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/sha.h>
16 #include <crypto/algapi.h>
17 #include <keys/user-type.h>
18 #include <keys/asymmetric-type.h>
23 * ubifs_node_calc_hash - calculate the hash of a UBIFS node
24 * @c: UBIFS file-system description object
25 * @node: the node to calculate a hash for
26 * @hash: the returned hash
28 * Returns 0 for success or a negative error code otherwise.
30 int __ubifs_node_calc_hash(const struct ubifs_info *c, const void *node,
33 const struct ubifs_ch *ch = node;
34 SHASH_DESC_ON_STACK(shash, c->hash_tfm);
37 shash->tfm = c->hash_tfm;
39 err = crypto_shash_digest(shash, node, le32_to_cpu(ch->len), hash);
46 * ubifs_hash_calc_hmac - calculate a HMAC from a hash
47 * @c: UBIFS file-system description object
48 * @hash: the node to calculate a HMAC for
49 * @hmac: the returned HMAC
51 * Returns 0 for success or a negative error code otherwise.
53 static int ubifs_hash_calc_hmac(const struct ubifs_info *c, const u8 *hash,
56 SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
59 shash->tfm = c->hmac_tfm;
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 struct ubifs_auth_node *auth = node;
82 u8 hash[UBIFS_HASH_ARR_SZ];
86 SHASH_DESC_ON_STACK(hash_desc, c->hash_tfm);
88 hash_desc->tfm = c->hash_tfm;
89 ubifs_shash_copy_state(c, inhash, hash_desc);
91 err = crypto_shash_final(hash_desc, hash);
96 err = ubifs_hash_calc_hmac(c, hash, auth->hmac);
100 auth->ch.node_type = UBIFS_AUTH_NODE;
101 ubifs_prepare_node(c, auth, ubifs_auth_node_sz(c), 0);
105 static struct shash_desc *ubifs_get_desc(const struct ubifs_info *c,
106 struct crypto_shash *tfm)
108 struct shash_desc *desc;
111 if (!ubifs_authenticated(c))
114 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL);
116 return ERR_PTR(-ENOMEM);
120 err = crypto_shash_init(desc);
130 * __ubifs_hash_get_desc - get a descriptor suitable for hashing a node
131 * @c: UBIFS file-system description object
133 * This function returns a descriptor suitable for hashing a node. Free after use
136 struct shash_desc *__ubifs_hash_get_desc(const struct ubifs_info *c)
138 return ubifs_get_desc(c, c->hash_tfm);
142 * ubifs_bad_hash - Report hash mismatches
143 * @c: UBIFS file-system description object
145 * @hash: the expected hash
146 * @lnum: the LEB @node was read from
147 * @offs: offset in LEB @node was read from
149 * This function reports a hash mismatch when a node has a different hash than
152 void ubifs_bad_hash(const struct ubifs_info *c, const void *node, const u8 *hash,
155 int len = min(c->hash_len, 20);
156 int cropped = len != c->hash_len;
157 const char *cont = cropped ? "..." : "";
159 u8 calc[UBIFS_HASH_ARR_SZ];
161 __ubifs_node_calc_hash(c, node, calc);
163 ubifs_err(c, "hash mismatch on node at LEB %d:%d", lnum, offs);
164 ubifs_err(c, "hash expected: %*ph%s", len, hash, cont);
165 ubifs_err(c, "hash calculated: %*ph%s", len, calc, cont);
169 * __ubifs_node_check_hash - check the hash of a node against given hash
170 * @c: UBIFS file-system description object
172 * @expected: the expected hash
174 * This function calculates a hash over a node and compares it to the given hash.
175 * Returns 0 if both hashes are equal or authentication is disabled, otherwise a
176 * negative error code is returned.
178 int __ubifs_node_check_hash(const struct ubifs_info *c, const void *node,
181 u8 calc[UBIFS_HASH_ARR_SZ];
184 err = __ubifs_node_calc_hash(c, node, calc);
188 if (ubifs_check_hash(c, expected, calc))
195 * ubifs_sb_verify_signature - verify the signature of a superblock
196 * @c: UBIFS file-system description object
197 * @sup: The superblock node
199 * To support offline signed images the superblock can be signed with a
200 * PKCS#7 signature. The signature is placed directly behind the superblock
201 * node in an ubifs_sig_node.
