1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright 2001 Niels Provos <provos@citi.umich.edu> 5 * Copyright 2011 Alexander Bluhm <bluhm@openbsd.org> 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 * 28 * $OpenBSD: pf_norm.c,v 1.114 2009/01/29 14:11:45 henning Exp $ 29 */ 30 31 #include <sys/cdefs.h> 32 __FBSDID("$FreeBSD$"); 33 34 #include "opt_inet.h" 35 #include "opt_inet6.h" 36 #include "opt_pf.h" 37 38 #include <sys/param.h> 39 #include <sys/kernel.h> 40 #include <sys/lock.h> 41 #include <sys/mbuf.h> 42 #include <sys/mutex.h> 43 #include <sys/refcount.h> 44 #include <sys/socket.h> 45 46 #include <net/if.h> 47 #include <net/vnet.h> 48 #include <net/pfvar.h> 49 #include <net/if_pflog.h> 50 51 #include <netinet/in.h> 52 #include <netinet/ip.h> 53 #include <netinet/ip_var.h> 54 #include <netinet6/ip6_var.h> 55 #include <netinet/tcp.h> 56 #include <netinet/tcp_fsm.h> 57 #include <netinet/tcp_seq.h> 58 59 #ifdef INET6 60 #include <netinet/ip6.h> 61 #endif /* INET6 */ 62 63 struct pf_frent { 64 TAILQ_ENTRY(pf_frent) fr_next; 65 struct mbuf *fe_m; 66 uint16_t fe_hdrlen; /* ipv4 header length with ip options 67 ipv6, extension, fragment header */ 68 uint16_t fe_extoff; /* last extension header offset or 0 */ 69 uint16_t fe_len; /* fragment length */ 70 uint16_t fe_off; /* fragment offset */ 71 uint16_t fe_mff; /* more fragment flag */ 72 }; 73 74 struct pf_fragment_cmp { 75 struct pf_addr frc_src; 76 struct pf_addr frc_dst; 77 uint32_t frc_id; 78 sa_family_t frc_af; 79 uint8_t frc_proto; 80 }; 81 82 struct pf_fragment { 83 struct pf_fragment_cmp fr_key; 84 #define fr_src fr_key.frc_src 85 #define fr_dst fr_key.frc_dst 86 #define fr_id fr_key.frc_id 87 #define fr_af fr_key.frc_af 88 #define fr_proto fr_key.frc_proto 89 90 RB_ENTRY(pf_fragment) fr_entry; 91 TAILQ_ENTRY(pf_fragment) frag_next; 92 uint32_t fr_timeout; 93 uint16_t fr_maxlen; /* maximum length of single fragment */ 94 uint16_t fr_entries; /* Total number of pf_fragment entries */ 95 TAILQ_HEAD(pf_fragq, pf_frent) fr_queue; 96 }; 97 #define PF_MAX_FRENT_PER_FRAGMENT 64 98 99 struct pf_fragment_tag { 100 uint16_t ft_hdrlen; /* header length of reassembled pkt */ 101 uint16_t ft_extoff; /* last extension header offset or 0 */ 102 uint16_t ft_maxlen; /* maximum fragment payload length */ 103 uint32_t ft_id; /* fragment id */ 104 }; 105 106 static struct mtx pf_frag_mtx; 107 MTX_SYSINIT(pf_frag_mtx, &pf_frag_mtx, "pf fragments", MTX_DEF); 108 #define PF_FRAG_LOCK() mtx_lock(&pf_frag_mtx) 109 #define PF_FRAG_UNLOCK() mtx_unlock(&pf_frag_mtx) 110 #define PF_FRAG_ASSERT() mtx_assert(&pf_frag_mtx, MA_OWNED) 111 112 VNET_DEFINE(uma_zone_t, pf_state_scrub_z); /* XXX: shared with pfsync */ 113 114 VNET_DEFINE_STATIC(uma_zone_t, pf_frent_z); 115 #define V_pf_frent_z VNET(pf_frent_z) 116 VNET_DEFINE_STATIC(uma_zone_t, pf_frag_z); 117 #define V_pf_frag_z VNET(pf_frag_z) 118 119 TAILQ_HEAD(pf_fragqueue, pf_fragment); 120 TAILQ_HEAD(pf_cachequeue, pf_fragment); 121 VNET_DEFINE_STATIC(struct pf_fragqueue, pf_fragqueue); 122 #define V_pf_fragqueue VNET(pf_fragqueue) 123 RB_HEAD(pf_frag_tree, pf_fragment); 124 VNET_DEFINE_STATIC(struct pf_frag_tree, pf_frag_tree); 125 #define V_pf_frag_tree VNET(pf_frag_tree) 126 static int pf_frag_compare(struct pf_fragment *, 127 struct pf_fragment *); 128 static RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); 129 static RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); 130 131 static void pf_flush_fragments(void); 132 static void pf_free_fragment(struct pf_fragment *); 133 static void pf_remove_fragment(struct pf_fragment *); 134 static int pf_normalize_tcpopt(struct pf_rule *, struct mbuf *, 135 struct tcphdr *, int, sa_family_t); 136 static struct pf_frent *pf_create_fragment(u_short *); 137 static struct pf_fragment *pf_find_fragment(struct pf_fragment_cmp *key, 138 struct pf_frag_tree *tree); 139 static struct pf_fragment *pf_fillup_fragment(struct pf_fragment_cmp *, 140 struct pf_frent *, u_short *); 141 static int pf_isfull_fragment(struct pf_fragment *); 142 static struct mbuf *pf_join_fragment(struct pf_fragment *); 143 #ifdef INET 144 static void pf_scrub_ip(struct mbuf **, uint32_t, uint8_t, uint8_t); 145 static int pf_reassemble(struct mbuf **, struct ip *, int, u_short *); 146 #endif /* INET */ 147 #ifdef INET6 148 static int pf_reassemble6(struct mbuf **, struct ip6_hdr *, 149 struct ip6_frag *, uint16_t, uint16_t, u_short *); 150 static void pf_scrub_ip6(struct mbuf **, uint8_t); 151 #endif /* INET6 */ 152 153 #define DPFPRINTF(x) do { \ 154 if (V_pf_status.debug >= PF_DEBUG_MISC) { \ 155 printf("%s: ", __func__); \ 156 printf x ; \ 157 } \ 158 } while(0) 159 160 #ifdef INET 161 static void 162 pf_ip2key(struct ip *ip, int dir, struct pf_fragment_cmp *key) 163 { 164 165 key->frc_src.v4 = ip->ip_src; 166 key->frc_dst.v4 = ip->ip_dst; 167 key->frc_af = AF_INET; 168 key->frc_proto = ip->ip_p; 169 key->frc_id = ip->ip_id; 170 } 171 #endif /* INET */ 172 173 void 174 pf_normalize_init(void) 175 { 176 177 V_pf_frag_z = uma_zcreate("pf frags", sizeof(struct pf_fragment), 178 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 179 V_pf_frent_z = uma_zcreate("pf frag entries", sizeof(struct pf_frent), 180 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 181 V_pf_state_scrub_z = uma_zcreate("pf state scrubs", 182 sizeof(struct pf_state_scrub), NULL, NULL, NULL, NULL, 183 UMA_ALIGN_PTR, 0); 184 185 V_pf_limits[PF_LIMIT_FRAGS].zone = V_pf_frent_z; 186 V_pf_limits[PF_LIMIT_FRAGS].limit = PFFRAG_FRENT_HIWAT; 187 uma_zone_set_max(V_pf_frent_z, PFFRAG_FRENT_HIWAT); 188 uma_zone_set_warning(V_pf_frent_z, "PF frag entries limit reached"); 189 190 TAILQ_INIT(&V_pf_fragqueue); 191 } 192 193 void 194 pf_normalize_cleanup(void) 195 { 196 197 uma_zdestroy(V_pf_state_scrub_z); 198 uma_zdestroy(V_pf_frent_z); 199 uma_zdestroy(V_pf_frag_z); 200 } 201 202 static int 203 pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b) 204 { 205 int diff; 206 207 if ((diff = a->fr_id - b->fr_id) != 0) 208 return (diff); 209 if ((diff = a->fr_proto - b->fr_proto) != 0) 210 return (diff); 211 if ((diff = a->fr_af - b->fr_af) != 0) 212 return (diff); 213 if ((diff = pf_addr_cmp(&a->fr_src, &b->fr_src, a->fr_af)) != 0) 214 return (diff); 215 if ((diff = pf_addr_cmp(&a->fr_dst, &b->fr_dst, a->fr_af)) != 0) 216 return (diff); 217 return (0); 218 } 219 220 void 221 pf_purge_expired_fragments(void) 222 { 223 u_int32_t expire = time_uptime - 224 V_pf_default_rule.timeout[PFTM_FRAG]; 225 226 pf_purge_fragments(expire); 227 } 228 229 void 230 pf_purge_fragments(uint32_t expire) 231 { 232 struct pf_fragment *frag; 233 234 PF_FRAG_LOCK(); 235 while ((frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue)) != NULL) { 236 if (frag->fr_timeout > expire) 237 break; 238 239 DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag)); 240 pf_free_fragment(frag); 241 } 242 243 PF_FRAG_UNLOCK(); 244 } 245 246 /* 247 * Try to flush old fragments to make space for new ones 248 */ 249 static void 250 pf_flush_fragments(void) 251 { 252 struct pf_fragment *frag; 253 int goal; 254 255 PF_FRAG_ASSERT(); 256 257 goal = uma_zone_get_cur(V_pf_frent_z) * 9 / 10; 258 DPFPRINTF(("trying to free %d frag entriess\n", goal)); 259 while (goal < uma_zone_get_cur(V_pf_frent_z)) { 260 frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue); 261 if (frag) 262 pf_free_fragment(frag); 263 else 264 break; 265 } 266 } 267 268 /* Frees the fragments and all associated entries */ 269 static void 270 pf_free_fragment(struct pf_fragment *frag) 271 { 272 struct pf_frent *frent; 273 274 PF_FRAG_ASSERT(); 275 276 /* Free all fragments */ 277 for (frent = TAILQ_FIRST(&frag->fr_queue); frent; 278 frent = TAILQ_FIRST(&frag->fr_queue)) { 279 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next); 280 281 m_freem(frent->fe_m); 282 uma_zfree(V_pf_frent_z, frent); 283 } 284 285 pf_remove_fragment(frag); 286 } 287 288 static struct pf_fragment * 289 pf_find_fragment(struct pf_fragment_cmp *key, struct pf_frag_tree *tree) 290 { 291 struct pf_fragment *frag; 292 293 PF_FRAG_ASSERT(); 294 295 frag = RB_FIND(pf_frag_tree, tree, (struct pf_fragment *)key); 296 if (frag != NULL) { 297 /* XXX Are we sure we want to update the timeout? */ 298 frag->fr_timeout = time_uptime; 299 TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next); 300 TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next); 301 } 302 303 return (frag); 304 } 305 306 /* Removes a fragment from the fragment queue and frees the fragment */ 307 static void 308 pf_remove_fragment(struct pf_fragment *frag) 309 { 310 311 PF_FRAG_ASSERT(); 312 313 RB_REMOVE(pf_frag_tree, &V_pf_frag_tree, frag); 314 TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next); 315 uma_zfree(V_pf_frag_z, frag); 316 } 317 318 static struct pf_frent * 319 pf_create_fragment(u_short *reason) 320 { 321 struct pf_frent *frent; 322 323 PF_FRAG_ASSERT(); 324 325 frent = uma_zalloc(V_pf_frent_z, M_NOWAIT); 326 if (frent == NULL) { 327 pf_flush_fragments(); 328 frent = uma_zalloc(V_pf_frent_z, M_NOWAIT); 329 if (frent == NULL) { 330 REASON_SET(reason, PFRES_MEMORY); 331 return (NULL); 332 } 333 } 334 335 return (frent); 336 } 337 338 static struct pf_fragment * 339 pf_fillup_fragment(struct pf_fragment_cmp *key, struct pf_frent *frent, 340 u_short *reason) 341 { 342 struct pf_frent *after, *next, *prev; 343 struct pf_fragment *frag; 344 uint16_t total; 345 346 PF_FRAG_ASSERT(); 347 348 /* No empty fragments. */ 349 if (frent->fe_len == 0) { 350 DPFPRINTF(("bad fragment: len 0")); 351 goto bad_fragment; 352 } 353 354 /* All fragments are 8 byte aligned. */ 355 if (frent->fe_mff && (frent->fe_len & 0x7)) { 356 DPFPRINTF(("bad fragment: mff and len %d", frent->fe_len)); 357 goto bad_fragment; 358 } 359 360 /* Respect maximum length, IP_MAXPACKET == IPV6_MAXPACKET. */ 361 if (frent->fe_off + frent->fe_len > IP_MAXPACKET) { 362 DPFPRINTF(("bad fragment: max packet %d", 363 frent->fe_off + frent->fe_len)); 364 goto bad_fragment; 365 } 366 367 DPFPRINTF((key->frc_af == AF_INET ? 368 "reass frag %d @ %d-%d" : "reass frag %#08x @ %d-%d", 369 key->frc_id, frent->fe_off, frent->fe_off + frent->fe_len)); 370 371 /* Fully buffer all of the fragments in this fragment queue. */ 372 frag = pf_find_fragment(key, &V_pf_frag_tree); 373 374 /* Create a new reassembly queue for this packet. */ 375 if (frag == NULL) { 376 frag = uma_zalloc(V_pf_frag_z, M_NOWAIT); 377 if (frag == NULL) { 378 pf_flush_fragments(); 379 frag = uma_zalloc(V_pf_frag_z, M_NOWAIT); 380 if (frag == NULL) { 381 REASON_SET(reason, PFRES_MEMORY); 382 goto drop_fragment; 383 } 384 } 385 386 *(struct pf_fragment_cmp *)frag = *key; 387 frag->fr_timeout = time_uptime; 388 frag->fr_maxlen = frent->fe_len; 389 frag->fr_entries = 0; 390 TAILQ_INIT(&frag->fr_queue); 391 392 RB_INSERT(pf_frag_tree, &V_pf_frag_tree, frag); 393 TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next); 394 395 /* We do not have a previous fragment. */ 396 TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next); 397 398 return (frag); 399 } 400 401 if (frag->fr_entries >= PF_MAX_FRENT_PER_FRAGMENT) 402 goto bad_fragment; 403 404 KASSERT(!TAILQ_EMPTY(&frag->fr_queue), ("!TAILQ_EMPTY()->fr_queue")); 405 406 /* Remember maximum fragment len for refragmentation. */ 407 if (frent->fe_len > frag->fr_maxlen) 408 frag->fr_maxlen = frent->fe_len; 409 410 /* Maximum data we have seen already. */ 411 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + 412 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; 413 414 /* Non terminal fragments must have more fragments flag. */ 415 if (frent->fe_off + frent->fe_len < total && !frent->fe_mff) 416 goto bad_fragment; 417 418 /* Check if we saw the last fragment already. */ 419 if (!TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_mff) { 420 if (frent->fe_off + frent->fe_len > total || 421 (frent->fe_off + frent->fe_len == total && frent->fe_mff)) 422 goto bad_fragment; 423 } else { 424 if (frent->fe_off + frent->fe_len == total && !frent->fe_mff) 425 goto bad_fragment; 426 } 427 428 /* Find a fragment after the current one. */ 429 prev = NULL; 430 TAILQ_FOREACH(after, &frag->fr_queue, fr_next) { 431 if (after->fe_off > frent->fe_off) 432 break; 433 prev = after; 434 } 435 436 KASSERT(prev != NULL || after != NULL, 437 ("prev != NULL || after != NULL")); 438 439 if (prev != NULL && prev->fe_off + prev->fe_len > frent->fe_off) { 440 uint16_t precut; 441 442 precut = prev->fe_off + prev->fe_len - frent->fe_off; 443 if (precut >= frent->fe_len) 444 goto bad_fragment; 445 DPFPRINTF(("overlap -%d", precut)); 446 m_adj(frent->fe_m, precut); 447 frent->fe_off += precut; 448 frent->fe_len -= precut; 449 } 450 451 for (; after != NULL && frent->fe_off + frent->fe_len > after->fe_off; 452 after = next) { 453 uint16_t aftercut; 454 455 aftercut = frent->fe_off + frent->fe_len - after->fe_off; 456 DPFPRINTF(("adjust overlap %d", aftercut)); 457 if (aftercut < after->fe_len) { 458 m_adj(after->fe_m, aftercut); 459 after->fe_off += aftercut; 460 after->fe_len -= aftercut; 461 break; 462 } 463 464 /* This fragment is completely overlapped, lose it. */ 465 next = TAILQ_NEXT(after, fr_next); 466 m_freem(after->fe_m); 467 TAILQ_REMOVE(&frag->fr_queue, after, fr_next); 468 uma_zfree(V_pf_frent_z, after); 469 } 470 471 if (prev == NULL) 472 TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next); 473 else 474 TAILQ_INSERT_AFTER(&frag->fr_queue, prev, frent, fr_next); 475 476 frag->fr_entries++; 477 478 return (frag); 479 480 bad_fragment: 481 REASON_SET(reason, PFRES_FRAG); 482 drop_fragment: 483 uma_zfree(V_pf_frent_z, frent); 484 return (NULL); 485 } 486 487 static int 488 pf_isfull_fragment(struct pf_fragment *frag) 489 { 490 struct pf_frent *frent, *next; 491 uint16_t off, total; 492 493 /* Check if we are completely reassembled */ 494 