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;
35 return crypto_shash_tfm_digest(c->hash_tfm, node, le32_to_cpu(ch->len),
40 * ubifs_hash_calc_hmac - calculate a HMAC from a hash
41 * @c: UBIFS file-system description object
42 * @hash: the node to calculate a HMAC for
43 * @hmac: the returned HMAC
45 * Returns 0 for success or a negative error code otherwise.
47 static int ubifs_hash_calc_hmac(const struct ubifs_info *c, const u8 *hash,
50 return crypto_shash_tfm_digest(c->hmac_tfm, hash, c->hash_len, hmac);
54 * ubifs_prepare_auth_node - Prepare an authentication node
55 * @c: UBIFS file-system description object
56 * @node: the node to calculate a hash for
57 * @inhash: input hash of previous nodes
59 * This function prepares an authentication node for writing onto flash.
60 * It creates a HMAC from the given input hash and writes it to the node.
62 * Returns 0 for success or a negative error code otherwise.
64 int ubifs_prepare_auth_node(struct ubifs_info *c, void *node,
65 struct shash_desc *inhash)
67 struct ubifs_auth_node *auth = node;
68 u8 hash[UBIFS_HASH_ARR_SZ];
72 SHASH_DESC_ON_STACK(hash_desc, c->hash_tfm);
74 hash_desc->tfm = c->hash_tfm;
75 ubifs_shash_copy_state(c, inhash, hash_desc);
77 err = crypto_shash_final(hash_desc, hash);
82 err = ubifs_hash_calc_hmac(c, hash, auth->hmac);
86 auth->ch.node_type = UBIFS_AUTH_NODE;
87 ubifs_prepare_node(c, auth, ubifs_auth_node_sz(c), 0);
91 static struct shash_desc *ubifs_get_desc(const struct ubifs_info *c,
92 struct crypto_shash *tfm)
94 struct shash_desc *desc;
97 if (!ubifs_authenticated(c))
100 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL);
102 return ERR_PTR(-ENOMEM);
106 err = crypto_shash_init(desc);
116 * __ubifs_hash_get_desc - get a descriptor suitable for hashing a node
117 * @c: UBIFS file-system description object
119 * This function returns a descriptor suitable for hashing a node. Free after use
122 struct shash_desc *__ubifs_hash_get_desc(const struct ubifs_info *c)
124 return ubifs_get_desc(c, c->hash_tfm);
128 * ubifs_bad_hash - Report hash mismatches
129 * @c: UBIFS file-system description object
131 * @hash: the expected hash
132 * @lnum: the LEB @node was read from
133 * @offs: offset in LEB @node was read from
135 * This function reports a hash mismatch when a node has a different hash than
138 void ubifs_bad_hash(const struct ubifs_info *c, const void *node, const u8 *hash,
141 int len = min(c->hash_len, 20);
142 int cropped = len != c->hash_len;
143 const char *cont = cropped ? "..." : "";
145 u8 calc[UBIFS_HASH_ARR_SZ];
147 __ubifs_node_calc_hash(c, node, calc);
149 ubifs_err(c, "hash mismatch on node at LEB %d:%d", lnum, offs);
150 ubifs_err(c, "hash expected: %*ph%s", len, hash, cont);
151 ubifs_err(c, "hash calculated: %*ph%s", len, calc, cont);
155 * __ubifs_node_check_hash - check the hash of a node against given hash
156 * @c: UBIFS file-system description object
158 * @expected: the expected hash
160 * This function calculates a hash over a node and compares it to the given hash.
161 * Returns 0 if both hashes are equal or authentication is disabled, otherwise a
162 * negative error code is returned.
164 int __ubifs_node_check_hash(const struct ubifs_info *c, const void *node,
167 u8 calc[UBIFS_HASH_ARR_SZ];
170 err = __ubifs_node_calc_hash(c, node, calc);
174 if (ubifs_check_hash(c, expected, calc))
181 * ubifs_sb_verify_signature - verify the signature of a superblock
182 * @c: UBIFS file-system description object
183 * @sup: The superblock node
185 * To support offline signed images the superblock can be signed with a
186 * PKCS#7 signature. The signature is placed directly behind the superblock
187 * node in an ubifs_sig_node.
