1 /*-
2 * Copyright 2001 Niels Provos <provos@citi.umich.edu>
3 * Copyright 2011 Alexander Bluhm <bluhm@openbsd.org>
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 *
26 * $OpenBSD: pf_norm.c,v 1.114 2009/01/29 14:11:45 henning Exp $
27 */
28
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD$");
31
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/vnet.h>
46 #include <net/pfvar.h>
47 #include <net/if_pflog.h>
48
49 #include <netinet/in.h>
50 #include <netinet/ip.h>
51 #include <netinet/ip_var.h>
52 #include <netinet6/ip6_var.h>
53 #include <netinet/tcp.h>
54 #include <netinet/tcp_fsm.h>
55 #include <netinet/tcp_seq.h>
56
57 #ifdef INET6
58 #include <netinet/ip6.h>
59 #endif /* INET6 */
60
61 struct pf_frent {
62 TAILQ_ENTRY(pf_frent) fr_next;
63 struct mbuf *fe_m;
64 uint16_t fe_hdrlen; /* ipv4 header length with ip options
65 ipv6, extension, fragment header */
66 uint16_t fe_extoff; /* last extension header offset or 0 */
67 uint16_t fe_len; /* fragment length */
68 uint16_t fe_off; /* fragment offset */
69 uint16_t fe_mff; /* more fragment flag */
70 };
71
72 struct pf_fragment_cmp {
73 struct pf_addr frc_src;
74 struct pf_addr frc_dst;
75 uint32_t frc_id;
76 sa_family_t frc_af;
77 uint8_t frc_proto;
78 };
79
80 struct pf_fragment {
81 struct pf_fragment_cmp fr_key;
82 #define fr_src fr_key.frc_src
83 #define fr_dst fr_key.frc_dst
84 #define fr_id fr_key.frc_id
85 #define fr_af fr_key.frc_af
86 #define fr_proto fr_key.frc_proto
87
88 RB_ENTRY(pf_fragment) fr_entry;
89 TAILQ_ENTRY(pf_fragment) frag_next;
90 uint32_t fr_timeout;
91 uint16_t fr_maxlen; /* maximum length of single fragment */
92 uint16_t fr_entries; /* Total number of pf_fragment entries */
93 TAILQ_HEAD(pf_fragq, pf_frent) fr_queue;
94 };
95 #define PF_MAX_FRENT_PER_FRAGMENT 64
96
97 struct pf_fragment_tag {
98 uint16_t ft_hdrlen; /* header length of reassembled pkt */
99 uint16_t ft_extoff; /* last extension header offset or 0 */
100 uint16_t ft_maxlen; /* maximum fragment payload length */
101 uint32_t ft_id; /* fragment id */
102 };
103
104 static struct mtx pf_frag_mtx;
105 MTX_SYSINIT(pf_frag_mtx, &pf_frag_mtx, "pf fragments", MTX_DEF);
106 #define PF_FRAG_LOCK() mtx_lock(&pf_frag_mtx)
107 #define PF_FRAG_UNLOCK() mtx_unlock(&pf_frag_mtx)
108 #define PF_FRAG_ASSERT() mtx_assert(&pf_frag_mtx, MA_OWNED)
109
110 VNET_DEFINE(uma_zone_t, pf_state_scrub_z); /* XXX: shared with pfsync */
111
112 static VNET_DEFINE(uma_zone_t, pf_frent_z);
113 #define V_pf_frent_z VNET(pf_frent_z)
114 static VNET_DEFINE(uma_zone_t, pf_frag_z);
115 #define V_pf_frag_z VNET(pf_frag_z)
116
117 TAILQ_HEAD(pf_fragqueue, pf_fragment);
118 TAILQ_HEAD(pf_cachequeue, pf_fragment);
119 static VNET_DEFINE(struct pf_fragqueue, pf_fragqueue);
120 #define V_pf_fragqueue VNET(pf_fragqueue)
121 RB_HEAD(pf_frag_tree, pf_fragment);
122 static VNET_DEFINE(struct pf_frag_tree, pf_frag_tree);
123 #define V_pf_frag_tree VNET(pf_frag_tree)
124 static int pf_frag_compare(struct pf_fragment *,
125 struct pf_fragment *);
126 static RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare);
127 static RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare);
128
129 static void pf_flush_fragments(void);
130 static void pf_free_fragment(struct pf_fragment *);
131 static void pf_remove_fragment(struct pf_fragment *);
132 static int pf_normalize_tcpopt(struct pf_rule *, struct mbuf *,
133 struct tcphdr *, int, sa_family_t);
134 static struct pf_frent *pf_create_fragment(u_short *);
135 static struct pf_fragment *pf_find_fragment(struct pf_fragment_cmp *key,
136 struct pf_frag_tree *tree);
137 static struct pf_fragment *pf_fillup_fragment(struct pf_fragment_cmp *,
138 struct pf_frent *, u_short *);
139 static int pf_isfull_fragment(struct pf_fragment *);
140 static struct mbuf *pf_join_fragment(struct pf_fragment *);
141 #ifdef INET
142 static void pf_scrub_ip(struct mbuf **, uint32_t, uint8_t, uint8_t);
143 static int pf_reassemble(struct mbuf **, struct ip *, int, u_short *);
144 #endif /* INET */
145 #ifdef INET6
146 static int pf_reassemble6(struct mbuf **, struct ip6_hdr *,
147 struct ip6_frag *, uint16_t, uint16_t, u_short *);
148 static void pf_scrub_ip6(struct mbuf **, uint8_t);
149 #endif /* INET6 */
150
151 #define DPFPRINTF(x) do { \
152 if (V_pf_status.debug >= PF_DEBUG_MISC) { \
153 printf("%s: ", __func__); \
154 printf x ; \
155 } \
156 } while(0)
157
158 #ifdef INET
159 static void
pf_ip2key(struct ip * ip,int dir,struct pf_fragment_cmp * key)160 pf_ip2key(struct ip *ip, int dir, struct pf_fragment_cmp *key)
161 {
162
163 key->frc_src.v4 = ip->ip_src;
164 key->frc_dst.v4 = ip->ip_dst;
165 key->frc_af = AF_INET;
166 key->frc_proto = ip->ip_p;
167 key->frc_id = ip->ip_id;
168 }
169 #endif /* INET */
170
171 void
pf_normalize_init(void)172 pf_normalize_init(void)
173 {
174
175 V_pf_frag_z = uma_zcreate("pf frags", sizeof(struct pf_fragment),
176 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
177 V_pf_frent_z = uma_zcreate("pf frag entries", sizeof(struct pf_frent),
178 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
179 V_pf_state_scrub_z = uma_zcreate("pf state scrubs",
180 sizeof(struct pf_state_scrub), NULL, NULL, NULL, NULL,
181 UMA_ALIGN_PTR, 0);
182
183 V_pf_limits[PF_LIMIT_FRAGS].zone = V_pf_frent_z;
184 V_pf_limits[PF_LIMIT_FRAGS].limit = PFFRAG_FRENT_HIWAT;
185 uma_zone_set_max(V_pf_frent_z, PFFRAG_FRENT_HIWAT);
186 uma_zone_set_warning(V_pf_frent_z, "PF frag entries limit reached");
187
188 TAILQ_INIT(&V_pf_fragqueue);
189 }
190
191 void
pf_normalize_cleanup(void)192 pf_normalize_cleanup(void)
193 {
194
195 uma_zdestroy(V_pf_state_scrub_z);
196 uma_zdestroy(V_pf_frent_z);
197 uma_zdestroy(V_pf_frag_z);
198 }
199
200 static int
pf_frag_compare(struct pf_fragment * a,struct pf_fragment * b)201 pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b)
202 {
203 int diff;
204
205 if ((diff = a->fr_id - b->fr_id) != 0)
206 return (diff);
207 if ((diff = a->fr_proto - b->fr_proto) != 0)
208 return (diff);
209 if ((diff = a->fr_af - b->fr_af) != 0)
210 return (diff);
211 if ((diff = pf_addr_cmp(&a->fr_src, &b->fr_src, a->fr_af)) != 0)
212 return (diff);
213 if ((diff = pf_addr_cmp(&a->fr_dst, &b->fr_dst, a->fr_af)) != 0)
214 return (diff);
215 return (0);
216 }
217
218 void
pf_purge_expired_fragments(void)219 pf_purge_expired_fragments(void)
220 {
221 struct pf_fragment *frag;
222 u_int32_t expire = time_uptime -
223 V_pf_default_rule.timeout[PFTM_FRAG];
224
225 PF_FRAG_LOCK();
226 while ((frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue)) != NULL) {
227 if (frag->fr_timeout > expire)
228 break;
229
230 DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag));
231 pf_free_fragment(frag);
232 }
233
234 PF_FRAG_UNLOCK();
235 }
236
237 /*
238 * Try to flush old fragments to make space for new ones
239 */
240 static void
pf_flush_fragments(void)241 pf_flush_fragments(void)
242 {
243 struct pf_fragment *frag;
244 int goal;
245
246 PF_FRAG_ASSERT();
247
248 goal = uma_zone_get_cur(V_pf_frent_z) * 9 / 10;
249 DPFPRINTF(("trying to free %d frag entriess\n", goal));
250 while (goal < uma_zone_get_cur(V_pf_frent_z)) {
251 frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue);
252 if (frag)
253 pf_free_fragment(frag);
254 else
255 break;
256 }
257 }
258
259 /* Frees the fragments and all associated entries */
260 static void
pf_free_fragment(struct pf_fragment * frag)261 pf_free_fragment(struct pf_fragment *frag)
262 {
263 struct pf_frent *frent;
264
265 PF_FRAG_ASSERT();
266
267 /* Free all fragments */
268 for (frent = TAILQ_FIRST(&frag->fr_queue); frent;
269 frent = TAILQ_FIRST(&frag->fr_queue)) {
270 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
