1/* 2 * Copyright (c) 2000-2011 Apple Inc. All rights reserved. 3 * 4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ 5 * 6 * This file contains Original Code and/or Modifications of Original Code 7 * as defined in and that are subject to the Apple Public Source License 8 * Version 2.0 (the 'License'). You may not use this file except in 9 * compliance with the License. The rights granted to you under the License 10 * may not be used to create, or enable the creation or redistribution of, 11 * unlawful or unlicensed copies of an Apple operating system, or to 12 * circumvent, violate, or enable the circumvention or violation of, any 13 * terms of an Apple operating system software license agreement. 14 * 15 * Please obtain a copy of the License at 16 * http://www.opensource.apple.com/apsl/ and read it before using this file. 17 * 18 * The Original Code and all software distributed under the License are 19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 23 * Please see the License for the specific language governing rights and 24 * limitations under the License. 25 * 26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ 27 */ 28/* 29 * Copyright (c) 1990, 1991, 1993 30 * The Regents of the University of California. All rights reserved. 31 * 32 * This code is derived from the Stanford/CMU enet packet filter, 33 * (net/enet.c) distributed as part of 4.3BSD, and code contributed 34 * to Berkeley by Steven McCanne and Van Jacobson both of Lawrence 35 * Berkeley Laboratory. 36 * 37 * Redistribution and use in source and binary forms, with or without 38 * modification, are permitted provided that the following conditions 39 * are met: 40 * 1. Redistributions of source code must retain the above copyright 41 * notice, this list of conditions and the following disclaimer. 42 * 2. Redistributions in binary form must reproduce the above copyright 43 * notice, this list of conditions and the following disclaimer in the 44 * documentation and/or other materials provided with the distribution. 45 * 3. All advertising materials mentioning features or use of this software 46 * must display the following acknowledgement: 47 * This product includes software developed by the University of 48 * California, Berkeley and its contributors. 49 * 4. Neither the name of the University nor the names of its contributors 50 * may be used to endorse or promote products derived from this software 51 * without specific prior written permission. 52 * 53 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 54 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 55 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 56 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 57 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 58 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 59 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 60 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 61 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 62 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 63 * SUCH DAMAGE. 