1 /* $NetBSD: pf_norm.c,v 1.26 2011/11/28 08:05:05 tls 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 1.26 2011/11/28 08:05:05 tls 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 int ip_off; 871 872 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 873 while (r != NULL) { 874 r->evaluations++; 875 if (pfi_kif_match(r->kif, kif) == r->ifnot) 876 r = r->skip[PF_SKIP_IFP].ptr; 877 else if (r->direction && r->direction != dir) 878 r = r->skip[PF_SKIP_DIR].ptr; 879 else if (r->af && r->af != AF_INET) 880 r = r->skip[PF_SKIP_AF].ptr; 881 else if (r->proto && r->proto != h->ip_p) 882 r = r->skip[PF_SKIP_PROTO].ptr; 883 else if (PF_MISMATCHAW(&r->src.addr, 884 (struct pf_addr *)&h->ip_src.s_addr, AF_INET, 885 r->src.neg, kif)) 886 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 887 else if (PF_MISMATCHAW(&r->dst.addr, 888 (struct pf_addr *)&h->ip_dst.s_addr, AF_INET, 889 r->dst.neg, NULL)) 890 r = r->skip[PF_SKIP_DST_ADDR].ptr; 891 else 892 break; 893 } 894 895 if (r == NULL || r->action == PF_NOSCRUB) 896 return (PF_PASS); 897 else { 898 r->packets[dir == PF_OUT]++; 899 r->bytes[dir == PF_OUT] += pd->tot_len; 900 } 901 902 /* Check for illegal packets */ 903 if (hlen < (int)sizeof(struct ip)) 904 goto drop; 905 906 if (hlen > ntohs(h->ip_len)) 907 goto drop; 908 909 /* Clear IP_DF if the rule uses the no-df option */ 910 if (r->rule_flag & PFRULE_NODF && h->ip_off & htons(IP_DF)) { 911 u_int16_t off = h->ip_off; 912 913 h->ip_off &= htons(~IP_DF); 914 h->ip_sum = pf_cksum_fixup(h->ip_sum, off, h->ip_off, 0); 915 } 916 917 /* We will need other tests here */ 918 if (!fragoff && !mff) 919 goto no_fragment; 920 921 /* We're dealing with a fragment now. Don't allow fragments 922 * with IP_DF to enter the cache. If the flag was cleared by 923 * no-df above, fine. Otherwise drop it. 924 */ 925 if (h->ip_off & htons(IP_DF)) { 926 DPFPRINTF(("IP_DF\n")); 927 goto bad; 928 } 929 930 ip_len = ntohs(h->ip_len) - hlen; 931 ip_off = (ntohs(h->ip_off) & IP_OFFMASK) << 3; 932 933 /* All fragments are 8 byte aligned */ 934 if (mff && (ip_len & 0x7)) { 935 DPFPRINTF(("mff and %d\n", ip_len)); 936 goto bad; 937 } 938 939 /* Respect maximum length */ 940 if (fragoff + ip_len > IP_MAXPACKET) { 941 DPFPRINTF(("max packet %d\n", fragoff + ip_len)); 942 goto bad; 943 } 944 frmax = fragoff + ip_len; 945 946 if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0) { 947 /* Fully buffer all of the fragments */ 948 949 frag = pf_find_fragment(h, &pf_frag_tree); 950 951 /* Check if we saw the last fragment already */ 952 if (frag != NULL && (frag->fr_flags & PFFRAG_SEENLAST) && 953 frmax > frag->fr_max) 954 goto bad; 955 956 /* Get an entry for the fragment queue */ 957 frent = pool_get(&pf_frent_pl, PR_NOWAIT); 958 if (frent == NULL) { 959 REASON_SET(reason, PFRES_MEMORY); 960 return (PF_DROP); 961 } 962 pf_nfrents++; 963 frent->fr_ip = h; 964 frent->fr_m = m; 965 966 /* Might return a completely reassembled mbuf, or NULL */ 967 DPFPRINTF(("reass frag %d @ %d-%d\n", h->ip_id, fragoff, frmax)); 968 *m0 = m = pf_reassemble(m0, &frag, frent, mff); 969 970 if (m == NULL) 971 return (PF_DROP); 972 973 if (frag != NULL && (frag->fr_flags & PFFRAG_DROP)) 974 goto drop; 975 976 h = mtod(m, struct ip *); 977 } else { 978 /* non-buffering fragment cache (drops or masks overlaps) */ 979 int nomem = 0; 980 981 #ifdef __NetBSD__ 982 struct pf_mtag *pf_mtag = pf_find_mtag(m); 983 KASSERT(pf_mtag != NULL); 984 985 if (dir == PF_OUT && pf_mtag->flags & PF_TAG_FRAGCACHE) { 986 #else 987 if (dir == PF_OUT && m->m_pkthdr.pf.flags & PF_TAG_FRAGCACHE) { 988 #endif /* !__NetBSD__ */ 989 /* 990 * Already passed the fragment cache in the 991 * input direction. If we continued, it would 992 * appear to be a dup and would be dropped. 993 */ 994 goto fragment_pass; 995 } 996 997 frag = pf_find_fragment(h, &pf_cache_tree); 998 999 /* Check if we saw the last fragment already */ 1000 if (frag != NULL && (frag->fr_flags & PFFRAG_SEENLAST) && 1001 frmax > frag->fr_max) { 1002 if (r->rule_flag & PFRULE_FRAGDROP) 1003 frag->fr_flags |= PFFRAG_DROP; 1004 goto bad; 1005 } 1006 1007 *m0 = m = pf_fragcache(m0, h, &frag, mff, 1008 (r->rule_flag & PFRULE_FRAGDROP) ? 