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