if (TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_mff) 495 return (0); 496 497 /* Maximum data we have seen already */ 498 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + 499 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; 500 501 /* Check if we have all the data */ 502 off = 0; 503 for (frent = TAILQ_FIRST(&frag->fr_queue); frent; frent = next) { 504 next = TAILQ_NEXT(frent, fr_next); 505 506 off += frent->fe_len; 507 if (off < total && (next == NULL || next->fe_off != off)) { 508 DPFPRINTF(("missing fragment at %d, next %d, total %d", 509 off, next == NULL ? -1 : next->fe_off, total)); 510 return (0); 511 } 512 } 513 DPFPRINTF(("%d < %d?", off, total)); 514 if (off < total) 515 return (0); 516 KASSERT(off == total, ("off == total")); 517 518 return (1); 519 } 520 521 static struct mbuf * 522 pf_join_fragment(struct pf_fragment *frag) 523 { 524 struct mbuf *m, *m2; 525 struct pf_frent *frent, *next; 526 527 frent = TAILQ_FIRST(&frag->fr_queue); 528 next = TAILQ_NEXT(frent, fr_next); 529 530 m = frent->fe_m; 531 m_adj(m, (frent->fe_hdrlen + frent->fe_len) - m->m_pkthdr.len); 532 uma_zfree(V_pf_frent_z, frent); 533 for (frent = next; frent != NULL; frent = next) { 534 next = TAILQ_NEXT(frent, fr_next); 535 536 m2 = frent->fe_m; 537 /* Strip off ip header. */ 538 m_adj(m2, frent->fe_hdrlen); 539 /* Strip off any trailing bytes. */ 540 m_adj(m2, frent->fe_len - m2->m_pkthdr.len); 541 542 uma_zfree(V_pf_frent_z, frent); 543 m_cat(m, m2); 544 } 545 546 /* Remove from fragment queue. */ 547 pf_remove_fragment(frag); 548 549 return (m); 550 } 551 552 #ifdef INET 553 static int 554 pf_reassemble(struct mbuf **m0, struct ip *ip, int dir, u_short *reason) 555 { 556 struct mbuf *m = *m0; 557 struct pf_frent *frent; 558 struct pf_fragment *frag; 559 struct pf_fragment_cmp key; 560 uint16_t total, hdrlen; 561 562 /* Get an entry for the fragment queue */ 563 if ((frent = pf_create_fragment(reason)) == NULL) 564 return (PF_DROP); 565 566 frent->fe_m = m; 567 frent->fe_hdrlen = ip->ip_hl << 2; 568 frent->fe_extoff = 0; 569 frent->fe_len = ntohs(ip->ip_len) - (ip->ip_hl << 2); 570 frent->fe_off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3; 571 frent->fe_mff = ntohs(ip->ip_off) & IP_MF; 572 573 pf_ip2key(ip, dir, &key); 574 575 if ((frag = pf_fillup_fragment(&key, frent, reason)) == NULL) 576 return (PF_DROP); 577 578 /* The mbuf is part of the fragment entry, no direct free or access */ 579 m = *m0 = NULL; 580 581 if (!pf_isfull_fragment(frag)) 582 return (PF_PASS); /* drop because *m0 is NULL, no error */ 583 584 /* We have all the data */ 585 frent = TAILQ_FIRST(&frag->fr_queue); 586 KASSERT(frent != NULL, ("frent != NULL")); 587 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + 588 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; 589 hdrlen = frent->fe_hdrlen; 590 591 m = *m0 = pf_join_fragment(frag); 592 frag = NULL; 593 594 if (m->m_flags & M_PKTHDR) { 595 int plen = 0; 596 for (m = *m0; m; m = m->m_next) 597 plen += m->m_len; 598 m = *m0; 599 m->m_pkthdr.len = plen; 600 } 601 602 ip = mtod(m, struct ip *); 603 ip->ip_len = htons(hdrlen + total); 604 ip->ip_off &= ~(IP_MF|IP_OFFMASK); 605 606 if (hdrlen + total > IP_MAXPACKET) { 607 DPFPRINTF(("drop: too big: %d", total)); 608 ip->ip_len = 0; 609 REASON_SET(reason, PFRES_SHORT); 610 /* PF_DROP requires a valid mbuf *m0 in pf_test() */ 611 return (PF_DROP); 612 } 613 614 DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip->ip_len))); 615 return (PF_PASS); 616 } 617 #endif /* INET */ 618 619 #ifdef INET6 620 static int 621 pf_reassemble6(struct mbuf **m0, struct ip6_hdr *ip6, struct ip6_frag *fraghdr, 622 uint16_t hdrlen, uint16_t extoff, u_short *reason) 623 { 624 struct mbuf *m = *m0; 625 struct pf_frent *frent; 626 struct pf_fragment *frag; 627 struct pf_fragment_cmp key; 628 struct m_tag *mtag; 629 struct pf_fragment_tag *ftag; 630 int off; 631 uint32_t frag_id; 632 uint16_t total, maxlen; 633 uint8_t proto; 634 635 PF_FRAG_LOCK(); 636 637 /* Get an entry for the fragment queue. */ 638 if ((frent = pf_create_fragment(reason)) == NULL) { 639 PF_FRAG_UNLOCK(); 640 return (PF_DROP); 641 } 642 643 frent->fe_m = m; 644 frent->fe_hdrlen = hdrlen; 645 frent->fe_extoff = extoff; 646 frent->fe_len = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - hdrlen; 647 frent->fe_off = ntohs(fraghdr->ip6f_offlg & IP6F_OFF_MASK); 648 frent->fe_mff = fraghdr->ip6f_offlg & IP6F_MORE_FRAG; 649 650 key.frc_src.v6 = ip6->ip6_src; 651 key.frc_dst.v6 = ip6->ip6_dst; 652 key.frc_af = AF_INET6; 653 /* Only the first fragment's protocol is relevant. */ 654 key.frc_proto = 0; 655 key.frc_id = fraghdr->ip6f_ident; 656 657 if ((frag = pf_fillup_fragment(&key, frent, reason)) == NULL) { 658 PF_FRAG_UNLOCK(); 659 return (PF_DROP); 660 } 661 662 /* The mbuf is part of the fragment entry, no direct free or access. */ 663 m = *m0 = NULL; 664 665 if (!pf_isfull_fragment(frag)) { 666 PF_FRAG_UNLOCK(); 667 return (PF_PASS); /* Drop because *m0 is NULL, no error. */ 668 } 669 670 /* We have all the data. */ 671 extoff = frent->fe_extoff; 672 maxlen = frag->fr_maxlen; 673 frag_id = frag->fr_id; 674 frent = TAILQ_FIRST(&frag->fr_queue); 675 KASSERT(frent != NULL, ("frent != NULL")); 676 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + 677 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; 678 hdrlen = frent->fe_hdrlen - sizeof(struct ip6_frag); 679 680 m = *m0 = pf_join_fragment(frag); 681 frag = NULL; 682 683 PF_FRAG_UNLOCK(); 684 685 /* Take protocol from first fragment header. */ 686 m = m_getptr(m, hdrlen + offsetof(struct ip6_frag, ip6f_nxt), &off); 687 KASSERT(m, ("%s: short mbuf chain", __func__)); 688 proto = *(mtod(m, caddr_t) + off); 689 m = *m0; 690 691 /* Delete frag6 header */ 692 if (ip6_deletefraghdr(m, hdrlen, M_NOWAIT) != 0) 693 goto fail; 694 695 if (m->m_flags & M_PKTHDR) { 696 int plen = 0; 697 for (m = *m0; m; m = m->m_next) 698 plen += m->m_len; 699 m = *m0; 700 m->m_pkthdr.len = plen; 701 } 702 703 if ((mtag = m_tag_get(PF_REASSEMBLED, sizeof(struct pf_fragment_tag), 704 M_NOWAIT)) == NULL) 705 goto fail; 706 ftag = (struct pf_fragment_tag *)(mtag + 1); 707 ftag->ft_hdrlen = hdrlen; 708 ftag->ft_extoff = extoff; 709 ftag->ft_maxlen = maxlen; 710 ftag->ft_id = frag_id; 711 m_tag_prepend(m, mtag); 712 713 ip6 = mtod(m, struct ip6_hdr *); 714 ip6->ip6_plen = htons(hdrlen - sizeof(struct ip6_hdr) + total); 715 if (extoff) { 716 /* Write protocol into next field of last extension header. */ 717 m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt), 718 &off); 719 KASSERT(m, ("%s: short mbuf chain", __func__)); 720 *(mtod(m, char *) + off) = proto; 721 m = *m0; 722 } else 723 ip6->ip6_nxt = proto; 724 725 if (hdrlen - sizeof(struct ip6_hdr) + total > IPV6_MAXPACKET) { 726 DPFPRINTF(("drop: too big: %d", total)); 727 ip6->ip6_plen = 0; 728 REASON_SET(reason, PFRES_SHORT); 729 /* PF_DROP requires a valid mbuf *m0 in pf_test6(). */ 730 return (PF_DROP); 731 } 732 733 DPFPRINTF(("complete: %p(%d)", m, ntohs(ip6->ip6_plen))); 734 return (PF_PASS); 735 736 fail: 737 REASON_SET(reason, PFRES_MEMORY); 738 /* PF_DROP requires a valid mbuf *m0 in pf_test6(), will free later. */ 739 return (PF_DROP); 740 } 741 #endif /* INET6 */ 742 743 #ifdef INET6 744 int 745 pf_refragment6(struct ifnet *ifp, struct mbuf **m0, struct m_tag *mtag) 746 { 747 struct mbuf *m = *m0, *t; 748 struct pf_fragment_tag *ftag = (struct pf_fragment_tag *)(mtag + 1); 749 struct pf_pdesc pd; 750 uint32_t frag_id; 751 uint16_t hdrlen, extoff, maxlen; 752 uint8_t proto; 753 int error, action; 754 755 hdrlen = ftag->ft_hdrlen; 756 extoff = ftag->ft_extoff; 757 maxlen = ftag->ft_maxlen; 758 frag_id = ftag->ft_id; 759 m_tag_delete(m, mtag); 760 mtag = NULL; 761 ftag = NULL; 762 763 if (extoff) { 764 int off; 765 766 /* Use protocol from next field of last extension header */ 767 m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt), 768 &off); 769 KASSERT((m != NULL), ("pf_refragment6: short mbuf chain")); 770 proto = *(mtod(m, caddr_t) + off); 771 *(mtod(m, char *) + off) = IPPROTO_FRAGMENT; 772 m = *m0; 773 } else { 774 struct ip6_hdr *hdr; 775 776 hdr = mtod(m, struct ip6_hdr *); 777 proto = hdr->ip6_nxt; 778 hdr->ip6_nxt = IPPROTO_FRAGMENT; 779 } 780 781 /* The MTU must be a multiple of 8 bytes, or we risk doing the 782 * fragmentation wrong. */ 783 maxlen = maxlen & ~7; 784 785 /* 786 * Maxlen may be less than 8 if there was only a single 787 * fragment. As it was fragmented before, add a fragment 788 * header also for a single fragment. If total or maxlen 789 * is less than 8, ip6_fragment() will return EMSGSIZE and 790 * we drop the packet. 791 */ 792 error = ip6_fragment(ifp, m, hdrlen, proto, maxlen, frag_id); 793 m = (*m0)->m_nextpkt; 794 (*m0)->m_nextpkt = NULL; 795 if (error == 0) { 796 /* The first mbuf contains the unfragmented packet. */ 797 m_freem(*m0); 798 *m0 = NULL; 799 action = PF_PASS; 800 } else { 801 /* Drop expects an mbuf to free. */ 802 DPFPRINTF(("refragment error %d", error)); 803 action = PF_DROP; 804 } 805 for (t = m; m; m = t) { 806 t = m->m_nextpkt; 807 m->m_nextpkt = NULL; 808 m->m_flags |= M_SKIP_FIREWALL; 809 memset(&pd, 0, sizeof(pd)); 810 pd.pf_mtag = pf_find_mtag(m); 811 if (error == 0) 812 ip6_forward(m, 0); 813 else 814 m_freem(m); 815 } 816 817 return (action); 818 } 819 #endif /* INET6 */ 820 821 #ifdef INET 822 int 823 pf_normalize_ip(struct mbuf **m0, int dir, struct pfi_kif *kif, u_short *reason, 824 struct pf_pdesc *pd) 825 { 826 struct mbuf *m = *m0; 827 struct pf_rule *r; 828 struct ip *h = mtod(m, struct ip *); 829 int mff = (ntohs(h->ip_off) & IP_MF); 830 int hlen = h->ip_hl << 2; 831 u_int16_t fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3; 832 u_int16_t max; 833 int ip_len; 834 int ip_off; 835 int tag = -1; 836 int verdict; 837 838 PF_RULES_RASSERT(); 839 840 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 841 while (r != NULL) { 842 r->evaluations++; 843 if (pfi_kif_match(r->kif, kif) == r->ifnot) 844 r = r->skip[PF_SKIP_IFP].ptr; 845 else if (r->direction && r->direction != dir) 846 r = r->skip[PF_SKIP_DIR].ptr; 847 else if (r->af && r->af != AF_INET) 848 r = r->skip[PF_SKIP_AF].ptr; 849 else if (r->proto && r->proto != h->ip_p) 850 r = r->skip[PF_SKIP_PROTO].ptr; 851 else if (PF_MISMATCHAW(&r->src.addr, 852 (struct pf_addr *)&h->ip_src.s_addr, AF_INET, 853 r->src.neg, kif, M_GETFIB(m))) 854 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 855 else if (PF_MISMATCHAW(&r->dst.addr, 856 (struct pf_addr *)&h->ip_dst.s_addr, AF_INET, 857 r->dst.neg, NULL, M_GETFIB(m))) 858 r = r->skip[PF_SKIP_DST_ADDR].ptr; 859 else if (r->match_tag && !pf_match_tag(m, r, &tag, 860 pd->pf_mtag ? pd->pf_mtag->tag : 0)) 861 r = TAILQ_NEXT(r, entries); 862 else 863 break; 864 } 865 866 if (r == NULL || r->action == PF_NOSCRUB) 867 return (PF_PASS); 868 else { 869 r->packets[dir == PF_OUT]++; 870 r->bytes[dir == PF_OUT] += pd->tot_len; 871 } 872 873 /* Check for illegal packets */ 874 if (hlen < (int)sizeof(struct ip)) { 875 REASON_SET(reason, PFRES_NORM); 876 goto drop; 877 } 878 879 if (hlen > ntohs(h->ip_len)) { 880 REASON_SET(reason, PFRES_NORM); 881 goto drop; 882 } 883 884 /* Clear IP_DF if the rule uses the no-df option */ 885 if (r->rule_flag & PFRULE_NODF && h->ip_off & htons(IP_DF)) { 886 u_int16_t ip_off = h->ip_off; 887 888 h->ip_off &= htons(~IP_DF); 889 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0); 890 } 891 892 /* We will need other tests here */ 893 if (!fragoff && !mff) 894 goto no_fragment; 895 896 /* We're dealing with a fragment now. Don't allow fragments 897 * with IP_DF to enter the cache. If the flag was cleared by 898 * no-df above, fine. Otherwise drop it. 899 */ 900 if (h->ip_off & htons(IP_DF)) { 901 DPFPRINTF(("IP_DF\n")); 902 goto bad; 903 } 904 905 ip_len = ntohs(h->ip_len) - hlen; 906 ip_off = (ntohs(h->ip_off) & IP_OFFMASK) << 3; 907 908 /* All fragments are 8 byte aligned */ 909 if (mff && (ip_len & 0x7)) { 910 DPFPRINTF(("mff and %d\n", ip_len)); 911 goto bad; 912 } 913 914 /* Respect maximum length */ 915 if (fragoff + ip_len > IP_MAXPACKET) { 916 DPFPRINTF(("max packet %d\n", fragoff + ip_len)); 917 goto bad; 918 } 919 max = fragoff + ip_len; 920 921 /* Fully buffer all of the fragments 922 * Might return a completely reassembled mbuf, or NULL */ 923 PF_FRAG_LOCK(); 924 DPFPRINTF(("reass frag %d @ %d-%d\n", h->ip_id, fragoff, max)); 925 verdict = pf_reassemble(m0, h, dir, reason); 926 PF_FRAG_UNLOCK(); 927 928 if (verdict != PF_PASS) 929 return (PF_DROP); 930 931 m = *m0; 932 if (m == NULL) 933 return (PF_DROP); 934 935 h = mtod(m, struct ip *); 936 937 no_fragment: 938 /* At this point, only IP_DF is allowed in ip_off */ 939 if (h->ip_off & ~htons(IP_DF)) { 940 u_int16_t ip_off = h->ip_off; 941 942 h->ip_off &= htons(IP_DF); 943 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0); 944 } 945 946 pf_scrub_ip(&m, r->rule_flag, r->min_ttl, r->set_tos); 947 948 return (PF_PASS); 949 950 bad: 951 DPFPRINTF(("dropping bad fragment\n")); 952 REASON_SET(reason, PFRES_FRAG); 953 drop: 954 if (r != NULL && r->log) 955 PFLOG_PACKET(kif, m, AF_INET, dir, *reason, r, NULL, NULL, pd, 956 1); 957 958 return (PF_DROP); 959 } 960 #endif 961 962 #ifdef INET6 963 int 964 pf_normalize_ip6(struct mbuf **m0, int dir, struct pfi_kif *kif, 965 u_short *reason, struct pf_pdesc *pd) 966 { 967 struct mbuf *m = *m0; 968 struct pf_rule *r; 969 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 970 int extoff; 971 int off; 972 struct ip6_ext ext; 973 struct ip6_opt opt; 974 struct ip6_opt_jumbo jumbo; 975 struct ip6_frag frag; 976 u_int32_t jumbolen = 0, plen; 977 int optend; 978 int ooff; 979 u_int8_t proto; 980 int terminal; 981 982 PF_RULES_RASSERT(); 983 984 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 985 while (r != NULL) { 986 r->evaluations++; 