1 /*- 2 * Copyright (c) 1990, 1991, 1993 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 * 4. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)bpf_filter.c 8.1 (Berkeley) 6/10/93 35 */ 36 37 #include <sys/cdefs.h> 38 __FBSDID("$FreeBSD$"); 39 40 #include <sys/param.h> 41 42 #if !defined(_KERNEL) || defined(sun) 43 #include <netinet/in.h> 44 #endif 45 46 #ifndef __i386__ 47 #define BPF_ALIGN 48 #endif 49 50 #ifndef BPF_ALIGN 51 #define EXTRACT_SHORT(p) ((u_int16_t)ntohs(*(u_int16_t *)p)) 52 #define EXTRACT_LONG(p) (ntohl(*(u_int32_t *)p)) 53 #else 54 #define EXTRACT_SHORT(p)\ 55 ((u_int16_t)\ 56 ((u_int16_t)*((u_char *)p+0)<<8|\ 57 (u_int16_t)*((u_char *)p+1)<<0)) 58 #define EXTRACT_LONG(p)\ 59 ((u_int32_t)*((u_char *)p+0)<<24|\ 60 (u_int32_t)*((u_char *)p+1)<<16|\ 61 (u_int32_t)*((u_char *)p+2)<<8|\ 62 (u_int32_t)*((u_char *)p+3)<<0) 63 #endif 64 65 #ifdef _KERNEL 66 #include <sys/mbuf.h> 67 #else 68 #include <stdlib.h> 69 #endif 70 #include <net/bpf.h> 71 #ifdef _KERNEL 72 #define MINDEX(m, k) \ 73 { \ 74 register int len = m->m_len; \ 75 \ 76 while (k >= len) { \ 77 k -= len; \ 78 m = m->m_next; \ 79 if (m == 0) \ 80 return (0); \ 81 len = m->m_len; \ 82 } \ 83 } 84 85 static u_int16_t m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err); 86 static u_int32_t m_xword(struct mbuf *m, bpf_u_int32 k, int *err); 87 88 static u_int32_t 89 m_xword(struct mbuf *m, bpf_u_int32 k, int *err) 90 { 91 size_t len; 92 u_char *cp, *np; 93 struct mbuf *m0; 94 95 len = m->m_len; 96 while (k >= len) { 97 k -= len; 98 m = m->m_next; 99 if (m == 0) 100 goto bad; 101 len = m->m_len; 102 } 103 cp = mtod(m, u_char *) + k; 104 if (len - k >= 4) { 105 *err = 0; 106 return (EXTRACT_LONG(cp)); 107 } 108 m0 = m->m_next; 109 if (m0 == 0 || m0->m_len + len - k < 4) 110 goto bad; 111 *err = 0; 112 np = mtod(m0, u_char *); 113 switch (len - k) { 114 case 1: 115 return (((u_int32_t)cp[0] << 24) | 116 ((u_int32_t)np[0] << 16) | 117 ((u_int32_t)np[1] << 8) | 118 (u_int32_t)np[2]); 119 120 case 2: 121 return (((u_int32_t)cp[0] << 24) | 122 ((u_int32_t)cp[1] << 16) | 123 ((u_int32_t)np[0] << 8) | 124 (u_int32_t)np[1]); 125 126 default: 127 return (((u_int32_t)cp[0] << 24) | 128 ((u_int32_t)cp[1] << 16) | 129 ((u_int32_t)cp[2] << 8) | 130 (u_int32_t)np[0]); 131 } 132 bad: 133 *err = 1; 134 return (0); 135 } 136 137 static u_int16_t 138 m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err) 139 { 140 size_t len; 141 u_char *cp; 142 struct mbuf *m0; 143 144 len = m->m_len; 145 while (k >= len) { 146 k -= len; 147 m = m->m_next; 148 if (m == 0) 149 goto bad; 150 len = m->m_len; 151 } 152 cp = mtod(m, u_char *) + k; 153 if (len - k >= 2) { 154 *err = 0; 155 return (EXTRACT_SHORT(cp)); 156 } 157 m0 = m->m_next; 158 if (m0 == 0) 159 goto bad; 160 *err = 0; 161 return ((cp[0] << 8) | mtod(m0, u_char *)[0]); 162 bad: 