FreeBSD/Linux Kernel Cross Reference
sys/net/bpf_filter.c
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 * 4. 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
37 #include <sys/cdefs.h>
38 __FBSDID("$FreeBSD: releng/10.0/sys/net/bpf_filter.c 224044 2011-07-14 21:06:22Z mp $");
39
40 #include <sys/param.h>
41
42 #if !defined(_KERNEL) || defined(sun)
43 #include <netinet/in.h>
44 #endif
45
46 #ifndef __i386__
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 #else
68 #include <stdlib.h>
69 #endif
70 #include <net/bpf.h>
71 #ifdef _KERNEL
72 #define MINDEX(m, k) \
73 { \
74 register int len = m->m_len; \
75 \
76 while (k >= len) { \
77 k -= len; \
78 m = m->m_next; \
79 if (m == 0) \
80 return (0); \
81 len = m->m_len; \
82 } \
83 }
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 case 1:
115 return (((u_int32_t)cp[0] << 24) |
116 ((u_int32_t)np[0] << 16) |
117 ((u_int32_t)np[1] << 8) |
118 (u_int32_t)np[2]);
119
120 case 2:
121 return (((u_int32_t)cp[0] << 24) |
122 ((u_int32_t)cp[1] << 16) |
123 ((u_int32_t)np[0] << 8) |
124 (u_int32_t)np[1]);
125
126 default:
127 return (((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 == 0)
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 == 0)
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 --pc;
189 while (1) {
190 ++pc;
191 switch (pc->code) {
192 default:
193 #ifdef _KERNEL
194 return (0);
195 #else
196 abort();
197 #endif
198
199 case BPF_RET|BPF_K:
200 return ((u_int)pc->k);
201
202 case BPF_RET|BPF_A:
203 return ((u_int)A);
204
205 case BPF_LD|BPF_W|BPF_ABS:
206 k = pc->k;
207 if (k > buflen || sizeof(int32_t) > buflen - k) {
208 #ifdef _KERNEL
209 int merr;
210
211 if (buflen != 0)
212 return (0);
213 A = m_xword((struct mbuf *)p, k, &merr);
214 if (merr != 0)
215 return (0);
216 continue;
217 #else
218 return (0);
219 #endif
220 }
221 #ifdef BPF_ALIGN
222 if (((intptr_t)(p + k) & 3) != 0)
223 A = EXTRACT_LONG(&p[k]);
224 else
225 #endif
226 A = ntohl(*(int32_t *)(p + k));
227 continue;
228
229 case BPF_LD|BPF_H|BPF_ABS:
230 k = pc->k;
231 if (k > buflen || sizeof(int16_t) > buflen - k) {
232 #ifdef _KERNEL
233 int merr;
234
235 if (buflen != 0)
236 return (0);
237 A = m_xhalf((struct mbuf *)p, k, &merr);
238 continue;
239 #else
240 return (0);
241 #endif
242 }
243 A = EXTRACT_SHORT(&p[k]);
244 continue;
245
246 case BPF_LD|BPF_B|BPF_ABS:
247 k = pc->k;
248 if (k >= buflen) {
249 #ifdef _KERNEL
250 struct mbuf *m;
251
252 if (buflen != 0)
253 return (0);
254 m = (struct mbuf *)p;
255 MINDEX(m, k);
256 A = mtod(m, u_char *)[k];
257 continue;
258 #else
259 return (0);
260 #endif
261 }
262 A = p[k];
263 continue;
264
265 case BPF_LD|BPF_W|BPF_LEN:
266 A = wirelen;
267 continue;
268
269 case BPF_LDX|BPF_W|BPF_LEN:
270 X = wirelen;
271 continue;
272
273 case BPF_LD|BPF_W|BPF_IND:
274 k = X + pc->k;
275 if (pc->k > buflen || X > buflen - pc->k ||
276 sizeof(int32_t) > buflen - k) {
277 #ifdef _KERNEL
278 int merr;
279
280 if (buflen != 0)
281 return (0);
282 A = m_xword((struct mbuf *)p, k, &merr);
283 if (merr != 0)
284 return (0);
285 continue;
286 #else
287 return (0);
288 #endif
289 }
