1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * AppArmor security module 4 * 5 * This file contains AppArmor dfa based regular expression matching engine 6 * 7 * Copyright (C) 1998-2008 Novell/SUSE 8 * Copyright 2009-2012 Canonical Ltd. 9 */ 10 11 #include <linux/errno.h> 12 #include <linux/kernel.h> 13 #include <linux/mm.h> 14 #include <linux/slab.h> 15 #include <linux/vmalloc.h> 16 #include <linux/err.h> 17 #include <linux/kref.h> 18 19 #include "include/lib.h" 20 #include "include/match.h" 21 22 #define base_idx(X) ((X) & 0xffffff) 23 24 static char nulldfa_src[] = { 25 #include "nulldfa.in" 26 }; 27 struct aa_dfa *nulldfa; 28 29 static char stacksplitdfa_src[] = { 30 #include "stacksplitdfa.in" 31 }; 32 struct aa_dfa *stacksplitdfa; 33 34 int aa_setup_dfa_engine(void) 35 { 36 int error; 37 38 nulldfa = aa_dfa_unpack(nulldfa_src, sizeof(nulldfa_src), 39 TO_ACCEPT1_FLAG(YYTD_DATA32) | 40 TO_ACCEPT2_FLAG(YYTD_DATA32)); 41 if (IS_ERR(nulldfa)) { 42 error = PTR_ERR(nulldfa); 43 nulldfa = NULL; 44 return error; 45 } 46 47 stacksplitdfa = aa_dfa_unpack(stacksplitdfa_src, 48 sizeof(stacksplitdfa_src), 49 TO_ACCEPT1_FLAG(YYTD_DATA32) | 50 TO_ACCEPT2_FLAG(YYTD_DATA32)); 51 if (IS_ERR(stacksplitdfa)) { 52 aa_put_dfa(nulldfa); 53 nulldfa = NULL; 54 error = PTR_ERR(stacksplitdfa); 55 stacksplitdfa = NULL; 56 return error; 57 } 58 59 return 0; 60 } 61 62 void aa_teardown_dfa_engine(void) 63 { 64 aa_put_dfa(stacksplitdfa); 65 aa_put_dfa(nulldfa); 66 } 67 68 /** 69 * unpack_table - unpack a dfa table (one of accept, default, base, next check) 70 * @blob: data to unpack (NOT NULL) 71 * @bsize: size of blob 72 * 73 * Returns: pointer to table else NULL on failure 74 * 75 * NOTE: must be freed by kvfree (not kfree) 76 */ 77 static struct table_header *unpack_table(char *blob, size_t bsize) 78 { 79 struct table_header *table = NULL; 80 struct table_header th; 81 size_t tsize; 82 83 if (bsize < sizeof(struct table_header)) 84 goto out; 85 86 /* loaded td_id's start at 1, subtract 1 now to avoid doing 87 * it every time we use td_id as an index 88 */ 89 th.td_id = be16_to_cpu(*(__be16 *) (blob)) - 1; 90 if (th.td_id > YYTD_ID_MAX) 91 goto out; 92 th.td_flags = be16_to_cpu(*(__be16 *) (blob + 2)); 93 th.td_lolen = be32_to_cpu(*(__be32 *) (blob + 8)); 94 blob += sizeof(struct table_header); 95 96 if (!(th.td_flags == YYTD_DATA16 || th.td_flags == YYTD_DATA32 || 97 th.td_flags == YYTD_DATA8)) 98 goto out; 99 100 tsize = table_size(th.td_lolen, th.td_flags); 101 if (bsize < tsize) 102 goto out; 103 104 table = kvzalloc(tsize, GFP_KERNEL); 105 if (table) { 106 table->td_id = th.td_id; 107 table->td_flags = th.td_flags; 108 table->td_lolen = th.td_lolen; 109 if (th.td_flags == YYTD_DATA8) 110 UNPACK_ARRAY(table->td_data, blob, th.td_lolen, 111 u8, u8, byte_to_byte); 112 else if (th.td_flags == YYTD_DATA16) 113 UNPACK_ARRAY(table->td_data, blob, th.td_lolen, 114 u16, __be16, be16_to_cpu); 115 else if (th.td_flags == YYTD_DATA32) 116 UNPACK_ARRAY(table->td_data, blob, th.td_lolen, 117 u32, __be32, be32_to_cpu); 118 else 119 goto fail; 120 /* if table was vmalloced make sure the page tables are synced 121 * before it is used, as it goes live to all cpus. 122 */ 123 if (is_vmalloc_addr(table)) 124 vm_unmap_aliases(); 125 } 126 127 out: 128 return table; 129 fail: 130 kvfree(table); 131 return NULL; 132 } 133 134 /** 135 * verify_table_headers - verify that the tables