1 /*
2 * Copyright (c) 2000-2021 Apple Inc. All rights reserved.
3 *
4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
5 *
6 * This file contains Original Code and/or Modifications of Original Code
7 * as defined in and that are subject to the Apple Public Source License
8 * Version 2.0 (the 'License'). You may not use this file except in
9 * compliance with the License. The rights granted to you under the License
10 * may not be used to create, or enable the creation or redistribution of,
11 * unlawful or unlicensed copies of an Apple operating system, or to
12 * circumvent, violate, or enable the circumvention or violation of, any
13 * terms of an Apple operating system software license agreement.
14 *
15 * Please obtain a copy of the License at
16 * http://www.opensource.apple.com/apsl/ and read it before using this file.
17 *
18 * The Original Code and all software distributed under the License are
19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
23 * Please see the License for the specific language governing rights and
24 * limitations under the License.
25 *
26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
27 */
28 /*
29 * Copyright (c) 1990, 1991, 1993
30 * The Regents of the University of California. All rights reserved.
31 *
32 * This code is derived from the Stanford/CMU enet packet filter,
33 * (net/enet.c) distributed as part of 4.3BSD, and code contributed
34 * to Berkeley by Steven McCanne and Van Jacobson both of Lawrence
35 * Berkeley Laboratory.
36 *
37 * Redistribution and use in source and binary forms, with or without
38 * modification, are permitted provided that the following conditions
39 * are met:
40 * 1. Redistributions of source code must retain the above copyright
41 * notice, this list of conditions and the following disclaimer.
42 * 2. Redistributions in binary form must reproduce the above copyright
43 * notice, this list of conditions and the following disclaimer in the
44 * documentation and/or other materials provided with the distribution.
45 * 3. All advertising materials mentioning features or use of this software
46 * must display the following acknowledgement:
47 * This product includes software developed by the University of
48 * California, Berkeley and its contributors.
49 * 4. Neither the name of the University nor the names of its contributors
50 * may be used to endorse or promote products derived from this software
51 * without specific prior written permission.
52 *
53 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
54 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
55 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
56 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
57 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
58 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
59 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
60 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
61 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
62 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
63 * SUCH DAMAGE.
64 *
65 * @(#)bpf_filter.c 8.1 (Berkeley) 6/10/93
66 *
67 * $FreeBSD: src/sys/net/bpf_filter.c,v 1.17 1999/12/29 04:38:31 peter Exp $
68 */
69
70 #include <sys/param.h>
