Commit | Line | Data |
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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> |
a992b20c | 12 | #include <linux/random.h> |
0109ce76 | 13 | |
3325bea5 | 14 | #include "fscrypt_private.h" |
0adda907 | 15 | |
85af90e5 | 16 | struct fscrypt_mode fscrypt_modes[] = { |
3b6df59b | 17 | [FSCRYPT_MODE_AES_256_XTS] = { |
e1cc40e5 EB |
18 | .friendly_name = "AES-256-XTS", |
19 | .cipher_str = "xts(aes)", | |
20 | .keysize = 64, | |
7f595d6a | 21 | .security_strength = 32, |
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, | |
7f595d6a | 29 | .security_strength = 32, |
8094c3ce | 30 | .ivsize = 16, |
e1cc40e5 | 31 | }, |
3b6df59b | 32 | [FSCRYPT_MODE_AES_128_CBC] = { |
4006d799 EB |
33 | .friendly_name = "AES-128-CBC-ESSIV", |
34 | .cipher_str = "essiv(cbc(aes),sha256)", | |
e1cc40e5 | 35 | .keysize = 16, |
7f595d6a | 36 | .security_strength = 16, |
8094c3ce | 37 | .ivsize = 16, |
5fee3609 | 38 | .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV, |
e1cc40e5 | 39 | }, |
3b6df59b | 40 | [FSCRYPT_MODE_AES_128_CTS] = { |
e1cc40e5 EB |
41 | .friendly_name = "AES-128-CTS-CBC", |
42 | .cipher_str = "cts(cbc(aes))", | |
43 | .keysize = 16, | |
7f595d6a | 44 | .security_strength = 16, |
8094c3ce | 45 | .ivsize = 16, |
e0cefada TZ |
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-CTS-CBC", | |
57 | .cipher_str = "cts(cbc(sm4))", | |
58 | .keysize = 16, | |
59 | .security_strength = 16, | |
60 | .ivsize = 16, | |
8094c3ce | 61 | }, |
3b6df59b | 62 | [FSCRYPT_MODE_ADIANTUM] = { |
8094c3ce EB |
63 | .friendly_name = "Adiantum", |
64 | .cipher_str = "adiantum(xchacha12,aes)", | |
65 | .keysize = 32, | |
7f595d6a | 66 | .security_strength = 32, |
8094c3ce | 67 | .ivsize = 32, |
5fee3609 | 68 | .blk_crypto_mode = BLK_ENCRYPTION_MODE_ADIANTUM, |
e1cc40e5 | 69 | }, |
6b2a51ff NH |
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 | }, | |
b7e7cf7a DW |
77 | }; |
78 | ||
e3b1078b EB |
79 | static DEFINE_MUTEX(fscrypt_mode_key_setup_mutex); |
80 | ||
e1cc40e5 | 81 | static struct fscrypt_mode * |
5dae460c EB |
82 | select_encryption_mode(const union fscrypt_policy *policy, |
83 | const struct inode *inode) | |
8f39850d | 84 | { |
3ceb6543 EB |
85 | BUILD_BUG_ON(ARRAY_SIZE(fscrypt_modes) != FSCRYPT_MODE_MAX + 1); |
86 | ||
e1cc40e5 | 87 | if (S_ISREG(inode->i_mode)) |
85af90e5 | 88 | return &fscrypt_modes[fscrypt_policy_contents_mode(policy)]; |
e1cc40e5 EB |
89 | |
90 | if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) | |
85af90e5 | 91 | return &fscrypt_modes[fscrypt_policy_fnames_mode(policy)]; |
8f39850d | 92 | |
e1cc40e5 EB |
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(-EINVAL); | |
8f39850d EB |
96 | } |
97 | ||
3ec4f2a6 | 98 | /* Create a symmetric cipher object for the given encryption mode and key */ |
5fee3609 ST |
99 | static struct crypto_skcipher * |
100 | fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key, | |
101 | const struct inode *inode) | |
8094c3ce EB |
102 | { |
103 | struct crypto_skcipher *tfm; | |
104 | int err; | |
105 | ||
106 | tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0); | |
107 | if (IS_ERR(tfm)) { | |
29a98c1c | 108 | if (PTR_ERR(tfm) == -ENOENT) { |
a4d14e91 EB |
109 | fscrypt_warn(inode, |
110 | "Missing crypto API support for %s (API name: \"%s\")", | |
111 | mode->friendly_name, mode->cipher_str); | |
29a98c1c EB |
112 | return ERR_PTR(-ENOPKG); |
113 | } | |
114 | fscrypt_err(inode, "Error allocating '%s' transform: %ld", | |
115 | mode->cipher_str, PTR_ERR(tfm)); | |
8094c3ce EB |
116 | return tfm; |
117 | } | |
a7a5bc5f | 118 | if (!xchg(&mode->logged_cryptoapi_impl, 1)) { |
8094c3ce EB |
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 | |
ff73c2c0 | 123 | * first time a mode is used. |
8094c3ce | 124 | */ |
8094c3ce | 125 | pr_info("fscrypt: %s using implementation \"%s\"\n", |
6e1adb88 | 126 | mode->friendly_name, crypto_skcipher_driver_name(tfm)); |
8094c3ce | 127 | } |
41b2ad80 | 128 | if (WARN_ON_ONCE(crypto_skcipher_ivsize(tfm) != mode->ivsize)) { |
