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f-stack/freebsd/net/bpf_filter.c

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/*-
* Copyright (c) 1990, 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from the Stanford/CMU enet packet filter,
* (net/enet.c) distributed as part of 4.3BSD, and code contributed
* to Berkeley by Steven McCanne and Van Jacobson both of Lawrence
* Berkeley Laboratory.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)bpf_filter.c 8.1 (Berkeley) 6/10/93
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#if !defined(_KERNEL)
#include <strings.h>
#endif
#if !defined(_KERNEL) || defined(sun)
#include <netinet/in.h>
#endif
#ifndef __i386__
#define BPF_ALIGN
#endif
#ifndef BPF_ALIGN
#define EXTRACT_SHORT(p) ((u_int16_t)ntohs(*(u_int16_t *)p))
#define EXTRACT_LONG(p) (ntohl(*(u_int32_t *)p))
#else
#define EXTRACT_SHORT(p)\
((u_int16_t)\
((u_int16_t)*((u_char *)p+0)<<8|\
(u_int16_t)*((u_char *)p+1)<<0))
#define EXTRACT_LONG(p)\
((u_int32_t)*((u_char *)p+0)<<24|\
(u_int32_t)*((u_char *)p+1)<<16|\
(u_int32_t)*((u_char *)p+2)<<8|\
(u_int32_t)*((u_char *)p+3)<<0)
#endif
#ifdef _KERNEL
#include <sys/mbuf.h>
#else
#include <stdlib.h>
#endif
#include <net/bpf.h>
#ifdef _KERNEL
#define MINDEX(m, k) \
{ \
register int len = m->m_len; \
\
while (k >= len) { \
k -= len; \
m = m->m_next; \
if (m == 0) \
return (0); \
len = m->m_len; \
} \
}
static u_int16_t m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err);
static u_int32_t m_xword(struct mbuf *m, bpf_u_int32 k, int *err);
static u_int32_t
m_xword(struct mbuf *m, bpf_u_int32 k, int *err)
{
size_t len;
u_char *cp, *np;
struct mbuf *m0;
len = m->m_len;
while (k >= len) {
k -= len;
m = m->m_next;
if (m == NULL)
goto bad;
len = m->m_len;
}
cp = mtod(m, u_char *) + k;
if (len - k >= 4) {
*err = 0;
return (EXTRACT_LONG(cp));
}
m0 = m->m_next;
if (m0 == NULL || m0->m_len + len - k < 4)
goto bad;
*err = 0;
np = mtod(m0, u_char *);
switch (len - k) {
case 1:
return (((u_int32_t)cp[0] << 24) |
((u_int32_t)np[0] << 16) |
((u_int32_t)np[1] << 8) |
(u_int32_t)np[2]);
case 2:
return (((u_int32_t)cp[0] << 24) |
((u_int32_t)cp[1] << 16) |
((u_int32_t)np[0] << 8) |
(u_int32_t)np[1]);
default:
return (((u_int32_t)cp[0] << 24) |
((u_int32_t)cp[1] << 16) |
((u_int32_t)cp[2] << 8) |
(u_int32_t)np[0]);
}
bad:
*err = 1;
return (0);
}
static u_int16_t
m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err)
{
size_t len;
u_char *cp;
struct mbuf *m0;
len = m->m_len;
while (k >= len) {
k -= len;
m = m->m_next;
if (m == NULL)
goto bad;
len = m->m_len;
}
cp = mtod(m, u_char *) + k;
if (len - k >= 2) {
*err = 0;
return (EXTRACT_SHORT(cp));
}
m0 = m->m_next;
if (m0 == NULL)
goto bad;
*err = 0;
return ((cp[0] << 8) | mtod(m0, u_char *)[0]);
bad:
*err = 1;
return (0);
}
#endif
/*
* Execute the filter program starting at pc on the packet p
* wirelen is the length of the original packet
* buflen is the amount of data present
*/
u_int
bpf_filter(const struct bpf_insn *pc, u_char *p, u_int wirelen, u_int buflen)
{
u_int32_t A = 0, X = 0;
bpf_u_int32 k;
u_int32_t mem[BPF_MEMWORDS];
bzero(mem, sizeof(mem));
if (pc == NULL)
/*
* No filter means accept all.
