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 FS_KEY_DERIVATION_NONCE_SIZE 16
23 #define FSCRYPT_MIN_KEY_SIZE 16
25 #define FSCRYPT_CONTEXT_V1 1
26 #define FSCRYPT_CONTEXT_V2 2
28 struct fscrypt_context_v1 {
29 u8 version; /* FSCRYPT_CONTEXT_V1 */
30 u8 contents_encryption_mode;
31 u8 filenames_encryption_mode;
33 u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
34 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
37 struct fscrypt_context_v2 {
38 u8 version; /* FSCRYPT_CONTEXT_V2 */
39 u8 contents_encryption_mode;
40 u8 filenames_encryption_mode;
43 u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
44 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
48 * fscrypt_context - the encryption context of an inode
50 * This is the on-disk equivalent of an fscrypt_policy, stored alongside each
51 * encrypted file usually in a hidden extended attribute. It contains the
52 * fields from the fscrypt_policy, in order to identify the encryption algorithm
53 * and key with which the file is encrypted. It also contains a nonce that was
54 * randomly generated by fscrypt itself; this is used as KDF input or as a tweak
55 * to cause different files to be encrypted differently.
57 union fscrypt_context {
59 struct fscrypt_context_v1 v1;
60 struct fscrypt_context_v2 v2;
64 * Return the size expected for the given fscrypt_context based on its version
65 * number, or 0 if the context version is unrecognized.
67 static inline int fscrypt_context_size(const union fscrypt_context *ctx)
69 switch (ctx->version) {
70 case FSCRYPT_CONTEXT_V1:
71 BUILD_BUG_ON(sizeof(ctx->v1) != 28);
72 return sizeof(ctx->v1);
73 case FSCRYPT_CONTEXT_V2:
74 BUILD_BUG_ON(sizeof(ctx->v2) != 40);
75 return sizeof(ctx->v2);
80 /* Check whether an fscrypt_context has a recognized version number and size */
81 static inline bool fscrypt_context_is_valid(const union fscrypt_context *ctx,
84 return ctx_size >= 1 && ctx_size == fscrypt_context_size(ctx);
87 /* Retrieve the context's nonce, assuming the context was already validated */
88 static inline const u8 *fscrypt_context_nonce(const union fscrypt_context *ctx)
90 switch (ctx->version) {
91 case FSCRYPT_CONTEXT_V1:
93 case FSCRYPT_CONTEXT_V2:
100 #undef fscrypt_policy
101 union fscrypt_policy {
103 struct fscrypt_policy_v1 v1;
104 struct fscrypt_policy_v2 v2;
108 * Return the size expected for the given fscrypt_policy based on its version
109 * number, or 0 if the policy version is unrecognized.
111 static inline int fscrypt_policy_size(const union fscrypt_policy *policy)
113 switch (policy->version) {
114 case FSCRYPT_POLICY_V1:
115 return sizeof(policy->v1);
116 case FSCRYPT_POLICY_V2:
117 return sizeof(policy->v2);
122 /* Return the contents encryption mode of a valid encryption policy */
124 fscrypt_policy_contents_mode(const union fscrypt_policy *policy)
126 switch (policy->version) {
127 case FSCRYPT_POLICY_V1:
128 return policy->v1.contents_encryption_mode;
129 case FSCRYPT_POLICY_V2:
130 return policy->v2.contents_encryption_mode;
135 /* Return the filenames encryption mode of a valid encryption policy */
137 fscrypt_policy_fnames_mode(const union fscrypt_policy *policy)
139 switch (policy->version) {
140 case FSCRYPT_POLICY_V1:
141 return policy->v1.filenames_encryption_mode;
142 case FSCRYPT_POLICY_V2:
143 return policy->v2.filenames_encryption_mode;
148 /* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */
150 fscrypt_policy_flags(const union fscrypt_policy *policy)
152 switch (policy->version) {
153 case FSCRYPT_POLICY_V1:
154 return policy->v1.flags;
155 case FSCRYPT_POLICY_V2:
156 return policy->v2.flags;
162 * For encrypted symlinks, the ciphertext length is stored at the beginning
163 * of the string in little-endian format.
