1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright 2001 Niels Provos <provos@citi.umich.edu>
5 * Copyright 2011-2018 Alexander Bluhm <bluhm@openbsd.org>
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * $OpenBSD: pf_norm.c,v 1.114 2009/01/29 14:11:45 henning Exp $
29 */
30
31 #include <sys/cdefs.h>
32 #include "opt_inet.h"
33 #include "opt_inet6.h"
34 #include "opt_pf.h"
35
36 #include <sys/param.h>
37 #include <sys/kernel.h>
38 #include <sys/lock.h>
39 #include <sys/mbuf.h>
40 #include <sys/mutex.h>
41 #include <sys/refcount.h>
42 #include <sys/socket.h>
43
44 #include <net/if.h>
45 #include <net/if_var.h>
46 #include <net/vnet.h>
47 #include <net/pfvar.h>
48 #include <net/if_pflog.h>
49
50 #include <netinet/in.h>
51 #include <netinet/ip.h>
52 #include <netinet/ip_var.h>
53 #include <netinet6/in6_var.h>
54 #include <netinet6/nd6.h>
55 #include <netinet6/ip6_var.h>
56 #include <netinet6/scope6_var.h>
57 #include <netinet/tcp.h>
58 #include <netinet/tcp_fsm.h>
59 #include <netinet/tcp_seq.h>
60 #include <netinet/sctp_constants.h>
61 #include <netinet/sctp_header.h>
62
63 #ifdef INET6
64 #include <netinet/ip6.h>
65 #endif /* INET6 */
66
67 struct pf_frent {
68 TAILQ_ENTRY(pf_frent) fr_next;
69 struct mbuf *fe_m;
70 uint16_t fe_hdrlen; /* ipv4 header length with ip options
71 ipv6, extension, fragment header */
72 uint16_t fe_extoff; /* last extension header offset or 0 */
73 uint16_t fe_len; /* fragment length */
74 uint16_t fe_off; /* fragment offset */
75 uint16_t fe_mff; /* more fragment flag */
76 };
77
78 struct pf_fragment_cmp {
79 struct pf_addr frc_src;
80 struct pf_addr frc_dst;
81 uint32_t frc_id;
82 sa_family_t frc_af;
83 uint8_t frc_proto;
84 };
85
86 struct pf_fragment {
87 struct pf_fragment_cmp fr_key;
88 #define fr_src fr_key.frc_src
89 #define fr_dst fr_key.frc_dst
90 #define fr_id fr_key.frc_id
91 #define fr_af fr_key.frc_af
92 #define fr_proto fr_key.frc_proto
93
94 /* pointers to queue element */
95 struct pf_frent *fr_firstoff[PF_FRAG_ENTRY_POINTS];
96 /* count entries between pointers */
97 uint8_t fr_entries[PF_FRAG_ENTRY_POINTS];
98 RB_ENTRY(pf_fragment) fr_entry;
99 TAILQ_ENTRY(pf_fragment) frag_next;
100 uint32_t fr_timeout;
101 TAILQ_HEAD(pf_fragq, pf_frent) fr_queue;
102 uint16_t fr_maxlen; /* maximum length of single fragment */
103 u_int16_t fr_holes; /* number of holes in the queue */
104 };
105
106 VNET_DEFINE_STATIC(struct mtx, pf_frag_mtx);
107 #define V_pf_frag_mtx VNET(pf_frag_mtx)
108 #define PF_FRAG_LOCK() mtx_lock(&V_pf_frag_mtx)
109 #define PF_FRAG_UNLOCK() mtx_unlock(&V_pf_frag_mtx)
110 #define PF_FRAG_ASSERT() mtx_assert(&V_pf_frag_mtx, MA_OWNED)
111
112 VNET_DEFINE(uma_zone_t, pf_state_scrub_z); /* XXX: shared with pfsync */
113
114 VNET_DEFINE_STATIC(uma_zone_t, pf_frent_z);
115 #define V_pf_frent_z VNET(pf_frent_z)
116 VNET_DEFINE_STATIC(uma_zone_t, pf_frag_z);
117 #define V_pf_frag_z VNET(pf_frag_z)
118
119 TAILQ_HEAD(pf_fragqueue, pf_fragment);
120 TAILQ_HEAD(pf_cachequeue, pf_fragment);
121 VNET_DEFINE_STATIC(struct pf_fragqueue, pf_fragqueue);
122 #define V_pf_fragqueue VNET(pf_fragqueue)
123 RB_HEAD(pf_frag_tree, pf_fragment);
124 VNET_DEFINE_STATIC(struct pf_frag_tree, pf_frag_tree);
125 #define V_pf_frag_tree VNET(pf_frag_tree)
126 static int pf_frag_compare(struct pf_fragment *,
127 struct pf_fragment *);
128 static RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare);
129 static RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare);
130
131 static void pf_flush_fragments(void);
132 static void pf_free_fragment(struct pf_fragment *);
133
134 static struct pf_frent *pf_create_fragment(u_short *);
135 static int pf_frent_holes(struct pf_frent *frent);
136 static struct pf_fragment *pf_find_fragment(struct pf_fragment_cmp *key,
137 struct pf_frag_tree *tree);
138 static inline int pf_frent_index(struct pf_frent *);
139 static int pf_frent_insert(struct pf_fragment *,
140 struct pf_frent *, struct pf_frent *);
141 void pf_frent_remove(struct pf_fragment *,
142 struct pf_frent *);
143 struct pf_frent *pf_frent_previous(struct pf_fragment *,
144 struct pf_frent *);
145 static struct pf_fragment *pf_fillup_fragment(struct pf_fragment_cmp *,
146 struct pf_frent *, u_short *);
147 static struct mbuf *pf_join_fragment(struct pf_fragment *);
148 #ifdef INET
149 static int pf_reassemble(struct mbuf **, int, u_short *);
150 #endif /* INET */
151 #ifdef INET6
152 static int pf_reassemble6(struct mbuf **,
153 struct ip6_frag *, uint16_t, uint16_t, u_short *);
154 #endif /* INET6 */
155
156 #define DPFPRINTF(x) do { \
157 if (V_pf_status.debug >= PF_DEBUG_MISC) { \
158 printf("%s: ", __func__); \
159 printf x ; \
160 } \
161 } while(0)
162
163 #ifdef INET
164 static void
pf_ip2key(struct ip * ip,int dir,struct pf_fragment_cmp * key)165 pf_ip2key(struct ip *ip, int dir, struct pf_fragment_cmp *key)
166 {
167
168 key->frc_src.v4 = ip->ip_src;
169 key->frc_dst.v4 = ip->ip_dst;
170 key->frc_af = AF_INET;
171 key->frc_proto = ip->ip_p;
172 key->frc_id = ip->ip_id;
173 }
174 #endif /* INET */
175
176 void
pf_normalize_init(void)177 pf_normalize_init(void)
178 {
179
180 V_pf_frag_z = uma_zcreate("pf frags", sizeof(struct pf_fragment),
181 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
182 V_pf_frent_z = uma_zcreate("pf frag entries", sizeof(struct pf_frent),
183 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
184 V_pf_state_scrub_z = uma_zcreate("pf state scrubs",
185 sizeof(struct pf_state_scrub), NULL, NULL, NULL, NULL,
186 UMA_ALIGN_PTR, 0);
187
188 mtx_init(&V_pf_frag_mtx, "pf fragments", NULL, MTX_DEF);
189
190 V_pf_limits[PF_LIMIT_FRAGS].zone = V_pf_frent_z;
191 V_pf_limits[PF_LIMIT_FRAGS].limit = PFFRAG_FRENT_HIWAT;
192 uma_zone_set_max(V_pf_frent_z, PFFRAG_FRENT_HIWAT);
193 uma_zone_set_warning(V_pf_frent_z, "PF frag entries limit reached");
194
195 TAILQ_INIT(&V_pf_fragqueue);
196 }
197
198 void
pf_normalize_cleanup(void)199 pf_normalize_cleanup(void)
200 {
201
202 uma_zdestroy(V_pf_state_scrub_z);
203 uma_zdestroy(V_pf_frent_z);
204 uma_zdestroy(V_pf_frag_z);
205
206 mtx_destroy(&V_pf_frag_mtx);
207 }
208
209 static int
pf_frag_compare(struct pf_fragment * a,struct pf_fragment * b)210 pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b)
211 {
212 int diff;
213
214 if ((diff = a->fr_id - b->fr_id) != 0)
215 return (diff);
216 if ((diff = a->fr_proto - b->fr_proto) != 0)
217 return (diff);
218 if ((diff = a->fr_af - b->fr_af) != 0)
219 return (diff);
220 if ((diff = pf_addr_cmp(&a->fr_src, &b->fr_src, a->fr_af)) != 0)
221 return (diff);
222 if ((diff = pf_addr_cmp(&a->fr_dst, &b->fr_dst, a->fr_af)) != 0)
223 return (diff);
224 return (0);
225 }
226
227 void
pf_purge_expired_fragments(void)228 pf_purge_expired_fragments(void)
229 {
230 u_int32_t expire = time_uptime -
231 V_pf_default_rule.timeout[PFTM_FRAG];
232
233 pf_purge_fragments(expire);
234 }
235
236 void
pf_purge_fragments(uint32_t expire)237 pf_purge_fragments(uint32_t expire)
238 {
239 struct pf_fragment *frag;
240
241 PF_FRAG_LOCK();
242 while ((frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue)) != NULL) {
243 if (frag->fr_timeout > expire)
244 break;
245
246 DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag));
247 pf_free_fragment(frag);
248 }
249
250 PF_FRAG_UNLOCK();
251 }
252
253 /*
254 * Try to flush old fragments to make space for new ones
255 */
256 static void
pf_flush_fragments(void)257 pf_flush_fragments(void)
258 {
259 struct pf_fragment *frag;
260 int goal;
261
262 PF_FRAG_ASSERT();
263
264 goal = uma_zone_get_cur(V_pf_frent_z) * 9 / 10;
265 DPFPRINTF(("trying to free %d frag entriess\n", goal));
266 while (goal < uma_zone_get_cur(V_pf_frent_z)) {
267 frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue);
268 if (frag)
269 pf_free_fragment(frag);
270 else
271 break;
272 }
273 }
274
275 /*
276 * Remove a fragment from the fragment queue, free its fragment entries,
277 * and free the fragment itself.
278 */
279 static void
pf_free_fragment(struct pf_fragment * frag)280 pf_free_fragment(struct pf_fragment *frag)
281 {
282 struct pf_frent *frent;
283
284 PF_FRAG_ASSERT();
285
286 RB_REMOVE(pf_frag_tree, &V_pf_frag_tree, frag);
287 TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next);
288
289 /* Free all fragment entries */
290 while ((frent = TAILQ_FIRST(&frag->fr_queue)) != NULL) {
291 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
292
293 m_freem(frent->fe_m);
294 uma_zfree(V_pf_frent_z, frent);
295 }
296
297 uma_zfree(V_pf_frag_z, frag);
298 }
299
300 static struct pf_fragment *
pf_find_fragment(struct pf_fragment_cmp * key,struct pf_frag_tree * tree)301 pf_find_fragment(struct pf_fragment_cmp *key, struct pf_frag_tree *tree)
302 {
303 struct pf_fragment *frag;
304
305 PF_FRAG_ASSERT();
306
307 frag = RB_FIND(pf_frag_tree, tree, (struct pf_fragment *)key);
308 if (frag != NULL) {
309 /* XXX Are we sure we want to update the timeout? */
310 frag->fr_timeout = time_uptime;
311 TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next);
312 TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next);
313 }
314
315 return (frag);
316 }
317
318 static struct pf_frent *
pf_create_fragment(u_short * reason)319 pf_create_fragment(u_short *reason)
320 {
321 struct pf_frent *frent;
322
323 PF_FRAG_ASSERT();
324
325 frent = uma_zalloc(V_pf_frent_z, M_NOWAIT);
326 if (frent == NULL) {
327 pf_flush_fragments();
328 frent = uma_zalloc(V_pf_frent_z, M_NOWAIT);
329 if (frent == NULL) {
330 REASON_SET(reason, PFRES_MEMORY);
331 return (NULL);
332 }
333 }
334
335 return (frent);
336 }
337
338 /*
339 * Calculate the additional holes that were created in the fragment
340 * queue by inserting this fragment. A fragment in the middle
341 * creates one more hole by splitting. For each connected side,
342 * it loses one hole.
