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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Key setup facility for FS encryption support.
4 *
5 * Copyright (C) 2015, Google, Inc.
6 *
7 * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
8 * Heavily modified since then.
9 */
10
11#include <crypto/aes.h>
12#include <crypto/sha.h>
13#include <crypto/skcipher.h>
14#include <linux/key.h>
15
16#include "fscrypt_private.h"
17
18static struct crypto_shash *essiv_hash_tfm;
19
20static struct fscrypt_mode available_modes[] = {
21 [FSCRYPT_MODE_AES_256_XTS] = {
22 .friendly_name = "AES-256-XTS",
23 .cipher_str = "xts(aes)",
24 .keysize = 64,
25 .ivsize = 16,
26 },
27 [FSCRYPT_MODE_AES_256_CTS] = {
28 .friendly_name = "AES-256-CTS-CBC",
29 .cipher_str = "cts(cbc(aes))",
30 .keysize = 32,
31 .ivsize = 16,
32 },
33 [FSCRYPT_MODE_AES_128_CBC] = {
34 .friendly_name = "AES-128-CBC",
35 .cipher_str = "cbc(aes)",
36 .keysize = 16,
37 .ivsize = 16,
38 .needs_essiv = true,
39 },
40 [FSCRYPT_MODE_AES_128_CTS] = {
41 .friendly_name = "AES-128-CTS-CBC",
42 .cipher_str = "cts(cbc(aes))",
43 .keysize = 16,
44 .ivsize = 16,
45 },
46 [FSCRYPT_MODE_ADIANTUM] = {
47 .friendly_name = "Adiantum",
48 .cipher_str = "adiantum(xchacha12,aes)",
49 .keysize = 32,
50 .ivsize = 32,
51 },
52};
53
54static struct fscrypt_mode *
55select_encryption_mode(const union fscrypt_policy *policy,
56 const struct inode *inode)
57{
58 if (S_ISREG(inode->i_mode))
59 return &available_modes[fscrypt_policy_contents_mode(policy)];
60
61 if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
62 return &available_modes[fscrypt_policy_fnames_mode(policy)];
63
64 WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
65 inode->i_ino, (inode->i_mode & S_IFMT));
66 return ERR_PTR(-EINVAL);
67}
68
69/* Create a symmetric cipher object for the given encryption mode and key */
70struct crypto_skcipher *fscrypt_allocate_skcipher(struct fscrypt_mode *mode,
71 const u8 *raw_key,
72 const struct inode *inode)
73{
74 struct crypto_skcipher *tfm;
75 int err;
76
77 tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
78 if (IS_ERR(tfm)) {
79 if (PTR_ERR(tfm) == -ENOENT) {
80 fscrypt_warn(inode,
81 "Missing crypto API support for %s (API name: \"%s\")",
82 mode->friendly_name, mode->cipher_str);
83 return ERR_PTR(-ENOPKG);
84 }
85 fscrypt_err(inode, "Error allocating '%s' transform: %ld",
86 mode->cipher_str, PTR_ERR(tfm));
87 return tfm;
88 }
89 if (unlikely(!mode->logged_impl_name)) {
90 /*
91 * fscrypt performance can vary greatly depending on which
92 * crypto algorithm implementation is used. Help people debug
93 * performance problems by logging the ->cra_driver_name the
94 * first time a mode is used. Note that multiple threads can
95 * race here, but it doesn't really matter.
96 */
97 mode->logged_impl_name = true;
98 pr_info("fscrypt: %s using implementation \"%s\"\n",
99 mode->friendly_name,
100 crypto_skcipher_alg(tfm)->base.cra_driver_name);
101 }
102 crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
103 err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize);
104 if (err)
105 goto err_free_tfm;
106
107 return tfm;
108
109err_free_tfm:
110 crypto_free_skcipher(tfm);
111 return ERR_PTR(err);
112}
113
114static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt)
115{
116 struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm);
117
118 /* init hash transform on demand */
119 if (unlikely(!tfm)) {
120 struct crypto_shash *prev_tfm;
121
122 tfm = crypto_alloc_shash("sha256", 0, 0);
123 if (IS_ERR(tfm)) {
124 if (PTR_ERR(tfm) == -ENOENT) {
125 fscrypt_warn(NULL,
126 "Missing crypto API support for SHA-256");
127 return -ENOPKG;
128 }
129 fscrypt_err(NULL,
130 "Error allocating SHA-256 transform: %ld",
131 PTR_ERR(tfm));
132 return PTR_ERR(tfm);
133 }
134 prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);
135 if (prev_tfm) {
136 crypto_free_shash(tfm);
137 tfm = prev_tfm;
138 }
139 }
140
141 {
142 SHASH_DESC_ON_STACK(desc, tfm);
143 desc->tfm = tfm;
144
145 return crypto_shash_digest(desc, key, keysize, salt);
146 }
147}
148
149static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key,
150 int keysize)
151{
152 int err;
153 struct crypto_cipher *essiv_tfm;
154 u8 salt[SHA256_DIGEST_SIZE];
155
156 if (WARN_ON(ci->ci_mode->ivsize != AES_BLOCK_SIZE))
157 return -EINVAL;
158
159 essiv_tfm = crypto_alloc_cipher("aes", 0, 0);
160 if (IS_ERR(essiv_tfm))
161 return PTR_ERR(essiv_tfm);
162
163 ci->ci_essiv_tfm = essiv_tfm;
164
165 err = derive_essiv_salt(raw_key, keysize, salt);
166 if (err)
167 goto out;
168
169 /*
170 * Using SHA256 to derive the salt/key will result in AES-256 being
171 * used for IV generation. File contents encryption will still use the
172 * configured keysize (AES-128) nevertheless.