189 * Returns 0 when the signature can be successfully verified or a negative
192 int ubifs_sb_verify_signature(struct ubifs_info *c,
193 const struct ubifs_sb_node *sup)
196 struct ubifs_scan_leb *sleb;
197 struct ubifs_scan_node *snod;
198 const struct ubifs_sig_node *signode;
200 sleb = ubifs_scan(c, UBIFS_SB_LNUM, UBIFS_SB_NODE_SZ, c->sbuf, 0);
206 if (sleb->nodes_cnt == 0) {
207 ubifs_err(c, "Unable to find signature node");
212 snod = list_first_entry(&sleb->nodes, struct ubifs_scan_node, list);
214 if (snod->type != UBIFS_SIG_NODE) {
215 ubifs_err(c, "Signature node is of wrong type");
220 signode = snod->node;
222 if (le32_to_cpu(signode->len) > snod->len + sizeof(struct ubifs_sig_node)) {
223 ubifs_err(c, "invalid signature len %d", le32_to_cpu(signode->len));
228 if (le32_to_cpu(signode->type) != UBIFS_SIGNATURE_TYPE_PKCS7) {
229 ubifs_err(c, "Signature type %d is not supported\n",
230 le32_to_cpu(signode->type));
235 err = verify_pkcs7_signature(sup, sizeof(struct ubifs_sb_node),
236 signode->sig, le32_to_cpu(signode->len),
237 NULL, VERIFYING_UNSPECIFIED_SIGNATURE,
241 ubifs_err(c, "Failed to verify signature");
243 ubifs_msg(c, "Successfully verified super block signature");
246 ubifs_scan_destroy(sleb);
252 * ubifs_init_authentication - initialize UBIFS authentication support
253 * @c: UBIFS file-system description object
255 * This function returns 0 for success or a negative error code otherwise.
257 int ubifs_init_authentication(struct ubifs_info *c)
259 struct key *keyring_key;
260 const struct user_key_payload *ukp;
262 char hmac_name[CRYPTO_MAX_ALG_NAME];
264 if (!c->auth_hash_name) {
265 ubifs_err(c, "authentication hash name needed with authentication");
269 c->auth_hash_algo = match_string(hash_algo_name, HASH_ALGO__LAST,
271 if ((int)c->auth_hash_algo < 0) {
272 ubifs_err(c, "Unknown hash algo %s specified",
277 snprintf(hmac_name, CRYPTO_MAX_ALG_NAME, "hmac(%s)",
280 keyring_key = request_key(&key_type_logon, c->auth_key_name, NULL);
282 if (IS_ERR(keyring_key)) {
283 ubifs_err(c, "Failed to request key: %ld",
284 PTR_ERR(keyring_key));
285 return PTR_ERR(keyring_key);
288 down_read(&keyring_key->sem);
290 if (keyring_key->type != &key_type_logon) {
291 ubifs_err(c, "key type must be logon");
296 ukp = user_key_payload_locked(keyring_key);
298 /* key was revoked before we acquired its semaphore */
303 c->hash_tfm = crypto_alloc_shash(c->auth_hash_name, 0, 0);
304 if (IS_ERR(c->hash_tfm)) {
305 err = PTR_ERR(c->hash_tfm);
306 ubifs_err(c, "Can not allocate %s: %d",
307 c->auth_hash_name, err);
311 c->hash_len = crypto_shash_digestsize(c->hash_tfm);
312 if (c->hash_len > UBIFS_HASH_ARR_SZ) {
313 ubifs_err(c, "hash %s is bigger than maximum allowed hash size (%d > %d)",
314 c->auth_hash_name, c->hash_len, UBIFS_HASH_ARR_SZ);
319 c->hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0);
320 if (IS_ERR(c->hmac_tfm)) {
321 err = PTR_ERR(c->hmac_tfm);
322 ubifs_err(c, "Can not allocate %s: %d", hmac_name, err);
326 c->hmac_desc_len = crypto_shash_digestsize(c->hmac_tfm);
327 if (c->hmac_desc_len > UBIFS_HMAC_ARR_SZ) {
328 ubifs_err(c, "hmac %s is bigger than maximum allowed hmac size (%d > %d)",
329 hmac_name, c->hmac_desc_len, UBIFS_HMAC_ARR_SZ);
334 err = crypto_shash_setkey(c->hmac_tfm, ukp->data, ukp->datalen);
338 c->authenticated = true;
340 c->log_hash = ubifs_hash_get_desc(c);
341 if (IS_ERR(c->log_hash)) {
342 err = PTR_ERR(c->log_hash);
350 crypto_free_shash(c->hmac_tfm);
353 crypto_free_shash(c->hash_tfm);
355 up_read(&keyring_key->sem);
356 key_put(keyring_key);
362 * __ubifs_exit_authentication - release resource
363 * @c: UBIFS file-system description object
365 * This function releases the authentication related resources.
