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/random.h> |
13 | |
14 | #include "fscrypt_private.h" |
15 | |
16 | struct fscrypt_mode fscrypt_modes[] = { |
17 | [FSCRYPT_MODE_AES_256_XTS] = { |
18 | .friendly_name = "AES-256-XTS" , |
19 | .cipher_str = "xts(aes)" , |
20 | .keysize = 64, |
21 | .security_strength = 32, |
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-CBC-CTS" , |
27 | .cipher_str = "cts(cbc(aes))" , |
28 | .keysize = 32, |
29 | .security_strength = 32, |
30 | .ivsize = 16, |
31 | }, |
32 | [FSCRYPT_MODE_AES_128_CBC] = { |
33 | .friendly_name = "AES-128-CBC-ESSIV" , |
34 | .cipher_str = "essiv(cbc(aes),sha256)" , |
35 | .keysize = 16, |
36 | .security_strength = 16, |
37 | .ivsize = 16, |
38 | .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV, |
39 | }, |
40 | [FSCRYPT_MODE_AES_128_CTS] = { |
41 | .friendly_name = "AES-128-CBC-CTS" , |
42 | .cipher_str = "cts(cbc(aes))" , |
43 | .keysize = 16, |
44 | .security_strength = 16, |
45 | .ivsize = 16, |
46 | }, |
47 | [FSCRYPT_MODE_SM4_XTS] = { |
48 | .friendly_name = "SM4-XTS" , |
49 | .cipher_str = "xts(sm4)" , |
50 | .keysize = 32, |
51 | .security_strength = 16, |
52 | .ivsize = 16, |
53 | .blk_crypto_mode = BLK_ENCRYPTION_MODE_SM4_XTS, |
54 | }, |
55 | [FSCRYPT_MODE_SM4_CTS] = { |
56 | .friendly_name = "SM4-CBC-CTS" , |
57 | .cipher_str = "cts(cbc(sm4))" , |
58 | .keysize = 16, |
59 | .security_strength = 16, |
60 | .ivsize = 16, |
61 | }, |
62 | [FSCRYPT_MODE_ADIANTUM] = { |
63 | .friendly_name = "Adiantum" , |
64 | .cipher_str = "adiantum(xchacha12,aes)" , |
65 | .keysize = 32, |
66 | .security_strength = 32, |
67 | .ivsize = 32, |
68 | .blk_crypto_mode = BLK_ENCRYPTION_MODE_ADIANTUM, |
69 | }, |
70 | [FSCRYPT_MODE_AES_256_HCTR2] = { |
71 | .friendly_name = "AES-256-HCTR2" , |
72 | .cipher_str = "hctr2(aes)" , |
73 | .keysize = 32, |
74 | .security_strength = 32, |
75 | .ivsize = 32, |
76 | }, |
77 | }; |
78 | |
79 | static DEFINE_MUTEX(fscrypt_mode_key_setup_mutex); |
80 | |
81 | static struct fscrypt_mode * |
82 | select_encryption_mode(const union fscrypt_policy *policy, |
83 | const struct inode *inode) |
84 | { |
85 | BUILD_BUG_ON(ARRAY_SIZE(fscrypt_modes) != FSCRYPT_MODE_MAX + 1); |
86 | |
87 | if (S_ISREG(inode->i_mode)) |
88 | return &fscrypt_modes[fscrypt_policy_contents_mode(policy)]; |
89 | |
90 | if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) |
91 | return &fscrypt_modes[fscrypt_policy_fnames_mode(policy)]; |
92 | |
93 | WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n" , |
94 | inode->i_ino, (inode->i_mode & S_IFMT)); |
95 | return ERR_PTR(error: -EINVAL); |
96 | } |
97 | |
98 | /* Create a symmetric cipher object for the given encryption mode and key */ |
99 | static struct crypto_skcipher * |
100 | fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key, |
101 | const struct inode *inode) |
102 | { |
103 | struct crypto_skcipher *tfm; |
104 | int err; |
105 | |
106 | tfm = crypto_alloc_skcipher(alg_name: mode->cipher_str, type: 0, mask: 0); |
107 | if (IS_ERR(ptr: tfm)) { |
108 | if (PTR_ERR(ptr: tfm) == -ENOENT) { |
109 | fscrypt_warn(inode, |
110 | "Missing crypto API support for %s (API name: \"%s\")" , |
111 | mode->friendly_name, mode->cipher_str); |
112 | return ERR_PTR(error: -ENOPKG); |
113 | } |
114 | fscrypt_err(inode, "Error allocating '%s' transform: %ld" , |
115 | mode->cipher_str, PTR_ERR(tfm)); |
116 | return tfm; |
117 | } |
118 | if (!xchg(&mode->logged_cryptoapi_impl, 1)) { |
119 | /* |
120 | * fscrypt performance can vary greatly depending on which |
121 | * crypto algorithm implementation is used. Help people debug |
122 | * performance problems by logging the ->cra_driver_name the |
123 | * first time a mode is used. |
124 | */ |
