1 // SPDX-License-Identifier: GPL-2.0-only
3 * AppArmor security module
5 * This file contains AppArmor dfa based regular expression matching engine
7 * Copyright (C) 1998-2008 Novell/SUSE
8 * Copyright 2009-2012 Canonical Ltd.
11 #include <linux/errno.h>
12 #include <linux/kernel.h>
14 #include <linux/slab.h>
15 #include <linux/vmalloc.h>
16 #include <linux/err.h>
17 #include <linux/kref.h>
19 #include "include/lib.h"
20 #include "include/match.h"
22 #define base_idx(X) ((X) & 0xffffff)
24 static char nulldfa_src[] = {
27 struct aa_dfa *nulldfa;
29 static char stacksplitdfa_src[] = {
30 #include "stacksplitdfa.in"
32 struct aa_dfa *stacksplitdfa;
34 int aa_setup_dfa_engine(void)
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);
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)) {
54 error = PTR_ERR(stacksplitdfa);
62 void aa_teardown_dfa_engine(void)
64 aa_put_dfa(stacksplitdfa);
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
73 * Returns: pointer to table else NULL on failure
75 * NOTE: must be freed by kvfree (not kfree)
77 static struct table_header *unpack_table(char *blob, size_t bsize)
79 struct table_header *table = NULL;
80 struct table_header th;
83 if (bsize < sizeof(struct table_header))
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
89 th.td_id = be16_to_cpu(*(__be16 *) (blob)) - 1;
90 if (th.td_id > YYTD_ID_MAX)
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);
96 if (!(th.td_flags == YYTD_DATA16 || th.td_flags == YYTD_DATA32 ||
97 th.td_flags == YYTD_DATA8))
100 tsize = table_size(th.td_lolen, th.td_flags);
104 table = kvzalloc(tsize, GFP_KERNEL);
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);
120 /* if table was vmalloced make sure the page tables are synced
121 * before it is used, as it goes live to all cpus.
123 if (is_vmalloc_addr(table))
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
139 * Assumes dfa has gone through the first pass verification done by unpacking
140 * NOTE: this does not valid accept table values
142 * Returns: %0 else error code on failure to verify
144 static int verify_table_headers(struct table_header **tables, int flags)
146 size_t state_count, trans_count;
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]))
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])
159 if (state_count != tables[YYTD_ID_ACCEPT]->td_lolen)
162 if (ACCEPT2_FLAGS(flags)) {
163 if (!tables[YYTD_ID_ACCEPT2])
165 if (state_count != tables[YYTD_ID_ACCEPT2]->td_lolen)
168 if (state_count != tables[YYTD_ID_DEF]->td_lolen)
171 /* next.size == chk.size */
172 trans_count = tables[YYTD_ID_NXT]->td_lolen;
173 if (trans_count != tables[YYTD_ID_CHK]->td_lolen)
176 /* if equivalence classes then its table size must be 256 */
177 if (tables[YYTD_ID_EC] && tables[YYTD_ID_EC]->td_lolen != 256)
186 * verify_dfa - verify that transitions and states in the tables are in bounds.
187 * @dfa: dfa to test (NOT NULL)
189 * Assumes dfa has gone through the first pass verification done by unpacking
190 * NOTE: this does not valid accept table values
192 * Returns: %0 else error code on failure to verify
194 static int verify_dfa(struct aa_dfa *dfa)
196 size_t i, state_count, trans_count;
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))
205 if (base_idx(BASE_TABLE(dfa)[i]) + 255 >= trans_count) {
206 pr_err("AppArmor DFA next/check upper bounds error\n");
211 for (i = 0; i < trans_count; i++) {
212 if (NEXT_TABLE(dfa)[i] >= state_count)
214 if (CHECK_TABLE(dfa)[i] >= state_count)
218 /* Now that all the other tables are verified, verify diffencoding */
219 for (i = 0; i < state_count; i++) {
223 (BASE_TABLE(dfa)[j] & MATCH_FLAG_DIFF_ENCODE) &&
224 !(BASE_TABLE(dfa)[j] & MARK_DIFF_ENCODE);
226 k = DEFAULT_TABLE(dfa)[j];
230 break; /* already verified */
231 BASE_TABLE(dfa)[j] |= MARK_DIFF_ENCODE;
241 * dfa_free - free a dfa allocated by aa_dfa_unpack
242 * @dfa: the dfa to free (MAYBE NULL)
244 * Requires: reference count to dfa == 0
246 static void dfa_free(struct aa_dfa *dfa)
251 for (i = 0; i < ARRAY_SIZE(dfa->tables); i++) {
252 kvfree(dfa->tables[i]);
253 dfa->tables[i] = NULL;
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)
263 void aa_dfa_free_kref(struct kref *kref)
265 struct aa_dfa *dfa = container_of(kref, struct aa_dfa, count);
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
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
279 * Returns: an unpacked dfa ready for matching or ERR_PTR on failure
281 struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags)
286 struct table_header *table = NULL;
287 struct aa_dfa *dfa = kzalloc(sizeof(struct aa_dfa), GFP_KERNEL);
291 kref_init(&dfa->count);
295 /* get dfa table set header */
296 if (size < sizeof(struct table_set_header))
299 if (ntohl(*(__be32 *) data) != YYTH_MAGIC)
302 hsize = ntohl(*(__be32 *) (data + 4));
306 dfa->flags = ntohs(*(__be16 *) (data + 12));
307 if (dfa->flags != 0 && dfa->flags != YYTH_FLAG_DIFF_ENCODE)
314 table = unpack_table(data, size);
318 switch (table->td_id) {
320 if (!(table->td_flags & ACCEPT1_FLAGS(flags)))
323 case YYTD_ID_ACCEPT2:
324 if (!(table->td_flags & ACCEPT2_FLAGS(flags)))
328 if (table->td_flags != YYTD_DATA32)
334 if (table->td_flags != YYTD_DATA16)
338 if (table->td_flags != YYTD_DATA8)
344 /* check for duplicate table entry */
345 if (dfa->tables[table->td_id])
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);
352 error = verify_table_headers(dfa->tables, flags);
356 if (flags & DFA_FLAG_VERIFY_STATES) {
357 error = verify_dfa(dfa);
367 return ERR_PTR(error);
370 #define match_char(state, def, base, next, check, C) \
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) \
380 (state) = (next)[pos]; \
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
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.