71 #include <string.h>
72
73 #ifdef sun
74 #include <netinet/in.h>
75 #endif
76
77 #ifdef KERNEL
78 #include <sys/mbuf.h>
79 #include <net/sockaddr_utils.h>
80 #endif
81 #include <net/bpf.h>
82 #ifdef KERNEL
83
84 extern unsigned int bpf_maxbufsize;
85
86 static inline u_int32_t
get_word_from_buffers(u_char * __indexable cp,u_char * __indexable np,size_t num_from_cp)87 get_word_from_buffers(u_char *__indexable cp, u_char *__indexable np, size_t num_from_cp)
88 {
89 u_int32_t val;
90
91 switch (num_from_cp) {
92 case 1:
93 val = ((u_int32_t)cp[0] << 24) |
94 ((u_int32_t)np[0] << 16) |
95 ((u_int32_t)np[1] << 8) |
96 (u_int32_t)np[2];
97 break;
98
99 case 2:
100 val = ((u_int32_t)cp[0] << 24) |
101 ((u_int32_t)cp[1] << 16) |
102 ((u_int32_t)np[0] << 8) |
103 (u_int32_t)np[1];
104 break;
105 default:
106 val = ((u_int32_t)cp[0] << 24) |
107 ((u_int32_t)cp[1] << 16) |
108 ((u_int32_t)cp[2] << 8) |
109 (u_int32_t)np[0];
110 break;
111 }
112 return val;
113 }
114
115 static u_char *__indexable
m_hdr_offset(struct mbuf ** m_p,void * __sized_by (hdrlen)hdr,size_t hdrlen,bpf_u_int32 * k_p,size_t * len_p)116 m_hdr_offset(struct mbuf **m_p, void *__sized_by(hdrlen) hdr, size_t hdrlen, bpf_u_int32 * k_p,
117 size_t * len_p)
118 {
119 size_t len;
120 u_char *cp;
121 bpf_u_int32 k = *k_p;
122
123 if (k >= hdrlen) {
124 struct mbuf *m = *m_p;
125
126 /* there's no header or the offset we want is past the header */
127 k -= hdrlen;
128
129 len = m->m_len;
130 while (k >= len) {
131 k -= len;
132 m = m->m_next;
133 if (m == NULL) {
134 return NULL;
135 }
136 len = m->m_len;
137 }
138 cp = mtod(m, u_char *) + k;
139
140 /* return next mbuf, in case it's needed */
141 *m_p = m->m_next;
142
143 /* update the offset */
144 *k_p = k;
145 } else {
146 len = hdrlen;
147 cp = (u_char *)hdr + k;
148 }
149 *len_p = len;
150 return cp;
151 }
152
153 static u_int32_t
m_xword(struct mbuf * m,void * __sized_by (hdrlen)hdr,size_t hdrlen,bpf_u_int32 k,int * err)154 m_xword(struct mbuf *m, void *__sized_by(hdrlen) hdr, size_t hdrlen, bpf_u_int32 k, int *err)
155 {
156 size_t len;
157 u_char *cp, *np;
158
159 cp = m_hdr_offset(&m, hdr, hdrlen, &k, &len);
160 if (cp == NULL) {
161 goto bad;
162 }
163 if (len - k >= 4) {
164 *err = 0;
165 return EXTRACT_LONG(cp);
166 }
167 if (m == 0 || m->m_len + len - k < 4) {
168 goto bad;
169 }
170 *err = 0;
171 np = mtod(m, u_char *);
172 return get_word_from_buffers(cp, np, len - k);
173
174 bad:
175 *err = 1;
176 return 0;
177 }
178
179 static uint16_t
m_xhalf(struct mbuf * m,void * __sized_by (hdrlen)hdr,size_t hdrlen,bpf_u_int32 k,int * err)180 m_xhalf(struct mbuf *m, void *__sized_by(hdrlen) hdr, size_t hdrlen, bpf_u_int32 k, int *err)
181 {
182 size_t len;
183 u_char *cp;
184
185 cp = m_hdr_offset(&m, hdr, hdrlen, &k, &len);
186 if (cp == NULL) {
187 goto bad;
188 }
189 if (len - k >= 2) {
190 *err = 0;
191 return EXTRACT_SHORT(cp);
192 }
193 if (m == 0) {
194 goto bad;
195 }
196 *err = 0;
197 return (uint16_t)((cp[0] << 8) | mtod(m, u_char *)[0]);
198 bad:
199 *err = 1;
200 return 0;
201 }
202
203 static u_int8_t
m_xbyte(struct mbuf * m,void * __sized_by (hdrlen)hdr,size_t hdrlen,bpf_u_int32 k,int * err)204 m_xbyte(struct mbuf *m, void *__sized_by(hdrlen) hdr, size_t hdrlen, bpf_u_int32 k, int *err)
