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e06f75a6 JJ |
1 | /* |
2 | * AppArmor security module | |
3 | * | |
4 | * This file contains AppArmor dfa based regular expression matching engine | |
5 | * | |
6 | * Copyright (C) 1998-2008 Novell/SUSE | |
8e4ff109 | 7 | * Copyright 2009-2012 Canonical Ltd. |
e06f75a6 JJ |
8 | * |
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 | |
12 | * License. | |
13 | */ | |
14 | ||
15 | #include <linux/errno.h> | |
16 | #include <linux/kernel.h> | |
17 | #include <linux/mm.h> | |
18 | #include <linux/slab.h> | |
19 | #include <linux/vmalloc.h> | |
20 | #include <linux/err.h> | |
21 | #include <linux/kref.h> | |
22 | ||
23 | #include "include/apparmor.h" | |
24 | #include "include/match.h" | |
25 | ||
ed686308 JJ |
26 | #define base_idx(X) ((X) & 0xffffff) |
27 | ||
e06f75a6 JJ |
28 | /** |
29 | * unpack_table - unpack a dfa table (one of accept, default, base, next check) | |
30 | * @blob: data to unpack (NOT NULL) | |
31 | * @bsize: size of blob | |
32 | * | |
33 | * Returns: pointer to table else NULL on failure | |
34 | * | |
0ca554b9 | 35 | * NOTE: must be freed by kvfree (not kfree) |
e06f75a6 JJ |
36 | */ |
37 | static struct table_header *unpack_table(char *blob, size_t bsize) | |
38 | { | |
39 | struct table_header *table = NULL; | |
40 | struct table_header th; | |
41 | size_t tsize; | |
42 | ||
43 | if (bsize < sizeof(struct table_header)) | |
44 | goto out; | |
45 | ||
46 | /* loaded td_id's start at 1, subtract 1 now to avoid doing | |
47 | * it every time we use td_id as an index | |
48 | */ | |
49 | th.td_id = be16_to_cpu(*(u16 *) (blob)) - 1; | |
15756178 JJ |
50 | if (th.td_id > YYTD_ID_MAX) |
51 | goto out; | |
e06f75a6 JJ |
52 | th.td_flags = be16_to_cpu(*(u16 *) (blob + 2)); |
53 | th.td_lolen = be32_to_cpu(*(u32 *) (blob + 8)); | |
54 | blob += sizeof(struct table_header); | |
55 | ||
56 | if (!(th.td_flags == YYTD_DATA16 || th.td_flags == YYTD_DATA32 || | |
57 | th.td_flags == YYTD_DATA8)) | |
58 | goto out; | |
59 | ||
60 | tsize = table_size(th.td_lolen, th.td_flags); | |
61 | if (bsize < tsize) | |
62 | goto out; | |
63 | ||
0ca554b9 | 64 | table = kvzalloc(tsize); |
e06f75a6 | 65 | if (table) { |
f4ee2def HS |
66 | table->td_id = th.td_id; |
67 | table->td_flags = th.td_flags; | |
68 | table->td_lolen = th.td_lolen; | |
e06f75a6 JJ |
69 | if (th.td_flags == YYTD_DATA8) |
70 | UNPACK_ARRAY(table->td_data, blob, th.td_lolen, | |
71 | u8, byte_to_byte); | |
72 | else if (th.td_flags == YYTD_DATA16) | |
73 | UNPACK_ARRAY(table->td_data, blob, th.td_lolen, | |
74 | u16, be16_to_cpu); | |
75 | else if (th.td_flags == YYTD_DATA32) | |
76 | UNPACK_ARRAY(table->td_data, blob, th.td_lolen, | |
77 | u32, be32_to_cpu); | |
78 | else | |
79 | goto fail; | |
3197f5ad JJ |
80 | /* if table was vmalloced make sure the page tables are synced |
81 | * before it is used, as it goes live to all cpus. | |
82 | */ | |
83 | if (is_vmalloc_addr(table)) | |
84 | vm_unmap_aliases(); | |
e06f75a6 JJ |
85 | } |
86 | ||
87 | out: | |
e06f75a6 JJ |
88 | return table; |
89 | fail: | |
90 | kvfree(table); | |
91 | return NULL; | |
92 | } | |
93 | ||
94 | /** | |
95 | * verify_dfa - verify that transitions and states in the tables are in bounds. | |
96 | * @dfa: dfa to test (NOT NULL) | |
97 | * @flags: flags controlling what type of accept table are acceptable | |
98 | * | |
99 | * Assumes dfa has gone through the first pass verification done by unpacking | |
100 | * NOTE: this does not valid accept table values | |
101 | * | |
102 | * Returns: %0 else error code on failure to verify | |
103 | */ | |
104 | static int verify_dfa(struct aa_dfa *dfa, int flags) | |
105 | { | |
106 | size_t i, state_count, trans_count; | |