125 | pr_info("fscrypt: %s using implementation \"%s\"\n" , |
126 | mode->friendly_name, crypto_skcipher_driver_name(tfm)); |
127 | } |
128 | if (WARN_ON_ONCE(crypto_skcipher_ivsize(tfm) != mode->ivsize)) { |
129 | err = -EINVAL; |
130 | goto err_free_tfm; |
131 | } |
132 | crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); |
133 | err = crypto_skcipher_setkey(tfm, key: raw_key, keylen: mode->keysize); |
134 | if (err) |
135 | goto err_free_tfm; |
136 | |
137 | return tfm; |
138 | |
139 | err_free_tfm: |
140 | crypto_free_skcipher(tfm); |
141 | return ERR_PTR(error: err); |
142 | } |
143 | |
144 | /* |
145 | * Prepare the crypto transform object or blk-crypto key in @prep_key, given the |
146 | * raw key, encryption mode (@ci->ci_mode), flag indicating which encryption |
147 | * implementation (fs-layer or blk-crypto) will be used (@ci->ci_inlinecrypt), |
148 | * and IV generation method (@ci->ci_policy.flags). |
149 | */ |
150 | int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key, |
151 | const u8 *raw_key, const struct fscrypt_inode_info *ci) |
152 | { |
153 | struct crypto_skcipher *tfm; |
154 | |
155 | if (fscrypt_using_inline_encryption(ci)) |
156 | return fscrypt_prepare_inline_crypt_key(prep_key, raw_key, ci); |
157 | |
158 | tfm = fscrypt_allocate_skcipher(mode: ci->ci_mode, raw_key, inode: ci->ci_inode); |
159 | if (IS_ERR(ptr: tfm)) |
160 | return PTR_ERR(ptr: tfm); |
161 | /* |
162 | * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared(). |
163 | * I.e., here we publish ->tfm with a RELEASE barrier so that |
164 | * concurrent tasks can ACQUIRE it. Note that this concurrency is only |
165 | * possible for per-mode keys, not for per-file keys. |
166 | */ |
167 | smp_store_release(&prep_key->tfm, tfm); |
168 | return 0; |
169 | } |
170 | |
171 | /* Destroy a crypto transform object and/or blk-crypto key. */ |
172 | void fscrypt_destroy_prepared_key(struct super_block *sb, |
173 | struct fscrypt_prepared_key *prep_key) |
174 | { |
175 | crypto_free_skcipher(tfm: prep_key->tfm); |
176 | fscrypt_destroy_inline_crypt_key(sb, prep_key); |
177 | memzero_explicit(s: prep_key, count: sizeof(*prep_key)); |
178 | } |
179 | |
180 | /* Given a per-file encryption key, set up the file's crypto transform object */ |
181 | int fscrypt_set_per_file_enc_key(struct fscrypt_inode_info *ci, |
182 | const u8 *raw_key) |
183 | { |
184 | ci->ci_owns_key = true; |
185 | return fscrypt_prepare_key(prep_key: &ci->ci_enc_key, raw_key, ci); |
186 | } |
187 | |
188 | static int setup_per_mode_enc_key(struct fscrypt_inode_info *ci, |
189 | struct fscrypt_master_key *mk, |
190 | struct fscrypt_prepared_key *keys, |
191 | u8 hkdf_context, bool include_fs_uuid) |
192 | { |
193 | const struct inode *inode = ci->ci_inode; |
194 | const struct super_block *sb = inode->i_sb; |
195 | struct fscrypt_mode *mode = ci->ci_mode; |
196 | const u8 mode_num = mode - fscrypt_modes; |
197 | struct fscrypt_prepared_key *prep_key; |
198 | u8 mode_key[FSCRYPT_MAX_KEY_SIZE]; |
199 | u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)]; |
200 | unsigned int hkdf_infolen = 0; |
201 | int err; |
202 | |
203 | if (WARN_ON_ONCE(mode_num > FSCRYPT_MODE_MAX)) |
204 | return -EINVAL; |
205 | |
206 | prep_key = &keys[mode_num]; |
207 | if (fscrypt_is_key_prepared(prep_key, ci)) { |
208 | ci->ci_enc_key = *prep_key; |
209 | return 0; |
210 | } |
211 | |
212 | mutex_lock(&fscrypt_mode_key_setup_mutex); |
213 | |
214 | if (fscrypt_is_key_prepared(prep_key, ci)) |
215 | goto done_unlock; |
216 | |
217 | BUILD_BUG_ON(sizeof(mode_num) != 1); |
218 | BUILD_BUG_ON(sizeof(sb->s_uuid) != 16); |
219 | BUILD_BUG_ON(sizeof(hkdf_info) != 17); |
220 | hkdf_info[hkdf_infolen++] = mode_num; |
221 | if (include_fs_uuid) { |
222 | memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid, |