173 */
174 err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt));
175 if (err)
176 goto out;
177
178out:
179 memzero_explicit(salt, sizeof(salt));
180 return err;
181}
182
183/* Given the per-file key, set up the file's crypto transform object(s) */
184int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key)
185{
186 struct fscrypt_mode *mode = ci->ci_mode;
187 struct crypto_skcipher *ctfm;
188 int err;
189
190 ctfm = fscrypt_allocate_skcipher(mode, derived_key, ci->ci_inode);
191 if (IS_ERR(ctfm))
192 return PTR_ERR(ctfm);
193
194 ci->ci_ctfm = ctfm;
195
196 if (mode->needs_essiv) {
197 err = init_essiv_generator(ci, derived_key, mode->keysize);
198 if (err) {
199 fscrypt_warn(ci->ci_inode,
200 "Error initializing ESSIV generator: %d",
201 err);
202 return err;
203 }
204 }
205 return 0;
206}
207
208static int setup_per_mode_key(struct fscrypt_info *ci,
209 struct fscrypt_master_key *mk)
210{
211 struct fscrypt_mode *mode = ci->ci_mode;
212 u8 mode_num = mode - available_modes;
213 struct crypto_skcipher *tfm, *prev_tfm;
214 u8 mode_key[FSCRYPT_MAX_KEY_SIZE];
215 int err;
216
217 if (WARN_ON(mode_num >= ARRAY_SIZE(mk->mk_mode_keys)))
218 return -EINVAL;
219
220 /* pairs with cmpxchg() below */
221 tfm = READ_ONCE(mk->mk_mode_keys[mode_num]);
222 if (likely(tfm != NULL))
223 goto done;
224
225 BUILD_BUG_ON(sizeof(mode_num) != 1);
226 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
227 HKDF_CONTEXT_PER_MODE_KEY,
228 &mode_num, sizeof(mode_num),
229 mode_key, mode->keysize);
230 if (err)
231 return err;
232 tfm = fscrypt_allocate_skcipher(mode, mode_key, ci->ci_inode);
233 memzero_explicit(mode_key, mode->keysize);
234 if (IS_ERR(tfm))
235 return PTR_ERR(tfm);
236
237 /* pairs with READ_ONCE() above */
238 prev_tfm = cmpxchg(&mk->mk_mode_keys[mode_num], NULL, tfm);
239 if (prev_tfm != NULL) {
240 crypto_free_skcipher(tfm);
241 tfm = prev_tfm;
242 }
243done:
244 ci->ci_ctfm = tfm;
245 return 0;
246}
247
248static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
249 struct fscrypt_master_key *mk)
250{
251 u8 derived_key[FSCRYPT_MAX_KEY_SIZE];
252 int err;
253
254 if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
255 /*
256 * DIRECT_KEY: instead of deriving per-file keys, the per-file
257 * nonce will be included in all the IVs. But unlike v1
258 * policies, for v2 policies in this case we don't encrypt with
259 * the master key directly but rather derive a per-mode key.
260 * This ensures that the master key is consistently used only
261 * for HKDF, avoiding key reuse issues.
262 */
263 if (!fscrypt_mode_supports_direct_key(ci->ci_mode)) {
264 fscrypt_warn(ci->ci_inode,
265 "Direct key flag not allowed with %s",
266 ci->ci_mode->friendly_name);
267 return -EINVAL;
268 }
269 return setup_per_mode_key(ci, mk);
270 }
271
272 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
273 HKDF_CONTEXT_PER_FILE_KEY,
274 ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE,
275 derived_key, ci->ci_mode->keysize);
276 if (err)
277 return err;
278
279 err = fscrypt_set_derived_key(ci, derived_key);
280 memzero_explicit(derived_key, ci->ci_mode->keysize);
281 return err;
282}
283
284/*
285 * Find the master key, then set up the inode's actual encryption key.
286 *
287 * If the master key is found in the filesystem-level keyring, then the
288 * corresponding 'struct key' is returned in *master_key_ret with
289 * ->mk_secret_sem read-locked. This is needed to ensure that only one task
290 * links the fscrypt_info into ->mk_decrypted_inodes (as multiple tasks may race
291 * to create an fscrypt_info for the same inode), and to synchronize the master
292 * key being removed with a new inode starting to use it.
293 */
294static int setup_file_encryption_key(struct fscrypt_info *ci,
295 struct key **master_key_ret)
296{
297 struct key *key;
298 struct fscrypt_master_key *mk = NULL;
299 struct fscrypt_key_specifier mk_spec;
300 int err;
301
302 switch (ci->ci_policy.version) {
303 case FSCRYPT_POLICY_V1:
304 mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
305 memcpy(mk_spec.u.descriptor,
306 ci->ci_policy.v1.master_key_descriptor,
307 FSCRYPT_KEY_DESCRIPTOR_SIZE);
308 break;
309 case FSCRYPT_POLICY_V2:
310 mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
311 memcpy(mk_spec.u.identifier,
312 ci->ci_policy.v2.master_key_identifier,
313 FSCRYPT_KEY_IDENTIFIER_SIZE);
314 break;
315 default:
316 WARN_ON(1);
317 return -EINVAL;
318 }
319
320 key = fscrypt_find_master_key(ci->ci_inode->i_sb, &mk_spec);
321 if (IS_ERR(key)) {
322 if (key != ERR_PTR(-ENOKEY) ||
323 ci->ci_policy.version != FSCRYPT_POLICY_V1)
324 return PTR_ERR(key);
325
326 /*
327 * As a legacy fallback for v1 policies, search for the key in
328 * the current task's subscribed keyrings too. Don't move this
329 * to before the search of ->s_master_keys, since users
330 * shouldn't be able to override filesystem-level keys.
331 */
332 return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
333 }
334
335 mk = key->payload.data[0];
336 down_read(&mk->mk_secret_sem);
337
338 /* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */
339 if (!is_master_key_secret_present(&mk->mk_secret)) {
340 err = -ENOKEY;
341 goto out_release_key;
342 }
343
344 /*
345 * Require that the master key be at least as long as the derived key.
