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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 <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>
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 */
30int __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;
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 */
53static 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;
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 */
78int ubifs_prepare_auth_node(struct ubifs_info *c, void *node,
79 struct shash_desc *inhash)
80{
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
89 {
90 SHASH_DESC_ON_STACK(hash_desc, c->hash_tfm);
91
92 hash_desc->tfm = c->hash_tfm;
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 }
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;
108out:
109 kfree(hash);
110
111 return err;
112}
113
114static 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;
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 */
145struct shash_desc *__ubifs_hash_get_desc(const struct ubifs_info *c)
146{
147 return ubifs_get_desc(c, c->hash_tfm);
148}
149
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 */
161void 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 */
187int __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
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 */
215int 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
268out_destroy:
269 ubifs_scan_destroy(sleb);
270
271 return err;
272}
273
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 */
280int 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
326 c->hash_tfm = crypto_alloc_shash(c->auth_hash_name, 0, 0);
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
342 c->hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0);
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
369out_free_hmac:
370 if (err)
371 crypto_free_shash(c->hmac_tfm);
372out_free_hash:
373 if (err)
374 crypto_free_shash(c->hash_tfm);
375out:
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 */
388void __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 */
410static 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;
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 */
454int __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 */
470int __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);
482 if (err) {
483 kfree(hmac);
484 return err;
485 }
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
497int __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
513out:
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 */
531int 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;
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}
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 */
565bool ubifs_hmac_zero(struct ubifs_info *c, const u8 *hmac)
566{
567 return !memchr_inv(hmac, 0, c->hmac_desc_len);
568}