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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> | |
13 | #include <crypto/hash.h> | |
14 | #include <crypto/sha.h> | |
15 | #include <crypto/algapi.h> | |
16 | #include <keys/user-type.h> | |
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; | |
32 | SHASH_DESC_ON_STACK(shash, c->hash_tfm); | |
33 | int err; | |
34 | ||
35 | shash->tfm = c->hash_tfm; | |
49525e5e SH |
36 | |
37 | err = crypto_shash_digest(shash, node, le32_to_cpu(ch->len), hash); | |
38 | if (err < 0) | |
39 | return err; | |
40 | return 0; | |
41 | } | |
42 | ||
43 | /** | |
44 | * ubifs_hash_calc_hmac - calculate a HMAC from a hash | |
45 | * @c: UBIFS file-system description object | |
46 | * @hash: the node to calculate a HMAC for | |
47 | * @hmac: the returned HMAC | |
48 | * | |
49 | * Returns 0 for success or a negative error code otherwise. | |
50 | */ | |
51 | static int ubifs_hash_calc_hmac(const struct ubifs_info *c, const u8 *hash, | |
52 | u8 *hmac) | |
53 | { | |
54 | SHASH_DESC_ON_STACK(shash, c->hmac_tfm); | |
55 | int err; | |
56 | ||
57 | shash->tfm = c->hmac_tfm; | |
49525e5e SH |
58 | |
59 | err = crypto_shash_digest(shash, hash, c->hash_len, hmac); | |
60 | if (err < 0) | |
61 | return err; | |
62 | return 0; | |
63 | } | |
64 | ||
65 | /** | |
66 | * ubifs_prepare_auth_node - Prepare an authentication node | |
67 | * @c: UBIFS file-system description object | |
68 | * @node: the node to calculate a hash for | |
69 | * @hash: input hash of previous nodes | |
70 | * | |
71 | * This function prepares an authentication node for writing onto flash. | |
72 | * It creates a HMAC from the given input hash and writes it to the node. | |
73 | * | |
74 | * Returns 0 for success or a negative error code otherwise. | |
75 | */ | |
76 | int ubifs_prepare_auth_node(struct ubifs_info *c, void *node, | |
77 | struct shash_desc *inhash) | |
78 | { | |
49525e5e SH |
79 | struct ubifs_auth_node *auth = node; |
80 | u8 *hash; | |
81 | int err; | |
82 | ||
83 | hash = kmalloc(crypto_shash_descsize(c->hash_tfm), GFP_NOFS); | |
84 | if (!hash) | |
85 | return -ENOMEM; | |
86 | ||
f4844b35 AB |
87 | { |
88 | SHASH_DESC_ON_STACK(hash_desc, c->hash_tfm); | |
49525e5e | 89 | |
f4844b35 | 90 | hash_desc->tfm = c->hash_tfm; |
f4844b35 AB |
91 | ubifs_shash_copy_state(c, inhash, hash_desc); |
92 | ||
93 | err = crypto_shash_final(hash_desc, hash); | |
94 | if (err) | |
95 | goto out; | |
96 | } | |
49525e5e SH |
97 | |
98 | err = ubifs_hash_calc_hmac(c, hash, auth->hmac); | |
99 | if (err) | |
100 | goto out; | |
101 | ||
102 | auth->ch.node_type = UBIFS_AUTH_NODE; | |
103 | ubifs_prepare_node(c, auth, ubifs_auth_node_sz(c), 0); | |
104 | ||
105 | err = 0; | |
106 | out: | |
107 | kfree(hash); | |
108 | ||
109 | return err; | |
110 | } | |
111 | ||
112 | static struct shash_desc *ubifs_get_desc(const struct ubifs_info *c, | |
113 | struct crypto_shash *tfm) | |
114 | { | |
115 | struct shash_desc *desc; | |
116 | int err; | |
117 | ||
118 | if (!ubifs_authenticated(c)) | |
119 | return NULL; | |