205 {
206 size_t len;
207 u_char *cp;
208
209 cp = m_hdr_offset(&m, hdr, hdrlen, &k, &len);
210 if (cp == NULL) {
211 goto bad;
212 }
213 *err = 0;
214 return *cp;
215 bad:
216 *err = 1;
217 return 0;
218 }
219
220 #if SKYWALK
221
222 #include <skywalk/os_skywalk_private.h>
223
224 static void *__indexable
buflet_get_address(kern_buflet_t buflet)225 buflet_get_address(kern_buflet_t buflet)
226 {
227 uint8_t *addr;
228 uint32_t offset;
229 uint32_t limit;
230
231 limit = kern_buflet_get_data_limit(buflet);
232 addr = __unsafe_forge_bidi_indexable(uint8_t *,
233 kern_buflet_get_data_address(buflet),
234 limit);
235 if (addr == NULL) {
236 return NULL;
237 }
238 offset = kern_buflet_get_data_offset(buflet);
239 return __unsafe_forge_bidi_indexable(uint8_t *,
240 addr + offset,
241 limit - offset);
242 }
243
244 static u_char *__indexable
p_hdr_offset(kern_packet_t p,void * __sized_by (hdrlen)hdr,size_t hdrlen,bpf_u_int32 * k_p,size_t * len_p,kern_buflet_t * buflet_p)245 p_hdr_offset(kern_packet_t p, void *__sized_by(hdrlen) hdr, size_t hdrlen, bpf_u_int32 * k_p,
246 size_t * len_p, kern_buflet_t * buflet_p)
247 {
248 u_char *cp = NULL;
249 bpf_u_int32 k = *k_p;
250 size_t len;
251 kern_buflet_t __single buflet = NULL;
252
253 if (k >= hdrlen) {
254 k -= hdrlen;
255 for (;;) {
256 buflet = kern_packet_get_next_buflet(p, buflet);
257 if (buflet == NULL) {
258 break;
259 }
260 len = kern_buflet_get_data_length(buflet);
261 if (k < len) {
262 break;
263 }
264 k -= len;
265 }
266 if (buflet == NULL) {
267 return NULL;
268 }
269 cp = (u_char *)buflet_get_address(buflet) + k;
270 /* update the offset */
271 *k_p = k;
272 } else {
273 len = hdrlen;
274 cp = (u_char *)hdr + k;
275 }
276 *len_p = len;
277 *buflet_p = buflet;
278 return cp;
279 }
280
281 static u_int32_t
p_xword(kern_packet_t p,void * __sized_by (hdrlen)hdr,size_t hdrlen,bpf_u_int32 k,int * err)282 p_xword(kern_packet_t p, void *__sized_by(hdrlen) hdr, size_t hdrlen, bpf_u_int32 k, int *err)
283 {
284 kern_buflet_t __single buflet = NULL;
285 u_char *cp;
286 size_t len = 0;
287 u_char *np;
288
289 cp = p_hdr_offset(p, hdr, hdrlen, &k, &len, &buflet);
290 if (cp == NULL) {
291 goto bad;
292 }
293 if ((len - k) >= 4) {
294 *err = 0;
295 return EXTRACT_LONG(cp);
296 }
297 buflet = kern_packet_get_next_buflet(p, buflet);
298 if (buflet == NULL ||
299 (kern_buflet_get_data_length(buflet) + len - k) < 4) {
300 goto bad;
301 }
302 *err = 0;
303 np = (u_char *)buflet_get_address(buflet);
304 return get_word_from_buffers(cp, np, len - k);
305
306 bad:
307 *err = 1;
308 return 0;
309 }
310
311 static uint16_t
p_xhalf(kern_packet_t p,void * __sized_by (hdrlen)hdr,size_t hdrlen,bpf_u_int32 k,int * err)312 p_xhalf(kern_packet_t p, void *__sized_by(hdrlen) hdr, size_t hdrlen, bpf_u_int32 k, int *err)
313 {
314 kern_buflet_t __single buflet = NULL;
315 u_char *cp;
316 size_t len = 0;
317 u_char *np;
318
319 cp = p_hdr_offset(p, hdr, hdrlen, &k, &len, &buflet);
320 if (cp == NULL) {
321 goto bad;
322 }
323 if ((len - k) >= 2) {
324 *err = 0;
325 return EXTRACT_SHORT(cp);
326 }
327 buflet = kern_packet_get_next_buflet(p, buflet);
328 if (buflet == NULL || kern_buflet_get_data_length(buflet) == 0) {