367 void __ubifs_exit_authentication(struct ubifs_info *c)
369 if (!ubifs_authenticated(c))
372 crypto_free_shash(c->hmac_tfm);
373 crypto_free_shash(c->hash_tfm);
378 * ubifs_node_calc_hmac - calculate the HMAC of a UBIFS node
379 * @c: UBIFS file-system description object
380 * @node: the node to insert a HMAC into.
381 * @len: the length of the node
382 * @ofs_hmac: the offset in the node where the HMAC is inserted
383 * @hmac: returned HMAC
385 * This function calculates a HMAC of a UBIFS node. The HMAC is expected to be
386 * embedded into the node, so this area is not covered by the HMAC. Also not
387 * covered is the UBIFS_NODE_MAGIC and the CRC of the node.
389 static int ubifs_node_calc_hmac(const struct ubifs_info *c, const void *node,
390 int len, int ofs_hmac, void *hmac)
392 SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
393 int hmac_len = c->hmac_desc_len;
396 ubifs_assert(c, ofs_hmac > 8);
397 ubifs_assert(c, ofs_hmac + hmac_len < len);
399 shash->tfm = c->hmac_tfm;
401 err = crypto_shash_init(shash);
405 /* behind common node header CRC up to HMAC begin */
406 err = crypto_shash_update(shash, node + 8, ofs_hmac - 8);
410 /* behind HMAC, if any */
411 if (len - ofs_hmac - hmac_len > 0) {
412 err = crypto_shash_update(shash, node + ofs_hmac + hmac_len,
413 len - ofs_hmac - hmac_len);
418 return crypto_shash_final(shash, hmac);
422 * __ubifs_node_insert_hmac - insert a HMAC into a UBIFS node
423 * @c: UBIFS file-system description object
424 * @node: the node to insert a HMAC into.
425 * @len: the length of the node
426 * @ofs_hmac: the offset in the node where the HMAC is inserted
428 * This function inserts a HMAC at offset @ofs_hmac into the node given in
431 * This function returns 0 for success or a negative error code otherwise.
433 int __ubifs_node_insert_hmac(const struct ubifs_info *c, void *node, int len,
436 return ubifs_node_calc_hmac(c, node, len, ofs_hmac, node + ofs_hmac);
440 * __ubifs_node_verify_hmac - verify the HMAC of UBIFS node
441 * @c: UBIFS file-system description object
442 * @node: the node to insert a HMAC into.
443 * @len: the length of the node
444 * @ofs_hmac: the offset in the node where the HMAC is inserted
446 * This function verifies the HMAC at offset @ofs_hmac of the node given in
447 * @node. Returns 0 if successful or a negative error code otherwise.
449 int __ubifs_node_verify_hmac(const struct ubifs_info *c, const void *node,
450 int len, int ofs_hmac)
452 int hmac_len = c->hmac_desc_len;
456 hmac = kmalloc(hmac_len, GFP_NOFS);
460 err = ubifs_node_calc_hmac(c, node, len, ofs_hmac, hmac);
466 err = crypto_memneq(hmac, node + ofs_hmac, hmac_len);
476 int __ubifs_shash_copy_state(const struct ubifs_info *c, struct shash_desc *src,
477 struct shash_desc *target)
482 state = kmalloc(crypto_shash_descsize(src->tfm), GFP_NOFS);
486 err = crypto_shash_export(src, state);
490 err = crypto_shash_import(target, state);
499 * ubifs_hmac_wkm - Create a HMAC of the well known message
500 * @c: UBIFS file-system description object
501 * @hmac: The HMAC of the well known message
503 * This function creates a HMAC of a well known message. This is used
504 * to check if the provided key is suitable to authenticate a UBIFS
505 * image. This is only a convenience to the user to provide a better
506 * error message when the wrong key is provided.
508 * This function returns 0 for success or a negative error code otherwise.
510 int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac)
512 SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
514 const char well_known_message[] = "UBIFS";
516 if (!ubifs_authenticated(c))
519 shash->tfm = c->hmac_tfm;
521 err = crypto_shash_init(shash);
525 err = crypto_shash_update(shash, well_known_message,
526 sizeof(well_known_message) - 1);
530 err = crypto_shash_final(shash, hmac);
537 * ubifs_hmac_zero - test if a HMAC is zero
538 * @c: UBIFS file-system description object
539 * @hmac: the HMAC to test
541 * This function tests if a HMAC is zero and returns true if it is
542 * and false otherwise.
544 bool ubifs_hmac_zero(struct ubifs_info *c, const u8 *hmac)
546 return !memchr_inv(hmac, 0, c->hmac_desc_len);