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sys/net/pf_norm.c
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1 /* $OpenBSD: pf_norm.c,v 1.226 2022/11/06 18:05:05 dlg 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 if ((frag = pf_fillup_fragment(&key, ip->ip_id, frent, reason)) 805 == NULL) 806 return (PF_DROP); 807 808 /* The mbuf is part of the fragment entry, no direct free or access */ 809 m = *m0 = NULL; 810 811 if (frag->fr_holes) { 812 DPFPRINTF(LOG_DEBUG, "frag %d, holes %d", 813 frag->fr_id, frag->fr_holes); 814 return (PF_PASS); /* drop because *m0 is NULL, no error */ 815 } 816 817 /* We have all the data */ 818 frent = TAILQ_FIRST(&frag->fr_queue); 819 KASSERT(frent != NULL); 820 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + 821 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; 822 hdrlen = frent->fe_hdrlen; 823 m = *m0 = pf_join_fragment(frag); 824 frag = NULL; 825 m_calchdrlen(m); 826 827 ip = mtod(m, struct ip *); 828 ip->ip_len = htons(hdrlen + total); 829 ip->ip_off &= ~(IP_MF|IP_OFFMASK); 830 831 if (hdrlen + total > IP_MAXPACKET) { 832 DPFPRINTF(LOG_NOTICE, "drop: too big: %d", total); 833 ip->ip_len = 0; 834 REASON_SET(reason, PFRES_SHORT); 835 /* PF_DROP requires a valid mbuf *m0 in pf_test() */ 836 return (PF_DROP); 837 } 838 839 DPFPRINTF(LOG_INFO, "complete: %p(%d)", m, ntohs(ip->ip_len)); 840 return (PF_PASS); 841 } 842 843 #ifdef INET6 844 int 845 pf_reassemble6(struct mbuf **m0, struct ip6_frag *fraghdr, 846 u_int16_t hdrlen, u_int16_t extoff, int dir, u_short *reason) 847 { 848 struct mbuf *m = *m0; 849 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 850 struct m_tag *mtag; 851 struct pf_fragment_tag *ftag; 852 struct pf_frent *frent; 853 struct pf_fragment *frag; 854 struct pf_frnode key; 855 int off; 856 u_int16_t total, maxlen; 857 u_int8_t proto; 858 859 /* Get an entry for the fragment queue */ 860 if ((frent = pf_create_fragment(reason)) == NULL) 861 return (PF_DROP); 862 863 frent->fe_m = m; 864 frent->fe_hdrlen = hdrlen; 865 frent->fe_extoff = extoff; 866 frent->fe_len = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - hdrlen; 867 frent->fe_off = ntohs(fraghdr->ip6f_offlg & IP6F_OFF_MASK); 868 frent->fe_mff = fraghdr->ip6f_offlg & IP6F_MORE_FRAG; 869 870 key.fn_src.v6 = ip6->ip6_src; 871 key.fn_dst.v6 = ip6->ip6_dst; 872 key.fn_af = AF_INET6; 873 /* Only the first fragment's protocol is relevant */ 874 key.fn_proto = 0; 875 key.fn_direction = dir; 876 877 if ((frag = pf_fillup_fragment(&key, fraghdr->ip6f_ident, frent, 878 reason)) == NULL) 879 return (PF_DROP); 880 881 /* The mbuf is part of the fragment entry, no direct free or access */ 882 m = *m0 = NULL; 883 884 if (frag->fr_holes) { 885 DPFPRINTF(LOG_DEBUG, "frag %#08x, holes %d", 886 frag->fr_id, frag->fr_holes); 887 return (PF_PASS); /* drop because *m0 is NULL, no error */ 888 } 889 890 /* We have all the data */ 891 frent = TAILQ_FIRST(&frag->fr_queue); 892 KASSERT(frent != NULL); 893 extoff = frent->fe_extoff; 894 maxlen = frag->fr_maxlen; 895 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + 896 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; 897 hdrlen = frent->fe_hdrlen - sizeof(struct ip6_frag); 898 m = *m0 = pf_join_fragment(frag); 899 frag = NULL; 900 901 /* Take protocol from first fragment header */ 902 if ((m = m_getptr(m, hdrlen + offsetof(struct ip6_frag, ip6f_nxt), 903 &off)) == NULL) 904 panic("%s: short frag mbuf chain", __func__); 905 proto = *(mtod(m, caddr_t) + off); 906 m = *m0; 907 908 /* Delete frag6 header */ 909 if (frag6_deletefraghdr(m, hdrlen) != 0) 910 goto fail; 911 912 m_calchdrlen(m); 913 914 if ((mtag = m_tag_get(PACKET_TAG_PF_REASSEMBLED, sizeof(struct 915 pf_fragment_tag), M_NOWAIT)) == NULL) 