107 | int error = -EPROTO; | |
108 | ||
109 | /* check that required tables exist */ | |
110 | if (!(dfa->tables[YYTD_ID_DEF] && | |
111 | dfa->tables[YYTD_ID_BASE] && | |
112 | dfa->tables[YYTD_ID_NXT] && dfa->tables[YYTD_ID_CHK])) | |
113 | goto out; | |
114 | ||
115 | /* accept.size == default.size == base.size */ | |
116 | state_count = dfa->tables[YYTD_ID_BASE]->td_lolen; | |
117 | if (ACCEPT1_FLAGS(flags)) { | |
118 | if (!dfa->tables[YYTD_ID_ACCEPT]) | |
119 | goto out; | |
120 | if (state_count != dfa->tables[YYTD_ID_ACCEPT]->td_lolen) | |
121 | goto out; | |
122 | } | |
123 | if (ACCEPT2_FLAGS(flags)) { | |
124 | if (!dfa->tables[YYTD_ID_ACCEPT2]) | |
125 | goto out; | |
126 | if (state_count != dfa->tables[YYTD_ID_ACCEPT2]->td_lolen) | |
127 | goto out; | |
128 | } | |
129 | if (state_count != dfa->tables[YYTD_ID_DEF]->td_lolen) | |
130 | goto out; | |
131 | ||
132 | /* next.size == chk.size */ | |
133 | trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen; | |
134 | if (trans_count != dfa->tables[YYTD_ID_CHK]->td_lolen) | |
135 | goto out; | |
136 | ||
137 | /* if equivalence classes then its table size must be 256 */ | |
138 | if (dfa->tables[YYTD_ID_EC] && | |
139 | dfa->tables[YYTD_ID_EC]->td_lolen != 256) | |
140 | goto out; | |
141 | ||
142 | if (flags & DFA_FLAG_VERIFY_STATES) { | |
143 | for (i = 0; i < state_count; i++) { | |
144 | if (DEFAULT_TABLE(dfa)[i] >= state_count) | |
145 | goto out; | |
ed686308 | 146 | if (base_idx(BASE_TABLE(dfa)[i]) + 255 >= trans_count) { |
e06f75a6 JJ |
147 | printk(KERN_ERR "AppArmor DFA next/check upper " |
148 | "bounds error\n"); | |
149 | goto out; | |
150 | } | |
151 | } | |
152 | ||
153 | for (i = 0; i < trans_count; i++) { | |
154 | if (NEXT_TABLE(dfa)[i] >= state_count) | |
155 | goto out; | |
156 | if (CHECK_TABLE(dfa)[i] >= state_count) | |
157 | goto out; | |
158 | } | |
159 | } | |
160 | ||
161 | error = 0; | |
162 | out: | |
163 | return error; | |
164 | } | |
165 | ||
166 | /** | |
167 | * dfa_free - free a dfa allocated by aa_dfa_unpack | |
168 | * @dfa: the dfa to free (MAYBE NULL) | |
169 | * | |
170 | * Requires: reference count to dfa == 0 | |
171 | */ | |
172 | static void dfa_free(struct aa_dfa *dfa) | |
173 | { | |
174 | if (dfa) { | |
175 | int i; | |
176 | ||
177 | for (i = 0; i < ARRAY_SIZE(dfa->tables); i++) { | |
178 | kvfree(dfa->tables[i]); | |
179 | dfa->tables[i] = NULL; | |
180 | } | |
181 | kfree(dfa); | |
182 | } | |
183 | } | |
184 | ||
185 | /** | |
186 | * aa_dfa_free_kref - free aa_dfa by kref (called by aa_put_dfa) | |
187 | * @kr: kref callback for freeing of a dfa (NOT NULL) | |
188 | */ | |
189 | void aa_dfa_free_kref(struct kref *kref) | |
190 | { | |
191 | struct aa_dfa *dfa = container_of(kref, struct aa_dfa, count); | |
192 | dfa_free(dfa); | |
193 | } | |
194 | ||
195 | /** | |
196 | * aa_dfa_unpack - unpack the binary tables of a serialized dfa | |
197 | * @blob: aligned serialized stream of data to unpack (NOT NULL) | |
198 | * @size: size of data to unpack | |
199 | * @flags: flags controlling what type of accept tables are acceptable | |
200 | * | |
201 | * Unpack a dfa that has been serialized. To find information on the dfa | |
d410fa4e | 202 | * format look in Documentation/security/apparmor.txt |
25985edc | 203 | * Assumes the dfa @blob stream has been aligned on a 8 byte boundary |
e06f75a6 JJ |
204 | * |
205 | * Returns: an unpacked dfa ready for matching or ERR_PTR on failure | |
206 | */ | |
207 | struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags) | |
208 | { | |
209 | int hsize; | |
210 | int error = -ENOMEM; | |
211 | char *data = blob; | |
212 | struct table_header *table = NULL; | |