346 * Otherwise, the derived key cannot possibly contain as much entropy as
347 * that required by the encryption mode it will be used for. For v1
348 * policies it's also required for the KDF to work at all.
349 */
350 if (mk->mk_secret.size < ci->ci_mode->keysize) {
351 fscrypt_warn(NULL,
352 "key with %s %*phN is too short (got %u bytes, need %u+ bytes)",
353 master_key_spec_type(&mk_spec),
354 master_key_spec_len(&mk_spec), (u8 *)&mk_spec.u,
355 mk->mk_secret.size, ci->ci_mode->keysize);
356 err = -ENOKEY;
357 goto out_release_key;
358 }
359
360 switch (ci->ci_policy.version) {
361 case FSCRYPT_POLICY_V1:
362 err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
363 break;
364 case FSCRYPT_POLICY_V2:
365 err = fscrypt_setup_v2_file_key(ci, mk);
366 break;
367 default:
368 WARN_ON(1);
369 err = -EINVAL;
370 break;
371 }
372 if (err)
373 goto out_release_key;
374
375 *master_key_ret = key;
376 return 0;
377
378out_release_key:
379 up_read(&mk->mk_secret_sem);
380 key_put(key);
381 return err;
382}
383
384static void put_crypt_info(struct fscrypt_info *ci)
385{
386 struct key *key;
387
388 if (!ci)
389 return;
390
391 if (ci->ci_direct_key) {
392 fscrypt_put_direct_key(ci->ci_direct_key);
393 } else if ((ci->ci_ctfm != NULL || ci->ci_essiv_tfm != NULL) &&
394 !fscrypt_is_direct_key_policy(&ci->ci_policy)) {
395 crypto_free_skcipher(ci->ci_ctfm);
396 crypto_free_cipher(ci->ci_essiv_tfm);
397 }
398
399 key = ci->ci_master_key;
400 if (key) {
401 struct fscrypt_master_key *mk = key->payload.data[0];
402
403 /*
404 * Remove this inode from the list of inodes that were unlocked
405 * with the master key.
406 *
407 * In addition, if we're removing the last inode from a key that
408 * already had its secret removed, invalidate the key so that it
409 * gets removed from ->s_master_keys.
410 */
411 spin_lock(&mk->mk_decrypted_inodes_lock);
412 list_del(&ci->ci_master_key_link);
413 spin_unlock(&mk->mk_decrypted_inodes_lock);
414 if (refcount_dec_and_test(&mk->mk_refcount))
415 key_invalidate(key);
416 key_put(key);
417 }
418 kmem_cache_free(fscrypt_info_cachep, ci);
419}
420
421int fscrypt_get_encryption_info(struct inode *inode)
422{
423 struct fscrypt_info *crypt_info;
424 union fscrypt_context ctx;
425 struct fscrypt_mode *mode;
426 struct key *master_key = NULL;
427 int res;
428
429 if (fscrypt_has_encryption_key(inode))
430 return 0;
431
432 res = fscrypt_initialize(inode->i_sb->s_cop->flags);
433 if (res)
434 return res;
435
436 res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
437 if (res < 0) {
438 if (!fscrypt_dummy_context_enabled(inode) ||
439 IS_ENCRYPTED(inode)) {
440 fscrypt_warn(inode,
441 "Error %d getting encryption context",
442 res);
443 return res;
444 }
445 /* Fake up a context for an unencrypted directory */
446 memset(&ctx, 0, sizeof(ctx));
447 ctx.version = FSCRYPT_CONTEXT_V1;
448 ctx.v1.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS;
449 ctx.v1.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS;
450 memset(ctx.v1.master_key_descriptor, 0x42,
451 FSCRYPT_KEY_DESCRIPTOR_SIZE);
452 res = sizeof(ctx.v1);
453 }
454
455 crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS);
456 if (!crypt_info)
457 return -ENOMEM;
458
459 crypt_info->ci_inode = inode;
460
461 res = fscrypt_policy_from_context(&crypt_info->ci_policy, &ctx, res);
462 if (res) {
463 fscrypt_warn(inode,
464 "Unrecognized or corrupt encryption context");
465 goto out;
466 }
467
468 switch (ctx.version) {
469 case FSCRYPT_CONTEXT_V1:
470 memcpy(crypt_info->ci_nonce, ctx.v1.nonce,
471 FS_KEY_DERIVATION_NONCE_SIZE);
472 break;
473 case FSCRYPT_CONTEXT_V2:
474 memcpy(crypt_info->ci_nonce, ctx.v2.nonce,
475 FS_KEY_DERIVATION_NONCE_SIZE);
476 break;
477 default:
478 WARN_ON(1);
479 res = -EINVAL;
480 goto out;
481 }
482
483 if (!fscrypt_supported_policy(&crypt_info->ci_policy, inode)) {
484 res = -EINVAL;
485 goto out;
486 }
487
488 mode = select_encryption_mode(&crypt_info->ci_policy, inode);
489 if (IS_ERR(mode)) {
490 res = PTR_ERR(mode);
491 goto out;
492 }
493 WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE);
494 crypt_info->ci_mode = mode;
495
496 res = setup_file_encryption_key(crypt_info, &master_key);
497 if (res)
498 goto out;
499
500 if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) {
501 if (master_key) {
502 struct fscrypt_master_key *mk =
503 master_key->payload.data[0];
504
505 refcount_inc(&mk->mk_refcount);
506 crypt_info->ci_master_key = key_get(master_key);
507 spin_lock(&mk->mk_decrypted_inodes_lock);
508 list_add(&crypt_info->ci_master_key_link,
509 &mk->mk_decrypted_inodes);
510 spin_unlock(&mk->mk_decrypted_inodes_lock);
511 }
512 crypt_info = NULL;
513 }
514 res = 0;
515out:
516 if (master_key) {
517 struct fscrypt_master_key *mk = master_key->payload.data[0];
518
519 up_read(&mk->mk_secret_sem);
520 key_put(master_key);
521 }
522 if (res == -ENOKEY)
523 res = 0;
524 put_crypt_info(crypt_info);
525 return res;
526}
527EXPORT_SYMBOL(fscrypt_get_encryption_info);
528
529/**
530 * fscrypt_put_encryption_info - free most of an inode's fscrypt data
531 *
532 * Free the inode's fscrypt_info. Filesystems must call this when the inode is
533 * being evicted. An RCU grace period need not have elapsed yet.