395 * This function will happily match again the 0 byte and only finishes
396 * when @len input is consumed.
398 * Returns: final state reached after input is consumed
400 unsigned int aa_dfa_match_len(struct aa_dfa *dfa, unsigned int start,
401 const char *str, int len)
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;
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);
417 match_char(state, def, base, next, check,
420 /* default is direct to next state */
422 match_char(state, def, base, next, check, (u8) *str++);
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)
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.
438 * Returns: final state reached after input is consumed
440 unsigned int aa_dfa_match(struct aa_dfa *dfa, unsigned int start,
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;
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 */
458 match_char(state, def, base, next, check,
461 /* default is direct to next state */
463 match_char(state, def, base, next, check, (u8) *str++);
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
475 * aa_dfa_match will step through the dfa by one input character @c
477 * Returns: state reach after input @c
479 unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int state,
482 u16 *def = DEFAULT_TABLE(dfa);
483 u32 *base = BASE_TABLE(dfa);
484 u16 *next = NEXT_TABLE(dfa);
485 u16 *check = CHECK_TABLE(dfa);
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]);
493 match_char(state, def, base, next, check, (u8) c);
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
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.
509 * Returns: final state reached after input is consumed
511 unsigned int aa_dfa_match_until(struct aa_dfa *dfa, unsigned int start,
512 const char *str, const char **retpos)
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;
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 */
530 pos = base_idx(base[state]) + equiv[(u8) *str++];
531 if (check[pos] == state)
539 /* default is direct to next state */
541 pos = base_idx(base[state]) + (u8) *str++;
542 if (check[pos] == state)
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
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.
567 * This function will happily match again the 0 byte and only finishes
568 * when @n input is consumed.
570 * Returns: final state reached after input is consumed
572 unsigned int aa_dfa_matchn_until(struct aa_dfa *dfa, unsigned int start,
573 const char *str, int n, const char **retpos)
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;
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 */
592 pos = base_idx(base[state]) + equiv[(u8) *str++];
593 if (check[pos] == state)
601 /* default is direct to next state */
603 pos = base_idx(base[state]) + (u8) *str++;
604 if (check[pos] == state)
617 #define inc_wb_pos(wb) \
619 wb->pos = (wb->pos + 1) & (wb->size - 1); \
620 wb->len = (wb->len + 1) & (wb->size - 1); \
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)
627 unsigned int pos = wb->pos;
630 if (wb->history[pos] < state)
633 for (i = 0; i <= wb->len; i++) {
634 if (wb->history[pos] == state) {
647 static unsigned int leftmatch_fb(struct aa_dfa *dfa, unsigned int start,
648 const char *str, struct match_workbuf *wb,
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;
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 */
674 wb->history[wb->pos] = state;
675 pos = base_idx(base[state]) + equiv[(u8) *str++];
676 if (check[pos] == state)
680 if (is_loop(wb, state, &adjust)) {
681 state = aa_dfa_match(dfa, state, str);
689 /* default is direct to next state */
693 wb->history[wb->pos] = state;
694 pos = base_idx(base[state]) + (u8) *str++;
695 if (check[pos] == state)
699 if (is_loop(wb, state, &adjust)) {
700 state = aa_dfa_match(dfa, state, str);
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.
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.
726 * Returns: final state reached after input is consumed
728 unsigned int aa_dfa_leftmatch(struct aa_dfa *dfa, unsigned int start,
729 const char *str, unsigned int *count)
733 /* TODO: match for extended state dfas */
735 return leftmatch_fb(dfa, start, str, &wb, count);