a->fr_id - b->fr_id)) 199 return (diff); 200 else if ((diff = a->fr_p - b->fr_p)) 201 return (diff); 202 else if (a->fr_src.s_addr < b->fr_src.s_addr) 203 return (-1); 204 else if (a->fr_src.s_addr > b->fr_src.s_addr) 205 return (1); 206 else if (a->fr_dst.s_addr < b->fr_dst.s_addr) 207 return (-1); 208 else if (a->fr_dst.s_addr > b->fr_dst.s_addr) 209 return (1); 210 return (0); 211 } 212 213 void 214 pf_purge_expired_fragments(void) 215 { 216 struct pf_fragment *frag; 217 u_int32_t expire = time_second - 218 pf_default_rule.timeout[PFTM_FRAG]; 219 220 while ((frag = TAILQ_LAST(&pf_fragqueue, pf_fragqueue)) != NULL) { 221 KASSERT(BUFFER_FRAGMENTS(frag)); 222 if (frag->fr_timeout > expire) 223 break; 224 225 DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag)); 226 pf_free_fragment(frag); 227 } 228 229 while ((frag = TAILQ_LAST(&pf_cachequeue, pf_cachequeue)) != NULL) { 230 KASSERT(!BUFFER_FRAGMENTS(frag)); 231 if (frag->fr_timeout > expire) 232 break; 233 234 DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag)); 235 pf_free_fragment(frag); 236 KASSERT(TAILQ_EMPTY(&pf_cachequeue) || 237 TAILQ_LAST(&pf_cachequeue, pf_cachequeue) != frag); 238 } 239 } 240 241 /* 242 * Try to flush old fragments to make space for new ones 243 */ 244 245 void 246 pf_flush_fragments(void) 247 { 248 struct pf_fragment *frag; 249 int goal; 250 251 goal = pf_nfrents * 9 / 10; 252 DPFPRINTF(("trying to free > %d frents\n", 253 pf_nfrents - goal)); 254 while (goal < pf_nfrents) { 255 frag = TAILQ_LAST(&pf_fragqueue, pf_fragqueue); 256 if (frag == NULL) 257 break; 258 pf_free_fragment(frag); 259 } 260 261 262 goal = pf_ncache * 9 / 10; 263 DPFPRINTF(("trying to free > %d cache entries\n", 264 pf_ncache - goal)); 265 while (goal < pf_ncache) { 266 frag = TAILQ_LAST(&pf_cachequeue, pf_cachequeue); 267 if (frag == NULL) 268 break; 269 pf_free_fragment(frag); 270 } 271 } 272 273 /* Frees the fragments and all associated entries */ 274 275 void 276 pf_free_fragment(struct pf_fragment *frag) 277 { 278 struct pf_frent *frent; 279 struct pf_frcache *frcache; 280 281 /* Free all fragments */ 282 if (BUFFER_FRAGMENTS(frag)) { 283 for (frent = LIST_FIRST(&frag->fr_queue); frent; 284 frent = LIST_FIRST(&frag->fr_queue)) { 285 LIST_REMOVE(frent, fr_next); 286 287 m_freem(frent->fr_m); 288 pool_put(&pf_frent_pl, frent); 289 pf_nfrents--; 290 } 291 } else { 292 for (frcache = LIST_FIRST(&frag->fr_cache); frcache; 293 frcache = LIST_FIRST(&frag->fr_cache)) { 294 LIST_REMOVE(frcache, fr_next); 295 296 KASSERT(LIST_EMPTY(&frag->fr_cache) || 297 LIST_FIRST(&frag->fr_cache)->fr_off > 298 frcache->fr_end); 299 300 pool_put(&pf_cent_pl, frcache); 301 pf_ncache--; 302 } 303 } 304 305 pf_remove_fragment(frag); 306 } 307 308 void 309 pf_ip2key(struct pf_fragment *key, struct ip *ip) 310 { 311 key->fr_p = ip->ip_p; 312 key->fr_id = ip->ip_id; 313 key->fr_src.s_addr = ip->ip_src.s_addr; 314 key->fr_dst.s_addr = ip->ip_dst.s_addr; 315 } 316 317 struct pf_fragment * 318 pf_find_fragment(struct ip *ip, struct pf_frag_tree *tree) 319 { 320 struct pf_fragment key; 321 struct pf_fragment *frag; 322 323 pf_ip2key(&key, ip); 324 325 frag = RB_FIND(pf_frag_tree, tree, &key); 326 if (frag != NULL) { 327 /* XXX Are we sure we want to update the timeout? */ 328 frag->fr_timeout = time_second; 329 if (BUFFER_FRAGMENTS(frag)) { 330 TAILQ_REMOVE(&pf_fragqueue, frag, frag_next); 331 TAILQ_INSERT_HEAD(&pf_fragqueue, frag, frag_next); 332 } else { 333 TAILQ_REMOVE(&pf_cachequeue, frag, frag_next); 334 TAILQ_INSERT_HEAD(&pf_cachequeue, frag, frag_next); 335 } 336 } 337 338 return (frag); 339 } 340 341 /* Removes a fragment from the fragment queue and frees the fragment */ 342 343 void 344 pf_remove_fragment(struct pf_fragment *frag) 345 { 346 if (BUFFER_FRAGMENTS(frag)) { 347 RB_REMOVE(pf_frag_tree, &pf_frag_tree, frag); 348 TAILQ_REMOVE(&pf_fragqueue, frag, frag_next); 349 pool_put(&pf_frag_pl, frag); 350 } else { 351 RB_REMOVE(pf_frag_tree, &pf_cache_tree, frag); 352 TAILQ_REMOVE(&pf_cachequeue, frag, frag_next); 353 pool_put(&pf_cache_pl, frag); 354 } 355 } 356 357 #define FR_IP_OFF(fr) ((ntohs((fr)->fr_ip->ip_off) & IP_OFFMASK) << 3) 358 struct mbuf * 359 pf_reassemble(struct mbuf **m0, struct pf_fragment **frag, 360 struct pf_frent *frent, int mff) 361 { 362 struct mbuf *m = *m0, *m2; 363 struct pf_frent *frea, *next; 364 struct pf_frent *frep = NULL; 365 struct ip *ip = frent->fr_ip; 366 int hlen = ip->ip_hl << 2; 367 u_int16_t off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3; 368 u_int16_t ip_len = ntohs(ip->ip_len) - ip->ip_hl * 4; 369 u_int16_t frmax = ip_len + off; 370 371 KASSERT(*frag == NULL || BUFFER_FRAGMENTS(*frag)); 372 373 /* Strip off ip header */ 374 m->m_data += hlen; 375 m->m_len -= hlen; 376 377 /* Create a new reassembly queue for this packet */ 378 if (*frag == NULL) { 379 *frag = pool_get(&pf_frag_pl, PR_NOWAIT); 380 if (*frag == NULL) { 381 pf_flush_fragments(); 382 *frag = pool_get(&pf_frag_pl, PR_NOWAIT); 383 if (*frag == NULL) 384 goto drop_fragment; 385 } 386 387 (*frag)->fr_flags = 0; 388 (*frag)->fr_max = 0; 389 (*frag)->fr_src = frent->fr_ip->ip_src; 390 (*frag)->fr_dst = frent->fr_ip->ip_dst; 391 (*frag)->fr_p = frent->fr_ip->ip_p; 392 (*frag)->fr_id = frent->fr_ip->ip_id; 393 (*frag)->fr_timeout = time_second; 394 LIST_INIT(&(*frag)->fr_queue); 395 396 RB_INSERT(pf_frag_tree, &pf_frag_tree, *frag); 397 TAILQ_INSERT_HEAD(&pf_fragqueue, *frag, frag_next); 398 399 /* We do not have a previous fragment */ 400 frep = NULL; 401 goto insert; 402 } 403 404 /* 405 * Find a fragment after the current one: 406 * - off contains the real shifted offset. 