290 #ifdef BPF_ALIGN
291 if (((intptr_t)(p + k) & 3) != 0)
292 A = EXTRACT_LONG(&p[k]);
293 else
294 #endif
295 A = ntohl(*(int32_t *)(p + k));
296 continue;
297
298 case BPF_LD|BPF_H|BPF_IND:
299 k = X + pc->k;
300 if (X > buflen || pc->k > buflen - X ||
301 sizeof(int16_t) > buflen - k) {
302 #ifdef _KERNEL
303 int merr;
304
305 if (buflen != 0)
306 return (0);
307 A = m_xhalf((struct mbuf *)p, k, &merr);
308 if (merr != 0)
309 return (0);
310 continue;
311 #else
312 return (0);
313 #endif
314 }
315 A = EXTRACT_SHORT(&p[k]);
316 continue;
317
318 case BPF_LD|BPF_B|BPF_IND:
319 k = X + pc->k;
320 if (pc->k >= buflen || X >= buflen - pc->k) {
321 #ifdef _KERNEL
322 struct mbuf *m;
323
324 if (buflen != 0)
325 return (0);
326 m = (struct mbuf *)p;
327 MINDEX(m, k);
328 A = mtod(m, u_char *)[k];
329 continue;
330 #else
331 return (0);
332 #endif
333 }
334 A = p[k];
335 continue;
336
337 case BPF_LDX|BPF_MSH|BPF_B:
338 k = pc->k;
339 if (k >= buflen) {
340 #ifdef _KERNEL
341 register struct mbuf *m;
342
343 if (buflen != 0)
344 return (0);
345 m = (struct mbuf *)p;
346 MINDEX(m, k);
347 X = (mtod(m, u_char *)[k] & 0xf) << 2;
348 continue;
349 #else
350 return (0);
351 #endif
352 }
353 X = (p[pc->k] & 0xf) << 2;
354 continue;
355
356 case BPF_LD|BPF_IMM:
357 A = pc->k;
358 continue;
359
360 case BPF_LDX|BPF_IMM:
361 X = pc->k;
362 continue;
363
364 case BPF_LD|BPF_MEM:
365 A = mem[pc->k];
366 continue;
367
368 case BPF_LDX|BPF_MEM:
369 X = mem[pc->k];
370 continue;
371
372 case BPF_ST:
373 mem[pc->k] = A;
374 continue;
375
376 case BPF_STX:
377 mem[pc->k] = X;
378 continue;
379
380 case BPF_JMP|BPF_JA:
381 pc += pc->k;
382 continue;
383
384 case BPF_JMP|BPF_JGT|BPF_K:
385 pc += (A > pc->k) ? pc->jt : pc->jf;
386 continue;
387
388 case BPF_JMP|BPF_JGE|BPF_K:
389 pc += (A >= pc->k) ? pc->jt : pc->jf;
390 continue;
391
392 case BPF_JMP|BPF_JEQ|BPF_K:
393 pc += (A == pc->k) ? pc->jt : pc->jf;
394 continue;
395
396 case BPF_JMP|BPF_JSET|BPF_K:
397 pc += (A & pc->k) ? pc->jt : pc->jf;
398 continue;
399
400 case BPF_JMP|BPF_JGT|BPF_X:
401 pc += (A > X) ? pc->jt : pc->jf;
402 continue;
403
404 case BPF_JMP|BPF_JGE|BPF_X:
405 pc += (A >= X) ? pc->jt : pc->jf;
406 continue;
407
408 case BPF_JMP|BPF_JEQ|BPF_X:
409 pc += (A == X) ? pc->jt : pc->jf;
410 continue;
411
412 case BPF_JMP|BPF_JSET|BPF_X:
413 pc += (A & X) ? pc->jt : pc->jf;
414 continue;
415
416 case BPF_ALU|BPF_ADD|BPF_X:
417 A += X;
418 continue;
419
420 case BPF_ALU|BPF_SUB|BPF_X:
421 A -= X;
422 continue;
423
424 case BPF_ALU|BPF_MUL|BPF_X:
425 A *= X;
426 continue;
427
428 case BPF_ALU|BPF_DIV|BPF_X:
429 if (X == 0)
430 return (0);
431 A /= X;
432 continue;
433
434 case BPF_ALU|BPF_AND|BPF_X:
435 A &= X;
436 continue;
437
438 case BPF_ALU|BPF_OR|BPF_X:
439 A |= X;
440 continue;
441
442 case BPF_ALU|BPF_LSH|BPF_X:
443 A <<= X;
444 continue;
445
446 case BPF_ALU|BPF_RSH|BPF_X:
447 A >>= X;
448 continue;
449
450 case BPF_ALU|BPF_ADD|BPF_K:
451 A += pc->k;
452 continue;
453
454 case BPF_ALU|BPF_SUB|BPF_K:
455 A -= pc->k;
456 continue;
457
458 case BPF_ALU|BPF_MUL|BPF_K:
459 A *= pc->k;
460 continue;
461
462 case BPF_ALU|BPF_DIV|BPF_K:
