1 /*- 2 * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997 3 * The Regents of the University of California. 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 * @(#)bpf.c 7.5 (Berkeley) 7/15/91 39 */ 40 41 #ifdef HAVE_CONFIG_H 42 #include <config.h> 43 #endif 44 45 #include <pcap/pcap-inttypes.h> 46 #include "pcap-types.h" 47 48 #ifndef _WIN32 49 #include <sys/param.h> 50 #include <sys/types.h> 51 #include <sys/time.h> 52 #endif /* _WIN32 */ 53 54 #include <pcap/bpf.h> 55 56 #include <stdlib.h> 57 58 #define int32 bpf_int32 59 #define u_int32 bpf_u_int32 60 61 #ifndef LBL_ALIGN 62 /* 63 * XXX - IA-64? If not, this probably won't work on Win64 IA-64 64 * systems, unless LBL_ALIGN is defined elsewhere for them. 65 * XXX - SuperH? If not, this probably won't work on WinCE SuperH 66 * systems, unless LBL_ALIGN is defined elsewhere for them. 67 */ 68 #if defined(sparc) || defined(__sparc__) || defined(mips) || \ 69 defined(ibm032) || defined(__alpha) || defined(__hpux) || \ 70 defined(__arm__) 71 #define LBL_ALIGN 72 #endif 73 #endif 74 75 #ifndef LBL_ALIGN 76 #ifndef _WIN32 77 #include <netinet/in.h> 78 #endif 79 80 #define EXTRACT_SHORT(p) ((u_short)ntohs(*(u_short *)p)) 81 #define EXTRACT_LONG(p) (ntohl(*(u_int32 *)p)) 82 #else 83 #define EXTRACT_SHORT(p)\ 84 ((u_short)\ 85 ((u_short)*((u_char *)p+0)<<8|\ 86 (u_short)*((u_char *)p+1)<<0)) 87 #define EXTRACT_LONG(p)\ 88 ((u_int32)*((u_char *)p+0)<<24|\ 89 (u_int32)*((u_char *)p+1)<<16|\ 90 (u_int32)*((u_char *)p+2)<<8|\ 91 (u_int32)*((u_char *)p+3)<<0) 92 #endif 93 94 #ifdef __linux__ 95 #include <linux/types.h> 96 #include <linux/if_packet.h> 97 #include <linux/filter.h> 98 #endif 99 100 enum { 101 BPF_S_ANC_NONE, 102 BPF_S_ANC_VLAN_TAG, 103 BPF_S_ANC_VLAN_TAG_PRESENT, 104 }; 105 106 /* 107 * Execute the filter program starting at pc on the packet p 108 * wirelen is the length of the original packet 109 * buflen is the amount of data present 110 * aux_data is auxiliary data, currently used only when interpreting 111 * filters intended for the Linux kernel in cases where the kernel 112 * rejects the filter; it contains VLAN tag information 113 * For the kernel, p is assumed to be a pointer to an mbuf if buflen is 0, 114 * in all other cases, p is a pointer to a buffer and buflen is its size. 115 * 116 * Thanks to Ani Sinha <ani (at) arista.com> for providing initial implementation 117 */ 118 u_int 119 bpf_filter_with_aux_data(const struct bpf_insn *pc, const u_char *p, 120 u_int wirelen, u_int buflen, const struct bpf_aux_data *aux_data) 121 { 122 register u_int32 A, X; 123 register bpf_u_int32 k; 124 u_int32 mem[BPF_MEMWORDS]; 125 126 if (pc == 0) 127 /* 128 * No filter means accept all. 129 */ 130 return (u_int)-1; 131 A = 0; 132 X = 0; 133 --pc; 134 for (;;) { 135 ++pc; 136 