203 * Returns 0 when the signature can be successfully verified or a negative
206 int ubifs_sb_verify_signature(struct ubifs_info *c,
207 const struct ubifs_sb_node *sup)
210 struct ubifs_scan_leb *sleb;
211 struct ubifs_scan_node *snod;
212 const struct ubifs_sig_node *signode;
214 sleb = ubifs_scan(c, UBIFS_SB_LNUM, UBIFS_SB_NODE_SZ, c->sbuf, 0);
220 if (sleb->nodes_cnt == 0) {
221 ubifs_err(c, "Unable to find signature node");
226 snod = list_first_entry(&sleb->nodes, struct ubifs_scan_node, list);
228 if (snod->type != UBIFS_SIG_NODE) {
229 ubifs_err(c, "Signature node is of wrong type");
234 signode = snod->node;
236 if (le32_to_cpu(signode->len) > snod->len + sizeof(struct ubifs_sig_node)) {
237 ubifs_err(c, "invalid signature len %d", le32_to_cpu(signode->len));
242 if (le32_to_cpu(signode->type) != UBIFS_SIGNATURE_TYPE_PKCS7) {
243 ubifs_err(c, "Signature type %d is not supported\n",
244 le32_to_cpu(signode->type));
249 err = verify_pkcs7_signature(sup, sizeof(struct ubifs_sb_node),
250 signode->sig, le32_to_cpu(signode->len),
251 NULL, VERIFYING_UNSPECIFIED_SIGNATURE,
255 ubifs_err(c, "Failed to verify signature");
257 ubifs_msg(c, "Successfully verified super block signature");
260 ubifs_scan_destroy(sleb);
266 * ubifs_init_authentication - initialize UBIFS authentication support
267 * @c: UBIFS file-system description object
269 * This function returns 0 for success or a negative error code otherwise.
271 int ubifs_init_authentication(struct ubifs_info *c)
273 struct key *keyring_key;
274 const struct user_key_payload *ukp;
276 char hmac_name[CRYPTO_MAX_ALG_NAME];
278 if (!c->auth_hash_name) {
279 ubifs_err(c, "authentication hash name needed with authentication");
283 c->auth_hash_algo = match_string(hash_algo_name, HASH_ALGO__LAST,
285 if ((int)c->auth_hash_algo < 0) {
286 ubifs_err(c, "Unknown hash algo %s specified",
291 snprintf(hmac_name, CRYPTO_MAX_ALG_NAME, "hmac(%s)",
294 keyring_key = request_key(&key_type_logon, c->auth_key_name, NULL);
296 if (IS_ERR(keyring_key)) {
297 ubifs_err(c, "Failed to request key: %ld",
298 PTR_ERR(keyring_key));
299 return PTR_ERR(keyring_key);
302 down_read(&keyring_key->sem);
304 if (keyring_key->type != &key_type_logon) {
305 ubifs_err(c, "key type must be logon");
310 ukp = user_key_payload_locked(keyring_key);
312 /* key was revoked before we acquired its semaphore */
317 c->hash_tfm = crypto_alloc_shash(c->auth_hash_name, 0, 0);
318 if (IS_ERR(c->hash_tfm)) {
319 err = PTR_ERR(c->hash_tfm);
320 ubifs_err(c, "Can not allocate %s: %d",
321 c->auth_hash_name, err);
325 c->hash_len = crypto_shash_digestsize(c->hash_tfm);
326 if (c->hash_len > UBIFS_HASH_ARR_SZ) {
327 ubifs_err(c, "hash %s is bigger than maximum allowed hash size (%d > %d)",
328 c->auth_hash_name, c->hash_len, UBIFS_HASH_ARR_SZ);
333 c->hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0);
334 if (IS_ERR(c->hmac_tfm)) {
335 err = PTR_ERR(c->hmac_tfm);
336 ubifs_err(c, "Can not allocate %s: %d", hmac_name, err);
340 c->hmac_desc_len = crypto_shash_digestsize(c->hmac_tfm);
341 if (c->hmac_desc_len > UBIFS_HMAC_ARR_SZ) {
342 ubifs_err(c, "hmac %s is bigger than maximum allowed hmac size (%d > %d)",
343 hmac_name, c->hmac_desc_len, UBIFS_HMAC_ARR_SZ);
348 err = crypto_shash_setkey(c->hmac_tfm, ukp->data, ukp->datalen);
352 c->authenticated = true;
354 c->log_hash = ubifs_hash_get_desc(c);
355 if (IS_ERR(c->log_hash)) {
356 err = PTR_ERR(c->log_hash);
364 crypto_free_shash(c->hmac_tfm);
367 crypto_free_shash(c->hash_tfm);
369 up_read(&keyring_key->sem);
370 key_put(keyring_key);
376 * __ubifs_exit_authentication - release resource
377 * @c: UBIFS file-system description object
379 * This function releases the authentication related resources.