223 | sizeof(sb->s_uuid)); |
224 | hkdf_infolen += sizeof(sb->s_uuid); |
225 | } |
226 | err = fscrypt_hkdf_expand(hkdf: &mk->mk_secret.hkdf, |
227 | context: hkdf_context, info: hkdf_info, infolen: hkdf_infolen, |
228 | okm: mode_key, okmlen: mode->keysize); |
229 | if (err) |
230 | goto out_unlock; |
231 | err = fscrypt_prepare_key(prep_key, raw_key: mode_key, ci); |
232 | memzero_explicit(s: mode_key, count: mode->keysize); |
233 | if (err) |
234 | goto out_unlock; |
235 | done_unlock: |
236 | ci->ci_enc_key = *prep_key; |
237 | err = 0; |
238 | out_unlock: |
239 | mutex_unlock(lock: &fscrypt_mode_key_setup_mutex); |
240 | return err; |
241 | } |
242 | |
243 | /* |
244 | * Derive a SipHash key from the given fscrypt master key and the given |
245 | * application-specific information string. |
246 | * |
247 | * Note that the KDF produces a byte array, but the SipHash APIs expect the key |
248 | * as a pair of 64-bit words. Therefore, on big endian CPUs we have to do an |
249 | * endianness swap in order to get the same results as on little endian CPUs. |
250 | */ |
251 | static int fscrypt_derive_siphash_key(const struct fscrypt_master_key *mk, |
252 | u8 context, const u8 *info, |
253 | unsigned int infolen, siphash_key_t *key) |
254 | { |
255 | int err; |
256 | |
257 | err = fscrypt_hkdf_expand(hkdf: &mk->mk_secret.hkdf, context, info, infolen, |
258 | okm: (u8 *)key, okmlen: sizeof(*key)); |
259 | if (err) |
260 | return err; |
261 | |
262 | BUILD_BUG_ON(sizeof(*key) != 16); |
263 | BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2); |
264 | le64_to_cpus(&key->key[0]); |
265 | le64_to_cpus(&key->key[1]); |
266 | return 0; |
267 | } |
268 | |
269 | int fscrypt_derive_dirhash_key(struct fscrypt_inode_info *ci, |
270 | const struct fscrypt_master_key *mk) |
271 | { |
272 | int err; |
273 | |
274 | err = fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY, |
275 | info: ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, |
276 | key: &ci->ci_dirhash_key); |
277 | if (err) |
278 | return err; |
279 | ci->ci_dirhash_key_initialized = true; |
280 | return 0; |
281 | } |
282 | |
283 | void fscrypt_hash_inode_number(struct fscrypt_inode_info *ci, |
284 | const struct fscrypt_master_key *mk) |
285 | { |
286 | WARN_ON_ONCE(ci->ci_inode->i_ino == 0); |
287 | WARN_ON_ONCE(!mk->mk_ino_hash_key_initialized); |
288 | |
289 | ci->ci_hashed_ino = (u32)siphash_1u64(a: ci->ci_inode->i_ino, |
290 | key: &mk->mk_ino_hash_key); |
291 | } |
292 | |
293 | static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_inode_info *ci, |
294 | struct fscrypt_master_key *mk) |
295 | { |
296 | int err; |
297 | |
298 | err = setup_per_mode_enc_key(ci, mk, keys: mk->mk_iv_ino_lblk_32_keys, |
299 | HKDF_CONTEXT_IV_INO_LBLK_32_KEY, include_fs_uuid: true); |
300 | if (err) |
301 | return err; |
302 | |
303 | /* pairs with smp_store_release() below */ |
304 | if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) { |
305 | |
306 | mutex_lock(&fscrypt_mode_key_setup_mutex); |
307 | |
308 | if (mk->mk_ino_hash_key_initialized) |
309 | goto unlock; |
310 | |
311 | err = fscrypt_derive_siphash_key(mk, |
312 | HKDF_CONTEXT_INODE_HASH_KEY, |
313 | NULL, infolen: 0, key: &mk->mk_ino_hash_key); |
314 | if (err) |
315 | goto unlock; |
316 | /* pairs with smp_load_acquire() above */ |
317 | smp_store_release(&mk->mk_ino_hash_key_initialized, true); |
318 | unlock: |
319 | mutex_unlock(lock: &fscrypt_mode_key_setup_mutex); |
320 | if (err) |
321 | return err; |
322 | } |
323 | |
324 | /* |
325 | * New inodes may not have an inode number assigned yet. |
326 | * Hashing their inode number is delayed until later. |
327 | */ |
328 | if (ci->ci_inode->i_ino) |
329 | fscrypt_hash_inode_number(ci, mk); |
