1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright 2001 Niels Provos <provos@citi.umich.edu> 5 * Copyright 2011-2018 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 /* pointers to queue element */ 91 struct pf_frent *fr_firstoff[PF_FRAG_ENTRY_POINTS]; 92 /* count entries between pointers */ 93 uint8_t fr_entries[PF_FRAG_ENTRY_POINTS]; 94 RB_ENTRY(pf_fragment) fr_entry; 95 TAILQ_ENTRY(pf_fragment) frag_next; 96 uint32_t fr_timeout; 97 uint16_t fr_maxlen; /* maximum length of single fragment */ 98 u_int16_t fr_holes; /* number of holes in the queue */ 99 TAILQ_HEAD(pf_fragq, pf_frent) fr_queue; 100 }; 101 102 struct pf_fragment_tag { 103 uint16_t ft_hdrlen; /* header length of reassembled pkt */ 104 uint16_t ft_extoff; /* last extension header offset or 0 */ 105 uint16_t ft_maxlen; /* maximum fragment payload length */ 106 uint32_t ft_id; /* fragment id */ 107 }; 108 109 VNET_DEFINE_STATIC(struct mtx, pf_frag_mtx); 110 #define V_pf_frag_mtx VNET(pf_frag_mtx) 111 #define PF_FRAG_LOCK() mtx_lock(&V_pf_frag_mtx) 112 #define PF_FRAG_UNLOCK() mtx_unlock(&V_pf_frag_mtx) 113 #define PF_FRAG_ASSERT() mtx_assert(&V_pf_frag_mtx, MA_OWNED) 114 115 VNET_DEFINE(uma_zone_t, pf_state_scrub_z); /* XXX: shared with pfsync */ 116 117 VNET_DEFINE_STATIC(uma_zone_t, pf_frent_z); 118 #define V_pf_frent_z VNET(pf_frent_z) 119 VNET_DEFINE_STATIC(uma_zone_t, pf_frag_z); 120 #define V_pf_frag_z VNET(pf_frag_z) 121 122 TAILQ_HEAD(pf_fragqueue, pf_fragment); 123 TAILQ_HEAD(pf_cachequeue, pf_fragment); 124 VNET_DEFINE_STATIC(struct pf_fragqueue, pf_fragqueue); 125 #define V_pf_fragqueue VNET(pf_fragqueue) 126 RB_HEAD(pf_frag_tree, pf_fragment); 127 VNET_DEFINE_STATIC(struct pf_frag_tree, pf_frag_tree); 128 #define V_pf_frag_tree VNET(pf_frag_tree) 129 static int pf_frag_compare(struct pf_fragment *, 130 struct pf_fragment *); 131 static RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); 132 static RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); 133 134 static void pf_flush_fragments(void); 135 static void pf_free_fragment(struct pf_fragment *); 136 static void pf_remove_fragment(struct pf_fragment *); 137 static int pf_normalize_tcpopt(struct pf_rule *, struct mbuf *, 138 struct tcphdr *, int, sa_family_t); 139 static struct pf_frent *pf_create_fragment(u_short *); 140 static int pf_frent_holes(struct pf_frent *frent); 141 static struct pf_fragment *pf_find_fragment(struct pf_fragment_cmp *key, 142 struct pf_frag_tree *tree); 143 static inline int pf_frent_index(struct pf_frent *); 144 static int pf_frent_insert(struct pf_fragment *, 145 struct pf_frent *, struct pf_frent *); 146 void pf_frent_remove(struct pf_fragment *, 147 struct pf_frent *); 148 struct pf_frent *pf_frent_previous(struct pf_fragment *, 149 struct pf_frent *); 150 static struct pf_fragment *pf_fillup_fragment(struct pf_fragment_cmp *, 151 struct pf_frent *, u_short *); 152 static struct mbuf *pf_join_fragment(struct pf_fragment *); 153 #ifdef INET 154 static void pf_scrub_ip(struct mbuf **, uint32_t, uint8_t, uint8_t); 155 static int pf_reassemble(struct mbuf **, struct ip *, int, u_short *); 156 #endif /* INET */ 157 #ifdef INET6 158 static int pf_reassemble6(struct mbuf **, struct ip6_hdr *, 159 struct ip6_frag *, uint16_t, uint16_t, u_short *); 160 static void pf_scrub_ip6(struct mbuf **, uint8_t); 161 #endif /* INET6 */ 162 163 #define DPFPRINTF(x) do { \ 164 if (V_pf_status.debug >= PF_DEBUG_MISC) { \ 165 printf("%s: ", __func__); \ 166 printf x ; \ 167 } \ 168 } while(0) 169 170 #ifdef INET 171 static void 172 pf_ip2key(struct ip *ip, int dir, struct pf_fragment_cmp *key) 173 { 174 175 key->frc_src.v4 = ip->ip_src; 176 key->frc_dst.v4 = ip->ip_dst; 177 key->frc_af = AF_INET; 178 key->frc_proto = ip->ip_p; 179 key->frc_id = ip->ip_id; 180 } 181 #endif /* INET */ 182 183 void 184 pf_normalize_init(void) 185 { 186 187 V_pf_frag_z = uma_zcreate("pf frags", sizeof(struct pf_fragment), 188 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 189 V_pf_frent_z = uma_zcreate("pf frag entries", sizeof(struct pf_frent), 190 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 191 V_pf_state_scrub_z = uma_zcreate("pf state scrubs", 192 sizeof(struct pf_state_scrub), NULL, NULL, NULL, NULL, 193 UMA_ALIGN_PTR, 0); 194 195 mtx_init(&V_pf_frag_mtx, "pf fragments", NULL, MTX_DEF); 196 197 V_pf_limits[PF_LIMIT_FRAGS].zone = V_pf_frent_z; 198 V_pf_limits[PF_LIMIT_FRAGS].limit = PFFRAG_FRENT_HIWAT; 199 uma_zone_set_max(V_pf_frent_z, PFFRAG_FRENT_HIWAT); 200 uma_zone_set_warning(V_pf_frent_z, "PF frag entries limit reached"); 201 202 TAILQ_INIT(&V_pf_fragqueue); 203 } 204 205 void 206 pf_normalize_cleanup(void) 207 { 208 209 uma_zdestroy(V_pf_state_scrub_z); 210 uma_zdestroy(V_pf_frent_z); 211 uma_zdestroy(V_pf_frag_z); 212 213 mtx_destroy(&V_pf_frag_mtx); 214 } 215 216 static int 217 pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b) 218 { 219 int diff; 220 221 if ((diff = a->fr_id - b->fr_id) != 0) 222 return (diff); 223 if ((diff = a->fr_proto - b->fr_proto) != 0) 224 return (diff); 225 if ((diff = a->fr_af - b->fr_af) != 0) 226 return (diff); 227 if ((diff = pf_addr_cmp(&a->fr_src, &b->fr_src, a->fr_af)) != 0) 228 return (diff); 229 if ((diff = pf_addr_cmp(&a->fr_dst, &b->fr_dst, a->fr_af)) != 0) 230 return (diff); 231 return (0); 232 } 233 234 void 235 pf_purge_expired_fragments(void) 236 { 237 u_int32_t expire = time_uptime - 238 V_pf_default_rule.timeout[PFTM_FRAG]; 239 240 pf_purge_fragments(expire); 241 } 242 243 void 244 pf_purge_fragments(uint32_t expire) 245 { 246 struct pf_fragment *frag; 247 248 PF_FRAG_LOCK(); 249 while ((frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue)) != NULL) { 250 if (frag->fr_timeout > expire) 251 break; 252 253 DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag)); 254 pf_free_fragment(frag); 255 } 256 257 PF_FRAG_UNLOCK(); 258 } 259 260 /* 261 * Try to flush old fragments to make space for new ones 262 */ 263 static void 264 pf_flush_fragments(void) 265 { 266 struct pf_fragment *frag; 267 int goal; 268 269 PF_FRAG_ASSERT(); 270 271 goal = uma_zone_get_cur(V_pf_frent_z) * 9 / 10; 272 DPFPRINTF(("trying to free %d frag entriess\n", goal)); 273 while (goal < uma_zone_get_cur(V_pf_frent_z)) { 274 frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue); 275 if (frag) 276 pf_free_fragment(frag); 277 else 278 break; 279 } 280 } 281 282 /* Frees the fragments and all associated entries */ 283 static void 284 pf_free_fragment(struct pf_fragment *frag) 285 { 286 struct pf_frent *frent; 287 288 PF_FRAG_ASSERT(); 289 290 /* Free all fragments */ 291 for (frent = TAILQ_FIRST(&frag->fr_queue); frent; 292 frent = TAILQ_FIRST(&frag->fr_queue)) { 293 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next); 294 295 m_freem(frent->fe_m); 296 uma_zfree(V_pf_frent_z, frent); 297 } 298 299 pf_remove_fragment(frag); 300 } 301 302 static struct pf_fragment * 303 pf_find_fragment(struct pf_fragment_cmp *key, struct pf_frag_tree *tree) 304 { 305 struct pf_fragment *frag; 306 307 PF_FRAG_ASSERT(); 308 309 frag = RB_FIND(pf_frag_tree, tree, (struct pf_fragment *)key); 310 if (frag != NULL) { 311 /* XXX Are we sure we want to update the timeout? */ 312 frag->fr_timeout = time_uptime; 313 TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next); 314 TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next); 315 } 316 317 return (frag); 318 } 319 320 /* Removes a fragment from the fragment queue and frees the fragment */ 321 static void 322 pf_remove_fragment(struct pf_fragment *frag) 323 { 324 325 PF_FRAG_ASSERT(); 326 KASSERT(frag, ("frag != NULL")); 327 328 RB_REMOVE(pf_frag_tree, &V_pf_frag_tree, frag); 329 TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next); 330 uma_zfree(V_pf_frag_z, frag); 331 } 332 333 static struct pf_frent * 334 pf_create_fragment(u_short *reason) 335 { 336 struct pf_frent *frent; 337 338 PF_FRAG_ASSERT(); 339 340 frent = uma_zalloc(V_pf_frent_z, M_NOWAIT); 341 if (frent == NULL) { 342 pf_flush_fragments(); 343 frent = uma_zalloc(V_pf_frent_z, M_NOWAIT); 344 if (frent == NULL) { 345 REASON_SET(reason, PFRES_MEMORY); 346 return (NULL); 347 } 348 } 349 350 return (frent); 351 } 352 353 /* 354 * Calculate the additional holes that were created in the fragment 355 * queue by inserting this fragment. A fragment in the middle 356 * creates one more hole by splitting. For each connected side, 357 * it loses one hole. 358 * Fragment entry must be in the queue when calling this function. 