1 /*- 2 * Copyright (c) 1990-1991 The Regents of the University of California. 3 * 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 * static char rcsid[] = 41 * "$Header: bpf_filter.c,v 1.16 91/10/27 21:22:35 mccanne Exp $"; 42 */ 43 #if !(defined(lint) || defined(KERNEL)) 44 static char rcsid[] = 45 "@(#) $Header: bpf_filter.c,v 1.16 91/10/27 21:22:35 mccanne Exp $ (LBL)"; 46 #endif 47 48 #include <sys/param.h> 49 #include <sys/types.h> 50 #include <sys/time.h> 51 #include <net/bpf.h> 52 53 #ifdef sun 54 #include <netinet/in.h> 55 #endif 56 57 #if defined(sparc) || defined(mips) || defined(ibm032) 58 #define ALIGN 59 #endif 60 61 #ifndef ALIGN 62 #define EXTRACT_SHORT(p) (ntohs(*(u_short *)p)) 63 #define EXTRACT_LONG(p) (ntohl(*(u_long *)p)) 64 #else 65 #define EXTRACT_SHORT(p)\ 66 ((u_short)\ 67 (*((u_char *)(p)+0)<<8|\ 68 *((u_char *)(p)+1)<<0)) 69 #define EXTRACT_LONG(p)\ 70 (*((u_char *)(p)+0)<<24|\ 71 *((u_char *)(p)+1)<<16|\ 72 *((u_char *)(p)+2)<<8|\ 73 *((u_char *)(p)+3)<<0) 74 #endif 75 76 #ifdef KERNEL 77 #include <sys/mbuf.h> 78 #define MINDEX(m, k) \ 79 { \ 80 register int len = m->m_len; \ 81 \ 82 while (k >= len) { \ 83 k -= len; \ 84 m = m->m_next; \ 85 if (m == 0) \ 86 return 0; \ 87 len = m->m_len; \ 88 } \ 89 } 90 91 static int 92 m_xword(m, k, err) 93 register struct mbuf *m; 94 register int k, *err; 95 { 96 register int len; 97 register u_char *cp, *np; 98 register struct mbuf *m0; 99 100 len = m->m_len; 101 while (k >= len) { 102 k -= len; 103 m = m->m_next; 104 if (m == 0) 105 goto bad; 106 len = m->m_len; 107 } 108 cp = mtod(m, u_char *) + k; 109 if (len - k >= 4) { 110 *err = 0; 111 return EXTRACT_LONG(cp); 112 } 113 m0 = m->m_next; 114 if (m0 == 0 || m0->m_len + len - k < 4) 115 goto bad; 116 *err = 0; 117 np = mtod(m0, u_char *); 118 switch (len - k) { 119 120 case 1: 121 return (cp[k] << 24) | (np[0] << 16) | (np[1] << 8) | np[2]; 122 123 case 2: 124 return (cp[k] << 24) | (cp[k + 1] << 16) | (np[0] << 8) | 125 np[1]; 126 127 default: 128 return (cp[k] << 24) | (cp[k + 1] << 16) | (cp[k + 2] << 8) | 129 np[0]; 130 } 131 bad: 132 *err = 1; 133 return 0; 134 } 135 136 static int 137 m_xhalf(m, k, err) 138 register struct mbuf *m; 139 register int k, *err; 140 { 141 register int len; 142 register u_char *cp; 143 register struct mbuf *m0; 144 145 len = m->m_len; 146 while (k >= len) { 147 k -= len; 148 m = m->m_next; 149 if (m == 0) 150 goto bad; 151 len = m->m_len; 152 } 153 cp = mtod(m, u_char *) + k; 154 if (len - k >= 2) { 155 *err = 0; 156 return EXTRACT_SHORT(cp); 157 } 158 m0 = m->m_next; 159 if (m0 == 0) 160 goto bad; 161 *err = 0; 162 return (cp[k] << 8) | mtod(m0, u_char *)[0]; 163 bad: 164 *err = 1; 165 return 0; 166 } 167 168 169 #endif 170 171 /* 172 * Execute the filter program starting at pc on the packet p 173 * wirelen is the length of the original packet 174 * buflen is the amount of data present 175 */ 176 u_int 177 bpf_filter(pc, p, wirelen, buflen) 178 register struct bpf_insn *pc; 179 register u_char *p; 180 u_int wirelen; 181 register u_int buflen; 182 { 183 register long A, X; 184 register int k; 185 long mem[BPF_MEMWORDS]; 186 187 if (pc == 0) 188 /* 189 * No filter means accept all. 190 */ 191 return (u_int)-1; 192 #ifdef lint 193 A = 0; 194 X = 0; 195 #endif 196 --pc; 197 while (1) { 198 ++pc; 