407 */ 408 LIST_FOREACH(frea, &(*frag)->fr_queue, fr_next) { 409 if (FR_IP_OFF(frea) > off) 410 break; 411 frep = frea; 412 } 413 414 KASSERT(frep != NULL || frea != NULL); 415 416 if (frep != NULL && 417 FR_IP_OFF(frep) + ntohs(frep->fr_ip->ip_len) - frep->fr_ip->ip_hl * 418 4 > off) 419 { 420 u_int16_t precut; 421 422 precut = FR_IP_OFF(frep) + ntohs(frep->fr_ip->ip_len) - 423 frep->fr_ip->ip_hl * 4 - off; 424 if (precut >= ip_len) 425 goto drop_fragment; 426 m_adj(frent->fr_m, precut); 427 DPFPRINTF(("overlap -%d\n", precut)); 428 /* Enforce 8 byte boundaries */ 429 ip->ip_off = htons(ntohs(ip->ip_off) + (precut >> 3)); 430 off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3; 431 ip_len -= precut; 432 ip->ip_len = htons(ip_len); 433 } 434 435 for (; frea != NULL && ip_len + off > FR_IP_OFF(frea); 436 frea = next) 437 { 438 u_int16_t aftercut; 439 440 aftercut = ip_len + off - FR_IP_OFF(frea); 441 DPFPRINTF(("adjust overlap %d\n", aftercut)); 442 if (aftercut < ntohs(frea->fr_ip->ip_len) - frea->fr_ip->ip_hl 443 * 4) 444 { 445 frea->fr_ip->ip_len = 446 htons(ntohs(frea->fr_ip->ip_len) - aftercut); 447 frea->fr_ip->ip_off = htons(ntohs(frea->fr_ip->ip_off) + 448 (aftercut >> 3)); 449 m_adj(frea->fr_m, aftercut); 450 break; 451 } 452 453 /* This fragment is completely overlapped, lose it */ 454 next = LIST_NEXT(frea, fr_next); 455 m_freem(frea->fr_m); 456 LIST_REMOVE(frea, fr_next); 457 pool_put(&pf_frent_pl, frea); 458 pf_nfrents--; 459 } 460 461 insert: 462 /* Update maximum data size */ 463 if ((*frag)->fr_max < frmax) 464 (*frag)->fr_max = frmax; 465 /* This is the last segment */ 466 if (!mff) 467 (*frag)->fr_flags |= PFFRAG_SEENLAST; 468 469 if (frep == NULL) 470 LIST_INSERT_HEAD(&(*frag)->fr_queue, frent, fr_next); 471 else 472 LIST_INSERT_AFTER(frep, frent, fr_next); 473 474 /* Check if we are completely reassembled */ 475 if (!((*frag)->fr_flags & PFFRAG_SEENLAST)) 476 return (NULL); 477 478 /* Check if we have all the data */ 479 off = 0; 480 for (frep = LIST_FIRST(&(*frag)->fr_queue); frep; frep = next) { 481 next = LIST_NEXT(frep, fr_next); 482 483 off += ntohs(frep->fr_ip->ip_len) - frep->fr_ip->ip_hl * 4; 484 if (off < (*frag)->fr_max && 485 (next == NULL || FR_IP_OFF(next) != off)) 486 { 487 DPFPRINTF(("missing fragment at %d, next %d, max %d\n", 488 off, next == NULL ? -1 : FR_IP_OFF(next), 489 (*frag)->fr_max)); 490 return (NULL); 491 } 492 } 493 DPFPRINTF(("%d < %d?\n", off, (*frag)->fr_max)); 494 if (off < (*frag)->fr_max) 495 return (NULL); 496 497 /* We have all the data */ 498 frent = LIST_FIRST(&(*frag)->fr_queue); 499 KASSERT(frent != NULL); 500 if ((frent->fr_ip->ip_hl << 2) + off > IP_MAXPACKET) { 501 DPFPRINTF(("drop: too big: %d\n", off)); 502 pf_free_fragment(*frag); 503 *frag = NULL; 504 return (NULL); 505 } 506 next = LIST_NEXT(frent, fr_next); 507 508 /* Magic from ip_input */ 509 ip = frent->fr_ip; 510 m = frent->fr_m; 511 m2 = m->m_next; 512 m->m_next = NULL; 513 m_cat(m, m2); 514 pool_put(&pf_frent_pl, frent); 515 pf_nfrents--; 516 for (frent = next; frent != NULL; frent = next) { 517 next = LIST_NEXT(frent, fr_next); 518 519 m2 = frent->fr_m; 520 pool_put(&pf_frent_pl, frent); 521 pf_nfrents--; 522 m_cat(m, m2); 523 } 524 525 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 #ifdef __NetBSD__ 545 m->m_pkthdr.csum_flags = 0; 546 #endif /* __NetBSD__ */ 547 } 548 549 DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip->ip_len))); 550 return (m); 551 552 drop_fragment: 553 /* Oops - fail safe - drop packet */ 554 pool_put(&pf_frent_pl, frent); 555 pf_nfrents--; 556 m_freem(m); 557 return (NULL); 558 } 559 560 struct mbuf * 561 pf_fragcache(struct mbuf **m0, struct ip *h, struct pf_fragment **frag, int mff, 562 int drop, int *nomem) 563 { 564 struct mbuf *m = *m0; 565 struct pf_frcache *frp, *fra, *cur = NULL; 566 int ip_len = ntohs(h->ip_len) - (h->ip_hl << 2); 567 u_int16_t off = ntohs(h->ip_off) << 3; 568 u_int16_t frmax = ip_len + off; 569 int hosed = 0; 570 571 KASSERT(*frag == NULL || !BUFFER_FRAGMENTS(*frag)); 572 573 /* Create a new range queue for this packet */ 574 if (*frag == NULL) { 575 *frag = pool_get(&pf_cache_pl, PR_NOWAIT); 576 if (*frag == NULL) { 577 pf_flush_fragments(); 578 *frag = pool_get(&pf_cache_pl, PR_NOWAIT); 579 if (*frag == NULL) 580 goto no_mem; 581 } 582 583 /* Get an entry for the queue */ 584 cur = pool_get(&pf_cent_pl, PR_NOWAIT); 585 if (cur == NULL) { 586 pool_put(&pf_cache_pl, *frag); 587 *frag = NULL; 588 goto no_mem; 589 } 590 pf_ncache++; 591 592 (*frag)->fr_flags = PFFRAG_NOBUFFER; 593 (*frag)->fr_max = 0; 594 (*frag)->fr_src = h->ip_src; 595 (*frag)->fr_dst = h->ip_dst; 596 (*frag)->fr_p = h->ip_p; 597 (*frag)->fr_id = h->ip_id; 598 (*frag)->fr_timeout = time_second; 599 600 cur->fr_off = off; 601 cur->fr_end = frmax; 602 LIST_INIT(&(*frag)->fr_cache); 603 LIST_INSERT_HEAD(&(*frag)->fr_cache, cur, fr_next); 604 605 RB_INSERT(pf_frag_tree, &pf_cache_tree, *frag); 606 TAILQ_INSERT_HEAD(&pf_cachequeue, *frag, frag_next); 607 608 DPFPRINTF(("fragcache[%d]: new %d-%d\n", h->ip_id, off, frmax)); 609 610 goto pass; 611 } 612 613 /* 614 * Find a fragment after the current one: 615 * - off contains the real shifted offset. 