1 /* $OpenBSD: pf_norm.c,v 1.223 2021/03/10 10:21:48 jsg Exp $ */ 2 3 /* 4 * Copyright 2001 Niels Provos <provos@citi.umich.edu> 5 * Copyright 2009 Henning Brauer <henning@openbsd.org> 6 * Copyright 2011-2018 Alexander Bluhm <bluhm@openbsd.org> 7 * All rights reserved. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 */ 29 30 #include "pflog.h" 31 32 #include <sys/param.h> 33 #include <sys/systm.h> 34 #include <sys/mbuf.h> 35 #include <sys/filio.h> 36 #include <sys/fcntl.h> 37 #include <sys/socket.h> 38 #include <sys/kernel.h> 39 #include <sys/time.h> 40 #include <sys/pool.h> 41 #include <sys/syslog.h> 42 #include <sys/mutex.h> 43 44 #include <net/if.h> 45 #include <net/if_var.h> 46 #include <net/if_pflog.h> 47 48 #include <netinet/in.h> 49 #include <netinet/ip.h> 50 #include <netinet/ip_var.h> 51 #include <netinet/ip_icmp.h> 52 #include <netinet/tcp.h> 53 #include <netinet/tcp_seq.h> 54 #include <netinet/tcp_fsm.h> 55 #include <netinet/udp.h> 56 57 #ifdef INET6 58 #include <netinet6/in6_var.h> 59 #include <netinet/ip6.h> 60 #include <netinet6/ip6_var.h> 61 #include <netinet/icmp6.h> 62 #include <netinet6/nd6.h> 63 #endif /* INET6 */ 64 65 #include <net/pfvar.h> 66 #include <net/pfvar_priv.h> 67 68 struct pf_frent { 69 TAILQ_ENTRY(pf_frent) fr_next; 70 struct mbuf *fe_m; 71 u_int16_t fe_hdrlen; /* ipv4 header length with ip options 72 ipv6, extension, fragment header */ 73 u_int16_t fe_extoff; /* last extension header offset or 0 */ 74 u_int16_t fe_len; /* fragment length */ 75 u_int16_t fe_off; /* fragment offset */ 76 u_int16_t fe_mff; /* more fragment flag */ 77 }; 78 79 RB_HEAD(pf_frag_tree, pf_fragment); 80 struct pf_frnode { 81 struct pf_addr fn_src; /* ip source address */ 82 struct pf_addr fn_dst; /* ip destination address */ 83 sa_family_t fn_af; /* address family */ 84 u_int8_t fn_proto; /* protocol for fragments in fn_tree */ 85 u_int8_t fn_direction; /* pf packet direction */ 86 u_int32_t fn_fragments; /* number of entries in fn_tree */ 87 u_int32_t fn_gen; /* fr_gen of newest entry in fn_tree */ 88 89 RB_ENTRY(pf_frnode) fn_entry; 90 struct pf_frag_tree fn_tree; /* matching fragments, lookup by id */ 91 }; 92 93 struct pf_fragment { 94 struct pf_frent *fr_firstoff[PF_FRAG_ENTRY_POINTS]; 95 /* pointers to queue element */ 96 u_int8_t fr_entries[PF_FRAG_ENTRY_POINTS]; 97 /* count entries between pointers */ 98 RB_ENTRY(pf_fragment) fr_entry; 99 TAILQ_ENTRY(pf_fragment) frag_next; 100 TAILQ_HEAD(pf_fragq, pf_frent) fr_queue; 101 u_int32_t fr_id; /* fragment id for reassemble */ 102 int32_t fr_timeout; 103 u_int32_t fr_gen; /* generation number (per pf_frnode) */ 104 u_int16_t fr_maxlen; /* maximum length of single fragment */ 105 u_int16_t fr_holes; /* number of holes in the queue */ 106 struct pf_frnode *fr_node; /* ip src/dst/proto/af for fragments */ 107 }; 108 109 struct pf_fragment_tag { 110 u_int16_t ft_hdrlen; /* header length of reassembled pkt */ 111 u_int16_t ft_extoff; /* last extension header offset or 0 */ 112 u_int16_t ft_maxlen; /* maximum fragment payload length */ 113 }; 114 115 TAILQ_HEAD(pf_fragqueue, pf_fragment) pf_fragqueue; 116 117 static __inline int pf_frnode_compare(struct pf_frnode *, 118 struct pf_frnode *); 119 RB_HEAD(pf_frnode_tree, pf_frnode) pf_frnode_tree; 120 RB_PROTOTYPE(pf_frnode_tree, pf_frnode, fn_entry, pf_frnode_compare); 121 RB_GENERATE(pf_frnode_tree, pf_frnode, fn_entry, pf_frnode_compare); 122 123 static __inline int pf_frag_compare(struct pf_fragment *, 124 struct pf_fragment *); 125 RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); 126 RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare); 127 128 /* Private prototypes */ 129 void pf_flush_fragments(void); 130 void pf_free_fragment(struct pf_fragment *); 131 struct pf_fragment *pf_find_fragment(struct pf_frnode *, u_int32_t); 132 struct pf_frent *pf_create_fragment(u_short *); 133 int pf_frent_holes(struct pf_frent *); 134 static inline int pf_frent_index(struct pf_frent *); 135 int pf_frent_insert(struct pf_fragment *, 136 struct pf_frent *, struct pf_frent *); 137 void pf_frent_remove(struct pf_fragment *, 138 struct pf_frent *); 139 struct pf_frent *pf_frent_previous(struct pf_fragment *, 140 struct pf_frent *); 141 struct pf_fragment *pf_fillup_fragment(struct pf_frnode *, u_int32_t, 142 struct pf_frent *, u_short *); 143 struct mbuf *pf_join_fragment(struct pf_fragment *); 144 int pf_reassemble(struct mbuf **, int, u_short *); 145 #ifdef INET6 146 int pf_reassemble6(struct mbuf **, struct ip6_frag *, 147 u_int16_t, u_int16_t, int, u_short *); 148 #endif /* INET6 */ 149 150 /* Globals */ 151 struct pool pf_frent_pl, pf_frag_pl, pf_frnode_pl; 152 struct pool pf_state_scrub_pl; 153 int pf_nfrents; 154 155 struct mutex pf_frag_mtx; 156 157 #define PF_FRAG_LOCK_INIT() mtx_init(&pf_frag_mtx, IPL_SOFTNET) 158 #define PF_FRAG_LOCK() mtx_enter(&pf_frag_mtx) 159 #define PF_FRAG_UNLOCK() mtx_leave(&pf_frag_mtx) 160 161 void 162 pf_normalize_init(void) 163 { 164 pool_init(&pf_frent_pl, sizeof(struct pf_frent), 0, 165 IPL_SOFTNET, 0, "pffrent", NULL); 166 pool_init(&pf_frnode_pl, sizeof(struct pf_frnode), 0, 167 IPL_SOFTNET, 0, "pffrnode", NULL); 168 pool_init(&pf_frag_pl, sizeof(struct pf_fragment), 0, 169 IPL_SOFTNET, 0, "pffrag", NULL); 170 pool_init(&pf_state_scrub_pl, sizeof(struct pf_state_scrub), 0, 171 IPL_SOFTNET, 0, "pfstscr", NULL); 172 173 pool_sethiwat(&pf_frag_pl, PFFRAG_FRAG_HIWAT); 174 pool_sethardlimit(&pf_frent_pl, PFFRAG_FRENT_HIWAT, NULL, 0); 175 176 TAILQ_INIT(&pf_fragqueue); 177 178 PF_FRAG_LOCK_INIT(); 179 } 180 181 static __inline int 182 pf_frnode_compare(struct pf_frnode *a, struct pf_frnode *b) 183 { 184 int diff; 185 186 if ((diff = a->fn_proto - b->fn_proto) != 0) 187 return (diff); 188 if ((diff = a->fn_af - b->fn_af) != 0) 189 return (diff); 190 if ((diff = pf_addr_compare(&a->fn_src, &b->fn_src, a->fn_af)) != 0) 191 return (diff); 192 if ((diff = pf_addr_compare(&a->fn_dst, &b->fn_dst, a->fn_af)) != 0) 193 return (diff); 194 195 return (0); 196 } 197 198 static __inline int 199 pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b) 200 { 201 int diff; 202 203 if ((diff = a->fr_id - b->fr_id) != 0) 204 return (diff); 205 206 return (0); 207 } 208 209 void 210 pf_purge_expired_fragments(void) 211 { 212 struct pf_fragment *frag; 213 int32_t expire; 214 215 PF_ASSERT_UNLOCKED(); 216 217 expire = getuptime() - pf_default_rule.timeout[PFTM_FRAG]; 218 219 PF_FRAG_LOCK(); 220 while ((frag = TAILQ_LAST(&pf_fragqueue, pf_fragqueue)) != NULL) { 221 if (frag->fr_timeout > expire) 222 break; 223 DPFPRINTF(LOG_NOTICE, "expiring %d(%p)", frag->fr_id, frag); 224 pf_free_fragment(frag); 225 } 226 PF_FRAG_UNLOCK(); 227 } 228 229 /* 230 * Try to flush old fragments to make space for new ones 231 */ 232 void 233 pf_flush_fragments(void) 234 { 235 struct pf_fragment *frag; 236 int goal; 237 238 goal = pf_nfrents * 9 / 10; 239 DPFPRINTF(LOG_NOTICE, "trying to free > %d frents", pf_nfrents - goal); 240 while (goal < pf_nfrents) { 241 if ((frag = TAILQ_LAST(&pf_fragqueue, pf_fragqueue)) == NULL) 242 break; 243 pf_free_fragment(frag); 244 } 245 } 246 247 /* 248 * Remove a fragment from the fragment queue, free its fragment entries, 249 * and free the fragment itself. 