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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] = { |
2f944c66 | 26 | .friendly_name = "AES-256-CBC-CTS", |
e1cc40e5 EB |
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] = { |
2f944c66 | 41 | .friendly_name = "AES-128-CBC-CTS", |
e1cc40e5 EB |
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] = { | |
2f944c66 | 56 | .friendly_name = "SM4-CBC-CTS", |
e0cefada TZ |
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, | |
3e7807d5 | 151 | const u8 *raw_key, const struct fscrypt_inode_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 | 180 | /* Given a per-file encryption key, set up the file's crypto transform object */ |
3e7807d5 JB |
181 | int fscrypt_set_per_file_enc_key(struct fscrypt_inode_info *ci, |
182 | const u8 *raw_key) | |
5fee3609 | 183 | { |
b103fb76 | 184 | ci->ci_owns_key = true; |
5fee3609 | 185 | return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci); |
8094c3ce EB |
186 | } |
187 | ||
3e7807d5 | 188 | static int setup_per_mode_enc_key(struct fscrypt_inode_info *ci, |
f592efe7 | 189 | struct fscrypt_master_key *mk, |
5fee3609 | 190 | struct fscrypt_prepared_key *keys, |
f592efe7 | 191 | u8 hkdf_context, bool include_fs_uuid) |
5dae460c | 192 | { |
b103fb76 EB |
193 | const struct inode *inode = ci->ci_inode; |
194 | const struct super_block *sb = inode->i_sb; | |
5dae460c | 195 | struct fscrypt_mode *mode = ci->ci_mode; |
85af90e5 | 196 | const u8 mode_num = mode - fscrypt_modes; |
5fee3609 | 197 | struct fscrypt_prepared_key *prep_key; |
5dae460c | 198 | u8 mode_key[FSCRYPT_MAX_KEY_SIZE]; |
b103fb76 EB |
199 | u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)]; |
200 | unsigned int hkdf_infolen = 0; | |
5dae460c EB |
201 | int err; |
202 | ||
41b2ad80 | 203 | if (WARN_ON_ONCE(mode_num > FSCRYPT_MODE_MAX)) |
5dae460c EB |
204 | return -EINVAL; |
205 | ||
5fee3609 ST |
206 | prep_key = &keys[mode_num]; |
207 | if (fscrypt_is_key_prepared(prep_key, ci)) { | |
208 | ci->ci_enc_key = *prep_key; | |
e3b1078b EB |
209 | return 0; |
210 | } | |
211 | ||
212 | mutex_lock(&fscrypt_mode_key_setup_mutex); | |
213 | ||
5fee3609 | 214 | if (fscrypt_is_key_prepared(prep_key, ci)) |
e3b1078b | 215 | goto done_unlock; |
5dae460c EB |
216 | |
217 | BUILD_BUG_ON(sizeof(mode_num) != 1); | |
b103fb76 EB |
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 | } | |
5dae460c | 226 | err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, |
b103fb76 | 227 | hkdf_context, hkdf_info, hkdf_infolen, |
5dae460c EB |
228 | mode_key, mode->keysize); |
229 | if (err) | |
e3b1078b | 230 | goto out_unlock; |
5fee3609 | 231 | err = fscrypt_prepare_key(prep_key, mode_key, ci); |
5dae460c | 232 | memzero_explicit(mode_key, mode->keysize); |
5fee3609 | 233 | if (err) |
e3b1078b | 234 | goto out_unlock; |
e3b1078b | 235 | done_unlock: |
5fee3609 | 236 | ci->ci_enc_key = *prep_key; |
e3b1078b EB |
237 | err = 0; |
238 | out_unlock: | |
239 | mutex_unlock(&fscrypt_mode_key_setup_mutex); | |
240 | return err; | |
5dae460c EB |
241 | } |
242 | ||
2fc2b430 EB |
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(&mk->mk_secret.hkdf, context, info, infolen, | |
258 | (u8 *)key, 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 | ||
3e7807d5 | 269 | int fscrypt_derive_dirhash_key(struct fscrypt_inode_info *ci, |
aa408f83 DR |
270 | const struct fscrypt_master_key *mk) |
271 | { | |
272 | int err; | |
273 | ||
2fc2b430 EB |
274 | err = fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY, |
275 | ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, | |
276 | &ci->ci_dirhash_key); | |
aa408f83 DR |