916 goto fail; 917 ftag = (struct pf_fragment_tag *)(mtag + 1); 918 ftag->ft_hdrlen = hdrlen; 919 ftag->ft_extoff = extoff; 920 ftag->ft_maxlen = maxlen; 921 m_tag_prepend(m, mtag); 922 923 ip6 = mtod(m, struct ip6_hdr *); 924 ip6->ip6_plen = htons(hdrlen - sizeof(struct ip6_hdr) + total); 925 if (extoff) { 926 /* Write protocol into next field of last extension header */ 927 if ((m = m_getptr(m, extoff + offsetof(struct ip6_ext, 928 ip6e_nxt), &off)) == NULL) 929 panic("%s: short ext mbuf chain", __func__); 930 *(mtod(m, caddr_t) + off) = proto; 931 m = *m0; 932 } else 933 ip6->ip6_nxt = proto; 934 935 if (hdrlen - sizeof(struct ip6_hdr) + total > IPV6_MAXPACKET) { 936 DPFPRINTF(LOG_NOTICE, "drop: too big: %d", total); 937 ip6->ip6_plen = 0; 938 REASON_SET(reason, PFRES_SHORT); 939 /* PF_DROP requires a valid mbuf *m0 in pf_test6() */ 940 return (PF_DROP); 941 } 942 943 DPFPRINTF(LOG_INFO, "complete: %p(%d)", m, ntohs(ip6->ip6_plen)); 944 return (PF_PASS); 945 946 fail: 947 REASON_SET(reason, PFRES_MEMORY); 948 /* PF_DROP requires a valid mbuf *m0 in pf_test6(), will free later */ 949 return (PF_DROP); 950 } 951 952 int 953 pf_refragment6(struct mbuf **m0, struct m_tag *mtag, struct sockaddr_in6 *dst, 954 struct ifnet *ifp, struct rtentry *rt) 955 { 956 struct mbuf *m = *m0; 957 struct mbuf_list fml; 958 struct pf_fragment_tag *ftag = (struct pf_fragment_tag *)(mtag + 1); 959 u_int32_t mtu; 960 u_int16_t hdrlen, extoff, maxlen; 961 u_int8_t proto; 962 int error; 963 964 hdrlen = ftag->ft_hdrlen; 965 extoff = ftag->ft_extoff; 966 maxlen = ftag->ft_maxlen; 967 m_tag_delete(m, mtag); 968 mtag = NULL; 969 ftag = NULL; 970 971 /* Checksum must be calculated for the whole packet */ 972 in6_proto_cksum_out(m, NULL); 973 974 if (extoff) { 975 int off; 976 977 /* Use protocol from next field of last extension header */ 978 if ((m = m_getptr(m, extoff + offsetof(struct ip6_ext, 979 ip6e_nxt), &off)) == NULL) 980 panic("%s: short ext mbuf chain", __func__); 981 proto = *(mtod(m, caddr_t) + off); 982 *(mtod(m, caddr_t) + off) = IPPROTO_FRAGMENT; 983 m = *m0; 984 } else { 985 struct ip6_hdr *hdr; 986 987 hdr = mtod(m, struct ip6_hdr *); 988 proto = hdr->ip6_nxt; 989 hdr->ip6_nxt = IPPROTO_FRAGMENT; 990 } 991 992 /* 993 * Maxlen may be less than 8 iff there was only a single 994 * fragment. As it was fragmented before, add a fragment 995 * header also for a single fragment. If total or maxlen 996 * is less than 8, ip6_fragment() will return EMSGSIZE and 997 * we drop the packet. 998 */ 999 mtu = hdrlen + sizeof(struct ip6_frag) + maxlen; 1000 error = ip6_fragment(m, &fml, hdrlen, proto, mtu); 1001 *m0 = NULL; /* ip6_fragment() has consumed original packet. */ 1002 if (error) { 1003 DPFPRINTF(LOG_NOTICE, "refragment error %d", error); 1004 return (PF_DROP); 1005 } 1006 1007 while ((m = ml_dequeue(&fml)) != NULL) { 1008 m->m_pkthdr.pf.flags |= PF_TAG_REFRAGMENTED; 1009 if (ifp == NULL) { 1010 ip6_forward(m, NULL, 0); 1011 } else if ((u_long)m->m_pkthdr.len <= ifp->if_mtu) { 1012 ifp->if_output(ifp, m, sin6tosa(dst), rt); 1013 } else { 1014 icmp6_error(m, ICMP6_PACKET_TOO_BIG, 0, ifp->if_mtu); 1015 } 1016 } 1017 1018 return (PF_PASS); 1019 } 1020 #endif /* INET6 */ 1021 1022 int 1023 pf_normalize_ip(struct pf_pdesc *pd, u_short *reason) 1024 { 1025 struct ip *h = mtod(pd->m, struct ip *); 1026 u_int16_t fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3; 1027 u_int16_t mff = (ntohs(h->ip_off) & IP_MF); 1028 1029 if (!fragoff && !mff) 1030 goto no_fragment; 1031 1032 /* Clear IP_DF if we're in no-df mode */ 1033 if (pf_status.reass & PF_REASS_NODF && h->ip_off & htons(IP_DF)) 1034 h->ip_off &= htons(~IP_DF); 1035 1036 /* We're dealing with a fragment now. Don't allow