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libm: Fix misleading indent.
[dragonfly.git] / sys / net / bpf_filter.c
blobc059535fb3fdde96cfd47c7613689a27320a37f4
1 /*
2 * Copyright (c) 1990, 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from the Stanford/CMU enet packet filter,
6 * (net/enet.c) distributed as part of 4.3BSD, and code contributed
7 * to Berkeley by Steven McCanne and Van Jacobson both of Lawrence
8 * Berkeley Laboratory.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
34 * @(#)bpf_filter.c 8.1 (Berkeley) 6/10/93
35 *
36 * $FreeBSD: src/sys/net/bpf_filter.c,v 1.17 1999/12/29 04:38:31 peter Exp $
37 */
38
39 #include <sys/systm.h>
40 #include <sys/param.h>
41
42 #if defined(sparc) || defined(mips) || defined(ibm032)
43 #define BPF_ALIGN
44 #endif
45
46 #ifndef BPF_ALIGN
47 #define EXTRACT_SHORT(p) ((u_int16_t)ntohs(*(u_int16_t *)p))
48 #define EXTRACT_LONG(p) (ntohl(*(u_int32_t *)p))
49 #else
50 #define EXTRACT_SHORT(p)\
51 ((u_int16_t)\
52 ((u_int16_t)*((u_char *)p+0)<<8|\
53 (u_int16_t)*((u_char *)p+1)<<0))
54 #define EXTRACT_LONG(p)\
55 ((u_int32_t)*((u_char *)p+0)<<24|\
56 (u_int32_t)*((u_char *)p+1)<<16|\
57 (u_int32_t)*((u_char *)p+2)<<8|\
58 (u_int32_t)*((u_char *)p+3)<<0)
59 #endif
60
61 #ifdef _KERNEL
62 #include <sys/mbuf.h>
63 #endif
64 #include <net/bpf.h>
65 #ifdef _KERNEL
66 #define MINDEX(m, k) \
67 { \
68 int len = m->m_len; \
69 \
70 while (k >= len) { \
71 k -= len; \
72 m = m->m_next; \
73 if (m == 0) \
74 return 0; \
75 len = m->m_len; \
76 } \
77 }
78
79 extern int bpf_maxbufsize;
80
81 static u_int16_t m_xhalf (struct mbuf *m, bpf_u_int32 k, int *err);
82 static u_int32_t m_xword (struct mbuf *m, bpf_u_int32 k, int *err);
83
84 static u_int32_t
85 m_xword(struct mbuf *m, bpf_u_int32 k, int *err)
86 {
87 size_t len;
88 u_char *cp, *np;
89 struct mbuf *m0;
90
91 len = m->m_len;
92 while (k >= len) {
93 k -= len;
94 m = m->m_next;
95 if (m == NULL)
96 goto bad;
97 len = m->m_len;
98 }
99 cp = mtod(m, u_char *) + k;
100 if (len - k >= 4) {
101 *err = 0;
102 return EXTRACT_LONG(cp);
103 }
104 m0 = m->m_next;
105 if (m0 == NULL || m0->m_len + len - k < 4)
106 goto bad;
107 *err = 0;
108 np = mtod(m0, u_char *);
109 switch (len - k) {
110
111 case 1:
112 return
113 ((u_int32_t)cp[0] << 24) |
114 ((u_int32_t)np[0] << 16) |
115 ((u_int32_t)np[1] << 8) |
116 (u_int32_t)np[2];
117
118 case 2:
119 return
120 ((u_int32_t)cp[0] << 24) |
121 ((u_int32_t)cp[1] << 16) |
122 ((u_int32_t)np[0] << 8) |
123 (u_int32_t)np[1];
124
125 default:
126 return
127 ((u_int32_t)cp[0] << 24) |
128 ((u_int32_t)cp[1] << 16) |
129 ((u_int32_t)cp[2] << 8) |
130 (u_int32_t)np[0];
131 }
132 bad:
133 *err = 1;
134 return 0;
135 }
136
137 static u_int16_t
138 m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err)
139 {
140 size_t len;
141 u_char *cp;
142 struct mbuf *m0;
143
144 len = m->m_len;
145 while (k >= len) {
146 k -= len;
147 m = m->m_next;
148 if (m == NULL)
149 goto bad;
150 len = m->m_len;
151 }
152 cp = mtod(m, u_char *) + k;
153 if (len - k >= 2) {
154 *err = 0;
155 return EXTRACT_SHORT(cp);
156 }
157 m0 = m->m_next;
158 if (m0 == NULL)
159 goto bad;
160 *err = 0;
161 return (cp[0] << 8) | mtod(m0, u_char *)[0];
162 bad:
163 *err = 1;
164 return 0;
165 }
166 #endif
167
168 /*
169 * Execute the filter program starting at pc on the packet p
170 * wirelen is the length of the original packet
171 * buflen is the amount of data present
172 */
173 u_int
174 bpf_filter(const struct bpf_insn *pc, u_char *p, u_int wirelen, u_int buflen)
175 {
176 u_int32_t A = 0, X = 0;
177 bpf_u_int32 k;
178 u_int32_t mem[BPF_MEMWORDS];
179
180 bzero(mem, sizeof(mem));
181
182 if (pc == NULL) {
183 /*
184 * No filter means accept all.
