1 /*- 2 * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from the Stanford/CMU enet packet filter, 6 * (net/enet.c) distributed as part of 4.3BSD, and code contributed 7 * to Berkeley by Steven McCanne and Van Jacobson both of Lawrence 8 * Berkeley Laboratory. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * @(#)bpf.c 7.5 (Berkeley) 7/15/91 39 */ 40 41 #ifdef HAVE_CONFIG_H 42 #include "config.h" 43 #endif 44 45 #ifdef WIN32 46 47 #include <pcap-stdinc.h> 48 49 #else /* WIN32 */ 50 51 #if HAVE_INTTYPES_H 52 #include <inttypes.h> 53 #elif HAVE_STDINT_H 54 #include <stdint.h> 55 #endif 56 #ifdef HAVE_SYS_BITYPES_H 57 #include <sys/bitypes.h> 58 #endif 59 60 #include <sys/param.h> 61 #include <sys/types.h> 62 #include <sys/time.h> 63 64 #define SOLARIS (defined(sun) && (defined(__SVR4) || defined(__svr4__))) 65 #if defined(__hpux) || SOLARIS 66 # include <sys/sysmacros.h> 67 # include <sys/stream.h> 68 # define mbuf msgb 69 # define m_next b_cont 70 # define MLEN(m) ((m)->b_wptr - (m)->b_rptr) 71 # define mtod(m,t) ((t)(m)->b_rptr) 72 #else /* defined(__hpux) || SOLARIS */ 73 # define MLEN(m) ((m)->m_len) 74 #endif /* defined(__hpux) || SOLARIS */ 75 76 #endif /* WIN32 */ 77 78 #include <pcap/bpf.h> 79 80 #if !defined(KERNEL) && !defined(_KERNEL) 81 #include <stdlib.h> 82 #endif 83 84 #define int32 bpf_int32 85 #define u_int32 bpf_u_int32 86 87 #ifndef LBL_ALIGN 88 /* 89 * XXX - IA-64? If not, this probably won't work on Win64 IA-64 90 * systems, unless LBL_ALIGN is defined elsewhere for them. 91 * XXX - SuperH? If not, this probably won't work on WinCE SuperH 92 * systems, unless LBL_ALIGN is defined elsewhere for them. 93 */ 94 #if defined(sparc) || defined(__sparc__) || defined(mips) || \ 95 defined(ibm032) || defined(__alpha) || defined(__hpux) || \ 96 defined(__arm__) 97 #define LBL_ALIGN 98 #endif 99 #endif 100 101 #ifndef LBL_ALIGN 102 #ifndef WIN32 103 #include <netinet/in.h> 104 #endif 105 106 #define EXTRACT_SHORT(p) ((u_short)ntohs(*(u_short *)p)) 107 #define EXTRACT_LONG(p) (ntohl(*(u_int32 *)p)) 108 #else 109 #define EXTRACT_SHORT(p)\ 110 ((u_short)\ 111 ((u_short)*((u_char *)p+0)<<8|\ 112 (u_short)*((u_char *)p+1)<<0)) 113 #define EXTRACT_LONG(p)\ 114 ((u_int32)*((u_char *)p+0)<<24|\ 115 (u_int32)*((u_char *)p+1)<<16|\ 116 (u_int32)*((u_char *)p+2)<<8|\ 117 (u_int32)*((u_char *)p+3)<<0) 118 #endif 119 120 #if defined(KERNEL) || defined(_KERNEL) 121 # if !defined(__hpux) && !SOLARIS 122 #include <sys/mbuf.h> 123 # endif 124 #define MINDEX(len, _m, _k) \ 125 { \ 126 len = MLEN(m); \ 127 while ((_k) >= len) { \ 128 (_k) -= len; \ 129 (_m) = (_m)->m_next; \ 130 if ((_m) == 0) \ 131 return 0; \ 132 len = MLEN(m); \ 133 } \ 134 } 135 136 static int 137 m_xword(m, k, err) 138 register struct mbuf *m; 139 register int k, *err; 140 { 141 register int len; 142 register u_char *cp, *np; 143 register struct mbuf *m0; 144 145 MINDEX(len, m, k); 146 cp = mtod(m, u_char *) + k; 147 if (len - k >= 4) { 148 *err = 0; 149 return EXTRACT_LONG(cp); 150 } 151 m0 = m->m_next; 152 if (m0 == 0 || MLEN(m0) + len - k < 4) 153 goto bad; 154 *err = 0; 155 np = mtod(m0, u_char *); 156 switch (len - k) { 157 158 case 1: 