bpf_filter.c revision 1.11
1 /* $NetBSD: bpf_filter.c,v 1.11 1995/04/22 13:26:39 cgd 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 (defined(__NetBSD__) && !defined(UNALIGNED_ACCESS)) 53 #define BPF_ALIGN 54 #endif 55 56 #ifndef BPF_ALIGN 57 #define EXTRACT_SHORT(p) ((u_int16_t)ntohs(*(u_int16_t *)p)) 58 #define EXTRACT_LONG(p) (ntohl(*(u_int32_t *)p)) 59 #else 60 #define EXTRACT_SHORT(p)\ 61 ((u_int16_t)\ 62 ((u_int16_t)*((u_char *)p+0)<<8|\ 63 (u_int16_t)*((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(len, m, k) \ 74 { \ 75 len = m->m_len; \ 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 MINDEX(len, m, k); 95 cp = mtod(m, u_char *) + k; 96 if (len - k >= 4) { 97 *err = 0; 98 return EXTRACT_LONG(cp); 99 } 100 m0 = m->m_next; 101 if (m0 == 0 || m0->m_len + len - k < 4) 102 goto bad; 103 *err = 0; 104 np = mtod(m0, u_char *); 105 switch (len - k) { 106 107 case 1: 108 return (cp[0] << 24) | (np[0] << 16) | (np[1] << 8) | np[2]; 109 110 case 2: 111 return (cp[0] << 24) | (cp[1] << 16) | (np[0] << 8) | np[1]; 112 113 default: 114 return (cp[0] << 24) | (cp[1] << 16) | (cp[2] << 8) | np[0]; 115 } 116 bad: 117 *err = 1; 118 return 0; 119 } 120 121 static int 122 m_xhalf(m, k, err) 123 register struct mbuf *m; 124 register int k, *err; 125 { 126 register int len; 127 register u_char *cp; 128 register struct mbuf *m0; 129 130 MINDEX(len, m, k); 131 cp = mtod(m, u_char *) + k; 132 if (len - k >= 2) { 133 *err = 0; 134 return EXTRACT_SHORT(cp); 135 } 136 m0 = m->m_next; 137 if (m0 == 0) 138 goto bad; 139 *err = 0; 140 return (cp[0] << 8) | mtod(m0, u_char *)[0]; 141 bad: 142 *err = 1; 143 return 0; 144 } 145 #endif 146 147 #include <net/bpf.h> 148 149 /* 150 * Execute the filter program starting at pc on the packet p 151 * wirelen is the length of the original packet 152 * buflen is the amount of data present 153 */ 154 u_int 155 bpf_filter(pc, p, wirelen, buflen) 156 register struct bpf_insn *pc; 157 register u_char *p; 158 u_int wirelen; 159 register u_int buflen; 160 { 161 register u_int32_t A, X; 162 register int k; 163 int32_t mem[BPF_MEMWORDS]; 164 165 if (pc == 0) 166 /* 167 * No filter means accept all. 168 */ 169 return (u_int)-1; 170 #ifdef lint 171 A = 0; 172 X = 0; 173 #endif 174 --pc; 175 while (1) { 176 ++pc; 177 switch (pc->code) { 178 179 default: 180 #ifdef _KERNEL 181 return 0; 182 #else 183 abort(); 184 #endif 185 case BPF_RET|BPF_K: 186 return (u_int)pc->k; 187 188 case BPF_RET|BPF_A: 189 return (u_int)A; 190 191 case BPF_LD|BPF_W|BPF_ABS: 192 k = pc->k; 193 if (k + sizeof(int32_t) > buflen) { 194 #ifdef _KERNEL 195 int merr; 196 197 if (buflen != 0) 198 return 0; 199 A = m_xword((struct mbuf *)p, k, &merr); 200 if (merr != 0) 201 return 0; 202 continue; 203 #else 204 return 0; 205 #endif 206 } 207 A = EXTRACT_LONG(&p[k]); 208 continue; 209 210 case BPF_LD|BPF_H|BPF_ABS: 211 k = pc->k; 212 if (k + sizeof(int16_t) > buflen) { 213 #ifdef _KERNEL 214 int merr; 215 216 