bpf_filter.c revision 145519
1145519Sdarrenr/* $FreeBSD: head/contrib/ipfilter/bpf_filter.c 145519 2005-04-25 18:20:15Z darrenr $ */ 2145510Sdarrenr 3145510Sdarrenr/*- 4145510Sdarrenr * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997 5145510Sdarrenr * The Regents of the University of California. All rights reserved. 6145510Sdarrenr * 7145510Sdarrenr * This code is derived from the Stanford/CMU enet packet filter, 8145510Sdarrenr * (net/enet.c) distributed as part of 4.3BSD, and code contributed 9145510Sdarrenr * to Berkeley by Steven McCanne and Van Jacobson both of Lawrence 10145510Sdarrenr * Berkeley Laboratory. 11145510Sdarrenr * 12145510Sdarrenr * Redistribution and use in source and binary forms, with or without 13145510Sdarrenr * modification, are permitted provided that the following conditions 14145510Sdarrenr * are met: 15145510Sdarrenr * 1. Redistributions of source code must retain the above copyright 16145510Sdarrenr * notice, this list of conditions and the following disclaimer. 17145510Sdarrenr * 2. Redistributions in binary form must reproduce the above copyright 18145510Sdarrenr * notice, this list of conditions and the following disclaimer in the 19145510Sdarrenr * documentation and/or other materials provided with the distribution. 20145510Sdarrenr * 3. All advertising materials mentioning features or use of this software 21145510Sdarrenr * must display the following acknowledgement: 22145510Sdarrenr * This product includes software developed by the University of 23145510Sdarrenr * California, Berkeley and its contributors. 24145510Sdarrenr * 4. Neither the name of the University nor the names of its contributors 25145510Sdarrenr * may be used to endorse or promote products derived from this software 26145510Sdarrenr * without specific prior written permission. 27145510Sdarrenr * 28145510Sdarrenr * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29145510Sdarrenr * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30145510Sdarrenr * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31145510Sdarrenr * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32145510Sdarrenr * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33145510Sdarrenr * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34145510Sdarrenr * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35145510Sdarrenr * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36145510Sdarrenr * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37145510Sdarrenr * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38145510Sdarrenr * SUCH DAMAGE. 39145510Sdarrenr * 40145510Sdarrenr * @(#)bpf.c 7.5 (Berkeley) 7/15/91 41145510Sdarrenr */ 42145510Sdarrenr 43145510Sdarrenr#if !