329 goto bad;
330 }
331 np = (u_char *)buflet_get_address(buflet);
332 *err = 0;
333 return (uint16_t)((cp[0] << 8) | np[0]);
334 bad:
335 *err = 1;
336 return 0;
337 }
338
339 static u_int8_t
p_xbyte(kern_packet_t p,void * __sized_by (hdrlen)hdr,size_t hdrlen,bpf_u_int32 k,int * err)340 p_xbyte(kern_packet_t p, void *__sized_by(hdrlen) hdr, size_t hdrlen, bpf_u_int32 k, int *err)
341 {
342 kern_buflet_t __single buflet = NULL;
343 u_char *cp;
344 size_t len = 0;
345
346 cp = p_hdr_offset(p, hdr, hdrlen, &k, &len, &buflet);
347 if (cp == NULL) {
348 goto bad;
349 }
350 *err = 0;
351 return *cp;
352 bad:
353 *err = 1;
354 return 0;
355 }
356
357 #endif /* SKYWALK */
358
359 static u_int32_t
bp_xword(struct bpf_packet * bp,bpf_u_int32 k,int * err)360 bp_xword(struct bpf_packet *bp, bpf_u_int32 k, int *err)
361 {
362 size_t hdrlen = bp->bpfp_header_length;
363 void *hdr = bp->bpfp_header;
364
365 switch (bp->bpfp_type) {
366 case BPF_PACKET_TYPE_MBUF:
367 return m_xword(bp->bpfp_mbuf, hdr, hdrlen, k, err);
368 #if SKYWALK
369 case BPF_PACKET_TYPE_PKT:
370 return p_xword(bp->bpfp_pkt, hdr, hdrlen, k, err);
371 #endif /* SKYWALK */
372 default:
373 break;
374 }
375 *err = 1;
376 return 0;
377 }
378
379 static u_int16_t
bp_xhalf(struct bpf_packet * bp,bpf_u_int32 k,int * err)380 bp_xhalf(struct bpf_packet *bp, bpf_u_int32 k, int *err)
381 {
382 size_t hdrlen = bp->bpfp_header_length;
383 void *hdr = bp->bpfp_header;
384
385 switch (bp->bpfp_type) {
386 case BPF_PACKET_TYPE_MBUF:
387 return m_xhalf(bp->bpfp_mbuf, hdr, hdrlen, k, err);
388 #if SKYWALK
389 case BPF_PACKET_TYPE_PKT:
390 return p_xhalf(bp->bpfp_pkt, hdr, hdrlen, k, err);
391 #endif /* SKYWALK */
392 default:
393 break;
394 }
395 *err = 1;
396 return 0;
397 }
398
399 static u_int8_t
bp_xbyte(struct bpf_packet * bp,bpf_u_int32 k,int * err)400 bp_xbyte(struct bpf_packet *bp, bpf_u_int32 k, int *err)
401 {
402 size_t hdrlen = bp->bpfp_header_length;
403 void *hdr = bp->bpfp_header;
404
405 switch (bp->bpfp_type) {
406 case BPF_PACKET_TYPE_MBUF:
407 return m_xbyte(bp->bpfp_mbuf, hdr, hdrlen, k, err);
408 #if SKYWALK
409 case BPF_PACKET_TYPE_PKT:
410 return p_xbyte(bp->bpfp_pkt, hdr, hdrlen, k, err);
411 #endif /* SKYWALK */
412 default:
413 break;
414 }
415 *err = 1;
416 return 0;
417 }
418
419 #endif
420
421 /*
422 * Execute the filter program starting at pc on the packet p
423 * wirelen is the length of the original packet
424 * buflen is the amount of data present
425 */
426 u_int
bpf_filter(const struct bpf_insn * __counted_by (pc_len)pc_orig,u_int pc_len,u_char * __sized_by (sizeof (struct bpf_packet))p,u_int wirelen,u_int buflen)427 bpf_filter(const struct bpf_insn *__counted_by(pc_len) pc_orig, u_int pc_len,
428 u_char *__sized_by(sizeof(struct bpf_packet)) p, u_int wirelen, u_int buflen)
429 {
430 u_int32_t A = 0, X = 0;
431 bpf_u_int32 k;
432 int32_t mem[BPF_MEMWORDS];
433 const struct bpf_insn *pc = pc_orig;
434 #ifdef KERNEL
435 int merr;
436 struct bpf_packet * bp = (struct bpf_packet *)(void *)p;
437 #endif /* KERNEL */
438 /* Ignore warning without -fbounds-safety. */
439 (void)pc_len;
440
441 bzero(mem, sizeof(mem));
442
443 if (pc == 0) {
444 /*
445 * No filter means accept all.