163 *err = 1; 164 return (0); 165 } 166 #endif 167 168 /* 169 * Execute the filter program starting at pc on the packet p 170 * wirelen is the length of the original packet 171 * buflen is the amount of data present 172 */ 173 u_int 174 bpf_filter(const struct bpf_insn *pc, u_char *p, u_int wirelen, u_int buflen) 175 { 176 u_int32_t A = 0, X = 0; 177 bpf_u_int32 k; 178 u_int32_t mem[BPF_MEMWORDS]; 179 180 bzero(mem, sizeof(mem)); 181 182 if (pc == NULL) 183 /* 184 * No filter means accept all. 185 */ 186 return ((u_int)-1); 187 188 --pc; 189 while (1) { 190 ++pc; 191 switch (pc->code) { 192 default: 193 #ifdef _KERNEL 194 return (0); 195 #else 196 abort(); 197 #endif 198 199 case BPF_RET|BPF_K: 200 return ((u_int)pc->k); 201 202 case BPF_RET|BPF_A: 203 return ((u_int)A); 204 205 case BPF_LD|BPF_W|BPF_ABS: 206 k = pc->k; 207 if (k > buflen || sizeof(int32_t) > buflen - k) { 208 #ifdef _KERNEL 209 int merr; 210 211 if (buflen != 0) 212 return (0); 213 A = m_xword((struct mbuf *)p, k, &merr); 214 if (merr != 0) 215 return (0); 216 continue; 217 #else 218 return (0); 219 #endif 220 } 221 #ifdef BPF_ALIGN 222 if (((intptr_t)(p + k) & 3) != 0) 223 A = EXTRACT_LONG(&p[k]); 224 else 225 #endif 226 A = ntohl(*(int32_t *)(p + k)); 227 continue; 228 229 case BPF_LD|BPF_H|BPF_ABS: 230 k = pc->k; 231 if (k > buflen || sizeof(int16_t) > buflen - k) { 232 #ifdef _KERNEL 233 int merr; 234 235 if (buflen != 0) 236 return (0); 237 A = m_xhalf((struct mbuf *)p, k, &merr); 238 continue; 239 #else 240 return (0); 241 #endif 242 } 243 A = EXTRACT_SHORT(&p[k]); 244 continue; 245 246 case BPF_LD|BPF_B|BPF_ABS: 247 k = pc->k; 248 if (k >= buflen) { 249 #ifdef _KERNEL 250 struct mbuf *m; 251 252 if (buflen != 0) 253 return (0); 254 m = (struct mbuf *)p; 255 MINDEX(m, k); 256 A = mtod(m, u_char *)[k]; 257 continue; 258 #else 259 return (0); 260 #endif 261 } 262 A = p[k]; 263 continue; 264 265 case BPF_LD|BPF_W|BPF_LEN: 266 A = wirelen; 267 continue; 268 269 case BPF_LDX|BPF_W|BPF_LEN: 270 X = wirelen; 271 continue; 272 273 case BPF_LD|BPF_W|BPF_IND: 274 k = X + pc->k; 275 if (pc->k > buflen || X > buflen - pc->k || 276 sizeof(int32_t) > buflen - k) { 277 #ifdef _KERNEL 278 int merr; 279 280 if (buflen != 0) 281 return (0); 282 A = m_xword((struct mbuf *)p, k, &merr); 283 if (merr != 0) 284 return (0); 285 continue; 286 #else 287 return (0); 288 #endif 289 } 290 #ifdef BPF_ALIGN 291 if (((intptr_t)(p + k) & 3) != 0) 292 A = EXTRACT_LONG(&p[k]); 293 else 294 #endif 295 A = ntohl(*(int32_t *)(p + k)); 296 continue; 297 298 case BPF_LD|BPF_H|BPF_IND: 299 k = X + pc->k; 300 if (X > buflen || pc->k > buflen - X || 301 sizeof(int16_t) > buflen - k) { 302 #ifdef _KERNEL 303 int merr; 304 305 if (buflen != 0) 306 return (0); 307 A = m_xhalf((struct mbuf *)p, k, &merr); 308 if (merr != 0) 309 return (0); 310 continue; 311 #else 