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 * 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_filter.c 8.1 (Berkeley) 6/10/93 39 * 40 * $FreeBSD: src/sys/net/bpf_filter.c,v 1.17 1999/12/29 04:38:31 peter Exp $ 41 * $DragonFly: src/sys/net/bpf_filter.c,v 1.7 2005/04/20 16:05:51 cpressey Exp $ 42 */ 43 44 #include <sys/param.h> 45 46 #if defined(sparc) || defined(mips) || defined(ibm032) || defined(__alpha__) 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 #endif 68 #include <net/bpf.h> 69 #ifdef _KERNEL 70 #define MINDEX(m, k) \ 71 { \ 72 int len = m->m_len; \ 73 \ 74 while (k >= len) { \ 75 k -= len; \ 76 m = m->m_next; \ 77 if (m == 0) \ 78 return 0; \ 79 len = m->m_len; \ 80 } \ 81 } 82 83 static u_int16_t m_xhalf (struct mbuf *m, bpf_u_int32 k, int *err); 84 static u_int32_t m_xword (struct mbuf *m, bpf_u_int32 k, int *err); 85 86 static u_int32_t 87 m_xword(struct mbuf *m, bpf_u_int32 k, int *err) 88 { 89 size_t len; 90 u_char *cp, *np; 91 struct mbuf *m0; 92 93 len = m->m_len; 94 while (k >= len) { 95 k -= len; 96 m = m->m_next; 97 if (m == 0) 98 goto bad; 99 len = m->m_len; 100 } 101 cp = mtod(m, u_char *) + k; 102 if (len - k >= 4) { 103 *err = 0; 104 return EXTRACT_LONG(cp); 105 } 106 m0 = m->m_next; 107 if (m0 == 0 || m0->m_len + len - k < 4) 108 goto bad; 109 *err = 0; 110 np = mtod(m0, u_char *); 111 switch (len - k) { 112 113 case 1: 114 return 115 ((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 122 ((u_int32_t)cp[0] << 24) | 123 ((u_int32_t)cp[1] << 16) | 124 ((u_int32_t)np[0] << 8) | 125 (u_int32_t)np[1]; 126 127 default: 128 return 129 ((u_int32_t)cp[0] << 24) | 130 ((u_int32_t)cp[1] << 16) | 131 ((u_int32_t)cp[2] << 8) | 132 (u_int32_t)np[0]; 133 } 134 bad: 135 *err = 1; 136 return 0; 137 } 138 139 static u_int16_t 140 m_xhalf(struct mbuf *m, bpf_u_int32 k, int *err) 141 { 142 size_t len; 143 u_char *cp; 144 struct mbuf *m0; 145 146 len = m->m_len; 147 while (k >= len) { 148 k -= len; 149 m = m->m_next; 150 if (m == 0) 151 goto bad; 152 len = m->m_len; 153 } 154 cp = mtod(m, u_char *) + k; 155 if (len - k >= 2) { 156 *err = 0; 157 return EXTRACT_SHORT(cp); 158 } 159 m0 = m->m_next; 160 if (m0 == 0) 161 goto bad; 162 *err = 0; 163 return (cp[0] << 8) | mtod(m0, u_char *)[0]; 164 bad: 165 *err = 1; 166 return 0; 167 } 168 #endif 169 170 /* 171 * Execute the filter program starting at pc on the packet p 172 * wirelen is the length of the original packet 173 * buflen is the amount of data present 174 */ 175 u_int 176 bpf_filter(const struct bpf_insn *pc, u_char *p, u_int wirelen, u_int buflen) 177 { 178 u_int32_t A = 0, X = 0; 179 bpf_u_int32 k; 180 int32_t mem[BPF_MEMWORDS]; 181 182 if (pc == 0) { 183 /* 184 * No filter means accept all. 185 */ 186 return (u_int)-1; 187 } 188 189 --pc; 190 while (1) { 191 ++pc; 192 switch (pc->code) { 193 194 default: 195 #ifdef _KERNEL 196 return 0; 197 #else 198 abort(); 199 #endif 200 case BPF_RET|BPF_K: 201 return (u_int)pc->k; 202 203 case BPF_RET|BPF_A: 204 return (u_int)A; 205 206 case BPF_LD|BPF_W|BPF_ABS: 207 k = pc->k; 208 if (k > buflen || sizeof(int32_t) > buflen - k) { 209 #ifdef _KERNEL 210 int merr; 211 212 if (buflen != 0) 213 return 0; 214 A = m_xword((struct mbuf *)p, k, &merr); 215 if (merr != 0) 216 return 0; 217 continue; 218 #else 219 return 0; 220 #endif 221 } 222 #ifdef BPF_ALIGN 223 if (((intptr_t)(p + k) & 3) != 0) 224 A = EXTRACT_LONG(&p[k]); 225 else 226 #endif 227 A = ntohl(*(int32_t *)(p + k)); 228 continue; 229 230 case BPF_LD|BPF_H|BPF_ABS: 231 k = pc->k; 232 if (k > buflen || sizeof(int16_t) > buflen - k) { 233 #ifdef _KERNEL 234 int merr; 235 236 if (buflen != 0) 237 return 0; 238 A = m_xhalf((struct mbuf *)p, k, &merr); 239 continue; 240 #else 241 return 0; 242 #endif 243 } 244 A = EXTRACT_SHORT(&p[k]); 245 continue; 246 247 case BPF_LD|BPF_B|BPF_ABS: 248 k = pc->k; 249 if (k >= buflen) { 250 #ifdef _KERNEL 251 struct mbuf *m; 252 253 if (buflen != 0) 254 return 0; 255 m = (struct mbuf *)p; 256 MINDEX(m, k); 257 A = mtod(m, u_char *)[k]; 258 continue; 259 #else 260 return 0; 261 #endif 262 } 263 A = p[k]; 264 continue; 265 266 case BPF_LD|BPF_W|BPF_LEN: 267 A = wirelen; 268 continue; 269 270 case BPF_LDX|BPF_W|BPF_LEN: 271 X = wirelen; 272 continue; 273 274 case BPF_LD|BPF_W|BPF_IND: 275 k = X + pc->k; 276 if (pc->k > buflen || X > buflen - pc->k || 277 sizeof(int32_t) > buflen - k) { 278 #ifdef _KERNEL 279 int merr; 280 281 if (buflen != 0) 282 return 0; 283 A = m_xword((struct mbuf *)p, k, &merr); 284 if (merr != 0) 285 return 0; 286 continue; 287 #else 288 return 0; 289 #endif 290 } 291 #ifdef BPF_ALIGN 292 if (((intptr_t)(p + k) & 3) != 0) 293 A = EXTRACT_LONG(&p[k]); 294 else 295 #endif 296 A = ntohl(*(int32_t *)(p + k)); 297 continue; 298 299 case BPF_LD|BPF_H|BPF_IND: 300 k = X + pc->k; 301 if (X > buflen || pc->k > buflen - X || 302 sizeof(int16_t) > buflen - k) { 303 #ifdef _KERNEL 304 int merr; 305 306 if (buflen != 0) 307 return 0; 308 A = m_xhalf((struct mbuf *)p, k, &merr); 309 if (merr != 0) 310 return 0; 311 continue; 312 #else 313 return 0; 314 #endif 315 } 316 A = EXTRACT_SHORT(&p[k]); 317 continue; 318 319 case BPF_LD|BPF_B|BPF_IND: 320 k = X + pc->k; 321 if (pc->k >= buflen || X >= buflen - pc->k) { 322 #ifdef _KERNEL 323 struct mbuf *m; 324 325 if (buflen != 0) 326 return 0; 327 m = (struct mbuf *)p; 328 MINDEX(m, k); 329 A = mtod(m, char *)[k]; 330 continue; 331 #else 332 return 0; 333 #endif 334 } 335 A = p[k]; 336 continue; 337 338 case BPF_LDX|BPF_MSH|BPF_B: 339 k = pc->k; 340 if (k >= buflen) { 341 #ifdef _KERNEL 342 struct mbuf *m; 343 344 if (buflen != 0) 345 return 0; 346 m = (struct mbuf *)p; 347 MINDEX(m, k); 348 X = (mtod(m, char *)[k] & 0xf) << 2; 349 continue; 350 #else 351 return 0; 352 #endif 353 } 354 X = (p[pc->k] & 0xf) << 2; 355 continue; 356 357 case BPF_LD|BPF_IMM: 358 A = pc->k; 359 continue; 360 361 case BPF_LDX|BPF_IMM: 362 X = pc->k; 363 continue; 364 365 case BPF_LD|BPF_MEM: 366 A = mem[pc->k]; 367 continue; 368 369 case BPF_LDX|BPF_MEM: 370 X = mem[pc->k]; 371 continue; 372 373 case BPF_ST: 374 mem[pc->k] = A; 375 continue; 376 377 case BPF_STX: 378 mem[pc->k] = X; 379 continue; 380 381 case BPF_JMP|BPF_JA: 382 pc += pc->k; 383 continue; 384 385 case BPF_JMP|BPF_JGT|BPF_K: 386 pc += (A > pc->k) ? pc->jt : pc->jf; 387 continue; 388 389 case