1 /* $OpenBSD: pf_norm.c,v 1.113 2008/05/07 07:07:29 markus Exp $ */ 2 3 /* 4 * Copyright (c) 2010 The DragonFly Project. All rights reserved. 5 * 6 * Copyright 2001 Niels Provos <provos@citi.umich.edu> 7 * All rights reserved. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 */ 29 30 #include "opt_inet.h" 31 #include "opt_inet6.h" 32 33 #include <sys/param.h> 34 #include <sys/systm.h> 35 #include <sys/mbuf.h> 36 #include <sys/filio.h> 37 #include <sys/fcntl.h> 38 #include <sys/malloc.h> 39 #include <sys/socket.h> 40 #include <sys/kernel.h> 41 #include <sys/time.h> 42 43 #include <net/if.h> 44 #include <net/if_var.h> 45 #include <net/if_types.h> 46 #include <net/bpf.h> 47 #include <net/route.h> 48 #include <net/pf/if_pflog.h> 49 50 #include <netinet/in.h> 51 #include <netinet/in_var.h> 52 #include <netinet/in_systm.h> 53 #include <netinet/ip.h> 54 #include <netinet/ip_var.h> 55 #include <netinet/tcp.h> 56 #include <netinet/tcp_seq.h> 57 #include <netinet/udp.h> 58 #include <netinet/ip_icmp.h> 59 60 #ifdef INET6 61 #include <netinet/ip6.h> 62 #endif /* INET6 */ 63 64 #include <net/pf/pfvar.h> 65 66 #define PFFRAG_SEENLAST 0x0001 /* Seen the last fragment for this */ 67 #define PFFRAG_NOBUFFER 0x0002 /* Non-buffering fragment cache */ 68 #define PFFRAG_DROP 0x0004 /* Drop all fragments */ 69 #define BUFFER_FRAGMENTS(fr) (!((fr)->fr_flags & PFFRAG_NOBUFFER)) 70 71 72 TAILQ_HEAD(pf_fragqueue, pf_fragment) *pf_fragqueue; 73 TAILQ_HEAD(pf_cachequeue, pf_fragment) *pf_cachequeue; 74 75 static __inline int pf_frag_compare(struct pf_fragment *, 76 struct pf_fragment *); 77 RB_HEAD(pf_frag_tree, pf_fragment) *pf_frag_tree, 78 *pf_cache_tree; 79 RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); 80 RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); 81 82 /* Private prototypes */ 83 void pf_ip2key(struct pf_fragment *, struct ip *); 84 void pf_remove_fragment(struct pf_fragment *); 85 void pf_flush_fragments(void); 86 void pf_free_fragment(struct pf_fragment *); 87 struct pf_fragment *pf_find_fragment(struct ip *, struct pf_frag_tree *); 88 struct mbuf *pf_reassemble(struct mbuf **, struct pf_fragment **, 89 struct pf_frent *, int); 90 struct mbuf *pf_fragcache(struct mbuf **, struct ip*, 91 struct pf_fragment **, int, int, int *); 92 int pf_normalize_tcpopt(struct pf_rule *, struct mbuf *, 93 struct tcphdr *, int, sa_family_t); 94 95 #define DPFPRINTF(x) do { \ 96 if (pf_status.debug >= PF_DEBUG_MISC) { \ 97 kprintf("%s: ", __func__); \ 98 kprintf x ; \ 99 } \ 100 } while(0) 101 102 static MALLOC_DEFINE(M_PFFRAGPL, "pffrag", "pf fragment pool list"); 103 static MALLOC_DEFINE(M_PFCACHEPL, "pffrcache", "pf fragment cache pool list"); 104 static MALLOC_DEFINE(M_PFFRENTPL, "pffrent", "pf frent pool list"); 105 static MALLOC_DEFINE(M_PFCENTPL, "pffrcent", "pf fragment cent pool list"); 106 static MALLOC_DEFINE(M_PFSTATESCRUBPL, "pfstatescrub", "pf state scrub pool list"); 107 108 /* Globals */ 109 struct malloc_type *pf_frent_pl, *pf_frag_pl, *pf_cache_pl, *pf_cent_pl; 110 struct malloc_type *pf_state_scrub_pl; 111 int pf_nfrents, pf_ncache; 112 113 void 114 pf_normalize_init(void) 115 { 116 int n; 117 118 /* XXX 119 pool_sethiwat(&pf_frag_pl, PFFRAG_FRAG_HIWAT); 120 pool_sethardlimit(&pf_frent_pl, PFFRAG_FRENT_HIWAT, NULL, 0); 121 pool_sethardlimit(&pf_cache_pl, PFFRAG_FRCACHE_HIWAT, NULL, 0); 122 pool_sethardlimit(&pf_cent_pl, PFFRAG_FRCENT_HIWAT, NULL, 0); 123 */ 124 125 /* 126 * pcpu queues and trees 127 */ 128 pf_fragqueue = kmalloc(sizeof(*pf_fragqueue) * ncpus, 129 M_PF, M_WAITOK | M_ZERO); 130 pf_cachequeue = kmalloc(sizeof(*pf_cachequeue) * ncpus, 131 M_PF, M_WAITOK | M_ZERO); 132 pf_frag_tree = kmalloc(sizeof(*pf_frag_tree) * ncpus, 133 M_PF, M_WAITOK | M_ZERO); 134 pf_cache_tree = kmalloc(sizeof(*pf_cache_tree) * ncpus, 135 M_PF, M_WAITOK | M_ZERO); 136 137 for (n = 0; n < ncpus; ++n) { 138 TAILQ_INIT(&pf_fragqueue[n]); 139 TAILQ_INIT(&pf_cachequeue[n]); 140 RB_INIT(&pf_frag_tree[n]); 141 RB_INIT(&pf_cache_tree[n]); 142 } 143 } 144 145 void 146 pf_normalize_unload(void) 147 { 148 kfree(pf_fragqueue, M_PF); 149 kfree(pf_cachequeue, M_PF); 150 kfree(pf_frag_tree, M_PF); 151 kfree(pf_cache_tree, M_PF); 152 } 153 154 static __inline int 155 pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b) 156 { 157 int diff; 158 159 if ((diff = a->fr_id - b->fr_id)) 160 return (diff); 161 else if ((diff = a->fr_p - b->fr_p)) 162 return (diff); 163 else if (a->fr_src.s_addr < b->fr_src.s_addr) 164 return (-1); 165 else if (a->fr_src.s_addr > b->fr_src.s_addr) 166 return (1); 167 else if (a->fr_dst.s_addr < b->fr_dst.s_addr) 168 return (-1); 169 else if (a->fr_dst.s_addr > b->fr_dst.s_addr) 170 return (1); 171 return (0); 172 } 173 174 void 175 pf_purge_expired_fragments(void) 176 { 177 struct pf_fragment *frag; 178 u_int32_t expire; 179 int cpu = mycpu->gd_cpuid; 180 181 expire = time_second - pf_default_rule.timeout[PFTM_FRAG]; 182 183 while ((frag = TAILQ_LAST(&pf_fragqueue[cpu], pf_fragqueue)) != NULL) { 184 KASSERT((BUFFER_FRAGMENTS(frag)), 185 ("BUFFER_FRAGMENTS(frag) == 0: %s", __func__)); 186 if (frag->fr_timeout > expire) 187 break; 188 189 DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag)); 190 pf_free_fragment(frag); 191 } 192 193 while ((frag = TAILQ_LAST(&pf_cachequeue[cpu], pf_cachequeue)) != NULL) { 194 KASSERT((!BUFFER_FRAGMENTS(frag)), 195 ("BUFFER_FRAGMENTS(frag) != 0: %s", __func__)); 196 if (frag->fr_timeout > expire) 197 break; 198 199 DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag)); 200 pf_free_fragment(frag); 201 KASSERT((TAILQ_EMPTY(&pf_cachequeue[cpu]) || 202 TAILQ_LAST(&pf_cachequeue[cpu], pf_cachequeue) != frag), 203 ("!(TAILQ_EMPTY() || TAILQ_LAST() == farg): %s", 204 __func__)); 205 } 206 } 207 208 /* 209 * Try to flush old fragments to make space for new ones 210 */ 211 212 void 213 pf_flush_fragments(void) 214 { 215 struct pf_fragment *frag; 216 int goal; 217 int cpu = mycpu->gd_cpuid; 218 219 goal = pf_nfrents * 9 / 10; 220 DPFPRINTF(("trying to free > %d frents\n", 221 pf_nfrents - goal)); 222 while (goal < pf_nfrents) { 223 frag = TAILQ_LAST(&pf_fragqueue[cpu], pf_fragqueue); 224 if (frag == NULL) 225 break; 226 pf_free_fragment(frag); 227 } 228 229 230 goal = pf_ncache * 9 / 10; 231 DPFPRINTF(("trying to free > %d cache entries\n", 232 pf_ncache - goal)); 233 while (goal < pf_ncache) { 234 frag = TAILQ_LAST(&pf_cachequeue[cpu], pf_cachequeue); 235 if (frag == NULL) 236 break; 237 pf_free_fragment(frag); 238 } 239 } 240 241 /* Frees the fragments and all associated entries */ 242 243 void 244 pf_free_fragment(struct pf_fragment *frag) 245 { 246 struct pf_frent *frent; 247 struct pf_frcache *frcache; 248 249 /* Free all fragments */ 250 if (BUFFER_FRAGMENTS(frag)) { 251 for (frent = LIST_FIRST(&frag->fr_queue); frent; 252 frent = LIST_FIRST(&frag->fr_queue)) { 253 LIST_REMOVE(frent, fr_next); 254 255 m_freem(frent->fr_m); 256 kfree(frent, M_PFFRENTPL); 257 pf_nfrents--; 258 } 259 } else { 260 for (frcache = LIST_FIRST(&frag->fr_cache); frcache; 261 frcache = LIST_FIRST(&frag->fr_cache)) { 262 LIST_REMOVE(frcache, fr_next); 