1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright 2001 Niels Provos <provos@citi.umich.edu>
5 * Copyright 2011-2018 Alexander Bluhm <bluhm@openbsd.org>
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * $OpenBSD: pf_norm.c,v 1.114 2009/01/29 14:11:45 henning Exp $
29 */
30
31 #include <sys/cdefs.h>
32 __FBSDID("$FreeBSD: stable/12/sys/netpfil/pf/pf_norm.c 373157 2023-08-04 14:14:08Z kp $");
33
34 #include "opt_inet.h"
35 #include "opt_inet6.h"
36 #include "opt_pf.h"
37
38 #include <sys/param.h>
39 #include <sys/kernel.h>
40 #include <sys/lock.h>
41 #include <sys/mbuf.h>
42 #include <sys/mutex.h>
43 #include <sys/refcount.h>
44 #include <sys/socket.h>
45
46 #include <net/if.h>
47 #include <net/vnet.h>
48 #include <net/pfvar.h>
49 #include <net/if_pflog.h>
50
51 #include <netinet/in.h>
52 #include <netinet/ip.h>
53 #include <netinet/ip_var.h>
54 #include <netinet6/ip6_var.h>
55 #include <netinet/tcp.h>
56 #include <netinet/tcp_fsm.h>
57 #include <netinet/tcp_seq.h>
58
59 #ifdef INET6
60 #include <netinet/ip6.h>
61 #endif /* INET6 */
62
63 struct pf_frent {
64 TAILQ_ENTRY(pf_frent) fr_next;
65 struct mbuf *fe_m;
66 uint16_t fe_hdrlen; /* ipv4 header length with ip options
67 ipv6, extension, fragment header */
68 uint16_t fe_extoff; /* last extension header offset or 0 */
69 uint16_t fe_len; /* fragment length */
70 uint16_t fe_off; /* fragment offset */
71 uint16_t fe_mff; /* more fragment flag */
72 };
73
74 struct pf_fragment_cmp {
75 struct pf_addr frc_src;
76 struct pf_addr frc_dst;
77 uint32_t frc_id;
78 sa_family_t frc_af;
79 uint8_t frc_proto;
80 };
81
82 struct pf_fragment {
83 struct pf_fragment_cmp fr_key;
84 #define fr_src fr_key.frc_src
85 #define fr_dst fr_key.frc_dst
86 #define fr_id fr_key.frc_id
87 #define fr_af fr_key.frc_af
88 #define fr_proto fr_key.frc_proto
89
90 /* pointers to queue element */
91 struct pf_frent *fr_firstoff[PF_FRAG_ENTRY_POINTS];
92 /* count entries between pointers */
93 uint8_t fr_entries[PF_FRAG_ENTRY_POINTS];
94 RB_ENTRY(pf_fragment) fr_entry;
95 TAILQ_ENTRY(pf_fragment) frag_next;
96 uint32_t fr_timeout;
97 uint16_t fr_maxlen; /* maximum length of single fragment */
98 u_int16_t fr_holes; /* number of holes in the queue */
99 TAILQ_HEAD(pf_fragq, pf_frent) fr_queue;
100 };
101
102 struct pf_fragment_tag {
103 uint16_t ft_hdrlen; /* header length of reassembled pkt */
104 uint16_t ft_extoff; /* last extension header offset or 0 */
105 uint16_t ft_maxlen; /* maximum fragment payload length */
106 uint32_t ft_id; /* fragment id */
107 };
108
109 static struct mtx pf_frag_mtx;
110 MTX_SYSINIT(pf_frag_mtx, &pf_frag_mtx, "pf fragments", MTX_DEF);
111 #define PF_FRAG_LOCK() mtx_lock(&pf_frag_mtx)
112 #define PF_FRAG_UNLOCK() mtx_unlock(&pf_frag_mtx)
113 #define PF_FRAG_ASSERT() mtx_assert(&pf_frag_mtx, MA_OWNED)
114
115 VNET_DEFINE(uma_zone_t, pf_state_scrub_z); /* XXX: shared with pfsync */
116
117 VNET_DEFINE_STATIC(uma_zone_t, pf_frent_z);
118 #define V_pf_frent_z VNET(pf_frent_z)
119 VNET_DEFINE_STATIC(uma_zone_t, pf_frag_z);
120 #define V_pf_frag_z VNET(pf_frag_z)
121
122 TAILQ_HEAD(pf_fragqueue, pf_fragment);
123 TAILQ_HEAD(pf_cachequeue, pf_fragment);
124 VNET_DEFINE_STATIC(struct pf_fragqueue, pf_fragqueue);
125 #define V_pf_fragqueue VNET(pf_fragqueue)
126 RB_HEAD(pf_frag_tree, pf_fragment);
127 VNET_DEFINE_STATIC(struct pf_frag_tree, pf_frag_tree);
128 #define V_pf_frag_tree VNET(pf_frag_tree)
129 static int pf_frag_compare(struct pf_fragment *,
130 struct pf_fragment *);
131 static RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare);
132 static RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare);
133
134 static void pf_flush_fragments(void);
135 static void pf_free_fragment(struct pf_fragment *);
136 static void pf_remove_fragment(struct pf_fragment *);
137 static int pf_normalize_tcpopt(struct pf_krule *, struct mbuf *,
138 struct tcphdr *, int, sa_family_t);
139 static struct pf_frent *pf_create_fragment(u_short *);
140 static int pf_frent_holes(struct pf_frent *frent);
141 static struct pf_fragment *pf_find_fragment(struct pf_fragment_cmp *key,
142 struct pf_frag_tree *tree);
143 static inline int pf_frent_index(struct pf_frent *);
144 static int pf_frent_insert(struct pf_fragment *,
145 struct pf_frent *, struct pf_frent *);
146 void pf_frent_remove(struct pf_fragment *,
147 struct pf_frent *);
148 struct pf_frent *pf_frent_previous(struct pf_fragment *,
149 struct pf_frent *);
150 static struct pf_fragment *pf_fillup_fragment(struct pf_fragment_cmp *,
151 struct pf_frent *, u_short *);
152 static struct mbuf *pf_join_fragment(struct pf_fragment *);
153 #ifdef INET
154 static void pf_scrub_ip(struct mbuf **, uint32_t, uint8_t, uint8_t);
155 static int pf_reassemble(struct mbuf **, struct ip *, int, u_short *);
156 #endif /* INET */
157 #ifdef INET6
158 static int pf_reassemble6(struct mbuf **, struct ip6_hdr *,
159 struct ip6_frag *, uint16_t, uint16_t, u_short *);
160 static void pf_scrub_ip6(struct mbuf **, uint8_t);
161 #endif /* INET6 */
162
163 #define DPFPRINTF(x) do { \
164 if (V_pf_status.debug >= PF_DEBUG_MISC) { \
165 printf("%s: ", __func__); \
166 printf x ; \
167 } \
168 } while(0)
169
170 #ifdef INET
171 static void
pf_ip2key(struct ip * ip,int dir,struct pf_fragment_cmp * key)172 pf_ip2key(struct ip *ip, int dir, struct pf_fragment_cmp *key)
173 {
174
175 key->frc_src.v4 = ip->ip_src;
176 key->frc_dst.v4 = ip->ip_dst;
177 key->frc_af = AF_INET;
178 key->frc_proto = ip->ip_p;
179 key->frc_id = ip->ip_id;
180 }
181 #endif /* INET */
182
183 void
pf_normalize_init(void)184 pf_normalize_init(void)
185 {
186
187 V_pf_frag_z = uma_zcreate("pf frags", sizeof(struct pf_fragment),
188 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
189 V_pf_frent_z = uma_zcreate("pf frag entries", sizeof(struct pf_frent),
190 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
191 V_pf_state_scrub_z = uma_zcreate("pf state scrubs",
192 sizeof(struct pf_state_scrub), NULL, NULL, NULL, NULL,
193 UMA_ALIGN_PTR, 0);
194
195 V_pf_limits[PF_LIMIT_FRAGS].zone = V_pf_frent_z;
196 V_pf_limits[PF_LIMIT_FRAGS].limit = PFFRAG_FRENT_HIWAT;
197 uma_zone_set_max(V_pf_frent_z, PFFRAG_FRENT_HIWAT);
198 uma_zone_set_warning(V_pf_frent_z, "PF frag entries limit reached");
199
200 TAILQ_INIT(&V_pf_fragqueue);
201 }
202
203 void
pf_normalize_cleanup(void)204 pf_normalize_cleanup(void)
205 {
206
207 uma_zdestroy(V_pf_state_scrub_z);
208 uma_zdestroy(V_pf_frent_z);
209 uma_zdestroy(V_pf_frag_z);
210 }
211
212 static int
pf_frag_compare(struct pf_fragment * a,struct pf_fragment * b)213 pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b)
214 {
215 int diff;
216
217 if ((diff = a->fr_id - b->fr_id) != 0)
218 return (diff);
219 if ((diff = a->fr_proto - b->fr_proto) != 0)
220 return (diff);
221 if ((diff = a->fr_af - b->fr_af) != 0)
222 return (diff);
223 if ((diff = pf_addr_cmp(&a->fr_src, &b->fr_src, a->fr_af)) != 0)
224 return (diff);
225 if ((diff = pf_addr_cmp(&a->fr_dst, &b->fr_dst, a->fr_af)) != 0)
226 return (diff);
227 return (0);
228 }
229
230 void
pf_purge_expired_fragments(void)231 pf_purge_expired_fragments(void)
232 {
233 u_int32_t expire = time_uptime -
234 V_pf_default_rule.timeout[PFTM_FRAG];
235
236 pf_purge_fragments(expire);
237 }
238
239 void
pf_purge_fragments(uint32_t expire)240 pf_purge_fragments(uint32_t expire)
241 {
242 struct pf_fragment *frag;
243
244 PF_FRAG_LOCK();
245 while ((frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue)) != NULL) {
246 if (frag->fr_timeout > expire)
247 break;
248
249 DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag));
250 pf_free_fragment(frag);
251 }
252
253 PF_FRAG_UNLOCK();
254 }
255
256 /*
257 * Try to flush old fragments to make space for new ones
258 */
259 static void
pf_flush_fragments(void)260 pf_flush_fragments(void)
261 {
262 struct pf_fragment *frag;
263 int goal;
264
265 PF_FRAG_ASSERT();
266
267 goal = uma_zone_get_cur(V_pf_frent_z) * 9 / 10;
268 DPFPRINTF(("trying to free %d frag entriess\n", goal));
269 while (goal < uma_zone_get_cur(V_pf_frent_z)) {
270 frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue);
271 if (frag)
272 pf_free_fragment(frag);
273 else
274 break;
275 }
276 }
277
278 /* Frees the fragments and all associated entries */
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 /* Free all fragments */
287 for (frent = TAILQ_FIRST(&frag->fr_queue); frent;
288 frent = TAILQ_FIRST(&frag->fr_queue)) {
289 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
290
291 m_freem(frent->fe_m);
292 uma_zfree(V_pf_frent_z, frent);
293 }
294
295 pf_remove_fragment(frag);
296 }
297
298 static struct pf_fragment *
pf_find_fragment(struct pf_fragment_cmp * key,struct pf_frag_tree * tree)299 pf_find_fragment(struct pf_fragment_cmp *key, struct pf_frag_tree *tree)
300 {
301 struct pf_fragment *frag;
302
303 PF_FRAG_ASSERT();
304
305 frag = RB_FIND(pf_frag_tree, tree, (struct pf_fragment *)key);
306 if (frag != NULL) {
307 /* XXX Are we sure we want to update the timeout? */
308 frag->fr_timeout = time_uptime;
309 TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next);
310 TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next);
311 }
312
313 return (frag);
314 }
315
316 /* Removes a fragment from the fragment queue and frees the fragment */
317 static void
pf_remove_fragment(struct pf_fragment * frag)318 pf_remove_fragment(struct pf_fragment *frag)
319 {
320
321 PF_FRAG_ASSERT();
322 KASSERT(frag, ("frag != NULL"));
323
324 RB_REMOVE(pf_frag_tree, &V_pf_frag_tree, frag);
325 TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next);
326 uma_zfree(V_pf_frag_z, frag);
327 }
328
329 static struct pf_frent *
pf_create_fragment(u_short * reason)330 pf_create_fragment(u_short *reason)
331 {
332 struct pf_frent *frent;
333
334 PF_FRAG_ASSERT();
335
336 frent = uma_zalloc(V_pf_frent_z, M_NOWAIT);
337 if (frent == NULL) {
338 pf_flush_fragments();
339 frent = uma_zalloc(V_pf_frent_z, M_NOWAIT);
340 if (frent == NULL) {
341 REASON_SET(reason, PFRES_MEMORY);
342 return (NULL);
343 }
344 }
345
346 return (frent);
347 }
348
349 /*
350 * Calculate the additional holes that were created in the fragment
351 * queue by inserting this fragment. A fragment in the middle
352 * creates one more hole by splitting. For each connected side,
353 * it loses one hole.
