1 /* SPDX-License-Identifier: GPL-2.0 */
5 * Copyright (C) 2015, Google, Inc.
7 * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
8 * Heavily modified since then.
11 #ifndef _FSCRYPT_PRIVATE_H
12 #define _FSCRYPT_PRIVATE_H
14 #include <linux/fscrypt.h>
15 #include <linux/siphash.h>
16 #include <crypto/hash.h>
17 #include <linux/blk-crypto.h>
19 #define CONST_STRLEN(str) (sizeof(str) - 1)
21 #define FSCRYPT_FILE_NONCE_SIZE 16
24 * Minimum size of an fscrypt master key. Note: a longer key will be required
25 * if ciphers with a 256-bit security strength are used. This is just the
26 * absolute minimum, which applies when only 128-bit encryption is used.
28 #define FSCRYPT_MIN_KEY_SIZE 16
30 #define FSCRYPT_CONTEXT_V1 1
31 #define FSCRYPT_CONTEXT_V2 2
33 /* Keep this in sync with include/uapi/linux/fscrypt.h */
34 #define FSCRYPT_MODE_MAX FSCRYPT_MODE_AES_256_HCTR2
36 struct fscrypt_context_v1 {
37 u8 version; /* FSCRYPT_CONTEXT_V1 */
38 u8 contents_encryption_mode;
39 u8 filenames_encryption_mode;
41 u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
42 u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
45 struct fscrypt_context_v2 {
46 u8 version; /* FSCRYPT_CONTEXT_V2 */
47 u8 contents_encryption_mode;
48 u8 filenames_encryption_mode;
51 u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
52 u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
56 * fscrypt_context - the encryption context of an inode
58 * This is the on-disk equivalent of an fscrypt_policy, stored alongside each
59 * encrypted file usually in a hidden extended attribute. It contains the
60 * fields from the fscrypt_policy, in order to identify the encryption algorithm
61 * and key with which the file is encrypted. It also contains a nonce that was
62 * randomly generated by fscrypt itself; this is used as KDF input or as a tweak
63 * to cause different files to be encrypted differently.
65 union fscrypt_context {
67 struct fscrypt_context_v1 v1;
68 struct fscrypt_context_v2 v2;
72 * Return the size expected for the given fscrypt_context based on its version
73 * number, or 0 if the context version is unrecognized.
75 static inline int fscrypt_context_size(const union fscrypt_context *ctx)
77 switch (ctx->version) {
78 case FSCRYPT_CONTEXT_V1:
79 BUILD_BUG_ON(sizeof(ctx->v1) != 28);
80 return sizeof(ctx->v1);
81 case FSCRYPT_CONTEXT_V2:
82 BUILD_BUG_ON(sizeof(ctx->v2) != 40);
83 return sizeof(ctx->v2);
88 /* Check whether an fscrypt_context has a recognized version number and size */
89 static inline bool fscrypt_context_is_valid(const union fscrypt_context *ctx,
92 return ctx_size >= 1 && ctx_size == fscrypt_context_size(ctx);
95 /* Retrieve the context's nonce, assuming the context was already validated */
96 static inline const u8 *fscrypt_context_nonce(const union fscrypt_context *ctx)
98 switch (ctx->version) {
99 case FSCRYPT_CONTEXT_V1:
100 return ctx->v1.nonce;
101 case FSCRYPT_CONTEXT_V2:
102 return ctx->v2.nonce;
108 union fscrypt_policy {
110 struct fscrypt_policy_v1 v1;
111 struct fscrypt_policy_v2 v2;
115 * Return the size expected for the given fscrypt_policy based on its version
116 * number, or 0 if the policy version is unrecognized.
118 static inline int fscrypt_policy_size(const union fscrypt_policy *policy)
120 switch (policy->version) {
121 case FSCRYPT_POLICY_V1:
122 return sizeof(policy->v1);
123 case FSCRYPT_POLICY_V2:
124 return sizeof(policy->v2);
129 /* Return the contents encryption mode of a valid encryption policy */
131 fscrypt_policy_contents_mode(const union fscrypt_policy *policy)
133 switch (policy->version) {
134 case FSCRYPT_POLICY_V1:
135 return policy->v1.contents_encryption_mode;
136 case FSCRYPT_POLICY_V2:
137 return policy->v2.contents_encryption_mode;
142 /* Return the filenames encryption mode of a valid encryption policy */
144 fscrypt_policy_fnames_mode(const union fscrypt_policy *policy)
146 switch (policy->version) {
147 case FSCRYPT_POLICY_V1:
148 return policy->v1.filenames_encryption_mode;
149 case FSCRYPT_POLICY_V2:
150 return policy->v2.filenames_encryption_mode;
155 /* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */
157 fscrypt_policy_flags(const union fscrypt_policy *policy)
159 switch (policy->version) {
160 case FSCRYPT_POLICY_V1:
161 return policy->v1.flags;
162 case FSCRYPT_POLICY_V2:
163 return policy->v2.flags;
169 * For encrypted symlinks, the ciphertext length is stored at the beginning
170 * of the string in little-endian format.
