bsd/net/bpf_filter.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * Copyright (c) 1990, 1991, 1993
  27  *      The Regents of the University of California.  All rights reserved.
  28  *
  29  * This code is derived from the Stanford/CMU enet packet filter,
  30  * (net/enet.c) distributed as part of 4.3BSD, and code contributed
  31  * to Berkeley by Steven McCanne and Van Jacobson both of Lawrence
  32  * Berkeley Laboratory.
  33  *
  34  * Redistribution and use in source and binary forms, with or without
  35  * modification, are permitted provided that the following conditions
  36  * are met:
  37  * 1. Redistributions of source code must retain the above copyright
  38  *    notice, this list of conditions and the following disclaimer.
  39  * 2. Redistributions in binary form must reproduce the above copyright
  40  *    notice, this list of conditions and the following disclaimer in the
  41  *    documentation and/or other materials provided with the distribution.
  42  * 3. All advertising materials mentioning features or use of this software
  43  *    must display the following acknowledgement:
  44  *      This product includes software developed by the University of
  45  *      California, Berkeley and its contributors.
  46  * 4. Neither the name of the University nor the names of its contributors
  47  *    may be used to endorse or promote products derived from this software
  48  *    without specific prior written permission.
  49  *
  50  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  51  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  52  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  53  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  54  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  55  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  56  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  57  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  58  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  59  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  60  * SUCH DAMAGE.
  61  *
  62  *      @(#)bpf_filter.c        8.1 (Berkeley) 6/10/93
  63  *
  64  * $FreeBSD: src/sys/net/bpf_filter.c,v 1.17 1999/12/29 04:38:31 peter Exp $
  65  */
  66
  67 #include <sys/param.h>
  68
  69 #ifdef sun
  70 #include <netinet/in.h>
  71 #endif
  72
  73 #if defined(sparc) || defined(mips) || defined(ibm032) || defined(__alpha__)
  74 #define BPF_ALIGN
  75 #endif
  76
  77 #ifndef BPF_ALIGN
  78 #define EXTRACT_SHORT(p)        ((u_int16_t)ntohs(*(u_int16_t *)p))
  79 #define EXTRACT_LONG(p)         (ntohl(*(u_int32_t *)p))
  80 #else
  81 #define EXTRACT_SHORT(p)\
  82         ((u_int16_t)\
  83                 ((u_int16_t)*((u_char *)p+0)<<8|\
  84                  (u_int16_t)*((u_char *)p+1)<<0))
  85 #define EXTRACT_LONG(p)\
  86                 ((u_int32_t)*((u_char *)p+0)<<24|\
  87                  (u_int32_t)*((u_char *)p+1)<<16|\
  88                  (u_int32_t)*((u_char *)p+2)<<8|\
  89                  (u_int32_t)*((u_char *)p+3)<<0)
  90 #endif
  91
  92 #ifdef KERNEL
  93 #include <sys/mbuf.h>
  94 #endif
  95 #include <net/bpf.h>
  96 #ifdef KERNEL
  97 #define MINDEX(m, k) \
  98 { \
  99         register int len = m->m_len; \
 100  \
 101         while (k >= len) { \
 102                 k -= len; \
 103                 m = m->m_next; \
 104                 if (m == 0) \
 105                         return 0; \
 106                 len = m->m_len; \
 107         } \
 108 }
 109
 110 static u_int16_t        m_xhalf __P((struct mbuf *m, bpf_u_int32 k, int *err));
 111 static u_int32_t        m_xword __P((struct mbuf *m, bpf_u_int32 k, int *err));
 112
 113 static u_int32_t
 114 m_xword(m, k, err)
 115         register struct mbuf *m;
 116         register bpf_u_int32 k;
 117         register int *err;
 118 {
 119         register size_t len;
 120         register u_char *cp, *np;
 121         register struct mbuf *m0;
 122
 123         len = m->m_len;
 124         while (k >= len) {
 125                 k -= len;
 126                 m = m->m_next;
 127                 if (m == 0)
 128                         goto bad;
 129                 len = m->m_len;
 130         }
 131         cp = mtod(m, u_char *) + k;
 132         if (len - k >= 4) {
 133                 *err = 0;
 134                 return EXTRACT_LONG(cp);
 135         }
 136         m0 = m->m_next;
 137         if (m0 == 0 || m0->m_len + len - k < 4)
 138                 goto bad;
 139         *err = 0;
 140         np = mtod(m0, u_char *);
 141         switch (len - k) {
 142
 143         case 1:
 144                 return
 145                     ((u_int32_t)cp[0] << 24) |
 146                     ((u_int32_t)np[0] << 16) |
 147                     ((u_int32_t)np[1] << 8)  |
 148                     (u_int32_t)np[2];
 149
 150         case 2:
 151                 return
 152                     ((u_int32_t)cp[0] << 24) |
 153                     ((u_int32_t)cp[1] << 16) |
 154                     ((u_int32_t)np[0] << 8) |
 155                     (u_int32_t)np[1];
 156
 157         default:
