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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
0adda907 | 2 | /* |
3ec4f2a6 | 3 | * Key setup facility for FS encryption support. |
0adda907 JK |
4 | * |
5 | * Copyright (C) 2015, Google, Inc. | |
6 | * | |
3ec4f2a6 EB |
7 | * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar. |
8 | * Heavily modified since then. | |
0adda907 | 9 | */ |
0b81d077 | 10 | |
a575784c | 11 | #include <crypto/skcipher.h> |
0109ce76 | 12 | #include <linux/key.h> |
a992b20c | 13 | #include <linux/random.h> |
0109ce76 | 14 | |
3325bea5 | 15 | #include "fscrypt_private.h" |
0adda907 | 16 | |
85af90e5 | 17 | struct fscrypt_mode fscrypt_modes[] = { |
3b6df59b | 18 | [FSCRYPT_MODE_AES_256_XTS] = { |
e1cc40e5 EB |
19 | .friendly_name = "AES-256-XTS", |
20 | .cipher_str = "xts(aes)", | |
21 | .keysize = 64, | |
8094c3ce | 22 | .ivsize = 16, |
5fee3609 | 23 | .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_256_XTS, |
e1cc40e5 | 24 | }, |
3b6df59b | 25 | [FSCRYPT_MODE_AES_256_CTS] = { |
e1cc40e5 EB |
26 | .friendly_name = "AES-256-CTS-CBC", |
27 | .cipher_str = "cts(cbc(aes))", | |
28 | .keysize = 32, | |
8094c3ce | 29 | .ivsize = 16, |
e1cc40e5 | 30 | }, |
3b6df59b | 31 | [FSCRYPT_MODE_AES_128_CBC] = { |
4006d799 EB |
32 | .friendly_name = "AES-128-CBC-ESSIV", |
33 | .cipher_str = "essiv(cbc(aes),sha256)", | |
e1cc40e5 | 34 | .keysize = 16, |
8094c3ce | 35 | .ivsize = 16, |
5fee3609 | 36 | .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV, |
e1cc40e5 | 37 | }, |
3b6df59b | 38 | [FSCRYPT_MODE_AES_128_CTS] = { |
e1cc40e5 EB |
39 | .friendly_name = "AES-128-CTS-CBC", |
40 | .cipher_str = "cts(cbc(aes))", | |
41 | .keysize = 16, | |
8094c3ce EB |
42 | .ivsize = 16, |
43 | }, | |
3b6df59b | 44 | [FSCRYPT_MODE_ADIANTUM] = { |
8094c3ce EB |
45 | .friendly_name = "Adiantum", |
46 | .cipher_str = "adiantum(xchacha12,aes)", | |
47 | .keysize = 32, | |
48 | .ivsize = 32, | |
5fee3609 | 49 | .blk_crypto_mode = BLK_ENCRYPTION_MODE_ADIANTUM, |
e1cc40e5 | 50 | }, |
b7e7cf7a DW |
51 | }; |
52 | ||
e3b1078b EB |
53 | static DEFINE_MUTEX(fscrypt_mode_key_setup_mutex); |
54 | ||
e1cc40e5 | 55 | static struct fscrypt_mode * |
5dae460c EB |
56 | select_encryption_mode(const union fscrypt_policy *policy, |
57 | const struct inode *inode) | |
8f39850d | 58 | { |
e1cc40e5 | 59 | if (S_ISREG(inode->i_mode)) |
85af90e5 | 60 | return &fscrypt_modes[fscrypt_policy_contents_mode(policy)]; |
e1cc40e5 EB |
61 | |
62 | if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) | |
85af90e5 | 63 | return &fscrypt_modes[fscrypt_policy_fnames_mode(policy)]; |
8f39850d | 64 | |
e1cc40e5 EB |
65 | WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n", |
66 | inode->i_ino, (inode->i_mode & S_IFMT)); | |
67 | return ERR_PTR(-EINVAL); | |
8f39850d EB |
68 | } |
69 | ||
3ec4f2a6 | 70 | /* Create a symmetric cipher object for the given encryption mode and key */ |
5fee3609 ST |
71 | static struct crypto_skcipher * |
72 | fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key, | |
73 | const struct inode *inode) | |
8094c3ce EB |
74 | { |
75 | struct crypto_skcipher *tfm; | |
76 | int err; | |
77 | ||
78 | tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0); | |
79 | if (IS_ERR(tfm)) { | |
29a98c1c | 80 | if (PTR_ERR(tfm) == -ENOENT) { |
a4d14e91 EB |
81 | fscrypt_warn(inode, |
82 | "Missing crypto API support for %s (API name: \"%s\")", | |
83 | mode->friendly_name, mode->cipher_str); | |
29a98c1c EB |
84 | return ERR_PTR(-ENOPKG); |
85 | } | |
86 | fscrypt_err(inode, "Error allocating '%s' transform: %ld", | |
87 | mode->cipher_str, PTR_ERR(tfm)); | |
8094c3ce EB |
88 | return tfm; |
89 | } | |
ff73c2c0 | 90 | if (!xchg(&mode->logged_impl_name, 1)) { |
8094c3ce EB |
91 | /* |
