1 // SPDX-License-Identifier: GPL-2.0
3 * This file is part of UBIFS.
5 * Copyright (C) 2018 Pengutronix, Sascha Hauer <s.hauer@pengutronix.de>
9 * This file implements various helper functions for UBIFS authentication support
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>
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
26 * Returns 0 for success or a negative error code otherwise.
28 int __ubifs_node_calc_hash(const struct ubifs_info *c, const void *node,
31 const struct ubifs_ch *ch = node;
32 SHASH_DESC_ON_STACK(shash, c->hash_tfm);
35 shash->tfm = c->hash_tfm;
36 shash->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
38 err = crypto_shash_digest(shash, node, le32_to_cpu(ch->len), hash);
45 * ubifs_hash_calc_hmac - calculate a HMAC from a hash
46 * @c: UBIFS file-system description object
47 * @hash: the node to calculate a HMAC for
48 * @hmac: the returned HMAC
50 * Returns 0 for success or a negative error code otherwise.
52 static int ubifs_hash_calc_hmac(const struct ubifs_info *c, const u8 *hash,
55 SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
58 shash->tfm = c->hmac_tfm;
59 shash->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
61 err = crypto_shash_digest(shash, hash, c->hash_len, hmac);
68 * ubifs_prepare_auth_node - Prepare an authentication node
69 * @c: UBIFS file-system description object
70 * @node: the node to calculate a hash for
71 * @hash: input hash of previous nodes
73 * This function prepares an authentication node for writing onto flash.
74 * It creates a HMAC from the given input hash and writes it to the node.
76 * Returns 0 for success or a negative error code otherwise.
78 int ubifs_prepare_auth_node(struct ubifs_info *c, void *node,
79 struct shash_desc *inhash)
81 SHASH_DESC_ON_STACK(hash_desc, c->hash_tfm);
82 struct ubifs_auth_node *auth = node;
86 hash = kmalloc(crypto_shash_descsize(c->hash_tfm), GFP_NOFS);
90 hash_desc->tfm = c->hash_tfm;
91 hash_desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
92 ubifs_shash_copy_state(c, inhash, hash_desc);
94 err = crypto_shash_final(hash_desc, hash);
98 err = ubifs_hash_calc_hmac(c, hash, auth->hmac);
102 auth->ch.node_type = UBIFS_AUTH_NODE;
103 ubifs_prepare_node(c, auth, ubifs_auth_node_sz(c), 0);
112 static struct shash_desc *ubifs_get_desc(const struct ubifs_info *c,
113 struct crypto_shash *tfm)
115 struct shash_desc *desc;
118 if (!ubifs_authenticated(c))
121 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL);
123 return ERR_PTR(-ENOMEM);
126 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
128 err = crypto_shash_init(desc);
138 * __ubifs_hash_get_desc - get a descriptor suitable for hashing a node
139 * @c: UBIFS file-system description object
141 * This function returns a descriptor suitable for hashing a node. Free after use
144 struct shash_desc *__ubifs_hash_get_desc(const struct ubifs_info *c)
146 return ubifs_get_desc(c, c->hash_tfm);
150 * ubifs_bad_hash - Report hash mismatches
151 * @c: UBIFS file-system description object
153 * @hash: the expected hash
154 * @lnum: the LEB @node was read from
155 * @offs: offset in LEB @node was read from
157 * This function reports a hash mismatch when a node has a different hash than
160 void ubifs_bad_hash(const struct ubifs_info *c, const void *node, const u8 *hash,
163 int len = min(c->hash_len, 20);
164 int cropped = len != c->hash_len;
165 const char *cont = cropped ? "..." : "";
167 u8 calc[UBIFS_HASH_ARR_SZ];
169 __ubifs_node_calc_hash(c, node, calc);
171 ubifs_err(c, "hash mismatch on node at LEB %d:%d", lnum, offs);
172 ubifs_err(c, "hash expected: %*ph%s", len, hash, cont);
173 ubifs_err(c, "hash calculated: %*ph%s", len, calc, cont);
177 * __ubifs_node_check_hash - check the hash of a node against given hash
178 * @c: UBIFS file-system description object
180 * @expected: the expected hash
182 * This function calculates a hash over a node and compares it to the given hash.