359 */ 360 static int 361 pf_frent_holes(struct pf_frent *frent) 362 { 363 struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next); 364 struct pf_frent *next = TAILQ_NEXT(frent, fr_next); 365 int holes = 1; 366 367 if (prev == NULL) { 368 if (frent->fe_off == 0) 369 holes--; 370 } else { 371 KASSERT(frent->fe_off != 0, ("frent->fe_off != 0")); 372 if (frent->fe_off == prev->fe_off + prev->fe_len) 373 holes--; 374 } 375 if (next == NULL) { 376 if (!frent->fe_mff) 377 holes--; 378 } else { 379 KASSERT(frent->fe_mff, ("frent->fe_mff")); 380 if (next->fe_off == frent->fe_off + frent->fe_len) 381 holes--; 382 } 383 return holes; 384 } 385 386 static inline int 387 pf_frent_index(struct pf_frent *frent) 388 { 389 /* 390 * We have an array of 16 entry points to the queue. A full size 391 * 65535 octet IP packet can have 8192 fragments. So the queue 392 * traversal length is at most 512 and at most 16 entry points are 393 * checked. We need 128 additional bytes on a 64 bit architecture. 394 */ 395 CTASSERT(((u_int16_t)0xffff &~ 7) / (0x10000 / PF_FRAG_ENTRY_POINTS) == 396 16 - 1); 397 CTASSERT(((u_int16_t)0xffff >> 3) / PF_FRAG_ENTRY_POINTS == 512 - 1); 398 399 return frent->fe_off / (0x10000 / PF_FRAG_ENTRY_POINTS); 400 } 401 402 static int 403 pf_frent_insert(struct pf_fragment *frag, struct pf_frent *frent, 404 struct pf_frent *prev) 405 { 406 int index; 407 408 CTASSERT(PF_FRAG_ENTRY_LIMIT <= 0xff); 409 410 /* 411 * A packet has at most 65536 octets. With 16 entry points, each one 412 * spawns 4096 octets. We limit these to 64 fragments each, which 413 * means on average every fragment must have at least 64 octets. 414 */ 415 index = pf_frent_index(frent); 416 if (frag->fr_entries[index] >= PF_FRAG_ENTRY_LIMIT) 417 return ENOBUFS; 418 frag->fr_entries[index]++; 419 420 if (prev == NULL) { 421 TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next); 422 } else { 423 KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off, 424 ("overlapping fragment")); 425 TAILQ_INSERT_AFTER(&frag->fr_queue, prev, frent, fr_next); 426 } 427 428 if (frag->fr_firstoff[index] == NULL) { 429 KASSERT(prev == NULL || pf_frent_index(prev) < index, 430 ("prev == NULL || pf_frent_index(pref) < index")); 431 frag->fr_firstoff[index] = frent; 432 } else { 433 if (frent->fe_off < frag->fr_firstoff[index]->fe_off) { 434 KASSERT(prev == NULL || pf_frent_index(prev) < index, 435 ("prev == NULL || pf_frent_index(pref) < index")); 436 frag->fr_firstoff[index] = frent; 437 } else { 438 KASSERT(prev != NULL, ("prev != NULL")); 439 KASSERT(pf_frent_index(prev) == index, 440 ("pf_frent_index(prev) == index")); 441 } 442 } 443 444 frag->fr_holes += pf_frent_holes(frent); 445 446 return 0; 447 } 448 449 void 450 pf_frent_remove(struct pf_fragment *frag, struct pf_frent *frent) 451 { 452 #ifdef INVARIANTS 453 struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next); 454 #endif 455 struct pf_frent *next = TAILQ_NEXT(frent, fr_next); 456 int index; 457 458 frag->fr_holes -= pf_frent_holes(frent); 459 460 index = pf_frent_index(frent); 461 KASSERT(frag->fr_firstoff[index] != NULL, ("frent not found")); 462 if (frag->fr_firstoff[index]->fe_off == frent->fe_off) { 463 if (next == NULL) { 464 frag->fr_firstoff[index] = NULL; 465 } else { 466 KASSERT(frent->fe_off + frent->fe_len <= next->fe_off, 467 ("overlapping fragment")); 468 if (pf_frent_index(next) == index) { 469 frag->fr_firstoff[index] = next; 470 } else { 471 frag->fr_firstoff[index] = NULL; 472 } 473 } 474 } else { 475 KASSERT(frag->fr_firstoff[index]->fe_off < frent->fe_off, 476 ("frag->fr_firstoff[index]->fe_off < frent->fe_off")); 477 KASSERT(prev != NULL, ("prev != NULL")); 478 KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off, 479 ("overlapping fragment")); 480 KASSERT(pf_frent_index(prev) == index, 481 ("pf_frent_index(prev) == index")); 482 } 483 484 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next); 485 486 KASSERT(frag->fr_entries[index] > 0, ("No fragments remaining")); 487 frag->fr_entries[index]--; 488 } 489 490 struct pf_frent * 491 pf_frent_previous(struct pf_fragment *frag, struct pf_frent *frent) 492 { 493 struct pf_frent *prev, *next; 494 int index; 495 496 /* 497 * If there are no fragments after frag, take the final one. Assume 498 * that the global queue is not empty. 499 */ 500 prev = TAILQ_LAST(&frag->fr_queue, pf_fragq); 501 KASSERT(prev != NULL, ("prev != NULL")); 502 if (prev->fe_off <= frent->fe_off) 503 return prev; 504 /* 505 * We want to find a fragment entry that is before frag, but still 506 * close to it. Find the first fragment entry that is in the same 507 * entry point or in the first entry point after that. As we have 508 * already checked that there are entries behind frag, this will 509 * succeed. 510 */ 511 for (index = pf_frent_index(frent); index < PF_FRAG_ENTRY_POINTS; 512 index++) { 513 prev = frag->fr_firstoff[index]; 514 if (prev != NULL) 515 break; 516 } 517 KASSERT(prev != NULL, ("prev != NULL")); 518 /* 519 * In prev we may have a fragment from the same entry point that is 520 * before frent, or one that is just one position behind frent. 521 * In the latter case, we go back one step and have the predecessor. 522 * There may be none if the new fragment will be the first one. 523 */ 524 if (prev->fe_off > frent->fe_off) { 525 prev = TAILQ_PREV(prev, pf_fragq, fr_next); 526 if (prev == NULL) 527 return NULL; 528 KASSERT(prev->fe_off <= frent->fe_off, 529 ("prev->fe_off <= frent->fe_off")); 530 return prev; 531 } 532 /* 533 * In prev is the first fragment of the entry point. The offset 534 * of frag is behind it. Find the closest previous fragment. 535 */ 536 for (next = TAILQ_NEXT(prev, fr_next); next != NULL; 537 next = TAILQ_NEXT(next, fr_next)) { 538 if (next->fe_off > frent->fe_off) 539 break; 540 prev = next; 541 } 542 return prev; 543 } 544 545 static struct pf_fragment * 546 pf_fillup_fragment(struct pf_fragment_cmp *key, struct pf_frent *frent, 547 u_short *reason) 548 { 549 struct pf_frent *after, *next, *prev; 550 struct pf_fragment *frag; 551 uint16_t total; 552 553 PF_FRAG_ASSERT(); 554 555 /* No empty fragments. */ 556 if (frent->fe_len == 0) { 557 DPFPRINTF(("bad fragment: len 0\n")); 558 goto bad_fragment; 559 } 560 561 /* All fragments are 8 byte aligned. */ 562 if (frent->fe_mff && (frent->fe_len & 0x7)) { 563 DPFPRINTF(("bad fragment: mff and len %d\n", frent->fe_len)); 564 goto bad_fragment; 565 } 566 567 /* Respect maximum length, IP_MAXPACKET == IPV6_MAXPACKET. */ 568 if (frent->fe_off + frent->fe_len > IP_MAXPACKET) { 569 DPFPRINTF(("bad fragment: max packet %d\n", 570 frent->fe_off + frent->fe_len)); 571 goto bad_fragment; 572 } 573 574 DPFPRINTF((key->frc_af == AF_INET ? 