| 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 | * from: @(#)bpf.c 7.5 (Berkeley) 7/15/91 |
| 39 | * $Id: bpf_filter.c,v 1.2 1993/10/16 17:43:07 rgrimes Exp $ |
| 40 | */ |
| 41 | |
| 42 | #include <sys/param.h> |
| 43 | #include <sys/types.h> |
| 44 | #include <sys/time.h> |
| 45 | #include <net/bpf.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_long *)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_long)*((u_char *)p+0)<<24|\ |
| 65 | (u_long)*((u_char *)p+1)<<16|\ |
| 66 | (u_long)*((u_char *)p+2)<<8|\ |
| 67 | (u_long)*((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 | /* |
| 164 | * Execute the filter program starting at pc on the packet p |
| 165 | * wirelen is the length of the original packet |
| 166 | * buflen is the amount of data present |
| 167 | */ |
| 168 | u_int |
| 169 | bpf_filter(pc, p, wirelen, buflen) |
| 170 | register struct bpf_insn *pc; |
| 171 | register u_char *p; |
| 172 | u_int wirelen; |
| 173 | register u_int buflen; |
| 174 | { |
| 175 | register u_long A = 0, X = 0; |
| 176 | register int k; |
| 177 | long mem[BPF_MEMWORDS]; |
| 178 | |
| 179 | if (pc == 0) |
| 180 | /* |
| 181 | * No filter means accept all. |
| 182 | */ |
| 183 | return (u_int)-1; |
| 184 | #ifdef lint |
| 185 | A = 0; |
| 186 | X = 0; |
| 187 | #endif |
| 188 | --pc; |
| 189 | while (1) { |
| 190 | ++pc; |
| 191 | switch (pc->code) { |
| 192 | |
| 193 | default: |
| 194 | #ifdef KERNEL |
| 195 | return 0; |
| 196 | #else |
| 197 | abort(); |
| 198 | #endif |
| 199 | case BPF_RET|BPF_K: |
| 200 | return (u_int)pc->k; |
| 201 | |
| 202 | case BPF_RET|BPF_A: |
| 203 | return (u_int)A; |
| 204 | |
| 205 | case BPF_LD|BPF_W|BPF_ABS: |
| 206 | k = pc->k; |
| 207 | if (k + sizeof(long) > buflen) { |
| 208 | #ifdef KERNEL |
| 209 | int merr; |
| 210 | |
| 211 | if (buflen != 0) |
| 212 | return 0; |
| 213 | A = m_xword((struct mbuf *)p, k, &merr); |
| 214 | if (merr != 0) |
| 215 | return 0; |
| 216 | continue; |
| 217 | #else |
| 218 | return 0; |
| 219 | #endif |
| 220 | } |
| 221 | #ifdef BPF_ALIGN |
| 222 | if (((int)(p + k) & 3) != 0) |
| 223 | A = EXTRACT_LONG(&p[k]); |
| 224 | else |
| 225 | #endif |
| 226 | A = ntohl(*(long *)(p + k)); |
| 227 | continue; |
| 228 | |
| 229 | case BPF_LD|BPF_H|BPF_ABS: |
| 230 | k = pc->k; |
| 231 | if (k + sizeof(short) > buflen) { |
| 232 | #ifdef KERNEL |
| 233 | int merr; |
| 234 | |
| 235 | if (buflen != 0) |
| 236 | return 0; |
| 237 | A = m_xhalf((struct mbuf *)p, k, &merr); |
| 238 | continue; |
| 239 | #else |
| 240 | return 0; |
| 241 | #endif |
| 242 | } |
| 243 | A = EXTRACT_SHORT(&p[k]); |
| 244 | continue; |
| 245 | |
| 246 | case BPF_LD|BPF_B|BPF_ABS: |
| 247 | k = pc->k; |
| 248 | if (k >= buflen) { |
| 249 | #ifdef KERNEL |
| 250 | register struct mbuf *m; |
| 251 | |
| 252 | if (buflen != 0) |
| 253 | return 0; |
| 254 | m = (struct mbuf *)p; |
| 255 | MINDEX(m, k); |
| 256 | A = mtod(m, u_char *)[k]; |
| 257 | continue; |
| 258 | #else |
| 259 | return 0; |
| 260 | #endif |
| 261 | } |
| 262 | A = p[k]; |
| 263 | continue; |
| 264 | |
| 265 | case BPF_LD|BPF_W|BPF_LEN: |
| 266 | A = wirelen; |
| 267 | continue; |
| 268 | |
| 269 | case BPF_LDX|BPF_W|BPF_LEN: |
| 270 | X = wirelen; |
| 271 | continue; |
| 272 | |
| 273 | case BPF_LD|BPF_W|BPF_IND: |
| 274 | k = X + pc->k; |
| 275 | if (k + sizeof(long) > buflen) { |
| 276 | #ifdef KERNEL |