fragments 1037 * with IP_DF to enter the cache. If the flag was cleared by 1038 * no-df above, fine. Otherwise drop it. 1039 */ 1040 if (h->ip_off & htons(IP_DF)) { 1041 DPFPRINTF(LOG_NOTICE, "bad fragment: IP_DF"); 1042 REASON_SET(reason, PFRES_FRAG); 1043 return (PF_DROP); 1044 } 1045 1046 if (!pf_status.reass) 1047 return (PF_PASS); /* no reassembly */ 1048 1049 /* Returns PF_DROP or m is NULL or completely reassembled mbuf */ 1050 PF_FRAG_LOCK(); 1051 if (pf_reassemble(&pd->m, pd->dir, reason) != PF_PASS) { 1052 PF_FRAG_UNLOCK(); 1053 return (PF_DROP); 1054 } 1055 PF_FRAG_UNLOCK(); 1056 if (pd->m == NULL) 1057 return (PF_PASS); /* packet has been reassembled, no error */ 1058 1059 h = mtod(pd->m, struct ip *); 1060 1061 no_fragment: 1062 /* At this point, only IP_DF is allowed in ip_off */ 1063 if (h->ip_off & ~htons(IP_DF)) 1064 h->ip_off &= htons(IP_DF); 1065 1066 return (PF_PASS); 1067 } 1068 1069 #ifdef INET6 1070 int 1071 pf_normalize_ip6(struct pf_pdesc *pd, u_short *reason) 1072 { 1073 struct ip6_frag frag; 1074 1075 if (pd->fragoff == 0) 1076 goto no_fragment; 1077 1078 if (!pf_pull_hdr(pd->m, pd->fragoff, &frag, sizeof(frag), NULL, reason, 1079 AF_INET6)) 1080 return (PF_DROP); 1081 1082 if (!pf_status.reass) 1083 return (PF_PASS); /* no reassembly */ 1084 1085 /* Returns PF_DROP or m is NULL or completely reassembled mbuf */ 1086 PF_FRAG_LOCK(); 1087 if (pf_reassemble6(&pd->m, &frag, pd->fragoff + sizeof(frag), 1088 pd->extoff, pd->dir, reason) != PF_PASS) { 1089 PF_FRAG_UNLOCK(); 1090 return (PF_DROP); 1091 } 1092 PF_FRAG_UNLOCK(); 1093 if (pd->m == NULL) 1094 return (PF_PASS); /* packet has been reassembled, no error */ 1095 1096 no_fragment: 1097 return (PF_PASS); 1098 } 1099 #endif /* INET6 */ 1100 1101 int 1102 pf_normalize_tcp_alloc(struct pf_state_peer *src) 1103 { 1104 src->scrub = pool_get(&pf_state_scrub_pl, PR_NOWAIT | PR_ZERO); 1105 if (src->scrub == NULL) 1106 return (ENOMEM); 1107 1108 return (0); 1109 } 1110 1111 int 1112 pf_normalize_tcp(struct pf_pdesc *pd) 1113 { 1114 struct tcphdr *th = &pd->hdr.tcp; 1115 u_short reason; 1116 u_int8_t flags; 1117 u_int rewrite = 0; 1118 1119 flags = th->th_flags; 1120 if (flags & TH_SYN) { 1121 /* Illegal packet */ 1122 if (flags & TH_RST) 1123 goto tcp_drop; 1124 1125 if (flags & TH_FIN) /* XXX why clear instead of drop? */ 1126 flags &= ~TH_FIN; 1127 } else { 1128 /* Illegal packet */ 1129 if (!(flags & (TH_ACK|TH_RST))) 1130 goto tcp_drop; 1131 } 1132 1133 if (!(flags & TH_ACK)) { 1134 /* These flags are only valid if ACK is set */ 1135 if (flags & (TH_FIN|TH_PUSH|TH_URG)) 1136 goto tcp_drop; 1137 } 1138 1139 /* If flags changed, or reserved data set, then adjust */ 1140 if (flags != th->th_flags || th->th_x2 != 0) { 1141 /* hack: set 4-bit th_x2 = 0 */ 1142 u_int8_t *th_off = (u_int8_t*)(&th->th_ack+1); 1143 pf_patch_8(pd, th_off, th->th_off << 4, PF_HI); 1144 1145 pf_patch_8(pd, &th->th_flags, flags, PF_LO); 1146 rewrite = 1; 1147 } 1148 1149 /* Remove urgent pointer, if TH_URG is not set */ 1150 if (!(flags & TH_URG) && th->th_urp) { 1151 pf_patch_16(pd, &th->th_urp, 0); 1152 rewrite = 1; 1153 } 1154 1155 /* copy back packet headers if we sanitized */ 1156 if (rewrite) { 1157 m_copyback(pd->m, pd->off, sizeof(*th), th, M_NOWAIT); 1158 } 1159 1160 return (PF_PASS); 1161 1162 tcp_drop: 1163 REASON_SET(&reason, PFRES_NORM); 1164 return (PF_DROP); 1165 } 1166 1167 int 1168 pf_normalize_tcp_init(struct pf_pdesc *pd, struct pf_state_peer *src) 1169 { 1170 struct tcphdr *th = &pd->hdr.tcp; 1171 u_int32_t tsval, tsecr; 1172 int olen; 1173 u_int8_t opts[MAX_TCPOPTLEN], *opt; 1174 1175 1176 KASSERT(src->scrub == NULL); 1177 1178 if (pf_normalize_tcp_alloc(src) != 0) 1179 return (1); 1180 1181 switch (pd->af) { 1182 case AF_INET: { 1183 struct ip *h = mtod(pd->m, struct ip *); 1184 src->scrub->pfss_ttl = h->ip_ttl; 1185 break; 1186 } 1187 #ifdef INET6 1188 case AF_INET6: { 1189 struct ip6_hdr *h = mtod(pd->m, struct ip6_hdr *); 1190 src->scrub->pfss_ttl = h->ip6_hlim; 1191 break; 1192 } 1193 #endif /* INET6 */ 1194 default: 1195 unhandled_af(pd->af); 1196 } 1197 1198 /* 1199 * All normalizations below are only begun if we see the start of 1200 * the connections. They must all set an enabled bit in pfss_flags 1201 */ 1202 if ((th->th_flags & TH_SYN) == 0) 1203 return (0); 1204 1205 olen = (th->th_off << 2) - sizeof(*th); 1206 if (olen < TCPOLEN_TIMESTAMP || !pf_pull_hdr(pd->m, 1207 pd->off + sizeof(*th), opts, olen, NULL, NULL, pd->af)) 1208 return (0); 1209 1210 opt = opts; 1211 while ((opt = pf_find_tcpopt(opt, opts, olen, 1212 TCPOPT_TIMESTAMP, TCPOLEN_TIMESTAMP)) != NULL) { 1213 1214 src->scrub->pfss_flags |= PFSS_TIMESTAMP; 1215 src->scrub->pfss_ts_mod = arc4random(); 1216 /* note PFSS_PAWS not set yet */ 1217 memcpy(&tsval, &opt[2], sizeof(u_int32_t)); 1218 memcpy(&tsecr, &opt[6], sizeof(u_int32_t)); 1219 src->scrub->pfss_tsval0 = ntohl(tsval); 1220 src->scrub->pfss_tsval = ntohl(tsval); 1221 src->scrub->pfss_tsecr = ntohl(tsecr); 1222 getmicrouptime(&src->scrub->pfss_last); 1223 1224 opt += opt[1]; 1225 } 1226 1227 return (0); 1228 } 1229 1230 void 1231 pf_normalize_tcp_cleanup(struct pf_state *state) 1232 { 1233 if (state->src.scrub) 1234 pool_put(&pf_state_scrub_pl, state->src.scrub); 1235 if (state->dst.scrub) 1236 pool_put(&pf_state_scrub_pl, state->dst.scrub); 1237 1238 /* Someday... flush the TCP segment reassembly descriptors. */ 1239 } 1240 1241 int 1242 pf_normalize_tcp_stateful(struct pf_pdesc *pd, u_short *reason, 1243 struct pf_state *state, struct pf_state_peer *src, 1244 struct pf_state_peer *dst, int *writeback) 1245 { 1246 struct tcphdr *th = &pd->hdr.tcp; 1247 struct timeval uptime; 1248 u_int tsval_from_last; 1249 u_int32_t tsval, tsecr; 1250 int copyback = 0; 1251 int got_ts = 0; 1252 int olen; 1253 u_int8_t opts[MAX_TCPOPTLEN], *opt; 1254 1255 KASSERT(src->scrub || dst->scrub); 1256 1257 /* 1258 * Enforce the minimum TTL seen for this connection. Negate a common 1259 * technique to evade an intrusion detection system and confuse 1260 * firewall state code. 1261 */ 1262 switch (pd->af) { 1263 case AF_INET: 1264 if (src->scrub) { 1265 struct ip *h = mtod(pd->m, struct ip *); 1266 if (h->ip_ttl > src->scrub->pfss_ttl) 1267 src->scrub->pfss_ttl = h->ip_ttl; 1268 h->ip_ttl = src->scrub->pfss_ttl; 1269 } 1270 break; 1271 #ifdef INET6 1272 case AF_INET6: 1273 if (src->scrub) { 1274 struct ip6_hdr *h = mtod(pd->m, struct ip6_hdr *); 1275 if (h->ip6_hlim > src->scrub->pfss_ttl) 1276 src->scrub->pfss_ttl = h->ip6_hlim; 1277 h->ip6_hlim = src->scrub->pfss_ttl; 1278 } 1279 break; 1280 #endif /* INET6 */ 1281 default: 1282 unhandled_af(pd->af); 1283 } 1284 1285 olen = (th->th_off << 2) - sizeof(*th); 1286 1287 if (olen >= TCPOLEN_TIMESTAMP && 1288 ((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) || 1289 (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) && 1290 pf_pull_hdr(pd->m, pd->off + sizeof(*th), opts, olen, NULL, NULL, 1291 pd->af)) { 1292 1293 /* Modulate the timestamps. Can be used for NAT detection, OS 1294 * uptime determination or reboot detection. 