534 */
535void fscrypt_put_encryption_info(struct inode *inode)
536{
537 put_crypt_info(inode->i_crypt_info);
538 inode->i_crypt_info = NULL;
539}
540EXPORT_SYMBOL(fscrypt_put_encryption_info);
541
542/**
543 * fscrypt_free_inode - free an inode's fscrypt data requiring RCU delay
544 *
545 * Free the inode's cached decrypted symlink target, if any. Filesystems must
546 * call this after an RCU grace period, just before they free the inode.
547 */
548void fscrypt_free_inode(struct inode *inode)
549{
550 if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) {
551 kfree(inode->i_link);
552 inode->i_link = NULL;
553 }
554}
555EXPORT_SYMBOL(fscrypt_free_inode);
556
557/**
558 * fscrypt_drop_inode - check whether the inode's master key has been removed
559 *
560 * Filesystems supporting fscrypt must call this from their ->drop_inode()
561 * method so that encrypted inodes are evicted as soon as they're no longer in
562 * use and their master key has been removed.
563 *
564 * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0
565 */
566int fscrypt_drop_inode(struct inode *inode)
567{
568 const struct fscrypt_info *ci = READ_ONCE(inode->i_crypt_info);
569 const struct fscrypt_master_key *mk;
570
571 /*
572 * If ci is NULL, then the inode doesn't have an encryption key set up
573 * so it's irrelevant. If ci_master_key is NULL, then the master key
574 * was provided via the legacy mechanism of the process-subscribed
575 * keyrings, so we don't know whether it's been removed or not.
576 */
577 if (!ci || !ci->ci_master_key)
578 return 0;
579 mk = ci->ci_master_key->payload.data[0];
580
581 /*
582 * Note: since we aren't holding ->mk_secret_sem, the result here can
583 * immediately become outdated. But there's no correctness problem with
584 * unnecessarily evicting. Nor is there a correctness problem with not
585 * evicting while iput() is racing with the key being removed, since
586 * then the thread removing the key will either evict the inode itself
587 * or will correctly detect that it wasn't evicted due to the race.
588 */
589 return !is_master_key_secret_present(&mk->mk_secret);
590}
591EXPORT_SYMBOL_GPL(fscrypt_drop_inode);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Key setup facility for FS encryption support.
4 *
5 * Copyright (C) 2015, Google, Inc.
6 *
7 * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
8 * Heavily modified since then.
9 */
10
11#include <crypto/skcipher.h>
12#include <linux/key.h>
13#include <linux/random.h>
14
15#include "fscrypt_private.h"
16
17struct fscrypt_mode fscrypt_modes[] = {
18 [FSCRYPT_MODE_AES_256_XTS] = {
19 .friendly_name = "AES-256-XTS",
20 .cipher_str = "xts(aes)",
21 .keysize = 64,
22 .ivsize = 16,
23 .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_256_XTS,
24 },
25 [FSCRYPT_MODE_AES_256_CTS] = {
26 .friendly_name = "AES-256-CTS-CBC",
27 .cipher_str = "cts(cbc(aes))",
28 .keysize = 32,
29 .ivsize = 16,
30 },
31 [FSCRYPT_MODE_AES_128_CBC] = {
32 .friendly_name = "AES-128-CBC-ESSIV",
33 .cipher_str = "essiv(cbc(aes),sha256)",
34 .keysize = 16,
35 .ivsize = 16,
36 .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV,
37 },
38 [FSCRYPT_MODE_AES_128_CTS] = {
39 .friendly_name = "AES-128-CTS-CBC",
40 .cipher_str = "cts(cbc(aes))",
41 .keysize = 16,
42 .ivsize = 16,
43 },
44 [FSCRYPT_MODE_ADIANTUM] = {
45 .friendly_name = "Adiantum",
46 .cipher_str = "adiantum(xchacha12,aes)",
47 .keysize = 32,
48 .ivsize = 32,
49 .blk_crypto_mode = BLK_ENCRYPTION_MODE_ADIANTUM,
50 },
51};
52
53static DEFINE_MUTEX(fscrypt_mode_key_setup_mutex);
54
55static struct fscrypt_mode *
56select_encryption_mode(const union fscrypt_policy *policy,
57 const struct inode *inode)
58{
59 BUILD_BUG_ON(ARRAY_SIZE(fscrypt_modes) != FSCRYPT_MODE_MAX + 1);
60
61 if (S_ISREG(inode->i_mode))
62 return &fscrypt_modes[fscrypt_policy_contents_mode(policy)];
63
64 if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
65 return &fscrypt_modes[fscrypt_policy_fnames_mode(policy)];
66
67 WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
68 inode->i_ino, (inode->i_mode & S_IFMT));
69 return ERR_PTR(-EINVAL);
70}
71
72/* Create a symmetric cipher object for the given encryption mode and key */
73static struct crypto_skcipher *
74fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key,
75 const struct inode *inode)
76{
77 struct crypto_skcipher *tfm;
78 int err;
79
80 tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
81 if (IS_ERR(tfm)) {
82 if (PTR_ERR(tfm) == -ENOENT) {
83 fscrypt_warn(inode,
84 "Missing crypto API support for %s (API name: \"%s\")",
85 mode->friendly_name, mode->cipher_str);
86 return ERR_PTR(-ENOPKG);
87 }
88 fscrypt_err(inode, "Error allocating '%s' transform: %ld",
89 mode->cipher_str, PTR_ERR(tfm));
90 return tfm;
91 }
92 if (!xchg(&mode->logged_impl_name, 1)) {
93 /*
94 * fscrypt performance can vary greatly depending on which
95 * crypto algorithm implementation is used. Help people debug
96 * performance problems by logging the ->cra_driver_name the
97 * first time a mode is used.
