Sascha Hauer | 49525e5 | 2018-09-07 14:36:32 +0200 | [diff] [blame] | 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; |
Sascha Hauer | 49525e5 | 2018-09-07 14:36:32 +0200 | [diff] [blame] | 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; |
Sascha Hauer | 49525e5 | 2018-09-07 14:36:32 +0200 | [diff] [blame] | 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 | { |
Sascha Hauer | 49525e5 | 2018-09-07 14:36:32 +0200 | [diff] [blame] | 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 | |
Arnd Bergmann | f4844b3 | 2019-03-24 20:44:51 +0100 | [diff] [blame] | 87 | { |
| 88 | SHASH_DESC_ON_STACK(hash_desc, c->hash_tfm); |
Sascha Hauer | 49525e5 | 2018-09-07 14:36:32 +0200 | [diff] [blame] | 89 | |
Arnd Bergmann | f4844b3 | 2019-03-24 20:44:51 +0100 | [diff] [blame] | 90 | hash_desc->tfm = c->hash_tfm; |
Arnd Bergmann | f4844b3 | 2019-03-24 20:44:51 +0100 | [diff] [blame] | 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 | } |
Sascha Hauer | 49525e5 | 2018-09-07 14:36:32 +0200 | [diff] [blame] | 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; |
Sascha Hauer | 49525e5 | 2018-09-07 14:36:32 +0200 | [diff] [blame] | 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 | /** |
Sascha Hauer | 49525e5 | 2018-09-07 14:36:32 +0200 | [diff] [blame] | 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 | |
David Howells | 2e12256 | 2019-06-27 23:03:07 +0100 | [diff] [blame^] | 230 | keyring_key = request_key(&key_type_logon, c->auth_key_name, NULL, NULL); |
Sascha Hauer | 49525e5 | 2018-09-07 14:36:32 +0200 | [diff] [blame] | 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 | |
Eric Biggers | 3d234b3 | 2018-11-14 12:21:11 -0800 | [diff] [blame] | 253 | c->hash_tfm = crypto_alloc_shash(c->auth_hash_name, 0, 0); |
Sascha Hauer | 49525e5 | 2018-09-07 14:36:32 +0200 | [diff] [blame] | 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 | |
Eric Biggers | 3d234b3 | 2018-11-14 12:21:11 -0800 | [diff] [blame] | 269 | c->hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0); |
Sascha Hauer | 49525e5 | 2018-09-07 14:36:32 +0200 | [diff] [blame] | 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; |
Sascha Hauer | 49525e5 | 2018-09-07 14:36:32 +0200 | [diff] [blame] | 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; |
Sascha Hauer | 49525e5 | 2018-09-07 14:36:32 +0200 | [diff] [blame] | 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 | } |