312 return (0); 313 #endif 314 } 315 A = EXTRACT_SHORT(&p[k]); 316 continue; 317 318 case BPF_LD|BPF_B|BPF_IND: 319 k = X + pc->k; 320 if (pc->k >= buflen || X >= buflen - pc->k) { 321 #ifdef _KERNEL 322 struct mbuf *m; 323 324 if (buflen != 0) 325 return (0); 326 m = (struct mbuf *)p; 327 MINDEX(m, k); 328 A = mtod(m, u_char *)[k]; 329 continue; 330 #else 331 return (0); 332 #endif 333 } 334 A = p[k]; 335 continue; 336 337 case BPF_LDX|BPF_MSH|BPF_B: 338 k = pc->k; 339 if (k >= buflen) { 340 #ifdef _KERNEL 341 register struct mbuf *m; 342 343 if (buflen != 0) 344 return (0); 345 m = (struct mbuf *)p; 346 MINDEX(m, k); 347 X = (mtod(m, u_char *)[k] & 0xf) << 2; 348 continue; 349 #else 350 return (0); 351 #endif 352 } 353 X = (p[pc->k] & 0xf) << 2; 354 continue; 355 356 case BPF_LD|BPF_IMM: 357 A = pc->k; 358 continue; 359 360 case BPF_LDX|BPF_IMM: 361 X = pc->k; 362 continue; 363 364 case BPF_LD|BPF_MEM: 365 A = mem[pc->k]; 366 continue; 367 368 case BPF_LDX|BPF_MEM: 369 X = mem[pc->k]; 370 continue; 371 372 case BPF_ST: 373 mem[pc->k] = A; 374 continue; 375 376 case BPF_STX: 377 mem[pc->k] = X; 378 continue; 379 380 case BPF_JMP|BPF_JA: 381 pc += pc->k; 382 continue; 383 384 case BPF_JMP|BPF_JGT|BPF_K: 385 pc += (A > pc->k) ? pc->jt : pc->jf; 386 continue; 387 388 case BPF_JMP|BPF_JGE|BPF_K: 389 pc += (A >= pc->k) ? pc->jt : pc->jf; 390 continue; 391 392 case BPF_JMP|BPF_JEQ|BPF_K: 393 pc += (A == pc->k) ? pc->jt : pc->jf; 394 continue; 395 396 case BPF_JMP|BPF_JSET|BPF_K: 397 pc += (A & pc->k) ? pc->jt : pc->jf; 398 continue; 399 400 case BPF_JMP|BPF_JGT|BPF_X: 401 pc += (A > X) ? pc->jt : pc->jf; 402 continue; 403 404 case BPF_JMP|BPF_JGE|BPF_X: 405 pc += (A >= X) ? pc->jt : pc->jf; 406 continue; 407 408 case BPF_JMP|BPF_JEQ|BPF_X: 409 pc += (A == X) ? pc->jt : pc->jf; 410 continue; 411 412 case BPF_JMP|BPF_JSET|BPF_X: 413 pc += (A & X) ? pc->jt : pc->jf; 414 continue; 415 416 case BPF_ALU|BPF_ADD|BPF_X: 417 A += X; 418 continue; 419 420 case BPF_ALU|BPF_SUB|BPF_X: 421 A -= X; 422 continue; 423 424 case BPF_ALU|BPF_MUL|BPF_X: 425 A *= X; 426 continue; 427 428 case BPF_ALU|BPF_DIV|BPF_X: 429 if (X == 0) 430 return (0); 431 A /= X; 432 continue; 433 434 case BPF_ALU|BPF_AND|BPF_X: 435 A &= X; 436 continue; 437 438 case BPF_ALU|BPF_OR|BPF_X: 439 A |= X; 440 continue; 441 442 case BPF_ALU|BPF_LSH|BPF_X: 443 A <<= X; 444 continue; 445 446 case BPF_ALU|BPF_RSH|BPF_X: 447 A >>= X; 448 continue; 449 450 case BPF_ALU|BPF_ADD|BPF_K: 451 A += pc->k; 452 continue; 453 454 case BPF_ALU|BPF_SUB|BPF_K: 455 A -= pc->k; 456 continue; 457 458 case BPF_ALU|BPF_MUL|BPF_K: 459 A *= pc->k; 460 continue; 461 462 case BPF_ALU|BPF_DIV|BPF_K: 463 A /= pc->k; 464 continue; 465 466 case BPF_ALU|BPF_AND|BPF_K: 467 A &= pc->k; 468 continue; 469 470 case BPF_ALU|BPF_OR|BPF_K: 471 A |= pc->k; 472 continue; 473 474 case