summaryrefslogtreecommitdiffstats
path: root/fs/ubifs/auth.c
blob: b758004085c4758c0127c1d51c7fc172db8c7ac1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
// SPDX-License-Identifier: GPL-2.0
/*
 * This file is part of UBIFS.
 *
 * Copyright (C) 2018 Pengutronix, Sascha Hauer <s.hauer@pengutronix.de>
 */

/*
 * This file implements various helper functions for UBIFS authentication support
 */

#include <linux/crypto.h>
#include <crypto/hash.h>
#include <crypto/sha.h>
#include <crypto/algapi.h>
#include <keys/user-type.h>

#include "ubifs.h"

/**
 * ubifs_node_calc_hash - calculate the hash of a UBIFS node
 * @c: UBIFS file-system description object
 * @node: the node to calculate a hash for
 * @hash: the returned hash
 *
 * Returns 0 for success or a negative error code otherwise.
 */
int __ubifs_node_calc_hash(const struct ubifs_info *c, const void *node,
			    u8 *hash)
{
	const struct ubifs_ch *ch = node;
	SHASH_DESC_ON_STACK(shash, c->hash_tfm);
	int err;

	shash->tfm = c->hash_tfm;

	err = crypto_shash_digest(shash, node, le32_to_cpu(ch->len), hash);
	if (err < 0)
		return err;
	return 0;
}

/**
 * ubifs_hash_calc_hmac - calculate a HMAC from a hash
 * @c: UBIFS file-system description object
 * @hash: the node to calculate a HMAC for
 * @hmac: the returned HMAC
 *
 * Returns 0 for success or a negative error code otherwise.
 */
static int ubifs_hash_calc_hmac(const struct ubifs_info *c, const u8 *hash,
				 u8 *hmac)
{
	SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
	int err;

	shash->tfm = c->hmac_tfm;

	err = crypto_shash_digest(shash, hash, c->hash_len, hmac);
	if (err < 0)
		return err;
	return 0;
}

/**
 * ubifs_prepare_auth_node - Prepare an authentication node
 * @c: UBIFS file-system description object
 * @node: the node to calculate a hash for
 * @hash: input hash of previous nodes
 *
 * This function prepares an authentication node for writing onto flash.
 * It creates a HMAC from the given input hash and writes it to the node.
 *
 * Returns 0 for success or a negative error code otherwise.
 */
int ubifs_prepare_auth_node(struct ubifs_info *c, void *node,
			     struct shash_desc *inhash)
{
	SHASH_DESC_ON_STACK(hash_desc, c->hash_tfm);
	struct ubifs_auth_node *auth = node;
	u8 *hash;
	int err;

	hash = kmalloc(crypto_shash_descsize(c->hash_tfm), GFP_NOFS);
	if (!hash)
		return -ENOMEM;

	hash_desc->tfm = c->hash_tfm;
	ubifs_shash_copy_state(c, inhash, hash_desc);

	err = crypto_shash_final(hash_desc, hash);
	if (err)
		goto out;

	err = ubifs_hash_calc_hmac(c, hash, auth->hmac);
	if (err)
		goto out;

	auth->ch.node_type = UBIFS_AUTH_NODE;
	ubifs_prepare_node(c, auth, ubifs_auth_node_sz(c), 0);

	err = 0;
out:
	kfree(hash);

	return err;
}

static struct shash_desc *ubifs_get_desc(const struct ubifs_info *c,
					 struct crypto_shash *tfm)
{
	struct shash_desc *desc;
	int err;

	if (!ubifs_authenticated(c))
		return NULL;

	desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL);
	if (!desc)
		return ERR_PTR(-ENOMEM);

	desc->tfm = tfm;

	err = crypto_shash_init(desc);
	if (err) {
		kfree(desc);
		return ERR_PTR(err);
	}

	return desc;
}

/**
 * __ubifs_hash_get_desc - get a descriptor suitable for hashing a node
 * @c: UBIFS file-system description object
 *
 * This function returns a descriptor suitable for hashing a node. Free after use
 * with kfree.
 */
struct shash_desc *__ubifs_hash_get_desc(const struct ubifs_info *c)
{
	return ubifs_get_desc(c, c->hash_tfm);
}

/**
 * __ubifs_shash_final - finalize shash
 * @c: UBIFS file-system description object
 * @desc: the descriptor
 * @out: the output hash
 *
 * Simple wrapper around crypto_shash_final(), safe to be called with
 * disabled authentication.
 */
int __ubifs_shash_final(const struct ubifs_info *c, struct shash_desc *desc,
			u8 *out)
{
	if (ubifs_authenticated(c))
		return crypto_shash_final(desc, out);

	return 0;
}

/**
 * ubifs_bad_hash - Report hash mismatches
 * @c: UBIFS file-system description object
 * @node: the node
 * @hash: the expected hash
 * @lnum: the LEB @node was read from
 * @offs: offset in LEB @node was read from
 *
 * This function reports a hash mismatch when a node has a different hash than
 * expected.
 */
void ubifs_bad_hash(const struct ubifs_info *c, const void *node, const u8 *hash,
		    int lnum, int offs)
{
	int len = min(c->hash_len, 20);
	int cropped = len != c->hash_len;
	const char *cont = cropped ? "..." : "";

	u8 calc[UBIFS_HASH_ARR_SZ];

