531 lines · c
1// SPDX-License-Identifier: GPL-2.02/*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 support10 */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 node22 * @c: UBIFS file-system description object23 * @node: the node to calculate a hash for24 * @hash: the returned hash25 *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 hash39 * @c: UBIFS file-system description object40 * @hash: the node to calculate a HMAC for41 * @hmac: the returned HMAC42 *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 node53 * @c: UBIFS file-system description object54 * @node: the node to calculate a hash for55 * @inhash: input hash of previous nodes56 *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 node115 * @c: UBIFS file-system description object116 *117 * This function returns a descriptor suitable for hashing a node. Free after use118 * 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 mismatches127 * @c: UBIFS file-system description object128 * @node: the node129 * @hash: the expected hash130 * @lnum: the LEB @node was read from131 * @offs: offset in LEB @node was read from132 *133 * This function reports a hash mismatch when a node has a different hash than134 * 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 hash154 * @c: UBIFS file-system description object155 * @node: the node156 * @expected: the expected hash157 *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 a160 * 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 superblock180 * @c: UBIFS file-system description object181 * @sup: The superblock node182 *183 * To support offline signed images the superblock can be signed with a184 * PKCS#7 signature. The signature is placed directly behind the superblock185 * node in an ubifs_sig_node.186 *187 * Returns 0 when the signature can be successfully verified or a negative188 * 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 else241 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 support251 * @c: UBIFS file-system description object252 *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 resource361 * @c: UBIFS file-system description object362 *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 node377 * @c: UBIFS file-system description object378 * @node: the node to insert a HMAC into.379 * @len: the length of the node380 * @ofs_hmac: the offset in the node where the HMAC is inserted381 * @hmac: returned HMAC382 *383 * This function calculates a HMAC of a UBIFS node. The HMAC is expected to be384 * embedded into the node, so this area is not covered by the HMAC. Also not385 * 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 node421 * @c: UBIFS file-system description object422 * @node: the node to insert a HMAC into.423 * @len: the length of the node424 * @ofs_hmac: the offset in the node where the HMAC is inserted425 *426 * This function inserts a HMAC at offset @ofs_hmac into the node given in427 * @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 node439 * @c: UBIFS file-system description object440 * @node: the node to insert a HMAC into.441 * @len: the length of the node442 * @ofs_hmac: the offset in the node where the HMAC is inserted443 *444 * This function verifies the HMAC at offset @ofs_hmac of the node given in445 * @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 message498 * @c: UBIFS file-system description object499 * @hmac: The HMAC of the well known message500 *501 * This function creates a HMAC of a well known message. This is used502 * to check if the provided key is suitable to authenticate a UBIFS503 * image. This is only a convenience to the user to provide a better504 * 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 zero521 * @c: UBIFS file-system description object522 * @hmac: the HMAC to test523 *524 * This function tests if a HMAC is zero and returns true if it is525 * 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