987 if (pfi_kif_match(r->kif, kif) == r->ifnot) 988 r = r->skip[PF_SKIP_IFP].ptr; 989 else if (r->direction && r->direction != dir) 990 r = r->skip[PF_SKIP_DIR].ptr; 991 else if (r->af && r->af != AF_INET6) 992 r = r->skip[PF_SKIP_AF].ptr; 993 #if 0 /* header chain! */ 994 else if (r->proto && r->proto != h->ip6_nxt) 995 r = r->skip[PF_SKIP_PROTO].ptr; 996 #endif 997 else if (PF_MISMATCHAW(&r->src.addr, 998 (struct pf_addr *)&h->ip6_src, AF_INET6, 999 r->src.neg, kif, M_GETFIB(m))) 1000 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 1001 else if (PF_MISMATCHAW(&r->dst.addr, 1002 (struct pf_addr *)&h->ip6_dst, AF_INET6, 1003 r->dst.neg, NULL, M_GETFIB(m))) 1004 r = r->skip[PF_SKIP_DST_ADDR].ptr; 1005 else 1006 break; 1007 } 1008 1009 if (r == NULL || r->action == PF_NOSCRUB) 1010 return (PF_PASS); 1011 else { 1012 r->packets[dir == PF_OUT]++; 1013 r->bytes[dir == PF_OUT] += pd->tot_len; 1014 } 1015 1016 /* Check for illegal packets */ 1017 if (sizeof(struct ip6_hdr) + IPV6_MAXPACKET < m->m_pkthdr.len) 1018 goto drop; 1019 1020 extoff = 0; 1021 off = sizeof(struct ip6_hdr); 1022 proto = h->ip6_nxt; 1023 terminal = 0; 1024 do { 1025 switch (proto) { 1026 case IPPROTO_FRAGMENT: 1027 goto fragment; 1028 break; 1029 case IPPROTO_AH: 1030 case IPPROTO_ROUTING: 1031 case IPPROTO_DSTOPTS: 1032 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL, 1033 NULL, AF_INET6)) 1034 goto shortpkt; 1035 extoff = off; 1036 if (proto == IPPROTO_AH) 1037 off += (ext.ip6e_len + 2) * 4; 1038 else 1039 off += (ext.ip6e_len + 1) * 8; 1040 proto = ext.ip6e_nxt; 1041 break; 1042 case IPPROTO_HOPOPTS: 1043 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL, 1044 NULL, AF_INET6)) 1045 goto shortpkt; 1046 extoff = off; 1047 optend = off + (ext.ip6e_len + 1) * 8; 1048 ooff = off + sizeof(ext); 1049 do { 1050 if (!pf_pull_hdr(m, ooff, &opt.ip6o_type, 1051 sizeof(opt.ip6o_type), NULL, NULL, 1052 AF_INET6)) 1053 goto shortpkt; 1054 if (opt.ip6o_type == IP6OPT_PAD1) { 1055 ooff++; 1056 continue; 1057 } 1058 if (!pf_pull_hdr(m, ooff, &opt, sizeof(opt), 1059 NULL, NULL, AF_INET6)) 1060 goto shortpkt; 1061 if (ooff + sizeof(opt) + opt.ip6o_len > optend) 1062 goto drop; 1063 switch (opt.ip6o_type) { 1064 case IP6OPT_JUMBO: 1065 if (h->ip6_plen != 0) 1066 goto drop; 1067 if (!pf_pull_hdr(m, ooff, &jumbo, 1068 sizeof(jumbo), NULL, NULL, 1069 AF_INET6)) 1070 goto shortpkt; 1071 memcpy(&jumbolen, jumbo.ip6oj_jumbo_len, 1072 sizeof(jumbolen)); 1073 jumbolen = ntohl(jumbolen); 1074 if (jumbolen <= IPV6_MAXPACKET) 1075 goto drop; 1076 if (sizeof(struct ip6_hdr) + jumbolen != 1077 m->m_pkthdr.len) 1078 goto drop; 1079 break; 1080 default: 1081 break; 1082 } 1083 ooff += sizeof(opt) + opt.ip6o_len; 1084 } while (ooff < optend); 1085 1086 off = optend; 1087 proto = ext.ip6e_nxt; 1088 break; 1089 default: 1090 terminal = 1; 1091 break; 1092 } 1093 } while (!terminal); 1094 1095 /* jumbo payload option must be present, or plen > 0 */ 1096 if (ntohs(h->ip6_plen) == 0) 1097 plen = jumbolen; 1098 else 1099 plen = ntohs(h->ip6_plen); 1100 if (plen == 0) 1101 goto drop; 1102 if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len) 1103 goto shortpkt; 1104 1105 pf_scrub_ip6(&m, r->min_ttl); 1106 1107 return (PF_PASS); 1108 1109 fragment: 1110 /* Jumbo payload packets cannot be fragmented. */ 1111 plen = ntohs(h->ip6_plen); 1112 if (plen == 0 || jumbolen) 1113 goto drop; 1114 if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len) 1115 goto shortpkt; 1116 1117 if (!pf_pull_hdr(m, off, &frag, sizeof(frag), NULL, NULL, AF_INET6)) 1118 goto shortpkt; 1119 1120 /* Offset now points to data portion. */ 1121 off += sizeof(frag); 1122 1123 /* Returns PF_DROP or *m0 is NULL or completely reassembled mbuf. */ 1124 if (pf_reassemble6(m0, h, &frag, off, extoff, reason) != PF_PASS) 1125 return (PF_DROP); 1126 m = *m0; 1127 if (m == NULL) 1128 return (PF_DROP); 1129 1130 pd->flags |= PFDESC_IP_REAS; 1131 return (PF_PASS); 1132 1133 shortpkt: 1134 REASON_SET(reason, PFRES_SHORT); 1135 if (r != NULL && r->log) 1136 PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd, 1137 1); 1138 return (PF_DROP); 1139 1140 drop: 1141 REASON_SET(reason, PFRES_NORM); 1142 if (r != NULL && r->log) 1143 PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd, 1144 1); 1145 return (PF_DROP); 1146 } 1147 #endif /* INET6 */ 1148 1149 int 1150 pf_normalize_tcp(int dir, struct pfi_kif *kif, struct mbuf *m, int ipoff, 1151 int off, void *h, struct pf_pdesc *pd) 1152 { 1153 struct pf_rule *r, *rm = NULL; 1154 struct tcphdr *th = pd->hdr.tcp; 1155 int rewrite = 0; 1156 u_short reason; 1157 u_int8_t flags; 1158 sa_family_t af = pd->af; 1159 1160 PF_RULES_RASSERT(); 1161 1162 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 1163 while (r != NULL) { 1164 r->evaluations++; 1165 if (pfi_kif_match(r->kif, kif) == r->ifnot) 1166 r = r->skip[PF_SKIP_IFP].ptr; 1167 else if (r->direction && r->direction != dir) 1168 r = r->skip[PF_SKIP_DIR].ptr; 1169 else if (r->af && r->af != af) 1170 r = r->skip[PF_SKIP_AF].ptr; 1171 else if (r->proto && r->proto != pd->proto) 1172 r = r->skip[PF_SKIP_PROTO].ptr; 1173 else if (PF_MISMATCHAW(&r->src.addr, pd->src, af, 1174 r->src.neg, kif, M_GETFIB(m))) 1175 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 1176 else if (r->src.port_op && !pf_match_port(r->src.port_op, 1177 r->src.port[0], r->src.port[1], th->th_sport)) 1178 r = r->skip[PF_SKIP_SRC_PORT].ptr; 1179 else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af, 1180 r->dst.neg, NULL, M_GETFIB(m))) 1181 r = r->skip[PF_SKIP_DST_ADDR].ptr; 1182 else if (r->dst.port_op && !pf_match_port(r->dst.port_op, 1183 r->dst.port[0], r->dst.port[1], th->th_dport)) 1184 r = r->skip[PF_SKIP_DST_PORT].ptr; 1185 else if (r->os_fingerprint != PF_OSFP_ANY && !pf_osfp_match( 1186 pf_osfp_fingerprint(pd, m, off, th), 1187 r->os_fingerprint)) 1188 r = TAILQ_NEXT(r, entries); 1189 else { 1190 rm = r; 1191 break; 1192 } 1193 } 1194 1195 if (rm == NULL || rm->action == PF_NOSCRUB) 1196 return (PF_PASS); 1197 else { 1198 r->packets[dir == PF_OUT]++; 1199 r->bytes[dir == PF_OUT] += pd->tot_len; 1200 } 1201 1202 if (rm->rule_flag & PFRULE_REASSEMBLE_TCP) 1203 pd->flags |= PFDESC_TCP_NORM; 1204 1205 flags = th->th_flags; 1206 if (flags & TH_SYN) { 1207 /* Illegal packet */ 1208 if (flags & TH_RST) 1209 goto tcp_drop; 1210 1211 if (flags & TH_FIN) 1212 goto tcp_drop; 1213 } else { 1214 /* Illegal packet */ 1215 if (!(flags & (TH_ACK|TH_RST))) 1216 goto tcp_drop; 1217 } 1218 1219 if (!(flags & TH_ACK)) { 1220 /* These flags are only valid if ACK is set */ 1221 if ((flags & TH_FIN) || (flags & TH_PUSH) || (flags & TH_URG)) 1222 goto tcp_drop; 1223 } 1224 1225 /* Check for illegal header length */ 1226 if (th->th_off < (sizeof(struct tcphdr) >> 2)) 1227 goto tcp_drop; 1228 1229 /* If flags changed, or reserved data set, then adjust */ 1230 if (flags != th->th_flags || th->th_x2 != 0) { 1231 u_int16_t ov, nv; 1232 1233 ov = *(u_int16_t *)(&th->th_ack + 1); 1234 th->th_flags = flags; 1235 th->th_x2 = 0; 1236 nv = *(u_int16_t *)(&th->th_ack + 1); 1237 1238 th->th_sum = pf_proto_cksum_fixup(m, th->th_sum, ov, nv, 0); 1239 rewrite = 1; 1240 } 1241 1242 /* Remove urgent pointer, if TH_URG is not set */ 1243 if (!