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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 | |
7 | * Copyright 2009-2010 Canonical Ltd. | |
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 | ||
26 | /** | |
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 | |
30 | * | |
31 | * Returns: pointer to table else NULL on failure | |
32 | * | |
33 | * NOTE: must be freed by kvfree (not kmalloc) | |
34 | */ | |
35 | static struct table_header *unpack_table(char *blob, size_t bsize) | |
36 | { | |
37 | struct table_header *table = NULL; | |
38 | struct table_header th; | |
39 | size_t tsize; | |
40 | ||
41 | if (bsize < sizeof(struct table_header)) | |
42 | goto out; | |
43 | ||
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 | |
46 | */ | |
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); | |
51 | ||
52 | if (!(th.td_flags == YYTD_DATA16 || th.td_flags == YYTD_DATA32 || | |
53 | th.td_flags == YYTD_DATA8)) | |
54 | goto out; | |
55 | ||
56 | tsize = table_size(th.td_lolen, th.td_flags); | |
57 | if (bsize < tsize) | |
58 | goto out; | |
59 | ||
60 | table = kvmalloc(tsize); | |
61 | if (table) { | |
62 | *table = th; | |
63 | if (th.td_flags == YYTD_DATA8) | |
64 | UNPACK_ARRAY(table->td_data, blob, th.td_lolen, | |
65 | u8, byte_to_byte); | |
66 | else if (th.td_flags == YYTD_DATA16) | |
67 | UNPACK_ARRAY(table->td_data, blob, th.td_lolen, | |
68 | u16, be16_to_cpu); | |
69 | else if (th.td_flags == YYTD_DATA32) | |
70 | UNPACK_ARRAY(table->td_data, blob, th.td_lolen, | |
71 | u32, be32_to_cpu); | |
72 | else | |
73 | goto fail; | |
74 | } | |
75 | ||
76 | out: | |
77 | /* if table was vmalloced make sure the page tables are synced | |
78 | * before it is used, as it goes live to all cpus. | |
79 | */ | |
80 | if (is_vmalloc_addr(table)) | |
81 | vm_unmap_aliases(); | |
82 | return table; | |
83 | fail: | |
84 | kvfree(table); | |
85 | return NULL; | |
86 | } | |
87 | ||
88 | /** | |
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 | |
92 | * | |
93 | * Assumes dfa has gone through the first pass verification done by unpacking | |
94 | * NOTE: this does not valid accept table values | |
95 | * | |
96 | * Returns: %0 else error code on failure to verify | |
97 | */ | |
98 | static int verify_dfa(struct aa_dfa *dfa, int flags) | |
99 | { | |
100 | size_t i, state_count, trans_count; | |
101 | int error = -EPROTO; | |
102 | ||
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])) | |
107 | goto out; | |
108 | ||
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]) | |
113 | goto out; | |
114 | if (state_count != dfa->tables[YYTD_ID_ACCEPT]->td_lolen) | |
115 | goto out; | |
116 | } | |
117 | if (ACCEPT2_FLAGS(flags)) { | |
118 | if (!dfa->tables[YYTD_ID_ACCEPT2]) | |
119 | goto out; | |
120 | if (state_count != dfa->tables[YYTD_ID_ACCEPT2]->td_lolen) | |
121 | goto out; | |
122 | } | |
123 | if (state_count != dfa->tables[YYTD_ID_DEF]->td_lolen) | |
124 | goto out; | |
125 | ||
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) | |
129 | goto out; | |
130 | ||
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) | |
134 | goto out; | |
135 | ||
136 | if (flags & DFA_FLAG_VERIFY_STATES) { | |
137 | for (i = 0; i < state_count; i++) { | |
138 | if (DEFAULT_TABLE(dfa)[i] >= state_count) | |
139 | goto out; | |
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 " | |
143 | "bounds error\n"); | |
144 | goto out; | |
145 | } | |
146 | } | |
147 | ||
148 | for (i = 0; i < trans_count; i++) { | |
149 | if (NEXT_TABLE(dfa)[i] >= state_count) | |
150 | goto out; | |
151 | if (CHECK_TABLE(dfa)[i] >= state_count) | |
152 | goto out; | |
153 | } | |
154 | } | |
155 | ||
156 | error = 0; | |
157 | out: | |
158 | return error; | |
159 | } | |
160 | ||
161 | /** | |
