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49525e5e SH |
1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* | |
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 support | |
10 | */ | |
11 | ||
817aa094 | 12 | #include <linux/verification.h> |
49525e5e | 13 | #include <crypto/hash.h> |
8622bd19 | 14 | #include <crypto/utils.h> |
49525e5e | 15 | #include <keys/user-type.h> |
817aa094 | 16 | #include <keys/asymmetric-type.h> |
49525e5e SH |
17 | |
18 | #include "ubifs.h" | |
19 | ||
20 | /** | |
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 | |
25 | * | |
26 | * Returns 0 for success or a negative error code otherwise. | |
27 | */ | |
28 | int __ubifs_node_calc_hash(const struct ubifs_info *c, const void *node, | |
29 | u8 *hash) | |
30 | { | |
31 | const struct ubifs_ch *ch = node; | |
49525e5e | 32 | |
f80df385 EB |
33 | return crypto_shash_tfm_digest(c->hash_tfm, node, le32_to_cpu(ch->len), |
34 | hash); | |
49525e5e SH |
35 | } |
36 | ||
37 | /** | |
38 | * ubifs_hash_calc_hmac - calculate a HMAC from a hash | |
39 | * @c: UBIFS file-system description object | |
40 | * @hash: the node to calculate a HMAC for | |
41 | * @hmac: the returned HMAC | |
42 | * | |
43 | * Returns 0 for success or a negative error code otherwise. | |
44 | */ | |
45 | static int ubifs_hash_calc_hmac(const struct ubifs_info *c, const u8 *hash, | |
46 | u8 *hmac) | |
47 | { | |
f80df385 | 48 | return crypto_shash_tfm_digest(c->hmac_tfm, hash, c->hash_len, hmac); |
49525e5e SH |
49 | } |
50 | ||
51 | /** | |
52 | * ubifs_prepare_auth_node - Prepare an authentication node | |
53 | * @c: UBIFS file-system description object | |
54 | * @node: the node to calculate a hash for | |
f39d9f4c | 55 | * @inhash: input hash of previous nodes |
49525e5e SH |
56 | * |
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 | */ | |
62 | int ubifs_prepare_auth_node(struct ubifs_info *c, void *node, | |
63 | struct shash_desc *inhash) | |
64 | { | |
49525e5e | 65 | struct ubifs_auth_node *auth = node; |
3c3c32f8 | 66 | u8 hash[UBIFS_HASH_ARR_SZ]; |
49525e5e SH |
67 | int err; |
68 | ||
f4844b35 AB |
69 | { |
70 | SHASH_DESC_ON_STACK(hash_desc, c->hash_tfm); | |
49525e5e | 71 | |
f4844b35 | 72 | hash_desc->tfm = c->hash_tfm; |
f4844b35 AB |
73 | ubifs_shash_copy_state(c, inhash, hash_desc); |
74 | ||
75 | err = crypto_shash_final(hash_desc, hash); | |
76 | if (err) | |
3c3c32f8 | 77 | return err; |
f4844b35 | 78 | } |
49525e5e SH |
79 | |
80 | err = ubifs_hash_calc_hmac(c, hash, auth->hmac); | |
81 | if (err) | |
3c3c32f8 | 82 | return err; |
49525e5e SH |
83 | |
84 | auth->ch.node_type = UBIFS_AUTH_NODE; | |
85 | ubifs_prepare_node(c, auth, ubifs_auth_node_sz(c), 0); | |
3c3c32f8 | 86 | return 0; |
49525e5e SH |
87 | } |
88 | ||
89 | static 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; | |
49525e5e SH |
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 node | |
115 | * @c: UBIFS file-system description object | |
116 | * | |
117 | * This function returns a descriptor suitable for hashing a node. Free after use | |
118 | * with kfree. | |
119 | */ | |
120 | struct shash_desc *__ubifs_hash_get_desc(const struct ubifs_info *c) | |
121 | { | |
122 | return ubifs_get_desc(c, c->hash_tfm); | |
123 | } | |
124 | ||
49525e5e SH |
125 | /** |
126 | * ubifs_bad_hash - Report hash mismatches | |
127 | * @c: UBIFS file-system description object | |
128 | * @node: the node | |
129 | * @hash: the expected hash | |
130 | * @lnum: the LEB @node was read from | |
131 | * @offs: offset in LEB @node was read from | |
132 | * | |
133 | * This function reports a hash mismatch when a node has a different hash than | |
134 | * expected. | |
135 | */ | |
136 | void 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 hash | |
154 | * @c: UBIFS file-system description object | |
155 | * @node: the node | |
156 | * @expected: the expected hash | |
157 | * | |
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 a | |
160 | * negative error code is returned. | |
161 | */ | |
162 | int __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 | ||
817aa094 SH |
178 | /** |
179 | * ubifs_sb_verify_signature - verify the signature of a superblock | |
180 | * @c: UBIFS file-system description object | |
181 | * @sup: The superblock node | |
182 | * | |
183 | * To support offline signed images the superblock can be signed with a | |
184 | * PKCS#7 signature. The signature is placed directly behind the superblock | |
185 | * node in an ubifs_sig_node. | |
186 | * | |
187 | * Returns 0 when the signature can be successfully verified or a negative | |
188 | * error code if not. | |
189 | */ | |
190 | int 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 | else | |
241 | ubifs_msg(c, "Successfully verified super block signature"); | |
242 | ||
243 | out_destroy: | |
244 | ubifs_scan_destroy(sleb); | |
245 | ||
246 | return err; | |
247 | } | |
248 | ||
49525e5e SH |
249 | /** |