1295 */ 1296 opt = opts; 1297 while ((opt = pf_find_tcpopt(opt, opts, olen, 1298 TCPOPT_TIMESTAMP, TCPOLEN_TIMESTAMP)) != NULL) { 1299 1300 u_int8_t *ts = opt + 2; 1301 u_int8_t *tsr = opt + 6; 1302 1303 if (got_ts) { 1304 /* Huh? Multiple timestamps!? */ 1305 if (pf_status.debug >= LOG_NOTICE) { 1306 log(LOG_NOTICE, 1307 "pf: %s: multiple TS??", __func__); 1308 pf_print_state(state); 1309 addlog("\n"); 1310 } 1311 REASON_SET(reason, PFRES_TS); 1312 return (PF_DROP); 1313 } 1314 1315 memcpy(&tsval, ts, sizeof(u_int32_t)); 1316 memcpy(&tsecr, tsr, sizeof(u_int32_t)); 1317 1318 /* modulate TS */ 1319 if (tsval && src->scrub && 1320 (src->scrub->pfss_flags & PFSS_TIMESTAMP)) { 1321 /* tsval used further on */ 1322 tsval = ntohl(tsval); 1323 pf_patch_32_unaligned(pd, 1324 ts, htonl(tsval + src->scrub->pfss_ts_mod), 1325 PF_ALGNMNT(ts - opts)); 1326 copyback = 1; 1327 } 1328 1329 /* modulate TS reply if any (!0) */ 1330 if (tsecr && dst->scrub && 1331 (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) { 1332 /* tsecr used further on */ 1333 tsecr = ntohl(tsecr) - dst->scrub->pfss_ts_mod; 1334 pf_patch_32_unaligned(pd, 1335 tsr, htonl(tsecr), PF_ALGNMNT(tsr - opts)); 1336 copyback = 1; 1337 } 1338 1339 got_ts = 1; 1340 opt += opt[1]; 1341 } 1342 1343 if (copyback) { 1344 /* Copyback the options, caller copies back header */ 1345 *writeback = 1; 1346 m_copyback(pd->m, pd->off + sizeof(*th), olen, opts, M_NOWAIT); 1347 } 1348 } 1349 1350 1351 /* 1352 * Must invalidate PAWS checks on connections idle for too long. 1353 * The fastest allowed timestamp clock is 1ms. That turns out to 1354 * be about 24 days before it wraps. XXX Right now our lowerbound 1355 * TS echo check only works for the first 12 days of a connection 1356 * when the TS has exhausted half its 32bit space 1357 */ 1358 #define TS_MAX_IDLE (24*24*60*60) 1359 #define TS_MAX_CONN (12*24*60*60) /* XXX remove when better tsecr check */ 1360 1361 getmicrouptime(&uptime); 1362 if (src->scrub && (src->scrub->pfss_flags & PFSS_PAWS) && 1363 (uptime.tv_sec - src->scrub->pfss_last.tv_sec > TS_MAX_IDLE || 1364 getuptime() - state->creation > TS_MAX_CONN)) { 1365 if (pf_status.debug >= LOG_NOTICE) { 1366 log(LOG_NOTICE, "pf: src idled out of PAWS "); 1367 pf_print_state(state); 1368 addlog("\n"); 1369 } 1370 src->scrub->pfss_flags = 1371 (src->scrub->pfss_flags & ~PFSS_PAWS) | PFSS_PAWS_IDLED; 1372 } 1373 if (dst->scrub && (dst->scrub->pfss_flags & PFSS_PAWS) && 1374 uptime.tv_sec - dst->scrub->pfss_last.tv_sec > TS_MAX_IDLE) { 1375 if (pf_status.debug >= LOG_NOTICE) { 1376 log(LOG_NOTICE, "pf: dst idled out of PAWS "); 1377 pf_print_state(state); 1378 addlog("\n"); 1379 } 1380 dst->scrub->pfss_flags = 1381 (dst->scrub->pfss_flags & ~PFSS_PAWS) | PFSS_PAWS_IDLED; 1382 } 1383 1384 if (got_ts && src->scrub && dst->scrub && 1385 (src->scrub->pfss_flags & PFSS_PAWS) && 1386 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1387 /* Validate that the timestamps are "in-window". 1388 * RFC1323 describes TCP Timestamp options that allow 1389 * measurement of RTT (round trip time) and PAWS 1390 * (protection against wrapped sequence numbers). PAWS 1391 * gives us a set of rules for rejecting packets on 1392 * long fat pipes (packets that were somehow delayed 1393 * in transit longer than the time it took to send the 1394 * full TCP sequence space of 4Gb). We can use these 1395 * rules and infer a few others that will let us treat 1396 * the 32bit timestamp and the 32bit echoed timestamp 1397 * as sequence numbers to prevent a blind attacker from 1398 * inserting packets into a connection. 1399 * 1400 * RFC1323 tells us: 1401 * - The timestamp on this packet must be greater than 1402 * or equal to the last value echoed by the other 1403 * endpoint. The RFC says those will be discarded 1404 * since it is a dup that has already been acked. 1405 * This gives us a lowerbound on the timestamp. 1406 * timestamp >= other last echoed timestamp 1407 * - The timestamp will be less than or equal to 1408 * the last timestamp plus the time between the 1409 * last packet and now. The RFC defines the max 1410 * clock rate as 1ms. We will allow clocks to be 1411 * up to 10% fast and will allow a total difference 1412 * or 30 seconds due to a route change. And this 1413 * gives us an upperbound on the timestamp. 