64 * 65 * @(#)bpf_filter.c 8.1 (Berkeley) 6/10/93 66 * 67 * $FreeBSD: src/sys/net/bpf_filter.c,v 1.17 1999/12/29 04:38:31 peter Exp $ 68 */ 69 70#include <sys/param.h> 71#include <string.h> 72 73#ifdef sun 74#include <netinet/in.h> 75#endif 76 77#if !defined(__i386__) && !defined(__x86_64__) 78#define BPF_ALIGN 1 79#else /* defined(__i386__) || defined(__x86_64__) */ 80#define BPF_ALIGN 0 81#endif /* defined(__i386__) || defined(__x86_64__) */ 82 83#if !BPF_ALIGN 84#define EXTRACT_SHORT(p) ((u_int16_t)ntohs(*(u_int16_t *)(void *)p)) 85#define EXTRACT_LONG(p) (ntohl(*(u_int32_t *)(void *)p)) 86#else 87#define EXTRACT_SHORT(p)\ 88 ((u_int16_t)\ 89 ((u_int16_t)*((u_char *)p+0)<<8|\ 90 (u_int16_t)*((u_char *)p+1)<<0)) 91#define EXTRACT_LONG(p)\ 92 ((u_int32_t)*((u_char *)p+0)<<24|\ 93 (u_int32_t)*((u_char *)p+1)<<16|\ 94 (u_int32_t)*((u_char *)p+2)<<8|\ 95 (u_int32_t)*((u_char *)p+3)<<0) 96#endif 97 98#ifdef KERNEL 99#include <sys/mbuf.h> 100#endif 101#include <net/bpf.h> 102#ifdef KERNEL 103#define MINDEX(m, k) \ 104{ \ 105 register unsigned int len = m->m_len; \ 106 \ 107 while (k >= len) { \ 108 k -= len; \ 109 m = m->m_next; \ 110 if (m == 0) \ 111 return 0; \ 112 len = m->m_len; \ 113 } \ 114} 115 116extern unsigned int bpf_maxbufsize; 117 118static u_int16_t m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err); 119static u_int32_t m_xword(struct mbuf *m, bpf_u_int32 k, int *err); 120 121static u_int32_t 122m_xword(struct mbuf *m, bpf_u_int32 k, int *err) 123{ 124 register size_t len; 125 register u_char *cp, *np; 126 register struct mbuf *m0; 127 128 len = m->m_len; 129 while (k >= len) { 130 k -= len; 131 m = m->m_next; 132 if (m == 0) 133 goto bad; 134 len = m->m_len; 135 } 136 cp = mtod(m, u_char *) + k; 137 if (len - k >= 4) { 138 *err = 0; 139 return EXTRACT_LONG(cp); 140 } 141 m0 = m->m_next; 142 if (m0 == 0 || m0->m_len + len - k < 4) 143 goto bad; 144 *err = 0; 145 np = mtod(m0, u_char *); 146 switch (len - k) { 147 148 case 1: 149 return 150 ((u_int32_t)cp[0] << 24) | 151 ((u_int32_t)np[0] << 16) | 152 ((u_int32_t)np[1] << 8) | 153 (u_int32_t)np[2]; 154 155 case 2: 156 return 157 ((u_int32_t)cp[0] << 24) | 158 ((u_int32_t)cp[1] << 16) | 159 ((u_int32_t)np[0] << 8) | 160 (u_int32_t)np[1]; 161 162 default: 163 return 164 ((u_int32_t)cp[0] << 24) | 165 ((u_int32_t)cp[1] << 16) | 166 ((u_int32_t)cp[2] << 8) | 167 (u_int32_t)np[0]; 168 } 169 bad: 170 *err = 1; 171 return 0; 172} 173 174static u_int16_t 175m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err) 176{ 177 register size_t len; 178 register u_char *cp; 179 register struct mbuf *m0; 180 181 len = m->m_len; 182 while (k >= len) { 183 k -= len; 184 m = m->m_next; 185 if (m == 0) 186 goto bad; 187 len = m->m_len; 188 } 189 cp = mtod(m, u_char *) + k; 190 if (len - k >= 2) { 191 *err = 0; 192 return EXTRACT_SHORT(cp); 193 } 194 m0 = m->m_next; 195 if (m0 == 0) 196 goto bad; 197 *err = 0; 198 return (cp[0] << 8) | mtod(m0, u_char *)[0]; 199 bad: 200 *err = 1; 201 return 