165 struct fscrypt_symlink_data {
167 char encrypted_path[1];
171 * struct fscrypt_prepared_key - a key prepared for actual encryption/decryption
172 * @tfm: crypto API transform object
173 * @blk_key: key for blk-crypto
175 * Normally only one of the fields will be non-NULL.
177 struct fscrypt_prepared_key {
178 struct crypto_skcipher *tfm;
179 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
180 struct fscrypt_blk_crypto_key *blk_key;
185 * fscrypt_info - the "encryption key" for an inode
187 * When an encrypted file's key is made available, an instance of this struct is
188 * allocated and stored in ->i_crypt_info. Once created, it remains until the
191 struct fscrypt_info {
193 /* The key in a form prepared for actual encryption/decryption */
194 struct fscrypt_prepared_key ci_enc_key;
196 /* True if ci_enc_key should be freed when this fscrypt_info is freed */
199 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
201 * True if this inode will use inline encryption (blk-crypto) instead of
202 * the traditional filesystem-layer encryption.
208 * Encryption mode used for this inode. It corresponds to either the
209 * contents or filenames encryption mode, depending on the inode type.
211 struct fscrypt_mode *ci_mode;
213 /* Back-pointer to the inode */
214 struct inode *ci_inode;
217 * The master key with which this inode was unlocked (decrypted). This
218 * will be NULL if the master key was found in a process-subscribed
219 * keyring rather than in the filesystem-level keyring.
221 struct key *ci_master_key;
224 * Link in list of inodes that were unlocked with the master key.
225 * Only used when ->ci_master_key is set.
227 struct list_head ci_master_key_link;
230 * If non-NULL, then encryption is done using the master key directly
231 * and ci_enc_key will equal ci_direct_key->dk_key.
233 struct fscrypt_direct_key *ci_direct_key;
236 * This inode's hash key for filenames. This is a 128-bit SipHash-2-4
237 * key. This is only set for directories that use a keyed dirhash over
238 * the plaintext filenames -- currently just casefolded directories.
240 siphash_key_t ci_dirhash_key;
241 bool ci_dirhash_key_initialized;
243 /* The encryption policy used by this inode */
244 union fscrypt_policy ci_policy;
246 /* This inode's nonce, copied from the fscrypt_context */
247 u8 ci_nonce[FS_KEY_DERIVATION_NONCE_SIZE];
249 /* Hashed inode number. Only set for IV_INO_LBLK_32 */
256 } fscrypt_direction_t;
259 extern struct kmem_cache *fscrypt_info_cachep;
260 int fscrypt_initialize(unsigned int cop_flags);
261 int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
262 u64 lblk_num, struct page *src_page,
263 struct page *dest_page, unsigned int len,
264 unsigned int offs, gfp_t gfp_flags);
265 struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags);
267 void __printf(3, 4) __cold
268 fscrypt_msg(const struct inode *inode, const char *level, const char *fmt, ...);
270 #define fscrypt_warn(inode, fmt, ...) \
271 fscrypt_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
272 #define fscrypt_err(inode, fmt, ...) \
273 fscrypt_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
275 #define FSCRYPT_MAX_IV_SIZE 32
279 /* logical block number within the file */
282 /* per-file nonce; only set in DIRECT_KEY mode */
283 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
285 u8 raw[FSCRYPT_MAX_IV_SIZE];
286 __le64 dun[FSCRYPT_MAX_IV_SIZE / sizeof(__le64)];
289 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
290 const struct fscrypt_info *ci);
293 int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname,
294 u8 *out, unsigned int olen);
295 bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
296 u32 max_len, u32 *encrypted_len_ret);
297 extern const struct dentry_operations fscrypt_d_ops;
301 struct fscrypt_hkdf {
302 struct crypto_shash *hmac_tfm;
305 int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
306 unsigned int master_key_size);
309 * The list of contexts in which fscrypt uses HKDF. These values are used as
310 * the first byte of the HKDF application-specific info string to guarantee that
311 * info strings are never repeated between contexts. This ensures that all HKDF
312 * outputs are unique and cryptographically isolated, i.e. knowledge of one
313 * output doesn't reveal another.