343 * Fragment entry must be in the queue when calling this function.
344 */
345 static int
pf_frent_holes(struct pf_frent * frent)346 pf_frent_holes(struct pf_frent *frent)
347 {
348 struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next);
349 struct pf_frent *next = TAILQ_NEXT(frent, fr_next);
350 int holes = 1;
351
352 if (prev == NULL) {
353 if (frent->fe_off == 0)
354 holes--;
355 } else {
356 KASSERT(frent->fe_off != 0, ("frent->fe_off != 0"));
357 if (frent->fe_off == prev->fe_off + prev->fe_len)
358 holes--;
359 }
360 if (next == NULL) {
361 if (!frent->fe_mff)
362 holes--;
363 } else {
364 KASSERT(frent->fe_mff, ("frent->fe_mff"));
365 if (next->fe_off == frent->fe_off + frent->fe_len)
366 holes--;
367 }
368 return holes;
369 }
370
371 static inline int
pf_frent_index(struct pf_frent * frent)372 pf_frent_index(struct pf_frent *frent)
373 {
374 /*
375 * We have an array of 16 entry points to the queue. A full size
376 * 65535 octet IP packet can have 8192 fragments. So the queue
377 * traversal length is at most 512 and at most 16 entry points are
378 * checked. We need 128 additional bytes on a 64 bit architecture.
379 */
380 CTASSERT(((u_int16_t)0xffff &~ 7) / (0x10000 / PF_FRAG_ENTRY_POINTS) ==
381 16 - 1);
382 CTASSERT(((u_int16_t)0xffff >> 3) / PF_FRAG_ENTRY_POINTS == 512 - 1);
383
384 return frent->fe_off / (0x10000 / PF_FRAG_ENTRY_POINTS);
385 }
386
387 static int
pf_frent_insert(struct pf_fragment * frag,struct pf_frent * frent,struct pf_frent * prev)388 pf_frent_insert(struct pf_fragment *frag, struct pf_frent *frent,
389 struct pf_frent *prev)
390 {
391 int index;
392
393 CTASSERT(PF_FRAG_ENTRY_LIMIT <= 0xff);
394
395 /*
396 * A packet has at most 65536 octets. With 16 entry points, each one
397 * spawns 4096 octets. We limit these to 64 fragments each, which
398 * means on average every fragment must have at least 64 octets.
399 */
400 index = pf_frent_index(frent);
401 if (frag->fr_entries[index] >= PF_FRAG_ENTRY_LIMIT)
402 return ENOBUFS;
403 frag->fr_entries[index]++;
404
405 if (prev == NULL) {
406 TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next);
407 } else {
408 KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off,
409 ("overlapping fragment"));
410 TAILQ_INSERT_AFTER(&frag->fr_queue, prev, frent, fr_next);
411 }
412
413 if (frag->fr_firstoff[index] == NULL) {
414 KASSERT(prev == NULL || pf_frent_index(prev) < index,
415 ("prev == NULL || pf_frent_index(pref) < index"));
416 frag->fr_firstoff[index] = frent;
417 } else {
418 if (frent->fe_off < frag->fr_firstoff[index]->fe_off) {
419 KASSERT(prev == NULL || pf_frent_index(prev) < index,
420 ("prev == NULL || pf_frent_index(pref) < index"));
421 frag->fr_firstoff[index] = frent;
422 } else {
423 KASSERT(prev != NULL, ("prev != NULL"));
424 KASSERT(pf_frent_index(prev) == index,
425 ("pf_frent_index(prev) == index"));
426 }
427 }
428
429 frag->fr_holes += pf_frent_holes(frent);
430
431 return 0;
432 }
433
434 void
pf_frent_remove(struct pf_fragment * frag,struct pf_frent * frent)435 pf_frent_remove(struct pf_fragment *frag, struct pf_frent *frent)
436 {
437 #ifdef INVARIANTS
438 struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next);
439 #endif
440 struct pf_frent *next = TAILQ_NEXT(frent, fr_next);
441 int index;
442
443 frag->fr_holes -= pf_frent_holes(frent);
444
445 index = pf_frent_index(frent);
446 KASSERT(frag->fr_firstoff[index] != NULL, ("frent not found"));
447 if (frag->fr_firstoff[index]->fe_off == frent->fe_off) {
448 if (next == NULL) {
449 frag->fr_firstoff[index] = NULL;
450 } else {
451 KASSERT(frent->fe_off + frent->fe_len <= next->fe_off,
452 ("overlapping fragment"));
453 if (pf_frent_index(next) == index) {
454 frag->fr_firstoff[index] = next;
455 } else {
456 frag->fr_firstoff[index] = NULL;
457 }
458 }
459 } else {
460 KASSERT(frag->fr_firstoff[index]->fe_off < frent->fe_off,
461 ("frag->fr_firstoff[index]->fe_off < frent->fe_off"));
462 KASSERT(prev != NULL, ("prev != NULL"));
463 KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off,
464 ("overlapping fragment"));
465 KASSERT(pf_frent_index(prev) == index,
466 ("pf_frent_index(prev) == index"));
467 }
468
469 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
470
471 KASSERT(frag->fr_entries[index] > 0, ("No fragments remaining"));
472 frag->fr_entries[index]--;
473 }
474
475 struct pf_frent *
pf_frent_previous(struct pf_fragment * frag,struct pf_frent * frent)476 pf_frent_previous(struct pf_fragment *frag, struct pf_frent *frent)
477 {
478 struct pf_frent *prev, *next;
479 int index;
480
481 /*
482 * If there are no fragments after frag, take the final one. Assume
483 * that the global queue is not empty.
484 */
485 prev = TAILQ_LAST(&frag->fr_queue, pf_fragq);
486 KASSERT(prev != NULL, ("prev != NULL"));
487 if (prev->fe_off <= frent->fe_off)
488 return prev;
489 /*
490 * We want to find a fragment entry that is before frag, but still
491 * close to it. Find the first fragment entry that is in the same
492 * entry point or in the first entry point after that. As we have
493 * already checked that there are entries behind frag, this will
494 * succeed.
495 */
496 for (index = pf_frent_index(frent); index < PF_FRAG_ENTRY_POINTS;
497 index++) {
498 prev = frag->fr_firstoff[index];
499 if (prev != NULL)
500 break;
501 }
502 KASSERT(prev != NULL, ("prev != NULL"));
503 /*
504 * In prev we may have a fragment from the same entry point that is
505 * before frent, or one that is just one position behind frent.
506 * In the latter case, we go back one step and have the predecessor.
507 * There may be none if the new fragment will be the first one.
508 */
509 if (prev->fe_off > frent->fe_off) {
510 prev = TAILQ_PREV(prev, pf_fragq, fr_next);
511 if (prev == NULL)
512 return NULL;
513 KASSERT(prev->fe_off <= frent->fe_off,
514 ("prev->fe_off <= frent->fe_off"));
515 return prev;
516 }
517 /*
518 * In prev is the first fragment of the entry point. The offset
519 * of frag is behind it. Find the closest previous fragment.
520 */
521 for (next = TAILQ_NEXT(prev, fr_next); next != NULL;
522 next = TAILQ_NEXT(next, fr_next)) {
523 if (next->fe_off > frent->fe_off)
524 break;
525 prev = next;
526 }
527 return prev;
528 }
529
530 static struct pf_fragment *
pf_fillup_fragment(struct pf_fragment_cmp * key,struct pf_frent * frent,u_short * reason)531 pf_fillup_fragment(struct pf_fragment_cmp *key, struct pf_frent *frent,
532 u_short *reason)
533 {
534 struct pf_frent *after, *next, *prev;
535 struct pf_fragment *frag;
536 uint16_t total;
537 int old_index, new_index;
538
539 PF_FRAG_ASSERT();
540
541 /* No empty fragments. */
542 if (frent->fe_len == 0) {
543 DPFPRINTF(("bad fragment: len 0\n"));
544 goto bad_fragment;
545 }
546
547 /* All fragments are 8 byte aligned. */
548 if (frent->fe_mff && (frent->fe_len & 0x7)) {
549 DPFPRINTF(("bad fragment: mff and len %d\n", frent->fe_len));
550 goto bad_fragment;
551 }
552
553 /* Respect maximum length, IP_MAXPACKET == IPV6_MAXPACKET. */
554 if (frent->fe_off + frent->fe_len > IP_MAXPACKET) {
555 DPFPRINTF(("bad fragment: max packet %d\n",
556 frent->fe_off + frent->fe_len));
557 goto bad_fragment;
