security/apparmor/match.c

   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/lib.h"
  24 #include "include/match.h"
  25
  26 #define base_idx(X) ((X) & 0xffffff)
  27
  28 static char nulldfa_src[] = {
  29         #include "nulldfa.in"
  30 };
  31 struct aa_dfa *nulldfa;
  32
  33 int aa_setup_dfa_engine(void)
  34 {
  35         int error;
  36
  37         nulldfa = aa_dfa_unpack(nulldfa_src, sizeof(nulldfa_src),
  38                                 TO_ACCEPT1_FLAG(YYTD_DATA32) |
  39                                 TO_ACCEPT2_FLAG(YYTD_DATA32));
  40         if (!IS_ERR(nulldfa))
  41                 return 0;
  42
  43         error = PTR_ERR(nulldfa);
  44         nulldfa = NULL;
  45
  46         return error;
  47 }
  48
  49 void aa_teardown_dfa_engine(void)
  50 {
  51         aa_put_dfa(nulldfa);
  52         nulldfa = NULL;
  53 }
  54
  55 /**
  56  * unpack_table - unpack a dfa table (one of accept, default, base, next check)
  57  * @blob: data to unpack (NOT NULL)
  58  * @bsize: size of blob
  59  *
  60  * Returns: pointer to table else NULL on failure
  61  *
  62  * NOTE: must be freed by kvfree (not kfree)
  63  */
  64 static struct table_header *unpack_table(char *blob, size_t bsize)
  65 {
  66         struct table_header *table = NULL;
  67         struct table_header th;
  68         size_t tsize;
  69
  70         if (bsize < sizeof(struct table_header))
  71                 goto out;
  72
  73         /* loaded td_id's start at 1, subtract 1 now to avoid doing
  74          * it every time we use td_id as an index
  75          */
  76         th.td_id = be16_to_cpu(*(__be16 *) (blob)) - 1;
  77         if (th.td_id > YYTD_ID_MAX)
  78                 goto out;
  79         th.td_flags = be16_to_cpu(*(__be16 *) (blob + 2));
  80         th.td_lolen = be32_to_cpu(*(__be32 *) (blob + 8));
  81         blob += sizeof(struct table_header);
  82
  83         if (!(th.td_flags == YYTD_DATA16 || th.td_flags == YYTD_DATA32 ||
  84               th.td_flags == YYTD_DATA8))
  85                 goto out;
  86
  87         tsize = table_size(th.td_lolen, th.td_flags);
  88         if (bsize < tsize)
  89                 goto out;
  90
  91         table = kvzalloc(tsize);
  92         if (table) {
  93                 table->td_id = th.td_id;
  94                 table->td_flags = th.td_flags;
  95                 table->td_lolen = th.td_lolen;
  96                 if (th.td_flags == YYTD_DATA8)
  97                         UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
  98                                      u8, u8, byte_to_byte);
  99                 else if (th.td_flags == YYTD_DATA16)
 100                         UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
 101                                      u16, __be16, be16_to_cpu);
 102                 else if (th.td_flags == YYTD_DATA32)
 103                         UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
 104                                      u32, __be32, be32_to_cpu);
 105                 else
 106                         goto fail;
 107                 /* if table was vmalloced make sure the page tables are synced
 108                  * before it is used, as it goes live to all cpus.
 109                  */
 110                 if (is_vmalloc_addr(table))
 111                         vm_unmap_aliases();
 112         }
 113
 114 out:
 115         return table;
 116 fail:
 117         kvfree(table);
 118         return NULL;
 119 }
 120
 121 /**
 122  * verify_dfa - verify that transitions and states in the tables are in bounds.
