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/verification.h> 13#include <crypto/hash.h> 14#include <crypto/utils.h> 15#include <keys/user-type.h> 16#include <keys/asymmetric-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 */ 28int __ubifs_node_calc_hash(const struct ubifs_info *c, const void *node, 29 u8 *hash) 30{ 31 const struct ubifs_ch *ch = node; 32 33 return crypto_shash_tfm_digest(c->hash_tfm, node, le32_to_cpu(ch->len), 34 hash); 35} 36 37/** 38 * ubifs_hash_calc_hmac - calculate a HMAC from a hash 39 * @c: UBIFS file-system description object 40 * @hash: the node to calculate a HMAC for 41 * @hmac: the returned HMAC 42 * 43 * Returns 0 for success or a negative error code otherwise. 44 */ 45static int ubifs_hash_calc_hmac(const struct ubifs_info *c, const u8 *hash, 46 u8 *hmac) 47{ 48 return crypto_shash_tfm_digest(c->hmac_tfm, hash, c->hash_len, hmac); 49} 50 51/** 52 * ubifs_prepare_auth_node - Prepare an authentication node 53 * @c: UBIFS file-system description object 54 * @node: the node to calculate a hash for 55 * @inhash: input hash of previous nodes 56 * 57 * This function prepares an authentication node for writing onto flash. 58 * It creates a HMAC from the given input hash and writes it to the node. 59 * 60 * Returns 0 for success or a negative error code otherwise. 61 */ 62int ubifs_prepare_auth_node(struct ubifs_info *c, void *node, 63 struct shash_desc *inhash) 64{ 65 struct ubifs_auth_node *auth = node; 66 u8 hash[UBIFS_HASH_ARR_SZ]; 67 int err; 68 69 { 70 SHASH_DESC_ON_STACK(hash_desc, c->hash_tfm); 71 72 hash_desc->tfm = c->hash_tfm; 73 ubifs_shash_copy_state(c, inhash, hash_desc); 74 75 err = crypto_shash_final(hash_desc, hash); 76 if (err) 77 return err; 78 } 79 80 err = ubifs_hash_calc_hmac(c, hash, auth->hmac); 81 if (err) 82 return err; 83 84 auth->ch.node_type = UBIFS_AUTH_NODE; 85 ubifs_prepare_node(c, auth, ubifs_auth_node_sz(c), 0); 86 return 0; 87} 88 89static struct shash_desc *ubifs_get_desc(const struct ubifs_info *c, 90 struct crypto_shash *tfm) 91{ 92 struct shash_desc *desc; 93 int err; 94 95 if (!ubifs_authenticated(c)) 96 return NULL; 97 98 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL); 99 if (!desc) 100 return ERR_PTR(-ENOMEM); 101 102 desc->tfm = tfm; 103 104 err = crypto_shash_init(desc); 105 if (err) { 106 kfree(desc); 107 return ERR_PTR(err); 108 } 109 110 return desc; 111} 112 113/** 114 * __ubifs_hash_get_desc - get a descriptor suitable for hashing a node 115 * @c: UBIFS file-system description object 116 * 117 * This function returns a descriptor suitable for hashing a node. Free after use 118 * with kfree. 119 */ 120struct shash_desc *__ubifs_hash_get_desc(const struct ubifs_info *c) 121{ 122 return ubifs_get_desc(c, c->hash_tfm); 123} 124 125/** 126 * ubifs_bad_hash - Report hash mismatches 127 * @c: UBIFS file-system description object 128 * @node: the node 129 * @hash: the expected hash 130 * @lnum: the LEB @node was read from 131 * @offs: offset in LEB @node was read from 132 * 133 * This function reports a hash mismatch when a node has a different hash than 134 * expected. 