558 }
559
560 DPFPRINTF((key->frc_af == AF_INET ?
561 "reass frag %d @ %d-%d\n" : "reass frag %#08x @ %d-%d\n",
562 key->frc_id, frent->fe_off, frent->fe_off + frent->fe_len));
563
564 /* Fully buffer all of the fragments in this fragment queue. */
565 frag = pf_find_fragment(key, &V_pf_frag_tree);
566
567 /* Create a new reassembly queue for this packet. */
568 if (frag == NULL) {
569 frag = uma_zalloc(V_pf_frag_z, M_NOWAIT);
570 if (frag == NULL) {
571 pf_flush_fragments();
572 frag = uma_zalloc(V_pf_frag_z, M_NOWAIT);
573 if (frag == NULL) {
574 REASON_SET(reason, PFRES_MEMORY);
575 goto drop_fragment;
576 }
577 }
578
579 *(struct pf_fragment_cmp *)frag = *key;
580 memset(frag->fr_firstoff, 0, sizeof(frag->fr_firstoff));
581 memset(frag->fr_entries, 0, sizeof(frag->fr_entries));
582 frag->fr_timeout = time_uptime;
583 TAILQ_INIT(&frag->fr_queue);
584 frag->fr_maxlen = frent->fe_len;
585 frag->fr_holes = 1;
586
587 RB_INSERT(pf_frag_tree, &V_pf_frag_tree, frag);
588 TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next);
589
590 /* We do not have a previous fragment, cannot fail. */
591 pf_frent_insert(frag, frent, NULL);
592
593 return (frag);
594 }
595
596 KASSERT(!TAILQ_EMPTY(&frag->fr_queue), ("!TAILQ_EMPTY()->fr_queue"));
597
598 /* Remember maximum fragment len for refragmentation. */
599 if (frent->fe_len > frag->fr_maxlen)
600 frag->fr_maxlen = frent->fe_len;
601
602 /* Maximum data we have seen already. */
603 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
604 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
605
606 /* Non terminal fragments must have more fragments flag. */
607 if (frent->fe_off + frent->fe_len < total && !frent->fe_mff)
608 goto bad_fragment;
609
610 /* Check if we saw the last fragment already. */
611 if (!TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_mff) {
612 if (frent->fe_off + frent->fe_len > total ||
613 (frent->fe_off + frent->fe_len == total && frent->fe_mff))
614 goto bad_fragment;
615 } else {
616 if (frent->fe_off + frent->fe_len == total && !frent->fe_mff)
617 goto bad_fragment;
618 }
619
620 /* Find neighbors for newly inserted fragment */
621 prev = pf_frent_previous(frag, frent);
622 if (prev == NULL) {
623 after = TAILQ_FIRST(&frag->fr_queue);
624 KASSERT(after != NULL, ("after != NULL"));
625 } else {
626 after = TAILQ_NEXT(prev, fr_next);
627 }
628
629 if (prev != NULL && prev->fe_off + prev->fe_len > frent->fe_off) {
630 uint16_t precut;
631
632 if (frag->fr_af == AF_INET6)
633 goto free_fragment;
634
635 precut = prev->fe_off + prev->fe_len - frent->fe_off;
636 if (precut >= frent->fe_len) {
637 DPFPRINTF(("new frag overlapped\n"));
638 goto drop_fragment;
639 }
640 DPFPRINTF(("frag head overlap %d\n", precut));
641 m_adj(frent->fe_m, precut);
642 frent->fe_off += precut;
643 frent->fe_len -= precut;
644 }
645
646 for (; after != NULL && frent->fe_off + frent->fe_len > after->fe_off;
647 after = next) {
648 uint16_t aftercut;
649
650 aftercut = frent->fe_off + frent->fe_len - after->fe_off;
651 DPFPRINTF(("adjust overlap %d\n", aftercut));
652 if (aftercut < after->fe_len) {
653 m_adj(after->fe_m, aftercut);
654 old_index = pf_frent_index(after);
655 after->fe_off += aftercut;
656 after->fe_len -= aftercut;
657 new_index = pf_frent_index(after);
658 if (old_index != new_index) {
659 DPFPRINTF(("frag index %d, new %d\n",
660 old_index, new_index));
661 /* Fragment switched queue as fe_off changed */
662 after->fe_off -= aftercut;
663 after->fe_len += aftercut;
664 /* Remove restored fragment from old queue */
665 pf_frent_remove(frag, after);
666 after->fe_off += aftercut;
667 after->fe_len -= aftercut;
668 /* Insert into correct queue */
669 if (pf_frent_insert(frag, after, prev)) {
670 DPFPRINTF(
671 ("fragment requeue limit exceeded\n"));
672 m_freem(after->fe_m);
673 uma_zfree(V_pf_frent_z, after);
674 /* There is not way to recover */
675 goto bad_fragment;
676 }
677 }
678 break;
679 }
680
681 /* This fragment is completely overlapped, lose it. */
682 DPFPRINTF(("old frag overlapped\n"));
683 next = TAILQ_NEXT(after, fr_next);
684 pf_frent_remove(frag, after);
685 m_freem(after->fe_m);
686 uma_zfree(V_pf_frent_z, after);
687 }
688
689 /* If part of the queue gets too long, there is not way to recover. */
690 if (pf_frent_insert(frag, frent, prev)) {
691 DPFPRINTF(("fragment queue limit exceeded\n"));
692 goto bad_fragment;
693 }
694
695 return (frag);
696
697 free_fragment:
698 /*
699 * RFC 5722, Errata 3089: When reassembling an IPv6 datagram, if one
700 * or more its constituent fragments is determined to be an overlapping
701 * fragment, the entire datagram (and any constituent fragments) MUST
702 * be silently discarded.
703 */
704 DPFPRINTF(("flush overlapping fragments\n"));
705 pf_free_fragment(frag);
706
707 bad_fragment:
708 REASON_SET(reason, PFRES_FRAG);
709 drop_fragment:
710 uma_zfree(V_pf_frent_z, frent);
711 return (NULL);
712 }
713
714 static struct mbuf *
pf_join_fragment(struct pf_fragment * frag)715 pf_join_fragment(struct pf_fragment *frag)
716 {
717 struct mbuf *m, *m2;
718 struct pf_frent *frent;
719
720 frent = TAILQ_FIRST(&frag->fr_queue);
721 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
722
723 m = frent->fe_m;
724 m_adj(m, (frent->fe_hdrlen + frent->fe_len) - m->m_pkthdr.len);
725 uma_zfree(V_pf_frent_z, frent);
726 while ((frent = TAILQ_FIRST(&frag->fr_queue)) != NULL) {
727 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
728
729 m2 = frent->fe_m;
730 /* Strip off ip header. */
731 m_adj(m2, frent->fe_hdrlen);
732 /* Strip off any trailing bytes. */
733 m_adj(m2, frent->fe_len - m2->m_pkthdr.len);
734
735 uma_zfree(V_pf_frent_z, frent);
736 m_cat(m, m2);
737 }
738
739 /* Remove from fragment queue. */
740 pf_free_fragment(frag);
741
742 return (m);
743 }
744
745 #ifdef INET
746 static int
pf_reassemble(struct mbuf ** m0,int dir,u_short * reason)747 pf_reassemble(struct mbuf **m0, int dir, u_short *reason)
748 {
749 struct mbuf *m = *m0;
750 struct ip *ip = mtod(m, struct ip *);
751 struct pf_frent *frent;
752 struct pf_fragment *frag;
753 struct m_tag *mtag;
754 struct pf_fragment_tag *ftag;
755 struct pf_fragment_cmp key;
756 uint16_t total, hdrlen;
757 uint32_t frag_id;
758 uint16_t maxlen;
759
760 /* Get an entry for the fragment queue */
761 if ((frent = pf_create_fragment(reason)) == NULL)
762 return (PF_DROP);
763
764 frent->fe_m = m;
765 frent->fe_hdrlen = ip->ip_hl << 2;
766 frent->fe_extoff = 0;
767 frent->fe_len = ntohs(ip->ip_len) - (ip->ip_hl << 2);
768 frent->fe_off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3;
769 frent->fe_mff = ntohs(ip->ip_off) & IP_MF;
770
771 pf_ip2key(ip, dir, &key);
772
773 if ((frag = pf_fillup_fragment(&key, frent, reason)) == NULL)
774 return (PF_DROP);
775
776 /* The mbuf is part of the fragment entry, no direct free or access */
777 m = *m0 = NULL;
778
779 if (frag->fr_holes) {
780 DPFPRINTF(("frag %d, holes %d\n", frag->fr_id, frag->fr_holes));
781 return (PF_PASS); /* drop because *m0 is NULL, no error */
782 }
783
784 /* We have all the data */
785 frent = TAILQ_FIRST(&frag->fr_queue);
786 KASSERT(frent != NULL, ("frent != NULL"));
787 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
788 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
789 hdrlen = frent->fe_hdrlen;
790
791 maxlen = frag->fr_maxlen;
792 frag_id = frag->fr_id;
793 m = *m0 = pf_join_fragment(frag);
794 frag = NULL;
795
796 if (m->m_flags & M_PKTHDR) {
797 int plen = 0;
798 for (m = *m0; m; m = m->m_next)
799 plen += m->m_len;
800 m = *m0;
801 m->m_pkthdr.len = plen;
802 }
803
804 if ((mtag = m_tag_get(PACKET_TAG_PF_REASSEMBLED,
805 sizeof(struct pf_fragment_tag), M_NOWAIT)) == NULL) {
806 REASON_SET(reason, PFRES_SHORT);
807 /* PF_DROP requires a valid mbuf *m0 in pf_test() */
808 return (PF_DROP);
809 }
810 ftag = (struct pf_fragment_tag *)(mtag + 1);
811 ftag->ft_hdrlen = hdrlen;
812 ftag->ft_extoff = 0;
813 ftag->ft_maxlen = maxlen;
814 ftag->ft_id = frag_id;
815 m_tag_prepend(m, mtag);
816
817 ip = mtod(m, struct ip *);
818 ip->ip_sum = pf_cksum_fixup(ip->ip_sum, ip->ip_len,
819 htons(hdrlen + total), 0);
820 ip->ip_len = htons(hdrlen + total);
821 ip->ip_sum = pf_cksum_fixup(ip->ip_sum, ip->ip_off,
822 ip->ip_off & ~(IP_MF|IP_OFFMASK), 0);
823 ip->ip_off &= ~(IP_MF|IP_OFFMASK);
824
825 if (hdrlen + total > IP_MAXPACKET) {
826 DPFPRINTF(("drop: too big: %d\n", total));
827 ip->ip_len = 0;
828 REASON_SET(reason, PFRES_SHORT);
829 /* PF_DROP requires a valid mbuf *m0 in pf_test() */
830 return (PF_DROP);
831 }
832
833 DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip->ip_len)));
834 return (PF_PASS);
835 }
836 #endif /* INET */
837
838 #ifdef INET6
839 static int
pf_reassemble6(struct mbuf ** m0,struct ip6_frag * fraghdr,uint16_t hdrlen,uint16_t extoff,u_short * reason)840 pf_reassemble6(struct mbuf **m0, struct ip6_frag *fraghdr,
841 uint16_t hdrlen, uint16_t extoff, u_short *reason)
842 {
843 struct mbuf *m = *m0;
844 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
845 struct pf_frent *frent;
846 struct pf_fragment *frag;
847 struct pf_fragment_cmp key;
848 struct m_tag *mtag;
849 struct pf_fragment_tag *ftag;
850 int off;
851 uint32_t frag_id;
852 uint16_t total, maxlen;
853 uint8_t proto;
854
855 PF_FRAG_LOCK();
856
857 /* Get an entry for the fragment queue. */
858 if ((frent = pf_create_fragment(reason)) == NULL) {
859 PF_FRAG_UNLOCK();
860 return (PF_DROP);
861 }
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.frc_src.v6 = ip6->ip6_src;