120 | ||
121 | desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL); | |
122 | if (!desc) | |
123 | return ERR_PTR(-ENOMEM); | |
124 | ||
125 | desc->tfm = tfm; | |
49525e5e SH |
126 | |
127 | err = crypto_shash_init(desc); | |
128 | if (err) { | |
129 | kfree(desc); | |
130 | return ERR_PTR(err); | |
131 | } | |
132 | ||
133 | return desc; | |
134 | } | |
135 | ||
136 | /** | |
137 | * __ubifs_hash_get_desc - get a descriptor suitable for hashing a node | |
138 | * @c: UBIFS file-system description object | |
139 | * | |
140 | * This function returns a descriptor suitable for hashing a node. Free after use | |
141 | * with kfree. | |
142 | */ | |
143 | struct shash_desc *__ubifs_hash_get_desc(const struct ubifs_info *c) | |
144 | { | |
145 | return ubifs_get_desc(c, c->hash_tfm); | |
146 | } | |
147 | ||
49525e5e SH |
148 | /** |
149 | * ubifs_bad_hash - Report hash mismatches | |
150 | * @c: UBIFS file-system description object | |
151 | * @node: the node | |
152 | * @hash: the expected hash | |
153 | * @lnum: the LEB @node was read from | |
154 | * @offs: offset in LEB @node was read from | |
155 | * | |
156 | * This function reports a hash mismatch when a node has a different hash than | |
157 | * expected. | |
158 | */ | |
159 | void ubifs_bad_hash(const struct ubifs_info *c, const void *node, const u8 *hash, | |
160 | int lnum, int offs) | |
161 | { | |
162 | int len = min(c->hash_len, 20); | |
163 | int cropped = len != c->hash_len; | |
164 | const char *cont = cropped ? "..." : ""; | |
165 | ||
166 | u8 calc[UBIFS_HASH_ARR_SZ]; | |
167 | ||
168 | __ubifs_node_calc_hash(c, node, calc); | |
169 | ||
170 | ubifs_err(c, "hash mismatch on node at LEB %d:%d", lnum, offs); | |
171 | ubifs_err(c, "hash expected: %*ph%s", len, hash, cont); | |
172 | ubifs_err(c, "hash calculated: %*ph%s", len, calc, cont); | |
173 | } | |
174 | ||
175 | /** | |
176 | * __ubifs_node_check_hash - check the hash of a node against given hash | |
177 | * @c: UBIFS file-system description object | |
178 | * @node: the node | |
179 | * @expected: the expected hash | |
180 | * | |
181 | * This function calculates a hash over a node and compares it to the given hash. | |
182 | * Returns 0 if both hashes are equal or authentication is disabled, otherwise a | |
183 | * negative error code is returned. | |
184 | */ | |
185 | int __ubifs_node_check_hash(const struct ubifs_info *c, const void *node, | |
186 | const u8 *expected) | |
187 | { | |
188 | u8 calc[UBIFS_HASH_ARR_SZ]; | |
189 | int err; | |
190 | ||
191 | err = __ubifs_node_calc_hash(c, node, calc); | |
192 | if (err) | |
193 | return err; | |
194 | ||
195 | if (ubifs_check_hash(c, expected, calc)) | |
196 | return -EPERM; | |
197 | ||
198 | return 0; | |
199 | } | |
200 | ||
201 | /** | |
202 | * ubifs_init_authentication - initialize UBIFS authentication support | |
203 | * @c: UBIFS file-system description object | |
204 | * | |
205 | * This function returns 0 for success or a negative error code otherwise. | |
206 | */ | |
207 | int ubifs_init_authentication(struct ubifs_info *c) | |