354 * Fragment entry must be in the queue when calling this function.
355 */
356 static int
pf_frent_holes(struct pf_frent * frent)357 pf_frent_holes(struct pf_frent *frent)
358 {
359 struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next);
360 struct pf_frent *next = TAILQ_NEXT(frent, fr_next);
361 int holes = 1;
362
363 if (prev == NULL) {
364 if (frent->fe_off == 0)
365 holes--;
366 } else {
367 KASSERT(frent->fe_off != 0, ("frent->fe_off != 0"));
368 if (frent->fe_off == prev->fe_off + prev->fe_len)
369 holes--;
370 }
371 if (next == NULL) {
372 if (!frent->fe_mff)
373 holes--;
374 } else {
375 KASSERT(frent->fe_mff, ("frent->fe_mff"));
376 if (next->fe_off == frent->fe_off + frent->fe_len)
377 holes--;
378 }
379 return holes;
380 }
381
382 static inline int
pf_frent_index(struct pf_frent * frent)383 pf_frent_index(struct pf_frent *frent)
384 {
385 /*
386 * We have an array of 16 entry points to the queue. A full size
387 * 65535 octet IP packet can have 8192 fragments. So the queue
388 * traversal length is at most 512 and at most 16 entry points are
389 * checked. We need 128 additional bytes on a 64 bit architecture.
390 */
391 CTASSERT(((u_int16_t)0xffff &~ 7) / (0x10000 / PF_FRAG_ENTRY_POINTS) ==
392 16 - 1);
393 CTASSERT(((u_int16_t)0xffff >> 3) / PF_FRAG_ENTRY_POINTS == 512 - 1);
394
395 return frent->fe_off / (0x10000 / PF_FRAG_ENTRY_POINTS);
396 }
397
398 static int
pf_frent_insert(struct pf_fragment * frag,struct pf_frent * frent,struct pf_frent * prev)399 pf_frent_insert(struct pf_fragment *frag, struct pf_frent *frent,
400 struct pf_frent *prev)
401 {
402 int index;
403
404 CTASSERT(PF_FRAG_ENTRY_LIMIT <= 0xff);
405
406 /*
407 * A packet has at most 65536 octets. With 16 entry points, each one
408 * spawns 4096 octets. We limit these to 64 fragments each, which
409 * means on average every fragment must have at least 64 octets.
410 */
411 index = pf_frent_index(frent);
412 if (frag->fr_entries[index] >= PF_FRAG_ENTRY_LIMIT)
413 return ENOBUFS;
414 frag->fr_entries[index]++;
415
416 if (prev == NULL) {
417 TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next);
418 } else {
419 KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off,
420 ("overlapping fragment"));
421 TAILQ_INSERT_AFTER(&frag->fr_queue, prev, frent, fr_next);
422 }
423
424 if (frag->fr_firstoff[index] == NULL) {
425 KASSERT(prev == NULL || pf_frent_index(prev) < index,
426 ("prev == NULL || pf_frent_index(pref) < index"));
427 frag->fr_firstoff[index] = frent;
428 } else {
429 if (frent->fe_off < frag->fr_firstoff[index]->fe_off) {
430 KASSERT(prev == NULL || pf_frent_index(prev) < index,
431 ("prev == NULL || pf_frent_index(pref) < index"));
432 frag->fr_firstoff[index] = frent;
433 } else {
434 KASSERT(prev != NULL, ("prev != NULL"));
435 KASSERT(pf_frent_index(prev) == index,
436 ("pf_frent_index(prev) == index"));
437 }
438 }
439
440 frag->fr_holes += pf_frent_holes(frent);
441
442 return 0;
443 }
444
445 void
pf_frent_remove(struct pf_fragment * frag,struct pf_frent * frent)446 pf_frent_remove(struct pf_fragment *frag, struct pf_frent *frent)
447 {
448 #ifdef INVARIANTS
449 struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next);
450 #endif
451 struct pf_frent *next = TAILQ_NEXT(frent, fr_next);
452 int index;
453
454 frag->fr_holes -= pf_frent_holes(frent);
455
456 index = pf_frent_index(frent);
457 KASSERT(frag->fr_firstoff[index] != NULL, ("frent not found"));
458 if (frag->fr_firstoff[index]->fe_off == frent->fe_off) {
459 if (next == NULL) {
460 frag->fr_firstoff[index] = NULL;
461 } else {
462 KASSERT(frent->fe_off + frent->fe_len <= next->fe_off,
463 ("overlapping fragment"));
464 if (pf_frent_index(next) == index) {
465 frag->fr_firstoff[index] = next;
466 } else {
467 frag->fr_firstoff[index] = NULL;
468 }
469 }
470 } else {
471 KASSERT(frag->fr_firstoff[index]->fe_off < frent->fe_off,
472 ("frag->fr_firstoff[index]->fe_off < frent->fe_off"));
473 KASSERT(prev != NULL, ("prev != NULL"));
474 KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off,
475 ("overlapping fragment"));
476 KASSERT(pf_frent_index(prev) == index,
477 ("pf_frent_index(prev) == index"));
478 }
479
480 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
481
482 KASSERT(frag->fr_entries[index] > 0, ("No fragments remaining"));
483 frag->fr_entries[index]--;
484 }
485
486 struct pf_frent *
pf_frent_previous(struct pf_fragment * frag,struct pf_frent * frent)487 pf_frent_previous(struct pf_fragment *frag, struct pf_frent *frent)
488 {
489 struct pf_frent *prev, *next;
490 int index;
491
492 /*
493 * If there are no fragments after frag, take the final one. Assume
494 * that the global queue is not empty.
495 */
496 prev = TAILQ_LAST(&frag->fr_queue, pf_fragq);
497 KASSERT(prev != NULL, ("prev != NULL"));
498 if (prev->fe_off <= frent->fe_off)
499 return prev;
500 /*
501 * We want to find a fragment entry that is before frag, but still
502 * close to it. Find the first fragment entry that is in the same
503 * entry point or in the first entry point after that. As we have
504 * already checked that there are entries behind frag, this will
505 * succeed.
506 */
507 for (index = pf_frent_index(frent); index < PF_FRAG_ENTRY_POINTS;
508 index++) {
509 prev = frag->fr_firstoff[index];
510 if (prev != NULL)
511 break;
512 }
513 KASSERT(prev != NULL, ("prev != NULL"));
514 /*
515 * In prev we may have a fragment from the same entry point that is
516 * before frent, or one that is just one position behind frent.
517 * In the latter case, we go back one step and have the predecessor.
518 * There may be none if the new fragment will be the first one.
519 */
520 if (prev->fe_off > frent->fe_off) {
521 prev = TAILQ_PREV(prev, pf_fragq, fr_next);
522 if (prev == NULL)
523 return NULL;
524 KASSERT(prev->fe_off <= frent->fe_off,
525 ("prev->fe_off <= frent->fe_off"));
526 return prev;
527 }
528 /*
529 * In prev is the first fragment of the entry point. The offset
530 * of frag is behind it. Find the closest previous fragment.