263 264 KASSERT((LIST_EMPTY(&frag->fr_cache) || 265 LIST_FIRST(&frag->fr_cache)->fr_off > 266 frcache->fr_end), 267 ("! (LIST_EMPTY() || LIST_FIRST()->fr_off >" 268 " frcache->fr_end): %s", __func__)); 269 270 kfree(frcache, M_PFCENTPL); 271 pf_ncache--; 272 } 273 } 274 275 pf_remove_fragment(frag); 276 } 277 278 void 279 pf_ip2key(struct pf_fragment *key, struct ip *ip) 280 { 281 key->fr_p = ip->ip_p; 282 key->fr_id = ip->ip_id; 283 key->fr_src.s_addr = ip->ip_src.s_addr; 284 key->fr_dst.s_addr = ip->ip_dst.s_addr; 285 } 286 287 struct pf_fragment * 288 pf_find_fragment(struct ip *ip, struct pf_frag_tree *tree) 289 { 290 struct pf_fragment key; 291 struct pf_fragment *frag; 292 int cpu = mycpu->gd_cpuid; 293 294 pf_ip2key(&key, ip); 295 296 frag = RB_FIND(pf_frag_tree, tree, &key); 297 if (frag != NULL) { 298 /* XXX Are we sure we want to update the timeout? */ 299 frag->fr_timeout = time_second; 300 if (BUFFER_FRAGMENTS(frag)) { 301 TAILQ_REMOVE(&pf_fragqueue[cpu], frag, frag_next); 302 TAILQ_INSERT_HEAD(&pf_fragqueue[cpu], frag, frag_next); 303 } else { 304 TAILQ_REMOVE(&pf_cachequeue[cpu], frag, frag_next); 305 TAILQ_INSERT_HEAD(&pf_cachequeue[cpu], frag, frag_next); 306 } 307 } 308 309 return (frag); 310 } 311 312 /* Removes a fragment from the fragment queue and frees the fragment */ 313 314 void 315 pf_remove_fragment(struct pf_fragment *frag) 316 { 317 int cpu = mycpu->gd_cpuid; 318 319 if (BUFFER_FRAGMENTS(frag)) { 320 RB_REMOVE(pf_frag_tree, &pf_frag_tree[cpu], frag); 321 TAILQ_REMOVE(&pf_fragqueue[cpu], frag, frag_next); 322 kfree(frag, M_PFFRAGPL); 323 } else { 324 RB_REMOVE(pf_frag_tree, &pf_cache_tree[cpu], frag); 325 TAILQ_REMOVE(&pf_cachequeue[cpu], frag, frag_next); 326 kfree(frag, M_PFCACHEPL); 327 } 328 } 329 330 #define FR_IP_OFF(fr) (((fr)->fr_ip->ip_off & IP_OFFMASK) << 3) 331 struct mbuf * 332 pf_reassemble(struct mbuf **m0, struct pf_fragment **frag, 333 struct pf_frent *frent, int mff) 334 { 335 struct mbuf *m = *m0, *m2; 336 struct pf_frent *frea, *next; 337 struct pf_frent *frep = NULL; 338 struct ip *ip = frent->fr_ip; 339 int hlen = ip->ip_hl << 2; 340 u_int16_t off = (ip->ip_off & IP_OFFMASK) << 3; 341 u_int16_t ip_len = ip->ip_len - ip->ip_hl * 4; 342 u_int16_t max = ip_len + off; 343 int cpu = mycpu->gd_cpuid; 344 345 KASSERT((*frag == NULL || BUFFER_FRAGMENTS(*frag)), 346 ("! (*frag == NULL || BUFFER_FRAGMENTS(*frag)): %s", __func__)); 347 348 /* Strip off ip header */ 349 m->m_data += hlen; 350 m->m_len -= hlen; 351 352 /* Create a new reassembly queue for this packet */ 353 if (*frag == NULL) { 354 *frag = kmalloc(sizeof(struct pf_fragment), M_PFFRAGPL, M_NOWAIT); 355 if (*frag == NULL) { 356 pf_flush_fragments(); 357 *frag = kmalloc(sizeof(struct pf_fragment), M_PFFRAGPL, M_NOWAIT); 358 if (*frag == NULL) 359 goto drop_fragment; 360 } 361 362 (*frag)->fr_flags = 0; 363 (*frag)->fr_max = 0; 364 (*frag)->fr_src = frent->fr_ip->ip_src; 365 (*frag)->fr_dst = frent->fr_ip->ip_dst; 366 (*frag)->fr_p = frent->fr_ip->ip_p; 367 (*frag)->fr_id = frent->fr_ip->ip_id; 368 (*frag)->fr_timeout = time_second; 369 LIST_INIT(&(*frag)->fr_queue); 370 371 RB_INSERT(pf_frag_tree, &pf_frag_tree[cpu], *frag); 372 TAILQ_INSERT_HEAD(&pf_fragqueue[cpu], *frag, frag_next); 373 374 /* We do not have a previous fragment */ 375 frep = NULL; 376 goto insert; 377 } 378 379 /* 380 * Find a fragment after the current one: 381 * - off contains the real shifted offset. 382 */ 383 LIST_FOREACH(frea, &(*frag)->fr_queue, fr_next) { 384 if (FR_IP_OFF(frea) > off) 385 break; 386 frep = frea; 387 } 388 389 KASSERT((frep != NULL || frea != NULL), 390 ("!(frep != NULL || frea != NULL): %s", __func__)); 391 392 if (frep != NULL && 393 FR_IP_OFF(frep) + frep->fr_ip->ip_len - frep->fr_ip->ip_hl * 394 4 > off) 395 { 396 u_int16_t precut; 397 398 precut = FR_IP_OFF(frep) + frep->fr_ip->ip_len - 399 frep->fr_ip->ip_hl * 4 - off; 400 if (precut >= ip_len) 401 goto drop_fragment; 402 m_adj(frent->fr_m, precut); 403 DPFPRINTF(("overlap -%d\n", precut)); 404 /* Enforce 8 byte boundaries */ 405 ip->ip_off = ip->ip_off + (precut >> 3); 406 off = (ip->ip_off & IP_OFFMASK) << 3; 407 ip_len -= precut; 408 ip->ip_len = ip_len; 409 } 410 411 for (; frea != NULL && ip_len + off > FR_IP_OFF(frea); 412 frea = next) 413 { 414 u_int16_t aftercut; 415 416 aftercut = ip_len + off - FR_IP_OFF(frea); 417 DPFPRINTF(("adjust overlap %d\n", aftercut)); 418 if (aftercut < frea->fr_ip->ip_len - frea->fr_ip->ip_hl 419 * 4) 420 { 421 frea->fr_ip->ip_len = 422 frea->fr_ip->ip_len - aftercut; 423 frea->fr_ip->ip_off = frea->fr_ip->ip_off + 424 (aftercut >> 3); 425 m_adj(frea->fr_m, aftercut); 426 break; 427 } 428 429 /* This fragment is completely overlapped, lose it */ 430 next = LIST_NEXT(frea, fr_next); 431 m_freem(frea->fr_m); 432 LIST_REMOVE(frea, fr_next); 433 kfree(frea, M_PFFRENTPL); 434 pf_nfrents--; 435 } 436 437 insert: 438 /* Update maximum data size */ 439 if ((*frag)->fr_max < max) 440 (*frag)->fr_max = max; 441 /* This is the last segment */ 442 if (!mff) 443 (*frag)->fr_flags |= PFFRAG_SEENLAST; 444 445 if (frep == NULL) 446 LIST_INSERT_HEAD(&(*frag)->fr_queue, frent, fr_next); 447 else 448 LIST_INSERT_AFTER(frep, frent, fr_next); 449 450 /* Check if we are completely reassembled */ 451 if (!((*frag)->fr_flags & PFFRAG_SEENLAST)) 452 return (NULL); 453 454 /* Check if we have all the data */ 455 off = 0; 456 for (frep = LIST_FIRST(&(*frag)->fr_queue); frep; frep = next) { 457 next = LIST_NEXT(frep, fr_next); 458 459 off += frep->fr_ip->ip_len - frep->fr_ip->ip_hl * 4; 460 if (off < (*frag)->fr_max && 461 (next == NULL || FR_IP_OFF(next) != off)) 462 { 463 DPFPRINTF(("missing fragment at %d, next %d, max %d\n", 464 off, next == NULL ? -1 : FR_IP_OFF(next), 465 (*frag)->fr_max)); 466 return (NULL); 467 } 468 } 469 DPFPRINTF(("%d < %d?\n", off, (*frag)->fr_max)); 470 if (off < (*frag)->fr_max) 471 return (NULL); 472 473 /* We have all the data */ 474 frent = LIST_FIRST(&(*frag)->fr_queue); 475 KASSERT((frent != NULL), ("frent == NULL: %s", __func__)); 476 if ((frent->fr_ip->ip_hl << 2) + off > IP_MAXPACKET) { 477 DPFPRINTF(("drop: too big: %d\n", off)); 478 pf_free_fragment(*frag); 479 *frag = NULL; 480 return (NULL); 481 } 482 next = LIST_NEXT(frent, fr_next); 483 484 /* Magic from ip_input */ 485 ip = frent->fr_ip; 486 m = frent->fr_m; 487 m2 = m->m_next; 488 m->m_next = NULL; 489 m_cat(m, m2); 490 kfree(frent, M_PFFRENTPL); 491 pf_nfrents--; 492 for (frent = next; frent != NULL; frent = next) { 493 next = LIST_NEXT(frent, fr_next); 494 495 m2 = frent->fr_m; 496 kfree(frent, M_PFFRENTPL); 497 pf_nfrents--; 498 m_cat(m, m2); 499 } 500 501 ip->ip_src = (*frag)->fr_src; 502 ip->ip_dst = (*frag)->fr_dst; 503 504 /* Remove from fragment queue */ 505 pf_remove_fragment(*frag); 506 *frag = NULL; 507 508 hlen = ip->ip_hl << 2; 509 ip->ip_len = off + hlen; 510 m->m_len += hlen; 511 m->m_data -= hlen; 512 513 /* some debugging cruft by sklower, below, will go away soon */ 514 /* XXX this should be done elsewhere */ 515 if (m->m_flags & M_PKTHDR) { 516 int plen = 0; 517 for (m2 = m; m2; m2 = m2->m_next) 518 plen += m2->m_len; 519 m->m_pkthdr.len = plen; 520 } 521 522 DPFPRINTF(("complete: %p(%d)\n", m, ip->ip_len)); 523 return (m); 524 525 drop_fragment: 526 /* Oops - fail safe - drop packet */ 527 kfree(frent, M_PFFRENTPL); 528 pf_nfrents--; 529 m_freem(m); 530 return (NULL); 531 } 532 533 struct mbuf * 534 pf_fragcache(struct mbuf **m0, struct ip *h, struct pf_fragment **frag, int mff, 535 int drop, int *nomem) 536 { 537 struct mbuf *m = *m0; 538 struct pf_frcache *frp, *fra, *cur = NULL; 539 int ip_len = h->ip_len - (h->ip_hl << 2); 540 u_int16_t off = h->ip_off << 3; 541 u_int16_t max = ip_len + off; 542 int hosed = 0; 543 int cpu = mycpu->gd_cpuid; 544 545 KASSERT((*frag == NULL || !BUFFER_FRAGMENTS(*frag)), 546 ("!