271
272 m_freem(frent->fe_m);
273 uma_zfree(V_pf_frent_z, frent);
274 }
275
276 pf_remove_fragment(frag);
277 }
278
279 static struct pf_fragment *
pf_find_fragment(struct pf_fragment_cmp * key,struct pf_frag_tree * tree)280 pf_find_fragment(struct pf_fragment_cmp *key, struct pf_frag_tree *tree)
281 {
282 struct pf_fragment *frag;
283
284 PF_FRAG_ASSERT();
285
286 frag = RB_FIND(pf_frag_tree, tree, (struct pf_fragment *)key);
287 if (frag != NULL) {
288 /* XXX Are we sure we want to update the timeout? */
289 frag->fr_timeout = time_uptime;
290 TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next);
291 TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next);
292 }
293
294 return (frag);
295 }
296
297 /* Removes a fragment from the fragment queue and frees the fragment */
298 static void
pf_remove_fragment(struct pf_fragment * frag)299 pf_remove_fragment(struct pf_fragment *frag)
300 {
301
302 PF_FRAG_ASSERT();
303
304 RB_REMOVE(pf_frag_tree, &V_pf_frag_tree, frag);
305 TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next);
306 uma_zfree(V_pf_frag_z, frag);
307 }
308
309 static struct pf_frent *
pf_create_fragment(u_short * reason)310 pf_create_fragment(u_short *reason)
311 {
312 struct pf_frent *frent;
313
314 PF_FRAG_ASSERT();
315
316 frent = uma_zalloc(V_pf_frent_z, M_NOWAIT);
317 if (frent == NULL) {
318 pf_flush_fragments();
319 frent = uma_zalloc(V_pf_frent_z, M_NOWAIT);
320 if (frent == NULL) {
321 REASON_SET(reason, PFRES_MEMORY);
322 return (NULL);
323 }
324 }
325
326 return (frent);
327 }
328
329 static struct pf_fragment *
pf_fillup_fragment(struct pf_fragment_cmp * key,struct pf_frent * frent,u_short * reason)330 pf_fillup_fragment(struct pf_fragment_cmp *key, struct pf_frent *frent,
331 u_short *reason)
332 {
333 struct pf_frent *after, *next, *prev;
334 struct pf_fragment *frag;
335 uint16_t total;
336
337 PF_FRAG_ASSERT();
338
339 /* No empty fragments. */
340 if (frent->fe_len == 0) {
341 DPFPRINTF(("bad fragment: len 0"));
342 goto bad_fragment;
343 }
344
345 /* All fragments are 8 byte aligned. */
346 if (frent->fe_mff && (frent->fe_len & 0x7)) {
347 DPFPRINTF(("bad fragment: mff and len %d", frent->fe_len));
348 goto bad_fragment;
349 }
350
351 /* Respect maximum length, IP_MAXPACKET == IPV6_MAXPACKET. */
352 if (frent->fe_off + frent->fe_len > IP_MAXPACKET) {
353 DPFPRINTF(("bad fragment: max packet %d",
354 frent->fe_off + frent->fe_len));
355 goto bad_fragment;
356 }
357
358 DPFPRINTF((key->frc_af == AF_INET ?
359 "reass frag %d @ %d-%d" : "reass frag %#08x @ %d-%d",
360 key->frc_id, frent->fe_off, frent->fe_off + frent->fe_len));
361
362 /* Fully buffer all of the fragments in this fragment queue. */
363 frag = pf_find_fragment(key, &V_pf_frag_tree);
364
365 /* Create a new reassembly queue for this packet. */
366 if (frag == NULL) {
367 frag = uma_zalloc(V_pf_frag_z, M_NOWAIT);
368 if (frag == NULL) {
369 pf_flush_fragments();
370 frag = uma_zalloc(V_pf_frag_z, M_NOWAIT);
371 if (frag == NULL) {
372 REASON_SET(reason, PFRES_MEMORY);
373 goto drop_fragment;
374 }
375 }
376
377 *(struct pf_fragment_cmp *)frag = *key;
378 frag->fr_timeout = time_uptime;
379 frag->fr_maxlen = frent->fe_len;
380 frag->fr_entries = 0;
381 TAILQ_INIT(&frag->fr_queue);
382
383 RB_INSERT(pf_frag_tree, &V_pf_frag_tree, frag);
384 TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next);
385
386 /* We do not have a previous fragment. */
387 TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next);
388
389 return (frag);
390 }
391
392 if (frag->fr_entries >= PF_MAX_FRENT_PER_FRAGMENT)
393 goto bad_fragment;
394
395 KASSERT(!TAILQ_EMPTY(&frag->fr_queue), ("!TAILQ_EMPTY()->fr_queue"));
396
397 /* Remember maximum fragment len for refragmentation. */
398 if (frent->fe_len > frag->fr_maxlen)
399 frag->fr_maxlen = frent->fe_len;
400
401 /* Maximum data we have seen already. */
402 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
403 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
404
405 /* Non terminal fragments must have more fragments flag. */
406 if (frent->fe_off + frent->fe_len < total && !frent->fe_mff)
407 goto bad_fragment;
408
409 /* Check if we saw the last fragment already. */
410 if (!TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_mff) {
411 if (frent->fe_off + frent->fe_len > total ||
412 (frent->fe_off + frent->fe_len == total && frent->fe_mff))
413 goto bad_fragment;
414 } else {
415 if (frent->fe_off + frent->fe_len == total && !frent->fe_mff)
416 goto bad_fragment;
417 }
418
419 /* Find a fragment after the current one. */
420 prev = NULL;
421 TAILQ_FOREACH(after, &frag->fr_queue, fr_next) {
422 if (after->fe_off > frent->fe_off)
423 break;
424 prev = after;
425 }
426
427 KASSERT(prev != NULL || after != NULL,
428 ("prev != NULL || after != NULL"));
429
430 if (prev != NULL && prev->fe_off + prev->fe_len > frent->fe_off) {
431 uint16_t precut;
432
433 precut = prev->fe_off + prev->fe_len - frent->fe_off;
434 if (precut >= frent->fe_len)
435 goto bad_fragment;
436 DPFPRINTF(("overlap -%d", precut));
437 m_adj(frent->fe_m, precut);
438 frent->fe_off += precut;
439 frent->fe_len -= precut;
440 }
441
442 for (; after != NULL && frent->fe_off + frent->fe_len > after->fe_off;
443 after = next) {
444 uint16_t aftercut;
445
446 aftercut = frent->fe_off + frent->fe_len - after->fe_off;
447 DPFPRINTF(("adjust overlap %d", aftercut));
448 if (aftercut < after->fe_len) {
449 m_adj(after->fe_m, aftercut);
450 after->fe_off += aftercut;
451 after->fe_len -= aftercut;
452 break;
453 }
454
455 /* This fragment is completely overlapped, lose it. */
456 next = TAILQ_NEXT(after, fr_next);
457 m_freem(after->fe_m);
458 TAILQ_REMOVE(&frag->fr_queue, after, fr_next);
459 uma_zfree(V_pf_frent_z, after);
460 }
461
462 if (prev == NULL)
463 TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next);
464 else
465 TAILQ_INSERT_AFTER(&frag->fr_queue, prev, frent, fr_next);
466
467 frag->fr_entries++;
468
469 return (frag);
470
471 bad_fragment:
472 REASON_SET(reason, PFRES_FRAG);
473 drop_fragment:
474 uma_zfree(V_pf_frent_z, frent);
475 return (NULL);
476 }
477
478 static int
pf_isfull_fragment(struct pf_fragment * frag)479 pf_isfull_fragment(struct pf_fragment *frag)
480 {
481 struct pf_frent *frent, *next;
482 uint16_t off, total;
483
484 /* Check if we are completely reassembled */
485 if (TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_mff)
486 return (0);
487
488 /* Maximum data we have seen already */
489 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
490 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
491
492 /* Check if we have all the data */
493 off = 0;
494 for (frent = TAILQ_FIRST(&frag->fr_queue); frent; frent = next) {
495 next = TAILQ_NEXT(frent, fr_next);
496
497 off += frent->fe_len;
498 if (off < total && (next == NULL || next->fe_off != off)) {
499 DPFPRINTF(("missing fragment at %d, next %d, total %d",
500 off, next == NULL ? -1 : next->fe_off, total));
501 return (0);
502 }
503 }
504 DPFPRINTF(("%d < %d?", off, total));
505 if (off < total)
506 return (0);
507 KASSERT(off == total, ("off == total"));
508
509 return (1);
510 }
511
512 static struct mbuf *
pf_join_fragment(struct pf_fragment * frag)513 pf_join_fragment(struct pf_fragment *frag)
514 {
515 struct mbuf *m, *m2;
516 struct pf_frent *frent, *next;
517
518 frent = TAILQ_FIRST(&frag->fr_queue);
519 next = TAILQ_NEXT(frent, fr_next);
520
521 m = frent->fe_m;
522 m_adj(m, (frent->fe_hdrlen + frent->fe_len) - m->m_pkthdr.len);
523 uma_zfree(V_pf_frent_z, frent);
524 for (frent = next; frent != NULL; frent = next) {
525 next = TAILQ_NEXT(frent, fr_next);
526
527 m2 = frent->fe_m;
