1/* $NetBSD: bpf_filter.c,v 1.35 2008/08/20 13:01:54 joerg Exp $ */ 2 3/* 4 * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from the Stanford/CMU enet packet filter, 8 * (net/enet.c) distributed as part of 4.3BSD, and code contributed 9 * to Berkeley by Steven McCanne and Van Jacobson both of Lawrence 10 * Berkeley Laboratory. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#)bpf_filter.c 8.1 (Berkeley) 6/10/93 37 */ 38/* 39 * Copyright 2009 Sun Microsystems, Inc. All rights reserved. 40 * Use is subject to license terms. 41 */ 42 43#include <sys/param.h> 44#include <sys/time.h> 45#include <sys/stream.h> 46#include <sys/byteorder.h> 47#include <sys/sdt.h> 48 49#define EXTRACT_SHORT(p) BE_IN16(p) 50#define EXTRACT_LONG(p) BE_IN32(p) 51 52#ifdef _KERNEL 53#define M_LEN(_m) ((_m)->b_wptr - (_m)->b_rptr) 54#define mtod(_a, _t) ((_t)((_a)->b_rptr)) 55#define MINDEX(len, m, k) \ 56{ \ 57 len = M_LEN(m); \ 58 while (k >= len) { \ 59 k -= len; \ 60 m = m->b_cont; \ 61 if (m == 0) \ 62 return (0); \ 63 len = M_LEN(m); \ 64 } \ 65} 66 67static int m_xword(mblk_t *, uint32_t, int *); 68static int m_xhalf(mblk_t *, uint32_t, int *); 69 70static int 71m_xword(mblk_t *m, uint32_t k, int *err) 72{ 73 int len; 74 uchar_t *cp, *np; 75 mblk_t *m0; 76 77 *err = 1; 78 MINDEX(len, m, k); 79 cp = mtod(m, uchar_t *) + k; 80 if (len >= k + 4) { 81 *err = 0; 82 return (EXTRACT_LONG(cp)); 83 } 84 m0 = m->b_cont; 85 if (m0 == 0 || M_LEN(m0) + len - k < 4) { 86 DTRACE_PROBE3(mblk_xword_fail, mblk_t *, m0, int, len, int, k); 87 return (0); 88 } 89 *err = 0; 90 np = mtod(m0, uchar_t *); 91 switch (len - k) { 92 93 case 1: 94 return ((cp[0] << 24) | (np[0] << 16) | (np[1] << 8) | np[2]); 95 96 case 2: 97 return ((cp[0] << 24) | (cp[1] << 16) | (np[0] << 8) | np[1]); 98 99 default: 100 return ((cp[0] << 24) | (cp[1] << 16) | (cp[2] << 8) | np[0]); 101 } 102} 103 104static int 105m_xhalf(mblk_t *m, uint32_t k, int *err) 106{ 107 int len; 108 uchar_t *cp; 109 mblk_t *m0; 110 111 *err = 1; 112 MINDEX(len, m, k); 113 cp = mtod(m, uchar_t *) + k; 114 if (len >= k + 2) { 115 *err = 0; 116 return (EXTRACT_SHORT(cp)); 117 } 118 m0 = m->b_cont; 119 if (m0 == 0) { 120 DTRACE_PROBE3(mblk_xhalf_fail, mblk_t *, m0, int, len, int, k); 121 return (0); 122 } 123 *err = 0; 124 return ((cp[0] << 8) | mtod(m0, uchar_t *)[0]); 125} 126#else /* _KERNEL */ 127#include <stdlib.h> 128#endif /* !_KERNEL */ 129 130#include <net/bpf.h> 131 132/* 133 * Execute the filter program starting at pc on the packet p 134 * wirelen is the length of the original packet 135 * buflen is the amount of data present 136 * When buflen is non-0, p is a pointer to a the start of the packet and the 137 * packet is only in one mblk_t. 138 * When buflen is 0, p is an mblk_t pointer. 