98 */
99 pr_info("fscrypt: %s using implementation \"%s\"\n",
100 mode->friendly_name, crypto_skcipher_driver_name(tfm));
101 }
102 if (WARN_ON(crypto_skcipher_ivsize(tfm) != mode->ivsize)) {
103 err = -EINVAL;
104 goto err_free_tfm;
105 }
106 crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
107 err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize);
108 if (err)
109 goto err_free_tfm;
110
111 return tfm;
112
113err_free_tfm:
114 crypto_free_skcipher(tfm);
115 return ERR_PTR(err);
116}
117
118/*
119 * Prepare the crypto transform object or blk-crypto key in @prep_key, given the
120 * raw key, encryption mode, and flag indicating which encryption implementation
121 * (fs-layer or blk-crypto) will be used.
122 */
123int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key,
124 const u8 *raw_key, const struct fscrypt_info *ci)
125{
126 struct crypto_skcipher *tfm;
127
128 if (fscrypt_using_inline_encryption(ci))
129 return fscrypt_prepare_inline_crypt_key(prep_key, raw_key, ci);
130
131 tfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, ci->ci_inode);
132 if (IS_ERR(tfm))
133 return PTR_ERR(tfm);
134 /*
135 * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared().
136 * I.e., here we publish ->tfm with a RELEASE barrier so that
137 * concurrent tasks can ACQUIRE it. Note that this concurrency is only
138 * possible for per-mode keys, not for per-file keys.
139 */
140 smp_store_release(&prep_key->tfm, tfm);
141 return 0;
142}
143
144/* Destroy a crypto transform object and/or blk-crypto key. */
145void fscrypt_destroy_prepared_key(struct fscrypt_prepared_key *prep_key)
146{
147 crypto_free_skcipher(prep_key->tfm);
148 fscrypt_destroy_inline_crypt_key(prep_key);
149}
150
151/* Given a per-file encryption key, set up the file's crypto transform object */
152int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key)
153{
154 ci->ci_owns_key = true;
155 return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci);
156}
157
158static int setup_per_mode_enc_key(struct fscrypt_info *ci,
159 struct fscrypt_master_key *mk,
160 struct fscrypt_prepared_key *keys,
161 u8 hkdf_context, bool include_fs_uuid)
162{
163 const struct inode *inode = ci->ci_inode;
164 const struct super_block *sb = inode->i_sb;
165 struct fscrypt_mode *mode = ci->ci_mode;
166 const u8 mode_num = mode - fscrypt_modes;
167 struct fscrypt_prepared_key *prep_key;
168 u8 mode_key[FSCRYPT_MAX_KEY_SIZE];
169 u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)];
170 unsigned int hkdf_infolen = 0;
171 int err;
172
173 if (WARN_ON(mode_num > FSCRYPT_MODE_MAX))
174 return -EINVAL;
175
176 prep_key = &keys[mode_num];
177 if (fscrypt_is_key_prepared(prep_key, ci)) {
178 ci->ci_enc_key = *prep_key;
179 return 0;
180 }
181
182 mutex_lock(&fscrypt_mode_key_setup_mutex);
183
184 if (fscrypt_is_key_prepared(prep_key, ci))
185 goto done_unlock;
186
187 BUILD_BUG_ON(sizeof(mode_num) != 1);
188 BUILD_BUG_ON(sizeof(sb->s_uuid) != 16);
189 BUILD_BUG_ON(sizeof(hkdf_info) != 17);
190 hkdf_info[hkdf_infolen++] = mode_num;
191 if (include_fs_uuid) {
192 memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid,
193 sizeof(sb->s_uuid));
194 hkdf_infolen += sizeof(sb->s_uuid);
195 }
196 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
197 hkdf_context, hkdf_info, hkdf_infolen,
198 mode_key, mode->keysize);
199 if (err)
200 goto out_unlock;
201 err = fscrypt_prepare_key(prep_key, mode_key, ci);
202 memzero_explicit(mode_key, mode->keysize);
203 if (err)
204 goto out_unlock;
205done_unlock:
206 ci->ci_enc_key = *prep_key;
207 err = 0;
208out_unlock:
209 mutex_unlock(&fscrypt_mode_key_setup_mutex);
210 return err;
211}
212
213/*
214 * Derive a SipHash key from the given fscrypt master key and the given
215 * application-specific information string.
216 *
217 * Note that the KDF produces a byte array, but the SipHash APIs expect the key
218 * as a pair of 64-bit words. Therefore, on big endian CPUs we have to do an
219 * endianness swap in order to get the same results as on little endian CPUs.