	__ubifs_node_calc_hash(c, node, calc);

	ubifs_err(c, "hash mismatch on node at LEB %d:%d", lnum, offs);
	ubifs_err(c, "hash expected:   %*ph%s", len, hash, cont);
	ubifs_err(c, "hash calculated: %*ph%s", len, calc, cont);
}

/**
 * __ubifs_node_check_hash - check the hash of a node against given hash
 * @c: UBIFS file-system description object
 * @node: the node
 * @expected: the expected hash
 *
 * This function calculates a hash over a node and compares it to the given hash.
 * Returns 0 if both hashes are equal or authentication is disabled, otherwise a
 * negative error code is returned.
 */
int __ubifs_node_check_hash(const struct ubifs_info *c, const void *node,
			    const u8 *expected)
{
	u8 calc[UBIFS_HASH_ARR_SZ];
	int err;

	err = __ubifs_node_calc_hash(c, node, calc);
	if (err)
		return err;

	if (ubifs_check_hash(c, expected, calc))
		return -EPERM;

	return 0;
}

/**
 * ubifs_init_authentication - initialize UBIFS authentication support
 * @c: UBIFS file-system description object
 *
 * This function returns 0 for success or a negative error code otherwise.
 */
int ubifs_init_authentication(struct ubifs_info *c)
{
	struct key *keyring_key;
	const struct user_key_payload *ukp;
	int err;
	char hmac_name[CRYPTO_MAX_ALG_NAME];

	if (!c->auth_hash_name) {
		ubifs_err(c, "authentication hash name needed with authentication");
		return -EINVAL;
	}

	c->auth_hash_algo = match_string(hash_algo_name, HASH_ALGO__LAST,
					 c->auth_hash_name);
	if ((int)c->auth_hash_algo < 0) {
		ubifs_err(c, "Unknown hash algo %s specified",
			  c->auth_hash_name);
		return -EINVAL;
	}

	snprintf(hmac_name, CRYPTO_MAX_ALG_NAME, "hmac(%s)",
		 c->auth_hash_name);

	keyring_key = request_key(&key_type_logon, c->auth_key_name, NULL);

	if (IS_ERR(keyring_key)) {
		ubifs_err(c, "Failed to request key: %ld",
			  PTR_ERR(keyring_key));
		return PTR_ERR(keyring_key);
	}

	down_read(&keyring_key->sem);

	if (keyring_key->type != &key_type_logon) {
		ubifs_err(c, "key type must be logon");
		err = -ENOKEY;
		goto out;
	}

	ukp = user_key_payload_locked(keyring_key);
	if (!ukp) {
		/* key was revoked before we acquired its semaphore */
		err = -EKEYREVOKED;
		goto out;
	}

	c->hash_tfm = crypto_alloc_shash(c->auth_hash_name, 0, 0);
	if (IS_ERR(c->hash_tfm)) {
		err = PTR_ERR(c->hash_tfm);
		ubifs_err(c, "Can not allocate %s: %d",
			  c->auth_hash_name, err);
		goto out;
	}

	c->hash_len = crypto_shash_digestsize(c->hash_tfm);
	if (c->hash_len > UBIFS_HASH_ARR_SZ) {
		ubifs_err(c, "hash %s is bigger than maximum allowed hash size (%d > %d)",
			  c->auth_hash_name, c->hash_len, UBIFS_HASH_ARR_SZ);
		err = -EINVAL;
		goto out_free_hash;
	}

	c->hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0);
	if (IS_ERR(c->hmac_tfm)) {
		err = PTR_ERR(c->hmac_tfm);
		ubifs_err(c, "Can not allocate %s: %d", hmac_name, err);
		goto out_free_hash;
	}

	c->hmac_desc_len = crypto_shash_digestsize(c->hmac_tfm);
	if (c->hmac_desc_len > UBIFS_HMAC_ARR_SZ) {
		ubifs_err(c, "hmac %s is bigger than maximum allowed hmac size (%d > %d)",
			  hmac_name, c->hmac_desc_len, UBIFS_HMAC_ARR_SZ);
		err = -EINVAL;
		goto out_free_hash;
	}

	err = crypto_shash_setkey(c->hmac_tfm, ukp->data, ukp->datalen);
	if (err)
		goto out_free_hmac;

	c->authenticated = true;

	c->log_hash = ubifs_hash_get_desc(c);
	if (IS_ERR(c->log_hash))
		goto out_free_hmac;

	err = 0;

out_free_hmac:
	if (err)
		crypto_free_shash(c->hmac_tfm);
out_free_hash:
	if (err)
		crypto_free_shash(c->hash_tfm);
out:
	up_read(&keyring_key->sem);
	key_put(keyring_key);

	return err;
}

/**
 * __ubifs_exit_authentication - release resource
 * @c: UBIFS file-system description object
 *
 * This function releases the authentication related resources.
 */
void __ubifs_exit_authentication(struct ubifs_info *c)
{
	if (!ubifs_authenticated(c))
		return;

	crypto_free_shash(c->hmac_tfm);
	crypto_free_shash(c->hash_tfm);
	kfree(c->log_hash);
}