0; 202} 203#endif 204 205/* 206 * Execute the filter program starting at pc on the packet p 207 * wirelen is the length of the original packet 208 * buflen is the amount of data present 209 */ 210u_int 211bpf_filter(const struct bpf_insn *pc, u_char *p, u_int wirelen, u_int buflen) 212{ 213 register u_int32_t A = 0, X = 0; 214 register bpf_u_int32 k; 215 int32_t mem[BPF_MEMWORDS]; 216 217 bzero(mem, sizeof(mem)); 218 219 if (pc == 0) 220 /* 221 * No filter means accept all. 222 */ 223 return (u_int)-1; 224 225 --pc; 226 while (1) { 227 ++pc; 228 switch (pc->code) { 229 230 default: 231#ifdef KERNEL 232 return 0; 233#else 234 abort(); 235#endif 236 case BPF_RET|BPF_K: 237 return (u_int)pc->k; 238 239 case BPF_RET|BPF_A: 240 return (u_int)A; 241 242 case BPF_LD|BPF_W|BPF_ABS: 243 k = pc->k; 244 if (k > buflen || sizeof(int32_t) > buflen - k) { 245#ifdef KERNEL 246 int merr; 247 248 if (buflen != 0) 249 return 0; 250 A = m_xword((struct mbuf *)(void *)p, k, &merr); 251 if (merr != 0) 252 return 0; 253 continue; 254#else 255 return 0; 256#endif 257 } 258#if BPF_ALIGN 259 if (((intptr_t)(p + k) & 3) != 0) 260 A = EXTRACT_LONG(&p[k]); 261 else 262#endif 263 A = ntohl(*(int32_t *)(void *)(p + k)); 264 continue; 265 266 case BPF_LD|BPF_H|BPF_ABS: 267 k = pc->k; 268 if (k > buflen || sizeof(int16_t) > buflen - k) { 269#ifdef KERNEL 270 int merr; 271 272 if (buflen != 0) 273 return 0; 274 A = m_xhalf((struct mbuf *)(void *)p, k, &merr); 275 continue; 276#else 277 return 0; 278#endif 279 } 280 A = EXTRACT_SHORT(&p[k]); 281 continue; 282 283 case BPF_LD|BPF_B|BPF_ABS: 284 k = pc->k; 285 if (k >= buflen) { 286#ifdef KERNEL 287 register struct mbuf *m; 288 289 if (buflen != 0) 290 return 0; 291 m = (struct mbuf *)(void *)p; 292 MINDEX(m, k); 293 A = mtod(m, u_char *)[k]; 294 continue; 295#else 296 return 0; 297#endif 298 } 299 A = p[k]; 300 continue; 301 302 case BPF_LD|BPF_W|BPF_LEN: 303 A = wirelen; 304 continue; 305 306 case BPF_LDX|BPF_W|BPF_LEN: 307 X = wirelen; 308 continue; 309 310 case BPF_LD|BPF_W|BPF_IND: 311 k = X + pc->k; 312 if (pc->k > buflen || X > buflen - pc->k || 313 sizeof(int32_t) > buflen - k) { 314#ifdef KERNEL 315 int merr; 316 317 if (buflen != 0) 318 return 0; 319 A = m_xword((struct mbuf *)(void *)p, k, &merr); 320 if (merr != 0) 321 return 0; 322 continue; 323#else 324 return 0; 325#endif 326 } 327#if BPF_ALIGN 328 if (((intptr_t)(p + k) & 3) != 0) 329 A = EXTRACT_LONG(&p[k]); 330 else 331#endif 332 A = ntohl(*(int32_t *)(void *)(p + k)); 333 continue; 334 335 case BPF_LD|BPF_H|BPF_IND: 336 k = X + pc->k; 337 if (X > buflen || pc->k > buflen - X || 338 sizeof(int16_t) > buflen - k) { 339#ifdef KERNEL 340 int merr; 341 342 if (buflen != 0) 343 return 0; 344 A = m_xhalf((struct mbuf *)(void *)p, k, &merr); 345 if (merr != 0) 346 return 0; 347 continue; 348#else 349 return 0; 350#endif 351 } 352 A = EXTRACT_SHORT(&p[k]); 353 continue; 354 355 case BPF_LD|BPF_B|BPF_IND: 356 k = X + pc->k; 357 if (pc->k >= buflen || X >= buflen - pc->k) { 358#ifdef KERNEL 359 