1 /* $NetBSD: bpf_filter.c,v 1.35 2008/08/20 13:01:54 joerg Exp $ */
2
3 /*
4 * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from the Stanford/CMU enet packet filter,
8 * (net/enet.c) distributed as part of 4.3BSD, and code contributed
9 * to Berkeley by Steven McCanne and Van Jacobson both of Lawrence
10 * Berkeley Laboratory.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 *
36 * @(#)bpf_filter.c 8.1 (Berkeley) 6/10/93
37 */
38 /*
39 * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
40 * Use is subject to license terms.
41 */
42
43 #include <sys/param.h>
44 #include <sys/time.h>
45 #include <sys/stream.h>
46 #include <sys/byteorder.h>
47 #include <sys/sdt.h>
48
49 #define EXTRACT_SHORT(p) BE_IN16(p)
50 #define EXTRACT_LONG(p) BE_IN32(p)
51
52 #ifdef _KERNEL
53 #define M_LEN(_m) ((_m)->b_wptr - (_m)->b_rptr)
54 #define mtod(_a, _t) ((_t)((_a)->b_rptr))
55 #define MINDEX(len, m, k) \
56 { \
57 len = M_LEN(m); \
58 while (k >= len) { \
59 k -= len; \
60 m = m->b_cont; \
61 if (m == 0) \
62 return (0); \
63 len = M_LEN(m); \
64 } \
65 }
66
67 static int m_xword(mblk_t *, uint32_t, int *);
68 static int m_xhalf(mblk_t *, uint32_t, int *);
69
70 static int
m_xword(mblk_t * m,uint32_t k,int * err)71 m_xword(mblk_t *m, uint32_t k, int *err)
72 {
73 int len;
74 uchar_t *cp, *np;
75 mblk_t *m0;
76
77 *err = 1;
78 MINDEX(len, m, k);
79 cp = mtod(m, uchar_t *) + k;
80 if (len >= k + 4) {
81 *err = 0;
82 return (EXTRACT_LONG(cp));
83 }
84 m0 = m->b_cont;
85 if (m0 == 0 || M_LEN(m0) + len - k < 4) {
86 DTRACE_PROBE3(mblk_xword_fail, mblk_t *, m0, int, len, int, k);
87 return (0);
88 }
89 *err = 0;
90 np = mtod(m0, uchar_t *);
91 switch (len - k) {
92
93 case 1:
94 return ((cp[0] << 24) | (np[0] << 16) | (np[1] << 8) | np[2]);
95
96 case 2:
97 return ((cp[0] << 24) | (cp[1] << 16) | (np[0] << 8) | np[1]);
98
99 default:
100 return ((cp[0] << 24) | (cp[1] << 16) | (cp[2] << 8) | np[0]);
101 }
102 }
103
104 static int
m_xhalf(mblk_t * m,uint32_t k,int * err)105 m_xhalf(mblk_t *m, uint32_t k, int *err)
106 {
107 int len;
108 uchar_t *cp;
109 mblk_t *m0;
110
111 *err = 1;
112 MINDEX(len, m, k);
113 cp = mtod(m, uchar_t *) + k;
114 if (len >= k + 2) {
115 *err = 0;
116 return (EXTRACT_SHORT(cp));
117 }
118 m0 = m->b_cont;
119 if (m0 == 0) {
120 DTRACE_PROBE3(mblk_xhalf_fail, mblk_t *, m0, int, len, int, k);
121 return (0);
122 }
123 *err = 0;
124 return ((cp[0] << 8) | mtod(m0, uchar_t *)[0]);
125 }
126 #else /* _KERNEL */
127 #include <stdlib.h>
128 #endif /* !_KERNEL */
129
130 #include <net/bpf.h>
131
132 /*
133 * Execute the filter program starting at pc on the packet p
134 * wirelen is the length of the original packet
135 * buflen is the amount of data present
136 * When buflen is non-0, p is a pointer to a the start of the packet and the
137 * packet is only in one mblk_t.
138 * When buflen is 0, p is an mblk_t pointer.