183 * Returns 0 if both hashes are equal or authentication is disabled, otherwise a
184 * negative error code is returned.
186 int __ubifs_node_check_hash(const struct ubifs_info *c, const void *node,
189 u8 calc[UBIFS_HASH_ARR_SZ];
192 err = __ubifs_node_calc_hash(c, node, calc);
196 if (ubifs_check_hash(c, expected, calc))
203 * ubifs_init_authentication - initialize UBIFS authentication support
204 * @c: UBIFS file-system description object
206 * This function returns 0 for success or a negative error code otherwise.
208 int ubifs_init_authentication(struct ubifs_info *c)
210 struct key *keyring_key;
211 const struct user_key_payload *ukp;
213 char hmac_name[CRYPTO_MAX_ALG_NAME];
215 if (!c->auth_hash_name) {
216 ubifs_err(c, "authentication hash name needed with authentication");
220 c->auth_hash_algo = match_string(hash_algo_name, HASH_ALGO__LAST,
222 if ((int)c->auth_hash_algo < 0) {
223 ubifs_err(c, "Unknown hash algo %s specified",
228 snprintf(hmac_name, CRYPTO_MAX_ALG_NAME, "hmac(%s)",
231 keyring_key = request_key(&key_type_logon, c->auth_key_name, NULL);
233 if (IS_ERR(keyring_key)) {
234 ubifs_err(c, "Failed to request key: %ld",
235 PTR_ERR(keyring_key));
236 return PTR_ERR(keyring_key);
239 down_read(&keyring_key->sem);
241 if (keyring_key->type != &key_type_logon) {
242 ubifs_err(c, "key type must be logon");
247 ukp = user_key_payload_locked(keyring_key);
249 /* key was revoked before we acquired its semaphore */
254 c->hash_tfm = crypto_alloc_shash(c->auth_hash_name, 0, 0);
255 if (IS_ERR(c->hash_tfm)) {
256 err = PTR_ERR(c->hash_tfm);
257 ubifs_err(c, "Can not allocate %s: %d",
258 c->auth_hash_name, err);
262 c->hash_len = crypto_shash_digestsize(c->hash_tfm);
263 if (c->hash_len > UBIFS_HASH_ARR_SZ) {
264 ubifs_err(c, "hash %s is bigger than maximum allowed hash size (%d > %d)",
265 c->auth_hash_name, c->hash_len, UBIFS_HASH_ARR_SZ);
270 c->hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0);
271 if (IS_ERR(c->hmac_tfm)) {
272 err = PTR_ERR(c->hmac_tfm);
273 ubifs_err(c, "Can not allocate %s: %d", hmac_name, err);
277 c->hmac_desc_len = crypto_shash_digestsize(c->hmac_tfm);
278 if (c->hmac_desc_len > UBIFS_HMAC_ARR_SZ) {
279 ubifs_err(c, "hmac %s is bigger than maximum allowed hmac size (%d > %d)",
280 hmac_name, c->hmac_desc_len, UBIFS_HMAC_ARR_SZ);
285 err = crypto_shash_setkey(c->hmac_tfm, ukp->data, ukp->datalen);
289 c->authenticated = true;
291 c->log_hash = ubifs_hash_get_desc(c);
292 if (IS_ERR(c->log_hash))
299 crypto_free_shash(c->hmac_tfm);
302 crypto_free_shash(c->hash_tfm);
304 up_read(&keyring_key->sem);
305 key_put(keyring_key);
311 * __ubifs_exit_authentication - release resource
312 * @c: UBIFS file-system description object
314 * This function releases the authentication related resources.
316 void __ubifs_exit_authentication(struct ubifs_info *c)
318 if (!ubifs_authenticated(c))
321 crypto_free_shash(c->hmac_tfm);
322 crypto_free_shash(c->hash_tfm);
327 * ubifs_node_calc_hmac - calculate the HMAC of a UBIFS node
328 * @c: UBIFS file-system description object
329 * @node: the node to insert a HMAC into.