(*frag == NULL || !BUFFER_FRAGMENTS(*frag)): %s", __func__)); 547 548 /* Create a new range queue for this packet */ 549 if (*frag == NULL) { 550 *frag = kmalloc(sizeof(struct pf_fragment), M_PFCACHEPL, M_NOWAIT); 551 if (*frag == NULL) { 552 pf_flush_fragments(); 553 *frag = kmalloc(sizeof(struct pf_fragment), M_PFCACHEPL, M_NOWAIT); 554 if (*frag == NULL) 555 goto no_mem; 556 } 557 558 /* Get an entry for the queue */ 559 cur = kmalloc(sizeof(struct pf_frcache), M_PFCENTPL, M_NOWAIT); 560 if (cur == NULL) { 561 kfree(*frag, M_PFCACHEPL); 562 *frag = NULL; 563 goto no_mem; 564 } 565 pf_ncache++; 566 567 (*frag)->fr_flags = PFFRAG_NOBUFFER; 568 (*frag)->fr_max = 0; 569 (*frag)->fr_src = h->ip_src; 570 (*frag)->fr_dst = h->ip_dst; 571 (*frag)->fr_p = h->ip_p; 572 (*frag)->fr_id = h->ip_id; 573 (*frag)->fr_timeout = time_second; 574 575 cur->fr_off = off; 576 cur->fr_end = max; 577 LIST_INIT(&(*frag)->fr_cache); 578 LIST_INSERT_HEAD(&(*frag)->fr_cache, cur, fr_next); 579 580 RB_INSERT(pf_frag_tree, &pf_cache_tree[cpu], *frag); 581 TAILQ_INSERT_HEAD(&pf_cachequeue[cpu], *frag, frag_next); 582 583 DPFPRINTF(("fragcache[%d]: new %d-%d\n", h->ip_id, off, max)); 584 585 goto pass; 586 } 587 588 /* 589 * Find a fragment after the current one: 590 * - off contains the real shifted offset. 591 */ 592 frp = NULL; 593 LIST_FOREACH(fra, &(*frag)->fr_cache, fr_next) { 594 if (fra->fr_off > off) 595 break; 596 frp = fra; 597 } 598 599 KASSERT((frp != NULL || fra != NULL), 600 ("!(frp != NULL || fra != NULL): %s", __func__)); 601 602 if (frp != NULL) { 603 int precut; 604 605 precut = frp->fr_end - off; 606 if (precut >= ip_len) { 607 /* Fragment is entirely a duplicate */ 608 DPFPRINTF(("fragcache[%d]: dead (%d-%d) %d-%d\n", 609 h->ip_id, frp->fr_off, frp->fr_end, off, max)); 610 goto drop_fragment; 611 } 612 if (precut == 0) { 613 /* They are adjacent. Fixup cache entry */ 614 DPFPRINTF(("fragcache[%d]: adjacent (%d-%d) %d-%d\n", 615 h->ip_id, frp->fr_off, frp->fr_end, off, max)); 616 frp->fr_end = max; 617 } else if (precut > 0) { 618 /* The first part of this payload overlaps with a 619 * fragment that has already been passed. 620 * Need to trim off the first part of the payload. 621 * But to do so easily, we need to create another 622 * mbuf to throw the original header into. 623 */ 624 625 DPFPRINTF(("fragcache[%d]: chop %d (%d-%d) %d-%d\n", 626 h->ip_id, precut, frp->fr_off, frp->fr_end, off, 627 max)); 628 629 off += precut; 630 max -= precut; 631 /* Update the previous frag to encompass this one */ 632 frp->fr_end = max; 633 634 if (!drop) { 635 /* XXX Optimization opportunity 636 * This is a very heavy way to trim the payload. 637 * we could do it much faster by diddling mbuf 638 * internals but that would be even less legible 639 * than this mbuf magic. For my next trick, 640 * I'll pull a rabbit out of my laptop. 641 */ 642 *m0 = m_dup(m, M_NOWAIT); 643 /* From KAME Project : We have missed this! */ 644 m_adj(*m0, (h->ip_hl << 2) - 645 (*m0)->m_pkthdr.len); 646 if (*m0 == NULL) 647 goto no_mem; 648 KASSERT(((*m0)->m_next == NULL), 649 ("(*m0)->m_next != NULL: %s", 650 __func__)); 651 m_adj(m, precut + (h->ip_hl << 2)); 652 m_cat(*m0, m); 653 m = *m0; 654 if (m->m_flags & M_PKTHDR) { 655 int plen = 0; 656 struct mbuf *t; 657 for (t = m; t; t = t->m_next) 658 plen += t->m_len; 659 m->m_pkthdr.len = plen; 660 } 661 662 663 h = mtod(m, struct ip *); 664 665 KASSERT(((int)m->m_len == 666 h->ip_len - precut), 667 ("m->m_len != h->ip_len - precut: %s", 668 __func__)); 669 h->ip_off = h->ip_off + 670 (precut >> 3); 671 h->ip_len = h->ip_len - precut; 672 } else { 673 hosed++; 674 } 675 } else { 676 /* There is a gap between fragments */ 677 678 DPFPRINTF(("fragcache[%d]: gap %d (%d-%d) %d-%d\n", 679 h->ip_id, -precut, frp->fr_off, frp->fr_end, off, 680 max)); 681 682 cur = kmalloc(sizeof(struct pf_frcache), M_PFCENTPL, M_NOWAIT); 683 if (cur == NULL) 684 goto no_mem; 685 pf_ncache++; 686 687 cur->fr_off = off; 688 cur->fr_end = max; 689 LIST_INSERT_AFTER(frp, cur, fr_next); 690 } 691 } 692 693 if (fra != NULL) { 694 int aftercut; 695 int merge = 0; 696 697 aftercut = max - fra->fr_off; 698 if (aftercut == 0) { 699 /* Adjacent fragments */ 700 DPFPRINTF(("fragcache[%d]: adjacent %d-%d (%d-%d)\n", 701 h->ip_id, off, max, fra->fr_off, fra->fr_end)); 702 fra->fr_off = off; 703 merge = 1; 704 } else if (aftercut > 0) { 705 /* Need to chop off the tail of this fragment */ 706 DPFPRINTF(("fragcache[%d]: chop %d %d-%d (%d-%d)\n", 707 h->ip_id, aftercut, off, max, fra->fr_off, 708 fra->fr_end)); 709 fra->fr_off = off; 710 max -= aftercut; 711 712 merge = 1; 713 714 if (!drop) { 715 m_adj(m, -aftercut); 716 if (m->m_flags & M_PKTHDR) { 717 int plen = 0; 718 struct mbuf *t; 719 for (t = m; t; t = t->m_next) 720 plen += t->m_len; 721 m->m_pkthdr.len = plen; 722 } 723 h = mtod(m, struct ip *); 724 KASSERT(((int)m->m_len == h->ip_len - aftercut), 725 ("m->m_len != h->ip_len - aftercut: %s", 726 __func__)); 727 h->ip_len = h->ip_len - aftercut; 728 } else { 729 hosed++; 730 } 731 } else if (frp == NULL) { 732 /* There is a gap between fragments */ 733 DPFPRINTF(("fragcache[%d]: gap %d %d-%d (%d-%d)\n", 734 h->ip_id, -aftercut, off, max, fra->fr_off, 735 fra->fr_end)); 736 737 cur = kmalloc(sizeof(struct pf_frcache), M_PFCENTPL, M_NOWAIT); 738 if (cur == NULL) 739 goto no_mem; 740 pf_ncache++; 741 742 cur->fr_off = off; 743 cur->fr_end = max; 744 LIST_INSERT_BEFORE(fra, cur, fr_next); 745 } 746 747 748 /* Need to glue together two separate fragment descriptors */ 749 if (merge) { 750 if (cur && fra->fr_off <= cur->fr_end) { 751 /* Need to merge in a previous 'cur' */ 752 DPFPRINTF(("fragcache[%d]: adjacent(merge " 753 "%d-%d) %d-%d (%d-%d)\n", 754 h->ip_id, cur->fr_off, cur->fr_end, off, 755 max, fra->fr_off, fra->fr_end)); 756 fra->fr_off = cur->fr_off; 757 LIST_REMOVE(cur, fr_next); 758 kfree(cur, M_PFCENTPL); 759 pf_ncache--; 760 cur = NULL; 761 762 } else if (frp && fra->fr_off <= frp->fr_end) { 763 /* Need to merge in a modified 'frp' */ 764 KASSERT((cur == NULL), ("cur != NULL: %s", 765 __func__)); 766 DPFPRINTF(("fragcache[%d]: adjacent(merge " 767 "%d-%d) %d-%d (%d-%d)\n", 768 h->ip_id, frp->fr_off, frp->fr_end, off, 769 max, fra->fr_off, fra->fr_end)); 770 fra->fr_off = frp->fr_off; 771 LIST_REMOVE(frp, fr_next); 772 kfree(frp, M_PFCENTPL); 773 pf_ncache--; 774 