(defined(lint) || defined(KERNEL) || defined(_KERNEL)) 44145510Sdarrenrstatic const char rcsid[] = 45145510Sdarrenr "@(#) $Header: /devel/CVS/IP-Filter/bpf_filter.c,v 2.2 2003/08/19 16:49:58 darrenr Exp $ (LBL)"; 46145510Sdarrenr#endif 47145510Sdarrenr 48145510Sdarrenr#include <sys/param.h> 49145510Sdarrenr#include <sys/types.h> 50145510Sdarrenr#include <sys/time.h> 51145510Sdarrenr#include <sys/socket.h> 52145510Sdarrenr 53145510Sdarrenr#include <netinet/in.h> 54145510Sdarrenr#include <net/if.h> 55145510Sdarrenr 56145510Sdarrenr#include "ip_compat.h" 57145510Sdarrenr#include "bpf-ipf.h" 58145510Sdarrenr 59145510Sdarrenr 60145510Sdarrenr#if (defined(__hpux) || SOLARIS) && (defined(_KERNEL) || defined(KERNEL)) 61145510Sdarrenr# include <sys/sysmacros.h> 62145510Sdarrenr# include <sys/stream.h> 63145510Sdarrenr#endif 64145510Sdarrenr 65145510Sdarrenr#include "pcap-ipf.h" 66145510Sdarrenr 67145510Sdarrenr#if !defined(KERNEL) && !defined(_KERNEL) 68145510Sdarrenr#include <stdlib.h> 69145510Sdarrenr#endif 70145510Sdarrenr 71145510Sdarrenr#define int32 bpf_int32 72145510Sdarrenr#define u_int32 bpf_u_int32 73145510Sdarrenr 74145510Sdarrenrstatic int m_xword __P((mb_t *, int, int *)); 75145510Sdarrenrstatic int m_xhalf __P((mb_t *, int, int *)); 76145510Sdarrenr 77145510Sdarrenr#ifndef LBL_ALIGN 78145510Sdarrenr/* 79145510Sdarrenr * XXX - IA-64? If not, this probably won't work on Win64 IA-64 80145510Sdarrenr * systems, unless LBL_ALIGN is defined elsewhere for them. 81145510Sdarrenr * XXX - SuperH? If not, this probably won't work on WinCE SuperH 82145510Sdarrenr * systems, unless LBL_ALIGN is defined elsewhere for them. 83145510Sdarrenr */ 84145510Sdarrenr#if defined(sparc) || defined(__sparc__) || defined(mips) || \ 85145510Sdarrenr defined(ibm032) || defined(__alpha) || defined(__hpux) || \ 86145510Sdarrenr defined(__arm__) 87145510Sdarrenr#define LBL_ALIGN 88145510Sdarrenr#endif 89145510Sdarrenr#endif 90145510Sdarrenr 91145510Sdarrenr#ifndef LBL_ALIGN 92145510Sdarrenr 93145510Sdarrenr#define EXTRACT_SHORT(p) ((u_short)ntohs(*(u_short *)p)) 94145510Sdarrenr#define EXTRACT_LONG(p) (ntohl(*(u_int32 *)p)) 95145510Sdarrenr#else 96145510Sdarrenr#define EXTRACT_SHORT(p)\ 97145510Sdarrenr ((u_short)\ 98145510Sdarrenr ((u_short)*((u_char *)p+0)<<8|\ 99145510Sdarrenr (u_short)*((u_char *)p+1)<<0)) 100145510Sdarrenr#define EXTRACT_LONG(p)\ 101145510Sdarrenr ((u_int32)*((u_char *)p+0)<<24|\ 102145510Sdarrenr (u_int32)*((u_char *)p+1)<<16|\ 103145510Sdarrenr (u_int32)*((u_char *)p+2)<<8|\ 104145510Sdarrenr (u_int32)*((u_char *)p+3)<<0) 105145510Sdarrenr#endif 106145510Sdarrenr 107145510Sdarrenr#define MINDEX(len, _m, _k) \ 108145510Sdarrenr{ \ 109145510Sdarrenr len = M_LEN(m); \ 110145510Sdarrenr while ((_k) >= len) { \ 111145510Sdarrenr (_k) -= len; \ 112145510Sdarrenr (_m) = (_m)->m_next; \ 113145510Sdarrenr if ((_m) == 0) \ 114145510Sdarrenr return 0; \ 115145510Sdarrenr len = M_LEN(m); \ 116145510Sdarrenr } \ 117145510Sdarrenr} 118145510Sdarrenr 119145510Sdarrenrstatic int 120145510Sdarrenrm_xword(m, k, err) 121145510Sdarrenr register mb_t *m; 122145510Sdarrenr register int k, *err; 123145510Sdarrenr{ 124145510Sdarrenr register int len; 125145510Sdarrenr register u_char *cp, *np; 126145510Sdarrenr register mb_t *m0; 127145510Sdarrenr 128145510Sdarrenr MINDEX(len, m, k); 129145510Sdarrenr cp = MTOD(m, u_char *) + k; 130145510Sdarrenr if (len - k >= 4) { 131145510Sdarrenr *err = 0; 132145510Sdarrenr return EXTRACT_LONG(cp); 133145510Sdarrenr } 134145510Sdarrenr m0 = m->m_next; 135145510Sdarrenr if (m0 == 0 || M_LEN(m0) + len - k < 4) 136145510Sdarrenr goto bad; 137145510Sdarrenr *err = 0; 138145510Sdarrenr