139 */
140 uint_t
bpf_filter(struct bpf_insn * pc,uchar_t * p,uint_t wirelen,uint_t buflen)141 bpf_filter(struct bpf_insn *pc, uchar_t *p, uint_t wirelen, uint_t buflen)
142 {
143 uint32_t A, X, k;
144 uint32_t mem[BPF_MEMWORDS];
145
146 if (pc == 0)
147 /*
148 * No filter means accept all.
149 */
150 return ((uint_t)-1);
151 A = 0;
152 X = 0;
153 --pc;
154 /* CONSTCOND */
155 while (1) {
156 ++pc;
157 switch (pc->code) {
158
159 default:
160 #ifdef _KERNEL
161 DTRACE_PROBE1(bpf_insn_unknown,
162 struct bpf_insn *, pc);
163 return (0);
164 #else
165 abort();
166 #endif
167 case BPF_RET|BPF_K:
168 return ((uint_t)pc->k);
169
170 case BPF_RET|BPF_A:
171 return ((uint_t)A);
172
173 case BPF_LD|BPF_W|BPF_ABS:
174 k = pc->k;
175 if (k + sizeof (int32_t) > buflen) {
176 #ifdef _KERNEL
177 int merr = 0;
178
179 if (buflen != 0)
180 return (0);
181 A = m_xword((mblk_t *)p, k, &merr);
182 if (merr != 0)
183 return (0);
184 continue;
185 #else
186 return (0);
187 #endif
188 }
189 A = EXTRACT_LONG(&p[k]);
190 continue;
191
192 case BPF_LD|BPF_H|BPF_ABS:
193 k = pc->k;
194 if (k + sizeof (int16_t) > buflen) {
195 #ifdef _KERNEL
196 int merr;
197
198 if (buflen != 0)
199 return (0);
200 A = m_xhalf((mblk_t *)p, k, &merr);
201 if (merr != 0)
202 return (0);
203 continue;
204 #else
205 return (0);
206 #endif
207 }
208 A = EXTRACT_SHORT(&p[k]);
209 continue;
210
211 case BPF_LD|BPF_B|BPF_ABS:
212 k = pc->k;
213 if (k >= buflen) {
214 #ifdef _KERNEL
215 mblk_t *m;
216 int len;
217
218 if (buflen != 0)
219 return (0);
220 m = (mblk_t *)p;
221 MINDEX(len, m, k);
222 A = mtod(m, uchar_t *)[k];
223 continue;
224 #else
225 return (0);
226 #endif
227 }
228 A = p[k];
229 continue;
230
231 case BPF_LD|BPF_W|BPF_LEN:
232 A = wirelen;
233 continue;
234
235 case BPF_LDX|BPF_W|BPF_LEN:
236 X = wirelen;
237 continue;
238
239 case BPF_LD|BPF_W|BPF_IND:
240 k = X + pc->k;
241 if (k + sizeof (int32_t) > buflen) {
242 #ifdef _KERNEL
243 int merr = 0;
244
245 if (buflen != 0)
246 return (0);
247 A = m_xword((mblk_t *)p, k, &merr);
248 if (merr != 0)
249 return (0);
250 continue;
251 #else
252 return (0);
253 #endif
254 }
255 A = EXTRACT_LONG(&p[k]);
256 continue;
257
258 case BPF_LD|BPF_H|BPF_IND:
259 k = X + pc->k;
260 if (k + sizeof (int16_t) > buflen) {
261 #ifdef _KERNEL
262 int merr = 0;
263
264 if (buflen != 0)
265 return (0);
266 A = m_xhalf((mblk_t *)p, k, &merr);
267 if (merr != 0)
268 return (0);
269 continue;
270 #else
271 return (0);
272 #endif
273 }
274 A = EXTRACT_SHORT(&p[k]);
275 continue;
276
277 case BPF_LD|BPF_B|BPF_IND:
278 k = X + pc->k;
279 if (k >= buflen) {
280 #ifdef _KERNEL
281 mblk_t *m;
282 int len;
283
284 if (buflen != 0)
285 return (0);
286 m = (mblk_t *)p;
287 MINDEX(len, m, k);
288 A = mtod(m, uchar_t *)[k];
289 continue;
290 #else
291 return (0);
292 #endif
293 }
294 A = p[k];
295 continue;
