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 if (pc == NULL) 181 /* 182 * No filter means accept all. 183 */ 184 return ((u_int)-1); 185 186 --pc; 187 while (1) { 188 ++pc; 189 switch (pc->code) { 190 default: 191 #ifdef _KERNEL 192 return (0); 193 #else 194 abort(); 195 #endif 196 197 case BPF_RET|BPF_K: 198 return ((u_int)pc->k); 199 200 case BPF_RET|BPF_A: 201 return ((u_int)A); 202 203 case BPF_LD|BPF_W|BPF_ABS: 204 k = pc->k; 205 if (k > buflen || sizeof(int32_t) > buflen - k) { 206 #ifdef _KERNEL 207 int merr; 208 209 if (buflen != 0) 210 return (0); 211 A = m_xword((struct mbuf *)p, k, &merr); 212 if (merr != 0) 213 return (0); 214 continue; 215 #else 216 return (0); 217 #endif 218 } 219 #ifdef BPF_ALIGN 220 if (((intptr_t)(p + k) & 3) != 0) 221 A = EXTRACT_LONG(&p[k]); 222 else 223 #endif 224 A = ntohl(*(int32_t *)(p + k)); 225 continue; 226 227 case BPF_LD|BPF_H|BPF_ABS: 228 k = pc->k; 229 if (k > buflen || sizeof(int16_t) > buflen - k) { 230 #ifdef _KERNEL 231 int merr; 232 233 if (buflen != 0) 234 return (0); 235 A = m_xhalf((struct mbuf *)p, k, &merr); 236 continue; 237 #else 238 return (0); 239 #endif 240 } 241 A = EXTRACT_SHORT(&p[k]); 242 continue; 243 244 case BPF_LD|BPF_B|BPF_ABS: 245 k = pc->k; 246 if (k >= buflen) { 247 #ifdef _KERNEL 248 struct mbuf *m; 249 250 if (buflen != 0) 251 return (0); 252 m = (struct mbuf *)p; 253 MINDEX(m, k); 254 A = mtod(m, u_char *)[k]; 255 continue; 256 #else 257 return (0); 258 #endif 259 } 260 A = p[k]; 261 continue; 262 263 case BPF_LD|BPF_W|BPF_LEN: 264 A = wirelen; 265 continue; 266 267 case BPF_LDX|BPF_W|BPF_LEN: 268 X = wirelen; 269 continue; 270 271 case BPF_LD|BPF_W|BPF_IND: 272 k = X + pc->k; 273 if (pc->k > buflen || X > buflen - pc->k || 274 sizeof(int32_t) > buflen - k) { 275 #ifdef _KERNEL 276 int merr; 277 278 if (buflen != 0) 279 return (0); 280 A = m_xword((struct mbuf *)p, k, &merr); 281 if (merr != 0) 282 return (0); 283 continue; 284 #else 285 return (0); 286 #endif 287 } 288 #ifdef BPF_ALIGN 289 if (((intptr_t)(p + k) & 3) != 0) 290 A = EXTRACT_LONG(&p[k]); 291 else 292 #endif 293 A = ntohl(*(int32_t *)(p + k)); 294 continue; 295 296 case BPF_LD|BPF_H|BPF_IND: 297 k = X + pc->k; 298 if (X > buflen || pc->k > buflen - X || 299 sizeof(int16_t) > buflen - k) { 300 #ifdef _KERNEL 301 int merr; 302 303 if (buflen != 0) 304 return (0); 305 A = m_xhalf((struct mbuf *)p, k, &merr); 306 if (merr != 0) 307 return (0); 308 continue; 309 #else 310 return (0); 311 #endif 312 } 313 A = EXTRACT_SHORT(&p[k]); 314 continue; 315 316 case BPF_LD|BPF_B|BPF_IND: 317 k = X + pc->k; 318 if (pc->k >= buflen || X >= buflen - pc->k) { 319 #ifdef _KERNEL 320 struct mbuf *m; 321 322 if (buflen != 0) 323 return (0); 