if (buflen != 0) 217 return 0; 218 A = m_xhalf((struct mbuf *)p, k, &merr); 219 continue; 220 #else 221 return 0; 222 #endif 223 } 224 A = EXTRACT_SHORT(&p[k]); 225 continue; 226 227 case BPF_LD|BPF_B|BPF_ABS: 228 k = pc->k; 229 if (k >= buflen) { 230 #ifdef _KERNEL 231 register struct mbuf *m; 232 register int len; 233 234 if (buflen != 0) 235 return 0; 236 m = (struct mbuf *)p; 237 MINDEX(len, m, k); 238 A = mtod(m, u_char *)[k]; 239 continue; 240 #else 241 return 0; 242 #endif 243 } 244 A = p[k]; 245 continue; 246 247 case BPF_LD|BPF_W|BPF_LEN: 248 A = wirelen; 249 continue; 250 251 case BPF_LDX|BPF_W|BPF_LEN: 252 X = wirelen; 253 continue; 254 255 case BPF_LD|BPF_W|BPF_IND: 256 k = X + pc->k; 257 if (k + sizeof(int32_t) > buflen) { 258 #ifdef _KERNEL 259 int merr; 260 261 if (buflen != 0) 262 return 0; 263 A = m_xword((struct mbuf *)p, k, &merr); 264 if (merr != 0) 265 return 0; 266 continue; 267 #else 268 return 0; 269 #endif 270 } 271 A = EXTRACT_LONG(&p[k]); 272 continue; 273 274 case BPF_LD|BPF_H|BPF_IND: 275 k = X + pc->k; 276 if (k + sizeof(int16_t) > buflen) { 277 #ifdef _KERNEL 278 int merr; 279 280 if (buflen != 0) 281 return 0; 282 A = m_xhalf((struct mbuf *)p, k, &merr); 283 if (merr != 0) 284 return 0; 285 continue; 286 #else 287 return 0; 288 #endif 289 } 290 A = EXTRACT_SHORT(&p[k]); 291 continue; 292 293 case BPF_LD|BPF_B|BPF_IND: 294 k = X + pc->k; 295 if (k >= buflen) { 296 #ifdef _KERNEL 297 register struct mbuf *m; 298 register int len; 299 300 if (buflen != 0) 301 return 0; 302 m = (struct mbuf *)p; 303 MINDEX(len, m, k); 304 A = mtod(m, char *)[k]; 305 continue; 306 #else 307 return 0; 308 #endif 309 } 310 A = p[k]; 311 continue; 312 313 case BPF_LDX|BPF_MSH|BPF_B: 314 k = pc->k; 315 if (k >= buflen) { 316 #ifdef _KERNEL 317 register struct mbuf *m; 318 register int len; 319 320 if (buflen != 0) 321 return 0; 322 m = (struct mbuf *)p; 323 MINDEX(len, m, k); 324 X = (mtod(m, char *)[k] & 0xf) << 2; 325 continue; 326 #else 327 return 0; 328 #endif 329 } 330 X = (p[pc->k] & 0xf) << 2; 331 continue; 332 333 case BPF_LD|BPF_IMM: 334 A = pc->k; 335 continue; 336 337 case BPF_LDX|BPF_IMM: 338 X = pc->k; 339 continue; 340 341 case BPF_LD|BPF_MEM: 342 A = mem[pc->k]; 343 continue; 344 345 case BPF_LDX|BPF_MEM: 346 X = mem[pc->k]; 347 continue; 348 349 case BPF_ST: 350 mem[pc->k] = A; 351 continue; 352 353 case BPF_STX: 354 mem[pc->k] = X; 355 continue; 356 357 case BPF_JMP|BPF_JA: 358 pc += pc->k; 359 continue; 360 361 case BPF_JMP|BPF_JGT|BPF_K: 362 pc += (A > pc->k) ? pc->jt : pc->jf; 363 continue; 364 365 case BPF_JMP|BPF_JGE|BPF_K: 366 pc += (A >= pc->k) ? pc->jt : pc->jf; 367 continue; 368 369 case BPF_JMP|BPF_JEQ|BPF_K: 370 pc += (A == pc->k) ? pc->jt : pc->jf; 371 continue; 372 373 case BPF_JMP|BPF_JSET|BPF_K: 374 pc += (A & pc->k) ? pc->jt : pc->jf; 375 continue; 376 377 case BPF_JMP|BPF_JGT|BPF_X: 378 pc += (A > X) ? pc->jt : pc->jf; 379 continue; 380 381 case