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 <linux/verification.h> 14 #include <crypto/hash.h> 15 #include <crypto/sha.h> 16 #include <crypto/algapi.h> 17 #include <keys/user-type.h> 18 #include <keys/asymmetric-type.h> 19 20 #include "ubifs.h" 21 22 /** 23 * ubifs_node_calc_hash - calculate the hash of a UBIFS node 24 * @c: UBIFS file-system description object 25 * @node: the node to calculate a hash for 26 * @hash: the returned hash 27 * 28 * Returns 0 for success or a negative error code otherwise. 29 */ 30 int __ubifs_node_calc_hash(const struct ubifs_info *c, const void *node, 31 u8 *hash) 32 { 33 const struct ubifs_ch *ch = node; 34 35 return crypto_shash_tfm_digest(c->hash_tfm, node, le32_to_cpu(ch->len), 36 hash); 37 } 38 39 /** 40 * ubifs_hash_calc_hmac - calculate a HMAC from a hash 41 * @c: UBIFS file-system description object 42 * @hash: the node to calculate a HMAC for 43 * @hmac: the returned HMAC 44 * 45 * Returns 0 for success or a negative error code otherwise. 46 */ 47 static int ubifs_hash_calc_hmac(const struct ubifs_info *c, const u8 *hash, 48 u8 *hmac) 49 { 50 return crypto_shash_tfm_digest(c->hmac_tfm, hash, c->hash_len, hmac); 51 } 52 53 /** 54 * ubifs_prepare_auth_node - Prepare an authentication node 55 * @c: UBIFS file-system description object 56 * @node: the node to calculate a hash for 57 * @hash: input hash of previous nodes 58 * 59 * This function prepares an authentication node for writing onto flash. 60 * It creates a HMAC from the given input hash and writes it to the node. 61 * 62 * Returns 0 for success or a negative error code otherwise. 63 */ 64 int ubifs_prepare_auth_node(struct ubifs_info *c, void *node, 65 struct shash_desc *inhash) 66 { 67 struct ubifs_auth_node *auth = node; 68 u8 hash[UBIFS_HASH_ARR_SZ]; 69 int err; 70 71 { 72 SHASH_DESC_ON_STACK(hash_desc, c->hash_tfm); 73 74 hash_desc->tfm = c->hash_tfm; 75 ubifs_shash_copy_state(c, inhash, hash_desc); 76 77 err = crypto_shash_final(hash_desc, hash); 78 if (err) 79 return err; 80 } 81 82 err = ubifs_hash_calc_hmac(c, hash, auth->hmac); 83 if (err) 84 return err; 85 86 auth->ch.node_type = UBIFS_AUTH_NODE; 87 ubifs_prepare_node(c, auth, ubifs_auth_node_sz(c), 0); 88 return 0; 89 } 90 91 static struct shash_desc *ubifs_get_desc(const struct ubifs_info *c, 92 struct crypto_shash *tfm) 93 { 94 struct shash_desc *desc; 95 int err; 96 97 if (!ubifs_authenticated(c)) 98 return NULL; 99 100 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL); 101 if (!desc) 102 return ERR_PTR(-ENOMEM); 103 104 desc->tfm = tfm; 105 106 err = crypto_shash_init(desc); 107 if (err) { 108 kfree(desc); 109 return ERR_PTR(err); 110 } 111 112 return desc; 113 } 114 115 /** 116 * __ubifs_hash_get_desc - get a descriptor suitable for hashing a node 117 * @c: UBIFS file-system description object 118 * 119 * This function returns a descriptor suitable for hashing a node. Free after use 120 * with kfree. 121 */ 122 struct shash_desc *__ubifs_hash_get_desc(const struct ubifs_info *c) 123 { 124 return ubifs_get_desc(c, c->hash_tfm); 125 } 126 127 /** 128 * ubifs_bad_hash - Report hash mismatches 129 * @c: UBIFS file-system description object 130 * @node: the node 131 * @hash: the expected hash 132 * @lnum: the LEB @node was read from 133 * @offs: offset in LEB @node was read from 134 * 135 * This function reports a hash mismatch when a node has a different hash than 136 * expected. 