 123  * @dfa: dfa to test  (NOT NULL)
 124  * @flags: flags controlling what type of accept table are acceptable
 125  *
 126  * Assumes dfa has gone through the first pass verification done by unpacking
 127  * NOTE: this does not valid accept table values
 128  *
 129  * Returns: %0 else error code on failure to verify
 130  */
 131 static int verify_dfa(struct aa_dfa *dfa, int flags)
 132 {
 133         size_t i, state_count, trans_count;
 134         int error = -EPROTO;
 135
 136         /* check that required tables exist */
 137         if (!(dfa->tables[YYTD_ID_DEF] &&
 138               dfa->tables[YYTD_ID_BASE] &&
 139               dfa->tables[YYTD_ID_NXT] && dfa->tables[YYTD_ID_CHK]))
 140                 goto out;
 141
 142         /* accept.size == default.size == base.size */
 143         state_count = dfa->tables[YYTD_ID_BASE]->td_lolen;
 144         if (ACCEPT1_FLAGS(flags)) {
 145                 if (!dfa->tables[YYTD_ID_ACCEPT])
 146                         goto out;
 147                 if (state_count != dfa->tables[YYTD_ID_ACCEPT]->td_lolen)
 148                         goto out;
 149         }
 150         if (ACCEPT2_FLAGS(flags)) {
 151                 if (!dfa->tables[YYTD_ID_ACCEPT2])
 152                         goto out;
 153                 if (state_count != dfa->tables[YYTD_ID_ACCEPT2]->td_lolen)
 154                         goto out;
 155         }
 156         if (state_count != dfa->tables[YYTD_ID_DEF]->td_lolen)
 157                 goto out;
 158
 159         /* next.size == chk.size */
 160         trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen;
 161         if (trans_count != dfa->tables[YYTD_ID_CHK]->td_lolen)
 162                 goto out;
 163
 164         /* if equivalence classes then its table size must be 256 */
 165         if (dfa->tables[YYTD_ID_EC] &&
 166             dfa->tables[YYTD_ID_EC]->td_lolen != 256)
 167                 goto out;
 168
 169         if (flags & DFA_FLAG_VERIFY_STATES) {
 170                 for (i = 0; i < state_count; i++) {
 171                         if (DEFAULT_TABLE(dfa)[i] >= state_count)
 172                                 goto out;
 173                         if (base_idx(BASE_TABLE(dfa)[i]) + 255 >= trans_count) {
 174                                 printk(KERN_ERR "AppArmor DFA next/check upper "
 175                                        "bounds error\n");
 176                                 goto out;
 177                         }
 178                 }
 179
 180                 for (i = 0; i < trans_count; i++) {
 181                         if (NEXT_TABLE(dfa)[i] >= state_count)
 182                                 goto out;
 183                         if (CHECK_TABLE(dfa)[i] >= state_count)
 184                                 goto out;
 185                 }
 186         }
 187
 188         error = 0;
 189 out:
 190         return error;
 191 }
 192
 193 /**
 194  * dfa_free - free a dfa allocated by aa_dfa_unpack
 195  * @dfa: the dfa to free  (MAYBE NULL)
 196  *
 197  * Requires: reference count to dfa == 0
 198  */
 199 static void dfa_free(struct aa_dfa *dfa)
 200 {
 201         if (dfa) {
 202                 int i;
 203
 204                 for (i = 0; i < ARRAY_SIZE(dfa->tables); i++) {
 205                         kvfree(dfa->tables[i]);
 206                         dfa->tables[i] = NULL;
 207                 }
 208                 kfree(dfa);
 209         }
 210 }
 211
 212 /**
 213  * aa_dfa_free_kref - free aa_dfa by kref (called by aa_put_dfa)
 214  * @kr: kref callback for freeing of a dfa  (NOT NULL)
 215  */
 216 void aa_dfa_free_kref(struct kref *kref)
 217 {
 218         struct aa_dfa *dfa = container_of(kref, struct aa_dfa, count);
 219         dfa_free(dfa);
 220 }
 221
 222 /**
 223  * aa_dfa_unpack - unpack the binary tables of a serialized dfa
 224  * @blob: aligned serialized stream of data to unpack  (NOT NULL)
 225  * @size: size of data to unpack