315 #define HKDF_CONTEXT_KEY_IDENTIFIER 1 /* info=<empty> */
316 #define HKDF_CONTEXT_PER_FILE_ENC_KEY 2 /* info=file_nonce */
317 #define HKDF_CONTEXT_DIRECT_KEY 3 /* info=mode_num */
318 #define HKDF_CONTEXT_IV_INO_LBLK_64_KEY 4 /* info=mode_num||fs_uuid */
319 #define HKDF_CONTEXT_DIRHASH_KEY 5 /* info=file_nonce */
320 #define HKDF_CONTEXT_IV_INO_LBLK_32_KEY 6 /* info=mode_num||fs_uuid */
321 #define HKDF_CONTEXT_INODE_HASH_KEY 7 /* info=<empty> */
323 int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
324 const u8 *info, unsigned int infolen,
325 u8 *okm, unsigned int okmlen);
327 void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf);
330 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
331 int fscrypt_select_encryption_impl(struct fscrypt_info *ci);
334 fscrypt_using_inline_encryption(const struct fscrypt_info *ci)
336 return ci->ci_inlinecrypt;
339 int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
341 const struct fscrypt_info *ci);
343 void fscrypt_destroy_inline_crypt_key(struct fscrypt_prepared_key *prep_key);
346 * Check whether the crypto transform or blk-crypto key has been allocated in
347 * @prep_key, depending on which encryption implementation the file will use.
350 fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
351 const struct fscrypt_info *ci)
354 * The READ_ONCE() here pairs with the smp_store_release() in
355 * fscrypt_prepare_key(). (This only matters for the per-mode keys,
356 * which are shared by multiple inodes.)
358 if (fscrypt_using_inline_encryption(ci))
359 return READ_ONCE(prep_key->blk_key) != NULL;
360 return READ_ONCE(prep_key->tfm) != NULL;
363 #else /* CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
365 static inline int fscrypt_select_encryption_impl(struct fscrypt_info *ci)
371 fscrypt_using_inline_encryption(const struct fscrypt_info *ci)
377 fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
379 const struct fscrypt_info *ci)
386 fscrypt_destroy_inline_crypt_key(struct fscrypt_prepared_key *prep_key)
391 fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
392 const struct fscrypt_info *ci)
394 return READ_ONCE(prep_key->tfm) != NULL;
396 #endif /* !CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
401 * fscrypt_master_key_secret - secret key material of an in-use master key
403 struct fscrypt_master_key_secret {
406 * For v2 policy keys: HKDF context keyed by this master key.
407 * For v1 policy keys: not set (hkdf.hmac_tfm == NULL).
409 struct fscrypt_hkdf hkdf;
411 /* Size of the raw key in bytes. Set even if ->raw isn't set. */
414 /* For v1 policy keys: the raw key. Wiped for v2 policy keys. */
415 u8 raw[FSCRYPT_MAX_KEY_SIZE];
417 } __randomize_layout;
420 * fscrypt_master_key - an in-use master key
422 * This represents a master encryption key which has been added to the
423 * filesystem and can be used to "unlock" the encrypted files which were
426 struct fscrypt_master_key {
429 * The secret key material. After FS_IOC_REMOVE_ENCRYPTION_KEY is
430 * executed, this is wiped and no new inodes can be unlocked with this
431 * key; however, there may still be inodes in ->mk_decrypted_inodes
432 * which could not be evicted. As long as some inodes still remain,
433 * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or
434 * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again.
436 * Locking: protected by key->sem (outer) and mk_secret_sem (inner).
437 * The reason for two locks is that key->sem also protects modifying
438 * mk_users, which ranks it above the semaphore for the keyring key
439 * type, which is in turn above page faults (via keyring_read). But
440 * sometimes filesystems call fscrypt_get_encryption_info() from within
441 * a transaction, which ranks it below page faults. So we need a
442 * separate lock which protects mk_secret but not also mk_users.
444 struct fscrypt_master_key_secret mk_secret;
445 struct rw_semaphore mk_secret_sem;
448 * For v1 policy keys: an arbitrary key descriptor which was assigned by
449 * userspace (->descriptor).
451 * For v2 policy keys: a cryptographic hash of this key (->identifier).