(flags & TH_URG) && th->th_urp) { 1244 th->th_sum = pf_proto_cksum_fixup(m, th->th_sum, th->th_urp, 1245 0, 0); 1246 th->th_urp = 0; 1247 rewrite = 1; 1248 } 1249 1250 /* Process options */ 1251 if (r->max_mss && pf_normalize_tcpopt(r, m, th, off, pd->af)) 1252 rewrite = 1; 1253 1254 /* copy back packet headers if we sanitized */ 1255 if (rewrite) 1256 m_copyback(m, off, sizeof(*th), (caddr_t)th); 1257 1258 return (PF_PASS); 1259 1260 tcp_drop: 1261 REASON_SET(&reason, PFRES_NORM); 1262 if (rm != NULL && r->log) 1263 PFLOG_PACKET(kif, m, AF_INET, dir, reason, r, NULL, NULL, pd, 1264 1); 1265 return (PF_DROP); 1266 } 1267 1268 int 1269 pf_normalize_tcp_init(struct mbuf *m, int off, struct pf_pdesc *pd, 1270 struct tcphdr *th, struct pf_state_peer *src, struct pf_state_peer *dst) 1271 { 1272 u_int32_t tsval, tsecr; 1273 u_int8_t hdr[60]; 1274 u_int8_t *opt; 1275 1276 KASSERT((src->scrub == NULL), 1277 ("pf_normalize_tcp_init: src->scrub != NULL")); 1278 1279 src->scrub = uma_zalloc(V_pf_state_scrub_z, M_ZERO | M_NOWAIT); 1280 if (src->scrub == NULL) 1281 return (1); 1282 1283 switch (pd->af) { 1284 #ifdef INET 1285 case AF_INET: { 1286 struct ip *h = mtod(m, struct ip *); 1287 src->scrub->pfss_ttl = h->ip_ttl; 1288 break; 1289 } 1290 #endif /* INET */ 1291 #ifdef INET6 1292 case AF_INET6: { 1293 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1294 src->scrub->pfss_ttl = h->ip6_hlim; 1295 break; 1296 } 1297 #endif /* INET6 */ 1298 } 1299 1300 1301 /* 1302 * All normalizations below are only begun if we see the start of 1303 * the connections. They must all set an enabled bit in pfss_flags 1304 */ 1305 if ((th->th_flags & TH_SYN) == 0) 1306 return (0); 1307 1308 1309 if (th->th_off > (sizeof(struct tcphdr) >> 2) && src->scrub && 1310 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) { 1311 /* Diddle with TCP options */ 1312 int hlen; 1313 opt = hdr + sizeof(struct tcphdr); 1314 hlen = (th->th_off << 2) - sizeof(struct tcphdr); 1315 while (hlen >= TCPOLEN_TIMESTAMP) { 1316 switch (*opt) { 1317 case TCPOPT_EOL: /* FALLTHROUGH */ 1318 case TCPOPT_NOP: 1319 opt++; 1320 hlen--; 1321 break; 1322 case TCPOPT_TIMESTAMP: 1323 if (opt[1] >= TCPOLEN_TIMESTAMP) { 1324 src->scrub->pfss_flags |= 1325 PFSS_TIMESTAMP; 1326 src->scrub->pfss_ts_mod = 1327 htonl(arc4random()); 1328 1329 /* note PFSS_PAWS not set yet */ 1330 memcpy(&tsval, &opt[2], 1331 sizeof(u_int32_t)); 1332 memcpy(&tsecr, &opt[6], 1333 sizeof(u_int32_t)); 1334 src->scrub->pfss_tsval0 = ntohl(tsval); 1335 src->scrub->pfss_tsval = ntohl(tsval); 1336 src->scrub->pfss_tsecr = ntohl(tsecr); 1337 getmicrouptime(&src->scrub->pfss_last); 1338 } 1339 /* FALLTHROUGH */ 1340 default: 1341 hlen -= MAX(opt[1], 2); 1342 opt += MAX(opt[1], 2); 1343 break; 1344 } 1345 } 1346 } 1347 1348 return (0); 1349 } 1350 1351 void 1352 pf_normalize_tcp_cleanup(struct pf_state *state) 1353 { 1354 if (state->src.scrub) 1355 uma_zfree(V_pf_state_scrub_z, state->src.scrub); 1356 if (state->dst.scrub) 1357 uma_zfree(V_pf_state_scrub_z, state->dst.scrub); 1358 1359 /* Someday... flush the TCP segment reassembly descriptors. */ 1360 } 1361 1362 int 1363 pf_normalize_tcp_stateful(struct mbuf *m, int off, struct pf_pdesc *pd, 1364 u_short *reason, struct tcphdr *th, struct pf_state *state, 1365 struct pf_state_peer *src, struct pf_state_peer *dst, int *writeback) 1366 { 1367 struct timeval uptime; 1368 u_int32_t tsval, tsecr; 1369 u_int tsval_from_last; 1370 u_int8_t hdr[60]; 1371 u_int8_t *opt; 1372 int copyback = 0; 1373 int got_ts = 0; 1374 1375 KASSERT((src->scrub || dst->scrub), 1376 ("%s: src->scrub && dst->scrub!", __func__)); 1377 1378 /* 1379 * Enforce the minimum TTL seen for this connection. Negate a common 1380 * technique to evade an intrusion detection system and confuse 1381 * firewall state code. 1382 */ 1383 switch (pd->af) { 1384 #ifdef INET 1385 case AF_INET: { 1386 if (src->scrub) { 1387 struct ip *h = mtod(m, struct ip *); 1388 if (h->ip_ttl > src->scrub->pfss_ttl) 1389 src->scrub->pfss_ttl = h->ip_ttl; 1390 h->ip_ttl = src->scrub->pfss_ttl; 1391 } 1392 break; 1393 } 1394 #endif /* INET */ 1395 #ifdef INET6 1396 case AF_INET6: { 1397 if (src->scrub) { 1398 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1399 if (h->ip6_hlim > src->scrub->pfss_ttl) 1400 src->scrub->pfss_ttl = h->ip6_hlim; 1401 h->ip6_hlim = src->scrub->pfss_ttl; 1402 } 1403 break; 1404 } 1405 #endif /* INET6 */ 1406 } 1407 1408 if (th->th_off > (sizeof(struct tcphdr) >> 2) && 1409 ((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) || 1410 (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) && 1411 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) { 1412 /* Diddle with TCP options */ 1413 int hlen; 1414 opt = hdr + sizeof(struct tcphdr); 1415 hlen = (th->th_off << 2) - sizeof(struct tcphdr); 1416 while (hlen >= TCPOLEN_TIMESTAMP) { 1417 switch (*opt) { 1418 case TCPOPT_EOL: /* FALLTHROUGH */ 1419 case TCPOPT_NOP: 1420 opt++; 1421 hlen--; 1422 break; 1423 case TCPOPT_TIMESTAMP: 1424 /* Modulate the timestamps. Can be used for 1425 * NAT detection, OS uptime determination or 1426 * reboot detection. 1427 */ 1428 1429 if (got_ts) { 1430 /* Huh? Multiple timestamps!? */ 1431 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1432 DPFPRINTF(("multiple TS??")); 1433 pf_print_state(state); 1434 printf("\n"); 1435 } 1436 REASON_SET(reason, PFRES_TS); 1437 return (PF_DROP); 1438 } 1439 if (opt[1] >= TCPOLEN_TIMESTAMP) { 1440 memcpy(&tsval, &opt[2], 1441 sizeof(u_int32_t)); 1442 if (tsval && src->scrub && 1443 (src->scrub->pfss_flags & 1444 PFSS_TIMESTAMP)) { 1445 tsval = ntohl(tsval); 1446 pf_change_proto_a(m, &opt[2], 1447 &th->th_sum, 1448 htonl(tsval + 1449 src->scrub->pfss_ts_mod), 1450 0); 1451 copyback = 1; 1452 } 1453 1454 /* Modulate TS reply iff valid (!0) */ 1455 memcpy(&tsecr, &opt[6], 1456 sizeof(u_int32_t)); 1457 if (tsecr && dst->scrub && 1458 (dst->scrub->pfss_flags & 1459 PFSS_TIMESTAMP)) { 1460 tsecr = ntohl(tsecr) 1461 - dst->scrub->pfss_ts_mod; 1462 pf_change_proto_a(m, &opt[6], 1463 &th->th_sum, htonl(tsecr), 1464 0); 1465 copyback = 1; 1466 } 1467 got_ts = 1; 1468 } 1469 /* FALLTHROUGH */ 1470 default: 1471 hlen -= MAX(opt[1], 2); 1472 opt += MAX(opt[1], 2); 1473 break; 1474 } 1475 } 1476 if (copyback) { 1477 /* Copyback the options, caller copys back header */ 1478 *writeback = 1; 1479 m_copyback(m, off + sizeof(struct tcphdr), 1480 (th->th_off << 2) - sizeof(struct tcphdr), hdr + 1481 sizeof(struct tcphdr)); 1482 } 1483 } 1484 1485 1486 /* 1487 * Must invalidate PAWS checks on connections idle for too long. 1488 * The fastest