2 * AppArmor security module
4 * This file contains AppArmor dfa based regular expression matching engine
6 * Copyright (C) 1998-2008 Novell/SUSE
7 * Copyright 2009-2010 Canonical Ltd.
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License as
11 * published by the Free Software Foundation, version 2 of the
15 #include <linux/errno.h>
16 #include <linux/kernel.h>
18 #include <linux/slab.h>
19 #include <linux/vmalloc.h>
20 #include <linux/err.h>
21 #include <linux/kref.h>
23 #include "include/apparmor.h"
24 #include "include/match.h"
27 * unpack_table - unpack a dfa table (one of accept, default, base, next check)
28 * @blob: data to unpack (NOT NULL)
29 * @bsize: size of blob
31 * Returns: pointer to table else NULL on failure
33 * NOTE: must be freed by kvfree (not kmalloc)
35 static struct table_header
*unpack_table(char *blob
, size_t bsize
)
37 struct table_header
*table
= NULL
;
38 struct table_header th
;
41 if (bsize
< sizeof(struct table_header
))
44 /* loaded td_id's start at 1, subtract 1 now to avoid doing
45 * it every time we use td_id as an index
47 th
.td_id
= be16_to_cpu(*(u16
*) (blob
)) - 1;
48 if (th
.td_id
> YYTD_ID_MAX
)
50 th
.td_flags
= be16_to_cpu(*(u16
*) (blob
+ 2));
51 th
.td_lolen
= be32_to_cpu(*(u32
*) (blob
+ 8));
52 blob
+= sizeof(struct table_header
);
54 if (!(th
.td_flags
== YYTD_DATA16
|| th
.td_flags
== YYTD_DATA32
||
55 th
.td_flags
== YYTD_DATA8
))
58 tsize
= table_size(th
.td_lolen
, th
.td_flags
);
62 table
= kvmalloc(tsize
);
65 if (th
.td_flags
== YYTD_DATA8
)
66 UNPACK_ARRAY(table
->td_data
, blob
, th
.td_lolen
,
68 else if (th
.td_flags
== YYTD_DATA16
)
69 UNPACK_ARRAY(table
->td_data
, blob
, th
.td_lolen
,
71 else if (th
.td_flags
== YYTD_DATA32
)
72 UNPACK_ARRAY(table
->td_data
, blob
, th
.td_lolen
,
76 /* if table was vmalloced make sure the page tables are synced
77 * before it is used, as it goes live to all cpus.
79 if (is_vmalloc_addr(table
))
91 * verify_dfa - verify that transitions and states in the tables are in bounds.
92 * @dfa: dfa to test (NOT NULL)
93 * @flags: flags controlling what type of accept table are acceptable
95 * Assumes dfa has gone through the first pass verification done by unpacking
96 * NOTE: this does not valid accept table values
98 * Returns: %0 else error code on failure to verify
100 static int verify_dfa(struct aa_dfa
*dfa
, int flags
)
102 size_t i
, state_count
, trans_count
;
105 /* check that required tables exist */
106 if (!(dfa
->tables
[YYTD_ID_DEF
] &&
107 dfa
->tables
[YYTD_ID_BASE
] &&
108 dfa
->tables
[YYTD_ID_NXT
] && dfa
->tables
[YYTD_ID_CHK
]))
111 /* accept.size == default.size == base.size */
112 state_count
= dfa
->tables
[YYTD_ID_BASE
]->td_lolen
;
113 if (ACCEPT1_FLAGS(flags
)) {
114 if (!dfa
->tables
[YYTD_ID_ACCEPT
])
116 if (state_count
!= dfa
->tables
[YYTD_ID_ACCEPT
]->td_lolen
)
119 if (ACCEPT2_FLAGS(flags
)) {
120 if (!dfa
->tables
[YYTD_ID_ACCEPT2
])
122 if (state_count
!= dfa
->tables
[YYTD_ID_ACCEPT2
]->td_lolen
)
125 if (state_count
!= dfa
->tables
[YYTD_ID_DEF
]->td_lolen
)
128 /* next.size == chk.size */
129 trans_count
= dfa
->tables
[YYTD_ID_NXT
]->td_lolen
;
130 if (trans_count
!= dfa
->tables
[YYTD_ID_CHK
]->td_lolen
)