BPF_JMP|BPF_JGE|BPF_X: 382 pc += (A >= X) ? pc->jt : pc->jf; 383 continue; 384 385 case BPF_JMP|BPF_JEQ|BPF_X: 386 pc += (A == X) ? pc->jt : pc->jf; 387 continue; 388 389 case BPF_JMP|BPF_JSET|BPF_X: 390 pc += (A & X) ? pc->jt : pc->jf; 391 continue; 392 393 case BPF_ALU|BPF_ADD|BPF_X: 394 A += X; 395 continue; 396 397 case BPF_ALU|BPF_SUB|BPF_X: 398 A -= X; 399 continue; 400 401 case BPF_ALU|BPF_MUL|BPF_X: 402 A *= X; 403 continue; 404 405 case BPF_ALU|BPF_DIV|BPF_X: 406 if (X == 0) 407 return 0; 408 A /= X; 409 continue; 410 411 case BPF_ALU|BPF_AND|BPF_X: 412 A &= X; 413 continue; 414 415 case BPF_ALU|BPF_OR|BPF_X: 416 A |= X; 417 continue; 418 419 case BPF_ALU|BPF_LSH|BPF_X: 420 A <<= X; 421 continue; 422 423 case BPF_ALU|BPF_RSH|BPF_X: 424 A >>= X; 425 continue; 426 427 case BPF_ALU|BPF_ADD|BPF_K: 428 A += pc->k; 429 continue; 430 431 case BPF_ALU|BPF_SUB|BPF_K: 432 A -= pc->k; 433 continue; 434 435 case BPF_ALU|BPF_MUL|BPF_K: 436 A *= pc->k; 437 continue; 438 439 case BPF_ALU|BPF_DIV|BPF_K: 440 A /= pc->k; 441 continue; 442 443 case BPF_ALU|BPF_AND|BPF_K: 444 A &= pc->k; 445 continue; 446 447 case BPF_ALU|BPF_OR|BPF_K: 448 A |= pc->k; 449 continue; 450 451 case BPF_ALU|BPF_LSH|BPF_K: 452 A <<= pc->k; 453 continue; 454 455 case BPF_ALU|BPF_RSH|BPF_K: 456 A >>= pc->k; 457 continue; 458 459 case BPF_ALU|BPF_NEG: 460 A = -A; 461 continue; 462 463 case BPF_MISC|BPF_TAX: 464 X = A; 465 continue; 466 467 case BPF_MISC|BPF_TXA: 468 A = X; 469 continue; 470 } 471 } 472 } 473 474 #ifdef _KERNEL 475 /* 476 * Return true if the 'fcode' is a valid filter program. 477 * The constraints are that each jump be forward and to a valid 478 * code. The code must terminate with either an accept or reject. 479 * 'valid' is an array for use by the routine (it must be at least 480 * 'len' bytes long). 481 * 482 * The kernel needs to be able to verify an application's filter code. 483 * Otherwise, a bogus program could easily crash the system. 484 */ 485 int 486 bpf_validate(f, len) 487 struct bpf_insn *f; 488 int len; 489 { 490 register int i; 491 register struct bpf_insn *p; 492 493 for (i = 0; i < len; ++i) { 494 /* 495 * Check that that jumps are forward, and within 496 * the code block. 497 */ 498 p = &f[i]; 499 if (BPF_CLASS(p->code) == BPF_JMP) { 500 register int from = i + 1; 501 502 if (BPF_OP(p->code) == BPF_JA) { 503 if (from + p->k >= len) 504 return 0; 505 } 506 else if (from + p->jt >= len || from + p->jf >= len) 507 return 0; 508 } 509 /* 510 * Check that memory operations use valid addresses. 511 */ 512 if ((BPF_CLASS(p->code) == BPF_ST || 513 (BPF_CLASS(p->code) == BPF_LD && 514 (p->code & 0xe0) == BPF_MEM)) && 515 (p->k >= BPF_MEMWORDS || p->k < 0)) 516 return 0; 517 /* 518 * Check for constant division by 0. 519 */ 520 if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0) 521 return 0; 522 } 523 return BPF_CLASS(f[len - 1].code) == BPF_RET; 524 } 525 #endif 526
Indexes created Tue Sep 30 07:10:03 GMT 2025