250 */ 251 void 252 pf_free_fragment(struct pf_fragment *frag) 253 { 254 struct pf_frent *frent; 255 struct pf_frnode *frnode; 256 257 frnode = frag->fr_node; 258 RB_REMOVE(pf_frag_tree, &frnode->fn_tree, frag); 259 KASSERT(frnode->fn_fragments >= 1); 260 frnode->fn_fragments--; 261 if (frnode->fn_fragments == 0) { 262 KASSERT(RB_EMPTY(&frnode->fn_tree)); 263 RB_REMOVE(pf_frnode_tree, &pf_frnode_tree, frnode); 264 pool_put(&pf_frnode_pl, frnode); 265 } 266 TAILQ_REMOVE(&pf_fragqueue, frag, frag_next); 267 268 /* Free all fragment entries */ 269 while ((frent = TAILQ_FIRST(&frag->fr_queue)) != NULL) { 270 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next); 271 m_freem(frent->fe_m); 272 pool_put(&pf_frent_pl, frent); 273 pf_nfrents--; 274 } 275 pool_put(&pf_frag_pl, frag); 276 } 277 278 struct pf_fragment * 279 pf_find_fragment(struct pf_frnode *key, u_int32_t id) 280 { 281 struct pf_fragment *frag, idkey; 282 struct pf_frnode *frnode; 283 u_int32_t stale; 284 285 frnode = RB_FIND(pf_frnode_tree, &pf_frnode_tree, key); 286 if (frnode == NULL) 287 return (NULL); 288 KASSERT(frnode->fn_fragments >= 1); 289 idkey.fr_id = id; 290 frag = RB_FIND(pf_frag_tree, &frnode->fn_tree, &idkey); 291 if (frag == NULL) 292 return (NULL); 293 /* 294 * Limit the number of fragments we accept for each (proto,src,dst,af) 295 * combination (aka pf_frnode), so we can deal better with a high rate 296 * of fragments. Problem analysis is in RFC 4963. 297 * Store the current generation for each pf_frnode in fn_gen and on 298 * lookup discard 'stale' fragments (pf_fragment, based on the fr_gen 299 * member). Instead of adding another button interpret the pf fragment 300 * timeout in multiples of 200 fragments. This way the default of 60s 301 * means: pf_fragment objects older than 60*200 = 12,000 generations 302 * are considered stale. 303 */ 304 stale = pf_default_rule.timeout[PFTM_FRAG] * PF_FRAG_STALE; 305 if ((frnode->fn_gen - frag->fr_gen) >= stale) { 306 DPFPRINTF(LOG_NOTICE, "stale fragment %d(%p), gen %u, num %u", 307 frag->fr_id, frag, frag->fr_gen, frnode->fn_fragments); 308 pf_free_fragment(frag); 309 return (NULL); 310 } 311 TAILQ_REMOVE(&pf_fragqueue, frag, frag_next); 312 TAILQ_INSERT_HEAD(&pf_fragqueue, frag, frag_next); 313 314 return (frag); 315 } 316 317 struct pf_frent * 318 pf_create_fragment(u_short *reason) 319 { 320 struct pf_frent *frent; 321 322 frent = pool_get(&pf_frent_pl, PR_NOWAIT); 323 if (frent == NULL) { 324 pf_flush_fragments(); 325 frent = pool_get(&pf_frent_pl, PR_NOWAIT); 326 if (frent == NULL) { 327 REASON_SET(reason, PFRES_MEMORY); 328 return (NULL); 329 } 330 } 331 pf_nfrents++; 332 333 return (frent); 334 } 335 336 /* 337 * Calculate the additional holes that were created in the fragment 338 * queue by inserting this fragment. A fragment in the middle 339 * creates one more hole by splitting. For each connected side, 340 * it loses one hole. 341 * Fragment entry must be in the queue when calling this function. 342 */ 343 int 344 pf_frent_holes(struct pf_frent *frent) 345 { 346 struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next); 347 struct pf_frent *next = TAILQ_NEXT(frent, fr_next); 348 int holes = 1; 349 350 if (prev == NULL) { 351 if (frent->fe_off == 0) 352 holes--; 353 } else { 354 KASSERT(frent->fe_off != 0); 355 if (frent->fe_off == prev->fe_off + prev->fe_len) 356 holes--; 357 } 358 if (next == NULL) { 359 if (!frent->fe_mff) 360 holes--; 361 } else { 362 KASSERT(frent->fe_mff); 363 if (next->fe_off == frent->fe_off + frent->fe_len) 364 holes--; 365 } 366 return holes; 367 } 368 369 static inline int 370 pf_frent_index(struct pf_frent *frent) 371 { 372 /* 373 * We have an array of 16 entry points to the queue. A full size 374 * 65535 octet IP packet can have 8192 fragments. So the queue 375 * traversal length is at most 512 and at most 16 entry points are 376 * checked. We need 128 additional bytes on a 64 bit architecture. 377 */ 378 CTASSERT(((u_int16_t)0xffff &~ 7) / (0x10000 / PF_FRAG_ENTRY_POINTS) == 379 16 - 1); 380 CTASSERT(((u_int16_t)0xffff >> 3) / PF_FRAG_ENTRY_POINTS == 512 - 1); 381 382 return frent->fe_off / (0x10000 / PF_FRAG_ENTRY_POINTS); 383 } 384 385 int 386 pf_frent_insert(struct pf_fragment *frag, struct pf_frent *frent, 387 struct pf_frent *prev) 388 { 389 CTASSERT(PF_FRAG_ENTRY_LIMIT <= 0xff); 390 int index; 391 392 /* 393 * A packet has at most 65536 octets. With 16 entry points, each one 394 * spawns 4096 octets. We limit these to 64 fragments each, which 395 * means on average every fragment must have at least 64 octets. 396 */ 397 index = pf_frent_index(frent); 398 if (frag->fr_entries[index] >= PF_FRAG_ENTRY_LIMIT) 399 return ENOBUFS; 400 frag->fr_entries[index]++; 401 402 if (prev == NULL) { 403 TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next); 404 } else { 405 KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off); 406 TAILQ_INSERT_AFTER(&frag->fr_queue, prev, frent, fr_next); 407 } 408 409 if (frag->fr_firstoff[index] == NULL) { 410 KASSERT(prev == NULL || pf_frent_index(prev) < index); 411 frag->fr_firstoff[index] = frent; 412 } else { 413 if (frent->fe_off < frag->fr_firstoff[index]->fe_off) { 414 KASSERT(prev == NULL || pf_frent_index(prev) < index); 415 frag->fr_firstoff[index] = frent; 416 } else { 417 KASSERT(prev != NULL); 418 KASSERT(pf_frent_index(prev) == index); 419 } 420 } 421 422 frag->fr_holes += pf_frent_holes(frent); 423 424 return 0; 425 } 426 427 void 428 pf_frent_remove(struct pf_fragment *frag, struct pf_frent *frent) 429 { 430 #ifdef DIAGNOSTIC 431 struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next); 432 #endif 433 struct pf_frent *next = TAILQ_NEXT(frent, fr_next); 434 int index; 435 436 frag->fr_holes -= pf_frent_holes(frent); 437 438 index = pf_frent_index(frent); 439 KASSERT(frag->fr_firstoff[index] != NULL); 440 if (frag->fr_firstoff[index]->fe_off == frent->fe_off) { 441 if (next == NULL) { 442 frag->fr_firstoff[index] = NULL; 443 } else { 444 KASSERT(frent->fe_off + frent->fe_len <= next->fe_off); 445 if (pf_frent_index(next) == index) { 446 frag->fr_firstoff[index] = next; 447 } else { 448 frag->fr_firstoff[index] = NULL; 449 } 450 } 451 } else { 452 KASSERT(frag->fr_firstoff[index]->fe_off < frent->fe_off); 453 KASSERT(prev != NULL); 454 KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off); 455 KASSERT(pf_frent_index(prev) == index); 456 } 457 458 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next); 459 460 KASSERT(frag->fr_entries[index] > 0); 461 frag->fr_entries[index]--; 462 } 463 464 struct pf_frent * 465 pf_frent_previous(struct pf_fragment *frag, struct pf_frent *frent) 466 { 467 struct pf_frent *prev, *next; 468 int index; 469 470 /* 471 * If there are no fragments after frag, take the final one. Assume 472 * that the global queue is not empty. 