register struct mbuf *m; 360 361 if (buflen != 0) 362 return 0; 363 m = (struct mbuf *)(void *)p; 364 MINDEX(m, k); 365 A = mtod(m, u_char *)[k]; 366 continue; 367#else 368 return 0; 369#endif 370 } 371 A = p[k]; 372 continue; 373 374 case BPF_LDX|BPF_MSH|BPF_B: 375 k = pc->k; 376 if (k >= buflen) { 377#ifdef KERNEL 378 register struct mbuf *m; 379 380 if (buflen != 0) 381 return 0; 382 m = (struct mbuf *)(void *)p; 383 MINDEX(m, k); 384 X = (mtod(m, u_char *)[k] & 0xf) << 2; 385 continue; 386#else 387 return 0; 388#endif 389 } 390 X = (p[pc->k] & 0xf) << 2; 391 continue; 392 393 case BPF_LD|BPF_IMM: 394 A = pc->k; 395 continue; 396 397 case BPF_LDX|BPF_IMM: 398 X = pc->k; 399 continue; 400 401 case BPF_LD|BPF_MEM: 402 A = mem[pc->k]; 403 continue; 404 405 case BPF_LDX|BPF_MEM: 406 X = mem[pc->k]; 407 continue; 408 409 case BPF_ST: 410 if (pc->k >= BPF_MEMWORDS) 411 return 0; 412 mem[pc->k] = A; 413 continue; 414 415 case BPF_STX: 416 if (pc->k >= BPF_MEMWORDS) 417 return 0; 418 mem[pc->k] = X; 419 continue; 420 421 case BPF_JMP|BPF_JA: 422 pc += pc->k; 423 continue; 424 425 case BPF_JMP|BPF_JGT|BPF_K: 426 pc += (A > pc->k) ? pc->jt : pc->jf; 427 continue; 428 429 case BPF_JMP|BPF_JGE|BPF_K: 430 pc += (A >= pc->k) ? pc->jt : pc->jf; 431 continue; 432 433 case BPF_JMP|BPF_JEQ|BPF_K: 434 pc += (A == pc->k) ? pc->jt : pc->jf; 435 continue; 436 437 case BPF_JMP|BPF_JSET|BPF_K: 438 pc += (A & pc->k) ? pc->jt : pc->jf; 439 continue; 440 441 case BPF_JMP|BPF_JGT|BPF_X: 442 pc += (A > X) ? pc->jt : pc->jf; 443 continue; 444 445 case BPF_JMP|BPF_JGE|BPF_X: 446 pc += (A >= X) ? pc->jt : pc->jf; 447 continue; 448 449 case BPF_JMP|BPF_JEQ|BPF_X: 450 pc += (A == X) ? pc->jt : pc->jf; 451 continue; 452 453 case BPF_JMP|BPF_JSET|BPF_X: 454 pc += (A & X) ? pc->jt : pc->jf; 455 continue; 456 457 case BPF_ALU|BPF_ADD|BPF_X: 458 A += X; 459 continue; 460 461 case BPF_ALU|BPF_SUB|BPF_X: 462 A -= X; 463 continue; 464 465 case BPF_ALU|BPF_MUL|BPF_X: 466 A *= X; 467 continue; 468 469 case BPF_ALU|BPF_DIV|BPF_X: 470 if (X == 0) 471 return 0; 472 A /= X; 473 continue; 474 475 case BPF_ALU|BPF_AND|BPF_X: 476 A &= X; 477 continue; 478 479 case BPF_ALU|BPF_OR|BPF_X: 480 A |= X; 481 continue; 482 483 case BPF_ALU|BPF_LSH|BPF_X: 484 A <<= X; 485 continue; 486 487 case BPF_ALU|BPF_RSH|BPF_X: 488 A >>= X; 489 continue; 490 491 case BPF_ALU|BPF_ADD|BPF_K: 492 A += pc->k; 493 continue; 494 495 case BPF_ALU|BPF_SUB|BPF_K: 496 A -= pc->k; 497 continue; 498 499 case BPF_ALU|BPF_MUL|BPF_K: 500 A *= pc->k; 501 continue; 502 503 case BPF_ALU|BPF_DIV|BPF_K: 504 A /= pc->k; 505 continue; 506 507 case BPF_ALU|BPF_AND|BPF_K: 508 A &= pc->k; 509 continue; 510 511 case BPF_ALU|BPF_OR|BPF_K: 512 A |= pc->k; 513 continue; 514 515 case BPF_ALU|BPF_LSH|BPF_K: 516 A <<= pc->k; 517 continue; 518 519 case BPF_ALU|BPF_RSH|BPF_K: 520 A >>= pc->k; 521 continue; 522 523 case BPF_ALU|BPF_NEG: 524 A = -A; 525 continue; 526 527 case BPF_MISC|BPF_TAX: 528 X = A; 529 continue; 530 531 case BPF_MISC|BPF_TXA: 532 A = X; 533 continue; 534 } 535 } 536} 537 538#ifdef KERNEL 539/* 540 * Return true if the 'fcode' is a valid filter program. 