330 | return 0; |
331 | } |
332 | |
333 | static int fscrypt_setup_v2_file_key(struct fscrypt_inode_info *ci, |
334 | struct fscrypt_master_key *mk, |
335 | bool need_dirhash_key) |
336 | { |
337 | int err; |
338 | |
339 | if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { |
340 | /* |
341 | * DIRECT_KEY: instead of deriving per-file encryption keys, the |
342 | * per-file nonce will be included in all the IVs. But unlike |
343 | * v1 policies, for v2 policies in this case we don't encrypt |
344 | * with the master key directly but rather derive a per-mode |
345 | * encryption key. This ensures that the master key is |
346 | * consistently used only for HKDF, avoiding key reuse issues. |
347 | */ |
348 | err = setup_per_mode_enc_key(ci, mk, keys: mk->mk_direct_keys, |
349 | HKDF_CONTEXT_DIRECT_KEY, include_fs_uuid: false); |
350 | } else if (ci->ci_policy.v2.flags & |
351 | FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { |
352 | /* |
353 | * IV_INO_LBLK_64: encryption keys are derived from (master_key, |
354 | * mode_num, filesystem_uuid), and inode number is included in |
355 | * the IVs. This format is optimized for use with inline |
356 | * encryption hardware compliant with the UFS standard. |
357 | */ |
358 | err = setup_per_mode_enc_key(ci, mk, keys: mk->mk_iv_ino_lblk_64_keys, |
359 | HKDF_CONTEXT_IV_INO_LBLK_64_KEY, |
360 | include_fs_uuid: true); |
361 | } else if (ci->ci_policy.v2.flags & |
362 | FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { |
363 | err = fscrypt_setup_iv_ino_lblk_32_key(ci, mk); |
364 | } else { |
365 | u8 derived_key[FSCRYPT_MAX_KEY_SIZE]; |
366 | |
367 | err = fscrypt_hkdf_expand(hkdf: &mk->mk_secret.hkdf, |
368 | HKDF_CONTEXT_PER_FILE_ENC_KEY, |
369 | info: ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, |
370 | okm: derived_key, okmlen: ci->ci_mode->keysize); |
371 | if (err) |
372 | return err; |
373 | |
374 | err = fscrypt_set_per_file_enc_key(ci, raw_key: derived_key); |
375 | memzero_explicit(s: derived_key, count: ci->ci_mode->keysize); |
376 | } |
377 | if (err) |
378 | return err; |
379 | |
380 | /* Derive a secret dirhash key for directories that need it. */ |
381 | if (need_dirhash_key) { |
382 | err = fscrypt_derive_dirhash_key(ci, mk); |
383 | if (err) |
384 | return err; |
385 | } |
386 | |
387 | return 0; |
388 | } |
389 | |
390 | /* |
391 | * Check whether the size of the given master key (@mk) is appropriate for the |
392 | * encryption settings which a particular file will use (@ci). |
393 | * |
394 | * If the file uses a v1 encryption policy, then the master key must be at least |
395 | * as long as the derived key, as this is a requirement of the v1 KDF. |
396 | * |
397 | * Otherwise, the KDF can accept any size key, so we enforce a slightly looser |
398 | * requirement: we require that the size of the master key be at least the |
399 | * maximum security strength of any algorithm whose key will be derived from it |
400 | * (but in practice we only need to consider @ci->ci_mode, since any other |
401 | * possible subkeys such as DIRHASH and INODE_HASH will never increase the |
402 | * required key size over @ci->ci_mode). This allows AES-256-XTS keys to be |
403 | * derived from a 256-bit master key, which is cryptographically sufficient, |
404 | * rather than requiring a 512-bit master key which is unnecessarily long. (We |
405 | * still allow 512-bit master keys if the user chooses to use them, though.) |
406 | */ |
407 | static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk, |
408 | const struct fscrypt_inode_info *ci) |
409 | { |
410 | unsigned int min_keysize; |
411 | |
412 | if (ci->ci_policy.version == FSCRYPT_POLICY_V1) |
413 | min_keysize = ci->ci_mode->keysize; |
414 | else |
415 | min_keysize = ci->ci_mode->security_strength; |