allowed timestamp clock is 1ms. That turns out to 1489 * be about 24 days before it wraps. XXX Right now our lowerbound 1490 * TS echo check only works for the first 12 days of a connection 1491 * when the TS has exhausted half its 32bit space 1492 */ 1493 #define TS_MAX_IDLE (24*24*60*60) 1494 #define TS_MAX_CONN (12*24*60*60) /* XXX remove when better tsecr check */ 1495 1496 getmicrouptime(&uptime); 1497 if (src->scrub && (src->scrub->pfss_flags & PFSS_PAWS) && 1498 (uptime.tv_sec - src->scrub->pfss_last.tv_sec > TS_MAX_IDLE || 1499 time_uptime - state->creation > TS_MAX_CONN)) { 1500 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1501 DPFPRINTF(("src idled out of PAWS\n")); 1502 pf_print_state(state); 1503 printf("\n"); 1504 } 1505 src->scrub->pfss_flags = (src->scrub->pfss_flags & ~PFSS_PAWS) 1506 | PFSS_PAWS_IDLED; 1507 } 1508 if (dst->scrub && (dst->scrub->pfss_flags & PFSS_PAWS) && 1509 uptime.tv_sec - dst->scrub->pfss_last.tv_sec > TS_MAX_IDLE) { 1510 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1511 DPFPRINTF(("dst idled out of PAWS\n")); 1512 pf_print_state(state); 1513 printf("\n"); 1514 } 1515 dst->scrub->pfss_flags = (dst->scrub->pfss_flags & ~PFSS_PAWS) 1516 | PFSS_PAWS_IDLED; 1517 } 1518 1519 if (got_ts && src->scrub && dst->scrub && 1520 (src->scrub->pfss_flags & PFSS_PAWS) && 1521 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1522 /* Validate that the timestamps are "in-window". 1523 * RFC1323 describes TCP Timestamp options that allow 1524 * measurement of RTT (round trip time) and PAWS 1525 * (protection against wrapped sequence numbers). PAWS 1526 * gives us a set of rules for rejecting packets on 1527 * long fat pipes (packets that were somehow delayed 1528 * in transit longer than the time it took to send the 1529 * full TCP sequence space of 4Gb). We can use these 1530 * rules and infer a few others that will let us treat 1531 * the 32bit timestamp and the 32bit echoed timestamp 1532 * as sequence numbers to prevent a blind attacker from 1533 * inserting packets into a connection. 1534 * 1535 * RFC1323 tells us: 1536 * - The timestamp on this packet must be greater than 1537 * or equal to the last value echoed by the other 1538 * endpoint. The RFC says those will be discarded 1539 * since it is a dup that has already been acked. 1540 * This gives us a lowerbound on the timestamp. 1541 * timestamp >= other last echoed timestamp 1542 * - The timestamp will be less than or equal to 1543 * the last timestamp plus the time between the 1544 * last packet and now. The RFC defines the max 1545 * clock rate as 1ms. We will allow clocks to be 1546 * up to 10% fast and will allow a total difference 1547 * or 30 seconds due to a route change. And this 1548 * gives us an upperbound on the timestamp. 1549 * timestamp <= last timestamp + max ticks 1550 * We have to be careful here. Windows will send an 1551 * initial timestamp of zero and then initialize it 1552 * to a random value after the 3whs; presumably to 1553 * avoid a DoS by having to call an expensive RNG 1554 * during a SYN flood. Proof MS has at least one 1555 * good security geek. 1556 * 1557 * - The TCP timestamp option must also echo the other 1558 * endpoints timestamp. The timestamp echoed is the 1559 * one carried on the earliest unacknowledged segment 1560 * on the left edge of the sequence window. The RFC 1561 * states that the host will reject any echoed 1562 * timestamps that were larger than any ever sent. 1563 * This gives us an upperbound on the TS echo. 1564 * tescr <= largest_tsval 1565 * - The lowerbound on the TS echo is a little more 1566 * tricky to determine. The other endpoint's echoed 1567 * values will not decrease. But there may be 1568 * network conditions that re-order packets and 1569 * cause our view of them to decrease. For now the 1570 * only lowerbound we can safely determine is that 1571 * the TS echo will never be less than the original 1572 * TS. XXX There is probably a better lowerbound. 1573 * Remove TS_MAX_CONN with better lowerbound check. 1574 * tescr >= other original TS 1575 * 1576 * It is also important to note that the fastest 1577 * timestamp clock of 1ms will wrap its 32bit space in 1578 * 24 days. So we just disable TS checking after 24 1579 * days of idle time. We actually must use a 12d 1580 * connection limit until we can come up with a better 1581 * lowerbound to the TS echo check. 1582 */ 1583 struct timeval delta_ts; 1584 int ts_fudge; 1585 1586 1587 /* 1588 * PFTM_TS_DIFF is how many seconds of leeway to allow 1589 * a host's timestamp. This can happen if the previous 1590 * packet got delayed in transit for much longer than 1591 * this packet. 1592 */ 1593 if ((ts_fudge = state->rule.ptr->timeout[PFTM_TS_DIFF]) == 0) 1594 ts_fudge = V_pf_default_rule.timeout[PFTM_TS_DIFF]; 1595 1596 /* Calculate max ticks since the last timestamp */ 1597 #define TS_MAXFREQ 1100 /* RFC max TS freq of 1Khz + 10% skew */ 1598 #define TS_MICROSECS 1000000 /* microseconds per second */ 1599 delta_ts = uptime; 1600 timevalsub(&delta_ts, &src->scrub->pfss_last); 1601 tsval_from_last = (delta_ts.tv_sec + ts_fudge) * TS_MAXFREQ; 1602 tsval_from_last += delta_ts.tv_usec / (TS_MICROSECS/TS_MAXFREQ); 1603 1604 if ((src->state >= TCPS_ESTABLISHED && 1605 dst->state >= TCPS_ESTABLISHED) && 1606 (SEQ_LT(tsval, dst->scrub->pfss_tsecr) || 1607 SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) || 1608 (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) || 1609 SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) { 1610 /* Bad RFC1323 implementation or an insertion attack. 1611 * 1612 * - Solaris 2.6 and 2.7 are known to send another ACK 1613 * after the FIN,FIN|ACK,ACK closing that carries 1614 * an old timestamp. 1615 */ 1616 1617 DPFPRINTF(("Timestamp failed %c%c%c%c\n", 1618 SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '0' : ' ', 1619 SEQ_GT(tsval, src->scrub->pfss_tsval + 1620 tsval_from_last) ? '1' : ' ', 1621 SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ', 1622 SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' ')); 1623 DPFPRINTF((" tsval: %u tsecr: %u +ticks: %u " 1624 "idle: %jus %lums\n", 1625 tsval, tsecr, tsval_from_last, 1626 (uintmax_t)delta_ts.tv_sec, 1627 delta_ts.tv_usec / 1000)); 1628 DPFPRINTF((" src->tsval: %u tsecr: %u\n", 1629 src->scrub->pfss_tsval, src->scrub->pfss_tsecr)); 1630 DPFPRINTF((" dst->tsval: %u tsecr: %u tsval0: %u" 1631 "\n", dst->scrub->pfss_tsval, 1632 dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0)); 1633 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1634 pf_print_state(state); 1635 pf_print_flags(th->th_flags); 1636 printf("\n"); 1637 } 1638 REASON_SET(reason, PFRES_TS); 1639 return (PF_DROP); 1640 } 1641 1642 /* XXX I'd really like to require tsecr but it's optional */ 1643 1644 } else if (!got_ts && (th->th_flags & TH_RST) == 0 && 1645 ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED) 1646 || pd->p_len > 0 || (th->th_flags & TH_SYN)) && 1647 src->scrub && dst->scrub && 1648 (src->scrub->pfss_flags & PFSS_PAWS) && 1649 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1650 /* Didn't send a timestamp. Timestamps aren't really useful 1651 * when: 1652 * - connection opening or closing (often not even sent). 