1 /*-
2 * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
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.c 7.5 (Berkeley) 7/15/91
39 */
40
41 #if !(defined(lint) || defined(KERNEL) || defined(_KERNEL))
42 static const char rcsid[] _U_ =
43 "@(#) $Header: /tcpdump/master/libpcap/bpf/net/bpf_filter.c,v 1.46 2008-01-02 04:16:46 guy Exp $ (LBL)";
44 #endif
45
46 #ifdef HAVE_CONFIG_H
47 #include "config.h"
48 #endif
49
50 #ifdef WIN32
51
52 #include <pcap-stdinc.h>
53
54 #else /* WIN32 */
55
56 #if HAVE_INTTYPES_H
57 #include <inttypes.h>
58 #elif HAVE_STDINT_H
59 #include <stdint.h>
60 #endif
61 #ifdef HAVE_SYS_BITYPES_H
62 #include <sys/bitypes.h>
63 #endif
64
65 #include <sys/param.h>
66 #include <sys/types.h>
67 #include <sys/time.h>
68
69 #define SOLARIS (defined(sun) && (defined(__SVR4) || defined(__svr4__)))
70 #if defined(__hpux) || SOLARIS
71 # include <sys/sysmacros.h>
72 # include <sys/stream.h>
73 # define mbuf msgb
74 # define m_next b_cont
75 # define MLEN(m) ((m)->b_wptr - (m)->b_rptr)
76 # define mtod(m,t) ((t)(m)->b_rptr)
77 #else /* defined(__hpux) || SOLARIS */
78 # define MLEN(m) ((m)->m_len)
79 #endif /* defined(__hpux) || SOLARIS */
80
81 #endif /* WIN32 */
82
83 #include <pcap/bpf.h>
84
85 #if !defined(KERNEL) && !defined(_KERNEL)
86 #include <stdlib.h>
87 #endif
88
89 #define int32 bpf_int32
90 #define u_int32 bpf_u_int32
91
92 #ifndef LBL_ALIGN
93 /*
94 * XXX - IA-64? If not, this probably won't work on Win64 IA-64
95 * systems, unless LBL_ALIGN is defined elsewhere for them.
96 * XXX - SuperH? If not, this probably won't work on WinCE SuperH
97 * systems, unless LBL_ALIGN is defined elsewhere for them.
98 */
99 #if defined(sparc) || defined(__sparc__) || defined(mips) || \
100 defined(ibm032) || defined(__alpha) || defined(__hpux) || \
101 defined(__arm__)
102 #define LBL_ALIGN
103 #endif
104 #endif
105
106 #ifndef LBL_ALIGN
107 #ifndef WIN32
108 #include <netinet/in.h>
109 #endif
110
111 #define EXTRACT_SHORT(p) ((u_short)ntohs(*(u_short *)p))
112 #define EXTRACT_LONG(p) (ntohl(*(u_int32 *)p))
113 #else
114 #define EXTRACT_SHORT(p)\
115 ((u_short)\
116 ((u_short)*((u_char *)p+0)<<8|\
117 (u_short)*((u_char *)p+1)<<0))
118 #define EXTRACT_LONG(p)\
119 ((u_int32)*((u_char *)p+0)<<24|\
120 (u_int32)*((u_char *)p+1)<<16|\
121 (u_int32)*((u_char *)p+2)<<8|\
122 (u_int32)*((u_char *)p+3)<<0)
123 #endif
124
125 #if defined(KERNEL) || defined(_KERNEL)
