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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 | ||
12 | #include <linux/crypto.h> | |
817aa094 | 13 | #include <linux/verification.h> |
49525e5e SH |
14 | #include <crypto/hash.h> |
15 | #include <crypto/sha.h> | |
16 | #include <crypto/algapi.h> | |
17 | #include <keys/user-type.h> | |
817aa094 | 18 | #include <keys/asymmetric-type.h> |
49525e5e SH |
19 | |
20 | #include "ubifs.h" | |
21 | ||
22 | /** | |
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 | |
27 | * | |
28 | * Returns 0 for success or a negative error code otherwise. | |
29 | */ | |
30 | int __ubifs_node_calc_hash(const struct ubifs_info *c, const void *node, | |
31 | u8 *hash) | |
32 | { | |
33 | const struct ubifs_ch *ch = node; | |
34 | SHASH_DESC_ON_STACK(shash, c->hash_tfm); | |
35 | int err; | |
36 | ||
37 | shash->tfm = c->hash_tfm; | |
49525e5e SH |
38 | |
39 | err = crypto_shash_digest(shash, node, le32_to_cpu(ch->len), hash); | |
40 | if (err < 0) | |
41 | return err; | |
42 | return 0; | |
43 | } | |
44 | ||
45 | /** | |
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 | |
50 | * | |
51 | * Returns 0 for success or a negative error code otherwise. | |
52 | */ | |
53 | static int ubifs_hash_calc_hmac(const struct ubifs_info *c, const u8 *hash, | |
54 | u8 *hmac) | |
55 | { | |
56 | SHASH_DESC_ON_STACK(shash, c->hmac_tfm); | |
57 | int err; | |
58 | ||
59 | shash->tfm = c->hmac_tfm; | |
49525e5e SH |
60 | |
61 | err = crypto_shash_digest(shash, hash, c->hash_len, hmac); | |
62 | if (err < 0) | |
63 | return err; | |
64 | return 0; | |
65 | } | |
66 | ||
67 | /** | |
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 | |
72 | * | |
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. | |
75 | * | |
76 | * Returns 0 for success or a negative error code otherwise. | |
77 | */ | |
78 | int ubifs_prepare_auth_node(struct ubifs_info *c, void *node, | |
79 | struct shash_desc *inhash) | |
80 | { | |
49525e5e SH |
81 | struct ubifs_auth_node *auth = node; |
82 | u8 *hash; | |
83 | int err; | |
84 | ||
85 | hash = kmalloc(crypto_shash_descsize(c->hash_tfm), GFP_NOFS); | |
86 | if (!hash) | |
87 | return -ENOMEM; | |
88 | ||
f4844b35 AB |
89 | { |
90 | SHASH_DESC_ON_STACK(hash_desc, c->hash_tfm); | |
49525e5e | 91 | |
f4844b35 | 92 | hash_desc->tfm = c->hash_tfm; |
f4844b35 AB |
93 | ubifs_shash_copy_state(c, inhash, hash_desc); |
94 | ||
95 | err = crypto_shash_final(hash_desc, hash); | |
96 | if (err) | |
97 | goto out; | |
98 | } | |
49525e5e SH |
99 | |
100 | err = ubifs_hash_calc_hmac(c, hash, auth->hmac); | |
101 | if (err) | |
102 | goto out; | |
103 | ||
104 | auth->ch.node_type = UBIFS_AUTH_NODE; | |
105 | ubifs_prepare_node(c, auth, ubifs_auth_node_sz(c), 0); | |
106 | ||
107 | err = 0; | |
108 | out: | |
109 | kfree(hash); | |
110 | ||
111 | return err; | |
112 | } | |
113 | ||
114 | static struct shash_desc *ubifs_get_desc(const struct ubifs_info *c, | |
115 | struct crypto_shash *tfm) | |
116 | { | |
117 | struct shash_desc *desc; | |
118 | int err; | |
119 | ||