172 struct fscrypt_symlink_data {
174 char encrypted_path[1];
178 * struct fscrypt_prepared_key - a key prepared for actual encryption/decryption
179 * @tfm: crypto API transform object
180 * @blk_key: key for blk-crypto
182 * Normally only one of the fields will be non-NULL.
184 struct fscrypt_prepared_key {
185 struct crypto_skcipher *tfm;
186 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
187 struct fscrypt_blk_crypto_key *blk_key;
192 * fscrypt_info - the "encryption key" for an inode
194 * When an encrypted file's key is made available, an instance of this struct is
195 * allocated and stored in ->i_crypt_info. Once created, it remains until the
198 struct fscrypt_info {
200 /* The key in a form prepared for actual encryption/decryption */
201 struct fscrypt_prepared_key ci_enc_key;
203 /* True if ci_enc_key should be freed when this fscrypt_info is freed */
206 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
208 * True if this inode will use inline encryption (blk-crypto) instead of
209 * the traditional filesystem-layer encryption.
215 * Encryption mode used for this inode. It corresponds to either the
216 * contents or filenames encryption mode, depending on the inode type.
218 struct fscrypt_mode *ci_mode;
220 /* Back-pointer to the inode */
221 struct inode *ci_inode;
224 * The master key with which this inode was unlocked (decrypted). This
225 * will be NULL if the master key was found in a process-subscribed
226 * keyring rather than in the filesystem-level keyring.
228 struct key *ci_master_key;
231 * Link in list of inodes that were unlocked with the master key.
232 * Only used when ->ci_master_key is set.
234 struct list_head ci_master_key_link;
237 * If non-NULL, then encryption is done using the master key directly
238 * and ci_enc_key will equal ci_direct_key->dk_key.
240 struct fscrypt_direct_key *ci_direct_key;
243 * This inode's hash key for filenames. This is a 128-bit SipHash-2-4
244 * key. This is only set for directories that use a keyed dirhash over
245 * the plaintext filenames -- currently just casefolded directories.
247 siphash_key_t ci_dirhash_key;
248 bool ci_dirhash_key_initialized;
250 /* The encryption policy used by this inode */
251 union fscrypt_policy ci_policy;
253 /* This inode's nonce, copied from the fscrypt_context */
254 u8 ci_nonce[FSCRYPT_FILE_NONCE_SIZE];
256 /* Hashed inode number. Only set for IV_INO_LBLK_32 */
263 } fscrypt_direction_t;
266 extern struct kmem_cache *fscrypt_info_cachep;
267 int fscrypt_initialize(unsigned int cop_flags);
268 int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
269 u64 lblk_num, struct page *src_page,
270 struct page *dest_page, unsigned int len,
271 unsigned int offs, gfp_t gfp_flags);
272 struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags);
274 void __printf(3, 4) __cold
275 fscrypt_msg(const struct inode *inode, const char *level, const char *fmt, ...);
277 #define fscrypt_warn(inode, fmt, ...) \
278 fscrypt_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
279 #define fscrypt_err(inode, fmt, ...) \
280 fscrypt_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
282 #define FSCRYPT_MAX_IV_SIZE 32
286 /* logical block number within the file */
289 /* per-file nonce; only set in DIRECT_KEY mode */
290 u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
292 u8 raw[FSCRYPT_MAX_IV_SIZE];
293 __le64 dun[FSCRYPT_MAX_IV_SIZE / sizeof(__le64)];
296 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
297 const struct fscrypt_info *ci);
300 bool __fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
301 u32 orig_len, u32 max_len,
302 u32 *encrypted_len_ret);
305 struct fscrypt_hkdf {
306 struct crypto_shash *hmac_tfm;
309 int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
310 unsigned int master_key_size);
313 * The list of contexts in which fscrypt uses HKDF. These values are used as
314 * the first byte of the HKDF application-specific info string to guarantee that
315 * info strings are never repeated between contexts. This ensures that all HKDF
316 * outputs are unique and cryptographically isolated, i.e. knowledge of one
317 * output doesn't reveal another.