92 | * fscrypt performance can vary greatly depending on which | |
93 | * crypto algorithm implementation is used. Help people debug | |
94 | * performance problems by logging the ->cra_driver_name the | |
ff73c2c0 | 95 | * first time a mode is used. |
8094c3ce | 96 | */ |
8094c3ce | 97 | pr_info("fscrypt: %s using implementation \"%s\"\n", |
6e1adb88 | 98 | mode->friendly_name, crypto_skcipher_driver_name(tfm)); |
8094c3ce | 99 | } |
c64cfb98 EB |
100 | if (WARN_ON(crypto_skcipher_ivsize(tfm) != mode->ivsize)) { |
101 | err = -EINVAL; | |
102 | goto err_free_tfm; | |
103 | } | |
231baecd | 104 | crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); |
8094c3ce EB |
105 | err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize); |
106 | if (err) | |
107 | goto err_free_tfm; | |
108 | ||
109 | return tfm; | |
110 | ||
111 | err_free_tfm: | |
112 | crypto_free_skcipher(tfm); | |
113 | return ERR_PTR(err); | |
114 | } | |
115 | ||
5fee3609 ST |
116 | /* |
117 | * Prepare the crypto transform object or blk-crypto key in @prep_key, given the | |
118 | * raw key, encryption mode, and flag indicating which encryption implementation | |
119 | * (fs-layer or blk-crypto) will be used. | |
120 | */ | |
121 | int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key, | |
122 | const u8 *raw_key, const struct fscrypt_info *ci) | |
8094c3ce | 123 | { |
4006d799 | 124 | struct crypto_skcipher *tfm; |
3ec4f2a6 | 125 | |
5fee3609 ST |
126 | if (fscrypt_using_inline_encryption(ci)) |
127 | return fscrypt_prepare_inline_crypt_key(prep_key, raw_key, ci); | |
128 | ||
f592efe7 | 129 | tfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, ci->ci_inode); |
4006d799 EB |
130 | if (IS_ERR(tfm)) |
131 | return PTR_ERR(tfm); | |
5fee3609 | 132 | /* |
97c6327f EB |
133 | * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared(). |
134 | * I.e., here we publish ->tfm with a RELEASE barrier so that | |
135 | * concurrent tasks can ACQUIRE it. Note that this concurrency is only | |
136 | * possible for per-mode keys, not for per-file keys. | |
5fee3609 ST |
137 | */ |
138 | smp_store_release(&prep_key->tfm, tfm); | |
139 | return 0; | |
140 | } | |
141 | ||
142 | /* Destroy a crypto transform object and/or blk-crypto key. */ | |
143 | void fscrypt_destroy_prepared_key(struct fscrypt_prepared_key *prep_key) | |
144 | { | |
145 | crypto_free_skcipher(prep_key->tfm); | |
146 | fscrypt_destroy_inline_crypt_key(prep_key); | |
147 | } | |
8094c3ce | 148 | |
5fee3609 ST |
149 | /* Given a per-file encryption key, set up the file's crypto transform object */ |
150 | int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key) | |
151 | { | |
b103fb76 | 152 | ci->ci_owns_key = true; |
5fee3609 | 153 | return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci); |
8094c3ce EB |
154 | } |
155 | ||
f592efe7 EB |
156 | static int setup_per_mode_enc_key(struct fscrypt_info *ci, |
157 | struct fscrypt_master_key *mk, | |
5fee3609 | 158 | struct fscrypt_prepared_key *keys, |
f592efe7 | 159 | u8 hkdf_context, bool include_fs_uuid) |
5dae460c | 160 | { |
b103fb76 EB |
161 | const struct inode *inode = ci->ci_inode; |
162 | const struct super_block *sb = inode->i_sb; | |
5dae460c | 163 | struct fscrypt_mode *mode = ci->ci_mode; |
85af90e5 | 164 | const u8 mode_num = mode - fscrypt_modes; |
5fee3609 | 165 | struct fscrypt_prepared_key *prep_key; |
5dae460c | 166 | u8 mode_key[FSCRYPT_MAX_KEY_SIZE]; |
b103fb76 EB |
167 | u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)]; |
168 | unsigned int hkdf_infolen = 0; | |
5dae460c EB |
169 | int err; |
170 | ||
b103fb76 | 171 | if (WARN_ON(mode_num > __FSCRYPT_MODE_MAX)) |
5dae460c EB |
172 | return -EINVAL; |
173 | ||
5fee3609 ST |
174 | prep_key = &keys[mode_num]; |