541 * The constraints are that each jump be forward and to a valid 542 * code, that memory accesses are within valid ranges (to the 543 * extent that this can be checked statically; loads of packet data 544 * have to be, and are, also checked at run time), and that 545 * the code terminates with either an accept or reject. 546 * 547 * The kernel needs to be able to verify an application's filter code. 548 * Otherwise, a bogus program could easily crash the system. 549 */ 550int 551bpf_validate(const struct bpf_insn *f, int len) 552{ 553 u_int i, from; 554 const struct bpf_insn *p; 555 556 if (len < 1 || len > BPF_MAXINSNS) 557 return 0; 558 559 for (i = 0; i < ((u_int)len); ++i) { 560 p = &f[i]; 561 switch (BPF_CLASS(p->code)) { 562 /* 563 * Check that memory operations use valid addresses 564 */ 565 case BPF_LD: 566 case BPF_LDX: 567 switch (BPF_MODE(p->code)) { 568 case BPF_IMM: 569 break; 570 case BPF_ABS: 571 case BPF_IND: 572 case BPF_MSH: 573 /* 574 * More strict check with actual packet length 575 * is done runtime. 576 */ 577 if (p->k >= bpf_maxbufsize) 578 return 0; 579 break; 580 case BPF_MEM: 581 if (p->k >= BPF_MEMWORDS) 582 return 0; 583 break; 584 case BPF_LEN: 585 break; 586 default: 587 return 0; 588 } 589 break; 590 case BPF_ST: 591 case BPF_STX: 592 if (p->k >= BPF_MEMWORDS) 593 return 0; 594 break; 595 case BPF_ALU: 596 switch (BPF_OP(p->code)) { 597 case BPF_ADD: 598 case BPF_SUB: 599 case BPF_MUL: 600 case BPF_OR: 601 case BPF_AND: 602 case BPF_LSH: 603 case BPF_RSH: 604 case BPF_NEG: 605 break; 606 case BPF_DIV: 607 /* 608 * Check for constant division by 0 609 */ 610 if(BPF_SRC(p->code) == BPF_K && p->k == 0) 611 return 0; 612 break; 613 default: 614 return 0; 615 } 616 break; 617 case BPF_JMP: 618 /* 619 * Check that jumps are within the code block, 620 * and that unconditional branches don't go 621 * backwards as a result of an overflow. 622 * Unconditional branches have a 32-bit offset, 623 * so they could overflow; we check to make 624 * sure they don't. Conditional branches have 625 * an 8-bit offset, and the from address is 626 * less than equal to BPF_MAXINSNS, and we assume that 627 * BPF_MAXINSNS is sufficiently small that adding 255 628 * to it won't overlflow 629 * 630 * We know that len is <= BPF_MAXINSNS, and we 631 * assume that BPF_MAXINSNS is less than the maximum 632 * size of a u_int, so that i+1 doesn't overflow 633 */ 634 from = i+1; 635 switch (BPF_OP(p->code)) { 636 case BPF_JA: 637 if (from + p->k < from || from + p->k >= ((u_int)len)) 638 return 0; 639 break; 640 case BPF_JEQ: 641 case BPF_JGT: 642 case BPF_JGE: 643 case BPF_JSET: 644 if (from + p->jt >= ((u_int)len) || from + p->jf >= ((u_int)len)) 645 return 0; 646 break; 647 default: 648 return 0; 649 } 650 break; 651 case BPF_RET: 652 break; 653 case BPF_MISC: 654 break; 655 default: 656 return 0; 657 } 658 } 659 return BPF_CLASS(f[len - 1].code) == BPF_RET; 660} 661#endif 662