531 */
532 for (next = TAILQ_NEXT(prev, fr_next); next != NULL;
533 next = TAILQ_NEXT(next, fr_next)) {
534 if (next->fe_off > frent->fe_off)
535 break;
536 prev = next;
537 }
538 return prev;
539 }
540
541 static struct pf_fragment *
pf_fillup_fragment(struct pf_fragment_cmp * key,struct pf_frent * frent,u_short * reason)542 pf_fillup_fragment(struct pf_fragment_cmp *key, struct pf_frent *frent,
543 u_short *reason)
544 {
545 struct pf_frent *after, *next, *prev;
546 struct pf_fragment *frag;
547 uint16_t total;
548 int old_index, new_index;
549
550 PF_FRAG_ASSERT();
551
552 /* No empty fragments. */
553 if (frent->fe_len == 0) {
554 DPFPRINTF(("bad fragment: len 0\n"));
555 goto bad_fragment;
556 }
557
558 /* All fragments are 8 byte aligned. */
559 if (frent->fe_mff && (frent->fe_len & 0x7)) {
560 DPFPRINTF(("bad fragment: mff and len %d\n", frent->fe_len));
561 goto bad_fragment;
562 }
563
564 /* Respect maximum length, IP_MAXPACKET == IPV6_MAXPACKET. */
565 if (frent->fe_off + frent->fe_len > IP_MAXPACKET) {
566 DPFPRINTF(("bad fragment: max packet %d\n",
567 frent->fe_off + frent->fe_len));
568 goto bad_fragment;
569 }
570
571 DPFPRINTF((key->frc_af == AF_INET ?
572 "reass frag %d @ %d-%d\n" : "reass frag %#08x @ %d-%d\n",
573 key->frc_id, frent->fe_off, frent->fe_off + frent->fe_len));
574
575 /* Fully buffer all of the fragments in this fragment queue. */
576 frag = pf_find_fragment(key, &V_pf_frag_tree);
577
578 /* Create a new reassembly queue for this packet. */
579 if (frag == NULL) {
580 frag = uma_zalloc(V_pf_frag_z, M_NOWAIT);
581 if (frag == NULL) {
582 pf_flush_fragments();
583 frag = uma_zalloc(V_pf_frag_z, M_NOWAIT);
584 if (frag == NULL) {
585 REASON_SET(reason, PFRES_MEMORY);
586 goto drop_fragment;
587 }
588 }
589
590 *(struct pf_fragment_cmp *)frag = *key;
591 memset(frag->fr_firstoff, 0, sizeof(frag->fr_firstoff));
592 memset(frag->fr_entries, 0, sizeof(frag->fr_entries));
593 frag->fr_timeout = time_uptime;
594 frag->fr_maxlen = frent->fe_len;
595 frag->fr_holes = 1;
596 TAILQ_INIT(&frag->fr_queue);
597
598 RB_INSERT(pf_frag_tree, &V_pf_frag_tree, frag);
599 TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next);
600
601 /* We do not have a previous fragment, cannot fail. */
602 pf_frent_insert(frag, frent, NULL);
603
604 return (frag);
605 }
606
607 KASSERT(!TAILQ_EMPTY(&frag->fr_queue), ("!TAILQ_EMPTY()->fr_queue"));
608
609 /* Remember maximum fragment len for refragmentation. */
610 if (frent->fe_len > frag->fr_maxlen)
611 frag->fr_maxlen = frent->fe_len;
612
613 /* Maximum data we have seen already. */
614 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
615 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
616
617 /* Non terminal fragments must have more fragments flag. */
618 if (frent->fe_off + frent->fe_len < total && !frent->fe_mff)
619 goto bad_fragment;
620
621 /* Check if we saw the last fragment already. */
622 if (!TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_mff) {
623 if (frent->fe_off + frent->fe_len > total ||
624 (frent->fe_off + frent->fe_len == total && frent->fe_mff))
625 goto bad_fragment;
626 } else {
627 if (frent->fe_off + frent->fe_len == total && !frent->fe_mff)
628 goto bad_fragment;
629 }
630
631 /* Find neighbors for newly inserted fragment */
632 prev = pf_frent_previous(frag, frent);
633 if (prev == NULL) {
634 after = TAILQ_FIRST(&frag->fr_queue);
635 KASSERT(after != NULL, ("after != NULL"));
636 } else {
637 after = TAILQ_NEXT(prev, fr_next);
638 }
639
640 if (prev != NULL && prev->fe_off + prev->fe_len > frent->fe_off) {
641 uint16_t precut;
642
643 precut = prev->fe_off + prev->fe_len - frent->fe_off;
644 if (precut >= frent->fe_len)
645 goto bad_fragment;
646 DPFPRINTF(("overlap -%d\n", precut));
647 m_adj(frent->fe_m, precut);
648 frent->fe_off += precut;
649 frent->fe_len -= precut;
650 }
651
652 for (; after != NULL && frent->fe_off + frent->fe_len > after->fe_off;
653 after = next) {
654 uint16_t aftercut;
655
656 aftercut = frent->fe_off + frent->fe_len - after->fe_off;
657 DPFPRINTF(("adjust overlap %d\n", aftercut));
658 if (aftercut < after->fe_len) {
659 m_adj(after->fe_m, aftercut);
660 old_index = pf_frent_index(after);
661 after->fe_off += aftercut;
662 after->fe_len -= aftercut;
663 new_index = pf_frent_index(after);
664 if (old_index != new_index) {
665 DPFPRINTF(("frag index %d, new %d",
666 old_index, new_index));
667 /* Fragment switched queue as fe_off changed */
668 after->fe_off -= aftercut;
669 after->fe_len += aftercut;
670 /* Remove restored fragment from old queue */
671 pf_frent_remove(frag, after);
672 after->fe_off += aftercut;
673 after->fe_len -= aftercut;
674 /* Insert into correct queue */
675 if (pf_frent_insert(frag, after, prev)) {
676 DPFPRINTF(
677 ("fragment requeue limit exceeded"));
678 m_freem(after->fe_m);
679 uma_zfree(V_pf_frent_z, after);
680 /* There is not way to recover */
681 goto bad_fragment;
682 }
683 }
684 break;
685 }
686
687 /* This fragment is completely overlapped, lose it. */
688 next = TAILQ_NEXT(after, fr_next);
689 pf_frent_remove(frag, after);
690 m_freem(after->fe_m);
691 uma_zfree(V_pf_frent_z, after);
692 }
693
694 /* If part of the queue gets too long, there is not way to recover. */
695 if (pf_frent_insert(frag, frent, prev)) {
696 DPFPRINTF(("fragment queue limit exceeded\n"));
697 goto bad_fragment;
698 }
699
700 return (frag);
701
702 bad_fragment:
703 REASON_SET(reason, PFRES_FRAG);
704 drop_fragment:
705 uma_zfree(V_pf_frent_z, frent);
706 return (NULL);
707 }
708
709 static struct mbuf *
pf_join_fragment(struct pf_fragment * frag)710 pf_join_fragment(struct pf_fragment *frag)
711 {
712 struct mbuf *m, *m2;
713 struct pf_frent *frent, *next;
714
715 frent = TAILQ_FIRST(&frag->fr_queue);
716 next = TAILQ_NEXT(frent, fr_next);
717
718 m = frent->fe_m;
719 m_adj(m, (frent->fe_hdrlen + frent->fe_len) - m->m_pkthdr.len);
720 uma_zfree(V_pf_frent_z, frent);
721 for (frent = next; frent != NULL; frent = next) {
722 next = TAILQ_NEXT(frent, fr_next);
723
724 m2 = frent->fe_m;
725 /* Strip off ip header. */
726 m_adj(m2, frent->fe_hdrlen);
727 /* Strip off any trailing bytes. */
728 m_adj(m2, frent->fe_len - m2->m_pkthdr.len);
729
730 uma_zfree(V_pf_frent_z, frent);
731 m_cat(m, m2);
732 }
733
734 /* Remove from fragment queue. */
735 pf_remove_fragment(frag);
736
737 return (m);
738 }
739
740 #ifdef INET
741 static int
pf_reassemble(struct mbuf ** m0,struct ip * ip,int dir,u_short * reason)742 pf_reassemble(struct mbuf **m0, struct ip *ip, int dir, u_short *reason)
743 {
744 struct mbuf *m = *m0;
745 struct pf_frent *frent;
746 struct pf_fragment *frag;
747 struct pf_fragment_cmp key;
748 uint16_t total, hdrlen;
749
750 /* Get an entry for the fragment queue */
751 if ((frent = pf_create_fragment(reason)) == NULL)
752 return (PF_DROP);
753
754 frent->fe_m = m;
755 frent->fe_hdrlen = ip->ip_hl << 2;
756 frent->fe_extoff = 0;
757 frent->fe_len = ntohs(ip->ip_len) - (ip->ip_hl << 2);
758 frent->fe_off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3;
759 frent->fe_mff = ntohs(ip->ip_off) & IP_MF;
760
761 pf_ip2key(ip, dir, &key);
762
763 if ((frag = pf_fillup_fragment(&key, frent, reason)) == NULL)
764 return (PF_DROP);
765
766 /* The mbuf is part of the fragment entry, no direct free or access */
767 m = *m0 = NULL;
768
769 if (frag->fr_holes) {
770 DPFPRINTF(("frag %d, holes %d\n", frag->fr_id, frag->fr_holes));
771 return (PF_PASS); /* drop because *m0 is NULL, no error */
772 }
773
774 /* We have all the data */
775 frent = TAILQ_FIRST(&frag->fr_queue);
776 KASSERT(frent != NULL, ("frent != NULL"));
777 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
778 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
779 hdrlen = frent->fe_hdrlen;
780
781 m = *m0 = pf_join_fragment(frag);
782 frag = NULL;
783
784 if (m->m_flags & M_PKTHDR) {
785 int plen = 0;
786 for (m = *m0; m; m = m->m_next)
787 plen += m->m_len;
788 m = *m0;
789 m->m_pkthdr.len = plen;
790 }
791
792 ip = mtod(m, struct ip *);
793 ip->ip_sum = pf_cksum_fixup(ip->ip_sum, ip->ip_len,
794 htons(hdrlen + total), 0);
795 ip->ip_len = htons(hdrlen + total);
796 ip->ip_sum = pf_cksum_fixup(ip->ip_sum, ip->ip_off,
797 ip->ip_off & ~(IP_MF|IP_OFFMASK), 0);
798 ip->ip_off &= ~(IP_MF|IP_OFFMASK);
799
800 if (hdrlen + total > IP_MAXPACKET) {
801 DPFPRINTF(("drop: too big: %d\n", total));
802 ip->ip_len = 0;
803 REASON_SET(reason, PFRES_SHORT);
804 /* PF_DROP requires a valid mbuf *m0 in pf_test() */
805 return (PF_DROP);
806 }
807
808 DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip->ip_len)));
809 return (PF_PASS);
810 }
811 #endif /* INET */
812
813 #ifdef INET6
814 static int