871 key.frc_dst.v6 = ip6->ip6_dst;
872 key.frc_af = AF_INET6;
873 /* Only the first fragment's protocol is relevant. */
874 key.frc_proto = 0;
875 key.frc_id = fraghdr->ip6f_ident;
876
877 if ((frag = pf_fillup_fragment(&key, frent, reason)) == NULL) {
878 PF_FRAG_UNLOCK();
879 return (PF_DROP);
880 }
881
882 /* The mbuf is part of the fragment entry, no direct free or access. */
883 m = *m0 = NULL;
884
885 if (frag->fr_holes) {
886 DPFPRINTF(("frag %d, holes %d\n", frag->fr_id,
887 frag->fr_holes));
888 PF_FRAG_UNLOCK();
889 return (PF_PASS); /* Drop because *m0 is NULL, no error. */
890 }
891
892 /* We have all the data. */
893 frent = TAILQ_FIRST(&frag->fr_queue);
894 KASSERT(frent != NULL, ("frent != NULL"));
895 extoff = frent->fe_extoff;
896 maxlen = frag->fr_maxlen;
897 frag_id = frag->fr_id;
898 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
899 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
900 hdrlen = frent->fe_hdrlen - sizeof(struct ip6_frag);
901
902 m = *m0 = pf_join_fragment(frag);
903 frag = NULL;
904
905 PF_FRAG_UNLOCK();
906
907 /* Take protocol from first fragment header. */
908 m = m_getptr(m, hdrlen + offsetof(struct ip6_frag, ip6f_nxt), &off);
909 KASSERT(m, ("%s: short mbuf chain", __func__));
910 proto = *(mtod(m, uint8_t *) + off);
911 m = *m0;
912
913 /* Delete frag6 header */
914 if (ip6_deletefraghdr(m, hdrlen, M_NOWAIT) != 0)
915 goto fail;
916
917 if (m->m_flags & M_PKTHDR) {
918 int plen = 0;
919 for (m = *m0; m; m = m->m_next)
920 plen += m->m_len;
921 m = *m0;
922 m->m_pkthdr.len = plen;
923 }
924
925 if ((mtag = m_tag_get(PACKET_TAG_PF_REASSEMBLED,
926 sizeof(struct pf_fragment_tag), M_NOWAIT)) == NULL)
927 goto fail;
928 ftag = (struct pf_fragment_tag *)(mtag + 1);
929 ftag->ft_hdrlen = hdrlen;
930 ftag->ft_extoff = extoff;
931 ftag->ft_maxlen = maxlen;
932 ftag->ft_id = frag_id;
933 m_tag_prepend(m, mtag);
934
935 ip6 = mtod(m, struct ip6_hdr *);
936 ip6->ip6_plen = htons(hdrlen - sizeof(struct ip6_hdr) + total);
937 if (extoff) {
938 /* Write protocol into next field of last extension header. */
939 m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt),
940 &off);
941 KASSERT(m, ("%s: short mbuf chain", __func__));
942 *(mtod(m, char *) + off) = proto;
943 m = *m0;
944 } else
945 ip6->ip6_nxt = proto;
946
947 if (hdrlen - sizeof(struct ip6_hdr) + total > IPV6_MAXPACKET) {
948 DPFPRINTF(("drop: too big: %d\n", total));
949 ip6->ip6_plen = 0;
950 REASON_SET(reason, PFRES_SHORT);
951 /* PF_DROP requires a valid mbuf *m0 in pf_test6(). */
952 return (PF_DROP);
953 }
954
955 DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip6->ip6_plen)));
956 return (PF_PASS);
957
958 fail:
959 REASON_SET(reason, PFRES_MEMORY);
960 /* PF_DROP requires a valid mbuf *m0 in pf_test6(), will free later. */
961 return (PF_DROP);
962 }
963 #endif /* INET6 */
964
965 #ifdef INET6
966 int
pf_max_frag_size(struct mbuf * m)967 pf_max_frag_size(struct mbuf *m)
968 {
969 struct m_tag *tag;
970 struct pf_fragment_tag *ftag;
971
972 tag = m_tag_find(m, PACKET_TAG_PF_REASSEMBLED, NULL);
973 if (tag == NULL)
974 return (m->m_pkthdr.len);
975
976 ftag = (struct pf_fragment_tag *)(tag + 1);
977
978 return (ftag->ft_maxlen);
979 }
980
981 int
pf_refragment6(struct ifnet * ifp,struct mbuf ** m0,struct m_tag * mtag,struct ifnet * rt,bool forward)982 pf_refragment6(struct ifnet *ifp, struct mbuf **m0, struct m_tag *mtag,
983 struct ifnet *rt, bool forward)
984 {
985 struct mbuf *m = *m0, *t;
986 struct ip6_hdr *hdr;
987 struct pf_fragment_tag *ftag = (struct pf_fragment_tag *)(mtag + 1);
988 struct pf_pdesc pd;
989 uint32_t frag_id;
990 uint16_t hdrlen, extoff, maxlen;
991 uint8_t proto;
992 int error, action;
993
994 hdrlen = ftag->ft_hdrlen;
995 extoff = ftag->ft_extoff;
996 maxlen = ftag->ft_maxlen;
997 frag_id = ftag->ft_id;
998 m_tag_delete(m, mtag);
999 mtag = NULL;
1000 ftag = NULL;
1001
1002 if (extoff) {
1003 int off;
1004
1005 /* Use protocol from next field of last extension header */
1006 m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt),
1007 &off);
1008 KASSERT((m != NULL), ("pf_refragment6: short mbuf chain"));
1009 proto = *(mtod(m, uint8_t *) + off);
1010 *(mtod(m, char *) + off) = IPPROTO_FRAGMENT;
1011 m = *m0;
1012 } else {
1013 hdr = mtod(m, struct ip6_hdr *);
1014 proto = hdr->ip6_nxt;
1015 hdr->ip6_nxt = IPPROTO_FRAGMENT;
1016 }
1017
1018 /* In case of link-local traffic we'll need a scope set. */
1019 hdr = mtod(m, struct ip6_hdr *);
1020
1021 in6_setscope(&hdr->ip6_src, ifp, NULL);
1022 in6_setscope(&hdr->ip6_dst, ifp, NULL);
1023
1024 /* The MTU must be a multiple of 8 bytes, or we risk doing the
1025 * fragmentation wrong. */
1026 maxlen = maxlen & ~7;
1027
1028 /*
1029 * Maxlen may be less than 8 if there was only a single
1030 * fragment. As it was fragmented before, add a fragment
1031 * header also for a single fragment. If total or maxlen
1032 * is less than 8, ip6_fragment() will return EMSGSIZE and
1033 * we drop the packet.
1034 */
1035 error = ip6_fragment(ifp, m, hdrlen, proto, maxlen, frag_id);
1036 m = (*m0)->m_nextpkt;
1037 (*m0)->m_nextpkt = NULL;
1038 if (error == 0) {
1039 /* The first mbuf contains the unfragmented packet. */
1040 m_freem(*m0);
1041 *m0 = NULL;
1042 action = PF_PASS;
1043 } else {
1044 /* Drop expects an mbuf to free. */
1045 DPFPRINTF(("refragment error %d\n", error));
1046 action = PF_DROP;
1047 }
1048 for (; m; m = t) {
1049 t = m->m_nextpkt;
1050 m->m_nextpkt = NULL;
1051 m->m_flags |= M_SKIP_FIREWALL;
1052 memset(&pd, 0, sizeof(pd));
1053 pd.pf_mtag = pf_find_mtag(m);
1054 if (error != 0) {
1055 m_freem(m);
1056 continue;
1057 }
1058 if (rt != NULL) {
1059 struct sockaddr_in6 dst;
1060 hdr = mtod(m, struct ip6_hdr *);
1061
1062 bzero(&dst, sizeof(dst));
1063 dst.sin6_family = AF_INET6;
1064 dst.sin6_len = sizeof(dst);
1065 dst.sin6_addr = hdr->ip6_dst;
1066
1067 nd6_output_ifp(rt, rt, m, &dst, NULL);
1068 } else if (forward) {
1069 MPASS(m->m_pkthdr.rcvif != NULL);
1070 ip6_forward(m, 0);
1071 } else {
1072 (void)ip6_output(m, NULL, NULL, 0, NULL, NULL,
1073 NULL);
1074 }
1075 }
1076
1077 return (action);
1078 }
1079 #endif /* INET6 */
1080
1081 #ifdef INET
1082 int
pf_normalize_ip(u_short * reason,struct pf_pdesc * pd)1083 pf_normalize_ip(u_short *reason, struct pf_pdesc *pd)
1084 {
1085 struct pf_krule *r;
1086 struct ip *h = mtod(pd->m, struct ip *);
1087 int mff = (ntohs(h->ip_off) & IP_MF);
1088 int hlen = h->ip_hl << 2;
1089 u_int16_t fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3;
1090 u_int16_t max;
1091 int ip_len;
1092 int tag = -1;
1093 int verdict;
1094 bool scrub_compat;
1095
1096 PF_RULES_RASSERT();
1097
1098 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
1099 /*
1100 * Check if there are any scrub rules, matching or not.
1101 * Lack of scrub rules means:
1102 * - enforced packet normalization operation just like in OpenBSD
1103 * - fragment reassembly depends on V_pf_status.reass
1104 * With scrub rules:
1105 * - packet normalization is performed if there is a matching scrub rule
1106 * - fragment reassembly is performed if the matching rule has no
1107 * PFRULE_FRAGMENT_NOREASS flag
1108 */
1109 scrub_compat = (r != NULL);
1110 while (r != NULL) {
1111 pf_counter_u64_add(&r->evaluations, 1);
1112 if (pfi_kkif_match(r->kif, pd->kif) == r->ifnot)
1113 r = r->skip[PF_SKIP_IFP];
1114 else if (r->direction && r->direction != pd->dir)
1115 r = r->skip[PF_SKIP_DIR];
1116 else if (r->af && r->af != AF_INET)
1117 r = r->skip[PF_SKIP_AF];
1118 else if (r->proto && r->proto != h->ip_p)
1119 r = r->skip[PF_SKIP_PROTO];
1120 else if (PF_MISMATCHAW(&r->src.addr,
1121 (struct pf_addr *)&h->ip_src.s_addr, AF_INET,
1122 r->src.neg, pd->kif, M_GETFIB(pd->m)))
1123 r = r->skip[PF_SKIP_SRC_ADDR];
1124 else if (PF_MISMATCHAW(&r->dst.addr,
1125 (struct pf_addr *)&h->ip_dst.s_addr, AF_INET,
1126 r->dst.neg, NULL, M_GETFIB(pd->m)))
1127 r = r->skip[PF_SKIP_DST_ADDR];
1128 else if (r->match_tag && !pf_match_tag(pd->m, r, &tag,
1129 pd->pf_mtag ? pd->pf_mtag->tag : 0))
1130 r = TAILQ_NEXT(r, entries);
1131 else
1132 break;
1133 }
1134
1135 if (scrub_compat) {
1136 /* With scrub rules present IPv4 normalization happens only
1137 * if one of rules has matched and it's not a "no scrub" rule */
1138 if (r == NULL || r->action == PF_NOSCRUB)
1139 return (PF_PASS);
1140
1141 pf_counter_u64_critical_enter();
1142 pf_counter_u64_add_protected(&r->packets[pd->dir == PF_OUT], 1);
1143 pf_counter_u64_add_protected(&r->bytes[pd->dir == PF_OUT], pd->tot_len);
1144 pf_counter_u64_critical_exit();
1145 pf_rule_to_actions(r, &pd->act);
1146 }
1147
1148 /* Check for illegal packets */
1149 if (hlen < (int)sizeof(struct ip)) {
1150 REASON_SET(reason, PFRES_NORM);
1151 goto drop;
1152 }
1153
1154 if (hlen > ntohs(h->ip_len)) {
1155 REASON_SET(reason, PFRES_NORM);
1156 goto drop;
1157 }
1158
1159 /* Clear IP_DF if the rule uses the no-df option or we're in no-df mode */
1160 if (((!scrub_compat && V_pf_status.reass & PF_REASS_NODF) ||
1161 (r != NULL && r->rule_flag & PFRULE_NODF)) &&
1162 (h->ip_off & htons(IP_DF))
1163 ) {
1164 u_int16_t ip_off = h->ip_off;
1165
1166 h->ip_off &= htons(~IP_DF);
1167 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
1168 }
1169
1170 /* We will need other tests here */
1171 if (!fragoff && !mff)
1172 goto no_fragment;
1173
1174 /* We're dealing with a fragment now. Don't allow fragments
1175 * with IP_DF to enter the cache. If the flag was cleared by
1176 * no-df above, fine. Otherwise drop it.