switch (pc->code) { 137 138 default: 139 abort(); 140 case BPF_RET|BPF_K: 141 return (u_int)pc->k; 142 143 case BPF_RET|BPF_A: 144 return (u_int)A; 145 146 case BPF_LD|BPF_W|BPF_ABS: 147 k = pc->k; 148 if (k > buflen || sizeof(int32_t) > buflen - k) { 149 return 0; 150 } 151 A = EXTRACT_LONG(&p[k]); 152 continue; 153 154 case BPF_LD|BPF_H|BPF_ABS: 155 k = pc->k; 156 if (k > buflen || sizeof(int16_t) > buflen - k) { 157 return 0; 158 } 159 A = EXTRACT_SHORT(&p[k]); 160 continue; 161 162 case BPF_LD|BPF_B|BPF_ABS: 163 switch (pc->k) { 164 165 #if defined(SKF_AD_VLAN_TAG_PRESENT) 166 case SKF_AD_OFF + SKF_AD_VLAN_TAG: 167 if (!aux_data) 168 return 0; 169 A = aux_data->vlan_tag; 170 break; 171 172 case SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT: 173 if (!aux_data) 174 return 0; 175 A = aux_data->vlan_tag_present; 176 break; 177 #endif 178 default: 179 k = pc->k; 180 if (k >= buflen) { 181 return 0; 182 } 183 A = p[k]; 184 break; 185 } 186 continue; 187 188 case BPF_LD|BPF_W|BPF_LEN: 189 A = wirelen; 190 continue; 191 192 case BPF_LDX|BPF_W|BPF_LEN: 193 X = wirelen; 194 continue; 195 196 case BPF_LD|BPF_W|BPF_IND: 197 k = X + pc->k; 198 if (pc->k > buflen || X > buflen - pc->k || 199 sizeof(int32_t) > buflen - k) { 200 return 0; 201 } 202 A = EXTRACT_LONG(&p[k]); 203 continue; 204 205 case BPF_LD|BPF_H|BPF_IND: 206 k = X + pc->k; 207 if (X > buflen || pc->k > buflen - X || 208 sizeof(int16_t) > buflen - k) { 209 return 0; 210 } 211 A = EXTRACT_SHORT(&p[k]); 212 continue; 213 214 case BPF_LD|BPF_B|BPF_IND: 215 k = X + pc->k; 216 if (pc->k >= buflen || X >= buflen - pc->k) { 217 return 0; 218 } 219 A = p[k]; 220 continue; 221 222 case BPF_LDX|BPF_MSH|BPF_B: 223 k = pc->k; 224 if (k >= buflen) { 225 return 0; 226 } 227 X = (p[pc->k] & 0xf) << 2; 228 continue; 229 230 case BPF_LD|BPF_IMM: 231 A = pc->k; 232 continue; 233 234 case BPF_LDX|BPF_IMM: 235 X = pc->k; 236 continue; 237 238 case BPF_LD|BPF_MEM: 239 A = mem[pc->k]; 240 continue; 241 242 case BPF_LDX|BPF_MEM: 243 X = mem[pc->k]; 244 continue; 245 246 case BPF_ST: 247 mem[pc->k] = A; 248 continue; 249 250 case BPF_STX: 251 mem[pc->k] = X; 252 continue; 253 254 case BPF_JMP|BPF_JA: 255 /* 256 * XXX - we currently implement "ip6 protochain" 257 * with backward jumps, so sign-extend pc->k. 258 */ 259 pc += (bpf_int32)pc->k; 260 continue; 261 262 case BPF_JMP|BPF_JGT|BPF_K: 263 pc += (A > pc->k) ? pc->jt : pc->jf; 264 continue; 265 266 case BPF_JMP|BPF_JGE|BPF_K: 267 pc += (A >= pc->k) ? pc->jt : pc->jf; 268 continue; 269 270 case BPF_JMP|BPF_JEQ|BPF_K: 271 pc += (A == pc->k) ? pc->jt : pc->jf; 272 continue; 273 274 case BPF_JMP|BPF_JSET|BPF_K: 275 pc += (A & pc->k) ? pc->jt : pc->jf; 276 continue; 277 278 case BPF_JMP|BPF_JGT|BPF_X: 279 pc += (A > X) ? pc->jt : pc->jf; 280 