120 | if (!ubifs_authenticated(c)) | |
121 | return NULL; | |
122 | ||
123 | desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL); | |
124 | if (!desc) | |
125 | return ERR_PTR(-ENOMEM); | |
126 | ||
127 | desc->tfm = tfm; | |
49525e5e SH |
128 | |
129 | err = crypto_shash_init(desc); | |
130 | if (err) { | |
131 | kfree(desc); | |
132 | return ERR_PTR(err); | |
133 | } | |
134 | ||
135 | return desc; | |
136 | } | |
137 | ||
138 | /** | |
139 | * __ubifs_hash_get_desc - get a descriptor suitable for hashing a node | |
140 | * @c: UBIFS file-system description object | |
141 | * | |
142 | * This function returns a descriptor suitable for hashing a node. Free after use | |
143 | * with kfree. | |
144 | */ | |
145 | struct shash_desc *__ubifs_hash_get_desc(const struct ubifs_info *c) | |
146 | { | |
147 | return ubifs_get_desc(c, c->hash_tfm); | |
148 | } | |
149 | ||
49525e5e SH |
150 | /** |
151 | * ubifs_bad_hash - Report hash mismatches | |
152 | * @c: UBIFS file-system description object | |
153 | * @node: the node | |
154 | * @hash: the expected hash | |
155 | * @lnum: the LEB @node was read from | |
156 | * @offs: offset in LEB @node was read from | |
157 | * | |
158 | * This function reports a hash mismatch when a node has a different hash than | |
159 | * expected. | |
160 | */ | |
161 | void ubifs_bad_hash(const struct ubifs_info *c, const void *node, const u8 *hash, | |
162 | int lnum, int offs) | |
163 | { | |
164 | int len = min(c->hash_len, 20); | |
165 | int cropped = len != c->hash_len; | |
166 | const char *cont = cropped ? "..." : ""; | |
167 | ||
168 | u8 calc[UBIFS_HASH_ARR_SZ]; | |
169 | ||
170 | __ubifs_node_calc_hash(c, node, calc); | |
171 | ||
172 | ubifs_err(c, "hash mismatch on node at LEB %d:%d", lnum, offs); | |
173 | ubifs_err(c, "hash expected: %*ph%s", len, hash, cont); | |
174 | ubifs_err(c, "hash calculated: %*ph%s", len, calc, cont); | |
175 | } | |
176 | ||
177 | /** | |
178 | * __ubifs_node_check_hash - check the hash of a node against given hash | |
179 | * @c: UBIFS file-system description object | |
180 | * @node: the node | |
181 | * @expected: the expected hash | |
182 | * | |
183 | * This function calculates a hash over a node and compares it to the given hash. | |
184 | * Returns 0 if both hashes are equal or authentication is disabled, otherwise a | |
185 | * negative error code is returned. | |
186 | */ | |
187 | int __ubifs_node_check_hash(const struct ubifs_info *c, const void *node, | |
188 | const u8 *expected) | |
189 | { | |
190 | u8 calc[UBIFS_HASH_ARR_SZ]; | |
191 | int err; | |
192 | ||
193 | err = __ubifs_node_calc_hash(c, node, calc); | |
194 | if (err) | |
195 | return err; | |
196 | ||
197 | if (ubifs_check_hash(c, expected, calc)) | |
198 | return -EPERM; | |
199 | ||
200 | return 0; | |
201 | } | |
202 | ||
817aa094 SH |
203 | /** |
204 | * ubifs_sb_verify_signature - verify the signature of a superblock | |
205 | * @c: UBIFS file-system description object | |
206 | * @sup: The superblock node | |
207 | * | |
208 | * To support offline signed images the superblock can be signed with a | |