208 | { | |
209 | struct key *keyring_key; | |
210 | const struct user_key_payload *ukp; | |
211 | int err; | |
212 | char hmac_name[CRYPTO_MAX_ALG_NAME]; | |
213 | ||
214 | if (!c->auth_hash_name) { | |
215 | ubifs_err(c, "authentication hash name needed with authentication"); | |
216 | return -EINVAL; | |
217 | } | |
218 | ||
219 | c->auth_hash_algo = match_string(hash_algo_name, HASH_ALGO__LAST, | |
220 | c->auth_hash_name); | |
221 | if ((int)c->auth_hash_algo < 0) { | |
222 | ubifs_err(c, "Unknown hash algo %s specified", | |
223 | c->auth_hash_name); | |
224 | return -EINVAL; | |
225 | } | |
226 | ||
227 | snprintf(hmac_name, CRYPTO_MAX_ALG_NAME, "hmac(%s)", | |
228 | c->auth_hash_name); | |
229 | ||
230 | keyring_key = request_key(&key_type_logon, c->auth_key_name, NULL); | |
231 | ||
232 | if (IS_ERR(keyring_key)) { | |
233 | ubifs_err(c, "Failed to request key: %ld", | |
234 | PTR_ERR(keyring_key)); | |
235 | return PTR_ERR(keyring_key); | |
236 | } | |
237 | ||
238 | down_read(&keyring_key->sem); | |
239 | ||
240 | if (keyring_key->type != &key_type_logon) { | |
241 | ubifs_err(c, "key type must be logon"); | |
242 | err = -ENOKEY; | |
243 | goto out; | |
244 | } | |
245 | ||
246 | ukp = user_key_payload_locked(keyring_key); | |
247 | if (!ukp) { | |
248 | /* key was revoked before we acquired its semaphore */ | |
249 | err = -EKEYREVOKED; | |
250 | goto out; | |
251 | } | |
252 | ||
3d234b33 | 253 | c->hash_tfm = crypto_alloc_shash(c->auth_hash_name, 0, 0); |
49525e5e SH |
254 | if (IS_ERR(c->hash_tfm)) { |
255 | err = PTR_ERR(c->hash_tfm); | |
256 | ubifs_err(c, "Can not allocate %s: %d", | |
257 | c->auth_hash_name, err); | |
258 | goto out; | |
259 | } | |
260 | ||
261 | c->hash_len = crypto_shash_digestsize(c->hash_tfm); | |
262 | if (c->hash_len > UBIFS_HASH_ARR_SZ) { | |
263 | ubifs_err(c, "hash %s is bigger than maximum allowed hash size (%d > %d)", | |
264 | c->auth_hash_name, c->hash_len, UBIFS_HASH_ARR_SZ); | |
265 | err = -EINVAL; | |
266 | goto out_free_hash; | |
267 | } | |
268 | ||
3d234b33 | 269 | c->hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0); |
49525e5e SH |
270 | if (IS_ERR(c->hmac_tfm)) { |
271 | err = PTR_ERR(c->hmac_tfm); | |
272 | ubifs_err(c, "Can not allocate %s: %d", hmac_name, err); | |
273 | goto out_free_hash; | |
274 | } | |
275 | ||
276 | c->hmac_desc_len = crypto_shash_digestsize(c->hmac_tfm); | |
277 | if (c->hmac_desc_len > UBIFS_HMAC_ARR_SZ) { | |
278 | ubifs_err(c, "hmac %s is bigger than maximum allowed hmac size (%d > %d)", | |
279 | hmac_name, c->hmac_desc_len, UBIFS_HMAC_ARR_SZ); | |
280 | err = -EINVAL; | |
281 | goto out_free_hash; | |
282 | } | |
283 | ||
284 | err = crypto_shash_setkey(c->hmac_tfm, ukp->data, ukp->datalen); | |
285 | if (err) | |
286 | goto out_free_hmac; | |
287 | ||
288 | c->authenticated = true; | |
289 | ||
290 | c->log_hash = ubifs_hash_get_desc(c); | |
291 | if (IS_ERR(c->log_hash)) | |
292 | goto out_free_hmac; | |
293 | ||
294 | err = 0; | |
295 | ||
296 | out_free_hmac: | |
297 | if (err) | |
298 | crypto_free_shash(c->hmac_tfm); | |