453 struct fscrypt_key_specifier mk_spec;
456 * Keyring which contains a key of type 'key_type_fscrypt_user' for each
457 * user who has added this key. Normally each key will be added by just
458 * one user, but it's possible that multiple users share a key, and in
459 * that case we need to keep track of those users so that one user can't
460 * remove the key before the others want it removed too.
462 * This is NULL for v1 policy keys; those can only be added by root.
464 * Locking: in addition to this keyrings own semaphore, this is
465 * protected by the master key's key->sem, so we can do atomic
466 * search+insert. It can also be searched without taking any locks, but
467 * in that case the returned key may have already been removed.
469 struct key *mk_users;
472 * Length of ->mk_decrypted_inodes, plus one if mk_secret is present.
473 * Once this goes to 0, the master key is removed from ->s_master_keys.
474 * The 'struct fscrypt_master_key' will continue to live as long as the
475 * 'struct key' whose payload it is, but we won't let this reference
478 refcount_t mk_refcount;
481 * List of inodes that were unlocked using this key. This allows the
482 * inodes to be evicted efficiently if the key is removed.
484 struct list_head mk_decrypted_inodes;
485 spinlock_t mk_decrypted_inodes_lock;
488 * Per-mode encryption keys for the various types of encryption policies
489 * that use them. Allocated and derived on-demand.
491 struct fscrypt_prepared_key mk_direct_keys[__FSCRYPT_MODE_MAX + 1];
492 struct fscrypt_prepared_key mk_iv_ino_lblk_64_keys[__FSCRYPT_MODE_MAX + 1];
493 struct fscrypt_prepared_key mk_iv_ino_lblk_32_keys[__FSCRYPT_MODE_MAX + 1];
495 /* Hash key for inode numbers. Initialized only when needed. */
496 siphash_key_t mk_ino_hash_key;
497 bool mk_ino_hash_key_initialized;
499 } __randomize_layout;
502 is_master_key_secret_present(const struct fscrypt_master_key_secret *secret)
505 * The READ_ONCE() is only necessary for fscrypt_drop_inode() and
506 * fscrypt_key_describe(). These run in atomic context, so they can't
507 * take ->mk_secret_sem and thus 'secret' can change concurrently which
508 * would be a data race. But they only need to know whether the secret
509 * *was* present at the time of check, so READ_ONCE() suffices.
511 return READ_ONCE(secret->size) != 0;
514 static inline const char *master_key_spec_type(
515 const struct fscrypt_key_specifier *spec)
517 switch (spec->type) {
518 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
520 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
526 static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
528 switch (spec->type) {
529 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
530 return FSCRYPT_KEY_DESCRIPTOR_SIZE;
531 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
532 return FSCRYPT_KEY_IDENTIFIER_SIZE;
538 fscrypt_find_master_key(struct super_block *sb,
539 const struct fscrypt_key_specifier *mk_spec);
541 int fscrypt_add_test_dummy_key(struct super_block *sb,
542 struct fscrypt_key_specifier *key_spec);
544 int fscrypt_verify_key_added(struct super_block *sb,
545 const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
547 int __init fscrypt_init_keyring(void);
551 struct fscrypt_mode {
552 const char *friendly_name;
553 const char *cipher_str;
556 int logged_impl_name;
557 enum blk_crypto_mode_num blk_crypto_mode;
560 extern struct fscrypt_mode fscrypt_modes[];
562 int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key,
563 const u8 *raw_key, const struct fscrypt_info *ci);
565 void fscrypt_destroy_prepared_key(struct fscrypt_prepared_key *prep_key);
567 int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key);
569 int fscrypt_derive_dirhash_key(struct fscrypt_info *ci,
570 const struct fscrypt_master_key *mk);
574 void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
576 int fscrypt_setup_v1_file_key(struct fscrypt_info *ci,
577 const u8 *raw_master_key);
579 int fscrypt_setup_v1_file_key_via_subscribed_keyrings(struct fscrypt_info *ci);
583 bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
584 const union fscrypt_policy *policy2);
585 bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
586 const struct inode *inode);
587 int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
588 const union fscrypt_context *ctx_u,
591 #endif /* _FSCRYPT_PRIVATE_H */