headers are as expected 136 * @tables - array of dfa tables to check (NOT NULL) 137 * @flags: flags controlling what type of accept table are acceptable 138 * 139 * Assumes dfa has gone through the first pass verification done by unpacking 140 * NOTE: this does not valid accept table values 141 * 142 * Returns: %0 else error code on failure to verify 143 */ 144 static int verify_table_headers(struct table_header **tables, int flags) 145 { 146 size_t state_count, trans_count; 147 int error = -EPROTO; 148 149 /* check that required tables exist */ 150 if (!(tables[YYTD_ID_DEF] && tables[YYTD_ID_BASE] && 151 tables[YYTD_ID_NXT] && tables[YYTD_ID_CHK])) 152 goto out; 153 154 /* accept.size == default.size == base.size */ 155 state_count = tables[YYTD_ID_BASE]->td_lolen; 156 if (ACCEPT1_FLAGS(flags)) { 157 if (!tables[YYTD_ID_ACCEPT]) 158 goto out; 159 if (state_count != tables[YYTD_ID_ACCEPT]->td_lolen) 160 goto out; 161 } 162 if (ACCEPT2_FLAGS(flags)) { 163 if (!tables[YYTD_ID_ACCEPT2]) 164 goto out; 165 if (state_count != tables[YYTD_ID_ACCEPT2]->td_lolen) 166 goto out; 167 } 168 if (state_count != tables[YYTD_ID_DEF]->td_lolen) 169 goto out; 170 171 /* next.size == chk.size */ 172 trans_count = tables[YYTD_ID_NXT]->td_lolen; 173 if (trans_count != tables[YYTD_ID_CHK]->td_lolen) 174 goto out; 175 176 /* if equivalence classes then its table size must be 256 */ 177 if (tables[YYTD_ID_EC] && tables[YYTD_ID_EC]->td_lolen != 256) 178 goto out; 179 180 error = 0; 181 out: 182 return error; 183 } 184 185 /** 186 * verify_dfa - verify that transitions and states in the tables are in bounds. 187 * @dfa: dfa to test (NOT NULL) 188 * 189 * Assumes dfa has gone through the first pass verification done by unpacking 190 * NOTE: this does not valid accept table values 191 * 192 * Returns: %0 else error code on failure to verify 193 */ 194 static int verify_dfa(struct aa_dfa *dfa) 195 { 196 size_t i, state_count, trans_count; 197 int error = -EPROTO; 198 199 state_count = dfa->tables[YYTD_ID_BASE]->td_lolen; 200 trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen; 201 for (i = 0; i < state_count; i++) { 202 if (!(BASE_TABLE(dfa)[i] & MATCH_FLAG_DIFF_ENCODE) && 203 (DEFAULT_TABLE(dfa)[i] >= state_count)) 204 goto out; 205 if (base_idx(BASE_TABLE(dfa)[i]) + 255 >= trans_count) { 206 pr_err("AppArmor DFA next/check upper bounds error\n"); 207 goto out; 208 } 209 } 210 211 for (i = 0; i < trans_count; i++) { 212 if (NEXT_TABLE(dfa)[i] >= state_count) 213 goto out; 214 if (CHECK_TABLE(dfa)[i] >= state_count) 215 goto out; 216 } 217 218 /* Now that all the other tables are verified, verify diffencoding */ 219 for (i = 0; i < state_count; i++) { 220 size_t j, k; 221 222 for (j = i; 223 (BASE_TABLE(dfa)[j] & MATCH_FLAG_DIFF_ENCODE) && 224 !(BASE_TABLE(dfa)[j] & MARK_DIFF_ENCODE); 225 j = k) { 226 k = DEFAULT_TABLE(dfa)[j]; 227 if (j == k) 228 goto out; 229 if (k < j) 230 break; /* already verified */ 231 BASE_TABLE(dfa)[j] |= MARK_DIFF_ENCODE; 232 } 233 } 234 error = 0; 235 236 out: 237 return error; 238 } 239 240 /** 241 * dfa_free - free a dfa allocated by aa_dfa_unpack 242 * @dfa: the dfa to free (MAYBE NULL) 243 * 244 * Requires: reference count to dfa == 0 245 */ 246 static void dfa_free(struct aa_dfa *dfa) 247 { 248 if (dfa) { 249 int i; 250 251 for (i = 0; i < ARRAY_SIZE(dfa->tables); i++) { 252 kvfree(dfa->tables[i]); 253 dfa->tables[i] = NULL; 254 } 255 kfree(dfa); 