277 | if (err) |
278 | return err; | |
279 | ci->ci_dirhash_key_initialized = true; | |
280 | return 0; | |
281 | } | |
282 | ||
3e7807d5 | 283 | void fscrypt_hash_inode_number(struct fscrypt_inode_info *ci, |
a992b20c EB |
284 | const struct fscrypt_master_key *mk) |
285 | { | |
41b2ad80 EB |
286 | WARN_ON_ONCE(ci->ci_inode->i_ino == 0); |
287 | WARN_ON_ONCE(!mk->mk_ino_hash_key_initialized); | |
a992b20c EB |
288 | |
289 | ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino, | |
290 | &mk->mk_ino_hash_key); | |
291 | } | |
292 | ||
3e7807d5 | 293 | static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_inode_info *ci, |
e3b1078b EB |
294 | struct fscrypt_master_key *mk) |
295 | { | |
296 | int err; | |
297 | ||
298 | err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys, | |
299 | HKDF_CONTEXT_IV_INO_LBLK_32_KEY, 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 | ||
2fc2b430 EB |
311 | err = fscrypt_derive_siphash_key(mk, |
312 | HKDF_CONTEXT_INODE_HASH_KEY, | |
313 | NULL, 0, &mk->mk_ino_hash_key); | |
e3b1078b EB |
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(&fscrypt_mode_key_setup_mutex); | |
320 | if (err) | |
321 | return err; | |
322 | } | |
323 | ||
a992b20c EB |
324 | /* |
325 | * New inodes may not have an inode number assigned yet. | |
326 | * Hashing their inode number is delayed until later. | |
327 | */ | |
92cfcd03 | 328 | if (ci->ci_inode->i_ino) |
a992b20c | 329 | fscrypt_hash_inode_number(ci, mk); |
e3b1078b EB |
330 | return 0; |
331 | } | |
332 | ||
3e7807d5 | 333 | static int fscrypt_setup_v2_file_key(struct fscrypt_inode_info *ci, |
a992b20c EB |
334 | struct fscrypt_master_key *mk, |
335 | bool need_dirhash_key) | |
5dae460c | 336 | { |
5dae460c EB |
337 | int err; |
338 | ||
339 | if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { | |
340 | /* | |
f592efe7 EB |
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. | |
5dae460c | 347 | */ |
e3b1078b | 348 | err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys, |
f592efe7 | 349 | HKDF_CONTEXT_DIRECT_KEY, false); |
b103fb76 EB |
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 | |
e3b1078b | 356 | * encryption hardware compliant with the UFS standard. |
b103fb76 | 357 | */ |
e3b1078b | 358 | err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys, |
f592efe7 EB |
359 | HKDF_CONTEXT_IV_INO_LBLK_64_KEY, |
360 | true); | |
e3b1078b EB |
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); | |
aa408f83 DR |
364 | } else { |
365 | u8 derived_key[FSCRYPT_MAX_KEY_SIZE]; | |
5dae460c | 366 | |
aa408f83 | 367 | err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, |
f592efe7 | 368 | HKDF_CONTEXT_PER_FILE_ENC_KEY, |
1d6217a4 | 369 | ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, |
aa408f83 DR |
370 | derived_key, ci->ci_mode->keysize); |
371 | if (err) | |
372 | return err; | |
373 | ||
f592efe7 | 374 | err = fscrypt_set_per_file_enc_key(ci, derived_key); |
aa408f83 DR |
375 | memzero_explicit(derived_key, ci->ci_mode->keysize); |
376 | } | |
5dae460c EB |
377 | if (err) |
378 | return err; | |
379 | ||
aa408f83 | 380 | /* Derive a secret dirhash key for directories that need it. */ |
a992b20c | 381 | if (need_dirhash_key) { |
aa408f83 DR |
382 | err = fscrypt_derive_dirhash_key(ci, mk); |
383 | if (err) | |
384 | return err; | |
385 | } | |
386 | ||
387 | return 0; | |
5dae460c EB |
388 | } |
389 | ||
7f595d6a EB |
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, | |
3e7807d5 | 408 | const struct fscrypt_inode_info *ci) |
7f595d6a EB |
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 | ||
3ec4f2a6 EB |
429 | /* |