c64cfb98 EB |
129 | err = -EINVAL; |
130 | goto err_free_tfm; | |
131 | } | |
231baecd | 132 | crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); |
8094c3ce EB |
133 | err = crypto_skcipher_setkey(tfm, raw_key, 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(err); | |
142 | } | |
143 | ||
5fee3609 ST |
144 | /* |
145 | * Prepare the crypto transform object or blk-crypto key in @prep_key, given the | |
b7e072f9 EB |
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). | |
5fee3609 ST |
149 | */ |
150 | int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key, | |
151 | const u8 *raw_key, const struct fscrypt_info *ci) | |
8094c3ce | 152 | { |
4006d799 | 153 | struct crypto_skcipher *tfm; |
3ec4f2a6 | 154 | |
5fee3609 ST |
155 | if (fscrypt_using_inline_encryption(ci)) |
156 | return fscrypt_prepare_inline_crypt_key(prep_key, raw_key, ci); | |
157 | ||
f592efe7 | 158 | tfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, ci->ci_inode); |
4006d799 EB |
159 | if (IS_ERR(tfm)) |
160 | return PTR_ERR(tfm); | |
5fee3609 | 161 | /* |
97c6327f EB |
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. | |
5fee3609 ST |
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. */ | |
22e9947a EB |
172 | void fscrypt_destroy_prepared_key(struct super_block *sb, |
173 | struct fscrypt_prepared_key *prep_key) | |
5fee3609 ST |
174 | { |
175 | crypto_free_skcipher(prep_key->tfm); | |
22e9947a | 176 | fscrypt_destroy_inline_crypt_key(sb, prep_key); |
d7e7b9af | 177 | memzero_explicit(prep_key, sizeof(*prep_key)); |
5fee3609 | 178 | } |
8094c3ce | 179 | |
5fee3609 ST |
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_info *ci, const u8 *raw_key) | |
182 | { | |
b103fb76 | 183 | ci->ci_owns_key = true; |
5fee3609 | 184 | return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci); |
8094c3ce EB |
185 | } |
186 | ||
f592efe7 EB |
187 | static int setup_per_mode_enc_key(struct fscrypt_info *ci, |
188 | struct fscrypt_master_key *mk, | |
5fee3609 | 189 | struct fscrypt_prepared_key *keys, |
f592efe7 | 190 | u8 hkdf_context, bool include_fs_uuid) |
5dae460c | 191 | { |
b103fb76 EB |
192 | const struct inode *inode = ci->ci_inode; |
193 | const struct super_block *sb = inode->i_sb; | |
5dae460c | 194 | struct fscrypt_mode *mode = ci->ci_mode; |
85af90e5 | 195 | const u8 mode_num = mode - fscrypt_modes; |
5fee3609 | 196 | struct fscrypt_prepared_key *prep_key; |
5dae460c | 197 | u8 mode_key[FSCRYPT_MAX_KEY_SIZE]; |
b103fb76 EB |
198 | u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)]; |
199 | unsigned int hkdf_infolen = 0; | |
5dae460c EB |
200 | int err; |
201 | ||
41b2ad80 | 202 | if (WARN_ON_ONCE(mode_num > FSCRYPT_MODE_MAX)) |
5dae460c EB |
203 | return -EINVAL; |
204 | ||
5fee3609 ST |
205 | prep_key = &keys[mode_num]; |
206 | if (fscrypt_is_key_prepared(prep_key, ci)) { | |
207 | ci->ci_enc_key = *prep_key; | |
e3b1078b EB |
208 | return 0; |
209 | } | |
210 | ||
211 | mutex_lock(&fscrypt_mode_key_setup_mutex); | |
212 | ||
5fee3609 | 213 | if (fscrypt_is_key_prepared(prep_key, ci)) |
e3b1078b | 214 | goto done_unlock; |
5dae460c EB |
215 | |
216 | BUILD_BUG_ON(sizeof(mode_num) != 1); | |
b103fb76 EB |
217 | BUILD_BUG_ON(sizeof(sb->s_uuid) != 16); |
218 | BUILD_BUG_ON(sizeof(hkdf_info) != 17); | |
219 | hkdf_info[hkdf_infolen++] = mode_num; | |
220 | if (include_fs_uuid) { | |
221 | memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid, | |
222 | sizeof(sb->s_uuid)); | |
223 | hkdf_infolen += sizeof(sb->s_uuid); | |
224 | } | |
5dae460c | 225 | err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, |
b103fb76 | 226 | hkdf_context, hkdf_info, hkdf_infolen, |
5dae460c EB |
227 | mode_key, mode->keysize); |
228 | if (err) | |
e3b1078b | 229 | goto out_unlock; |
5fee3609 | 230 | err = fscrypt_prepare_key(prep_key, mode_key, ci); |
5dae460c | 231 | memzero_explicit(mode_key, mode->keysize); |
5fee3609 | 232 | if (err) |
e3b1078b | 233 | goto out_unlock; |
e3b1078b | 234 | done_unlock: |
5fee3609 | 235 | ci->ci_enc_key = *prep_key; |