159 return (cp[0] << 24) | (np[0] << 16) | (np[1] << 8) | np[2]; 160 161 case 2: 162 return (cp[0] << 24) | (cp[1] << 16) | (np[0] << 8) | np[1]; 163 164 default: 165 return (cp[0] << 24) | (cp[1] << 16) | (cp[2] << 8) | np[0]; 166 } 167 bad: 168 *err = 1; 169 return 0; 170 } 171 172 static int 173 m_xhalf(m, k, err) 174 register struct mbuf *m; 175 register int k, *err; 176 { 177 register int len; 178 register u_char *cp; 179 register struct mbuf *m0; 180 181 MINDEX(len, m, k); 182 cp = mtod(m, u_char *) + k; 183 if (len - k >= 2) { 184 *err = 0; 185 return EXTRACT_SHORT(cp); 186 } 187 m0 = m->m_next; 188 if (m0 == 0) 189 goto bad; 190 *err = 0; 191 return (cp[0] << 8) | mtod(m0, u_char *)[0]; 192 bad: 193 *err = 1; 194 return 0; 195 } 196 #endif 197 198 #ifdef __linux__ 199 #include <linux/types.h> 200 #include <linux/if_packet.h> 201 #include <linux/filter.h> 202 #endif 203 204 enum { 205 BPF_S_ANC_NONE, 206 BPF_S_ANC_VLAN_TAG, 207 BPF_S_ANC_VLAN_TAG_PRESENT, 208 }; 209 210 /* 211 * Execute the filter program starting at pc on the packet p 212 * wirelen is the length of the original packet 213 * buflen is the amount of data present 214 * aux_data is auxiliary data, currently used only when interpreting 215 * filters intended for the Linux kernel in cases where the kernel 216 * rejects the filter; it contains VLAN tag information 217 * For the kernel, p is assumed to be a pointer to an mbuf if buflen is 0, 218 * in all other cases, p is a pointer to a buffer and buflen is its size. 219 */ 220 u_int 221 bpf_filter_with_aux_data(pc, p, wirelen, buflen, aux_data) 222 register const struct bpf_insn *pc; 223 register const u_char *p; 224 u_int wirelen; 225 register u_int buflen; 226 register const struct bpf_aux_data *aux_data; 227 { 228 register u_int32 A, X; 229 register bpf_u_int32 k; 230 u_int32 mem[BPF_MEMWORDS]; 231 #if defined(KERNEL) || defined(_KERNEL) 232 struct mbuf *m, *n; 233 int merr, len; 234 235 if (buflen == 0) { 236 m = (struct mbuf *)p; 237 p = mtod(m, u_char *); 238 buflen = MLEN(m); 239 } else 240 m = NULL; 241 #endif 242 243 if (pc == 0) 244 /* 245 * No filter means accept all. 246 */ 247 return (u_int)-1; 248 A = 0; 249 X = 0; 250 --pc; 251 while (1) { 252 ++pc; 253 switch (pc->code) { 254 255 default: 256 #if defined(KERNEL) || defined(_KERNEL) 257 return 0; 258 #else 259 abort(); 260 #endif 261 case BPF_RET|BPF_K: 262 return (u_int)pc->k; 263 264 case BPF_RET|BPF_A: 265 return (u_int)A; 266 267 case BPF_LD|BPF_W|BPF_ABS: 268 k = pc->k; 269 if (k > buflen || sizeof(int32_t) > buflen - k) { 270 #if defined(KERNEL) || defined(_KERNEL) 271 if (m == NULL) 272 return 0; 273 A = m_xword(m, k, &merr); 274 if (merr != 0) 275 return 0; 276 continue; 277 #else 278 return 0; 279 #endif 280 } 281 A = EXTRACT_LONG(&p[k]); 282 continue; 283 284 case BPF_LD|BPF_H|BPF_ABS: 285 k = pc->k; 286 if (k > buflen || sizeof(int16_t) > buflen - k) { 287 #if defined(KERNEL) || defined(_KERNEL) 288 if (m == NULL) 289 return 0; 290 A = m_xhalf(m, k, &merr); 291 if (merr != 0) 292 return 0; 293 continue; 294 #else 295 return 0; 296 #endif 297 } 298 A = EXTRACT_SHORT(&p[k]); 299 continue; 300 301 case BPF_LD|BPF_B|BPF_ABS: 