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 <linux/verification.h>
14 #include <crypto/hash.h>
15 #include <crypto/algapi.h>
16 #include <keys/user-type.h>
17 #include <keys/asymmetric-type.h>
22 * ubifs_node_calc_hash - calculate the hash of a UBIFS node
23 * @c: UBIFS file-system description object
24 * @node: the node to calculate a hash for
25 * @hash: the returned hash
27 * Returns 0 for success or a negative error code otherwise.
29 int __ubifs_node_calc_hash(const struct ubifs_info
*c
, const void *node
,
32 const struct ubifs_ch
*ch
= node
;
34 return crypto_shash_tfm_digest(c
->hash_tfm
, node
, le32_to_cpu(ch
->len
),
39 * ubifs_hash_calc_hmac - calculate a HMAC from a hash
40 * @c: UBIFS file-system description object
41 * @hash: the node to calculate a HMAC for
42 * @hmac: the returned HMAC
44 * Returns 0 for success or a negative error code otherwise.
46 static int ubifs_hash_calc_hmac(const struct ubifs_info
*c
, const u8
*hash
,
49 return crypto_shash_tfm_digest(c
->hmac_tfm
, hash
, c
->hash_len
, hmac
);
53 * ubifs_prepare_auth_node - Prepare an authentication node
54 * @c: UBIFS file-system description object
55 * @node: the node to calculate a hash for
56 * @inhash: input hash of previous nodes
58 * This function prepares an authentication node for writing onto flash.
59 * It creates a HMAC from the given input hash and writes it to the node.
61 * Returns 0 for success or a negative error code otherwise.
63 int ubifs_prepare_auth_node(struct ubifs_info
*c
, void *node
,
64 struct shash_desc
*inhash
)
66 struct ubifs_auth_node
*auth
= node
;
67 u8 hash
[UBIFS_HASH_ARR_SZ
];
71 SHASH_DESC_ON_STACK(hash_desc
, c
->hash_tfm
);
73 hash_desc
->tfm
= c
->hash_tfm
;
74 ubifs_shash_copy_state(c
, inhash
, hash_desc
);
76 err
= crypto_shash_final(hash_desc
, hash
);
81 err
= ubifs_hash_calc_hmac(c
, hash
, auth
->hmac
);
85 auth
->ch
.node_type
= UBIFS_AUTH_NODE
;
86 ubifs_prepare_node(c
, auth
, ubifs_auth_node_sz(c
), 0);
90 static struct shash_desc
*ubifs_get_desc(const struct ubifs_info
*c
,
91 struct crypto_shash
*tfm
)
93 struct shash_desc
*desc
;
96 if (!ubifs_authenticated(c
))
99 desc
= kmalloc(sizeof(*desc
) + crypto_shash_descsize(tfm
), GFP_KERNEL
);
101 return ERR_PTR(-ENOMEM
);
105 err
= crypto_shash_init(desc
);
115 * __ubifs_hash_get_desc - get a descriptor suitable for hashing a node
116 * @c: UBIFS file-system description object
118 * This function returns a descriptor suitable for hashing a node. Free after use
121 struct shash_desc
*__ubifs_hash_get_desc(const struct ubifs_info
*c
)
123 return ubifs_get_desc(c
, c
->hash_tfm
);
127 * ubifs_bad_hash - Report hash mismatches
128 * @c: UBIFS file-system description object
130 * @hash: the expected hash
131 * @lnum: the LEB @node was read from
132 * @offs: offset in LEB @node was read from
134 * This function reports a hash mismatch when a node has a different hash than
137 void ubifs_bad_hash(const struct ubifs_info
*c
, const void *node
, const u8
*hash
,
140 int len
= min(c
->hash_len
, 20);
141 int cropped
= len
!= c
->hash_len
;
142 const char *cont
= cropped
? "..." : "";
144 u8 calc
[UBIFS_HASH_ARR_SZ
];
146 __ubifs_node_calc_hash(c
, node
, calc
);
148 ubifs_err(c
, "hash mismatch on node at LEB %d:%d", lnum
, offs
);
149 ubifs_err(c
, "hash expected: %*ph%s", len
, hash
, cont
);
150 ubifs_err(c
, "hash calculated: %*ph%s", len
, calc
, cont
);
154 * __ubifs_node_check_hash - check the hash of a node against given hash
155 * @c: UBIFS file-system description object
157 * @expected: the expected hash
159 * This function calculates a hash over a node and compares it to the given hash.