213 | struct aa_dfa *dfa = kzalloc(sizeof(struct aa_dfa), GFP_KERNEL); | |
214 | if (!dfa) | |
215 | goto fail; | |
216 | ||
217 | kref_init(&dfa->count); | |
218 | ||
219 | error = -EPROTO; | |
220 | ||
221 | /* get dfa table set header */ | |
222 | if (size < sizeof(struct table_set_header)) | |
223 | goto fail; | |
224 | ||
225 | if (ntohl(*(u32 *) data) != YYTH_MAGIC) | |
226 | goto fail; | |
227 | ||
228 | hsize = ntohl(*(u32 *) (data + 4)); | |
229 | if (size < hsize) | |
230 | goto fail; | |
231 | ||
232 | dfa->flags = ntohs(*(u16 *) (data + 12)); | |
233 | data += hsize; | |
234 | size -= hsize; | |
235 | ||
236 | while (size > 0) { | |
237 | table = unpack_table(data, size); | |
238 | if (!table) | |
239 | goto fail; | |
240 | ||
241 | switch (table->td_id) { | |
242 | case YYTD_ID_ACCEPT: | |
243 | if (!(table->td_flags & ACCEPT1_FLAGS(flags))) | |
244 | goto fail; | |
245 | break; | |
246 | case YYTD_ID_ACCEPT2: | |
247 | if (!(table->td_flags & ACCEPT2_FLAGS(flags))) | |
248 | goto fail; | |
249 | break; | |
250 | case YYTD_ID_BASE: | |
251 | if (table->td_flags != YYTD_DATA32) | |
252 | goto fail; | |
253 | break; | |
254 | case YYTD_ID_DEF: | |
255 | case YYTD_ID_NXT: | |
256 | case YYTD_ID_CHK: | |
257 | if (table->td_flags != YYTD_DATA16) | |
258 | goto fail; | |
259 | break; | |
260 | case YYTD_ID_EC: | |
261 | if (table->td_flags != YYTD_DATA8) | |
262 | goto fail; | |
263 | break; | |
264 | default: | |
265 | goto fail; | |
266 | } | |
267 | /* check for duplicate table entry */ | |
268 | if (dfa->tables[table->td_id]) | |
269 | goto fail; | |
270 | dfa->tables[table->td_id] = table; | |
271 | data += table_size(table->td_lolen, table->td_flags); | |
272 | size -= table_size(table->td_lolen, table->td_flags); | |
273 | table = NULL; | |
274 | } | |
275 | ||
276 | error = verify_dfa(dfa, flags); | |
277 | if (error) | |
278 | goto fail; | |
279 | ||
280 | return dfa; | |
281 | ||
282 | fail: | |
283 | kvfree(table); | |
284 | dfa_free(dfa); | |
285 | return ERR_PTR(error); | |
286 | } | |
287 | ||
288 | /** | |
289 | * aa_dfa_match_len - traverse @dfa to find state @str stops at | |
290 | * @dfa: the dfa to match @str against (NOT NULL) | |
291 | * @start: the state of the dfa to start matching in | |
292 | * @str: the string of bytes to match against the dfa (NOT NULL) | |
293 | * @len: length of the string of bytes to match | |
294 | * | |
295 | * aa_dfa_match_len will match @str against the dfa and return the state it | |
296 | * finished matching in. The final state can be used to look up the accepting | |
297 | * label, or as the start state of a continuing match. | |
298 | * | |
299 | * This function will happily match again the 0 byte and only finishes | |
300 | * when @len input is consumed. | |
301 | * | |
302 | * Returns: final state reached after input is consumed | |
303 | */ | |
304 | unsigned int aa_dfa_match_len(struct aa_dfa *dfa, unsigned int start, | |
305 | const char *str, int len) | |
306 | { | |
307 | u16 *def = DEFAULT_TABLE(dfa); | |
308 | u32 *base = BASE_TABLE(dfa); | |
309 | u16 *next = NEXT_TABLE(dfa); | |
310 | u16 *check = CHECK_TABLE(dfa); | |
311 | unsigned int state = start, pos; | |
312 | ||
313 | if (state == 0) | |
314 | return 0; | |
315 | ||
316 | /* current state is <state>, matching character *str */ | |
317 | if (dfa->tables[YYTD_ID_EC]) { | |
318 | /* Equivalence class table defined */ | |
319 | u8 *equiv = EQUIV_TABLE(dfa); | |
320 | /* default is direct to next state */ | |
321 | for (; len; len--) { | |
ed686308 | 322 | pos = base_idx(base[state]) + equiv[(u8) *str++]; |
e06f75a6 JJ |
323 | if (check[pos] == state) |
324 | state = next[pos]; | |
325 | else | |
326 | state = def[state]; | |