pf_reassemble6(struct mbuf ** m0,struct ip6_hdr * ip6,struct ip6_frag * fraghdr,uint16_t hdrlen,uint16_t extoff,u_short * reason)815 pf_reassemble6(struct mbuf **m0, struct ip6_hdr *ip6, struct ip6_frag *fraghdr,
816 uint16_t hdrlen, uint16_t extoff, u_short *reason)
817 {
818 struct mbuf *m = *m0;
819 struct pf_frent *frent;
820 struct pf_fragment *frag;
821 struct pf_fragment_cmp key;
822 struct m_tag *mtag;
823 struct pf_fragment_tag *ftag;
824 int off;
825 uint32_t frag_id;
826 uint16_t total, maxlen;
827 uint8_t proto;
828
829 PF_FRAG_LOCK();
830
831 /* Get an entry for the fragment queue. */
832 if ((frent = pf_create_fragment(reason)) == NULL) {
833 PF_FRAG_UNLOCK();
834 return (PF_DROP);
835 }
836
837 frent->fe_m = m;
838 frent->fe_hdrlen = hdrlen;
839 frent->fe_extoff = extoff;
840 frent->fe_len = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - hdrlen;
841 frent->fe_off = ntohs(fraghdr->ip6f_offlg & IP6F_OFF_MASK);
842 frent->fe_mff = fraghdr->ip6f_offlg & IP6F_MORE_FRAG;
843
844 key.frc_src.v6 = ip6->ip6_src;
845 key.frc_dst.v6 = ip6->ip6_dst;
846 key.frc_af = AF_INET6;
847 /* Only the first fragment's protocol is relevant. */
848 key.frc_proto = 0;
849 key.frc_id = fraghdr->ip6f_ident;
850
851 if ((frag = pf_fillup_fragment(&key, frent, reason)) == NULL) {
852 PF_FRAG_UNLOCK();
853 return (PF_DROP);
854 }
855
856 /* The mbuf is part of the fragment entry, no direct free or access. */
857 m = *m0 = NULL;
858
859 if (frag->fr_holes) {
860 DPFPRINTF(("frag %d, holes %d\n", frag->fr_id,
861 frag->fr_holes));
862 PF_FRAG_UNLOCK();
863 return (PF_PASS); /* Drop because *m0 is NULL, no error. */
864 }
865
866 /* We have all the data. */
867 frent = TAILQ_FIRST(&frag->fr_queue);
868 KASSERT(frent != NULL, ("frent != NULL"));
869 extoff = frent->fe_extoff;
870 maxlen = frag->fr_maxlen;
871 frag_id = frag->fr_id;
872 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
873 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
874 hdrlen = frent->fe_hdrlen - sizeof(struct ip6_frag);
875
876 m = *m0 = pf_join_fragment(frag);
877 frag = NULL;
878
879 PF_FRAG_UNLOCK();
880
881 /* Take protocol from first fragment header. */
882 m = m_getptr(m, hdrlen + offsetof(struct ip6_frag, ip6f_nxt), &off);
883 KASSERT(m, ("%s: short mbuf chain", __func__));
884 proto = *(mtod(m, caddr_t) + off);
885 m = *m0;
886
887 /* Delete frag6 header */
888 if (ip6_deletefraghdr(m, hdrlen, M_NOWAIT) != 0)
889 goto fail;
890
891 if (m->m_flags & M_PKTHDR) {
892 int plen = 0;
893 for (m = *m0; m; m = m->m_next)
894 plen += m->m_len;
895 m = *m0;
896 m->m_pkthdr.len = plen;
897 }
898
899 if ((mtag = m_tag_get(PF_REASSEMBLED, sizeof(struct pf_fragment_tag),
900 M_NOWAIT)) == NULL)
901 goto fail;
902 ftag = (struct pf_fragment_tag *)(mtag + 1);
903 ftag->ft_hdrlen = hdrlen;
904 ftag->ft_extoff = extoff;
905 ftag->ft_maxlen = maxlen;
906 ftag->ft_id = frag_id;
907 m_tag_prepend(m, mtag);
908
909 ip6 = mtod(m, struct ip6_hdr *);
910 ip6->ip6_plen = htons(hdrlen - sizeof(struct ip6_hdr) + total);
911 if (extoff) {
912 /* Write protocol into next field of last extension header. */
913 m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt),
914 &off);
915 KASSERT(m, ("%s: short mbuf chain", __func__));
916 *(mtod(m, char *) + off) = proto;
917 m = *m0;
918 } else
919 ip6->ip6_nxt = proto;
920
921 if (hdrlen - sizeof(struct ip6_hdr) + total > IPV6_MAXPACKET) {
922 DPFPRINTF(("drop: too big: %d\n", total));
923 ip6->ip6_plen = 0;
924 REASON_SET(reason, PFRES_SHORT);
925 /* PF_DROP requires a valid mbuf *m0 in pf_test6(). */
926 return (PF_DROP);
927 }
928
929 DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip6->ip6_plen)));
930 return (PF_PASS);
931
932 fail:
933 REASON_SET(reason, PFRES_MEMORY);
934 /* PF_DROP requires a valid mbuf *m0 in pf_test6(), will free later. */
935 return (PF_DROP);
936 }
937 #endif /* INET6 */
938
939 #ifdef INET6
940 int
pf_refragment6(struct ifnet * ifp,struct mbuf ** m0,struct m_tag * mtag)941 pf_refragment6(struct ifnet *ifp, struct mbuf **m0, struct m_tag *mtag)
942 {
943 struct mbuf *m = *m0, *t;
944 struct pf_fragment_tag *ftag = (struct pf_fragment_tag *)(mtag + 1);
945 struct pf_pdesc pd;
946 uint32_t frag_id;
947 uint16_t hdrlen, extoff, maxlen;
948 uint8_t proto;
949 int error, action;
950
951 hdrlen = ftag->ft_hdrlen;
952 extoff = ftag->ft_extoff;
953 maxlen = ftag->ft_maxlen;
954 frag_id = ftag->ft_id;
955 m_tag_delete(m, mtag);
956 mtag = NULL;
957 ftag = NULL;
958
959 if (extoff) {
960 int off;
961
962 /* Use protocol from next field of last extension header */
963 m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt),
964 &off);
965 KASSERT((m != NULL), ("pf_refragment6: short mbuf chain"));
966 proto = *(mtod(m, caddr_t) + off);
967 *(mtod(m, char *) + off) = IPPROTO_FRAGMENT;
968 m = *m0;
969 } else {
970 struct ip6_hdr *hdr;
971
972 hdr = mtod(m, struct ip6_hdr *);
973 proto = hdr->ip6_nxt;
974 hdr->ip6_nxt = IPPROTO_FRAGMENT;
975 }
976
977 /* The MTU must be a multiple of 8 bytes, or we risk doing the
978 * fragmentation wrong. */
979 maxlen = maxlen & ~7;
980
981 /*
982 * Maxlen may be less than 8 if there was only a single
983 * fragment. As it was fragmented before, add a fragment
984 * header also for a single fragment. If total or maxlen
985 * is less than 8, ip6_fragment() will return EMSGSIZE and
986 * we drop the packet.
987 */
988 error = ip6_fragment(ifp, m, hdrlen, proto, maxlen, frag_id);
989 m = (*m0)->m_nextpkt;
990 (*m0)->m_nextpkt = NULL;
991 if (error == 0) {
992 /* The first mbuf contains the unfragmented packet. */
993 m_freem(*m0);
994 *m0 = NULL;
995 action = PF_PASS;
996 } else {
997 /* Drop expects an mbuf to free. */
998 DPFPRINTF(("refragment error %d\n", error));
999 action = PF_DROP;
1000 }
1001 for (t = m; m; m = t) {
1002 t = m->m_nextpkt;
1003 m->m_nextpkt = NULL;
1004 m->m_flags |= M_SKIP_FIREWALL;
1005 memset(&pd, 0, sizeof(pd));
1006 pd.pf_mtag = pf_find_mtag(m);
1007 if (error == 0)
1008 ip6_forward(m, 0);
1009 else
1010 m_freem(m);
1011 }
1012
1013 return (action);
1014 }
1015 #endif /* INET6 */
1016
1017 #ifdef INET
1018 int
pf_normalize_ip(struct mbuf ** m0,int dir,struct pfi_kkif * kif,u_short * reason,struct pf_pdesc * pd)1019 pf_normalize_ip(struct mbuf **m0, int dir, struct pfi_kkif *kif, u_short *reason,
1020 struct pf_pdesc *pd)
1021 {
1022 struct mbuf *m = *m0;
1023 struct pf_krule *r;
1024 struct ip *h = mtod(m, struct ip *);
1025 int mff = (ntohs(h->ip_off) & IP_MF);
1026 int hlen = h->ip_hl << 2;
1027 u_int16_t fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3;
1028 u_int16_t max;
1029 int ip_len;
1030 int tag = -1;
1031 int verdict;
1032
1033 PF_RULES_RASSERT();
1034
1035 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
1036 while (r != NULL) {
1037 pf_counter_u64_add(&r->evaluations, 1);
1038 if (pfi_kkif_match(r->kif, kif) == r->ifnot)
1039 r = r->skip[PF_SKIP_IFP].ptr;
1040 else if (r->direction && r->direction != dir)
1041 r = r->skip[PF_SKIP_DIR].ptr;
1042 else if (r->af && r->af != AF_INET)
1043 r = r->skip[PF_SKIP_AF].ptr;
1044 else if (r->proto && r->proto != h->ip_p)
1045 r = r->skip[PF_SKIP_PROTO].ptr;
1046 else if (PF_MISMATCHAW(&r->src.addr,
1047 (struct pf_addr *)&h->ip_src.s_addr, AF_INET,
1048 r->src.neg, kif, M_GETFIB(m)))
1049 r = r->skip[PF_SKIP_SRC_ADDR].ptr;
1050 else if (PF_MISMATCHAW(&r->dst.addr,
1051 (struct pf_addr *)&h->ip_dst.s_addr, AF_INET,
1052 r->dst.neg, NULL, M_GETFIB(m)))
1053 r = r->skip[PF_SKIP_DST_ADDR].ptr;
1054 else if (r->match_tag && !pf_match_tag(m, r, &tag,
1055 pd->pf_mtag ? pd->pf_mtag->tag : 0))
1056 r = TAILQ_NEXT(r, entries);
1057 else
1058 break;
1059 }
1060
1061 if (r == NULL || r->action == PF_NOSCRUB)
1062 return (PF_PASS);
1063
1064 pf_counter_u64_critical_enter();
1065 pf_counter_u64_add_protected(&r->packets[dir == PF_OUT], 1);
1066 pf_counter_u64_add_protected(&r->bytes[dir == PF_OUT], pd->tot_len);
1067 pf_counter_u64_critical_exit();
1068
1069 /* Check for illegal packets */
1070 if (hlen < (int)sizeof(struct ip)) {
1071 REASON_SET(reason, PFRES_NORM);
1072 goto drop;
1073 }
1074
1075 if (hlen > ntohs(h->ip_len)) {
1076 REASON_SET(reason, PFRES_NORM);
1077 goto drop;
1078 }
1079
1080 /* Clear IP_DF if the rule uses the no-df option */
1081 if (r->rule_flag & PFRULE_NODF && h->ip_off & htons(IP_DF)) {
1082 u_int16_t ip_off = h->ip_off;
1083
1084 h->ip_off &= htons(~IP_DF);
1085 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
1086 }
1087
1088 /* We will need other tests here */
1089 if (!fragoff && !mff)
1090 goto no_fragment;
1091
1092 /* We're dealing with a fragment now. Don't allow fragments
1093 * with IP_DF to enter the cache. If the flag was cleared by
1094 * no-df above, fine. Otherwise drop it.