1177 */
1178 if (h->ip_off & htons(IP_DF)) {
1179 DPFPRINTF(("IP_DF\n"));
1180 goto bad;
1181 }
1182
1183 ip_len = ntohs(h->ip_len) - hlen;
1184
1185 /* All fragments are 8 byte aligned */
1186 if (mff && (ip_len & 0x7)) {
1187 DPFPRINTF(("mff and %d\n", ip_len));
1188 goto bad;
1189 }
1190
1191 /* Respect maximum length */
1192 if (fragoff + ip_len > IP_MAXPACKET) {
1193 DPFPRINTF(("max packet %d\n", fragoff + ip_len));
1194 goto bad;
1195 }
1196
1197 if ((!scrub_compat && V_pf_status.reass) ||
1198 (r != NULL && !(r->rule_flag & PFRULE_FRAGMENT_NOREASS))
1199 ) {
1200 max = fragoff + ip_len;
1201
1202 /* Fully buffer all of the fragments
1203 * Might return a completely reassembled mbuf, or NULL */
1204 PF_FRAG_LOCK();
1205 DPFPRINTF(("reass frag %d @ %d-%d\n", h->ip_id, fragoff, max));
1206 verdict = pf_reassemble(&pd->m, pd->dir, reason);
1207 PF_FRAG_UNLOCK();
1208
1209 if (verdict != PF_PASS)
1210 return (PF_DROP);
1211
1212 if (pd->m == NULL)
1213 return (PF_DROP);
1214
1215 h = mtod(pd->m, struct ip *);
1216 pd->tot_len = htons(h->ip_len);
1217
1218 no_fragment:
1219 /* At this point, only IP_DF is allowed in ip_off */
1220 if (h->ip_off & ~htons(IP_DF)) {
1221 u_int16_t ip_off = h->ip_off;
1222
1223 h->ip_off &= htons(IP_DF);
1224 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
1225 }
1226 }
1227
1228 return (PF_PASS);
1229
1230 bad:
1231 DPFPRINTF(("dropping bad fragment\n"));
1232 REASON_SET(reason, PFRES_FRAG);
1233 drop:
1234 if (r != NULL && r->log)
1235 PFLOG_PACKET(PF_DROP, *reason, r, NULL, NULL, pd, 1);
1236
1237 return (PF_DROP);
1238 }
1239 #endif
1240
1241 #ifdef INET6
1242 int
pf_normalize_ip6(int off,u_short * reason,struct pf_pdesc * pd)1243 pf_normalize_ip6(int off, u_short *reason,
1244 struct pf_pdesc *pd)
1245 {
1246 struct pf_krule *r;
1247 struct ip6_hdr *h;
1248 struct ip6_frag frag;
1249 bool scrub_compat;
1250
1251 PF_RULES_RASSERT();
1252
1253 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
1254 /*
1255 * Check if there are any scrub rules, matching or not.
1256 * Lack of scrub rules means:
1257 * - enforced packet normalization operation just like in OpenBSD
1258 * With scrub rules:
1259 * - packet normalization is performed if there is a matching scrub rule
1260 * XXX: Fragment reassembly always performed for IPv6!
1261 */
1262 scrub_compat = (r != NULL);
1263 while (r != NULL) {
1264 pf_counter_u64_add(&r->evaluations, 1);
1265 if (pfi_kkif_match(r->kif, pd->kif) == r->ifnot)
1266 r = r->skip[PF_SKIP_IFP];
1267 else if (r->direction && r->direction != pd->dir)
1268 r = r->skip[PF_SKIP_DIR];
1269 else if (r->af && r->af != AF_INET6)
1270 r = r->skip[PF_SKIP_AF];
1271 else if (r->proto && r->proto != pd->proto)
1272 r = r->skip[PF_SKIP_PROTO];
1273 else if (PF_MISMATCHAW(&r->src.addr,
1274 (struct pf_addr *)&pd->src, AF_INET6,
1275 r->src.neg, pd->kif, M_GETFIB(pd->m)))
1276 r = r->skip[PF_SKIP_SRC_ADDR];
1277 else if (PF_MISMATCHAW(&r->dst.addr,
1278 (struct pf_addr *)&pd->dst, AF_INET6,
1279 r->dst.neg, NULL, M_GETFIB(pd->m)))
1280 r = r->skip[PF_SKIP_DST_ADDR];
1281 else
1282 break;
1283 }
1284
1285 if (scrub_compat) {
1286 /* With scrub rules present IPv6 normalization happens only
1287 * if one of rules has matched and it's not a "no scrub" rule */
1288 if (r == NULL || r->action == PF_NOSCRUB)
1289 return (PF_PASS);
1290
1291 pf_counter_u64_critical_enter();
1292 pf_counter_u64_add_protected(&r->packets[pd->dir == PF_OUT], 1);
1293 pf_counter_u64_add_protected(&r->bytes[pd->dir == PF_OUT], pd->tot_len);
1294 pf_counter_u64_critical_exit();
1295 pf_rule_to_actions(r, &pd->act);
1296 }
1297
1298 if (!pf_pull_hdr(pd->m, off, &frag, sizeof(frag), NULL, reason, AF_INET6))
1299 return (PF_DROP);
1300
1301 /* Offset now points to data portion. */
1302 off += sizeof(frag);
1303
1304 if (pd->virtual_proto == PF_VPROTO_FRAGMENT) {
1305 /* Returns PF_DROP or *m0 is NULL or completely reassembled
1306 * mbuf. */
1307 if (pf_reassemble6(&pd->m, &frag, off, pd->extoff, reason) != PF_PASS)
1308 return (PF_DROP);
1309 if (pd->m == NULL)
1310 return (PF_DROP);
1311 h = mtod(pd->m, struct ip6_hdr *);
1312 pd->tot_len = ntohs(h->ip6_plen) + sizeof(struct ip6_hdr);
1313 }
1314
1315 return (PF_PASS);
1316 }
1317 #endif /* INET6 */
1318
1319 int
pf_normalize_tcp(struct pf_pdesc * pd)1320 pf_normalize_tcp(struct pf_pdesc *pd)
1321 {
1322 struct pf_krule *r, *rm = NULL;
1323 struct tcphdr *th = &pd->hdr.tcp;
1324 int rewrite = 0;
1325 u_short reason;
1326 u_int16_t flags;
1327 sa_family_t af = pd->af;
1328 int srs;
1329
1330 PF_RULES_RASSERT();
1331
1332 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
1333 /* Check if there any scrub rules. Lack of scrub rules means enforced
1334 * packet normalization operation just like in OpenBSD. */
1335 srs = (r != NULL);
1336 while (r != NULL) {
1337 pf_counter_u64_add(&r->evaluations, 1);
1338 if (pfi_kkif_match(r->kif, pd->kif) == r->ifnot)
1339 r = r->skip[PF_SKIP_IFP];
1340 else if (r->direction && r->direction != pd->dir)
1341 r = r->skip[PF_SKIP_DIR];
1342 else if (r->af && r->af != af)
1343 r = r->skip[PF_SKIP_AF];
1344 else if (r->proto && r->proto != pd->proto)
1345 r = r->skip[PF_SKIP_PROTO];
1346 else if (PF_MISMATCHAW(&r->src.addr, pd->src, af,
1347 r->src.neg, pd->kif, M_GETFIB(pd->m)))
1348 r = r->skip[PF_SKIP_SRC_ADDR];
1349 else if (r->src.port_op && !pf_match_port(r->src.port_op,
1350 r->src.port[0], r->src.port[1], th->th_sport))
1351 r = r->skip[PF_SKIP_SRC_PORT];
1352 else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af,
1353 r->dst.neg, NULL, M_GETFIB(pd->m)))
1354 r = r->skip[PF_SKIP_DST_ADDR];
1355 else if (r->dst.port_op && !pf_match_port(r->dst.port_op,
1356 r->dst.port[0], r->dst.port[1], th->th_dport))
1357 r = r->skip[PF_SKIP_DST_PORT];
1358 else if (r->os_fingerprint != PF_OSFP_ANY && !pf_osfp_match(
1359 pf_osfp_fingerprint(pd, th),
1360 r->os_fingerprint))
1361 r = TAILQ_NEXT(r, entries);
1362 else {
1363 rm = r;
1364 break;
1365 }
1366 }
1367
1368 if (srs) {
1369 /* With scrub rules present TCP normalization happens only
1370 * if one of rules has matched and it's not a "no scrub" rule */
1371 if (rm == NULL || rm->action == PF_NOSCRUB)
1372 return (PF_PASS);
1373
1374 pf_counter_u64_critical_enter();
1375 pf_counter_u64_add_protected(&r->packets[pd->dir == PF_OUT], 1);
1376 pf_counter_u64_add_protected(&r->bytes[pd->dir == PF_OUT], pd->tot_len);
1377 pf_counter_u64_critical_exit();
1378 pf_rule_to_actions(rm, &pd->act);
1379 }
1380
1381 if (rm && rm->rule_flag & PFRULE_REASSEMBLE_TCP)
1382 pd->flags |= PFDESC_TCP_NORM;
1383
1384 flags = tcp_get_flags(th);
1385 if (flags & TH_SYN) {
1386 /* Illegal packet */
1387 if (flags & TH_RST)
1388 goto tcp_drop;
1389
1390 if (flags & TH_FIN)
1391 goto tcp_drop;
1392 } else {
1393 /* Illegal packet */
1394 if (!(flags & (TH_ACK|TH_RST)))
1395 goto tcp_drop;
1396 }
1397
1398 if (!(flags & TH_ACK)) {
1399 /* These flags are only valid if ACK is set */
1400 if ((flags & TH_FIN) || (flags & TH_PUSH) || (flags & TH_URG))
1401 goto tcp_drop;
1402 }
1403
1404 /* Check for illegal header length */
1405 if (th->th_off < (sizeof(struct tcphdr) >> 2))
1406 goto tcp_drop;
1407
1408 /* If flags changed, or reserved data set, then adjust */
1409 if (flags != tcp_get_flags(th) ||
1410 (tcp_get_flags(th) & (TH_RES1|TH_RES2|TH_RES2)) != 0) {
1411 u_int16_t ov, nv;
1412
1413 ov = *(u_int16_t *)(&th->th_ack + 1);
1414 flags &= ~(TH_RES1 | TH_RES2 | TH_RES3);
1415 tcp_set_flags(th, flags);
1416 nv = *(u_int16_t *)(&th->th_ack + 1);
1417
1418 th->th_sum = pf_proto_cksum_fixup(pd->m, th->th_sum, ov, nv, 0);
1419 rewrite = 1;
1420 }
1421
1422 /* Remove urgent pointer, if TH_URG is not set */
1423 if (!(flags & TH_URG) && th->th_urp) {
1424 th->th_sum = pf_proto_cksum_fixup(pd->m, th->th_sum, th->th_urp,
1425 0, 0);
1426 th->th_urp = 0;
1427 rewrite = 1;
1428 }
1429
1430 /* copy back packet headers if we sanitized */
1431 if (rewrite)
1432 m_copyback(pd->m, pd->off, sizeof(*th), (caddr_t)th);
1433
1434 return (PF_PASS);
1435
1436 tcp_drop:
1437 REASON_SET(&reason, PFRES_NORM);
1438 if (rm != NULL && r->log)
1439 PFLOG_PACKET(PF_DROP, reason, r, NULL, NULL, pd, 1);
1440 return (PF_DROP);
1441 }
1442
1443 int
pf_normalize_tcp_init(struct pf_pdesc * pd,struct tcphdr * th,struct pf_state_peer * src,struct pf_state_peer * dst)1444 pf_normalize_tcp_init(struct pf_pdesc *pd, struct tcphdr *th,
1445 struct pf_state_peer *src, struct pf_state_peer *dst)
1446 {
1447 u_int32_t tsval, tsecr;
1448 u_int8_t hdr[60];
1449 u_int8_t *opt;
1450
1451 KASSERT((src->scrub == NULL),
1452 ("pf_normalize_tcp_init: src->scrub != NULL"));
1453
