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darrenr 2012-01-30 19:38:45 +00:00
parent 56581d9c24
commit 3646154e14
1 changed files with 595 additions and 0 deletions
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/* $NetBSD: bpf_filter.c,v 1.4 2012/01/30 19:38:45 darrenr Exp $ */
/*-
* Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 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.c 7.5 (Berkeley) 7/15/91
*/
#if !(defined(lint) || defined(KERNEL) || defined(_KERNEL))
static const char rcsid[] =
"@(#) Header: /devel/CVS/IP-Filter/bpf_filter.c,v 2.2.2.3 2006/10/03 11:25:56 darrenr Exp (LBL)";
#endif
#include <sys/param.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <net/if.h>
#include "netinet/ip_compat.h"
#include "bpf-ipf.h"
#if (defined(__hpux) || SOLARIS) && (defined(_KERNEL) || defined(KERNEL))
# include <sys/sysmacros.h>
# include <sys/stream.h>
#endif
#include "pcap-ipf.h"
#if !defined(KERNEL) && !defined(_KERNEL)
#include <stdlib.h>
#endif
#define int32 bpf_int32
#define u_int32 bpf_u_int32
static int m_xword __P((mb_t *, int, int *));
static int m_xhalf __P((mb_t *, int, int *));
#ifndef LBL_ALIGN
/*
* XXX - IA-64? If not, this probably won't work on Win64 IA-64
* systems, unless LBL_ALIGN is defined elsewhere for them.
* XXX - SuperH? If not, this probably won't work on WinCE SuperH
* systems, unless LBL_ALIGN is defined elsewhere for them.
*/
#if defined(sparc) || defined(__sparc__) || defined(mips) || \
defined(ibm032) || defined(__alpha) || defined(__hpux) || \
defined(__arm__)
#define LBL_ALIGN
#endif
#endif
#ifndef LBL_ALIGN
#define EXTRACT_SHORT(p) ((u_short)ntohs(*(u_short *)p))
#define EXTRACT_LONG(p) (ntohl(*(u_int32 *)p))
#else
#define EXTRACT_SHORT(p)\
((u_short)\
((u_short)*((u_char *)p+0)<<8|\
(u_short)*((u_char *)p+1)<<0))
#define EXTRACT_LONG(p)\
((u_int32)*((u_char *)p+0)<<24|\
(u_int32)*((u_char *)p+1)<<16|\
(u_int32)*((u_char *)p+2)<<8|\
(u_int32)*((u_char *)p+3)<<0)
#endif
#define MINDEX(len, _m, _k) \
{ \
len = M_LEN(m); \
while ((_k) >= len) { \
(_k) -= len; \
(_m) = (_m)->m_next; \
if ((_m) == 0) \
return 0; \
len = M_LEN(m); \
} \
}
static int
m_xword(m, k, err)
register mb_t *m;
register int k, *err;
{
register int len;
register u_char *cp, *np;
register mb_t *m0;
MINDEX(len, m, k);
cp = MTOD(m, u_char *) + k;
if (len - k >= 4) {
*err = 0;
return EXTRACT_LONG(cp);
}
m0 = m->m_next;
if (m0 == 0 || M_LEN(m0) + len - k < 4)
goto bad;
*err = 0;
np = MTOD(m0, u_char *);
switch (len - k) {
case 1:
return (cp[0] << 24) | (np[0] << 16) | (np[1] << 8) | np[2];
case 2:
return (cp[0] << 24) | (cp[1] << 16) | (np[0] << 8) | np[1];
default:
return (cp[0] << 24) | (cp[1] << 16) | (cp[2] << 8) | np[0];
}
bad:
*err = 1;
return 0;
}
static int
m_xhalf(m, k, err)
register mb_t *m;
register int k, *err;
{
register int len;
register u_char *cp;
register mb_t *m0;
MINDEX(len, m, k);
cp = MTOD(m, u_char *) + k;
if (len - k >= 2) {
*err = 0;
return EXTRACT_SHORT(cp);
}
m0 = m->m_next;
if (m0 == 0)
goto bad;
*err = 0;
return (cp[0] << 8) | MTOD(m0, u_char *)[0];
bad:
*err = 1;
return 0;
}
/*
* 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
* For the kernel, p is assumed to be a pointer to an mbuf if buflen is 0,
* in all other cases, p is a pointer to a buffer and buflen is its size.
*/
u_int
bpf_filter(pc, p, wirelen, buflen)
register struct bpf_insn *pc;
register u_char *p;
u_int wirelen;
register u_int buflen;
{
register u_int32 A, X;
register int k;
int32 mem[BPF_MEMWORDS];
mb_t *m, *n;
int merr = 0; /* XXX: GCC */
int len;
if (buflen == 0) {
m = (mb_t *)p;
p = MTOD(m, u_char *);
buflen = M_LEN(m);
} else
m = NULL;
if (pc == 0)
/*
* No filter means accept all.