1095 */
1096 if (h->ip_off & htons(IP_DF)) {
1097 DPFPRINTF(("IP_DF\n"));
1098 goto bad;
1099 }
1100
1101 ip_len = ntohs(h->ip_len) - hlen;
1102
1103 /* All fragments are 8 byte aligned */
1104 if (mff && (ip_len & 0x7)) {
1105 DPFPRINTF(("mff and %d\n", ip_len));
1106 goto bad;
1107 }
1108
1109 /* Respect maximum length */
1110 if (fragoff + ip_len > IP_MAXPACKET) {
1111 DPFPRINTF(("max packet %d\n", fragoff + ip_len));
1112 goto bad;
1113 }
1114 max = fragoff + ip_len;
1115
1116 /* Fully buffer all of the fragments
1117 * Might return a completely reassembled mbuf, or NULL */
1118 PF_FRAG_LOCK();
1119 DPFPRINTF(("reass frag %d @ %d-%d\n", h->ip_id, fragoff, max));
1120 verdict = pf_reassemble(m0, h, dir, reason);
1121 PF_FRAG_UNLOCK();
1122
1123 if (verdict != PF_PASS)
1124 return (PF_DROP);
1125
1126 m = *m0;
1127 if (m == NULL)
1128 return (PF_DROP);
1129
1130 h = mtod(m, struct ip *);
1131
1132 no_fragment:
1133 /* At this point, only IP_DF is allowed in ip_off */
1134 if (h->ip_off & ~htons(IP_DF)) {
1135 u_int16_t ip_off = h->ip_off;
1136
1137 h->ip_off &= htons(IP_DF);
1138 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
1139 }
1140
1141 pf_scrub_ip(&m, r->rule_flag, r->min_ttl, r->set_tos);
1142
1143 return (PF_PASS);
1144
1145 bad:
1146 DPFPRINTF(("dropping bad fragment\n"));
1147 REASON_SET(reason, PFRES_FRAG);
1148 drop:
1149 if (r != NULL && r->log)
1150 PFLOG_PACKET(kif, m, AF_INET, dir, *reason, r, NULL, NULL, pd,
1151 1);
1152
1153 return (PF_DROP);
1154 }
1155 #endif
1156
1157 #ifdef INET6
1158 int
pf_normalize_ip6(struct mbuf ** m0,int dir,struct pfi_kkif * kif,u_short * reason,struct pf_pdesc * pd)1159 pf_normalize_ip6(struct mbuf **m0, int dir, struct pfi_kkif *kif,
1160 u_short *reason, struct pf_pdesc *pd)
1161 {
1162 struct mbuf *m = *m0;
1163 struct pf_krule *r;
1164 struct ip6_hdr *h = mtod(m, struct ip6_hdr *);
1165 int extoff;
1166 int off;
1167 struct ip6_ext ext;
1168 struct ip6_opt opt;
1169 struct ip6_opt_jumbo jumbo;
1170 struct ip6_frag frag;
1171 u_int32_t jumbolen = 0, plen;
1172 int optend;
1173 int ooff;
1174 u_int8_t proto;
1175 int terminal;
1176
1177 PF_RULES_RASSERT();
1178
1179 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
1180 while (r != NULL) {
1181 pf_counter_u64_add(&r->evaluations, 1);
1182 if (pfi_kkif_match(r->kif, kif) == r->ifnot)
1183 r = r->skip[PF_SKIP_IFP].ptr;
1184 else if (r->direction && r->direction != dir)
1185 r = r->skip[PF_SKIP_DIR].ptr;
1186 else if (r->af && r->af != AF_INET6)
1187 r = r->skip[PF_SKIP_AF].ptr;
1188 #if 0 /* header chain! */
1189 else if (r->proto && r->proto != h->ip6_nxt)
1190 r = r->skip[PF_SKIP_PROTO].ptr;
1191 #endif
1192 else if (PF_MISMATCHAW(&r->src.addr,
1193 (struct pf_addr *)&h->ip6_src, AF_INET6,
1194 r->src.neg, kif, M_GETFIB(m)))
1195 r = r->skip[PF_SKIP_SRC_ADDR].ptr;
1196 else if (PF_MISMATCHAW(&r->dst.addr,
1197 (struct pf_addr *)&h->ip6_dst, AF_INET6,
1198 r->dst.neg, NULL, M_GETFIB(m)))
1199 r = r->skip[PF_SKIP_DST_ADDR].ptr;
1200 else
1201 break;
1202 }
1203
1204 if (r == NULL || r->action == PF_NOSCRUB)
1205 return (PF_PASS);
1206
1207 pf_counter_u64_critical_enter();
1208 pf_counter_u64_add_protected(&r->packets[dir == PF_OUT], 1);
1209 pf_counter_u64_add_protected(&r->bytes[dir == PF_OUT], pd->tot_len);
1210 pf_counter_u64_critical_exit();
1211
1212 /* Check for illegal packets */
1213 if (sizeof(struct ip6_hdr) + IPV6_MAXPACKET < m->m_pkthdr.len)
1214 goto drop;
1215
1216 again:
1217 h = mtod(m, struct ip6_hdr *);
1218 extoff = 0;
1219 off = sizeof(struct ip6_hdr);
1220 proto = h->ip6_nxt;
1221 terminal = 0;
1222 do {
1223 switch (proto) {
1224 case IPPROTO_FRAGMENT:
1225 goto fragment;
1226 break;
1227 case IPPROTO_AH:
1228 case IPPROTO_ROUTING:
1229 case IPPROTO_DSTOPTS:
1230 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL,
1231 NULL, AF_INET6))
1232 goto shortpkt;
1233 extoff = off;
1234 if (proto == IPPROTO_AH)
1235 off += (ext.ip6e_len + 2) * 4;
1236 else
1237 off += (ext.ip6e_len + 1) * 8;
1238 proto = ext.ip6e_nxt;
1239 break;
1240 case IPPROTO_HOPOPTS:
1241 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL,
1242 NULL, AF_INET6))
1243 goto shortpkt;
1244 extoff = off;
1245 optend = off + (ext.ip6e_len + 1) * 8;
1246 ooff = off + sizeof(ext);
1247 do {
1248 if (!pf_pull_hdr(m, ooff, &opt.ip6o_type,
1249 sizeof(opt.ip6o_type), NULL, NULL,
1250 AF_INET6))
1251 goto shortpkt;
1252 if (opt.ip6o_type == IP6OPT_PAD1) {
1253 ooff++;
1254 continue;
1255 }
1256 if (!pf_pull_hdr(m, ooff, &opt, sizeof(opt),
1257 NULL, NULL, AF_INET6))
1258 goto shortpkt;
1259 if (ooff + sizeof(opt) + opt.ip6o_len > optend)
1260 goto drop;
1261 switch (opt.ip6o_type) {
1262 case IP6OPT_JUMBO:
1263 if (h->ip6_plen != 0)
1264 goto drop;
1265 if (!pf_pull_hdr(m, ooff, &jumbo,
1266 sizeof(jumbo), NULL, NULL,
1267 AF_INET6))
1268 goto shortpkt;
1269 memcpy(&jumbolen, jumbo.ip6oj_jumbo_len,
1270 sizeof(jumbolen));
1271 jumbolen = ntohl(jumbolen);
1272 if (jumbolen <= IPV6_MAXPACKET)
1273 goto drop;
1274 if (sizeof(struct ip6_hdr) + jumbolen !=
1275 m->m_pkthdr.len)
1276 goto drop;
1277 break;
1278 default:
1279 break;
1280 }
1281 ooff += sizeof(opt) + opt.ip6o_len;
1282 } while (ooff < optend);
1283
1284 off = optend;
1285 proto = ext.ip6e_nxt;
1286 break;
1287 default:
1288 terminal = 1;
1289 break;
1290 }
1291 } while (!terminal);
1292
1293 /* jumbo payload option must be present, or plen > 0 */
1294 if (ntohs(h->ip6_plen) == 0)
1295 plen = jumbolen;
1296 else
1297 plen = ntohs(h->ip6_plen);
1298 if (plen == 0)
1299 goto drop;
1300 if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len)
1301 goto shortpkt;
1302
1303 pf_scrub_ip6(&m, r->min_ttl);
1304
1305 return (PF_PASS);
1306
1307 fragment:
1308 if (pd->flags & PFDESC_IP_REAS)
1309 return (PF_DROP);
1310 /* Jumbo payload packets cannot be fragmented. */
1311 plen = ntohs(h->ip6_plen);
1312 if (plen == 0 || jumbolen)
1313 goto drop;
1314 if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len)
1315 goto shortpkt;
1316
1317 if (!pf_pull_hdr(m, off, &frag, sizeof(frag), NULL, NULL, AF_INET6))
1318 goto shortpkt;
1319
1320 /* Offset now points to data portion. */
1321 off += sizeof(frag);
1322
1323 /* Returns PF_DROP or *m0 is NULL or completely reassembled mbuf. */
1324 if (pf_reassemble6(m0, h, &frag, off, extoff, reason) != PF_PASS)
1325 return (PF_DROP);
1326 m = *m0;
1327 if (m == NULL)
1328 return (PF_DROP);
1329
1330 pd->flags |= PFDESC_IP_REAS;
1331 goto again;
1332
1333 shortpkt:
1334 REASON_SET(reason, PFRES_SHORT);
1335 if (r != NULL && r->log)
1336 PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd,
1337 1);
1338 return (PF_DROP);
1339
1340 drop:
1341 REASON_SET(reason, PFRES_NORM);
1342 if (r != NULL && r->log)
1343 PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd,
1344 1);
1345 return (PF_DROP);
1346 }
1347 #endif /* INET6 */
1348
1349 int
pf_normalize_tcp(int dir,struct pfi_kkif * kif,struct mbuf * m,int ipoff,int off,void * h,struct pf_pdesc * pd)1350 pf_normalize_tcp(int dir, struct pfi_kkif *kif, struct mbuf *m, int ipoff,