160 * Returns 0 if both hashes are equal or authentication is disabled, otherwise a
161 * negative error code is returned.
163 int __ubifs_node_check_hash(const struct ubifs_info
*c
, const void *node
,
166 u8 calc
[UBIFS_HASH_ARR_SZ
];
169 err
= __ubifs_node_calc_hash(c
, node
, calc
);
173 if (ubifs_check_hash(c
, expected
, calc
))
180 * ubifs_sb_verify_signature - verify the signature of a superblock
181 * @c: UBIFS file-system description object
182 * @sup: The superblock node
184 * To support offline signed images the superblock can be signed with a
185 * PKCS#7 signature. The signature is placed directly behind the superblock
186 * node in an ubifs_sig_node.
188 * Returns 0 when the signature can be successfully verified or a negative
191 int ubifs_sb_verify_signature(struct ubifs_info
*c
,
192 const struct ubifs_sb_node
*sup
)
195 struct ubifs_scan_leb
*sleb
;
196 struct ubifs_scan_node
*snod
;
197 const struct ubifs_sig_node
*signode
;
199 sleb
= ubifs_scan(c
, UBIFS_SB_LNUM
, UBIFS_SB_NODE_SZ
, c
->sbuf
, 0);
205 if (sleb
->nodes_cnt
== 0) {
206 ubifs_err(c
, "Unable to find signature node");
211 snod
= list_first_entry(&sleb
->nodes
, struct ubifs_scan_node
, list
);
213 if (snod
->type
!= UBIFS_SIG_NODE
) {
214 ubifs_err(c
, "Signature node is of wrong type");
219 signode
= snod
->node
;
221 if (le32_to_cpu(signode
->len
) > snod
->len
+ sizeof(struct ubifs_sig_node
)) {
222 ubifs_err(c
, "invalid signature len %d", le32_to_cpu(signode
->len
));
227 if (le32_to_cpu(signode
->type
) != UBIFS_SIGNATURE_TYPE_PKCS7
) {
228 ubifs_err(c
, "Signature type %d is not supported\n",
229 le32_to_cpu(signode
->type
));
234 err
= verify_pkcs7_signature(sup
, sizeof(struct ubifs_sb_node
),
235 signode
->sig
, le32_to_cpu(signode
->len
),
236 NULL
, VERIFYING_UNSPECIFIED_SIGNATURE
,
240 ubifs_err(c
, "Failed to verify signature");
242 ubifs_msg(c
, "Successfully verified super block signature");
245 ubifs_scan_destroy(sleb
);
251 * ubifs_init_authentication - initialize UBIFS authentication support
252 * @c: UBIFS file-system description object
254 * This function returns 0 for success or a negative error code otherwise.