1 : 0, &nomem); 1009 if (m == NULL) { 1010 if (nomem) 1011 goto no_mem; 1012 goto drop; 1013 } 1014 1015 if (dir == PF_IN) 1016 #ifdef __NetBSD__ 1017 pf_mtag = pf_find_mtag(m); 1018 KASSERT(pf_mtag != NULL); 1019 1020 pf_mtag->flags |= PF_TAG_FRAGCACHE; 1021 #else 1022 m->m_pkthdr.pf.flags |= PF_TAG_FRAGCACHE; 1023 #endif /* !__NetBSD__ */ 1024 1025 if (frag != NULL && (frag->fr_flags & PFFRAG_DROP)) 1026 goto drop; 1027 goto fragment_pass; 1028 } 1029 1030 no_fragment: 1031 /* At this point, only IP_DF is allowed in ip_off */ 1032 if (h->ip_off & ~htons(IP_DF)) { 1033 u_int16_t off = h->ip_off; 1034 1035 h->ip_off &= htons(IP_DF); 1036 h->ip_sum = pf_cksum_fixup(h->ip_sum, off, h->ip_off, 0); 1037 } 1038 1039 /* Enforce a minimum ttl, may cause endless packet loops */ 1040 if (r->min_ttl && h->ip_ttl < r->min_ttl) { 1041 u_int16_t ip_ttl = h->ip_ttl; 1042 1043 h->ip_ttl = r->min_ttl; 1044 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0); 1045 } 1046 1047 if (r->rule_flag & PFRULE_RANDOMID) { 1048 u_int16_t id = h->ip_id; 1049 1050 h->ip_id = ip_randomid(ip_ids, 0); 1051 h->ip_sum = pf_cksum_fixup(h->ip_sum, id, h->ip_id, 0); 1052 } 1053 if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0) 1054 pd->flags |= PFDESC_IP_REAS; 1055 1056 return (PF_PASS); 1057 1058 fragment_pass: 1059 /* Enforce a minimum ttl, may cause endless packet loops */ 1060 if (r->min_ttl && h->ip_ttl < r->min_ttl) { 1061 u_int16_t ip_ttl = h->ip_ttl; 1062 1063 h->ip_ttl = r->min_ttl; 1064 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0); 1065 } 1066 if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0) 1067 pd->flags |= PFDESC_IP_REAS; 1068 return (PF_PASS); 1069 1070 no_mem: 1071 REASON_SET(reason, PFRES_MEMORY); 1072 if (r != NULL && r->log) 1073 PFLOG_PACKET(kif, h, m, AF_INET, dir, *reason, r, NULL, NULL, pd); 1074 return (PF_DROP); 1075 1076 drop: 1077 REASON_SET(reason, PFRES_NORM); 1078 if (r != NULL && r->log) 1079 PFLOG_PACKET(kif, h, m, AF_INET, dir, *reason, r, NULL, NULL, pd); 1080 return (PF_DROP); 1081 1082 bad: 1083 DPFPRINTF(("dropping bad fragment\n")); 1084 1085 /* Free associated fragments */ 1086 if (frag != NULL) 1087 pf_free_fragment(frag); 1088 1089 REASON_SET(reason, PFRES_FRAG); 1090 if (r != NULL && r->log) 1091 PFLOG_PACKET(kif, h, m, AF_INET, dir, *reason, r, NULL, NULL, pd); 1092 1093 return (PF_DROP); 1094 } 1095 1096 #ifdef INET6 1097 int 1098 pf_normalize_ip6(struct mbuf **m0, int dir, struct pfi_kif *kif, 1099 u_short *reason, struct pf_pdesc *pd) 1100 { 1101 struct mbuf *m = *m0; 1102 struct pf_rule *r; 1103 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1104 int off; 1105 struct ip6_ext ext; 1106 struct ip6_opt opt; 1107 struct ip6_opt_jumbo jumbo; 1108 struct ip6_frag frag; 1109 u_int32_t jumbolen = 0, plen; 1110 u_int16_t fragoff = 0; 1111 int optend; 1112 int ooff; 1113 u_int8_t proto; 1114 int terminal; 1115 1116 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 1117 while (r != NULL) { 1118 r->evaluations++; 1119 if (pfi_kif_match(r->kif, kif) == r->ifnot) 1120 r = r->skip[PF_SKIP_IFP].ptr; 1121 else if (r->direction && r->direction != dir) 1122 r = r->skip[PF_SKIP_DIR].ptr; 1123 else if (r->af && r->af != AF_INET6) 1124 r = r->skip[PF_SKIP_AF].ptr; 1125 #if 0 /* header chain! */ 1126 else if (r->proto && r->proto != h->ip6_nxt) 1127 r = r->skip[PF_SKIP_PROTO].ptr; 1128 #endif 1129 else if (PF_MISMATCHAW(&r->src.addr, 1130 (struct pf_addr *)&h->ip6_src, AF_INET6, 1131 r->src.neg, kif)) 1132 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 1133 else if (PF_MISMATCHAW(&r->dst.addr, 1134 (struct pf_addr *)&h->ip6_dst, AF_INET6, 1135 r->dst.neg, NULL)) 1136 r = r->skip[PF_SKIP_DST_ADDR].ptr; 1137 else 1138 break; 1139 } 1140 1141 if (r == NULL || r->action == PF_NOSCRUB) 1142 return (PF_PASS); 1143 else { 1144 r->packets[dir == PF_OUT]++; 1145 r->bytes[dir == PF_OUT] += pd->tot_len; 1146 } 1147 1148 /* Check for illegal packets */ 1149 if (sizeof(struct ip6_hdr) + IPV6_MAXPACKET < m->m_pkthdr.len) 1150 goto drop; 1151 1152 off = sizeof(struct ip6_hdr); 1153 proto = h->ip6_nxt; 1154 terminal = 0; 1155 do { 1156 switch (proto) { 1157 case IPPROTO_FRAGMENT: 1158 goto fragment; 1159 break; 1160 case IPPROTO_AH: 1161 case IPPROTO_ROUTING: 1162 case IPPROTO_DSTOPTS: 1163 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL, 1164 NULL, AF_INET6)) 1165 goto shortpkt; 1166 if (proto == IPPROTO_AH) 1167 off += (ext.ip6e_len + 2) * 4; 1168 else 1169 off += (ext.ip6e_len + 1) * 8; 1170 proto = ext.ip6e_nxt; 1171 break; 1172 case IPPROTO_HOPOPTS: 1173 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL, 1174 NULL, AF_INET6)) 1175 goto shortpkt; 1176 optend = off + (ext.ip6e_len + 1) * 8; 1177 ooff = off + sizeof(ext); 1178 do { 1179 if (!pf_pull_hdr(m, ooff, &opt.ip6o_type, 1180 sizeof(opt.ip6o_type), NULL, NULL, 1181 AF_INET6)) 1182 goto shortpkt; 1183 if (opt.ip6o_type == IP6OPT_PAD1) { 1184 ooff++; 1185 continue; 1186 } 1187 if (!pf_pull_hdr(m, ooff, &opt, sizeof(opt), 1188 NULL, NULL, AF_INET6)) 1189 goto shortpkt; 1190 if (ooff + sizeof(opt) + opt.ip6o_len > optend) 1191 goto drop; 1192 switch (opt.ip6o_type) { 1193 case IP6OPT_JUMBO: 1194 if (h->ip6_plen != 0) 1195 goto drop; 1196 if (!pf_pull_hdr(m, ooff, &jumbo, 1197 sizeof(jumbo), NULL, NULL, 1198 AF_INET6)) 1199 goto shortpkt; 1200 memcpy(&jumbolen, jumbo.ip6oj_jumbo_len, 1201 sizeof(jumbolen)); 1202 jumbolen = ntohl(jumbolen); 1203 if (jumbolen <= IPV6_MAXPACKET) 1204 goto drop; 1205 if (sizeof(struct ip6_hdr) + jumbolen != 1206 m->m_pkthdr.len) 1207 goto drop; 1208 break; 1209 default: 1210 break; 1211 } 1212 ooff += sizeof(opt) + opt.ip6o_len; 1213 } while (ooff < optend); 1214 1215 off = optend; 1216 proto = ext.ip6e_nxt; 1217 break; 1218 default: 1219 terminal = 1; 1220 break; 1221 } 1222 } while (!terminal); 1223 1224 /* jumbo payload option must be present, or plen > 0 */ 1225 if (ntohs(h->ip6_plen) == 0) 1226 plen = jumbolen; 1227 else 1228 plen = ntohs(h->ip6_plen); 1229 if (plen == 0) 1230 goto drop; 1231 if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len) 1232 goto shortpkt; 1233 1234 /* Enforce a minimum ttl, may cause endless packet loops */ 1235 if (r->min_ttl && h->ip6_hlim < r->min_ttl) 1236 h->ip6_hlim = r->min_ttl; 1237 1238 return (PF_PASS); 1239 1240 fragment: 1241 if (ntohs(h->ip6_plen) == 0 || jumbolen) 1242 goto drop; 1243 plen = ntohs(h->ip6_plen); 1244 1245 if (!pf_pull_hdr(m, off, &frag, sizeof(frag), NULL, NULL, AF_INET6)) 1246 goto shortpkt; 1247 fragoff = ntohs(frag.ip6f_offlg & IP6F_OFF_MASK); 1248 if (fragoff + (plen - off - sizeof(frag)) > IPV6_MAXPACKET) 1249 goto badfrag; 1250 1251 /* do something about it */ 1252 /* remember to set pd->flags |= PFDESC_IP_REAS */ 1253 return (PF_PASS); 1254 1255 shortpkt: 1256 REASON_SET(reason, PFRES_SHORT); 1257 if (r != NULL && r->log) 1258 PFLOG_PACKET(kif, h, m, AF_INET6, dir, *reason, r, NULL, NULL, pd); 1259 return (PF_DROP); 1260 1261 drop: 1262 REASON_SET(reason, PFRES_NORM); 1263 if (r != NULL && r->log) 1264 PFLOG_PACKET(kif, h, m, AF_INET6, dir, *reason, r, NULL, NULL, pd); 1265 return (PF_DROP); 1266 1267 badfrag: 1268 REASON_SET(reason, PFRES_FRAG); 1269 if (r != NULL && r->log) 1270 PFLOG_PACKET(kif, h, m, AF_INET6, dir, *reason, r, NULL, NULL, pd); 1271 return (PF_DROP); 1272 } 1273 #endif /* INET6 */ 1274 1275 int 1276 pf_normalize_tcp(int dir, struct pfi_kif *kif, struct mbuf *m, 1277 int ipoff, int off, void *h, struct pf_pdesc *pd) 1278 { 1279 struct pf_rule *r, *rm = NULL; 1280 struct tcphdr *th = pd->hdr.tcp; 1281 int rewrite = 0; 1282 u_short reason; 1283 u_int8_t flags; 1284 sa_family_t af = pd->af; 1285 1286 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 1287 while (r != NULL) { 1288 r->evaluations++; 1289 if (pfi_kif_match(r->kif, kif) == r->ifnot) 1290 r = r->skip[PF_SKIP_IFP].ptr; 1291 else if (r->direction && r->direction != dir) 1292 r = r->skip[PF_SKIP_DIR].ptr; 