528 /* Strip off ip header. */
529 m_adj(m2, frent->fe_hdrlen);
530 /* Strip off any trailing bytes. */
531 m_adj(m2, frent->fe_len - m2->m_pkthdr.len);
532
533 uma_zfree(V_pf_frent_z, frent);
534 m_cat(m, m2);
535 }
536
537 /* Remove from fragment queue. */
538 pf_remove_fragment(frag);
539
540 return (m);
541 }
542
543 #ifdef INET
544 static int
pf_reassemble(struct mbuf ** m0,struct ip * ip,int dir,u_short * reason)545 pf_reassemble(struct mbuf **m0, struct ip *ip, int dir, u_short *reason)
546 {
547 struct mbuf *m = *m0;
548 struct pf_frent *frent;
549 struct pf_fragment *frag;
550 struct pf_fragment_cmp key;
551 uint16_t total, hdrlen;
552
553 /* Get an entry for the fragment queue */
554 if ((frent = pf_create_fragment(reason)) == NULL)
555 return (PF_DROP);
556
557 frent->fe_m = m;
558 frent->fe_hdrlen = ip->ip_hl << 2;
559 frent->fe_extoff = 0;
560 frent->fe_len = ntohs(ip->ip_len) - (ip->ip_hl << 2);
561 frent->fe_off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3;
562 frent->fe_mff = ntohs(ip->ip_off) & IP_MF;
563
564 pf_ip2key(ip, dir, &key);
565
566 if ((frag = pf_fillup_fragment(&key, frent, reason)) == NULL)
567 return (PF_DROP);
568
569 /* The mbuf is part of the fragment entry, no direct free or access */
570 m = *m0 = NULL;
571
572 if (!pf_isfull_fragment(frag))
573 return (PF_PASS); /* drop because *m0 is NULL, no error */
574
575 /* We have all the data */
576 frent = TAILQ_FIRST(&frag->fr_queue);
577 KASSERT(frent != NULL, ("frent != NULL"));
578 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
579 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
580 hdrlen = frent->fe_hdrlen;
581
582 m = *m0 = pf_join_fragment(frag);
583 frag = NULL;
584
585 if (m->m_flags & M_PKTHDR) {
586 int plen = 0;
587 for (m = *m0; m; m = m->m_next)
588 plen += m->m_len;
589 m = *m0;
590 m->m_pkthdr.len = plen;
591 }
592
593 ip = mtod(m, struct ip *);
594 ip->ip_len = htons(hdrlen + total);
595 ip->ip_off &= ~(IP_MF|IP_OFFMASK);
596
597 if (hdrlen + total > IP_MAXPACKET) {
598 DPFPRINTF(("drop: too big: %d", total));
599 ip->ip_len = 0;
600 REASON_SET(reason, PFRES_SHORT);
601 /* PF_DROP requires a valid mbuf *m0 in pf_test() */
602 return (PF_DROP);
603 }
604
605 DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip->ip_len)));
606 return (PF_PASS);
607 }
608 #endif /* INET */
609
610 #ifdef INET6
611 static int
pf_reassemble6(struct mbuf ** m0,struct ip6_hdr * ip6,struct ip6_frag * fraghdr,uint16_t hdrlen,uint16_t extoff,u_short * reason)612 pf_reassemble6(struct mbuf **m0, struct ip6_hdr *ip6, struct ip6_frag *fraghdr,
613 uint16_t hdrlen, uint16_t extoff, u_short *reason)
614 {
615 struct mbuf *m = *m0;
616 struct pf_frent *frent;
617 struct pf_fragment *frag;
618 struct pf_fragment_cmp key;
619 struct m_tag *mtag;
620 struct pf_fragment_tag *ftag;
621 int off;
622 uint32_t frag_id;
623 uint16_t total, maxlen;
624 uint8_t proto;
625
626 PF_FRAG_LOCK();
627
628 /* Get an entry for the fragment queue. */
629 if ((frent = pf_create_fragment(reason)) == NULL) {
630 PF_FRAG_UNLOCK();
631 return (PF_DROP);
632 }
633
634 frent->fe_m = m;
635 frent->fe_hdrlen = hdrlen;
636 frent->fe_extoff = extoff;
637 frent->fe_len = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - hdrlen;
638 frent->fe_off = ntohs(fraghdr->ip6f_offlg & IP6F_OFF_MASK);
639 frent->fe_mff = fraghdr->ip6f_offlg & IP6F_MORE_FRAG;
640
641 key.frc_src.v6 = ip6->ip6_src;
642 key.frc_dst.v6 = ip6->ip6_dst;
643 key.frc_af = AF_INET6;
644 /* Only the first fragment's protocol is relevant. */
645 key.frc_proto = 0;
646 key.frc_id = fraghdr->ip6f_ident;
647
648 if ((frag = pf_fillup_fragment(&key, frent, reason)) == NULL) {
649 PF_FRAG_UNLOCK();
650 return (PF_DROP);
651 }
652
653 /* The mbuf is part of the fragment entry, no direct free or access. */
654 m = *m0 = NULL;
655
656 if (!pf_isfull_fragment(frag)) {
657 PF_FRAG_UNLOCK();
658 return (PF_PASS); /* Drop because *m0 is NULL, no error. */
659 }
660
661 /* We have all the data. */
662 frent = TAILQ_FIRST(&frag->fr_queue);
663 KASSERT(frent != NULL, ("frent != NULL"));
664 extoff = frent->fe_extoff;
665 maxlen = frag->fr_maxlen;
666 frag_id = frag->fr_id;
667 total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
668 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
669 hdrlen = frent->fe_hdrlen - sizeof(struct ip6_frag);
670
671 m = *m0 = pf_join_fragment(frag);
672 frag = NULL;
673
674 PF_FRAG_UNLOCK();
675
676 /* Take protocol from first fragment header. */
677 m = m_getptr(m, hdrlen + offsetof(struct ip6_frag, ip6f_nxt), &off);
678 KASSERT(m, ("%s: short mbuf chain", __func__));
679 proto = *(mtod(m, caddr_t) + off);
680 m = *m0;
681
682 /* Delete frag6 header */
683 if (ip6_deletefraghdr(m, hdrlen, M_NOWAIT) != 0)
684 goto fail;
685
686 if (m->m_flags & M_PKTHDR) {
687 int plen = 0;
688 for (m = *m0; m; m = m->m_next)
689 plen += m->m_len;
690 m = *m0;
691 m->m_pkthdr.len = plen;
692 }
693
694 if ((mtag = m_tag_get(PF_REASSEMBLED, sizeof(struct pf_fragment_tag),
695 M_NOWAIT)) == NULL)
696 goto fail;
697 ftag = (struct pf_fragment_tag *)(mtag + 1);
698 ftag->ft_hdrlen = hdrlen;
699 ftag->ft_extoff = extoff;
700 ftag->ft_maxlen = maxlen;
701 ftag->ft_id = frag_id;
702 m_tag_prepend(m, mtag);
703
704 ip6 = mtod(m, struct ip6_hdr *);
705 ip6->ip6_plen = htons(hdrlen - sizeof(struct ip6_hdr) + total);
706 if (extoff) {
707 /* Write protocol into next field of last extension header. */
708 m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt),
709 &off);
710 KASSERT(m, ("%s: short mbuf chain", __func__));
711 *(mtod(m, char *) + off) = proto;
712 m = *m0;
713 } else
714 ip6->ip6_nxt = proto;
715
716 if (hdrlen - sizeof(struct ip6_hdr) + total > IPV6_MAXPACKET) {
717 DPFPRINTF(("drop: too big: %d", total));
718 ip6->ip6_plen = 0;
719 REASON_SET(reason, PFRES_SHORT);
720 /* PF_DROP requires a valid mbuf *m0 in pf_test6(). */
721 return (PF_DROP);
722 }
723
724 DPFPRINTF(("complete: %p(%d)", m, ntohs(ip6->ip6_plen)));
725 return (PF_PASS);
726
727 fail:
728 REASON_SET(reason, PFRES_MEMORY);
729 /* PF_DROP requires a valid mbuf *m0 in pf_test6(), will free later. */
730 return (PF_DROP);
731 }
732 #endif /* INET6 */
733
734 #ifdef INET6
735 int
pf_refragment6(struct ifnet * ifp,struct mbuf ** m0,struct m_tag * mtag)736 pf_refragment6(struct ifnet *ifp, struct mbuf **m0, struct m_tag *mtag)
737 {
738 struct mbuf *m = *m0, *t;
739 struct pf_fragment_tag *ftag = (struct pf_fragment_tag *)(mtag + 1);
740 struct pf_pdesc pd;
741 uint32_t frag_id;
742 uint16_t hdrlen, extoff, maxlen;
743 uint8_t proto;
744 int error, action;
745
746 hdrlen = ftag->ft_hdrlen;
747 extoff = ftag->ft_extoff;
748 maxlen = ftag->ft_maxlen;
749 frag_id = ftag->ft_id;
750 m_tag_delete(m, mtag);
751 mtag = NULL;
752 ftag = NULL;
753
754 if (extoff) {
755 int off;
756
757 /* Use protocol from next field of last extension header */
758 m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt),
759 &off);
760 KASSERT((m != NULL), ("pf_refragment6: short mbuf chain"));
761 proto = *(mtod(m, caddr_t) + off);
762 *(mtod(m, char *) + off) = IPPROTO_FRAGMENT;
763 m = *m0;
764 } else {
765 struct ip6_hdr *hdr;
766
767 hdr = mtod(m, struct ip6_hdr *);
768 proto = hdr->ip6_nxt;
769 hdr->ip6_nxt = IPPROTO_FRAGMENT;
770 }
771
772 /* The MTU must be a multiple of 8 bytes, or we risk doing the
773 * fragmentation wrong. */
774 maxlen = maxlen & ~7;
775
776 /*
777 * Maxlen may be less than 8 if there was only a single
778 * fragment. As it was fragmented before, add a fragment
779 * header also for a single fragment. If total or maxlen
780 * is less than 8, ip6_fragment() will return EMSGSIZE and
781 * we drop the packet.
