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 th
.td_flags
= be16_to_cpu(*(u16
*) (blob
+ 2));
49 th
.td_lolen
= be32_to_cpu(*(u32
*) (blob
+ 8));
50 blob
+= sizeof(struct table_header
);
52 if (!(th
.td_flags
== YYTD_DATA16
|| th
.td_flags
== YYTD_DATA32
||
53 th
.td_flags
== YYTD_DATA8
))
56 tsize
= table_size(th
.td_lolen
, th
.td_flags
);
60 table
= kvmalloc(tsize
);
63 if (th
.td_flags
== YYTD_DATA8
)
64 UNPACK_ARRAY(table
->td_data
, blob
, th
.td_lolen
,
66 else if (th
.td_flags
== YYTD_DATA16
)
67 UNPACK_ARRAY(table
->td_data
, blob
, th
.td_lolen
,
69 else if (th
.td_flags
== YYTD_DATA32
)
70 UNPACK_ARRAY(table
->td_data
, blob
, th
.td_lolen
,
77 /* if table was vmalloced make sure the page tables are synced
78 * before it is used, as it goes live to all cpus.
80 if (is_vmalloc_addr(table
))
89 * verify_dfa - verify that transitions and states in the tables are in bounds.
90 * @dfa: dfa to test (NOT NULL)
91 * @flags: flags controlling what type of accept table are acceptable
93 * Assumes dfa has gone through the first pass verification done by unpacking
94 * NOTE: this does not valid accept table values
96 * Returns: %0 else error code on failure to verify
98 static int verify_dfa(struct aa_dfa
*dfa
, int flags
)
100 size_t i
, state_count
, trans_count
;
103 /* check that required tables exist */
104 if (!(dfa
->tables
[YYTD_ID_DEF
] &&
105 dfa
->tables
[YYTD_ID_BASE
] &&
106 dfa
->tables
[YYTD_ID_NXT
] && dfa
->tables
[YYTD_ID_CHK
]))
109 /* accept.size == default.size == base.size */
110 state_count
= dfa
->tables
[YYTD_ID_BASE
]->td_lolen
;
111 if (ACCEPT1_FLAGS(flags
)) {
112 if (!dfa
->tables
[YYTD_ID_ACCEPT
])
114 if (state_count
!= dfa
->tables
[YYTD_ID_ACCEPT
]->td_lolen
)
117 if (ACCEPT2_FLAGS(flags
)) {
118 if (!dfa
->tables
[YYTD_ID_ACCEPT2
])
120 if (state_count
!= dfa
->tables
[YYTD_ID_ACCEPT2
]->td_lolen
)
123 if (state_count
!= dfa
->tables
[YYTD_ID_DEF
]->td_lolen
)
126 /* next.size == chk.size */
127 trans_count
= dfa
->tables
[YYTD_ID_NXT
]->td_lolen
;
128 if (trans_count
!= dfa
->tables
[YYTD_ID_CHK
]->td_lolen
)
131 /* if equivalence classes then its table size must be 256 */
132 if (dfa
->tables
[YYTD_ID_EC
] &&
133 dfa
->tables
[YYTD_ID_EC
]->td_lolen
!= 256)
136 if (flags
& DFA_FLAG_VERIFY_STATES
) {
137 for (i
= 0; i
< state_count
; i
++) {
138 if (DEFAULT_TABLE(dfa
)[i
] >= state_count
)
140 /* TODO: do check that DEF state recursion terminates */
141 if (BASE_TABLE(dfa
)[i
] + 255 >= trans_count
) {
142 printk(KERN_ERR
"AppArmor DFA next/check upper "
148 for (i
= 0; i
< trans_count
; i
++) {
149 if (NEXT_TABLE(dfa
)[i
] >= state_count
)
151 if (CHECK_TABLE(dfa
)[i
] >= state_count
)
162 * dfa_free - free a dfa allocated by aa_dfa_unpack
163 * @dfa: the dfa to free (MAYBE NULL)
165 * Requires: reference count to dfa == 0
167 static void dfa_free(struct aa_dfa
*dfa
)
172 for (i
= 0; i
< ARRAY_SIZE(dfa
->tables
); i
++) {
173 kvfree(dfa
->tables
[i
]);
174 dfa
->tables
[i
] = NULL
;
181 * aa_dfa_free_kref - free aa_dfa by kref (called by aa_put_dfa)
182 * @kr: kref callback for freeing of a dfa (NOT NULL)
184 void aa_dfa_free_kref(struct kref
*kref
)
186 struct aa_dfa
*dfa
= container_of(kref
, struct aa_dfa
, count
);
191 * aa_dfa_unpack - unpack the binary tables of a serialized dfa
192 * @blob: aligned serialized stream of data to unpack (NOT NULL)
193 * @size: size of data to unpack
194 * @flags: flags controlling what type of accept tables are acceptable