BPF_ALU|BPF_LSH|BPF_K: 475 A <<= pc->k; 476 continue; 477 478 case BPF_ALU|BPF_RSH|BPF_K: 479 A >>= pc->k; 480 continue; 481 482 case BPF_ALU|BPF_NEG: 483 A = -A; 484 continue; 485 486 case BPF_MISC|BPF_TAX: 487 X = A; 488 continue; 489 490 case BPF_MISC|BPF_TXA: 491 A = X; 492 continue; 493 } 494 } 495 } 496 497 #ifdef _KERNEL 498 static const u_short bpf_code_map[] = { 499 0x10ff, /* 0x00-0x0f: 1111111100001000 */ 500 0x3070, /* 0x10-0x1f: 0000111000001100 */ 501 0x3131, /* 0x20-0x2f: 1000110010001100 */ 502 0x3031, /* 0x30-0x3f: 1000110000001100 */ 503 0x3131, /* 0x40-0x4f: 1000110010001100 */ 504 0x1011, /* 0x50-0x5f: 1000100000001000 */ 505 0x1013, /* 0x60-0x6f: 1100100000001000 */ 506 0x1010, /* 0x70-0x7f: 0000100000001000 */ 507 0x0093, /* 0x80-0x8f: 1100100100000000 */ 508 0x0000, /* 0x90-0x9f: 0000000000000000 */ 509 0x0000, /* 0xa0-0xaf: 0000000000000000 */ 510 0x0002, /* 0xb0-0xbf: 0100000000000000 */ 511 0x0000, /* 0xc0-0xcf: 0000000000000000 */ 512 0x0000, /* 0xd0-0xdf: 0000000000000000 */ 513 0x0000, /* 0xe0-0xef: 0000000000000000 */ 514 0x0000 /* 0xf0-0xff: 0000000000000000 */ 515 }; 516 517 #define BPF_VALIDATE_CODE(c) \ 518 ((c) <= 0xff && (bpf_code_map[(c) >> 4] & (1 << ((c) & 0xf))) != 0) 519 520 /* 521 * Return true if the 'fcode' is a valid filter program. 522 * The constraints are that each jump be forward and to a valid 523 * code. The code must terminate with either an accept or reject. 524 * 525 * The kernel needs to be able to verify an application's filter code. 526 * Otherwise, a bogus program could easily crash the system. 527 */ 528 int 529 bpf_validate(const struct bpf_insn *f, int len) 530 { 531 register int i; 532 register const struct bpf_insn *p; 533 534 /* Do not accept negative length filter. */ 535 if (len < 0) 536 return (0); 537 538 /* An empty filter means accept all. */ 539 if (len == 0) 540 return (1); 541 542 for (i = 0; i < len; ++i) { 543 p = &f[i]; 544 /* 545 * Check that the code is valid. 546 */ 547 if (!BPF_VALIDATE_CODE(p->code)) 548 return (0); 549 /* 550 * Check that that jumps are forward, and within 551 * the code block. 552 */ 553 if (BPF_CLASS(p->code) == BPF_JMP) { 554 register u_int offset; 555 556 if (p->code == (BPF_JMP|BPF_JA)) 557 offset = p->k; 558 else 559 offset = p->jt > p->jf ? p->jt : p->jf; 560 if (offset >= (u_int)(len - i) - 1) 561 return (0); 562 continue; 563 } 564 /* 565 * Check that memory operations use valid addresses. 566 */ 567 if (p->code == BPF_ST || p->code == BPF_STX || 568 p->code == (BPF_LD|BPF_MEM) || 569 p->code == (BPF_LDX|BPF_MEM)) { 570 if (p->k >= BPF_MEMWORDS) 571 return (0); 572 continue; 573 } 574 /* 575 * Check for constant division by 0. 576 */ 577 if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0) 578 return (0); 579 } 580 return (BPF_CLASS(f[len - 1].code) == BPF_RET); 581 } 582 #endif 583