302 { 303 #if defined(SKF_AD_VLAN_TAG) && defined(SKF_AD_VLAN_TAG_PRESENT) 304 int code = BPF_S_ANC_NONE; 305 #define ANCILLARY(CODE) case SKF_AD_OFF + SKF_AD_##CODE: \ 306 code = BPF_S_ANC_##CODE; \ 307 if (!aux_data) \ 308 return 0; \ 309 break; 310 311 switch (pc->k) { 312 ANCILLARY(VLAN_TAG); 313 ANCILLARY(VLAN_TAG_PRESENT); 314 default : 315 #endif 316 k = pc->k; 317 if (k >= buflen) { 318 #if defined(KERNEL) || defined(_KERNEL) 319 if (m == NULL) 320 return 0; 321 n = m; 322 MINDEX(len, n, k); 323 A = mtod(n, u_char *)[k]; 324 continue; 325 #else 326 return 0; 327 #endif 328 } 329 A = p[k]; 330 #if defined(SKF_AD_VLAN_TAG) && defined(SKF_AD_VLAN_TAG_PRESENT) 331 } 332 switch (code) { 333 case BPF_S_ANC_VLAN_TAG: 334 if (aux_data) 335 A = aux_data->vlan_tag; 336 break; 337 338 case BPF_S_ANC_VLAN_TAG_PRESENT: 339 if (aux_data) 340 A = aux_data->vlan_tag_present; 341 break; 342 } 343 #endif 344 continue; 345 } 346 case BPF_LD|BPF_W|BPF_LEN: 347 A = wirelen; 348 continue; 349 350 case BPF_LDX|BPF_W|BPF_LEN: 351 X = wirelen; 352 continue; 353 354 case BPF_LD|BPF_W|BPF_IND: 355 k = X + pc->k; 356 if (pc->k > buflen || X > buflen - pc->k || 357 sizeof(int32_t) > buflen - k) { 358 #if defined(KERNEL) || defined(_KERNEL) 359 if (m == NULL) 360 return 0; 361 A = m_xword(m, k, &merr); 362 if (merr != 0) 363 return 0; 364 continue; 365 #else 366 return 0; 367 #endif 368 } 369 A = EXTRACT_LONG(&p[k]); 370 continue; 371 372 case BPF_LD|BPF_H|BPF_IND: 373 k = X + pc->k; 374 if (X > buflen || pc->k > buflen - X || 375 sizeof(int16_t) > buflen - k) { 376 #if defined(KERNEL) || defined(_KERNEL) 377 if (m == NULL) 378 return 0; 379 A = m_xhalf(m, k, &merr); 380 if (merr != 0) 381 return 0; 382 continue; 383 #else 384 return 0; 385 #endif 386 } 387 A = EXTRACT_SHORT(&p[k]); 388 continue; 389 390 case BPF_LD|BPF_B|BPF_IND: 391 k = X + pc->k; 392 if (pc->k >= buflen || X >= buflen - pc->k) { 393 #if defined(KERNEL) || defined(_KERNEL) 394 if (m == NULL) 395 return 0; 396 n = m; 397 MINDEX(len, n, k); 398 A = mtod(n, u_char *)[k]; 399 continue; 400 #else 401 return 0; 402 #endif 403 } 404 A = p[k]; 405 continue; 406 407 case BPF_LDX|BPF_MSH|BPF_B: 408 k = pc->k; 409 if (k >= buflen) { 410 #if defined(KERNEL) || defined(_KERNEL) 411 if (m == NULL) 412 return 0; 413 n = m; 414 MINDEX(len, n, k); 415 X = (mtod(n, char *)[k] & 0xf) << 2; 416 continue; 417 #else 418 return 0; 419 #endif 420 } 421 X = (p[pc->k] & 0xf) << 2; 422 continue; 423 424 case BPF_LD|BPF_IMM: 425 A = pc->k; 426 continue; 427 428 case BPF_LDX|BPF_IMM: 429 X = pc->k; 430 continue; 431 432 case BPF_LD|BPF_MEM: 433 A = mem[pc->k]; 434 continue; 435 436 case BPF_LDX|BPF_MEM: 437 X = mem[pc->k]; 438 continue; 439 440 case BPF_ST: 441 mem[pc->k] = A; 442 continue; 443 444 case BPF_STX: 445 mem[pc->k] = X; 446 continue; 447 448 case BPF_JMP|BPF_JA: 449 #if defined(KERNEL) || defined(_KERNEL) 450 /* 451 * No backward jumps allowed. 