416 | |
417 | if (mk->mk_secret.size < min_keysize) { |
418 | fscrypt_warn(NULL, |
419 | "key with %s %*phN is too short (got %u bytes, need %u+ bytes)" , |
420 | master_key_spec_type(&mk->mk_spec), |
421 | master_key_spec_len(&mk->mk_spec), |
422 | (u8 *)&mk->mk_spec.u, |
423 | mk->mk_secret.size, min_keysize); |
424 | return false; |
425 | } |
426 | return true; |
427 | } |
428 | |
429 | /* |
430 | * Find the master key, then set up the inode's actual encryption key. |
431 | * |
432 | * If the master key is found in the filesystem-level keyring, then it is |
433 | * returned in *mk_ret with its semaphore read-locked. This is needed to ensure |
434 | * that only one task links the fscrypt_inode_info into ->mk_decrypted_inodes |
435 | * (as multiple tasks may race to create an fscrypt_inode_info for the same |
436 | * inode), and to synchronize the master key being removed with a new inode |
437 | * starting to use it. |
438 | */ |
439 | static int setup_file_encryption_key(struct fscrypt_inode_info *ci, |
440 | bool need_dirhash_key, |
441 | struct fscrypt_master_key **mk_ret) |
442 | { |
443 | struct super_block *sb = ci->ci_inode->i_sb; |
444 | struct fscrypt_key_specifier mk_spec; |
445 | struct fscrypt_master_key *mk; |
446 | int err; |
447 | |
448 | err = fscrypt_select_encryption_impl(ci); |
449 | if (err) |
450 | return err; |
451 | |
452 | err = fscrypt_policy_to_key_spec(policy: &ci->ci_policy, key_spec: &mk_spec); |
453 | if (err) |
454 | return err; |
455 | |
456 | mk = fscrypt_find_master_key(sb, mk_spec: &mk_spec); |
457 | if (unlikely(!mk)) { |
458 | const union fscrypt_policy *dummy_policy = |
459 | fscrypt_get_dummy_policy(sb); |
460 | |
461 | /* |
462 | * Add the test_dummy_encryption key on-demand. In principle, |
463 | * it should be added at mount time. Do it here instead so that |
464 | * the individual filesystems don't need to worry about adding |
465 | * this key at mount time and cleaning up on mount failure. |
466 | */ |
467 | if (dummy_policy && |
468 | fscrypt_policies_equal(policy1: dummy_policy, policy2: &ci->ci_policy)) { |
469 | err = fscrypt_add_test_dummy_key(sb, key_spec: &mk_spec); |
470 | if (err) |
471 | return err; |
472 | mk = fscrypt_find_master_key(sb, mk_spec: &mk_spec); |
473 | } |
474 | } |
475 | if (unlikely(!mk)) { |
476 | if (ci->ci_policy.version != FSCRYPT_POLICY_V1) |
477 | return -ENOKEY; |
478 | |
479 | /* |
480 | * As a legacy fallback for v1 policies, search for the key in |
481 | * the current task's subscribed keyrings too. Don't move this |
482 | * to before the search of ->s_master_keys, since users |
483 | * shouldn't be able to override filesystem-level keys. |
484 | */ |
485 | return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); |
486 | } |
487 | down_read(sem: &mk->mk_sem); |
488 | |
489 | if (!mk->mk_present) { |
490 | /* FS_IOC_REMOVE_ENCRYPTION_KEY has been executed on this key */ |
491 | err = -ENOKEY; |
492 | goto out_release_key; |
493 | } |
494 | |
495 | if (!fscrypt_valid_master_key_size(mk, ci)) { |
496 | err = -ENOKEY; |
497 | goto out_release_key; |
498 | } |
499 | |
500 | switch (ci->ci_policy.version) { |
501 | case FSCRYPT_POLICY_V1: |
502 | err = fscrypt_setup_v1_file_key(ci, raw_master_key: mk->mk_secret.raw); |
503 | break; |
504 | case FSCRYPT_POLICY_V2: |
505 | err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key); |
506 | break; |
507 | default: |
508 | WARN_ON_ONCE(1); |
509 | err = -EINVAL; |
510 | break; |
511 | } |
512 | if (err) |
513 | goto out_release_key; |
514 | |
515 | *mk_ret = mk; |
516 | return 0; |
517 | |
518 | out_release_key: |
519 | up_read(sem: &mk->mk_sem); |
520 | fscrypt_put_master_key(mk); |
521 | return err; |
522 | } |
523 | |