330 * @len: the length of the node
331 * @ofs_hmac: the offset in the node where the HMAC is inserted
332 * @hmac: returned HMAC
334 * This function calculates a HMAC of a UBIFS node. The HMAC is expected to be
335 * embedded into the node, so this area is not covered by the HMAC. Also not
336 * covered is the UBIFS_NODE_MAGIC and the CRC of the node.
338 static int ubifs_node_calc_hmac(const struct ubifs_info *c, const void *node,
339 int len, int ofs_hmac, void *hmac)
341 SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
342 int hmac_len = c->hmac_desc_len;
345 ubifs_assert(c, ofs_hmac > 8);
346 ubifs_assert(c, ofs_hmac + hmac_len < len);
348 shash->tfm = c->hmac_tfm;
349 shash->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
351 err = crypto_shash_init(shash);
355 /* behind common node header CRC up to HMAC begin */
356 err = crypto_shash_update(shash, node + 8, ofs_hmac - 8);
360 /* behind HMAC, if any */
361 if (len - ofs_hmac - hmac_len > 0) {
362 err = crypto_shash_update(shash, node + ofs_hmac + hmac_len,
363 len - ofs_hmac - hmac_len);
368 return crypto_shash_final(shash, hmac);
372 * __ubifs_node_insert_hmac - insert a HMAC into a UBIFS node
373 * @c: UBIFS file-system description object
374 * @node: the node to insert a HMAC into.
375 * @len: the length of the node
376 * @ofs_hmac: the offset in the node where the HMAC is inserted
378 * This function inserts a HMAC at offset @ofs_hmac into the node given in
381 * This function returns 0 for success or a negative error code otherwise.
383 int __ubifs_node_insert_hmac(const struct ubifs_info *c, void *node, int len,
386 return ubifs_node_calc_hmac(c, node, len, ofs_hmac, node + ofs_hmac);
390 * __ubifs_node_verify_hmac - verify the HMAC of UBIFS node
391 * @c: UBIFS file-system description object
392 * @node: the node to insert a HMAC into.
393 * @len: the length of the node
394 * @ofs_hmac: the offset in the node where the HMAC is inserted
396 * This function verifies the HMAC at offset @ofs_hmac of the node given in
397 * @node. Returns 0 if successful or a negative error code otherwise.
399 int __ubifs_node_verify_hmac(const struct ubifs_info *c, const void *node,
400 int len, int ofs_hmac)
402 int hmac_len = c->hmac_desc_len;
406 hmac = kmalloc(hmac_len, GFP_NOFS);
410 err = ubifs_node_calc_hmac(c, node, len, ofs_hmac, hmac);
414 err = crypto_memneq(hmac, node + ofs_hmac, hmac_len);
424 int __ubifs_shash_copy_state(const struct ubifs_info *c, struct shash_desc *src,
425 struct shash_desc *target)
430 state = kmalloc(crypto_shash_descsize(src->tfm), GFP_NOFS);
434 err = crypto_shash_export(src, state);
438 err = crypto_shash_import(target, state);
447 * ubifs_hmac_wkm - Create a HMAC of the well known message
448 * @c: UBIFS file-system description object
449 * @hmac: The HMAC of the well known message
451 * This function creates a HMAC of a well known message. This is used
452 * to check if the provided key is suitable to authenticate a UBIFS
453 * image. This is only a convenience to the user to provide a better
454 * error message when the wrong key is provided.
456 * This function returns 0 for success or a negative error code otherwise.
458 int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac)
460 SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
462 const char well_known_message[] = "UBIFS";
464 if (!ubifs_authenticated(c))
467 shash->tfm = c->hmac_tfm;
468 shash->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
470 err = crypto_shash_init(shash);
474 err = crypto_shash_update(shash, well_known_message,
475 sizeof(well_known_message) - 1);
479 err = crypto_shash_final(shash, hmac);