319 #define HKDF_CONTEXT_KEY_IDENTIFIER 1 /* info=<empty> */
320 #define HKDF_CONTEXT_PER_FILE_ENC_KEY 2 /* info=file_nonce */
321 #define HKDF_CONTEXT_DIRECT_KEY 3 /* info=mode_num */
322 #define HKDF_CONTEXT_IV_INO_LBLK_64_KEY 4 /* info=mode_num||fs_uuid */
323 #define HKDF_CONTEXT_DIRHASH_KEY 5 /* info=file_nonce */
324 #define HKDF_CONTEXT_IV_INO_LBLK_32_KEY 6 /* info=mode_num||fs_uuid */
325 #define HKDF_CONTEXT_INODE_HASH_KEY 7 /* info=<empty> */
327 int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
328 const u8 *info, unsigned int infolen,
329 u8 *okm, unsigned int okmlen);
331 void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf);
334 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
335 int fscrypt_select_encryption_impl(struct fscrypt_info *ci);
338 fscrypt_using_inline_encryption(const struct fscrypt_info *ci)
340 return ci->ci_inlinecrypt;
343 int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
345 const struct fscrypt_info *ci);
347 void fscrypt_destroy_inline_crypt_key(struct fscrypt_prepared_key *prep_key);
350 * Check whether the crypto transform or blk-crypto key has been allocated in
351 * @prep_key, depending on which encryption implementation the file will use.
354 fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
355 const struct fscrypt_info *ci)
358 * The two smp_load_acquire()'s here pair with the smp_store_release()'s
359 * in fscrypt_prepare_inline_crypt_key() and fscrypt_prepare_key().
360 * I.e., in some cases (namely, if this prep_key is a per-mode
361 * encryption key) another task can publish blk_key or tfm concurrently,
362 * executing a RELEASE barrier. We need to use smp_load_acquire() here
363 * to safely ACQUIRE the memory the other task published.
365 if (fscrypt_using_inline_encryption(ci))
366 return smp_load_acquire(&prep_key->blk_key) != NULL;
367 return smp_load_acquire(&prep_key->tfm) != NULL;
370 #else /* CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
372 static inline int fscrypt_select_encryption_impl(struct fscrypt_info *ci)
378 fscrypt_using_inline_encryption(const struct fscrypt_info *ci)
384 fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
386 const struct fscrypt_info *ci)
393 fscrypt_destroy_inline_crypt_key(struct fscrypt_prepared_key *prep_key)
398 fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
399 const struct fscrypt_info *ci)
401 return smp_load_acquire(&prep_key->tfm) != NULL;
403 #endif /* !CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
408 * fscrypt_master_key_secret - secret key material of an in-use master key
410 struct fscrypt_master_key_secret {
413 * For v2 policy keys: HKDF context keyed by this master key.
414 * For v1 policy keys: not set (hkdf.hmac_tfm == NULL).
416 struct fscrypt_hkdf hkdf;
419 * Size of the raw key in bytes. This remains set even if ->raw was
420 * zeroized due to no longer being needed. I.e. we still remember the
421 * size of the key even if we don't need to remember the key itself.
425 /* For v1 policy keys: the raw key. Wiped for v2 policy keys. */
426 u8 raw[FSCRYPT_MAX_KEY_SIZE];
428 } __randomize_layout;
431 * fscrypt_master_key - an in-use master key
433 * This represents a master encryption key which has been added to the
434 * filesystem and can be used to "unlock" the encrypted files which were
437 struct fscrypt_master_key {
440 * The secret key material. After FS_IOC_REMOVE_ENCRYPTION_KEY is
441 * executed, this is wiped and no new inodes can be unlocked with this
442 * key; however, there may still be inodes in ->mk_decrypted_inodes
443 * which could not be evicted. As long as some inodes still remain,
444 * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or
445 * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again.
447 * Locking: protected by this master key's key->sem.
449 struct fscrypt_master_key_secret mk_secret;
452 * For v1 policy keys: an arbitrary key descriptor which was assigned by
453 * userspace (->descriptor).
455 * For v2 policy keys: a cryptographic hash of this key (->identifier).
457 struct fscrypt_key_specifier mk_spec;
460 * Keyring which contains a key of type 'key_type_fscrypt_user' for each
461 * user who has added this key. Normally each key will be added by just
462 * one user, but it's possible that multiple users share a key, and in
463 * that case we need to keep track of those users so that one user can't
464 * remove the key before the others want it removed too.
466 * This is NULL for v1 policy keys; those can only be added by root.
468 * Locking: in addition to this keyring's own semaphore, this is
469 * protected by this master key's key->sem, so we can do atomic
470 * search+insert. It can also be searched without taking any locks, but
471 * in that case the returned key may have already been removed.
473 struct key *mk_users;
476 * Length of ->mk_decrypted_inodes, plus one if mk_secret is present.
