bpf_filter.c revision 1.9
1 /* $NetBSD: bpf_filter.c,v 1.9 1995/03/28 20:01:10 jtc 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 47 #ifdef sun 48 #include <netinet/in.h> 49 #endif 50 51 #if defined(sparc) || defined(mips) || defined(ibm032) 52 #define BPF_ALIGN 53 #endif 54 55 #ifndef BPF_ALIGN 56 #define EXTRACT_SHORT(p) ((u_short)ntohs(*(u_short *)p)) 57 #define EXTRACT_LONG(p) (ntohl(*(u_int32_t *)p)) 58 #else 59 #define EXTRACT_SHORT(p)\ 60 ((u_short)\ 61 ((u_short)*((u_char *)p+0)<<8|\ 62 (u_short)*((u_char *)p+1)<<0)) 63 #define EXTRACT_LONG(p)\ 64 ((u_int32_t)*((u_char *)p+0)<<24|\ 65 (u_int32_t)*((u_char *)p+1)<<16|\ 66 (u_int32_t)*((u_char *)p+2)<<8|\ 67 (u_int32_t)*((u_char *)p+3)<<0) 68 #endif 69 70 #ifdef _KERNEL 71 #include <sys/mbuf.h> 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 int 86 m_xword(m, k, err) 87 register struct mbuf *m; 88 register int k, *err; 89 { 90 register int len; 91 register u_char *cp, *np; 92 register struct mbuf *m0; 93 94 len = m->m_len; 95 while (k >= len) { 96 k -= len; 97 m = m->m_next; 98 if (m == 0) 99 goto bad; 100 len = m->m_len; 101 } 102 cp = mtod(m, u_char *) + k; 103 if (len - k >= 4) { 104 *err = 0; 105 return EXTRACT_LONG(cp); 106 } 107 m0 = m->m_next; 108 if (m0 == 0 || m0->m_len + len - k < 4) 109 goto bad; 110 *err = 0; 111 np = mtod(m0, u_char *); 112 switch (len - k) { 113 114 case 1: 115 return (cp[k] << 24) | (np[0] << 16) | (np[1] << 8) | np[2]; 116 117 case 2: 118 return (cp[k] << 24) | (cp[k + 1] << 16) | (np[0] << 8) | 119 np[1]; 120 121 default: 122 return (cp[k] << 24) | (cp[k + 1] << 16) | (cp[k + 2] << 8) | 123 np[0]; 124 } 125 bad: 126 *err = 1; 127 return 0; 128 } 129 130 static int 131 m_xhalf(m, k, err) 132 register struct mbuf *m; 133 register int k, *err; 134 { 135 register int len; 136 register u_char *cp; 137 register struct mbuf *m0; 138 139 len = m->m_len; 140 while (k >= len) { 141 k -= len; 142 m = m->m_next; 143 if (m == 0) 144 goto bad; 145 len = m->m_len; 146 } 147 cp = mtod(m, u_char *) + k; 148 if (len - k >= 2) { 149 *err = 0; 150 return EXTRACT_SHORT(cp); 151 } 152 m0 = m->m_next; 153 if (m0 == 0) 154 goto bad; 155 *err = 0; 156 return (cp[k] << 8) | mtod(m0, u_char *)[0]; 157 bad: 158 *err = 1; 159 return 0; 160 } 161 #endif 162 163 #include <net/bpf.h> 164 165 /* 166 * Execute the filter program starting at pc on the packet p 167 * wirelen is the length of the original packet 168 * buflen is the amount of data present 169 */ 170 u_int 171 bpf_filter(pc, p, wirelen, buflen) 172 register struct bpf_insn *pc; 173 register u_char *p; 174 u_int wirelen; 175 register u_int buflen; 176 { 177 register u_int32_t A, X; 178 register int k; 179 int32_t mem[BPF_MEMWORDS]; 180 181 if (pc == 0) 182 /* 183 * No filter means accept all. 184 */ 185 return (u_int)-1; 186 #ifdef lint 187 A = 0; 188 X = 0; 189 #endif 190 --pc; 191 while (1) { 192 ++pc; 193 switch (pc->code) { 194 195 default: 196 #ifdef _KERNEL 197 return 0; 198 #else 199 abort(); 200 #endif 201 case BPF_RET|BPF_K: 202 return (u_int)pc->k; 203 204 case BPF_RET|BPF_A: 205 return (u_int)A; 206 207 case BPF_LD|BPF_W|BPF_ABS: 