256 } 257 } 258 259 /** 260 * aa_dfa_free_kref - free aa_dfa by kref (called by aa_put_dfa) 261 * @kr: kref callback for freeing of a dfa (NOT NULL) 262 */ 263 void aa_dfa_free_kref(struct kref *kref) 264 { 265 struct aa_dfa *dfa = container_of(kref, struct aa_dfa, count); 266 dfa_free(dfa); 267 } 268 269 /** 270 * aa_dfa_unpack - unpack the binary tables of a serialized dfa 271 * @blob: aligned serialized stream of data to unpack (NOT NULL) 272 * @size: size of data to unpack 273 * @flags: flags controlling what type of accept tables are acceptable 274 * 275 * Unpack a dfa that has been serialized. To find information on the dfa 276 * format look in Documentation/admin-guide/LSM/apparmor.rst 277 * Assumes the dfa @blob stream has been aligned on a 8 byte boundary 278 * 279 * Returns: an unpacked dfa ready for matching or ERR_PTR on failure 280 */ 281 struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags) 282 { 283 int hsize; 284 int error = -ENOMEM; 285 char *data = blob; 286 struct table_header *table = NULL; 287 struct aa_dfa *dfa = kzalloc(sizeof(struct aa_dfa), GFP_KERNEL); 288 if (!dfa) 289 goto fail; 290 291 kref_init(&dfa->count); 292 293 error = -EPROTO; 294 295 /* get dfa table set header */ 296 if (size < sizeof(struct table_set_header)) 297 goto fail; 298 299 if (ntohl(*(__be32 *) data) != YYTH_MAGIC) 300 goto fail; 301 302 hsize = ntohl(*(__be32 *) (data + 4)); 303 if (size < hsize) 304 goto fail; 305 306 dfa->flags = ntohs(*(__be16 *) (data + 12)); 307 if (dfa->flags != 0 && dfa->flags != YYTH_FLAG_DIFF_ENCODE) 308 goto fail; 309 310 data += hsize; 311 size -= hsize; 312 313 while (size > 0) { 314 table = unpack_table(data, size); 315 if (!table) 316 goto fail; 317 318 switch (table->td_id) { 319 case YYTD_ID_ACCEPT: 320 if (!(table->td_flags & ACCEPT1_FLAGS(flags))) 321 goto fail; 322 break; 323 case YYTD_ID_ACCEPT2: 324 if (!(table->td_flags & ACCEPT2_FLAGS(flags))) 325 goto fail; 326 break; 327 case YYTD_ID_BASE: 328 if (table->td_flags != YYTD_DATA32) 329 goto fail; 330 break; 331 case YYTD_ID_DEF: 332 case YYTD_ID_NXT: 333 case YYTD_ID_CHK: 334 if (table->td_flags != YYTD_DATA16) 335 goto fail; 336 break; 337 case YYTD_ID_EC: 338 if (table->td_flags != YYTD_DATA8) 339 goto fail; 340 break; 341 default: 342 goto fail; 343 } 344 /* check for duplicate table entry */ 345 if (dfa->tables[table->td_id]) 346 goto fail; 347 dfa->tables[table->td_id] = table; 348 data += table_size(table->td_lolen, table->td_flags); 349 size -= table_size(table->td_lolen, table->td_flags); 350 table = NULL; 351 } 352 error = verify_table_headers(dfa->tables, flags); 353 if (error) 354 goto fail; 355 356 if (flags & DFA_FLAG_VERIFY_STATES) { 357 error = verify_dfa(dfa); 358 if (error) 359 goto fail; 360 } 361 362 return dfa; 363 364 fail: 365 kvfree(table); 366 dfa_free(dfa); 367 return ERR_PTR(error); 368 } 369 370 #define match_char(state, def, base, next, check, C) \ 371 do { \ 372 u32 b = (base)[(state)]; \ 373 unsigned int pos = base_idx(b) + (C); \ 374 if ((check)[pos] != (state)) { \ 375 (state) = (def)[(state)]; \ 376 if (b & MATCH_FLAG_DIFF_ENCODE) \ 377 continue; \ 378 break; \ 379 } \ 380 (state) = (next)[pos]; \ 381 break; \ 382 } while (1) 383 384 /** 385 * aa_dfa_match_len - traverse @dfa to find state @str stops at 386 * @dfa: the dfa to match @str against (NOT NULL) 387 * @start: the state of the dfa to start matching in 388 * @str: the string of bytes to match against the dfa (NOT NULL) 389 * @len: length of the string of bytes to match 390 * 391 * aa_dfa_match_len will match @str against the dfa and return the state it 392 * finished matching in. The final state can be used to look up the accepting 393 * label, or as the start state of a continuing match. 