296
297 case BPF_LDX|BPF_MSH|BPF_B:
298 k = pc->k;
299 if (k >= buflen) {
300 #ifdef _KERNEL
301 mblk_t *m;
302 int len;
303
304 if (buflen != 0)
305 return (0);
306 m = (mblk_t *)p;
307 MINDEX(len, m, k);
308 X = (mtod(m, char *)[k] & 0xf) << 2;
309 continue;
310 #else
311 return (0);
312 #endif
313 }
314 X = (p[pc->k] & 0xf) << 2;
315 continue;
316
317 case BPF_LD|BPF_IMM:
318 A = pc->k;
319 continue;
320
321 case BPF_LDX|BPF_IMM:
322 X = pc->k;
323 continue;
324
325 case BPF_LD|BPF_MEM:
326 A = mem[pc->k];
327 continue;
328
329 case BPF_LDX|BPF_MEM:
330 X = mem[pc->k];
331 continue;
332
333 case BPF_ST:
334 mem[pc->k] = A;
335 continue;
336
337 case BPF_STX:
338 mem[pc->k] = X;
339 continue;
340
341 case BPF_JMP|BPF_JA:
342 pc += pc->k;
343 continue;
344
345 case BPF_JMP|BPF_JGT|BPF_K:
346 pc += (A > pc->k) ? pc->jt : pc->jf;
347 continue;
348
349 case BPF_JMP|BPF_JGE|BPF_K:
350 pc += (A >= pc->k) ? pc->jt : pc->jf;
351 continue;
352
353 case BPF_JMP|BPF_JEQ|BPF_K:
354 pc += (A == pc->k) ? pc->jt : pc->jf;
355 continue;
356
357 case BPF_JMP|BPF_JSET|BPF_K:
358 pc += (A & pc->k) ? pc->jt : pc->jf;
359 continue;
360
361 case BPF_JMP|BPF_JGT|BPF_X:
362 pc += (A > X) ? pc->jt : pc->jf;
363 continue;
364
365 case BPF_JMP|BPF_JGE|BPF_X:
366 pc += (A >= X) ? pc->jt : pc->jf;
367 continue;
368
369 case BPF_JMP|BPF_JEQ|BPF_X:
370 pc += (A == X) ? pc->jt : pc->jf;
371 continue;
372
373 case BPF_JMP|BPF_JSET|BPF_X:
374 pc += (A & X) ? pc->jt : pc->jf;
375 continue;
376
377 case BPF_ALU|BPF_ADD|BPF_X:
378 A += X;
379 continue;
380
381 case BPF_ALU|BPF_SUB|BPF_X:
382 A -= X;
383 continue;
384
385 case BPF_ALU|BPF_MUL|BPF_X:
386 A *= X;
387 continue;
388
389 case BPF_ALU|BPF_DIV|BPF_X:
390 if (X == 0)
391 return (0);
392 A /= X;
393 continue;
394
395 case BPF_ALU|BPF_AND|BPF_X:
396 A &= X;
397 continue;
398
399 case BPF_ALU|BPF_OR|BPF_X:
400 A |= X;
401 continue;
402
403 case BPF_ALU|BPF_LSH|BPF_X:
404 A <<= X;
405 continue;
406
407 case BPF_ALU|BPF_RSH|BPF_X:
408 A >>= X;
409 continue;
410
411 case BPF_ALU|BPF_ADD|BPF_K:
412 A += pc->k;
413 continue;
414
415 case BPF_ALU|BPF_SUB|BPF_K:
416 A -= pc->k;
417 continue;
418
419 case BPF_ALU|BPF_MUL|BPF_K:
420 A *= pc->k;
421 continue;
422
423 case BPF_ALU|BPF_DIV|BPF_K:
424 A /= pc->k;
425 continue;
426
427 case BPF_ALU|BPF_AND|BPF_K:
428 A &= pc->k;
429 continue;
430
431 case BPF_ALU|BPF_OR|BPF_K:
432 A |= pc->k;
433 continue;
434
435 case BPF_ALU|BPF_LSH|BPF_K:
436 A <<= pc->k;
437 continue;
438
439 case BPF_ALU|BPF_RSH|BPF_K:
440 A >>= pc->k;
441 continue;
442
443 case BPF_ALU|BPF_NEG:
444 A = -A;
445 continue;
446
447 case BPF_MISC|BPF_TAX:
448 X = A;
449 continue;
450
451 case BPF_MISC|BPF_TXA:
452 A = X;
453 continue;
454 }
455 }
456 /* NOTREACHED */
457 }
458
459 #ifdef _KERNEL
460 /*
461 * Return true if the 'fcode' is a valid filter program.