430 | * Find the master key, then set up the inode's actual encryption key. | |
b1c0ec35 | 431 | * |
d7e7b9af EB |
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 | |
3e7807d5 JB |
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. | |
3ec4f2a6 | 438 | */ |
3e7807d5 | 439 | static int setup_file_encryption_key(struct fscrypt_inode_info *ci, |
a992b20c | 440 | bool need_dirhash_key, |
d7e7b9af | 441 | struct fscrypt_master_key **mk_ret) |
3ec4f2a6 | 442 | { |
60e463f0 | 443 | struct super_block *sb = ci->ci_inode->i_sb; |
22d94f49 | 444 | struct fscrypt_key_specifier mk_spec; |
d7e7b9af | 445 | struct fscrypt_master_key *mk; |
22d94f49 EB |
446 | int err; |
447 | ||
5fee3609 ST |
448 | err = fscrypt_select_encryption_impl(ci); |
449 | if (err) | |
450 | return err; | |
451 | ||
bfb9700b EB |
452 | err = fscrypt_policy_to_key_spec(&ci->ci_policy, &mk_spec); |
453 | if (err) | |
454 | return err; | |
22d94f49 | 455 | |
60e463f0 EB |
456 | mk = fscrypt_find_master_key(sb, &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(dummy_policy, &ci->ci_policy)) { | |
097d7c1f | 469 | err = fscrypt_add_test_dummy_key(sb, &mk_spec); |
60e463f0 EB |
470 | if (err) |
471 | return err; | |
472 | mk = fscrypt_find_master_key(sb, &mk_spec); | |
473 | } | |
474 | } | |
475 | if (unlikely(!mk)) { | |
d7e7b9af EB |
476 | if (ci->ci_policy.version != FSCRYPT_POLICY_V1) |
477 | return -ENOKEY; | |
22d94f49 | 478 | |
5dae460c EB |
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 | */ | |
22d94f49 EB |
485 | return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); |
486 | } | |
d7e7b9af | 487 | down_read(&mk->mk_sem); |
b1c0ec35 | 488 | |
15baf554 EB |
489 | if (!mk->mk_present) { |
490 | /* FS_IOC_REMOVE_ENCRYPTION_KEY has been executed on this key */ | |
b1c0ec35 EB |
491 | err = -ENOKEY; |
492 | goto out_release_key; | |
493 | } | |
22d94f49 | 494 | |
7f595d6a | 495 | if (!fscrypt_valid_master_key_size(mk, ci)) { |
22d94f49 EB |
496 | err = -ENOKEY; |
497 | goto out_release_key; | |
498 | } | |
499 | ||
5dae460c EB |
500 | switch (ci->ci_policy.version) { |
501 | case FSCRYPT_POLICY_V1: | |
502 | err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw); | |
503 | break; | |
504 | case FSCRYPT_POLICY_V2: | |
a992b20c | 505 | err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key); |
5dae460c EB |
506 | break; |
507 | default: | |
41b2ad80 | 508 | WARN_ON_ONCE(1); |
5dae460c EB |
509 | err = -EINVAL; |
510 | break; | |
511 | } | |
b1c0ec35 EB |
512 | if (err) |
513 | goto out_release_key; | |
514 | ||
d7e7b9af | 515 | *mk_ret = mk; |
b1c0ec35 | 516 | return 0; |
22d94f49 EB |
517 | |
518 | out_release_key: | |
d7e7b9af EB |
519 | up_read(&mk->mk_sem); |
520 | fscrypt_put_master_key(mk); | |
22d94f49 | 521 | return err; |
3ec4f2a6 EB |
522 | } |
523 | ||
3e7807d5 | 524 | static void put_crypt_info(struct fscrypt_inode_info *ci) |
8094c3ce | 525 | { |
d7e7b9af | 526 | struct fscrypt_master_key *mk; |
b1c0ec35 | 527 | |
8094c3ce EB |
528 | if (!ci) |
529 | return; | |
530 | ||
4006d799 | 531 | if (ci->ci_direct_key) |
0109ce76 | 532 | fscrypt_put_direct_key(ci->ci_direct_key); |
b103fb76 | 533 | else if (ci->ci_owns_key) |
22e9947a EB |
534 | fscrypt_destroy_prepared_key(ci->ci_inode->i_sb, |
535 | &ci->ci_enc_key); | |
b1c0ec35 | 536 | |
d7e7b9af EB |
537 | mk = ci->ci_master_key; |
538 | if (mk) { | |
b1c0ec35 EB |
539 | /* |
540 | * Remove this inode from the list of inodes that were unlocked | |
d7e7b9af | 541 | * with the master key. In addition, if we're removing the last |
15baf554 EB |
542 | * inode from an incompletely removed key, then complete the |
543 | * full removal of the key. | |