np = MTOD(m0, u_char *); 139145510Sdarrenr switch (len - k) { 140145510Sdarrenr 141145510Sdarrenr case 1: 142145510Sdarrenr return (cp[0] << 24) | (np[0] << 16) | (np[1] << 8) | np[2]; 143145510Sdarrenr 144145510Sdarrenr case 2: 145145510Sdarrenr return (cp[0] << 24) | (cp[1] << 16) | (np[0] << 8) | np[1]; 146145510Sdarrenr 147145510Sdarrenr default: 148145510Sdarrenr return (cp[0] << 24) | (cp[1] << 16) | (cp[2] << 8) | np[0]; 149145510Sdarrenr } 150145510Sdarrenr bad: 151145510Sdarrenr *err = 1; 152145510Sdarrenr return 0; 153145510Sdarrenr} 154145510Sdarrenr 155145510Sdarrenrstatic int 156145510Sdarrenrm_xhalf(m, k, err) 157145510Sdarrenr register mb_t *m; 158145510Sdarrenr register int k, *err; 159145510Sdarrenr{ 160145510Sdarrenr register int len; 161145510Sdarrenr register u_char *cp; 162145510Sdarrenr register mb_t *m0; 163145510Sdarrenr 164145510Sdarrenr MINDEX(len, m, k); 165145510Sdarrenr cp = MTOD(m, u_char *) + k; 166145510Sdarrenr if (len - k >= 2) { 167145510Sdarrenr *err = 0; 168145510Sdarrenr return EXTRACT_SHORT(cp); 169145510Sdarrenr } 170145510Sdarrenr m0 = m->m_next; 171145510Sdarrenr if (m0 == 0) 172145510Sdarrenr goto bad; 173145510Sdarrenr *err = 0; 174145510Sdarrenr return (cp[0] << 8) | MTOD(m0, u_char *)[0]; 175145510Sdarrenr bad: 176145510Sdarrenr *err = 1; 177145510Sdarrenr return 0; 178145510Sdarrenr} 179145510Sdarrenr 180145510Sdarrenr/* 181145510Sdarrenr * Execute the filter program starting at pc on the packet p 182145510Sdarrenr * wirelen is the length of the original packet 183145510Sdarrenr * buflen is the amount of data present 184145510Sdarrenr * For the kernel, p is assumed to be a pointer to an mbuf if buflen is 0, 185145510Sdarrenr * in all other cases, p is a pointer to a buffer and buflen is its size. 186145510Sdarrenr */ 187145510Sdarrenru_int 188145510Sdarrenrbpf_filter(pc, p, wirelen, buflen) 189145510Sdarrenr register struct bpf_insn *pc; 190145510Sdarrenr register u_char *p; 191145510Sdarrenr u_int wirelen; 192145510Sdarrenr register u_int buflen; 193145510Sdarrenr{ 194145510Sdarrenr register u_int32 A, X; 195145510Sdarrenr register int k; 196145510Sdarrenr int32 mem[BPF_MEMWORDS]; 197145510Sdarrenr mb_t *m, *n; 198145510Sdarrenr int merr, len; 199145510Sdarrenr 200145510Sdarrenr if (buflen == 0) { 201145510Sdarrenr m = (mb_t *)p; 202145510Sdarrenr p = MTOD(m, u_char *); 203145510Sdarrenr buflen = M_LEN(m); 204145510Sdarrenr } else 205145510Sdarrenr m = NULL; 206145510Sdarrenr 207145510Sdarrenr if (pc == 0) 208145510Sdarrenr /* 209145510Sdarrenr * No filter means accept all. 210145510Sdarrenr */ 211145510Sdarrenr return (u_int)-1; 212145510Sdarrenr A = 0; 213145510Sdarrenr X = 0; 214145510Sdarrenr --pc; 215145510Sdarrenr while (1) { 216145510Sdarrenr ++pc; 217145510Sdarrenr switch (pc->code) { 218145510Sdarrenr 219145510Sdarrenr default: 220145510Sdarrenr return 0; 221145510Sdarrenr case BPF_RET|BPF_K: 222145510Sdarrenr return (u_int)pc->k; 223145510Sdarrenr 224145510Sdarrenr case BPF_RET|BPF_A: 225145510Sdarrenr return (u_int)A; 226145510Sdarrenr 227145510Sdarrenr case BPF_LD|BPF_W|BPF_ABS: 228145510Sdarrenr k = pc->k; 229145510Sdarrenr if (k + sizeof(int32) > buflen) { 