 226  * @flags: flags controlling what type of accept tables are acceptable
 227  *
 228  * Unpack a dfa that has been serialized.  To find information on the dfa
 229  * format look in Documentation/security/apparmor.txt
 230  * Assumes the dfa @blob stream has been aligned on a 8 byte boundary
 231  *
 232  * Returns: an unpacked dfa ready for matching or ERR_PTR on failure
 233  */
 234 struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags)
 235 {
 236         int hsize;
 237         int error = -ENOMEM;
 238         char *data = blob;
 239         struct table_header *table = NULL;
 240         struct aa_dfa *dfa = kzalloc(sizeof(struct aa_dfa), GFP_KERNEL);
 241         if (!dfa)
 242                 goto fail;
 243
 244         kref_init(&dfa->count);
 245
 246         error = -EPROTO;
 247
 248         /* get dfa table set header */
 249         if (size < sizeof(struct table_set_header))
 250                 goto fail;
 251
 252         if (ntohl(*(__be32 *) data) != YYTH_MAGIC)
 253                 goto fail;
 254
 255         hsize = ntohl(*(__be32 *) (data + 4));
 256         if (size < hsize)
 257                 goto fail;
 258
 259         dfa->flags = ntohs(*(__be16 *) (data + 12));
 260         data += hsize;
 261         size -= hsize;
 262
 263         while (size > 0) {
 264                 table = unpack_table(data, size);
 265                 if (!table)
 266                         goto fail;
 267
 268                 switch (table->td_id) {
 269                 case YYTD_ID_ACCEPT:
 270                         if (!(table->td_flags & ACCEPT1_FLAGS(flags)))
 271                                 goto fail;
 272                         break;
 273                 case YYTD_ID_ACCEPT2:
 274                         if (!(table->td_flags & ACCEPT2_FLAGS(flags)))
 275                                 goto fail;
 276                         break;
 277                 case YYTD_ID_BASE:
 278                         if (table->td_flags != YYTD_DATA32)
 279                                 goto fail;
 280                         break;
 281                 case YYTD_ID_DEF:
 282                 case YYTD_ID_NXT:
 283                 case YYTD_ID_CHK:
 284                         if (table->td_flags != YYTD_DATA16)
 285                                 goto fail;
 286                         break;
 287                 case YYTD_ID_EC:
 288                         if (table->td_flags != YYTD_DATA8)
 289                                 goto fail;
 290                         break;
 291                 default:
 292                         goto fail;
 293                 }
 294                 /* check for duplicate table entry */
 295                 if (dfa->tables[table->td_id])
 296                         goto fail;
 297                 dfa->tables[table->td_id] = table;
 298                 data += table_size(table->td_lolen, table->td_flags);
 299                 size -= table_size(table->td_lolen, table->td_flags);
 300                 table = NULL;
 301         }
 302
 303         error = verify_dfa(dfa, flags);
 304         if (error)
 305                 goto fail;
 306
 307         return dfa;
 308
 309 fail:
 310         kvfree(table);
 311         dfa_free(dfa);
 312         return ERR_PTR(error);
 313 }
 314
 315 /**
 316  * aa_dfa_match_len - traverse @dfa to find state @str stops at
 317  * @dfa: the dfa to match @str against  (NOT NULL)
 318  * @start: the state of the dfa to start matching in
 319  * @str: the string of bytes to match against the dfa  (NOT NULL)
 320  * @len: length of the string of bytes to match
 321  *
 322  * aa_dfa_match_len will match @str against the dfa and return the state it
 323  * finished matching in. The final state can be used to look up the accepting
 324  * label, or as the start state of a continuing match.
 325  *
 326  * This function will happily match again the 0 byte and only finishes
 327  * when @len input is consumed.