 158                 return
 159                     ((u_int32_t)cp[0] << 24) |
 160                     ((u_int32_t)cp[1] << 16) |
 161                     ((u_int32_t)cp[2] << 8) |
 162                     (u_int32_t)np[0];
 163         }
 164     bad:
 165         *err = 1;
 166         return 0;
 167 }
 168
 169 static u_int16_t
 170 m_xhalf(m, k, err)
 171         register struct mbuf *m;
 172         register bpf_u_int32 k;
 173         register int *err;
 174 {
 175         register size_t len;
 176         register u_char *cp;
 177         register struct mbuf *m0;
 178
 179         len = m->m_len;
 180         while (k >= len) {
 181                 k -= len;
 182                 m = m->m_next;
 183                 if (m == 0)
 184                         goto bad;
 185                 len = m->m_len;
 186         }
 187         cp = mtod(m, u_char *) + k;
 188         if (len - k >= 2) {
 189                 *err = 0;
 190                 return EXTRACT_SHORT(cp);
 191         }
 192         m0 = m->m_next;
 193         if (m0 == 0)
 194                 goto bad;
 195         *err = 0;
 196         return (cp[0] << 8) | mtod(m0, u_char *)[0];
 197  bad:
 198         *err = 1;
 199         return 0;
 200 }
 201 #endif
 202
 203 /*
 204  * Execute the filter program starting at pc on the packet p
 205  * wirelen is the length of the original packet
 206  * buflen is the amount of data present
 207  */
 208 u_int
 209 bpf_filter(pc, p, wirelen, buflen)
 210         register const struct bpf_insn *pc;
 211         register u_char *p;
 212         u_int wirelen;
 213         register u_int buflen;
 214 {
 215         register u_int32_t A = 0, X = 0;
 216         register bpf_u_int32 k;
 217         int32_t mem[BPF_MEMWORDS];
 218
 219         if (pc == 0)
 220                 /*
 221                  * No filter means accept all.
 222                  */
 223                 return (u_int)-1;
 224
 225         --pc;
 226         while (1) {
 227                 ++pc;
 228                 switch (pc->code) {
 229
 230                 default:
 231 #ifdef KERNEL
 232                         return 0;
 233 #else
 234                         abort();
 235 #endif
 236                 case BPF_RET|BPF_K:
 237                         return (u_int)pc->k;
 238
 239                 case BPF_RET|BPF_A:
 240                         return (u_int)A;
 241
 242                 case BPF_LD|BPF_W|BPF_ABS:
 243                         k = pc->k;
 244                         if (k > buflen || sizeof(int32_t) > buflen - k) {
 245 #ifdef KERNEL
 246                                 int merr;
 247
 248                                 if (buflen != 0)
 249                                         return 0;
 250                                 A = m_xword((struct mbuf *)p, k, &merr);
 251                                 if (merr != 0)
 252                                         return 0;
 253                                 continue;
 254 #else
 255                                 return 0;
 256 #endif
 257                         }
 258 #if BPF_ALIGN
 259                         if (((intptr_t)(p + k) & 3) != 0)
 260                                 A = EXTRACT_LONG(&p[k]);
 261                         else
 262 #endif
 263                                 A = ntohl(*(int32_t *)(p + k));
 264                         continue;
 265
 266                 case BPF_LD|BPF_H|BPF_ABS:
 267                         k = pc->k;
 268                         if (k > buflen || sizeof(int16_t) > buflen - k) {
 269 #ifdef KERNEL
 270                                 int merr;
 271
 272                                 if (buflen != 0)
 273                                         return 0;
 274                                 A = m_xhalf((struct mbuf *)p, k, &merr);
 275                                 continue;
 276 #else
 277                                 return 0;
 278 #endif
 279                         }
 280                         A = EXTRACT_SHORT(&p[k]);
 281                         continue;
 282
 283                 case BPF_LD|BPF_B|BPF_ABS:
 284                         k = pc->k;
 285                         if (k >= buflen) {
 286 #ifdef KERNEL
 287                                 register struct mbuf *m;
 288
 289                                 if (buflen != 0)
 290                                         return 0;
 291                                 m = (struct mbuf *)p;
 292                                 MINDEX(m, k);
 293                                 A = mtod(m, u_char *)[k];
 294                                 continue;
 295 #else
 296                                 return 0;
 297 #endif
 298                         }
 299                         A = p[k];
 300                         continue;
 301
 302                 case BPF_LD|BPF_W|BPF_LEN:
 303                         A = wirelen;
 304                         continue;
 305
 306                 case BPF_LDX|BPF_W|BPF_LEN:
 307                         X = wirelen;
 308                         continue;
 309
 310                 case BPF_LD|BPF_W|BPF_IND:
 311                         k = X + pc->k;