220 */
221static int fscrypt_derive_siphash_key(const struct fscrypt_master_key *mk,
222 u8 context, const u8 *info,
223 unsigned int infolen, siphash_key_t *key)
224{
225 int err;
226
227 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, context, info, infolen,
228 (u8 *)key, sizeof(*key));
229 if (err)
230 return err;
231
232 BUILD_BUG_ON(sizeof(*key) != 16);
233 BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2);
234 le64_to_cpus(&key->key[0]);
235 le64_to_cpus(&key->key[1]);
236 return 0;
237}
238
239int fscrypt_derive_dirhash_key(struct fscrypt_info *ci,
240 const struct fscrypt_master_key *mk)
241{
242 int err;
243
244 err = fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY,
245 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE,
246 &ci->ci_dirhash_key);
247 if (err)
248 return err;
249 ci->ci_dirhash_key_initialized = true;
250 return 0;
251}
252
253void fscrypt_hash_inode_number(struct fscrypt_info *ci,
254 const struct fscrypt_master_key *mk)
255{
256 WARN_ON(ci->ci_inode->i_ino == 0);
257 WARN_ON(!mk->mk_ino_hash_key_initialized);
258
259 ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino,
260 &mk->mk_ino_hash_key);
261}
262
263static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_info *ci,
264 struct fscrypt_master_key *mk)
265{
266 int err;
267
268 err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys,
269 HKDF_CONTEXT_IV_INO_LBLK_32_KEY, true);
270 if (err)
271 return err;
272
273 /* pairs with smp_store_release() below */
274 if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) {
275
276 mutex_lock(&fscrypt_mode_key_setup_mutex);
277
278 if (mk->mk_ino_hash_key_initialized)
279 goto unlock;
280
281 err = fscrypt_derive_siphash_key(mk,
282 HKDF_CONTEXT_INODE_HASH_KEY,
283 NULL, 0, &mk->mk_ino_hash_key);
284 if (err)
285 goto unlock;
286 /* pairs with smp_load_acquire() above */
287 smp_store_release(&mk->mk_ino_hash_key_initialized, true);
288unlock:
289 mutex_unlock(&fscrypt_mode_key_setup_mutex);
290 if (err)
291 return err;
292 }
293
294 /*
295 * New inodes may not have an inode number assigned yet.
296 * Hashing their inode number is delayed until later.
297 */
298 if (ci->ci_inode->i_ino)
299 fscrypt_hash_inode_number(ci, mk);
300 return 0;
301}
302
303static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
304 struct fscrypt_master_key *mk,
305 bool need_dirhash_key)
306{
307 int err;
308
309 if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
310 /*
311 * DIRECT_KEY: instead of deriving per-file encryption keys, the
312 * per-file nonce will be included in all the IVs. But unlike
313 * v1 policies, for v2 policies in this case we don't encrypt
314 * with the master key directly but rather derive a per-mode
315 * encryption key. This ensures that the master key is
316 * consistently used only for HKDF, avoiding key reuse issues.
317 */
318 err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys,
319 HKDF_CONTEXT_DIRECT_KEY, false);
320 } else if (ci->ci_policy.v2.flags &
321 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) {
322 /*
323 * IV_INO_LBLK_64: encryption keys are derived from (master_key,
324 * mode_num, filesystem_uuid), and inode number is included in
325 * the IVs. This format is optimized for use with inline
326 * encryption hardware compliant with the UFS standard.
327 */
328 err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys,
329 HKDF_CONTEXT_IV_INO_LBLK_64_KEY,
330 true);
331 } else if (ci->ci_policy.v2.flags &
332 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) {
333 err = fscrypt_setup_iv_ino_lblk_32_key(ci, mk);
334 } else {
335 u8 derived_key[FSCRYPT_MAX_KEY_SIZE];
336
337 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
338 HKDF_CONTEXT_PER_FILE_ENC_KEY,
339 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE,
340 derived_key, ci->ci_mode->keysize);
341 if (err)
342 return err;
343
344 err = fscrypt_set_per_file_enc_key(ci, derived_key);
345 memzero_explicit(derived_key, ci->ci_mode->keysize);
346 }
347 if (err)
348 return err;
349
350 /* Derive a secret dirhash key for directories that need it. */
351 if (need_dirhash_key) {
352 err = fscrypt_derive_dirhash_key(ci, mk);
353 if (err)
354 return err;
355 }
356
357 return 0;
358}
359
360/*
361 * Find the master key, then set up the inode's actual encryption key.
362 *
363 * If the master key is found in the filesystem-level keyring, then the
364 * corresponding 'struct key' is returned in *master_key_ret with its semaphore
365 * read-locked. This is needed to ensure that only one task links the
366 * fscrypt_info into ->mk_decrypted_inodes (as multiple tasks may race to create
367 * an fscrypt_info for the same inode), and to synchronize the master key being
368 * removed with a new inode starting to use it.
369 */
370static int setup_file_encryption_key(struct fscrypt_info *ci,
371 bool need_dirhash_key,
372 struct key **master_key_ret)
373{
374 struct key *key;
375 struct fscrypt_master_key *mk = NULL;
376 struct fscrypt_key_specifier mk_spec;
377 int err;
378
379 err = fscrypt_select_encryption_impl(ci);
380 if (err)
381 return err;
382
383 switch (ci->ci_policy.version) {
384 case FSCRYPT_POLICY_V1:
385 mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
386 memcpy(mk_spec.u.descriptor,
387 ci->ci_policy.v1.master_key_descriptor,
388 FSCRYPT_KEY_DESCRIPTOR_SIZE);
389 break;
390 case FSCRYPT_POLICY_V2:
391 mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
392 memcpy(mk_spec.u.identifier,
393 ci->ci_policy.v2.master_key_identifier,
394 FSCRYPT_KEY_IDENTIFIER_SIZE);
395 break;
396 default:
397 WARN_ON(1);
398 return -EINVAL;
399 }
400
401 key = fscrypt_find_master_key(ci->ci_inode->i_sb, &mk_spec);
402 if (IS_ERR(key)) {
403 if (key != ERR_PTR(-ENOKEY) ||
404 ci->ci_policy.version != FSCRYPT_POLICY_V1)
405 return PTR_ERR(key);
406
407 /*
408 * As a legacy fallback for v1 policies, search for the key in
409 * the current task's subscribed keyrings too. Don't move this
410 * to before the search of ->s_master_keys, since users
411 * shouldn't be able to override filesystem-level keys.
412 */
413 return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
414 }
415
416 mk = key->payload.data[0];
417 down_read(&key->sem);
418
419 /* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */
420 if (!is_master_key_secret_present(&mk->mk_secret)) {
421 err = -ENOKEY;
422 goto out_release_key;
423 }
424
425 /*
426 * Require that the master key be at least as long as the derived key.