BPF_JMP|BPF_JGE|BPF_K: 390 pc += (A >= pc->k) ? pc->jt : pc->jf; 391 continue; 392 393 case BPF_JMP|BPF_JEQ|BPF_K: 394 pc += (A == pc->k) ? pc->jt : pc->jf; 395 continue; 396 397 case BPF_JMP|BPF_JSET|BPF_K: 398 pc += (A & pc->k) ? pc->jt : pc->jf; 399 continue; 400 401 case BPF_JMP|BPF_JGT|BPF_X: 402 pc += (A > X) ? pc->jt : pc->jf; 403 continue; 404 405 case BPF_JMP|BPF_JGE|BPF_X: 406 pc += (A >= X) ? pc->jt : pc->jf; 407 continue; 408 409 case BPF_JMP|BPF_JEQ|BPF_X: 410 pc += (A == X) ? pc->jt : pc->jf; 411 continue; 412 413 case BPF_JMP|BPF_JSET|BPF_X: 414 pc += (A & X) ? pc->jt : pc->jf; 415 continue; 416 417 case BPF_ALU|BPF_ADD|BPF_X: 418 A += X; 419 continue; 420 421 case BPF_ALU|BPF_SUB|BPF_X: 422 A -= X; 423 continue; 424 425 case BPF_ALU|BPF_MUL|BPF_X: 426 A *= X; 427 continue; 428 429 case BPF_ALU|BPF_DIV|BPF_X: 430 if (X == 0) 431 return 0; 432 A /= X; 433 continue; 434 435 case BPF_ALU|BPF_AND|BPF_X: 436 A &= X; 437 continue; 438 439 case BPF_ALU|BPF_OR|BPF_X: 440 A |= X; 441 continue; 442 443 case BPF_ALU|BPF_LSH|BPF_X: 444 A <<= X; 445 continue; 446 447 case BPF_ALU|BPF_RSH|BPF_X: 448 A >>= X; 449 continue; 450 451 case BPF_ALU|BPF_ADD|BPF_K: 452 A += pc->k; 453 continue; 454 455 case BPF_ALU|BPF_SUB|BPF_K: 456 A -= pc->k; 457 continue; 458 459 case BPF_ALU|BPF_MUL|BPF_K: 460 A *= pc->k; 461 continue; 462 463 case BPF_ALU|BPF_DIV|BPF_K: 464 A /= pc->k; 465 continue; 466 467 case BPF_ALU|BPF_AND|BPF_K: 468 A &= pc->k; 469 continue; 470 471 case BPF_ALU|BPF_OR|BPF_K: 472 A |= pc->k; 473 continue; 474 475 case BPF_ALU|BPF_LSH|BPF_K: 476 A <<= pc->k; 477 continue; 478 479 case BPF_ALU|BPF_RSH|BPF_K: 480 A >>= pc->k; 481 continue; 482 483 case BPF_ALU|BPF_NEG: 484 A = -A; 485 continue; 486 487 case BPF_MISC|BPF_TAX: 488 X = A; 489 continue; 490 491 case BPF_MISC|BPF_TXA: 492 A = X; 493 continue; 494 } 495 } 496 } 497 498 #ifdef _KERNEL 499 /* 500 * Return true if the 'fcode' is a valid filter program. 501 * The constraints are that jump and memory accesses are within valid 502 * ranges, and that the code terminates with either an accept or reject. 503 * 504 * The kernel needs to be able to verify an application's filter code. 505 * Otherwise, a bogus program could easily crash the system. 506 */ 507 int 508 bpf_validate(const struct bpf_insn *f, int len) 509 { 510 int i; 511 const struct bpf_insn *p; 512 513 for (i = 0; i < len; ++i) { 514 /* 515 * Check that that jumps are within the code block. 516 */ 517 p = &f[i]; 518 if (BPF_CLASS(p->code) == BPF_JMP) { 519 int from = i + 1; 520 521 if (BPF_OP(p->code) == BPF_JA) { 522 if (from >= len || p->k >= len - from) 523 return 0; 524 } 525 else if (from >= len || p->jt >= len - from || 526 p->jf >= len - from) 527 return 0; 528 } 529 /* 530 * Check that memory operations use valid addresses. 531 */ 532 if ((BPF_CLASS(p->code) == BPF_ST || 533 (BPF_CLASS(p->code) == BPF_LD && 534 (p->code & 0xe0) == BPF_MEM)) && 535 p->k >= BPF_MEMWORDS) 536 return 0; 537 /* 538 * Check for constant division by 0. 539 */ 540 if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0) 541 return 0; 542 } 543 return BPF_CLASS(f[len - 1].code) == BPF_RET; 544 } 545 #endif 546