616 */ 617 frp = NULL; 618 LIST_FOREACH(fra, &(*frag)->fr_cache, fr_next) { 619 if (fra->fr_off > off) 620 break; 621 frp = fra; 622 } 623 624 KASSERT(frp != NULL || fra != NULL); 625 626 if (frp != NULL) { 627 int precut; 628 629 precut = frp->fr_end - off; 630 if (precut >= ip_len) { 631 /* Fragment is entirely a duplicate */ 632 DPFPRINTF(("fragcache[%d]: dead (%d-%d) %d-%d\n", 633 h->ip_id, frp->fr_off, frp->fr_end, off, frmax)); 634 goto drop_fragment; 635 } 636 if (precut == 0) { 637 /* They are adjacent. Fixup cache entry */ 638 DPFPRINTF(("fragcache[%d]: adjacent (%d-%d) %d-%d\n", 639 h->ip_id, frp->fr_off, frp->fr_end, off, frmax)); 640 frp->fr_end = frmax; 641 } else if (precut > 0) { 642 /* The first part of this payload overlaps with a 643 * fragment that has already been passed. 644 * Need to trim off the first part of the payload. 645 * But to do so easily, we need to create another 646 * mbuf to throw the original header into. 647 */ 648 649 DPFPRINTF(("fragcache[%d]: chop %d (%d-%d) %d-%d\n", 650 h->ip_id, precut, frp->fr_off, frp->fr_end, off, 651 frmax)); 652 653 off += precut; 654 frmax -= precut; 655 /* Update the previous frag to encompass this one */ 656 frp->fr_end = frmax; 657 658 if (!drop) { 659 /* XXX Optimization opportunity 660 * This is a very heavy way to trim the payload. 661 * we could do it much faster by diddling mbuf 662 * internals but that would be even less legible 663 * than this mbuf magic. For my next trick, 664 * I'll pull a rabbit out of my laptop. 665 */ 666 *m0 = m_dup(m, 0, h->ip_hl << 2, M_NOWAIT); 667 if (*m0 == NULL) 668 goto no_mem; 669 KASSERT((*m0)->m_next == NULL); 670 m_adj(m, precut + (h->ip_hl << 2)); 671 m_cat(*m0, m); 672 m = *m0; 673 if (m->m_flags & M_PKTHDR) { 674 int plen = 0; 675 struct mbuf *t; 676 for (t = m; t; t = t->m_next) 677 plen += t->m_len; 678 m->m_pkthdr.len = plen; 679 } 680 681 682 h = mtod(m, struct ip *); 683 684 685 KASSERT((int)m->m_len == 686 ntohs(h->ip_len) - precut); 687 h->ip_off = htons(ntohs(h->ip_off) + 688 (precut >> 3)); 689 h->ip_len = htons(ntohs(h->ip_len) - precut); 690 } else { 691 hosed++; 692 } 693 } else { 694 /* There is a gap between fragments */ 695 696 DPFPRINTF(("fragcache[%d]: gap %d (%d-%d) %d-%d\n", 697 h->ip_id, -precut, frp->fr_off, frp->fr_end, off, 698 frmax)); 699 700 cur = pool_get(&pf_cent_pl, PR_NOWAIT); 701 if (cur == NULL) 702 goto no_mem; 703 pf_ncache++; 704 705 cur->fr_off = off; 706 cur->fr_end = frmax; 707 LIST_INSERT_AFTER(frp, cur, fr_next); 708 } 709 } 710 711 if (fra != NULL) { 712 int aftercut; 713 int merge = 0; 714 715 aftercut = frmax - fra->fr_off; 716 if (aftercut == 0) { 717 /* Adjacent fragments */ 718 DPFPRINTF(("fragcache[%d]: adjacent %d-%d (%d-%d)\n", 719 h->ip_id, off, frmax, fra->fr_off, fra->fr_end)); 720 fra->fr_off = off; 721 merge = 1; 722 } else if (aftercut > 0) { 723 /* Need to chop off the tail of this fragment */ 724 DPFPRINTF(("fragcache[%d]: chop %d %d-%d (%d-%d)\n", 725 h->ip_id, aftercut, off, frmax, fra->fr_off, 726 fra->fr_end)); 727 fra->fr_off = off; 728 frmax -= aftercut; 729 730 merge = 1; 731 732 if (!drop) { 733 m_adj(m, -aftercut); 734 if (m->m_flags & M_PKTHDR) { 735 int plen = 0; 736 struct mbuf *t; 737 for (t = m; t; t = t->m_next) 738 plen += t->m_len; 739 m->m_pkthdr.len = plen; 740 } 741 h = mtod(m, struct ip *); 742 KASSERT((int)m->m_len == 743 ntohs(h->ip_len) - aftercut); 744 h->ip_len = htons(ntohs(h->ip_len) - aftercut); 745 } else { 746 hosed++; 747 } 748 } else if (frp == NULL) { 749 /* There is a gap between fragments */ 750 DPFPRINTF(("fragcache[%d]: gap %d %d-%d (%d-%d)\n", 751 h->ip_id, -aftercut, off, frmax, fra->fr_off, 752 fra->fr_end)); 753 754 cur = pool_get(&pf_cent_pl, PR_NOWAIT); 755 if (cur == NULL) 756 goto no_mem; 757 pf_ncache++; 758 759 cur->fr_off = off; 760 cur->fr_end = frmax; 761 LIST_INSERT_BEFORE(fra, cur, fr_next); 762 } 763 764 765 /* Need to glue together two separate fragment descriptors */ 766 if (merge) { 767 if (cur && fra->fr_off <= cur->fr_end) { 768 /* Need to merge in a previous 'cur' */ 769 DPFPRINTF(("fragcache[%d]: adjacent(merge " 770 "%d-%d) %d-%d (%d-%d)\n", 771 h->ip_id, cur->fr_off, cur->fr_end, off, 772 frmax, fra->fr_off, fra->fr_end)); 773 fra->fr_off = cur->fr_off; 774 LIST_REMOVE(cur, fr_next); 775 pool_put(&pf_cent_pl, cur); 776 pf_ncache--; 777 cur = NULL; 778 779 } else if (frp && fra->fr_off <= frp->fr_end) { 780 /* Need to merge in a modified 'frp' */ 781 KASSERT(cur == NULL); 782 DPFPRINTF(("fragcache[%d]: adjacent(merge " 783 "%d-%d) %d-%d (%d-%d)\n", 784 h->ip_id, frp->fr_off, frp->fr_end, off, 785 frmax, fra->fr_off, fra->fr_end)); 786 fra->fr_off = frp->fr_off; 787 LIST_REMOVE(frp, fr_next); 788 pool_put(&pf_cent_pl, frp); 789 pf_ncache--; 790 frp = NULL; 791 792 } 793 } 794 } 795 796 if (hosed) { 797 /* 798 * We must keep tracking the overall fragment even when 799 * we're going to drop it anyway so that we know when to 800 * free the overall descriptor. Thus we drop the frag late. 801 */ 802 goto drop_fragment; 803 } 804 805 806 pass: 807 /* Update maximum data size */ 808 if ((*frag)->fr_max < frmax) 809 (*frag)->fr_max = frmax; 810 811 /* This is the last segment */ 812 if (!mff) 813 (*frag)->fr_flags |= PFFRAG_SEENLAST; 814 815 /* Check if we are completely reassembled */ 816 if (((*frag)->fr_flags & PFFRAG_SEENLAST) && 817 LIST_FIRST(&(*frag)->fr_cache)->fr_off == 0 && 818 LIST_FIRST(&(*frag)->fr_cache)->fr_end == (*frag)->fr_max) { 819 /* Remove from fragment queue */ 820 DPFPRINTF(("fragcache[%d]: done 0-%d\n", h->ip_id, 821 (*frag)->fr_max)); 822 pf_free_fragment(*frag); 823 *frag = NULL; 824 } 825 826 return (m); 827 828 no_mem: 829 *nomem = 1; 830 831 /* Still need to pay attention to !IP_MF */ 832 if (!mff && *frag != NULL) 833 (*frag)->fr_flags |= PFFRAG_SEENLAST; 834 835 m_freem(m); 836 return (NULL); 837 838 drop_fragment: 839 840 /* Still need to pay attention to !IP_MF */ 841 if (!mff && *frag != NULL) 842 (*frag)->fr_flags |= PFFRAG_SEENLAST; 843 844 if (drop) { 845 /* This fragment has been deemed bad. Don't reass */ 846 if (((*frag)->fr_flags & PFFRAG_DROP) == 0) 847 DPFPRINTF(("fragcache[%d]: dropping overall fragment\n", 848 h->ip_id)); 849 (*frag)->fr_flags |= PFFRAG_DROP; 850 } 851 852 m_freem(m); 853 return (NULL); 854 } 855 856 int 857 pf_normalize_ip(struct mbuf **m0, int dir, struct pfi_kif *kif, u_short *reason, 858 struct pf_pdesc *pd) 859 { 860 struct mbuf *m = *m0; 861 struct pf_rule *r; 862 struct pf_frent *frent; 863 struct pf_fragment *frag = NULL; 864 struct ip *h = mtod(m, struct ip *); 865 int mff = (ntohs(h->ip_off) & IP_MF); 866 int hlen = h->ip_hl << 2; 867 u_int16_t fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3; 868 u_int16_t frmax; 869 int ip_len; 870 871 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 872 while (r != NULL) { 873 r->evaluations++; 874 if (pfi_kif_match(r->kif, kif) == r->ifnot) 875 r = r->skip[PF_SKIP_IFP].ptr; 876 else if (r->direction && r->direction != dir) 877 r = r->skip[PF_SKIP_DIR].ptr; 878 else if (r->af && r->af != AF_INET) 879 r = r->skip[PF_SKIP_AF].ptr; 880 else if (r->proto && r->proto != h->ip_p) 881 r = r->skip[PF_SKIP_PROTO].ptr; 882 else if (PF_MISMATCHAW(&r->src.addr, 883 (struct pf_addr *)&h->ip_src.s_addr, AF_INET, 884 r->src.neg, kif)) 885 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 886 else if (PF_MISMATCHAW(&r->dst.addr, 887 (struct pf_addr *)&h->ip_dst.s_addr, AF_INET, 888 r->dst.neg, NULL)) 889 r = r->skip[PF_SKIP_DST_ADDR].ptr; 890 else 891 break; 892 } 893 894 if (r == NULL || r->action == PF_NOSCRUB) 895 return (PF_PASS); 896 else { 897 r->packets[dir == PF_OUT]++; 898 r->bytes[dir == PF_OUT] += pd->tot_len; 899 } 900 901 /* Check for illegal packets */ 902 if (hlen < (int)sizeof(struct ip)) 903 goto drop; 904 905 if (hlen > ntohs(h->ip_len)) 906 goto drop; 907 908 /* Clear IP_DF if the rule uses the no-df option */ 909 if (r->rule_flag & PFRULE_NODF && h->ip_off & htons(IP_DF)) { 910 u_int16_t off = h->ip_off; 911 912 h->ip_off &= htons(~IP_DF); 913 h->ip_sum = pf_cksum_fixup(h->ip_sum, off, h->ip_off, 0); 914 } 915 916 /* We will need other tests here */ 917 if (!fragoff && !mff) 918 goto no_fragment; 919 920 /* We're dealing with a fragment now. Don't allow fragments 921 * with IP_DF to enter the cache. If the flag was cleared by 922 * no-df above, fine. Otherwise drop it. 923 */ 924 if (h->ip_off & htons(IP_DF)) { 925 DPFPRINTF(("IP_DF\n")); 926 goto bad; 927 } 928 929 ip_len = ntohs(h->ip_len) - hlen; 930 931 /* All fragments are 8 byte aligned */ 932 if (mff && (ip_len & 0x7)) { 933 DPFPRINTF(("mff and %d\n", ip_len)); 934 goto bad; 935 } 936 937 /* Respect maximum length */ 938 if (fragoff + ip_len > IP_MAXPACKET) { 939 DPFPRINTF(("max packet %d\n", fragoff + ip_len)); 940 goto bad; 941 } 942 frmax = fragoff + ip_len; 943 944 if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0) { 945 /* Fully buffer all of the fragments */ 946 947 frag = pf_find_fragment(h, &pf_frag_tree); 948 949 /* Check if we saw the last fragment already */ 950 if (frag != NULL && (frag->fr_flags & PFFRAG_SEENLAST) && 951 frmax > frag->fr_max) 952 goto bad; 953 954 /* Get an entry for the fragment queue */ 955 frent = pool_get(&pf_frent_pl, PR_NOWAIT); 956 if (frent == NULL) { 957 REASON_SET(reason, PFRES_MEMORY); 958 return (PF_DROP); 959 } 960 pf_nfrents++; 961 frent->fr_ip = h; 962 frent->fr_m = m; 963 964 /* Might return a completely reassembled mbuf, or NULL */ 965 DPFPRINTF(("reass frag %d @ %d-%d\n", h->ip_id, fragoff, frmax)); 966 *m0 = m = pf_reassemble(m0, &frag, frent, mff); 967 968 if (m == NULL) 969 return (PF_DROP); 970 971 if (frag != NULL && (frag->fr_flags & PFFRAG_DROP)) 972 goto drop; 973 974 h = mtod(m, struct ip *); 975 } else { 976 /* non-buffering fragment cache (drops or masks overlaps) */ 977 int nomem = 0; 978 979 #ifdef __NetBSD__ 980 struct pf_mtag *pf_mtag = pf_find_mtag(m); 981 KASSERT(pf_mtag != NULL); 982 983 if (dir == PF_OUT && pf_mtag->flags & PF_TAG_FRAGCACHE) { 984 #else 985 if (dir == PF_OUT && m->m_pkthdr.pf.flags & PF_TAG_FRAGCACHE) { 986 #endif /* !__NetBSD__ */ 987 /* 988 * Already passed the fragment cache in the 989 * input direction. If we continued, it would 990 * appear to be a dup and would be dropped. 