1351 int off, void *h, struct pf_pdesc *pd)
1352 {
1353 struct pf_krule *r, *rm = NULL;
1354 struct tcphdr *th = &pd->hdr.tcp;
1355 int rewrite = 0;
1356 u_short reason;
1357 u_int8_t flags;
1358 sa_family_t af = pd->af;
1359
1360 PF_RULES_RASSERT();
1361
1362 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
1363 while (r != NULL) {
1364 pf_counter_u64_add(&r->evaluations, 1);
1365 if (pfi_kkif_match(r->kif, kif) == r->ifnot)
1366 r = r->skip[PF_SKIP_IFP].ptr;
1367 else if (r->direction && r->direction != dir)
1368 r = r->skip[PF_SKIP_DIR].ptr;
1369 else if (r->af && r->af != af)
1370 r = r->skip[PF_SKIP_AF].ptr;
1371 else if (r->proto && r->proto != pd->proto)
1372 r = r->skip[PF_SKIP_PROTO].ptr;
1373 else if (PF_MISMATCHAW(&r->src.addr, pd->src, af,
1374 r->src.neg, kif, M_GETFIB(m)))
1375 r = r->skip[PF_SKIP_SRC_ADDR].ptr;
1376 else if (r->src.port_op && !pf_match_port(r->src.port_op,
1377 r->src.port[0], r->src.port[1], th->th_sport))
1378 r = r->skip[PF_SKIP_SRC_PORT].ptr;
1379 else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af,
1380 r->dst.neg, NULL, M_GETFIB(m)))
1381 r = r->skip[PF_SKIP_DST_ADDR].ptr;
1382 else if (r->dst.port_op && !pf_match_port(r->dst.port_op,
1383 r->dst.port[0], r->dst.port[1], th->th_dport))
1384 r = r->skip[PF_SKIP_DST_PORT].ptr;
1385 else if (r->os_fingerprint != PF_OSFP_ANY && !pf_osfp_match(
1386 pf_osfp_fingerprint(pd, m, off, th),
1387 r->os_fingerprint))
1388 r = TAILQ_NEXT(r, entries);
1389 else {
1390 rm = r;
1391 break;
1392 }
1393 }
1394
1395 if (rm == NULL || rm->action == PF_NOSCRUB)
1396 return (PF_PASS);
1397
1398 pf_counter_u64_critical_enter();
1399 pf_counter_u64_add_protected(&r->packets[dir == PF_OUT], 1);
1400 pf_counter_u64_add_protected(&r->bytes[dir == PF_OUT], pd->tot_len);
1401 pf_counter_u64_critical_exit();
1402
1403 if (rm->rule_flag & PFRULE_REASSEMBLE_TCP)
1404 pd->flags |= PFDESC_TCP_NORM;
1405
1406 flags = th->th_flags;
1407 if (flags & TH_SYN) {
1408 /* Illegal packet */
1409 if (flags & TH_RST)
1410 goto tcp_drop;
1411
1412 if (flags & TH_FIN)
1413 goto tcp_drop;
1414 } else {
1415 /* Illegal packet */
1416 if (!(flags & (TH_ACK|TH_RST)))
1417 goto tcp_drop;
1418 }
1419
1420 if (!(flags & TH_ACK)) {
1421 /* These flags are only valid if ACK is set */
1422 if ((flags & TH_FIN) || (flags & TH_PUSH) || (flags & TH_URG))
1423 goto tcp_drop;
1424 }
1425
1426 /* Check for illegal header length */
1427 if (th->th_off < (sizeof(struct tcphdr) >> 2))
1428 goto tcp_drop;
1429
1430 /* If flags changed, or reserved data set, then adjust */
1431 if (flags != th->th_flags || th->th_x2 != 0) {
1432 u_int16_t ov, nv;
1433
1434 ov = *(u_int16_t *)(&th->th_ack + 1);
1435 th->th_flags = flags;
1436 th->th_x2 = 0;
1437 nv = *(u_int16_t *)(&th->th_ack + 1);
1438
1439 th->th_sum = pf_proto_cksum_fixup(m, th->th_sum, ov, nv, 0);
1440 rewrite = 1;
1441 }
1442
1443 /* Remove urgent pointer, if TH_URG is not set */
1444 if (!(flags & TH_URG) && th->th_urp) {
1445 th->th_sum = pf_proto_cksum_fixup(m, th->th_sum, th->th_urp,
1446 0, 0);
1447 th->th_urp = 0;
1448 rewrite = 1;
1449 }
1450
1451 /* Process options */
1452 if (r->max_mss && pf_normalize_tcpopt(r, m, th, off, pd->af))
1453 rewrite = 1;
1454
1455 /* copy back packet headers if we sanitized */
1456 if (rewrite)
1457 m_copyback(m, off, sizeof(*th), (caddr_t)th);
1458
1459 return (PF_PASS);
1460
1461 tcp_drop:
1462 REASON_SET(&reason, PFRES_NORM);
1463 if (rm != NULL && r->log)
1464 PFLOG_PACKET(kif, m, AF_INET, dir, reason, r, NULL, NULL, pd,
1465 1);
1466 return (PF_DROP);
1467 }
1468
1469 int
pf_normalize_tcp_init(struct mbuf * m,int off,struct pf_pdesc * pd,struct tcphdr * th,struct pf_state_peer * src,struct pf_state_peer * dst)1470 pf_normalize_tcp_init(struct mbuf *m, int off, struct pf_pdesc *pd,
1471 struct tcphdr *th, struct pf_state_peer *src, struct pf_state_peer *dst)
1472 {
1473 u_int32_t tsval, tsecr;
1474 u_int8_t hdr[60];
1475 u_int8_t *opt;
1476
1477 KASSERT((src->scrub == NULL),
1478 ("pf_normalize_tcp_init: src->scrub != NULL"));
1479
1480 src->scrub = uma_zalloc(V_pf_state_scrub_z, M_ZERO | M_NOWAIT);
1481 if (src->scrub == NULL)
1482 return (1);
1483
1484 switch (pd->af) {
1485 #ifdef INET
1486 case AF_INET: {
1487 struct ip *h = mtod(m, struct ip *);
1488 src->scrub->pfss_ttl = h->ip_ttl;
1489 break;
1490 }
1491 #endif /* INET */
1492 #ifdef INET6
1493 case AF_INET6: {
1494 struct ip6_hdr *h = mtod(m, struct ip6_hdr *);
1495 src->scrub->pfss_ttl = h->ip6_hlim;
1496 break;
1497 }
1498 #endif /* INET6 */
1499 }
1500
1501
1502 /*
1503 * All normalizations below are only begun if we see the start of
1504 * the connections. They must all set an enabled bit in pfss_flags
1505 */
1506 if ((th->th_flags & TH_SYN) == 0)
1507 return (0);
1508
1509
1510 if (th->th_off > (sizeof(struct tcphdr) >> 2) && src->scrub &&
1511 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) {
1512 /* Diddle with TCP options */
1513 int hlen;
1514 opt = hdr + sizeof(struct tcphdr);
1515 hlen = (th->th_off << 2) - sizeof(struct tcphdr);
1516 while (hlen >= TCPOLEN_TIMESTAMP) {
1517 switch (*opt) {
1518 case TCPOPT_EOL: /* FALLTHROUGH */
1519 case TCPOPT_NOP:
1520 opt++;
1521 hlen--;
1522 break;
1523 case TCPOPT_TIMESTAMP:
1524 if (opt[1] >= TCPOLEN_TIMESTAMP) {
1525 src->scrub->pfss_flags |=
1526 PFSS_TIMESTAMP;
1527 src->scrub->pfss_ts_mod =
1528 htonl(arc4random());
1529
1530 /* note PFSS_PAWS not set yet */
1531 memcpy(&tsval, &opt[2],
1532 sizeof(u_int32_t));
1533 memcpy(&tsecr, &opt[6],
1534 sizeof(u_int32_t));
1535 src->scrub->pfss_tsval0 = ntohl(tsval);
1536 src->scrub->pfss_tsval = ntohl(tsval);
1537 src->scrub->pfss_tsecr = ntohl(tsecr);
1538 getmicrouptime(&src->scrub->pfss_last);
1539 }
1540 /* FALLTHROUGH */
1541 default:
1542 hlen -= MAX(opt[1], 2);
1543 opt += MAX(opt[1], 2);
1544 break;
1545 }
1546 }
1547 }
1548
1549 return (0);
1550 }
1551
1552 void
pf_normalize_tcp_cleanup(struct pf_kstate * state)1553 pf_normalize_tcp_cleanup(struct pf_kstate *state)
1554 {
1555 if (state->src.scrub)
1556 uma_zfree(V_pf_state_scrub_z, state->src.scrub);
1557 if (state->dst.scrub)
1558 uma_zfree(V_pf_state_scrub_z, state->dst.scrub);
1559
1560 /* Someday... flush the TCP segment reassembly descriptors. */
1561 }
1562
1563 int
pf_normalize_tcp_stateful(struct mbuf * m,int off,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)1564 pf_normalize_tcp_stateful(struct mbuf *m, int off, struct pf_pdesc *pd,
1565 u_short *reason, struct tcphdr *th, struct pf_kstate *state,
1566 struct pf_state_peer *src, struct pf_state_peer *dst, int *writeback)
1567 {
1568 struct timeval uptime;
1569 u_int32_t tsval, tsecr;
1570 u_int tsval_from_last;
1571 u_int8_t hdr[60];
1572 u_int8_t *opt;
1573 int copyback = 0;
1574 int got_ts = 0;
1575 size_t startoff;
1576
1577 KASSERT((src->scrub || dst->scrub),
1578 ("%s: src->scrub && dst->scrub!", __func__));
1579
1580 /*
1581 * Enforce the minimum TTL seen for this connection. Negate a common
1582 * technique to evade an intrusion detection system and confuse
1583 * firewall state code.