1293 else if (r->af && r->af != af) 1294 r = r->skip[PF_SKIP_AF].ptr; 1295 else if (r->proto && r->proto != pd->proto) 1296 r = r->skip[PF_SKIP_PROTO].ptr; 1297 else if (PF_MISMATCHAW(&r->src.addr, pd->src, af, 1298 r->src.neg, kif)) 1299 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 1300 else if (r->src.port_op && !pf_match_port(r->src.port_op, 1301 r->src.port[0], r->src.port[1], th->th_sport)) 1302 r = r->skip[PF_SKIP_SRC_PORT].ptr; 1303 else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af, 1304 r->dst.neg, NULL)) 1305 r = r->skip[PF_SKIP_DST_ADDR].ptr; 1306 else if (r->dst.port_op && !pf_match_port(r->dst.port_op, 1307 r->dst.port[0], r->dst.port[1], th->th_dport)) 1308 r = r->skip[PF_SKIP_DST_PORT].ptr; 1309 else if (r->os_fingerprint != PF_OSFP_ANY && !pf_osfp_match( 1310 pf_osfp_fingerprint(pd, m, off, th), 1311 r->os_fingerprint)) 1312 r = TAILQ_NEXT(r, entries); 1313 else { 1314 rm = r; 1315 break; 1316 } 1317 } 1318 1319 if (rm == NULL || rm->action == PF_NOSCRUB) 1320 return (PF_PASS); 1321 else { 1322 r->packets[dir == PF_OUT]++; 1323 r->bytes[dir == PF_OUT] += pd->tot_len; 1324 } 1325 1326 if (rm->rule_flag & PFRULE_REASSEMBLE_TCP) 1327 pd->flags |= PFDESC_TCP_NORM; 1328 1329 flags = th->th_flags; 1330 if (flags & TH_SYN) { 1331 /* Illegal packet */ 1332 if (flags & TH_RST) 1333 goto tcp_drop; 1334 1335 if (flags & TH_FIN) 1336 flags &= ~TH_FIN; 1337 } else { 1338 /* Illegal packet */ 1339 if (!(flags & (TH_ACK|TH_RST))) 1340 goto tcp_drop; 1341 } 1342 1343 if (!(flags & TH_ACK)) { 1344 /* These flags are only valid if ACK is set */ 1345 if ((flags & TH_FIN) || (flags & TH_PUSH) || (flags & TH_URG)) 1346 goto tcp_drop; 1347 } 1348 1349 /* Check for illegal header length */ 1350 if (th->th_off < (sizeof(struct tcphdr) >> 2)) 1351 goto tcp_drop; 1352 1353 /* If flags changed, or reserved data set, then adjust */ 1354 if (flags != th->th_flags || th->th_x2 != 0) { 1355 u_int16_t ov, nv; 1356 1357 ov = *(u_int16_t *)(&th->th_ack + 1); 1358 th->th_flags = flags; 1359 th->th_x2 = 0; 1360 nv = *(u_int16_t *)(&th->th_ack + 1); 1361 1362 th->th_sum = pf_cksum_fixup(th->th_sum, ov, nv, 0); 1363 rewrite = 1; 1364 } 1365 1366 /* Remove urgent pointer, if TH_URG is not set */ 1367 if (!(flags & TH_URG) && th->th_urp) { 1368 th->th_sum = pf_cksum_fixup(th->th_sum, th->th_urp, 0, 0); 1369 th->th_urp = 0; 1370 rewrite = 1; 1371 } 1372 1373 /* Process options */ 1374 if (r->max_mss && pf_normalize_tcpopt(r, m, th, off)) 1375 rewrite = 1; 1376 1377 /* copy back packet headers if we sanitized */ 1378 if (rewrite) 1379 m_copyback(m, off, sizeof(*th), th); 1380 1381 return (PF_PASS); 1382 1383 tcp_drop: 1384 REASON_SET(&reason, PFRES_NORM); 1385 if (rm != NULL && r->log) 1386 PFLOG_PACKET(kif, h, m, AF_INET, dir, reason, r, NULL, NULL, pd); 1387 return (PF_DROP); 1388 } 1389 1390 int 1391 pf_normalize_tcp_init(struct mbuf *m, int off, struct pf_pdesc *pd, 1392 struct tcphdr *th, struct pf_state_peer *src, 1393 struct pf_state_peer *dst) 1394 { 1395 u_int32_t tsval, tsecr; 1396 u_int8_t hdr[60]; 1397 u_int8_t *opt; 1398 1399 KASSERT(src->scrub == NULL); 1400 1401 src->scrub = pool_get(&pf_state_scrub_pl, PR_NOWAIT); 1402 if (src->scrub == NULL) 1403 return (1); 1404 bzero(src->scrub, sizeof(*src->scrub)); 1405 1406 switch (pd->af) { 1407 #ifdef INET 1408 case AF_INET: { 1409 struct ip *h = mtod(m, struct ip *); 1410 src->scrub->pfss_ttl = h->ip_ttl; 1411 break; 1412 } 1413 #endif /* INET */ 1414 #ifdef INET6 1415 case AF_INET6: { 1416 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1417 src->scrub->pfss_ttl = h->ip6_hlim; 1418 break; 1419 } 1420 #endif /* INET6 */ 1421 } 1422 1423 1424 /* 1425 * All normalizations below are only begun if we see the start of 1426 * the connections. They must all set an enabled bit in pfss_flags 1427 */ 1428 if ((th->th_flags & TH_SYN) == 0) 1429 return (0); 1430 1431 1432 if (th->th_off > (sizeof(struct tcphdr) >> 2) && src->scrub && 1433 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) { 1434 /* Diddle with