782 */
783 error = ip6_fragment(ifp, m, hdrlen, proto, maxlen, frag_id);
784 m = (*m0)->m_nextpkt;
785 (*m0)->m_nextpkt = NULL;
786 if (error == 0) {
787 /* The first mbuf contains the unfragmented packet. */
788 m_freem(*m0);
789 *m0 = NULL;
790 action = PF_PASS;
791 } else {
792 /* Drop expects an mbuf to free. */
793 DPFPRINTF(("refragment error %d", error));
794 action = PF_DROP;
795 }
796 for (t = m; m; m = t) {
797 t = m->m_nextpkt;
798 m->m_nextpkt = NULL;
799 m->m_flags |= M_SKIP_FIREWALL;
800 memset(&pd, 0, sizeof(pd));
801 pd.pf_mtag = pf_find_mtag(m);
802 if (error == 0)
803 ip6_forward(m, 0);
804 else
805 m_freem(m);
806 }
807
808 return (action);
809 }
810 #endif /* INET6 */
811
812 #ifdef INET
813 int
pf_normalize_ip(struct mbuf ** m0,int dir,struct pfi_kif * kif,u_short * reason,struct pf_pdesc * pd)814 pf_normalize_ip(struct mbuf **m0, int dir, struct pfi_kif *kif, u_short *reason,
815 struct pf_pdesc *pd)
816 {
817 struct mbuf *m = *m0;
818 struct pf_rule *r;
819 struct ip *h = mtod(m, struct ip *);
820 int mff = (ntohs(h->ip_off) & IP_MF);
821 int hlen = h->ip_hl << 2;
822 u_int16_t fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3;
823 u_int16_t max;
824 int ip_len;
825 int ip_off;
826 int tag = -1;
827 int verdict;
828
829 PF_RULES_RASSERT();
830
831 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
832 while (r != NULL) {
833 r->evaluations++;
834 if (pfi_kif_match(r->kif, kif) == r->ifnot)
835 r = r->skip[PF_SKIP_IFP].ptr;
836 else if (r->direction && r->direction != dir)
837 r = r->skip[PF_SKIP_DIR].ptr;
838 else if (r->af && r->af != AF_INET)
839 r = r->skip[PF_SKIP_AF].ptr;
840 else if (r->proto && r->proto != h->ip_p)
841 r = r->skip[PF_SKIP_PROTO].ptr;
842 else if (PF_MISMATCHAW(&r->src.addr,
843 (struct pf_addr *)&h->ip_src.s_addr, AF_INET,
844 r->src.neg, kif, M_GETFIB(m)))
845 r = r->skip[PF_SKIP_SRC_ADDR].ptr;
846 else if (PF_MISMATCHAW(&r->dst.addr,
847 (struct pf_addr *)&h->ip_dst.s_addr, AF_INET,
848 r->dst.neg, NULL, M_GETFIB(m)))
849 r = r->skip[PF_SKIP_DST_ADDR].ptr;
850 else if (r->match_tag && !pf_match_tag(m, r, &tag,
851 pd->pf_mtag ? pd->pf_mtag->tag : 0))
852 r = TAILQ_NEXT(r, entries);
853 else
854 break;
855 }
856
857 if (r == NULL || r->action == PF_NOSCRUB)
858 return (PF_PASS);
859 else {
860 r->packets[dir == PF_OUT]++;
861 r->bytes[dir == PF_OUT] += pd->tot_len;
862 }
863
864 /* Check for illegal packets */
865 if (hlen < (int)sizeof(struct ip)) {
866 REASON_SET(reason, PFRES_NORM);
867 goto drop;
868 }
869
870 if (hlen > ntohs(h->ip_len)) {
871 REASON_SET(reason, PFRES_NORM);
872 goto drop;
873 }
874
875 /* Clear IP_DF if the rule uses the no-df option */
876 if (r->rule_flag & PFRULE_NODF && h->ip_off & htons(IP_DF)) {
877 u_int16_t ip_off = h->ip_off;
878
879 h->ip_off &= htons(~IP_DF);
880 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
881 }
882
883 /* We will need other tests here */
884 if (!fragoff && !mff)
885 goto no_fragment;
886
887 /* We're dealing with a fragment now. Don't allow fragments
888 * with IP_DF to enter the cache. If the flag was cleared by
889 * no-df above, fine. Otherwise drop it.
890 */
891 if (h->ip_off & htons(IP_DF)) {
892 DPFPRINTF(("IP_DF\n"));
893 goto bad;
894 }
895
896 ip_len = ntohs(h->ip_len) - hlen;
897 ip_off = (ntohs(h->ip_off) & IP_OFFMASK) << 3;
898
899 /* All fragments are 8 byte aligned */
900 if (mff && (ip_len & 0x7)) {
901 DPFPRINTF(("mff and %d\n", ip_len));
902 goto bad;
903 }
904
905 /* Respect maximum length */
906 if (fragoff + ip_len > IP_MAXPACKET) {
907 DPFPRINTF(("max packet %d\n", fragoff + ip_len));
908 goto bad;
909 }
910 max = fragoff + ip_len;
911
912 /* Fully buffer all of the fragments
913 * Might return a completely reassembled mbuf, or NULL */
914 PF_FRAG_LOCK();
915 DPFPRINTF(("reass frag %d @ %d-%d\n", h->ip_id, fragoff, max));
916 verdict = pf_reassemble(m0, h, dir, reason);
917 PF_FRAG_UNLOCK();
918
919 if (verdict != PF_PASS)
920 return (PF_DROP);
921
922 m = *m0;
923 if (m == NULL)
924 return (PF_DROP);
925
926 h = mtod(m, struct ip *);
927
928 no_fragment:
929 /* At this point, only IP_DF is allowed in ip_off */
930 if (h->ip_off & ~htons(IP_DF)) {
931 u_int16_t ip_off = h->ip_off;
932
933 h->ip_off &= htons(IP_DF);
934 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
935 }
936
937 pf_scrub_ip(&m, r->rule_flag, r->min_ttl, r->set_tos);
938
939 return (PF_PASS);
940
941 bad:
942 DPFPRINTF(("dropping bad fragment\n"));
943 REASON_SET(reason, PFRES_FRAG);
944 drop:
945 if (r != NULL && r->log)
946 PFLOG_PACKET(kif, m, AF_INET, dir, *reason, r, NULL, NULL, pd,
947 1);
948
949 return (PF_DROP);
950 }
951 #endif
952
953 #ifdef INET6
954 int
pf_normalize_ip6(struct mbuf ** m0,int dir,struct pfi_kif * kif,u_short * reason,struct pf_pdesc * pd)955 pf_normalize_ip6(struct mbuf **m0, int dir, struct pfi_kif *kif,
956 u_short *reason, struct pf_pdesc *pd)
957 {
958 struct mbuf *m = *m0;
959 struct pf_rule *r;
960 struct ip6_hdr *h = mtod(m, struct ip6_hdr *);
961 int extoff;
962 int off;
963 struct ip6_ext ext;
964 struct ip6_opt opt;
965 struct ip6_opt_jumbo jumbo;
966 struct ip6_frag frag;
967 u_int32_t jumbolen = 0, plen;
968 int optend;
969 int ooff;
970 u_int8_t proto;
971 int terminal;
972
973 PF_RULES_RASSERT();
974
975 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
976 while (r != NULL) {
977 r->evaluations++;
978 if (pfi_kif_match(r->kif, kif) == r->ifnot)
979 r = r->skip[PF_SKIP_IFP].ptr;
980 else if (r->direction && r->direction != dir)
981 r = r->skip[PF_SKIP_DIR].ptr;
982 else if (r->af && r->af != AF_INET6)
983 r = r->skip[PF_SKIP_AF].ptr;
984 #if 0 /* header chain! */
985 else if (r->proto && r->proto != h->ip6_nxt)
986 r = r->skip[PF_SKIP_PROTO].ptr;
987 #endif
988 else if (PF_MISMATCHAW(&r->src.addr,
989 (struct pf_addr *)&h->ip6_src, AF_INET6,
990 r->src.neg, kif, M_GETFIB(m)))
991 r = r->skip[PF_SKIP_SRC_ADDR].ptr;
992 else if (PF_MISMATCHAW(&r->dst.addr,
993 (struct pf_addr *)&h->ip6_dst, AF_INET6,
994 r->dst.neg, NULL, M_GETFIB(m)))