1653 * but we must not let an attacker to put a FIN on a 1654 * data packet to sneak it through our ESTABLISHED check. 1655 * - on a TCP reset. RFC suggests not even looking at TS. 1656 * - on an empty ACK. The TS will not be echoed so it will 1657 * probably not help keep the RTT calculation in sync and 1658 * there isn't as much danger when the sequence numbers 1659 * got wrapped. So some stacks don't include TS on empty 1660 * ACKs :-( 1661 * 1662 * To minimize the disruption to mostly RFC1323 conformant 1663 * stacks, we will only require timestamps on data packets. 1664 * 1665 * And what do ya know, we cannot require timestamps on data 1666 * packets. There appear to be devices that do legitimate 1667 * TCP connection hijacking. There are HTTP devices that allow 1668 * a 3whs (with timestamps) and then buffer the HTTP request. 1669 * If the intermediate device has the HTTP response cache, it 1670 * will spoof the response but not bother timestamping its 1671 * packets. So we can look for the presence of a timestamp in 1672 * the first data packet and if there, require it in all future 1673 * packets. 1674 */ 1675 1676 if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) { 1677 /* 1678 * Hey! Someone tried to sneak a packet in. Or the 1679 * stack changed its RFC1323 behavior?!?! 1680 */ 1681 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1682 DPFPRINTF(("Did not receive expected RFC1323 " 1683 "timestamp\n")); 1684 pf_print_state(state); 1685 pf_print_flags(th->th_flags); 1686 printf("\n"); 1687 } 1688 REASON_SET(reason, PFRES_TS); 1689 return (PF_DROP); 1690 } 1691 } 1692 1693 1694 /* 1695 * We will note if a host sends his data packets with or without 1696 * timestamps. And require all data packets to contain a timestamp 1697 * if the first does. PAWS implicitly requires that all data packets be 1698 * timestamped. But I think there are middle-man devices that hijack 1699 * TCP streams immediately after the 3whs and don't timestamp their 1700 * packets (seen in a WWW accelerator or cache). 1701 */ 1702 if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags & 1703 (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) { 1704 if (got_ts) 1705 src->scrub->pfss_flags |= PFSS_DATA_TS; 1706 else { 1707 src->scrub->pfss_flags |= PFSS_DATA_NOTS; 1708 if (V_pf_status.debug >= PF_DEBUG_MISC && dst->scrub && 1709 (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) { 1710 /* Don't warn if other host rejected RFC1323 */ 1711 DPFPRINTF(("Broken RFC1323 stack did not " 1712 "timestamp data packet. Disabled PAWS " 1713 "security.\n")); 1714 pf_print_state(state); 1715 pf_print_flags(th->th_flags); 1716 printf("\n"); 1717 } 1718 } 1719 } 1720 1721 1722 /* 1723 * Update PAWS values 1724 */ 1725 if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags & 1726 (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) { 1727 getmicrouptime(&src->scrub->pfss_last); 1728 if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) || 1729 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1730 src->scrub->pfss_tsval = tsval; 1731 1732 if (tsecr) { 1733 if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) || 1734 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1735 src->scrub->pfss_tsecr = tsecr; 1736 1737 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 && 1738 (SEQ_LT(tsval, src->scrub->pfss_tsval0) || 1739 src->scrub->pfss_tsval0 == 0)) { 1740 /* tsval0 MUST be the lowest timestamp */ 1741 src->scrub->pfss_tsval0 = tsval; 1742 } 1743 1744 /* Only fully initialized after a TS gets echoed */ 1745 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0) 1746 src->scrub->pfss_flags |= PFSS_PAWS; 1747 } 1748 } 1749 1750 /* I have a dream.... TCP segment reassembly.... */ 1751 return (0); 1752 } 1753 1754 static int 1755 pf_normalize_tcpopt(struct pf_rule *r, struct mbuf *m, struct tcphdr *th, 1756 int off, sa_family_t af) 1757 { 1758 u_int16_t *mss; 1759 int thoff; 1760 int opt, cnt, optlen = 0; 1761 int rewrite = 0; 1762 u_char opts[TCP_MAXOLEN]; 1763 u_char *optp = opts; 1764 1765 thoff = th->th_off << 2; 1766 cnt = thoff - sizeof(struct tcphdr); 1767 1768 if (cnt > 0 && !pf_pull_hdr(m, off + sizeof(*th), opts, cnt, 1769 NULL, NULL, af)) 1770 return (rewrite); 1771 1772 for (; cnt > 0; cnt -= optlen, optp += optlen) { 1773 opt = optp[0]; 1774 if (opt == TCPOPT_EOL) 1775 break; 1776 if (opt == TCPOPT_NOP) 1777 optlen = 1; 1778 else { 1779 if (cnt < 2) 1780 break; 1781 optlen = optp[1]; 1782 if (optlen < 2 || optlen > cnt) 1783 break; 1784 } 1785 switch (opt) { 1786 case TCPOPT_MAXSEG: 1787 mss = (u_int16_t *)(optp + 2); 1788 if ((ntohs(*mss)) > r->max_mss) { 1789 th->th_sum = pf_proto_cksum_fixup(m, 1790 th->th_sum, *mss, htons(r->max_mss), 0); 1791 *mss = htons(r->max_mss); 1792 rewrite = 1; 1793 } 1794 break; 1795 default: 1796 break; 1797 } 1798 } 1799 1800 if (rewrite) 1801 m_copyback(m, off + sizeof(*th), thoff - sizeof(*th), opts); 1802 1803 return (rewrite); 1804 } 1805 1806 #ifdef INET 1807 static void 1808 pf_scrub_ip(struct mbuf **m0, u_int32_t flags, u_int8_t min_ttl, u_int8_t tos) 1809 { 1810 struct mbuf *m = *m0; 1811 struct ip *h = mtod(m, struct ip *); 1812 1813 /* Clear IP_DF if no-df was requested */ 1814 if (flags & PFRULE_NODF && h->ip_off & htons(IP_DF)) { 1815 u_int16_t ip_off = h->ip_off; 1816 1817 h->ip_off &= htons(~IP_DF); 1818 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0); 1819 } 1820 1821 /* Enforce a minimum ttl, may cause endless packet loops */ 1822 if (min_ttl && h->ip_ttl < min_ttl) { 1823 u_int16_t ip_ttl = h->ip_ttl; 1824 1825 h->ip_ttl = min_ttl; 1826 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0); 1827 } 1828 1829 /* Enforce tos */ 1830 if (flags & PFRULE_SET_TOS) { 1831 u_int16_t ov, nv; 1832 1833 ov = *(u_int16_t *)h; 1834 h->ip_tos = tos | (h->ip_tos & IPTOS_ECN_MASK); 1835 nv = *(u_int16_t *)h; 1836 1837 h->ip_sum = pf_cksum_fixup(h->ip_sum, ov, nv, 0); 1838 } 1839 1840 /* random-id, but not for fragments */ 1841 if (flags & PFRULE_RANDOMID && !(h->ip_off & ~htons(IP_DF))) { 1842 uint16_t ip_id = h->ip_id; 1843 1844 ip_fillid(h); 1845 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_id, h->ip_id, 0); 1846 } 1847 } 1848 #endif /* INET */ 1849 1850 #ifdef INET6 1851 static void 1852 pf_scrub_ip6(struct mbuf **m0, u_int8_t min_ttl) 1853 { 1854 struct mbuf *m = *m0; 1855 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1856 1857 /* Enforce a minimum ttl, may cause endless packet loops */ 1858 if (min_ttl && h->ip6_hlim < min_ttl) 1859 h->ip6_hlim = min_ttl; 1860 } 1861 #endif 1862