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 #include "extract.h" 48 #include "diag-control.h" 49 50 #define EXTRACT_SHORT EXTRACT_BE_U_2 51 #define EXTRACT_LONG EXTRACT_BE_U_4 52 53 #ifndef _WIN32 54 #include <sys/param.h> 55 #include <sys/types.h> 56 #include <sys/time.h> 57 #endif /* _WIN32 */ 58 59 #include <pcap-int.h> 60 61 #include <stdlib.h> 62 63 #ifdef __linux__ 64 #include <linux/types.h> 65 #include <linux/if_packet.h> 66 #include <linux/filter.h> 67 #endif 68 69 enum { 70 BPF_S_ANC_NONE, 71 BPF_S_ANC_VLAN_TAG, 72 BPF_S_ANC_VLAN_TAG_PRESENT, 73 }; 74 75 /* 76 * Execute the filter program starting at pc on the packet p 77 * wirelen is the length of the original packet 78 * buflen is the amount of data present 79 * aux_data is auxiliary data, currently used only when interpreting 80 * filters intended for the Linux kernel in cases where the kernel 81 * rejects the filter; it contains VLAN tag information 82 * For the kernel, p is assumed to be a pointer to an mbuf if buflen is 0, 83 * in all other cases, p is a pointer to a buffer and buflen is its size. 84 * 85 * Thanks to Ani Sinha <ani@arista.com> for providing initial implementation 86 */ 87 #if defined(SKF_AD_VLAN_TAG_PRESENT) 88 u_int 89 pcap_filter_with_aux_data(const struct bpf_insn *pc, const u_char *p, 90 u_int wirelen, u_int buflen, const struct pcap_bpf_aux_data *aux_data) 91 #else 92 u_int 93 pcap_filter_with_aux_data(const struct bpf_insn *pc, const u_char *p, 94 u_int wirelen, u_int buflen, const struct pcap_bpf_aux_data *aux_data _U_) 95 #endif 96 { 97 register uint32_t A, X; 98 register bpf_u_int32 k; 99 uint32_t mem[BPF_MEMWORDS]; 100 101 if (pc == 0) 102 /* 103 * No filter means accept all. 104 */ 105 return (u_int)-1; 106 A = 0; 107 X = 0; 108 --pc; 109 for (;;) { 110 ++pc; 111 switch (pc->code) { 112 113 default: 114 abort(); 115 case BPF_RET|BPF_K: 116 return (u_int)pc->k; 117 118 case BPF_RET|BPF_A: 119 return (u_int)A; 120 121 case BPF_LD|BPF_W|BPF_ABS: 122 k = pc->k; 123 if (k > buflen || sizeof(int32_t) > buflen - k) { 124 return 0; 125 } 126 A = EXTRACT_LONG(&p[k]); 127 continue; 128 129 case BPF_LD|BPF_H|BPF_ABS: 130 k = pc->k; 131 if (k > buflen || sizeof(int16_t) > buflen - k) { 132 return 0; 133 } 134 A = EXTRACT_SHORT(&p[k]); 135 continue; 136 137 case BPF_LD|BPF_B|BPF_ABS: 138 /* 139 * Yes, we know, this switch doesn't do 140 * anything unless we're building for 141 * a Linux kernel with removed VLAN 142 * tags available as meta-data. 143 */ 144 DIAG_OFF_DEFAULT_ONLY_SWITCH 145 switch (pc->k) { 146 147 #if defined(SKF_AD_VLAN_TAG_PRESENT) 148 case SKF_AD_OFF + SKF_AD_VLAN_TAG: 149 if (!aux_data) 150 return 0; 151 A = aux_data->vlan_tag; 152 break; 153 154 case SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT: 155 if (!aux_data) 156 return 0; 157 A = aux_data->vlan_tag_present; 158 break; 159 #endif 160 default: 161 k = pc->k; 162 if (k >= buflen) { 163 return 0; 164 } 165 A = p[k]; 166 break; 167 } 168 DIAG_ON_DEFAULT_ONLY_SWITCH 169 continue; 170 171 case BPF_LD|BPF_W|BPF_LEN: 172 A = wirelen; 173 continue; 174 175 case BPF_LDX|BPF_W|BPF_LEN: 176 X = wirelen; 177 continue; 178 179 case BPF_LD|BPF_W|BPF_IND: 180 k = X + pc->k; 181 if (pc->k > buflen || X > buflen - pc->k || 182 sizeof(int32_t) > buflen - k) { 183 return 0; 184 } 185 A = EXTRACT_LONG(&p[k]); 186 continue; 187 188 case BPF_LD|BPF_H|BPF_IND: 189 k = X + pc->k; 190 if (X > buflen || pc->k > buflen - X || 191 sizeof(int16_t) > buflen - k) { 192 return 0; 193 } 194 A = EXTRACT_SHORT(&p[k]); 195 continue; 196 197 case BPF_LD|BPF_B|BPF_IND: 198 k = X + pc->k; 199 if (pc->k >= buflen || X >= buflen - pc->k) { 200 return 0; 201 } 202 