*/
return ((u_int)-1);
--pc;
while (1) {
++pc;
switch (pc->code) {
default:
#ifdef _KERNEL
return (0);
#else
abort();
#endif
case BPF_RET|BPF_K:
return ((u_int)pc->k);
case BPF_RET|BPF_A:
return ((u_int)A);
case BPF_LD|BPF_W|BPF_ABS:
k = pc->k;
if (k > buflen || sizeof(int32_t) > buflen - k) {
#ifdef _KERNEL
int merr;
if (buflen != 0)
return (0);
A = m_xword((struct mbuf *)p, k, &merr);
if (merr != 0)
return (0);
continue;
#else
return (0);
#endif
}
#ifdef BPF_ALIGN
if (((intptr_t)(p + k) & 3) != 0)
A = EXTRACT_LONG(&p[k]);
else
#endif
A = ntohl(*(int32_t *)(p + k));
continue;
case BPF_LD|BPF_H|BPF_ABS:
k = pc->k;
if (k > buflen || sizeof(int16_t) > buflen - k) {
#ifdef _KERNEL
int merr;
if (buflen != 0)
return (0);
A = m_xhalf((struct mbuf *)p, k, &merr);
continue;
#else
return (0);
#endif
}
A = EXTRACT_SHORT(&p[k]);
continue;
case BPF_LD|BPF_B|BPF_ABS:
k = pc->k;
if (k >= buflen) {
#ifdef _KERNEL
struct mbuf *m;
if (buflen != 0)
return (0);
m = (struct mbuf *)p;
MINDEX(m, k);
A = mtod(m, u_char *)[k];
continue;
#else
return (0);
#endif
}
A = p[k];
continue;
case BPF_LD|BPF_W|BPF_LEN:
A = wirelen;
continue;
case BPF_LDX|BPF_W|BPF_LEN:
X = wirelen;
continue;
case BPF_LD|BPF_W|BPF_IND:
k = X + pc->k;
if (pc->k > buflen || X > buflen - pc->k ||
sizeof(int32_t) > buflen - k) {
#ifdef _KERNEL
int merr;
if (buflen != 0)
return (0);
A = m_xword((struct mbuf *)p, k, &merr);
if (merr != 0)
return (0);
continue;
#else
return (0);
#endif
}
#ifdef BPF_ALIGN
if (((intptr_t)(p + k) & 3) != 0)
A = EXTRACT_LONG(&p[k]);
else
#endif
A = ntohl(*(int32_t *)(p + k));
continue;
case BPF_LD|BPF_H|BPF_IND:
k = X + pc->k;
if (X > buflen || pc->k > buflen - X ||
sizeof(int16_t) > buflen - k) {
#ifdef _KERNEL
int merr;
if (buflen != 0)
return (0);
A = m_xhalf((struct mbuf *)p, k, &merr);
if (merr != 0)
return (0);
continue;
#else
return (0);
#endif
}
A = EXTRACT_SHORT(&p[k]);
continue;
case BPF_LD|BPF_B|BPF_IND:
k = X + pc->k;
if (pc->k >= buflen || X >= buflen - pc->k) {
#ifdef _KERNEL
struct mbuf *m;
if (buflen != 0)
return (0);
m = (struct mbuf *)p;
MINDEX(m, k);
A = mtod(m, u_char *)[k];
continue;
#else
return (0);
#endif
}
A = p[k];
continue;
case BPF_LDX|BPF_MSH|BPF_B:
k = pc->k;
if (k >= buflen) {
#ifdef _KERNEL
register struct mbuf *m;
if (buflen != 0)
return (0);
m = (struct mbuf *)p;
MINDEX(m, k);
X = (mtod(m, u_char *)[k] & 0xf) << 2;
continue;
#else
return (0);
#endif
}
X = (p[pc->k] & 0xf) << 2;
continue;
case BPF_LD|BPF_IMM:
A = pc->k;
continue;
case BPF_LDX|BPF_IMM:
X = pc->k;
continue;
case BPF_LD|BPF_MEM:
A = mem[pc->k];
continue;
case BPF_LDX|BPF_MEM:
X = mem[pc->k];
continue;
case BPF_ST:
mem[pc->k] = A;
continue;
case BPF_STX:
mem[pc->k] = X;
continue;
case BPF_JMP|BPF_JA:
pc += pc->k;
continue;
case BPF_JMP|BPF_JGT|BPF_K:
pc += (A > pc->k) ? pc->jt : pc->jf;
continue;
case BPF_JMP|BPF_JGE|BPF_K:
pc += (A >= pc->k) ? pc->jt : pc->jf;
continue;
case BPF_JMP|BPF_JEQ|BPF_K:
pc += (A == pc->k) ? pc->jt : pc->jf;
continue;
case BPF_JMP|BPF_JSET|BPF_K:
pc += (A & pc->k) ? pc->jt : pc->jf;
continue;
case BPF_JMP|BPF_JGT|BPF_X:
pc += (A > X) ? pc->jt : pc->jf;
continue;
case BPF_JMP|BPF_JGE|BPF_X:
pc += (A >= X) ? pc->jt : pc->jf;
continue;
case BPF_JMP|BPF_JEQ|BPF_X:
pc += (A == X) ? pc->jt : pc->jf;