e3b1078b EB |
236 | err = 0; |
237 | out_unlock: | |
238 | mutex_unlock(&fscrypt_mode_key_setup_mutex); | |
239 | return err; | |
5dae460c EB |
240 | } |
241 | ||
2fc2b430 EB |
242 | /* |
243 | * Derive a SipHash key from the given fscrypt master key and the given | |
244 | * application-specific information string. | |
245 | * | |
246 | * Note that the KDF produces a byte array, but the SipHash APIs expect the key | |
247 | * as a pair of 64-bit words. Therefore, on big endian CPUs we have to do an | |
248 | * endianness swap in order to get the same results as on little endian CPUs. | |
249 | */ | |
250 | static int fscrypt_derive_siphash_key(const struct fscrypt_master_key *mk, | |
251 | u8 context, const u8 *info, | |
252 | unsigned int infolen, siphash_key_t *key) | |
253 | { | |
254 | int err; | |
255 | ||
256 | err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, context, info, infolen, | |
257 | (u8 *)key, sizeof(*key)); | |
258 | if (err) | |
259 | return err; | |
260 | ||
261 | BUILD_BUG_ON(sizeof(*key) != 16); | |
262 | BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2); | |
263 | le64_to_cpus(&key->key[0]); | |
264 | le64_to_cpus(&key->key[1]); | |
265 | return 0; | |
266 | } | |
267 | ||
aa408f83 DR |
268 | int fscrypt_derive_dirhash_key(struct fscrypt_info *ci, |
269 | const struct fscrypt_master_key *mk) | |
270 | { | |
271 | int err; | |
272 | ||
2fc2b430 EB |
273 | err = fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY, |
274 | ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, | |
275 | &ci->ci_dirhash_key); | |
aa408f83 DR |
276 | if (err) |
277 | return err; | |
278 | ci->ci_dirhash_key_initialized = true; | |
279 | return 0; | |
280 | } | |
281 | ||
a992b20c EB |
282 | void fscrypt_hash_inode_number(struct fscrypt_info *ci, |
283 | const struct fscrypt_master_key *mk) | |
284 | { | |
41b2ad80 EB |
285 | WARN_ON_ONCE(ci->ci_inode->i_ino == 0); |
286 | WARN_ON_ONCE(!mk->mk_ino_hash_key_initialized); | |
a992b20c EB |
287 | |
288 | ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino, | |
289 | &mk->mk_ino_hash_key); | |
290 | } | |
291 | ||
e3b1078b EB |
292 | static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_info *ci, |
293 | struct fscrypt_master_key *mk) | |
294 | { | |
295 | int err; | |
296 | ||
297 | err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys, | |
298 | HKDF_CONTEXT_IV_INO_LBLK_32_KEY, true); | |
299 | if (err) | |
300 | return err; | |
301 | ||
302 | /* pairs with smp_store_release() below */ | |
303 | if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) { | |
304 | ||
305 | mutex_lock(&fscrypt_mode_key_setup_mutex); | |
306 | ||
307 | if (mk->mk_ino_hash_key_initialized) | |
308 | goto unlock; | |
309 | ||
2fc2b430 EB |
310 | err = fscrypt_derive_siphash_key(mk, |
311 | HKDF_CONTEXT_INODE_HASH_KEY, | |
312 | NULL, 0, &mk->mk_ino_hash_key); | |
e3b1078b EB |
313 | if (err) |
314 | goto unlock; | |
315 | /* pairs with smp_load_acquire() above */ | |
316 | smp_store_release(&mk->mk_ino_hash_key_initialized, true); | |
317 | unlock: | |
318 | mutex_unlock(&fscrypt_mode_key_setup_mutex); | |
319 | if (err) | |
320 | return err; | |
321 | } | |
322 | ||
a992b20c EB |
323 | /* |
324 | * New inodes may not have an inode number assigned yet. | |
325 | * Hashing their inode number is delayed until later. | |
326 | */ | |
92cfcd03 | 327 | if (ci->ci_inode->i_ino) |
a992b20c | 328 | fscrypt_hash_inode_number(ci, mk); |
e3b1078b EB |
329 | return 0; |
330 | } | |
331 | ||
5dae460c | 332 | static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci, |
a992b20c EB |
333 | struct fscrypt_master_key *mk, |
334 | bool need_dirhash_key) | |
5dae460c | 335 | { |
5dae460c EB |
336 | int err; |
337 | ||
338 | if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { | |
339 | /* | |
f592efe7 EB |
340 | * DIRECT_KEY: instead of deriving per-file encryption keys, the |
341 | * per-file nonce will be included in all the IVs. But unlike | |
342 | * v1 policies, for v2 policies in this case we don't encrypt | |