continue; 281 282 case BPF_JMP|BPF_JGE|BPF_X: 283 pc += (A >= X) ? pc->jt : pc->jf; 284 continue; 285 286 case BPF_JMP|BPF_JEQ|BPF_X: 287 pc += (A == X) ? pc->jt : pc->jf; 288 continue; 289 290 case BPF_JMP|BPF_JSET|BPF_X: 291 pc += (A & X) ? pc->jt : pc->jf; 292 continue; 293 294 case BPF_ALU|BPF_ADD|BPF_X: 295 A += X; 296 continue; 297 298 case BPF_ALU|BPF_SUB|BPF_X: 299 A -= X; 300 continue; 301 302 case BPF_ALU|BPF_MUL|BPF_X: 303 A *= X; 304 continue; 305 306 case BPF_ALU|BPF_DIV|BPF_X: 307 if (X == 0) 308 return 0; 309 A /= X; 310 continue; 311 312 case BPF_ALU|BPF_MOD|BPF_X: 313 if (X == 0) 314 return 0; 315 A %= X; 316 continue; 317 318 case BPF_ALU|BPF_AND|BPF_X: 319 A &= X; 320 continue; 321 322 case BPF_ALU|BPF_OR|BPF_X: 323 A |= X; 324 continue; 325 326 case BPF_ALU|BPF_XOR|BPF_X: 327 A ^= X; 328 continue; 329 330 case BPF_ALU|BPF_LSH|BPF_X: 331 A <<= X; 332 continue; 333 334 case BPF_ALU|BPF_RSH|BPF_X: 335 A >>= X; 336 continue; 337 338 case BPF_ALU|BPF_ADD|BPF_K: 339 A += pc->k; 340 continue; 341 342 case BPF_ALU|BPF_SUB|BPF_K: 343 A -= pc->k; 344 continue; 345 346 case BPF_ALU|BPF_MUL|BPF_K: 347 A *= pc->k; 348 continue; 349 350 case BPF_ALU|BPF_DIV|BPF_K: 351 A /= pc->k; 352 continue; 353 354 case BPF_ALU|BPF_MOD|BPF_K: 355 A %= pc->k; 356 continue; 357 358 case BPF_ALU|BPF_AND|BPF_K: 359 A &= pc->k; 360 continue; 361 362 case BPF_ALU|BPF_OR|BPF_K: 363 A |= pc->k; 364 continue; 365 366 case BPF_ALU|BPF_XOR|BPF_K: 367 A ^= pc->k; 368 continue; 369 370 case BPF_ALU|BPF_LSH|BPF_K: 371 A <<= pc->k; 372 continue; 373 374 case BPF_ALU|BPF_RSH|BPF_K: 375 A >>= pc->k; 376 continue; 377 378 case BPF_ALU|BPF_NEG: 379 /* 380 * Most BPF arithmetic is unsigned, but negation 381 * can't be unsigned; throw some casts to 382 * specify what we're trying to do. 383 */ 384 A = (u_int32)(-(int32)A); 385 continue; 386 387 case BPF_MISC|BPF_TAX: 388 X = A; 389 continue; 390 391 case BPF_MISC|BPF_TXA: 392 A = X; 393 continue; 394 } 395 } 396 } 397 398 u_int 399 bpf_filter(const struct bpf_insn *pc, const u_char *p, u_int wirelen, 400 u_int buflen) 401 { 402 return bpf_filter_with_aux_data(pc, p, wirelen, buflen, NULL); 403 } 404 405 406 /* 407 * Return true if the 'fcode' is a valid filter program. 408 * The constraints are that each jump be forward and to a valid 409 * code, that memory accesses are within valid ranges (to the 410 * extent that this can be checked statically; loads of packet 411 * data have to be, and are, also checked at run time), and that 412 * the code terminates with either an accept or reject. 413 * 414 * The kernel needs to be able to verify an application's filter code. 415 * Otherwise, a bogus program could easily crash the system. 