209 | * PKCS#7 signature. The signature is placed directly behind the superblock | |
210 | * node in an ubifs_sig_node. | |
211 | * | |
212 | * Returns 0 when the signature can be successfully verified or a negative | |
213 | * error code if not. | |
214 | */ | |
215 | int ubifs_sb_verify_signature(struct ubifs_info *c, | |
216 | const struct ubifs_sb_node *sup) | |
217 | { | |
218 | int err; | |
219 | struct ubifs_scan_leb *sleb; | |
220 | struct ubifs_scan_node *snod; | |
221 | const struct ubifs_sig_node *signode; | |
222 | ||
223 | sleb = ubifs_scan(c, UBIFS_SB_LNUM, UBIFS_SB_NODE_SZ, c->sbuf, 0); | |
224 | if (IS_ERR(sleb)) { | |
225 | err = PTR_ERR(sleb); | |
226 | return err; | |
227 | } | |
228 | ||
229 | if (sleb->nodes_cnt == 0) { | |
230 | ubifs_err(c, "Unable to find signature node"); | |
231 | err = -EINVAL; | |
232 | goto out_destroy; | |
233 | } | |
234 | ||
235 | snod = list_first_entry(&sleb->nodes, struct ubifs_scan_node, list); | |
236 | ||
237 | if (snod->type != UBIFS_SIG_NODE) { | |
238 | ubifs_err(c, "Signature node is of wrong type"); | |
239 | err = -EINVAL; | |
240 | goto out_destroy; | |
241 | } | |
242 | ||
243 | signode = snod->node; | |
244 | ||
245 | if (le32_to_cpu(signode->len) > snod->len + sizeof(struct ubifs_sig_node)) { | |
246 | ubifs_err(c, "invalid signature len %d", le32_to_cpu(signode->len)); | |
247 | err = -EINVAL; | |
248 | goto out_destroy; | |
249 | } | |
250 | ||
251 | if (le32_to_cpu(signode->type) != UBIFS_SIGNATURE_TYPE_PKCS7) { | |
252 | ubifs_err(c, "Signature type %d is not supported\n", | |
253 | le32_to_cpu(signode->type)); | |
254 | err = -EINVAL; | |
255 | goto out_destroy; | |
256 | } | |
257 | ||
258 | err = verify_pkcs7_signature(sup, sizeof(struct ubifs_sb_node), | |
259 | signode->sig, le32_to_cpu(signode->len), | |
260 | NULL, VERIFYING_UNSPECIFIED_SIGNATURE, | |
261 | NULL, NULL); | |
262 | ||
263 | if (err) | |
264 | ubifs_err(c, "Failed to verify signature"); | |
265 | else | |
266 | ubifs_msg(c, "Successfully verified super block signature"); | |
267 | ||
268 | out_destroy: | |
269 | ubifs_scan_destroy(sleb); | |
270 | ||
271 | return err; | |
272 | } | |
273 | ||
49525e5e SH |
274 | /** |
275 | * ubifs_init_authentication - initialize UBIFS authentication support | |
276 | * @c: UBIFS file-system description object | |
277 | * | |
278 | * This function returns 0 for success or a negative error code otherwise. | |
279 | */ | |
280 | int ubifs_init_authentication(struct ubifs_info *c) | |
281 | { | |
282 | struct key *keyring_key; | |
283 | const struct user_key_payload *ukp; | |
284 | int err; | |
285 | char hmac_name[CRYPTO_MAX_ALG_NAME]; | |
286 | ||
287 | if (!c->auth_hash_name) { | |
288 | ubifs_err(c, "authentication hash name needed with authentication"); | |
289 | return -EINVAL; | |
290 | } | |
291 | ||
292 | c->auth_hash_algo = match_string(hash_algo_name, HASH_ALGO__LAST, | |
293 | c->auth_hash_name); | |
294 | if ((int)c->auth_hash_algo < 0) { | |
295 | ubifs_err(c, "Unknown hash algo %s specified", | |