208 k = pc->k; 209 if (k + sizeof(int32_t) > buflen) { 210 #ifdef _KERNEL 211 int merr; 212 213 if (buflen != 0) 214 return 0; 215 A = m_xword((struct mbuf *)p, k, &merr); 216 if (merr != 0) 217 return 0; 218 continue; 219 #else 220 return 0; 221 #endif 222 } 223 A = EXTRACT_LONG(&p[k]); 224 continue; 225 226 case BPF_LD|BPF_H|BPF_ABS: 227 k = pc->k; 228 if (k + sizeof(short) > buflen) { 229 #ifdef _KERNEL 230 int merr; 231 232 if (buflen != 0) 233 return 0; 234 A = m_xhalf((struct mbuf *)p, k, &merr); 235 continue; 236 #else 237 return 0; 238 #endif 239 } 240 A = EXTRACT_SHORT(&p[k]); 241 continue; 242 243 case BPF_LD|BPF_B|BPF_ABS: 244 k = pc->k; 245 if (k >= buflen) { 246 #ifdef _KERNEL 247 register struct mbuf *m; 248 249 if (buflen != 0) 250 return 0; 251 m = (struct mbuf *)p; 252 MINDEX(m, k); 253 A = mtod(m, u_char *)[k]; 254 continue; 255 #else 256 return 0; 257 #endif 258 } 259 A = p[k]; 260 continue; 261 262 case BPF_LD|BPF_W|BPF_LEN: 263 A = wirelen; 264 continue; 265 266 case BPF_LDX|BPF_W|BPF_LEN: 267 X = wirelen; 268 continue; 269 270 case BPF_LD|BPF_W|BPF_IND: 271 k = X + pc->k; 272 if (k + sizeof(int32_t) > buflen) { 273 #ifdef _KERNEL 274 int merr; 275 276 if (buflen != 0) 277 return 0; 278 A = m_xword((struct mbuf *)p, k, &merr); 279 if (merr != 0) 280 return 0; 281 continue; 282 #else 283 return 0; 284 #endif 285 } 286 A = EXTRACT_LONG(&p[k]); 287 continue; 288 289 case BPF_LD|BPF_H|BPF_IND: 290 k = X + pc->k; 291 if (k + sizeof(short) > buflen) { 292 #ifdef _KERNEL 293 int merr; 294 295 if (buflen != 0) 296 return 0; 297 A = m_xhalf((struct mbuf *)p, k, &merr); 298 if (merr != 0) 299 return 0; 300 continue; 301 #else 302 return 0; 303 #endif 304 } 305 A = EXTRACT_SHORT(&p[k]); 306 continue; 307 308 case BPF_LD|BPF_B|BPF_IND: 309 k = X + pc->k; 310 if (k >= buflen) { 311 #ifdef _KERNEL 312 register struct mbuf *m; 313 314 if (buflen != 0) 315 return 0; 316 m = (struct mbuf *)p; 317 MINDEX(m, k); 318 A = mtod(m, char *)[k]; 319 continue; 320 #else 321 return 0; 322 #endif 323 } 324 A = p[k]; 325 continue; 326 327 case BPF_LDX|BPF_MSH|BPF_B: 328 k = pc->k; 329 if (k >= buflen) { 330 #ifdef _KERNEL 331 register struct mbuf *m; 332 333 if (buflen != 0) 334 return 0; 335 m = (struct mbuf *)p; 336 MINDEX(m, k); 337 X = (mtod(m, char *)[k] & 0xf) << 2; 338 continue; 339 #else 340 return 0; 341 #endif 342 } 343 X = (p[pc->k] & 0xf) << 2; 344 continue; 345 346 case BPF_LD|BPF_IMM: 347 A = pc->k; 348 continue; 349 350 case BPF_LDX|BPF_IMM: 351 X = pc->k; 352 continue; 353 354 case BPF_LD|BPF_MEM: 355 A = mem[pc->k]; 356 continue; 357 358 case BPF_LDX|BPF_MEM: 359 X = mem[pc->k]; 360 continue; 361 362 case BPF_ST: 363 mem[pc->k] = A; 364 continue; 365 366 case BPF_STX: 367 mem[pc->k] = X; 368 continue; 369 370 case BPF_JMP|BPF_JA: 371 pc += pc->k; 372 continue; 373 374 case BPF_JMP|BPF_JGT|BPF_K: 375 pc += (A > pc->k) ? pc->jt : pc->jf; 376 continue; 377 378 case BPF_JMP|BPF_JGE|BPF_K: 379 pc += (A >= pc->k) ? pc->jt : pc->jf; 380 continue; 381 382 case BPF_JMP|BPF_JEQ|BPF_K: 383 pc += (A == pc->k) ? pc->jt : pc->jf; 384 continue; 385 386 case BPF_JMP|BPF_JSET|BPF_K: 