175 | if (fscrypt_is_key_prepared(prep_key, ci)) { | |
176 | ci->ci_enc_key = *prep_key; | |
e3b1078b EB |
177 | return 0; |
178 | } | |
179 | ||
180 | mutex_lock(&fscrypt_mode_key_setup_mutex); | |
181 | ||
5fee3609 | 182 | if (fscrypt_is_key_prepared(prep_key, ci)) |
e3b1078b | 183 | goto done_unlock; |
5dae460c EB |
184 | |
185 | BUILD_BUG_ON(sizeof(mode_num) != 1); | |
b103fb76 EB |
186 | BUILD_BUG_ON(sizeof(sb->s_uuid) != 16); |
187 | BUILD_BUG_ON(sizeof(hkdf_info) != 17); | |
188 | hkdf_info[hkdf_infolen++] = mode_num; | |
189 | if (include_fs_uuid) { | |
190 | memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid, | |
191 | sizeof(sb->s_uuid)); | |
192 | hkdf_infolen += sizeof(sb->s_uuid); | |
193 | } | |
5dae460c | 194 | err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, |
b103fb76 | 195 | hkdf_context, hkdf_info, hkdf_infolen, |
5dae460c EB |
196 | mode_key, mode->keysize); |
197 | if (err) | |
e3b1078b | 198 | goto out_unlock; |
5fee3609 | 199 | err = fscrypt_prepare_key(prep_key, mode_key, ci); |
5dae460c | 200 | memzero_explicit(mode_key, mode->keysize); |
5fee3609 | 201 | if (err) |
e3b1078b | 202 | goto out_unlock; |
e3b1078b | 203 | done_unlock: |
5fee3609 | 204 | ci->ci_enc_key = *prep_key; |
e3b1078b EB |
205 | err = 0; |
206 | out_unlock: | |
207 | mutex_unlock(&fscrypt_mode_key_setup_mutex); | |
208 | return err; | |
5dae460c EB |
209 | } |
210 | ||
aa408f83 DR |
211 | int fscrypt_derive_dirhash_key(struct fscrypt_info *ci, |
212 | const struct fscrypt_master_key *mk) | |
213 | { | |
214 | int err; | |
215 | ||
216 | err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, HKDF_CONTEXT_DIRHASH_KEY, | |
1d6217a4 | 217 | ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, |
aa408f83 DR |
218 | (u8 *)&ci->ci_dirhash_key, |
219 | sizeof(ci->ci_dirhash_key)); | |
220 | if (err) | |
221 | return err; | |
222 | ci->ci_dirhash_key_initialized = true; | |
223 | return 0; | |
224 | } | |
225 | ||
a992b20c EB |
226 | void fscrypt_hash_inode_number(struct fscrypt_info *ci, |
227 | const struct fscrypt_master_key *mk) | |
228 | { | |
229 | WARN_ON(ci->ci_inode->i_ino == 0); | |
230 | WARN_ON(!mk->mk_ino_hash_key_initialized); | |
231 | ||
232 | ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino, | |
233 | &mk->mk_ino_hash_key); | |
234 | } | |
235 | ||
e3b1078b EB |
236 | static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_info *ci, |
237 | struct fscrypt_master_key *mk) | |
238 | { | |
239 | int err; | |
240 | ||
241 | err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys, | |
242 | HKDF_CONTEXT_IV_INO_LBLK_32_KEY, true); | |
243 | if (err) | |
244 | return err; | |
245 | ||
246 | /* pairs with smp_store_release() below */ | |
247 | if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) { | |
248 | ||
249 | mutex_lock(&fscrypt_mode_key_setup_mutex); | |
250 | ||
251 | if (mk->mk_ino_hash_key_initialized) | |
252 | goto unlock; | |
253 | ||
254 | err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, | |
255 | HKDF_CONTEXT_INODE_HASH_KEY, NULL, 0, | |
256 | (u8 *)&mk->mk_ino_hash_key, | |
257 | sizeof(mk->mk_ino_hash_key)); | |
258 | if (err) | |
259 | goto unlock; | |
260 | /* pairs with smp_load_acquire() above */ | |
261 | smp_store_release(&mk->mk_ino_hash_key_initialized, true); | |
262 | unlock: | |
263 | mutex_unlock(&fscrypt_mode_key_setup_mutex); | |
264 | if (err) | |
265 | return err; | |
266 | } | |
267 | ||
a992b20c EB |
268 | /* |
269 | * New inodes may not have an inode number assigned yet. | |
270 | * Hashing their inode number is delayed until later. | |
271 | */ | |
272 | if (ci->ci_inode->i_ino == 0) | |
273 | WARN_ON(!(ci->ci_inode->i_state & I_CREATING)); | |
274 | else | |
275 | fscrypt_hash_inode_number(ci, mk); | |
e3b1078b EB |
276 | return 0; |