343 | * with the master key directly but rather derive a per-mode | |
344 | * encryption key. This ensures that the master key is | |
345 | * consistently used only for HKDF, avoiding key reuse issues. | |
5dae460c | 346 | */ |
e3b1078b | 347 | err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys, |
f592efe7 | 348 | HKDF_CONTEXT_DIRECT_KEY, false); |
b103fb76 EB |
349 | } else if (ci->ci_policy.v2.flags & |
350 | FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { | |
351 | /* | |
352 | * IV_INO_LBLK_64: encryption keys are derived from (master_key, | |
353 | * mode_num, filesystem_uuid), and inode number is included in | |
354 | * the IVs. This format is optimized for use with inline | |
e3b1078b | 355 | * encryption hardware compliant with the UFS standard. |
b103fb76 | 356 | */ |
e3b1078b | 357 | err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys, |
f592efe7 EB |
358 | HKDF_CONTEXT_IV_INO_LBLK_64_KEY, |
359 | true); | |
e3b1078b EB |
360 | } else if (ci->ci_policy.v2.flags & |
361 | FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { | |
362 | err = fscrypt_setup_iv_ino_lblk_32_key(ci, mk); | |
aa408f83 DR |
363 | } else { |
364 | u8 derived_key[FSCRYPT_MAX_KEY_SIZE]; | |
5dae460c | 365 | |
aa408f83 | 366 | err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, |
f592efe7 | 367 | HKDF_CONTEXT_PER_FILE_ENC_KEY, |
1d6217a4 | 368 | ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, |
aa408f83 DR |
369 | derived_key, ci->ci_mode->keysize); |
370 | if (err) | |
371 | return err; | |
372 | ||
f592efe7 | 373 | err = fscrypt_set_per_file_enc_key(ci, derived_key); |
aa408f83 DR |
374 | memzero_explicit(derived_key, ci->ci_mode->keysize); |
375 | } | |
5dae460c EB |
376 | if (err) |
377 | return err; | |
378 | ||
aa408f83 | 379 | /* Derive a secret dirhash key for directories that need it. */ |
a992b20c | 380 | if (need_dirhash_key) { |
aa408f83 DR |
381 | err = fscrypt_derive_dirhash_key(ci, mk); |
382 | if (err) | |
383 | return err; | |
384 | } | |
385 | ||
386 | return 0; | |
5dae460c EB |
387 | } |
388 | ||
7f595d6a EB |
389 | /* |
390 | * Check whether the size of the given master key (@mk) is appropriate for the | |
391 | * encryption settings which a particular file will use (@ci). | |
392 | * | |
393 | * If the file uses a v1 encryption policy, then the master key must be at least | |
394 | * as long as the derived key, as this is a requirement of the v1 KDF. | |
395 | * | |
396 | * Otherwise, the KDF can accept any size key, so we enforce a slightly looser | |
397 | * requirement: we require that the size of the master key be at least the | |
398 | * maximum security strength of any algorithm whose key will be derived from it | |
399 | * (but in practice we only need to consider @ci->ci_mode, since any other | |
400 | * possible subkeys such as DIRHASH and INODE_HASH will never increase the | |
401 | * required key size over @ci->ci_mode). This allows AES-256-XTS keys to be | |
402 | * derived from a 256-bit master key, which is cryptographically sufficient, | |
403 | * rather than requiring a 512-bit master key which is unnecessarily long. (We | |
404 | * still allow 512-bit master keys if the user chooses to use them, though.) | |
405 | */ | |
406 | static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk, | |
407 | const struct fscrypt_info *ci) | |
408 | { | |
409 | unsigned int min_keysize; | |
410 | ||
411 | if (ci->ci_policy.version == FSCRYPT_POLICY_V1) | |
412 | min_keysize = ci->ci_mode->keysize; | |
413 | else | |
414 | min_keysize = ci->ci_mode->security_strength; | |
415 | ||
416 | if (mk->mk_secret.size < min_keysize) { | |
417 | fscrypt_warn(NULL, | |
418 | "key with %s %*phN is too short (got %u bytes, need %u+ bytes)", | |
419 | master_key_spec_type(&mk->mk_spec), | |
420 | master_key_spec_len(&mk->mk_spec), | |
421 | (u8 *)&mk->mk_spec.u, | |
422 | mk->mk_secret.size, min_keysize); | |
423 | return false; | |
424 | } | |
425 | return true; | |
426 | } | |
427 | ||
3ec4f2a6 EB |
428 | /* |