139 */ 140uint_t 141bpf_filter(struct bpf_insn *pc, uchar_t *p, uint_t wirelen, uint_t buflen) 142{ 143 uint32_t A, X, k; 144 uint32_t mem[BPF_MEMWORDS]; 145 146 if (pc == 0) 147 /* 148 * No filter means accept all. 149 */ 150 return ((uint_t)-1); 151 A = 0; 152 X = 0; 153 --pc; 154 /* CONSTCOND */ 155 while (1) { 156 ++pc; 157 switch (pc->code) { 158 159 default: 160#ifdef _KERNEL 161 DTRACE_PROBE1(bpf_insn_unknown, 162 struct bpf_insn *, pc); 163 return (0); 164#else 165 abort(); 166#endif 167 case BPF_RET|BPF_K: 168 return ((uint_t)pc->k); 169 170 case BPF_RET|BPF_A: 171 return ((uint_t)A); 172 173 case BPF_LD|BPF_W|BPF_ABS: 174 k = pc->k; 175 if (k + sizeof (int32_t) > buflen) { 176#ifdef _KERNEL 177 int merr = 0; 178 179 if (buflen != 0) 180 return (0); 181 A = m_xword((mblk_t *)p, k, &merr); 182 if (merr != 0) 183 return (0); 184 continue; 185#else 186 return (0); 187#endif 188 } 189 A = EXTRACT_LONG(&p[k]); 190 continue; 191 192 case BPF_LD|BPF_H|BPF_ABS: 193 k = pc->k; 194 if (k + sizeof (int16_t) > buflen) { 195#ifdef _KERNEL 196 int merr; 197 198 if (buflen != 0) 199 return (0); 200 A = m_xhalf((mblk_t *)p, k, &merr); 201 if (merr != 0) 202 return (0); 203 continue; 204#else 205 return (0); 206#endif 207 } 208 A = EXTRACT_SHORT(&p[k]); 209 continue; 210 211 case BPF_LD|BPF_B|BPF_ABS: 212 k = pc->k; 213 if (k >= buflen) { 214#ifdef _KERNEL 215 mblk_t *m; 216 int len; 217 218 if (buflen != 0) 219 return (0); 220 m = (mblk_t *)p; 221 MINDEX(len, m, k); 222 A = mtod(m, uchar_t *)[k]; 223 continue; 224#else 225 return (0); 226#endif 227 } 228 A = p[k]; 229 continue; 230 231 case BPF_LD|BPF_W|BPF_LEN: 232 A = wirelen; 233 continue; 234 235 case BPF_LDX|BPF_W|BPF_LEN: 236 X = wirelen; 237 continue; 238 239 case BPF_LD|BPF_W|BPF_IND: 240 k = X + pc->k; 241 if (k + sizeof (int32_t) > buflen) { 242#ifdef _KERNEL 243 int merr = 0; 244 245 if (buflen != 0) 246 return (0); 247 A = m_xword((mblk_t *)p, k, &merr); 248 if (merr != 0) 249 return (0); 250 continue; 251#else 252 return (0); 253#endif 254 } 255 A = EXTRACT_LONG(&p[k]); 256 continue; 257 258 case BPF_LD|BPF_H|BPF_IND: 259 k = X + pc->k; 260 if (k + sizeof (int16_t) > buflen) { 261#ifdef _KERNEL 262 int merr = 0; 263 264 if (buflen != 0) 265 return (0); 266 A = m_xhalf((mblk_t *)p, k, &merr); 267 if (merr != 0) 268 return (0); 269 continue; 270#else 271 return (0); 272#endif 273 } 274 A = EXTRACT_SHORT(&p[k]); 275 continue; 276 277 case BPF_LD|BPF_B|BPF_IND: 278 k = X + pc->k; 279 if (k >= buflen) { 280#ifdef _KERNEL 281 mblk_t *m; 282 int len; 283 284 if (buflen != 0) 285 return (0); 286 m = (mblk_t *)p; 287 MINDEX(len, m, k); 288 A = mtod(m, uchar_t *)[k]; 289 continue; 290#else 291 return (0); 292#endif 293 } 294 A = p[k]; 295 continue; 296 297 case BPF_LDX|BPF_MSH|BPF_B: 298 k = pc->k; 299 if (k >= buflen) { 300#ifdef _KERNEL 301 mblk_t *m; 302 int len; 303 304 if (buflen != 0) 305 return (0); 306 m = (mblk_t *)p; 307 MINDEX(len, m, k); 308 X = (mtod(m, char *)[k] & 0xf) << 2; 309 continue; 310#else 311 return (0); 312#endif 313 } 314 X = (p[pc->k] & 0xf) << 2; 315 continue; 316 317 case BPF_LD|BPF_IMM: 318 A = pc->k; 319 continue; 320 321 case BPF_LDX|BPF_IMM: 322 X = pc->k; 323 continue; 324 325 case BPF_LD|BPF_MEM: 326 A = mem[pc->k]; 327 continue; 328 329 case BPF_LDX|BPF_MEM: 330 X = mem[pc->k]; 331 continue; 332 333 case BPF_ST: 334 mem[pc->k] = A; 335 continue; 336 337 case BPF_STX: 338 mem[pc->k] = X; 339 continue; 340 341 case BPF_JMP|BPF_JA: 342 pc += pc->k; 343 continue; 344 345 case BPF_JMP|BPF_JGT|BPF_K: 346 pc += (A > pc->k) ? pc->jt : pc->jf; 347 continue; 348 349 case BPF_JMP|BPF_JGE|BPF_K: 350 pc += (A >= pc->k) ? pc->jt : pc->jf; 351 continue; 352 353 case BPF_JMP|BPF_JEQ|BPF_K: 354 pc += (A == pc->k) ? pc->jt : pc->jf; 355 continue; 356 357 case BPF_JMP|BPF_JSET|BPF_K: 358 pc += (A & pc->k) ? pc->jt : pc->jf; 359 continue; 360 361 case BPF_JMP|BPF_JGT|BPF_X: 362 pc += (A > X) ? pc->jt : pc->jf; 363 continue; 364 365 case BPF_JMP|BPF_JGE|BPF_X: 366 pc += (A >= X) ? pc->jt : pc->jf; 367 continue; 368 369 case BPF_JMP|BPF_JEQ|BPF_X: 370 pc += (A == X) ? pc->jt : pc->jf; 371 continue; 372 373 case BPF_JMP|BPF_JSET|BPF_X: 374 pc += (A & X) ? pc->jt : pc->jf; 375 continue; 376 377 case BPF_ALU|BPF_ADD|BPF_X: 378 A += X; 379 continue; 380 381 case BPF_ALU|BPF_SUB|BPF_X: 382 A -= X; 383 continue; 384 385 case BPF_ALU|BPF_MUL|BPF_X: 386 A *= X; 387 continue; 388 389 case BPF_ALU|BPF_DIV|BPF_X: 390 if (X == 0) 391 return (0); 392 A /= X; 393 continue; 394 395 case BPF_ALU|BPF_AND|BPF_X: 396 A &= X; 397 continue; 398 399 case BPF_ALU|BPF_OR|BPF_X: 400 A |= X; 401 continue; 402 403 case BPF_ALU|BPF_LSH|BPF_X: 404 A <<= X; 405 continue; 406 407 case BPF_ALU|BPF_RSH|BPF_X: 408 A >>= X; 409 continue; 410 411 case BPF_ALU|BPF_ADD|BPF_K: 412 A += pc->k; 413 continue; 414 415 case BPF_ALU|BPF_SUB|BPF_K: 416 A -= pc->k; 417 continue; 418 419 case BPF_ALU|BPF_MUL|BPF_K: 420 A *= pc->k; 421 continue; 422 423 case BPF_ALU|BPF_DIV|BPF_K: 424 A /= pc->k; 425 continue; 426 427 case BPF_ALU|BPF_AND|BPF_K: 428 A &= pc->k; 429 continue; 430 431 case BPF_ALU|BPF_OR|BPF_K: 432 A |= pc->k; 433 continue; 434 435 case BPF_ALU|BPF_LSH|BPF_K: 436 A <<= pc->k; 437 continue; 438 439 case BPF_ALU|BPF_RSH|BPF_K: 440 A >>= pc->k; 441 continue; 442 443 case BPF_ALU|BPF_NEG: 444 A = -A; 445 continue; 446 447 case BPF_MISC|BPF_TAX: 448 X = A; 449 continue; 450 451 case BPF_MISC|BPF_TXA: 452 A = X; 453 continue; 454 } 455 } 456 /* NOTREACHED */ 457} 458 459#ifdef _KERNEL 460/* 461 * Return true if the 'fcode' is a valid filter program. 