frp = NULL; 775 776 } 777 } 778 } 779 780 if (hosed) { 781 /* 782 * We must keep tracking the overall fragment even when 783 * we're going to drop it anyway so that we know when to 784 * free the overall descriptor. Thus we drop the frag late. 785 */ 786 goto drop_fragment; 787 } 788 789 790 pass: 791 /* Update maximum data size */ 792 if ((*frag)->fr_max < max) 793 (*frag)->fr_max = max; 794 795 /* This is the last segment */ 796 if (!mff) 797 (*frag)->fr_flags |= PFFRAG_SEENLAST; 798 799 /* Check if we are completely reassembled */ 800 if (((*frag)->fr_flags & PFFRAG_SEENLAST) && 801 LIST_FIRST(&(*frag)->fr_cache)->fr_off == 0 && 802 LIST_FIRST(&(*frag)->fr_cache)->fr_end == (*frag)->fr_max) { 803 /* Remove from fragment queue */ 804 DPFPRINTF(("fragcache[%d]: done 0-%d\n", h->ip_id, 805 (*frag)->fr_max)); 806 pf_free_fragment(*frag); 807 *frag = NULL; 808 } 809 810 return (m); 811 812 no_mem: 813 *nomem = 1; 814 815 /* Still need to pay attention to !IP_MF */ 816 if (!mff && *frag != NULL) 817 (*frag)->fr_flags |= PFFRAG_SEENLAST; 818 819 m_freem(m); 820 return (NULL); 821 822 drop_fragment: 823 824 /* Still need to pay attention to !IP_MF */ 825 if (!mff && *frag != NULL) 826 (*frag)->fr_flags |= PFFRAG_SEENLAST; 827 828 if (drop) { 829 /* This fragment has been deemed bad. Don't reass */ 830 if (((*frag)->fr_flags & PFFRAG_DROP) == 0) 831 DPFPRINTF(("fragcache[%d]: dropping overall fragment\n", 832 h->ip_id)); 833 (*frag)->fr_flags |= PFFRAG_DROP; 834 } 835 836 m_freem(m); 837 return (NULL); 838 } 839 840 int 841 pf_normalize_ip(struct mbuf **m0, int dir, struct pfi_kif *kif, u_short *reason, 842 struct pf_pdesc *pd) 843 { 844 struct mbuf *m = *m0; 845 struct pf_rule *r; 846 struct pf_frent *frent; 847 struct pf_fragment *frag = NULL; 848 struct ip *h = mtod(m, struct ip *); 849 int mff = (h->ip_off & IP_MF); 850 int hlen = h->ip_hl << 2; 851 u_int16_t fragoff = (h->ip_off & IP_OFFMASK) << 3; 852 u_int16_t max; 853 int ip_len; 854 int tag = -1; 855 int cpu = mycpu->gd_cpuid; 856 857 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 858 while (r != NULL) { 859 r->evaluations++; 860 if (pfi_kif_match(r->kif, kif) == r->ifnot) 861 r = r->skip[PF_SKIP_IFP].ptr; 862 else if (r->direction && r->direction != dir) 863 r = r->skip[PF_SKIP_DIR].ptr; 864 else if (r->af && r->af != AF_INET) 865 r = r->skip[PF_SKIP_AF].ptr; 866 else if (r->proto && r->proto != h->ip_p) 867 r = r->skip[PF_SKIP_PROTO].ptr; 868 else if (PF_MISMATCHAW(&r->src.addr, 869 (struct pf_addr *)&h->ip_src.s_addr, AF_INET, 870 r->src.neg, kif)) 871 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 872 else if (PF_MISMATCHAW(&r->dst.addr, 873 (struct pf_addr *)&h->ip_dst.s_addr, AF_INET, 874 r->dst.neg, NULL)) 875 r = r->skip[PF_SKIP_DST_ADDR].ptr; 876 else if (r->match_tag && !pf_match_tag(m, r, &tag)) 877 r = TAILQ_NEXT(r, entries); 878 else 879 break; 880 } 881 882 if (r == NULL || r->action == PF_NOSCRUB) 883 return (PF_PASS); 884 else { 885 r->packets[dir == PF_OUT]++; 886 r->bytes[dir == PF_OUT] += pd->tot_len; 887 } 888 889 /* Check for illegal packets */ 890 if (hlen < (int)sizeof(struct ip)) 891 goto drop; 892 893 if (hlen > h->ip_len) 894 goto drop; 895 896 /* Clear IP_DF if the rule uses the no-df option */ 897 if (r->rule_flag & PFRULE_NODF && h->ip_off & IP_DF) { 898 u_int16_t ip_off = h->ip_off; 899 900 h->ip_off &= ~IP_DF; 901 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0); 902 } 903 904 /* We will need other tests here */ 905 if (!fragoff && !mff) 906 goto no_fragment; 907 908 /* A fragment; rehash required. */ 909 m->m_flags &= ~M_HASH; 910 911 /* We're dealing with a fragment now. Don't allow fragments 912 * with IP_DF to enter the cache. If the flag was cleared by 913 * no-df above, fine. Otherwise drop it. 914 */ 915 if (h->ip_off & IP_DF) { 916 DPFPRINTF(("IP_DF\n")); 917 goto bad; 918 } 919 920 ip_len = h->ip_len - hlen; 921 922 /* All fragments are 8 byte aligned */ 923 if (mff && (ip_len & 0x7)) { 924 DPFPRINTF(("mff and %d\n", ip_len)); 925 goto bad; 926 } 927 928 /* Respect maximum length */ 929 if (fragoff + ip_len > IP_MAXPACKET) { 930 DPFPRINTF(("max packet %d\n", fragoff + ip_len)); 931 goto bad; 932 } 933 max = fragoff + ip_len; 934 935 if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0) { 936 /* Fully buffer all of the fragments */ 937 938 frag = pf_find_fragment(h, &pf_frag_tree[cpu]); 939 940 /* Check if we saw the last fragment already */ 941 if (frag != NULL && (frag->fr_flags & PFFRAG_SEENLAST) && 942 max > frag->fr_max) 943 goto bad; 944 945 /* Get an entry for the fragment queue */ 946 frent = kmalloc(sizeof(struct pf_frent), M_PFFRENTPL, M_NOWAIT); 947 if (frent == NULL) { 948 REASON_SET(reason, PFRES_MEMORY); 949 return (PF_DROP); 950 } 951 pf_nfrents++; 952 frent->fr_ip = h; 953 frent->fr_m = m; 954 955 /* Might return a completely reassembled mbuf, or NULL */ 956 DPFPRINTF(("reass frag %d @ %d-%d\n", h->ip_id, fragoff, max)); 957 *m0 = m = pf_reassemble(m0, &frag, frent, mff); 958 959 if (m == NULL) 960 return (PF_DROP); 961 962 if (frag != NULL && (frag->fr_flags & PFFRAG_DROP)) 963 goto drop; 964 965 h = mtod(m, struct ip *); 966 } else { 967 /* non-buffering fragment cache (drops or masks overlaps) */ 968 int nomem = 0; 969 970 if (dir == PF_OUT && m->m_pkthdr.pf.flags & PF_TAG_FRAGCACHE) { 971 /* 972 * Already passed the fragment cache in the 973 * input direction. If we continued, it would 974 * appear to be a dup and would be dropped. 975 */ 976 goto fragment_pass; 977 } 978 979 frag = pf_find_fragment(h, &pf_cache_tree[cpu]); 980 981 /* Check if we saw the last fragment already */ 982 if (frag != NULL && (frag->fr_flags & PFFRAG_SEENLAST) && 983 max > frag->fr_max) { 984 if (r->rule_flag & PFRULE_FRAGDROP) 985 frag->fr_flags |= PFFRAG_DROP; 986 goto bad; 987 } 988 989 *m0 = m = pf_fragcache(m0, h, &frag, mff, 990 (r->rule_flag & PFRULE_FRAGDROP) ? 1 : 0, &nomem); 991 if (m == NULL) { 992 if (nomem) 993 goto no_mem; 994 goto drop; 995 } 996 997 if (dir == PF_IN) 998 m->m_pkthdr.pf.flags |= PF_TAG_FRAGCACHE; 999 1000 if (frag != NULL && (frag->fr_flags & PFFRAG_DROP)) 1001 goto drop; 1002 goto fragment_pass; 1003 } 1004 1005 no_fragment: 1006 /* At this point, only IP_DF is allowed in ip_off */ 1007 if (h->ip_off & ~IP_DF) { 1008 u_int16_t ip_off = h->ip_off; 1009 1010 h->ip_off &= IP_DF; 1011 h->ip_sum = pf_cksum_fixup(h->ip_sum, htons(ip_off), htons(h->ip_off), 0); 1012 } 1013 1014 /* Enforce a minimum ttl, may cause endless packet loops */ 1015 if (r->min_ttl && h->ip_ttl < r->min_ttl) { 1016 u_int16_t ip_ttl = h->ip_ttl; 1017 1018 h->ip_ttl = r->min_ttl; 1019 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0); 1020 } 1021 1022 /* Enforce tos */ 1023 if (r->rule_flag & PFRULE_SET_TOS) { 1024 u_int16_t ov, nv; 1025 1026 ov = *(u_int16_t *)h; 1027 h->ip_tos = r->set_tos; 1028 nv = *(u_int16_t *)h; 1029 1030 h->ip_sum = pf_cksum_fixup(h->ip_sum, ov, nv, 0); 1031 } 1032 1033 if (r->rule_flag & PFRULE_RANDOMID) { 1034 u_int16_t ip_id = h->ip_id; 1035 1036 h->ip_id = ip_randomid(); 1037 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_id, h->ip_id, 