277 | } | |
278 | ||
5dae460c | 279 | static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci, |
a992b20c EB |
280 | struct fscrypt_master_key *mk, |
281 | bool need_dirhash_key) | |
5dae460c | 282 | { |
5dae460c EB |
283 | int err; |
284 | ||
285 | if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { | |
286 | /* | |
f592efe7 EB |
287 | * DIRECT_KEY: instead of deriving per-file encryption keys, the |
288 | * per-file nonce will be included in all the IVs. But unlike | |
289 | * v1 policies, for v2 policies in this case we don't encrypt | |
290 | * with the master key directly but rather derive a per-mode | |
291 | * encryption key. This ensures that the master key is | |
292 | * consistently used only for HKDF, avoiding key reuse issues. | |
5dae460c | 293 | */ |
e3b1078b | 294 | err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys, |
f592efe7 | 295 | HKDF_CONTEXT_DIRECT_KEY, false); |
b103fb76 EB |
296 | } else if (ci->ci_policy.v2.flags & |
297 | FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { | |
298 | /* | |
299 | * IV_INO_LBLK_64: encryption keys are derived from (master_key, | |
300 | * mode_num, filesystem_uuid), and inode number is included in | |
301 | * the IVs. This format is optimized for use with inline | |
e3b1078b | 302 | * encryption hardware compliant with the UFS standard. |
b103fb76 | 303 | */ |
e3b1078b | 304 | err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys, |
f592efe7 EB |
305 | HKDF_CONTEXT_IV_INO_LBLK_64_KEY, |
306 | true); | |
e3b1078b EB |
307 | } else if (ci->ci_policy.v2.flags & |
308 | FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { | |
309 | err = fscrypt_setup_iv_ino_lblk_32_key(ci, mk); | |
aa408f83 DR |
310 | } else { |
311 | u8 derived_key[FSCRYPT_MAX_KEY_SIZE]; | |
5dae460c | 312 | |
aa408f83 | 313 | err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, |
f592efe7 | 314 | HKDF_CONTEXT_PER_FILE_ENC_KEY, |
1d6217a4 | 315 | ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, |
aa408f83 DR |
316 | derived_key, ci->ci_mode->keysize); |
317 | if (err) | |
318 | return err; | |
319 | ||
f592efe7 | 320 | err = fscrypt_set_per_file_enc_key(ci, derived_key); |
aa408f83 DR |
321 | memzero_explicit(derived_key, ci->ci_mode->keysize); |
322 | } | |
5dae460c EB |
323 | if (err) |
324 | return err; | |
325 | ||
aa408f83 | 326 | /* Derive a secret dirhash key for directories that need it. */ |
a992b20c | 327 | if (need_dirhash_key) { |
aa408f83 DR |
328 | err = fscrypt_derive_dirhash_key(ci, mk); |
329 | if (err) | |
330 | return err; | |
331 | } | |
332 | ||
333 | return 0; | |
5dae460c EB |
334 | } |
335 | ||
3ec4f2a6 EB |
336 | /* |
337 | * Find the master key, then set up the inode's actual encryption key. | |
b1c0ec35 EB |
338 | * |
339 | * If the master key is found in the filesystem-level keyring, then the | |
340 | * corresponding 'struct key' is returned in *master_key_ret with | |
23c688b5 EB |
341 | * ->mk_secret_sem read-locked. This is needed to ensure that only one task |
342 | * links the fscrypt_info into ->mk_decrypted_inodes (as multiple tasks may race | |
343 | * to create an fscrypt_info for the same inode), and to synchronize the master | |
344 | * key being removed with a new inode starting to use it. | |
3ec4f2a6 | 345 | */ |
b1c0ec35 | 346 | static int setup_file_encryption_key(struct fscrypt_info *ci, |
a992b20c | 347 | bool need_dirhash_key, |
b1c0ec35 | 348 | struct key **master_key_ret) |
3ec4f2a6 | 349 | { |
22d94f49 EB |
350 | struct key *key; |
351 | struct fscrypt_master_key *mk = NULL; | |
352 | struct fscrypt_key_specifier mk_spec; | |
353 | int err; | |
354 | ||
5fee3609 ST |
355 | err = fscrypt_select_encryption_impl(ci); |
356 | if (err) | |
357 | return err; | |
358 | ||
5dae460c EB |
