xref: /illumos-gate/usr/src/uts/common/io/bpf/bpf_filter.c (revision 0a0e9771)

/*	$NetBSD: bpf_filter.c,v 1.35 2008/08/20 13:01:54 joerg 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. 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
 */
/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <sys/param.h>
#include <sys/time.h>
#include <sys/stream.h>
#include <sys/byteorder.h>
#include <sys/sdt.h>

#define	EXTRACT_SHORT(p)	BE_IN16(p)
#define	EXTRACT_LONG(p)		BE_IN32(p)

#ifdef _KERNEL
#define	M_LEN(_m)	((_m)->b_wptr - (_m)->b_rptr)
#define	mtod(_a, _t)	((_t)((_a)->b_rptr))
#define	MINDEX(len, m, k) 		\
{ 					\
	len = M_LEN(m); 		\
	while (k >= len) { 		\
		k -= len; 		\
		m = m->b_cont; 		\
		if (m == 0) 		\
			return (0); 	\
		len = M_LEN(m); 	\
	} 				\
}

static int m_xword(mblk_t *, uint32_t, int *);
static int m_xhalf(mblk_t *, uint32_t, int *);

static int
m_xword(mblk_t *m, uint32_t k, int *err)
{
	int len;
	uchar_t *cp, *np;
	mblk_t *m0;

	*err = 1;
	MINDEX(len, m, k);
	cp = mtod(m, uchar_t *) + k;
	if (len >= k + 4) {
		*err = 0;
		return (EXTRACT_LONG(cp));
	}
	m0 = m->b_cont;
	if (m0 == 0 || M_LEN(m0) + len - k < 4) {
		DTRACE_PROBE3(mblk_xword_fail, mblk_t *, m0, int, len, int, k);
		return (0);
	}
	*err = 0;
	np = mtod(m0, uchar_t *);
	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]);
	}
}

static int
m_xhalf(mblk_t *m, uint32_t k, int *err)
{
	int len;
	uchar_t *cp;
	mblk_t *m0;

	*err = 1;
	MINDEX(len, m, k);
	cp = mtod(m, uchar_t *) + k;
	if (len >= k + 2) {
		*err = 0;
		return (EXTRACT_SHORT(cp));
	}
	m0 = m->b_cont;
	if (m0 == 0) {
		DTRACE_PROBE3(mblk_xhalf_fail, mblk_t *, m0, int, len, int, k);
		return (0);
	}
	*err = 0;
	return ((cp[0] << 8) | mtod(m0, uchar_t *)[0]);
}
#else /* _KERNEL */
#include <stdlib.h>
#endif /* !_KERNEL */

#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
 * When buflen is non-0, p is a pointer to a the start of the packet and the
 * packet is only in one mblk_t.
 * When buflen is 0, p is an mblk_t pointer.
 */
uint_t
bpf_filter(struct bpf_insn *pc, uchar_t *p, uint_t wirelen, uint_t buflen)
{
	uint32_t A, X, k;
	uint32_t mem[BPF_MEMWORDS];

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

		default:
#ifdef _KERNEL
			DTRACE_PROBE1(bpf_insn_unknown,
			    struct bpf_insn *, pc);
			return (0);
#else
			abort();
#endif
		case BPF_RET|BPF_K:
			return ((uint_t)pc->k);

		case BPF_RET|BPF_A:
			return ((uint_t)A);

		case BPF_LD|BPF_W|BPF_ABS:
			k = pc->k;
			if (k + sizeof (int32_t) > buflen) {
#ifdef _KERNEL
				int merr = 0;

				if (buflen != 0)
					return (0);
				A = m_xword((mblk_t *)p, 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 (int16_t) > buflen) {
#ifdef _KERNEL
				int merr;

				if (buflen != 0)
					return (0);
				A = m_xhalf((mblk_t *)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_ABS:
			k = pc->k;
			if (k >= buflen) {
#ifdef _KERNEL
				mblk_t *m;
				int len;

				if (buflen != 0)
					return (0);
				m = (mblk_t *)p;
				MINDEX(len, m, k);
				A = mtod(m, uchar_t *)[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_t) > buflen) {
#ifdef _KERNEL
				int merr = 0;

				if (buflen != 0)
					return (0);
				A = m_xword((mblk_t *)p, 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 (int16_t) > buflen) {
#ifdef _KERNEL
				int merr = 0;

				if (buflen != 0)
					return (0);
				A = m_xhalf((mblk_t *)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
				mblk_t *m;
				int len;

				if (buflen != 0)
					return (0);
				m = (mblk_t *)p;
				MINDEX(len, m, k);
				A = mtod(m, uchar_t *)[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
				mblk_t *m;
				int len;

				if (buflen != 0)
					return (0);
				m = (mblk_t *)p;
				MINDEX(len, 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;
		}
	}
	/* NOTREACHED */
}

#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(struct bpf_insn *f, int len)
{
	uint_t i, from;
	struct bpf_insn *p;

	if (len < 1 || len > BPF_MAXINSNS)
		return (0);

	for (i = 0; i < len; ++i) {
		p = &f[i];
		DTRACE_PROBE1(bpf_valid_insn, struct bpf_insn *, p);
		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_MEM:
				if (p->k >= BPF_MEMWORDS)
					return (0);
				break;
			case BPF_ABS:
			case BPF_IND:
			case BPF_MSH:
			case BPF_IMM:
			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_RVAL(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 uint_t, 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