299 | out_free_hash: | |
300 | if (err) | |
301 | crypto_free_shash(c->hash_tfm); | |
302 | out: | |
303 | up_read(&keyring_key->sem); | |
304 | key_put(keyring_key); | |
305 | ||
306 | return err; | |
307 | } | |
308 | ||
309 | /** | |
310 | * __ubifs_exit_authentication - release resource | |
311 | * @c: UBIFS file-system description object | |
312 | * | |
313 | * This function releases the authentication related resources. | |
314 | */ | |
315 | void __ubifs_exit_authentication(struct ubifs_info *c) | |
316 | { | |
317 | if (!ubifs_authenticated(c)) | |
318 | return; | |
319 | ||
320 | crypto_free_shash(c->hmac_tfm); | |
321 | crypto_free_shash(c->hash_tfm); | |
322 | kfree(c->log_hash); | |
323 | } | |
324 | ||
325 | /** | |
326 | * ubifs_node_calc_hmac - calculate the HMAC of a UBIFS node | |
327 | * @c: UBIFS file-system description object | |
328 | * @node: the node to insert a HMAC into. | |
329 | * @len: the length of the node | |
330 | * @ofs_hmac: the offset in the node where the HMAC is inserted | |
331 | * @hmac: returned HMAC | |
332 | * | |
333 | * This function calculates a HMAC of a UBIFS node. The HMAC is expected to be | |
334 | * embedded into the node, so this area is not covered by the HMAC. Also not | |
335 | * covered is the UBIFS_NODE_MAGIC and the CRC of the node. | |
336 | */ | |
337 | static int ubifs_node_calc_hmac(const struct ubifs_info *c, const void *node, | |
338 | int len, int ofs_hmac, void *hmac) | |
339 | { | |
340 | SHASH_DESC_ON_STACK(shash, c->hmac_tfm); | |
341 | int hmac_len = c->hmac_desc_len; | |
342 | int err; | |
343 | ||
344 | ubifs_assert(c, ofs_hmac > 8); | |
345 | ubifs_assert(c, ofs_hmac + hmac_len < len); | |
346 | ||
347 | shash->tfm = c->hmac_tfm; | |
49525e5e SH |
348 | |
349 | err = crypto_shash_init(shash); | |
350 | if (err) | |
351 | return err; | |
352 | ||
353 | /* behind common node header CRC up to HMAC begin */ | |
354 | err = crypto_shash_update(shash, node + 8, ofs_hmac - 8); | |
355 | if (err < 0) | |
356 | return err; | |
357 | ||
358 | /* behind HMAC, if any */ | |
359 | if (len - ofs_hmac - hmac_len > 0) { | |
360 | err = crypto_shash_update(shash, node + ofs_hmac + hmac_len, | |
361 | len - ofs_hmac - hmac_len); | |
362 | if (err < 0) | |
363 | return err; | |
364 | } | |
365 | ||
366 | return crypto_shash_final(shash, hmac); | |
367 | } | |
368 | ||
369 | /** | |
370 | * __ubifs_node_insert_hmac - insert a HMAC into a UBIFS node | |
371 | * @c: UBIFS file-system description object | |
372 | * @node: the node to insert a HMAC into. | |
373 | * @len: the length of the node | |
374 | * @ofs_hmac: the offset in the node where the HMAC is inserted | |
375 | * | |
376 | * This function inserts a HMAC at offset @ofs_hmac into the node given in | |
377 | * @node. | |
378 | * | |
379 | * This function returns 0 for success or a negative error code otherwise. | |
380 | */ | |
381 | int __ubifs_node_insert_hmac(const struct ubifs_info *c, void *node, int len, | |
382 | int ofs_hmac) | |
383 | { | |