359 | switch (ci->ci_policy.version) { |
360 | case FSCRYPT_POLICY_V1: | |
361 | mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR; | |
362 | memcpy(mk_spec.u.descriptor, | |
363 | ci->ci_policy.v1.master_key_descriptor, | |
364 | FSCRYPT_KEY_DESCRIPTOR_SIZE); | |
365 | break; | |
366 | case FSCRYPT_POLICY_V2: | |
367 | mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER; | |
368 | memcpy(mk_spec.u.identifier, | |
369 | ci->ci_policy.v2.master_key_identifier, | |
370 | FSCRYPT_KEY_IDENTIFIER_SIZE); | |
371 | break; | |
372 | default: | |
373 | WARN_ON(1); | |
374 | return -EINVAL; | |
375 | } | |
22d94f49 EB |
376 | |
377 | key = fscrypt_find_master_key(ci->ci_inode->i_sb, &mk_spec); | |
378 | if (IS_ERR(key)) { | |
5dae460c EB |
379 | if (key != ERR_PTR(-ENOKEY) || |
380 | ci->ci_policy.version != FSCRYPT_POLICY_V1) | |
22d94f49 EB |
381 | return PTR_ERR(key); |
382 | ||
5dae460c EB |
383 | /* |
384 | * As a legacy fallback for v1 policies, search for the key in | |
385 | * the current task's subscribed keyrings too. Don't move this | |
386 | * to before the search of ->s_master_keys, since users | |
387 | * shouldn't be able to override filesystem-level keys. | |
388 | */ | |
22d94f49 EB |
389 | return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); |
390 | } | |
391 | ||
392 | mk = key->payload.data[0]; | |
23c688b5 | 393 | down_read(&mk->mk_secret_sem); |
b1c0ec35 EB |
394 | |
395 | /* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */ | |
396 | if (!is_master_key_secret_present(&mk->mk_secret)) { | |
397 | err = -ENOKEY; | |
398 | goto out_release_key; | |
399 | } | |
22d94f49 | 400 | |
5dae460c EB |
401 | /* |
402 | * Require that the master key be at least as long as the derived key. | |
403 | * Otherwise, the derived key cannot possibly contain as much entropy as | |
404 | * that required by the encryption mode it will be used for. For v1 | |
405 | * policies it's also required for the KDF to work at all. | |
406 | */ | |
22d94f49 EB |
407 | if (mk->mk_secret.size < ci->ci_mode->keysize) { |
408 | fscrypt_warn(NULL, | |
409 | "key with %s %*phN is too short (got %u bytes, need %u+ bytes)", | |
410 | master_key_spec_type(&mk_spec), | |
411 | master_key_spec_len(&mk_spec), (u8 *)&mk_spec.u, | |
412 | mk->mk_secret.size, ci->ci_mode->keysize); | |
413 | err = -ENOKEY; | |
414 | goto out_release_key; | |
415 | } | |
416 | ||
5dae460c EB |
417 | switch (ci->ci_policy.version) { |
418 | case FSCRYPT_POLICY_V1: | |
419 | err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw); | |
420 | break; | |
421 | case FSCRYPT_POLICY_V2: | |
a992b20c | 422 | err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key); |
5dae460c EB |
423 | break; |
424 | default: | |
425 | WARN_ON(1); | |
426 | err = -EINVAL; | |
427 | break; | |
428 | } | |
b1c0ec35 EB |
429 | if (err) |
430 | goto out_release_key; | |
431 | ||
432 | *master_key_ret = key; | |
433 | return 0; | |
22d94f49 EB |
434 | |
435 | out_release_key: | |
23c688b5 | 436 | up_read(&mk->mk_secret_sem); |
22d94f49 EB |
437 | key_put(key); |
438 | return err; | |
3ec4f2a6 EB |
439 | } |
440 | ||
8094c3ce EB |
441 | static void put_crypt_info(struct fscrypt_info *ci) |
442 | { | |
b1c0ec35 EB |
443 | struct key *key; |
444 | ||
8094c3ce EB |
445 | if (!ci) |
446 | return; | |
447 | ||
4006d799 | 448 | if (ci->ci_direct_key) |
0109ce76 | 449 | fscrypt_put_direct_key(ci->ci_direct_key); |
b103fb76 | 450 | else if (ci->ci_owns_key) |
5fee3609 | 451 | fscrypt_destroy_prepared_key(&ci->ci_enc_key); |
b1c0ec35 EB |
452 | |
453 | key = ci->ci_master_key; | |
454 | if (key) { | |
455 | struct fscrypt_master_key *mk = key->payload.data[0]; | |
456 | ||
457 | /* | |
458 | * Remove this inode from the list of inodes that were unlocked | |