477 * Once this goes to 0, the master key is removed from ->s_master_keys.
478 * The 'struct fscrypt_master_key' will continue to live as long as the
479 * 'struct key' whose payload it is, but we won't let this reference
482 refcount_t mk_refcount;
485 * List of inodes that were unlocked using this key. This allows the
486 * inodes to be evicted efficiently if the key is removed.
488 struct list_head mk_decrypted_inodes;
489 spinlock_t mk_decrypted_inodes_lock;
492 * Per-mode encryption keys for the various types of encryption policies
493 * that use them. Allocated and derived on-demand.
495 struct fscrypt_prepared_key mk_direct_keys[FSCRYPT_MODE_MAX + 1];
496 struct fscrypt_prepared_key mk_iv_ino_lblk_64_keys[FSCRYPT_MODE_MAX + 1];
497 struct fscrypt_prepared_key mk_iv_ino_lblk_32_keys[FSCRYPT_MODE_MAX + 1];
499 /* Hash key for inode numbers. Initialized only when needed. */
500 siphash_key_t mk_ino_hash_key;
501 bool mk_ino_hash_key_initialized;
503 } __randomize_layout;
506 is_master_key_secret_present(const struct fscrypt_master_key_secret *secret)
509 * The READ_ONCE() is only necessary for fscrypt_drop_inode() and
510 * fscrypt_key_describe(). These run in atomic context, so they can't
511 * take the key semaphore and thus 'secret' can change concurrently
512 * which would be a data race. But they only need to know whether the
513 * secret *was* present at the time of check, so READ_ONCE() suffices.
515 return READ_ONCE(secret->size) != 0;
518 static inline const char *master_key_spec_type(
519 const struct fscrypt_key_specifier *spec)
521 switch (spec->type) {
522 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
524 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
530 static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
532 switch (spec->type) {
533 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
534 return FSCRYPT_KEY_DESCRIPTOR_SIZE;
535 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
536 return FSCRYPT_KEY_IDENTIFIER_SIZE;
542 fscrypt_find_master_key(struct super_block *sb,
543 const struct fscrypt_key_specifier *mk_spec);
545 int fscrypt_get_test_dummy_key_identifier(
546 u8 key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
548 int fscrypt_verify_key_added(struct super_block *sb,
549 const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
551 int __init fscrypt_init_keyring(void);
555 struct fscrypt_mode {
556 const char *friendly_name;
557 const char *cipher_str;
558 int keysize; /* key size in bytes */
559 int security_strength; /* security strength in bytes */
560 int ivsize; /* IV size in bytes */
561 int logged_cryptoapi_impl;
562 int logged_blk_crypto_native;
563 int logged_blk_crypto_fallback;
564 enum blk_crypto_mode_num blk_crypto_mode;
567 extern struct fscrypt_mode fscrypt_modes[];
569 int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key,
570 const u8 *raw_key, const struct fscrypt_info *ci);
572 void fscrypt_destroy_prepared_key(struct fscrypt_prepared_key *prep_key);
574 int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key);
576 int fscrypt_derive_dirhash_key(struct fscrypt_info *ci,
577 const struct fscrypt_master_key *mk);
579 void fscrypt_hash_inode_number(struct fscrypt_info *ci,
580 const struct fscrypt_master_key *mk);
582 int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported);
585 * fscrypt_require_key() - require an inode's encryption key
586 * @inode: the inode we need the key for
588 * If the inode is encrypted, set up its encryption key if not already done.
589 * Then require that the key be present and return -ENOKEY otherwise.
591 * No locks are needed, and the key will live as long as the struct inode --- so
592 * it won't go away from under you.
594 * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
595 * if a problem occurred while setting up the encryption key.
597 static inline int fscrypt_require_key(struct inode *inode)
599 if (IS_ENCRYPTED(inode)) {
600 int err = fscrypt_get_encryption_info(inode, false);
604 if (!fscrypt_has_encryption_key(inode))
612 void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
614 int fscrypt_setup_v1_file_key(struct fscrypt_info *ci,
615 const u8 *raw_master_key);
617 int fscrypt_setup_v1_file_key_via_subscribed_keyrings(struct fscrypt_info *ci);
621 bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
622 const union fscrypt_policy *policy2);
623 int fscrypt_policy_to_key_spec(const union fscrypt_policy *policy,
624 struct fscrypt_key_specifier *key_spec);
625 bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
626 const struct inode *inode);
627 int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
628 const union fscrypt_context *ctx_u,
630 const union fscrypt_policy *fscrypt_policy_to_inherit(struct inode *dir);
632 #endif /* _FSCRYPT_PRIVATE_H */