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 /* if we have a table it must have some entries */
101 if (th.td_lolen == 0)
103 tsize = table_size(th.td_lolen, th.td_flags);
107 table = kvzalloc(tsize, GFP_KERNEL);
109 table->td_id = th.td_id;
110 table->td_flags = th.td_flags;
111 table->td_lolen = th.td_lolen;
112 if (th.td_flags == YYTD_DATA8)
113 UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
114 u8, u8, byte_to_byte);
115 else if (th.td_flags == YYTD_DATA16)
116 UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
117 u16, __be16, be16_to_cpu);
118 else if (th.td_flags == YYTD_DATA32)
119 UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
120 u32, __be32, be32_to_cpu);
123 /* if table was vmalloced make sure the page tables are synced
124 * before it is used, as it goes live to all cpus.
126 if (is_vmalloc_addr(table))
138 * verify_table_headers - verify that the tables headers are as expected
139 * @tables - array of dfa tables to check (NOT NULL)
140 * @flags: flags controlling what type of accept table are acceptable
142 * Assumes dfa has gone through the first pass verification done by unpacking
143 * NOTE: this does not valid accept table values
145 * Returns: %0 else error code on failure to verify
147 static int verify_table_headers(struct table_header **tables, int flags)
149 size_t state_count, trans_count;
152 /* check that required tables exist */
153 if (!(tables[YYTD_ID_DEF] && tables[YYTD_ID_BASE] &&
154 tables[YYTD_ID_NXT] && tables[YYTD_ID_CHK]))
157 /* accept.size == default.size == base.size */
158 state_count = tables[YYTD_ID_BASE]->td_lolen;
159 if (ACCEPT1_FLAGS(flags)) {
160 if (!tables[YYTD_ID_ACCEPT])
162 if (state_count != tables[YYTD_ID_ACCEPT]->td_lolen)
165 if (ACCEPT2_FLAGS(flags)) {
166 if (!tables[YYTD_ID_ACCEPT2])
168 if (state_count != tables[YYTD_ID_ACCEPT2]->td_lolen)
171 if (state_count != tables[YYTD_ID_DEF]->td_lolen)
174 /* next.size == chk.size */
175 trans_count = tables[YYTD_ID_NXT]->td_lolen;
176 if (trans_count != tables[YYTD_ID_CHK]->td_lolen)
179 /* if equivalence classes then its table size must be 256 */
180 if (tables[YYTD_ID_EC] && tables[YYTD_ID_EC]->td_lolen != 256)
189 * verify_dfa - verify that transitions and states in the tables are in bounds.
190 * @dfa: dfa to test (NOT NULL)
192 * Assumes dfa has gone through the first pass verification done by unpacking
193 * NOTE: this does not valid accept table values
195 * Returns: %0 else error code on failure to verify
197 static int verify_dfa(struct aa_dfa *dfa)
199 size_t i, state_count, trans_count;
202 state_count = dfa->tables[YYTD_ID_BASE]->td_lolen;
203 trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen;
204 if (state_count == 0)
206 for (i = 0; i < state_count; i++) {
207 if (!(BASE_TABLE(dfa)[i] & MATCH_FLAG_DIFF_ENCODE) &&
208 (DEFAULT_TABLE(dfa)[i] >= state_count))
210 if (BASE_TABLE(dfa)[i] & MATCH_FLAGS_INVALID) {
211 pr_err("AppArmor DFA state with invalid match flags");
214 if ((BASE_TABLE(dfa)[i] & MATCH_FLAG_DIFF_ENCODE)) {
215 if (!(dfa->flags & YYTH_FLAG_DIFF_ENCODE)) {
216 pr_err("AppArmor DFA diff encoded transition state without header flag");
220 if ((BASE_TABLE(dfa)[i] & MATCH_FLAG_OOB_TRANSITION)) {
221 if (base_idx(BASE_TABLE(dfa)[i]) < dfa->max_oob) {
222 pr_err("AppArmor DFA out of bad transition out of range");
225 if (!(dfa->flags & YYTH_FLAG_OOB_TRANS)) {
226 pr_err("AppArmor DFA out of bad transition state without header flag");
230 if (base_idx(BASE_TABLE(dfa)[i]) + 255 >= trans_count) {
231 pr_err("AppArmor DFA next/check upper bounds error\n");
236 for (i = 0; i < trans_count; i++) {
237 if (NEXT_TABLE(dfa)[i] >= state_count)
239 if (CHECK_TABLE(dfa)[i] >= state_count)