394 * 395 * This function will happily match again the 0 byte and only finishes 396 * when @len input is consumed. 397 * 398 * Returns: final state reached after input is consumed 399 */ 400 unsigned int aa_dfa_match_len(struct aa_dfa *dfa, unsigned int start, 401 const char *str, int len) 402 { 403 u16 *def = DEFAULT_TABLE(dfa); 404 u32 *base = BASE_TABLE(dfa); 405 u16 *next = NEXT_TABLE(dfa); 406 u16 *check = CHECK_TABLE(dfa); 407 unsigned int state = start; 408 409 if (state == 0) 410 return 0; 411 412 /* current state is <state>, matching character *str */ 413 if (dfa->tables[YYTD_ID_EC]) { 414 /* Equivalence class table defined */ 415 u8 *equiv = EQUIV_TABLE(dfa); 416 for (; len; len--) 417 match_char(state, def, base, next, check, 418 equiv[(u8) *str++]); 419 } else { 420 /* default is direct to next state */ 421 for (; len; len--) 422 match_char(state, def, base, next, check, (u8) *str++); 423 } 424 425 return state; 426 } 427 428 /** 429 * aa_dfa_match - traverse @dfa to find state @str stops at 430 * @dfa: the dfa to match @str against (NOT NULL) 431 * @start: the state of the dfa to start matching in 432 * @str: the null terminated string of bytes to match against the dfa (NOT NULL) 433 * 434 * aa_dfa_match will match @str against the dfa and return the state it 435 * finished matching in. The final state can be used to look up the accepting 436 * label, or as the start state of a continuing match. 437 * 438 * Returns: final state reached after input is consumed 439 */ 440 unsigned int aa_dfa_match(struct aa_dfa *dfa, unsigned int start, 441 const char *str) 442 { 443 u16 *def = DEFAULT_TABLE(dfa); 444 u32 *base = BASE_TABLE(dfa); 445 u16 *next = NEXT_TABLE(dfa); 446 u16 *check = CHECK_TABLE(dfa); 447 unsigned int state = start; 448 449 if (state == 0) 450 return 0; 451 452 /* current state is <state>, matching character *str */ 453 if (dfa->tables[YYTD_ID_EC]) { 454 /* Equivalence class table defined */ 455 u8 *equiv = EQUIV_TABLE(dfa); 456 /* default is direct to next state */ 457 while (*str) 458 match_char(state, def, base, next, check, 459 equiv[(u8) *str++]); 460 } else { 461 /* default is direct to next state */ 462 while (*str) 463 match_char(state, def, base, next, check, (u8) *str++); 464 } 465 466 return state; 467 } 468 469 /** 470 * aa_dfa_next - step one character to the next state in the dfa 471 * @dfa: the dfa to traverse (NOT NULL) 472 * @state: the state to start in 473 * @c: the input character to transition on 474 * 475 * aa_dfa_match will step through the dfa by one input character @c 476 * 477 * Returns: state reach after input @c 478 */ 479 unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int state, 480 const char c) 481 { 482 u16 *def = DEFAULT_TABLE(dfa); 483 u32 *base = BASE_TABLE(dfa); 484 u16 *next = NEXT_TABLE(dfa); 485 u16 *check = CHECK_TABLE(dfa); 486 487 /* current state is <state>, matching character *str */ 488 if (dfa->tables[YYTD_ID_EC]) { 489 /* Equivalence class table defined */ 490 u8 *equiv = EQUIV_TABLE(dfa); 491 match_char(state, def, base, next, check, equiv[(u8) c]); 