524 | static void put_crypt_info(struct fscrypt_inode_info *ci) |
525 | { |
526 | struct fscrypt_master_key *mk; |
527 | |
528 | if (!ci) |
529 | return; |
530 | |
531 | if (ci->ci_direct_key) |
532 | fscrypt_put_direct_key(dk: ci->ci_direct_key); |
533 | else if (ci->ci_owns_key) |
534 | fscrypt_destroy_prepared_key(sb: ci->ci_inode->i_sb, |
535 | prep_key: &ci->ci_enc_key); |
536 | |
537 | mk = ci->ci_master_key; |
538 | if (mk) { |
539 | /* |
540 | * Remove this inode from the list of inodes that were unlocked |
541 | * with the master key. In addition, if we're removing the last |
542 | * inode from an incompletely removed key, then complete the |
543 | * full removal of the key. |
544 | */ |
545 | spin_lock(lock: &mk->mk_decrypted_inodes_lock); |
546 | list_del(entry: &ci->ci_master_key_link); |
547 | spin_unlock(lock: &mk->mk_decrypted_inodes_lock); |
548 | fscrypt_put_master_key_activeref(sb: ci->ci_inode->i_sb, mk); |
549 | } |
550 | memzero_explicit(s: ci, count: sizeof(*ci)); |
551 | kmem_cache_free(s: fscrypt_inode_info_cachep, objp: ci); |
552 | } |
553 | |
554 | static int |
555 | fscrypt_setup_encryption_info(struct inode *inode, |
556 | const union fscrypt_policy *policy, |
557 | const u8 nonce[FSCRYPT_FILE_NONCE_SIZE], |
558 | bool need_dirhash_key) |
559 | { |
560 | struct fscrypt_inode_info *crypt_info; |
561 | struct fscrypt_mode *mode; |
562 | struct fscrypt_master_key *mk = NULL; |
563 | int res; |
564 | |
565 | res = fscrypt_initialize(sb: inode->i_sb); |
566 | if (res) |
567 | return res; |
568 | |
569 | crypt_info = kmem_cache_zalloc(k: fscrypt_inode_info_cachep, GFP_KERNEL); |
570 | if (!crypt_info) |
571 | return -ENOMEM; |
572 | |
573 | crypt_info->ci_inode = inode; |
574 | crypt_info->ci_policy = *policy; |
575 | memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE); |
576 | |
577 | mode = select_encryption_mode(policy: &crypt_info->ci_policy, inode); |
578 | if (IS_ERR(ptr: mode)) { |
579 | res = PTR_ERR(ptr: mode); |
580 | goto out; |
581 | } |
582 | WARN_ON_ONCE(mode->ivsize > FSCRYPT_MAX_IV_SIZE); |
583 | crypt_info->ci_mode = mode; |
584 | |
585 | crypt_info->ci_data_unit_bits = |
586 | fscrypt_policy_du_bits(policy: &crypt_info->ci_policy, inode); |
587 | crypt_info->ci_data_units_per_block_bits = |
588 | inode->i_blkbits - crypt_info->ci_data_unit_bits; |
589 | |
590 | res = setup_file_encryption_key(ci: crypt_info, need_dirhash_key, mk_ret: &mk); |
591 | if (res) |
592 | goto out; |
593 | |
594 | /* |
595 | * For existing inodes, multiple tasks may race to set ->i_crypt_info. |
596 | * So use cmpxchg_release(). This pairs with the smp_load_acquire() in |
597 | * fscrypt_get_inode_info(). I.e., here we publish ->i_crypt_info with |
598 | * a RELEASE barrier so that other tasks can ACQUIRE it. |
599 | */ |
600 | if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) { |
601 | /* |
602 | * We won the race and set ->i_crypt_info to our crypt_info. |
603 | * Now link it into the master key's inode list. |
604 | */ |
605 | if (mk) { |
606 | crypt_info->ci_master_key = mk; |
607 | refcount_inc(r: &mk->mk_active_refs); |
608 | spin_lock(lock: &mk->mk_decrypted_inodes_lock); |
609 | list_add(new: &crypt_info->ci_master_key_link, |
610 | head: &mk->mk_decrypted_inodes); |
611 | spin_unlock(lock: &mk->mk_decrypted_inodes_lock); |
612 | } |
613 | crypt_info = NULL; |
614 | } |
615 | res = 0; |
616 | out: |
617 | if (mk) { |
618 | up_read(sem: &mk->mk_sem); |
619 | fscrypt_put_master_key(mk); |
620 | } |
621 | put_crypt_info(ci: crypt_info); |
622 | return res; |
623 | } |
624 | |
625 | /** |
626 | * fscrypt_get_encryption_info() - set up an inode's encryption key |
627 | * @inode: the inode to set up the key for. Must be encrypted. |
628 | * @allow_unsupported: if %true, treat an unsupported encryption policy (or |