327 | } | |
328 | } else { | |
329 | /* default is direct to next state */ | |
330 | for (; len; len--) { | |
ed686308 | 331 | pos = base_idx(base[state]) + (u8) *str++; |
e06f75a6 JJ |
332 | if (check[pos] == state) |
333 | state = next[pos]; | |
334 | else | |
335 | state = def[state]; | |
336 | } | |
337 | } | |
338 | ||
339 | return state; | |
340 | } | |
341 | ||
342 | /** | |
0fe1212d | 343 | * aa_dfa_match - traverse @dfa to find state @str stops at |
e06f75a6 JJ |
344 | * @dfa: the dfa to match @str against (NOT NULL) |
345 | * @start: the state of the dfa to start matching in | |
346 | * @str: the null terminated string of bytes to match against the dfa (NOT NULL) | |
347 | * | |
0fe1212d | 348 | * aa_dfa_match will match @str against the dfa and return the state it |
e06f75a6 JJ |
349 | * finished matching in. The final state can be used to look up the accepting |
350 | * label, or as the start state of a continuing match. | |
351 | * | |
352 | * Returns: final state reached after input is consumed | |
353 | */ | |
354 | unsigned int aa_dfa_match(struct aa_dfa *dfa, unsigned int start, | |
355 | const char *str) | |
356 | { | |
0fe1212d JJ |
357 | u16 *def = DEFAULT_TABLE(dfa); |
358 | u32 *base = BASE_TABLE(dfa); | |
359 | u16 *next = NEXT_TABLE(dfa); | |
360 | u16 *check = CHECK_TABLE(dfa); | |
361 | unsigned int state = start, pos; | |
362 | ||
363 | if (state == 0) | |
364 | return 0; | |
365 | ||
366 | /* current state is <state>, matching character *str */ | |
367 | if (dfa->tables[YYTD_ID_EC]) { | |
368 | /* Equivalence class table defined */ | |
369 | u8 *equiv = EQUIV_TABLE(dfa); | |
370 | /* default is direct to next state */ | |
371 | while (*str) { | |
ed686308 | 372 | pos = base_idx(base[state]) + equiv[(u8) *str++]; |
0fe1212d JJ |
373 | if (check[pos] == state) |
374 | state = next[pos]; | |
375 | else | |
376 | state = def[state]; | |
377 | } | |
378 | } else { | |
379 | /* default is direct to next state */ | |
380 | while (*str) { | |
ed686308 | 381 | pos = base_idx(base[state]) + (u8) *str++; |
0fe1212d JJ |
382 | if (check[pos] == state) |
383 | state = next[pos]; | |
384 | else | |
385 | state = def[state]; | |
386 | } | |
387 | } | |
388 | ||
389 | return state; | |
390 | } | |
391 | ||
392 | /** | |
393 | * aa_dfa_next - step one character to the next state in the dfa | |
394 | * @dfa: the dfa to tranverse (NOT NULL) | |
395 | * @state: the state to start in | |
396 | * @c: the input character to transition on | |
397 | * | |
398 | * aa_dfa_match will step through the dfa by one input character @c | |
399 | * | |
400 | * Returns: state reach after input @c | |
401 | */ | |
402 | unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int state, | |
403 | const char c) | |
404 | { | |
405 | u16 *def = DEFAULT_TABLE(dfa); | |
406 | u32 *base = BASE_TABLE(dfa); | |
407 | u16 *next = NEXT_TABLE(dfa); | |
408 | u16 *check = CHECK_TABLE(dfa); | |
409 | unsigned int pos; | |
410 | ||
411 | /* current state is <state>, matching character *str */ | |
412 | if (dfa->tables[YYTD_ID_EC]) { | |
413 | /* Equivalence class table defined */ | |
414 | u8 *equiv = EQUIV_TABLE(dfa); | |
415 | /* default is direct to next state */ | |
416 | ||
ed686308 | 417 | pos = base_idx(base[state]) + equiv[(u8) c]; |
0fe1212d JJ |
418 | if (check[pos] == state) |
419 | state = next[pos]; | |
420 | else | |
421 | state = def[state]; | |
422 | } else { | |
423 | /* default is direct to next state */ | |
ed686308 | 424 | pos = base_idx(base[state]) + (u8) c; |
0fe1212d JJ |
425 | if (check[pos] == state) |
426 | state = next[pos]; | |
427 | else | |
428 | state = def[state]; | |
429 | } | |
430 | ||
431 | return state; | |
e06f75a6 | 432 | } |