387 pc += (A & pc->k) ? pc->jt : pc->jf; 388 continue; 389 390 case BPF_JMP|BPF_JGT|BPF_X: 391 pc += (A > X) ? pc->jt : pc->jf; 392 continue; 393 394 case BPF_JMP|BPF_JGE|BPF_X: 395 pc += (A >= X) ? pc->jt : pc->jf; 396 continue; 397 398 case BPF_JMP|BPF_JEQ|BPF_X: 399 pc += (A == X) ? pc->jt : pc->jf; 400 continue; 401 402 case BPF_JMP|BPF_JSET|BPF_X: 403 pc += (A & X) ? pc->jt : pc->jf; 404 continue; 405 406 case BPF_ALU|BPF_ADD|BPF_X: 407 A += X; 408 continue; 409 410 case BPF_ALU|BPF_SUB|BPF_X: 411 A -= X; 412 continue; 413 414 case BPF_ALU|BPF_MUL|BPF_X: 415 A *= X; 416 continue; 417 418 case BPF_ALU|BPF_DIV|BPF_X: 419 if (X == 0) 420 return 0; 421 A /= X; 422 continue; 423 424 case BPF_ALU|BPF_AND|BPF_X: 425 A &= X; 426 continue; 427 428 case BPF_ALU|BPF_OR|BPF_X: 429 A |= X; 430 continue; 431 432 case BPF_ALU|BPF_LSH|BPF_X: 433 A <<= X; 434 continue; 435 436 case BPF_ALU|BPF_RSH|BPF_X: 437 A >>= X; 438 continue; 439 440 case BPF_ALU|BPF_ADD|BPF_K: 441 A += pc->k; 442 continue; 443 444 case BPF_ALU|BPF_SUB|BPF_K: 445 A -= pc->k; 446 continue; 447 448 case BPF_ALU|BPF_MUL|BPF_K: 449 A *= pc->k; 450 continue; 451 452 case BPF_ALU|BPF_DIV|BPF_K: 453 A /= pc->k; 454 continue; 455 456 case BPF_ALU|BPF_AND|BPF_K: 457 A &= pc->k; 458 continue; 459 460 case BPF_ALU|BPF_OR|BPF_K: 461 A |= pc->k; 462 continue; 463 464 case BPF_ALU|BPF_LSH|BPF_K: 465 A <<= pc->k; 466 continue; 467 468 case BPF_ALU|BPF_RSH|BPF_K: 469 A >>= pc->k; 470 continue; 471 472 case BPF_ALU|BPF_NEG: 473 A = -A; 474 continue; 475 476 case BPF_MISC|BPF_TAX: 477 X = A; 478 continue; 479 480 case BPF_MISC|BPF_TXA: 481 A = X; 482 continue; 483 } 484 } 485 } 486 487 #ifdef _KERNEL 488 /* 489 * Return true if the 'fcode' is a valid filter program. 490 * The constraints are that each jump be forward and to a valid 491 * code. The code must terminate with either an accept or reject. 492 * 'valid' is an array for use by the routine (it must be at least 493 * 'len' bytes long). 494 * 495 * The kernel needs to be able to verify an application's filter code. 496 * Otherwise, a bogus program could easily crash the system. 497 */ 498 int 499 bpf_validate(f, len) 500 struct bpf_insn *f; 501 int len; 502 { 503 register int i; 504 register struct bpf_insn *p; 505 506 for (i = 0; i < len; ++i) { 507 /* 508 * Check that that jumps are forward, and within 509 * the code block. 510 */ 511 p = &f[i]; 512 if (BPF_CLASS(p->code) == BPF_JMP) { 513 register int from = i + 1; 514 515 if (BPF_OP(p->code) == BPF_JA) { 516 if (from + p->k >= len) 517 return 0; 518 } 519 else if (from + p->jt >= len || from + p->jf >= len) 520 return 0; 521 } 522 /* 523 * Check that memory operations use valid addresses. 524 */ 525 if ((BPF_CLASS(p->code) == BPF_ST || 526 (BPF_CLASS(p->code) == BPF_LD && 527 (p->code & 0xe0) == BPF_MEM)) && 528 (p->k >= BPF_MEMWORDS || p->k < 0)) 529 return 0; 530 /* 531 * Check for constant division by 0. 532 */ 533 if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0) 534 return 0; 535 } 536 return BPF_CLASS(f[len - 1].code) == BPF_RET; 537 } 538 #endif 539
Indexes created Tue Sep 30 07:10:03 GMT 2025