*/
return (u_int)-1;
A = 0;
X = 0;
--pc;
while (1) {
++pc;
switch (pc->code) {
default:
return 0;
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 + sizeof(int32) > buflen) {
if (m == NULL)
return 0;
A = m_xword(m, k, &merr);
if (merr != 0)
return 0;
continue;
}
A = EXTRACT_LONG(&p[k]);
continue;
case BPF_LD|BPF_H|BPF_ABS:
k = pc->k;
if (k + sizeof(short) > buflen) {
if (m == NULL)
return 0;
A = m_xhalf(m, k, &merr);
if (merr != 0)
return 0;
continue;
}
A = EXTRACT_SHORT(&p[k]);
continue;
case BPF_LD|BPF_B|BPF_ABS:
k = pc->k;
if (k >= buflen) {
if (m == NULL)
return 0;
n = m;
MINDEX(len, n, k);
A = MTOD(n, u_char *)[k];
continue;
}
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 (k + sizeof(int32) > buflen) {
if (m == NULL)
return 0;
A = m_xword(m, k, &merr);
if (merr != 0)
return 0;
continue;
}
A = EXTRACT_LONG(&p[k]);
continue;
case BPF_LD|BPF_H|BPF_IND:
k = X + pc->k;
if (k + sizeof(short) > buflen) {
if (m == NULL)
return 0;
A = m_xhalf(m, k, &merr);
if (merr != 0)
return 0;
continue;
}
A = EXTRACT_SHORT(&p[k]);
continue;
case BPF_LD|BPF_B|BPF_IND:
k = X + pc->k;
if (k >= buflen) {
if (m == NULL)
return 0;
n = m;
MINDEX(len, n, k);
A = MTOD(n, u_char *)[k];
continue;
}
A = p[k];
continue;
case BPF_LDX|BPF_MSH|BPF_B:
k = pc->k;
if (k >= buflen) {
if (m == NULL)
return 0;
n = m;
MINDEX(len, n, k);
X = (MTOD(n, char *)[k] & 0xf) << 2;
continue;
}
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;
}
}
}
/*
* Return true if the 'fcode' is a valid filter program.
* The constraints are that each jump be forward and to a valid
* code, that memory accesses are within valid ranges (to the
* extent that this can be checked statically; loads of packet
* data have to be, and are, also checked at run time), and that
* the code terminates 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(f, len)
struct bpf_insn *f;
int len;
{
u_int i, from;
const struct bpf_insn *p;
if (len == 0)
return 1;
if (len < 1 || len > BPF_MAXINSNS)
return 0;
for (i = 0; i < len; ++i) {
p = &f[i];
switch (BPF_CLASS(p->code)) {
/*
* Check that memory operations use valid addresses.
*/
case BPF_LD:
case BPF_LDX:
switch (BPF_MODE(p->code)) {
case BPF_IMM:
break;
case BPF_ABS:
case BPF_IND:
case BPF_MSH:
/*
* More strict check with actual packet length
* is done runtime.
*/
#if 0
if (p->k >= bpf_maxbufsize)
return 0;
#endif
break;
case BPF_MEM:
if (p->k >= BPF_MEMWORDS)
return 0;
break;
case BPF_LEN:
break;
default:
return 0;
}
break;
case BPF_ST:
case BPF_STX:
if (p->k >= BPF_MEMWORDS)
return 0;
break;
case BPF_ALU:
switch (BPF_OP(p->code)) {
case BPF_ADD:
case BPF_SUB:
case BPF_OR:
case BPF_AND:
case BPF_LSH:
case BPF_RSH:
case BPF_NEG:
break;
case BPF_DIV:
/*
* Check for constant division by 0.
*/
if (BPF_RVAL(p->code) == BPF_K && p->k == 0)
return 0;
default:
return 0;
}
break;
case BPF_JMP:
/*
* Check that jumps are within the code block,
* and that unconditional branches don't go
* backwards as a result of an overflow.
* Unconditional branches have a 32-bit offset,
* so they could overflow; we check to make
* sure they don't. Conditional branches have
* an 8-bit offset, and the from address is <=
* BPF_MAXINSNS, and we assume that BPF_MAXINSNS
* is sufficiently small that adding 255 to it
* won't overflow.
*
* We know that len is <= BPF_MAXINSNS, and we
* assume that BPF_MAXINSNS is < the maximum size
* of a u_int, so that i + 1 doesn't overflow.
*/
from = i + 1;
switch (BPF_OP(p->code)) {
case BPF_JA:
if (from + p->k < from || from + p->k >= len)
return 0;
break;
case BPF_JEQ:
case BPF_JGT:
case BPF_JGE:
case BPF_JSET:
if (from + p->jt >= len || from + p->jf >= len)
return 0;
break;
default:
return 0;
}
break;
case BPF_RET:
break;
case BPF_MISC:
break;
default:
return 0;
}
}
return BPF_CLASS(f[len - 1].code) == BPF_RET;
}