429 | * Find the master key, then set up the inode's actual encryption key. | |
b1c0ec35 | 430 | * |
d7e7b9af EB |
431 | * If the master key is found in the filesystem-level keyring, then it is |
432 | * returned in *mk_ret with its semaphore read-locked. This is needed to ensure | |
433 | * that only one task links the fscrypt_info into ->mk_decrypted_inodes (as | |
434 | * multiple tasks may race to create an fscrypt_info for the same inode), and to | |
435 | * synchronize the master key being removed with a new inode starting to use it. | |
3ec4f2a6 | 436 | */ |
b1c0ec35 | 437 | static int setup_file_encryption_key(struct fscrypt_info *ci, |
a992b20c | 438 | bool need_dirhash_key, |
d7e7b9af | 439 | struct fscrypt_master_key **mk_ret) |
3ec4f2a6 | 440 | { |
60e463f0 | 441 | struct super_block *sb = ci->ci_inode->i_sb; |
22d94f49 | 442 | struct fscrypt_key_specifier mk_spec; |
d7e7b9af | 443 | struct fscrypt_master_key *mk; |
22d94f49 EB |
444 | int err; |
445 | ||
5fee3609 ST |
446 | err = fscrypt_select_encryption_impl(ci); |
447 | if (err) | |
448 | return err; | |
449 | ||
bfb9700b EB |
450 | err = fscrypt_policy_to_key_spec(&ci->ci_policy, &mk_spec); |
451 | if (err) | |
452 | return err; | |
22d94f49 | 453 | |
60e463f0 EB |
454 | mk = fscrypt_find_master_key(sb, &mk_spec); |
455 | if (unlikely(!mk)) { | |
456 | const union fscrypt_policy *dummy_policy = | |
457 | fscrypt_get_dummy_policy(sb); | |
458 | ||
459 | /* | |
460 | * Add the test_dummy_encryption key on-demand. In principle, | |
461 | * it should be added at mount time. Do it here instead so that | |
462 | * the individual filesystems don't need to worry about adding | |
463 | * this key at mount time and cleaning up on mount failure. | |
464 | */ | |
465 | if (dummy_policy && | |
466 | fscrypt_policies_equal(dummy_policy, &ci->ci_policy)) { | |
097d7c1f | 467 | err = fscrypt_add_test_dummy_key(sb, &mk_spec); |
60e463f0 EB |
468 | if (err) |
469 | return err; | |
470 | mk = fscrypt_find_master_key(sb, &mk_spec); | |
471 | } | |
472 | } | |
473 | if (unlikely(!mk)) { | |
d7e7b9af EB |
474 | if (ci->ci_policy.version != FSCRYPT_POLICY_V1) |
475 | return -ENOKEY; | |
22d94f49 | 476 | |
5dae460c EB |
477 | /* |
478 | * As a legacy fallback for v1 policies, search for the key in | |
479 | * the current task's subscribed keyrings too. Don't move this | |
480 | * to before the search of ->s_master_keys, since users | |
481 | * shouldn't be able to override filesystem-level keys. | |
482 | */ | |
22d94f49 EB |
483 | return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); |
484 | } | |
d7e7b9af | 485 | down_read(&mk->mk_sem); |
b1c0ec35 EB |
486 | |
487 | /* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */ | |
488 | if (!is_master_key_secret_present(&mk->mk_secret)) { | |
489 | err = -ENOKEY; | |
490 | goto out_release_key; | |
491 | } | |
22d94f49 | 492 | |
7f595d6a | 493 | if (!fscrypt_valid_master_key_size(mk, ci)) { |
22d94f49 EB |
494 | err = -ENOKEY; |
495 | goto out_release_key; | |
496 | } | |
497 | ||
5dae460c EB |
498 | switch (ci->ci_policy.version) { |
499 | case FSCRYPT_POLICY_V1: | |
500 | err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw); | |
501 | break; | |
502 | case FSCRYPT_POLICY_V2: | |
a992b20c | 503 | err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key); |
5dae460c EB |
504 | break; |
505 | default: | |
41b2ad80 | 506 | WARN_ON_ONCE(1); |
5dae460c EB |
507 | err = -EINVAL; |
508 | break; | |
509 | } | |
b1c0ec35 EB |
510 | if (err) |
511 | goto out_release_key; | |
512 | ||
d7e7b9af | 513 | *mk_ret = mk; |
b1c0ec35 | 514 | return 0; |
22d94f49 EB |
515 | |
516 | out_release_key: | |
d7e7b9af EB |
517 | up_read(&mk->mk_sem); |
518 | fscrypt_put_master_key(mk); | |
22d94f49 | 519 | return err; |
3ec4f2a6 EB |
520 | } |
521 | ||
8094c3ce EB |
522 | static void put_crypt_info(struct fscrypt_info *ci) |
523 | { | |
d7e7b9af | 524 | struct fscrypt_master_key *mk; |
b1c0ec35 | 525 | |
8094c3ce EB |
526 | if (!ci) |
527 | return; | |
528 | ||
4006d799 | 529 | if (ci->ci_direct_key) |
