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 197 * format look in Documentation/apparmor.txt 198 * Assumes the dfa @blob stream has been aligned on a 8 byte boundry 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 /** 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) 342 * 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. 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 { 352 return aa_dfa_match_len(dfa, start, str, strlen(str)); 353 } 354