2 * Copyright (c) 1990, 1991, 1993
3 * The Regents of the University of California. All rights reserved.
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
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
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.
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
38 * @(#)bpf_filter.c 8.1 (Berkeley) 6/10/93
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 $
44 #include <sys/param.h>
46 #if defined(sparc) || defined(mips) || defined(ibm032)
51 #define EXTRACT_SHORT(p) ((u_int16_t)ntohs(*(u_int16_t *)p))
52 #define EXTRACT_LONG(p) (ntohl(*(u_int32_t *)p))
54 #define EXTRACT_SHORT(p)\
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)
70 #define MINDEX(m, k) \
83 extern int bpf_maxbufsize;
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);
89 m_xword(struct mbuf *m, bpf_u_int32 k, int *err)
103 cp = mtod(m, u_char *) + k;
106 return EXTRACT_LONG(cp);
109 if (m0 == 0 || m0->m_len + len - k < 4)
112 np = mtod(m0, u_char *);
117 ((u_int32_t)cp[0] << 24) |
118 ((u_int32_t)np[0] << 16) |
119 ((u_int32_t)np[1] << 8) |
124 ((u_int32_t)cp[0] << 24) |
125 ((u_int32_t)cp[1] << 16) |
126 ((u_int32_t)np[0] << 8) |
131 ((u_int32_t)cp[0] << 24) |
132 ((u_int32_t)cp[1] << 16) |
133 ((u_int32_t)cp[2] << 8) |
142 m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err)
156 cp = mtod(m, u_char *) + k;
159 return EXTRACT_SHORT(cp);
165 return (cp[0] << 8) | mtod(m0, u_char *)[0];
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
178 bpf_filter(const struct bpf_insn *pc, u_char *p, u_int wirelen, u_int buflen)
180 u_int32_t A = 0, X = 0;
182 int32_t mem[BPF_MEMWORDS];
186 * No filter means accept all.
208 case BPF_LD|BPF_W|BPF_ABS:
210 if (k > buflen || sizeof(int32_t) > buflen - k) {
216 A = m_xword((struct mbuf *)p, k, &merr);
225 if (((intptr_t)(p + k) & 3) != 0)
226 A = EXTRACT_LONG(&p[k]);
229 A = ntohl(*(int32_t *)(p + k));
232 case BPF_LD|BPF_H|BPF_ABS:
234 if (k > buflen || sizeof(int16_t) > buflen - k) {
240 A = m_xhalf((struct mbuf *)p, k, &merr);
246 A = EXTRACT_SHORT(&p[k]);
249 case BPF_LD|BPF_B|BPF_ABS:
257 m = (struct mbuf *)p;
259 A = mtod(m, u_char *)[k];
268 case BPF_LD|BPF_W|BPF_LEN:
272 case BPF_LDX|BPF_W|BPF_LEN:
276 case BPF_LD|BPF_W|BPF_IND:
278 if (pc->k > buflen || X > buflen - pc->k ||
279 sizeof(int32_t) > buflen - k) {
285 A = m_xword((struct mbuf *)p, k, &merr);
294 if (((intptr_t)(p + k) & 3) != 0)
295 A = EXTRACT_LONG(&p[k]);
298 A = ntohl(*(int32_t *)(p + k));
301 case BPF_LD|BPF_H|BPF_IND:
303 if (X > buflen || pc->k > buflen - X ||
304 sizeof(int16_t) > buflen - k) {
310 A = m_xhalf((struct mbuf *)p, k, &merr);
318 A = EXTRACT_SHORT(&p[k]);
321 case BPF_LD|BPF_B|BPF_IND:
323 if (pc->k >= buflen || X >= buflen - pc->k) {
329 m = (struct mbuf *)p;
331 A = mtod(m, u_char *)[k];
340 case BPF_LDX|BPF_MSH|BPF_B:
348 m = (struct mbuf *)p;
350 X = (mtod(m, char *)[k] & 0xf) << 2;
356 X = (p[pc->k] & 0xf) << 2;
363 case BPF_LDX|BPF_IMM:
371 case BPF_LDX|BPF_MEM:
387 case BPF_JMP|BPF_JGT|BPF_K:
388 pc += (A > pc->k) ? pc->jt : pc->jf;
391 case BPF_JMP|BPF_JGE|BPF_K:
392 pc += (A >= pc->k) ? pc->jt : pc->jf;
395 case BPF_JMP|BPF_JEQ|BPF_K:
396 pc += (A == pc->k) ? pc->jt : pc->jf;
399 case BPF_JMP|BPF_JSET|BPF_K:
400 pc += (A & pc->k) ? pc->jt : pc->jf;
403 case BPF_JMP|BPF_JGT|BPF_X:
404 pc += (A > X) ? pc->jt : pc->jf;
407 case BPF_JMP|BPF_JGE|BPF_X:
408 pc += (A >= X) ? pc->jt : pc->jf;
411 case BPF_JMP|BPF_JEQ|BPF_X:
412 pc += (A == X) ? pc->jt : pc->jf;
415 case BPF_JMP|BPF_JSET|BPF_X:
416 pc += (A & X) ? pc->jt : pc->jf;
419 case BPF_ALU|BPF_ADD|BPF_X:
423 case BPF_ALU|BPF_SUB|BPF_X:
427 case BPF_ALU|BPF_MUL|BPF_X:
431 case BPF_ALU|BPF_DIV|BPF_X:
437 case BPF_ALU|BPF_AND|BPF_X:
441 case BPF_ALU|BPF_OR|BPF_X:
445 case BPF_ALU|BPF_LSH|BPF_X:
449 case BPF_ALU|BPF_RSH|BPF_X:
453 case BPF_ALU|BPF_ADD|BPF_K:
457 case BPF_ALU|BPF_SUB|BPF_K:
461 case BPF_ALU|BPF_MUL|BPF_K:
465 case BPF_ALU|BPF_DIV|BPF_K:
469 case BPF_ALU|BPF_AND|BPF_K:
473 case BPF_ALU|BPF_OR|BPF_K:
477 case BPF_ALU|BPF_LSH|BPF_K:
481 case BPF_ALU|BPF_RSH|BPF_K:
485 case BPF_ALU|BPF_NEG:
489 case BPF_MISC|BPF_TAX:
493 case BPF_MISC|BPF_TXA:
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.
509 * The kernel needs to be able to verify an application's filter code.
510 * Otherwise, a bogus program could easily crash the system.
513 bpf_validate(const struct bpf_insn *f, int len)
516 const struct bpf_insn *p;
518 if (len < 1 || len > BPF_MAXINSNS)
521 for (i = 0; i < len; ++i) {
523 switch (BPF_CLASS(p->code)) {
525 * Check that memory operations use valid addresses.
529 switch (BPF_MODE(p->code)) {
536 * More strict check with actual packet length
539 if (p->k >= bpf_maxbufsize)
543 if (p->k >= BPF_MEMWORDS)
554 if (p->k >= BPF_MEMWORDS)
558 switch (BPF_OP(p->code)) {
570 * Check for constant division by 0.
572 if (BPF_RVAL(p->code) == BPF_K && p->k == 0)
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
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.
597 switch (BPF_OP(p->code)) {
599 if (from + p->k < from || from + p->k >= len)
606 if (from + p->jt >= len || from + p->jf >= len)
621 return BPF_CLASS(f[len - 1].code) == BPF_RET;