185 */
186 return (u_int)-1;
187 }
188
189 --pc;
190 while (1) {
191 ++pc;
192 switch (pc->code) {
193
194 default:
195 #ifdef _KERNEL
196 return 0;
197 #else
198 abort();
199 #endif
200 case BPF_RET|BPF_K:
201 return (u_int)pc->k;
202
203 case BPF_RET|BPF_A:
204 return (u_int)A;
205
206 case BPF_LD|BPF_W|BPF_ABS:
207 k = pc->k;
208 if (k > buflen || sizeof(int32_t) > buflen - k) {
209 #ifdef _KERNEL
210 int merr;
211
212 if (buflen != 0)
213 return 0;
214 A = m_xword((struct mbuf *)p, k, &merr);
215 if (merr != 0)
216 return 0;
217 continue;
218 #else
219 return 0;
220 #endif
221 }
222 #ifdef BPF_ALIGN
223 if (((intptr_t)(p + k) & 3) != 0)
224 A = EXTRACT_LONG(&p[k]);
225 else
226 #endif
227 A = ntohl(*(int32_t *)(p + k));
228 continue;
229
230 case BPF_LD|BPF_H|BPF_ABS:
231 k = pc->k;
232 if (k > buflen || sizeof(int16_t) > buflen - k) {
233 #ifdef _KERNEL
234 int merr;
235
236 if (buflen != 0)
237 return 0;
238 A = m_xhalf((struct mbuf *)p, k, &merr);
239 continue;
240 #else
241 return 0;
242 #endif
243 }
244 A = EXTRACT_SHORT(&p[k]);
245 continue;
246
247 case BPF_LD|BPF_B|BPF_ABS:
248 k = pc->k;
249 if (k >= buflen) {
250 #ifdef _KERNEL
251 struct mbuf *m;
252
253 if (buflen != 0)
254 return 0;
255 m = (struct mbuf *)p;
256 MINDEX(m, k);
257 A = mtod(m, u_char *)[k];
258 continue;
259 #else
260 return 0;
261 #endif
262 }
263 A = p[k];
264 continue;
265
266 case BPF_LD|BPF_W|BPF_LEN:
267 A = wirelen;
268 continue;
269
270 case BPF_LDX|BPF_W|BPF_LEN:
271 X = wirelen;
272 continue;
273
274 case BPF_LD|BPF_W|BPF_IND:
275 k = X + pc->k;
276 if (pc->k > buflen || X > buflen - pc->k ||
277 sizeof(int32_t) > buflen - k) {
278 #ifdef _KERNEL
279 int merr;
280
281 if (buflen != 0)
282 return 0;
283 A = m_xword((struct mbuf *)p, k, &merr);
284 if (merr != 0)
285 return 0;
286 continue;
287 #else
288 return 0;
289 #endif
290 }
291 #ifdef BPF_ALIGN
292 if (((intptr_t)(p + k) & 3) != 0)
293 A = EXTRACT_LONG(&p[k]);
294 else
295 #endif
296 A = ntohl(*(int32_t *)(p + k));
297 continue;
298
299 case BPF_LD|BPF_H|BPF_IND:
300 k = X + pc->k;
301 if (X > buflen || pc->k > buflen - X ||
302 sizeof(int16_t) > buflen - k) {
303 #ifdef _KERNEL
304 int merr;
305
306 if (buflen != 0)
307 return 0;
308 A = m_xhalf((struct mbuf *)p, k, &merr);
309 if (merr != 0)
310 return 0;
311 continue;
312 #else
313 return 0;
314 #endif
315 }
316 A = EXTRACT_SHORT(&p[k]);
317 continue;
318
319 case BPF_LD|BPF_B|BPF_IND:
320 k = X + pc->k;
321 if (pc->k >= buflen || X >= buflen - pc->k) {
322 #ifdef _KERNEL
323 struct mbuf *m;
324
325 if (buflen != 0)
326 return 0;
327 m = (struct mbuf *)p;
328 MINDEX(m, k);
329 A = mtod(m, u_char *)[k];
330 continue;
331 #else
332 return 0;
333 #endif
334 }
335 A = p[k];
336 continue;
337
338 case BPF_LDX|BPF_MSH|BPF_B:
339 k = pc->k;
340 if (k >= buflen) {
341 #ifdef _KERNEL
342 struct mbuf *m;
343
344 if (buflen != 0)
345 return 0;
346 m = (struct mbuf *)p;
347 MINDEX(m, k);
348 X = (mtod(m, char *)[k] & 0xf) << 2;
349 continue;
350 #else
351 return 0;
352 #endif
353 }
354 X = (p[pc->k] & 0xf) << 2;
355 continue;
356
357 case BPF_LD|BPF_IMM:
358 A = pc->k;
359 continue;
360
361 case BPF_LDX|BPF_IMM:
362 X = pc->k;
363 continue;
364
365 case BPF_LD|BPF_MEM:
366 A = mem[pc->k];
367 continue;
368
369 case BPF_LDX|BPF_MEM:
370 X = mem[pc->k];
371 continue;
372
373 case BPF_ST:
374 mem[pc->k] = A;
375 continue;
376
377 case BPF_STX:
378 mem[pc->k] = X;
379 continue;
380
381 case BPF_JMP|BPF_JA:
382 pc += pc->k;
383 continue;
384
385 case BPF_JMP|BPF_JGT|BPF_K:
386 pc += (A > pc->k) ? pc->jt : pc->jf;
387 continue;
388
389 case BPF_JMP|BPF_JGE|BPF_K:
390 pc += (A >= pc->k) ? pc->jt : pc->jf;
391 continue;
392
393 case BPF_JMP|BPF_JEQ|BPF_K:
394 pc += (A == pc->k) ? pc->jt : pc->jf;
395 continue;
396
397 case BPF_JMP|BPF_JSET|BPF_K:
398 pc += (A & pc->k) ? pc->jt : pc->jf;
399 continue;
400
401 case BPF_JMP|BPF_JGT|BPF_X:
402 pc += (A > X) ? pc->jt : pc->jf;
403 continue;
404
405 case BPF_JMP|BPF_JGE|BPF_X:
406 pc += (A >= X) ? pc->jt : pc->jf;
407 continue;
408
409 case BPF_JMP|BPF_JEQ|BPF_X:
410 pc += (A == X) ? pc->jt : pc->jf;
411 continue;
412
413 case BPF_JMP|BPF_JSET|BPF_X:
414 pc += (A & X) ? pc->jt : pc->jf;
415 continue;
416
417 case BPF_ALU|BPF_ADD|BPF_X:
418 A += X;
419 continue;
420
421 case BPF_ALU|BPF_SUB|BPF_X:
422 A -= X;
423 continue;
424
425 case BPF_ALU|BPF_MUL|BPF_X:
426 A *= X;
427 continue;
428
429 case BPF_ALU|BPF_DIV|BPF_X:
430 if (X == 0)
431 return 0;
432 A /= X;
433 continue;
434
435 case BPF_ALU|BPF_AND|BPF_X:
436 A &= X;
437 continue;
438
439 case BPF_ALU|BPF_OR|BPF_X:
440 A |= X;
441 continue;
442
443 case BPF_ALU|BPF_LSH|BPF_X:
444 A <<= X;
445 continue;
446
447 case BPF_ALU|BPF_RSH|BPF_X:
448 A >>= X;
449 continue;
450
451 case BPF_ALU|BPF_ADD|BPF_K:
452 A += pc->k;
453 continue;
454
455 case BPF_ALU|BPF_SUB|BPF_K:
456 A -= pc->k;
457 continue;
458
459 case BPF_ALU|BPF_MUL|BPF_K:
460 A *= pc->k;
461 continue;
462
463 case BPF_ALU|BPF_DIV|BPF_K:
464 A /= pc->k;
465 continue;
466
467 case BPF_ALU|BPF_AND|BPF_K:
468 A &= pc->k;
469 continue;
470
471 case BPF_ALU|BPF_OR|BPF_K:
472 A |= pc->k;
473 continue;
474
475 case BPF_ALU|BPF_LSH|BPF_K:
476 A <<= pc->k;
477 continue;
478
479 case BPF_ALU|BPF_RSH|BPF_K:
480 A >>= pc->k;
481 continue;
482
483 case BPF_ALU|BPF_NEG:
484 A = -A;
485 continue;
486
487 case BPF_MISC|BPF_TAX:
488 X = A;
489 continue;
490
491 case BPF_MISC|BPF_TXA:
492 A = X;
493 continue;
494 }
495 }
496 }
497
498 #ifdef _KERNEL
499 /*
500 * Return true if the 'fcode' is a valid filter program.
