bpf_filter.c revision 1.7
1 /* $NetBSD: bpf_filter.c,v 1.7 1995/03/06 10:56:08 mycroft Exp $ */ 2 3 /* 4 * Copyright (c) 1990, 1991, 1992, 1993 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. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by the University of 23 * California, Berkeley and its contributors. 24 * 4. Neither the name of the University nor the names of its contributors 25 * may be used to endorse or promote products derived from this software 26 * without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38 * SUCH DAMAGE. 39 * 40 * @(#)bpf_filter.c 8.1 (Berkeley) 6/10/93 41 */ 42 43 #include <sys/param.h> 44 #include <sys/types.h> 45 #include <sys/time.h> 46 #include <net/bpf.h> 47 48 #ifdef sun 49 #include <netinet/in.h> 50 #endif 51 52 #if defined(sparc) || defined(mips) || defined(ibm032) 53 #define BPF_ALIGN 54 #endif 55 56 #ifndef BPF_ALIGN 57 #define EXTRACT_SHORT(p) ((u_short)ntohs(*(u_short *)p)) 58 #define EXTRACT_LONG(p) (ntohl(*(u_int32_t *)p)) 59 #else 60 #define EXTRACT_SHORT(p)\ 61 ((u_short)\ 62 ((u_short)*((u_char *)p+0)<<8|\ 63 (u_short)*((u_char *)p+1)<<0)) 64 #define EXTRACT_LONG(p)\ 65 ((u_int32_t)*((u_char *)p+0)<<24|\ 66 (u_int32_t)*((u_char *)p+1)<<16|\ 67 (u_int32_t)*((u_char *)p+2)<<8|\ 68 (u_int32_t)*((u_char *)p+3)<<0) 69 #endif 70 71 #ifdef KERNEL 72 #include <sys/mbuf.h> 73 #define MINDEX(m, k) \ 74 { \ 75 register int len = m->m_len; \ 76 \ 77 while (k >= len) { \ 78 k -= len; \ 79 m = m->m_next; \ 80 if (m == 0) \ 81 return 0; \ 82 len = m->m_len; \ 83 } \ 84 } 85 86 static int 87 m_xword(m, k, err) 88 register struct mbuf *m; 89 register int k, *err; 90 { 91 register int len; 92 register u_char *cp, *np; 93 register 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) { 114 115 case 1: 116 return (cp[k] << 24) | (np[0] << 16) | (np[1] << 8) | np[2]; 117 118 case 2: 119 return (cp[k] << 24) | (cp[k + 1] << 16) | (np[0] << 8) | 120 np[1]; 121 122 default: 123 return (cp[k] << 24) | (cp[k + 1] << 16) | (cp[k + 2] << 8) | 124 np[0]; 125 } 126 bad: 127 *err = 1; 128 return 0; 129 } 130 131 static int 132 m_xhalf(m, k, err) 133 register struct mbuf *m; 134 register int k, *err; 135 { 136 register int len; 137 register u_char *cp; 138 register struct mbuf *m0; 139 140 len = m->m_len; 141 while (k >= len) { 142 k -= len; 143 m = m->m_next; 144 if (m == 0) 145 goto bad; 146 len = m->m_len; 147 } 148 cp = mtod(m, u_char *) + k; 149 if (len - k >= 2) { 150 *err = 0; 151 return EXTRACT_SHORT(cp); 152 } 153 m0 = m->m_next; 154 if (m0 == 0) 155 goto bad; 156 *err = 0; 157 return (cp[k] << 8) | mtod(m0, u_char *)[0]; 158 bad: 159 *err = 1; 160 return 0; 161 } 162 #endif 163 164 /* 165 * Execute the filter program starting at pc on the packet p 166 * wirelen is the length of the original packet 167 * buflen is the amount of data present 168 */ 169 u_int 170 bpf_filter(pc, p, wirelen, buflen) 171 register struct bpf_insn *pc; 172 register u_char *p; 173 u_int wirelen; 174 register u_int buflen; 175 { 176 register u_int32_t A, X; 177 register int k; 178 int32_t mem[BPF_MEMWORDS]; 179 180 if (pc == 0) 181 /* 182 * No filter means accept all. 183 */ 184 return (u_int)-1; 185 #ifdef lint 186 A = 0; 187 X = 0; 188 #endif 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 + sizeof(int32_t) > buflen) { 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 A = EXTRACT_LONG(&p[k]); 223 continue; 224 225 case BPF_LD|BPF_H|BPF_ABS: 226 k = pc->k; 227 if (k + sizeof(short) > buflen) { 228 #ifdef KERNEL 229 int merr; 230 231 if (buflen != 0) 232 return 0; 233 A = m_xhalf((struct mbuf *)p, k, &merr); 234 continue; 235 #else 236 return 0; 237 #endif 238 } 239 A = EXTRACT_SHORT(&p[k]); 240 continue; 241 242 case BPF_LD|BPF_B|BPF_ABS: 243 k = pc->k; 244 if (k >= buflen) { 245 #ifdef KERNEL 246 register struct mbuf *m; 247 248 if (buflen != 0) 249 return 0; 250 m = (struct mbuf *)p; 251 MINDEX(m, k); 252 A = mtod(m, u_char *)[k]; 253 continue; 254 #else 255 return 0; 256 #endif 257 } 258 A = p[k]; 259 continue; 260 261 case BPF_LD|BPF_W|BPF_LEN: 262 A = wirelen; 263 continue; 264 265 case BPF_LDX|BPF_W|BPF_LEN: 266 X = wirelen; 267 continue; 268 269 case BPF_LD|BPF_W|BPF_IND: 270 k = X + pc->k; 271 if (k + sizeof(int32_t) > buflen) { 272 #ifdef KERNEL 273 int merr; 274 275 if (buflen != 0) 276 return 0; 277 A = m_xword((struct mbuf *)p, k, &merr); 278 if (merr != 0) 279 return 0; 280 continue; 281 #else 282 return 0; 283 #endif 284 } 285 A = EXTRACT_LONG(&p[k]); 286 continue; 287 288 case BPF_LD|BPF_H|BPF_IND: 289 k = X + pc->k; 290 if (k + sizeof(short) > buflen) { 291 #ifdef KERNEL 292 int merr; 293 294 if (buflen != 0) 295 return 0; 296 A = m_xhalf((struct mbuf *)p, k, &merr); 297 if (merr != 0) 298 return 0; 299 continue; 300 #else 301 return 0; 302 #endif 303 } 304 A = EXTRACT_SHORT(&p[k]); 305 continue; 306 307 case BPF_LD|BPF_B|BPF_IND: 308 k = X + pc->k; 309 if (k >= buflen) { 310 #ifdef KERNEL 311 register struct mbuf *m; 312 313 if (buflen != 0) 314 return 0; 315 m = (struct mbuf *)p; 316 MINDEX(m, k); 317 A = mtod(m, char *)[k]; 318 continue; 319 #else 320 return 0; 321 #endif 322 } 323 A = p[k]; 324 continue; 325 326 case BPF_LDX|BPF_MSH|BPF_B: 327 k = pc->k; 328 if (k >= buflen) { 329 #ifdef KERNEL 330 register struct mbuf *m; 331 332 if (buflen != 0) 333 return 0; 334 m = (struct mbuf *)p; 335 MINDEX(m, k); 336 X = (mtod(m, char *)[k] & 0xf) << 2; 337 continue; 338 #else 339 return 0; 340 #endif 341 } 342 X = (p[pc->k] & 0xf) << 2; 343 continue; 344 345 case BPF_LD|BPF_IMM: 346 A = pc->k; 347 continue; 348 349 case BPF_LDX|BPF_IMM: 350 X = pc->k; 351 continue; 352 353 case BPF_LD|BPF_MEM: 354 A = mem[pc->k]; 355 continue; 356 357 case BPF_LDX|BPF_MEM: 358 X = mem[pc->k]; 359 continue; 360 361 case BPF_ST: 362 mem[pc->k] = A; 363 continue; 364 365 case BPF_STX: 366 mem[pc->k] = X; 367 continue; 368 369 case BPF_JMP|BPF_JA: 370 pc += pc->k; 371 continue; 372 373 case BPF_JMP|BPF_JGT|BPF_K: 374 pc += (A > pc->k) ? pc->jt : pc->jf; 375 continue; 376 377 case BPF_JMP|BPF_JGE|BPF_K: 378 pc += (A >= pc->k) ? pc->jt : pc->jf; 379 continue; 380 381 case BPF_JMP|BPF_JEQ|BPF_K: 382 pc += (A == pc->k) ? pc->jt : pc->jf; 383 continue; 384 385 case BPF_JMP|BPF_JSET|BPF_K: 386 