162 | * dfa_free - free a dfa allocated by aa_dfa_unpack | |
163 | * @dfa: the dfa to free (MAYBE NULL) | |
164 | * | |
165 | * Requires: reference count to dfa == 0 | |
166 | */ | |
167 | static void dfa_free(struct aa_dfa *dfa) | |
168 | { | |
169 | if (dfa) { | |
170 | int i; | |
171 | ||
172 | for (i = 0; i < ARRAY_SIZE(dfa->tables); i++) { | |
173 | kvfree(dfa->tables[i]); | |
174 | dfa->tables[i] = NULL; | |
175 | } | |
176 | kfree(dfa); | |
177 | } | |
178 | } | |
179 | ||
180 | /** | |
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) | |
183 | */ | |
184 | void aa_dfa_free_kref(struct kref *kref) | |
185 | { | |
186 | struct aa_dfa *dfa = container_of(kref, struct aa_dfa, count); | |
187 | dfa_free(dfa); | |
188 | } | |
189 | ||
190 | /** | |
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 | |
195 | * | |
196 | * Unpack a dfa that has been serialized. To find information on the dfa | |
d410fa4e | 197 | * format look in Documentation/security/apparmor.txt |
25985edc | 198 | * Assumes the dfa @blob stream has been aligned on a 8 byte boundary |
e06f75a6 JJ |
199 | * |
200 | * Returns: an unpacked dfa ready for matching or ERR_PTR on failure | |
201 | */ | |
202 | struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags) | |
203 | { | |
204 | int hsize; | |
205 | int error = -ENOMEM; | |
206 | char *data = blob; | |
207 | struct table_header *table = NULL; | |
208 | struct aa_dfa *dfa = kzalloc(sizeof(struct aa_dfa), GFP_KERNEL); | |
209 | if (!dfa) | |
210 | goto fail; | |
211 | ||
212 | kref_init(&dfa->count); | |
213 | ||
214 | error = -EPROTO; | |
215 | ||
216 | /* get dfa table set header */ | |
217 | if (size < sizeof(struct table_set_header)) | |
218 | goto fail; | |
219 | ||
220 | if (ntohl(*(u32 *) data) != YYTH_MAGIC) | |
221 | goto fail; | |
222 | ||
223 | hsize = ntohl(*(u32 *) (data + 4)); | |
224 | if (size < hsize) | |
225 | goto fail; | |
226 | ||
227 | dfa->flags = ntohs(*(u16 *) (data + 12)); | |
228 | data += hsize; | |
229 | size -= hsize; | |
230 | ||
231 | while (size > 0) { | |
232 | table = unpack_table(data, size); | |
233 | if (!table) | |
234 | goto fail; | |
235 | ||
236 | switch (table->td_id) { | |
237 | case YYTD_ID_ACCEPT: | |
238 | if (!(table->td_flags & ACCEPT1_FLAGS(flags))) | |
239 | goto fail; | |
240 | break; | |
241 | case YYTD_ID_ACCEPT2: | |
242 | if (!(table->td_flags & ACCEPT2_FLAGS(flags))) | |
243 | goto fail; | |
244 | break; | |
245 | case YYTD_ID_BASE: | |
246 | if (table->td_flags != YYTD_DATA32) | |
247 | goto fail; | |
248 | break; | |
249 | case YYTD_ID_DEF: | |
250 | case YYTD_ID_NXT: | |
251 | case YYTD_ID_CHK: | |
252 | if (table->td_flags != YYTD_DATA16) | |
253 | goto fail; | |
254 | break; | |
255 | case YYTD_ID_EC: | |
256 | if (table->td_flags != YYTD_DATA8) | |
257 | goto fail; | |
258 | break; | |
259 | default: | |
260 | goto fail; | |
261 | } | |
262 | /* check for duplicate table entry */ | |
263 | if (dfa->tables[table->td_id]) | |
264 | goto fail; | |
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); | |
268 | table = NULL; | |
269 | } | |
270 | ||
271 | error = verify_dfa(dfa, flags); | |
272 | if (error) | |
273 | goto fail; | |
274 | ||
275 | return dfa; | |
276 | ||
277 | fail: | |
278 | kvfree(table); | |
279 | dfa_free(dfa); | |
280 | return ERR_PTR(error); | |
281 | } | |
282 | ||
283 | /** | |
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 | |
289 | * | |
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. | |
293 | * | |
294 | * This function will happily match again the 0 byte and only finishes | |
295 | * when @len input is consumed. | |
296 | * | |
297 | * Returns: final state reached after input is consumed | |
298 | */ | |
299 | unsigned int aa_dfa_match_len(struct aa_dfa *dfa, unsigned int start, | |