199 switch (pc->code) { 200 201 default: 202 #ifdef KERNEL 203 return 0; 204 #else 205 abort(); 206 #endif 207 case BPF_RET|BPF_K: 208 return (u_int)pc->k; 209 210 case BPF_RET|BPF_A: 211 return (u_int)A; 212 213 case BPF_LD|BPF_W|BPF_ABS: 214 k = pc->k; 215 if (k + sizeof(long) > buflen) { 216 #ifdef KERNEL 217 int merr; 218 219 if (buflen != 0) 220 return 0; 221 A = m_xword((struct mbuf *)p, k, &merr); 222 if (merr != 0) 223 return 0; 224 continue; 225 #else 226 return 0; 227 #endif 228 } 229 #ifdef ALIGN 230 if (((int)(p + k) & 3) != 0) 231 A = EXTRACT_LONG(&p[k]); 232 else 233 #endif 234 A = *(long *)(p + k); 235 continue; 236 237 case BPF_LD|BPF_H|BPF_ABS: 238 k = pc->k; 239 if (k + sizeof(short) > buflen) { 240 #ifdef KERNEL 241 int merr; 242 243 if (buflen != 0) 244 return 0; 245 A = m_xhalf((struct mbuf *)p, k, &merr); 246 continue; 247 #else 248 return 0; 249 #endif 250 } 251 A = EXTRACT_SHORT(&p[k]); 252 continue; 253 254 case BPF_LD|BPF_B|BPF_ABS: 255 k = pc->k; 256 if (k >= buflen) { 257 #ifdef KERNEL 258 register struct mbuf *m; 259 260 if (buflen != 0) 261 return 0; 262 m = (struct mbuf *)p; 263 MINDEX(m, k); 264 A = mtod(m, u_char *)[k]; 265 continue; 266 #else 267 return 0; 268 #endif 269 } 270 A = p[k]; 271 continue; 272 273 case BPF_LD|BPF_W|BPF_LEN: 274 A = wirelen; 275 continue; 276 277 case BPF_LDX|BPF_W|BPF_LEN: 278 X = wirelen; 279 continue; 280 281 case BPF_LD|BPF_W|BPF_IND: 282 k = X + pc->k; 283 if (k + sizeof(long) > buflen) { 284 #ifdef KERNEL 285 int merr; 286 287 if (buflen != 0) 288 return 0; 289 A = m_xword((struct mbuf *)p, k, &merr); 290 if (merr != 0) 291 return 0; 292 continue; 293 #else 294 return 0; 295 #endif 296 } 297 #ifdef ALIGN 298 if (((int)(p + k) & 3) != 0) 299 A = EXTRACT_LONG(&p[k]); 300 else 301 #endif 302 A = *(long *)(p + k); 303 continue; 304 305 case BPF_LD|BPF_H|BPF_IND: 306 k = X + pc->k; 307 if (k + sizeof(short) > buflen) { 308 #ifdef KERNEL 309 int merr; 310 311 if (buflen != 0) 312 return 0; 313 A = m_xhalf((struct mbuf *)p, k, &merr); 314 if (merr != 0) 315 return 0; 316 continue; 317 #else 318 return 0; 319 #endif 320 } 321 A = EXTRACT_SHORT(&p[k]); 322 continue; 323 324 case BPF_LD|BPF_B|BPF_IND: 325 k = X + pc->k; 326 if (k >= buflen) { 327 #ifdef KERNEL 328 register struct mbuf *m; 329 330 if (buflen != 0) 331 return 0; 332 m = (struct mbuf *)p; 333 MINDEX(m, k); 334 A = mtod(m, char *)[k]; 335 continue; 336 #else 337 return 0; 338 #endif 339 } 340 A = p[k]; 341 continue; 342 343 case BPF_LDX|BPF_MSH|BPF_B: 344 k = pc->k; 345 if (k >= buflen) { 346 #ifdef KERNEL 347 register struct mbuf *m; 348 349 if (buflen != 0) 350 return 0; 351 m = (struct mbuf *)p; 352 MINDEX(m, k); 353 X = (mtod(m, char *)[k] & 0xf) << 2; 354 continue; 355 #else 356 return 0; 357 #endif 358 } 359 X = (p[pc->k] & 0xf) << 2; 360 continue; 361 362 case BPF_LD|BPF_IMM: 363 A = pc->k; 364 continue; 365 366 case BPF_LDX|BPF_IMM: 367 X = pc->k; 368 continue; 369 370 case BPF_LD|BPF_MEM: 371 A = mem[pc->k]; 372 continue; 373 374 case BPF_LDX|BPF_MEM: 375 X = mem[pc->k]; 376 continue; 377 378 case BPF_ST: 379 mem[pc->k] = A; 380 continue; 381 382 case BPF_STX: 383 mem[pc->k] = X; 384 continue; 385 386 case BPF_JMP|BPF_JA: 387 pc += pc->k; 388 continue; 389 390 case BPF_JMP|BPF_JGT|BPF_K: 391 pc += (A > pc->k) ? pc->jt : pc->jf; 392 continue; 393 394 case BPF_JMP|BPF_JGE|BPF_K: 395 pc += (A >= pc->k) ? pc->jt : pc->jf; 396 continue; 397 398 case BPF_JMP|BPF_JEQ|BPF_K: 399 pc += (A == pc->k) ? pc->jt : pc->jf; 400 continue; 401 402 case BPF_JMP|BPF_JSET|BPF_K: 403 pc += (A & pc->k) ? pc->jt : pc->jf; 404 continue; 405 406 case BPF_JMP|BPF_JGT|BPF_X: 407 pc += (A > X) ? pc->jt : pc->jf; 408 continue; 409 410 case BPF_JMP|BPF_JGE|BPF_X: 411 pc += (A >= X) ? pc->jt : pc->jf; 412 continue; 413 414 case BPF_JMP|BPF_JEQ|BPF_X: 415 pc += (A == X) ? pc->jt : pc->jf; 416 continue; 417 418 case BPF_JMP|BPF_JSET|BPF_X: 419 pc += (A & X) ? pc->jt : pc->jf; 420 continue; 421 422 case BPF_ALU|BPF_ADD|BPF_X: 423 A += X; 424 continue; 425 426 case BPF_ALU|BPF_SUB|BPF_X: 427 A -= X; 428 continue; 429 430 case BPF_ALU|BPF_MUL|BPF_X: 431 A *= X; 432 continue; 433 434 case BPF_ALU|BPF_DIV|BPF_X: 435 if (X == 0) 436 return 0; 437 A /= X; 438 continue; 439 440 case BPF_ALU|BPF_AND|BPF_X: 441 A &= X; 442 continue; 443 444 case BPF_ALU|BPF_OR|BPF_X: 445 A |= X; 446 continue; 447 448 case BPF_ALU|BPF_LSH|BPF_X: 449 A <<= X; 450 continue; 451 452 case BPF_ALU|BPF_RSH|BPF_X: 453 A >>= X; 454 continue; 455 456 case BPF_ALU|BPF_ADD|BPF_K: 457 A += pc->k; 458 continue; 459 460 case BPF_ALU|BPF_SUB|BPF_K: 461 A -= pc->k; 462 continue; 463 464 case BPF_ALU|BPF_MUL|BPF_K: 465 A *= pc->k; 466 continue; 467 468 case BPF_ALU|BPF_DIV|BPF_K: 469 A /= pc->k; 470 continue; 471 472 case BPF_ALU|BPF_AND|BPF_K: 473 A &= pc->k; 474 continue; 475 476 case BPF_ALU|BPF_OR|BPF_K: 477 A |= pc->k; 478 continue; 479 480 case BPF_ALU|BPF_LSH|BPF_K: 481 A <<= pc->k; 482 continue; 483 484 case BPF_ALU|BPF_RSH|BPF_K: 485 A >>= pc->k; 486 continue; 487 488 case BPF_ALU|BPF_NEG: 489 A = -A; 490 continue; 491 492 case BPF_MISC|BPF_TAX: 493 X = A; 494 continue; 495 496 case BPF_MISC|BPF_TXA: 497 A = X; 498 continue; 499 } 500 } 501 } 502 503 #ifdef KERNEL 504 /* 505 * Return true if the 'fcode' is a valid filter program. 506 * The constraints are that each jump be forward and to a valid 507 * code. The code must terminate with either an accept or reject. 508 * 'valid' is an array for use by the routine (it must be at least 509 * 'len' bytes long). 510 * 511 * The kernel needs to be able to verify an application's filter code. 512 * Otherwise, a bogus program could easily crash the system. 513 */ 514 int 515 bpf_validate(f, len) 516 struct bpf_insn *f; 517 int len; 518 { 519 register int i; 520 register struct bpf_insn *p; 521 522 for (i = 0; i < len; ++i) { 523 /* 524 * Check that that jumps are forward, and within 525 * the code block. 526 */ 527 p = &f[i]; 528 if (BPF_CLASS(p->code) == BPF_JMP) { 529 register int from = i + 1; 530 531 if (BPF_OP(p->code) == BPF_JA) { 532 if (from + p->k >= len) 533 return 0; 534 } 535 else if (from + p->jt >= len || from + p->jf >= len) 536 return 0; 537 } 538 /* 539 * Check that memory operations use valid addresses. 540 */ 541 if ((BPF_CLASS(p->code) == BPF_ST || 542 (BPF_CLASS(p->code) == BPF_LD && 543 (p->code & 0xe0) == BPF_MEM)) && 544 (p->k >= BPF_MEMWORDS || p->k < 0)) 545 return 0; 546 /* 547 * Check for constant division by 0. 548 */ 549 if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0) 550 return 0; 551 } 552 return BPF_CLASS(f[len - 1].code) == BPF_RET; 553 } 554 #endif 555