575 "reass frag %d @ %d-%d\n" : "reass frag %#08x @ %d-%d\n", 576 key->frc_id, frent->fe_off, frent->fe_off + frent->fe_len)); 577 578 /* Fully buffer all of the fragments in this fragment queue. */ 579 frag = pf_find_fragment(key, &V_pf_frag_tree); 580 581 /* Create a new reassembly queue for this packet. */ 582 if (frag == NULL) { 583 frag = uma_zalloc(V_pf_frag_z, M_NOWAIT); 584 if (frag == NULL) { 585 pf_flush_fragments(); 586 frag = uma_zalloc(V_pf_frag_z, M_NOWAIT); 587 if (frag == NULL) { 588 REASON_SET(reason, PFRES_MEMORY); 589 goto drop_fragment; 590 } 591 } 592 593 *(struct pf_fragment_cmp *)frag = *key; 594 memset(frag->fr_firstoff, 0, sizeof(frag->fr_firstoff)); 595 memset(frag->fr_entries, 0, sizeof(frag->fr_entries)); 596 frag->fr_timeout = time_uptime; 597 frag->fr_maxlen = frent->fe_len; 598 frag->fr_holes = 1; 599 TAILQ_INIT(&frag->fr_queue); 600 601 RB_INSERT(pf_frag_tree, &V_pf_frag_tree, frag); 602 TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next); 603 604 /* We do not have a previous fragment, cannot fail. */ 605 pf_frent_insert(frag, frent, NULL); 606 607 return (frag); 608 } 609 610 KASSERT(!TAILQ_EMPTY(&frag->fr_queue), ("!TAILQ_EMPTY()->fr_queue")); 611 612 /* Remember maximum fragment len for refragmentation. */ 613 if (frent->fe_len > frag->fr_maxlen) 614 frag->fr_maxlen = frent->fe_len; 615 616 /* Maximum data we have seen already. */ 617 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + 618 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; 619 620 /* Non terminal fragments must have more fragments flag. */ 621 if (frent->fe_off + frent->fe_len < total && !frent->fe_mff) 622 goto bad_fragment; 623 624 /* Check if we saw the last fragment already. */ 625 if (!TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_mff) { 626 if (frent->fe_off + frent->fe_len > total || 627 (frent->fe_off + frent->fe_len == total && frent->fe_mff)) 628 goto bad_fragment; 629 } else { 630 if (frent->fe_off + frent->fe_len == total && !frent->fe_mff) 631 goto bad_fragment; 632 } 633 634 /* Find neighbors for newly inserted fragment */ 635 prev = pf_frent_previous(frag, frent); 636 if (prev == NULL) { 637 after = TAILQ_FIRST(&frag->fr_queue); 638 KASSERT(after != NULL, ("after != NULL")); 639 } else { 640 after = TAILQ_NEXT(prev, fr_next); 641 } 642 643 if (prev != NULL && prev->fe_off + prev->fe_len > frent->fe_off) { 644 uint16_t precut; 645 646 precut = prev->fe_off + prev->fe_len - frent->fe_off; 647 if (precut >= frent->fe_len) 648 goto bad_fragment; 649 DPFPRINTF(("overlap -%d\n", precut)); 650 m_adj(frent->fe_m, precut); 651 frent->fe_off += precut; 652 frent->fe_len -= precut; 653 } 654 655 for (; after != NULL && frent->fe_off + frent->fe_len > after->fe_off; 656 after = next) { 657 uint16_t aftercut; 658 659 aftercut = frent->fe_off + frent->fe_len - after->fe_off; 660 DPFPRINTF(("adjust overlap %d\n", aftercut)); 661 if (aftercut < after->fe_len) { 662 m_adj(after->fe_m, aftercut); 663 after->fe_off += aftercut; 664 after->fe_len -= aftercut; 665 break; 666 } 667 668 /* This fragment is completely overlapped, lose it. */ 669 next = TAILQ_NEXT(after, fr_next); 670 pf_frent_remove(frag, after); 671 m_freem(after->fe_m); 672 uma_zfree(V_pf_frent_z, after); 673 } 674 675 /* If part of the queue gets too long, there is not way to recover. */ 676 if (pf_frent_insert(frag, frent, prev)) { 677 DPFPRINTF(("fragment queue limit exceeded\n")); 678 goto bad_fragment; 679 } 680 681 return (frag); 682 683 bad_fragment: 684 REASON_SET(reason, PFRES_FRAG); 685 drop_fragment: 686 uma_zfree(V_pf_frent_z, frent); 687 return (NULL); 688 } 689 690 static struct mbuf * 691 pf_join_fragment(struct pf_fragment *frag) 692 { 693 struct mbuf *m, *m2; 694 struct pf_frent *frent, *next; 695 696 frent = TAILQ_FIRST(&frag->fr_queue); 697 next = TAILQ_NEXT(frent, fr_next); 698 699 m = frent->fe_m; 700 m_adj(m, (frent->fe_hdrlen + frent->fe_len) - m->m_pkthdr.len); 701 uma_zfree(V_pf_frent_z, frent); 702 for (frent = next; frent != NULL; frent = next) { 703 next = TAILQ_NEXT(frent, fr_next); 704 705 m2 = frent->fe_m; 706 /* Strip off ip header. */ 707 m_adj(m2, frent->fe_hdrlen); 708 /* Strip off any trailing bytes. */ 709 m_adj(m2, frent->fe_len - m2->m_pkthdr.len); 710 711 uma_zfree(V_pf_frent_z, frent); 712 m_cat(m, m2); 713 } 714 715 /* Remove from fragment queue. */ 716 pf_remove_fragment(frag); 717 718 return (m); 719 } 720 721 #ifdef INET 722 static int 723 pf_reassemble(struct mbuf **m0, struct ip *ip, int dir, u_short *reason) 724 { 725 struct mbuf *m = *m0; 726 struct pf_frent *frent; 727 struct pf_fragment *frag; 728 struct pf_fragment_cmp key; 729 uint16_t total, hdrlen; 730 731 /* Get an entry for the fragment queue */ 732 if ((frent = pf_create_fragment(reason)) == NULL) 733 return (PF_DROP); 734 735 frent->fe_m = m; 736 frent->fe_hdrlen = ip->ip_hl << 2; 737 frent->fe_extoff = 0; 738 frent->fe_len = ntohs(ip->ip_len) - (ip->ip_hl << 2); 739 frent->fe_off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3; 740 frent->fe_mff = ntohs(ip->ip_off) & IP_MF; 741 742 pf_ip2key(ip, dir, &key); 743 744 if ((frag = pf_fillup_fragment(&key, frent, reason)) == NULL) 745 return (PF_DROP); 746 747 /* The mbuf is part of the fragment entry, no direct free or access */ 748 m = *m0 = NULL; 749 750 if (frag->fr_holes) { 751 DPFPRINTF(("frag %d, holes %d\n", frag->fr_id, frag->fr_holes)); 752 return (PF_PASS); /* drop because *m0 is NULL, no error */ 753 } 754 755 /* We have all the data */ 756 frent = TAILQ_FIRST(&frag->fr_queue); 757 KASSERT(frent != NULL, ("frent != NULL")); 758 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + 759 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; 760 hdrlen = frent->fe_hdrlen; 761 762 m = *m0 = pf_join_fragment(frag); 763 frag = NULL; 764 765 if (m->m_flags & M_PKTHDR) { 766 int plen = 0; 767 for (m = *m0; m; m = m->m_next) 768 plen += m->m_len; 769 m = *m0; 770 m->m_pkthdr.len = plen; 771 } 772 773 ip = mtod(m, struct ip *); 774 ip->ip_len = htons(hdrlen + total); 775 ip->ip_off &= ~(IP_MF|IP_OFFMASK); 776 777 if (hdrlen + total > IP_MAXPACKET) { 778 DPFPRINTF(("drop: too big: %d\n", total)); 779 ip->ip_len = 0; 780 REASON_SET(reason, PFRES_SHORT); 781 /* PF_DROP requires a valid mbuf *m0 in pf_test() */ 782 return (PF_DROP); 783 } 784 785 DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip->ip_len))); 786 return (PF_PASS); 787 } 788 #endif /* INET */ 789 790 #ifdef INET6 791 static int 792 pf_reassemble6(struct mbuf **m0, struct ip6_hdr *ip6, struct ip6_frag *fraghdr, 793 uint16_t hdrlen, uint16_t extoff, u_short *reason) 794 { 795 struct mbuf *m = *m0; 796 struct pf_frent *frent; 797 struct pf_fragment *frag; 798 struct pf_fragment_cmp key; 799 struct m_tag *mtag; 800 struct pf_fragment_tag *ftag; 801 int off; 802 uint32_t frag_id; 803 uint16_t total, maxlen; 804 uint8_t proto; 805 806 PF_FRAG_LOCK(); 807 808 /* Get an entry for the fragment queue. */ 809 if ((frent = pf_create_fragment(reason)) == NULL) { 810 PF_FRAG_UNLOCK(); 811 return (PF_DROP); 812 } 813 814 frent->fe_m = m; 815 frent->fe_hdrlen = hdrlen; 816 frent->fe_extoff = extoff; 817 frent->fe_len = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - hdrlen; 818 frent->fe_off = ntohs(fraghdr->ip6f_offlg & IP6F_OFF_MASK); 819 frent->fe_mff = fraghdr->ip6f_offlg & IP6F_MORE_FRAG; 820 821 key.frc_src.v6 = ip6->ip6_src; 822 key.frc_dst.v6 = ip6->ip6_dst; 823 key.frc_af = AF_INET6; 824 /* Only the first fragment's protocol is relevant. */ 825 key.frc_proto = 0; 826 key.frc_id = fraghdr->ip6f_ident; 827 828 if ((frag = pf_fillup_fragment(&key, frent, reason)) == NULL) { 829 PF_FRAG_UNLOCK(); 830 return (PF_DROP); 831 } 832 833 /* The mbuf is part of the fragment entry, no direct free or access. */ 834 m = *m0 = NULL; 835 836 if (frag->fr_holes) { 837 DPFPRINTF(("frag %d, holes %d\n", frag->fr_id, 838 frag->fr_holes)); 839 PF_FRAG_UNLOCK(); 840 return (PF_PASS); /* Drop because *m0 is NULL, no error. */ 841 } 842 843 /* We have all the data. */ 844 frent = TAILQ_FIRST(&frag->fr_queue); 845 KASSERT(frent != NULL, ("frent != NULL")); 846 extoff = frent->fe_extoff; 847 maxlen = frag->fr_maxlen; 848 frag_id = frag->fr_id; 849 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + 850 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; 851 hdrlen = frent->fe_hdrlen - sizeof(struct ip6_frag); 852 853 m = *m0 = pf_join_fragment(frag); 854 frag = NULL; 855 856 PF_FRAG_UNLOCK(); 857 858 /* Take protocol from first fragment header. */ 859 m = m_getptr(m, hdrlen + offsetof(struct ip6_frag, ip6f_nxt), &off); 860 KASSERT(m, ("%s: short mbuf chain", __func__)); 861 proto = *(mtod(m, caddr_t) + off); 862 m = *m0; 863 864 /* Delete frag6 header */ 865 if (ip6_deletefraghdr(m, hdrlen, M_NOWAIT) != 0) 866 goto fail; 867 868 if (m->m_flags & M_PKTHDR) { 869 int plen = 0; 870 for (m = *m0; m; m = m->m_next) 871 plen += m->m_len; 872 m = *m0; 873 m->m_pkthdr.len = plen; 874 } 875 876 if ((mtag = m_tag_get(PF_REASSEMBLED, sizeof(struct pf_fragment_tag), 877 M_NOWAIT)) == NULL) 878 goto fail; 879 ftag = (struct pf_fragment_tag *)(mtag + 1); 880 ftag->ft_hdrlen = hdrlen; 881 ftag->ft_extoff = extoff; 882 ftag->ft_maxlen = maxlen; 883 ftag->ft_id = frag_id; 884 m_tag_prepend(m, mtag); 885 886 ip6 = mtod(m, struct ip6_hdr *); 887 ip6->ip6_plen = htons(hdrlen - sizeof(struct ip6_hdr) + total); 888 if (extoff) { 889 /* Write protocol into next field of last extension header. */ 890 m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt), 891 &off); 892 KASSERT(m, ("%s: short mbuf chain", __func__)); 893 *(mtod(m, char *) + off) = proto; 894 m = *m0; 895 } else 896 ip6->ip6_nxt = proto; 897 898 if (hdrlen - sizeof(struct ip6_hdr) + total > IPV6_MAXPACKET) { 899 DPFPRINTF(("drop: too big: %d\n", total)); 900 ip6->ip6_plen = 0; 901 REASON_SET(reason, PFRES_SHORT); 902 /* PF_DROP requires a valid mbuf *m0 in pf_test6(). */ 903 return (PF_DROP); 904 } 905 906 DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip6->ip6_plen))); 907 return (PF_PASS); 908 909 fail: 910 REASON_SET(reason, PFRES_MEMORY); 911 /* PF_DROP requires a valid mbuf *m0 in pf_test6(), will free later. */ 912 return (PF_DROP); 913 } 914 #endif /* INET6 */ 915 916 #ifdef INET6 917 int 918 pf_refragment6(struct ifnet *ifp, struct mbuf **m0, struct m_tag *mtag) 919 { 920 struct mbuf *m = *m0, *t; 921 struct pf_fragment_tag *ftag = (struct pf_fragment_tag *)(mtag + 1); 922 struct pf_pdesc pd; 923 uint32_t frag_id; 924 uint16_t hdrlen, extoff, maxlen; 925 uint8_t proto; 926 int error, action; 927 928 hdrlen = ftag->ft_hdrlen; 929 extoff = ftag->ft_extoff; 930 maxlen = ftag->ft_maxlen; 931 frag_id = ftag->ft_id; 932 m_tag_delete(m, mtag); 933 mtag = NULL; 934 ftag = NULL; 935 936 if (extoff) { 937 int off; 938 939 /* Use protocol from next field of last extension header */ 940 m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt), 941 &off); 942 KASSERT((m != NULL), ("pf_refragment6: short mbuf chain")); 943 proto = *(mtod(m, caddr_t) + off); 944 *(mtod(m, char *) + off) = IPPROTO_FRAGMENT; 945 m = *m0; 946 } else { 947 struct ip6_hdr *hdr; 948 949 hdr = mtod(m, struct ip6_hdr *); 950 proto = hdr->ip6_nxt; 951 hdr->ip6_nxt = IPPROTO_FRAGMENT; 952 } 953 954 /* The MTU must be a multiple of 8 bytes, or we risk doing the 955 * fragmentation wrong. */ 956 maxlen = maxlen & ~7; 957 958 /* 959 * Maxlen may be less than 8 if there was only a single 960 * fragment. As it was fragmented before, add a fragment 961 * header also for a single fragment. If total or maxlen 962 * is less than 8, ip6_fragment() will return EMSGSIZE and 963 * we drop the packet. 964 */ 965 error = ip6_fragment(ifp, m, hdrlen, proto, maxlen, frag_id); 966 m = (*m0)->m_nextpkt; 967 (*m0)->m_nextpkt = NULL; 968 if (error == 0) { 969 /* The first mbuf contains the unfragmented packet. */ 970 m_freem(*m0); 971 *m0 = NULL; 972 action = PF_PASS; 973 } else { 974 /* Drop expects an mbuf to free. */ 975 DPFPRINTF(("refragment error %d\n", error)); 976 action = PF_DROP; 977 } 978 for (t = m; m; m = t) { 979 t = m->m_nextpkt; 980 m->m_nextpkt = NULL; 981 m->m_flags |= M_SKIP_FIREWALL; 982 memset(&pd, 0, sizeof(pd)); 983 pd.pf_mtag = pf_find_mtag(m); 984 if (error == 0) 985 ip6_forward(m, 0); 986 else 987 m_freem(m); 988 } 989 990 return (action); 991 } 992 #endif /* INET6 */ 993 994 #ifdef INET 995 int 996 pf_normalize_ip(struct mbuf **m0, int dir, struct pfi_kif *kif, u_short *reason, 997 struct pf_pdesc *pd) 998 { 999 struct mbuf *m = *m0; 1000 struct pf_rule *r; 1001 struct ip *h = mtod(m, struct ip *); 1002 int mff = (ntohs(h->ip_off) & IP_MF); 1003 int hlen = h->ip_hl << 2; 1004 u_int16_t fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3; 1005 u_int16_t max; 1006 int ip_len; 1007 int ip_off; 1008 int tag = -1; 1009 int verdict; 1010 1011 PF_RULES_RASSERT(); 1012 1013 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 1014 while (r != NULL) { 1015 r->evaluations++; 1016 if (pfi_kif_match(r->kif, kif) == r->ifnot) 1017 r = r->skip[PF_SKIP_IFP].ptr; 1018 else if (r->direction && r->direction != dir) 1019 r = r->skip[PF_SKIP_DIR].ptr; 1020 else if (r->af && r->af != AF_INET) 1021 r = r->skip[PF_SKIP_AF].ptr; 1022 else if (r->proto && r->proto != h->ip_p) 1023 r = r->skip[PF_SKIP_PROTO].ptr; 1024 else if (PF_MISMATCHAW(&r->src.addr, 1025 (struct pf_addr *)&h->ip_src.s_addr, AF_INET, 1026 r->src.neg, kif, M_GETFIB(m))) 1027 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 1028 else if (PF_MISMATCHAW(&r->dst.addr, 1029 (struct pf_addr *)&h->ip_dst.s_addr, AF_INET, 1030 r->dst.neg, NULL, M_GETFIB(m))) 1031 r = r->skip[PF_SKIP_DST_ADDR].ptr; 1032 else if (r->match_tag && !pf_match_tag(m, r, &tag, 1033 pd->pf_mtag ? pd->pf_mtag->tag : 0)) 1034 r = TAILQ_NEXT(r, entries); 1035 else 1036 break; 1037 } 1038 1039 if (r == NULL || r->action == PF_NOSCRUB) 1040 return (PF_PASS); 1041 else { 1042 r->packets[dir == PF_OUT]++; 1043 r->bytes[dir == PF_OUT] += pd->tot_len; 1044 } 1045 1046 /* Check for illegal packets */ 1047 if (hlen < (int)sizeof(struct ip)) { 1048 REASON_SET(reason, PFRES_NORM); 1049 goto drop; 1050 } 1051 1052 if (hlen > ntohs(h->ip_len)) { 1053 REASON_SET(reason, PFRES_NORM); 1054 goto drop; 1055 } 1056 1057 /* Clear IP_DF if the rule uses the no-df option */ 1058 if (r->rule_flag & PFRULE_NODF && h->ip_off & htons(IP_DF)) { 1059 u_int16_t ip_off = h->ip_off; 1060 1061 h->ip_off &= htons(~IP_DF); 1062 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0); 1063 } 1064 1065 /* We will need other tests here */ 1066 if (!fragoff && !mff) 1067 goto no_fragment; 1068 1069 /* We're dealing with a fragment now. Don't allow fragments 1070 * with IP_DF to enter the cache. If the flag was cleared by 1071 * no-df above, fine. Otherwise drop it. 1072 */ 1073 if (h->ip_off & htons(IP_DF)) { 1074 DPFPRINTF(("IP_DF\n")); 1075 goto bad; 1076 } 1077 1078 ip_len = ntohs(h->ip_len) - hlen; 1079 ip_off = (ntohs(h->ip_off) & IP_OFFMASK) << 3; 1080 1081 /* All fragments are 8 byte aligned */ 1082 if (mff && (ip_len & 0x7)) { 1083 DPFPRINTF(("mff and %d\n", ip_len)); 1084 goto bad; 1085 } 1086 1087 /* Respect maximum length */ 1088 if (fragoff + ip_len > IP_MAXPACKET) { 1089 DPFPRINTF(("max packet %d\n", fragoff + ip_len)); 1090 goto bad; 1091 } 1092 max = fragoff + ip_len; 1093 1094 /* Fully buffer all of the fragments 1095 * Might return a completely reassembled mbuf, or NULL */ 1096 PF_FRAG_LOCK(); 1097 DPFPRINTF(("reass frag %d @ %d-%d\n", h->ip_id, fragoff, max)); 1098 verdict = pf_reassemble(m0, h, dir, reason); 1099 PF_FRAG_UNLOCK(); 1100 1101 if (verdict != PF_PASS) 1102 return (PF_DROP); 1103 1104 m = *m0; 1105 if (m == NULL) 1106 return (PF_DROP); 1107 1108 h = mtod(m, struct ip *); 1109 1110 no_fragment: 1111 /* At this point, only IP_DF is allowed in ip_off */ 1112 if (h->ip_off & ~htons(IP_DF)) { 1113 u_int16_t ip_off = h->ip_off; 1114 1115 h->ip_off &= htons(IP_DF); 1116 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0); 1117 } 1118 1119 pf_scrub_ip(&m, r->rule_flag, r->min_ttl, r->set_tos); 1120 1121 return (PF_PASS); 1122 1123 bad: 1124 DPFPRINTF(("dropping bad fragment\n")); 1125 REASON_SET(reason, PFRES_FRAG); 1126 drop: 1127 if (r != NULL && r->log) 1128 PFLOG_PACKET(kif, m, AF_INET, dir, *reason, r, NULL, NULL, pd, 1129 1); 1130 1131 return (PF_DROP); 1132 } 1133 #endif 1134 1135 #ifdef INET6 1136 int 1137 pf_normalize_ip6(struct mbuf **m0, int dir, struct pfi_kif *kif, 1138 u_short *reason, struct pf_pdesc *pd) 1139 { 1140 struct mbuf *m = *m0; 1141 struct pf_rule *r; 1142 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1143 int extoff; 1144 int off; 1145 struct ip6_ext ext; 1146 struct ip6_opt opt; 1147 struct ip6_frag frag; 1148 u_int32_t plen; 1149 int optend; 1150 int ooff; 1151 u_int8_t proto; 1152 int terminal; 1153 1154 PF_RULES_RASSERT(); 1155 1156 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 1157 while (r != NULL) { 1158 r->evaluations++; 1159 if (pfi_kif_match(r->kif, kif) == r->ifnot) 1160 r = r->skip[PF_SKIP_IFP].ptr; 1161 else if (r->direction && r->direction != dir) 1162 r = r->skip[PF_SKIP_DIR].ptr; 1163 else if (r->af && r->af != AF_INET6) 1164 r = r->skip[PF_SKIP_AF].ptr; 1165 #if 0 /* header chain! */ 1166 else if (r->proto && r->proto != h->ip6_nxt) 1167 r = r->skip[PF_SKIP_PROTO].ptr; 1168 #endif 1169 else if (PF_MISMATCHAW(&r->src.addr, 1170 (struct pf_addr *)&h->ip6_src, AF_INET6, 1171 r->src.neg, kif, M_GETFIB(m))) 1172 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 1173 else if (PF_MISMATCHAW(&r->dst.addr, 1174 (struct pf_addr *)&h->ip6_dst, AF_INET6, 1175 r->dst.neg, NULL, M_GETFIB(m))) 1176 r = r->skip[PF_SKIP_DST_ADDR].ptr; 1177 else 1178 break; 1179 } 1180 1181 if (r == NULL || r->action == PF_NOSCRUB) 1182 return (PF_PASS); 1183 else { 1184 r->packets[dir == PF_OUT]++; 1185 r->bytes[dir == PF_OUT] += pd->tot_len; 1186 } 1187 1188 /* Check for illegal packets */ 1189 if (sizeof(struct ip6_hdr) + IPV6_MAXPACKET < m->m_pkthdr.len) 1190 goto drop; 1191 1192 plen = ntohs(h->ip6_plen); 1193 /* jumbo payload option not supported */ 1194 if (plen == 0) 1195 goto drop; 1196 1197 extoff = 0; 1198 off = sizeof(struct ip6_hdr); 1199 proto = h->ip6_nxt; 1200 terminal = 0; 1201 do { 1202 switch (proto) { 1203 case IPPROTO_FRAGMENT: 1204 goto fragment; 1205 break; 1206 case IPPROTO_AH: 1207 case IPPROTO_ROUTING: 1208 case IPPROTO_DSTOPTS: 1209 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL, 1210 NULL, AF_INET6)) 1211 goto shortpkt; 1212 extoff = off; 1213 if (proto == IPPROTO_AH) 1214 off += (ext.ip6e_len + 2) * 4; 1215 else 1216 off += (ext.ip6e_len + 1) * 8; 1217 proto = ext.ip6e_nxt; 1218 break; 1219 case IPPROTO_HOPOPTS: 1220 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL, 1221 NULL, AF_INET6)) 1222 goto shortpkt; 1223 extoff = off; 1224 optend = off + (ext.ip6e_len + 1) * 8; 1225 ooff = off + sizeof(ext); 1226 do { 1227 if (!pf_pull_hdr(m, ooff, &opt.ip6o_type, 1228 sizeof(opt.ip6o_type), NULL, NULL, 1229 AF_INET6)) 1230 goto shortpkt; 1231 if (opt.ip6o_type == IP6OPT_PAD1) { 1232 ooff++; 1233 continue; 1234 } 1235 if (!pf_pull_hdr(m, ooff, &opt, sizeof(opt), 1236 NULL, NULL, AF_INET6)) 1237 goto shortpkt; 1238 if (ooff + sizeof(opt) + opt.ip6o_len > optend) 1239 goto drop; 1240 if (opt.ip6o_type == IP6OPT_JUMBO) 1241 goto drop; 1242 ooff += sizeof(opt) + opt.ip6o_len; 1243 } while (ooff < optend); 1244 1245 off = optend; 1246 proto = ext.ip6e_nxt; 1247 break; 1248 default: 1249 terminal = 1; 1250 break; 1251 } 1252 } while (!terminal); 1253 1254 if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len) 1255 goto shortpkt; 1256 1257 pf_scrub_ip6(&m, r->min_ttl); 1258 1259 return (PF_PASS); 1260 1261 fragment: 1262 if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len) 1263 goto shortpkt; 1264 1265 if (!pf_pull_hdr(m, off, &frag, sizeof(frag), NULL, NULL, AF_INET6)) 1266 goto shortpkt; 1267 1268 /* Offset now points to data portion. */ 1269 off += sizeof(frag); 1270 1271 /* Returns PF_DROP or *m0 is NULL or completely reassembled mbuf. */ 1272 if (pf_reassemble6(m0, h, &frag, off, extoff, reason) != PF_PASS) 1273 return (PF_DROP); 1274 m = *m0; 1275 if (m == NULL) 1276 return (PF_DROP); 1277 1278 pd->flags |= PFDESC_IP_REAS; 1279 return (PF_PASS); 1280 1281 shortpkt: 1282 REASON_SET(reason, PFRES_SHORT); 1283 if (r != NULL && r->log) 1284 PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd, 1285 1); 1286 return (PF_DROP); 1287 1288 drop: 1289 REASON_SET(reason, PFRES_NORM); 1290 if (r != NULL && r->log) 1291 PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd, 1292 1); 1293 return (PF_DROP); 1294 } 1295 #endif /* INET6 */ 1296 1297 int 1298 pf_normalize_tcp(int dir, struct pfi_kif *kif, struct mbuf *m, int ipoff, 1299 int off, void *h, struct pf_pdesc *pd) 1300 { 1301 struct pf_rule *r, *rm = NULL; 1302 struct tcphdr *th = pd->hdr.tcp; 1303 int rewrite = 0; 1304 u_short reason; 1305 u_int8_t flags; 1306 sa_family_t af = pd->af; 1307 1308 PF_RULES_RASSERT(); 1309 1310 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr); 1311 while (r != NULL) { 1312 r->evaluations++; 1313 if (pfi_kif_match(r->kif, kif) == r->ifnot) 1314 r = r->skip[PF_SKIP_IFP].ptr; 1315 else if (r->direction && r->direction != dir) 1316 r = r->skip[PF_SKIP_DIR].ptr; 1317 else if (r->af && r->af != af) 1318 r = r->skip[PF_SKIP_AF].ptr; 1319 else if (r->proto && r->proto != pd->proto) 1320 r = r->skip[PF_SKIP_PROTO].ptr; 1321 else if (PF_MISMATCHAW(&r->src.addr, pd->src, af, 1322 r->src.neg, kif, M_GETFIB(m))) 1323 r = r->skip[PF_SKIP_SRC_ADDR].ptr; 1324 else if (r->src.port_op && !pf_match_port(r->src.port_op, 1325 r->src.port[0], r->src.port[1], th->th_sport)) 1326 r = r->skip[PF_SKIP_SRC_PORT].ptr; 1327 else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af, 1328 r->dst.neg, NULL, M_GETFIB(m))) 1329 r = r->skip[PF_SKIP_DST_ADDR].ptr; 1330 else if (r->dst.port_op && !pf_match_port(r->dst.port_op, 1331 r->dst.port[0], r->dst.port[1], th->th_dport)) 1332 r = r->skip[PF_SKIP_DST_PORT].ptr; 1333 else if (r->os_fingerprint != PF_OSFP_ANY && !pf_osfp_match( 1334 pf_osfp_fingerprint(pd, m, off, th), 1335 r->os_fingerprint)) 1336 r = TAILQ_NEXT(r, entries); 1337 else { 1338 rm = r; 1339 break; 1340 } 1341 } 1342 1343 if (rm == NULL || rm->action == PF_NOSCRUB) 1344 return (PF_PASS); 1345 else { 1346 r->packets[dir == PF_OUT]++; 1347 r->bytes[dir == PF_OUT] += pd->tot_len; 1348 } 1349 1350 if (rm->rule_flag & PFRULE_REASSEMBLE_TCP) 1351 pd->flags |= PFDESC_TCP_NORM; 1352 1353 flags = th->th_flags; 1354 if (flags & TH_SYN) { 1355 /* Illegal packet */ 1356 if (flags & TH_RST) 1357 goto tcp_drop; 1358 1359 if (flags & TH_FIN) 1360 goto tcp_drop; 1361 } else { 1362 /* Illegal packet */ 1363 if (!