1584 */
1585 switch (pd->af) {
1586 #ifdef INET
1587 case AF_INET: {
1588 if (src->scrub) {
1589 struct ip *h = mtod(m, struct ip *);
1590 if (h->ip_ttl > src->scrub->pfss_ttl)
1591 src->scrub->pfss_ttl = h->ip_ttl;
1592 h->ip_ttl = src->scrub->pfss_ttl;
1593 }
1594 break;
1595 }
1596 #endif /* INET */
1597 #ifdef INET6
1598 case AF_INET6: {
1599 if (src->scrub) {
1600 struct ip6_hdr *h = mtod(m, struct ip6_hdr *);
1601 if (h->ip6_hlim > src->scrub->pfss_ttl)
1602 src->scrub->pfss_ttl = h->ip6_hlim;
1603 h->ip6_hlim = src->scrub->pfss_ttl;
1604 }
1605 break;
1606 }
1607 #endif /* INET6 */
1608 }
1609
1610 if (th->th_off > (sizeof(struct tcphdr) >> 2) &&
1611 ((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) ||
1612 (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) &&
1613 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) {
1614 /* Diddle with TCP options */
1615 int hlen;
1616 opt = hdr + sizeof(struct tcphdr);
1617 hlen = (th->th_off << 2) - sizeof(struct tcphdr);
1618 while (hlen >= TCPOLEN_TIMESTAMP) {
1619 startoff = opt - (hdr + sizeof(struct tcphdr));
1620 switch (*opt) {
1621 case TCPOPT_EOL: /* FALLTHROUGH */
1622 case TCPOPT_NOP:
1623 opt++;
1624 hlen--;
1625 break;
1626 case TCPOPT_TIMESTAMP:
1627 /* Modulate the timestamps. Can be used for
1628 * NAT detection, OS uptime determination or
1629 * reboot detection.
1630 */
1631
1632 if (got_ts) {
1633 /* Huh? Multiple timestamps!? */
1634 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1635 DPFPRINTF(("multiple TS??\n"));
1636 pf_print_state(state);
1637 printf("\n");
1638 }
1639 REASON_SET(reason, PFRES_TS);
1640 return (PF_DROP);
1641 }
1642 if (opt[1] >= TCPOLEN_TIMESTAMP) {
1643 memcpy(&tsval, &opt[2],
1644 sizeof(u_int32_t));
1645 if (tsval && src->scrub &&
1646 (src->scrub->pfss_flags &
1647 PFSS_TIMESTAMP)) {
1648 tsval = ntohl(tsval);
1649 pf_patch_32_unaligned(m,
1650 &th->th_sum,
1651 &opt[2],
1652 htonl(tsval +
1653 src->scrub->pfss_ts_mod),
1654 PF_ALGNMNT(startoff),
1655 0);
1656 copyback = 1;
1657 }
1658
1659 /* Modulate TS reply iff valid (!0) */
1660 memcpy(&tsecr, &opt[6],
1661 sizeof(u_int32_t));
1662 if (tsecr && dst->scrub &&
1663 (dst->scrub->pfss_flags &
1664 PFSS_TIMESTAMP)) {
1665 tsecr = ntohl(tsecr)
1666 - dst->scrub->pfss_ts_mod;
1667 pf_patch_32_unaligned(m,
1668 &th->th_sum,
1669 &opt[6],
1670 htonl(tsecr),
1671 PF_ALGNMNT(startoff),
1672 0);
1673 copyback = 1;
1674 }
1675 got_ts = 1;
1676 }
1677 /* FALLTHROUGH */
1678 default:
1679 hlen -= MAX(opt[1], 2);
1680 opt += MAX(opt[1], 2);
1681 break;
1682 }
1683 }
1684 if (copyback) {
1685 /* Copyback the options, caller copys back header */
1686 *writeback = 1;
1687 m_copyback(m, off + sizeof(struct tcphdr),
1688 (th->th_off << 2) - sizeof(struct tcphdr), hdr +
1689 sizeof(struct tcphdr));
1690 }
1691 }
1692
1693
1694 /*
1695 * Must invalidate PAWS checks on connections idle for too long.
1696 * The fastest allowed timestamp clock is 1ms. That turns out to
1697 * be about 24 days before it wraps. XXX Right now our lowerbound
1698 * TS echo check only works for the first 12 days of a connection
1699 * when the TS has exhausted half its 32bit space
1700 */
1701 #define TS_MAX_IDLE (24*24*60*60)
1702 #define TS_MAX_CONN (12*24*60*60) /* XXX remove when better tsecr check */
1703
1704 getmicrouptime(&uptime);
1705 if (src->scrub && (src->scrub->pfss_flags & PFSS_PAWS) &&
1706 (uptime.tv_sec - src->scrub->pfss_last.tv_sec > TS_MAX_IDLE ||
1707 time_uptime - state->creation > TS_MAX_CONN)) {
1708 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1709 DPFPRINTF(("src idled out of PAWS\n"));
1710 pf_print_state(state);
1711 printf("\n");
1712 }
1713 src->scrub->pfss_flags = (src->scrub->pfss_flags & ~PFSS_PAWS)
1714 | PFSS_PAWS_IDLED;
1715 }
1716 if (dst->scrub && (dst->scrub->pfss_flags & PFSS_PAWS) &&
1717 uptime.tv_sec - dst->scrub->pfss_last.tv_sec > TS_MAX_IDLE) {
1718 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1719 DPFPRINTF(("dst idled out of PAWS\n"));
1720 pf_print_state(state);
1721 printf("\n");
1722 }
1723 dst->scrub->pfss_flags = (dst->scrub->pfss_flags & ~PFSS_PAWS)
1724 | PFSS_PAWS_IDLED;
1725 }
1726
1727 if (got_ts && src->scrub && dst->scrub &&
1728 (src->scrub->pfss_flags & PFSS_PAWS) &&
1729 (dst->scrub->pfss_flags & PFSS_PAWS)) {
1730 /* Validate that the timestamps are "in-window".
1731 * RFC1323 describes TCP Timestamp options that allow
1732 * measurement of RTT (round trip time) and PAWS
1733 * (protection against wrapped sequence numbers). PAWS
1734 * gives us a set of rules for rejecting packets on
1735 * long fat pipes (packets that were somehow delayed
1736 * in transit longer than the time it took to send the
1737 * full TCP sequence space of 4Gb). We can use these
1738 * rules and infer a few others that will let us treat
1739 * the 32bit timestamp and the 32bit echoed timestamp
1740 * as sequence numbers to prevent a blind attacker from
1741 * inserting packets into a connection.
1742 *
1743 * RFC1323 tells us:
1744 * - The timestamp on this packet must be greater than
1745 * or equal to the last value echoed by the other
1746 * endpoint. The RFC says those will be discarded
1747 * since it is a dup that has already been acked.
1748 * This gives us a lowerbound on the timestamp.
1749 * timestamp >= other last echoed timestamp
1750 * - The timestamp will be less than or equal to
1751 * the last timestamp plus the time between the
1752 * last packet and now. The RFC defines the max
1753 * clock rate as 1ms. We will allow clocks to be
1754 * up to 10% fast and will allow a total difference
1755 * or 30 seconds due to a route change. And this
1756 * gives us an upperbound on the timestamp.
1757 * timestamp <= last timestamp + max ticks
1758 * We have to be careful here. Windows will send an
1759 * initial timestamp of zero and then initialize it
1760 * to a random value after the 3whs; presumably to
1761 * avoid a DoS by having to call an expensive RNG
1762 * during a SYN flood. Proof MS has at least one
1763 * good security geek.
1764 *
1765 * - The TCP timestamp option must also echo the other
1766 * endpoints timestamp. The timestamp echoed is the
1767 * one carried on the earliest unacknowledged segment
1768 * on the left edge of the sequence window. The RFC
1769 * states that the host will reject any echoed
1770 * timestamps that were larger than any ever sent.
1771 * This gives us an upperbound on the TS echo.
1772 * tescr <= largest_tsval
1773 * - The lowerbound on the TS echo is a little more
1774 * tricky to determine. The other endpoint's echoed
1775 * values will not decrease. But there may be
1776 * network conditions that re-order packets and
1777 * cause our view of them to decrease. For now the
1778 * only lowerbound we can safely determine is that
1779 * the TS echo will never be less than the original
1780 * TS. XXX There is probably a better lowerbound.
1781 * Remove TS_MAX_CONN with better lowerbound check.
1782 * tescr >= other original TS
1783 *
1784 * It is also important to note that the fastest
1785 * timestamp clock of 1ms will wrap its 32bit space in
1786 * 24 days. So we just disable TS checking after 24
1787 * days of idle time. We actually must use a 12d
1788 * connection limit until we can come up with a better
1789 * lowerbound to the TS echo check.
1790 */
1791 struct timeval delta_ts;
1792 int ts_fudge;
1793
1794
1795 /*
1796 * PFTM_TS_DIFF is how many seconds of leeway to allow
1797 * a host's timestamp. This can happen if the previous
1798 * packet got delayed in transit for much longer than
1799 * this packet.
1800 */
1801 if ((ts_fudge = state->rule.ptr->timeout[PFTM_TS_DIFF]) == 0)
1802 ts_fudge = V_pf_default_rule.timeout[PFTM_TS_DIFF];
1803
1804 /* Calculate max ticks since the last timestamp */
1805 #define TS_MAXFREQ 1100 /* RFC max TS freq of 1Khz + 10% skew */
1806 #define TS_MICROSECS 1000000 /* microseconds per second */
1807 delta_ts = uptime;
1808 timevalsub(&delta_ts, &src->scrub->pfss_last);
1809 tsval_from_last = (delta_ts.tv_sec + ts_fudge) * TS_MAXFREQ;
1810 tsval_from_last += delta_ts.tv_usec / (TS_MICROSECS/TS_MAXFREQ);
1811
1812 if ((src->state >= TCPS_ESTABLISHED &&
1813 dst->state >= TCPS_ESTABLISHED) &&
1814 (SEQ_LT(tsval, dst->scrub->pfss_tsecr) ||
1815 SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) ||
1816 (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) ||
1817 SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) {
1818 /* Bad RFC1323 implementation or an insertion attack.