296 | c->auth_hash_name); | |
297 | return -EINVAL; | |
298 | } | |
299 | ||
300 | snprintf(hmac_name, CRYPTO_MAX_ALG_NAME, "hmac(%s)", | |
301 | c->auth_hash_name); | |
302 | ||
303 | keyring_key = request_key(&key_type_logon, c->auth_key_name, NULL); | |
304 | ||
305 | if (IS_ERR(keyring_key)) { | |
306 | ubifs_err(c, "Failed to request key: %ld", | |
307 | PTR_ERR(keyring_key)); | |
308 | return PTR_ERR(keyring_key); | |
309 | } | |
310 | ||
311 | down_read(&keyring_key->sem); | |
312 | ||
313 | if (keyring_key->type != &key_type_logon) { | |
314 | ubifs_err(c, "key type must be logon"); | |
315 | err = -ENOKEY; | |
316 | goto out; | |
317 | } | |
318 | ||
319 | ukp = user_key_payload_locked(keyring_key); | |
320 | if (!ukp) { | |
321 | /* key was revoked before we acquired its semaphore */ | |
322 | err = -EKEYREVOKED; | |
323 | goto out; | |
324 | } | |
325 | ||
3d234b33 | 326 | c->hash_tfm = crypto_alloc_shash(c->auth_hash_name, 0, 0); |
49525e5e SH |
327 | if (IS_ERR(c->hash_tfm)) { |
328 | err = PTR_ERR(c->hash_tfm); | |
329 | ubifs_err(c, "Can not allocate %s: %d", | |
330 | c->auth_hash_name, err); | |
331 | goto out; | |
332 | } | |
333 | ||
334 | c->hash_len = crypto_shash_digestsize(c->hash_tfm); | |
335 | if (c->hash_len > UBIFS_HASH_ARR_SZ) { | |
336 | ubifs_err(c, "hash %s is bigger than maximum allowed hash size (%d > %d)", | |
337 | c->auth_hash_name, c->hash_len, UBIFS_HASH_ARR_SZ); | |
338 | err = -EINVAL; | |
339 | goto out_free_hash; | |
340 | } | |
341 | ||
3d234b33 | 342 | c->hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0); |
49525e5e SH |
343 | if (IS_ERR(c->hmac_tfm)) { |
344 | err = PTR_ERR(c->hmac_tfm); | |
345 | ubifs_err(c, "Can not allocate %s: %d", hmac_name, err); | |
346 | goto out_free_hash; | |
347 | } | |
348 | ||
349 | c->hmac_desc_len = crypto_shash_digestsize(c->hmac_tfm); | |
350 | if (c->hmac_desc_len > UBIFS_HMAC_ARR_SZ) { | |
351 | ubifs_err(c, "hmac %s is bigger than maximum allowed hmac size (%d > %d)", | |
352 | hmac_name, c->hmac_desc_len, UBIFS_HMAC_ARR_SZ); | |
353 | err = -EINVAL; | |
354 | goto out_free_hash; | |
355 | } | |
356 | ||
357 | err = crypto_shash_setkey(c->hmac_tfm, ukp->data, ukp->datalen); | |
358 | if (err) | |
359 | goto out_free_hmac; | |
360 | ||
361 | c->authenticated = true; | |
362 | ||
363 | c->log_hash = ubifs_hash_get_desc(c); | |
364 | if (IS_ERR(c->log_hash)) | |
365 | goto out_free_hmac; | |
366 | ||
367 | err = 0; | |
368 | ||
369 | out_free_hmac: | |
370 | if (err) | |
371 | crypto_free_shash(c->hmac_tfm); | |
372 | out_free_hash: | |
373 | if (err) | |
374 | crypto_free_shash(c->hash_tfm); | |
375 | out: | |
376 | up_read(&keyring_key->sem); | |
377 | key_put(keyring_key); | |
378 | ||
379 | return err; | |
380 | } | |
381 | ||
382 | /** | |
383 | * __ubifs_exit_authentication - release resource | |
384 | * @c: UBIFS file-system description object | |
385 | * | |
386 | * This function releases the authentication related resources. | |
387 | */ | |
388 | void __ubifs_exit_authentication(struct ubifs_info *c) | |
389 | { | |