126 # if !defined(__hpux) && !SOLARIS
127 #include <sys/mbuf.h>
128 # endif
129 #define MINDEX(len, _m, _k) \
130 { \
131 len = MLEN(m); \
132 while ((_k) >= len) { \
133 (_k) -= len; \
134 (_m) = (_m)->m_next; \
135 if ((_m) == 0) \
136 return 0; \
137 len = MLEN(m); \
138 } \
139 }
140
141 static int
m_xword(m,k,err)142 m_xword(m, k, err)
143 register struct mbuf *m;
144 register int k, *err;
145 {
146 register int len;
147 register u_char *cp, *np;
148 register struct mbuf *m0;
149
150 MINDEX(len, m, k);
151 cp = mtod(m, u_char *) + k;
152 if (len - k >= 4) {
153 *err = 0;
154 return EXTRACT_LONG(cp);
155 }
156 m0 = m->m_next;
157 if (m0 == 0 || MLEN(m0) + len - k < 4)
158 goto bad;
159 *err = 0;
160 np = mtod(m0, u_char *);
161 switch (len - k) {
162
163 case 1:
164 return (cp[0] << 24) | (np[0] << 16) | (np[1] << 8) | np[2];
165
166 case 2:
167 return (cp[0] << 24) | (cp[1] << 16) | (np[0] << 8) | np[1];
168
169 default:
170 return (cp[0] << 24) | (cp[1] << 16) | (cp[2] << 8) | np[0];
171 }
172 bad:
173 *err = 1;
174 return 0;
175 }
176
177 static int
m_xhalf(m,k,err)178 m_xhalf(m, k, err)
179 register struct mbuf *m;
180 register int k, *err;
181 {
182 register int len;
183 register u_char *cp;
184 register struct mbuf *m0;
185
186 MINDEX(len, m, k);
187 cp = mtod(m, u_char *) + k;
188 if (len - k >= 2) {
189 *err = 0;
190 return EXTRACT_SHORT(cp);
191 }
192 m0 = m->m_next;
193 if (m0 == 0)
194 goto bad;
195 *err = 0;
196 return (cp[0] << 8) | mtod(m0, u_char *)[0];
197 bad:
198 *err = 1;
199 return 0;
200 }
201 #endif
202
203 /*
204 * Execute the filter program starting at pc on the packet p
205 * wirelen is the length of the original packet
206 * buflen is the amount of data present
207 * For the kernel, p is assumed to be a pointer to an mbuf if buflen is 0,
208 * in all other cases, p is a pointer to a buffer and buflen is its size.
209 */
210 u_int
bpf_filter(pc,p,wirelen,buflen)211 bpf_filter(pc, p, wirelen, buflen)
212 register const struct bpf_insn *pc;
213 register const u_char *p;
214 u_int wirelen;
215 register u_int buflen;
216 {
217 register u_int32 A, X;
218 register int k;
219 int32 mem[BPF_MEMWORDS];
220 #if defined(KERNEL) || defined(_KERNEL)
221 struct mbuf *m, *n;
222 int merr, len;
223
224 if (buflen == 0) {
225 m = (struct mbuf *)p;
226 p = mtod(m, u_char *);
227 buflen = MLEN(m);
228 } else
229 m = NULL;
230 #endif
231
232 if (pc == 0)
233 /*
234 * No filter means accept all.