TCP options */ 1435 int hlen; 1436 opt = hdr + sizeof(struct tcphdr); 1437 hlen = (th->th_off << 2) - sizeof(struct tcphdr); 1438 while (hlen >= TCPOLEN_TIMESTAMP) { 1439 switch (*opt) { 1440 case TCPOPT_EOL: /* FALLTHROUGH */ 1441 case TCPOPT_NOP: 1442 opt++; 1443 hlen--; 1444 break; 1445 case TCPOPT_TIMESTAMP: 1446 if (opt[1] >= TCPOLEN_TIMESTAMP) { 1447 src->scrub->pfss_flags |= 1448 PFSS_TIMESTAMP; 1449 src->scrub->pfss_ts_mod = 1450 htonl(cprng_fast32()); 1451 1452 /* note PFSS_PAWS not set yet */ 1453 memcpy(&tsval, &opt[2], 1454 sizeof(u_int32_t)); 1455 memcpy(&tsecr, &opt[6], 1456 sizeof(u_int32_t)); 1457 src->scrub->pfss_tsval0 = ntohl(tsval); 1458 src->scrub->pfss_tsval = ntohl(tsval); 1459 src->scrub->pfss_tsecr = ntohl(tsecr); 1460 getmicrouptime(&src->scrub->pfss_last); 1461 } 1462 /* FALLTHROUGH */ 1463 default: 1464 hlen -= MAX(opt[1], 2); 1465 opt += MAX(opt[1], 2); 1466 break; 1467 } 1468 } 1469 } 1470 1471 return (0); 1472 } 1473 1474 void 1475 pf_normalize_tcp_cleanup(struct pf_state *state) 1476 { 1477 if (state->src.scrub) 1478 pool_put(&pf_state_scrub_pl, state->src.scrub); 1479 if (state->dst.scrub) 1480 pool_put(&pf_state_scrub_pl, state->dst.scrub); 1481 1482 /* Someday... flush the TCP segment reassembly descriptors. */ 1483 } 1484 1485 int 1486 pf_normalize_tcp_stateful(struct mbuf *m, int off, struct pf_pdesc *pd, 1487 u_short *reason, struct tcphdr *th, struct pf_state *state, 1488 struct pf_state_peer *src, struct pf_state_peer *dst, int *writeback) 1489 { 1490 struct timeval uptime; 1491 u_int32_t tsval = 0, tsecr = 0; 1492 u_int tsval_from_last; 1493 u_int8_t hdr[60]; 1494 u_int8_t *opt; 1495 int copyback = 0; 1496 int got_ts = 0; 1497 1498 KASSERT(src->scrub || dst->scrub); 1499 1500 /* 1501 * Enforce the minimum TTL seen for this connection. Negate a common 1502 * technique to evade an intrusion detection system and confuse 1503 * firewall state code. 1504 */ 1505 switch (pd->af) { 1506 #ifdef INET 1507 case AF_INET: { 1508 if (src->scrub) { 1509 struct ip *h = mtod(m, struct ip *); 1510 if (h->ip_ttl > src->scrub->pfss_ttl) 1511 src->scrub->pfss_ttl = h->ip_ttl; 1512 h->ip_ttl = src->scrub->pfss_ttl; 1513 } 1514 break; 1515 } 1516 #endif /* INET */ 1517 #ifdef INET6 1518 case AF_INET6: { 1519 if (src->scrub) { 1520 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1521 if (h->ip6_hlim > src->scrub->pfss_ttl) 1522 src->scrub->pfss_ttl = h->ip6_hlim; 1523 h->ip6_hlim = src->scrub->pfss_ttl; 1524 } 1525 break; 1526 } 1527 #endif /* INET6 */ 1528 } 1529 1530 if (th->th_off > (sizeof(struct tcphdr) >> 2) && 1531 ((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) || 1532 (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) && 1533 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) { 1534 /* Diddle with TCP options */ 1535 int hlen; 1536 opt = hdr + sizeof(struct tcphdr); 1537 hlen = (th->th_off << 2) - sizeof(struct tcphdr); 1538 while (hlen >= TCPOLEN_TIMESTAMP) { 1539 switch (*opt) { 1540 case TCPOPT_EOL: /* FALLTHROUGH */ 1541 case TCPOPT_NOP: 1542 opt++; 1543 hlen--; 1544 break; 1545 case TCPOPT_TIMESTAMP: 1546 /* Modulate the timestamps. Can be used for 1547 * NAT detection, OS uptime determination or 1548 * reboot detection. 1549 */ 1550 1551 if (got_ts) { 1552 /* Huh? Multiple timestamps!? */ 1553 if (pf_status.debug >= PF_DEBUG_MISC) { 1554 DPFPRINTF(("multiple TS??")); 1555 pf_print_state(state); 1556 printf("\n"); 1557 } 1558 REASON_SET(reason, PFRES_TS); 1559 return (PF_DROP); 1560 } 1561 if (opt[1] >= TCPOLEN_TIMESTAMP) { 1562 memcpy(&tsval, &opt[2], 1563 sizeof(u_int32_t)); 1564 if (tsval && src->scrub && 1565 (src->scrub->pfss_flags & 1566 PFSS_TIMESTAMP)) { 1567 tsval = ntohl(tsval); 1568 pf_change_a(&opt[2], 1569 &th->th_sum, 1570 htonl(tsval + 1571 src->scrub->pfss_ts_mod), 1572 0); 1573 copyback = 1; 1574 } 1575 1576 /* Modulate TS reply iff valid (!0) */ 1577 memcpy(&tsecr, &opt[6], 1578 sizeof(u_int32_t)); 1579 if (tsecr && dst->scrub && 1580 (dst->scrub->pfss_flags & 1581 PFSS_TIMESTAMP)) { 1582 tsecr = ntohl(tsecr) 1583 - dst->scrub->pfss_ts_mod; 1584 pf_change_a(&opt[6], 1585 &th->th_sum, htonl(tsecr), 1586 0); 1587 copyback = 1; 1588 } 1589 got_ts = 1; 1590 } 1591 /* FALLTHROUGH */ 1592 default: 1593 hlen -= MAX(opt[1], 2); 1594 opt += MAX(opt[1], 2); 1595 break; 1596 } 1597 } 1598 if (copyback) { 1599 /* Copyback the options, caller copys back header */ 1600 *writeback = 1; 1601 m_copyback(m, off + sizeof(struct tcphdr), 1602 (th->th_off << 2) - sizeof(struct tcphdr), hdr + 1603 sizeof(struct tcphdr)); 1604 } 1605 } 1606 1607 1608 /* 1609 * Must invalidate PAWS checks on connections idle for too long. 1610 * The fastest allowed timestamp clock is 1ms. That turns out to 1611 * be about 24 days before it wraps. XXX Right now our lowerbound 1612 * TS echo check only works for the first 12 days of a connection 1613 * when the TS has exhausted half its 32bit space 1614 */ 1615 #define TS_MAX_IDLE (24*24*60*60) 1616 #define TS_MAX_CONN (12*24*60*60) /* XXX remove when better tsecr check */ 1617 1618 getmicrouptime(&uptime); 1619 if (src->scrub && (src->scrub->pfss_flags & PFSS_PAWS) && 1620 (uptime.tv_sec - src->scrub->pfss_last.tv_sec > TS_MAX_IDLE || 1621 time_second - state->creation > TS_MAX_CONN)) { 1622 if (pf_status.debug >= PF_DEBUG_MISC) { 1623 DPFPRINTF(("src idled out of PAWS\n")); 1624 pf_print_state(state); 1625 printf("\n"); 1626 } 1627 src->scrub->pfss_flags = (src->scrub->pfss_flags & ~PFSS_PAWS) 1628 | PFSS_PAWS_IDLED; 1629 } 1630 if (dst->scrub && (dst->scrub->pfss_flags & PFSS_PAWS) && 1631 uptime.tv_sec - dst->scrub->pfss_last.tv_sec > TS_MAX_IDLE) { 1632 if (pf_status.debug >= PF_DEBUG_MISC) { 1633 DPFPRINTF(("dst idled out of PAWS\n")); 1634 pf_print_state(state); 1635 printf("\n"); 1636 } 1637 dst->scrub->pfss_flags = (dst->scrub->pfss_flags & ~PFSS_PAWS) 1638 | PFSS_PAWS_IDLED; 1639 } 1640 1641 if (got_ts && src->scrub && dst->scrub && 1642 (src->scrub->pfss_flags & PFSS_PAWS) && 1643 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1644 /* Validate that the timestamps are "in-window". 1645 * RFC1323 describes TCP Timestamp options that allow 1646 * measurement of RTT (round trip time) and PAWS 1647 * (protection against wrapped sequence numbers). PAWS 1648 * gives us a set of rules for rejecting packets on 1649 * long fat pipes (packets that were somehow delayed 1650 * in transit longer than the time it took to send the 1651 * full TCP sequence space of 4Gb). We can use these 1652 * rules and infer a few others that will let us treat 1653 * the 32bit timestamp and the 32bit echoed timestamp 1654 * as sequence numbers to prevent a blind attacker from 1655 * inserting packets into a connection. 1656 * 1657 * RFC1323 tells us: 1658 * - The timestamp on this packet must be greater than 1659 * or equal to the last value echoed by the other 1660 * endpoint. The RFC says those will be discarded 1661 * since it is a dup that has already been acked. 1662 * This gives us a lowerbound on the timestamp. 1663 * timestamp >= other last echoed timestamp 1664 * - The timestamp will be less than or equal to 1665 * the last timestamp plus the time between the 1666 * last packet and now. The RFC defines the max 1667 * clock rate as 1ms. We will allow clocks to be 1668 * up to 10% fast and will allow a total difference 1669 * or 30 seconds due to a route change. And this 1670 * gives us an upperbound on the timestamp. 1671 * timestamp <= last timestamp + max ticks 1672 * We have to be careful here. Windows will send an 1673 * initial timestamp of zero and then initialize it 1674 * to a random value after the 3whs; presumably to 1675 * avoid a DoS by having to call an expensive RNG 1676 * during a SYN flood. Proof MS has at least one 1677 * good security geek. 1678 * 1679 * - The TCP timestamp option must also echo the other 1680 * endpoints timestamp. The timestamp echoed is the 1681 * one carried on the earliest unacknowledged segment 1682 * on the left edge of the sequence window. The RFC 1683 * states that the host will reject any echoed 1684 * timestamps that were larger than any ever sent. 1685 * This gives us an upperbound on the TS echo. 1686 * tescr <= largest_tsval 1687 * - The lowerbound on the TS echo is a little more 1688 * tricky to determine. The other endpoint's echoed 1689 * values will not decrease. But there may be 1690 * network conditions that re-order packets and 1691 * cause our view of them to decrease. For now the 1692 * only lowerbound we can safely determine is that 1693 * the TS echo will never be less than the original 1694 * TS. XXX There is probably a better lowerbound. 