384 | return ubifs_node_calc_hmac(c, node, len, ofs_hmac, node + ofs_hmac); | |
385 | } | |
386 | ||
387 | /** | |
388 | * __ubifs_node_verify_hmac - verify the HMAC of UBIFS node | |
389 | * @c: UBIFS file-system description object | |
390 | * @node: the node to insert a HMAC into. | |
391 | * @len: the length of the node | |
392 | * @ofs_hmac: the offset in the node where the HMAC is inserted | |
393 | * | |
394 | * This function verifies the HMAC at offset @ofs_hmac of the node given in | |
395 | * @node. Returns 0 if successful or a negative error code otherwise. | |
396 | */ | |
397 | int __ubifs_node_verify_hmac(const struct ubifs_info *c, const void *node, | |
398 | int len, int ofs_hmac) | |
399 | { | |
400 | int hmac_len = c->hmac_desc_len; | |
401 | u8 *hmac; | |
402 | int err; | |
403 | ||
404 | hmac = kmalloc(hmac_len, GFP_NOFS); | |
405 | if (!hmac) | |
406 | return -ENOMEM; | |
407 | ||
408 | err = ubifs_node_calc_hmac(c, node, len, ofs_hmac, hmac); | |
409 | if (err) | |
410 | return err; | |
411 | ||
412 | err = crypto_memneq(hmac, node + ofs_hmac, hmac_len); | |
413 | ||
414 | kfree(hmac); | |
415 | ||
416 | if (!err) | |
417 | return 0; | |
418 | ||
419 | return -EPERM; | |
420 | } | |
421 | ||
422 | int __ubifs_shash_copy_state(const struct ubifs_info *c, struct shash_desc *src, | |
423 | struct shash_desc *target) | |
424 | { | |
425 | u8 *state; | |
426 | int err; | |
427 | ||
428 | state = kmalloc(crypto_shash_descsize(src->tfm), GFP_NOFS); | |
429 | if (!state) | |
430 | return -ENOMEM; | |
431 | ||
432 | err = crypto_shash_export(src, state); | |
433 | if (err) | |
434 | goto out; | |
435 | ||
436 | err = crypto_shash_import(target, state); | |
437 | ||
438 | out: | |
439 | kfree(state); | |
440 | ||
441 | return err; | |
442 | } | |
443 | ||
444 | /** | |
445 | * ubifs_hmac_wkm - Create a HMAC of the well known message | |
446 | * @c: UBIFS file-system description object | |
447 | * @hmac: The HMAC of the well known message | |
448 | * | |
449 | * This function creates a HMAC of a well known message. This is used | |
450 | * to check if the provided key is suitable to authenticate a UBIFS | |
451 | * image. This is only a convenience to the user to provide a better | |
452 | * error message when the wrong key is provided. | |
453 | * | |
454 | * This function returns 0 for success or a negative error code otherwise. | |
455 | */ | |
456 | int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac) | |
457 | { | |
458 | SHASH_DESC_ON_STACK(shash, c->hmac_tfm); | |
459 | int err; | |
460 | const char well_known_message[] = "UBIFS"; | |
461 | ||
462 | if (!ubifs_authenticated(c)) | |
463 | return 0; | |
464 | ||
465 | shash->tfm = c->hmac_tfm; | |
49525e5e SH |
466 | |
467 | err = crypto_shash_init(shash); | |
468 | if (err) | |
469 | return err; | |
470 | ||
471 | err = crypto_shash_update(shash, well_known_message, | |
472 | sizeof(well_known_message) - 1); | |
473 | if (err < 0) | |
474 | return err; | |
475 | ||
476 | err = crypto_shash_final(shash, hmac); | |
477 | if (err) | |
478 | return err; | |
479 | return 0; | |
480 | } |