473 */ 474 prev = TAILQ_LAST(&frag->fr_queue, pf_fragq); 475 KASSERT(prev != NULL); 476 if (prev->fe_off <= frent->fe_off) 477 return prev; 478 /* 479 * We want to find a fragment entry that is before frag, but still 480 * close to it. Find the first fragment entry that is in the same 481 * entry point or in the first entry point after that. As we have 482 * already checked that there are entries behind frag, this will 483 * succeed. 484 */ 485 for (index = pf_frent_index(frent); index < PF_FRAG_ENTRY_POINTS; 486 index++) { 487 prev = frag->fr_firstoff[index]; 488 if (prev != NULL) 489 break; 490 } 491 KASSERT(prev != NULL); 492 /* 493 * In prev we may have a fragment from the same entry point that is 494 * before frent, or one that is just one position behind frent. 495 * In the latter case, we go back one step and have the predecessor. 496 * There may be none if the new fragment will be the first one. 497 */ 498 if (prev->fe_off > frent->fe_off) { 499 prev = TAILQ_PREV(prev, pf_fragq, fr_next); 500 if (prev == NULL) 501 return NULL; 502 KASSERT(prev->fe_off <= frent->fe_off); 503 return prev; 504 } 505 /* 506 * In prev is the first fragment of the entry point. The offset 507 * of frag is behind it. Find the closest previous fragment. 508 */ 509 for (next = TAILQ_NEXT(prev, fr_next); next != NULL; 510 next = TAILQ_NEXT(next, fr_next)) { 511 if (next->fe_off > frent->fe_off) 512 break; 513 prev = next; 514 } 515 return prev; 516 } 517 518 struct pf_fragment * 519 pf_fillup_fragment(struct pf_frnode *key, u_int32_t id, 520 struct pf_frent *frent, u_short *reason) 521 { 522 struct pf_frent *after, *next, *prev; 523 struct pf_fragment *frag; 524 struct pf_frnode *frnode; 525 u_int16_t total; 526 527 /* No empty fragments */ 528 if (frent->fe_len == 0) { 529 DPFPRINTF(LOG_NOTICE, "bad fragment: len 0"); 530 goto bad_fragment; 531 } 532 533 /* All fragments are 8 byte aligned */ 534 if (frent->fe_mff && (frent->fe_len & 0x7)) { 535 DPFPRINTF(LOG_NOTICE, "bad fragment: mff and len %d", 536 frent->fe_len); 537 goto bad_fragment; 538 } 539 540 /* Respect maximum length, IP_MAXPACKET == IPV6_MAXPACKET */ 541 if (frent->fe_off + frent->fe_len > IP_MAXPACKET) { 542 DPFPRINTF(LOG_NOTICE, "bad fragment: max packet %d", 543 frent->fe_off + frent->fe_len); 544 goto bad_fragment; 545 } 546 547 DPFPRINTF(LOG_INFO, key->fn_af == AF_INET ? 548 "reass frag %d @ %d-%d" : "reass frag %#08x @ %d-%d", 549 id, frent->fe_off, frent->fe_off + frent->fe_len); 550 551 /* Fully buffer all of the fragments in this fragment queue */ 552 frag = pf_find_fragment(key, id); 553 554 /* Create a new reassembly queue for this packet */ 555 if (frag == NULL) { 556 frag = pool_get(&pf_frag_pl, PR_NOWAIT); 557 if (frag == NULL) { 558 pf_flush_fragments(); 559 frag = pool_get(&pf_frag_pl, PR_NOWAIT); 560 if (frag == NULL) { 561 REASON_SET(reason, PFRES_MEMORY); 562 goto drop_fragment; 563 } 564 } 565 frnode = RB_FIND(pf_frnode_tree, &pf_frnode_tree, key); 566 if (frnode == NULL) { 567 frnode = pool_get(&pf_frnode_pl, PR_NOWAIT); 568 if (frnode == NULL) { 569 pf_flush_fragments(); 570 frnode = pool_get(&pf_frnode_pl, PR_NOWAIT); 571 if (frnode == NULL) { 572 REASON_SET(reason, PFRES_MEMORY); 573 pool_put(&pf_frag_pl, frag); 574 goto drop_fragment; 575 } 576 } 577 *frnode = *key; 578 RB_INIT(&frnode->fn_tree); 579 frnode->fn_fragments = 0; 580 frnode->fn_gen = 0; 581 } 582 memset(frag->fr_firstoff, 0, sizeof(frag->fr_firstoff)); 583 memset(frag->fr_entries, 0, sizeof(frag->fr_entries)); 584 TAILQ_INIT(&frag->fr_queue); 585 frag->fr_id = id; 586 frag->fr_timeout = getuptime(); 587 frag->fr_gen = frnode->fn_gen++; 588 frag->fr_maxlen = frent->fe_len; 589 frag->fr_holes = 1; 590 frag->fr_node = frnode; 591 /* RB_INSERT cannot fail as pf_find_fragment() found nothing */ 592 RB_INSERT(pf_frag_tree, &frnode->fn_tree, frag); 593 frnode->fn_fragments++; 594 if (frnode->fn_fragments == 1) 595 RB_INSERT(pf_frnode_tree, &pf_frnode_tree, frnode); 596 TAILQ_INSERT_HEAD(&pf_fragqueue, frag, frag_next); 597 598 /* We do not have a previous fragment, cannot fail. */ 599 pf_frent_insert(frag, frent, NULL); 600 601 return (frag); 602 } 603 604 KASSERT(!TAILQ_EMPTY(&frag->fr_queue)); 605 KASSERT(frag->fr_node); 606 607 /* Remember maximum fragment len for refragmentation */ 608 if (frent->fe_len > frag->fr_maxlen) 609 frag->fr_maxlen = frent->fe_len; 610 611 /* Maximum data we have seen already */ 612 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + 613 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; 614 615 /* Non terminal fragments must have more fragments flag */ 616 if (frent->fe_off + frent->fe_len < total && !frent->fe_mff) 617 goto free_ipv6_fragment; 618 619 /* Check if we saw the last fragment already */ 620 if (!TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_mff) { 621 if (frent->fe_off + frent->fe_len > total || 622 (frent->fe_off + frent->fe_len == total && frent->fe_mff)) 623 goto free_ipv6_fragment; 624 } else { 625 if (frent->fe_off + frent->fe_len == total && !frent->fe_mff) 626 goto free_ipv6_fragment; 627 } 628 629 /* Find neighbors for newly inserted fragment */ 630 prev = pf_frent_previous(frag, frent); 631 if (prev == NULL) { 632 after = TAILQ_FIRST(&frag->fr_queue); 633 KASSERT(after != NULL); 634 } else { 635 after = TAILQ_NEXT(prev, fr_next); 636 } 637 638 if (prev != NULL && prev->fe_off + prev->fe_len > frent->fe_off) { 639 u_int16_t precut; 640 641 #ifdef INET6 642 if (frag->fr_node->fn_af == AF_INET6) 643 goto free_ipv6_fragment; 644 #endif /* INET6 */ 645 646 precut = prev->fe_off + prev->fe_len - frent->fe_off; 647 if (precut >= frent->fe_len) { 648 DPFPRINTF(LOG_NOTICE, "new frag overlapped"); 649 goto drop_fragment; 650 } 651 DPFPRINTF(LOG_NOTICE, "frag head overlap %d", precut); 652 m_adj(frent->fe_m, precut); 653 frent->fe_off += precut; 654 frent->fe_len -= precut; 655 } 656 657 for (; after != NULL && frent->fe_off + frent->fe_len > after->fe_off; 658 after = next) { 659 u_int16_t aftercut; 660 661 #ifdef INET6 662 if (frag->fr_node->fn_af == AF_INET6) 663 goto free_ipv6_fragment; 664 #endif /* INET6 */ 665 666 aftercut = frent->fe_off + frent->fe_len - after->fe_off; 667 if (aftercut < after->fe_len) { 668 int old_index, new_index; 669 670 DPFPRINTF(LOG_NOTICE, "frag tail overlap %d", aftercut); 671 m_adj(after->fe_m, aftercut); 672 old_index = pf_frent_index(after); 673 after->fe_off += aftercut; 674 after->fe_len -= aftercut; 675 new_index = pf_frent_index(after); 676 if (old_index != new_index) { 677 DPFPRINTF(LOG_DEBUG, "frag index %d, new %d", 678 old_index, new_index); 679 /* Fragment switched queue as fe_off changed */ 680 after->fe_off -= aftercut; 681 after->fe_len += aftercut; 682 /* Remove restored fragment from old queue */ 683 pf_frent_remove(frag, after); 684 after->fe_off += aftercut; 685 after->fe_len -= aftercut; 686 /* Insert into correct queue */ 687 if (pf_frent_insert(frag, after, prev)) { 688 DPFPRINTF(LOG_WARNING, 689 "fragment requeue limit exceeded"); 690 m_freem(after->fe_m); 691 pool_put(&pf_frent_pl, after); 692 pf_nfrents--; 693 /* There is not way to recover */ 694 goto free_fragment; 695 } 696 } 697 break; 698 } 699 700 /* This fragment is completely overlapped, lose it */ 701 DPFPRINTF(LOG_NOTICE, "old frag overlapped"); 702 next = TAILQ_NEXT(after, fr_next); 703 pf_frent_remove(frag, after); 704 m_freem(after->fe_m); 705 pool_put(&pf_frent_pl, after); 706 pf_nfrents--; 707 } 708 709 /* If part of the queue gets too long, there is not way to recover. */ 710 if (pf_frent_insert(frag, frent, prev)) { 711 DPFPRINTF(LOG_WARNING, "fragment queue limit exceeded"); 712 goto free_fragment; 713 } 714 715 return (frag); 716 717 free_ipv6_fragment: 718 if (frag->fr_node->fn_af == AF_INET) 719 goto bad_fragment; 720 /* 721 * RFC 5722, Errata 3089: When reassembling an IPv6 datagram, if one 722 * or more its constituent fragments is determined to be an overlapping 723 * fragment, the entire datagram (and any constituent fragments) MUST 724 * be silently discarded. 725 */ 726 DPFPRINTF(LOG_NOTICE, "flush overlapping fragments"); 727 free_fragment: 728 pf_free_fragment(frag); 729 bad_fragment: 730 REASON_SET(reason, PFRES_FRAG); 731 drop_fragment: 732 pool_put(&pf_frent_pl, frent); 733 pf_nfrents--; 734 return (NULL); 735 } 736 737 struct mbuf * 738 pf_join_fragment(struct pf_fragment *frag) 739 { 740 struct mbuf *m, *m2; 741 struct pf_frent *frent; 742 743 frent = TAILQ_FIRST(&frag->fr_queue); 744 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next); 745 746 m = frent->fe_m; 747 /* Strip off any trailing bytes */ 748 if ((frent->fe_hdrlen + frent->fe_len) < m->m_pkthdr.len) 749 m_adj(m, (frent->fe_hdrlen + frent->fe_len) - m->m_pkthdr.len); 750 /* Magic from ip_input */ 751 m2 = m->m_next; 752 m->m_next = NULL; 753 m_cat(m, m2); 754 pool_put(&pf_frent_pl, frent); 755 pf_nfrents--; 756 757 while ((frent = TAILQ_FIRST(&frag->fr_queue)) != NULL) { 758 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next); 759 m2 = frent->fe_m; 760 /* Strip off ip header */ 761 m_adj(m2, frent->fe_hdrlen); 762 /* Strip off any trailing bytes */ 763 if (frent->fe_len < m2->m_pkthdr.len) 764 m_adj(m2, frent->fe_len - m2->m_pkthdr.len); 765 pool_put(&pf_frent_pl, frent); 766 pf_nfrents--; 767 m_removehdr(m2); 768 m_cat(m, m2); 769 } 770 771 /* Remove from fragment queue */ 772 pf_free_fragment(frag); 773 774 return (m); 775 } 776 777 int 778 pf_reassemble(struct mbuf **m0, int dir, u_short *reason) 779 { 780 struct mbuf *m = *m0; 781 struct ip *ip = mtod(m, struct ip *); 782 struct pf_frent *frent; 783 struct pf_fragment *frag; 784 struct pf_frnode key; 785 u_int16_t total, hdrlen; 786 787 /* Get an entry for the fragment queue */ 788 if ((frent = pf_create_fragment(reason)) == NULL) 789 return (PF_DROP); 790 791 frent->fe_m = m; 792 frent->fe_hdrlen = ip->ip_hl << 2; 793 frent->fe_extoff = 0; 794 frent->fe_len = ntohs(ip->ip_len) - (ip->ip_hl << 2); 795 frent->fe_off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3; 796 frent->fe_mff = ntohs(ip->ip_off) & IP_MF; 797 798 key.fn_src.v4 = ip->ip_src; 799 key.fn_dst.v4 = ip->ip_dst; 800 key.fn_af = AF_INET; 801 key.fn_proto = ip->ip_p; 802 key.fn_direction = dir; 803 804 PF_FRAG_LOCK(); 805 if ((frag = pf_fillup_fragment(&key, ip->ip_id, frent, reason)) 806 == NULL) { 807 PF_FRAG_UNLOCK(); 808 return (PF_DROP); 809 } 810 811 /* The mbuf is part of the fragment entry, no direct free or access */ 812 m = *m0 = NULL; 813 814 if (frag->fr_holes) { 815 DPFPRINTF(LOG_DEBUG, "frag %d, holes %d", 816 frag->fr_id, frag->fr_holes); 817 PF_FRAG_UNLOCK(); 818 return (PF_PASS); /* drop because *m0 is NULL, no error */ 819 } 820 821 /* We have all the data */ 822 frent = TAILQ_FIRST(&frag->fr_queue); 823 KASSERT(frent != NULL); 824 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + 825 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; 826 hdrlen = frent->fe_hdrlen; 827 m = *m0 = pf_join_fragment(frag); 828 frag = NULL; 829 m_calchdrlen(m); 830 831 ip = mtod(m, struct ip *); 832 ip->ip_len = htons(hdrlen + total); 833 ip->ip_off &= ~(IP_MF|IP_OFFMASK); 834 835 if (hdrlen + total > IP_MAXPACKET) { 836 PF_FRAG_UNLOCK(); 837 DPFPRINTF(LOG_NOTICE, "drop: too big: %d", total); 838 ip->ip_len = 0; 839 REASON_SET(reason, PFRES_SHORT); 840 /* PF_DROP requires a valid mbuf *m0 in pf_test() */ 841 return (PF_DROP); 842 } 843 844 PF_FRAG_UNLOCK(); 845 DPFPRINTF(LOG_INFO, "complete: %p(%d)", m, ntohs(ip->ip_len)); 846 return (PF_PASS); 847 } 848 849 #ifdef INET6 850 int 851 pf_reassemble6(struct mbuf **m0, struct ip6_frag *fraghdr, 852 u_int16_t hdrlen, u_int16_t extoff, int dir, u_short *reason) 853 { 854 struct mbuf *m = *m0; 855 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 856 struct m_tag *mtag; 857 struct pf_fragment_tag *ftag; 858 struct pf_frent *frent; 859 struct pf_fragment *frag; 860 struct pf_frnode key; 861 int off; 862 u_int16_t total, maxlen; 863 u_int8_t proto; 864 865 /* Get an entry for the fragment queue */ 866 if ((frent = pf_create_fragment(reason)) == NULL) 867 return (PF_DROP); 868 869 frent->fe_m = m; 870 frent->fe_hdrlen = hdrlen; 871 frent->fe_extoff = extoff; 872 frent->fe_len = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - hdrlen; 873 frent->fe_off = ntohs(fraghdr->ip6f_offlg & IP6F_OFF_MASK); 874 frent->fe_mff = fraghdr->ip6f_offlg & IP6F_MORE_FRAG; 875 876 key.fn_src.v6 = ip6->ip6_src; 877 key.fn_dst.v6 = ip6->ip6_dst; 878 key.fn_af = AF_INET6; 879 /* Only the first fragment's protocol is relevant */ 880 key.fn_proto = 0; 881 key.fn_direction = dir; 882 883 PF_FRAG_LOCK(); 884 if ((frag = pf_fillup_fragment(&key, fraghdr->ip6f_ident, frent, 885 reason)) == NULL) { 886 PF_FRAG_UNLOCK(); 887 return (PF_DROP); 888 } 889 890 /* The mbuf is part of the fragment entry, no direct free or access */ 891 m = *m0 = NULL; 892 893 if (frag->fr_holes) { 894 DPFPRINTF(LOG_DEBUG, "frag %#08x, holes %d", 895 frag->fr_id, frag->fr_holes); 896 PF_FRAG_UNLOCK(); 897 return (PF_PASS); /* drop because *m0 is NULL, no error */ 898 } 899 900 /* We have all the data */ 901 frent = TAILQ_FIRST(&frag->fr_queue); 902 KASSERT(frent != NULL); 903 extoff = frent->fe_extoff; 904 maxlen = frag->fr_maxlen; 905 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + 906 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; 907 hdrlen = frent->fe_hdrlen - sizeof(struct ip6_frag); 908 m = *m0 = pf_join_fragment(frag); 909 frag = NULL; 910 911 /* Take protocol from first fragment header */ 912 if ((m = m_getptr(m, hdrlen + offsetof(struct ip6_frag, ip6f_nxt), 913 &off)) == NULL) 914 panic("%s: short frag mbuf chain", __func__); 915 proto = *(mtod(m, caddr_t) + off); 916 m = *m0; 917 918 /* Delete frag6 header */ 919 if (frag6_deletefraghdr(m, hdrlen) != 0) 920 goto fail; 921 922 m_calchdrlen(m); 923 924 if ((mtag = m_tag_get(PACKET_TAG_PF_REASSEMBLED, sizeof(struct 925 pf_fragment_tag), M_NOWAIT)) == NULL) 926 goto fail; 927 ftag = (struct pf_fragment_tag *)(mtag + 1); 928 ftag->ft_hdrlen = hdrlen; 929 ftag->ft_extoff = extoff; 930 ftag->ft_maxlen = maxlen; 931 m_tag_prepend(m, mtag); 932 933 ip6 = mtod(m, struct ip6_hdr *); 934 ip6->ip6_plen = htons(hdrlen - sizeof(struct ip6_hdr) + total); 935 if (extoff) { 936 /* Write protocol into next field of last extension header */ 937 if ((m = m_getptr(m, extoff + offsetof(struct ip6_ext, 938 ip6e_nxt), &off)) == NULL) 939 panic("%s: short ext mbuf chain", __func__); 940 *(mtod(m, caddr_t) + off) = proto; 941 m = *m0; 942 } else 943 ip6->ip6_nxt = proto; 944 945 if (hdrlen - sizeof(struct ip6_hdr) + total > IPV6_MAXPACKET) { 946 PF_FRAG_UNLOCK(); 947 DPFPRINTF(LOG_NOTICE, "drop: too big: %d", total); 948 ip6->ip6_plen = 0; 949 REASON_SET(reason, PFRES_SHORT); 950 /* PF_DROP requires a valid mbuf *m0 in pf_test6() */ 951 return (PF_DROP); 952 } 953 PF_FRAG_UNLOCK(); 954 955 DPFPRINTF(LOG_INFO, "complete: %p(%d)", m, ntohs(ip6->ip6_plen)); 956 return (PF_PASS); 957 958 fail: 959 PF_FRAG_UNLOCK(); 960 REASON_SET(reason, PFRES_MEMORY); 961 /* PF_DROP requires a valid mbuf *m0 in pf_test6(), will free later */ 962 return (PF_DROP); 963 } 964 965 int 966 pf_refragment6(struct mbuf **m0, struct m_tag *mtag, struct sockaddr_in6 *dst, 967 struct ifnet *ifp, struct rtentry *rt) 968 { 969 struct mbuf *m = *m0; 970 struct mbuf_list fml; 971 struct pf_fragment_tag *ftag = (struct pf_fragment_tag *)(mtag + 1); 972 u_int32_t mtu; 973 u_int16_t hdrlen, extoff, maxlen; 974 u_int8_t proto; 975 int error; 976 977 hdrlen = ftag->ft_hdrlen; 978 extoff = ftag->ft_extoff; 979 maxlen = ftag->ft_maxlen; 980 m_tag_delete(m, mtag); 981 mtag = NULL; 982 ftag = NULL; 983 984 /* Checksum must be calculated for the whole packet */ 985 in6_proto_cksum_out(m, NULL); 986 987 if (extoff) { 988 int off; 989 990 /* Use protocol from next field of last extension header */ 991 if ((m = m_getptr(m, extoff + offsetof(struct ip6_ext, 992 ip6e_nxt), &off)) == NULL) 993 panic("%s: short ext mbuf chain", __func__); 994 proto = *(mtod(m, caddr_t) + off); 995 *(mtod(m, caddr_t) + off) = IPPROTO_FRAGMENT; 996 m = *m0; 997 } else { 998 struct ip6_hdr *hdr; 999 1000 hdr = mtod(m, struct ip6_hdr *); 1001 proto = hdr->ip6_nxt; 1002 hdr->ip6_nxt = IPPROTO_FRAGMENT; 1003 } 1004 1005 /* 1006 * Maxlen may be less than 8 iff there was only a single 1007 * fragment. As it was fragmented before, add a fragment 1008 * header also for a single fragment. If total or maxlen 1009 * is less than 8, ip6_fragment() will return EMSGSIZE and 1010 * we drop the packet. 1011 */ 1012 mtu = hdrlen + sizeof(struct ip6_frag) + maxlen; 1013 error = ip6_fragment(m, &fml, hdrlen, proto, mtu); 1014 *m0 = NULL; /* ip6_fragment() has consumed original packet. */ 1015 if (error) { 1016 DPFPRINTF(LOG_NOTICE, "refragment error %d", error); 1017 return (PF_DROP); 1018 } 1019 1020 while ((m = ml_dequeue(&fml)) != NULL) { 1021 m->m_pkthdr.pf.flags |= PF_TAG_REFRAGMENTED; 1022 if (ifp == NULL) { 1023 ip6_forward(m, NULL, 0); 1024 } else if ((u_long)m->m_pkthdr.len <= ifp->if_mtu) { 1025 ifp->if_output(ifp, m, sin6tosa(dst), rt); 1026 } else { 1027 icmp6_error(m, ICMP6_PACKET_TOO_BIG, 0, ifp->if_mtu); 1028 } 1029 } 1030 1031 return (PF_PASS); 1032 } 1033 #endif /* INET6 */ 1034 1035 int 1036 pf_normalize_ip(struct pf_pdesc *pd, u_short *reason) 1037 { 1038 struct ip *h = mtod(pd->m, struct ip *); 1039 u_int16_t fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3; 1040 u_int16_t mff = (ntohs(h->ip_off) & IP_MF); 1041 1042 if (!fragoff && !mff) 1043 goto no_fragment; 1044 1045 /* Clear IP_DF if we're in no-df mode */ 1046 if (pf_status.reass & PF_REASS_NODF && h->ip_off & htons(IP_DF)) 1047 h->ip_off &= htons(~IP_DF); 1048 1049 /* We're dealing with a fragment now. Don't allow fragments 1050 * with IP_DF to enter the cache. If the flag was cleared by 1051 * no-df above, fine. Otherwise drop it. 1052 */ 1053 if (h->ip_off & htons(IP_DF)) { 1054 DPFPRINTF(LOG_NOTICE, "bad fragment: IP_DF"); 1055 REASON_SET(reason, PFRES_FRAG); 1056 return (PF_DROP); 1057 } 1058 1059 if (!pf_status.reass) 1060 return (PF_PASS); /* no reassembly */ 1061 1062 /* Returns PF_DROP or m is NULL or completely reassembled mbuf */ 1063 if (pf_reassemble(&pd->m, pd->dir, reason) != PF_PASS) 1064 return (PF_DROP); 1065 if (pd->m == NULL) 1066 return (PF_PASS); /* packet has been reassembled, no error */ 1067 1068 h = mtod(pd->m, struct ip *); 1069 1070 no_fragment: 1071 /* At this point, only IP_DF is allowed in ip_off */ 1072 if (h->ip_off & ~htons(IP_DF)) 1073 h->ip_off &= htons(IP_DF); 1074 1075 return (PF_PASS); 1076 } 1077 1078 #ifdef INET6 1079 int 1080 pf_normalize_ip6(struct pf_pdesc *pd, u_short *reason) 1081 { 1082 struct ip6_frag frag; 1083 1084 if (pd->fragoff == 0) 1085 goto no_fragment; 1086 1087 if (!pf_pull_hdr(pd->m, pd->fragoff, &frag, sizeof(frag), NULL, reason, 1088 AF_INET6)) 1089 return (PF_DROP); 1090 1091 if (!pf_status.reass) 1092 return (PF_PASS); /* no reassembly */ 1093 1094 /* Returns PF_DROP or m is NULL or completely reassembled mbuf */ 1095 if (pf_reassemble6(&pd->m, &frag, pd->fragoff + sizeof(frag), 1096 pd->extoff, pd->dir, reason) != PF_PASS) 1097 return (PF_DROP); 1098 if (pd->m == NULL) 1099 return (PF_PASS); /* packet has been reassembled, no error */ 1100 1101 no_fragment: 1102 return (PF_PASS); 1103 } 1104 #endif /* INET6 */ 1105 1106 int 1107 pf_normalize_tcp(struct pf_pdesc *pd) 1108 { 1109 struct tcphdr *th = &pd->hdr.tcp; 1110 u_short reason; 1111 u_int8_t flags; 1112 u_int rewrite = 0; 1113 1114 flags = th->th_flags; 1115 if (flags & TH_SYN) { 1116 /* Illegal packet */ 1117 if (flags & TH_RST) 1118 goto tcp_drop; 1119 1120 if (flags & TH_FIN) /* XXX why clear instead of drop? */ 1121 flags &= ~TH_FIN; 1122 } else { 1123 /* Illegal packet */ 1124 if (!