/*
 * 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. 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
 *
 * $FreeBSD: src/sys/net/bpf_filter.c,v 1.17 1999/12/29 04:38:31 peter Exp $
 */

#include <sys/systm.h>
#include <sys/param.h>

#if defined(sparc) || defined(mips) || defined(ibm032)
#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>
#endif
#include <net/bpf.h>
#ifdef _KERNEL
#define MINDEX(m, k)                                                    \
{                                                                       \
        int len = m->m_len;                                             \
                                                                        \
        while (k >= len) {                                              \
                k -= len;                                               \
                m = m->m_next;                                          \
                if (m == 0)                                             \
                        return 0;                                       \
                len = m->m_len;                                         \
        }                                                               \
}

extern int      bpf_maxbufsize;

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
                                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, 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(const struct bpf_insn *f, int len)
{
        u_int i, from;
        const 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:
                                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_AND:
                        case BPF_LSH:
                        case BPF_RSH:
                        case BPF_NEG:
                                break;
                        case BPF_DIV:
                                /*
                                 * 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 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;
}
#endif