(flags & (TH_ACK|TH_RST))) 1364 goto tcp_drop; 1365 } 1366 1367 if (!(flags & TH_ACK)) { 1368 /* These flags are only valid if ACK is set */ 1369 if ((flags & TH_FIN) || (flags & TH_PUSH) || (flags & TH_URG)) 1370 goto tcp_drop; 1371 } 1372 1373 /* Check for illegal header length */ 1374 if (th->th_off < (sizeof(struct tcphdr) >> 2)) 1375 goto tcp_drop; 1376 1377 /* If flags changed, or reserved data set, then adjust */ 1378 if (flags != th->th_flags || th->th_x2 != 0) { 1379 u_int16_t ov, nv; 1380 1381 ov = *(u_int16_t *)(&th->th_ack + 1); 1382 th->th_flags = flags; 1383 th->th_x2 = 0; 1384 nv = *(u_int16_t *)(&th->th_ack + 1); 1385 1386 th->th_sum = pf_proto_cksum_fixup(m, th->th_sum, ov, nv, 0); 1387 rewrite = 1; 1388 } 1389 1390 /* Remove urgent pointer, if TH_URG is not set */ 1391 if (!(flags & TH_URG) && th->th_urp) { 1392 th->th_sum = pf_proto_cksum_fixup(m, th->th_sum, th->th_urp, 1393 0, 0); 1394 th->th_urp = 0; 1395 rewrite = 1; 1396 } 1397 1398 /* Process options */ 1399 if (r->max_mss && pf_normalize_tcpopt(r, m, th, off, pd->af)) 1400 rewrite = 1; 1401 1402 /* copy back packet headers if we sanitized */ 1403 if (rewrite) 1404 m_copyback(m, off, sizeof(*th), (caddr_t)th); 1405 1406 return (PF_PASS); 1407 1408 tcp_drop: 1409 REASON_SET(&reason, PFRES_NORM); 1410 if (rm != NULL && r->log) 1411 PFLOG_PACKET(kif, m, AF_INET, dir, reason, r, NULL, NULL, pd, 1412 1); 1413 return (PF_DROP); 1414 } 1415 1416 int 1417 pf_normalize_tcp_init(struct mbuf *m, int off, struct pf_pdesc *pd, 1418 struct tcphdr *th, struct pf_state_peer *src, struct pf_state_peer *dst) 1419 { 1420 u_int32_t tsval, tsecr; 1421 u_int8_t hdr[60]; 1422 u_int8_t *opt; 1423 1424 KASSERT((src->scrub == NULL), 1425 ("pf_normalize_tcp_init: src->scrub != NULL")); 1426 1427 src->scrub = uma_zalloc(V_pf_state_scrub_z, M_ZERO | M_NOWAIT); 1428 if (src->scrub == NULL) 1429 return (1); 1430 1431 switch (pd->af) { 1432 #ifdef INET 1433 case AF_INET: { 1434 struct ip *h = mtod(m, struct ip *); 1435 src->scrub->pfss_ttl = h->ip_ttl; 1436 break; 1437 } 1438 #endif /* INET */ 1439 #ifdef INET6 1440 case AF_INET6: { 1441 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1442 src->scrub->pfss_ttl = h->ip6_hlim; 1443 break; 1444 } 1445 #endif /* INET6 */ 1446 } 1447 1448 /* 1449 * All normalizations below are only begun if we see the start of 1450 * the connections. They must all set an enabled bit in pfss_flags 1451 */ 1452 if ((th->th_flags & TH_SYN) == 0) 1453 return (0); 1454 1455 if (th->th_off > (sizeof(struct tcphdr) >> 2) && src->scrub && 1456 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) { 1457 /* Diddle with TCP options */ 1458 int hlen; 1459 opt = hdr + sizeof(struct tcphdr); 1460 hlen = (th->th_off << 2) - sizeof(struct tcphdr); 1461 while (hlen >= TCPOLEN_TIMESTAMP) { 1462 switch (*opt) { 1463 case TCPOPT_EOL: /* FALLTHROUGH */ 1464 case TCPOPT_NOP: 1465 opt++; 1466 hlen--; 1467 break; 1468 case TCPOPT_TIMESTAMP: 1469 if (opt[1] >= TCPOLEN_TIMESTAMP) { 1470 src->scrub->pfss_flags |= 1471 PFSS_TIMESTAMP; 1472 src->scrub->pfss_ts_mod = 1473 htonl(arc4random()); 1474 1475 /* note PFSS_PAWS not set yet */ 1476 memcpy(&tsval, &opt[2], 1477 sizeof(u_int32_t)); 1478 memcpy(&tsecr, &opt[6], 1479 sizeof(u_int32_t)); 1480 src->scrub->pfss_tsval0 = ntohl(tsval); 1481 src->scrub->pfss_tsval = ntohl(tsval); 1482 src->scrub->pfss_tsecr = ntohl(tsecr); 1483 getmicrouptime(&src->scrub->pfss_last); 1484 } 1485 /* FALLTHROUGH */ 1486 default: 1487 hlen -= MAX(opt[1], 2); 1488 opt += MAX(opt[1], 2); 1489 break; 1490 } 1491 } 1492 } 1493 1494 return (0); 1495 } 1496 1497 void 1498 pf_normalize_tcp_cleanup(struct pf_state *state) 1499 { 1500 if (state->src.scrub) 1501 uma_zfree(V_pf_state_scrub_z, state->src.scrub); 1502 if (state->dst.scrub) 1503 uma_zfree(V_pf_state_scrub_z, state->dst.scrub); 1504 1505 /* Someday... flush the TCP segment reassembly descriptors. */ 1506 } 1507 1508 int 1509 pf_normalize_tcp_stateful(struct mbuf *m, int off, struct pf_pdesc *pd, 1510 u_short *reason, struct tcphdr *th, struct pf_state *state, 1511 struct pf_state_peer *src, struct pf_state_peer *dst, int *writeback) 1512 { 1513 struct timeval uptime; 1514 u_int32_t tsval, tsecr; 1515 u_int tsval_from_last; 1516 u_int8_t hdr[60]; 1517 u_int8_t *opt; 1518 int copyback = 0; 1519 int got_ts = 0; 1520 1521 KASSERT((src->scrub || dst->scrub), 1522 ("%s: src->scrub && dst->scrub!", __func__)); 1523 1524 /* 1525 * Enforce the minimum TTL seen for this connection. Negate a common 1526 * technique to evade an intrusion detection system and confuse 1527 * firewall state code. 1528 */ 1529 switch (pd->af) { 1530 #ifdef INET 1531 case AF_INET: { 1532 if (src->scrub) { 1533 struct ip *h = mtod(m, struct ip *); 1534 if (h->ip_ttl > src->scrub->pfss_ttl) 1535 src->scrub->pfss_ttl = h->ip_ttl; 1536 h->ip_ttl = src->scrub->pfss_ttl; 1537 } 1538 break; 1539 } 1540 #endif /* INET */ 1541 #ifdef INET6 1542 case AF_INET6: { 1543 if (src->scrub) { 1544 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1545 if (h->ip6_hlim > src->scrub->pfss_ttl) 1546 src->scrub->pfss_ttl = h->ip6_hlim; 1547 h->ip6_hlim = src->scrub->pfss_ttl; 1548 } 1549 break; 1550 } 1551 #endif /* INET6 */ 1552 } 1553 1554 if (th->th_off > (sizeof(struct tcphdr) >> 2) && 1555 ((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) || 1556 (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) && 1557 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) { 1558 /* Diddle with TCP options */ 1559 int hlen; 1560 opt = hdr + sizeof(struct tcphdr); 1561 hlen = (th->th_off << 2) - sizeof(struct tcphdr); 1562 while (hlen >= TCPOLEN_TIMESTAMP) { 1563 switch (*opt) { 1564 case TCPOPT_EOL: /* FALLTHROUGH */ 1565 case TCPOPT_NOP: 1566 opt++; 1567 hlen--; 1568 break; 1569 case TCPOPT_TIMESTAMP: 1570 /* Modulate the timestamps. Can be used for 1571 * NAT detection, OS uptime determination or 1572 * reboot detection. 1573 */ 1574 1575 if (got_ts) { 1576 /* Huh? Multiple timestamps!? */ 1577 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1578 DPFPRINTF(("multiple TS??