1454 src->scrub = uma_zalloc(V_pf_state_scrub_z, M_ZERO | M_NOWAIT);
1455 if (src->scrub == NULL)
1456 return (1);
1457
1458 switch (pd->af) {
1459 #ifdef INET
1460 case AF_INET: {
1461 struct ip *h = mtod(pd->m, struct ip *);
1462 src->scrub->pfss_ttl = h->ip_ttl;
1463 break;
1464 }
1465 #endif /* INET */
1466 #ifdef INET6
1467 case AF_INET6: {
1468 struct ip6_hdr *h = mtod(pd->m, struct ip6_hdr *);
1469 src->scrub->pfss_ttl = h->ip6_hlim;
1470 break;
1471 }
1472 #endif /* INET6 */
1473 }
1474
1475 /*
1476 * All normalizations below are only begun if we see the start of
1477 * the connections. They must all set an enabled bit in pfss_flags
1478 */
1479 if ((tcp_get_flags(th) & TH_SYN) == 0)
1480 return (0);
1481
1482 if (th->th_off > (sizeof(struct tcphdr) >> 2) && src->scrub &&
1483 pf_pull_hdr(pd->m, pd->off, hdr, th->th_off << 2, NULL, NULL, pd->af)) {
1484 /* Diddle with TCP options */
1485 int hlen;
1486 opt = hdr + sizeof(struct tcphdr);
1487 hlen = (th->th_off << 2) - sizeof(struct tcphdr);
1488 while (hlen >= TCPOLEN_TIMESTAMP) {
1489 switch (*opt) {
1490 case TCPOPT_EOL: /* FALLTHROUGH */
1491 case TCPOPT_NOP:
1492 opt++;
1493 hlen--;
1494 break;
1495 case TCPOPT_TIMESTAMP:
1496 if (opt[1] >= TCPOLEN_TIMESTAMP) {
1497 src->scrub->pfss_flags |=
1498 PFSS_TIMESTAMP;
1499 src->scrub->pfss_ts_mod =
1500 htonl(arc4random());
1501
1502 /* note PFSS_PAWS not set yet */
1503 memcpy(&tsval, &opt[2],
1504 sizeof(u_int32_t));
1505 memcpy(&tsecr, &opt[6],
1506 sizeof(u_int32_t));
1507 src->scrub->pfss_tsval0 = ntohl(tsval);
1508 src->scrub->pfss_tsval = ntohl(tsval);
1509 src->scrub->pfss_tsecr = ntohl(tsecr);
1510 getmicrouptime(&src->scrub->pfss_last);
1511 }
1512 /* FALLTHROUGH */
1513 default:
1514 hlen -= MAX(opt[1], 2);
1515 opt += MAX(opt[1], 2);
1516 break;
1517 }
1518 }
1519 }
1520
1521 return (0);
1522 }
1523
1524 void
pf_normalize_tcp_cleanup(struct pf_kstate * state)1525 pf_normalize_tcp_cleanup(struct pf_kstate *state)
1526 {
1527 /* XXX Note: this also cleans up SCTP. */
1528 uma_zfree(V_pf_state_scrub_z, state->src.scrub);
1529 uma_zfree(V_pf_state_scrub_z, state->dst.scrub);
1530
1531 /* Someday... flush the TCP segment reassembly descriptors. */
1532 }
1533 int
pf_normalize_sctp_init(struct pf_pdesc * pd,struct pf_state_peer * src,struct pf_state_peer * dst)1534 pf_normalize_sctp_init(struct pf_pdesc *pd, struct pf_state_peer *src,
1535 struct pf_state_peer *dst)
1536 {
1537 src->scrub = uma_zalloc(V_pf_state_scrub_z, M_ZERO | M_NOWAIT);
1538 if (src->scrub == NULL)
1539 return (1);
1540
1541 dst->scrub = uma_zalloc(V_pf_state_scrub_z, M_ZERO | M_NOWAIT);
1542 if (dst->scrub == NULL) {
1543 uma_zfree(V_pf_state_scrub_z, src);
1544 return (1);
1545 }
1546
1547 dst->scrub->pfss_v_tag = pd->sctp_initiate_tag;
1548
1549 return (0);
1550 }
1551
1552 int
pf_normalize_tcp_stateful(struct pf_pdesc * pd,u_short * reason,struct tcphdr * th,struct pf_kstate * state,struct pf_state_peer * src,struct pf_state_peer * dst,int * writeback)1553 pf_normalize_tcp_stateful(struct pf_pdesc *pd,
1554 u_short *reason, struct tcphdr *th, struct pf_kstate *state,
1555 struct pf_state_peer *src, struct pf_state_peer *dst, int *writeback)
1556 {
1557 struct timeval uptime;
1558 u_int32_t tsval, tsecr;
1559 u_int tsval_from_last;
1560 u_int8_t hdr[60];
1561 u_int8_t *opt;
1562 int copyback = 0;
1563 int got_ts = 0;
1564 size_t startoff;
1565
1566 KASSERT((src->scrub || dst->scrub),
1567 ("%s: src->scrub && dst->scrub!", __func__));
1568
1569 /*
1570 * Enforce the minimum TTL seen for this connection. Negate a common
1571 * technique to evade an intrusion detection system and confuse
1572 * firewall state code.
1573 */
1574 switch (pd->af) {
1575 #ifdef INET
1576 case AF_INET: {
1577 if (src->scrub) {
1578 struct ip *h = mtod(pd->m, struct ip *);
1579 if (h->ip_ttl > src->scrub->pfss_ttl)
1580 src->scrub->pfss_ttl = h->ip_ttl;
1581 h->ip_ttl = src->scrub->pfss_ttl;
1582 }
1583 break;
1584 }
1585 #endif /* INET */
1586 #ifdef INET6
1587 case AF_INET6: {
1588 if (src->scrub) {
1589 struct ip6_hdr *h = mtod(pd->m, struct ip6_hdr *);
1590 if (h->ip6_hlim > src->scrub->pfss_ttl)
1591 src->scrub->pfss_ttl = h->ip6_hlim;
1592 h->ip6_hlim = src->scrub->pfss_ttl;
1593 }
1594 break;
1595 }
1596 #endif /* INET6 */
1597 }
1598
1599 if (th->th_off > (sizeof(struct tcphdr) >> 2) &&
1600 ((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) ||
1601 (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) &&
1602 pf_pull_hdr(pd->m, pd->off, hdr, th->th_off << 2, NULL, NULL, pd->af)) {
1603 /* Diddle with TCP options */
1604 int hlen;
1605 opt = hdr + sizeof(struct tcphdr);
1606 hlen = (th->th_off << 2) - sizeof(struct tcphdr);
1607 while (hlen >= TCPOLEN_TIMESTAMP) {
1608 startoff = opt - (hdr + sizeof(struct tcphdr));
1609 switch (*opt) {
1610 case TCPOPT_EOL: /* FALLTHROUGH */
1611 case TCPOPT_NOP:
1612 opt++;
1613 hlen--;
1614 break;
1615 case TCPOPT_TIMESTAMP:
1616 /* Modulate the timestamps. Can be used for
1617 * NAT detection, OS uptime determination or
1618 * reboot detection.
1619 */
1620
1621 if (got_ts) {
1622 /* Huh? Multiple timestamps!? */
1623 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1624 DPFPRINTF(("multiple TS??\n"));
1625 pf_print_state(state);
1626 printf("\n");
1627 }
1628 REASON_SET(reason, PFRES_TS);
1629 return (PF_DROP);
1630 }
1631 if (opt[1] >= TCPOLEN_TIMESTAMP) {
1632 memcpy(&tsval, &opt[2],
1633 sizeof(u_int32_t));
1634 if (tsval && src->scrub &&
1635 (src->scrub->pfss_flags &
1636 PFSS_TIMESTAMP)) {
1637 tsval = ntohl(tsval);
1638 pf_patch_32_unaligned(pd->m,
1639 &th->th_sum,
1640 &opt[2],
1641 htonl(tsval +
1642 src->scrub->pfss_ts_mod),
1643 PF_ALGNMNT(startoff),
1644 0);
1645 copyback = 1;
1646 }
1647
1648 /* Modulate TS reply iff valid (!0) */
1649 memcpy(&tsecr, &opt[6],
1650 sizeof(u_int32_t));
1651 if (tsecr && dst->scrub &&
1652 (dst->scrub->pfss_flags &
1653 PFSS_TIMESTAMP)) {
1654 tsecr = ntohl(tsecr)
1655 - dst->scrub->pfss_ts_mod;
1656 pf_patch_32_unaligned(pd->m,
1657 &th->th_sum,
1658 &opt[6],
1659 htonl(tsecr),
1660 PF_ALGNMNT(startoff),
1661 0);
1662 copyback = 1;
1663 }
1664 got_ts = 1;
1665 }
1666 /* FALLTHROUGH */
1667 default:
1668 hlen -= MAX(opt[1], 2);
1669 opt += MAX(opt[1], 2);
1670 break;
1671 }
1672 }
1673 if (copyback) {
1674 /* Copyback the options, caller copys back header */
1675 *writeback = 1;
1676 m_copyback(pd->m, pd->off + sizeof(struct tcphdr),
1677 (th->th_off << 2) - sizeof(struct tcphdr), hdr +
1678 sizeof(struct tcphdr));
1679 }
1680 }
1681
1682 /*
1683 * Must invalidate PAWS checks on connections idle for too long.
1684 * The fastest allowed timestamp clock is 1ms. That turns out to
1685 * be about 24 days before it wraps. XXX Right now our lowerbound
1686 * TS echo check only works for the first 12 days of a connection
1687 * when the TS has exhausted half its 32bit space
1688 */
1689 #define TS_MAX_IDLE (24*24*60*60)
1690 #define TS_MAX_CONN (12*24*60*60) /* XXX remove when better tsecr check */
1691
1692 getmicrouptime(&uptime);
1693 if (src->scrub && (src->scrub->pfss_flags & PFSS_PAWS) &&
1694 (uptime.tv_sec - src->scrub->pfss_last.tv_sec > TS_MAX_IDLE ||
1695 time_uptime - (state->creation / 1000) > TS_MAX_CONN)) {
1696 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1697 DPFPRINTF(("src idled out of PAWS\n"));
1698 pf_print_state(state);
1699 printf("\n");
1700 }
1701 src->scrub->pfss_flags = (src->scrub->pfss_flags & ~PFSS_PAWS)
1702 | PFSS_PAWS_IDLED;
1703 }
1704 if (dst->scrub && (dst->scrub->pfss_flags & PFSS_PAWS) &&
1705 uptime.tv_sec - dst->scrub->pfss_last.tv_sec > TS_MAX_IDLE) {
1706 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1707 DPFPRINTF(("dst idled out of PAWS\n"));
1708 pf_print_state(state);
1709 printf("\n");
1710 }
1711 dst->scrub->pfss_flags = (dst->scrub->pfss_flags & ~PFSS_PAWS)
1712 | PFSS_PAWS_IDLED;
1713 }
1714
1715 if (got_ts && src->scrub && dst->scrub &&
1716 (src->scrub->pfss_flags & PFSS_PAWS) &&
1717 (dst->scrub->pfss_flags & PFSS_PAWS)) {
1718 /* Validate that the timestamps are "in-window".
1719 * RFC1323 describes TCP Timestamp options that allow
1720 * measurement of RTT (round trip time) and PAWS
1721 * (protection against wrapped sequence numbers). PAWS
1722 * gives us a set of rules for rejecting packets on
1723 * long fat pipes (packets that were somehow delayed
1724 * in transit longer than the time it took to send the
1725 * full TCP sequence space of 4Gb). We can use these
1726 * rules and infer a few others that will let us treat
1727 * the 32bit timestamp and the 32bit echoed timestamp
1728 * as sequence numbers to prevent a blind attacker from
1729 * inserting packets into a connection.