(flags & (TH_ACK|TH_RST))) 1125 goto tcp_drop; 1126 } 1127 1128 if (!(flags & TH_ACK)) { 1129 /* These flags are only valid if ACK is set */ 1130 if (flags & (TH_FIN|TH_PUSH|TH_URG)) 1131 goto tcp_drop; 1132 } 1133 1134 /* If flags changed, or reserved data set, then adjust */ 1135 if (flags != th->th_flags || th->th_x2 != 0) { 1136 /* hack: set 4-bit th_x2 = 0 */ 1137 u_int8_t *th_off = (u_int8_t*)(&th->th_ack+1); 1138 pf_patch_8(pd, th_off, th->th_off << 4, PF_HI); 1139 1140 pf_patch_8(pd, &th->th_flags, flags, PF_LO); 1141 rewrite = 1; 1142 } 1143 1144 /* Remove urgent pointer, if TH_URG is not set */ 1145 if (!(flags & TH_URG) && th->th_urp) { 1146 pf_patch_16(pd, &th->th_urp, 0); 1147 rewrite = 1; 1148 } 1149 1150 /* copy back packet headers if we sanitized */ 1151 if (rewrite) { 1152 m_copyback(pd->m, pd->off, sizeof(*th), th, M_NOWAIT); 1153 } 1154 1155 return (PF_PASS); 1156 1157 tcp_drop: 1158 REASON_SET(&reason, PFRES_NORM); 1159 return (PF_DROP); 1160 } 1161 1162 int 1163 pf_normalize_tcp_init(struct pf_pdesc *pd, struct pf_state_peer *src) 1164 { 1165 struct tcphdr *th = &pd->hdr.tcp; 1166 u_int32_t tsval, tsecr; 1167 int olen; 1168 u_int8_t opts[MAX_TCPOPTLEN], *opt; 1169 1170 1171 KASSERT(src->scrub == NULL); 1172 1173 src->scrub = pool_get(&pf_state_scrub_pl, PR_NOWAIT); 1174 if (src->scrub == NULL) 1175 return (1); 1176 memset(src->scrub, 0, sizeof(*src->scrub)); 1177 1178 switch (pd->af) { 1179 case AF_INET: { 1180 struct ip *h = mtod(pd->m, struct ip *); 1181 src->scrub->pfss_ttl = h->ip_ttl; 1182 break; 1183 } 1184 #ifdef INET6 1185 case AF_INET6: { 1186 struct ip6_hdr *h = mtod(pd->m, struct ip6_hdr *); 1187 src->scrub->pfss_ttl = h->ip6_hlim; 1188 break; 1189 } 1190 #endif /* INET6 */ 1191 default: 1192 unhandled_af(pd->af); 1193 } 1194 1195 /* 1196 * All normalizations below are only begun if we see the start of 1197 * the connections. They must all set an enabled bit in pfss_flags 1198 */ 1199 if ((th->th_flags & TH_SYN) == 0) 1200 return (0); 1201 1202 olen = (th->th_off << 2) - sizeof(*th); 1203 if (olen < TCPOLEN_TIMESTAMP || !pf_pull_hdr(pd->m, 1204 pd->off + sizeof(*th), opts, olen, NULL, NULL, pd->af)) 1205 return (0); 1206 1207 opt = opts; 1208 while ((opt = pf_find_tcpopt(opt, opts, olen, 1209 TCPOPT_TIMESTAMP, TCPOLEN_TIMESTAMP)) != NULL) { 1210 1211 src->scrub->pfss_flags |= PFSS_TIMESTAMP; 1212 src->scrub->pfss_ts_mod = arc4random(); 1213 /* note PFSS_PAWS not set yet */ 1214 memcpy(&tsval, &opt[2], sizeof(u_int32_t)); 1215 memcpy(&tsecr, &opt[6], sizeof(u_int32_t)); 1216 src->scrub->pfss_tsval0 = ntohl(tsval); 1217 src->scrub->pfss_tsval = ntohl(tsval); 1218 src->scrub->pfss_tsecr = ntohl(tsecr); 1219 getmicrouptime(&src->scrub->pfss_last); 1220 1221 opt += opt[1]; 1222 } 1223 1224 return (0); 1225 } 1226 1227 void 1228 pf_normalize_tcp_cleanup(struct pf_state *state) 1229 { 1230 if (state->src.scrub) 1231 pool_put(&pf_state_scrub_pl, state->src.scrub); 1232 if (state->dst.scrub) 1233 pool_put(&pf_state_scrub_pl, state->dst.scrub); 1234 1235 /* Someday... flush the TCP segment reassembly descriptors. */ 1236 } 1237 1238 int 1239 pf_normalize_tcp_stateful(struct pf_pdesc *pd, u_short *reason, 1240 struct pf_state *state, struct pf_state_peer *src, 1241 struct pf_state_peer *dst, int *writeback) 1242 { 1243 struct tcphdr *th = &pd->hdr.tcp; 1244 struct timeval uptime; 1245 u_int tsval_from_last; 1246 u_int32_t tsval, tsecr; 1247 int copyback = 0; 1248 int got_ts = 0; 1249 int olen; 1250 u_int8_t opts[MAX_TCPOPTLEN], *opt; 1251 1252 KASSERT(src->scrub || dst->scrub); 1253 1254 /* 1255 * Enforce the minimum TTL seen for this connection. Negate a common 1256 * technique to evade an intrusion detection system and confuse 1257 * firewall state code. 1258 */ 1259 switch (pd->af) { 1260 case AF_INET: 1261 if (src->scrub) { 1262 struct ip *h = mtod(pd->m, struct ip *); 1263 if (h->ip_ttl > src->scrub->pfss_ttl) 1264 src->scrub->pfss_ttl = h->ip_ttl; 1265 h->ip_ttl = src->scrub->pfss_ttl; 1266 } 1267 break; 1268 #ifdef INET6 1269 case AF_INET6: 1270 if (src->scrub) { 1271 struct ip6_hdr *h = mtod(pd->m, struct ip6_hdr *); 1272 if (h->ip6_hlim > src->scrub->pfss_ttl) 1273 src->scrub->pfss_ttl = h->ip6_hlim; 1274 h->ip6_hlim = src->scrub->pfss_ttl; 1275 } 1276 break; 1277 #endif /* INET6 */ 1278 default: 1279 unhandled_af(pd->af); 1280 } 1281 1282 olen = (th->th_off << 2) - sizeof(*th); 1283 1284 if (olen >= TCPOLEN_TIMESTAMP && 1285 ((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) || 1286 (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) && 1287 pf_pull_hdr(pd->m, pd->off + sizeof(*th), opts, olen, NULL, NULL, 1288 pd->af)) { 1289 1290 /* Modulate the timestamps. Can be used for NAT detection, OS 1291 * uptime determination or reboot detection. 1292 */ 1293 opt = opts; 1294 while ((opt = pf_find_tcpopt(opt, opts, olen, 1295 TCPOPT_TIMESTAMP, TCPOLEN_TIMESTAMP)) != NULL) { 1296 1297 u_int8_t *ts = opt + 2; 1298 u_int8_t *tsr = opt + 6; 1299 1300 if (got_ts) { 1301 /* Huh? Multiple timestamps!? */ 1302 if (pf_status.debug >= LOG_NOTICE) { 1303 log(LOG_NOTICE, 1304 "pf: %s: multiple TS??", __func__); 1305 pf_print_state(state); 1306 addlog("\n"); 1307 } 1308 REASON_SET(reason, PFRES_TS); 1309 return (PF_DROP); 1310 } 1311 1312 memcpy(&tsval, ts, sizeof(u_int32_t)); 1313 memcpy(&tsecr, tsr, sizeof(u_int32_t)); 1314 1315 /* modulate TS */ 1316 if (tsval && src->scrub && 1317 (src->scrub->pfss_flags & PFSS_TIMESTAMP)) { 1318 /* tsval used further on */ 1319 tsval = ntohl(tsval); 1320 pf_patch_32_unaligned(pd, 1321 ts, htonl(tsval + src->scrub->pfss_ts_mod), 1322 PF_ALGNMNT(ts - opts)); 1323 copyback = 1; 1324 } 1325 1326 /* modulate TS reply if any (!0) */ 1327 if (tsecr && dst->scrub && 1328 (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) { 1329 /* tsecr used further on */ 1330 tsecr = ntohl(tsecr) - dst->scrub->pfss_ts_mod; 1331 pf_patch_32_unaligned(pd, 1332 tsr, htonl(tsecr), PF_ALGNMNT(tsr - opts)); 1333 copyback = 1; 1334 } 1335 1336 got_ts = 1; 1337 opt += opt[1]; 1338 } 1339 1340 if (copyback) { 1341 /* Copyback the options, caller copies back header */ 1342 *writeback = 1; 1343 m_copyback(pd->m, pd->off + sizeof(*th), olen, opts, M_NOWAIT); 1344 } 1345 } 1346 