995 r = r->skip[PF_SKIP_DST_ADDR].ptr;
996 else
997 break;
998 }
999
1000 if (r == NULL || r->action == PF_NOSCRUB)
1001 return (PF_PASS);
1002 else {
1003 r->packets[dir == PF_OUT]++;
1004 r->bytes[dir == PF_OUT] += pd->tot_len;
1005 }
1006
1007 /* Check for illegal packets */
1008 if (sizeof(struct ip6_hdr) + IPV6_MAXPACKET < m->m_pkthdr.len)
1009 goto drop;
1010
1011 extoff = 0;
1012 off = sizeof(struct ip6_hdr);
1013 proto = h->ip6_nxt;
1014 terminal = 0;
1015 do {
1016 switch (proto) {
1017 case IPPROTO_FRAGMENT:
1018 goto fragment;
1019 break;
1020 case IPPROTO_AH:
1021 case IPPROTO_ROUTING:
1022 case IPPROTO_DSTOPTS:
1023 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL,
1024 NULL, AF_INET6))
1025 goto shortpkt;
1026 extoff = off;
1027 if (proto == IPPROTO_AH)
1028 off += (ext.ip6e_len + 2) * 4;
1029 else
1030 off += (ext.ip6e_len + 1) * 8;
1031 proto = ext.ip6e_nxt;
1032 break;
1033 case IPPROTO_HOPOPTS:
1034 if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL,
1035 NULL, AF_INET6))
1036 goto shortpkt;
1037 extoff = off;
1038 optend = off + (ext.ip6e_len + 1) * 8;
1039 ooff = off + sizeof(ext);
1040 do {
1041 if (!pf_pull_hdr(m, ooff, &opt.ip6o_type,
1042 sizeof(opt.ip6o_type), NULL, NULL,
1043 AF_INET6))
1044 goto shortpkt;
1045 if (opt.ip6o_type == IP6OPT_PAD1) {
1046 ooff++;
1047 continue;
1048 }
1049 if (!pf_pull_hdr(m, ooff, &opt, sizeof(opt),
1050 NULL, NULL, AF_INET6))
1051 goto shortpkt;
1052 if (ooff + sizeof(opt) + opt.ip6o_len > optend)
1053 goto drop;
1054 switch (opt.ip6o_type) {
1055 case IP6OPT_JUMBO:
1056 if (h->ip6_plen != 0)
1057 goto drop;
1058 if (!pf_pull_hdr(m, ooff, &jumbo,
1059 sizeof(jumbo), NULL, NULL,
1060 AF_INET6))
1061 goto shortpkt;
1062 memcpy(&jumbolen, jumbo.ip6oj_jumbo_len,
1063 sizeof(jumbolen));
1064 jumbolen = ntohl(jumbolen);
1065 if (jumbolen <= IPV6_MAXPACKET)
1066 goto drop;
1067 if (sizeof(struct ip6_hdr) + jumbolen !=
1068 m->m_pkthdr.len)
1069 goto drop;
1070 break;
1071 default:
1072 break;
1073 }
1074 ooff += sizeof(opt) + opt.ip6o_len;
1075 } while (ooff < optend);
1076
1077 off = optend;
1078 proto = ext.ip6e_nxt;
1079 break;
1080 default:
1081 terminal = 1;
1082 break;
1083 }
1084 } while (!terminal);
1085
1086 /* jumbo payload option must be present, or plen > 0 */
1087 if (ntohs(h->ip6_plen) == 0)
1088 plen = jumbolen;
1089 else
1090 plen = ntohs(h->ip6_plen);
1091 if (plen == 0)
1092 goto drop;
1093 if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len)
1094 goto shortpkt;
1095
1096 pf_scrub_ip6(&m, r->min_ttl);
1097
1098 return (PF_PASS);
1099
1100 fragment:
1101 /* Jumbo payload packets cannot be fragmented. */
1102 plen = ntohs(h->ip6_plen);
1103 if (plen == 0 || jumbolen)
1104 goto drop;
1105 if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len)
1106 goto shortpkt;
1107
1108 if (!pf_pull_hdr(m, off, &frag, sizeof(frag), NULL, NULL, AF_INET6))
1109 goto shortpkt;
1110
1111 /* Offset now points to data portion. */
1112 off += sizeof(frag);
1113
1114 /* Returns PF_DROP or *m0 is NULL or completely reassembled mbuf. */
1115 if (pf_reassemble6(m0, h, &frag, off, extoff, reason) != PF_PASS)
1116 return (PF_DROP);
1117 m = *m0;
1118 if (m == NULL)
1119 return (PF_DROP);
1120
1121 pd->flags |= PFDESC_IP_REAS;
1122 return (PF_PASS);
1123
1124 shortpkt:
1125 REASON_SET(reason, PFRES_SHORT);
1126 if (r != NULL && r->log)
1127 PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd,
1128 1);
1129 return (PF_DROP);
1130
1131 drop:
1132 REASON_SET(reason, PFRES_NORM);
1133 if (r != NULL && r->log)
1134 PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd,
1135 1);
1136 return (PF_DROP);
1137 }
1138 #endif /* INET6 */
1139
1140 int
pf_normalize_tcp(int dir,struct pfi_kif * kif,struct mbuf * m,int ipoff,int off,void * h,struct pf_pdesc * pd)1141 pf_normalize_tcp(int dir, struct pfi_kif *kif, struct mbuf *m, int ipoff,
1142 int off, void *h, struct pf_pdesc *pd)
1143 {
1144 struct pf_rule *r, *rm = NULL;
1145 struct tcphdr *th = pd->hdr.tcp;
1146 int rewrite = 0;
1147 u_short reason;
1148 u_int8_t flags;
1149 sa_family_t af = pd->af;
1150
1151 PF_RULES_RASSERT();
1152
1153 r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
1154 while (r != NULL) {
1155 r->evaluations++;
1156 if (pfi_kif_match(r->kif, kif) == r->ifnot)
1157 r = r->skip[PF_SKIP_IFP].ptr;
1158 else if (r->direction && r->direction != dir)
1159 r = r->skip[PF_SKIP_DIR].ptr;
1160 else if (r->af && r->af != af)
1161 r = r->skip[PF_SKIP_AF].ptr;
1162 else if (r->proto && r->proto != pd->proto)
1163 r = r->skip[PF_SKIP_PROTO].ptr;
1164 else if (PF_MISMATCHAW(&r->src.addr, pd->src, af,
1165 r->src.neg, kif, M_GETFIB(m)))
1166 r = r->skip[PF_SKIP_SRC_ADDR].ptr;
1167 else if (r->src.port_op && !pf_match_port(r->src.port_op,
1168 r->src.port[0], r->src.port[1], th->th_sport))
1169 r = r->skip[PF_SKIP_SRC_PORT].ptr;
1170 else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af,
1171 r->dst.neg, NULL, M_GETFIB(m)))
1172 r = r->skip[PF_SKIP_DST_ADDR].ptr;
1173 else if (r->dst.port_op && !pf_match_port(r->dst.port_op,
1174 r->dst.port[0], r->dst.port[1], th->th_dport))
1175 r = r->skip[PF_SKIP_DST_PORT].ptr;
1176 else if (r->os_fingerprint != PF_OSFP_ANY && !pf_osfp_match(
1177 pf_osfp_fingerprint(pd, m, off, th),
1178 r->os_fingerprint))
1179 r = TAILQ_NEXT(r, entries);
1180 else {
1181 rm = r;
1182 break;
1183 }
1184 }
1185
1186 if (rm == NULL || rm->action == PF_NOSCRUB)
1187 return (PF_PASS);
1188 else {
1189 r->packets[dir == PF_OUT]++;
1190 r->bytes[dir == PF_OUT] += pd->tot_len;
1191 }
1192
1193 if (rm->rule_flag & PFRULE_REASSEMBLE_TCP)
1194 pd->flags |= PFDESC_TCP_NORM;
1195
1196 flags = th->th_flags;
1197 if (flags & TH_SYN) {
1198 /* Illegal packet */
1199 if (flags & TH_RST)
1200 goto tcp_drop;
1201
1202 if (flags & TH_FIN)
1203 goto tcp_drop;
1204 } else {
1205 /* Illegal packet */
1206 if (!(flags & (TH_ACK|TH_RST)))
1207 goto tcp_drop;
1208 }
1209
1210 if (!(flags & TH_ACK)) {
1211 /* These flags are only valid if ACK is set */
1212 if ((flags & TH_FIN) || (flags & TH_PUSH) || (flags & TH_URG))