0109ce76 | 530 | fscrypt_put_direct_key(ci->ci_direct_key); |
b103fb76 | 531 | else if (ci->ci_owns_key) |
22e9947a EB |
532 | fscrypt_destroy_prepared_key(ci->ci_inode->i_sb, |
533 | &ci->ci_enc_key); | |
b1c0ec35 | 534 | |
d7e7b9af EB |
535 | mk = ci->ci_master_key; |
536 | if (mk) { | |
b1c0ec35 EB |
537 | /* |
538 | * Remove this inode from the list of inodes that were unlocked | |
d7e7b9af EB |
539 | * with the master key. In addition, if we're removing the last |
540 | * inode from a master key struct that already had its secret | |
541 | * removed, then complete the full removal of the struct. | |
b1c0ec35 EB |
542 | */ |
543 | spin_lock(&mk->mk_decrypted_inodes_lock); | |
544 | list_del(&ci->ci_master_key_link); | |
545 | spin_unlock(&mk->mk_decrypted_inodes_lock); | |
02aef422 | 546 | fscrypt_put_master_key_activeref(ci->ci_inode->i_sb, mk); |
b1c0ec35 | 547 | } |
6f99756d | 548 | memzero_explicit(ci, sizeof(*ci)); |
8094c3ce EB |
549 | kmem_cache_free(fscrypt_info_cachep, ci); |
550 | } | |
551 | ||
a992b20c EB |
552 | static int |
553 | fscrypt_setup_encryption_info(struct inode *inode, | |
554 | const union fscrypt_policy *policy, | |
555 | const u8 nonce[FSCRYPT_FILE_NONCE_SIZE], | |
556 | bool need_dirhash_key) | |
0adda907 | 557 | { |
0b81d077 | 558 | struct fscrypt_info *crypt_info; |
e1cc40e5 | 559 | struct fscrypt_mode *mode; |
d7e7b9af | 560 | struct fscrypt_master_key *mk = NULL; |
0adda907 JK |
561 | int res; |
562 | ||
83e57e47 | 563 | res = fscrypt_initialize(inode->i_sb); |
cfc4d971 JK |
564 | if (res) |
565 | return res; | |
0b81d077 | 566 | |
9dad5feb | 567 | crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_KERNEL); |
0adda907 JK |
568 | if (!crypt_info) |
569 | return -ENOMEM; | |
570 | ||
59dc6a8e | 571 | crypt_info->ci_inode = inode; |
a992b20c EB |
572 | crypt_info->ci_policy = *policy; |
573 | memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE); | |
640778fb | 574 | |
5dae460c | 575 | mode = select_encryption_mode(&crypt_info->ci_policy, inode); |
e1cc40e5 EB |
576 | if (IS_ERR(mode)) { |
577 | res = PTR_ERR(mode); | |
26bf3dc7 | 578 | goto out; |
e1cc40e5 | 579 | } |
41b2ad80 | 580 | WARN_ON_ONCE(mode->ivsize > FSCRYPT_MAX_IV_SIZE); |
8094c3ce | 581 | crypt_info->ci_mode = mode; |
8f39850d | 582 | |
d7e7b9af | 583 | res = setup_file_encryption_key(crypt_info, need_dirhash_key, &mk); |
26bf3dc7 JK |
584 | if (res) |
585 | goto out; | |
586 | ||
ab673b98 | 587 | /* |
a992b20c EB |
588 | * For existing inodes, multiple tasks may race to set ->i_crypt_info. |
589 | * So use cmpxchg_release(). This pairs with the smp_load_acquire() in | |
ab673b98 EB |
590 | * fscrypt_get_info(). I.e., here we publish ->i_crypt_info with a |
591 | * RELEASE barrier so that other tasks can ACQUIRE it. | |
592 | */ | |
b1c0ec35 | 593 | if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) { |
ab673b98 EB |
594 | /* |
595 | * We won the race and set ->i_crypt_info to our crypt_info. | |
596 | * Now link it into the master key's inode list. | |
597 | */ | |
d7e7b9af EB |
598 | if (mk) { |
599 | crypt_info->ci_master_key = mk; | |
600 | refcount_inc(&mk->mk_active_refs); | |
b1c0ec35 EB |
601 | spin_lock(&mk->mk_decrypted_inodes_lock); |
602 | list_add(&crypt_info->ci_master_key_link, | |
603 | &mk->mk_decrypted_inodes); | |
604 | spin_unlock(&mk->mk_decrypted_inodes_lock); | |
605 | } | |
1b53cf98 | 606 | crypt_info = NULL; |
b1c0ec35 EB |
607 | } |
608 | res = 0; | |
26bf3dc7 | 609 | out: |
d7e7b9af EB |
610 | if (mk) { |
611 | up_read(&mk->mk_sem); | |
612 | fscrypt_put_master_key(mk); | |
b1c0ec35 | 613 | } |
a992b20c EB |
614 | put_crypt_info(crypt_info); |
615 | return res; | |
616 | } | |
617 | ||
618 | /** | |
619 | * fscrypt_get_encryption_info() - set up an inode's encryption key | |
ac4acb1f | 620 | * @inode: the inode to set up the key for. Must be encrypted. |
a14d0b67 EB |
621 | * @allow_unsupported: if %true, treat an unsupported encryption policy (or |
622 | * unrecognized encryption context) the same way as the key | |