390 | if (!ubifs_authenticated(c)) | |
391 | return; | |
392 | ||
393 | crypto_free_shash(c->hmac_tfm); | |
394 | crypto_free_shash(c->hash_tfm); | |
395 | kfree(c->log_hash); | |
396 | } | |
397 | ||
398 | /** | |
399 | * ubifs_node_calc_hmac - calculate the HMAC of a UBIFS node | |
400 | * @c: UBIFS file-system description object | |
401 | * @node: the node to insert a HMAC into. | |
402 | * @len: the length of the node | |
403 | * @ofs_hmac: the offset in the node where the HMAC is inserted | |
404 | * @hmac: returned HMAC | |
405 | * | |
406 | * This function calculates a HMAC of a UBIFS node. The HMAC is expected to be | |
407 | * embedded into the node, so this area is not covered by the HMAC. Also not | |
408 | * covered is the UBIFS_NODE_MAGIC and the CRC of the node. | |
409 | */ | |
410 | static int ubifs_node_calc_hmac(const struct ubifs_info *c, const void *node, | |
411 | int len, int ofs_hmac, void *hmac) | |
412 | { | |
413 | SHASH_DESC_ON_STACK(shash, c->hmac_tfm); | |
414 | int hmac_len = c->hmac_desc_len; | |
415 | int err; | |
416 | ||
417 | ubifs_assert(c, ofs_hmac > 8); | |
418 | ubifs_assert(c, ofs_hmac + hmac_len < len); | |
419 | ||
420 | shash->tfm = c->hmac_tfm; | |
49525e5e SH |
421 | |
422 | err = crypto_shash_init(shash); | |
423 | if (err) | |
424 | return err; | |
425 | ||
426 | /* behind common node header CRC up to HMAC begin */ | |
427 | err = crypto_shash_update(shash, node + 8, ofs_hmac - 8); | |
428 | if (err < 0) | |
429 | return err; | |
430 | ||
431 | /* behind HMAC, if any */ | |
432 | if (len - ofs_hmac - hmac_len > 0) { | |
433 | err = crypto_shash_update(shash, node + ofs_hmac + hmac_len, | |
434 | len - ofs_hmac - hmac_len); | |
435 | if (err < 0) | |
436 | return err; | |
437 | } | |
438 | ||
439 | return crypto_shash_final(shash, hmac); | |
440 | } | |
441 | ||
442 | /** | |
443 | * __ubifs_node_insert_hmac - insert a HMAC into a UBIFS node | |
444 | * @c: UBIFS file-system description object | |
445 | * @node: the node to insert a HMAC into. | |
446 | * @len: the length of the node | |
447 | * @ofs_hmac: the offset in the node where the HMAC is inserted | |
448 | * | |
449 | * This function inserts a HMAC at offset @ofs_hmac into the node given in | |
450 | * @node. | |
451 | * | |
452 | * This function returns 0 for success or a negative error code otherwise. | |
453 | */ | |
454 | int __ubifs_node_insert_hmac(const struct ubifs_info *c, void *node, int len, | |
455 | int ofs_hmac) | |
456 | { | |
457 | return ubifs_node_calc_hmac(c, node, len, ofs_hmac, node + ofs_hmac); | |
458 | } | |
459 | ||
460 | /** | |
461 | * __ubifs_node_verify_hmac - verify the HMAC of UBIFS node | |
462 | * @c: UBIFS file-system description object | |
463 | * @node: the node to insert a HMAC into. | |
464 | * @len: the length of the node | |
465 | * @ofs_hmac: the offset in the node where the HMAC is inserted | |
466 | * | |
467 | * This function verifies the HMAC at offset @ofs_hmac of the node given in | |
468 | * @node. Returns 0 if successful or a negative error code otherwise. | |