1213 goto tcp_drop;
1214 }
1215
1216 /* Check for illegal header length */
1217 if (th->th_off < (sizeof(struct tcphdr) >> 2))
1218 goto tcp_drop;
1219
1220 /* If flags changed, or reserved data set, then adjust */
1221 if (flags != th->th_flags || th->th_x2 != 0) {
1222 u_int16_t ov, nv;
1223
1224 ov = *(u_int16_t *)(&th->th_ack + 1);
1225 th->th_flags = flags;
1226 th->th_x2 = 0;
1227 nv = *(u_int16_t *)(&th->th_ack + 1);
1228
1229 th->th_sum = pf_proto_cksum_fixup(m, th->th_sum, ov, nv, 0);
1230 rewrite = 1;
1231 }
1232
1233 /* Remove urgent pointer, if TH_URG is not set */
1234 if (!(flags & TH_URG) && th->th_urp) {
1235 th->th_sum = pf_proto_cksum_fixup(m, th->th_sum, th->th_urp,
1236 0, 0);
1237 th->th_urp = 0;
1238 rewrite = 1;
1239 }
1240
1241 /* Process options */
1242 if (r->max_mss && pf_normalize_tcpopt(r, m, th, off, pd->af))
1243 rewrite = 1;
1244
1245 /* copy back packet headers if we sanitized */
1246 if (rewrite)
1247 m_copyback(m, off, sizeof(*th), (caddr_t)th);
1248
1249 return (PF_PASS);
1250
1251 tcp_drop:
1252 REASON_SET(&reason, PFRES_NORM);
1253 if (rm != NULL && r->log)
1254 PFLOG_PACKET(kif, m, AF_INET, dir, reason, r, NULL, NULL, pd,
1255 1);
1256 return (PF_DROP);
1257 }
1258
1259 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)1260 pf_normalize_tcp_init(struct mbuf *m, int off, struct pf_pdesc *pd,
1261 struct tcphdr *th, struct pf_state_peer *src, struct pf_state_peer *dst)
1262 {
1263 u_int32_t tsval, tsecr;
1264 u_int8_t hdr[60];
1265 u_int8_t *opt;
1266
1267 KASSERT((src->scrub == NULL),
1268 ("pf_normalize_tcp_init: src->scrub != NULL"));
1269
1270 src->scrub = uma_zalloc(V_pf_state_scrub_z, M_ZERO | M_NOWAIT);
1271 if (src->scrub == NULL)
1272 return (1);
1273
1274 switch (pd->af) {
1275 #ifdef INET
1276 case AF_INET: {
1277 struct ip *h = mtod(m, struct ip *);
1278 src->scrub->pfss_ttl = h->ip_ttl;
1279 break;
1280 }
1281 #endif /* INET */
1282 #ifdef INET6
1283 case AF_INET6: {
1284 struct ip6_hdr *h = mtod(m, struct ip6_hdr *);
1285 src->scrub->pfss_ttl = h->ip6_hlim;
1286 break;
1287 }
1288 #endif /* INET6 */
1289 }
1290
1291
1292 /*
1293 * All normalizations below are only begun if we see the start of
1294 * the connections. They must all set an enabled bit in pfss_flags
1295 */
1296 if ((th->th_flags & TH_SYN) == 0)
1297 return (0);
1298
1299
1300 if (th->th_off > (sizeof(struct tcphdr) >> 2) && src->scrub &&
1301 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) {
1302 /* Diddle with TCP options */
1303 int hlen;
1304 opt = hdr + sizeof(struct tcphdr);
1305 hlen = (th->th_off << 2) - sizeof(struct tcphdr);
1306 while (hlen >= TCPOLEN_TIMESTAMP) {
1307 switch (*opt) {
1308 case TCPOPT_EOL: /* FALLTHROUGH */
1309 case TCPOPT_NOP:
1310 opt++;
1311 hlen--;
1312 break;
1313 case TCPOPT_TIMESTAMP:
1314 if (opt[1] >= TCPOLEN_TIMESTAMP) {
1315 src->scrub->pfss_flags |=
1316 PFSS_TIMESTAMP;
1317 src->scrub->pfss_ts_mod =
1318 htonl(arc4random());
1319
1320 /* note PFSS_PAWS not set yet */
1321 memcpy(&tsval, &opt[2],
1322 sizeof(u_int32_t));
1323 memcpy(&tsecr, &opt[6],
1324 sizeof(u_int32_t));
1325 src->scrub->pfss_tsval0 = ntohl(tsval);
1326 src->scrub->pfss_tsval = ntohl(tsval);
1327 src->scrub->pfss_tsecr = ntohl(tsecr);
1328 getmicrouptime(&src->scrub->pfss_last);
1329 }
1330 /* FALLTHROUGH */
1331 default:
1332 hlen -= MAX(opt[1], 2);
1333 opt += MAX(opt[1], 2);
1334 break;
1335 }
1336 }
1337 }
1338
1339 return (0);
1340 }
1341
1342 void
pf_normalize_tcp_cleanup(struct pf_state * state)1343 pf_normalize_tcp_cleanup(struct pf_state *state)
1344 {
1345 if (state->src.scrub)
1346 uma_zfree(V_pf_state_scrub_z, state->src.scrub);
1347 if (state->dst.scrub)
1348 uma_zfree(V_pf_state_scrub_z, state->dst.scrub);
1349
1350 /* Someday... flush the TCP segment reassembly descriptors. */
1351 }
1352
1353 int
pf_normalize_tcp_stateful(struct mbuf * m,int off,struct pf_pdesc * pd,u_short * reason,struct tcphdr * th,struct pf_state * state,struct pf_state_peer * src,struct pf_state_peer * dst,int * writeback)1354 pf_normalize_tcp_stateful(struct mbuf *m, int off, struct pf_pdesc *pd,
1355 u_short *reason, struct tcphdr *th, struct pf_state *state,
1356 struct pf_state_peer *src, struct pf_state_peer *dst, int *writeback)
1357 {
1358 struct timeval uptime;
1359 u_int32_t tsval, tsecr;
1360 u_int tsval_from_last;
1361 u_int8_t hdr[60];
1362 u_int8_t *opt;
1363 int copyback = 0;
1364 int got_ts = 0;
1365
1366 KASSERT((src->scrub || dst->scrub),
1367 ("%s: src->scrub && dst->scrub!", __func__));
1368
1369 /*
1370 * Enforce the minimum TTL seen for this connection. Negate a common
1371 * technique to evade an intrusion detection system and confuse
1372 * firewall state code.
1373 */
1374 switch (pd->af) {
1375 #ifdef INET
1376 case AF_INET: {
1377 if (src->scrub) {
1378 struct ip *h = mtod(m, struct ip *);
1379 if (h->ip_ttl > src->scrub->pfss_ttl)
1380 src->scrub->pfss_ttl = h->ip_ttl;
1381 h->ip_ttl = src->scrub->pfss_ttl;
1382 }
1383 break;
1384 }
1385 #endif /* INET */
1386 #ifdef INET6
1387 case AF_INET6: {
1388 if (src->scrub) {
1389 struct ip6_hdr *h = mtod(m, struct ip6_hdr *);
1390 if (h->ip6_hlim > src->scrub->pfss_ttl)
1391 src->scrub->pfss_ttl = h->ip6_hlim;
1392 h->ip6_hlim = src->scrub->pfss_ttl;
1393 }
1394 break;
1395 }
1396 #endif /* INET6 */
1397 }
1398
1399 if (th->th_off > (sizeof(struct tcphdr) >> 2) &&
1400 ((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) ||
1401 (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) &&
1402 pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) {
1403 /* Diddle with TCP options */
1404 int hlen;
1405 opt = hdr + sizeof(struct tcphdr);
1406 hlen = (th->th_off << 2) - sizeof(struct tcphdr);
1407 while (hlen >= TCPOLEN_TIMESTAMP) {
1408 switch (*opt) {
1409 case TCPOPT_EOL: /* FALLTHROUGH */
1410 case TCPOPT_NOP:
1411 opt++;
1412 hlen--;
1413 break;
1414 case TCPOPT_TIMESTAMP:
1415 /* Modulate the timestamps. Can be used for
1416 * NAT detection, OS uptime determination or
1417 * reboot detection.