991 */ 992 goto fragment_pass; 993 } 994 995 frag = pf_find_fragment(h, &pf_cache_tree); 996 997 /* Check if we saw the last fragment already */ 998 if (frag != NULL && (frag->fr_flags & PFFRAG_SEENLAST) && 999 frmax > frag->fr_max) { 1000 if (r->rule_flag & PFRULE_FRAGDROP) 1001 frag->fr_flags |= PFFRAG_DROP; 1002 goto bad; 1003 } 1004 1005 *m0 = m = pf_fragcache(m0, h, &frag, mff, 1006 (r->rule_flag & PFRULE_FRAGDROP) ? 1 : 0, &nomem); 1007 if (m == NULL) { 1008 if (nomem) 1009 goto no_mem; 1010 goto drop; 1011 } 1012 1013 if (dir == PF_IN) 1014 #ifdef __NetBSD__ 1015 pf_mtag = pf_find_mtag(m); 1016 KASSERT(pf_mtag != NULL); 1017 1018 pf_mtag->flags |= PF_TAG_FRAGCACHE; 1019 #else 1020 m->m_pkthdr.pf.flags |= PF_TAG_FRAGCACHE; 1021 #endif /* !__NetBSD__ */ 1022 1023 if (frag != NULL && (frag->fr_flags & PFFRAG_DROP)) 1024 goto drop; 1025 goto fragment_pass; 1026 } 1027 1028 no_fragment: 1029 /* At this point, only IP_DF is allowed in ip_off */ 1030 if (h->ip_off & ~htons(IP_DF)) { 1031 u_int16_t off = h->ip_off; 1032 1033 h->ip_off &= htons(IP_DF); 1034 h->ip_sum = pf_cksum_fixup(h->ip_sum, off, h->ip_off, 0); 1035 } 1036 1037 /* Enforce a minimum ttl, may cause endless packet loops */ 1038 if (r->min_ttl && h->ip_ttl < r->min_ttl) { 1039 u_int16_t ip_ttl = h->ip_ttl; 1040 1041 h->ip_ttl = r->min_ttl; 1042 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0); 1043 } 1044 1045 if (r->rule_flag & PFRULE_RANDOMID) { 1046 u_int16_t id = h->ip_id; 1047 1048 h->ip_id = ip_randomid(ip_ids, 0); 1049 h->ip_sum = pf_cksum_fixup(h->ip_sum, id, h->ip_id, 0); 1050 } 1051 if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0) 1052 pd->flags |= PFDESC_IP_REAS; 1053 1054 return (PF_PASS); 1055 1056 fragment_pass: 1057 /* Enforce a minimum ttl, may cause endless packet loops */ 1058 if (r->min_ttl && h->ip_ttl < r->min_ttl) { 1059 u_int16_t ip_ttl = h->ip_ttl; 1060 1061 h->ip_ttl = r->min_ttl; 1062 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0); 1063 } 1064 if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0) 1065 pd->flags |= PFDESC_IP_REAS; 1066 return (PF_PASS); 1067 1068 no_mem: 1069 REASON_SET(reason, PFRES_MEMORY); 1070 if (r != NULL && r->log) 1071 PFLOG_PACKET(kif, h, m, AF_INET, dir, *reason, r, NULL, NULL, pd); 1072 return (PF_DROP); 1073 1074 drop: 1075 REASON_SET(reason, PFRES_NORM); 1076 if (r != NULL && r->log) 1077 PFLOG_PACKET(kif, h, m, AF_INET, dir, *reason, r, NULL, NULL, pd); 1078 return (PF_DROP); 1079 1080 bad: 1081 DPFPRINTF(("dropping bad fragment\n")); 1082 1083 /* Free associated fragments */ 1084 if (frag != NULL) 1085 pf_free_fragment(frag); 1086 1087 REASON_SET(reason, PFRES_FRAG); 1088 if (r != NULL && r->log) 1089 PFLOG_PACKET(kif, h, m, AF_INET, dir, *reason, r, NULL, NULL, pd); 1090 1091 return (PF_DROP); 1092 } 1093 1094 #ifdef INET6 1095 int 1096 pf_normalize_ip6(struct mbuf **m0, int dir, struct pfi_kif *kif, 1097 u_short *reason, struct pf_pdesc *pd) 1098 { 1099 struct mbuf *m = *m0; 1100 struct pf_rule *r; 1101 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1102 int off; 1103 struct ip6_ext ext; 1104 struct ip6_opt opt; 1105 struct ip6_opt_jumbo jumbo; 1106 struct ip6_frag frag; 1107 u_int32_t jumbolen = 0, plen; 1108 u_int16_t fragoff = 0; 1109 int optend; 1110 int ooff; 1111 u_int8_t proto; 1112 int terminal; 1113 1114 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 1115 while (r != NULL) { 1116 r->evaluations++; 1117 if (pfi_kif_match(r->kif, kif) == r->ifnot) 1118 r = r->skip[PF_SKIP_IFP].ptr; 1119 else if (r->direction && r->direction != dir) 1120 r = r->skip[PF_SKIP_DIR].ptr; 1121 else if (r->af && r->af != AF_INET6) 1122 r = r->skip[PF_SKIP_AF].ptr; 1123 #if 0 /* header chain! */ 1124 else if (r->proto && r->proto != h->ip6_nxt) 1125 r = r->skip[PF_SKIP_PROTO].ptr; 1126 #endif 1127 else if (PF_MISMATCHAW(&r->src.addr, 1128 (struct pf_addr *)&h->ip6_src, AF_INET6, 1129 r->src.neg, kif)) 1130 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 1131 else if (PF_MISMATCHAW(&r->dst.addr, 1132 (struct pf_addr *)&h->ip6_dst, AF_INET6, 1133 r->dst.neg, NULL)) 1134 r = r->skip[PF_SKIP_DST_ADDR].ptr; 1135 else 1136 break; 1137 } 1138 1139 if (r == NULL || r->action == PF_NOSCRUB) 1140 return (PF_PASS); 1141 else { 1142 r->packets[dir == PF_OUT]++; 1143 r->bytes[dir == PF_OUT] += pd->tot_len; 1144 } 1145 1146 /* Check for illegal packets */ 1147 if (sizeof(struct ip6_hdr) + IPV6_MAXPACKET < m->m_pkthdr.len) 1148 goto drop; 1149 1150 off = sizeof(struct ip6_hdr); 1151 proto = h->ip6_nxt; 1152 terminal = 0; 1153 do { 1154 switch (proto) { 1155 case IPPROTO_FRAGMENT: 1156 goto fragment; 1157 break; 1158 case IPPROTO_AH: 1159 case IPPROTO_ROUTING: 1160 case IPPROTO_DSTOPTS: 1161 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL, 1162 NULL, AF_INET6)) 1163 goto shortpkt; 1164 if (proto == IPPROTO_AH) 1165 off += (ext.ip6e_len + 2) * 4; 1166 else 1167 off += (ext.ip6e_len + 1) * 8; 1168 proto = ext.ip6e_nxt; 1169 break; 1170 case IPPROTO_HOPOPTS: 1171 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL, 1172 NULL, AF_INET6)) 1173 goto shortpkt; 1174 optend = off + (ext.ip6e_len + 1) * 8; 1175 ooff = off + sizeof(ext); 1176 do { 1177 if (!pf_pull_hdr(m, ooff, &opt.ip6o_type, 1178 sizeof(opt.ip6o_type), NULL, NULL, 1179 AF_INET6)) 1180 goto shortpkt; 1181 if (opt.ip6o_type == IP6OPT_PAD1) { 1182 ooff++; 1183 continue; 1184 } 1185 if (!pf_pull_hdr(m, ooff, &opt, sizeof(opt), 1186 NULL, NULL, AF_INET6)) 1187 goto shortpkt; 1188 if (ooff + sizeof(opt) + opt.ip6o_len > optend) 1189 goto drop; 1190 switch (opt.ip6o_type) { 1191 case IP6OPT_JUMBO: 1192 if (h->ip6_plen != 0) 1193 goto drop; 1194 if (!pf_pull_hdr(m, ooff, &jumbo, 1195 sizeof(jumbo), NULL, NULL, 1196 AF_INET6)) 1197 goto shortpkt; 1198 memcpy(&jumbolen, jumbo.ip6oj_jumbo_len, 1199 sizeof(jumbolen)); 1200 jumbolen = ntohl(jumbolen); 1201 if (jumbolen <= IPV6_MAXPACKET) 1202 goto drop; 1203 if (sizeof(struct ip6_hdr) + jumbolen != 1204 m->m_pkthdr.len) 1205 goto drop; 1206 break; 1207 default: 1208 break; 1209 } 1210 ooff += sizeof(opt) + opt.ip6o_len; 1211 } while (ooff < optend); 1212 1213 off = optend; 1214 proto = ext.ip6e_nxt; 1215 break; 1216 default: 1217 terminal = 1; 1218 break; 1219 } 1220 } while (!terminal); 1221 1222 /* jumbo payload option must be present, or plen > 0 */ 1223 if (ntohs(h->ip6_plen) == 0) 1224 plen = jumbolen; 1225 else 1226 plen = ntohs(h->ip6_plen); 1227 if (plen == 0) 1228 goto drop; 1229 if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len) 1230 goto shortpkt; 1231 1232 /* Enforce a minimum ttl, may cause endless packet loops */ 1233 if (r->min_ttl && h->ip6_hlim < r->min_ttl) 1234 h->ip6_hlim = r->min_ttl; 1235 1236 return (PF_PASS); 1237 1238 fragment: 1239 if (ntohs(h->ip6_plen) == 0 || jumbolen) 1240 goto drop; 1241 plen = ntohs(h->ip6_plen); 1242 1243 if (!pf_pull_hdr(m, off, &frag, sizeof(frag), NULL, NULL, AF_INET6)) 1244 goto shortpkt; 1245 fragoff = ntohs(frag.ip6f_offlg & IP6F_OFF_MASK); 1246 if (fragoff + (plen - off - sizeof(frag)) > IPV6_MAXPACKET) 1247 goto badfrag; 1248 1249 /* do something about it */ 1250 /* remember to set pd->flags |= PFDESC_IP_REAS */ 1251 return (PF_PASS); 1252 1253 shortpkt: 1254 REASON_SET(reason, PFRES_SHORT); 1255 if (r != NULL && r->log) 1256 PFLOG_PACKET(kif, h, m, AF_INET6, dir, *reason, r, NULL, NULL, pd); 1257 return (PF_DROP); 1258 1259 drop: 1260 REASON_SET(reason, PFRES_NORM); 1261 if (r != NULL && r->log) 1262 PFLOG_PACKET(kif, h, m, AF_INET6, dir, *reason, r, NULL, NULL, pd); 1263 return (PF_DROP); 1264 1265 badfrag: 1266 REASON_SET(reason, PFRES_FRAG); 1267 if (r != NULL && r->log) 1268 PFLOG_PACKET(kif, h, m, AF_INET6, dir, *reason, r, NULL, NULL, pd); 1269 return (PF_DROP); 1270 } 1271 #endif /* INET6 */ 1272 1273 int 1274 pf_normalize_tcp(int dir, struct pfi_kif *kif, struct mbuf *m, 1275 int ipoff, int off, void *h, struct pf_pdesc *pd) 1276 { 1277 struct pf_rule *r, *rm = NULL; 1278 struct tcphdr *th = pd->hdr.tcp; 1279 int rewrite = 0; 1280 u_short reason; 1281 u_int8_t flags; 1282 sa_family_t af = pd->af; 1283 1284 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 1285 while (r != NULL) { 1286 r->evaluations++; 1287 if (pfi_kif_match(r->kif, kif) == r->ifnot) 1288 r = r->skip[PF_SKIP_IFP].ptr; 1289 else if (r->direction && r->direction != dir) 1290 r = r->skip[PF_SKIP_DIR].ptr; 1291 else if (r->af && r->af != af) 1292 r = r->skip[PF_SKIP_AF].ptr; 1293 else if (r->proto && r->proto != pd->proto) 1294 r = r->skip[PF_SKIP_PROTO].ptr; 1295 else if (PF_MISMATCHAW(&r->src.addr, pd->src, af, 1296 r->src.neg, kif)) 1297 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 1298 else if (r->src.port_op && !pf_match_port(r->src.port_op, 1299 r->src.port[0], r->src.port[1], th->th_sport)) 1300 r = r->skip[PF_SKIP_SRC_PORT].ptr; 1301 else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af, 1302 r->dst.neg, NULL)) 1303 r = r->skip[PF_SKIP_DST_ADDR].ptr; 1304 else if (r->dst.port_op && !pf_match_port(r->dst.port_op, 1305 r->dst.port[0], r->dst.port[1], th->th_dport)) 1306 r = r->skip[PF_SKIP_DST_PORT].ptr; 1307 else if (r->os_fingerprint != PF_OSFP_ANY && !pf_osfp_match( 1308 pf_osfp_fingerprint(pd, m, off, th), 1309 r->os_fingerprint)) 1310 r = TAILQ_NEXT(r, entries); 1311 else { 1312 rm = r; 1313 break; 1314 } 1315 } 1316 1317 if (rm == NULL || rm->action == PF_NOSCRUB) 1318 return (PF_PASS); 1319 else { 1320 r->packets[dir == PF_OUT]++; 1321 r->bytes[dir == PF_OUT] += pd->tot_len; 1322 } 1323 1324 if (rm->rule_flag & PFRULE_REASSEMBLE_TCP) 1325 pd->flags |= PFDESC_TCP_NORM; 1326 1327 flags = th->th_flags; 1328 if (flags & TH_SYN) { 1329 /* Illegal packet */ 1330 if (flags & TH_RST) 1331 goto tcp_drop; 1332 1333 if (flags & TH_FIN) 1334 flags &= ~TH_FIN; 1335 } else { 1336 /* Illegal packet */ 1337 if (!(flags & (TH_ACK|TH_RST))) 1338 goto tcp_drop; 1339 } 1340 1341 if (!(flags & TH_ACK)) { 1342 /* These flags are only valid if ACK is set */ 1343 if ((flags & TH_FIN) || (flags & TH_PUSH) || (flags & TH_URG)) 1344 goto tcp_drop; 1345 } 1346 1347 /* Check for illegal header length */ 1348 if (th->th_off < (sizeof(struct tcphdr) >> 2)) 1349 goto tcp_drop; 1350 1351 /* If flags changed, or reserved data set, then adjust */ 1352 if (flags != th->th_flags || th->th_x2 != 0) { 1353 u_int16_t ov, nv; 1354 1355 ov = *(u_int16_t *)(&th->th_ack + 1); 1356 th->th_flags = flags; 1357 th->th_x2 = 0; 1358 nv = *(u_int16_t *)(&th->th_ack + 1); 1359 1360 th->th_sum = pf_cksum_fixup(th->th_sum, ov, nv, 0); 1361 rewrite = 1; 1362 } 1363 1364 /* Remove urgent pointer, if TH_URG is not set */ 1365 if (!