243 /* Now that all the other tables are verified, verify diffencoding */
244 for (i = 0; i < state_count; i++) {
248 (BASE_TABLE(dfa)[j] & MATCH_FLAG_DIFF_ENCODE) &&
249 !(BASE_TABLE(dfa)[j] & MARK_DIFF_ENCODE);
251 k = DEFAULT_TABLE(dfa)[j];
255 break; /* already verified */
256 BASE_TABLE(dfa)[j] |= MARK_DIFF_ENCODE;
266 * dfa_free - free a dfa allocated by aa_dfa_unpack
267 * @dfa: the dfa to free (MAYBE NULL)
269 * Requires: reference count to dfa == 0
271 static void dfa_free(struct aa_dfa *dfa)
276 for (i = 0; i < ARRAY_SIZE(dfa->tables); i++) {
277 kvfree(dfa->tables[i]);
278 dfa->tables[i] = NULL;
285 * aa_dfa_free_kref - free aa_dfa by kref (called by aa_put_dfa)
286 * @kr: kref callback for freeing of a dfa (NOT NULL)
288 void aa_dfa_free_kref(struct kref *kref)
290 struct aa_dfa *dfa = container_of(kref, struct aa_dfa, count);
295 * aa_dfa_unpack - unpack the binary tables of a serialized dfa
296 * @blob: aligned serialized stream of data to unpack (NOT NULL)
297 * @size: size of data to unpack
298 * @flags: flags controlling what type of accept tables are acceptable
300 * Unpack a dfa that has been serialized. To find information on the dfa
301 * format look in Documentation/admin-guide/LSM/apparmor.rst
302 * Assumes the dfa @blob stream has been aligned on a 8 byte boundary
304 * Returns: an unpacked dfa ready for matching or ERR_PTR on failure
306 struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags)
311 struct table_header *table = NULL;
312 struct aa_dfa *dfa = kzalloc(sizeof(struct aa_dfa), GFP_KERNEL);
316 kref_init(&dfa->count);
320 /* get dfa table set header */
321 if (size < sizeof(struct table_set_header))
324 if (ntohl(*(__be32 *) data) != YYTH_MAGIC)
327 hsize = ntohl(*(__be32 *) (data + 4));
331 dfa->flags = ntohs(*(__be16 *) (data + 12));
332 if (dfa->flags & ~(YYTH_FLAGS))
336 * TODO: needed for dfa to support more than 1 oob
337 * if (dfa->flags & YYTH_FLAGS_OOB_TRANS) {
338 * if (hsize < 16 + 4)
340 * dfa->max_oob = ntol(*(__be32 *) (data + 16));
341 * if (dfa->max <= MAX_OOB_SUPPORTED) {
342 * pr_err("AppArmor DFA OOB greater than supported\n");
353 table = unpack_table(data, size);
357 switch (table->td_id) {
359 if (!(table->td_flags & ACCEPT1_FLAGS(flags)))
362 case YYTD_ID_ACCEPT2:
363 if (!(table->td_flags & ACCEPT2_FLAGS(flags)))
367 if (table->td_flags != YYTD_DATA32)
373 if (table->td_flags != YYTD_DATA16)
377 if (table->td_flags != YYTD_DATA8)
383 /* check for duplicate table entry */
384 if (dfa->tables[table->td_id])
386 dfa->tables[table->td_id] = table;
387 data += table_size(table->td_lolen, table->td_flags);
388 size -= table_size(table->td_lolen, table->td_flags);
391 error = verify_table_headers(dfa->tables, flags);
395 if (flags & DFA_FLAG_VERIFY_STATES) {
396 error = verify_dfa(dfa);
406 return ERR_PTR(error);
409 #define match_char(state, def, base, next, check, C) \
411 u32 b = (base)[(state)]; \
412 unsigned int pos = base_idx(b) + (C); \
413 if ((check)[pos] != (state)) { \
414 (state) = (def)[(state)]; \
415 if (b & MATCH_FLAG_DIFF_ENCODE) \
419 (state) = (next)[pos]; \
424 * aa_dfa_match_len - traverse @dfa to find state @str stops at
425 * @dfa: the dfa to match @str against (NOT NULL)
426 * @start: the state of the dfa to start matching in
427 * @str: the string of bytes to match against the dfa (NOT NULL)
428 * @len: length of the string of bytes to match
430 * aa_dfa_match_len will match @str against the dfa and return the state it
431 * finished matching in. The final state can be used to look up the accepting
432 * label, or as the start state of a continuing match.
434 * This function will happily match again the 0 byte and only finishes
435 * when @len input is consumed.