1730 *
1731 * RFC1323 tells us:
1732 * - The timestamp on this packet must be greater than
1733 * or equal to the last value echoed by the other
1734 * endpoint. The RFC says those will be discarded
1735 * since it is a dup that has already been acked.
1736 * This gives us a lowerbound on the timestamp.
1737 * timestamp >= other last echoed timestamp
1738 * - The timestamp will be less than or equal to
1739 * the last timestamp plus the time between the
1740 * last packet and now. The RFC defines the max
1741 * clock rate as 1ms. We will allow clocks to be
1742 * up to 10% fast and will allow a total difference
1743 * or 30 seconds due to a route change. And this
1744 * gives us an upperbound on the timestamp.
1745 * timestamp <= last timestamp + max ticks
1746 * We have to be careful here. Windows will send an
1747 * initial timestamp of zero and then initialize it
1748 * to a random value after the 3whs; presumably to
1749 * avoid a DoS by having to call an expensive RNG
1750 * during a SYN flood. Proof MS has at least one
1751 * good security geek.
1752 *
1753 * - The TCP timestamp option must also echo the other
1754 * endpoints timestamp. The timestamp echoed is the
1755 * one carried on the earliest unacknowledged segment
1756 * on the left edge of the sequence window. The RFC
1757 * states that the host will reject any echoed
1758 * timestamps that were larger than any ever sent.
1759 * This gives us an upperbound on the TS echo.
1760 * tescr <= largest_tsval
1761 * - The lowerbound on the TS echo is a little more
1762 * tricky to determine. The other endpoint's echoed
1763 * values will not decrease. But there may be
1764 * network conditions that re-order packets and
1765 * cause our view of them to decrease. For now the
1766 * only lowerbound we can safely determine is that
1767 * the TS echo will never be less than the original
1768 * TS. XXX There is probably a better lowerbound.
1769 * Remove TS_MAX_CONN with better lowerbound check.
1770 * tescr >= other original TS
1771 *
1772 * It is also important to note that the fastest
1773 * timestamp clock of 1ms will wrap its 32bit space in
1774 * 24 days. So we just disable TS checking after 24
1775 * days of idle time. We actually must use a 12d
1776 * connection limit until we can come up with a better
1777 * lowerbound to the TS echo check.
1778 */
1779 struct timeval delta_ts;
1780 int ts_fudge;
1781
1782 /*
1783 * PFTM_TS_DIFF is how many seconds of leeway to allow
1784 * a host's timestamp. This can happen if the previous
1785 * packet got delayed in transit for much longer than
1786 * this packet.
1787 */
1788 if ((ts_fudge = state->rule->timeout[PFTM_TS_DIFF]) == 0)
1789 ts_fudge = V_pf_default_rule.timeout[PFTM_TS_DIFF];
1790
1791 /* Calculate max ticks since the last timestamp */
1792 #define TS_MAXFREQ 1100 /* RFC max TS freq of 1Khz + 10% skew */
1793 #define TS_MICROSECS 1000000 /* microseconds per second */
1794 delta_ts = uptime;
1795 timevalsub(&delta_ts, &src->scrub->pfss_last);
1796 tsval_from_last = (delta_ts.tv_sec + ts_fudge) * TS_MAXFREQ;
1797 tsval_from_last += delta_ts.tv_usec / (TS_MICROSECS/TS_MAXFREQ);
1798
1799 if ((src->state >= TCPS_ESTABLISHED &&
1800 dst->state >= TCPS_ESTABLISHED) &&
1801 (SEQ_LT(tsval, dst->scrub->pfss_tsecr) ||
1802 SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) ||
1803 (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) ||
1804 SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) {
1805 /* Bad RFC1323 implementation or an insertion attack.
1806 *
1807 * - Solaris 2.6 and 2.7 are known to send another ACK
1808 * after the FIN,FIN|ACK,ACK closing that carries
1809 * an old timestamp.
1810 */
1811
1812 DPFPRINTF(("Timestamp failed %c%c%c%c\n",
1813 SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '0' : ' ',
1814 SEQ_GT(tsval, src->scrub->pfss_tsval +
1815 tsval_from_last) ? '1' : ' ',
1816 SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ',
1817 SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' '));
1818 DPFPRINTF((" tsval: %u tsecr: %u +ticks: %u "
1819 "idle: %jus %lums\n",
1820 tsval, tsecr, tsval_from_last,
1821 (uintmax_t)delta_ts.tv_sec,
1822 delta_ts.tv_usec / 1000));
1823 DPFPRINTF((" src->tsval: %u tsecr: %u\n",
1824 src->scrub->pfss_tsval, src->scrub->pfss_tsecr));
1825 DPFPRINTF((" dst->tsval: %u tsecr: %u tsval0: %u"
1826 "\n", dst->scrub->pfss_tsval,
1827 dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0));
1828 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1829 pf_print_state(state);
1830 pf_print_flags(tcp_get_flags(th));
1831 printf("\n");
1832 }
1833 REASON_SET(reason, PFRES_TS);
1834 return (PF_DROP);
1835 }
1836
1837 /* XXX I'd really like to require tsecr but it's optional */
1838
1839 } else if (!got_ts && (tcp_get_flags(th) & TH_RST) == 0 &&
1840 ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED)
1841 || pd->p_len > 0 || (tcp_get_flags(th) & TH_SYN)) &&
1842 src->scrub && dst->scrub &&
1843 (src->scrub->pfss_flags & PFSS_PAWS) &&
1844 (dst->scrub->pfss_flags & PFSS_PAWS)) {
1845 /* Didn't send a timestamp. Timestamps aren't really useful
1846 * when:
1847 * - connection opening or closing (often not even sent).
1848 * but we must not let an attacker to put a FIN on a
1849 * data packet to sneak it through our ESTABLISHED check.
1850 * - on a TCP reset. RFC suggests not even looking at TS.
1851 * - on an empty ACK. The TS will not be echoed so it will
1852 * probably not help keep the RTT calculation in sync and
1853 * there isn't as much danger when the sequence numbers
1854 * got wrapped. So some stacks don't include TS on empty
1855 * ACKs :-(
1856 *
1857 * To minimize the disruption to mostly RFC1323 conformant
1858 * stacks, we will only require timestamps on data packets.
1859 *
1860 * And what do ya know, we cannot require timestamps on data
1861 * packets. There appear to be devices that do legitimate
1862 * TCP connection hijacking. There are HTTP devices that allow
1863 * a 3whs (with timestamps) and then buffer the HTTP request.
1864 * If the intermediate device has the HTTP response cache, it
1865 * will spoof the response but not bother timestamping its
1866 * packets. So we can look for the presence of a timestamp in
1867 * the first data packet and if there, require it in all future
1868 * packets.
1869 */
1870
1871 if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) {
1872 /*
1873 * Hey! Someone tried to sneak a packet in. Or the
1874 * stack changed its RFC1323 behavior?!?!
1875 */
1876 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1877 DPFPRINTF(("Did not receive expected RFC1323 "
1878 "timestamp\n"));
1879 pf_print_state(state);
1880 pf_print_flags(tcp_get_flags(th));
1881 printf("\n");
1882 }
1883 REASON_SET(reason, PFRES_TS);
1884 return (PF_DROP);
1885 }
1886 }
1887
1888 /*
1889 * We will note if a host sends his data packets with or without
1890 * timestamps. And require all data packets to contain a timestamp
1891 * if the first does. PAWS implicitly requires that all data packets be
1892 * timestamped. But I think there are middle-man devices that hijack
1893 * TCP streams immediately after the 3whs and don't timestamp their
1894 * packets (seen in a WWW accelerator or cache).
1895 */
1896 if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags &
1897 (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) {
1898 if (got_ts)
1899 src->scrub->pfss_flags |= PFSS_DATA_TS;
1900 else {
1901 src->scrub->pfss_flags |= PFSS_DATA_NOTS;
1902 if (V_pf_status.debug >= PF_DEBUG_MISC && dst->scrub &&
1903 (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) {
1904 /* Don't warn if other host rejected RFC1323 */
1905 DPFPRINTF(("Broken RFC1323 stack did not "
1906 "timestamp data packet. Disabled PAWS "
1907 "security.\n"));
1908 pf_print_state(state);
1909 pf_print_flags(tcp_get_flags(th));
1910 printf("\n");
1911 }
1912 }
1913 }
1914
1915 /*
1916 * Update PAWS values
1917 */
1918 if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags &
1919 (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) {
1920 getmicrouptime(&src->scrub->pfss_last);
1921 if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) ||
1922 (src->scrub->pfss_flags & PFSS_PAWS) == 0)
1923 src->scrub->pfss_tsval = tsval;
1924
1925 if (tsecr) {
1926 if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) ||
1927 (src->scrub->pfss_flags & PFSS_PAWS) == 0)
1928 src->scrub->pfss_tsecr = tsecr;
1929
1930 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 &&
1931 (SEQ_LT(tsval, src->scrub->pfss_tsval0) ||
1932 src->scrub->pfss_tsval0 == 0)) {
1933 /* tsval0 MUST be the lowest timestamp */
1934 src->scrub->pfss_tsval0 = tsval;
1935 }
1936
1937 /* Only fully initialized after a TS gets echoed */
1938 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0)
1939 src->scrub->pfss_flags |= PFSS_PAWS;
1940 }
1941 }
1942
1943 /* I have a dream.... TCP segment reassembly.... */
1944 return (0);
1945 }
1946
1947 int
pf_normalize_mss(struct pf_pdesc * pd)1948 pf_normalize_mss(struct pf_pdesc *pd)
1949 {
1950 struct tcphdr *th = &pd->hdr.tcp;
1951 u_int16_t *mss;
1952 int thoff;
1953 int opt, cnt, optlen = 0;
1954 u_char opts[TCP_MAXOLEN];
1955 u_char *optp = opts;
1956 size_t startoff;
1957
1958 thoff = th->th_off << 2;
1959 cnt = thoff - sizeof(struct tcphdr);
1960
1961 if (cnt > 0 && !pf_pull_hdr(pd->m, pd->off + sizeof(*th), opts, cnt,
1962 NULL, NULL, pd->af))
1963 return (0);
1964
1965 for (; cnt > 0; cnt -= optlen, optp += optlen) {
1966 startoff = optp - opts;
1967 opt = optp[0];
1968 if (opt == TCPOPT_EOL)
1969 break;
1970 if (opt == TCPOPT_NOP)
1971 optlen = 1;
1972 else {
1973 if (cnt < 2)
1974 break;
1975 optlen = optp[1];
1976 if (optlen < 2 || optlen > cnt)
1977 break;
1978 }
1979 switch (opt) {
1980 case TCPOPT_MAXSEG:
1981 mss = (u_int16_t *)(optp + 2);
1982 if ((ntohs(*mss)) > pd->act.max_mss) {
1983 pf_patch_16_unaligned(pd->m,
1984 &th->th_sum,
1985 mss, htons(pd->act.max_mss),
1986 PF_ALGNMNT(startoff),
1987 0);
1988 m_copyback(pd->m, pd->off + sizeof(*th),
1989 thoff - sizeof(*th), opts);
1990 m_copyback(pd->m, pd->off, sizeof(*th), (caddr_t)th);
1991 }
1992 break;
1993 default:
1994 break;
1995 }
1996 }
1997
1998 return (0);
1999 }
2000
2001 int
pf_scan_sctp(struct pf_pdesc * pd)2002 pf_scan_sctp(struct pf_pdesc *pd)
2003 {
2004 struct sctp_chunkhdr ch = { };
2005 int chunk_off = sizeof(struct sctphdr);
2006 int chunk_start;
2007 int ret;
2008
2009 while (pd->off + chunk_off < pd->tot_len) {
2010 if (!pf_pull_hdr(pd->m, pd->off + chunk_off, &ch, sizeof(ch), NULL,
2011 NULL, pd->af))
2012 return (PF_DROP);
2013
2014 /* Length includes the header, this must be at least 4. */
2015 if (ntohs(ch.chunk_length) < 4)
2016 return (PF_DROP);
2017
2018 chunk_start = chunk_off;
2019 chunk_off += roundup(ntohs(ch.chunk_length), 4);
2020
2021 switch (ch.chunk_type) {
2022 case SCTP_INITIATION:
2023 case SCTP_INITIATION_ACK: {
2024 struct sctp_init_chunk init;
2025
2026 if (!pf_pull_hdr(pd->m, pd->off + chunk_start, &init,
2027 sizeof(init), NULL, NULL, pd->af))
2028 return (PF_DROP);
2029
2030 /*
2031 * RFC 9620, Section 3.3.2, "The Initiate Tag is allowed to have
2032 * any value except 0."