1418 */
1419
1420 if (got_ts) {
1421 /* Huh? Multiple timestamps!? */
1422 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1423 DPFPRINTF(("multiple TS??"));
1424 pf_print_state(state);
1425 printf("\n");
1426 }
1427 REASON_SET(reason, PFRES_TS);
1428 return (PF_DROP);
1429 }
1430 if (opt[1] >= TCPOLEN_TIMESTAMP) {
1431 memcpy(&tsval, &opt[2],
1432 sizeof(u_int32_t));
1433 if (tsval && src->scrub &&
1434 (src->scrub->pfss_flags &
1435 PFSS_TIMESTAMP)) {
1436 tsval = ntohl(tsval);
1437 pf_change_proto_a(m, &opt[2],
1438 &th->th_sum,
1439 htonl(tsval +
1440 src->scrub->pfss_ts_mod),
1441 0);
1442 copyback = 1;
1443 }
1444
1445 /* Modulate TS reply iff valid (!0) */
1446 memcpy(&tsecr, &opt[6],
1447 sizeof(u_int32_t));
1448 if (tsecr && dst->scrub &&
1449 (dst->scrub->pfss_flags &
1450 PFSS_TIMESTAMP)) {
1451 tsecr = ntohl(tsecr)
1452 - dst->scrub->pfss_ts_mod;
1453 pf_change_proto_a(m, &opt[6],
1454 &th->th_sum, htonl(tsecr),
1455 0);
1456 copyback = 1;
1457 }
1458 got_ts = 1;
1459 }
1460 /* FALLTHROUGH */
1461 default:
1462 hlen -= MAX(opt[1], 2);
1463 opt += MAX(opt[1], 2);
1464 break;
1465 }
1466 }
1467 if (copyback) {
1468 /* Copyback the options, caller copys back header */
1469 *writeback = 1;
1470 m_copyback(m, off + sizeof(struct tcphdr),
1471 (th->th_off << 2) - sizeof(struct tcphdr), hdr +
1472 sizeof(struct tcphdr));
1473 }
1474 }
1475
1476
1477 /*
1478 * Must invalidate PAWS checks on connections idle for too long.
1479 * The fastest allowed timestamp clock is 1ms. That turns out to
1480 * be about 24 days before it wraps. XXX Right now our lowerbound
1481 * TS echo check only works for the first 12 days of a connection
1482 * when the TS has exhausted half its 32bit space
1483 */
1484 #define TS_MAX_IDLE (24*24*60*60)
1485 #define TS_MAX_CONN (12*24*60*60) /* XXX remove when better tsecr check */
1486
1487 getmicrouptime(&uptime);
1488 if (src->scrub && (src->scrub->pfss_flags & PFSS_PAWS) &&
1489 (uptime.tv_sec - src->scrub->pfss_last.tv_sec > TS_MAX_IDLE ||
1490 time_uptime - state->creation > TS_MAX_CONN)) {
1491 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1492 DPFPRINTF(("src idled out of PAWS\n"));
1493 pf_print_state(state);
1494 printf("\n");
1495 }
1496 src->scrub->pfss_flags = (src->scrub->pfss_flags & ~PFSS_PAWS)
1497 | PFSS_PAWS_IDLED;
1498 }
1499 if (dst->scrub && (dst->scrub->pfss_flags & PFSS_PAWS) &&
1500 uptime.tv_sec - dst->scrub->pfss_last.tv_sec > TS_MAX_IDLE) {
1501 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1502 DPFPRINTF(("dst idled out of PAWS\n"));
1503 pf_print_state(state);
1504 printf("\n");
1505 }
1506 dst->scrub->pfss_flags = (dst->scrub->pfss_flags & ~PFSS_PAWS)
1507 | PFSS_PAWS_IDLED;
1508 }
1509
1510 if (got_ts && src->scrub && dst->scrub &&
1511 (src->scrub->pfss_flags & PFSS_PAWS) &&
1512 (dst->scrub->pfss_flags & PFSS_PAWS)) {
1513 /* Validate that the timestamps are "in-window".
1514 * RFC1323 describes TCP Timestamp options that allow
1515 * measurement of RTT (round trip time) and PAWS
1516 * (protection against wrapped sequence numbers). PAWS
1517 * gives us a set of rules for rejecting packets on
1518 * long fat pipes (packets that were somehow delayed
1519 * in transit longer than the time it took to send the
1520 * full TCP sequence space of 4Gb). We can use these
1521 * rules and infer a few others that will let us treat
1522 * the 32bit timestamp and the 32bit echoed timestamp
1523 * as sequence numbers to prevent a blind attacker from
1524 * inserting packets into a connection.
1525 *
1526 * RFC1323 tells us:
1527 * - The timestamp on this packet must be greater than
1528 * or equal to the last value echoed by the other
1529 * endpoint. The RFC says those will be discarded
1530 * since it is a dup that has already been acked.
1531 * This gives us a lowerbound on the timestamp.
1532 * timestamp >= other last echoed timestamp
1533 * - The timestamp will be less than or equal to
1534 * the last timestamp plus the time between the
1535 * last packet and now. The RFC defines the max
1536 * clock rate as 1ms. We will allow clocks to be
1537 * up to 10% fast and will allow a total difference
1538 * or 30 seconds due to a route change. And this
1539 * gives us an upperbound on the timestamp.
1540 * timestamp <= last timestamp + max ticks
1541 * We have to be careful here. Windows will send an
1542 * initial timestamp of zero and then initialize it
1543 * to a random value after the 3whs; presumably to
1544 * avoid a DoS by having to call an expensive RNG
1545 * during a SYN flood. Proof MS has at least one
1546 * good security geek.
1547 *
1548 * - The TCP timestamp option must also echo the other
1549 * endpoints timestamp. The timestamp echoed is the
1550 * one carried on the earliest unacknowledged segment
1551 * on the left edge of the sequence window. The RFC
1552 * states that the host will reject any echoed
1553 * timestamps that were larger than any ever sent.
1554 * This gives us an upperbound on the TS echo.
1555 * tescr <= largest_tsval
1556 * - The lowerbound on the TS echo is a little more
1557 * tricky to determine. The other endpoint's echoed
1558 * values will not decrease. But there may be
1559 * network conditions that re-order packets and
1560 * cause our view of them to decrease. For now the
1561 * only lowerbound we can safely determine is that
1562 * the TS echo will never be less than the original
1563 * TS. XXX There is probably a better lowerbound.
1564 * Remove TS_MAX_CONN with better lowerbound check.
1565 * tescr >= other original TS
1566 *
1567 * It is also important to note that the fastest
1568 * timestamp clock of 1ms will wrap its 32bit space in
1569 * 24 days. So we just disable TS checking after 24
1570 * days of idle time. We actually must use a 12d
1571 * connection limit until we can come up with a better
1572 * lowerbound to the TS echo check.
1573 */
1574 struct timeval delta_ts;
1575 int ts_fudge;
1576
1577
1578 /*
1579 * PFTM_TS_DIFF is how many seconds of leeway to allow
1580 * a host's timestamp. This can happen if the previous
1581 * packet got delayed in transit for much longer than
1582 * this packet.
1583 */
1584 if ((ts_fudge = state->rule.ptr->timeout[PFTM_TS_DIFF]) == 0)
1585 ts_fudge = V_pf_default_rule.timeout[PFTM_TS_DIFF];
1586
1587 /* Calculate max ticks since the last timestamp */
1588 #define TS_MAXFREQ 1100 /* RFC max TS freq of 1Khz + 10% skew */
1589 #define TS_MICROSECS 1000000 /* microseconds per second */
1590 delta_ts = uptime;
1591 timevalsub(&delta_ts, &src->scrub->pfss_last);
1592 tsval_from_last = (delta_ts.tv_sec + ts_fudge) * TS_MAXFREQ;
1593 tsval_from_last += delta_ts.tv_usec / (TS_MICROSECS/TS_MAXFREQ);
1594
1595 if ((src->state >= TCPS_ESTABLISHED &&
1596 dst->state >= TCPS_ESTABLISHED) &&
1597 (SEQ_LT(tsval, dst->scrub->pfss_tsecr) ||
1598 SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) ||
1599 (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) ||
1600 SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) {
1601 /* Bad RFC1323 implementation or an insertion attack.
1602 *
1603 * - Solaris 2.6 and 2.7 are known to send another ACK
1604 * after the FIN,FIN|ACK,ACK closing that carries
1605 * an old timestamp.