629 | * unrecognized encryption context) the same way as the key |
630 | * being unavailable, instead of returning an error. Use |
631 | * %false unless the operation being performed is needed in |
632 | * order for files (or directories) to be deleted. |
633 | * |
634 | * Set up ->i_crypt_info, if it hasn't already been done. |
635 | * |
636 | * Note: unless ->i_crypt_info is already set, this isn't %GFP_NOFS-safe. So |
637 | * generally this shouldn't be called from within a filesystem transaction. |
638 | * |
639 | * Return: 0 if ->i_crypt_info was set or was already set, *or* if the |
640 | * encryption key is unavailable. (Use fscrypt_has_encryption_key() to |
641 | * distinguish these cases.) Also can return another -errno code. |
642 | */ |
643 | int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported) |
644 | { |
645 | int res; |
646 | union fscrypt_context ctx; |
647 | union fscrypt_policy policy; |
648 | |
649 | if (fscrypt_has_encryption_key(inode)) |
650 | return 0; |
651 | |
652 | res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); |
653 | if (res < 0) { |
654 | if (res == -ERANGE && allow_unsupported) |
655 | return 0; |
656 | fscrypt_warn(inode, "Error %d getting encryption context" , res); |
657 | return res; |
658 | } |
659 | |
660 | res = fscrypt_policy_from_context(policy_u: &policy, ctx_u: &ctx, ctx_size: res); |
661 | if (res) { |
662 | if (allow_unsupported) |
663 | return 0; |
664 | fscrypt_warn(inode, |
665 | "Unrecognized or corrupt encryption context" ); |
666 | return res; |
667 | } |
668 | |
669 | if (!fscrypt_supported_policy(policy_u: &policy, inode)) { |
670 | if (allow_unsupported) |
671 | return 0; |
672 | return -EINVAL; |
673 | } |
674 | |
675 | res = fscrypt_setup_encryption_info(inode, policy: &policy, |
676 | nonce: fscrypt_context_nonce(ctx: &ctx), |
677 | IS_CASEFOLDED(inode) && |
678 | S_ISDIR(inode->i_mode)); |
679 | |
680 | if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */ |
681 | res = 0; |
682 | if (res == -ENOKEY) |
683 | res = 0; |
684 | return res; |
685 | } |
686 | |
687 | /** |
688 | * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory |
689 | * @dir: a possibly-encrypted directory |
690 | * @inode: the new inode. ->i_mode and ->i_blkbits must be set already. |
691 | * ->i_ino doesn't need to be set yet. |
692 | * @encrypt_ret: (output) set to %true if the new inode will be encrypted |
693 | * |
694 | * If the directory is encrypted, set up its ->i_crypt_info in preparation for |
695 | * encrypting the name of the new file. Also, if the new inode will be |
696 | * encrypted, set up its ->i_crypt_info and set *encrypt_ret=true. |
697 | * |
698 | * This isn't %GFP_NOFS-safe, and therefore it should be called before starting |
699 | * any filesystem transaction to create the inode. For this reason, ->i_ino |
700 | * isn't required to be set yet, as the filesystem may not have set it yet. |
701 | * |
702 | * This doesn't persist the new inode's encryption context. That still needs to |
703 | * be done later by calling fscrypt_set_context(). |
704 | * |
705 | * Return: 0 on success, -ENOKEY if the encryption key is missing, or another |
706 | * -errno code |
707 | */ |
708 | int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode, |
709 | bool *encrypt_ret) |
710 | { |
711 | const union fscrypt_policy *policy; |
712 | u8 nonce[FSCRYPT_FILE_NONCE_SIZE]; |
713 | |
714 | policy = fscrypt_policy_to_inherit(dir); |
715 | if (policy == NULL) |
716 | return 0; |
717 | if (IS_ERR(ptr: policy)) |
718 | return PTR_ERR(ptr: policy); |
719 | |
720 | if (WARN_ON_ONCE(inode->i_blkbits == 0)) |
721 | return -EINVAL; |
722 | |
723 | if (WARN_ON_ONCE(inode->i_mode == 0)) |
724 | return -EINVAL; |
725 | |
726 | /* |
