/* $FreeBSD$ */ /*- * 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[] = "@(#) $Header: /devel/CVS/IP-Filter/bpf_filter.c,v 2.2.2.3 2006/10/03 11:25:56 darrenr Exp $ (LBL)"; #endif #include #include #include #include #include #include #include "netinet/ip_compat.h" #include "bpf-ipf.h" #if (defined(__hpux) || SOLARIS) && (defined(_KERNEL) || defined(KERNEL)) # include # include #endif #include "pcap-ipf.h" #if !defined(KERNEL) && !defined(_KERNEL) #include #endif #define int32 bpf_int32 #define u_int32 bpf_u_int32 static int m_xword __P((mb_t *, int, int *)); static int m_xhalf __P((mb_t *, int, int *)); #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 #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 #define MINDEX(len, _m, _k) \ { \ len = M_LEN(m); \ while ((_k) >= len) { \ (_k) -= len; \ (_m) = (_m)->m_next; \ if ((_m) == 0) \ return 0; \ len = M_LEN(m); \ } \ } static int m_xword(m, k, err) register mb_t *m; register int k, *err; { register int len; register u_char *cp, *np; register mb_t *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 || M_LEN(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 mb_t *m; register int k, *err; { register int len; register u_char *cp; register mb_t *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; } /* * 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]; mb_t *m, *n; int merr = 0; /* XXX: GCC */ int len; if (buflen == 0) { m = (mb_t *)p; p = MTOD(m, u_char *); buflen = M_LEN(m); } else m = NULL; if (pc == 0) /* * No filter means accept all. */ return (u_int)-1; A = 0; X = 0; --pc; while (1) { ++pc; switch (pc->code) { default: return 0; 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 (m == NULL) return 0; A = m_xword(m, k, &merr); if (merr != 0) return 0; continue; } A = EXTRACT_LONG(&p[k]); continue; case BPF_LD|BPF_H|BPF_ABS: k = pc->k; if (k + sizeof(short) > buflen) { if (m == NULL) return 0; A = m_xhalf(m, k, &merr); if (merr != 0) return 0; continue; } A = EXTRACT_SHORT(&p[k]); continue; case BPF_LD|BPF_B|BPF_ABS: k = pc->k; if (k >= buflen) { if (m == NULL) return 0; n = m; MINDEX(len, n, k); A = MTOD(n, u_char *)[k]; continue; } 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 (m == NULL) return 0; A = m_xword(m, k, &merr); if (merr != 0) return 0; continue; } A = EXTRACT_LONG(&p[k]); continue; case BPF_LD|BPF_H|BPF_IND: k = X + pc->k; if (k + sizeof(short) > buflen) { if (m == NULL) return 0; A = m_xhalf(m, k, &merr); if (merr != 0) return 0; continue; } A = EXTRACT_SHORT(&p[k]); continue; case BPF_LD|BPF_B|BPF_IND: k = X + pc->k; if (k >= buflen) { if (m == NULL) return 0; n = m; MINDEX(len, n, k); A = MTOD(n, u_char *)[k]; continue; } A = p[k]; continue; case BPF_LDX|BPF_MSH|BPF_B: k = pc->k; if (k >= buflen) { if (m == NULL) return 0; n = m; MINDEX(len, n, k); X = (MTOD(n, char *)[k] & 0xf) << 2; continue; } 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, 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(f, len) struct bpf_insn *f; int len; { u_int i, from; const struct bpf_insn *p; if (len == 0) return 1; 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 0 if (p->k >= bpf_maxbufsize) return 0; #endif 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_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; 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; }