462 * The constraints are that each jump be forward and to a valid
463 * code, that memory accesses are within valid ranges (to the
464 * extent that this can be checked statically; loads of packet
465 * data have to be, and are, also checked at run time), and that
466 * the code terminates with either an accept or reject.
467 *
468 * The kernel needs to be able to verify an application's filter code.
469 * Otherwise, a bogus program could easily crash the system.
470 */
471 int
bpf_validate(struct bpf_insn * f,int len)472 bpf_validate(struct bpf_insn *f, int len)
473 {
474 uint_t i, from;
475 struct bpf_insn *p;
476
477 if (len < 1 || len > BPF_MAXINSNS)
478 return (0);
479
480 for (i = 0; i < len; ++i) {
481 p = &f[i];
482 DTRACE_PROBE1(bpf_valid_insn, struct bpf_insn *, p);
483 switch (BPF_CLASS(p->code)) {
484 /*
485 * Check that memory operations use valid addresses.
486 */
487 case BPF_LD:
488 case BPF_LDX:
489 switch (BPF_MODE(p->code)) {
490 case BPF_MEM:
491 if (p->k >= BPF_MEMWORDS)
492 return (0);
493 break;
494 case BPF_ABS:
495 case BPF_IND:
496 case BPF_MSH:
497 case BPF_IMM:
498 case BPF_LEN:
499 break;
500 default:
501 return (0);
502 }
503 break;
504 case BPF_ST:
505 case BPF_STX:
506 if (p->k >= BPF_MEMWORDS)
507 return (0);
508 break;
509 case BPF_ALU:
510 switch (BPF_OP(p->code)) {
511 case BPF_ADD:
512 case BPF_SUB:
513 case BPF_MUL:
514 case BPF_OR:
515 case BPF_AND:
516 case BPF_LSH:
517 case BPF_RSH:
518 case BPF_NEG:
519 break;
520 case BPF_DIV:
521 /*
522 * Check for constant division by 0.
523 */
524 if (BPF_RVAL(p->code) == BPF_K && p->k == 0)
525 return (0);
526 break;
527 default:
528 return (0);
529 }
530 break;
531 case BPF_JMP:
532 /*
533 * Check that jumps are within the code block,
534 * and that unconditional branches don't go
535 * backwards as a result of an overflow.
536 * Unconditional branches have a 32-bit offset,
537 * so they could overflow; we check to make
538 * sure they don't. Conditional branches have
539 * an 8-bit offset, and the from address is <=
540 * BPF_MAXINSNS, and we assume that BPF_MAXINSNS
541 * is sufficiently small that adding 255 to it
542 * won't overflow.
543 *
544 * We know that len is <= BPF_MAXINSNS, and we
545 * assume that BPF_MAXINSNS is < the maximum size
546 * of a uint_t, so that i + 1 doesn't overflow.
547 */
548 from = i + 1;
549 switch (BPF_OP(p->code)) {
550 case BPF_JA:
551 if (from + p->k < from || from + p->k >= len)
552 return (0);
553 break;
554 case BPF_JEQ:
555 case BPF_JGT:
556 case BPF_JGE:
557 case BPF_JSET:
558 if (from + p->jt >= len || from + p->jf >= len)
559 return (0);
560 break;
561 default:
562 return (0);
563 }
564 break;
565 case BPF_RET:
566 break;
567 case BPF_MISC:
568 break;
569 default:
570 return (0);
571 }
572 }
573
574 return (BPF_CLASS(f[len - 1].code) == BPF_RET);
575 }
576 #endif
577