437 * Returns: final state reached after input is consumed
439 aa_state_t aa_dfa_match_len(struct aa_dfa *dfa, aa_state_t start,
440 const char *str, int len)
442 u16 *def = DEFAULT_TABLE(dfa);
443 u32 *base = BASE_TABLE(dfa);
444 u16 *next = NEXT_TABLE(dfa);
445 u16 *check = CHECK_TABLE(dfa);
446 aa_state_t state = start;
448 if (state == DFA_NOMATCH)
451 /* current state is <state>, matching character *str */
452 if (dfa->tables[YYTD_ID_EC]) {
453 /* Equivalence class table defined */
454 u8 *equiv = EQUIV_TABLE(dfa);
456 match_char(state, def, base, next, check,
459 /* default is direct to next state */
461 match_char(state, def, base, next, check, (u8) *str++);
468 * aa_dfa_match - traverse @dfa to find state @str stops at
469 * @dfa: the dfa to match @str against (NOT NULL)
470 * @start: the state of the dfa to start matching in
471 * @str: the null terminated string of bytes to match against the dfa (NOT NULL)
473 * aa_dfa_match will match @str against the dfa and return the state it
474 * finished matching in. The final state can be used to look up the accepting
475 * label, or as the start state of a continuing match.
477 * Returns: final state reached after input is consumed
479 aa_state_t aa_dfa_match(struct aa_dfa *dfa, aa_state_t start, const char *str)
481 u16 *def = DEFAULT_TABLE(dfa);
482 u32 *base = BASE_TABLE(dfa);
483 u16 *next = NEXT_TABLE(dfa);
484 u16 *check = CHECK_TABLE(dfa);
485 aa_state_t state = start;
487 if (state == DFA_NOMATCH)
490 /* current state is <state>, matching character *str */
491 if (dfa->tables[YYTD_ID_EC]) {
492 /* Equivalence class table defined */
493 u8 *equiv = EQUIV_TABLE(dfa);
494 /* default is direct to next state */
496 match_char(state, def, base, next, check,
499 /* default is direct to next state */
501 match_char(state, def, base, next, check, (u8) *str++);
508 * aa_dfa_next - step one character to the next state in the dfa
509 * @dfa: the dfa to traverse (NOT NULL)
510 * @state: the state to start in
511 * @c: the input character to transition on
513 * aa_dfa_match will step through the dfa by one input character @c
515 * Returns: state reach after input @c
517 aa_state_t aa_dfa_next(struct aa_dfa *dfa, aa_state_t state, const char c)
519 u16 *def = DEFAULT_TABLE(dfa);
520 u32 *base = BASE_TABLE(dfa);
521 u16 *next = NEXT_TABLE(dfa);
522 u16 *check = CHECK_TABLE(dfa);
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 match_char(state, def, base, next, check, equiv[(u8) c]);
530 match_char(state, def, base, next, check, (u8) c);
535 aa_state_t aa_dfa_outofband_transition(struct aa_dfa *dfa, aa_state_t state)
537 u16 *def = DEFAULT_TABLE(dfa);
538 u32 *base = BASE_TABLE(dfa);
539 u16 *next = NEXT_TABLE(dfa);
540 u16 *check = CHECK_TABLE(dfa);
541 u32 b = (base)[(state)];
543 if (!(b & MATCH_FLAG_OOB_TRANSITION))
546 /* No Equivalence class remapping for outofband transitions */
547 match_char(state, def, base, next, check, -1);
553 * aa_dfa_match_until - traverse @dfa until accept state or end of input
554 * @dfa: the dfa to match @str against (NOT NULL)
555 * @start: the state of the dfa to start matching in
556 * @str: the null terminated string of bytes to match against the dfa (NOT NULL)
557 * @retpos: first character in str after match OR end of string
559 * aa_dfa_match will match @str against the dfa and return the state it
560 * finished matching in. The final state can be used to look up the accepting
561 * label, or as the start state of a continuing match.
563 * Returns: final state reached after input is consumed
565 aa_state_t aa_dfa_match_until(struct aa_dfa *dfa, aa_state_t start,
566 const char *str, const char **retpos)
568 u16 *def = DEFAULT_TABLE(dfa);
569 u32 *base = BASE_TABLE(dfa);
570 u16 *next = NEXT_TABLE(dfa);
571 u16 *check = CHECK_TABLE(dfa);
572 u32 *accept = ACCEPT_TABLE(dfa);
573 aa_state_t state = start, pos;
575 if (state == DFA_NOMATCH)
578 /* current state is <state>, matching character *str */
579 if (dfa->tables[YYTD_ID_EC]) {
580 /* Equivalence class table defined */
581 u8 *equiv = EQUIV_TABLE(dfa);
582 /* default is direct to next state */
584 pos = base_idx(base[state]) + equiv[(u8) *str++];
585 if (check[pos] == state)
593 /* default is direct to next state */
595 pos = base_idx(base[state]) + (u8) *str++;
596 if (check[pos] == state)
610 * aa_dfa_matchn_until - traverse @dfa until accept or @n bytes consumed
611 * @dfa: the dfa to match @str against (NOT NULL)
612 * @start: the state of the dfa to start matching in
613 * @str: the string of bytes to match against the dfa (NOT NULL)
614 * @n: length of the string of bytes to match
615 * @retpos: first character in str after match OR str + n
617 * aa_dfa_match_len will match @str against the dfa and return the state it
618 * finished matching in. The final state can be used to look up the accepting
619 * label, or as the start state of a continuing match.