446 */
447 return (u_int) - 1;
448 }
449
450 --pc;
451 while (1) {
452 ++pc;
453 switch (pc->code) {
454 default:
455 #ifdef KERNEL
456 return 0;
457 #else /* KERNEL */
458 abort();
459 #endif /* KERNEL */
460 case BPF_RET | BPF_K:
461 return (u_int)pc->k;
462
463 case BPF_RET | BPF_A:
464 return (u_int)A;
465
466 case BPF_LD | BPF_W | BPF_ABS:
467 k = pc->k;
468 if (k > buflen || sizeof(int32_t) > buflen - k) {
469 #ifdef KERNEL
470 if (buflen != 0) {
471 return 0;
472 }
473 A = bp_xword(bp, k, &merr);
474 if (merr != 0) {
475 return 0;
476 }
477 continue;
478 #else /* KERNEL */
479 return 0;
480 #endif /* KERNEL */
481 }
482 #if BPF_ALIGN
483 if (((intptr_t)(p + k) & 3) != 0) {
484 A = EXTRACT_LONG(&p[k]);
485 } else
486 #endif /* BPF_ALIGN */
487 A = ntohl(*(int32_t *)(void *)(p + k));
488 continue;
489
490 case BPF_LD | BPF_H | BPF_ABS:
491 k = pc->k;
492 if (k > buflen || sizeof(int16_t) > buflen - k) {
493 #ifdef KERNEL
494 if (buflen != 0) {
495 return 0;
496 }
497 A = bp_xhalf(bp, k, &merr);
498 if (merr != 0) {
499 return 0;
500 }
501 continue;
502 #else /* KERNEL */
503 return 0;
504 #endif /* KERNEL */
505 }
506 A = EXTRACT_SHORT(&p[k]);
507 continue;
508
509 case BPF_LD | BPF_B | BPF_ABS:
510 k = pc->k;
511 if (k >= buflen) {
512 #ifdef KERNEL
513 if (buflen != 0) {
514 return 0;
515 }
516 A = bp_xbyte(bp, k, &merr);
517 if (merr != 0) {
518 return 0;
519 }
520 continue;
521 #else /* KERNEL */
522 return 0;
523 #endif /* KERNEL */
524 }
525 A = p[k];
526 continue;
527
528 case BPF_LD | BPF_W | BPF_LEN:
529 A = wirelen;
530 continue;
531
532 case BPF_LDX | BPF_W | BPF_LEN:
533 X = wirelen;
534 continue;
535
536 case BPF_LD | BPF_W | BPF_IND:
537 k = X + pc->k;
538 if (pc->k > buflen || X > buflen - pc->k ||
539 sizeof(int32_t) > buflen - k) {
540 #ifdef KERNEL
541 if (buflen != 0) {
542 return 0;
543 }
544 A = bp_xword(bp, k, &merr);
545 if (merr != 0) {
546 return 0;
547 }
548 continue;
549 #else /* KERNEL */
550 return 0;
551 #endif /* KERNEL */
552 }
553 #if BPF_ALIGN
554 if (((intptr_t)(p + k) & 3) != 0) {
555 A = EXTRACT_LONG(&p[k]);
556 } else
557 #endif /* BPF_ALIGN */
558 A = ntohl(*(int32_t *)(void *)(p + k));
559 continue;
560
561 case BPF_LD | BPF_H | BPF_IND:
562 k = X + pc->k;
563 if (X > buflen || pc->k > buflen - X ||
564 sizeof(int16_t) > buflen - k) {
565 #ifdef KERNEL
566 if (buflen != 0) {
567 return 0;
568 }
569 A = bp_xhalf(bp, k, &merr);
570 if (merr != 0) {
571 return 0;
572 }
573 continue;
574 #else /* KERNEL */
575 return 0;
576 #endif /* KERNEL */
577 }
578 A = EXTRACT_SHORT(&p[k]);
579 continue;
580
581 case BPF_LD | BPF_B | BPF_IND:
582 k = X + pc->k;
583 if (pc->k >= buflen || X >= buflen - pc->k) {
584 #ifdef KERNEL
585 if (buflen != 0) {
586 return 0;
587 }
588 A = bp_xbyte(bp, k, &merr);
589 if (merr != 0) {
590 return 0;
591 }
592 continue;
593 #else /* KERNEL */
594 return 0;
595 #endif /* KERNEL */
596 }
597 A = p[k];
598 continue;
599
600 case BPF_LDX | BPF_MSH | BPF_B:
601 k = pc->k;
602 if (k >= buflen) {
603 #ifdef KERNEL