\n")); 1579 pf_print_state(state); 1580 printf("\n"); 1581 } 1582 REASON_SET(reason, PFRES_TS); 1583 return (PF_DROP); 1584 } 1585 if (opt[1] >= TCPOLEN_TIMESTAMP) { 1586 memcpy(&tsval, &opt[2], 1587 sizeof(u_int32_t)); 1588 if (tsval && src->scrub && 1589 (src->scrub->pfss_flags & 1590 PFSS_TIMESTAMP)) { 1591 tsval = ntohl(tsval); 1592 pf_change_proto_a(m, &opt[2], 1593 &th->th_sum, 1594 htonl(tsval + 1595 src->scrub->pfss_ts_mod), 1596 0); 1597 copyback = 1; 1598 } 1599 1600 /* Modulate TS reply iff valid (!0) */ 1601 memcpy(&tsecr, &opt[6], 1602 sizeof(u_int32_t)); 1603 if (tsecr && dst->scrub && 1604 (dst->scrub->pfss_flags & 1605 PFSS_TIMESTAMP)) { 1606 tsecr = ntohl(tsecr) 1607 - dst->scrub->pfss_ts_mod; 1608 pf_change_proto_a(m, &opt[6], 1609 &th->th_sum, htonl(tsecr), 1610 0); 1611 copyback = 1; 1612 } 1613 got_ts = 1; 1614 } 1615 /* FALLTHROUGH */ 1616 default: 1617 hlen -= MAX(opt[1], 2); 1618 opt += MAX(opt[1], 2); 1619 break; 1620 } 1621 } 1622 if (copyback) { 1623 /* Copyback the options, caller copys back header */ 1624 *writeback = 1; 1625 m_copyback(m, off + sizeof(struct tcphdr), 1626 (th->th_off << 2) - sizeof(struct tcphdr), hdr + 1627 sizeof(struct tcphdr)); 1628 } 1629 } 1630 1631 /* 1632 * Must invalidate PAWS checks on connections idle for too long. 1633 * The fastest allowed timestamp clock is 1ms. That turns out to 1634 * be about 24 days before it wraps. XXX Right now our lowerbound 1635 * TS echo check only works for the first 12 days of a connection 1636 * when the TS has exhausted half its 32bit space 1637 */ 1638 #define TS_MAX_IDLE (24*24*60*60) 1639 #define TS_MAX_CONN (12*24*60*60) /* XXX remove when better tsecr check */ 1640 1641 getmicrouptime(&uptime); 1642 if (src->scrub && (src->scrub->pfss_flags & PFSS_PAWS) && 1643 (uptime.tv_sec - src->scrub->pfss_last.tv_sec > TS_MAX_IDLE || 1644 time_uptime - state->creation > TS_MAX_CONN)) { 1645 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1646 DPFPRINTF(("src idled out of PAWS\n")); 1647 pf_print_state(state); 1648 printf("\n"); 1649 } 1650 src->scrub->pfss_flags = (src->scrub->pfss_flags & ~PFSS_PAWS) 1651 | PFSS_PAWS_IDLED; 1652 } 1653 if (dst->scrub && (dst->scrub->pfss_flags & PFSS_PAWS) && 1654 uptime.tv_sec - dst->scrub->pfss_last.tv_sec > TS_MAX_IDLE) { 1655 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1656 DPFPRINTF(("dst idled out of PAWS\n")); 1657 pf_print_state(state); 1658 printf("\n"); 1659 } 1660 dst->scrub->pfss_flags = (dst->scrub->pfss_flags & ~PFSS_PAWS) 1661 | PFSS_PAWS_IDLED; 1662 } 1663 1664 if (got_ts && src->scrub && dst->scrub && 1665 (src->scrub->pfss_flags & PFSS_PAWS) && 1666 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1667 /* Validate that the timestamps are "in-window". 1668 * RFC1323 describes TCP Timestamp options that allow 1669 * measurement of RTT (round trip time) and PAWS 1670 * (protection against wrapped sequence numbers). PAWS 1671 * gives us a set of rules for rejecting packets on 1672 * long fat pipes (packets that were somehow delayed 1673 * in transit longer than the time it took to send the 1674 * full TCP sequence space of 4Gb). We can use these 1675 * rules and infer a few others that will let us treat 1676 * the 32bit timestamp and the 32bit echoed timestamp 1677 * as sequence numbers to prevent a blind attacker from 1678 * inserting packets into a connection. 1679 * 1680 * RFC1323 tells us: 1681 * - The timestamp on this packet must be greater than 1682 * or equal to the last value echoed by the other 1683 * endpoint. The RFC says those will be discarded 1684 * since it is a dup that has already been acked. 1685 * This gives us a lowerbound on the timestamp. 1686 * timestamp >= other last echoed timestamp 1687 * - The timestamp will be less than or equal to 1688 * the last timestamp plus the time between the 1689 * last packet and now. The RFC defines the max 1690 * clock rate as 1ms. We will allow clocks to be 1691 * up to 10% fast and will allow a total difference 1692 * or 30 seconds due to a route change. And this 1693 * gives us an upperbound on the timestamp. 1694 * timestamp <= last timestamp + max ticks 1695 * We have to be careful here. Windows will send an 1696 * initial timestamp of zero and then initialize it 1697 * to a random value after the 3whs; presumably to 1698 * avoid a DoS by having to call an expensive RNG 1699 * during a SYN flood. Proof MS has at least one 1700 * good security geek. 1701 * 1702 * - The TCP timestamp option must also echo the other 1703 * endpoints timestamp. The timestamp echoed is the 1704 * one carried on the earliest unacknowledged segment 1705 * on the left edge of the sequence window. The RFC 1706 * states that the host will reject any echoed 1707 * timestamps that were larger than any ever sent. 1708 * This gives us an upperbound on the TS echo. 1709 * tescr <= largest_tsval 1710 * - The lowerbound on the TS echo is a little more 1711 * tricky to determine. The other endpoint's echoed 1712 * values will not decrease. But there may be 1713 * network conditions that re-order packets and 1714 * cause our view of them to decrease. For now the 1715 * only lowerbound we can safely determine is that 1716 * the TS echo will never be less than the original 1717 * TS. XXX There is probably a better lowerbound. 1718 * Remove TS_MAX_CONN with better lowerbound check. 1719 * tescr >= other original TS 1720 * 1721 * It is also important to note that the fastest 1722 * timestamp clock of 1ms will wrap its 32bit space in 1723 * 24 days. So we just disable TS checking after 24 1724 * days of idle time. We actually must use a 12d 1725 * connection limit until we can come up with a better 1726 * lowerbound to the TS echo check. 1727 */ 1728 struct timeval delta_ts; 1729 int ts_fudge; 1730 1731 /* 1732 * PFTM_TS_DIFF is how many seconds of leeway to allow 1733 * a host's timestamp. This can happen if the previous 1734 * packet got delayed in transit for much longer than 1735 * this packet. 1736 */ 1737 if ((ts_fudge = state->rule.ptr->timeout[PFTM_TS_DIFF]) == 0) 1738 ts_fudge = V_pf_default_rule.timeout[PFTM_TS_DIFF]; 1739 1740 /* Calculate max ticks since the last timestamp */ 1741 #define TS_MAXFREQ 1100 /* RFC max TS freq of 1Khz + 10% skew */ 1742 #define TS_MICROSECS 1000000 /* microseconds per second */ 1743 delta_ts = uptime; 1744 timevalsub(&delta_ts, &src->scrub->pfss_last); 1745 tsval_from_last = (delta_ts.tv_sec + ts_fudge) * TS_MAXFREQ; 1746 tsval_from_last += delta_ts.tv_usec / (TS_MICROSECS/TS_MAXFREQ); 1747 1748 if ((src->state >= TCPS_ESTABLISHED && 1749 dst->state >= TCPS_ESTABLISHED) && 1750 (SEQ_LT(tsval, dst->scrub->pfss_tsecr) || 1751 SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) || 1752 (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) || 1753 SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) { 1754 /* Bad RFC1323 implementation or an insertion attack. 1755 * 1756 * - Solaris 2.6 and 2.7 are known to send another ACK 1757 * after the FIN,FIN|ACK,ACK closing that carries 1758 * an old timestamp. 