492 } else 493 match_char(state, def, base, next, check, (u8) c); 494 495 return state; 496 } 497 498 /** 499 * aa_dfa_match_until - traverse @dfa until accept state or end of input 500 * @dfa: the dfa to match @str against (NOT NULL) 501 * @start: the state of the dfa to start matching in 502 * @str: the null terminated string of bytes to match against the dfa (NOT NULL) 503 * @retpos: first character in str after match OR end of string 504 * 505 * aa_dfa_match will match @str against the dfa and return the state it 506 * finished matching in. The final state can be used to look up the accepting 507 * label, or as the start state of a continuing match. 508 * 509 * Returns: final state reached after input is consumed 510 */ 511 unsigned int aa_dfa_match_until(struct aa_dfa *dfa, unsigned int start, 512 const char *str, const char **retpos) 513 { 514 u16 *def = DEFAULT_TABLE(dfa); 515 u32 *base = BASE_TABLE(dfa); 516 u16 *next = NEXT_TABLE(dfa); 517 u16 *check = CHECK_TABLE(dfa); 518 u32 *accept = ACCEPT_TABLE(dfa); 519 unsigned int state = start, pos; 520 521 if (state == 0) 522 return 0; 523 524 /* current state is <state>, matching character *str */ 525 if (dfa->tables[YYTD_ID_EC]) { 526 /* Equivalence class table defined */ 527 u8 *equiv = EQUIV_TABLE(dfa); 528 /* default is direct to next state */ 529 while (*str) { 530 pos = base_idx(base[state]) + equiv[(u8) *str++]; 531 if (check[pos] == state) 532 state = next[pos]; 533 else 534 state = def[state]; 535 if (accept[state]) 536 break; 537 } 538 } else { 539 /* default is direct to next state */ 540 while (*str) { 541 pos = base_idx(base[state]) + (u8) *str++; 542 if (check[pos] == state) 543 state = next[pos]; 544 else 545 state = def[state]; 546 if (accept[state]) 547 break; 548 } 549 } 550 551 *retpos = str; 552 return state; 553 } 554 555 /** 556 * aa_dfa_matchn_until - traverse @dfa until accept or @n bytes consumed 557 * @dfa: the dfa to match @str against (NOT NULL) 558 * @start: the state of the dfa to start matching in 559 * @str: the string of bytes to match against the dfa (NOT NULL) 560 * @n: length of the string of bytes to match 561 * @retpos: first character in str after match OR str + n 562 * 563 * aa_dfa_match_len will match @str against the dfa and return the state it 564 * finished matching in. The final state can be used to look up the accepting 565 * label, or as the start state of a continuing match. 566 * 567 * This function will happily match again the 0 byte and only finishes 568 * when @n input is consumed. 569 * 570 * Returns: final state reached after input is consumed 571 */ 572 unsigned int aa_dfa_matchn_until(struct aa_dfa *dfa, unsigned int start, 573 const char *str, int n, const char **retpos) 574 { 575 u16 *def = DEFAULT_TABLE(dfa); 576 u32 *base = BASE_TABLE(dfa); 577 u16 *next = NEXT_TABLE(dfa); 578 u16 *check = CHECK_TABLE(dfa); 579 u32 *accept = ACCEPT_TABLE(dfa); 580 unsigned int state = start, pos; 581 582 *retpos = NULL; 583 if (state == 0) 584 return 0; 585 586 /* current state is <state>, matching character *str */ 587 if (dfa->tables[YYTD_ID_EC]) { 588 /* Equivalence class table defined */ 589 u8 *equiv = EQUIV_TABLE(dfa); 590 /* default is direct to next state */ 591 for (; n; n--) { 592 pos = base_idx(base[state]) + equiv[(u8) *str++]; 593 if (check[pos] == state) 594 state = next[pos]; 595 else 596 state = def[state]; 597 if (accept[state]) 598 