621 * This function will happily match again the 0 byte and only finishes
622 * when @n input is consumed.
624 * Returns: final state reached after input is consumed
626 aa_state_t aa_dfa_matchn_until(struct aa_dfa *dfa, aa_state_t start,
627 const char *str, int n, const char **retpos)
629 u16 *def = DEFAULT_TABLE(dfa);
630 u32 *base = BASE_TABLE(dfa);
631 u16 *next = NEXT_TABLE(dfa);
632 u16 *check = CHECK_TABLE(dfa);
633 u32 *accept = ACCEPT_TABLE(dfa);
634 aa_state_t state = start, pos;
637 if (state == DFA_NOMATCH)
640 /* current state is <state>, matching character *str */
641 if (dfa->tables[YYTD_ID_EC]) {
642 /* Equivalence class table defined */
643 u8 *equiv = EQUIV_TABLE(dfa);
644 /* default is direct to next state */
646 pos = base_idx(base[state]) + equiv[(u8) *str++];
647 if (check[pos] == state)
655 /* default is direct to next state */
657 pos = base_idx(base[state]) + (u8) *str++;
658 if (check[pos] == state)
671 #define inc_wb_pos(wb) \
673 wb->pos = (wb->pos + 1) & (WB_HISTORY_SIZE - 1); \
674 wb->len = (wb->len + 1) & (WB_HISTORY_SIZE - 1); \
677 /* For DFAs that don't support extended tagging of states */
678 static bool is_loop(struct match_workbuf *wb, aa_state_t state,
679 unsigned int *adjust)
681 aa_state_t pos = wb->pos;
684 if (wb->history[pos] < state)
687 for (i = 0; i <= wb->len; i++) {
688 if (wb->history[pos] == state) {
693 pos = WB_HISTORY_SIZE;
701 static aa_state_t leftmatch_fb(struct aa_dfa *dfa, aa_state_t start,
702 const char *str, struct match_workbuf *wb,
705 u16 *def = DEFAULT_TABLE(dfa);
706 u32 *base = BASE_TABLE(dfa);
707 u16 *next = NEXT_TABLE(dfa);
708 u16 *check = CHECK_TABLE(dfa);
709 aa_state_t state = start, pos;
717 if (state == DFA_NOMATCH)
720 /* current state is <state>, matching character *str */
721 if (dfa->tables[YYTD_ID_EC]) {
722 /* Equivalence class table defined */
723 u8 *equiv = EQUIV_TABLE(dfa);
724 /* default is direct to next state */
728 wb->history[wb->pos] = state;
729 pos = base_idx(base[state]) + equiv[(u8) *str++];
730 if (check[pos] == state)
734 if (is_loop(wb, state, &adjust)) {
735 state = aa_dfa_match(dfa, state, str);
743 /* default is direct to next state */
747 wb->history[wb->pos] = state;
748 pos = base_idx(base[state]) + (u8) *str++;
749 if (check[pos] == state)
753 if (is_loop(wb, state, &adjust)) {
754 state = aa_dfa_match(dfa, state, str);
770 * aa_dfa_leftmatch - traverse @dfa to find state @str stops at
771 * @dfa: the dfa to match @str against (NOT NULL)
772 * @start: the state of the dfa to start matching in
773 * @str: the null terminated string of bytes to match against the dfa (NOT NULL)
774 * @count: current count of longest left.
776 * aa_dfa_match will match @str against the dfa and return the state it
777 * finished matching in. The final state can be used to look up the accepting
778 * label, or as the start state of a continuing match.
780 * Returns: final state reached after input is consumed
782 aa_state_t aa_dfa_leftmatch(struct aa_dfa *dfa, aa_state_t start,
783 const char *str, unsigned int *count)
787 /* TODO: match for extended state dfas */
789 return leftmatch_fb(dfa, start, str, &wb, count);