(flags & TH_URG) && th->th_urp) { 1366 th->th_sum = pf_cksum_fixup(th->th_sum, th->th_urp, 0, 0); 1367 th->th_urp = 0; 1368 rewrite = 1; 1369 } 1370 1371 /* Process options */ 1372 if (r->max_mss && pf_normalize_tcpopt(r, m, th, off)) 1373 rewrite = 1; 1374 1375 /* copy back packet headers if we sanitized */ 1376 if (rewrite) 1377 m_copyback(m, off, sizeof(*th), th); 1378 1379 return (PF_PASS); 1380 1381 tcp_drop: 1382 REASON_SET_NOPTR(&reason, PFRES_NORM); 1383 if (rm != NULL && r->log) 1384 PFLOG_PACKET(kif, h, m, AF_INET, dir, reason, r, NULL, NULL, pd); 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, 1391 struct pf_state_peer *dst) 1392 { 1393 u_int32_t tsval, tsecr; 1394 u_int8_t hdr[60]; 1395 u_int8_t *opt; 1396 1397 KASSERT(src->scrub == NULL); 1398 1399 src->scrub = pool_get(&pf_state_scrub_pl, PR_NOWAIT); 1400 if (src->scrub == NULL) 1401 return (1); 1402 bzero(src->scrub, sizeof(*src->scrub)); 1403 1404 switch (pd->af) { 1405 #ifdef INET 1406 case AF_INET: { 1407 struct ip *h = mtod(m, struct ip *); 1408 src->scrub->pfss_ttl = h->ip_ttl; 1409 break; 1410 } 1411 #endif /* INET */ 1412 #ifdef INET6 1413 case AF_INET6: { 1414 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1415 src->scrub->pfss_ttl = h->ip6_hlim; 1416 break; 1417 } 1418 #endif /* INET6 */ 1419 } 1420 1421 1422 /* 1423 * All normalizations below are only begun if we see the start of 1424 * the connections. They must all set an enabled bit in pfss_flags 1425 */ 1426 if ((th->th_flags & TH_SYN) == 0) 1427 return (0); 1428 1429 1430 if (th->th_off > (sizeof(struct tcphdr) >> 2) && src->scrub && 1431 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) { 1432 /* Diddle with TCP options */ 1433 int hlen; 1434 opt = hdr + sizeof(struct tcphdr); 1435 hlen = (th->th_off << 2) - sizeof(struct tcphdr); 1436 while (hlen >= TCPOLEN_TIMESTAMP) { 1437 switch (*opt) { 1438 case TCPOPT_EOL: /* FALLTHROUGH */ 1439 case TCPOPT_NOP: 1440 opt++; 1441 hlen--; 1442 break; 1443 case TCPOPT_TIMESTAMP: 1444 if (opt[1] >= TCPOLEN_TIMESTAMP) { 1445 src->scrub->pfss_flags |= 1446 PFSS_TIMESTAMP; 1447 src->scrub->pfss_ts_mod = 1448 htonl(cprng_fast32()); 1449 1450 /* note PFSS_PAWS not set yet */ 1451 memcpy(&tsval, &opt[2], 1452 sizeof(u_int32_t)); 1453 memcpy(&tsecr, &opt[6], 1454 sizeof(u_int32_t)); 1455 src->scrub->pfss_tsval0 = ntohl(tsval); 1456 src->scrub->pfss_tsval = ntohl(tsval); 1457 src->scrub->pfss_tsecr = ntohl(tsecr); 1458 getmicrouptime(&src->scrub->pfss_last); 1459 } 1460 /* FALLTHROUGH */ 1461 default: 1462 hlen -= MAX(opt[1], 2); 1463 opt += MAX(opt[1], 2); 1464 break; 1465 } 1466 } 1467 } 1468 1469 return (0); 1470 } 1471 1472 void 1473 pf_normalize_tcp_cleanup(struct pf_state *state) 1474 { 1475 if (state->src.scrub) 1476 pool_put(&pf_state_scrub_pl, state->src.scrub); 1477 if (state->dst.scrub) 1478 pool_put(&pf_state_scrub_pl, state->dst.scrub); 1479 1480 /* Someday... flush the TCP segment reassembly descriptors. */ 1481 } 1482 1483 int 1484 pf_normalize_tcp_stateful(struct mbuf *m, int off, struct pf_pdesc *pd, 1485 u_short *reason, struct tcphdr *th, struct pf_state *state, 1486 struct pf_state_peer *src, struct pf_state_peer *dst, int *writeback) 1487 { 1488 struct timeval uptime; 1489 u_int32_t tsval = 0, tsecr = 0; 1490 u_int tsval_from_last; 1491 u_int8_t hdr[60]; 1492 u_int8_t *opt; 1493 int copyback = 0; 1494 int got_ts = 0; 1495 1496 KASSERT(src->scrub || dst->scrub); 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 (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_second - state->creation > TS_MAX_CONN)) { 1620 if (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 (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 = pf_default_rule.timeout[PFTM_TS_DIFF]; 1715 1716 1717 /* Calculate max ticks since the last timestamp */ 1718 #define TS_MAXFREQ 1100 /* RFC max TS freq of 1 kHz + 10% skew */ 1719 #define TS_MICROSECS 1000000 /* microseconds per second */ 1720 timersub(&uptime, &src->scrub->pfss_last, &delta_ts); 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 1725 if ((src->state >= TCPS_ESTABLISHED && 1726 dst->state >= TCPS_ESTABLISHED) && 1727 (SEQ_LT(tsval, dst->scrub->pfss_tsecr) || 1728 SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) || 1729 (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) || 1730 SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) { 1731 /* Bad RFC1323 implementation or an insertion attack. 1732 * 1733 * - Solaris 2.6 and 2.7 are known to send another ACK 1734 * after the FIN,FIN|ACK,ACK closing that carries 1735 * an old timestamp. 1736 */ 1737 1738 DPFPRINTF(("Timestamp failed %c%c%c%c\n", 1739 SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '0' : ' ', 1740 SEQ_GT(tsval, src->scrub->pfss_tsval + 1741 tsval_from_last) ? '1' : ' ', 1742 SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ', 1743 SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' ')); 1744 DPFPRINTF((" tsval: %" PRIu32 " tsecr: %" PRIu32 1745 " +ticks: %" PRIu32 " idle: %"PRIx64"s %ums\n", 1746 tsval, tsecr, tsval_from_last, delta_ts.tv_sec, 1747 delta_ts.tv_usec / 1000U)); 1748 DPFPRINTF((" src->tsval: %" PRIu32 " tsecr: %" PRIu32 1749 "\n", 1750 src->scrub->pfss_tsval, src->scrub->pfss_tsecr)); 1751 DPFPRINTF((" dst->tsval: %" PRIu32 " tsecr: %" PRIu32 1752 " tsval0: %" PRIu32 "\n", 1753 dst->scrub->pfss_tsval, 1754 dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0)); 1755 if (pf_status.debug >= PF_DEBUG_MISC) { 1756 pf_print_state(state); 1757 pf_print_flags(th->th_flags); 1758 printf("\n"); 1759 } 1760 REASON_SET(reason, PFRES_TS); 1761 return (PF_DROP); 1762 } 1763 1764 /* XXX I'd really like to require tsecr but it's optional */ 1765 1766 } else if (!got_ts && (th->th_flags & TH_RST) == 0 && 1767 ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED) 1768 || pd->p_len > 0 || (th->th_flags & TH_SYN)) && 1769 src->scrub && dst->scrub && 1770 (src->scrub->pfss_flags & PFSS_PAWS) && 1771 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1772 /* Didn't send a timestamp. Timestamps aren't really useful 1773 * when: 1774 * - connection opening or closing (often not even sent). 