235 */
236 return (u_int)-1;
237 A = 0;
238 X = 0;
239 --pc;
240 while (1) {
241 ++pc;
242 switch (pc->code) {
243
244 default:
245 #if defined(KERNEL) || defined(_KERNEL)
246 return 0;
247 #else
248 abort();
249 #endif
250 case BPF_RET|BPF_K:
251 return (u_int)pc->k;
252
253 case BPF_RET|BPF_A:
254 return (u_int)A;
255
256 case BPF_LD|BPF_W|BPF_ABS:
257 k = pc->k;
258 if (k + sizeof(int32) > buflen) {
259 #if defined(KERNEL) || defined(_KERNEL)
260 if (m == NULL)
261 return 0;
262 A = m_xword(m, k, &merr);
263 if (merr != 0)
264 return 0;
265 continue;
266 #else
267 return 0;
268 #endif
269 }
270 A = EXTRACT_LONG(&p[k]);
271 continue;
272
273 case BPF_LD|BPF_H|BPF_ABS:
274 k = pc->k;
275 if (k + sizeof(short) > buflen) {
276 #if defined(KERNEL) || defined(_KERNEL)
277 if (m == NULL)
278 return 0;
279 A = m_xhalf(m, k, &merr);
280 if (merr != 0)
281 return 0;
282 continue;
283 #else
284 return 0;
285 #endif
286 }
287 A = EXTRACT_SHORT(&p[k]);
288 continue;
289
290 case BPF_LD|BPF_B|BPF_ABS:
291 k = pc->k;
292 if (k >= buflen) {
293 #if defined(KERNEL) || defined(_KERNEL)
294 if (m == NULL)
295 return 0;
296 n = m;
297 MINDEX(len, n, k);
298 A = mtod(n, u_char *)[k];
299 continue;
300 #else
301 return 0;
302 #endif
303 }
304 A = p[k];
305 continue;
306
307 case BPF_LD|BPF_W|BPF_LEN:
308 A = wirelen;
309 continue;
310
311 case BPF_LDX|BPF_W|BPF_LEN:
312 X = wirelen;
313 continue;
314
315 case BPF_LD|BPF_W|BPF_IND:
316 k = X + pc->k;
317 if (k + sizeof(int32) > buflen) {
318 #if defined(KERNEL) || defined(_KERNEL)
319 if (m == NULL)
320 return 0;
321 A = m_xword(m, k, &merr);
322 if (merr != 0)
323 return 0;
324 continue;
325 #else
326 return 0;
327 #endif
328 }
329 A = EXTRACT_LONG(&p[k]);
330 continue;
331
332 case BPF_LD|BPF_H|BPF_IND:
333 k = X + pc->k;
334 if (k + sizeof(short) > buflen) {
335 #if defined(KERNEL) || defined(_KERNEL)
336 if (m == NULL)
337 return 0;
338 A = m_xhalf(m, k, &merr);
339 if (merr != 0)
340 return 0;
341 continue;
342 #else
343 return 0;
344 #endif
345 }
346 A = EXTRACT_SHORT(&p[k]);
347 continue;
348
349 case BPF_LD|BPF_B|BPF_IND:
350 k = X + pc->k;
351 if (k >= buflen) {
352 #if defined(KERNEL) || defined(_KERNEL)
353 if (m == NULL)
354 return 0;
355 n = m;
356 MINDEX(len, n, k);
357 A = mtod(n, u_char *)[k];
358 continue;
359 #else
360 return 0;
361 #endif
362 }
363 A = p[k];
364 continue;
365
366 case BPF_LDX|BPF_MSH|BPF_B:
367 k = pc->k;
368 if (k >= buflen) {
369 #if defined(KERNEL) || defined(_KERNEL)
370 if (m == NULL)
371 return 0;
372 n = m;
373 MINDEX(len, n, k);
374 X = (mtod(n, char *)[k] & 0xf) << 2;
375 continue;
376 #else
377 return 0;
378 #endif
379 }
380 X = (p[pc->k] & 0xf) << 2;
381 continue;
382
383 case BPF_LD|BPF_IMM:
384 A = pc->k;
385 continue;
386
387 case BPF_LDX|BPF_IMM:
388 X = pc->k;
389 continue;
390
391 case BPF_LD|BPF_MEM:
392 A = mem[pc->k];
393 continue;
394
395 case BPF_LDX|BPF_MEM:
396 X = mem[pc->k];
397 continue;
398
399 case BPF_ST:
400 mem[pc->k] = A;
401 continue;
402
403 case BPF_STX:
404 mem[pc->k] = X;
405 continue;
406
407 case BPF_JMP|BPF_JA:
408 #if defined(KERNEL) || defined(_KERNEL)
409 /*
410 * No backward jumps allowed.
411 */
412 pc += pc->k;
413 #else
414 /*
415 * XXX - we currently implement "ip6 protochain"
416 * with backward jumps, so sign-extend pc->k.