463 A /= pc->k;
464 continue;
465
466 case BPF_ALU|BPF_AND|BPF_K:
467 A &= pc->k;
468 continue;
469
470 case BPF_ALU|BPF_OR|BPF_K:
471 A |= pc->k;
472 continue;
473
474 case BPF_ALU|BPF_LSH|BPF_K:
475 A <<= pc->k;
476 continue;
477
478 case BPF_ALU|BPF_RSH|BPF_K:
479 A >>= pc->k;
480 continue;
481
482 case BPF_ALU|BPF_NEG:
483 A = -A;
484 continue;
485
486 case BPF_MISC|BPF_TAX:
487 X = A;
488 continue;
489
490 case BPF_MISC|BPF_TXA:
491 A = X;
492 continue;
493 }
494 }
495 }
496
497 #ifdef _KERNEL
498 static const u_short bpf_code_map[] = {
499 0x10ff, /* 0x00-0x0f: 1111111100001000 */
500 0x3070, /* 0x10-0x1f: 0000111000001100 */
501 0x3131, /* 0x20-0x2f: 1000110010001100 */
502 0x3031, /* 0x30-0x3f: 1000110000001100 */
503 0x3131, /* 0x40-0x4f: 1000110010001100 */
504 0x1011, /* 0x50-0x5f: 1000100000001000 */
505 0x1013, /* 0x60-0x6f: 1100100000001000 */
506 0x1010, /* 0x70-0x7f: 0000100000001000 */
507 0x0093, /* 0x80-0x8f: 1100100100000000 */
508 0x0000, /* 0x90-0x9f: 0000000000000000 */
509 0x0000, /* 0xa0-0xaf: 0000000000000000 */
510 0x0002, /* 0xb0-0xbf: 0100000000000000 */
511 0x0000, /* 0xc0-0xcf: 0000000000000000 */
512 0x0000, /* 0xd0-0xdf: 0000000000000000 */
513 0x0000, /* 0xe0-0xef: 0000000000000000 */
514 0x0000 /* 0xf0-0xff: 0000000000000000 */
515 };
516
517 #define BPF_VALIDATE_CODE(c) \
518 ((c) <= 0xff && (bpf_code_map[(c) >> 4] & (1 << ((c) & 0xf))) != 0)
519
520 /*
521 * Return true if the 'fcode' is a valid filter program.
522 * The constraints are that each jump be forward and to a valid
523 * code. The code must terminate with either an accept or reject.
524 *
525 * The kernel needs to be able to verify an application's filter code.
526 * Otherwise, a bogus program could easily crash the system.
527 */
528 int
529 bpf_validate(const struct bpf_insn *f, int len)
530 {
531 register int i;
532 register const struct bpf_insn *p;
533
534 /* Do not accept negative length filter. */
535 if (len < 0)
536 return (0);
537
538 /* An empty filter means accept all. */
539 if (len == 0)
540 return (1);
541
542 for (i = 0; i < len; ++i) {
543 p = &f[i];
544 /*
545 * Check that the code is valid.
546 */
547 if (!BPF_VALIDATE_CODE(p->code))
548 return (0);
549 /*
550 * Check that that jumps are forward, and within
551 * the code block.
552 */
553 if (BPF_CLASS(p->code) == BPF_JMP) {
554 register u_int offset;
555
556 if (p->code == (BPF_JMP|BPF_JA))
557 offset = p->k;
558 else
559 offset = p->jt > p->jf ? p->jt : p->jf;
560 if (offset >= (u_int)(len - i) - 1)
561 return (0);
562 continue;
563 }
564 /*
565 * Check that memory operations use valid addresses.
566 */
567 if (p->code == BPF_ST || p->code == BPF_STX ||
568 p->code == (BPF_LD|BPF_MEM) ||
569 p->code == (BPF_LDX|BPF_MEM)) {
570 if (p->k >= BPF_MEMWORDS)
571 return (0);
572 continue;
573 }
574 /*
575 * Check for constant division by 0.
576 */
577 if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0)
578 return (0);
579 }
580 return (BPF_CLASS(f[len - 1].code) == BPF_RET);
581 }
582 #endif
Cache object: 1e4939ab195158571e1237233d888b8c
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