/*      $OpenBSD: bpf_filter.c,v 1.37 2026/05/09 00:37:45 dlg Exp $     */
/*      $NetBSD: bpf_filter.c,v 1.12 1996/02/13 22:00:00 christos Exp $ */

/*
 * Copyright (c) 1990, 1991, 1992, 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. 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/param.h>
#ifndef _KERNEL
#include <stdlib.h>
#include <string.h>
#include "pcap.h"
#else
#include <sys/systm.h>
#endif

#ifdef _KERNEL
extern int bpf_maxbufsize;
#define Static
#else /* _KERNEL */
#define Static static
#endif /* _KERNEL */

#include <net/bpf.h>

struct bpf_mem {
        const u_char    *pkt;
        u_int            len;
};

Static u_int32_t        bpf_mem_ldw(const void *, u_int32_t, int *);
Static u_int32_t        bpf_mem_ldh(const void *, u_int32_t, int *);
Static u_int32_t        bpf_mem_ldb(const void *, u_int32_t, int *);

static const struct bpf_ops bpf_mem_ops = {
        bpf_mem_ldw,
        bpf_mem_ldh,
        bpf_mem_ldb,
};

Static int
bpf_memcpy(void *dst, const struct bpf_mem *bmp, u_int off, size_t len)
{
        struct bpf_mem bm = *bmp;

        if (bm.len < off)
                return -1;
        bm.len -= off;
        if (bm.len < len)
                return -1;
        bm.pkt += off;

        memcpy(dst, bm.pkt, len);

        return 0;
}

Static u_int32_t
bpf_mem_ldw(const void *mem, u_int32_t k, int *err)
{
        u_int32_t v;

        if (bpf_memcpy(&v, mem, k, sizeof(v)) == -1) {
                *err = 1;
                return (0);
        }

        *err = 0;
        return ntohl(v);
}

Static u_int32_t
bpf_mem_ldh(const void *mem, u_int32_t k, int *err)
{
        u_int16_t v;

        if (bpf_memcpy(&v, mem, k, sizeof(v)) == -1) {
                *err = 1;
                return (0);
        }

        *err = 0;
        return ntohs(v);
}

Static u_int32_t
bpf_mem_ldb(const void *mem, u_int32_t k, int *err)
{
        u_int8_t v;

        if (bpf_memcpy(&v, mem, k, sizeof(v)) == -1) {
                *err = 1;
                return (0);
        }

        *err = 0;
        return v;
}

/*
 * 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, const u_char *pkt,
    u_int wirelen, u_int buflen)
{
        struct bpf_mem bm;

        bm.pkt = pkt;
        bm.len = buflen;

        return _bpf_filter(pc, &bpf_mem_ops, &bm, wirelen);
}

u_int
_bpf_filter(const struct bpf_insn *pc, const struct bpf_ops *ops,
    const void *pkt, u_int wirelen)
{
        u_int32_t A = 0, X = 0;
        u_int32_t k;
        int32_t mem[BPF_MEMWORDS];
        int err;

        if (pc == NULL) {
                /*
                 * No filter means accept all.
                 */
                return (u_int)-1;
        }

        memset(mem, 0, sizeof(mem));

        --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:
                        A = ops->ldw(pkt, pc->k, &err);
                        if (err != 0)
                                return 0;
                        continue;

                case BPF_LD|BPF_H|BPF_ABS:
                        A = ops->ldh(pkt, pc->k, &err);
                        if (err != 0)
                                return 0;
                        continue;

                case BPF_LD|BPF_B|BPF_ABS:
                        A = ops->ldb(pkt, pc->k, &err);
                        if (err != 0)
                                return 0;
                        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_RND:
                        A = arc4random();
                        continue;

                case BPF_LD|BPF_W|BPF_IND:
                        k = X + pc->k;
                        A = ops->ldw(pkt, k, &err);
                        if (err != 0)
                                return 0;
                        continue;

                case BPF_LD|BPF_H|BPF_IND:
                        k = X + pc->k;
                        A = ops->ldh(pkt, k, &err);
                        if (err != 0)
                                return 0;
                        continue;

                case BPF_LD|BPF_B|BPF_IND:
                        k = X + pc->k;
                        A = ops->ldb(pkt, k, &err);
                        if (err != 0)
                                return 0;
                        continue;

                case BPF_LDX|BPF_MSH|BPF_B:
                        X = ops->ldb(pkt, pc->k, &err);
                        if (err != 0)
                                return 0;
                        X &= 0xf;
                        X <<= 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_MOD|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_XOR|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_MOD|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_XOR|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 and memory operations use valid addresses.  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(struct bpf_insn *f, int len)
{
        u_int i, from;
        struct bpf_insn *p;

        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 (p->k >= bpf_maxbufsize)
                                        return 0;
                                break;
                        case BPF_MEM:
                                if (p->k >= BPF_MEMWORDS)
                                        return 0;
                                break;
                        case BPF_LEN:
                        case BPF_RND:
                                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_MUL:
                        case BPF_OR:
                        case BPF_XOR:
                        case BPF_AND:
                        case BPF_LSH:
                        case BPF_RSH:
                        case BPF_NEG:
                                break;
                        case BPF_DIV:
                        case BPF_MOD:
                                /*
                                 * Check for constant division by 0.
                                 */
                                if (BPF_SRC(p->code) == BPF_K && p->k == 0)
                                        return 0;
                                break;
                        default:
                                return 0;
                        }
                        break;
                case BPF_JMP:
                        /*
                         * Check that jumps are forward, and within
                         * the code block.
                         */
                        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;
}
#endif