427 * Otherwise, the derived key cannot possibly contain as much entropy as
428 * that required by the encryption mode it will be used for. For v1
429 * policies it's also required for the KDF to work at all.
430 */
431 if (mk->mk_secret.size < ci->ci_mode->keysize) {
432 fscrypt_warn(NULL,
433 "key with %s %*phN is too short (got %u bytes, need %u+ bytes)",
434 master_key_spec_type(&mk_spec),
435 master_key_spec_len(&mk_spec), (u8 *)&mk_spec.u,
436 mk->mk_secret.size, ci->ci_mode->keysize);
437 err = -ENOKEY;
438 goto out_release_key;
439 }
440
441 switch (ci->ci_policy.version) {
442 case FSCRYPT_POLICY_V1:
443 err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
444 break;
445 case FSCRYPT_POLICY_V2:
446 err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key);
447 break;
448 default:
449 WARN_ON(1);
450 err = -EINVAL;
451 break;
452 }
453 if (err)
454 goto out_release_key;
455
456 *master_key_ret = key;
457 return 0;
458
459out_release_key:
460 up_read(&key->sem);
461 key_put(key);
462 return err;
463}
464
465static void put_crypt_info(struct fscrypt_info *ci)
466{
467 struct key *key;
468
469 if (!ci)
470 return;
471
472 if (ci->ci_direct_key)
473 fscrypt_put_direct_key(ci->ci_direct_key);
474 else if (ci->ci_owns_key)
475 fscrypt_destroy_prepared_key(&ci->ci_enc_key);
476
477 key = ci->ci_master_key;
478 if (key) {
479 struct fscrypt_master_key *mk = key->payload.data[0];
480
481 /*
482 * Remove this inode from the list of inodes that were unlocked
483 * with the master key.
484 *
485 * In addition, if we're removing the last inode from a key that
486 * already had its secret removed, invalidate the key so that it
487 * gets removed from ->s_master_keys.
488 */
489 spin_lock(&mk->mk_decrypted_inodes_lock);
490 list_del(&ci->ci_master_key_link);
491 spin_unlock(&mk->mk_decrypted_inodes_lock);
492 if (refcount_dec_and_test(&mk->mk_refcount))
493 key_invalidate(key);
494 key_put(key);
495 }
496 memzero_explicit(ci, sizeof(*ci));
497 kmem_cache_free(fscrypt_info_cachep, ci);
498}
499
500static int
501fscrypt_setup_encryption_info(struct inode *inode,
502 const union fscrypt_policy *policy,
503 const u8 nonce[FSCRYPT_FILE_NONCE_SIZE],
504 bool need_dirhash_key)
505{
506 struct fscrypt_info *crypt_info;
507 struct fscrypt_mode *mode;
508 struct key *master_key = NULL;
509 int res;
510
511 res = fscrypt_initialize(inode->i_sb->s_cop->flags);
512 if (res)
513 return res;
514
515 crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_KERNEL);
516 if (!crypt_info)
517 return -ENOMEM;
518
519 crypt_info->ci_inode = inode;
520 crypt_info->ci_policy = *policy;
521 memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE);
522
523 mode = select_encryption_mode(&crypt_info->ci_policy, inode);
524 if (IS_ERR(mode)) {
525 res = PTR_ERR(mode);
526 goto out;
527 }
528 WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE);
529 crypt_info->ci_mode = mode;
530
531 res = setup_file_encryption_key(crypt_info, need_dirhash_key,
532 &master_key);
533 if (res)
534 goto out;
535
536 /*
537 * For existing inodes, multiple tasks may race to set ->i_crypt_info.
538 * So use cmpxchg_release(). This pairs with the smp_load_acquire() in
539 * fscrypt_get_info(). I.e., here we publish ->i_crypt_info with a
540 * RELEASE barrier so that other tasks can ACQUIRE it.
541 */
542 if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) {
543 /*
544 * We won the race and set ->i_crypt_info to our crypt_info.
545 * Now link it into the master key's inode list.
546 */
547 if (master_key) {
548 struct fscrypt_master_key *mk =
549 master_key->payload.data[0];
550
551 refcount_inc(&mk->mk_refcount);
552 crypt_info->ci_master_key = key_get(master_key);
553 spin_lock(&mk->mk_decrypted_inodes_lock);
554 list_add(&crypt_info->ci_master_key_link,
555 &mk->mk_decrypted_inodes);
556 spin_unlock(&mk->mk_decrypted_inodes_lock);
557 }
558 crypt_info = NULL;
559 }
560 res = 0;
561out:
562 if (master_key) {
563 up_read(&master_key->sem);
564 key_put(master_key);
565 }
566 put_crypt_info(crypt_info);
567 return res;
568}
569
570/**
571 * fscrypt_get_encryption_info() - set up an inode's encryption key
572 * @inode: the inode to set up the key for. Must be encrypted.
573 * @allow_unsupported: if %true, treat an unsupported encryption policy (or
574 * unrecognized encryption context) the same way as the key
575 * being unavailable, instead of returning an error. Use
576 * %false unless the operation being performed is needed in
577 * order for files (or directories) to be deleted.
578 *
579 * Set up ->i_crypt_info, if it hasn't already been done.
580 *
581 * Note: unless ->i_crypt_info is already set, this isn't %GFP_NOFS-safe. So
582 * generally this shouldn't be called from within a filesystem transaction.
583 *
584 * Return: 0 if ->i_crypt_info was set or was already set, *or* if the
585 * encryption key is unavailable. (Use fscrypt_has_encryption_key() to
586 * distinguish these cases.) Also can return another -errno code.
