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1 /*
2 * Copyright (c) 2000 Apple Computer, 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
72 #ifdef sun
73 #include <netinet/in.h>
74 #endif
75
76 #if defined(sparc) || defined(mips) || defined(ibm032) || defined(__alpha__)
77 #define BPF_ALIGN
78 #endif
79
80 #ifndef BPF_ALIGN
81 #define EXTRACT_SHORT(p) ((u_int16_t)ntohs(*(u_int16_t *)p))
82 #define EXTRACT_LONG(p) (ntohl(*(u_int32_t *)p))
83 #else
84 #define EXTRACT_SHORT(p)\
85 ((u_int16_t)\
86 ((u_int16_t)*((u_char *)p+0)<<8|\
87 (u_int16_t)*((u_char *)p+1)<<0))
88 #define EXTRACT_LONG(p)\
89 ((u_int32_t)*((u_char *)p+0)<<24|\
90 (u_int32_t)*((u_char *)p+1)<<16|\
91 (u_int32_t)*((u_char *)p+2)<<8|\
92 (u_int32_t)*((u_char *)p+3)<<0)
93 #endif
94
95 #ifdef KERNEL
96 #include <sys/mbuf.h>
97 #endif
98 #include <net/bpf.h>
99 #ifdef KERNEL
100 #define MINDEX(m, k) \
101 { \
102 register unsigned int len = m->m_len; \
103 \
104 while (k >= len) { \
105 k -= len; \
106 m = m->m_next; \
107 if (m == 0) \
108 return 0; \
109 len = m->m_len; \
110 } \
111 }
112
113 extern unsigned int bpf_maxbufsize;
114
115 static u_int16_t m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err);
116 static u_int32_t m_xword(struct mbuf *m, bpf_u_int32 k, int *err);
117
118 static u_int32_t
119 m_xword(struct mbuf *m, bpf_u_int32 k, int *err)
120 {
121 register size_t len;
122 register u_char *cp, *np;
123 register struct mbuf *m0;
124
125 len = m->m_len;
126 while (k >= len) {
127 k -= len;
128 m = m->m_next;
129 if (m == 0)
130 goto bad;
131 len = m->m_len;
132 }
133 cp = mtod(m, u_char *) + k;
134 if (len - k >= 4) {
135 *err = 0;
136 return EXTRACT_LONG(cp);
137 }
138 m0 = m->m_next;
139 if (m0 == 0 || m0->m_len + len - k < 4)
140 goto bad;
141 *err = 0;
142 np = mtod(m0, u_char *);
143 switch (len - k) {
144
145 case 1:
146 return
147 ((u_int32_t)cp[0] << 24) |
148 ((u_int32_t)np[0] << 16) |
149 ((u_int32_t)np[1] << 8) |
150 (u_int32_t)np[2];
151
152 case 2:
153 return
154 ((u_int32_t)cp[0] << 24) |
155 ((u_int32_t)cp[1] << 16) |
156 ((u_int32_t)np[0] << 8) |
157 (u_int32_t)np[1];
158
159 default:
160 return
161 ((u_int32_t)cp[0] << 24) |
162 ((u_int32_t)cp[1] << 16) |
163 ((u_int32_t)cp[2] << 8) |
164 (u_int32_t)np[0];
165 }
166 bad:
167 *err = 1;
168 return 0;
169 }
170
171 static u_int16_t
172 m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err)
173 {
174 register size_t len;
175 register u_char *cp;
176 register struct mbuf *m0;
177
178 len = m->m_len;
179 while (k >= len) {
180 k -= len;
181 m = m->m_next;
182 if (m == 0)
183 goto bad;
184 len = m->m_len;
185 }
186 cp = mtod(m, u_char *) + k;
187 if (len - k >= 2) {
188 *err = 0;
189 return EXTRACT_SHORT(cp);
190 }
191 m0 = m->m_next;
192 if (m0 == 0)
193 goto bad;
194 *err = 0;
195 return (cp[0] << 8) | mtod(m0, u_char *)[0];
196 bad:
197 *err = 1;
198 return 0;
199 }
200 #endif
201
202 /*
203 * Execute the filter program starting at pc on the packet p
204 * wirelen is the length of the original packet
205 * buflen is the amount of data present
206 */
207 u_int
208 bpf_filter(const struct bpf_insn *pc, u_char *p, u_int wirelen, u_int buflen)
209 {
210 register u_int32_t A = 0, X = 0;
211 register bpf_u_int32 k;
212 int32_t mem[BPF_MEMWORDS];
213
214 if (pc == 0)
215 /*
216 * No filter means accept all.