1414 * timestamp <= last timestamp + max ticks 1415 * We have to be careful here. Windows will send an 1416 * initial timestamp of zero and then initialize it 1417 * to a random value after the 3whs; presumably to 1418 * avoid a DoS by having to call an expensive RNG 1419 * during a SYN flood. Proof MS has at least one 1420 * good security geek. 1421 * 1422 * - The TCP timestamp option must also echo the other 1423 * endpoints timestamp. The timestamp echoed is the 1424 * one carried on the earliest unacknowledged segment 1425 * on the left edge of the sequence window. The RFC 1426 * states that the host will reject any echoed 1427 * timestamps that were larger than any ever sent. 1428 * This gives us an upperbound on the TS echo. 1429 * tescr <= largest_tsval 1430 * - The lowerbound on the TS echo is a little more 1431 * tricky to determine. The other endpoint's echoed 1432 * values will not decrease. But there may be 1433 * network conditions that re-order packets and 1434 * cause our view of them to decrease. For now the 1435 * only lowerbound we can safely determine is that 1436 * the TS echo will never be less than the original 1437 * TS. XXX There is probably a better lowerbound. 1438 * Remove TS_MAX_CONN with better lowerbound check. 1439 * tescr >= other original TS 1440 * 1441 * It is also important to note that the fastest 1442 * timestamp clock of 1ms will wrap its 32bit space in 1443 * 24 days. So we just disable TS checking after 24 1444 * days of idle time. We actually must use a 12d 1445 * connection limit until we can come up with a better 1446 * lowerbound to the TS echo check. 1447 */ 1448 struct timeval delta_ts; 1449 int ts_fudge; 1450 1451 /* 1452 * PFTM_TS_DIFF is how many seconds of leeway to allow 1453 * a host's timestamp. This can happen if the previous 1454 * packet got delayed in transit for much longer than 1455 * this packet. 1456 */ 1457 if ((ts_fudge = state->rule.ptr->timeout[PFTM_TS_DIFF]) == 0) 1458 ts_fudge = pf_default_rule.timeout[PFTM_TS_DIFF]; 1459 1460 /* Calculate max ticks since the last timestamp */ 1461 #define TS_MAXFREQ 1100 /* RFC max TS freq of 1Khz + 10% skew */ 1462 #define TS_MICROSECS 1000000 /* microseconds per second */ 1463 timersub(&uptime, &src->scrub->pfss_last, &delta_ts); 1464 tsval_from_last = (delta_ts.tv_sec + ts_fudge) * TS_MAXFREQ; 1465 tsval_from_last += delta_ts.tv_usec / (TS_MICROSECS/TS_MAXFREQ); 1466 1467 if ((src->state >= TCPS_ESTABLISHED && 1468 dst->state >= TCPS_ESTABLISHED) && 1469 (SEQ_LT(tsval, dst->scrub->pfss_tsecr) || 1470 SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) || 1471 (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) || 1472 SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) { 1473 /* Bad RFC1323 implementation or an insertion attack. 1474 * 1475 * - Solaris 2.6 and 2.7 are known to send another ACK 1476 * after the FIN,FIN|ACK,ACK closing that carries 1477 * an old timestamp. 1478 */ 1479 1480 DPFPRINTF(LOG_NOTICE, "Timestamp failed %c%c%c%c", 1481 SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '' : ' ', 1482 SEQ_GT(tsval, src->scrub->pfss_tsval + 1483 tsval_from_last) ? '1' : ' ', 1484 SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ', 1485 SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' '); 1486 DPFPRINTF(LOG_NOTICE, " tsval: %u tsecr: %u " 1487 "+ticks: %u idle: %llu.