pc += (A & pc->k) ? pc->jt : pc->jf; 387 continue; 388 389 case BPF_JMP|BPF_JGT|BPF_X: 390 pc += (A > X) ? pc->jt : pc->jf; 391 continue; 392 393 case BPF_JMP|BPF_JGE|BPF_X: 394 pc += (A >= X) ? pc->jt : pc->jf; 395 continue; 396 397 case BPF_JMP|BPF_JEQ|BPF_X: 398 pc += (A == X) ? pc->jt : pc->jf; 399 continue; 400 401 case BPF_JMP|BPF_JSET|BPF_X: 402 pc += (A & X) ? pc->jt : pc->jf; 403 continue; 404 405 case BPF_ALU|BPF_ADD|BPF_X: 406 A += X; 407 continue; 408 409 case BPF_ALU|BPF_SUB|BPF_X: 410 A -= X; 411 continue; 412 413 case BPF_ALU|BPF_MUL|BPF_X: 414 A *= X; 415 continue; 416 417 case BPF_ALU|BPF_DIV|BPF_X: 418 if (X == 0) 419 return 0; 420 A /= X; 421 continue; 422 423 case BPF_ALU|BPF_AND|BPF_X: 424 A &= X; 425 continue; 426 427 case BPF_ALU|BPF_OR|BPF_X: 428 A |= X; 429 continue; 430 431 case BPF_ALU|BPF_LSH|BPF_X: 432 A <<= X; 433 continue; 434 435 case BPF_ALU|BPF_RSH|BPF_X: 436 A >>= X; 437 continue; 438 439 case BPF_ALU|BPF_ADD|BPF_K: 440 A += pc->k; 441 continue; 442 443 case BPF_ALU|BPF_SUB|BPF_K: 444 A -= pc->k; 445 continue; 446 447 case BPF_ALU|BPF_MUL|BPF_K: 448 A *= pc->k; 449 continue; 450 451 case BPF_ALU|BPF_DIV|BPF_K: 452 A /= pc->k; 453 continue; 454 455 case BPF_ALU|BPF_AND|BPF_K: 456 A &= pc->k; 457 continue; 458 459 case BPF_ALU|BPF_OR|BPF_K: 460 A |= pc->k; 461 continue; 462 463 case BPF_ALU|BPF_LSH|BPF_K: 464 A <<= pc->k; 465 continue; 466 467 case BPF_ALU|BPF_RSH|BPF_K: 468 A >>= pc->k; 469 continue; 470 471 case BPF_ALU|BPF_NEG: 472 A = -A; 473 continue; 474 475 case BPF_MISC|BPF_TAX: 476 X = A; 477 continue; 478 479 case BPF_MISC|BPF_TXA: 480 A = X; 481 continue; 482 } 483 } 484 } 485 486 #ifdef KERNEL 487 /* 488 * Return true if the 'fcode' is a valid filter program. 489 * The constraints are that each jump be forward and to a valid 490 * code. The code must terminate with either an accept or reject. 491 * 'valid' is an array for use by the routine (it must be at least 492 * 'len' bytes long). 493 * 494 * The kernel needs to be able to verify an application's filter code. 495 * Otherwise, a bogus program could easily crash the system. 496 */ 497 int 498 bpf_validate(f, len) 499 struct bpf_insn *f; 500 int len; 501 { 502 register int i; 503 register struct bpf_insn *p; 504 505 for (i = 0; i < len; ++i) { 506 /* 507 * Check that that jumps are forward, and within 508 * the code block. 509 */ 510 p = &f[i]; 511 if (BPF_CLASS(p->code) == BPF_JMP) { 512 register int from = i + 1; 513 514 if (BPF_OP(p->code) == BPF_JA) { 515 if (from + p->k >= len) 516 return 0; 517 } 518 else if (from + p->jt >= len || from + p->jf >= len) 519 return 0; 520 } 521 /* 522 * Check that memory operations use valid addresses. 523 */ 524 if ((BPF_CLASS(p->code) == BPF_ST || 525 (BPF_CLASS(p->code) == BPF_LD && 526 (p->code & 0xe0) == BPF_MEM)) && 527 (p->k >= BPF_MEMWORDS || p->k < 0)) 528 return 0; 529 /* 530 * Check for constant division by 0. 531 */ 532 if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0) 533 return 0; 534 } 535 return BPF_CLASS(f[len - 1].code) == BPF_RET; 536 } 537 #endif 538
Indexes created Tue Sep 30 07:10:03 GMT 2025