b1c0ec35 EB |
544 | */ |
545 | spin_lock(&mk->mk_decrypted_inodes_lock); | |
546 | list_del(&ci->ci_master_key_link); | |
547 | spin_unlock(&mk->mk_decrypted_inodes_lock); | |
02aef422 | 548 | fscrypt_put_master_key_activeref(ci->ci_inode->i_sb, mk); |
b1c0ec35 | 549 | } |
6f99756d | 550 | memzero_explicit(ci, sizeof(*ci)); |
3e7807d5 | 551 | kmem_cache_free(fscrypt_inode_info_cachep, ci); |
8094c3ce EB |
552 | } |
553 | ||
a992b20c EB |
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) | |
0adda907 | 559 | { |
3e7807d5 | 560 | struct fscrypt_inode_info *crypt_info; |
e1cc40e5 | 561 | struct fscrypt_mode *mode; |
d7e7b9af | 562 | struct fscrypt_master_key *mk = NULL; |
0adda907 JK |
563 | int res; |
564 | ||
83e57e47 | 565 | res = fscrypt_initialize(inode->i_sb); |
cfc4d971 JK |
566 | if (res) |
567 | return res; | |
0b81d077 | 568 | |
3e7807d5 | 569 | crypt_info = kmem_cache_zalloc(fscrypt_inode_info_cachep, GFP_KERNEL); |
0adda907 JK |
570 | if (!crypt_info) |
571 | return -ENOMEM; | |
572 | ||
59dc6a8e | 573 | crypt_info->ci_inode = inode; |
a992b20c EB |
574 | crypt_info->ci_policy = *policy; |
575 | memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE); | |
640778fb | 576 | |
5dae460c | 577 | mode = select_encryption_mode(&crypt_info->ci_policy, inode); |
e1cc40e5 EB |
578 | if (IS_ERR(mode)) { |
579 | res = PTR_ERR(mode); | |
26bf3dc7 | 580 | goto out; |
e1cc40e5 | 581 | } |
41b2ad80 | 582 | WARN_ON_ONCE(mode->ivsize > FSCRYPT_MAX_IV_SIZE); |
8094c3ce | 583 | crypt_info->ci_mode = mode; |
8f39850d | 584 | |
5b118884 EB |
585 | crypt_info->ci_data_unit_bits = |
586 | fscrypt_policy_du_bits(&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 | ||
d7e7b9af | 590 | res = setup_file_encryption_key(crypt_info, need_dirhash_key, &mk); |
26bf3dc7 JK |
591 | if (res) |
592 | goto out; | |
593 | ||
ab673b98 | 594 | /* |
a992b20c EB |
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 | |
3e7807d5 JB |
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. | |
ab673b98 | 599 | */ |
b1c0ec35 | 600 | if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) { |
ab673b98 EB |
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 | */ | |
d7e7b9af EB |
605 | if (mk) { |
606 | crypt_info->ci_master_key = mk; | |
607 | refcount_inc(&mk->mk_active_refs); | |
b1c0ec35 EB |
608 | spin_lock(&mk->mk_decrypted_inodes_lock); |
609 | list_add(&crypt_info->ci_master_key_link, | |
610 | &mk->mk_decrypted_inodes); | |
611 | spin_unlock(&mk->mk_decrypted_inodes_lock); | |
612 | } | |
1b53cf98 | 613 | crypt_info = NULL; |
b1c0ec35 EB |
614 | } |
615 | res = 0; | |
26bf3dc7 | 616 | out: |
d7e7b9af EB |
617 | if (mk) { |
618 | up_read(&mk->mk_sem); | |
619 | fscrypt_put_master_key(mk); | |
b1c0ec35 | 620 | } |
a992b20c EB |
621 | put_crypt_info(crypt_info); |
622 | return res; | |
623 | } | |
624 | ||
625 | /** | |
626 | * fscrypt_get_encryption_info() - set up an inode's encryption key | |
ac4acb1f | 627 | * @inode: the inode to set up the key for. Must be encrypted. |
a14d0b67 EB |
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. | |
a992b20c EB |
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 | */ | |
a14d0b67 | 643 | int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported) |
a992b20c EB |
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) { | |
a14d0b67 EB |
654 | if (res == -ERANGE && allow_unsupported) |
655 | return 0; | |
ac4acb1f EB |
656 | fscrypt_warn(inode, "Error %d getting encryption context", res); |
657 | return res; | |
a992b20c EB |
658 | } |
659 | ||
660 | res = fscrypt_policy_from_context(&policy, &ctx, res); | |