133 /* if equivalence classes then its table size must be 256 */
134 if (dfa
->tables
[YYTD_ID_EC
] &&
135 dfa
->tables
[YYTD_ID_EC
]->td_lolen
!= 256)
138 if (flags
& DFA_FLAG_VERIFY_STATES
) {
139 for (i
= 0; i
< state_count
; i
++) {
140 if (DEFAULT_TABLE(dfa
)[i
] >= state_count
)
142 /* TODO: do check that DEF state recursion terminates */
143 if (BASE_TABLE(dfa
)[i
] + 255 >= trans_count
) {
144 printk(KERN_ERR
"AppArmor DFA next/check upper "
150 for (i
= 0; i
< trans_count
; i
++) {
151 if (NEXT_TABLE(dfa
)[i
] >= state_count
)
153 if (CHECK_TABLE(dfa
)[i
] >= state_count
)
164 * dfa_free - free a dfa allocated by aa_dfa_unpack
165 * @dfa: the dfa to free (MAYBE NULL)
167 * Requires: reference count to dfa == 0
169 static void dfa_free(struct aa_dfa
*dfa
)
174 for (i
= 0; i
< ARRAY_SIZE(dfa
->tables
); i
++) {
175 kvfree(dfa
->tables
[i
]);
176 dfa
->tables
[i
] = NULL
;
183 * aa_dfa_free_kref - free aa_dfa by kref (called by aa_put_dfa)
184 * @kr: kref callback for freeing of a dfa (NOT NULL)
186 void aa_dfa_free_kref(struct kref
*kref
)
188 struct aa_dfa
*dfa
= container_of(kref
, struct aa_dfa
, count
);
193 * aa_dfa_unpack - unpack the binary tables of a serialized dfa
194 * @blob: aligned serialized stream of data to unpack (NOT NULL)
195 * @size: size of data to unpack
196 * @flags: flags controlling what type of accept tables are acceptable
198 * Unpack a dfa that has been serialized. To find information on the dfa
199 * format look in Documentation/security/apparmor.txt
200 * Assumes the dfa @blob stream has been aligned on a 8 byte boundary
202 * Returns: an unpacked dfa ready for matching or ERR_PTR on failure
204 struct aa_dfa
*aa_dfa_unpack(void *blob
, size_t size
, int flags
)
209 struct table_header
*table
= NULL
;
210 struct aa_dfa
*dfa
= kzalloc(sizeof(struct aa_dfa
), GFP_KERNEL
);
214 kref_init(&dfa
->count
);
218 /* get dfa table set header */
219 if (size
< sizeof(struct table_set_header
))
222 if (ntohl(*(u32
*) data
) != YYTH_MAGIC
)
225 hsize
= ntohl(*(u32
*) (data
+ 4));
229 dfa
->flags
= ntohs(*(u16
*) (data
+ 12));
234 table
= unpack_table(data
, size
);
238 switch (table
->td_id
) {
240 if (!(table
->td_flags
& ACCEPT1_FLAGS(flags
)))
243 case YYTD_ID_ACCEPT2
:
244 if (!(table
->td_flags
& ACCEPT2_FLAGS(flags
)))
248 if (table
->td_flags
!= YYTD_DATA32
)
254 if (table
->td_flags
!= YYTD_DATA16
)
258 if (table
->td_flags
!= YYTD_DATA8
)
264 /* check for duplicate table entry */
265 if (dfa
->tables
[table
->td_id
])
267 dfa
->tables
[table
->td_id
] = table
;
268 data
+= table_size(table
->td_lolen
, table
->td_flags
);
269 size
-= table_size(table
->td_lolen
, table
->td_flags
);
273 error
= verify_dfa(dfa
, flags
);
282 return ERR_PTR(error
);
286 * aa_dfa_match_len - traverse @dfa to find state @str stops at
287 * @dfa: the dfa to match @str against (NOT NULL)
288 * @start: the state of the dfa to start matching in
289 * @str: the string of bytes to match against the dfa (NOT NULL)
290 * @len: length of the string of bytes to match
292 * aa_dfa_match_len will match @str against the dfa and return the state it
293 * finished matching in. The final state can be used to look up the accepting
294 * label, or as the start state of a continuing match.