1347 1348 /* 1349 * Must invalidate PAWS checks on connections idle for too long. 1350 * The fastest allowed timestamp clock is 1ms. That turns out to 1351 * be about 24 days before it wraps. XXX Right now our lowerbound 1352 * TS echo check only works for the first 12 days of a connection 1353 * when the TS has exhausted half its 32bit space 1354 */ 1355 #define TS_MAX_IDLE (24*24*60*60) 1356 #define TS_MAX_CONN (12*24*60*60) /* XXX remove when better tsecr check */ 1357 1358 getmicrouptime(&uptime); 1359 if (src->scrub && (src->scrub->pfss_flags & PFSS_PAWS) && 1360 (uptime.tv_sec - src->scrub->pfss_last.tv_sec > TS_MAX_IDLE || 1361 getuptime() - state->creation > TS_MAX_CONN)) { 1362 if (pf_status.debug >= LOG_NOTICE) { 1363 log(LOG_NOTICE, "pf: src idled out of PAWS "); 1364 pf_print_state(state); 1365 addlog("\n"); 1366 } 1367 src->scrub->pfss_flags = 1368 (src->scrub->pfss_flags & ~PFSS_PAWS) | PFSS_PAWS_IDLED; 1369 } 1370 if (dst->scrub && (dst->scrub->pfss_flags & PFSS_PAWS) && 1371 uptime.tv_sec - dst->scrub->pfss_last.tv_sec > TS_MAX_IDLE) { 1372 if (pf_status.debug >= LOG_NOTICE) { 1373 log(LOG_NOTICE, "pf: dst idled out of PAWS "); 1374 pf_print_state(state); 1375 addlog("\n"); 1376 } 1377 dst->scrub->pfss_flags = 1378 (dst->scrub->pfss_flags & ~PFSS_PAWS) | PFSS_PAWS_IDLED; 1379 } 1380 1381 if (got_ts && src->scrub && dst->scrub && 1382 (src->scrub->pfss_flags & PFSS_PAWS) && 1383 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1384 /* Validate that the timestamps are "in-window". 1385 * RFC1323 describes TCP Timestamp options that allow 1386 * measurement of RTT (round trip time) and PAWS 1387 * (protection against wrapped sequence numbers). PAWS 1388 * gives us a set of rules for rejecting packets on 1389 * long fat pipes (packets that were somehow delayed 1390 * in transit longer than the time it took to send the 1391 * full TCP sequence space of 4Gb). We can use these 1392 * rules and infer a few others that will let us treat 1393 * the 32bit timestamp and the 32bit echoed timestamp 1394 * as sequence numbers to prevent a blind attacker from 1395 * inserting packets into a connection. 1396 * 1397 * RFC1323 tells us: 1398 * - The timestamp on this packet must be greater than 1399 * or equal to the last value echoed by the other 1400 * endpoint. The RFC says those will be discarded 1401 * since it is a dup that has already been acked. 1402 * This gives us a lowerbound on the timestamp. 1403 * timestamp >= other last echoed timestamp 1404 * - The timestamp will be less than or equal to 1405 * the last timestamp plus the time between the 1406 * last packet and now. The RFC defines the max 1407 * clock rate as 1ms. We will allow clocks to be 1408 * up to 10% fast and will allow a total difference 1409 * or 30 seconds due to a route change. And this 1410 * gives us an upperbound on the timestamp. 1411 * timestamp <= last timestamp + max ticks 1412 * We have to be careful here. Windows will send an 1413 * initial timestamp of zero and then initialize it 1414 * to a random value after the 3whs; presumably to 1415 * avoid a DoS by having to call an expensive RNG 1416 * during a SYN flood. Proof MS has at least one 1417 * good security geek. 1418 * 1419 * - The TCP timestamp option must also echo the other 1420 * endpoints timestamp. The timestamp echoed is the 1421 * one carried on the earliest unacknowledged segment 1422 * on the left edge of the sequence window. The RFC 1423 * states that the host will reject any echoed 1424 * timestamps that were larger than any ever sent. 1425 * This gives us an upperbound on the TS echo. 1426 * tescr <= largest_tsval 1427 * - The lowerbound on the TS echo is a little more 1428 * tricky to determine. The other endpoint's echoed 1429 * values will not decrease. But there may be 1430 * network conditions that re-order packets and 1431 * cause our view of them to decrease. For now the 1432 * only lowerbound we can safely determine is that 1433 * the TS echo will never be less than the original 1434 * TS. XXX There is probably a better lowerbound. 1435 * Remove TS_MAX_CONN with better lowerbound check. 1436 * tescr >= other original TS 1437 * 1438 * It is also important to note that the fastest 1439 * timestamp clock of 1ms will wrap its 32bit space in 1440 * 24 days. So we just disable TS checking after 24 1441 * days of idle time. We actually must use a 12d 1442 * connection limit until we can come up with a better 1443 * lowerbound to the TS echo check. 1444 */ 1445 struct timeval delta_ts; 1446 int ts_fudge; 1447 1448 /* 1449 * PFTM_TS_DIFF is how many seconds of leeway to allow 1450 * a host's timestamp. This can happen if the previous 1451 * packet got delayed in transit for much longer than 1452 * this packet. 1453 */ 1454 if ((ts_fudge = state->rule.ptr->timeout[PFTM_TS_DIFF]) == 0) 1455 ts_fudge = pf_default_rule.timeout[PFTM_TS_DIFF]; 1456 1457 /* Calculate max ticks since the last timestamp */ 1458 #define TS_MAXFREQ 1100 /* RFC max TS freq of 1Khz + 10% skew */ 1459 #define TS_MICROSECS 1000000 /* microseconds per second */ 1460 timersub(&uptime, &src->scrub->pfss_last, &delta_ts); 1461 tsval_from_last = (delta_ts.tv_sec + ts_fudge) * TS_MAXFREQ; 1462 tsval_from_last += delta_ts.tv_usec / (TS_MICROSECS/TS_MAXFREQ); 1463 1464 if ((src->state >= TCPS_ESTABLISHED && 1465 dst->state >= TCPS_ESTABLISHED) && 1466 (SEQ_LT(tsval, dst->scrub->pfss_tsecr) || 1467 SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) || 1468 (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) || 1469 SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) { 1470 /* Bad RFC1323 implementation or an insertion attack. 1471 * 1472 * - Solaris 2.6 and 2.7 are known to send another ACK 1473 * after the FIN,FIN|ACK,ACK closing that carries 1474 * an old timestamp. 1475 */ 1476 1477 DPFPRINTF(LOG_NOTICE, "Timestamp failed %c%c%c%c", 1478 SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '0' : ' ', 1479 SEQ_GT(tsval, src->scrub->pfss_tsval + 1480 tsval_from_last) ? '1' : ' ', 1481 SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ', 1482 SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' '); 1483 DPFPRINTF(LOG_NOTICE, " tsval: %u tsecr: %u " 1484 "+ticks: %u idle: %llu.