0); 1038 } 1039 if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0) 1040 pd->flags |= PFDESC_IP_REAS; 1041 1042 return (PF_PASS); 1043 1044 fragment_pass: 1045 /* Enforce a minimum ttl, may cause endless packet loops */ 1046 if (r->min_ttl && h->ip_ttl < r->min_ttl) { 1047 u_int16_t ip_ttl = h->ip_ttl; 1048 1049 h->ip_ttl = r->min_ttl; 1050 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0); 1051 } 1052 /* Enforce tos */ 1053 if (r->rule_flag & PFRULE_SET_TOS) { 1054 u_int16_t ov, nv; 1055 1056 ov = *(u_int16_t *)h; 1057 h->ip_tos = r->set_tos; 1058 nv = *(u_int16_t *)h; 1059 1060 h->ip_sum = pf_cksum_fixup(h->ip_sum, ov, nv, 0); 1061 } 1062 if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0) 1063 pd->flags |= PFDESC_IP_REAS; 1064 return (PF_PASS); 1065 1066 no_mem: 1067 REASON_SET(reason, PFRES_MEMORY); 1068 if (r != NULL && r->log) 1069 PFLOG_PACKET(kif, h, m, AF_INET, dir, *reason, r, NULL, NULL, pd); 1070 return (PF_DROP); 1071 1072 drop: 1073 REASON_SET(reason, PFRES_NORM); 1074 if (r != NULL && r->log) 1075 PFLOG_PACKET(kif, h, m, AF_INET, dir, *reason, r, NULL, NULL, pd); 1076 return (PF_DROP); 1077 1078 bad: 1079 DPFPRINTF(("dropping bad fragment\n")); 1080 1081 /* Free associated fragments */ 1082 if (frag != NULL) 1083 pf_free_fragment(frag); 1084 1085 REASON_SET(reason, PFRES_FRAG); 1086 if (r != NULL && r->log) 1087 PFLOG_PACKET(kif, h, m, AF_INET, dir, *reason, r, NULL, NULL, pd); 1088 1089 return (PF_DROP); 1090 } 1091 1092 #ifdef INET6 1093 int 1094 pf_normalize_ip6(struct mbuf **m0, int dir, struct pfi_kif *kif, 1095 u_short *reason, struct pf_pdesc *pd) 1096 { 1097 struct mbuf *m = *m0; 1098 struct pf_rule *r; 1099 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1100 int off; 1101 struct ip6_ext ext; 1102 struct ip6_opt opt; 1103 struct ip6_opt_jumbo jumbo; 1104 struct ip6_frag frag; 1105 u_int32_t jumbolen = 0, plen; 1106 u_int16_t fragoff = 0; 1107 int optend; 1108 int ooff; 1109 u_int8_t proto; 1110 int terminal; 1111 1112 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 1113 while (r != NULL) { 1114 r->evaluations++; 1115 if (pfi_kif_match(r->kif, kif) == r->ifnot) 1116 r = r->skip[PF_SKIP_IFP].ptr; 1117 else if (r->direction && r->direction != dir) 1118 r = r->skip[PF_SKIP_DIR].ptr; 1119 else if (r->af && r->af != AF_INET6) 1120 r = r->skip[PF_SKIP_AF].ptr; 1121 #if 0 /* header chain! */ 1122 else if (r->proto && r->proto != h->ip6_nxt) 1123 r = r->skip[PF_SKIP_PROTO].ptr; 1124 #endif 1125 else if (PF_MISMATCHAW(&r->src.addr, 1126 (struct pf_addr *)&h->ip6_src, AF_INET6, 1127 r->src.neg, kif)) 1128 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 1129 else if (PF_MISMATCHAW(&r->dst.addr, 1130 (struct pf_addr *)&h->ip6_dst, AF_INET6, 1131 r->dst.neg, NULL)) 1132 r = r->skip[PF_SKIP_DST_ADDR].ptr; 1133 else 1134 break; 1135 } 1136 1137 if (r == NULL || r->action == PF_NOSCRUB) 1138 return (PF_PASS); 1139 else { 1140 r->packets[dir == PF_OUT]++; 1141 r->bytes[dir == PF_OUT] += pd->tot_len; 1142 } 1143 1144 /* Check for illegal packets */ 1145 if (sizeof(struct ip6_hdr) + IPV6_MAXPACKET < m->m_pkthdr.len) 1146 goto drop; 1147 1148 off = sizeof(struct ip6_hdr); 1149 proto = h->ip6_nxt; 1150 terminal = 0; 1151 do { 1152 switch (proto) { 1153 case IPPROTO_FRAGMENT: 1154 goto fragment; 1155 break; 1156 case IPPROTO_AH: 1157 case IPPROTO_ROUTING: 1158 case IPPROTO_DSTOPTS: 1159 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL, 1160 NULL, AF_INET6)) 1161 goto shortpkt; 1162 if (proto == IPPROTO_AH) 1163 off += (ext.ip6e_len + 2) * 4; 1164 else 1165 off += (ext.ip6e_len + 1) * 8; 1166 proto = ext.ip6e_nxt; 1167 break; 1168 case IPPROTO_HOPOPTS: 1169 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL, 1170 NULL, AF_INET6)) 1171 goto shortpkt; 1172 optend = off + (ext.ip6e_len + 1) * 8; 1173 ooff = off + sizeof(ext); 1174 do { 1175 if (!pf_pull_hdr(m, ooff, &opt.ip6o_type, 1176 sizeof(opt.ip6o_type), NULL, NULL, 1177 AF_INET6)) 1178 goto shortpkt; 1179 if (opt.ip6o_type == IP6OPT_PAD1) { 1180 ooff++; 1181 continue; 1182 } 1183 if (!pf_pull_hdr(m, ooff, &opt, sizeof(opt), 1184 NULL, NULL, AF_INET6)) 1185 goto shortpkt; 1186 if (ooff + sizeof(opt) + opt.ip6o_len > optend) 1187 goto drop; 1188 switch (opt.ip6o_type) { 1189 case IP6OPT_JUMBO: 1190 if (h->ip6_plen != 0) 1191 goto drop; 1192 if (!pf_pull_hdr(m, ooff, &jumbo, 1193 sizeof(jumbo), NULL, NULL, 1194 AF_INET6)) 1195 goto shortpkt; 1196 memcpy(&jumbolen, jumbo.ip6oj_jumbo_len, 1197 sizeof(jumbolen)); 1198 jumbolen = ntohl(jumbolen); 1199 if (jumbolen <= IPV6_MAXPACKET) 1200 goto drop; 1201 if (sizeof(struct ip6_hdr) + jumbolen != 1202 m->m_pkthdr.len) 1203 goto drop; 1204 break; 1205 default: 1206 break; 1207 } 1208 ooff += sizeof(opt) + opt.ip6o_len; 1209 } while (ooff < optend); 1210 1211 off = optend; 1212 proto = ext.ip6e_nxt; 1213 break; 1214 default: 1215 terminal = 1; 1216 break; 1217 } 1218 } while (!terminal); 1219 1220 /* jumbo payload option must be present, or plen > 0 */ 1221 if (ntohs(h->ip6_plen) == 0) 1222 plen = jumbolen; 1223 else 1224 plen = ntohs(h->ip6_plen); 1225 if (plen == 0) 1226 goto drop; 1227 if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len) 1228 goto shortpkt; 1229 1230 /* Enforce a minimum ttl, may cause endless packet loops */ 1231 if (r->min_ttl && h->ip6_hlim < r->min_ttl) 1232 h->ip6_hlim = r->min_ttl; 1233 1234 return (PF_PASS); 1235 1236 fragment: 1237 if (ntohs(h->ip6_plen) == 0 || jumbolen) 1238 goto drop; 1239 plen = ntohs(h->ip6_plen); 1240 1241 if (!pf_pull_hdr(m, off, &frag, sizeof(frag), NULL, NULL, AF_INET6)) 1242 goto shortpkt; 1243 fragoff = ntohs(frag.ip6f_offlg & IP6F_OFF_MASK); 1244 if (fragoff + (plen - off - sizeof(frag)) > IPV6_MAXPACKET) 1245 goto badfrag; 1246 1247 /* do something about it */ 1248 /* remember to set pd->flags |= PFDESC_IP_REAS */ 1249 return (PF_PASS); 1250 1251 shortpkt: 1252 REASON_SET(reason, PFRES_SHORT); 1253 if (r != NULL && r->log) 1254 PFLOG_PACKET(kif, h, m, AF_INET6, dir, *reason, r, NULL, NULL, pd); 1255 return (PF_DROP); 1256 1257 drop: 1258 REASON_SET(reason, PFRES_NORM); 1259 if (r != NULL && r->log) 1260 PFLOG_PACKET(kif, h, m, AF_INET6, dir, *reason, r, NULL, NULL, pd); 1261 return (PF_DROP); 1262 1263 badfrag: 1264 REASON_SET(reason, PFRES_FRAG); 1265 if (r != NULL && r->log) 1266 PFLOG_PACKET(kif, h, m, AF_INET6, dir, *reason, r, NULL, NULL, pd); 1267 return (PF_DROP); 1268 } 1269 #endif /* INET6 */ 1270 1271 int 1272 pf_normalize_tcp(int dir, struct pfi_kif *kif, struct mbuf *m, int ipoff, 1273 int off, void *h, struct pf_pdesc *pd) 1274 { 1275 struct pf_rule *r, *rm = NULL; 1276 struct tcphdr *th = pd->hdr.tcp; 1277 int rewrite = 0; 1278 u_short reason; 1279 u_int8_t flags; 1280 sa_family_t af = pd->af; 1281 1282 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 1283 while (r != NULL) { 1284 r->evaluations++; 1285 if (pfi_kif_match(r->kif, kif) == r->ifnot) 1286 r = r->skip[PF_SKIP_IFP].ptr; 1287 else if (r->direction && r->direction != dir) 1288 r = r->skip[PF_SKIP_DIR].ptr; 1289 else if (r->af && r->af != af) 1290 r = r->skip[PF_SKIP_AF].ptr; 