1695 * Remove TS_MAX_CONN with better lowerbound check. 1696 * tescr >= other original TS 1697 * 1698 * It is also important to note that the fastest 1699 * timestamp clock of 1ms will wrap its 32bit space in 1700 * 24 days. So we just disable TS checking after 24 1701 * days of idle time. We actually must use a 12d 1702 * connection limit until we can come up with a better 1703 * lowerbound to the TS echo check. 1704 */ 1705 struct timeval delta_ts; 1706 int ts_fudge; 1707 1708 1709 /* 1710 * PFTM_TS_DIFF is how many seconds of leeway to allow 1711 * a host's timestamp. This can happen if the previous 1712 * packet got delayed in transit for much longer than 1713 * this packet. 1714 */ 1715 if ((ts_fudge = state->rule.ptr->timeout[PFTM_TS_DIFF]) == 0) 1716 ts_fudge = pf_default_rule.timeout[PFTM_TS_DIFF]; 1717 1718 1719 /* Calculate max ticks since the last timestamp */ 1720 #define TS_MAXFREQ 1100 /* RFC max TS freq of 1 kHz + 10% skew */ 1721 #define TS_MICROSECS 1000000 /* microseconds per second */ 1722 timersub(&uptime, &src->scrub->pfss_last, &delta_ts); 1723 tsval_from_last = (delta_ts.tv_sec + ts_fudge) * TS_MAXFREQ; 1724 tsval_from_last += delta_ts.tv_usec / (TS_MICROSECS/TS_MAXFREQ); 1725 1726 1727 if ((src->state >= TCPS_ESTABLISHED && 1728 dst->state >= TCPS_ESTABLISHED) && 1729 (SEQ_LT(tsval, dst->scrub->pfss_tsecr) || 1730 SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) || 1731 (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) || 1732 SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) { 1733 /* Bad RFC1323 implementation or an insertion attack. 1734 * 1735 * - Solaris 2.6 and 2.7 are known to send another ACK 1736 * after the FIN,FIN|ACK,ACK closing that carries 1737 * an old timestamp. 1738 */ 1739 1740 DPFPRINTF(("Timestamp failed %c%c%c%c\n", 1741 SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '0' : ' ', 1742 SEQ_GT(tsval, src->scrub->pfss_tsval + 1743 tsval_from_last) ? '1' : ' ', 1744 SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ', 1745 SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' ')); 1746 DPFPRINTF((" tsval: %" PRIu32 " tsecr: %" PRIu32 1747 " +ticks: %" PRIu32 " idle: %"PRIx64"s %ums\n", 1748 tsval, tsecr, tsval_from_last, delta_ts.tv_sec, 1749 delta_ts.tv_usec / 1000U)); 1750 DPFPRINTF((" src->tsval: %" PRIu32 " tsecr: %" PRIu32 1751 "\n", 1752 src->scrub->pfss_tsval, src->scrub->pfss_tsecr)); 1753 DPFPRINTF((" dst->tsval: %" PRIu32 " tsecr: %" PRIu32 1754 " tsval0: %" PRIu32 "\n", 1755 dst->scrub->pfss_tsval, 1756 dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0)); 1757 if (pf_status.debug >= PF_DEBUG_MISC) { 1758 pf_print_state(state); 1759 pf_print_flags(th->th_flags); 1760 printf("\n"); 1761 } 1762 REASON_SET(reason, PFRES_TS); 1763 return (PF_DROP); 1764 } 1765 1766 /* XXX I'd really like to require tsecr but it's optional */ 1767 1768 } else if (!got_ts && (th->th_flags & TH_RST) == 0 && 1769 ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED) 1770 || pd->p_len > 0 || (th->th_flags & TH_SYN)) && 1771 src->scrub && dst->scrub && 1772 (src->scrub->pfss_flags & PFSS_PAWS) && 1773 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1774 /* Didn't send a timestamp. Timestamps aren't really useful 1775 * when: 1776 * - connection opening or closing (often not even sent). 1777 * but we must not let an attacker to put a FIN on a 1778 * data packet to sneak it through our ESTABLISHED check. 