417 */
418 pc += (bpf_int32)pc->k;
419 #endif
420 continue;
421
422 case BPF_JMP|BPF_JGT|BPF_K:
423 pc += (A > pc->k) ? pc->jt : pc->jf;
424 continue;
425
426 case BPF_JMP|BPF_JGE|BPF_K:
427 pc += (A >= pc->k) ? pc->jt : pc->jf;
428 continue;
429
430 case BPF_JMP|BPF_JEQ|BPF_K:
431 pc += (A == pc->k) ? pc->jt : pc->jf;
432 continue;
433
434 case BPF_JMP|BPF_JSET|BPF_K:
435 pc += (A & pc->k) ? pc->jt : pc->jf;
436 continue;
437
438 case BPF_JMP|BPF_JGT|BPF_X:
439 pc += (A > X) ? pc->jt : pc->jf;
440 continue;
441
442 case BPF_JMP|BPF_JGE|BPF_X:
443 pc += (A >= X) ? pc->jt : pc->jf;
444 continue;
445
446 case BPF_JMP|BPF_JEQ|BPF_X:
447 pc += (A == X) ? pc->jt : pc->jf;
448 continue;
449
450 case BPF_JMP|BPF_JSET|BPF_X:
451 pc += (A & X) ? pc->jt : pc->jf;
452 continue;
453
454 case BPF_ALU|BPF_ADD|BPF_X:
455 A += X;
456 continue;
457
458 case BPF_ALU|BPF_SUB|BPF_X:
459 A -= X;
460 continue;
461
462 case BPF_ALU|BPF_MUL|BPF_X:
463 A *= X;
464 continue;
465
466 case BPF_ALU|BPF_DIV|BPF_X:
467 if (X == 0)
468 return 0;
469 A /= X;
470 continue;
471
472 case BPF_ALU|BPF_AND|BPF_X:
473 A &= X;
474 continue;
475
476 case BPF_ALU|BPF_OR|BPF_X:
477 A |= X;
478 continue;
479
480 case BPF_ALU|BPF_LSH|BPF_X:
481 A <<= X;
482 continue;
483
484 case BPF_ALU|BPF_RSH|BPF_X:
485 A >>= X;
486 continue;
487
488 case BPF_ALU|BPF_ADD|BPF_K:
489 A += pc->k;
490 continue;
491
492 case BPF_ALU|BPF_SUB|BPF_K:
493 A -= pc->k;
494 continue;
495
496 case BPF_ALU|BPF_MUL|BPF_K:
497 A *= pc->k;
498 continue;
499
500 case BPF_ALU|BPF_DIV|BPF_K:
501 A /= pc->k;
502 continue;
503
504 case BPF_ALU|BPF_AND|BPF_K:
505 A &= pc->k;
506 continue;
507
508 case BPF_ALU|BPF_OR|BPF_K:
509 A |= pc->k;
510 continue;
511
512 case BPF_ALU|BPF_LSH|BPF_K:
513 A <<= pc->k;
514 continue;
515
516 case BPF_ALU|BPF_RSH|BPF_K:
517 A >>= pc->k;
518 continue;
519
520 case BPF_ALU|BPF_NEG:
521 A = -A;
522 continue;
523
524 case BPF_MISC|BPF_TAX:
525 X = A;
526 continue;
527
528 case BPF_MISC|BPF_TXA:
529 A = X;
530 continue;
531 }
532 }
533 }
534
535 /*
536 * Return true if the 'fcode' is a valid filter program.
537 * The constraints are that each jump be forward and to a valid
538 * code, that memory accesses are within valid ranges (to the
539 * extent that this can be checked statically; loads of packet
540 * data have to be, and are, also checked at run time), and that
541 * the code terminates with either an accept or reject.
542 *
543 * The kernel needs to be able to verify an application's filter code.
544 * Otherwise, a bogus program could easily crash the system.
545 */
546 int
bpf_validate(f,len)547 bpf_validate(f, len)
548 const struct bpf_insn *f;
549 int len;
550 {
551 u_int i, from;
552 const struct bpf_insn *p;
553
554 if (len < 1)
555 return 0;
556 /*
557 * There's no maximum program length in userland.