1819 *
1820 * - Solaris 2.6 and 2.7 are known to send another ACK
1821 * after the FIN,FIN|ACK,ACK closing that carries
1822 * an old timestamp.
1823 */
1824
1825 DPFPRINTF(("Timestamp failed %c%c%c%c\n",
1826 SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '0' : ' ',
1827 SEQ_GT(tsval, src->scrub->pfss_tsval +
1828 tsval_from_last) ? '1' : ' ',
1829 SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ',
1830 SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' '));
1831 DPFPRINTF((" tsval: %u tsecr: %u +ticks: %u "
1832 "idle: %jus %lums\n",
1833 tsval, tsecr, tsval_from_last,
1834 (uintmax_t)delta_ts.tv_sec,
1835 delta_ts.tv_usec / 1000));
1836 DPFPRINTF((" src->tsval: %u tsecr: %u\n",
1837 src->scrub->pfss_tsval, src->scrub->pfss_tsecr));
1838 DPFPRINTF((" dst->tsval: %u tsecr: %u tsval0: %u"
1839 "\n", dst->scrub->pfss_tsval,
1840 dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0));
1841 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1842 pf_print_state(state);
1843 pf_print_flags(th->th_flags);
1844 printf("\n");
1845 }
1846 REASON_SET(reason, PFRES_TS);
1847 return (PF_DROP);
1848 }
1849
1850 /* XXX I'd really like to require tsecr but it's optional */
1851
1852 } else if (!got_ts && (th->th_flags & TH_RST) == 0 &&
1853 ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED)
1854 || pd->p_len > 0 || (th->th_flags & TH_SYN)) &&
1855 src->scrub && dst->scrub &&
1856 (src->scrub->pfss_flags & PFSS_PAWS) &&
1857 (dst->scrub->pfss_flags & PFSS_PAWS)) {
1858 /* Didn't send a timestamp. Timestamps aren't really useful
1859 * when:
1860 * - connection opening or closing (often not even sent).
1861 * but we must not let an attacker to put a FIN on a
1862 * data packet to sneak it through our ESTABLISHED check.
1863 * - on a TCP reset. RFC suggests not even looking at TS.
1864 * - on an empty ACK. The TS will not be echoed so it will
1865 * probably not help keep the RTT calculation in sync and
1866 * there isn't as much danger when the sequence numbers
1867 * got wrapped. So some stacks don't include TS on empty
1868 * ACKs :-(
1869 *
1870 * To minimize the disruption to mostly RFC1323 conformant
1871 * stacks, we will only require timestamps on data packets.
1872 *
1873 * And what do ya know, we cannot require timestamps on data
1874 * packets. There appear to be devices that do legitimate
1875 * TCP connection hijacking. There are HTTP devices that allow
1876 * a 3whs (with timestamps) and then buffer the HTTP request.
1877 * If the intermediate device has the HTTP response cache, it
1878 * will spoof the response but not bother timestamping its
1879 * packets. So we can look for the presence of a timestamp in
1880 * the first data packet and if there, require it in all future
1881 * packets.
1882 */
1883
1884 if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) {
1885 /*
1886 * Hey! Someone tried to sneak a packet in. Or the
1887 * stack changed its RFC1323 behavior?!?!
1888 */
1889 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1890 DPFPRINTF(("Did not receive expected RFC1323 "
1891 "timestamp\n"));
1892 pf_print_state(state);
1893 pf_print_flags(th->th_flags);
1894 printf("\n");
1895 }
1896 REASON_SET(reason, PFRES_TS);
1897 return (PF_DROP);
1898 }
1899 }
1900
1901
1902 /*
1903 * We will note if a host sends his data packets with or without
1904 * timestamps. And require all data packets to contain a timestamp
1905 * if the first does. PAWS implicitly requires that all data packets be
1906 * timestamped. But I think there are middle-man devices that hijack
1907 * TCP streams immediately after the 3whs and don't timestamp their
1908 * packets (seen in a WWW accelerator or cache).
1909 */
1910 if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags &
1911 (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) {
1912 if (got_ts)
1913 src->scrub->pfss_flags |= PFSS_DATA_TS;
1914 else {
1915 src->scrub->pfss_flags |= PFSS_DATA_NOTS;
1916 if (V_pf_status.debug >= PF_DEBUG_MISC && dst->scrub &&
1917 (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) {
1918 /* Don't warn if other host rejected RFC1323 */
1919 DPFPRINTF(("Broken RFC1323 stack did not "
1920 "timestamp data packet. Disabled PAWS "
1921 "security.\n"));
1922 pf_print_state(state);
1923 pf_print_flags(th->th_flags);
1924 printf("\n");
1925 }
1926 }
1927 }
1928
1929
1930 /*
1931 * Update PAWS values
1932 */
1933 if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags &
1934 (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) {
1935 getmicrouptime(&src->scrub->pfss_last);
1936 if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) ||
1937 (src->scrub->pfss_flags & PFSS_PAWS) == 0)
1938 src->scrub->pfss_tsval = tsval;
1939
1940 if (tsecr) {
1941 if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) ||
1942 (src->scrub->pfss_flags & PFSS_PAWS) == 0)
1943 src->scrub->pfss_tsecr = tsecr;
1944
1945 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 &&
1946 (SEQ_LT(tsval, src->scrub->pfss_tsval0) ||
1947 src->scrub->pfss_tsval0 == 0)) {
1948 /* tsval0 MUST be the lowest timestamp */
1949 src->scrub->pfss_tsval0 = tsval;
1950 }
1951
1952 /* Only fully initialized after a TS gets echoed */
1953 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0)
1954 src->scrub->pfss_flags |= PFSS_PAWS;
1955 }
1956 }
1957
1958 /* I have a dream.... TCP segment reassembly.... */
1959 return (0);
1960 }
1961
1962 static int
pf_normalize_tcpopt(struct pf_krule * r,struct mbuf * m,struct tcphdr * th,int off,sa_family_t af)1963 pf_normalize_tcpopt(struct pf_krule *r, struct mbuf *m, struct tcphdr *th,
1964 int off, sa_family_t af)
1965 {
1966 u_int16_t *mss;
1967 int thoff;
1968 int opt, cnt, optlen = 0;
1969 int rewrite = 0;
1970 u_char opts[TCP_MAXOLEN];
1971 u_char *optp = opts;
1972 size_t startoff;
1973
1974 thoff = th->th_off << 2;
1975 cnt = thoff - sizeof(struct tcphdr);
1976
1977 if (cnt > 0 && !pf_pull_hdr(m, off + sizeof(*th), opts, cnt,
1978 NULL, NULL, af))
1979 return (rewrite);
1980
1981 for (; cnt > 0; cnt -= optlen, optp += optlen) {
1982 startoff = optp - opts;
1983 opt = optp[0];
1984 if (opt == TCPOPT_EOL)
1985 break;
1986 if (opt == TCPOPT_NOP)
1987 optlen = 1;
1988 else {
1989 if (cnt < 2)
1990 break;
1991 optlen = optp[1];
1992 if (optlen < 2 || optlen > cnt)
1993 break;
1994 }
1995 switch (opt) {
1996 case TCPOPT_MAXSEG:
1997 mss = (u_int16_t *)(optp + 2);
1998 if ((ntohs(*mss)) > r->max_mss) {
1999 pf_patch_16_unaligned(m,
2000 &th->th_sum,
2001 mss, htons(r->max_mss),
2002 PF_ALGNMNT(startoff),
2003 0);
2004 rewrite = 1;
2005 }
2006 break;
2007 default:
2008 break;
2009 }
2010 }
2011
2012 if (rewrite)
2013 m_copyback(m, off + sizeof(*th), thoff - sizeof(*th), opts);
2014
2015 return (rewrite);
2016 }
2017
2018 #ifdef INET
2019 static void
pf_scrub_ip(struct mbuf ** m0,u_int32_t flags,u_int8_t min_ttl,u_int8_t tos)2020 pf_scrub_ip(struct mbuf **m0, u_int32_t flags, u_int8_t min_ttl, u_int8_t tos)
2021 {
2022 struct mbuf *m = *m0;
2023 struct ip *h = mtod(m, struct ip *);
2024
2025 /* Clear IP_DF if no-df was requested */
2026 if (flags & PFRULE_NODF && h->ip_off & htons(IP_DF)) {
2027 u_int16_t ip_off = h->ip_off;
2028
2029 h->ip_off &= htons(~IP_DF);
2030 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
2031 }
2032
2033 /* Enforce a minimum ttl, may cause endless packet loops */
2034 if (min_ttl && h->ip_ttl < min_ttl) {
2035 u_int16_t ip_ttl = h->ip_ttl;
2036
2037 h->ip_ttl = min_ttl;
2038 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0);
2039 }
2040
2041 /* Enforce tos */
2042 if (flags & PFRULE_SET_TOS) {
2043 u_int16_t ov, nv;
2044
2045 ov = *(u_int16_t *)h;
2046 h->ip_tos = tos | (h->ip_tos & IPTOS_ECN_MASK);
2047 nv = *(u_int16_t *)h;
2048
2049 h->ip_sum = pf_cksum_fixup(h->ip_sum, ov, nv, 0);
2050 }
2051
2052 /* random-id, but not for fragments */
2053 if (flags & PFRULE_RANDOMID && !(h->ip_off & ~htons(IP_DF))) {
2054 uint16_t ip_id = h->ip_id;
2055
2056 ip_fillid(h);
2057 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_id, h->ip_id, 0);
2058 }
2059 }
2060 #endif /* INET */
2061
2062 #ifdef INET6
2063 static void
pf_scrub_ip6(struct mbuf ** m0,u_int8_t min_ttl)2064 pf_scrub_ip6(struct mbuf **m0, u_int8_t min_ttl)
2065 {
2066 struct mbuf *m = *m0;
2067 struct ip6_hdr *h = mtod(m, struct ip6_hdr *);
2068
2069 /* Enforce a minimum ttl, may cause endless packet loops */
2070 if (min_ttl && h->ip6_hlim < min_ttl)
2071 h->ip6_hlim = min_ttl;
2072 }
2073 #endif
2074