135 */ 136void ubifs_bad_hash(const struct ubifs_info *c, const void *node, const u8 *hash, 137 int lnum, int offs) 138{ 139 int len = min(c->hash_len, 20); 140 int cropped = len != c->hash_len; 141 const char *cont = cropped ? "..." : ""; 142 143 u8 calc[UBIFS_HASH_ARR_SZ]; 144 145 __ubifs_node_calc_hash(c, node, calc); 146 147 ubifs_err(c, "hash mismatch on node at LEB %d:%d", lnum, offs); 148 ubifs_err(c, "hash expected: %*ph%s", len, hash, cont); 149 ubifs_err(c, "hash calculated: %*ph%s", len, calc, cont); 150} 151 152/** 153 * __ubifs_node_check_hash - check the hash of a node against given hash 154 * @c: UBIFS file-system description object 155 * @node: the node 156 * @expected: the expected hash 157 * 158 * This function calculates a hash over a node and compares it to the given hash. 159 * Returns 0 if both hashes are equal or authentication is disabled, otherwise a 160 * negative error code is returned. 161 */ 162int __ubifs_node_check_hash(const struct ubifs_info *c, const void *node, 163 const u8 *expected) 164{ 165 u8 calc[UBIFS_HASH_ARR_SZ]; 166 int err; 167 168 err = __ubifs_node_calc_hash(c, node, calc); 169 if (err) 170 return err; 171 172 if (ubifs_check_hash(c, expected, calc)) 173 return -EPERM; 174 175 return 0; 176} 177 178/** 179 * ubifs_sb_verify_signature - verify the signature of a superblock 180 * @c: UBIFS file-system description object 181 * @sup: The superblock node 182 * 183 * To support offline signed images the superblock can be signed with a 184 * PKCS#7 signature. The signature is placed directly behind the superblock 185 * node in an ubifs_sig_node. 186 * 187 * Returns 0 when the signature can be successfully verified or a negative 188 * error code if not. 189 */ 190int ubifs_sb_verify_signature(struct ubifs_info *c, 191 const struct ubifs_sb_node *sup) 192{ 193 int err; 194 struct ubifs_scan_leb *sleb; 195 struct ubifs_scan_node *snod; 196 const struct ubifs_sig_node *signode; 197 198 sleb = ubifs_scan(c, UBIFS_SB_LNUM, UBIFS_SB_NODE_SZ, c->sbuf, 0); 199 if (IS_ERR(sleb)) { 200 err = PTR_ERR(sleb); 201 return err; 202 } 203 204 if (sleb->nodes_cnt == 0) { 205 ubifs_err(c, "Unable to find signature node"); 206 err = -EINVAL; 207 goto out_destroy; 208 } 209 210 snod = list_first_entry(&sleb->nodes, struct ubifs_scan_node, list); 211 212 if (snod->type != UBIFS_SIG_NODE) { 213 ubifs_err(c, "Signature node is of wrong type"); 214 err = -EINVAL; 215 goto out_destroy; 216 } 217 218 signode = snod->node; 219 220 if (le32_to_cpu(signode->len) > snod->len + sizeof(struct ubifs_sig_node)) { 221 ubifs_err(c, "invalid signature len %d", le32_to_cpu(signode->len)); 222 err = -EINVAL; 223 goto out_destroy; 224 } 225 226 if (le32_to_cpu(signode->type) != UBIFS_SIGNATURE_TYPE_PKCS7) { 227 ubifs_err(c, "Signature type %d is not supported\n", 228 le32_to_cpu(signode->type)); 229 err = -EINVAL; 230 goto out_destroy; 231 } 232 233 err = verify_pkcs7_signature(sup, sizeof(struct ubifs_sb_node), 234 signode->sig, le32_to_cpu(signode->len), 235 NULL, VERIFYING_UNSPECIFIED_SIGNATURE, 236 NULL, NULL); 237 238 if (err) 239 ubifs_err(c, "Failed to verify signature"); 240 else 241 ubifs_msg(c, "Successfully verified super block signature"); 242 243out_destroy: 244 ubifs_scan_destroy(sleb); 245 246 return err; 247} 248 249/** 250 * ubifs_init_authentication - initialize UBIFS authentication support 251 * @c: UBIFS file-system description object 252 * 253 * This function returns 0 for success or a negative error code otherwise. 