continue;
case BPF_JMP|BPF_JSET|BPF_X:
pc += (A & X) ? pc->jt : pc->jf;
continue;
case BPF_ALU|BPF_ADD|BPF_X:
A += X;
continue;
case BPF_ALU|BPF_SUB|BPF_X:
A -= X;
continue;
case BPF_ALU|BPF_MUL|BPF_X:
A *= X;
continue;
case BPF_ALU|BPF_DIV|BPF_X:
if (X == 0)
return (0);
A /= X;
continue;
case BPF_ALU|BPF_AND|BPF_X:
A &= X;
continue;
case BPF_ALU|BPF_OR|BPF_X:
A |= X;
continue;
case BPF_ALU|BPF_LSH|BPF_X:
A <<= X;
continue;
case BPF_ALU|BPF_RSH|BPF_X:
A >>= X;
continue;
case BPF_ALU|BPF_ADD|BPF_K:
A += pc->k;
continue;
case BPF_ALU|BPF_SUB|BPF_K:
A -= pc->k;
continue;
case BPF_ALU|BPF_MUL|BPF_K:
A *= pc->k;
continue;
case BPF_ALU|BPF_DIV|BPF_K:
A /= pc->k;
continue;
case BPF_ALU|BPF_AND|BPF_K:
A &= pc->k;
continue;
case BPF_ALU|BPF_OR|BPF_K:
A |= pc->k;
continue;
case BPF_ALU|BPF_LSH|BPF_K:
A <<= pc->k;
continue;
case BPF_ALU|BPF_RSH|BPF_K:
A >>= pc->k;
continue;
case BPF_ALU|BPF_NEG:
A = -A;
continue;
case BPF_MISC|BPF_TAX:
X = A;
continue;
case BPF_MISC|BPF_TXA:
A = X;
continue;
}
}
}
#ifdef _KERNEL
static const u_short bpf_code_map[] = {
0x10ff, /* 0x00-0x0f: 1111111100001000 */
0x3070, /* 0x10-0x1f: 0000111000001100 */
0x3131, /* 0x20-0x2f: 1000110010001100 */
0x3031, /* 0x30-0x3f: 1000110000001100 */
0x3131, /* 0x40-0x4f: 1000110010001100 */
0x1011, /* 0x50-0x5f: 1000100000001000 */
0x1013, /* 0x60-0x6f: 1100100000001000 */
0x1010, /* 0x70-0x7f: 0000100000001000 */
0x0093, /* 0x80-0x8f: 1100100100000000 */
0x0000, /* 0x90-0x9f: 0000000000000000 */
0x0000, /* 0xa0-0xaf: 0000000000000000 */
0x0002, /* 0xb0-0xbf: 0100000000000000 */
0x0000, /* 0xc0-0xcf: 0000000000000000 */
0x0000, /* 0xd0-0xdf: 0000000000000000 */
0x0000, /* 0xe0-0xef: 0000000000000000 */
0x0000 /* 0xf0-0xff: 0000000000000000 */
};
#define BPF_VALIDATE_CODE(c) \
((c) <= 0xff && (bpf_code_map[(c) >> 4] & (1 << ((c) & 0xf))) != 0)
/*
* Return true if the 'fcode' is a valid filter program.
* The constraints are that each jump be forward and to a valid
* code. The code must terminate with either an accept or reject.
*
* The kernel needs to be able to verify an application's filter code.
* Otherwise, a bogus program could easily crash the system.
*/
int
bpf_validate(const struct bpf_insn *f, int len)
{
register int i;
register const struct bpf_insn *p;
/* Do not accept negative length filter. */
if (len < 0)
return (0);
/* An empty filter means accept all. */
if (len == 0)
return (1);
for (i = 0; i < len; ++i) {
p = &f[i];
/*
* Check that the code is valid.
*/
if (!BPF_VALIDATE_CODE(p->code))
return (0);
/*
* Check that that jumps are forward, and within
* the code block.
*/
if (BPF_CLASS(p->code) == BPF_JMP) {
register u_int offset;
if (p->code == (BPF_JMP|BPF_JA))
offset = p->k;
else
offset = p->jt > p->jf ? p->jt : p->jf;
if (offset >= (u_int)(len - i) - 1)
return (0);
continue;
}
/*
* Check that memory operations use valid addresses.
*/
if (p->code == BPF_ST || p->code == BPF_STX ||
p->code == (BPF_LD|BPF_MEM) ||
p->code == (BPF_LDX|BPF_MEM)) {
if (p->k >= BPF_MEMWORDS)
return (0);
continue;
}
/*
* Check for constant division by 0.
*/
if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0)
return (0);
}
return (BPF_CLASS(f[len - 1].code) == BPF_RET);
}
#endif
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