break; 599 } 600 } else { 601 /* default is direct to next state */ 602 for (; n; n--) { 603 pos = base_idx(base[state]) + (u8) *str++; 604 if (check[pos] == state) 605 state = next[pos]; 606 else 607 state = def[state]; 608 if (accept[state]) 609 break; 610 } 611 } 612 613 *retpos = str; 614 return state; 615 } 616 617 #define inc_wb_pos(wb) \ 618 do { \ 619 wb->pos = (wb->pos + 1) & (wb->size - 1); \ 620 wb->len = (wb->len + 1) & (wb->size - 1); \ 621 } while (0) 622 623 /* For DFAs that don't support extended tagging of states */ 624 static bool is_loop(struct match_workbuf *wb, unsigned int state, 625 unsigned int *adjust) 626 { 627 unsigned int pos = wb->pos; 628 unsigned int i; 629 630 if (wb->history[pos] < state) 631 return false; 632 633 for (i = 0; i <= wb->len; i++) { 634 if (wb->history[pos] == state) { 635 *adjust = i; 636 return true; 637 } 638 if (pos == 0) 639 pos = wb->size; 640 pos--; 641 } 642 643 *adjust = i; 644 return true; 645 } 646 647 static unsigned int leftmatch_fb(struct aa_dfa *dfa, unsigned int start, 648 const char *str, struct match_workbuf *wb, 649 unsigned int *count) 650 { 651 u16 *def = DEFAULT_TABLE(dfa); 652 u32 *base = BASE_TABLE(dfa); 653 u16 *next = NEXT_TABLE(dfa); 654 u16 *check = CHECK_TABLE(dfa); 655 unsigned int state = start, pos; 656 657 AA_BUG(!dfa); 658 AA_BUG(!str); 659 AA_BUG(!wb); 660 AA_BUG(!count); 661 662 *count = 0; 663 if (state == 0) 664 return 0; 665 666 /* current state is <state>, matching character *str */ 667 if (dfa->tables[YYTD_ID_EC]) { 668 /* Equivalence class table defined */ 669 u8 *equiv = EQUIV_TABLE(dfa); 670 /* default is direct to next state */ 671 while (*str) { 672 unsigned int adjust; 673 674 wb->history[wb->pos] = state; 675 pos = base_idx(base[state]) + equiv[(u8) *str++]; 676 if (check[pos] == state) 677 state = next[pos]; 678 else 679 state = def[state]; 680 if (is_loop(wb, state, &adjust)) { 681 state = aa_dfa_match(dfa, state, str); 682 *count -= adjust; 683 goto out; 684 } 685 inc_wb_pos(wb); 686 (*count)++; 687 } 688 } else { 689 /* default is direct to next state */ 690 while (*str) { 691 unsigned int adjust; 692 693 wb->history[wb->pos] = state; 694 pos = base_idx(base[state]) + (u8) *str++; 695 if (check[pos] == state) 696 state = next[pos]; 697 else 698 state = def[state]; 699 if (is_loop(wb, state, &adjust)) { 700 state = aa_dfa_match(dfa, state, str); 701 *count -= adjust; 702 goto out; 703 } 704 inc_wb_pos(wb); 705 (*count)++; 706 } 707 } 708 709 out: 710 if (!state) 711 *count = 0; 712 return state; 713 } 714 715 /** 716 * aa_dfa_leftmatch - traverse @dfa to find state @str stops at 717 * @dfa: the dfa to match @str against (NOT NULL) 718 * @start: the state of the dfa to start matching in 719 * @str: the null terminated string of bytes to match against the dfa (NOT NULL) 720 * @count: current count of longest left. 721 * 722 * aa_dfa_match will match @str against the dfa and return the state it 723 * finished matching in. The final state can be used to look up the accepting 724 * label, or as the start state of a continuing match. 725 * 726 * Returns: final state reached after input is consumed 727 */ 728 unsigned int aa_dfa_leftmatch(struct aa_dfa *dfa, unsigned int start, 729 const char *str, unsigned int *count) 730 { 731 DEFINE_MATCH_WB(wb); 732 733 /* TODO: match for extended state dfas */ 734 735 return leftmatch_fb(dfa, start, str, &wb, count); 736 } 737