300 | const char *str, int len) | |
301 | { | |
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; | |
307 | ||
308 | if (state == 0) | |
309 | return 0; | |
310 | ||
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 */ | |
316 | for (; len; len--) { | |
317 | pos = base[state] + equiv[(u8) *str++]; | |
318 | if (check[pos] == state) | |
319 | state = next[pos]; | |
320 | else | |
321 | state = def[state]; | |
322 | } | |
323 | } else { | |
324 | /* default is direct to next state */ | |
325 | for (; len; len--) { | |
326 | pos = base[state] + (u8) *str++; | |
327 | if (check[pos] == state) | |
328 | state = next[pos]; | |
329 | else | |
330 | state = def[state]; | |
331 | } | |
332 | } | |
333 | ||
334 | return state; | |
335 | } | |
336 | ||
337 | /** | |
0fe1212d | 338 | * aa_dfa_match - traverse @dfa to find state @str stops at |
e06f75a6 JJ |
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) | |
342 | * | |
0fe1212d | 343 | * aa_dfa_match will match @str against the dfa and return the state it |
e06f75a6 JJ |
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. | |
346 | * | |
347 | * Returns: final state reached after input is consumed | |
348 | */ | |
349 | unsigned int aa_dfa_match(struct aa_dfa *dfa, unsigned int start, | |
350 | const char *str) | |
351 | { | |
0fe1212d JJ |
352 | u16 *def = DEFAULT_TABLE(dfa); |
353 | u32 *base = BASE_TABLE(dfa); | |
354 | u16 *next = NEXT_TABLE(dfa); | |
355 | u16 *check = CHECK_TABLE(dfa); | |
356 | unsigned int state = start, pos; | |
357 | ||
358 | if (state == 0) | |
359 | return 0; | |
360 | ||
361 | /* current state is <state>, matching character *str */ | |
362 | if (dfa->tables[YYTD_ID_EC]) { | |
363 | /* Equivalence class table defined */ | |
364 | u8 *equiv = EQUIV_TABLE(dfa); | |
365 | /* default is direct to next state */ | |
366 | while (*str) { | |
367 | pos = base[state] + equiv[(u8) *str++]; | |
368 | if (check[pos] == state) | |
369 | state = next[pos]; | |
370 | else | |
371 | state = def[state]; | |
372 | } | |
373 | } else { | |
374 | /* default is direct to next state */ | |
375 | while (*str) { | |
376 | pos = base[state] + (u8) *str++; | |
377 | if (check[pos] == state) | |
378 | state = next[pos]; | |
379 | else | |
380 | state = def[state]; | |
381 | } | |
382 | } | |
383 | ||
384 | return state; | |
385 | } | |
386 | ||
387 | /** | |
388 | * aa_dfa_next - step one character to the next state in the dfa | |
389 | * @dfa: the dfa to tranverse (NOT NULL) | |
390 | * @state: the state to start in | |
391 | * @c: the input character to transition on | |
392 | * | |
393 | * aa_dfa_match will step through the dfa by one input character @c | |
394 | * | |
395 | * Returns: state reach after input @c | |
396 | */ | |
397 | unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int state, | |
398 | const char c) | |
399 | { | |
400 | u16 *def = DEFAULT_TABLE(dfa); | |
401 | u32 *base = BASE_TABLE(dfa); | |
402 | u16 *next = NEXT_TABLE(dfa); | |
403 | u16 *check = CHECK_TABLE(dfa); | |
404 | unsigned int pos; | |
405 | ||
406 | /* current state is <state>, matching character *str */ | |
407 | if (dfa->tables[YYTD_ID_EC]) { | |
408 | /* Equivalence class table defined */ | |
409 | u8 *equiv = EQUIV_TABLE(dfa); | |
410 | /* default is direct to next state */ | |
411 | ||
412 | pos = base[state] + equiv[(u8) c]; | |
413 | if (check[pos] == state) | |
414 | state = next[pos]; | |
415 | else | |
416 | state = def[state]; | |
417 | } else { | |
418 | /* default is direct to next state */ | |
419 | pos = base[state] + (u8) c; | |
420 | if (check[pos] == state) | |
421 | state = next[pos]; | |
422 | else | |
423 | state = def[state]; | |
424 | } | |
425 | ||
426 | return state; | |
e06f75a6 | 427 | } |