250 | * ubifs_init_authentication - initialize UBIFS authentication support | |
251 | * @c: UBIFS file-system description object | |
252 | * | |
253 | * This function returns 0 for success or a negative error code otherwise. | |
254 | */ | |
255 | int 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 | ||
3d234b33 | 301 | c->hash_tfm = crypto_alloc_shash(c->auth_hash_name, 0, 0); |
49525e5e SH |
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 | ||
3d234b33 | 317 | c->hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0); |
49525e5e SH |
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; | |
11b8ab38 | 329 | goto out_free_hmac; |
49525e5e SH |
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); | |
3cded663 WS |
339 | if (IS_ERR(c->log_hash)) { |
340 | err = PTR_ERR(c->log_hash); | |
49525e5e | 341 | goto out_free_hmac; |
3cded663 | 342 | } |
49525e5e SH |
343 | |
344 | err = 0; | |
345 | ||
346 | out_free_hmac: | |
347 | if (err) | |
348 | crypto_free_shash(c->hmac_tfm); | |
349 | out_free_hash: | |
350 | if (err) | |
351 | crypto_free_shash(c->hash_tfm); | |
352 | out: | |
353 | up_read(&keyring_key->sem); | |
354 | key_put(keyring_key); | |
355 | ||
356 | return err; | |
357 | } | |
358 | ||
359 | /** | |
360 | * __ubifs_exit_authentication - release resource | |
361 | * @c: UBIFS file-system description object | |
362 | * | |
363 | * This function releases the authentication related resources. | |
364 | */ | |
365 | void __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 node | |
377 | * @c: UBIFS file-system description object | |
378 | * @node: the node to insert a HMAC into. | |
379 | * @len: the length of the node | |
380 | * @ofs_hmac: the offset in the node where the HMAC is inserted | |
381 | * @hmac: returned HMAC | |
382 | * | |
383 | * This function calculates a HMAC of a UBIFS node. The HMAC is expected to be | |
384 | * embedded into the node, so this area is not covered by the HMAC. Also not | |
385 | * covered is the UBIFS_NODE_MAGIC and the CRC of the node. | |
386 | */ | |
387 | static 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; | |
49525e5e SH |
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 node | |
421 | * @c: UBIFS file-system description object | |
422 | * @node: the node to insert a HMAC into. | |
423 | * @len: the length of the node | |
424 | * @ofs_hmac: the offset in the node where the HMAC is inserted | |
425 | * | |
426 | * This function inserts a HMAC at offset @ofs_hmac into the node given in | |
427 | * @node. | |
428 | * | |
429 | * This function returns 0 for success or a negative error code otherwise. | |
430 | */ | |
431 | int __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 node | |
439 | * @c: UBIFS file-system description object | |
440 | * @node: the node to insert a HMAC into. | |
441 | * @len: the length of the node | |
442 | * @ofs_hmac: the offset in the node where the HMAC is inserted | |
443 | * | |
444 | * This function verifies the HMAC at offset @ofs_hmac of the node given in | |
445 | * @node. Returns 0 if successful or a negative error code otherwise. | |
446 | */ | |
447 | int __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); | |
7992e004 WW |
459 | if (err) { |
460 | kfree(hmac); | |
49525e5e | 461 | return err; |
7992e004 | 462 | } |
49525e5e SH |
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 | ||
474 | int __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 | ||
490 | out: | |
491 | kfree(state); | |
492 | ||
493 | return err; | |
494 | } | |
495 | ||
496 | /** | |
497 | * ubifs_hmac_wkm - Create a HMAC of the well known message | |
498 | * @c: UBIFS file-system description object | |
499 | * @hmac: The HMAC of the well known message | |
500 | * | |
501 | * This function creates a HMAC of a well known message. This is used | |
502 | * to check if the provided key is suitable to authenticate a UBIFS | |
503 | * image. This is only a convenience to the user to provide a better | |
504 | * error message when the wrong key is provided. | |
505 | * | |
506 | * This function returns 0 for success or a negative error code otherwise. | |
507 | */ | |
508 | int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac) | |
509 | { | |
49525e5e SH |
510 | const char well_known_message[] = "UBIFS"; |
511 | ||
512 | if (!ubifs_authenticated(c)) | |
513 | return 0; | |
514 | ||
738fadaa EB |
515 | return crypto_shash_tfm_digest(c->hmac_tfm, well_known_message, |
516 | sizeof(well_known_message) - 1, hmac); | |
49525e5e | 517 | } |
817aa094 SH |
518 | |
519 | /* | |
520 | * ubifs_hmac_zero - test if a HMAC is zero | |
521 | * @c: UBIFS file-system description object | |
522 | * @hmac: the HMAC to test | |
523 | * | |
524 | * This function tests if a HMAC is zero and returns true if it is | |
525 | * and false otherwise. | |
526 | */ | |
527 | bool ubifs_hmac_zero(struct ubifs_info *c, const u8 *hmac) | |
528 | { | |
529 | return !memchr_inv(hmac, 0, c->hmac_desc_len); | |
530 | } |