558 */
559 #if defined(KERNEL) || defined(_KERNEL)
560 if (len > BPF_MAXINSNS)
561 return 0;
562 #endif
563
564 for (i = 0; i < len; ++i) {
565 p = &f[i];
566 switch (BPF_CLASS(p->code)) {
567 /*
568 * Check that memory operations use valid addresses.
569 */
570 case BPF_LD:
571 case BPF_LDX:
572 switch (BPF_MODE(p->code)) {
573 case BPF_IMM:
574 break;
575 case BPF_ABS:
576 case BPF_IND:
577 case BPF_MSH:
578 /*
579 * There's no maximum packet data size
580 * in userland. The runtime packet length
581 * check suffices.
582 */
583 #if defined(KERNEL) || defined(_KERNEL)
584 /*
585 * More strict check with actual packet length
586 * is done runtime.
587 */
588 if (p->k >= bpf_maxbufsize)
589 return 0;
590 #endif
591 break;
592 case BPF_MEM:
593 if (p->k >= BPF_MEMWORDS)
594 return 0;
595 break;
596 case BPF_LEN:
597 break;
598 default:
599 return 0;
600 }
601 break;
602 case BPF_ST:
603 case BPF_STX:
604 if (p->k >= BPF_MEMWORDS)
605 return 0;
606 break;
607 case BPF_ALU:
608 switch (BPF_OP(p->code)) {
609 case BPF_ADD:
610 case BPF_SUB:
611 case BPF_MUL:
612 case BPF_OR:
613 case BPF_AND:
614 case BPF_LSH:
615 case BPF_RSH:
616 case BPF_NEG:
617 break;
618 case BPF_DIV:
619 /*
620 * Check for constant division by 0.
621 */
622 if (BPF_SRC(p->code) == BPF_K && p->k == 0)
623 return 0;
624 break;
625 default:
626 return 0;
627 }
628 break;
629 case BPF_JMP:
630 /*
631 * Check that jumps are within the code block,
632 * and that unconditional branches don't go
633 * backwards as a result of an overflow.
634 * Unconditional branches have a 32-bit offset,
635 * so they could overflow; we check to make
636 * sure they don't. Conditional branches have
637 * an 8-bit offset, and the from address is <=
638 * BPF_MAXINSNS, and we assume that BPF_MAXINSNS
639 * is sufficiently small that adding 255 to it
640 * won't overflow.
641 *
642 * We know that len is <= BPF_MAXINSNS, and we
643 * assume that BPF_MAXINSNS is < the maximum size
644 * of a u_int, so that i + 1 doesn't overflow.
645 *
646 * For userland, we don't know that the from
647 * or len are <= BPF_MAXINSNS, but we know that
648 * from <= len, and, except on a 64-bit system,
649 * it's unlikely that len, if it truly reflects
650 * the size of the program we've been handed,
651 * will be anywhere near the maximum size of
652 * a u_int. We also don't check for backward
653 * branches, as we currently support them in
654 * userland for the protochain operation.
655 */
656 from = i + 1;
657 switch (BPF_OP(p->code)) {
658 case BPF_JA:
659 #if defined(KERNEL) || defined(_KERNEL)
660 if (from + p->k < from || from + p->k >= len)
661 #else
662 if (from + p->k >= len)
663 #endif
664 return 0;
665 break;
666 case BPF_JEQ:
667 case BPF_JGT:
668 case BPF_JGE:
669 case BPF_JSET:
670 if (from + p->jt >= len || from + p->jf >= len)
671 return 0;
672 break;
673 default:
674 return 0;
675 }
676 break;
677 case BPF_RET:
678 break;
679 case BPF_MISC:
680 break;
681 default:
682 return 0;
683 }
684 }
685 return BPF_CLASS(f[len - 1].code) == BPF_RET;
686 }
687