296 * This function will happily match again the 0 byte and only finishes
297 * when @len input is consumed.
299 * Returns: final state reached after input is consumed
301 unsigned int aa_dfa_match_len(struct aa_dfa
*dfa
, unsigned int start
,
302 const char *str
, int len
)
304 u16
*def
= DEFAULT_TABLE(dfa
);
305 u32
*base
= BASE_TABLE(dfa
);
306 u16
*next
= NEXT_TABLE(dfa
);
307 u16
*check
= CHECK_TABLE(dfa
);
308 unsigned int state
= start
, pos
;
313 /* current state is <state>, matching character *str */
314 if (dfa
->tables
[YYTD_ID_EC
]) {
315 /* Equivalence class table defined */
316 u8
*equiv
= EQUIV_TABLE(dfa
);
317 /* default is direct to next state */
319 pos
= base
[state
] + equiv
[(u8
) *str
++];
320 if (check
[pos
] == state
)
326 /* default is direct to next state */
328 pos
= base
[state
] + (u8
) *str
++;
329 if (check
[pos
] == state
)
340 * aa_dfa_match - traverse @dfa to find state @str stops at
341 * @dfa: the dfa to match @str against (NOT NULL)
342 * @start: the state of the dfa to start matching in
343 * @str: the null terminated string of bytes to match against the dfa (NOT NULL)
345 * aa_dfa_match will match @str against the dfa and return the state it
346 * finished matching in. The final state can be used to look up the accepting
347 * label, or as the start state of a continuing match.
349 * Returns: final state reached after input is consumed
351 unsigned int aa_dfa_match(struct aa_dfa
*dfa
, unsigned int start
,
354 u16
*def
= DEFAULT_TABLE(dfa
);
355 u32
*base
= BASE_TABLE(dfa
);
356 u16
*next
= NEXT_TABLE(dfa
);
357 u16
*check
= CHECK_TABLE(dfa
);
358 unsigned int state
= start
, pos
;
363 /* current state is <state>, matching character *str */
364 if (dfa
->tables
[YYTD_ID_EC
]) {
365 /* Equivalence class table defined */
366 u8
*equiv
= EQUIV_TABLE(dfa
);
367 /* default is direct to next state */
369 pos
= base
[state
] + equiv
[(u8
) *str
++];
370 if (check
[pos
] == state
)
376 /* default is direct to next state */
378 pos
= base
[state
] + (u8
) *str
++;
379 if (check
[pos
] == state
)
390 * aa_dfa_next - step one character to the next state in the dfa
391 * @dfa: the dfa to tranverse (NOT NULL)
392 * @state: the state to start in
393 * @c: the input character to transition on
395 * aa_dfa_match will step through the dfa by one input character @c
397 * Returns: state reach after input @c
399 unsigned int aa_dfa_next(struct aa_dfa
*dfa
, unsigned int state
,
402 u16
*def
= DEFAULT_TABLE(dfa
);
403 u32
*base
= BASE_TABLE(dfa
);
404 u16
*next
= NEXT_TABLE(dfa
);
405 u16
*check
= CHECK_TABLE(dfa
);
408 /* current state is <state>, matching character *str */
409 if (dfa
->tables
[YYTD_ID_EC
]) {
410 /* Equivalence class table defined */
411 u8
*equiv
= EQUIV_TABLE(dfa
);
412 /* default is direct to next state */
414 pos
= base
[state
] + equiv
[(u8
) c
];
415 if (check
[pos
] == state
)
420 /* default is direct to next state */
421 pos
= base
[state
] + (u8
) c
;
422 if (check
[pos
] == state
)