623 | * being unavailable, instead of returning an error. Use | |
624 | * %false unless the operation being performed is needed in | |
625 | * order for files (or directories) to be deleted. | |
a992b20c EB |
626 | * |
627 | * Set up ->i_crypt_info, if it hasn't already been done. | |
628 | * | |
629 | * Note: unless ->i_crypt_info is already set, this isn't %GFP_NOFS-safe. So | |
630 | * generally this shouldn't be called from within a filesystem transaction. | |
631 | * | |
632 | * Return: 0 if ->i_crypt_info was set or was already set, *or* if the | |
633 | * encryption key is unavailable. (Use fscrypt_has_encryption_key() to | |
634 | * distinguish these cases.) Also can return another -errno code. | |
635 | */ | |
a14d0b67 | 636 | int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported) |
a992b20c EB |
637 | { |
638 | int res; | |
639 | union fscrypt_context ctx; | |
640 | union fscrypt_policy policy; | |
641 | ||
642 | if (fscrypt_has_encryption_key(inode)) | |
643 | return 0; | |
644 | ||
645 | res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); | |
646 | if (res < 0) { | |
a14d0b67 EB |
647 | if (res == -ERANGE && allow_unsupported) |
648 | return 0; | |
ac4acb1f EB |
649 | fscrypt_warn(inode, "Error %d getting encryption context", res); |
650 | return res; | |
a992b20c EB |
651 | } |
652 | ||
653 | res = fscrypt_policy_from_context(&policy, &ctx, res); | |
654 | if (res) { | |
a14d0b67 EB |
655 | if (allow_unsupported) |
656 | return 0; | |
a992b20c EB |
657 | fscrypt_warn(inode, |
658 | "Unrecognized or corrupt encryption context"); | |
659 | return res; | |
660 | } | |
661 | ||
a14d0b67 EB |
662 | if (!fscrypt_supported_policy(&policy, inode)) { |
663 | if (allow_unsupported) | |
664 | return 0; | |
a992b20c | 665 | return -EINVAL; |
a14d0b67 | 666 | } |
a992b20c EB |
667 | |
668 | res = fscrypt_setup_encryption_info(inode, &policy, | |
669 | fscrypt_context_nonce(&ctx), | |
670 | IS_CASEFOLDED(inode) && | |
671 | S_ISDIR(inode->i_mode)); | |
a14d0b67 EB |
672 | |
673 | if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */ | |
674 | res = 0; | |
0b81d077 | 675 | if (res == -ENOKEY) |
26bf3dc7 | 676 | res = 0; |
0adda907 JK |
677 | return res; |
678 | } | |
679 | ||
a992b20c EB |
680 | /** |
681 | * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory | |
682 | * @dir: a possibly-encrypted directory | |
683 | * @inode: the new inode. ->i_mode must be set already. | |
684 | * ->i_ino doesn't need to be set yet. | |
685 | * @encrypt_ret: (output) set to %true if the new inode will be encrypted | |
686 | * | |
687 | * If the directory is encrypted, set up its ->i_crypt_info in preparation for | |
688 | * encrypting the name of the new file. Also, if the new inode will be | |
689 | * encrypted, set up its ->i_crypt_info and set *encrypt_ret=true. | |
690 | * | |
691 | * This isn't %GFP_NOFS-safe, and therefore it should be called before starting | |
692 | * any filesystem transaction to create the inode. For this reason, ->i_ino | |
693 | * isn't required to be set yet, as the filesystem may not have set it yet. | |
694 | * | |
695 | * This doesn't persist the new inode's encryption context. That still needs to | |
696 | * be done later by calling fscrypt_set_context(). | |
697 | * | |
698 | * Return: 0 on success, -ENOKEY if the encryption key is missing, or another | |
699 | * -errno code | |
700 | */ | |
701 | int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode, | |
702 | bool *encrypt_ret) | |
703 | { | |
ac4acb1f | 704 | const union fscrypt_policy *policy; |
a992b20c EB |
705 | u8 nonce[FSCRYPT_FILE_NONCE_SIZE]; |
706 | ||
ac4acb1f EB |
707 | policy = fscrypt_policy_to_inherit(dir); |
708 | if (policy == NULL) | |
a992b20c | 709 | return 0; |
ac4acb1f EB |
710 | if (IS_ERR(policy)) |
711 | return PTR_ERR(policy); | |
a992b20c EB |
712 | |
713 | if (WARN_ON_ONCE(inode->i_mode == 0)) | |
714 | return -EINVAL; | |
715 | ||
716 | /* | |
717 | * Only regular files, directories, and symlinks are encrypted. | |