256 int ubifs_init_authentication(struct ubifs_info
*c
)
258 struct key
*keyring_key
;
259 const struct user_key_payload
*ukp
;
261 char hmac_name
[CRYPTO_MAX_ALG_NAME
];
263 if (!c
->auth_hash_name
) {
264 ubifs_err(c
, "authentication hash name needed with authentication");
268 c
->auth_hash_algo
= match_string(hash_algo_name
, HASH_ALGO__LAST
,
270 if ((int)c
->auth_hash_algo
< 0) {
271 ubifs_err(c
, "Unknown hash algo %s specified",
276 snprintf(hmac_name
, CRYPTO_MAX_ALG_NAME
, "hmac(%s)",
279 keyring_key
= request_key(&key_type_logon
, c
->auth_key_name
, NULL
);
281 if (IS_ERR(keyring_key
)) {
282 ubifs_err(c
, "Failed to request key: %ld",
283 PTR_ERR(keyring_key
));
284 return PTR_ERR(keyring_key
);
287 down_read(&keyring_key
->sem
);
289 if (keyring_key
->type
!= &key_type_logon
) {
290 ubifs_err(c
, "key type must be logon");
295 ukp
= user_key_payload_locked(keyring_key
);
297 /* key was revoked before we acquired its semaphore */
302 c
->hash_tfm
= crypto_alloc_shash(c
->auth_hash_name
, 0, 0);
303 if (IS_ERR(c
->hash_tfm
)) {
304 err
= PTR_ERR(c
->hash_tfm
);
305 ubifs_err(c
, "Can not allocate %s: %d",
306 c
->auth_hash_name
, err
);
310 c
->hash_len
= crypto_shash_digestsize(c
->hash_tfm
);
311 if (c
->hash_len
> UBIFS_HASH_ARR_SZ
) {
312 ubifs_err(c
, "hash %s is bigger than maximum allowed hash size (%d > %d)",
313 c
->auth_hash_name
, c
->hash_len
, UBIFS_HASH_ARR_SZ
);
318 c
->hmac_tfm
= crypto_alloc_shash(hmac_name
, 0, 0);
319 if (IS_ERR(c
->hmac_tfm
)) {
320 err
= PTR_ERR(c
->hmac_tfm
);
321 ubifs_err(c
, "Can not allocate %s: %d", hmac_name
, err
);
325 c
->hmac_desc_len
= crypto_shash_digestsize(c
->hmac_tfm
);
326 if (c
->hmac_desc_len
> UBIFS_HMAC_ARR_SZ
) {
327 ubifs_err(c
, "hmac %s is bigger than maximum allowed hmac size (%d > %d)",
328 hmac_name
, c
->hmac_desc_len
, UBIFS_HMAC_ARR_SZ
);
333 err
= crypto_shash_setkey(c
->hmac_tfm
, ukp
->data
, ukp
->datalen
);
337 c
->authenticated
= true;
339 c
->log_hash
= ubifs_hash_get_desc(c
);
340 if (IS_ERR(c
->log_hash
)) {
341 err
= PTR_ERR(c
->log_hash
);
349 crypto_free_shash(c
->hmac_tfm
);
352 crypto_free_shash(c
->hash_tfm
);
354 up_read(&keyring_key
->sem
);
355 key_put(keyring_key
);
361 * __ubifs_exit_authentication - release resource
362 * @c: UBIFS file-system description object
364 * This function releases the authentication related resources.
366 void __ubifs_exit_authentication(struct ubifs_info
*c
)
368 if (!ubifs_authenticated(c
))
371 crypto_free_shash(c
->hmac_tfm
);
372 crypto_free_shash(c
->hash_tfm
);
377 * ubifs_node_calc_hmac - calculate the HMAC of a UBIFS node
378 * @c: UBIFS file-system description object
379 * @node: the node to insert a HMAC into.
380 * @len: the length of the node
381 * @ofs_hmac: the offset in the node where the HMAC is inserted
382 * @hmac: returned HMAC
384 * This function calculates a HMAC of a UBIFS node. The HMAC is expected to be
385 * embedded into the node, so this area is not covered by the HMAC. Also not
386 * covered is the UBIFS_NODE_MAGIC and the CRC of the node.