324 m = (struct mbuf *)p; 325 MINDEX(m, k); 326 A = mtod(m, u_char *)[k]; 327 continue; 328 #else 329 return (0); 330 #endif 331 } 332 A = p[k]; 333 continue; 334 335 case BPF_LDX|BPF_MSH|BPF_B: 336 k = pc->k; 337 if (k >= buflen) { 338 #ifdef _KERNEL 339 register struct mbuf *m; 340 341 if (buflen != 0) 342 return (0); 343 m = (struct mbuf *)p; 344 MINDEX(m, k); 345 X = (mtod(m, u_char *)[k] & 0xf) << 2; 346 continue; 347 #else 348 return (0); 349 #endif 350 } 351 X = (p[pc->k] & 0xf) << 2; 352 continue; 353 354 case BPF_LD|BPF_IMM: 355 A = pc->k; 356 continue; 357 358 case BPF_LDX|BPF_IMM: 359 X = pc->k; 360 continue; 361 362 case BPF_LD|BPF_MEM: 363 A = mem[pc->k]; 364 continue; 365 366 case BPF_LDX|BPF_MEM: 367 X = mem[pc->k]; 368 continue; 369 370 case BPF_ST: 371 mem[pc->k] = A; 372 continue; 373 374 case BPF_STX: 375 mem[pc->k] = X; 376 continue; 377 378 case BPF_JMP|BPF_JA: 379 pc += pc->k; 380 continue; 381 382 case BPF_JMP|BPF_JGT|BPF_K: 383 pc += (A > pc->k) ? pc->jt : pc->jf; 384 continue; 385 386 case BPF_JMP|BPF_JGE|BPF_K: 387 pc += (A >= pc->k) ? pc->jt : pc->jf; 388 continue; 389 390 case BPF_JMP|BPF_JEQ|BPF_K: 391 pc += (A == pc->k) ? pc->jt : pc->jf; 392 continue; 393 394 case BPF_JMP|BPF_JSET|BPF_K: 395 pc += (A & pc->k) ? pc->jt : pc->jf; 396 continue; 397 398 case BPF_JMP|BPF_JGT|BPF_X: 399 pc += (A > X) ? pc->jt : pc->jf; 400 continue; 401 402 case BPF_JMP|BPF_JGE|BPF_X: 403 pc += (A >= X) ? pc->jt : pc->jf; 404 continue; 405 406 case BPF_JMP|BPF_JEQ|BPF_X: 407 pc += (A == X) ? pc->jt : pc->jf; 408 continue; 409 410 case BPF_JMP|BPF_JSET|BPF_X: 411 pc += (A & X) ? pc->jt : pc->jf; 412 continue; 413 414 case BPF_ALU|BPF_ADD|BPF_X: 415 A += X; 416 continue; 417 418 case BPF_ALU|BPF_SUB|BPF_X: 419 A -= X; 420 continue; 421 422 case BPF_ALU|BPF_MUL|BPF_X: 423 A *= X; 424 continue; 425 426 case BPF_ALU|BPF_DIV|BPF_X: 427 if (X == 0) 428 return (0); 429 A /= X; 430 continue; 431 432 case BPF_ALU|BPF_AND|BPF_X: 433 A &= X; 434 continue; 435 436 case BPF_ALU|BPF_OR|BPF_X: 437 A |= X; 438 continue; 439 440 case BPF_ALU|BPF_LSH|BPF_X: 441 A <<= X; 442 continue; 443 444 case BPF_ALU|BPF_RSH|BPF_X: 445 A >>= X; 446 continue; 447 448 case BPF_ALU|BPF_ADD|BPF_K: 449 A += pc->k; 450 continue; 451 452 case BPF_ALU|BPF_SUB|BPF_K: 453 A -= pc->k; 454 continue; 455 456 case BPF_ALU|BPF_MUL|BPF_K: 457 A *= pc->k; 458 continue; 459 460 case BPF_ALU|BPF_DIV|BPF_K: 461 A /= pc->k; 462 continue; 463 464 case BPF_ALU|BPF_AND|BPF_K: 465 A &= pc->k; 466 continue; 467 468 case BPF_ALU|BPF_OR|BPF_K: 469 A |= pc->k; 470 continue; 471 472 case BPF_ALU|BPF_LSH|BPF_K: 473 A <<= pc->k; 474 continue; 475 476 case BPF_ALU|BPF_RSH|BPF_K: 477 A >>= pc->k; 478 continue; 479 480 