727 | * Only regular files, directories, and symlinks are encrypted. |
728 | * Special files like device nodes and named pipes aren't. |
729 | */ |
730 | if (!S_ISREG(inode->i_mode) && |
731 | !S_ISDIR(inode->i_mode) && |
732 | !S_ISLNK(inode->i_mode)) |
733 | return 0; |
734 | |
735 | *encrypt_ret = true; |
736 | |
737 | get_random_bytes(buf: nonce, FSCRYPT_FILE_NONCE_SIZE); |
738 | return fscrypt_setup_encryption_info(inode, policy, nonce, |
739 | IS_CASEFOLDED(dir) && |
740 | S_ISDIR(inode->i_mode)); |
741 | } |
742 | EXPORT_SYMBOL_GPL(fscrypt_prepare_new_inode); |
743 | |
744 | /** |
745 | * fscrypt_put_encryption_info() - free most of an inode's fscrypt data |
746 | * @inode: an inode being evicted |
747 | * |
748 | * Free the inode's fscrypt_inode_info. Filesystems must call this when the |
749 | * inode is being evicted. An RCU grace period need not have elapsed yet. |
750 | */ |
751 | void fscrypt_put_encryption_info(struct inode *inode) |
752 | { |
753 | put_crypt_info(ci: inode->i_crypt_info); |
754 | inode->i_crypt_info = NULL; |
755 | } |
756 | EXPORT_SYMBOL(fscrypt_put_encryption_info); |
757 | |
758 | /** |
759 | * fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay |
760 | * @inode: an inode being freed |
761 | * |
762 | * Free the inode's cached decrypted symlink target, if any. Filesystems must |
763 | * call this after an RCU grace period, just before they free the inode. |
764 | */ |
765 | void fscrypt_free_inode(struct inode *inode) |
766 | { |
767 | if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) { |
768 | kfree(objp: inode->i_link); |
769 | inode->i_link = NULL; |
770 | } |
771 | } |
772 | EXPORT_SYMBOL(fscrypt_free_inode); |
773 | |
774 | /** |
775 | * fscrypt_drop_inode() - check whether the inode's master key has been removed |
776 | * @inode: an inode being considered for eviction |
777 | * |
778 | * Filesystems supporting fscrypt must call this from their ->drop_inode() |
779 | * method so that encrypted inodes are evicted as soon as they're no longer in |
780 | * use and their master key has been removed. |
781 | * |
782 | * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0 |
783 | */ |
784 | int fscrypt_drop_inode(struct inode *inode) |
785 | { |
786 | const struct fscrypt_inode_info *ci = fscrypt_get_inode_info(inode); |
787 | |
788 | /* |
789 | * If ci is NULL, then the inode doesn't have an encryption key set up |
790 | * so it's irrelevant. If ci_master_key is NULL, then the master key |
791 | * was provided via the legacy mechanism of the process-subscribed |
792 | * keyrings, so we don't know whether it's been removed or not. |
793 | */ |
794 | if (!ci || !ci->ci_master_key) |
795 | return 0; |
796 | |
797 | /* |
798 | * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes |
799 | * protected by the key were cleaned by sync_filesystem(). But if |
800 | * userspace is still using the files, inodes can be dirtied between |
801 | * then and now. We mustn't lose any writes, so skip dirty inodes here. |
802 | */ |
803 | if (inode->i_state & I_DIRTY_ALL) |
804 | return 0; |
805 | |
806 | /* |
807 | * We can't take ->mk_sem here, since this runs in atomic context. |
808 | * Therefore, ->mk_present can change concurrently, and our result may |
809 | * immediately become outdated. But there's no correctness problem with |
810 | * unnecessarily evicting. Nor is there a correctness problem with not |
811 | * evicting while iput() is racing with the key being removed, since |
812 | * then the thread removing the key will either evict the inode itself |
813 | * or will correctly detect that it wasn't evicted due to the race. |
814 | */ |
815 | return !READ_ONCE(ci->ci_master_key->mk_present); |
816 | } |
817 | EXPORT_SYMBOL_GPL(fscrypt_drop_inode); |
818 | |