661 | if (res) { | |
a14d0b67 EB |
662 | if (allow_unsupported) |
663 | return 0; | |
a992b20c EB |
664 | fscrypt_warn(inode, |
665 | "Unrecognized or corrupt encryption context"); | |
666 | return res; | |
667 | } | |
668 | ||
a14d0b67 EB |
669 | if (!fscrypt_supported_policy(&policy, inode)) { |
670 | if (allow_unsupported) | |
671 | return 0; | |
a992b20c | 672 | return -EINVAL; |
a14d0b67 | 673 | } |
a992b20c EB |
674 | |
675 | res = fscrypt_setup_encryption_info(inode, &policy, | |
676 | fscrypt_context_nonce(&ctx), | |
677 | IS_CASEFOLDED(inode) && | |
678 | S_ISDIR(inode->i_mode)); | |
a14d0b67 EB |
679 | |
680 | if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */ | |
681 | res = 0; | |
0b81d077 | 682 | if (res == -ENOKEY) |
26bf3dc7 | 683 | res = 0; |
0adda907 JK |
684 | return res; |
685 | } | |
686 | ||
a992b20c EB |
687 | /** |
688 | * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory | |
689 | * @dir: a possibly-encrypted directory | |
5befc19c | 690 | * @inode: the new inode. ->i_mode and ->i_blkbits must be set already. |
a992b20c EB |
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 | { | |
ac4acb1f | 711 | const union fscrypt_policy *policy; |
a992b20c EB |
712 | u8 nonce[FSCRYPT_FILE_NONCE_SIZE]; |
713 | ||
ac4acb1f EB |
714 | policy = fscrypt_policy_to_inherit(dir); |
715 | if (policy == NULL) | |
a992b20c | 716 | return 0; |
ac4acb1f EB |
717 | if (IS_ERR(policy)) |
718 | return PTR_ERR(policy); | |
a992b20c | 719 | |
5befc19c XL |
720 | if (WARN_ON_ONCE(inode->i_blkbits == 0)) |
721 | return -EINVAL; | |
722 | ||
a992b20c EB |
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(nonce, FSCRYPT_FILE_NONCE_SIZE); | |
ac4acb1f | 738 | return fscrypt_setup_encryption_info(inode, policy, nonce, |
a992b20c EB |
739 | IS_CASEFOLDED(dir) && |
740 | S_ISDIR(inode->i_mode)); | |
741 | } | |
742 | EXPORT_SYMBOL_GPL(fscrypt_prepare_new_inode); | |
743 | ||
2c58d548 | 744 | /** |
d2fe9754 EB |
745 | * fscrypt_put_encryption_info() - free most of an inode's fscrypt data |
746 | * @inode: an inode being evicted | |
2c58d548 | 747 | * |
3e7807d5 JB |
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. | |
2c58d548 | 750 | */ |
3d204e24 | 751 | void fscrypt_put_encryption_info(struct inode *inode) |
0adda907 | 752 | { |
3d204e24 EB |
753 | put_crypt_info(inode->i_crypt_info); |
754 | inode->i_crypt_info = NULL; | |
0b81d077 JK |
755 | } |
756 | EXPORT_SYMBOL(fscrypt_put_encryption_info); | |
2c58d548 EB |
757 | |
758 | /** | |
d2fe9754 EB |
759 | * fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay |
760 | * @inode: an inode being freed | |
2c58d548 EB |
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(inode->i_link); | |
769 | inode->i_link = NULL; | |
770 | } | |
771 | } | |
772 | EXPORT_SYMBOL(fscrypt_free_inode); | |
b1c0ec35 EB |
773 | |
774 | /** | |
d2fe9754 EB |
775 | * fscrypt_drop_inode() - check whether the inode's master key has been removed |
776 | * @inode: an inode being considered for eviction | |
b1c0ec35 EB |
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 | { | |
3e7807d5 | 786 | const struct fscrypt_inode_info *ci = fscrypt_get_inode_info(inode); |
b1c0ec35 EB |
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; | |
b1c0ec35 | 796 | |
2b4eae95 EB |
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 | ||
b1c0ec35 | 806 | /* |
15baf554 EB |
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 | |
b1c0ec35 EB |
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 | */ | |
15baf554 | 815 | return !READ_ONCE(ci->ci_master_key->mk_present); |
b1c0ec35 EB |
816 | } |
817 | EXPORT_SYMBOL_GPL(fscrypt_drop_inode); |