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Linux/security/apparmor/match.c

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

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