469 | */ | |
470 | int __ubifs_node_verify_hmac(const struct ubifs_info *c, const void *node, | |
471 | int len, int ofs_hmac) | |
472 | { | |
473 | int hmac_len = c->hmac_desc_len; | |
474 | u8 *hmac; | |
475 | int err; | |
476 | ||
477 | hmac = kmalloc(hmac_len, GFP_NOFS); | |
478 | if (!hmac) | |
479 | return -ENOMEM; | |
480 | ||
481 | err = ubifs_node_calc_hmac(c, node, len, ofs_hmac, hmac); | |
7992e004 WW |
482 | if (err) { |
483 | kfree(hmac); | |
49525e5e | 484 | return err; |
7992e004 | 485 | } |
49525e5e SH |
486 | |
487 | err = crypto_memneq(hmac, node + ofs_hmac, hmac_len); | |
488 | ||
489 | kfree(hmac); | |
490 | ||
491 | if (!err) | |
492 | return 0; | |
493 | ||
494 | return -EPERM; | |
495 | } | |
496 | ||
497 | int __ubifs_shash_copy_state(const struct ubifs_info *c, struct shash_desc *src, | |
498 | struct shash_desc *target) | |
499 | { | |
500 | u8 *state; | |
501 | int err; | |
502 | ||
503 | state = kmalloc(crypto_shash_descsize(src->tfm), GFP_NOFS); | |
504 | if (!state) | |
505 | return -ENOMEM; | |
506 | ||
507 | err = crypto_shash_export(src, state); | |
508 | if (err) | |
509 | goto out; | |
510 | ||
511 | err = crypto_shash_import(target, state); | |
512 | ||
513 | out: | |
514 | kfree(state); | |
515 | ||
516 | return err; | |
517 | } | |
518 | ||
519 | /** | |
520 | * ubifs_hmac_wkm - Create a HMAC of the well known message | |
521 | * @c: UBIFS file-system description object | |
522 | * @hmac: The HMAC of the well known message | |
523 | * | |
524 | * This function creates a HMAC of a well known message. This is used | |
525 | * to check if the provided key is suitable to authenticate a UBIFS | |
526 | * image. This is only a convenience to the user to provide a better | |
527 | * error message when the wrong key is provided. | |
528 | * | |
529 | * This function returns 0 for success or a negative error code otherwise. | |
530 | */ | |
531 | int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac) | |
532 | { | |
533 | SHASH_DESC_ON_STACK(shash, c->hmac_tfm); | |
534 | int err; | |
535 | const char well_known_message[] = "UBIFS"; | |
536 | ||
537 | if (!ubifs_authenticated(c)) | |
538 | return 0; | |
539 | ||
540 | shash->tfm = c->hmac_tfm; | |
49525e5e SH |
541 | |
542 | err = crypto_shash_init(shash); | |
543 | if (err) | |
544 | return err; | |
545 | ||
546 | err = crypto_shash_update(shash, well_known_message, | |
547 | sizeof(well_known_message) - 1); | |
548 | if (err < 0) | |
549 | return err; | |
550 | ||
551 | err = crypto_shash_final(shash, hmac); | |
552 | if (err) | |
553 | return err; | |
554 | return 0; | |
555 | } | |
817aa094 SH |
556 | |
557 | /* | |
558 | * ubifs_hmac_zero - test if a HMAC is zero | |
559 | * @c: UBIFS file-system description object | |
560 | * @hmac: the HMAC to test | |
561 | * | |
562 | * This function tests if a HMAC is zero and returns true if it is | |
563 | * and false otherwise. | |
564 | */ | |
565 | bool ubifs_hmac_zero(struct ubifs_info *c, const u8 *hmac) | |
566 | { | |
567 | return !memchr_inv(hmac, 0, c->hmac_desc_len); | |
568 | } |