%06lus", tsval, tsecr, 1485 tsval_from_last, (long long)delta_ts.tv_sec, 1486 delta_ts.tv_usec); 1487 DPFPRINTF(LOG_NOTICE, " src->tsval: %u tsecr: %u", 1488 src->scrub->pfss_tsval, src->scrub->pfss_tsecr); 1489 DPFPRINTF(LOG_NOTICE, " dst->tsval: %u tsecr: %u " 1490 "tsval0: %u", dst->scrub->pfss_tsval, 1491 dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0); 1492 if (pf_status.debug >= LOG_NOTICE) { 1493 log(LOG_NOTICE, "pf: "); 1494 pf_print_state(state); 1495 pf_print_flags(th->th_flags); 1496 addlog("\n"); 1497 } 1498 REASON_SET(reason, PFRES_TS); 1499 return (PF_DROP); 1500 } 1501 /* XXX I'd really like to require tsecr but it's optional */ 1502 } else if (!got_ts && (th->th_flags & TH_RST) == 0 && 1503 ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED) 1504 || pd->p_len > 0 || (th->th_flags & TH_SYN)) && 1505 src->scrub && dst->scrub && 1506 (src->scrub->pfss_flags & PFSS_PAWS) && 1507 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1508 /* Didn't send a timestamp. Timestamps aren't really useful 1509 * when: 1510 * - connection opening or closing (often not even sent). 1511 * but we must not let an attacker to put a FIN on a 1512 * data packet to sneak it through our ESTABLISHED check. 1513 * - on a TCP reset. RFC suggests not even looking at TS. 1514 * - on an empty ACK. The TS will not be echoed so it will 1515 * probably not help keep the RTT calculation in sync and 1516 * there isn't as much danger when the sequence numbers 1517 * got wrapped. So some stacks don't include TS on empty 1518 * ACKs :-( 1519 * 1520 * To minimize the disruption to mostly RFC1323 conformant 1521 * stacks, we will only require timestamps on data packets. 1522 * 1523 * And what do ya know, we cannot require timestamps on data 1524 * packets. There appear to be devices that do legitimate 1525 * TCP connection hijacking. There are HTTP devices that allow 1526 * a 3whs (with timestamps) and then buffer the HTTP request. 1527 * If the intermediate device has the HTTP response cache, it 1528 * will spoof the response but not bother timestamping its 1529 * packets. So we can look for the presence of a timestamp in 1530 * the first data packet and if there, require it in all future 1531 * packets. 1532 */ 1533 1534 if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) { 1535 /* 1536 * Hey! Someone tried to sneak a packet in. Or the 1537 * stack changed its RFC1323 behavior?!?! 1538 */ 1539 if (pf_status.debug >= LOG_NOTICE) { 1540 log(LOG_NOTICE, 1541 "pf: did not receive expected RFC1323 " 1542 "timestamp"); 1543 pf_print_state(state); 1544 pf_print_flags(th->th_flags); 1545 addlog("\n"); 1546 } 1547 REASON_SET(reason, PFRES_TS); 1548 return (PF_DROP); 1549 } 1550 } 1551 1552 /* 1553 * We will note if a host sends his data packets with or without 1554 * timestamps. And require all data packets to contain a timestamp 1555 * if the first does. PAWS implicitly requires that all data packets be 1556 * timestamped. But I think there are middle-man devices that hijack 1557 * TCP streams immediately after the 3whs and don't timestamp their 1558 * packets (seen in a WWW accelerator or cache). 1559 */ 1560 if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags & 1561 (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) { 1562 if (got_ts) 1563 src->scrub->pfss_flags |= PFSS_DATA_TS; 1564 else { 1565 src->scrub->pfss_flags |= PFSS_DATA_NOTS; 1566 if (pf_status.debug >= LOG_NOTICE && dst->scrub && 1567 (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) { 1568 /* Don't warn if other host rejected RFC1323 */ 1569 log(LOG_NOTICE, 1570 "pf: broken RFC1323 stack did not " 1571 "timestamp data packet. Disabled PAWS " 1572 "security."); 1573 pf_print_state(state); 1574 pf_print_flags(th->th_flags); 1575 addlog("\n"); 1576 } 1577 } 1578 } 1579 1580 /* 1581 * Update PAWS values 1582 */ 1583 if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags & 1584 (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) { 1585 getmicrouptime(&src->scrub->pfss_last); 1586 if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) || 1587 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1588 src->scrub->pfss_tsval = tsval; 1589 1590 if (tsecr) { 1591 if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) || 1592 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1593 src->scrub->pfss_tsecr = tsecr; 1594 1595 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 && 1596 (SEQ_LT(tsval, src->scrub->pfss_tsval0) || 1597 src->scrub->pfss_tsval0 == 0)) { 1598 /* tsval0 MUST be the lowest timestamp */ 1599 src->scrub->pfss_tsval0 = tsval; 1600 } 1601 1602 /* Only fully initialized after a TS gets echoed */ 1603 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0) 1604 src->scrub->pfss_flags |= PFSS_PAWS; 1605 } 1606 } 1607 1608 /* I have a dream.... TCP segment reassembly.... */ 1609 return (0); 1610 } 1611 1612 int 1613 pf_normalize_mss(struct pf_pdesc *pd, u_int16_t maxmss) 1614 { 1615 int olen, optsoff; 1616 u_int8_t opts[MAX_TCPOPTLEN], *opt; 1617 1618 olen = (pd->hdr.tcp.th_off << 2) - sizeof(struct tcphdr); 1619 optsoff = pd->off + sizeof(struct tcphdr); 1620 if (olen < TCPOLEN_MAXSEG || 1621 !pf_pull_hdr(pd->m, optsoff, opts, olen, NULL, NULL, pd->af)) 1622 return (0); 1623 1624 opt = opts; 1625 while ((opt = pf_find_tcpopt(opt, opts, olen, 1626 TCPOPT_MAXSEG, TCPOLEN_MAXSEG)) != NULL) { 1627 u_int16_t mss; 1628 u_int8_t *mssp = opt + 2; 1629 memcpy(&mss, mssp, sizeof(mss)); 1630 if (ntohs(mss) > maxmss) { 1631 size_t mssoffopts = mssp - opts; 1632 pf_patch_16_unaligned(pd, &mss, 1633 htons(maxmss), PF_ALGNMNT(mssoffopts)); 1634 m_copyback(pd->m, optsoff + mssoffopts, 1635 sizeof(mss), &mss, M_NOWAIT); 1636 m_copyback(pd->m, pd->off, 1637 sizeof(struct tcphdr), &pd->hdr.tcp, M_NOWAIT); 1638 } 1639 1640 opt += opt[1]; 1641 } 1642 1643 return (0); 1644 } 1645 1646 void 1647 pf_scrub(struct mbuf *m, u_int16_t flags, sa_family_t af, u_int8_t min_ttl, 1648 u_int8_t tos) 1649 { 1650 struct ip *h = mtod(m, struct ip *); 1651 #ifdef INET6 1652 struct ip6_hdr *h6 = mtod(m, struct ip6_hdr *); 1653 #endif /* INET6 */ 1654 1655 /* Clear IP_DF if no-df was requested */ 1656 if (flags & PFSTATE_NODF && af == AF_INET && h->ip_off & htons(IP_DF)) 1657 h->ip_off &= htons(~IP_DF); 1658 1659 /* Enforce a minimum ttl, may cause endless packet loops */ 1660 if (min_ttl && af == AF_INET && h->ip_ttl < min_ttl) 1661 h->ip_ttl = min_ttl; 1662 #ifdef INET6 1663 if (min_ttl && af == AF_INET6 && h6->ip6_hlim < min_ttl) 1664 h6->ip6_hlim = min_ttl; 1665 #endif /* INET6 */ 1666 1667 /* Enforce tos */ 1668 if (flags & PFSTATE_SETTOS) { 1669 if (af == AF_INET) 1670 h->ip_tos = tos | (h->ip_tos & IPTOS_ECN_MASK); 1671 #ifdef INET6 1672 if (af == AF_INET6) { 1673 /* drugs are unable to explain such idiocy */ 1674 h6->ip6_flow &= ~htonl(0x0fc00000); 1675 h6->ip6_flow |= htonl(((u_int32_t)tos) << 20); 1676 } 1677 #endif /* INET6 */ 1678 } 1679 1680 /* random-id, but not for fragments */ 1681 if (flags & PFSTATE_RANDOMID && af == AF_INET && 1682 !(h->ip_off & ~htons(IP_DF))) 1683 h->ip_id = htons(ip_randomid()); 1684 } 1685