 312                         if (pc->k > buflen || X > buflen - pc->k ||
 313                             sizeof(int32_t) > buflen - k) {
 314 #ifdef KERNEL
 315                                 int merr;
 316
 317                                 if (buflen != 0)
 318                                         return 0;
 319                                 A = m_xword((struct mbuf *)p, k, &merr);
 320                                 if (merr != 0)
 321                                         return 0;
 322                                 continue;
 323 #else
 324                                 return 0;
 325 #endif
 326                         }
 327 #if BPF_ALIGN
 328                         if (((intptr_t)(p + k) & 3) != 0)
 329                                 A = EXTRACT_LONG(&p[k]);
 330                         else
 331 #endif
 332                                 A = ntohl(*(int32_t *)(p + k));
 333                         continue;
 334
 335                 case BPF_LD|BPF_H|BPF_IND:
 336                         k = X + pc->k;
 337                         if (X > buflen || pc->k > buflen - X ||
 338                             sizeof(int16_t) > buflen - k) {
 339 #ifdef KERNEL
 340                                 int merr;
 341
 342                                 if (buflen != 0)
 343                                         return 0;
 344                                 A = m_xhalf((struct mbuf *)p, k, &merr);
 345                                 if (merr != 0)
 346                                         return 0;
 347                                 continue;
 348 #else
 349                                 return 0;
 350 #endif
 351                         }
 352                         A = EXTRACT_SHORT(&p[k]);
 353                         continue;
 354
 355                 case BPF_LD|BPF_B|BPF_IND:
 356                         k = X + pc->k;
 357                         if (pc->k >= buflen || X >= buflen - pc->k) {
 358 #ifdef KERNEL
 359                                 register struct mbuf *m;
 360
 361                                 if (buflen != 0)
 362                                         return 0;
 363                                 m = (struct mbuf *)p;
 364                                 MINDEX(m, k);
 365                                 A = mtod(m, char *)[k];
 366                                 continue;
 367 #else
 368                                 return 0;
 369 #endif
 370                         }
 371                         A = p[k];
 372                         continue;
 373
 374                 case BPF_LDX|BPF_MSH|BPF_B:
 375                         k = pc->k;
 376                         if (k >= buflen) {
 377 #ifdef KERNEL
 378                                 register struct mbuf *m;
 379
 380                                 if (buflen != 0)
 381                                         return 0;
 382                                 m = (struct mbuf *)p;
 383                                 MINDEX(m, k);
 384                                 X = (mtod(m, char *)[k] & 0xf) << 2;
 385                                 continue;
 386 #else
 387                                 return 0;
 388 #endif
 389                         }
 390                         X = (p[pc->k] & 0xf) << 2;
 391                         continue;
 392
 393                 case BPF_LD|BPF_IMM:
 394                         A = pc->k;
 395                         continue;
 396
 397                 case BPF_LDX|BPF_IMM:
 398                         X = pc->k;
 399                         continue;
 400
 401                 case BPF_LD|BPF_MEM:
 402                         A = mem[pc->k];
 403                         continue;
 404
 405                 case BPF_LDX|BPF_MEM:
 406                         X = mem[pc->k];
 407                         continue;
 408
 409                 case BPF_ST:
 410                         mem[pc->k] = A;
 411                         continue;
 412
 413                 case BPF_STX:
 414                         mem[pc->k] = X;
 415                         continue;
 416
 417                 case BPF_JMP|BPF_JA:
 418                         pc += pc->k;
 419                         continue;
 420
 421                 case BPF_JMP|BPF_JGT|BPF_K:
 422                         pc += (A > pc->k) ? pc->jt : pc->jf;
 423                         continue;
 424
 425                 case BPF_JMP|BPF_JGE|BPF_K:
 426                         pc += (A >= pc->k) ? pc->jt : pc->jf;
 427                         continue;
 428
 429                 case BPF_JMP|BPF_JEQ|BPF_K:
 430                         pc += (A == pc->k) ? pc->jt : pc->jf;
 431                         continue;
 432
 433                 case BPF_JMP|BPF_JSET|BPF_K:
 434                         pc += (A & pc->k) ? pc->jt : pc->jf;
 435                         continue;
 436
 437                 case BPF_JMP|BPF_JGT|BPF_X:
 438                         pc += (A > X) ? pc->jt : pc->jf;
 439                         continue;
 440
 441                 case BPF_JMP|BPF_JGE|BPF_X:
 442                         pc += (A >= X) ? pc->jt : pc->jf;