1775 * but we must not let an attacker to put a FIN on a 1776 * data packet to sneak it through our ESTABLISHED check. 1777 * - on a TCP reset. RFC suggests not even looking at TS. 1778 * - on an empty ACK. The TS will not be echoed so it will 1779 * probably not help keep the RTT calculation in sync and 1780 * there isn't as much danger when the sequence numbers 1781 * got wrapped. So some stacks don't include TS on empty 1782 * ACKs :-( 1783 * 1784 * To minimize the disruption to mostly RFC1323 conformant 1785 * stacks, we will only require timestamps on data packets. 1786 * 1787 * And what do ya know, we cannot require timestamps on data 1788 * packets. There appear to be devices that do legitimate 1789 * TCP connection hijacking. There are HTTP devices that allow 1790 * a 3whs (with timestamps) and then buffer the HTTP request. 1791 * If the intermediate device has the HTTP response cache, it 1792 * will spoof the response but not bother timestamping its 1793 * packets. So we can look for the presence of a timestamp in 1794 * the first data packet and if there, require it in all future 1795 * packets. 1796 */ 1797 1798 if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) { 1799 /* 1800 * Hey! Someone tried to sneak a packet in. Or the 1801 * stack changed its RFC1323 behavior?!?! 1802 */ 1803 if (pf_status.debug >= PF_DEBUG_MISC) { 1804 DPFPRINTF(("Did not receive expected RFC1323 " 1805 "timestamp\n")); 1806 pf_print_state(state); 1807 pf_print_flags(th->th_flags); 1808 printf("\n"); 1809 } 1810 REASON_SET(reason, PFRES_TS); 1811 return (PF_DROP); 1812 } 1813 } 1814 1815 1816 /* 1817 * We will note if a host sends his data packets with or without 1818 * timestamps. And require all data packets to contain a timestamp 1819 * if the first does. PAWS implicitly requires that all data packets be 1820 * timestamped. But I think there are middle-man devices that hijack 1821 * TCP streams immediately after the 3whs and don't timestamp their 1822 * packets (seen in a WWW accelerator or cache). 1823 */ 1824 if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags & 1825 (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) { 1826 if (got_ts) 1827 src->scrub->pfss_flags |= PFSS_DATA_TS; 1828 else { 1829 src->scrub->pfss_flags |= PFSS_DATA_NOTS; 1830 if (pf_status.debug >= PF_DEBUG_MISC && dst->scrub && 1831 (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) { 1832 /* Don't warn if other host rejected RFC1323 */ 1833 DPFPRINTF(("Broken RFC1323 stack did not " 1834 "timestamp data packet. Disabled PAWS " 1835 "security.\n")); 1836 pf_print_state(state); 1837 pf_print_flags(th->th_flags); 1838 printf("\n"); 1839 } 1840 } 1841 } 1842 1843 1844 /* 1845 * Update PAWS values 1846 */ 1847 if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags & 1848 (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) { 1849 getmicrouptime(&src->scrub->pfss_last); 1850 if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) || 1851 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1852 src->scrub->pfss_tsval = tsval; 1853 1854 if (tsecr) { 1855 if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) || 1856 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1857 src->scrub->pfss_tsecr = tsecr; 1858 1859 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 && 1860 (SEQ_LT(tsval, src->scrub->pfss_tsval0) || 1861 src->scrub->pfss_tsval0 == 0)) { 1862 /* tsval0 MUST be the lowest timestamp */ 1863 src->scrub->pfss_tsval0 = tsval; 1864 } 1865 1866 /* Only fully initialized after a TS gets echoed */ 1867 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0) 1868 src->scrub->pfss_flags |= PFSS_PAWS; 1869 } 1870 } 1871 1872 /* I have a dream.... TCP segment reassembly.... */ 1873 return (0); 1874 } 1875 1876 int 1877 pf_normalize_tcpopt(struct pf_rule *r, struct mbuf *m, struct tcphdr *th, 1878 int off) 1879 { 1880 u_int16_t *mss; 1881 int thoff; 1882 int opt, cnt, optlen = 0; 1883 int rewrite = 0; 1884 u_char *optp; 1885 1886 thoff = th->th_off << 2; 1887 cnt = thoff - sizeof(struct tcphdr); 1888 optp = mtod(m, u_char *) + off + sizeof(struct tcphdr); 1889 1890 for (; cnt > 0; cnt -= optlen, optp += optlen) { 1891 opt = optp[0]; 1892 if (opt == TCPOPT_EOL) 1893 break; 1894 if (opt == TCPOPT_NOP) 1895 optlen = 1; 1896 else { 1897 if (cnt < 2) 1898 break; 1899 optlen = optp[1]; 1900 if (optlen < 2 || optlen > cnt) 1901 break; 1902 } 1903 switch (opt) { 1904 case TCPOPT_MAXSEG: 1905 mss = (u_int16_t *)(optp + 2); 1906 if ((ntohs(*mss)) > r->max_mss) { 1907 th->th_sum = pf_cksum_fixup(th->th_sum, 1908 *mss, htons(r->max_mss), 0); 1909 *mss = htons(r->max_mss); 1910 rewrite = 1; 1911 } 1912 break; 1913 default: 1914 break; 1915 } 1916 } 1917 1918 return (rewrite); 1919 } 1920