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MFC r1.27:
[dragonfly.git] / sys / net / bpf_filter.c
blob1892e8bcb9937ef9913368a69947f41bcbc2d5e4
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. All advertising materials mentioning features or use of this software
19 * must display the following acknowledgement:
20 * This product includes software developed by the University of
21 * California, Berkeley and its contributors.
22 * 4. Neither the name of the University nor the names of its contributors
23 * may be used to endorse or promote products derived from this software
24 * without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 *
38 * @(#)bpf_filter.c 8.1 (Berkeley) 6/10/93
39 *
40 * $FreeBSD: src/sys/net/bpf_filter.c,v 1.17 1999/12/29 04:38:31 peter Exp $
41 * $DragonFly: src/sys/net/bpf_filter.c,v 1.10 2008/01/02 12:30:34 sephe Exp $
42 */
43
44 #include <sys/param.h>
45
46 #if defined(sparc) || defined(mips) || defined(ibm032)
47 #define BPF_ALIGN
48 #endif
49
50 #ifndef BPF_ALIGN
51 #define EXTRACT_SHORT(p) ((u_int16_t)ntohs(*(u_int16_t *)p))
52 #define EXTRACT_LONG(p) (ntohl(*(u_int32_t *)p))
53 #else
54 #define EXTRACT_SHORT(p)\
55 ((u_int16_t)\
56 ((u_int16_t)*((u_char *)p+0)<<8|\
57 (u_int16_t)*((u_char *)p+1)<<0))
58 #define EXTRACT_LONG(p)\
59 ((u_int32_t)*((u_char *)p+0)<<24|\
60 (u_int32_t)*((u_char *)p+1)<<16|\
61 (u_int32_t)*((u_char *)p+2)<<8|\
62 (u_int32_t)*((u_char *)p+3)<<0)
63 #endif
64
65 #ifdef _KERNEL
66 #include <sys/mbuf.h>
67 #endif
68 #include <net/bpf.h>
69 #ifdef _KERNEL
70 #define MINDEX(m, k) \
71 { \
72 int len = m->m_len; \
73 \
74 while (k >= len) { \
75 k -= len; \
76 m = m->m_next; \
77 if (m == 0) \
78 return 0; \
79 len = m->m_len; \
80 } \
81 }
82
83 extern int bpf_maxbufsize;
84
85 static u_int16_t m_xhalf (struct mbuf *m, bpf_u_int32 k, int *err);
86 static u_int32_t m_xword (struct mbuf *m, bpf_u_int32 k, int *err);
87
88 static u_int32_t
89 m_xword(struct mbuf *m, bpf_u_int32 k, int *err)
90 {
91 size_t len;
92 u_char *cp, *np;
93 struct mbuf *m0;
94
95 len = m->m_len;
96 while (k >= len) {
97 k -= len;
98 m = m->m_next;
99 if (m == 0)
100 goto bad;
101 len = m->m_len;
102 }
103 cp = mtod(m, u_char *) + k;
104 if (len - k >= 4) {
105 *err = 0;
106 return EXTRACT_LONG(cp);
107 }
108 m0 = m->m_next;
109 if (m0 == 0 || m0->m_len + len - k < 4)
110 goto bad;
111 *err = 0;
112 np = mtod(m0, u_char *);
113 switch (len - k) {
114
115 case 1:
116 return
117 ((u_int32_t)cp[0] << 24) |
118 ((u_int32_t)np[0] << 16) |
119 ((u_int32_t)np[1] << 8) |
120 (u_int32_t)np[2];
121
122 case 2:
123 return
124 ((u_int32_t)cp[0] << 24) |
125 ((u_int32_t)cp[1] << 16) |
126 ((u_int32_t)np[0] << 8) |
127 (u_int32_t)np[1];
128
129 default:
130 return
131 ((u_int32_t)cp[0] << 24) |
132 ((u_int32_t)cp[1] << 16) |
133 ((u_int32_t)cp[2] << 8) |
134 (u_int32_t)np[0];
135 }
136 bad:
137 *err = 1;
138 return 0;
139 }
140
141 static u_int16_t
142 m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err)
143 {
144 size_t len;
145 u_char *cp;
146 struct mbuf *m0;
147
148 len = m->m_len;
149 while (k >= len) {
150 k -= len;
151 m = m->m_next;
152 if (m == 0)
153 goto bad;
154 len = m->m_len;
155 }
156 cp = mtod(m, u_char *) + k;
157 if (len - k >= 2) {
158 *err = 0;
159 return EXTRACT_SHORT(cp);
160 }
161 m0 = m->m_next;
162 if (m0 == 0)
163 goto bad;
164 *err = 0;
165 return (cp[0] << 8) | mtod(m0, u_char *)[0];
166 bad:
167 *err = 1;
168 return 0;
169 }
170 #endif
171
172 /*
173 * Execute the filter program starting at pc on the packet p
174 * wirelen is the length of the original packet
175 * buflen is the amount of data present
176 */
177 u_int
178 bpf_filter(const struct bpf_insn *pc, u_char *p, u_int wirelen, u_int buflen)
179 {
180 u_int32_t A = 0, X = 0;
181 bpf_u_int32 k;
182 int32_t mem[BPF_MEMWORDS];
183
184 if (pc == 0) {
185 /*
186 * No filter means accept all.