254 */ 255int ubifs_init_authentication(struct ubifs_info *c) 256{ 257 struct key *keyring_key; 258 const struct user_key_payload *ukp; 259 int err; 260 char hmac_name[CRYPTO_MAX_ALG_NAME]; 261 262 if (!c->auth_hash_name) { 263 ubifs_err(c, "authentication hash name needed with authentication"); 264 return -EINVAL; 265 } 266 267 c->auth_hash_algo = match_string(hash_algo_name, HASH_ALGO__LAST, 268 c->auth_hash_name); 269 if ((int)c->auth_hash_algo < 0) { 270 ubifs_err(c, "Unknown hash algo %s specified", 271 c->auth_hash_name); 272 return -EINVAL; 273 } 274 275 snprintf(hmac_name, CRYPTO_MAX_ALG_NAME, "hmac(%s)", 276 c->auth_hash_name); 277 278 keyring_key = request_key(&key_type_logon, c->auth_key_name, NULL); 279 280 if (IS_ERR(keyring_key)) { 281 ubifs_err(c, "Failed to request key: %ld", 282 PTR_ERR(keyring_key)); 283 return PTR_ERR(keyring_key); 284 } 285 286 down_read(&keyring_key->sem); 287 288 if (keyring_key->type != &key_type_logon) { 289 ubifs_err(c, "key type must be logon"); 290 err = -ENOKEY; 291 goto out; 292 } 293 294 ukp = user_key_payload_locked(keyring_key); 295 if (!ukp) { 296 /* key was revoked before we acquired its semaphore */ 297 err = -EKEYREVOKED; 298 goto out; 299 } 300 301 c->hash_tfm = crypto_alloc_shash(c->auth_hash_name, 0, 0); 302 if (IS_ERR(c->hash_tfm)) { 303 err = PTR_ERR(c->hash_tfm); 304 ubifs_err(c, "Can not allocate %s: %d", 305 c->auth_hash_name, err); 306 goto out; 307 } 308 309 c->hash_len = crypto_shash_digestsize(c->hash_tfm); 310 if (c->hash_len > UBIFS_HASH_ARR_SZ) { 311 ubifs_err(c, "hash %s is bigger than maximum allowed hash size (%d > %d)", 312 c->auth_hash_name, c->hash_len, UBIFS_HASH_ARR_SZ); 313 err = -EINVAL; 314 goto out_free_hash; 315 } 316 317 c->hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0); 318 if (IS_ERR(c->hmac_tfm)) { 319 err = PTR_ERR(c->hmac_tfm); 320 ubifs_err(c, "Can not allocate %s: %d", hmac_name, err); 321 goto out_free_hash; 322 } 323 324 c->hmac_desc_len = crypto_shash_digestsize(c->hmac_tfm); 325 if (c->hmac_desc_len > UBIFS_HMAC_ARR_SZ) { 326 ubifs_err(c, "hmac %s is bigger than maximum allowed hmac size (%d > %d)", 327 hmac_name, c->hmac_desc_len, UBIFS_HMAC_ARR_SZ); 328 err = -EINVAL; 329 goto out_free_hmac; 330 } 331 332 err = crypto_shash_setkey(c->hmac_tfm, ukp->data, ukp->datalen); 333 if (err) 334 goto out_free_hmac; 335 336 c->authenticated = true; 337 338 c->log_hash = ubifs_hash_get_desc(c); 339 if (IS_ERR(c->log_hash)) { 340 err = PTR_ERR(c->log_hash); 341 goto out_free_hmac; 342 } 343 344 err = 0; 345 346out_free_hmac: 347 if (err) 348 crypto_free_shash(c->hmac_tfm); 349out_free_hash: 350 if (err) 351 crypto_free_shash(c->hash_tfm); 352out: 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 */ 365void __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 */ 387static 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 */ 431int __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 */ 447int __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 474int __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 490out: 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 */ 508int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac) 509{ 510 const char well_known_message[] = "UBIFS"; 511 512 if (!ubifs_authenticated(c)) 513 return 0; 514 515 return crypto_shash_tfm_digest(c->hmac_tfm, well_known_message, 516 sizeof(well_known_message) - 1, hmac); 517} 518 519/* 520 * ubifs_hmac_zero - test if a HMAC is zero 521 * @c: UBIFS file-system description object 522 * @hmac: the HMAC to test 523 * 524 * This function tests if a HMAC is zero and returns true if it is 525 * and false otherwise. 526 */ 527bool ubifs_hmac_zero(struct ubifs_info *c, const u8 *hmac) 528{ 529 return !memchr_inv(hmac, 0, c->hmac_desc_len); 530} 531