718 | * Special files like device nodes and named pipes aren't. | |
719 | */ | |
720 | if (!S_ISREG(inode->i_mode) && | |
721 | !S_ISDIR(inode->i_mode) && | |
722 | !S_ISLNK(inode->i_mode)) | |
723 | return 0; | |
724 | ||
725 | *encrypt_ret = true; | |
726 | ||
727 | get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE); | |
ac4acb1f | 728 | return fscrypt_setup_encryption_info(inode, policy, nonce, |
a992b20c EB |
729 | IS_CASEFOLDED(dir) && |
730 | S_ISDIR(inode->i_mode)); | |
731 | } | |
732 | EXPORT_SYMBOL_GPL(fscrypt_prepare_new_inode); | |
733 | ||
2c58d548 | 734 | /** |
d2fe9754 EB |
735 | * fscrypt_put_encryption_info() - free most of an inode's fscrypt data |
736 | * @inode: an inode being evicted | |
2c58d548 EB |
737 | * |
738 | * Free the inode's fscrypt_info. Filesystems must call this when the inode is | |
739 | * being evicted. An RCU grace period need not have elapsed yet. | |
740 | */ | |
3d204e24 | 741 | void fscrypt_put_encryption_info(struct inode *inode) |
0adda907 | 742 | { |
3d204e24 EB |
743 | put_crypt_info(inode->i_crypt_info); |
744 | inode->i_crypt_info = NULL; | |
0b81d077 JK |
745 | } |
746 | EXPORT_SYMBOL(fscrypt_put_encryption_info); | |
2c58d548 EB |
747 | |
748 | /** | |
d2fe9754 EB |
749 | * fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay |
750 | * @inode: an inode being freed | |
2c58d548 EB |
751 | * |
752 | * Free the inode's cached decrypted symlink target, if any. Filesystems must | |
753 | * call this after an RCU grace period, just before they free the inode. | |
754 | */ | |
755 | void fscrypt_free_inode(struct inode *inode) | |
756 | { | |
757 | if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) { | |
758 | kfree(inode->i_link); | |
759 | inode->i_link = NULL; | |
760 | } | |
761 | } | |
762 | EXPORT_SYMBOL(fscrypt_free_inode); | |
b1c0ec35 EB |
763 | |
764 | /** | |
d2fe9754 EB |
765 | * fscrypt_drop_inode() - check whether the inode's master key has been removed |
766 | * @inode: an inode being considered for eviction | |
b1c0ec35 EB |
767 | * |
768 | * Filesystems supporting fscrypt must call this from their ->drop_inode() | |
769 | * method so that encrypted inodes are evicted as soon as they're no longer in | |
770 | * use and their master key has been removed. | |
771 | * | |
772 | * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0 | |
773 | */ | |
774 | int fscrypt_drop_inode(struct inode *inode) | |
775 | { | |
ab673b98 | 776 | const struct fscrypt_info *ci = fscrypt_get_info(inode); |
b1c0ec35 EB |
777 | |
778 | /* | |
779 | * If ci is NULL, then the inode doesn't have an encryption key set up | |
780 | * so it's irrelevant. If ci_master_key is NULL, then the master key | |
781 | * was provided via the legacy mechanism of the process-subscribed | |
782 | * keyrings, so we don't know whether it's been removed or not. | |
783 | */ | |
784 | if (!ci || !ci->ci_master_key) | |
785 | return 0; | |
b1c0ec35 | 786 | |
2b4eae95 EB |
787 | /* |
788 | * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes | |
789 | * protected by the key were cleaned by sync_filesystem(). But if | |
790 | * userspace is still using the files, inodes can be dirtied between | |
791 | * then and now. We mustn't lose any writes, so skip dirty inodes here. | |
792 | */ | |
793 | if (inode->i_state & I_DIRTY_ALL) | |
794 | return 0; | |
795 | ||
b1c0ec35 | 796 | /* |
4a4b8721 | 797 | * Note: since we aren't holding the key semaphore, the result here can |
b1c0ec35 EB |
798 | * immediately become outdated. But there's no correctness problem with |
799 | * unnecessarily evicting. Nor is there a correctness problem with not | |
800 | * evicting while iput() is racing with the key being removed, since | |
801 | * then the thread removing the key will either evict the inode itself | |
802 | * or will correctly detect that it wasn't evicted due to the race. | |
803 | */ | |
d7e7b9af | 804 | return !is_master_key_secret_present(&ci->ci_master_key->mk_secret); |
b1c0ec35 EB |
805 | } |
806 | EXPORT_SYMBOL_GPL(fscrypt_drop_inode); |