388 static int ubifs_node_calc_hmac(const struct ubifs_info
*c
, const void *node
,
389 int len
, int ofs_hmac
, void *hmac
)
391 SHASH_DESC_ON_STACK(shash
, c
->hmac_tfm
);
392 int hmac_len
= c
->hmac_desc_len
;
395 ubifs_assert(c
, ofs_hmac
> 8);
396 ubifs_assert(c
, ofs_hmac
+ hmac_len
< len
);
398 shash
->tfm
= c
->hmac_tfm
;
400 err
= crypto_shash_init(shash
);
404 /* behind common node header CRC up to HMAC begin */
405 err
= crypto_shash_update(shash
, node
+ 8, ofs_hmac
- 8);
409 /* behind HMAC, if any */
410 if (len
- ofs_hmac
- hmac_len
> 0) {
411 err
= crypto_shash_update(shash
, node
+ ofs_hmac
+ hmac_len
,
412 len
- ofs_hmac
- hmac_len
);
417 return crypto_shash_final(shash
, hmac
);
421 * __ubifs_node_insert_hmac - insert a HMAC into a UBIFS node
422 * @c: UBIFS file-system description object
423 * @node: the node to insert a HMAC into.
424 * @len: the length of the node
425 * @ofs_hmac: the offset in the node where the HMAC is inserted
427 * This function inserts a HMAC at offset @ofs_hmac into the node given in
430 * This function returns 0 for success or a negative error code otherwise.
432 int __ubifs_node_insert_hmac(const struct ubifs_info
*c
, void *node
, int len
,
435 return ubifs_node_calc_hmac(c
, node
, len
, ofs_hmac
, node
+ ofs_hmac
);
439 * __ubifs_node_verify_hmac - verify the HMAC of UBIFS node
440 * @c: UBIFS file-system description object
441 * @node: the node to insert a HMAC into.
442 * @len: the length of the node
443 * @ofs_hmac: the offset in the node where the HMAC is inserted
445 * This function verifies the HMAC at offset @ofs_hmac of the node given in
446 * @node. Returns 0 if successful or a negative error code otherwise.
448 int __ubifs_node_verify_hmac(const struct ubifs_info
*c
, const void *node
,
449 int len
, int ofs_hmac
)
451 int hmac_len
= c
->hmac_desc_len
;
455 hmac
= kmalloc(hmac_len
, GFP_NOFS
);
459 err
= ubifs_node_calc_hmac(c
, node
, len
, ofs_hmac
, hmac
);
465 err
= crypto_memneq(hmac
, node
+ ofs_hmac
, hmac_len
);
475 int __ubifs_shash_copy_state(const struct ubifs_info
*c
, struct shash_desc
*src
,
476 struct shash_desc
*target
)
481 state
= kmalloc(crypto_shash_descsize(src
->tfm
), GFP_NOFS
);
485 err
= crypto_shash_export(src
, state
);
489 err
= crypto_shash_import(target
, state
);
498 * ubifs_hmac_wkm - Create a HMAC of the well known message
499 * @c: UBIFS file-system description object
500 * @hmac: The HMAC of the well known message
502 * This function creates a HMAC of a well known message. This is used
503 * to check if the provided key is suitable to authenticate a UBIFS
504 * image. This is only a convenience to the user to provide a better
505 * error message when the wrong key is provided.
507 * This function returns 0 for success or a negative error code otherwise.
509 int ubifs_hmac_wkm(struct ubifs_info
*c
, u8
*hmac
)
511 SHASH_DESC_ON_STACK(shash
, c
->hmac_tfm
);
513 const char well_known_message
[] = "UBIFS";
515 if (!ubifs_authenticated(c
))
518 shash
->tfm
= c
->hmac_tfm
;
520 err
= crypto_shash_init(shash
);
524 err
= crypto_shash_update(shash
, well_known_message
,
525 sizeof(well_known_message
) - 1);
529 err
= crypto_shash_final(shash
, hmac
);
536 * ubifs_hmac_zero - test if a HMAC is zero
537 * @c: UBIFS file-system description object
538 * @hmac: the HMAC to test
540 * This function tests if a HMAC is zero and returns true if it is
541 * and false otherwise.
543 bool ubifs_hmac_zero(struct ubifs_info
*c
, const u8
*hmac
)
545 return !memchr_inv(hmac
, 0, c
->hmac_desc_len
);