1291 else if (r->proto && r->proto != pd->proto) 1292 r = r->skip[PF_SKIP_PROTO].ptr; 1293 else if (PF_MISMATCHAW(&r->src.addr, pd->src, af, 1294 r->src.neg, kif)) 1295 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 1296 else if (r->src.port_op && !pf_match_port(r->src.port_op, 1297 r->src.port[0], r->src.port[1], th->th_sport)) 1298 r = r->skip[PF_SKIP_SRC_PORT].ptr; 1299 else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af, 1300 r->dst.neg, NULL)) 1301 r = r->skip[PF_SKIP_DST_ADDR].ptr; 1302 else if (r->dst.port_op && !pf_match_port(r->dst.port_op, 1303 r->dst.port[0], r->dst.port[1], th->th_dport)) 1304 r = r->skip[PF_SKIP_DST_PORT].ptr; 1305 else if (r->os_fingerprint != PF_OSFP_ANY && !pf_osfp_match( 1306 pf_osfp_fingerprint(pd, m, off, th), 1307 r->os_fingerprint)) 1308 r = TAILQ_NEXT(r, entries); 1309 else { 1310 rm = r; 1311 break; 1312 } 1313 } 1314 1315 if (rm == NULL || rm->action == PF_NOSCRUB) 1316 return (PF_PASS); 1317 else { 1318 r->packets[dir == PF_OUT]++; 1319 r->bytes[dir == PF_OUT] += pd->tot_len; 1320 } 1321 1322 if (rm->rule_flag & PFRULE_REASSEMBLE_TCP) 1323 pd->flags |= PFDESC_TCP_NORM; 1324 1325 flags = th->th_flags; 1326 if (flags & TH_SYN) { 1327 /* Illegal packet */ 1328 if (flags & TH_RST) 1329 goto tcp_drop; 1330 1331 if (flags & TH_FIN) 1332 flags &= ~TH_FIN; 1333 } else { 1334 /* Illegal packet */ 1335 if (!(flags & (TH_ACK|TH_RST))) 1336 goto tcp_drop; 1337 } 1338 1339 if (!(flags & TH_ACK)) { 1340 /* These flags are only valid if ACK is set */ 1341 if ((flags & TH_FIN) || (flags & TH_PUSH) || (flags & TH_URG)) 1342 goto tcp_drop; 1343 } 1344 1345 /* Check for illegal header length */ 1346 if (th->th_off < (sizeof(struct tcphdr) >> 2)) 1347 goto tcp_drop; 1348 1349 /* If flags changed, or reserved data set, then adjust */ 1350 if (flags != th->th_flags || th->th_x2 != 0) { 1351 u_int16_t ov, nv; 1352 1353 ov = *(u_int16_t *)(&th->th_ack + 1); 1354 th->th_flags = flags; 1355 th->th_x2 = 0; 1356 nv = *(u_int16_t *)(&th->th_ack + 1); 1357 1358 th->th_sum = pf_cksum_fixup(th->th_sum, ov, nv, 0); 1359 rewrite = 1; 1360 } 1361 1362 /* Remove urgent pointer, if TH_URG is not set */ 1363 if (!(flags & TH_URG) && th->th_urp) { 1364 th->th_sum = pf_cksum_fixup(th->th_sum, th->th_urp, 0, 0); 1365 th->th_urp = 0; 1366 rewrite = 1; 1367 } 1368 1369 /* Process options */ 1370 if (r->max_mss && pf_normalize_tcpopt(r, m, th, off, pd->af)) 1371 rewrite = 1; 1372 1373 /* copy back packet headers if we sanitized */ 1374 if (rewrite) 1375 m_copyback(m, off, sizeof(*th), (caddr_t)th); 1376 1377 return (PF_PASS); 1378 1379 tcp_drop: 1380 REASON_SET(&reason, PFRES_NORM); 1381 if (rm != NULL && r->log) 1382 PFLOG_PACKET(kif, h, m, AF_INET, dir, reason, r, NULL, NULL, pd); 1383 return (PF_DROP); 1384 } 1385 1386 int 1387 pf_normalize_tcp_init(struct mbuf *m, int off, struct pf_pdesc *pd, 1388 struct tcphdr *th, struct pf_state_peer *src, struct pf_state_peer *dst) 1389 { 1390 u_int32_t tsval, tsecr; 1391 u_int8_t hdr[60]; 1392 u_int8_t *opt; 1393 1394 KASSERT((src->scrub == NULL), 1395 ("pf_normalize_tcp_init: src->scrub != NULL")); 1396 1397 src->scrub = kmalloc(sizeof(struct pf_state_scrub), M_PFSTATESCRUBPL, 1398 M_NOWAIT | M_ZERO); 1399 if (src->scrub == NULL) 1400 return (1); 1401 1402 switch (pd->af) { 1403 #ifdef INET 1404 case AF_INET: { 1405 struct ip *h = mtod(m, struct ip *); 1406 src->scrub->pfss_ttl = h->ip_ttl; 1407 break; 1408 } 1409 #endif /* INET */ 1410 #ifdef INET6 1411 case AF_INET6: { 1412 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1413 src->scrub->pfss_ttl = h->ip6_hlim; 1414 break; 1415 } 1416 #endif /* INET6 */ 1417 } 1418 1419 1420 /* 1421 * All normalizations below are only begun if we see the start of 1422 * the connections. They must all set an enabled bit in pfss_flags 1423 */ 1424 if ((th->th_flags & TH_SYN) == 0) 1425 return (0); 1426 1427 1428 if (th->th_off > (sizeof(struct tcphdr) >> 2) && src->scrub && 1429 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) { 1430 /* Diddle with TCP options */ 1431 int hlen; 1432 opt = hdr + sizeof(struct tcphdr); 1433 hlen = (th->th_off << 2) - sizeof(struct tcphdr); 1434 while (hlen >= TCPOLEN_TIMESTAMP) { 1435 switch (*opt) { 1436 case TCPOPT_EOL: /* FALLTHROUGH */ 1437 case TCPOPT_NOP: 1438 opt++; 1439 hlen--; 1440 break; 1441 case TCPOPT_TIMESTAMP: 1442 if (opt[1] >= TCPOLEN_TIMESTAMP) { 1443 src->scrub->pfss_flags |= 1444 PFSS_TIMESTAMP; 1445 src->scrub->pfss_ts_mod = karc4random(); 1446 1447 /* note PFSS_PAWS not set yet */ 1448 memcpy(&tsval, &opt[2], 1449 sizeof(u_int32_t)); 1450 memcpy(&tsecr, &opt[6], 1451 sizeof(u_int32_t)); 1452 src->scrub->pfss_tsval0 = ntohl(tsval); 1453 src->scrub->pfss_tsval = ntohl(tsval); 1454 src->scrub->pfss_tsecr = ntohl(tsecr); 1455 getmicrouptime(&src->scrub->pfss_last); 1456 } 1457 /* FALLTHROUGH */ 1458 default: 1459 hlen -= MAX(opt[1], 2); 1460 opt += MAX(opt[1], 2); 1461 break; 1462 } 1463 } 1464 } 1465 1466 return (0); 1467 } 1468 1469 void 1470 pf_normalize_tcp_cleanup(struct pf_state *state) 1471 { 1472 if (state->src.scrub) 1473 kfree(state->src.scrub, M_PFSTATESCRUBPL); 1474 if (state->dst.scrub) 1475 kfree(state->dst.scrub, M_PFSTATESCRUBPL); 1476 1477 /* Someday... flush the TCP segment reassembly descriptors. */ 1478 } 1479 1480 int 1481 pf_normalize_tcp_stateful(struct mbuf *m, int off, struct pf_pdesc *pd, 1482 u_short *reason, struct tcphdr *th, struct pf_state *state, 1483 struct pf_state_peer *src, struct pf_state_peer *dst, int *writeback) 1484 { 1485 struct timeval uptime; 1486 u_int32_t tsval, tsecr; 1487 u_int tsval_from_last; 1488 u_int8_t hdr[60]; 1489 u_int8_t *opt; 1490 int copyback = 0; 1491 int got_ts = 0; 1492 1493 KASSERT((src->scrub || dst->scrub), 1494 ("pf_normalize_tcp_statefull: src->scrub && dst->scrub!")); 1495 1496 tsval = 0; /* avoid gcc complaint */ 1497 tsecr = 0; /* avoid gcc complaint */ 1498 1499 /* 1500 * Enforce the minimum TTL seen for this connection. Negate a common 1501 * technique to evade an intrusion detection system and confuse 1502 * firewall state code. 1503 */ 1504 switch (pd->af) { 1505 #ifdef INET 1506 case AF_INET: { 1507 if (src->scrub) { 1508 struct ip *h = mtod(m, struct ip *); 1509 if (h->ip_ttl > src->scrub->pfss_ttl) 1510 src->scrub->pfss_ttl = h->ip_ttl; 1511 h->ip_ttl = src->scrub->pfss_ttl; 1512 } 1513 break; 1514 } 1515 #endif /* INET */ 1516 #ifdef INET6 1517 case AF_INET6: { 1518 if (src->scrub) { 1519 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1520 if (h->ip6_hlim > src->scrub->pfss_ttl) 1521 src->scrub->pfss_ttl = h->ip6_hlim; 1522 h->ip6_hlim = src->scrub->pfss_ttl; 1523 } 1524 break; 1525 } 1526 #endif /* INET6 */ 1527 } 1528 1529 if (th->th_off > (sizeof(struct tcphdr) >> 2) && 1530 ((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) || 1531 (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) && 1532 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) { 1533 /* Diddle with TCP options */ 1534 int hlen; 1535 opt = hdr + sizeof(struct tcphdr); 1536 hlen = (th->th_off << 2) - sizeof(struct tcphdr); 1537 while (hlen >= TCPOLEN_TIMESTAMP) { 1538 switch (*opt) { 1539 case TCPOPT_EOL: /* FALLTHROUGH */ 1540 case TCPOPT_NOP: 1541 opt++; 1542 hlen--; 1543 break; 1544 case TCPOPT_TIMESTAMP: 1545 /* Modulate the timestamps. Can be used for 1546 * NAT detection, OS uptime determination or 1547 * reboot detection. 