604 if (buflen != 0) {
605 return 0;
606 }
607 X = bp_xbyte(bp, k, &merr);
608 if (merr != 0) {
609 return 0;
610 }
611 X = (X & 0xf) << 2;
612 continue;
613 #else
614 return 0;
615 #endif
616 }
617 X = (p[pc->k] & 0xf) << 2;
618 continue;
619
620 case BPF_LD | BPF_IMM:
621 A = pc->k;
622 continue;
623
624 case BPF_LDX | BPF_IMM:
625 X = pc->k;
626 continue;
627
628 case BPF_LD | BPF_MEM:
629 if (pc->k >= BPF_MEMWORDS) {
630 return 0;
631 }
632 A = mem[pc->k];
633 continue;
634
635 case BPF_LDX | BPF_MEM:
636 if (pc->k >= BPF_MEMWORDS) {
637 return 0;
638 }
639 X = mem[pc->k];
640 continue;
641
642 case BPF_ST:
643 if (pc->k >= BPF_MEMWORDS) {
644 return 0;
645 }
646 mem[pc->k] = A;
647 continue;
648
649 case BPF_STX:
650 if (pc->k >= BPF_MEMWORDS) {
651 return 0;
652 }
653 mem[pc->k] = X;
654 continue;
655
656 case BPF_JMP | BPF_JA:
657 pc += pc->k;
658 continue;
659
660 case BPF_JMP | BPF_JGT | BPF_K:
661 pc += (A > pc->k) ? pc->jt : pc->jf;
662 continue;
663
664 case BPF_JMP | BPF_JGE | BPF_K:
665 pc += (A >= pc->k) ? pc->jt : pc->jf;
666 continue;
667
668 case BPF_JMP | BPF_JEQ | BPF_K:
669 pc += (A == pc->k) ? pc->jt : pc->jf;
670 continue;
671
672 case BPF_JMP | BPF_JSET | BPF_K:
673 pc += (A & pc->k) ? pc->jt : pc->jf;
674 continue;
675
676 case BPF_JMP | BPF_JGT | BPF_X:
677 pc += (A > X) ? pc->jt : pc->jf;
678 continue;
679
680 case BPF_JMP | BPF_JGE | BPF_X:
681 pc += (A >= X) ? pc->jt : pc->jf;
682 continue;
683
684 case BPF_JMP | BPF_JEQ | BPF_X:
685 pc += (A == X) ? pc->jt : pc->jf;
686 continue;
687
688 case BPF_JMP | BPF_JSET | BPF_X:
689 pc += (A & X) ? pc->jt : pc->jf;
690 continue;
691
692 case BPF_ALU | BPF_ADD | BPF_X:
693 A += X;
694 continue;
695
696 case BPF_ALU | BPF_SUB | BPF_X:
697 A -= X;
698 continue;
699
700 case BPF_ALU | BPF_MUL | BPF_X:
701 A *= X;
702 continue;
703
704 case BPF_ALU | BPF_DIV | BPF_X:
705 if (X == 0) {
706 return 0;
707 }
708 A /= X;
709 continue;
710
711 case BPF_ALU | BPF_AND | BPF_X:
712 A &= X;
713 continue;
714
715 case BPF_ALU | BPF_OR | BPF_X:
716 A |= X;
717 continue;
718
719 case BPF_ALU | BPF_LSH | BPF_X:
720 A <<= X;
721 continue;
722
723 case BPF_ALU | BPF_RSH | BPF_X:
724 A >>= X;
725 continue;
726
727 case BPF_ALU | BPF_ADD | BPF_K:
728 A += pc->k;
729 continue;
730
731 case BPF_ALU | BPF_SUB | BPF_K:
732 A -= pc->k;
733 continue;
734
735 case BPF_ALU | BPF_MUL | BPF_K:
736 A *= pc->k;
737 continue;
738
739 case BPF_ALU | BPF_DIV | BPF_K:
740 A /= pc->k;
741 continue;
742
743 case BPF_ALU | BPF_AND | BPF_K:
744 A &= pc->k;
745 continue;
746
747 case BPF_ALU | BPF_OR | BPF_K:
748 A |= pc->k;
749 continue;
750
751 case BPF_ALU | BPF_LSH | BPF_K:
752 A <<= pc->k;
753 continue;
754
755 case BPF_ALU | BPF_RSH | BPF_K:
756 A >>= pc->k;
757 continue;
758
759 case BPF_ALU | BPF_NEG:
760 A = -A;
761 continue;
762
763 case BPF_MISC | BPF_TAX:
764 X = A;
765 continue;
766
767 case BPF_MISC | BPF_TXA:
768 A = X;
769 continue;
770 }
771 }
772 }
773
774 #ifdef KERNEL
775 /*
776 * Return true if the 'fcode' is a valid filter program.