381 void __ubifs_exit_authentication(struct ubifs_info *c)
383 if (!ubifs_authenticated(c))
386 crypto_free_shash(c->hmac_tfm);
387 crypto_free_shash(c->hash_tfm);
392 * ubifs_node_calc_hmac - calculate the HMAC of a UBIFS node
393 * @c: UBIFS file-system description object
394 * @node: the node to insert a HMAC into.
395 * @len: the length of the node
396 * @ofs_hmac: the offset in the node where the HMAC is inserted
397 * @hmac: returned HMAC
399 * This function calculates a HMAC of a UBIFS node. The HMAC is expected to be
400 * embedded into the node, so this area is not covered by the HMAC. Also not
401 * covered is the UBIFS_NODE_MAGIC and the CRC of the node.
403 static int ubifs_node_calc_hmac(const struct ubifs_info *c, const void *node,
404 int len, int ofs_hmac, void *hmac)
406 SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
407 int hmac_len = c->hmac_desc_len;
410 ubifs_assert(c, ofs_hmac > 8);
411 ubifs_assert(c, ofs_hmac + hmac_len < len);
413 shash->tfm = c->hmac_tfm;
415 err = crypto_shash_init(shash);
419 /* behind common node header CRC up to HMAC begin */
420 err = crypto_shash_update(shash, node + 8, ofs_hmac - 8);
424 /* behind HMAC, if any */
425 if (len - ofs_hmac - hmac_len > 0) {
426 err = crypto_shash_update(shash, node + ofs_hmac + hmac_len,
427 len - ofs_hmac - hmac_len);
432 return crypto_shash_final(shash, hmac);
436 * __ubifs_node_insert_hmac - insert a HMAC into a UBIFS node
437 * @c: UBIFS file-system description object
438 * @node: the node to insert a HMAC into.
439 * @len: the length of the node
440 * @ofs_hmac: the offset in the node where the HMAC is inserted
442 * This function inserts a HMAC at offset @ofs_hmac into the node given in
445 * This function returns 0 for success or a negative error code otherwise.
447 int __ubifs_node_insert_hmac(const struct ubifs_info *c, void *node, int len,
450 return ubifs_node_calc_hmac(c, node, len, ofs_hmac, node + ofs_hmac);
454 * __ubifs_node_verify_hmac - verify the HMAC of UBIFS node
455 * @c: UBIFS file-system description object
456 * @node: the node to insert a HMAC into.
457 * @len: the length of the node
458 * @ofs_hmac: the offset in the node where the HMAC is inserted
460 * This function verifies the HMAC at offset @ofs_hmac of the node given in
461 * @node. Returns 0 if successful or a negative error code otherwise.
463 int __ubifs_node_verify_hmac(const struct ubifs_info *c, const void *node,
464 int len, int ofs_hmac)
466 int hmac_len = c->hmac_desc_len;
470 hmac = kmalloc(hmac_len, GFP_NOFS);
474 err = ubifs_node_calc_hmac(c, node, len, ofs_hmac, hmac);
480 err = crypto_memneq(hmac, node + ofs_hmac, hmac_len);
490 int __ubifs_shash_copy_state(const struct ubifs_info *c, struct shash_desc *src,
491 struct shash_desc *target)
496 state = kmalloc(crypto_shash_descsize(src->tfm), GFP_NOFS);
500 err = crypto_shash_export(src, state);
504 err = crypto_shash_import(target, state);
513 * ubifs_hmac_wkm - Create a HMAC of the well known message
514 * @c: UBIFS file-system description object
515 * @hmac: The HMAC of the well known message
517 * This function creates a HMAC of a well known message. This is used
518 * to check if the provided key is suitable to authenticate a UBIFS
519 * image. This is only a convenience to the user to provide a better
520 * error message when the wrong key is provided.
522 * This function returns 0 for success or a negative error code otherwise.
524 int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac)
526 SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
528 const char well_known_message[] = "UBIFS";
530 if (!ubifs_authenticated(c))
533 shash->tfm = c->hmac_tfm;
535 err = crypto_shash_init(shash);
539 err = crypto_shash_update(shash, well_known_message,
540 sizeof(well_known_message) - 1);
544 err = crypto_shash_final(shash, hmac);
551 * ubifs_hmac_zero - test if a HMAC is zero
552 * @c: UBIFS file-system description object
553 * @hmac: the HMAC to test
555 * This function tests if a HMAC is zero and returns true if it is
556 * and false otherwise.
558 bool ubifs_hmac_zero(struct ubifs_info *c, const u8 *hmac)
560 return !memchr_inv(hmac, 0, c->hmac_desc_len);