1548 */ 1549 1550 if (got_ts) { 1551 /* Huh? Multiple timestamps!? */ 1552 if (pf_status.debug >= PF_DEBUG_MISC) { 1553 DPFPRINTF(("multiple TS??")); 1554 pf_print_state(state); 1555 kprintf("\n"); 1556 } 1557 REASON_SET(reason, PFRES_TS); 1558 return (PF_DROP); 1559 } 1560 if (opt[1] >= TCPOLEN_TIMESTAMP) { 1561 memcpy(&tsval, &opt[2], 1562 sizeof(u_int32_t)); 1563 if (tsval && src->scrub && 1564 (src->scrub->pfss_flags & 1565 PFSS_TIMESTAMP)) { 1566 tsval = ntohl(tsval); 1567 pf_change_a(&opt[2], 1568 &th->th_sum, 1569 htonl(tsval + 1570 src->scrub->pfss_ts_mod), 1571 0); 1572 copyback = 1; 1573 } 1574 1575 /* Modulate TS reply iff valid (!0) */ 1576 memcpy(&tsecr, &opt[6], 1577 sizeof(u_int32_t)); 1578 if (tsecr && dst->scrub && 1579 (dst->scrub->pfss_flags & 1580 PFSS_TIMESTAMP)) { 1581 tsecr = ntohl(tsecr) 1582 - dst->scrub->pfss_ts_mod; 1583 pf_change_a(&opt[6], 1584 &th->th_sum, htonl(tsecr), 1585 0); 1586 copyback = 1; 1587 } 1588 got_ts = 1; 1589 } 1590 /* FALLTHROUGH */ 1591 default: 1592 hlen -= MAX(opt[1], 2); 1593 opt += MAX(opt[1], 2); 1594 break; 1595 } 1596 } 1597 if (copyback) { 1598 /* Copyback the options, caller copys back header */ 1599 *writeback = 1; 1600 m_copyback(m, off + sizeof(struct tcphdr), 1601 (th->th_off << 2) - sizeof(struct tcphdr), hdr + 1602 sizeof(struct tcphdr)); 1603 } 1604 } 1605 1606 1607 /* 1608 * Must invalidate PAWS checks on connections idle for too long. 1609 * The fastest allowed timestamp clock is 1ms. That turns out to 1610 * be about 24 days before it wraps. XXX Right now our lowerbound 1611 * TS echo check only works for the first 12 days of a connection 1612 * when the TS has exhausted half its 32bit space 1613 */ 1614 #define TS_MAX_IDLE (24*24*60*60) 1615 #define TS_MAX_CONN (12*24*60*60) /* XXX remove when better tsecr check */ 1616 1617 getmicrouptime(&uptime); 1618 if (src->scrub && (src->scrub->pfss_flags & PFSS_PAWS) && 1619 (uptime.tv_sec - src->scrub->pfss_last.tv_sec > TS_MAX_IDLE || 1620 time_second - state->creation > TS_MAX_CONN)) { 1621 if (pf_status.debug >= PF_DEBUG_MISC) { 1622 DPFPRINTF(("src idled out of PAWS\n")); 1623 pf_print_state(state); 1624 kprintf("\n"); 1625 } 1626 src->scrub->pfss_flags = (src->scrub->pfss_flags & ~PFSS_PAWS) 1627 | PFSS_PAWS_IDLED; 1628 } 1629 if (dst->scrub && (dst->scrub->pfss_flags & PFSS_PAWS) && 1630 uptime.tv_sec - dst->scrub->pfss_last.tv_sec > TS_MAX_IDLE) { 1631 if (pf_status.debug >= PF_DEBUG_MISC) { 1632 DPFPRINTF(("dst idled out of PAWS\n")); 1633 pf_print_state(state); 1634 kprintf("\n"); 1635 } 1636 dst->scrub->pfss_flags = (dst->scrub->pfss_flags & ~PFSS_PAWS) 1637 | PFSS_PAWS_IDLED; 1638 } 1639 1640 if (got_ts && src->scrub && dst->scrub && 1641 (src->scrub->pfss_flags & PFSS_PAWS) && 1642 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1643 /* Validate that the timestamps are "in-window". 1644 * RFC1323 describes TCP Timestamp options that allow 1645 * measurement of RTT (round trip time) and PAWS 1646 * (protection against wrapped sequence numbers). PAWS 1647 * gives us a set of rules for rejecting packets on 1648 * long fat pipes (packets that were somehow delayed 1649 * in transit longer than the time it took to send the 1650 * full TCP sequence space of 4Gb). We can use these 1651 * rules and infer a few others that will let us treat 1652 * the 32bit timestamp and the 32bit echoed timestamp 1653 * as sequence numbers to prevent a blind attacker from 1654 * inserting packets into a connection. 1655 * 1656 * RFC1323 tells us: 1657 * - The timestamp on this packet must be greater than 1658 * or equal to the last value echoed by the other 1659 * endpoint. The RFC says those will be discarded 1660 * since it is a dup that has already been acked. 1661 * This gives us a lowerbound on the timestamp. 1662 * timestamp >= other last echoed timestamp 1663 * - The timestamp will be less than or equal to 1664 * the last timestamp plus the time between the 1665 * last packet and now. The RFC defines the max 1666 * clock rate as 1ms. We will allow clocks to be 1667 * up to 10% fast and will allow a total difference 1668 * or 30 seconds due to a route change. And this 1669 * gives us an upperbound on the timestamp. 1670 * timestamp <= last timestamp + max ticks 1671 * We have to be careful here. Windows will send an 1672 * initial timestamp of zero and then initialize it 1673 * to a random value after the 3whs; presumably to 1674 * avoid a DoS by having to call an expensive RNG 1675 * during a SYN flood. Proof MS has at least one 1676 * good security geek. 1677 * 1678 * - The TCP timestamp option must also echo the other 1679 * endpoints timestamp. The timestamp echoed is the 1680 * one carried on the earliest unacknowledged segment 1681 * on the left edge of the sequence window. The RFC 1682 * states that the host will reject any echoed 1683 * timestamps that were larger than any ever sent. 1684 * This gives us an upperbound on the TS echo. 1685 * tescr <= largest_tsval 1686 * - The lowerbound on the TS echo is a little more 1687 * tricky to determine. The other endpoint's echoed 1688 * values will not decrease. But there may be 1689 * network conditions that re-order packets and 1690 * cause our view of them to decrease. For now the 1691 * only lowerbound we can safely determine is that 1692 * the TS echo will never be less than the original 1693 * TS. XXX There is probably a better lowerbound. 1694 * Remove TS_MAX_CONN with better lowerbound check. 1695 * tescr >= other original TS 1696 * 1697 * It is also important to note that the fastest 1698 * timestamp clock of 1ms will wrap its 32bit space in 1699 * 24 days. So we just disable TS checking after 24 1700 * days of idle time. We actually must use a 12d 1701 * connection limit until we can come up with a better 1702 * lowerbound to the TS echo check. 1703 */ 1704 struct timeval delta_ts; 1705 int ts_fudge; 1706 1707 1708 /* 1709 * PFTM_TS_DIFF is how many seconds of leeway to allow 1710 * a host's timestamp. This can happen if the previous 1711 * packet got delayed in transit for much longer than 1712 * this packet. 1713 */ 1714 if ((ts_fudge = state->rule.ptr->timeout[PFTM_TS_DIFF]) == 0) 1715 ts_fudge = pf_default_rule.timeout[PFTM_TS_DIFF]; 1716 1717 1718 /* Calculate max ticks since the last timestamp */ 1719 #define TS_MAXFREQ 1100 /* RFC max TS freq of 1Khz + 10% skew */ 1720 #define TS_MICROSECS 1000000 /* microseconds per second */ 1721 #ifndef timersub 1722 #define timersub(tvp, uvp, vvp) \ 1723 do { \ 1724 (vvp)->tv_sec = (tvp)->tv_sec - (uvp)->tv_sec; \ 1725 (vvp)->tv_usec = (tvp)->tv_usec - (uvp)->tv_usec; \ 1726 if ((vvp)->tv_usec < 0) { \ 1727 (vvp)->tv_sec--; \ 1728 (vvp)->tv_usec += 1000000; \ 1729 } \ 1730 } while (0) 1731 #endif 1732 1733 timersub(&uptime, &src->scrub->pfss_last, &delta_ts); 1734 tsval_from_last = (delta_ts.tv_sec + ts_fudge) * TS_MAXFREQ; 1735 tsval_from_last += delta_ts.tv_usec / (TS_MICROSECS/TS_MAXFREQ); 1736 1737 1738 if ((src->state >= TCPS_ESTABLISHED && 1739 dst->state >= TCPS_ESTABLISHED) && 1740 (SEQ_LT(tsval, dst->scrub->pfss_tsecr) || 1741 SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) || 1742 (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) || 1743 SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) { 1744 /* Bad RFC1323 implementation or an insertion attack. 