459 | * with the master key. | |
460 | * | |
461 | * In addition, if we're removing the last inode from a key that | |
462 | * already had its secret removed, invalidate the key so that it | |
463 | * gets removed from ->s_master_keys. | |
464 | */ | |
465 | spin_lock(&mk->mk_decrypted_inodes_lock); | |
466 | list_del(&ci->ci_master_key_link); | |
467 | spin_unlock(&mk->mk_decrypted_inodes_lock); | |
468 | if (refcount_dec_and_test(&mk->mk_refcount)) | |
469 | key_invalidate(key); | |
470 | key_put(key); | |
471 | } | |
6f99756d | 472 | memzero_explicit(ci, sizeof(*ci)); |
8094c3ce EB |
473 | kmem_cache_free(fscrypt_info_cachep, ci); |
474 | } | |
475 | ||
a992b20c EB |
476 | static int |
477 | fscrypt_setup_encryption_info(struct inode *inode, | |
478 | const union fscrypt_policy *policy, | |
479 | const u8 nonce[FSCRYPT_FILE_NONCE_SIZE], | |
480 | bool need_dirhash_key) | |
0adda907 | 481 | { |
0b81d077 | 482 | struct fscrypt_info *crypt_info; |
e1cc40e5 | 483 | struct fscrypt_mode *mode; |
b1c0ec35 | 484 | struct key *master_key = NULL; |
0adda907 JK |
485 | int res; |
486 | ||
f32d7ac2 | 487 | res = fscrypt_initialize(inode->i_sb->s_cop->flags); |
cfc4d971 JK |
488 | if (res) |
489 | return res; | |
0b81d077 | 490 | |
9dad5feb | 491 | crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_KERNEL); |
0adda907 JK |
492 | if (!crypt_info) |
493 | return -ENOMEM; | |
494 | ||
59dc6a8e | 495 | crypt_info->ci_inode = inode; |
a992b20c EB |
496 | crypt_info->ci_policy = *policy; |
497 | memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE); | |
640778fb | 498 | |
5dae460c | 499 | mode = select_encryption_mode(&crypt_info->ci_policy, inode); |
e1cc40e5 EB |
500 | if (IS_ERR(mode)) { |
501 | res = PTR_ERR(mode); | |
26bf3dc7 | 502 | goto out; |
e1cc40e5 | 503 | } |
8094c3ce EB |
504 | WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE); |
505 | crypt_info->ci_mode = mode; | |
8f39850d | 506 | |
a992b20c EB |
507 | res = setup_file_encryption_key(crypt_info, need_dirhash_key, |
508 | &master_key); | |
26bf3dc7 JK |
509 | if (res) |
510 | goto out; | |
511 | ||
ab673b98 | 512 | /* |
a992b20c EB |
513 | * For existing inodes, multiple tasks may race to set ->i_crypt_info. |
514 | * So use cmpxchg_release(). This pairs with the smp_load_acquire() in | |
ab673b98 EB |
515 | * fscrypt_get_info(). I.e., here we publish ->i_crypt_info with a |
516 | * RELEASE barrier so that other tasks can ACQUIRE it. | |
517 | */ | |
b1c0ec35 | 518 | if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) { |
ab673b98 EB |
519 | /* |
520 | * We won the race and set ->i_crypt_info to our crypt_info. | |
521 | * Now link it into the master key's inode list. | |
522 | */ | |
b1c0ec35 EB |
523 | if (master_key) { |
524 | struct fscrypt_master_key *mk = | |
525 | master_key->payload.data[0]; | |
526 | ||
527 | refcount_inc(&mk->mk_refcount); | |
528 | crypt_info->ci_master_key = key_get(master_key); | |
529 | spin_lock(&mk->mk_decrypted_inodes_lock); | |
530 | list_add(&crypt_info->ci_master_key_link, | |
531 | &mk->mk_decrypted_inodes); | |
532 | spin_unlock(&mk->mk_decrypted_inodes_lock); | |
533 | } | |
1b53cf98 | 534 | crypt_info = NULL; |
b1c0ec35 EB |
535 | } |
536 | res = 0; | |
26bf3dc7 | 537 | out: |
b1c0ec35 | 538 | if (master_key) { |
23c688b5 EB |
539 | struct fscrypt_master_key *mk = master_key->payload.data[0]; |
540 | ||
541 | up_read(&mk->mk_secret_sem); | |
b1c0ec35 EB |
542 | key_put(master_key); |
543 | } | |
a992b20c EB |
544 | put_crypt_info(crypt_info); |
545 | return res; | |
546 | } | |
547 | ||
548 | /** | |
549 | * fscrypt_get_encryption_info() - set up an inode's encryption key | |
ac4acb1f | 550 | * @inode: the inode to set up the key for. Must be encrypted. |
a992b20c EB |
551 | * |