 443                         continue;
 444
 445                 case BPF_JMP|BPF_JEQ|BPF_X:
 446                         pc += (A == X) ? pc->jt : pc->jf;
 447                         continue;
 448
 449                 case BPF_JMP|BPF_JSET|BPF_X:
 450                         pc += (A & X) ? pc->jt : pc->jf;
 451                         continue;
 452
 453                 case BPF_ALU|BPF_ADD|BPF_X:
 454                         A += X;
 455                         continue;
 456
 457                 case BPF_ALU|BPF_SUB|BPF_X:
 458                         A -= X;
 459                         continue;
 460
 461                 case BPF_ALU|BPF_MUL|BPF_X:
 462                         A *= X;
 463                         continue;
 464
 465                 case BPF_ALU|BPF_DIV|BPF_X:
 466                         if (X == 0)
 467                                 return 0;
 468                         A /= X;
 469                         continue;
 470
 471                 case BPF_ALU|BPF_AND|BPF_X:
 472                         A &= X;
 473                         continue;
 474
 475                 case BPF_ALU|BPF_OR|BPF_X:
 476                         A |= X;
 477                         continue;
 478
 479                 case BPF_ALU|BPF_LSH|BPF_X:
 480                         A <<= X;
 481                         continue;
 482
 483                 case BPF_ALU|BPF_RSH|BPF_X:
 484                         A >>= X;
 485                         continue;
 486
 487                 case BPF_ALU|BPF_ADD|BPF_K:
 488                         A += pc->k;
 489                         continue;
 490
 491                 case BPF_ALU|BPF_SUB|BPF_K:
 492                         A -= pc->k;
 493                         continue;
 494
 495                 case BPF_ALU|BPF_MUL|BPF_K:
 496                         A *= pc->k;
 497                         continue;
 498
 499                 case BPF_ALU|BPF_DIV|BPF_K:
 500                         A /= pc->k;
 501                         continue;
 502
 503                 case BPF_ALU|BPF_AND|BPF_K:
 504                         A &= pc->k;
 505                         continue;
 506
 507                 case BPF_ALU|BPF_OR|BPF_K:
 508                         A |= pc->k;
 509                         continue;
 510
 511                 case BPF_ALU|BPF_LSH|BPF_K:
 512                         A <<= pc->k;
 513                         continue;
 514
 515                 case BPF_ALU|BPF_RSH|BPF_K:
 516                         A >>= pc->k;
 517                         continue;
 518
 519                 case BPF_ALU|BPF_NEG:
 520                         A = -A;
 521                         continue;
 522
 523                 case BPF_MISC|BPF_TAX:
 524                         X = A;
 525                         continue;
 526
 527                 case BPF_MISC|BPF_TXA:
 528                         A = X;
 529                         continue;
 530                 }
 531         }
 532 }
 533
 534 #ifdef KERNEL
 535 /*
 536  * Return true if the 'fcode' is a valid filter program.
 537  * The constraints are that each jump be forward and to a valid
 538  * code.  The code must terminate with either an accept or reject.
 539  * 'valid' is an array for use by the routine (it must be at least
 540  * 'len' bytes long).
 541  *
 542  * The kernel needs to be able to verify an application's filter code.
 543  * Otherwise, a bogus program could easily crash the system.
 544  */
 545 int
 546 bpf_validate(f, len)
 547         const struct bpf_insn *f;
 548         int len;
 549 {
 550         register int i;
 551         const struct bpf_insn *p;
 552
 553         for (i = 0; i < len; ++i) {
 554                 /*
 555                  * Check that that jumps are forward, and within
 556                  * the code block.
 557                  */
 558                 p = &f[i];
 559                 if (BPF_CLASS(p->code) == BPF_JMP) {
 560                         register int from = i + 1;
 561
 562                         if (BPF_OP(p->code) == BPF_JA) {
 563                                 if (from >= len || p->k >= len - from)
 564                                         return 0;
 565                         }
 566                         else if (from >= len || p->jt >= len - from ||
 567                                  p->jf >= len - from)
 568                                 return 0;
 569                 }
 570                 /*
 571                  * Check that memory operations use valid addresses.
 572                  */
 573                 if ((BPF_CLASS(p->code) == BPF_ST ||
 574                      (BPF_CLASS(p->code) == BPF_LD &&
 575                       (p->code & 0xe0) == BPF_MEM)) &&
 576                     p->k >= BPF_MEMWORDS)
 577                         return 0;
 578                 /*
 579                  * Check for constant division by 0.
 580                  */
 581                 if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0)
 582                         return 0;
 583         }
 584         return BPF_CLASS(f[len - 1].code) == BPF_RET;
 585 }
 586 #endif