1779 * - on a TCP reset. RFC suggests not even looking at TS. 1780 * - on an empty ACK. The TS will not be echoed so it will 1781 * probably not help keep the RTT calculation in sync and 1782 * there isn't as much danger when the sequence numbers 1783 * got wrapped. So some stacks don't include TS on empty 1784 * ACKs :-( 1785 * 1786 * To minimize the disruption to mostly RFC1323 conformant 1787 * stacks, we will only require timestamps on data packets. 1788 * 1789 * And what do ya know, we cannot require timestamps on data 1790 * packets. There appear to be devices that do legitimate 1791 * TCP connection hijacking. There are HTTP devices that allow 1792 * a 3whs (with timestamps) and then buffer the HTTP request. 1793 * If the intermediate device has the HTTP response cache, it 1794 * will spoof the response but not bother timestamping its 1795 * packets. So we can look for the presence of a timestamp in 1796 * the first data packet and if there, require it in all future 1797 * packets. 1798 */ 1799 1800 if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) { 1801 /* 1802 * Hey! Someone tried to sneak a packet in. Or the 1803 * stack changed its RFC1323 behavior?!?! 1804 */ 1805 if (pf_status.debug >= PF_DEBUG_MISC) { 1806 DPFPRINTF(("Did not receive expected RFC1323 " 1807 "timestamp\n")); 1808 pf_print_state(state); 1809 pf_print_flags(th->th_flags); 1810 printf("\n"); 1811 } 1812 REASON_SET(reason, PFRES_TS); 1813 return (PF_DROP); 1814 } 1815 } 1816 1817 1818 /* 1819 * We will note if a host sends his data packets with or without 1820 * timestamps. And require all data packets to contain a timestamp 1821 * if the first does. PAWS implicitly requires that all data packets be 1822 * timestamped. But I think there are middle-man devices that hijack 1823 * TCP streams immediately after the 3whs and don't timestamp their 1824 * packets (seen in a WWW accelerator or cache). 1825 */ 1826 if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags & 1827 (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) { 1828 if (got_ts) 1829 src->scrub->pfss_flags |= PFSS_DATA_TS; 1830 else { 1831 src->scrub->pfss_flags |= PFSS_DATA_NOTS; 1832 if (pf_status.debug >= PF_DEBUG_MISC && dst->scrub && 1833 (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) { 1834 /* Don't warn if other host rejected RFC1323 */ 1835 DPFPRINTF(("Broken RFC1323 stack did not " 1836 "timestamp data packet. Disabled PAWS " 1837 "security.\n")); 1838 pf_print_state(state); 1839 pf_print_flags(th->th_flags); 1840 printf("\n"); 1841 } 1842 } 1843 } 1844 1845 1846 /* 1847 * Update PAWS values 1848 */ 1849 if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags & 1850 (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) { 1851 getmicrouptime(&src->scrub->pfss_last); 1852 if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) || 1853 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1854 src->scrub->pfss_tsval = tsval; 1855 1856 if (tsecr) { 1857 if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) || 1858 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1859 src->scrub->pfss_tsecr = tsecr; 1860 1861 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 && 1862 (SEQ_LT(tsval, src->scrub->pfss_tsval0) || 1863 src->scrub->pfss_tsval0 == 0)) { 1864 /* tsval0 MUST be the lowest timestamp */ 1865 src->scrub->pfss_tsval0 = tsval; 1866 } 1867 1868 /* Only fully initialized after a TS gets echoed */ 1869 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0) 1870 src->scrub->pfss_flags |= PFSS_PAWS; 1871 } 1872 } 1873 1874 /* I have a dream.... TCP segment reassembly.... */ 1875 return (0); 1876 } 1877 1878 int 1879 pf_normalize_tcpopt(struct pf_rule *r, struct mbuf *m, struct tcphdr *th, 1880 int off) 1881 { 1882 u_int16_t *mss; 1883 int thoff; 1884 int opt, cnt, optlen = 0; 1885 int rewrite = 0; 1886 u_char *optp; 1887 1888 thoff = th->th_off << 2; 1889 cnt = thoff - sizeof(struct tcphdr); 1890 optp = mtod(m, u_char *) + off + sizeof(struct tcphdr); 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 return (rewrite); 1921 } 1922