230145510Sdarrenr if (m == NULL) 231145510Sdarrenr return 0; 232145510Sdarrenr A = m_xword(m, k, &merr); 233145510Sdarrenr if (merr != 0) 234145510Sdarrenr return 0; 235145510Sdarrenr continue; 236145510Sdarrenr } 237145510Sdarrenr A = EXTRACT_LONG(&p[k]); 238145510Sdarrenr continue; 239145510Sdarrenr 240145510Sdarrenr case BPF_LD|BPF_H|BPF_ABS: 241145510Sdarrenr k = pc->k; 242145510Sdarrenr if (k + sizeof(short) > buflen) { 243145510Sdarrenr if (m == NULL) 244145510Sdarrenr return 0; 245145510Sdarrenr A = m_xhalf(m, k, &merr); 246145510Sdarrenr if (merr != 0) 247145510Sdarrenr return 0; 248145510Sdarrenr continue; 249145510Sdarrenr } 250145510Sdarrenr A = EXTRACT_SHORT(&p[k]); 251145510Sdarrenr continue; 252145510Sdarrenr 253145510Sdarrenr case BPF_LD|BPF_B|BPF_ABS: 254145510Sdarrenr k = pc->k; 255145510Sdarrenr if (k >= buflen) { 256145510Sdarrenr if (m == NULL) 257145510Sdarrenr return 0; 258145510Sdarrenr n = m; 259145510Sdarrenr MINDEX(len, n, k); 260145510Sdarrenr A = MTOD(n, u_char *)[k]; 261145510Sdarrenr continue; 262145510Sdarrenr } 263145510Sdarrenr A = p[k]; 264145510Sdarrenr continue; 265145510Sdarrenr 266145510Sdarrenr case BPF_LD|BPF_W|BPF_LEN: 267145510Sdarrenr A = wirelen; 268145510Sdarrenr continue; 269145510Sdarrenr 270145510Sdarrenr case BPF_LDX|BPF_W|BPF_LEN: 271145510Sdarrenr X = wirelen; 272145510Sdarrenr continue; 273145510Sdarrenr 274145510Sdarrenr case BPF_LD|BPF_W|BPF_IND: 275145510Sdarrenr k = X + pc->k; 276145510Sdarrenr if (k + sizeof(int32) > buflen) { 277145510Sdarrenr if (m == NULL) 278145510Sdarrenr return 0; 279145510Sdarrenr A = m_xword(m, k, &merr); 280145510Sdarrenr if (merr != 0) 281145510Sdarrenr return 0; 282145510Sdarrenr continue; 283145510Sdarrenr } 284145510Sdarrenr A = EXTRACT_LONG(&p[k]); 285145510Sdarrenr continue; 286145510Sdarrenr 287145510Sdarrenr case BPF_LD|BPF_H|BPF_IND: 288145510Sdarrenr k = X + pc->k; 289145510Sdarrenr if (k + sizeof(short) > buflen) { 290145510Sdarrenr if (m == NULL) 291145510Sdarrenr return 0; 292145510Sdarrenr A = m_xhalf(m, k, &merr); 293145510Sdarrenr if (merr != 0) 294145510Sdarrenr return 0; 295145510Sdarrenr continue; 296145510Sdarrenr } 297145510Sdarrenr A = EXTRACT_SHORT(&p[k]); 298145510Sdarrenr continue; 299145510Sdarrenr 300145510Sdarrenr case BPF_LD|BPF_B|BPF_IND: 301145510Sdarrenr k = X + pc->k; 302145510Sdarrenr if (k >= buflen) { 303145510Sdarrenr if (m == NULL) 304145510Sdarrenr return 0; 305145510Sdarrenr n = m; 306145510Sdarrenr MINDEX(len, n, k); 307145510Sdarrenr A = MTOD(n, u_char *)[k]; 308145510Sdarrenr continue; 309145510Sdarrenr } 310145510Sdarrenr A = p[k]; 311145510Sdarrenr continue; 312145510Sdarrenr 313145510Sdarrenr case BPF_LDX|BPF_MSH|BPF_B: 314145510Sdarrenr k = pc->k; 315145510Sdarrenr if (k >= buflen) { 316145510Sdarrenr if (m == NULL) 317145510Sdarrenr return 0; 318145510Sdarrenr n = m; 319145510Sdarrenr MINDEX(len, n, k); 320145510Sdarrenr X = (MTOD(n, char *)[k] & 0xf) << 2; 321145510Sdarrenr continue; 322145510Sdarrenr } 323145510Sdarrenr X = (p[pc->k] & 0xf) << 2; 324145510Sdarrenr continue; 325145510Sdarrenr 326145510Sdarrenr case BPF_LD|BPF_IMM: 327145510Sdarrenr A = pc->k; 328145510Sdarrenr continue; 