| 277 | int merr; |
| 278 | |
| 279 | if (buflen != 0) |
| 280 | return 0; |
| 281 | A = m_xword((struct mbuf *)p, k, &merr); |
| 282 | if (merr != 0) |
| 283 | return 0; |
| 284 | continue; |
| 285 | #else |
| 286 | return 0; |
| 287 | #endif |
| 288 | } |
| 289 | #ifdef BPF_ALIGN |
| 290 | if (((int)(p + k) & 3) != 0) |
| 291 | A = EXTRACT_LONG(&p[k]); |
| 292 | else |
| 293 | #endif |
| 294 | A = ntohl(*(long *)(p + k)); |
| 295 | continue; |
| 296 | |
| 297 | case BPF_LD|BPF_H|BPF_IND: |
| 298 | k = X + pc->k; |
| 299 | if (k + sizeof(short) > buflen) { |
| 300 | #ifdef KERNEL |
| 301 | int merr; |
| 302 | |
| 303 | if (buflen != 0) |
| 304 | return 0; |
| 305 | A = m_xhalf((struct mbuf *)p, k, &merr); |
| 306 | if (merr != 0) |
| 307 | return 0; |
| 308 | continue; |
| 309 | #else |
| 310 | return 0; |
| 311 | #endif |
| 312 | } |
| 313 | A = EXTRACT_SHORT(&p[k]); |
| 314 | continue; |
| 315 | |
| 316 | case BPF_LD|BPF_B|BPF_IND: |
| 317 | k = X + pc->k; |
| 318 | if (k >= buflen) { |
| 319 | #ifdef KERNEL |
| 320 | register struct mbuf *m; |
| 321 | |
| 322 | if (buflen != 0) |
| 323 | return 0; |
| 324 | m = (struct mbuf *)p; |
| 325 | MINDEX(m, k); |
| 326 | A = mtod(m, char *)[k]; |
| 327 | continue; |
| 328 | #else |
| 329 | return 0; |
| 330 | #endif |
| 331 | } |
| 332 | A = p[k]; |
| 333 | continue; |
| 334 | |
| 335 | case BPF_LDX|BPF_MSH|BPF_B: |
| 336 | k = pc->k; |
| 337 | if (k >= buflen) { |
| 338 | #ifdef KERNEL |
| 339 | register struct mbuf *m; |
| 340 | |
| 341 | if (buflen != 0) |
| 342 | return 0; |
| 343 | m = (struct mbuf *)p; |
| 344 | MINDEX(m, k); |
| 345 | X = (mtod(m, char *)[k] & 0xf) << 2; |
| 346 | continue; |
| 347 | #else |
| 348 | return 0; |
| 349 | #endif |
| 350 | } |
| 351 | X = (p[pc->k] & 0xf) << 2; |
| 352 | continue; |
| 353 | |
| 354 | case BPF_LD|BPF_IMM: |
| 355 | A = pc->k; |
| 356 | continue; |
| 357 | |
| 358 | case BPF_LDX|BPF_IMM: |
| 359 | X = pc->k; |
| 360 | continue; |
| 361 | |
| 362 | case BPF_LD|BPF_MEM: |
| 363 | A = mem[pc->k]; |
| 364 | continue; |
| 365 | |
| 366 | case BPF_LDX|BPF_MEM: |
| 367 | X = mem[pc->k]; |
| 368 | continue; |
| 369 | |
| 370 | case BPF_ST: |
| 371 | mem[pc->k] = A; |
| 372 | continue; |
| 373 | |
| 374 | case BPF_STX: |
| 375 | mem[pc->k] = X; |
| 376 | continue; |
| 377 | |
| 378 | case BPF_JMP|BPF_JA: |
| 379 | pc += pc->k; |
| 380 | continue; |
| 381 | |
| 382 | case BPF_JMP|BPF_JGT|BPF_K: |
| 383 | pc += (A > pc->k) ? pc->jt : pc->jf; |
| 384 | continue; |
| 385 | |
| 386 | case BPF_JMP|BPF_JGE|BPF_K: |
| 387 | pc += (A >= pc->k) ? pc->jt : pc->jf; |
| 388 | continue; |
| 389 | |
| 390 | case BPF_JMP|BPF_JEQ|BPF_K: |
| 391 | pc += (A == pc->k) ? pc->jt : pc->jf; |
| 392 | continue; |
| 393 | |
| 394 | case BPF_JMP|BPF_JSET|BPF_K: |
| 395 | pc += (A & pc->k) ? pc->jt : pc->jf; |
| 396 | continue; |
| 397 | |
| 398 | case BPF_JMP|BPF_JGT|BPF_X: |
| 399 | pc += (A > X) ? pc->jt : pc->jf; |
| 400 | continue; |
| 401 | |
| 402 | case BPF_JMP|BPF_JGE|BPF_X: |
| 403 | pc += (A >= X) ? pc->jt : pc->jf; |
| 404 | continue; |
| 405 | |
| 406 | case BPF_JMP|BPF_JEQ|BPF_X: |
| 407 | pc += (A == X) ? pc->jt : pc->jf; |
| 408 | continue; |
| 409 | |
| 410 | case BPF_JMP|BPF_JSET|BPF_X: |
| 411 | pc += (A & X) ? pc->jt : pc->jf; |
| 412 | continue; |
| 413 | |
| 414 | case BPF_ALU|BPF_ADD|BPF_X: |
| 415 | A += X; |
| 416 | continue; |