416 */ 417 int 418 bpf_validate(const struct bpf_insn *f, int len) 419 { 420 u_int i, from; 421 const struct bpf_insn *p; 422 423 if (len < 1) 424 return 0; 425 426 for (i = 0; i < (u_int)len; ++i) { 427 p = &f[i]; 428 switch (BPF_CLASS(p->code)) { 429 /* 430 * Check that memory operations use valid addresses. 431 */ 432 case BPF_LD: 433 case BPF_LDX: 434 switch (BPF_MODE(p->code)) { 435 case BPF_IMM: 436 break; 437 case BPF_ABS: 438 case BPF_IND: 439 case BPF_MSH: 440 /* 441 * There's no maximum packet data size 442 * in userland. The runtime packet length 443 * check suffices. 444 */ 445 break; 446 case BPF_MEM: 447 if (p->k >= BPF_MEMWORDS) 448 return 0; 449 break; 450 case BPF_LEN: 451 break; 452 default: 453 return 0; 454 } 455 break; 456 case BPF_ST: 457 case BPF_STX: 458 if (p->k >= BPF_MEMWORDS) 459 return 0; 460 break; 461 case BPF_ALU: 462 switch (BPF_OP(p->code)) { 463 case BPF_ADD: 464 case BPF_SUB: 465 case BPF_MUL: 466 case BPF_OR: 467 case BPF_AND: 468 case BPF_XOR: 469 case BPF_LSH: 470 case BPF_RSH: 471 case BPF_NEG: 472 break; 473 case BPF_DIV: 474 case BPF_MOD: 475 /* 476 * Check for constant division or modulus 477 * by 0. 478 */ 479 if (BPF_SRC(p->code) == BPF_K && p->k == 0) 480 return 0; 481 break; 482 default: 483 return 0; 484 } 485 break; 486 case BPF_JMP: 487 /* 488 * Check that jumps are within the code block, 489 * and that unconditional branches don't go 490 * backwards as a result of an overflow. 491 * Unconditional branches have a 32-bit offset, 492 * so they could overflow; we check to make 493 * sure they don't. Conditional branches have 494 * an 8-bit offset, and the from address is <= 495 * BPF_MAXINSNS, and we assume that BPF_MAXINSNS 496 * is sufficiently small that adding 255 to it 497 * won't overflow. 498 * 499 * We know that len is <= BPF_MAXINSNS, and we 500 * assume that BPF_MAXINSNS is < the maximum size 501 * of a u_int, so that i + 1 doesn't overflow. 502 * 503 * For userland, we don't know that the from 504 * or len are <= BPF_MAXINSNS, but we know that 505 * from <= len, and, except on a 64-bit system, 506 * it's unlikely that len, if it truly reflects 507 * the size of the program we've been handed, 508 * will be anywhere near the maximum size of 509 * a u_int. We also don't check for backward 510 * branches, as we currently support them in 511 * userland for the protochain operation. 512 */ 513 from = i + 1; 514 switch (BPF_OP(p->code)) { 515 case BPF_JA: 516 if (from + p->k >= (u_int)len) 517 return 0; 518 break; 519 case BPF_JEQ: 520 case BPF_JGT: 521 case BPF_JGE: 522 case BPF_JSET: 523 if (from + p->jt >= (u_int)len || from + p->jf >= (u_int)len) 524 return 0; 525 break; 526 default: 527 return 0; 528 } 529 break; 530 case BPF_RET: 531 break; 532 case BPF_MISC: 533 break; 534 default: 535 return 0; 536 } 537 } 538 return BPF_CLASS(f[len - 1].code) == BPF_RET; 539 } 540