329145510Sdarrenr 330145510Sdarrenr case BPF_LDX|BPF_IMM: 331145510Sdarrenr X = pc->k; 332145510Sdarrenr continue; 333145510Sdarrenr 334145510Sdarrenr case BPF_LD|BPF_MEM: 335145510Sdarrenr A = mem[pc->k]; 336145510Sdarrenr continue; 337145510Sdarrenr 338145510Sdarrenr case BPF_LDX|BPF_MEM: 339145510Sdarrenr X = mem[pc->k]; 340145510Sdarrenr continue; 341145510Sdarrenr 342145510Sdarrenr case BPF_ST: 343145510Sdarrenr mem[pc->k] = A; 344145510Sdarrenr continue; 345145510Sdarrenr 346145510Sdarrenr case BPF_STX: 347145510Sdarrenr mem[pc->k] = X; 348145510Sdarrenr continue; 349145510Sdarrenr 350145510Sdarrenr case BPF_JMP|BPF_JA: 351145510Sdarrenr pc += pc->k; 352145510Sdarrenr continue; 353145510Sdarrenr 354145510Sdarrenr case BPF_JMP|BPF_JGT|BPF_K: 355145510Sdarrenr pc += (A > pc->k) ? pc->jt : pc->jf; 356145510Sdarrenr continue; 357145510Sdarrenr 358145510Sdarrenr case BPF_JMP|BPF_JGE|BPF_K: 359145510Sdarrenr pc += (A >= pc->k) ? pc->jt : pc->jf; 360145510Sdarrenr continue; 361145510Sdarrenr 362145510Sdarrenr case BPF_JMP|BPF_JEQ|BPF_K: 363145510Sdarrenr pc += (A == pc->k) ? pc->jt : pc->jf; 364145510Sdarrenr continue; 365145510Sdarrenr 366145510Sdarrenr case BPF_JMP|BPF_JSET|BPF_K: 367145510Sdarrenr pc += (A & pc->k) ? pc->jt : pc->jf; 368145510Sdarrenr continue; 369145510Sdarrenr 370145510Sdarrenr case BPF_JMP|BPF_JGT|BPF_X: 371145510Sdarrenr pc += (A > X) ? pc->jt : pc->jf; 372145510Sdarrenr continue; 373145510Sdarrenr 374145510Sdarrenr case BPF_JMP|BPF_JGE|BPF_X: 375145510Sdarrenr pc += (A >= X) ? pc->jt : pc->jf; 376145510Sdarrenr continue; 377145510Sdarrenr 378145510Sdarrenr case BPF_JMP|BPF_JEQ|BPF_X: 379145510Sdarrenr pc += (A == X) ? pc->jt : pc->jf; 380145510Sdarrenr continue; 381145510Sdarrenr 382145510Sdarrenr case BPF_JMP|BPF_JSET|BPF_X: 383145510Sdarrenr pc += (A & X) ? pc->jt : pc->jf; 384145510Sdarrenr continue; 385145510Sdarrenr 386145510Sdarrenr case BPF_ALU|BPF_ADD|BPF_X: 387145510Sdarrenr A += X; 388145510Sdarrenr continue; 389145510Sdarrenr 390145510Sdarrenr case BPF_ALU|BPF_SUB|BPF_X: 391145510Sdarrenr A -= X; 392145510Sdarrenr continue; 393145510Sdarrenr 394145510Sdarrenr case BPF_ALU|BPF_MUL|BPF_X: 395145510Sdarrenr A *= X; 396145510Sdarrenr continue; 397145510Sdarrenr 398145510Sdarrenr case BPF_ALU|BPF_DIV|BPF_X: 399145510Sdarrenr if (X == 0) 400145510Sdarrenr return 0; 401145510Sdarrenr A /= X; 402145510Sdarrenr continue; 403145510Sdarrenr 404145510Sdarrenr case BPF_ALU|BPF_AND|BPF_X: 405145510Sdarrenr A &= X; 406145510Sdarrenr continue; 407145510Sdarrenr 408145510Sdarrenr case BPF_ALU|BPF_OR|BPF_X: 409145510Sdarrenr A |= X; 410145510Sdarrenr continue; 411145510Sdarrenr 412145510Sdarrenr case BPF_ALU|BPF_LSH|BPF_X: 413145510Sdarrenr A <<= X; 414145510Sdarrenr continue; 415145510Sdarrenr 416145510Sdarrenr case BPF_ALU|BPF_RSH|BPF_X: 417145510Sdarrenr A >>= X; 418145510Sdarrenr continue; 419145510Sdarrenr 420145510Sdarrenr case BPF_ALU|BPF_ADD|BPF_K: 421145510Sdarrenr A += pc->k; 422145510Sdarrenr continue; 423145510Sdarrenr 424145510Sdarrenr case BPF_ALU|BPF_SUB|BPF_K: 425145510Sdarrenr A -= pc->k; 426145510Sdarrenr continue; 427145510Sdarrenr 428145510Sdarrenr case BPF_ALU|BPF_MUL|BPF_K: 429145510Sdarrenr