196 * Unpack a dfa that has been serialized. To find information on the dfa
197 * format look in Documentation/apparmor.txt
198 * Assumes the dfa @blob stream has been aligned on a 8 byte boundary
200 * Returns: an unpacked dfa ready for matching or ERR_PTR on failure
202 struct aa_dfa
*aa_dfa_unpack(void *blob
, size_t size
, int flags
)
207 struct table_header
*table
= NULL
;
208 struct aa_dfa
*dfa
= kzalloc(sizeof(struct aa_dfa
), GFP_KERNEL
);
212 kref_init(&dfa
->count
);
216 /* get dfa table set header */
217 if (size
< sizeof(struct table_set_header
))
220 if (ntohl(*(u32
*) data
) != YYTH_MAGIC
)
223 hsize
= ntohl(*(u32
*) (data
+ 4));
227 dfa
->flags
= ntohs(*(u16
*) (data
+ 12));
232 table
= unpack_table(data
, size
);
236 switch (table
->td_id
) {
238 if (!(table
->td_flags
& ACCEPT1_FLAGS(flags
)))
241 case YYTD_ID_ACCEPT2
:
242 if (!(table
->td_flags
& ACCEPT2_FLAGS(flags
)))
246 if (table
->td_flags
!= YYTD_DATA32
)
252 if (table
->td_flags
!= YYTD_DATA16
)
256 if (table
->td_flags
!= YYTD_DATA8
)
262 /* check for duplicate table entry */
263 if (dfa
->tables
[table
->td_id
])
265 dfa
->tables
[table
->td_id
] = table
;
266 data
+= table_size(table
->td_lolen
, table
->td_flags
);
267 size
-= table_size(table
->td_lolen
, table
->td_flags
);
271 error
= verify_dfa(dfa
, flags
);
280 return ERR_PTR(error
);
284 * aa_dfa_match_len - traverse @dfa to find state @str stops at
285 * @dfa: the dfa to match @str against (NOT NULL)
286 * @start: the state of the dfa to start matching in
287 * @str: the string of bytes to match against the dfa (NOT NULL)
288 * @len: length of the string of bytes to match
290 * aa_dfa_match_len will match @str against the dfa and return the state it
291 * finished matching in. The final state can be used to look up the accepting
292 * label, or as the start state of a continuing match.
294 * This function will happily match again the 0 byte and only finishes
295 * when @len input is consumed.
297 * Returns: final state reached after input is consumed
299 unsigned int aa_dfa_match_len(struct aa_dfa
*dfa
, unsigned int start
,
300 const char *str
, int len
)
302 u16
*def
= DEFAULT_TABLE(dfa
);
303 u32
*base
= BASE_TABLE(dfa
);
304 u16
*next
= NEXT_TABLE(dfa
);
305 u16
*check
= CHECK_TABLE(dfa
);
306 unsigned int state
= start
, pos
;
311 /* current state is <state>, matching character *str */
312 if (dfa
->tables
[YYTD_ID_EC
]) {
313 /* Equivalence class table defined */
314 u8
*equiv
= EQUIV_TABLE(dfa
);
315 /* default is direct to next state */
317 pos
= base
[state
] + equiv
[(u8
) *str
++];
318 if (check
[pos
] == state
)
324 /* default is direct to next state */
326 pos
= base
[state
] + (u8
) *str
++;
327 if (check
[pos
] == state
)
338 * aa_dfa_next_state - traverse @dfa to find state @str stops at
339 * @dfa: the dfa to match @str against (NOT NULL)
340 * @start: the state of the dfa to start matching in
341 * @str: the null terminated string of bytes to match against the dfa (NOT NULL)
343 * aa_dfa_next_state will match @str against the dfa and return the state it
344 * finished matching in. The final state can be used to look up the accepting
345 * label, or as the start state of a continuing match.
347 * Returns: final state reached after input is consumed
349 unsigned int aa_dfa_match(struct aa_dfa
*dfa
, unsigned int start
,
352 return aa_dfa_match_len(dfa
, start
, str
, strlen(str
));