587 */
588int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported)
589{
590 int res;
591 union fscrypt_context ctx;
592 union fscrypt_policy policy;
593
594 if (fscrypt_has_encryption_key(inode))
595 return 0;
596
597 res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
598 if (res < 0) {
599 if (res == -ERANGE && allow_unsupported)
600 return 0;
601 fscrypt_warn(inode, "Error %d getting encryption context", res);
602 return res;
603 }
604
605 res = fscrypt_policy_from_context(&policy, &ctx, res);
606 if (res) {
607 if (allow_unsupported)
608 return 0;
609 fscrypt_warn(inode,
610 "Unrecognized or corrupt encryption context");
611 return res;
612 }
613
614 if (!fscrypt_supported_policy(&policy, inode)) {
615 if (allow_unsupported)
616 return 0;
617 return -EINVAL;
618 }
619
620 res = fscrypt_setup_encryption_info(inode, &policy,
621 fscrypt_context_nonce(&ctx),
622 IS_CASEFOLDED(inode) &&
623 S_ISDIR(inode->i_mode));
624
625 if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */
626 res = 0;
627 if (res == -ENOKEY)
628 res = 0;
629 return res;
630}
631
632/**
633 * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory
634 * @dir: a possibly-encrypted directory
635 * @inode: the new inode. ->i_mode must be set already.
636 * ->i_ino doesn't need to be set yet.
637 * @encrypt_ret: (output) set to %true if the new inode will be encrypted
638 *
639 * If the directory is encrypted, set up its ->i_crypt_info in preparation for
640 * encrypting the name of the new file. Also, if the new inode will be
641 * encrypted, set up its ->i_crypt_info and set *encrypt_ret=true.
642 *
643 * This isn't %GFP_NOFS-safe, and therefore it should be called before starting
644 * any filesystem transaction to create the inode. For this reason, ->i_ino
645 * isn't required to be set yet, as the filesystem may not have set it yet.
646 *
647 * This doesn't persist the new inode's encryption context. That still needs to
648 * be done later by calling fscrypt_set_context().
649 *
650 * Return: 0 on success, -ENOKEY if the encryption key is missing, or another
651 * -errno code
652 */
653int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode,
654 bool *encrypt_ret)
655{
656 const union fscrypt_policy *policy;
657 u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
658
659 policy = fscrypt_policy_to_inherit(dir);
660 if (policy == NULL)
661 return 0;
662 if (IS_ERR(policy))
663 return PTR_ERR(policy);
664
665 if (WARN_ON_ONCE(inode->i_mode == 0))
666 return -EINVAL;
667
668 /*
669 * Only regular files, directories, and symlinks are encrypted.
670 * Special files like device nodes and named pipes aren't.
671 */
672 if (!S_ISREG(inode->i_mode) &&
673 !S_ISDIR(inode->i_mode) &&
674 !S_ISLNK(inode->i_mode))
675 return 0;
676
677 *encrypt_ret = true;
678
679 get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE);
680 return fscrypt_setup_encryption_info(inode, policy, nonce,
681 IS_CASEFOLDED(dir) &&
682 S_ISDIR(inode->i_mode));
683}
684EXPORT_SYMBOL_GPL(fscrypt_prepare_new_inode);
685
686/**
687 * fscrypt_put_encryption_info() - free most of an inode's fscrypt data
688 * @inode: an inode being evicted
689 *
690 * Free the inode's fscrypt_info. Filesystems must call this when the inode is
691 * being evicted. An RCU grace period need not have elapsed yet.
692 */
693void fscrypt_put_encryption_info(struct inode *inode)
694{
695 put_crypt_info(inode->i_crypt_info);
696 inode->i_crypt_info = NULL;
697}
698EXPORT_SYMBOL(fscrypt_put_encryption_info);
699
700/**
701 * fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay
702 * @inode: an inode being freed
703 *
704 * Free the inode's cached decrypted symlink target, if any. Filesystems must
705 * call this after an RCU grace period, just before they free the inode.
706 */
707void fscrypt_free_inode(struct inode *inode)
708{
709 if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) {
710 kfree(inode->i_link);
711 inode->i_link = NULL;
712 }
713}
714EXPORT_SYMBOL(fscrypt_free_inode);
715
716/**
717 * fscrypt_drop_inode() - check whether the inode's master key has been removed
718 * @inode: an inode being considered for eviction
719 *
720 * Filesystems supporting fscrypt must call this from their ->drop_inode()
721 * method so that encrypted inodes are evicted as soon as they're no longer in
722 * use and their master key has been removed.
723 *
724 * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0
725 */
726int fscrypt_drop_inode(struct inode *inode)
727{
728 const struct fscrypt_info *ci = fscrypt_get_info(inode);
729 const struct fscrypt_master_key *mk;
730
731 /*
732 * If ci is NULL, then the inode doesn't have an encryption key set up
733 * so it's irrelevant. If ci_master_key is NULL, then the master key
734 * was provided via the legacy mechanism of the process-subscribed
735 * keyrings, so we don't know whether it's been removed or not.
736 */
737 if (!ci || !ci->ci_master_key)
738 return 0;
739 mk = ci->ci_master_key->payload.data[0];
740
741 /*
742 * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes
743 * protected by the key were cleaned by sync_filesystem(). But if
744 * userspace is still using the files, inodes can be dirtied between
745 * then and now. We mustn't lose any writes, so skip dirty inodes here.
746 */
747 if (inode->i_state & I_DIRTY_ALL)
748 return 0;
749
750 /*
751 * Note: since we aren't holding the key semaphore, the result here can
752 * immediately become outdated. But there's no correctness problem with
753 * unnecessarily evicting. Nor is there a correctness problem with not
754 * evicting while iput() is racing with the key being removed, since
755 * then the thread removing the key will either evict the inode itself
756 * or will correctly detect that it wasn't evicted due to the race.
757 */
758 return !is_master_key_secret_present(&mk->mk_secret);
759}
760EXPORT_SYMBOL_GPL(fscrypt_drop_inode);