case BPF_ALU|BPF_NEG: 481 A = -A; 482 continue; 483 484 case BPF_MISC|BPF_TAX: 485 X = A; 486 continue; 487 488 case BPF_MISC|BPF_TXA: 489 A = X; 490 continue; 491 } 492 } 493 } 494 495 #ifdef _KERNEL 496 static const u_short bpf_code_map[] = { 497 0x10ff, /* 0x00-0x0f: 1111111100001000 */ 498 0x3070, /* 0x10-0x1f: 0000111000001100 */ 499 0x3131, /* 0x20-0x2f: 1000110010001100 */ 500 0x3031, /* 0x30-0x3f: 1000110000001100 */ 501 0x3131, /* 0x40-0x4f: 1000110010001100 */ 502 0x1011, /* 0x50-0x5f: 1000100000001000 */ 503 0x1013, /* 0x60-0x6f: 1100100000001000 */ 504 0x1010, /* 0x70-0x7f: 0000100000001000 */ 505 0x0093, /* 0x80-0x8f: 1100100100000000 */ 506 0x0000, /* 0x90-0x9f: 0000000000000000 */ 507 0x0000, /* 0xa0-0xaf: 0000000000000000 */ 508 0x0002, /* 0xb0-0xbf: 0100000000000000 */ 509 0x0000, /* 0xc0-0xcf: 0000000000000000 */ 510 0x0000, /* 0xd0-0xdf: 0000000000000000 */ 511 0x0000, /* 0xe0-0xef: 0000000000000000 */ 512 0x0000 /* 0xf0-0xff: 0000000000000000 */ 513 }; 514 515 #define BPF_VALIDATE_CODE(c) \ 516 ((c) <= 0xff && (bpf_code_map[(c) >> 4] & (1 << ((c) & 0xf))) != 0) 517 518 /* 519 * Return true if the 'fcode' is a valid filter program. 520 * The constraints are that each jump be forward and to a valid 521 * code. The code must terminate with either an accept or reject. 522 * 523 * The kernel needs to be able to verify an application's filter code. 524 * Otherwise, a bogus program could easily crash the system. 525 */ 526 int 527 bpf_validate(const struct bpf_insn *f, int len) 528 { 529 register int i; 530 register const struct bpf_insn *p; 531 532 /* Do not accept negative length filter. */ 533 if (len < 0) 534 return (0); 535 536 /* An empty filter means accept all. */ 537 if (len == 0) 538 return (1); 539 540 for (i = 0; i < len; ++i) { 541 p = &f[i]; 542 /* 543 * Check that the code is valid. 544 */ 545 if (!BPF_VALIDATE_CODE(p->code)) 546 return (0); 547 /* 548 * Check that that jumps are forward, and within 549 * the code block. 550 */ 551 if (BPF_CLASS(p->code) == BPF_JMP) { 552 register u_int offset; 553 554 if (p->code == (BPF_JMP|BPF_JA)) 555 offset = p->k; 556 else 557 offset = p->jt > p->jf ? p->jt : p->jf; 558 if (offset >= (u_int)(len - i) - 1) 559 return (0); 560 continue; 561 } 562 /* 563 * Check that memory operations use valid addresses. 564 */ 565 if (p->code == BPF_ST || p->code == BPF_STX || 566 p->code == (BPF_LD|BPF_MEM) || 567 p->code == (BPF_LDX|BPF_MEM)) { 568 if (p->k >= BPF_MEMWORDS) 569 return (0); 570 continue; 571 } 572 /* 573 * Check for constant division by 0. 574 */ 575 if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0) 576 return (0); 577 } 578 return (BPF_CLASS(f[len - 1].code) == BPF_RET); 579 } 580 #endif 581