137 */ 138 void ubifs_bad_hash(const struct ubifs_info *c, const void *node, const u8 *hash, 139 int lnum, int offs) 140 { 141 int len = min(c->hash_len, 20); 142 int cropped = len != c->hash_len; 143 const char *cont = cropped ? "..." : ""; 144 145 u8 calc[UBIFS_HASH_ARR_SZ]; 146 147 __ubifs_node_calc_hash(c, node, calc); 148 149 ubifs_err(c, "hash mismatch on node at LEB %d:%d", lnum, offs); 150 ubifs_err(c, "hash expected: %*ph%s", len, hash, cont); 151 ubifs_err(c, "hash calculated: %*ph%s", len, calc, cont); 152 } 153 154 /** 155 * __ubifs_node_check_hash - check the hash of a node against given hash 156 * @c: UBIFS file-system description object 157 * @node: the node 158 * @expected: the expected hash 159 * 160 * This function calculates a hash over a node and compares it to the given hash. 161 * Returns 0 if both hashes are equal or authentication is disabled, otherwise a 162 * negative error code is returned. 163 */ 164 int __ubifs_node_check_hash(const struct ubifs_info *c, const void *node, 165 const u8 *expected) 166 { 167 u8 calc[UBIFS_HASH_ARR_SZ]; 168 int err; 169 170 err = __ubifs_node_calc_hash(c, node, calc); 171 if (err) 172 return err; 173 174 if (ubifs_check_hash(c, expected, calc)) 175 return -EPERM; 176 177 return 0; 178 } 179 180 /** 181 * ubifs_sb_verify_signature - verify the signature of a superblock 182 * @c: UBIFS file-system description object 183 * @sup: The superblock node 184 * 185 * To support offline signed images the superblock can be signed with a 186 * PKCS#7 signature. The signature is placed directly behind the superblock 187 * node in an ubifs_sig_node. 188 * 189 * Returns 0 when the signature can be successfully verified or a negative 190 * error code if not. 191 */ 192 int ubifs_sb_verify_signature(struct ubifs_info *c, 193 const struct ubifs_sb_node *sup) 194 { 195 int err; 196 struct ubifs_scan_leb *sleb; 197 struct ubifs_scan_node *snod; 198 const struct ubifs_sig_node *signode; 199 200 sleb = ubifs_scan(c, UBIFS_SB_LNUM, UBIFS_SB_NODE_SZ, c->sbuf, 0); 201 if (IS_ERR(sleb)) { 202 err = PTR_ERR(sleb); 203 return err; 204 } 205 206 if (sleb->nodes_cnt == 0) { 207 ubifs_err(c, "Unable to find signature node"); 208 err = -EINVAL; 209 goto out_destroy; 210 } 211 212 snod = list_first_entry(&sleb->nodes, struct ubifs_scan_node, list); 213 214 if (snod->type != UBIFS_SIG_NODE) { 215 ubifs_err(c, "Signature node is of wrong type"); 216 err = -EINVAL; 217 goto out_destroy; 218 } 219 220 signode = snod->node; 221 222 if (le32_to_cpu(signode->len) > snod->len + sizeof(struct ubifs_sig_node)) { 223 ubifs_err(c, "invalid signature len %d", le32_to_cpu(signode->len)); 224 err = -EINVAL; 225 goto out_destroy; 226 } 227 228 if (le32_to_cpu(signode->type) != UBIFS_SIGNATURE_TYPE_PKCS7) { 229 ubifs_err(c, "Signature type %d is not supported\n", 230 le32_to_cpu(signode->type)); 231 err = -EINVAL; 232 goto out_destroy; 233 } 234 235 err = verify_pkcs7_signature(sup, sizeof(struct ubifs_sb_node), 236 signode->sig, le32_to_cpu(signode->len), 237 NULL, VERIFYING_UNSPECIFIED_SIGNATURE, 238 NULL, NULL); 239 240 if (err) 241 ubifs_err(c, "Failed to verify signature"); 242 else 243 ubifs_msg(c, "Successfully verified super block signature"); 244 245 out_destroy: 246 ubifs_scan_destroy(sleb); 247 248 return err; 249 } 250 251 /** 252 * ubifs_init_authentication - initialize UBIFS authentication support 253 * @c: UBIFS file-system description object 254 * 255 * This function returns 0 for success or a negative error code otherwise. 