1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * This file is part of UBIFS. 4 * 5 * Copyright (C) 2018 Pengutronix, Sascha Hauer <s.hauer@pengutronix.de> 6 */ 7 8 /* 9 * This file implements various helper functions for UBIFS authentication support 10 */ 11 12 #include <linux/crypto.h> 13 #include <crypto/hash.h> 14 #include <crypto/sha.h> 15 #include <crypto/algapi.h> 16 #include <keys/user-type.h> 17 18 #include "ubifs.h" 19 20 /** 21 * ubifs_node_calc_hash - calculate the hash of a UBIFS node 22 * @c: UBIFS file-system description object 23 * @node: the node to calculate a hash for 24 * @hash: the returned hash 25 * 26 * Returns 0 for success or a negative error code otherwise. 27 */ 28 int __ubifs_node_calc_hash(const struct ubifs_info *c, const void *node, 29 u8 *hash) 30 { 31 const struct ubifs_ch *ch = node; 32 SHASH_DESC_ON_STACK(shash, c->hash_tfm); 33 int err; 34 35 shash->tfm = c->hash_tfm; 36 37 err = crypto_shash_digest(shash, node, le32_to_cpu(ch->len), hash); 38 if (err < 0) 39 return err; 40 return 0; 41 } 42 43 /** 44 * ubifs_hash_calc_hmac - calculate a HMAC from a hash 45 * @c: UBIFS file-system description object 46 * @hash: the node to calculate a HMAC for 47 * @hmac: the returned HMAC 48 * 49 * Returns 0 for success or a negative error code otherwise. 50 */ 51 static int ubifs_hash_calc_hmac(const struct ubifs_info *c, const u8 *hash, 52 u8 *hmac) 53 { 54 SHASH_DESC_ON_STACK(shash, c->hmac_tfm); 55 int err; 56 57 shash->tfm = c->hmac_tfm; 58 59 err = crypto_shash_digest(shash, hash, c->hash_len, hmac); 60 if (err < 0) 61 return err; 62 return 0; 63 } 64 65 /** 66 * ubifs_prepare_auth_node - Prepare an authentication node 67 * @c: UBIFS file-system description object 68 * @node: the node to calculate a hash for 69 * @hash: input hash of previous nodes 70 * 71 * This function prepares an authentication node for writing onto flash. 72 * It creates a HMAC from the given input hash and writes it to the node. 73 * 74 * Returns 0 for success or a negative error code otherwise. 75 */ 76 int ubifs_prepare_auth_node(struct ubifs_info *c, void *node, 77 struct shash_desc *inhash) 78 { 79 struct ubifs_auth_node *auth = node; 80 u8 *hash; 81 int err; 82 83 hash = kmalloc(crypto_shash_descsize(c->hash_tfm), GFP_NOFS); 84 if (!hash) 85 return -ENOMEM; 86 87 { 88 SHASH_DESC_ON_STACK(hash_desc, c->hash_tfm); 89 90 hash_desc->tfm = c->hash_tfm; 91 ubifs_shash_copy_state(c, inhash, hash_desc); 92 93 err = crypto_shash_final(hash_desc, hash); 94 if (err) 95 goto out; 96 } 97 98 err = ubifs_hash_calc_hmac(c, hash, auth->hmac); 99 if (err) 100 goto out; 101 102 auth->ch.node_type = UBIFS_AUTH_NODE; 103 ubifs_prepare_node(c, auth, ubifs_auth_node_sz(c), 0); 104 105 err = 0; 106 out: 107 kfree(hash); 108 109 return err; 110 } 111 112 static struct shash_desc *ubifs_get_desc(const struct ubifs_info *c, 113 struct crypto_shash *tfm) 114 { 115 struct shash_desc *desc; 116 int err; 117 118 if (!ubifs_authenticated(c)) 119 return NULL; 120 121 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL); 122 if (!desc) 123 return ERR_PTR(-ENOMEM); 124 125 desc->tfm = tfm; 126 127 err = crypto_shash_init(desc); 128 if (err) { 129 kfree(desc); 130 return ERR_PTR(err); 131 } 132 133 return desc; 134 } 135 136 /** 137 * __ubifs_hash_get_desc - get a descriptor suitable for hashing a node 138 * @c: UBIFS file-system description object 139 * 140 * This function returns a descriptor suitable for hashing a node. Free after use 141 * with kfree. 