217 */
218 return (u_int)-1;
219
220 --pc;
221 while (1) {
222 ++pc;
223 switch (pc->code) {
224
225 default:
226 #ifdef KERNEL
227 return 0;
228 #else
229 abort();
230 #endif
231 case BPF_RET|BPF_K:
232 return (u_int)pc->k;
233
234 case BPF_RET|BPF_A:
235 return (u_int)A;
236
237 case BPF_LD|BPF_W|BPF_ABS:
238 k = pc->k;
239 if (k > buflen || sizeof(int32_t) > buflen - k) {
240 #ifdef KERNEL
241 int merr;
242
243 if (buflen != 0)
244 return 0;
245 A = m_xword((struct mbuf *)p, k, &merr);
246 if (merr != 0)
247 return 0;
248 continue;
249 #else
250 return 0;
251 #endif
252 }
253 #if BPF_ALIGN
254 if (((intptr_t)(p + k) & 3) != 0)
255 A = EXTRACT_LONG(&p[k]);
256 else
257 #endif
258 A = ntohl(*(int32_t *)(p + k));
259 continue;
260
261 case BPF_LD|BPF_H|BPF_ABS:
262 k = pc->k;
263 if (k > buflen || sizeof(int16_t) > buflen - k) {
264 #ifdef KERNEL
265 int merr;
266
267 if (buflen != 0)
268 return 0;
269 A = m_xhalf((struct mbuf *)p, k, &merr);
270 continue;
271 #else
272 return 0;
273 #endif
274 }
275 A = EXTRACT_SHORT(&p[k]);
276 continue;
277
278 case BPF_LD|BPF_B|BPF_ABS:
279 k = pc->k;
280 if (k >= buflen) {
281 #ifdef KERNEL
282 register struct mbuf *m;
283
284 if (buflen != 0)
285 return 0;
286 m = (struct mbuf *)p;
287 MINDEX(m, k);
288 A = mtod(m, u_char *)[k];
289 continue;
290 #else
291 return 0;
292 #endif
293 }
294 A = p[k];
295 continue;
296
297 case BPF_LD|BPF_W|BPF_LEN:
298 A = wirelen;
299 continue;
300
301 case BPF_LDX|BPF_W|BPF_LEN:
302 X = wirelen;
303 continue;
304
305 case BPF_LD|BPF_W|BPF_IND:
306 k = X + pc->k;
307 if (pc->k > buflen || X > buflen - pc->k ||
308 sizeof(int32_t) > buflen - k) {
309 #ifdef KERNEL
310 int merr;
311
312 if (buflen != 0)
313 return 0;
314 A = m_xword((struct mbuf *)p, k, &merr);
315 if (merr != 0)
316 return 0;
317 continue;
318 #else
319 return 0;
320 #endif
321 }
322 #if BPF_ALIGN
323 if (((intptr_t)(p + k) & 3) != 0)
324 A = EXTRACT_LONG(&p[k]);
325 else
326 #endif
327 A = ntohl(*(int32_t *)(p + k));
328 continue;
329
330 case BPF_LD|BPF_H|BPF_IND:
331 k = X + pc->k;
332 if (X > buflen || pc->k > buflen - X ||
333 sizeof(int16_t) > buflen - k) {
334 #ifdef KERNEL
335 int merr;
336
337 if (buflen != 0)
338 return 0;
339 A = m_xhalf((struct mbuf *)p, k, &merr);
340 if (merr != 0)
341 return 0;
342 continue;
343 #else
344 return 0;
345 #endif
346 }
347 A = EXTRACT_SHORT(&p[k]);
348 continue;
349
350 case BPF_LD|BPF_B|BPF_IND:
351 k = X + pc->k;
352 if (pc->k >= buflen || X >= buflen - pc->k) {
353 #ifdef KERNEL
354 register struct mbuf *m;
355
356 if (buflen != 0)
357 return 0;
358 m = (struct mbuf *)p;
359 MINDEX(m, k);
360 A = mtod(m, u_char *)[k];
361 continue;
362 #else
363 return 0;
364 #endif
365 }
366 A = p[k];
367 continue;
368
369 case BPF_LDX|BPF_MSH|BPF_B:
370 k = pc->k;
371 if (k >= buflen) {
372 #ifdef KERNEL
373 register struct mbuf *m;
374
375 if (buflen != 0)
376 return 0;
377 m = (struct mbuf *)p;
378 MINDEX(m, k);
379 X = (mtod(m, u_char *)[k] & 0xf) << 2;
380 continue;
381 #else
382 return 0;
383 #endif
384 }
385 X = (p[pc->k] & 0xf) << 2;
386 continue;
387
388 case BPF_LD|BPF_IMM:
389 A = pc->k;
390 continue;
391
392 case BPF_LDX|BPF_IMM:
393 X = pc->k;
394 continue;
395
396 case BPF_LD|BPF_MEM:
397 A = mem[pc->k];
398 continue;
399
400 case BPF_LDX|BPF_MEM:
401 X = mem[pc->k];
402 continue;
403
404 case BPF_ST:
405 mem[pc->k] = A;
406 continue;
407
408 case BPF_STX:
409 mem[pc->k] = X;
410 continue;
411
412 case BPF_JMP|BPF_JA:
413 pc += pc->k;
414 continue;
415
416 case BPF_JMP|BPF_JGT|BPF_K:
417 pc += (A > pc->k) ? pc->jt : pc->jf;
418 continue;
419
420 case BPF_JMP|BPF_JGE|BPF_K:
421 pc += (A >= pc->k) ? pc->jt : pc->jf;
422 continue;
423
424 case BPF_JMP|BPF_JEQ|BPF_K:
425 pc += (A == pc->k) ? pc->jt : pc->jf;
426 continue;
427
428 case BPF_JMP|BPF_JSET|BPF_K:
429 pc += (A & pc->k) ? pc->jt : pc->jf;
430 continue;
431
432 case BPF_JMP|BPF_JGT|BPF_X:
433 pc += (A > X) ? pc->jt : pc->jf;
434 continue;
435
436 case BPF_JMP|BPF_JGE|BPF_X:
437 pc += (A >= X) ? pc->jt : pc->jf;
438 continue;
439
440 case BPF_JMP|BPF_JEQ|BPF_X:
441 pc += (A == X) ? pc->jt : pc->jf;
442 continue;
443
444 case BPF_JMP|BPF_JSET|BPF_X:
445 pc += (A & X) ? pc->jt : pc->jf;
446 continue;
447
448 case BPF_ALU|BPF_ADD|BPF_X:
449 A += X;
450 continue;
451
452 case BPF_ALU|BPF_SUB|BPF_X:
453 A -= X;
454 continue;
455
456 case BPF_ALU|BPF_MUL|BPF_X:
457 A *= X;
458 continue;
459
460 case BPF_ALU|BPF_DIV|BPF_X:
461 if (X == 0)
462 return 0;
463 A /= X;
464 continue;
465
466 case BPF_ALU|BPF_AND|BPF_X:
467 A &= X;
468 continue;
469
470 case BPF_ALU|BPF_OR|BPF_X:
471 A |= X;
472 continue;
473
474 case BPF_ALU|BPF_LSH|BPF_X:
475 A <<= X;
476 continue;
477
478 case BPF_ALU|BPF_RSH|BPF_X:
479 A >>= X;
480 continue;
481
482 case BPF_ALU|BPF_ADD|BPF_K:
483 A += pc->k;
484 continue;
485
486 case BPF_ALU|BPF_SUB|BPF_K:
487 A -= pc->k;
488 continue;
489
490 case BPF_ALU|BPF_MUL|BPF_K:
491 A *= pc->k;
492 continue;
493
494 case BPF_ALU|BPF_DIV|BPF_K:
495 A /= pc->k;
496 continue;
497
498 case BPF_ALU|BPF_AND|BPF_K:
499 A &= pc->k;
500 continue;
501
502 case BPF_ALU|BPF_OR|BPF_K:
503 A |= pc->k;
504 continue;
505
506 case BPF_ALU|BPF_LSH|BPF_K:
507 A <<= pc->k;
508 continue;
509
510 case BPF_ALU|BPF_RSH|BPF_K:
511 A >>= pc->k;
512 continue;
513
514 case BPF_ALU|BPF_NEG:
515 A = -A;
516 continue;
517
518 case BPF_MISC|BPF_TAX:
519 X = A;
520 continue;
521
522 case BPF_MISC|BPF_TXA:
523 A = X;
524 continue;
525 }
526 }
527 }
528
529 #ifdef KERNEL
530 /*
531 * Return true if the 'fcode' is a valid filter program.
