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