%06lus", tsval, tsecr, 1488 tsval_from_last, (long long)delta_ts.tv_sec, 1489 delta_ts.tv_usec); 1490 DPFPRINTF(LOG_NOTICE, " src->tsval: %u tsecr: %u", 1491 src->scrub->pfss_tsval, src->scrub->pfss_tsecr); 1492 DPFPRINTF(LOG_NOTICE, " dst->tsval: %u tsecr: %u " 1493 "tsval0: %u", dst->scrub->pfss_tsval, 1494 dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0); 1495 if (pf_status.debug >= LOG_NOTICE) { 1496 log(LOG_NOTICE, "pf: "); 1497 pf_print_state(state); 1498 pf_print_flags(th->th_flags); 1499 addlog("\n"); 1500 } 1501 REASON_SET(reason, PFRES_TS); 1502 return (PF_DROP); 1503 } 1504 /* XXX I'd really like to require tsecr but it's optional */ 1505 } else if (!got_ts && (th->th_flags & TH_RST) == 0 && 1506 ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED) 1507 || pd->p_len > 0 || (th->th_flags & TH_SYN)) && 1508 src->scrub && dst->scrub && 1509 (src->scrub->pfss_flags & PFSS_PAWS) && 1510 (dst->scrub->pfss_flags & PFSS_PAWS)) { 1511 /* Didn't send a timestamp. Timestamps aren't really useful 1512 * when: 1513 * - connection opening or closing (often not even sent). 1514 * but we must not let an attacker to put a FIN on a 1515 * data packet to sneak it through our ESTABLISHED check. 1516 * - on a TCP reset. RFC suggests not even looking at TS. 1517 * - on an empty ACK. The TS will not be echoed so it will 1518 * probably not help keep the RTT calculation in sync and 1519 * there isn't as much danger when the sequence numbers 1520 * got wrapped. So some stacks don't include TS on empty 1521 * ACKs :-( 1522 * 1523 * To minimize the disruption to mostly RFC1323 conformant 1524 * stacks, we will only require timestamps on data packets. 1525 * 1526 * And what do ya know, we cannot require timestamps on data 1527 * packets. There appear to be devices that do legitimate 1528 * TCP connection hijacking. There are HTTP devices that allow 1529 * a 3whs (with timestamps) and then buffer the HTTP request. 1530 * If the intermediate device has the HTTP response cache, it 1531 * will spoof the response but not bother timestamping its 1532 * packets. So we can look for the presence of a timestamp in 1533 * the first data packet and if there, require it in all future 1534 * packets. 1535 */ 1536 1537 if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) { 1538 /* 1539 * Hey! Someone tried to sneak a packet in. Or the 1540 * stack changed its RFC1323 behavior?!?! 1541 */ 1542 if (pf_status.debug >= LOG_NOTICE) { 1543 log(LOG_NOTICE, 1544 "pf: did not receive expected RFC1323 " 1545 "timestamp"); 1546 pf_print_state(state); 1547 pf_print_flags(th->th_flags); 1548 addlog("\n"); 1549 } 1550 REASON_SET(reason, PFRES_TS); 1551 return (PF_DROP); 1552 } 1553 } 1554 1555 /* 1556 * We will note if a host sends his data packets with or without 1557 * timestamps. And require all data packets to contain a timestamp 1558 * if the first does. PAWS implicitly requires that all data packets be 1559 * timestamped. But I think there are middle-man devices that hijack 1560 * TCP streams immediately after the 3whs and don't timestamp their 1561 * packets (seen in a WWW accelerator or cache). 1562 */ 1563 if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags & 1564 (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) { 1565 if (got_ts) 1566 src->scrub->pfss_flags |= PFSS_DATA_TS; 1567 else { 1568 src->scrub->pfss_flags |= PFSS_DATA_NOTS; 1569 if (pf_status.debug >= LOG_NOTICE && dst->scrub && 1570 (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) { 1571 /* Don't warn if other host rejected RFC1323 */ 1572 log(LOG_NOTICE, 1573 "pf: broken RFC1323 stack did not " 1574 "timestamp data packet. Disabled PAWS " 1575 "security."); 1576 pf_print_state(state); 1577 pf_print_flags(th->th_flags); 1578 addlog("\n"); 1579 } 1580 } 1581 } 1582 1583 /* 1584 * Update PAWS values 1585 */ 1586 if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags & 1587 (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) { 1588 getmicrouptime(&src->scrub->pfss_last); 1589 if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) || 1590 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1591 src->scrub->pfss_tsval = tsval; 1592 1593 if (tsecr) { 1594 if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) || 1595 (src->scrub->pfss_flags & PFSS_PAWS) == 0) 1596 src->scrub->pfss_tsecr = tsecr; 1597 1598 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 && 1599 (SEQ_LT(tsval, src->scrub->pfss_tsval0) || 1600 src->scrub->pfss_tsval0 == 0)) { 1601 /* tsval0 MUST be the lowest timestamp */ 1602 src->scrub->pfss_tsval0 = tsval; 1603 } 1604 1605 /* Only fully initialized after a TS gets echoed */ 1606 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0) 1607 src->scrub->pfss_flags |= PFSS_PAWS; 1608 } 1609 } 1610 1611 /* I have a dream.... TCP segment reassembly.... */ 1612 return (0); 1613 } 1614 1615 int 1616 pf_normalize_mss(struct pf_pdesc *pd, u_int16_t maxmss) 1617 { 1618 int olen, optsoff; 1619 u_int8_t opts[MAX_TCPOPTLEN], *opt; 1620 1621 olen = (pd->hdr.tcp.th_off << 2) - sizeof(struct tcphdr); 1622 optsoff = pd->off + sizeof(struct tcphdr); 1623 if (olen < TCPOLEN_MAXSEG || 1624 !pf_pull_hdr(pd->m, optsoff, opts, olen, NULL, NULL, pd->af)) 1625 return (0); 1626 1627 opt = opts; 1628 while ((opt = pf_find_tcpopt(opt, opts, olen, 1629 TCPOPT_MAXSEG, TCPOLEN_MAXSEG)) != NULL) { 1630 u_int16_t mss; 1631 u_int8_t *mssp = opt + 2; 1632 memcpy(&mss, mssp, sizeof(mss)); 1633 if (ntohs(mss) > maxmss) { 1634 size_t mssoffopts = mssp - opts; 1635 pf_patch_16_unaligned(pd, &mss, 1636 htons(maxmss), PF_ALGNMNT(mssoffopts)); 1637 m_copyback(pd->m, optsoff + mssoffopts, 1638 sizeof(mss), &mss, M_NOWAIT); 1639 m_copyback(pd->m, pd->off, 1640 sizeof(struct tcphdr), &pd->hdr.tcp, M_NOWAIT); 1641 } 1642 1643 opt += opt[1]; 1644 } 1645 1646 return (0); 1647 } 1648 1649 void 1650 pf_scrub(struct mbuf *m, u_int16_t flags, sa_family_t af, u_int8_t min_ttl, 1651 u_int8_t tos) 1652 { 1653 struct ip *h = mtod(m, struct ip *); 1654 #ifdef INET6 1655 struct ip6_hdr *h6 = mtod(m, struct ip6_hdr *); 1656 #endif /* INET6 */ 1657 u_int16_t old; 1658 1659 /* Clear IP_DF if no-df was requested */ 1660 if (flags & PFSTATE_NODF && af == AF_INET && h->ip_off & htons(IP_DF)) { 1661 old = h->ip_off; 1662 h->ip_off &= htons(~IP_DF); 1663 pf_cksum_fixup(&h->ip_sum, old, h->ip_off, 0); 1664 } 1665 1666 /* Enforce a minimum ttl, may cause endless packet loops */ 1667 if (min_ttl && af == AF_INET && h->ip_ttl < min_ttl) { 1668 old = h->ip_ttl; 1669 h->ip_ttl = min_ttl; 1670 pf_cksum_fixup(&h->ip_sum, old, h->ip_ttl, 0); 1671 } 1672 #ifdef INET6 1673 if (min_ttl && af == AF_INET6 && h6->ip6_hlim < min_ttl) 1674 h6->ip6_hlim = min_ttl; 1675 #endif /* INET6 */ 1676 1677 /* Enforce tos */ 1678 if (flags & PFSTATE_SETTOS) { 1679 if (af == AF_INET) { 1680 /* 1681 * ip_tos is 8 bit field at offset 1. Use 16 bit value 1682 * at offset 0. 1683 */ 1684 old = *(u_int16_t *)h; 1685 h->ip_tos = tos | (h->ip_tos & IPTOS_ECN_MASK); 1686 pf_cksum_fixup(&h->ip_sum, old, *(u_int16_t *)h, 0); 1687 } 1688 #ifdef INET6 1689 if (af == AF_INET6) { 1690 /* drugs are unable to explain such idiocy */ 1691 h6->ip6_flow &= ~htonl(0x0fc00000); 1692 h6->ip6_flow |= htonl(((u_int32_t)tos) << 20); 1693 } 1694 #endif /* INET6 */ 1695 } 1696 1697 /* random-id, but not for fragments */ 1698 if (flags & PFSTATE_RANDOMID && af == AF_INET && 1699 !(h->ip_off & ~htons(IP_DF))) { 1700 old = h->ip_id; 1701 h->ip_id = htons(ip_randomid()); 1702 pf_cksum_fixup(&h->ip_sum, old, h->ip_id, 0); 1703 } 1704 }
Cache object: 009a4194b0e37ae3cc82799d4daa0a4d
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