501 * The constraints are that each jump be forward and to a valid
502 * code, that memory accesses are within valid ranges (to the
503 * extent that this can be checked statically; loads of packet
504 * data have to be, and are, also checked at run time), and that
505 * the code terminates with either an accept or reject.
506 *
507 * The kernel needs to be able to verify an application's filter code.
508 * Otherwise, a bogus program could easily crash the system.
509 */
510 int
511 bpf_validate(const struct bpf_insn *f, int len)
512 {
513 u_int i, from;
514 const struct bpf_insn *p;
515
516 if (len < 1 || len > BPF_MAXINSNS)
517 return 0;
518
519 for (i = 0; i < len; ++i) {
520 p = &f[i];
521 switch (BPF_CLASS(p->code)) {
522 /*
523 * Check that memory operations use valid addresses.
524 */
525 case BPF_LD:
526 case BPF_LDX:
527 switch (BPF_MODE(p->code)) {
528 case BPF_IMM:
529 break;
530 case BPF_ABS:
531 case BPF_IND:
532 case BPF_MSH:
533 /*
534 * More strict check with actual packet length
535 * is done runtime.
536 */
537 if (p->k >= bpf_maxbufsize)
538 return 0;
539 break;
540 case BPF_MEM:
541 if (p->k >= BPF_MEMWORDS)
542 return 0;
543 break;
544 case BPF_LEN:
545 break;
546 default:
547 return 0;
548 }
549 break;
550 case BPF_ST:
551 case BPF_STX:
552 if (p->k >= BPF_MEMWORDS)
553 return 0;
554 break;
555 case BPF_ALU:
556 switch (BPF_OP(p->code)) {
557 case BPF_ADD:
558 case BPF_SUB:
559 case BPF_MUL:
560 case BPF_OR:
561 case BPF_AND:
562 case BPF_LSH:
563 case BPF_RSH:
564 case BPF_NEG:
565 break;
566 case BPF_DIV:
567 /*
568 * Check for constant division by 0.
569 */
570 if (BPF_SRC(p->code) == BPF_K && p->k == 0)
571 return 0;
572 break;
573 default:
574 return 0;
575 }
576 break;
577 case BPF_JMP:
578 /*
579 * Check that jumps are within the code block,
580 * and that unconditional branches don't go
581 * backwards as a result of an overflow.
582 * Unconditional branches have a 32-bit offset,
583 * so they could overflow; we check to make
584 * sure they don't. Conditional branches have
585 * an 8-bit offset, and the from address is <=
586 * BPF_MAXINSNS, and we assume that BPF_MAXINSNS
587 * is sufficiently small that adding 255 to it
588 * won't overflow.
589 *
590 * We know that len is <= BPF_MAXINSNS, and we
591 * assume that BPF_MAXINSNS is < the maximum size
592 * of a u_int, so that i + 1 doesn't overflow.
593 */
594 from = i + 1;
595 switch (BPF_OP(p->code)) {
596 case BPF_JA:
597 if (from + p->k < from || from + p->k >= len)
598 return 0;
599 break;
600 case BPF_JEQ:
601 case BPF_JGT:
602 case BPF_JGE:
603 case BPF_JSET:
604 if (from + p->jt >= len || from + p->jf >= len)
605 return 0;
606 break;
607 default:
608 return 0;
609 }
610 break;
611 case BPF_RET:
612 break;
613 case BPF_MISC:
614 break;
615 default:
616 return 0;
617 }
618 }
619 return BPF_CLASS(f[len - 1].code) == BPF_RET;
620 }
621 #endif
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