 328  *
 329  * Returns: final state reached after input is consumed
 330  */
 331 unsigned int aa_dfa_match_len(struct aa_dfa *dfa, unsigned int start,
 332                               const char *str, int len)
 333 {
 334         u16 *def = DEFAULT_TABLE(dfa);
 335         u32 *base = BASE_TABLE(dfa);
 336         u16 *next = NEXT_TABLE(dfa);
 337         u16 *check = CHECK_TABLE(dfa);
 338         unsigned int state = start, pos;
 339
 340         if (state == 0)
 341                 return 0;
 342
 343         /* current state is <state>, matching character *str */
 344         if (dfa->tables[YYTD_ID_EC]) {
 345                 /* Equivalence class table defined */
 346                 u8 *equiv = EQUIV_TABLE(dfa);
 347                 /* default is direct to next state */
 348                 for (; len; len--) {
 349                         pos = base_idx(base[state]) + equiv[(u8) *str++];
 350                         if (check[pos] == state)
 351                                 state = next[pos];
 352                         else
 353                                 state = def[state];
 354                 }
 355         } else {
 356                 /* default is direct to next state */
 357                 for (; len; len--) {
 358                         pos = base_idx(base[state]) + (u8) *str++;
 359                         if (check[pos] == state)
 360                                 state = next[pos];
 361                         else
 362                                 state = def[state];
 363                 }
 364         }
 365
 366         return state;
 367 }
 368
 369 /**
 370  * aa_dfa_match - traverse @dfa to find state @str stops at
 371  * @dfa: the dfa to match @str against  (NOT NULL)
 372  * @start: the state of the dfa to start matching in
 373  * @str: the null terminated string of bytes to match against the dfa (NOT NULL)
 374  *
 375  * aa_dfa_match will match @str against the dfa and return the state it
 376  * finished matching in. The final state can be used to look up the accepting
 377  * label, or as the start state of a continuing match.
 378  *
 379  * Returns: final state reached after input is consumed
 380  */
 381 unsigned int aa_dfa_match(struct aa_dfa *dfa, unsigned int start,
 382                           const char *str)
 383 {
 384         u16 *def = DEFAULT_TABLE(dfa);
 385         u32 *base = BASE_TABLE(dfa);
 386         u16 *next = NEXT_TABLE(dfa);
 387         u16 *check = CHECK_TABLE(dfa);
 388         unsigned int state = start, pos;
 389
 390         if (state == 0)
 391                 return 0;
 392
 393         /* current state is <state>, matching character *str */
 394         if (dfa->tables[YYTD_ID_EC]) {
 395                 /* Equivalence class table defined */
 396                 u8 *equiv = EQUIV_TABLE(dfa);
 397                 /* default is direct to next state */
 398                 while (*str) {
 399                         pos = base_idx(base[state]) + equiv[(u8) *str++];
 400                         if (check[pos] == state)
 401                                 state = next[pos];
 402                         else
 403                                 state = def[state];
 404                 }
 405         } else {
 406                 /* default is direct to next state */
 407                 while (*str) {
 408                         pos = base_idx(base[state]) + (u8) *str++;
 409                         if (check[pos] == state)
 410                                 state = next[pos];
 411                         else
 412                                 state = def[state];
 413                 }
 414         }
 415
 416         return state;
 417 }
 418
 419 /**
 420  * aa_dfa_next - step one character to the next state in the dfa
 421  * @dfa: the dfa to tranverse (NOT NULL)
 422  * @state: the state to start in
 423  * @c: the input character to transition on
 424  *
 425  * aa_dfa_match will step through the dfa by one input character @c
 426  *
 427  * Returns: state reach after input @c
 428  */
 429 unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int state,
 430                           const char c)
 431 {
 432         u16 *def = DEFAULT_TABLE(dfa);
 433         u32 *base = BASE_TABLE(dfa);
 434         u16 *next = NEXT_TABLE(dfa);
 435         u16 *check = CHECK_TABLE(dfa);
 436         unsigned int pos;
 437
 438         /* current state is <state>, matching character *str */
 439         if (dfa->tables[YYTD_ID_EC]) {
 440                 /* Equivalence class table defined */
 441                 u8 *equiv = EQUIV_TABLE(dfa);
 442                 /* default is direct to next state */
 443
 444                 pos = base_idx(base[state]) + equiv[(u8) c];
 445                 if (check[pos] == state)
 446                         state = next[pos];
 447                 else
 448                         state = def[state];
 449         } else {
 450                 /* default is direct to next state */
 451                 pos = base_idx(base[state]) + (u8) c;
 452                 if (check[pos] == state)
 453                         state = next[pos];
 454                 else
 455                         state = def[state];
 456         }
 457
 458         return state;
 459 }