1606 */
1607
1608 DPFPRINTF(("Timestamp failed %c%c%c%c\n",
1609 SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '0' : ' ',
1610 SEQ_GT(tsval, src->scrub->pfss_tsval +
1611 tsval_from_last) ? '1' : ' ',
1612 SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ',
1613 SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' '));
1614 DPFPRINTF((" tsval: %u tsecr: %u +ticks: %u "
1615 "idle: %jus %lums\n",
1616 tsval, tsecr, tsval_from_last,
1617 (uintmax_t)delta_ts.tv_sec,
1618 delta_ts.tv_usec / 1000));
1619 DPFPRINTF((" src->tsval: %u tsecr: %u\n",
1620 src->scrub->pfss_tsval, src->scrub->pfss_tsecr));
1621 DPFPRINTF((" dst->tsval: %u tsecr: %u tsval0: %u"
1622 "\n", dst->scrub->pfss_tsval,
1623 dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0));
1624 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1625 pf_print_state(state);
1626 pf_print_flags(th->th_flags);
1627 printf("\n");
1628 }
1629 REASON_SET(reason, PFRES_TS);
1630 return (PF_DROP);
1631 }
1632
1633 /* XXX I'd really like to require tsecr but it's optional */
1634
1635 } else if (!got_ts && (th->th_flags & TH_RST) == 0 &&
1636 ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED)
1637 || pd->p_len > 0 || (th->th_flags & TH_SYN)) &&
1638 src->scrub && dst->scrub &&
1639 (src->scrub->pfss_flags & PFSS_PAWS) &&
1640 (dst->scrub->pfss_flags & PFSS_PAWS)) {
1641 /* Didn't send a timestamp. Timestamps aren't really useful
1642 * when:
1643 * - connection opening or closing (often not even sent).
1644 * but we must not let an attacker to put a FIN on a
1645 * data packet to sneak it through our ESTABLISHED check.
1646 * - on a TCP reset. RFC suggests not even looking at TS.
1647 * - on an empty ACK. The TS will not be echoed so it will
1648 * probably not help keep the RTT calculation in sync and
1649 * there isn't as much danger when the sequence numbers
1650 * got wrapped. So some stacks don't include TS on empty
1651 * ACKs :-(
1652 *
1653 * To minimize the disruption to mostly RFC1323 conformant
1654 * stacks, we will only require timestamps on data packets.
1655 *
1656 * And what do ya know, we cannot require timestamps on data
1657 * packets. There appear to be devices that do legitimate
1658 * TCP connection hijacking. There are HTTP devices that allow
1659 * a 3whs (with timestamps) and then buffer the HTTP request.
1660 * If the intermediate device has the HTTP response cache, it
1661 * will spoof the response but not bother timestamping its
1662 * packets. So we can look for the presence of a timestamp in
1663 * the first data packet and if there, require it in all future
1664 * packets.
1665 */
1666
1667 if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) {
1668 /*
1669 * Hey! Someone tried to sneak a packet in. Or the
1670 * stack changed its RFC1323 behavior?!?!
1671 */
1672 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1673 DPFPRINTF(("Did not receive expected RFC1323 "
1674 "timestamp\n"));
1675 pf_print_state(state);
1676 pf_print_flags(th->th_flags);
1677 printf("\n");
1678 }
1679 REASON_SET(reason, PFRES_TS);
1680 return (PF_DROP);
1681 }
1682 }
1683
1684
1685 /*
1686 * We will note if a host sends his data packets with or without
1687 * timestamps. And require all data packets to contain a timestamp
1688 * if the first does. PAWS implicitly requires that all data packets be
1689 * timestamped. But I think there are middle-man devices that hijack
1690 * TCP streams immediately after the 3whs and don't timestamp their
1691 * packets (seen in a WWW accelerator or cache).
1692 */
1693 if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags &
1694 (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) {
1695 if (got_ts)
1696 src->scrub->pfss_flags |= PFSS_DATA_TS;
1697 else {
1698 src->scrub->pfss_flags |= PFSS_DATA_NOTS;
1699 if (V_pf_status.debug >= PF_DEBUG_MISC && dst->scrub &&
1700 (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) {
1701 /* Don't warn if other host rejected RFC1323 */
1702 DPFPRINTF(("Broken RFC1323 stack did not "
1703 "timestamp data packet. Disabled PAWS "
1704 "security.\n"));
1705 pf_print_state(state);
1706 pf_print_flags(th->th_flags);
1707 printf("\n");
1708 }
1709 }
1710 }
1711
1712
1713 /*
1714 * Update PAWS values
1715 */
1716 if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags &
1717 (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) {
1718 getmicrouptime(&src->scrub->pfss_last);
1719 if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) ||
1720 (src->scrub->pfss_flags & PFSS_PAWS) == 0)
1721 src->scrub->pfss_tsval = tsval;
1722
1723 if (tsecr) {
1724 if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) ||
1725 (src->scrub->pfss_flags & PFSS_PAWS) == 0)
1726 src->scrub->pfss_tsecr = tsecr;
1727
1728 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 &&
1729 (SEQ_LT(tsval, src->scrub->pfss_tsval0) ||
1730 src->scrub->pfss_tsval0 == 0)) {
1731 /* tsval0 MUST be the lowest timestamp */
1732 src->scrub->pfss_tsval0 = tsval;
1733 }
1734
1735 /* Only fully initialized after a TS gets echoed */
1736 if ((src->scrub->pfss_flags & PFSS_PAWS) == 0)
1737 src->scrub->pfss_flags |= PFSS_PAWS;
1738 }
1739 }
1740
1741 /* I have a dream.... TCP segment reassembly.... */
1742 return (0);
1743 }
1744
1745 static int
pf_normalize_tcpopt(struct pf_rule * r,struct mbuf * m,struct tcphdr * th,int off,sa_family_t af)1746 pf_normalize_tcpopt(struct pf_rule *r, struct mbuf *m, struct tcphdr *th,
1747 int off, sa_family_t af)
1748 {
1749 u_int16_t *mss;
1750 int thoff;
1751 int opt, cnt, optlen = 0;
1752 int rewrite = 0;
1753 u_char opts[TCP_MAXOLEN];
1754 u_char *optp = opts;
1755
1756 thoff = th->th_off << 2;
1757 cnt = thoff - sizeof(struct tcphdr);
1758
1759 if (cnt > 0 && !pf_pull_hdr(m, off + sizeof(*th), opts, cnt,
1760 NULL, NULL, af))
1761 return (rewrite);
1762
1763 for (; cnt > 0; cnt -= optlen, optp += optlen) {
1764 opt = optp[0];
1765 if (opt == TCPOPT_EOL)
1766 break;
1767 if (opt == TCPOPT_NOP)
1768 optlen = 1;
1769 else {
1770 if (cnt < 2)
1771 break;
1772 optlen = optp[1];
1773 if (optlen < 2 || optlen > cnt)
1774 break;
1775 }
1776 switch (opt) {
1777 case TCPOPT_MAXSEG:
1778 mss = (u_int16_t *)(optp + 2);
1779 if ((ntohs(*mss)) > r->max_mss) {
1780 th->th_sum = pf_proto_cksum_fixup(m,
1781 th->th_sum, *mss, htons(r->max_mss), 0);
1782 *mss = htons(r->max_mss);
1783 rewrite = 1;
1784 }
1785 break;
1786 default:
1787 break;
1788 }
1789 }
1790
1791 if (rewrite)
1792 m_copyback(m, off + sizeof(*th), thoff - sizeof(*th), opts);
1793
1794 return (rewrite);
1795 }
1796
1797 #ifdef INET
1798 static void
pf_scrub_ip(struct mbuf ** m0,u_int32_t flags,u_int8_t min_ttl,u_int8_t tos)1799 pf_scrub_ip(struct mbuf **m0, u_int32_t flags, u_int8_t min_ttl, u_int8_t tos)
1800 {
1801 struct mbuf *m = *m0;
1802 struct ip *h = mtod(m, struct ip *);
1803
1804 /* Clear IP_DF if no-df was requested */
1805 if (flags & PFRULE_NODF && h->ip_off & htons(IP_DF)) {
1806 u_int16_t ip_off = h->ip_off;
1807
1808 h->ip_off &= htons(~IP_DF);
1809 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
1810 }
1811
1812 /* Enforce a minimum ttl, may cause endless packet loops */
1813 if (min_ttl && h->ip_ttl < min_ttl) {
1814 u_int16_t ip_ttl = h->ip_ttl;
1815
1816 h->ip_ttl = min_ttl;
1817 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0);
1818 }
1819
1820 /* Enforce tos */
1821 if (flags & PFRULE_SET_TOS) {
1822 u_int16_t ov, nv;
1823
1824 ov = *(u_int16_t *)h;
1825 h->ip_tos = tos;
1826 nv = *(u_int16_t *)h;
1827
1828 h->ip_sum = pf_cksum_fixup(h->ip_sum, ov, nv, 0);
1829 }
1830
1831 /* random-id, but not for fragments */
1832 if (flags & PFRULE_RANDOMID && !(h->ip_off & ~htons(IP_DF))) {
1833 uint16_t ip_id = h->ip_id;
1834
1835 ip_fillid(h);
1836 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_id, h->ip_id, 0);
1837 }
1838 }
1839 #endif /* INET */
1840
1841 #ifdef INET6
1842 static void
pf_scrub_ip6(struct mbuf ** m0,u_int8_t min_ttl)1843 pf_scrub_ip6(struct mbuf **m0, u_int8_t min_ttl)
1844 {
1845 struct mbuf *m = *m0;
1846 struct ip6_hdr *h = mtod(m, struct ip6_hdr *);
1847
1848 /* Enforce a minimum ttl, may cause endless packet loops */
1849 if (min_ttl && h->ip6_hlim < min_ttl)
1850 h->ip6_hlim = min_ttl;
1851 }
1852 #endif
1853