462 * The constraints are that each jump be forward and to a valid 463 * code, that memory accesses are within valid ranges (to the 464 * extent that this can be checked statically; loads of packet 465 * data have to be, and are, also checked at run time), and that 466 * the code terminates with either an accept or reject. 467 * 468 * The kernel needs to be able to verify an application's filter code. 469 * Otherwise, a bogus program could easily crash the system. 470 */ 471int 472bpf_validate(struct bpf_insn *f, int len) 473{ 474 uint_t i, from; 475 struct bpf_insn *p; 476 477 if (len < 1 || len > BPF_MAXINSNS) 478 return (0); 479 480 for (i = 0; i < len; ++i) { 481 p = &f[i]; 482 DTRACE_PROBE1(bpf_valid_insn, struct bpf_insn *, p); 483 switch (BPF_CLASS(p->code)) { 484 /* 485 * Check that memory operations use valid addresses. 486 */ 487 case BPF_LD: 488 case BPF_LDX: 489 switch (BPF_MODE(p->code)) { 490 case BPF_MEM: 491 if (p->k >= BPF_MEMWORDS) 492 return (0); 493 break; 494 case BPF_ABS: 495 case BPF_IND: 496 case BPF_MSH: 497 case BPF_IMM: 498 case BPF_LEN: 499 break; 500 default: 501 return (0); 502 } 503 break; 504 case BPF_ST: 505 case BPF_STX: 506 if (p->k >= BPF_MEMWORDS) 507 return (0); 508 break; 509 case BPF_ALU: 510 switch (BPF_OP(p->code)) { 511 case BPF_ADD: 512 case BPF_SUB: 513 case BPF_MUL: 514 case BPF_OR: 515 case BPF_AND: 516 case BPF_LSH: 517 case BPF_RSH: 518 case BPF_NEG: 519 break; 520 case BPF_DIV: 521 /* 522 * Check for constant division by 0. 523 */ 524 if (BPF_RVAL(p->code) == BPF_K && p->k == 0) 525 return (0); 526 break; 527 default: 528 return (0); 529 } 530 break; 531 case BPF_JMP: 532 /* 533 * Check that jumps are within the code block, 534 * and that unconditional branches don't go 535 * backwards as a result of an overflow. 536 * Unconditional branches have a 32-bit offset, 537 * so they could overflow; we check to make 538 * sure they don't. Conditional branches have 539 * an 8-bit offset, and the from address is <= 540 * BPF_MAXINSNS, and we assume that BPF_MAXINSNS 541 * is sufficiently small that adding 255 to it 542 * won't overflow. 543 * 544 * We know that len is <= BPF_MAXINSNS, and we 545 * assume that BPF_MAXINSNS is < the maximum size 546 * of a uint_t, so that i + 1 doesn't overflow. 547 */ 548 from = i + 1; 549 switch (BPF_OP(p->code)) { 550 case BPF_JA: 551 if (from + p->k < from || from + p->k >= len) 552 return (0); 553 break; 554 case BPF_JEQ: 555 case BPF_JGT: 556 case BPF_JGE: 557 case BPF_JSET: 558 if (from + p->jt >= len || from + p->jf >= len) 559 return (0); 560 break; 561 default: 562 return (0); 563 } 564 break; 565 case BPF_RET: 566 break; 567 case BPF_MISC: 568 break; 569 default: 570 return (0); 571 } 572 } 573 574 return (BPF_CLASS(f[len - 1].code) == BPF_RET); 575} 576#endif 577