| 417 | |
| 418 | case BPF_ALU|BPF_SUB|BPF_X: |
| 419 | A -= X; |
| 420 | continue; |
| 421 | |
| 422 | case BPF_ALU|BPF_MUL|BPF_X: |
| 423 | A *= X; |
| 424 | continue; |
| 425 | |
| 426 | case BPF_ALU|BPF_DIV|BPF_X: |
| 427 | if (X == 0) |
| 428 | return 0; |
| 429 | A /= X; |
| 430 | continue; |
| 431 | |
| 432 | case BPF_ALU|BPF_AND|BPF_X: |
| 433 | A &= X; |
| 434 | continue; |
| 435 | |
| 436 | case BPF_ALU|BPF_OR|BPF_X: |
| 437 | A |= X; |
| 438 | continue; |
| 439 | |
| 440 | case BPF_ALU|BPF_LSH|BPF_X: |
| 441 | A <<= X; |
| 442 | continue; |
| 443 | |
| 444 | case BPF_ALU|BPF_RSH|BPF_X: |
| 445 | A >>= X; |
| 446 | continue; |
| 447 | |
| 448 | case BPF_ALU|BPF_ADD|BPF_K: |
| 449 | A += pc->k; |
| 450 | continue; |
| 451 | |
| 452 | case BPF_ALU|BPF_SUB|BPF_K: |
| 453 | A -= pc->k; |
| 454 | continue; |
| 455 | |
| 456 | case BPF_ALU|BPF_MUL|BPF_K: |
| 457 | A *= pc->k; |
| 458 | continue; |
| 459 | |
| 460 | case BPF_ALU|BPF_DIV|BPF_K: |
| 461 | A /= pc->k; |
| 462 | continue; |
| 463 | |
| 464 | case BPF_ALU|BPF_AND|BPF_K: |
| 465 | A &= pc->k; |
| 466 | continue; |
| 467 | |
| 468 | case BPF_ALU|BPF_OR|BPF_K: |
| 469 | A |= pc->k; |
| 470 | continue; |
| 471 | |
| 472 | case BPF_ALU|BPF_LSH|BPF_K: |
| 473 | A <<= pc->k; |
| 474 | continue; |
| 475 | |
| 476 | case BPF_ALU|BPF_RSH|BPF_K: |
| 477 | A >>= pc->k; |
| 478 | continue; |
| 479 | |
| 480 | case BPF_ALU|BPF_NEG: |
| 481 | A = -A; |
| 482 | continue; |
| 483 | |
| 484 | case BPF_MISC|BPF_TAX: |
| 485 | X = A; |
| 486 | continue; |
| 487 | |
| 488 | case BPF_MISC|BPF_TXA: |
| 489 | A = X; |
| 490 | continue; |
| 491 | } |
| 492 | } |
| 493 | } |
| 494 | |
| 495 | #ifdef KERNEL |
| 496 | /* |
| 497 | * Return true if the 'fcode' is a valid filter program. |
| 498 | * The constraints are that each jump be forward and to a valid |
| 499 | * code. The code must terminate with either an accept or reject. |
| 500 | * 'valid' is an array for use by the routine (it must be at least |
| 501 | * 'len' bytes long). |
| 502 | * |
| 503 | * The kernel needs to be able to verify an application's filter code. |
| 504 | * Otherwise, a bogus program could easily crash the system. |
| 505 | */ |
| 506 | int |
| 507 | bpf_validate(f, len) |
| 508 | struct bpf_insn *f; |
| 509 | int len; |
| 510 | { |
| 511 | register int i; |
| 512 | register struct bpf_insn *p; |
| 513 | |
| 514 | for (i = 0; i < len; ++i) { |
| 515 | /* |
| 516 | * Check that that jumps are forward, and within |
| 517 | * the code block. |
| 518 | */ |
| 519 | p = &f[i]; |
| 520 | if (BPF_CLASS(p->code) == BPF_JMP) { |
| 521 | register int from = i + 1; |
| 522 | |
| 523 | if (BPF_OP(p->code) == BPF_JA) { |
| 524 | if (from + p->k >= len) |
| 525 | return 0; |
| 526 | } |
| 527 | else if (from + p->jt >= len || from + p->jf >= len) |
| 528 | return 0; |
| 529 | } |
| 530 | /* |
| 531 | * Check that memory operations use valid addresses. |
| 532 | */ |
| 533 | if ((BPF_CLASS(p->code) == BPF_ST || |
| 534 | (BPF_CLASS(p->code) == BPF_LD && |
| 535 | (p->code & 0xe0) == BPF_MEM)) && |
| 536 | (p->k >= BPF_MEMWORDS || p->k < 0)) |
| 537 | return 0; |
| 538 | /* |
| 539 | * Check for constant division by 0. |
| 540 | */ |
| 541 | if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0) |
| 542 | return 0; |
| 543 | } |
| 544 | return BPF_CLASS(f[len - 1].code) == BPF_RET; |
| 545 | } |
| 546 | #endif |