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bpf_filter.c

/*-
 * 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[] _U_ =
    "@(#) $Header: /tcpdump/master/libpcap/bpf/net/bpf_filter.c,v 1.44 2003/11/15 23:24:07 guy Exp $ (LBL)";
#endif

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef WIN32

#include <pcap-stdinc.h>

#else /* WIN32 */

#include <sys/param.h>
#include <sys/types.h>
#include <sys/time.h>

#define     SOLARIS     (defined(sun) && (defined(__SVR4) || defined(__svr4__)))
#if defined(__hpux) || SOLARIS
# include <sys/sysmacros.h>
# include <sys/stream.h>
# define    mbuf  msgb
# define    m_next      b_cont
# define    MLEN(m)     ((m)->b_wptr - (m)->b_rptr)
# define    mtod(m,t)   ((t)(m)->b_rptr)
#else
# define    MLEN(m)     ((m)->m_len)
#endif

#endif /* WIN32 */

#include <pcap-bpf.h>

#if !defined(KERNEL) && !defined(_KERNEL)
#include <stdlib.h>
#endif

#define int32 bpf_int32
#define u_int32 bpf_u_int32

#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
#ifndef WIN32
#include <netinet/in.h>
#endif

#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

#if defined(KERNEL) || defined(_KERNEL)
# if !defined(__hpux) && !SOLARIS
#include <sys/mbuf.h>
# endif
#define MINDEX(len, _m, _k) \
{ \
      len = MLEN(m); \
      while ((_k) >= len) { \
            (_k) -= len; \
            (_m) = (_m)->m_next; \
            if ((_m) == 0) \
                  return 0; \
            len = MLEN(m); \
      } \
}

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;

      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 || MLEN(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 struct mbuf *m;
      register int k, *err;
{
      register int len;
      register u_char *cp;
      register struct mbuf *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;
}
#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
 * 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];
#if defined(KERNEL) || defined(_KERNEL)
      struct mbuf *m, *n;
      int merr, len;

      if (buflen == 0) {
            m = (struct mbuf *)p;
            p = mtod(m, u_char *);
            buflen = MLEN(m);
      } else
            m = NULL;
#endif

      if (pc == 0)
            /*
             * No filter means accept all.
             */
            return (u_int)-1;
      A = 0;
      X = 0;
      --pc;
      while (1) {
            ++pc;
            switch (pc->code) {

            default:
#if defined(KERNEL) || defined(_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(int32) > buflen) {
#if defined(KERNEL) || defined(_KERNEL)
                        if (m == NULL)
                              return 0;
                        A = m_xword(m, k, &merr);
                        if (merr != 0)
                              return 0;
                        continue;
#else
                        return 0;
#endif
                  }
                  A = EXTRACT_LONG(&p[k]);
                  continue;

            case BPF_LD|BPF_H|BPF_ABS:
                  k = pc->k;
                  if (k + sizeof(short) > buflen) {
#if defined(KERNEL) || defined(_KERNEL)
                        if (m == NULL)
                              return 0;
                        A = m_xhalf(m, k, &merr);
                        if (merr != 0)
                              return 0;
                        continue;
#else
                        return 0;
#endif
                  }
                  A = EXTRACT_SHORT(&p[k]);
                  continue;

            case BPF_LD|BPF_B|BPF_ABS:
                  k = pc->k;
                  if (k >= buflen) {
#if defined(KERNEL) || defined(_KERNEL)
                        if (m == NULL)
                              return 0;
                        n = m;
                        MINDEX(len, n, k);
                        A = mtod(n, 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(int32) > buflen) {
#if defined(KERNEL) || defined(_KERNEL)
                        if (m == NULL)
                              return 0;
                        A = m_xword(m, k, &merr);
                        if (merr != 0)
                              return 0;
                        continue;
#else
                        return 0;
#endif
                  }
                  A = EXTRACT_LONG(&p[k]);
                  continue;

            case BPF_LD|BPF_H|BPF_IND:
                  k = X + pc->k;
                  if (k + sizeof(short) > buflen) {
#if defined(KERNEL) || defined(_KERNEL)
                        if (m == NULL)
                              return 0;
                        A = m_xhalf(m, 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) {
#if defined(KERNEL) || defined(_KERNEL)
                        if (m == NULL)
                              return 0;
                        n = m;
                        MINDEX(len, n, k);
                        A = mtod(n, 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) {
#if defined(KERNEL) || defined(_KERNEL)
                        if (m == NULL)
                              return 0;
                        n = m;
                        MINDEX(len, n, k);
                        X = (mtod(n, 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;
            }
      }
}


/*
 * 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 >= (unsigned)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;
}

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