187 */
188 return (u_int)-1;
189 }
190
191 --pc;
192 while (1) {
193 ++pc;
194 switch (pc->code) {
195
196 default:
197 #ifdef _KERNEL
198 return 0;
199 #else
200 abort();
201 #endif
202 case BPF_RET|BPF_K:
203 return (u_int)pc->k;
204
205 case BPF_RET|BPF_A:
206 return (u_int)A;
207
208 case BPF_LD|BPF_W|BPF_ABS:
209 k = pc->k;
210 if (k > buflen || sizeof(int32_t) > buflen - k) {
211 #ifdef _KERNEL
212 int merr;
213
214 if (buflen != 0)
215 return 0;
216 A = m_xword((struct mbuf *)p, k, &merr);
217 if (merr != 0)
218 return 0;
219 continue;
220 #else
221 return 0;
222 #endif
223 }
224 #ifdef BPF_ALIGN
225 if (((intptr_t)(p + k) & 3) != 0)
226 A = EXTRACT_LONG(&p[k]);
227 else
228 #endif
229 A = ntohl(*(int32_t *)(p + k));
230 continue;
231
232 case BPF_LD|BPF_H|BPF_ABS:
233 k = pc->k;
234 if (k > buflen || sizeof(int16_t) > buflen - k) {
235 #ifdef _KERNEL
236 int merr;
237
238 if (buflen != 0)
239 return 0;
240 A = m_xhalf((struct mbuf *)p, k, &merr);
241 continue;
242 #else
243 return 0;
244 #endif
245 }
246 A = EXTRACT_SHORT(&p[k]);
247 continue;
248
249 case BPF_LD|BPF_B|BPF_ABS:
250 k = pc->k;
251 if (k >= buflen) {
252 #ifdef _KERNEL
253 struct mbuf *m;
254
255 if (buflen != 0)
256 return 0;
257 m = (struct mbuf *)p;
258 MINDEX(m, k);
259 A = mtod(m, u_char *)[k];
260 continue;
261 #else
262 return 0;
263 #endif
264 }
265 A = p[k];
266 continue;
267
268 case BPF_LD|BPF_W|BPF_LEN:
269 A = wirelen;
270 continue;
271
272 case BPF_LDX|BPF_W|BPF_LEN:
273 X = wirelen;
274 continue;
275
276 case BPF_LD|BPF_W|BPF_IND:
277 k = X + pc->k;
278 if (pc->k > buflen || X > buflen - pc->k ||
279 sizeof(int32_t) > buflen - k) {
280 #ifdef _KERNEL
281 int merr;
282
283 if (buflen != 0)
284 return 0;
285 A = m_xword((struct mbuf *)p, k, &merr);
286 if (merr != 0)
287 return 0;
288 continue;
289 #else
290 return 0;
291 #endif
292 }
293 #ifdef BPF_ALIGN
294 if (((intptr_t)(p + k) & 3) != 0)
295 A = EXTRACT_LONG(&p[k]);
296 else
297 #endif
298 A = ntohl(*(int32_t *)(p + k));
299 continue;
300
301 case BPF_LD|BPF_H|BPF_IND:
302 k = X + pc->k;
303 if (X > buflen || pc->k > buflen - X ||
304 sizeof(int16_t) > buflen - k) {
305 #ifdef _KERNEL
306 int merr;
307
308 if (buflen != 0)
309 return 0;
310 A = m_xhalf((struct mbuf *)p, k, &merr);
311 if (merr != 0)
312 return 0;
313 continue;
314 #else
315 return 0;
316 #endif
317 }
318 A = EXTRACT_SHORT(&p[k]);
319 continue;
320
321 case BPF_LD|BPF_B|BPF_IND:
322 k = X + pc->k;
323 if (pc->k >= buflen || X >= buflen - pc->k) {
324 #ifdef _KERNEL
325 struct mbuf *m;
326
327 if (buflen != 0)
328 return 0;
329 m = (struct mbuf *)p;
330 MINDEX(m, k);
331 A = mtod(m, u_char *)[k];
332 continue;
333 #else
334 return 0;
335 #endif
336 }
337 A = p[k];
338 continue;
339
340 case BPF_LDX|BPF_MSH|BPF_B:
341 k = pc->k;
342 if (k >= buflen) {
343 #ifdef _KERNEL
344 struct mbuf *m;
345
346 if (buflen != 0)
347 return 0;
348 m = (struct mbuf *)p;
349 MINDEX(m, k);
350 X = (mtod(m, char *)[k] & 0xf) << 2;
351 continue;
352 #else
353 return 0;
354 #endif
355 }
356 X = (p[pc->k] & 0xf) << 2;
357 continue;
358
359 case BPF_LD|BPF_IMM:
360 A = pc->k;
361 continue;
362
363 case BPF_LDX|BPF_IMM:
364 X = pc->k;
365 continue;
366
367 case BPF_LD|BPF_MEM:
368 A = mem[pc->k];
369 continue;
370
371 case BPF_LDX|BPF_MEM:
372 X = mem[pc->k];
373 continue;
374
375 case BPF_ST:
376 mem[pc->k] = A;
377 continue;
378
379 case BPF_STX:
380 mem[pc->k] = X;
381 continue;
382
383 case BPF_JMP|BPF_JA:
384 pc += pc->k;
385 continue;
386
387 case BPF_JMP|BPF_JGT|BPF_K:
388 pc += (A > pc->k) ? pc->jt : pc->jf;
389 continue;
390
391 case BPF_JMP|BPF_JGE|BPF_K:
392 pc += (A >= pc->k) ? pc->jt : pc->jf;
393 continue;
394
395 case BPF_JMP|BPF_JEQ|BPF_K:
396 pc += (A == pc->k) ? pc->jt : pc->jf;
397 continue;
398
399 case BPF_JMP|BPF_JSET|BPF_K:
400 pc += (A & pc->k) ? pc->jt : pc->jf;
401 continue;
402
403 case BPF_JMP|BPF_JGT|BPF_X:
404 pc += (A > X) ? pc->jt : pc->jf;
405 continue;
406
407 case BPF_JMP|BPF_JGE|BPF_X:
408 pc += (A >= X) ? pc->jt : pc->jf;
409 continue;
410
411 case BPF_JMP|BPF_JEQ|BPF_X:
412 pc += (A == X) ? pc->jt : pc->jf;
413 continue;
414
415 case BPF_JMP|BPF_JSET|BPF_X:
416 pc += (A & X) ? pc->jt : pc->jf;
417 continue;
418
419 case BPF_ALU|BPF_ADD|BPF_X:
420 A += X;
421 continue;
422
423 case BPF_ALU|BPF_SUB|BPF_X:
424 A -= X;
425 continue;
426
427 case BPF_ALU|BPF_MUL|BPF_X:
428 A *= X;
429 continue;
430
431 case BPF_ALU|BPF_DIV|BPF_X:
432 if (X == 0)
433 return 0;
434 A /= X;
435 continue;
436
437 case BPF_ALU|BPF_AND|BPF_X:
438 A &= X;
439 continue;
440
441 case BPF_ALU|BPF_OR|BPF_X:
442 A |= X;
443 continue;
444
445 case BPF_ALU|BPF_LSH|BPF_X:
446 A <<= X;
447 continue;
448
449 case BPF_ALU|BPF_RSH|BPF_X:
450 A >>= X;
451 continue;
452
453 case BPF_ALU|BPF_ADD|BPF_K:
454 A += pc->k;
455 continue;
456
457 case BPF_ALU|BPF_SUB|BPF_K:
458 A -= pc->k;
459 continue;
460
461 case BPF_ALU|BPF_MUL|BPF_K:
462 A *= pc->k;
463 continue;
464
465 case BPF_ALU|BPF_DIV|BPF_K:
466 A /= pc->k;
467 continue;
468
469 case BPF_ALU|BPF_AND|BPF_K:
470 A &= pc->k;
471 continue;
472
473 case BPF_ALU|BPF_OR|BPF_K:
474 A |= pc->k;
475 continue;
476
477 case BPF_ALU|BPF_LSH|BPF_K:
478 A <<= pc->k;
479 continue;
480
481 case BPF_ALU|BPF_RSH|BPF_K:
482 A >>= pc->k;
483 continue;
484
485 case BPF_ALU|BPF_NEG:
486 A = -A;
487 continue;
488
489 case BPF_MISC|BPF_TAX:
490 X = A;
491 continue;
492
493 case BPF_MISC|BPF_TXA:
494 A = X;
495 continue;
496 }
497 }
498 }
499
500 #ifdef _KERNEL
501 /*
502 * Return true if the 'fcode' is a valid filter program.