142 */ 143 struct shash_desc *__ubifs_hash_get_desc(const struct ubifs_info *c) 144 { 145 return ubifs_get_desc(c, c->hash_tfm); 146 } 147 148 /** 149 * ubifs_bad_hash - Report hash mismatches 150 * @c: UBIFS file-system description object 151 * @node: the node 152 * @hash: the expected hash 153 * @lnum: the LEB @node was read from 154 * @offs: offset in LEB @node was read from 155 * 156 * This function reports a hash mismatch when a node has a different hash than 157 * expected. 158 */ 159 void ubifs_bad_hash(const struct ubifs_info *c, const void *node, const u8 *hash, 160 int lnum, int offs) 161 { 162 int len = min(c->hash_len, 20); 163 int cropped = len != c->hash_len; 164 const char *cont = cropped ? "..." : ""; 165 166 u8 calc[UBIFS_HASH_ARR_SZ]; 167 168 __ubifs_node_calc_hash(c, node, calc); 169 170 ubifs_err(c, "hash mismatch on node at LEB %d:%d", lnum, offs); 171 ubifs_err(c, "hash expected: %*ph%s", len, hash, cont); 172 ubifs_err(c, "hash calculated: %*ph%s", len, calc, cont); 173 } 174 175 /** 176 * __ubifs_node_check_hash - check the hash of a node against given hash 177 * @c: UBIFS file-system description object 178 * @node: the node 179 * @expected: the expected hash 180 * 181 * This function calculates a hash over a node and compares it to the given hash. 182 * Returns 0 if both hashes are equal or authentication is disabled, otherwise a 183 * negative error code is returned. 184 */ 185 int __ubifs_node_check_hash(const struct ubifs_info *c, const void *node, 186 const u8 *expected) 187 { 188 u8 calc[UBIFS_HASH_ARR_SZ]; 189 int err; 190 191 err = __ubifs_node_calc_hash(c, node, calc); 192 if (err) 193 return err; 194 195 if (ubifs_check_hash(c, expected, calc)) 196 return -EPERM; 197 198 return 0; 199 } 200 201 /** 202 * ubifs_init_authentication - initialize UBIFS authentication support 203 * @c: UBIFS file-system description object 204 * 205 * This function returns 0 for success or a negative error code otherwise. 206 */ 207 int ubifs_init_authentication(struct ubifs_info *c) 208 { 209 struct key *keyring_key; 210 const struct user_key_payload *ukp; 211 int err; 212 char hmac_name[CRYPTO_MAX_ALG_NAME]; 213 214 if (!c->auth_hash_name) { 215 ubifs_err(c, "authentication hash name needed with authentication"); 216 return -EINVAL; 217 } 218 219 c->auth_hash_algo = match_string(hash_algo_name, HASH_ALGO__LAST, 220 c->auth_hash_name); 221 if ((int)c->auth_hash_algo < 0) { 222 ubifs_err(c, "Unknown hash algo %s specified", 223 c->auth_hash_name); 224 return -EINVAL; 225 } 226 227 snprintf(hmac_name, CRYPTO_MAX_ALG_NAME, "hmac(%s)", 228 c->auth_hash_name); 229 230 keyring_key = request_key(&key_type_logon, c->auth_key_name, NULL); 231 232 if (IS_ERR(keyring_key)) { 233 ubifs_err(c, "Failed to request key: %ld", 234 PTR_ERR(keyring_key)); 235 return PTR_ERR(keyring_key); 236 } 237 238 down_read(&keyring_key->sem); 239 240 if (keyring_key->type != &key_type_logon) { 241 ubifs_err(c, "key type must be logon"); 242 err = -ENOKEY; 243 goto out; 244 } 245 246 ukp = user_key_payload_locked(keyring_key); 247 if (!ukp) { 248 /* key was revoked before we acquired its semaphore */ 249 err = -EKEYREVOKED; 250 goto out; 251 } 252 253 c->hash_tfm = crypto_alloc_shash(c->auth_hash_name, 0, 0); 254 if (IS_ERR(c->hash_tfm)) { 255 err = PTR_ERR(c->hash_tfm); 256 ubifs_err(c, "Can not allocate %s: %d", 257 c->auth_hash_name, err); 258 goto out; 259 } 260 261 c->hash_len = crypto_shash_digestsize(c->hash_tfm); 262 if (c->hash_len > UBIFS_HASH_ARR_SZ) { 263 ubifs_err(c, "hash %s is bigger than maximum allowed hash size (%d > %d)", 264 c->auth_hash_name, c->hash_len, UBIFS_HASH_ARR_SZ); 265 err = -EINVAL; 266 goto out_free_hash; 267 } 268 269 c->hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0); 270 if (IS_ERR(c->hmac_tfm)) { 271 err = PTR_ERR(c->hmac_tfm); 272 ubifs_err(c, "Can not allocate %s: %d", hmac_name, err); 273 goto out_free_hash; 274 } 275 276 c->hmac_desc_len = crypto_shash_digestsize(c->hmac_tfm); 277 if (c->hmac_desc_len > UBIFS_HMAC_ARR_SZ) { 278 ubifs_err(c, "hmac %s is bigger than maximum allowed hmac size (%d > %d)", 279 hmac_name, c->hmac_desc_len, UBIFS_HMAC_ARR_SZ); 280 err = -EINVAL; 281 goto out_free_hash; 282 } 283 284 err = crypto_shash_setkey(c->hmac_tfm, ukp->data, ukp->datalen); 285 if (err) 286 goto out_free_hmac; 287 288 c->authenticated = true; 289 290 c->log_hash = ubifs_hash_get_desc(c); 291 if (IS_ERR(c->log_hash)) 292 goto out_free_hmac; 293 294 err = 0; 295 296 out_free_hmac: 297 if (err) 298 crypto_free_shash(c->hmac_tfm); 299 out_free_hash: 300 if (err) 301 crypto_free_shash(c->hash_tfm); 302 out: 303 up_read(&keyring_key->sem); 304 key_put(keyring_key); 305 306 return err; 307 } 308 309 /** 310 * __ubifs_exit_authentication - release resource 311 * @c: UBIFS file-system description object 312 * 313 * This function releases the authentication related resources. 314 */ 315 void __ubifs_exit_authentication(struct ubifs_info *c) 316 { 317 if (!ubifs_authenticated(c)) 318 return; 319 320 crypto_free_shash(c->hmac_tfm); 321 crypto_free_shash(c->hash_tfm); 322 kfree(c->log_hash); 323 } 324 325 /** 326 * ubifs_node_calc_hmac - calculate the HMAC of a UBIFS node 327 * @c: UBIFS file-system description object 328 * @node: the node to insert a HMAC into. 329 * @len: the length of the node 330 * @ofs_hmac: the offset in the node where the HMAC is inserted 331 * @hmac: returned HMAC 332 * 333 * This function calculates a HMAC of a UBIFS node. The HMAC is expected to be 334 * embedded into the node, so this area is not covered by the HMAC. Also not 335 * covered is the UBIFS_NODE_MAGIC and the CRC of the node. 336 */ 337 static int ubifs_node_calc_hmac(const struct ubifs_info *c, const void *node, 338 int len, int ofs_hmac, void *hmac) 339 { 340 SHASH_DESC_ON_STACK(shash, c->hmac_tfm); 341 int hmac_len = c->hmac_desc_len; 342 int err; 343 344 ubifs_assert(c, ofs_hmac > 8); 345 ubifs_assert(c, ofs_hmac + hmac_len < len); 346 347 shash->tfm = c->hmac_tfm; 348 349 err = crypto_shash_init(shash); 350 if (err) 351 return err; 352 353 /* behind common node header CRC up to HMAC begin */ 354 err = crypto_shash_update(shash, node + 8, ofs_hmac - 8); 355 if (err < 0) 356 return err; 357 358 /* behind HMAC, if any */ 359 if (len - ofs_hmac - hmac_len > 0) { 360 err = crypto_shash_update(shash, node + ofs_hmac + hmac_len, 361 len - ofs_hmac - hmac_len); 362 if (err < 0) 363 return err; 364 } 365 366 return crypto_shash_final(shash, hmac); 367 } 368 369 /** 370 * __ubifs_node_insert_hmac - insert a HMAC into a UBIFS node 371 * @c: UBIFS file-system description object 372 * @node: the node to insert a HMAC into. 373 * @len: the length of the node 374 * @ofs_hmac: the offset in the node where the HMAC is inserted 375 * 376 * This function inserts a HMAC at offset @ofs_hmac into the node given in 377 * @node. 378 * 379 * This function returns 0 for success or a negative error code otherwise. 380 */ 381 int __ubifs_node_insert_hmac(const struct ubifs_info *c, void *node, int len, 382 int ofs_hmac) 383 { 384 return ubifs_node_calc_hmac(c, node, len, ofs_hmac, node + ofs_hmac); 385 } 386 387 /** 388 * __ubifs_node_verify_hmac - verify the HMAC of UBIFS node 389 * @c: UBIFS file-system description object 390 * @node: the node to insert a HMAC into. 391 * @len: the length of the node 392 * @ofs_hmac: the offset in the node where the HMAC is inserted 393 * 394 * This function verifies the HMAC at offset @ofs_hmac of the node given in 395 * @node. Returns 0 if successful or a negative error code otherwise. 396 */ 397 int __ubifs_node_verify_hmac(const struct ubifs_info *c, const void *node, 398 int len, int ofs_hmac) 399 { 400 int hmac_len = c->hmac_desc_len; 401 u8 *hmac; 402 int err; 403 404 hmac = kmalloc(hmac_len, GFP_NOFS); 405 if (!hmac) 406 return -ENOMEM; 407 408 err = ubifs_node_calc_hmac(c, node, len, ofs_hmac, hmac); 409 if (err) 410 return err; 411 412 err = crypto_memneq(hmac, node + ofs_hmac, hmac_len); 413 414 kfree(hmac); 415 416 if (!err) 417 return 0; 418 419 return -EPERM; 420 } 421 422 int __ubifs_shash_copy_state(const struct ubifs_info *c, struct shash_desc *src, 423 struct shash_desc *target) 424 { 425 u8 *state; 426 int err; 427 428 state = kmalloc(crypto_shash_descsize(src->tfm), GFP_NOFS); 429 if (!state) 430 return -ENOMEM; 431 432 err = crypto_shash_export(src, state); 433 if (err) 434 goto out; 435 436 err = crypto_shash_import(target, state); 437 438 out: 439 kfree(state); 440 441 return err; 442 } 443 444 /** 445 * ubifs_hmac_wkm - Create a HMAC of the well known message 446 * @c: UBIFS file-system description object 447 * @hmac: The HMAC of the well known message 448 * 449 * This function creates a HMAC of a well known message. This is used 450 * to check if the provided key is suitable to authenticate a UBIFS 451 * image. This is only a convenience to the user to provide a better 452 * error message when the wrong key is provided. 453 * 454 * This function returns 0 for success or a negative error code otherwise. 455 */ 456 int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac) 457 { 458 SHASH_DESC_ON_STACK(shash, c->hmac_tfm); 459 int err; 460 const char well_known_message[] = "UBIFS"; 461 462 if (!ubifs_authenticated(c)) 463 return 0; 464 465 shash->tfm = c->hmac_tfm; 466 467 err = crypto_shash_init(shash); 468 if (err) 469 return err; 470 471 err = crypto_shash_update(shash, well_known_message, 472 sizeof(well_known_message) - 1); 473 if (err < 0) 474 return err; 475 476 err = crypto_shash_final(shash, hmac); 477 if (err) 478 return err; 479 return 0; 480 } 481