A = p[k]; 203 continue; 204 205 case BPF_LDX|BPF_MSH|BPF_B: 206 k = pc->k; 207 if (k >= buflen) { 208 return 0; 209 } 210 X = (p[pc->k] & 0xf) << 2; 211 continue; 212 213 case BPF_LD|BPF_IMM: 214 A = pc->k; 215 continue; 216 217 case BPF_LDX|BPF_IMM: 218 X = pc->k; 219 continue; 220 221 case BPF_LD|BPF_MEM: 222 A = mem[pc->k]; 223 continue; 224 225 case BPF_LDX|BPF_MEM: 226 X = mem[pc->k]; 227 continue; 228 229 case BPF_ST: 230 mem[pc->k] = A; 231 continue; 232 233 case BPF_STX: 234 mem[pc->k] = X; 235 continue; 236 237 case BPF_JMP|BPF_JA: 238 /* 239 * XXX - we currently implement "ip6 protochain" 240 * with backward jumps, so sign-extend pc->k. 241 */ 242 pc += (bpf_int32)pc->k; 243 continue; 244 245 case BPF_JMP|BPF_JGT|BPF_K: 246 pc += (A > pc->k) ? pc->jt : pc->jf; 247 continue; 248 249 case BPF_JMP|BPF_JGE|BPF_K: 250 pc += (A >= pc->k) ? pc->jt : pc->jf; 251 continue; 252 253 case BPF_JMP|BPF_JEQ|BPF_K: 254 pc += (A == pc->k) ? pc->jt : pc->jf; 255 continue; 256 257 case BPF_JMP|BPF_JSET|BPF_K: 258 pc += (A & pc->k) ? pc->jt : pc->jf; 259 continue; 260 261 case BPF_JMP|BPF_JGT|BPF_X: 262 pc += (A > X) ? pc->jt : pc->jf; 263 continue; 264 265 case BPF_JMP|BPF_JGE|BPF_X: 266 pc += (A >= X) ? pc->jt : pc->jf; 267 continue; 268 269 case BPF_JMP|BPF_JEQ|BPF_X: 270 pc += (A == X) ? pc->jt : pc->jf; 271 continue; 272 273 case BPF_JMP|BPF_JSET|BPF_X: 274 pc += (A & X) ? pc->jt : pc->jf; 275 continue; 276 277 case BPF_ALU|BPF_ADD|BPF_X: 278 A += X; 279 continue; 280 281 case BPF_ALU|BPF_SUB|BPF_X: 282 A -= X; 283 continue; 284 285 case BPF_ALU|BPF_MUL|BPF_X: 286 A *= X; 287 continue; 288 289 case BPF_ALU|BPF_DIV|BPF_X: 290 if (X == 0) 291 return 0; 292 A /= X; 293 continue; 294 295 case BPF_ALU|BPF_MOD|BPF_X: 296 if (X == 0) 297 return 0; 298 A %= X; 299 continue; 300 301 case BPF_ALU|BPF_AND|BPF_X: 302 A &= X; 303 continue; 304 305 case BPF_ALU|BPF_OR|BPF_X: 306 A |= X; 307 continue; 308 309 case BPF_ALU|BPF_XOR|BPF_X: 310 A ^= X; 311 continue; 312 313 case BPF_ALU|BPF_LSH|BPF_X: 314 if (X < 32) 315 A <<= X; 316 else 317 A = 0; 318 continue; 319 320 case BPF_ALU|BPF_RSH|BPF_X: 321 if (X < 32) 322 A >>= X; 323 else 324 A = 0; 325 continue; 326 327 case BPF_ALU|BPF_ADD|BPF_K: 328 A += pc->k; 329 continue; 330 331 case BPF_ALU|BPF_SUB|BPF_K: 332 A -= pc->k; 333 continue; 334 335 case BPF_ALU|BPF_MUL|BPF_K: 336 A *= pc->k; 337 continue; 338 339 case BPF_ALU|BPF_DIV|BPF_K: 340 A /= pc->k; 341 continue; 342 343 case BPF_ALU|BPF_MOD|BPF_K: 344 A %= pc->k; 345 continue; 346 347 case BPF_ALU|BPF_AND|BPF_K: 348 A &= pc->k; 349 continue; 350 351 case BPF_ALU|BPF_OR|BPF_K: 352 A |= pc->k; 353 continue; 354 355 case BPF_ALU|BPF_XOR|BPF_K: 356 A ^= pc->k; 357 continue; 358 359 case BPF_ALU|BPF_LSH|BPF_K: 360 A <<= pc->k; 361 continue; 362 363 case BPF_ALU|BPF_RSH|BPF_K: 364 A >>= pc->k; 365 continue; 366 367 case BPF_ALU|BPF_NEG: 368 /* 369 * Most BPF arithmetic is unsigned, but negation 370 * can't be unsigned; respecify it as subtracting 371 * the accumulator from 0U, so that 1) we don't 372 * get compiler warnings about negating an unsigned 373 * value and 2) don't get UBSan warnings about 374 * the result of negating 0x80000000 being undefined. 375 */ 376 A = (0U - A); 377 continue; 378 379 case BPF_MISC|BPF_TAX: 380 X = A; 381 continue; 382 383 case BPF_MISC|BPF_TXA: 384 A = X; 385 continue; 386 } 387 } 388 } 389 390 u_int 391 pcap_filter(const struct bpf_insn *pc, const u_char *p, u_int wirelen, 392 u_int buflen) 393 { 394 return pcap_filter_with_aux_data(pc, p, wirelen, buflen, NULL); 395 } 396 397 /* 398 * Return true if the 'fcode' is a valid filter program. 