/**
 * ubifs_node_calc_hmac - calculate the HMAC of a UBIFS node
 * @c: UBIFS file-system description object
 * @node: the node to insert a HMAC into.
 * @len: the length of the node
 * @ofs_hmac: the offset in the node where the HMAC is inserted
 * @hmac: returned HMAC
 *
 * This function calculates a HMAC of a UBIFS node. The HMAC is expected to be
 * embedded into the node, so this area is not covered by the HMAC. Also not
 * covered is the UBIFS_NODE_MAGIC and the CRC of the node.
 */
static int ubifs_node_calc_hmac(const struct ubifs_info *c, const void *node,
				int len, int ofs_hmac, void *hmac)
{
	SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
	int hmac_len = c->hmac_desc_len;
	int err;

	ubifs_assert(c, ofs_hmac > 8);
	ubifs_assert(c, ofs_hmac + hmac_len < len);

	shash->tfm = c->hmac_tfm;

	err = crypto_shash_init(shash);
	if (err)
		return err;

	/* behind common node header CRC up to HMAC begin */
	err = crypto_shash_update(shash, node + 8, ofs_hmac - 8);
	if (err < 0)
		return err;

	/* behind HMAC, if any */
	if (len - ofs_hmac - hmac_len > 0) {
		err = crypto_shash_update(shash, node + ofs_hmac + hmac_len,
			    len - ofs_hmac - hmac_len);
		if (err < 0)
			return err;
	}

	return crypto_shash_final(shash, hmac);
}

/**
 * __ubifs_node_insert_hmac - insert a HMAC into a UBIFS node
 * @c: UBIFS file-system description object
 * @node: the node to insert a HMAC into.
 * @len: the length of the node
 * @ofs_hmac: the offset in the node where the HMAC is inserted
 *
 * This function inserts a HMAC at offset @ofs_hmac into the node given in
 * @node.
 *
 * This function returns 0 for success or a negative error code otherwise.
 */
int __ubifs_node_insert_hmac(const struct ubifs_info *c, void *node, int len,
			    int ofs_hmac)
{
	return ubifs_node_calc_hmac(c, node, len, ofs_hmac, node + ofs_hmac);
}

/**
 * __ubifs_node_verify_hmac - verify the HMAC of UBIFS node
 * @c: UBIFS file-system description object
 * @node: the node to insert a HMAC into.
 * @len: the length of the node
 * @ofs_hmac: the offset in the node where the HMAC is inserted
 *
 * This function verifies the HMAC at offset @ofs_hmac of the node given in
 * @node. Returns 0 if successful or a negative error code otherwise.
 */
int __ubifs_node_verify_hmac(const struct ubifs_info *c, const void *node,
			     int len, int ofs_hmac)
{
	int hmac_len = c->hmac_desc_len;
	u8 *hmac;
	int err;

	hmac = kmalloc(hmac_len, GFP_NOFS);
	if (!hmac)
		return -ENOMEM;

	err = ubifs_node_calc_hmac(c, node, len, ofs_hmac, hmac);
	if (err)
		return err;

	err = crypto_memneq(hmac, node + ofs_hmac, hmac_len);

	kfree(hmac);

	if (!err)
		return 0;

	return -EPERM;
}

int __ubifs_shash_copy_state(const struct ubifs_info *c, struct shash_desc *src,
			     struct shash_desc *target)
{
	u8 *state;
	int err;

	state = kmalloc(crypto_shash_descsize(src->tfm), GFP_NOFS);
	if (!state)
		return -ENOMEM;

	err = crypto_shash_export(src, state);
	if (err)
		goto out;

	err = crypto_shash_import(target, state);

out:
	kfree(state);

	return err;
}

/**
 * ubifs_hmac_wkm - Create a HMAC of the well known message
 * @c: UBIFS file-system description object
 * @hmac: The HMAC of the well known message
 *
 * This function creates a HMAC of a well known message. This is used
 * to check if the provided key is suitable to authenticate a UBIFS
 * image. This is only a convenience to the user to provide a better
 * error message when the wrong key is provided.
 *
 * This function returns 0 for success or a negative error code otherwise.
 */
int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac)
{
	SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
	int err;
	const char well_known_message[] = "UBIFS";

	if (!ubifs_authenticated(c))
		return 0;

	shash->tfm = c->hmac_tfm;

	err = crypto_shash_init(shash);
	if (err)
		return err;

	err = crypto_shash_update(shash, well_known_message,
				  sizeof(well_known_message) - 1);
	if (err < 0)
		return err;

	err = crypto_shash_final(shash, hmac);
	if (err)
		return err;
	return 0;
}