552 | * Set up ->i_crypt_info, if it hasn't already been done. | |
553 | * | |
554 | * Note: unless ->i_crypt_info is already set, this isn't %GFP_NOFS-safe. So | |
555 | * generally this shouldn't be called from within a filesystem transaction. | |
556 | * | |
557 | * Return: 0 if ->i_crypt_info was set or was already set, *or* if the | |
558 | * encryption key is unavailable. (Use fscrypt_has_encryption_key() to | |
559 | * distinguish these cases.) Also can return another -errno code. | |
560 | */ | |
561 | int fscrypt_get_encryption_info(struct inode *inode) | |
562 | { | |
563 | int res; | |
564 | union fscrypt_context ctx; | |
565 | union fscrypt_policy policy; | |
566 | ||
567 | if (fscrypt_has_encryption_key(inode)) | |
568 | return 0; | |
569 | ||
570 | res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); | |
571 | if (res < 0) { | |
ac4acb1f EB |
572 | fscrypt_warn(inode, "Error %d getting encryption context", res); |
573 | return res; | |
a992b20c EB |
574 | } |
575 | ||
576 | res = fscrypt_policy_from_context(&policy, &ctx, res); | |
577 | if (res) { | |
578 | fscrypt_warn(inode, | |
579 | "Unrecognized or corrupt encryption context"); | |
580 | return res; | |
581 | } | |
582 | ||
583 | if (!fscrypt_supported_policy(&policy, inode)) | |
584 | return -EINVAL; | |
585 | ||
586 | res = fscrypt_setup_encryption_info(inode, &policy, | |
587 | fscrypt_context_nonce(&ctx), | |
588 | IS_CASEFOLDED(inode) && | |
589 | S_ISDIR(inode->i_mode)); | |
0b81d077 | 590 | if (res == -ENOKEY) |
26bf3dc7 | 591 | res = 0; |
0adda907 JK |
592 | return res; |
593 | } | |
1b53cf98 | 594 | EXPORT_SYMBOL(fscrypt_get_encryption_info); |
0adda907 | 595 | |
a992b20c EB |
596 | /** |
597 | * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory | |
598 | * @dir: a possibly-encrypted directory | |
599 | * @inode: the new inode. ->i_mode must be set already. | |
600 | * ->i_ino doesn't need to be set yet. | |
601 | * @encrypt_ret: (output) set to %true if the new inode will be encrypted | |
602 | * | |
603 | * If the directory is encrypted, set up its ->i_crypt_info in preparation for | |
604 | * encrypting the name of the new file. Also, if the new inode will be | |
605 | * encrypted, set up its ->i_crypt_info and set *encrypt_ret=true. | |
606 | * | |
607 | * This isn't %GFP_NOFS-safe, and therefore it should be called before starting | |
608 | * any filesystem transaction to create the inode. For this reason, ->i_ino | |
609 | * isn't required to be set yet, as the filesystem may not have set it yet. | |
610 | * | |
611 | * This doesn't persist the new inode's encryption context. That still needs to | |
612 | * be done later by calling fscrypt_set_context(). | |
613 | * | |
614 | * Return: 0 on success, -ENOKEY if the encryption key is missing, or another | |
615 | * -errno code | |
616 | */ | |
617 | int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode, | |
618 | bool *encrypt_ret) | |
619 | { | |
ac4acb1f | 620 | const union fscrypt_policy *policy; |
a992b20c EB |
621 | u8 nonce[FSCRYPT_FILE_NONCE_SIZE]; |
622 | ||
ac4acb1f EB |
623 | policy = fscrypt_policy_to_inherit(dir); |
624 | if (policy == NULL) | |
a992b20c | 625 | return 0; |
ac4acb1f EB |
626 | if (IS_ERR(policy)) |
627 | return PTR_ERR(policy); | |
a992b20c EB |
628 | |
629 | if (WARN_ON_ONCE(inode->i_mode == 0)) | |
630 | return -EINVAL; | |
631 | ||
632 | /* | |
633 | * Only regular files, directories, and symlinks are encrypted. | |
634 | * Special files like device nodes and named pipes aren't. | |
635 | */ | |
636 | if (!S_ISREG(inode->i_mode) && | |
637 | !S_ISDIR(inode->i_mode) && | |
638 | !S_ISLNK(inode->i_mode)) | |
639 | return 0; | |
640 | ||
641 | *encrypt_ret = true; | |
642 | ||
643 | get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE); | |