452 */ 453 pc += pc->k; 454 #else 455 /* 456 * XXX - we currently implement "ip6 protochain" 457 * with backward jumps, so sign-extend pc->k. 458 */ 459 pc += (bpf_int32)pc->k; 460 #endif 461 continue; 462 463 case BPF_JMP|BPF_JGT|BPF_K: 464 pc += (A > pc->k) ? pc->jt : pc->jf; 465 continue; 466 467 case BPF_JMP|BPF_JGE|BPF_K: 468 pc += (A >= pc->k) ? pc->jt : pc->jf; 469 continue; 470 471 case BPF_JMP|BPF_JEQ|BPF_K: 472 pc += (A == pc->k) ? pc->jt : pc->jf; 473 continue; 474 475 case BPF_JMP|BPF_JSET|BPF_K: 476 pc += (A & pc->k) ? pc->jt : pc->jf; 477 continue; 478 479 case BPF_JMP|BPF_JGT|BPF_X: 480 pc += (A > X) ? pc->jt : pc->jf; 481 continue; 482 483 case BPF_JMP|BPF_JGE|BPF_X: 484 pc += (A >= X) ? pc->jt : pc->jf; 485 continue; 486 487 case BPF_JMP|BPF_JEQ|BPF_X: 488 pc += (A == X) ? pc->jt : pc->jf; 489 continue; 490 491 case BPF_JMP|BPF_JSET|BPF_X: 492 pc += (A & X) ? pc->jt : pc->jf; 493 continue; 494 495 case BPF_ALU|BPF_ADD|BPF_X: 496 A += X; 497 continue; 498 499 case BPF_ALU|BPF_SUB|BPF_X: 500 A -= X; 501 continue; 502 503 case BPF_ALU|BPF_MUL|BPF_X: 504 A *= X; 505 continue; 506 507 case BPF_ALU|BPF_DIV|BPF_X: 508 if (X == 0) 509 return 0; 510 A /= X; 511 continue; 512 513 case BPF_ALU|BPF_MOD|BPF_X: 514 if (X == 0) 515 return 0; 516 A %= X; 517 continue; 518 519 case BPF_ALU|BPF_AND|BPF_X: 520 A &= X; 521 continue; 522 523 case BPF_ALU|BPF_OR|BPF_X: 524 A |= X; 525 continue; 526 527 case BPF_ALU|BPF_XOR|BPF_X: 528 A ^= X; 529 continue; 530 531 case BPF_ALU|BPF_LSH|BPF_X: 532 A <<= X; 533 continue; 534 535 case BPF_ALU|BPF_RSH|BPF_X: 536 A >>= X; 537 continue; 538 539 case BPF_ALU|BPF_ADD|BPF_K: 540 A += pc->k; 541 continue; 542 543 case BPF_ALU|BPF_SUB|BPF_K: 544 A -= pc->k; 545 continue; 546 547 case BPF_ALU|BPF_MUL|BPF_K: 548 A *= pc->k; 549 continue; 550 551 case BPF_ALU|BPF_DIV|BPF_K: 552 A /= pc->k; 553 continue; 554 555 case BPF_ALU|BPF_MOD|BPF_K: 556 A %= pc->k; 557 continue; 558 559 case BPF_ALU|BPF_AND|BPF_K: 560 A &= pc->k; 561 continue; 562 563 case BPF_ALU|BPF_OR|BPF_K: 564 A |= pc->k; 565 continue; 566 567 case BPF_ALU|BPF_XOR|BPF_K: 568 A ^= pc->k; 569 continue; 570 571 case BPF_ALU|BPF_LSH|BPF_K: 572 A <<= pc->k; 573 continue; 574 575 case BPF_ALU|BPF_RSH|BPF_K: 576 A >>= pc->k; 577 continue; 578 579 case BPF_ALU|BPF_NEG: 580 A = -A; 581 continue; 582 583 case BPF_MISC|BPF_TAX: 584 X = A; 585 continue; 586 587 case BPF_MISC|BPF_TXA: 588 A = X; 589 continue; 590 } 591 } 592 } 593 594 u_int 595 bpf_filter(pc, p, wirelen, buflen) 596 register const struct bpf_insn *pc; 597 register const u_char *p; 598 u_int wirelen; 599 register u_int buflen; 600 { 601 return bpf_filter_with_aux_data(pc, p, wirelen, buflen, NULL); 602 } 603 604 605 /* 606 * Return true if the 'fcode' is a valid filter program. 607 * The constraints are that each jump be forward and to a valid 608 * code, that memory accesses are within valid ranges (to the 609 * extent that this can be checked statically; loads of packet 610 * data have to be, and are, also checked at run time), and that 611 * the code terminates with either an accept or reject. 612 * 613 * The kernel needs to be able to verify an application's filter code. 614 * Otherwise, a bogus program could easily crash the system. 615 */ 616 int 617 bpf_validate(f, len) 618 const struct bpf_insn *f; 619 int len; 620 { 621 u_int i, from; 622 const struct bpf_insn *p; 623 624 if (len < 1) 625 return 0; 626 /* 627 * There's no maximum program length in userland. 