256 */ 257 int ubifs_init_authentication(struct ubifs_info *c) 258 { 259 struct key *keyring_key; 260 const struct user_key_payload *ukp; 261 int err; 262 char hmac_name[CRYPTO_MAX_ALG_NAME]; 263 264 if (!c->auth_hash_name) { 265 ubifs_err(c, "authentication hash name needed with authentication"); 266 return -EINVAL; 267 } 268 269 c->auth_hash_algo = match_string(hash_algo_name, HASH_ALGO__LAST, 270 c->auth_hash_name); 271 if ((int)c->auth_hash_algo < 0) { 272 ubifs_err(c, "Unknown hash algo %s specified", 273 c->auth_hash_name); 274 return -EINVAL; 275 } 276 277 snprintf(hmac_name, CRYPTO_MAX_ALG_NAME, "hmac(%s)", 278 c->auth_hash_name); 279 280 keyring_key = request_key(&key_type_logon, c->auth_key_name, NULL); 281 282 if (IS_ERR(keyring_key)) { 283 ubifs_err(c, "Failed to request key: %ld", 284 PTR_ERR(keyring_key)); 285 return PTR_ERR(keyring_key); 286 } 287 288 down_read(&keyring_key->sem); 289 290 if (keyring_key->type != &key_type_logon) { 291 ubifs_err(c, "key type must be logon"); 292 err = -ENOKEY; 293 goto out; 294 } 295 296 ukp = user_key_payload_locked(keyring_key); 297 if (!ukp) { 298 /* key was revoked before we acquired its semaphore */ 299 err = -EKEYREVOKED; 300 goto out; 301 } 302 303 c->hash_tfm = crypto_alloc_shash(c->auth_hash_name, 0, 0); 304 if (IS_ERR(c->hash_tfm)) { 305 err = PTR_ERR(c->hash_tfm); 306 ubifs_err(c, "Can not allocate %s: %d", 307 c->auth_hash_name, err); 308 goto out; 309 } 310 311 c->hash_len = crypto_shash_digestsize(c->hash_tfm); 312 if (c->hash_len > UBIFS_HASH_ARR_SZ) { 313 ubifs_err(c, "hash %s is bigger than maximum allowed hash size (%d > %d)", 314 c->auth_hash_name, c->hash_len, UBIFS_HASH_ARR_SZ); 315 err = -EINVAL; 316 goto out_free_hash; 317 } 318 319 c->hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0); 320 if (IS_ERR(c->hmac_tfm)) { 321 err = PTR_ERR(c->hmac_tfm); 322 ubifs_err(c, "Can not allocate %s: %d", hmac_name, err); 323 goto out_free_hash; 324 } 325 326 c->hmac_desc_len = crypto_shash_digestsize(c->hmac_tfm); 327 if (c->hmac_desc_len > UBIFS_HMAC_ARR_SZ) { 328 ubifs_err(c, "hmac %s is bigger than maximum allowed hmac size (%d > %d)", 329 hmac_name, c->hmac_desc_len, UBIFS_HMAC_ARR_SZ); 330 err = -EINVAL; 331 goto out_free_hash; 332 } 333 334 err = crypto_shash_setkey(c->hmac_tfm, ukp->data, ukp->datalen); 335 if (err) 336 goto out_free_hmac; 337 338 c->authenticated = true; 339 340 c->log_hash = ubifs_hash_get_desc(c); 341 if (IS_ERR(c->log_hash)) 342 goto out_free_hmac; 343 344 err = 0; 345 346 out_free_hmac: 347 if (err) 348 crypto_free_shash(c->hmac_tfm); 349 out_free_hash: 350 if (err) 351 crypto_free_shash(c->hash_tfm); 352 out: 353 up_read(&keyring_key->sem); 354 key_put(keyring_key); 355 356 return err; 357 } 358 359 /** 360 * __ubifs_exit_authentication - release resource 361 * @c: UBIFS file-system description object 362 * 363 * This function releases the authentication related resources. 364 */ 365 void __ubifs_exit_authentication(struct ubifs_info *c) 366 { 367 if (!ubifs_authenticated(c)) 368 return; 369 370 crypto_free_shash(c->hmac_tfm); 371 crypto_free_shash(c->hash_tfm); 372 kfree(c->log_hash); 373 } 374 375 /** 376 * ubifs_node_calc_hmac - calculate the HMAC of a UBIFS node 377 * @c: UBIFS file-system description object 378 * @node: the node to insert a HMAC into. 379 * @len: the length of the node 380 * @ofs_hmac: the offset in the node where the HMAC is inserted 381 * @hmac: returned HMAC 382 * 383 * This function calculates a HMAC of a UBIFS node. The HMAC is expected to be 384 * embedded into the node, so this area is not covered by the HMAC. Also not 385 * covered is the UBIFS_NODE_MAGIC and the CRC of the node. 386 */ 387 static int ubifs_node_calc_hmac(const struct ubifs_info *c, const void *node, 388 int len, int ofs_hmac, void *hmac) 389 { 390 SHASH_DESC_ON_STACK(shash, c->hmac_tfm); 391 int hmac_len = c->hmac_desc_len; 392 int err; 393 394 ubifs_assert(c, ofs_hmac > 8); 395 ubifs_assert(c, ofs_hmac + hmac_len < len); 396 397 shash->tfm = c->hmac_tfm; 398 399 err = crypto_shash_init(shash); 400 if (err) 401 return err; 402 403 /* behind common node header CRC up to HMAC begin */ 404 err = crypto_shash_update(shash, node + 8, ofs_hmac - 8); 405 if (err < 0) 406 return err; 407 408 /* behind HMAC, if any */ 409 if (len - ofs_hmac - hmac_len > 0) { 410 err = crypto_shash_update(shash, node + ofs_hmac + hmac_len, 411 len - ofs_hmac - hmac_len); 412 if (err < 0) 413 return err; 414 } 415 416 return crypto_shash_final(shash, hmac); 417 } 418 419 /** 420 * __ubifs_node_insert_hmac - insert a HMAC into a UBIFS node 421 * @c: UBIFS file-system description object 422 * @node: the node to insert a HMAC into. 423 * @len: the length of the node 424 * @ofs_hmac: the offset in the node where the HMAC is inserted 425 * 426 * This function inserts a HMAC at offset @ofs_hmac into the node given in 427 * @node. 428 * 429 * This function returns 0 for success or a negative error code otherwise. 430 */ 431 int __ubifs_node_insert_hmac(const struct ubifs_info *c, void *node, int len, 432 int ofs_hmac) 433 { 434 return ubifs_node_calc_hmac(c, node, len, ofs_hmac, node + ofs_hmac); 435 } 436 437 /** 438 * __ubifs_node_verify_hmac - verify the HMAC of UBIFS node 439 * @c: UBIFS file-system description object 440 * @node: the node to insert a HMAC into. 441 * @len: the length of the node 442 * @ofs_hmac: the offset in the node where the HMAC is inserted 443 * 444 * This function verifies the HMAC at offset @ofs_hmac of the node given in 445 * @node. Returns 0 if successful or a negative error code otherwise. 446 */ 447 int __ubifs_node_verify_hmac(const struct ubifs_info *c, const void *node, 448 int len, int ofs_hmac) 449 { 450 int hmac_len = c->hmac_desc_len; 451 u8 *hmac; 452 int err; 453 454 hmac = kmalloc(hmac_len, GFP_NOFS); 455 if (!hmac) 456 return -ENOMEM; 457 458 err = ubifs_node_calc_hmac(c, node, len, ofs_hmac, hmac); 459 if (err) { 460 kfree(hmac); 461 return err; 462 } 463 464 err = crypto_memneq(hmac, node + ofs_hmac, hmac_len); 465 466 kfree(hmac); 467 468 if (!err) 469 return 0; 470 471 return -EPERM; 472 } 473 474 int __ubifs_shash_copy_state(const struct ubifs_info *c, struct shash_desc *src, 475 struct shash_desc *target) 476 { 477 u8 *state; 478 int err; 479 480 state = kmalloc(crypto_shash_descsize(src->tfm), GFP_NOFS); 481 if (!state) 482 return -ENOMEM; 483 484 err = crypto_shash_export(src, state); 485 if (err) 486 goto out; 487 488 err = crypto_shash_import(target, state); 489 490 out: 491 kfree(state); 492 493 return err; 494 } 495 496 /** 497 * ubifs_hmac_wkm - Create a HMAC of the well known message 498 * @c: UBIFS file-system description object 499 * @hmac: The HMAC of the well known message 500 * 501 * This function creates a HMAC of a well known message. This is used 502 * to check if the provided key is suitable to authenticate a UBIFS 503 * image. This is only a convenience to the user to provide a better 504 * error message when the wrong key is provided. 505 * 506 * This function returns 0 for success or a negative error code otherwise. 507 */ 508 int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac) 509 { 510 SHASH_DESC_ON_STACK(shash, c->hmac_tfm); 511 int err; 512 const char well_known_message[] = "UBIFS"; 513 514 if (!ubifs_authenticated(c)) 515 return 0; 516 517 shash->tfm = c->hmac_tfm; 518 519 err = crypto_shash_init(shash); 520 if (err) 521 return err; 522 523 err = crypto_shash_update(shash, well_known_message, 524 sizeof(well_known_message) - 1); 525 if (err < 0) 526 return err; 527 528 err = crypto_shash_final(shash, hmac); 529 if (err) 530 return err; 531 return 0; 532 } 533 534 /* 535 * ubifs_hmac_zero - test if a HMAC is zero 536 * @c: UBIFS file-system description object 537 * @hmac: the HMAC to test 538 * 539 * This function tests if a HMAC is zero and returns true if it is 540 * and false otherwise. 541 */ 542 bool ubifs_hmac_zero(struct ubifs_info *c, const u8 *hmac) 543 { 544 return !memchr_inv(hmac, 0, c->hmac_desc_len); 545 } 546