532 * The constraints are that each jump be forward and to a valid
533 * code, that memory accesses are within valid ranges (to the
534 * extent that this can be checked statically; loads of packet data
535 * have to be, and are, also checked at run time), and that
536 * the code terminates with either an accept or reject.
537 *
538 * The kernel needs to be able to verify an application's filter code.
539 * Otherwise, a bogus program could easily crash the system.
540 */
541 int
542 bpf_validate(const struct bpf_insn *f, int len)
543 {
544 u_int i, from;
545 const struct bpf_insn *p;
546
547 if (len < 1 || len > BPF_MAXINSNS)
548 return 0;
549
550 for (i = 0; i < ((u_int)len); ++i) {
551 p = &f[i];
552 switch (BPF_CLASS(p->code)) {
553 /*
554 * Check that memory operations use valid addresses
555 */
556 case BPF_LD:
557 case BPF_LDX:
558 switch (BPF_MODE(p->code)) {
559 case BPF_IMM:
560 break;
561 case BPF_ABS:
562 case BPF_IND:
563 case BPF_MSH:
564 /*
565 * More strict check with actual packet length
566 * is done runtime.
567 */
568 if (p->k >= bpf_maxbufsize)
569 return 0;
570 break;
571 case BPF_MEM:
572 if (p->k >= BPF_MEMWORDS)
573 return 0;
574 break;
575 case BPF_LEN:
576 break;
577 default:
578 return 0;
579 }
580 break;
581 case BPF_ST:
582 case BPF_STX:
583 if (p->k >= BPF_MEMWORDS)
584 return 0;
585 break;
586 case BPF_ALU:
587 switch (BPF_OP(p->code)) {
588 case BPF_ADD:
589 case BPF_SUB:
590 case BPF_MUL:
591 case BPF_OR:
592 case BPF_AND:
593 case BPF_LSH:
594 case BPF_RSH:
595 case BPF_NEG:
596 break;
597 case BPF_DIV:
598 /*
599 * Check for constant division by 0
600 */
601 if(BPF_SRC(p->code) == BPF_K && p->k == 0)
602 return 0;
603 break;
604 default:
605 return 0;
606 }
607 break;
608 case BPF_JMP:
609 /*
610 * Check that jumps are within the code block,
611 * and that unconditional branches don't go
612 * backwards as a result of an overflow.
613 * Unconditional branches have a 32-bit offset,
614 * so they could overflow; we check to make
615 * sure they don't. Conditional branches have
616 * an 8-bit offset, and the from address is
617 * less than equal to BPF_MAXINSNS, and we assume that
618 * BPF_MAXINSNS is sufficiently small that adding 255
619 * to it won't overlflow
620 *
621 * We know that len is <= BPF_MAXINSNS, and we
622 * assume that BPF_MAXINSNS is less than the maximum
623 * size of a u_int, so that i+1 doesn't overflow
624 */
625 from = i+1;
626 switch (BPF_OP(p->code)) {
627 case BPF_JA:
628 if (from + p->k < from || from + p->k >= ((u_int)len))
629 return 0;
630 break;
631 case BPF_JEQ:
632 case BPF_JGT:
633 case BPF_JGE:
634 case BPF_JSET:
635 if (from + p->jt >= ((u_int)len) || from + p->jf >= ((u_int)len))
636 return 0;
637 break;
638 default:
639 return 0;
640 }
641 break;
642 case BPF_RET:
643 break;
644 case BPF_MISC:
645 break;
646 default:
647 return 0;
648 }
649 }
650 return BPF_CLASS(f[len - 1].code) == BPF_RET;
651 }
652 #endif
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