628 */ 629 #if defined(KERNEL) || defined(_KERNEL) 630 if (len > BPF_MAXINSNS) 631 return 0; 632 #endif 633 634 for (i = 0; i < len; ++i) { 635 p = &f[i]; 636 switch (BPF_CLASS(p->code)) { 637 /* 638 * Check that memory operations use valid addresses. 639 */ 640 case BPF_LD: 641 case BPF_LDX: 642 switch (BPF_MODE(p->code)) { 643 case BPF_IMM: 644 break; 645 case BPF_ABS: 646 case BPF_IND: 647 case BPF_MSH: 648 /* 649 * There's no maximum packet data size 650 * in userland. The runtime packet length 651 * check suffices. 652 */ 653 #if defined(KERNEL) || defined(_KERNEL) 654 /* 655 * More strict check with actual packet length 656 * is done runtime. 657 */ 658 if (p->k >= bpf_maxbufsize) 659 return 0; 660 #endif 661 break; 662 case BPF_MEM: 663 if (p->k >= BPF_MEMWORDS) 664 return 0; 665 break; 666 case BPF_LEN: 667 break; 668 default: 669 return 0; 670 } 671 break; 672 case BPF_ST: 673 case BPF_STX: 674 if (p->k >= BPF_MEMWORDS) 675 return 0; 676 break; 677 case BPF_ALU: 678 switch (BPF_OP(p->code)) { 679 case BPF_ADD: 680 case BPF_SUB: 681 case BPF_MUL: 682 case BPF_OR: 683 case BPF_AND: 684 case BPF_XOR: 685 case BPF_LSH: 686 case BPF_RSH: 687 case BPF_NEG: 688 break; 689 case BPF_DIV: 690 case BPF_MOD: 691 /* 692 * Check for constant division or modulus 693 * by 0. 694 */ 695 if (BPF_SRC(p->code) == BPF_K && p->k == 0) 696 return 0; 697 break; 698 default: 699 return 0; 700 } 701 break; 702 case BPF_JMP: 703 /* 704 * Check that jumps are within the code block, 705 * and that unconditional branches don't go 706 * backwards as a result of an overflow. 707 * Unconditional branches have a 32-bit offset, 708 * so they could overflow; we check to make 709 * sure they don't. Conditional branches have 710 * an 8-bit offset, and the from address is <= 711 * BPF_MAXINSNS, and we assume that BPF_MAXINSNS 712 * is sufficiently small that adding 255 to it 713 * won't overflow. 714 * 715 * We know that len is <= BPF_MAXINSNS, and we 716 * assume that BPF_MAXINSNS is < the maximum size 717 * of a u_int, so that i + 1 doesn't overflow. 718 * 719 * For userland, we don't know that the from 720 * or len are <= BPF_MAXINSNS, but we know that 721 * from <= len, and, except on a 64-bit system, 722 * it's unlikely that len, if it truly reflects 723 * the size of the program we've been handed, 724 * will be anywhere near the maximum size of 725 * a u_int. We also don't check for backward 726 * branches, as we currently support them in 727 * userland for the protochain operation. 728 */ 729 from = i + 1; 730 switch (BPF_OP(p->code)) { 731 case BPF_JA: 732 #if defined(KERNEL) || defined(_KERNEL) 733 if (from + p->k < from || from + p->k >= len) 734 #else 735 if (from + p->k >= len) 736 #endif 737 return 0; 738 break; 739 case BPF_JEQ: 740 case BPF_JGT: 741 case BPF_JGE: 742 case BPF_JSET: 743 if (from + p->jt >= len || from + p->jf >= len) 744 return 0; 745 break; 746 default: 747 return 0; 748 } 749 break; 750 case BPF_RET: 751 break; 752 case BPF_MISC: 753 break; 754 default: 755 return 0; 756 } 757 } 758 return BPF_CLASS(f[len - 1].code) == BPF_RET; 759 } 760