503 * The constraints are that each jump be forward and to a valid
504 * code, that memory accesses are within valid ranges (to the
505 * extent that this can be checked statically; loads of packet
506 * data have to be, and are, also checked at run time), and that
507 * the code terminates with either an accept or reject.
508 *
509 * The kernel needs to be able to verify an application's filter code.
510 * Otherwise, a bogus program could easily crash the system.
511 */
512 int
513 bpf_validate(const struct bpf_insn *f, int len)
514 {
515 u_int i, from;
516 const struct bpf_insn *p;
517
518 if (len < 1 || len > BPF_MAXINSNS)
519 return 0;
520
521 for (i = 0; i < len; ++i) {
522 p = &f[i];
523 switch (BPF_CLASS(p->code)) {
524 /*
525 * Check that memory operations use valid addresses.
526 */
527 case BPF_LD:
528 case BPF_LDX:
529 switch (BPF_MODE(p->code)) {
530 case BPF_IMM:
531 break;
532 case BPF_ABS:
533 case BPF_IND:
534 case BPF_MSH:
535 /*
536 * More strict check with actual packet length
537 * is done runtime.
538 */
539 if (p->k >= bpf_maxbufsize)
540 return 0;
541 break;
542 case BPF_MEM:
543 if (p->k >= BPF_MEMWORDS)
544 return 0;
545 break;
546 case BPF_LEN:
547 break;
548 default:
549 return 0;
550 }
551 break;
552 case BPF_ST:
553 case BPF_STX:
554 if (p->k >= BPF_MEMWORDS)
555 return 0;
556 break;
557 case BPF_ALU:
558 switch (BPF_OP(p->code)) {
559 case BPF_ADD:
560 case BPF_SUB:
561 case BPF_MUL:
562 case BPF_OR:
563 case BPF_AND:
564 case BPF_LSH:
565 case BPF_RSH:
566 case BPF_NEG:
567 break;
568 case BPF_DIV:
569 /*
570 * Check for constant division by 0.
571 */
572 if (BPF_RVAL(p->code) == BPF_K && p->k == 0)
573 return 0;
574 break;
575 default:
576 return 0;
577 }
578 break;
579 case BPF_JMP:
580 /*
581 * Check that jumps are within the code block,
582 * and that unconditional branches don't go
583 * backwards as a result of an overflow.
584 * Unconditional branches have a 32-bit offset,
585 * so they could overflow; we check to make
586 * sure they don't. Conditional branches have
587 * an 8-bit offset, and the from address is <=
588 * BPF_MAXINSNS, and we assume that BPF_MAXINSNS
589 * is sufficiently small that adding 255 to it
590 * won't overflow.
591 *
592 * We know that len is <= BPF_MAXINSNS, and we
593 * assume that BPF_MAXINSNS is < the maximum size
594 * of a u_int, so that i + 1 doesn't overflow.
595 */
596 from = i + 1;
597 switch (BPF_OP(p->code)) {
598 case BPF_JA:
599 if (from + p->k < from || from + p->k >= len)
600 return 0;
601 break;
602 case BPF_JEQ:
603 case BPF_JGT:
604 case BPF_JGE:
605 case BPF_JSET:
606 if (from + p->jt >= len || from + p->jf >= len)
607 return 0;
608 break;
609 default:
610 return 0;
611 }
612 break;
613 case BPF_RET:
614 break;
615 case BPF_MISC:
616 break;
617 default:
618 return 0;
619 }
620 }
621 return BPF_CLASS(f[len - 1].code) == BPF_RET;
622 }
623 #endif
DragonFly BSD