777 * The constraints are that each jump be forward and to a valid
778 * code, that memory accesses are within valid ranges (to the
779 * extent that this can be checked statically; loads of packet data
780 * have to be, and are, also checked at run time), and that
781 * the code terminates with either an accept or reject.
782 *
783 * The kernel needs to be able to verify an application's filter code.
784 * Otherwise, a bogus program could easily crash the system.
785 */
786 int
bpf_validate(const struct bpf_insn * __counted_by (len)f,int len)787 bpf_validate(const struct bpf_insn *__counted_by(len) f, int len)
788 {
789 u_int i, from;
790 const struct bpf_insn *p;
791
792 if (len < 1 || len > BPF_MAXINSNS) {
793 return 0;
794 }
795
796 for (i = 0; i < ((u_int)len); ++i) {
797 p = &f[i];
798 switch (BPF_CLASS(p->code)) {
799 /*
800 * Check that memory operations use valid addresses
801 */
802 case BPF_LD:
803 case BPF_LDX:
804 switch (BPF_MODE(p->code)) {
805 case BPF_IMM:
806 break;
807 case BPF_ABS:
808 case BPF_IND:
809 case BPF_MSH:
810 /*
811 * More strict check with actual packet length
812 * is done runtime.
813 */
814 if (p->k >= bpf_maxbufsize) {
815 return 0;
816 }
817 break;
818 case BPF_MEM:
819 if (p->k >= BPF_MEMWORDS) {
820 return 0;
821 }
822 break;
823 case BPF_LEN:
824 break;
825 default:
826 return 0;
827 }
828 break;
829 case BPF_ST:
830 case BPF_STX:
831 if (p->k >= BPF_MEMWORDS) {
832 return 0;
833 }
834 break;
835 case BPF_ALU:
836 switch (BPF_OP(p->code)) {
837 case BPF_ADD:
838 case BPF_SUB:
839 case BPF_MUL:
840 case BPF_OR:
841 case BPF_AND:
842 case BPF_LSH:
843 case BPF_RSH:
844 case BPF_NEG:
845 break;
846 case BPF_DIV:
847 /*
848 * Check for constant division by 0
849 */
850 if (BPF_SRC(p->code) == BPF_K && p->k == 0) {
851 return 0;
852 }
853 break;
854 default:
855 return 0;
856 }
857 break;
858 case BPF_JMP:
859 /*
860 * Check that jumps are within the code block,
861 * and that unconditional branches don't go
862 * backwards as a result of an overflow.
863 * Unconditional branches have a 32-bit offset,
864 * so they could overflow; we check to make
865 * sure they don't. Conditional branches have
866 * an 8-bit offset, and the from address is
867 * less than equal to BPF_MAXINSNS, and we assume that
868 * BPF_MAXINSNS is sufficiently small that adding 255
869 * to it won't overlflow
870 *
871 * We know that len is <= BPF_MAXINSNS, and we
872 * assume that BPF_MAXINSNS is less than the maximum
873 * size of a u_int, so that i+1 doesn't overflow
874 */
875 from = i + 1;
876 switch (BPF_OP(p->code)) {
877 case BPF_JA:
878 if (from + p->k < from || from + p->k >= ((u_int)len)) {
879 return 0;
880 }
881 break;
882 case BPF_JEQ:
883 case BPF_JGT:
884 case BPF_JGE:
885 case BPF_JSET:
886 if (from + p->jt >= ((u_int)len) || from + p->jf >= ((u_int)len)) {
887 return 0;
888 }
889 break;
890 default:
891 return 0;
892 }
893 break;
894 case BPF_RET:
895 break;
896 case BPF_MISC:
897 break;
898 default:
899 return 0;
900 }
901 }
902 return BPF_CLASS(f[len - 1].code) == BPF_RET;
903 }
904 #endif
905