2033 */
2034 if (init.init.initiate_tag == 0)
2035 return (PF_DROP);
2036 if (init.init.num_inbound_streams == 0)
2037 return (PF_DROP);
2038 if (init.init.num_outbound_streams == 0)
2039 return (PF_DROP);
2040 if (ntohl(init.init.a_rwnd) < SCTP_MIN_RWND)
2041 return (PF_DROP);
2042
2043 /*
2044 * RFC 9260, Section 3.1, INIT chunks MUST have zero
2045 * verification tag.
2046 */
2047 if (ch.chunk_type == SCTP_INITIATION &&
2048 pd->hdr.sctp.v_tag != 0)
2049 return (PF_DROP);
2050
2051 pd->sctp_initiate_tag = init.init.initiate_tag;
2052
2053 if (ch.chunk_type == SCTP_INITIATION)
2054 pd->sctp_flags |= PFDESC_SCTP_INIT;
2055 else
2056 pd->sctp_flags |= PFDESC_SCTP_INIT_ACK;
2057
2058 ret = pf_multihome_scan_init(pd->off + chunk_start,
2059 ntohs(init.ch.chunk_length), pd);
2060 if (ret != PF_PASS)
2061 return (ret);
2062
2063 break;
2064 }
2065 case SCTP_ABORT_ASSOCIATION:
2066 pd->sctp_flags |= PFDESC_SCTP_ABORT;
2067 break;
2068 case SCTP_SHUTDOWN:
2069 case SCTP_SHUTDOWN_ACK:
2070 pd->sctp_flags |= PFDESC_SCTP_SHUTDOWN;
2071 break;
2072 case SCTP_SHUTDOWN_COMPLETE:
2073 pd->sctp_flags |= PFDESC_SCTP_SHUTDOWN_COMPLETE;
2074 break;
2075 case SCTP_COOKIE_ECHO:
2076 pd->sctp_flags |= PFDESC_SCTP_COOKIE;
2077 break;
2078 case SCTP_COOKIE_ACK:
2079 pd->sctp_flags |= PFDESC_SCTP_COOKIE_ACK;
2080 break;
2081 case SCTP_DATA:
2082 pd->sctp_flags |= PFDESC_SCTP_DATA;
2083 break;
2084 case SCTP_HEARTBEAT_REQUEST:
2085 pd->sctp_flags |= PFDESC_SCTP_HEARTBEAT;
2086 break;
2087 case SCTP_HEARTBEAT_ACK:
2088 pd->sctp_flags |= PFDESC_SCTP_HEARTBEAT_ACK;
2089 break;
2090 case SCTP_ASCONF:
2091 pd->sctp_flags |= PFDESC_SCTP_ASCONF;
2092
2093 ret = pf_multihome_scan_asconf(pd->off + chunk_start,
2094 ntohs(ch.chunk_length), pd);
2095 if (ret != PF_PASS)
2096 return (ret);
2097 break;
2098 default:
2099 pd->sctp_flags |= PFDESC_SCTP_OTHER;
2100 break;
2101 }
2102 }
2103
2104 /* Validate chunk lengths vs. packet length. */
2105 if (pd->off + chunk_off != pd->tot_len)
2106 return (PF_DROP);
2107
2108 /*
2109 * INIT, INIT_ACK or SHUTDOWN_COMPLETE chunks must always be the only
2110 * one in a packet.
2111 */
2112 if ((pd->sctp_flags & PFDESC_SCTP_INIT) &&
2113 (pd->sctp_flags & ~PFDESC_SCTP_INIT))
2114 return (PF_DROP);
2115 if ((pd->sctp_flags & PFDESC_SCTP_INIT_ACK) &&
2116 (pd->sctp_flags & ~PFDESC_SCTP_INIT_ACK))
2117 return (PF_DROP);
2118 if ((pd->sctp_flags & PFDESC_SCTP_SHUTDOWN_COMPLETE) &&
2119 (pd->sctp_flags & ~PFDESC_SCTP_SHUTDOWN_COMPLETE))
2120 return (PF_DROP);
2121 if ((pd->sctp_flags & PFDESC_SCTP_ABORT) &&
2122 (pd->sctp_flags & PFDESC_SCTP_DATA)) {
2123 /*
2124 * RFC4960 3.3.7: DATA chunks MUST NOT be
2125 * bundled with ABORT.
2126 */
2127 return (PF_DROP);
2128 }
2129
2130 return (PF_PASS);
2131 }
2132
2133 int
pf_normalize_sctp(struct pf_pdesc * pd)2134 pf_normalize_sctp(struct pf_pdesc *pd)
2135 {
2136 struct pf_krule *r, *rm = NULL;
2137 struct sctphdr *sh = &pd->hdr.sctp;
2138 u_short reason;
2139 sa_family_t af = pd->af;
2140 int srs;
2141
2142 PF_RULES_RASSERT();
2143
2144 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
2145 /* Check if there any scrub rules. Lack of scrub rules means enforced
2146 * packet normalization operation just like in OpenBSD. */
2147 srs = (r != NULL);
2148 while (r != NULL) {
2149 pf_counter_u64_add(&r->evaluations, 1);
2150 if (pfi_kkif_match(r->kif, pd->kif) == r->ifnot)
2151 r = r->skip[PF_SKIP_IFP];
2152 else if (r->direction && r->direction != pd->dir)
2153 r = r->skip[PF_SKIP_DIR];
2154 else if (r->af && r->af != af)
2155 r = r->skip[PF_SKIP_AF];
2156 else if (r->proto && r->proto != pd->proto)
2157 r = r->skip[PF_SKIP_PROTO];
2158 else if (PF_MISMATCHAW(&r->src.addr, pd->src, af,
2159 r->src.neg, pd->kif, M_GETFIB(pd->m)))
2160 r = r->skip[PF_SKIP_SRC_ADDR];
2161 else if (r->src.port_op && !pf_match_port(r->src.port_op,
2162 r->src.port[0], r->src.port[1], sh->src_port))
2163 r = r->skip[PF_SKIP_SRC_PORT];
2164 else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af,
2165 r->dst.neg, NULL, M_GETFIB(pd->m)))
2166 r = r->skip[PF_SKIP_DST_ADDR];
2167 else if (r->dst.port_op && !pf_match_port(r->dst.port_op,
2168 r->dst.port[0], r->dst.port[1], sh->dest_port))
2169 r = r->skip[PF_SKIP_DST_PORT];
2170 else {
2171 rm = r;
2172 break;
2173 }
2174 }
2175
2176 if (srs) {
2177 /* With scrub rules present SCTP normalization happens only
2178 * if one of rules has matched and it's not a "no scrub" rule */
2179 if (rm == NULL || rm->action == PF_NOSCRUB)
2180 return (PF_PASS);
2181
2182 pf_counter_u64_critical_enter();
2183 pf_counter_u64_add_protected(&r->packets[pd->dir == PF_OUT], 1);
2184 pf_counter_u64_add_protected(&r->bytes[pd->dir == PF_OUT], pd->tot_len);
2185 pf_counter_u64_critical_exit();
2186 }
2187
2188 /* Verify we're a multiple of 4 bytes long */
2189 if ((pd->tot_len - pd->off - sizeof(struct sctphdr)) % 4)
2190 goto sctp_drop;
2191
2192 /* INIT chunk needs to be the only chunk */
2193 if (pd->sctp_flags & PFDESC_SCTP_INIT)
2194 if (pd->sctp_flags & ~PFDESC_SCTP_INIT)
2195 goto sctp_drop;
2196
2197 return (PF_PASS);
2198
2199 sctp_drop:
2200 REASON_SET(&reason, PFRES_NORM);
2201 if (rm != NULL && r->log)
2202 PFLOG_PACKET(PF_DROP, reason, r, NULL, NULL, pd,
2203 1);
2204
2205 return (PF_DROP);
2206 }
2207
2208 #if defined(INET) || defined(INET6)
2209 void
pf_scrub(struct pf_pdesc * pd)2210 pf_scrub(struct pf_pdesc *pd)
2211 {
2212
2213 struct ip *h = mtod(pd->m, struct ip *);
2214 #ifdef INET6
2215 struct ip6_hdr *h6 = mtod(pd->m, struct ip6_hdr *);
2216 #endif
2217
2218 /* Clear IP_DF if no-df was requested */
2219 if (pd->af == AF_INET && pd->act.flags & PFSTATE_NODF &&
2220 h->ip_off & htons(IP_DF))
2221 {
2222 u_int16_t ip_off = h->ip_off;
2223
2224 h->ip_off &= htons(~IP_DF);
2225 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
2226 }
2227
2228 /* Enforce a minimum ttl, may cause endless packet loops */
2229 if (pd->af == AF_INET && pd->act.min_ttl &&
2230 h->ip_ttl < pd->act.min_ttl) {
2231 u_int16_t ip_ttl = h->ip_ttl;
2232
2233 h->ip_ttl = pd->act.min_ttl;
2234 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0);
2235 }
2236 #ifdef INET6
2237 /* Enforce a minimum ttl, may cause endless packet loops */
2238 if (pd->af == AF_INET6 && pd->act.min_ttl &&
2239 h6->ip6_hlim < pd->act.min_ttl)
2240 h6->ip6_hlim = pd->act.min_ttl;
2241 #endif
2242 /* Enforce tos */
2243 if (pd->act.flags & PFSTATE_SETTOS) {
2244 switch (pd->af) {
2245 case AF_INET: {
2246 u_int16_t ov, nv;
2247
2248 ov = *(u_int16_t *)h;
2249 h->ip_tos = pd->act.set_tos | (h->ip_tos & IPTOS_ECN_MASK);
2250 nv = *(u_int16_t *)h;
2251
2252 h->ip_sum = pf_cksum_fixup(h->ip_sum, ov, nv, 0);
2253 break;
2254 }
2255 #ifdef INET6
2256 case AF_INET6:
2257 h6->ip6_flow &= IPV6_FLOWLABEL_MASK | IPV6_VERSION_MASK;
2258 h6->ip6_flow |= htonl((pd->act.set_tos | IPV6_ECN(h6)) << 20);
2259 break;
2260 #endif
2261 }
2262 }
2263
2264 /* random-id, but not for fragments */
2265 #ifdef INET
2266 if (pd->af == AF_INET &&
2267 pd->act.flags & PFSTATE_RANDOMID && !(h->ip_off & ~htons(IP_DF))) {
2268 uint16_t ip_id = h->ip_id;
2269
2270 ip_fillid(h);
2271 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_id, h->ip_id, 0);
2272 }
2273 #endif
2274 }
2275 #endif
2276