399 * The constraints are that each jump be forward and to a valid 400 * code, that memory accesses are within valid ranges (to the 401 * extent that this can be checked statically; loads of packet 402 * data have to be, and are, also checked at run time), and that 403 * the code terminates with either an accept or reject. 404 * 405 * The kernel needs to be able to verify an application's filter code. 406 * Otherwise, a bogus program could easily crash the system. 407 */ 408 int 409 pcap_validate_filter(const struct bpf_insn *f, int len) 410 { 411 u_int i, from; 412 const struct bpf_insn *p; 413 414 if (len < 1) 415 return 0; 416 417 for (i = 0; i < (u_int)len; ++i) { 418 p = &f[i]; 419 switch (BPF_CLASS(p->code)) { 420 /* 421 * Check that memory operations use valid addresses. 422 */ 423 case BPF_LD: 424 case BPF_LDX: 425 switch (BPF_MODE(p->code)) { 426 case BPF_IMM: 427 break; 428 case BPF_ABS: 429 case BPF_IND: 430 case BPF_MSH: 431 /* 432 * There's no maximum packet data size 433 * in userland. The runtime packet length 434 * check suffices. 435 */ 436 break; 437 case BPF_MEM: 438 if (p->k >= BPF_MEMWORDS) 439 return 0; 440 break; 441 case BPF_LEN: 442 break; 443 default: 444 return 0; 445 } 446 break; 447 case BPF_ST: 448 case BPF_STX: 449 if (p->k >= BPF_MEMWORDS) 450 return 0; 451 break; 452 case BPF_ALU: 453 switch (BPF_OP(p->code)) { 454 case BPF_ADD: 455 case BPF_SUB: 456 case BPF_MUL: 457 case BPF_OR: 458 case BPF_AND: 459 case BPF_XOR: 460 case BPF_LSH: 461 case BPF_RSH: 462 case BPF_NEG: 463 break; 464 case BPF_DIV: 465 case BPF_MOD: 466 /* 467 * Check for constant division or modulus 468 * by 0. 469 */ 470 if (BPF_SRC(p->code) == BPF_K && p->k == 0) 471 return 0; 472 break; 473 default: 474 return 0; 475 } 476 break; 477 case BPF_JMP: 478 /* 479 * Check that jumps are within the code block, 480 * and that unconditional branches don't go 481 * backwards as a result of an overflow. 482 * Unconditional branches have a 32-bit offset, 483 * so they could overflow; we check to make 484 * sure they don't. Conditional branches have 485 * an 8-bit offset, and the from address is <= 486 * BPF_MAXINSNS, and we assume that BPF_MAXINSNS 487 * is sufficiently small that adding 255 to it 488 * won't overflow. 489 * 490 * We know that len is <= BPF_MAXINSNS, and we 491 * assume that BPF_MAXINSNS is < the maximum size 492 * of a u_int, so that i + 1 doesn't overflow. 493 * 494 * For userland, we don't know that the from 495 * or len are <= BPF_MAXINSNS, but we know that 496 * from <= len, and, except on a 64-bit system, 497 * it's unlikely that len, if it truly reflects 498 * the size of the program we've been handed, 499 * will be anywhere near the maximum size of 500 * a u_int. We also don't check for backward 501 * branches, as we currently support them in 502 * userland for the protochain operation. 503 */ 504 from = i + 1; 505 switch (BPF_OP(p->code)) { 506 case BPF_JA: 507 if (from + p->k >= (u_int)len) 508 return 0; 509 break; 510 case BPF_JEQ: 511 case BPF_JGT: 512 case BPF_JGE: 513 case BPF_JSET: 514 if (from + p->jt >= (u_int)len || from + p->jf >= (u_int)len) 515 return 0; 516 break; 517 default: 518 return 0; 519 } 520 break; 521 case BPF_RET: 522 break; 523 case BPF_MISC: 524 break; 525 default: 526 return 0; 527 } 528 } 529 return BPF_CLASS(f[len - 1].code) == BPF_RET; 530 } 531 532 /* 533 * Exported because older versions of libpcap exported them. 534 */ 535 u_int 536 bpf_filter(const struct bpf_insn *pc, const u_char *p, u_int wirelen, 537 u_int buflen) 538 { 539 return pcap_filter(pc, p, wirelen, buflen); 540 } 541 542 int 543 bpf_validate(const struct bpf_insn *f, int len) 544 { 545 return pcap_validate_filter(f, len); 546 } 547