ac4acb1f | 644 | return fscrypt_setup_encryption_info(inode, policy, nonce, |
a992b20c EB |
645 | IS_CASEFOLDED(dir) && |
646 | S_ISDIR(inode->i_mode)); | |
647 | } | |
648 | EXPORT_SYMBOL_GPL(fscrypt_prepare_new_inode); | |
649 | ||
2c58d548 | 650 | /** |
d2fe9754 EB |
651 | * fscrypt_put_encryption_info() - free most of an inode's fscrypt data |
652 | * @inode: an inode being evicted | |
2c58d548 EB |
653 | * |
654 | * Free the inode's fscrypt_info. Filesystems must call this when the inode is | |
655 | * being evicted. An RCU grace period need not have elapsed yet. | |
656 | */ | |
3d204e24 | 657 | void fscrypt_put_encryption_info(struct inode *inode) |
0adda907 | 658 | { |
3d204e24 EB |
659 | put_crypt_info(inode->i_crypt_info); |
660 | inode->i_crypt_info = NULL; | |
0b81d077 JK |
661 | } |
662 | EXPORT_SYMBOL(fscrypt_put_encryption_info); | |
2c58d548 EB |
663 | |
664 | /** | |
d2fe9754 EB |
665 | * fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay |
666 | * @inode: an inode being freed | |
2c58d548 EB |
667 | * |
668 | * Free the inode's cached decrypted symlink target, if any. Filesystems must | |
669 | * call this after an RCU grace period, just before they free the inode. | |
670 | */ | |
671 | void fscrypt_free_inode(struct inode *inode) | |
672 | { | |
673 | if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) { | |
674 | kfree(inode->i_link); | |
675 | inode->i_link = NULL; | |
676 | } | |
677 | } | |
678 | EXPORT_SYMBOL(fscrypt_free_inode); | |
b1c0ec35 EB |
679 | |
680 | /** | |
d2fe9754 EB |
681 | * fscrypt_drop_inode() - check whether the inode's master key has been removed |
682 | * @inode: an inode being considered for eviction | |
b1c0ec35 EB |
683 | * |
684 | * Filesystems supporting fscrypt must call this from their ->drop_inode() | |
685 | * method so that encrypted inodes are evicted as soon as they're no longer in | |
686 | * use and their master key has been removed. | |
687 | * | |
688 | * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0 | |
689 | */ | |
690 | int fscrypt_drop_inode(struct inode *inode) | |
691 | { | |
ab673b98 | 692 | const struct fscrypt_info *ci = fscrypt_get_info(inode); |
b1c0ec35 EB |
693 | const struct fscrypt_master_key *mk; |
694 | ||
695 | /* | |
696 | * If ci is NULL, then the inode doesn't have an encryption key set up | |
697 | * so it's irrelevant. If ci_master_key is NULL, then the master key | |
698 | * was provided via the legacy mechanism of the process-subscribed | |
699 | * keyrings, so we don't know whether it's been removed or not. | |
700 | */ | |
701 | if (!ci || !ci->ci_master_key) | |
702 | return 0; | |
703 | mk = ci->ci_master_key->payload.data[0]; | |
704 | ||
2b4eae95 EB |
705 | /* |
706 | * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes | |
707 | * protected by the key were cleaned by sync_filesystem(). But if | |
708 | * userspace is still using the files, inodes can be dirtied between | |
709 | * then and now. We mustn't lose any writes, so skip dirty inodes here. | |
710 | */ | |
711 | if (inode->i_state & I_DIRTY_ALL) | |
712 | return 0; | |
713 | ||
b1c0ec35 | 714 | /* |
23c688b5 | 715 | * Note: since we aren't holding ->mk_secret_sem, the result here can |
b1c0ec35 EB |
716 | * immediately become outdated. But there's no correctness problem with |
717 | * unnecessarily evicting. Nor is there a correctness problem with not | |
718 | * evicting while iput() is racing with the key being removed, since | |
719 | * then the thread removing the key will either evict the inode itself | |
720 | * or will correctly detect that it wasn't evicted due to the race. | |
721 | */ | |
722 | return !is_master_key_secret_present(&mk->mk_secret); | |
723 | } | |
724 | EXPORT_SYMBOL_GPL(fscrypt_drop_inode); |