1759 */ 1760 1761 DPFPRINTF(("Timestamp failed %c%c%c%c\n", 1762 SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '0' : ' ', 1763 SEQ_GT(tsval, src->scrub->pfss_tsval + 1764 tsval_from_last) ? '1' : ' ', 1765 SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ', 1766 SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' ')); 1767 DPFPRINTF((" tsval: %u tsecr: %u +ticks: %u " 1768 "idle: %jus %lums\n", 1769 tsval, tsecr, tsval_from_last, 1770 (uintmax_t)delta_ts.tv_sec, 1771 delta_ts.tv_usec / 1000)); 1772 DPFPRINTF((" src->tsval: %u tsecr: %u\n", 1773 src->scrub->pfss_tsval, src->scrub->pfss_tsecr)); 1774 DPFPRINTF((" dst->tsval: %u tsecr: %u tsval0: %u" 1775 "\n", dst->scrub->pfss_tsval, 1776 dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0)); 1777 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1778 pf_print_state(state); 1779 pf_print_flags(th->th_flags); 1780 printf("\n"); 1781 } 1782 REASON_SET(reason, PFRES_TS); 1783 return (PF_DROP); 1784 } 1785 1786 /* XXX I'd really like to require tsecr but it's optional */ 1787 1788 } else if (!got_ts && (th->th_flags & TH_RST) == 0 && 1789 ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED) 1790 || pd->p_len > 0 || (th->th_flags & TH_SYN)) && 1791 src->scrub && dst->scrub && 1792 (src->scrub->pfss_flags & PFSS_PAWS) && 1793 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1794 /* Didn't send a timestamp. Timestamps aren't really useful 1795 * when: 1796 * - connection opening or closing (often not even sent). 1797 * but we must not let an attacker to put a FIN on a 1798 * data packet to sneak it through our ESTABLISHED check. 1799 * - on a TCP reset. RFC suggests not even looking at TS. 1800 * - on an empty ACK. The TS will not be echoed so it will 1801 * probably not help keep the RTT calculation in sync and 1802 * there isn't as much danger when the sequence numbers 1803 * got wrapped. So some stacks don't include TS on empty 1804 * ACKs :-( 1805 * 1806 * To minimize the disruption to mostly RFC1323 conformant 1807 * stacks, we will only require timestamps on data packets. 1808 * 1809 * And what do ya know, we cannot require timestamps on data 1810 * packets. There appear to be devices that do legitimate 1811 * TCP connection hijacking. There are HTTP devices that allow 1812 * a 3whs (with timestamps) and then buffer the HTTP request. 1813 * If the intermediate device has the HTTP response cache, it 1814 * will spoof the response but not bother timestamping its 1815 * packets. So we can look for the presence of a timestamp in 1816 * the first data packet and if there, require it in all future 1817 * packets. 1818 */ 1819 1820 if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) { 1821 /* 1822 * Hey! Someone tried to sneak a packet in. Or the 1823 * stack changed its RFC1323 behavior?!?! 1824 */ 1825 if (V_pf_status.debug >= PF_DEBUG_MISC) { 1826 DPFPRINTF(("Did not receive expected RFC1323 " 1827 "timestamp\n")); 1828 pf_print_state(state); 1829 pf_print_flags(th->th_flags); 1830 printf("\n"); 1831 } 1832 REASON_SET(reason, PFRES_TS); 1833 return (PF_DROP); 1834 } 1835 } 1836 1837 /* 1838 * We will note if a host sends his data packets with or without 1839 * timestamps. And require all data packets to contain a timestamp 1840 * if the first does. PAWS implicitly requires that all data packets be 1841 * timestamped. But I think there are middle-man devices that hijack 1842 * TCP streams immediately after the 3whs and don't timestamp their 1843 * packets (seen in a WWW accelerator or cache). 1844 */ 1845 if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags & 1846 (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) { 1847 if (got_ts) 1848 src->scrub->pfss_flags |= PFSS_DATA_TS; 1849 else { 1850 src->scrub->pfss_flags |= PFSS_DATA_NOTS; 1851 if (V_pf_status.debug >= PF_DEBUG_MISC && dst->scrub && 1852 (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) { 1853 /* Don't warn if other host rejected RFC1323 */ 1854 DPFPRINTF(("Broken RFC1323 stack did not " 1855 "timestamp data packet. Disabled PAWS " 1856 "security.\n")); 1857 pf_print_state(state); 1858 pf_print_flags(th->th_flags); 1859 printf("\n"); 1860 } 1861 } 1862 } 1863 1864 /* 1865 * Update PAWS values 1866 */ 1867 if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags & 1868 (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) { 1869 getmicrouptime(&src->scrub->pfss_last); 1870 if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) || 1871 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1872 src->scrub->pfss_tsval = tsval; 1873 1874 if (tsecr) { 1875 if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) || 1876 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1877 src->scrub->pfss_tsecr = tsecr; 1878 1879 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 && 1880 (SEQ_LT(tsval, src->scrub->pfss_tsval0) || 1881 src->scrub->pfss_tsval0 == 0)) { 1882 /* tsval0 MUST be the lowest timestamp */ 1883 src->scrub->pfss_tsval0 = tsval; 1884 } 1885 1886 /* Only fully initialized after a TS gets echoed */ 1887 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0) 1888 src->scrub->pfss_flags |= PFSS_PAWS; 1889 } 1890 } 1891 1892 /* I have a dream.... TCP segment reassembly.... */ 1893 return (0); 1894 } 1895 1896 static int 1897 pf_normalize_tcpopt(struct pf_rule *r, struct mbuf *m, struct tcphdr *th, 1898 int off, sa_family_t af) 1899 { 1900 u_int16_t *mss; 1901 int thoff; 1902 int opt, cnt, optlen = 0; 1903 int rewrite = 0; 1904 u_char opts[TCP_MAXOLEN]; 1905 u_char *optp = opts; 1906 1907 thoff = th->th_off << 2; 1908 cnt = thoff - sizeof(struct tcphdr); 1909 1910 if (cnt > 0 && !pf_pull_hdr(m, off + sizeof(*th), opts, cnt, 1911 NULL, NULL, af)) 1912 return (rewrite); 1913 1914 for (; cnt > 0; cnt -= optlen, optp += optlen) { 1915 opt = optp[0]; 1916 if (opt == TCPOPT_EOL) 1917 break; 1918 if (opt == TCPOPT_NOP) 1919 optlen = 1; 1920 else { 1921 if (cnt < 2) 1922 break; 1923 optlen = optp[1]; 1924 if (optlen < 2 || optlen > cnt) 1925 break; 1926 } 1927 switch (opt) { 1928 case TCPOPT_MAXSEG: 1929 mss = (u_int16_t *)(optp + 2); 1930 if ((ntohs(*mss)) > r->max_mss) { 1931 th->th_sum = pf_proto_cksum_fixup(m, 1932 th->th_sum, *mss, htons(r->max_mss), 0); 1933 *mss = htons(r->max_mss); 1934 rewrite = 1; 1935 } 1936 break; 1937 default: 1938 break; 1939 } 1940 } 1941 1942 if (rewrite) 1943 m_copyback(m, off + sizeof(*th), thoff - sizeof(*th), opts); 1944 1945 return (rewrite); 1946 } 1947 1948 #ifdef INET 1949 static void 1950 pf_scrub_ip(struct mbuf **m0, u_int32_t flags, u_int8_t min_ttl, u_int8_t tos) 1951 { 1952 struct mbuf *m = *m0; 1953 struct ip *h = mtod(m, struct ip *); 1954 1955 /* Clear IP_DF if no-df was requested */ 1956 if (flags & PFRULE_NODF && h->ip_off & htons(IP_DF)) { 1957 u_int16_t ip_off = h->ip_off; 1958 1959 h->ip_off &= htons(~IP_DF); 1960 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0); 1961 } 1962 1963 /* Enforce a minimum ttl, may cause endless packet loops */ 1964 if (min_ttl && h->ip_ttl < min_ttl) { 1965 u_int16_t ip_ttl = h->ip_ttl; 1966 1967 h->ip_ttl = min_ttl; 1968 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0); 1969 } 1970 1971 /* Enforce tos */ 1972 if (flags & PFRULE_SET_TOS) { 1973 u_int16_t ov, nv; 1974 1975 ov = *(u_int16_t *)h; 1976 h->ip_tos = tos | (h->ip_tos & IPTOS_ECN_MASK); 1977 nv = *(u_int16_t *)h; 1978 1979 h->ip_sum = pf_cksum_fixup(h->ip_sum, ov, nv, 0); 1980 } 1981 1982 /* random-id, but not for fragments */ 1983 if (flags & PFRULE_RANDOMID && !(h->ip_off & ~htons(IP_DF))) { 1984 uint16_t ip_id = h->ip_id; 1985 1986 ip_fillid(h); 1987 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_id, h->ip_id, 0); 1988 } 1989 } 1990 #endif /* INET */ 1991 1992 #ifdef INET6 1993 static void 1994 pf_scrub_ip6(struct mbuf **m0, u_int8_t min_ttl) 1995 { 1996 struct mbuf *m = *m0; 1997 struct ip6_hdr *h = mtod(m, struct ip6_hdr *); 1998 1999 /* Enforce a minimum ttl, may cause endless packet loops */ 2000 if (min_ttl && h->ip6_hlim < min_ttl) 2001 h->ip6_hlim = min_ttl; 2002 } 2003 #endif 2004