A *= pc->k; 430145510Sdarrenr continue; 431145510Sdarrenr 432145510Sdarrenr case BPF_ALU|BPF_DIV|BPF_K: 433145510Sdarrenr A /= pc->k; 434145510Sdarrenr continue; 435145510Sdarrenr 436145510Sdarrenr case BPF_ALU|BPF_AND|BPF_K: 437145510Sdarrenr A &= pc->k; 438145510Sdarrenr continue; 439145510Sdarrenr 440145510Sdarrenr case BPF_ALU|BPF_OR|BPF_K: 441145510Sdarrenr A |= pc->k; 442145510Sdarrenr continue; 443145510Sdarrenr 444145510Sdarrenr case BPF_ALU|BPF_LSH|BPF_K: 445145510Sdarrenr A <<= pc->k; 446145510Sdarrenr continue; 447145510Sdarrenr 448145510Sdarrenr case BPF_ALU|BPF_RSH|BPF_K: 449145510Sdarrenr A >>= pc->k; 450145510Sdarrenr continue; 451145510Sdarrenr 452145510Sdarrenr case BPF_ALU|BPF_NEG: 453145510Sdarrenr A = -A; 454145510Sdarrenr continue; 455145510Sdarrenr 456145510Sdarrenr case BPF_MISC|BPF_TAX: 457145510Sdarrenr X = A; 458145510Sdarrenr continue; 459145510Sdarrenr 460145510Sdarrenr case BPF_MISC|BPF_TXA: 461145510Sdarrenr A = X; 462145510Sdarrenr continue; 463145510Sdarrenr } 464145510Sdarrenr } 465145510Sdarrenr} 466145510Sdarrenr 467145510Sdarrenr 468145510Sdarrenr/* 469145510Sdarrenr * Return true if the 'fcode' is a valid filter program. 470145510Sdarrenr * The constraints are that each jump be forward and to a valid 471145510Sdarrenr * code. The code must terminate with either an accept or reject. 472145510Sdarrenr * 'valid' is an array for use by the routine (it must be at least 473145510Sdarrenr * 'len' bytes long). 474145510Sdarrenr * 475145510Sdarrenr * The kernel needs to be able to verify an application's filter code. 476145510Sdarrenr * Otherwise, a bogus program could easily crash the system. 477145510Sdarrenr */ 478145510Sdarrenrint 479145510Sdarrenrbpf_validate(f, len) 480145510Sdarrenr struct bpf_insn *f; 481145510Sdarrenr int len; 482145510Sdarrenr{ 483145510Sdarrenr register int i; 484145510Sdarrenr register struct bpf_insn *p; 485145510Sdarrenr 486145510Sdarrenr for (i = 0; i < len; ++i) { 487145510Sdarrenr /* 488145510Sdarrenr * Check that that jumps are forward, and within 489145510Sdarrenr * the code block. 490145510Sdarrenr */ 491145510Sdarrenr p = &f[i]; 492145510Sdarrenr if (BPF_CLASS(p->code) == BPF_JMP) { 493145510Sdarrenr register int from = i + 1; 494145510Sdarrenr 495145510Sdarrenr if (BPF_OP(p->code) == BPF_JA) { 496145510Sdarrenr if (from + p->k >= (unsigned)len) 497145510Sdarrenr return 0; 498145510Sdarrenr } 499145510Sdarrenr else if (from + p->jt >= len || from + p->jf >= len) 500145510Sdarrenr return 0; 501145510Sdarrenr } 502145510Sdarrenr /* 503145510Sdarrenr * Check that memory operations use valid addresses. 504145510Sdarrenr */ 505145510Sdarrenr if ((BPF_CLASS(p->code) == BPF_ST || 506145510Sdarrenr (BPF_CLASS(p->code) == BPF_LD && 507145510Sdarrenr (p->code & 0xe0) == BPF_MEM)) && 508145510Sdarrenr (p->k >= BPF_MEMWORDS || p->k < 0)) 509145510Sdarrenr return 0; 510145510Sdarrenr /* 511145510Sdarrenr * Check for constant division by 0. 512145510Sdarrenr */ 513145510Sdarrenr if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0) 514145510Sdarrenr return 0; 515145510Sdarrenr } 516145510Sdarrenr return BPF_CLASS(f[len - 1].code) == BPF_RET; 517145510Sdarrenr} 518