/*
* 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.
* 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_filter.c 8.1 (Berkeley) 6/10/93
*
* $Id: bpf_filter.c,v 1.8 1997/02/22 09:40:57 peter Exp $
*/
#include <sys/param.h>
#ifdef sun
#include <netinet/in.h>
#endif
#if defined(sparc) || defined(mips) || defined(ibm032)
#define BPF_ALIGN
#endif
#ifndef BPF_ALIGN
#define EXTRACT_SHORT(p) ((u_short)ntohs(*(u_short *)p))
#define EXTRACT_LONG(p) (ntohl(*(u_long *)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_long)*((u_char *)p+0)<<24|\
(u_long)*((u_char *)p+1)<<16|\
(u_long)*((u_char *)p+2)<<8|\
(u_long)*((u_char *)p+3)<<0)
#endif
#ifdef KERNEL
#include <sys/mbuf.h>
#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 int m_xhalf __P((struct mbuf *m, int k, int *err));
static int m_xword __P((struct mbuf *m, int k, int *err));
static int
m_xword(m, k, err)
register struct mbuf *m;
register int k, *err;
{
register int len;
register u_char *cp, *np;
register struct mbuf *m0;
len = m->m_len;
while (k >= len) {
k -= len;
m = m->m_next;
if (m == 0)
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 == 0 || m0->m_len + 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 struct mbuf *m;
register int k, *err;
{
register int len;
register u_char *cp;
register struct mbuf *m0;
len = m->m_len;
while (k >= len) {
k -= len;
m = m->m_next;
if (m == 0)
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 == 0)
goto bad;
*err = 0;
return (cp[0] << 8) | mtod(m0, u_char *)[0];
bad:
*err = 1;
return 0;
}
#endif
#include <net/bpf.h>
/*
* 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(pc, p, wirelen, buflen)
register struct bpf_insn *pc;
register u_char *p;
u_int wirelen;
register u_int buflen;
{
register u_long A = 0, X = 0;
register int k;
long mem[BPF_MEMWORDS];
if (pc == 0)
/*
* 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 + sizeof(long) > buflen) {
#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 (((int)(p + k) & 3) != 0)
A = EXTRACT_LONG(&p[k]);
else
#endif
A = ntohl(*(long *)(p + k));
continue;
case BPF_LD|BPF_H|BPF_ABS:
k = pc->k;
if (k + sizeof(short) > buflen) {
#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
register 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 (k + sizeof(long) > buflen) {
#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 (((int)(p + k) & 3) != 0)
A = EXTRACT_LONG(&p[k]);
else
#endif
A = ntohl(*(long *)(p + k));
continue;
case BPF_LD|BPF_H|BPF_IND:
k = X + pc->k;
if (k + sizeof(short) > buflen) {
#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 (k >= buflen) {
#ifdef KERNEL
register struct mbuf *m;
if (buflen != 0)
return 0;
m = (struct mbuf *)p;
MINDEX(m, k);
A = mtod(m, 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, 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
/*
* 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.
* 'valid' is an array for use by the routine (it must be at least
* 'len' bytes long).
*
* 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;
{
register int i;
register struct bpf_insn *p;
for (i = 0; i < len; ++i) {
/*
* Check that that jumps are forward, and within
* the code block.
*/
p = &f[i];
if (BPF_CLASS(p->code) == BPF_JMP) {
register int from = i + 1;
if (BPF_OP(p->code) == BPF_JA) {
if (from + p->k >= len)
return 0;
}
else if (from + p->jt >= len || from + p->jf >= len)
return 0;
}
/*
* Check that memory operations use valid addresses.
*/
if ((BPF_CLASS(p->code) == BPF_ST ||
(BPF_CLASS(p->code) == BPF_LD &&
(p->code & 0xe0) == BPF_MEM)) &&
(p->k >= BPF_MEMWORDS || p->k < 0))
return 0;
/*
* 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