1745 * 1746 * - Solaris 2.6 and 2.7 are known to send another ACK 1747 * after the FIN,FIN|ACK,ACK closing that carries 1748 * an old timestamp. 1749 */ 1750 1751 DPFPRINTF(("Timestamp failed %c%c%c%c\n", 1752 SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '0' : ' ', 1753 SEQ_GT(tsval, src->scrub->pfss_tsval + 1754 tsval_from_last) ? '1' : ' ', 1755 SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ', 1756 SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' ')); 1757 DPFPRINTF((" tsval: %u tsecr: %u +ticks: %u " 1758 "idle: %lus %lums\n", 1759 tsval, tsecr, tsval_from_last, delta_ts.tv_sec, 1760 delta_ts.tv_usec / 1000)); 1761 DPFPRINTF((" src->tsval: %u tsecr: %u\n", 1762 src->scrub->pfss_tsval, src->scrub->pfss_tsecr)); 1763 DPFPRINTF((" dst->tsval: %u tsecr: %u tsval0: %u" 1764 "\n", dst->scrub->pfss_tsval, 1765 dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0)); 1766 if (pf_status.debug >= PF_DEBUG_MISC) { 1767 pf_print_state(state); 1768 pf_print_flags(th->th_flags); 1769 kprintf("\n"); 1770 } 1771 REASON_SET(reason, PFRES_TS); 1772 return (PF_DROP); 1773 } 1774 1775 /* XXX I'd really like to require tsecr but it's optional */ 1776 1777 } else if (!got_ts && (th->th_flags & TH_RST) == 0 && 1778 ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED) 1779 || pd->p_len > 0 || (th->th_flags & TH_SYN)) && 1780 src->scrub && dst->scrub && 1781 (src->scrub->pfss_flags & PFSS_PAWS) && 1782 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1783 /* Didn't send a timestamp. Timestamps aren't really useful 1784 * when: 1785 * - connection opening or closing (often not even sent). 1786 * but we must not let an attacker to put a FIN on a 1787 * data packet to sneak it through our ESTABLISHED check. 1788 * - on a TCP reset. RFC suggests not even looking at TS. 1789 * - on an empty ACK. The TS will not be echoed so it will 1790 * probably not help keep the RTT calculation in sync and 1791 * there isn't as much danger when the sequence numbers 1792 * got wrapped. So some stacks don't include TS on empty 1793 * ACKs :-( 1794 * 1795 * To minimize the disruption to mostly RFC1323 conformant 1796 * stacks, we will only require timestamps on data packets. 1797 * 1798 * And what do ya know, we cannot require timestamps on data 1799 * packets. There appear to be devices that do legitimate 1800 * TCP connection hijacking. There are HTTP devices that allow 1801 * a 3whs (with timestamps) and then buffer the HTTP request. 1802 * If the intermediate device has the HTTP response cache, it 1803 * will spoof the response but not bother timestamping its 1804 * packets. So we can look for the presence of a timestamp in 1805 * the first data packet and if there, require it in all future 1806 * packets. 1807 */ 1808 1809 if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) { 1810 /* 1811 * Hey! Someone tried to sneak a packet in. Or the 1812 * stack changed its RFC1323 behavior?!?! 1813 */ 1814 if (pf_status.debug >= PF_DEBUG_MISC) { 1815 DPFPRINTF(("Did not receive expected RFC1323 " 1816 "timestamp\n")); 1817 pf_print_state(state); 1818 pf_print_flags(th->th_flags); 1819 kprintf("\n"); 1820 } 1821 REASON_SET(reason, PFRES_TS); 1822 return (PF_DROP); 1823 } 1824 } 1825 1826 1827 /* 1828 * We will note if a host sends his data packets with or without 1829 * timestamps. And require all data packets to contain a timestamp 1830 * if the first does. PAWS implicitly requires that all data packets be 1831 * timestamped. But I think there are middle-man devices that hijack 1832 * TCP streams immediately after the 3whs and don't timestamp their 1833 * packets (seen in a WWW accelerator or cache). 1834 */ 1835 if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags & 1836 (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) { 1837 if (got_ts) 1838 src->scrub->pfss_flags |= PFSS_DATA_TS; 1839 else { 1840 src->scrub->pfss_flags |= PFSS_DATA_NOTS; 1841 if (pf_status.debug >= PF_DEBUG_MISC && dst->scrub && 1842 (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) { 1843 /* Don't warn if other host rejected RFC1323 */ 1844 DPFPRINTF(("Broken RFC1323 stack did not " 1845 "timestamp data packet. Disabled PAWS " 1846 "security.\n")); 1847 pf_print_state(state); 1848 pf_print_flags(th->th_flags); 1849 kprintf("\n"); 1850 } 1851 } 1852 } 1853 1854 1855 /* 1856 * Update PAWS values 1857 */ 1858 if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags & 1859 (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) { 1860 getmicrouptime(&src->scrub->pfss_last); 1861 if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) || 1862 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1863 src->scrub->pfss_tsval = tsval; 1864 1865 if (tsecr) { 1866 if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) || 1867 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1868 src->scrub->pfss_tsecr = tsecr; 1869 1870 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 && 1871 (SEQ_LT(tsval, src->scrub->pfss_tsval0) || 1872 src->scrub->pfss_tsval0 == 0)) { 1873 /* tsval0 MUST be the lowest timestamp */ 1874 src->scrub->pfss_tsval0 = tsval; 1875 } 1876 1877 /* Only fully initialized after a TS gets echoed */ 1878 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0) 1879 src->scrub->pfss_flags |= PFSS_PAWS; 1880 } 1881 } 1882 1883 /* I have a dream.... TCP segment reassembly.... */ 1884 return (0); 1885 } 1886 1887 int 1888 pf_normalize_tcpopt(struct pf_rule *r, struct mbuf *m, struct tcphdr *th, 1889 int off, sa_family_t af) 1890 { 1891 u_int16_t *mss; 1892 int thoff; 1893 int opt, cnt, optlen = 0; 1894 int rewrite = 0; 1895 u_char opts[TCP_MAXOLEN]; 1896 u_char *optp = opts; 1897 1898 thoff = th->th_off << 2; 1899 cnt = thoff - sizeof(struct tcphdr); 1900 1901 if (cnt > 0 && !pf_pull_hdr(m, off + sizeof(*th), opts, cnt, 1902 NULL, NULL, af)) 1903 return (rewrite); 1904 1905 for (; cnt > 0; cnt -= optlen, optp += optlen) { 1906 opt = optp[0]; 1907 if (opt == TCPOPT_EOL) 1908 break; 1909 if (opt == TCPOPT_NOP) 1910 optlen = 1; 1911 else { 1912 if (cnt < 2) 1913 break; 1914 optlen = optp[1]; 1915 if (optlen < 2 || optlen > cnt) 1916 break; 1917 } 1918 switch (opt) { 1919 case TCPOPT_MAXSEG: 1920 mss = (u_int16_t *)(optp + 2); 1921 if ((ntohs(*mss)) > r->max_mss) { 1922 th->th_sum = pf_cksum_fixup(th->th_sum, 1923 *mss, htons(r->max_mss), 0); 1924 *mss = htons(r->max_mss); 1925 rewrite = 1; 1926 } 1927 break; 1928 default: 1929 break; 1930 } 1931 } 1932 1933 if (rewrite) 1934 m_copyback(m, off + sizeof(*th), thoff - sizeof(*th), opts); 1935 1936 return (rewrite); 1937 } 1938