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
23 #define FSCRYPT_MIN_KEY_SIZE 16
25 #define FSCRYPT_CONTEXT_V1 1
26 #define FSCRYPT_CONTEXT_V2 2
28 /* Keep this in sync with include/uapi/linux/fscrypt.h */
29 #define FSCRYPT_MODE_MAX FSCRYPT_MODE_ADIANTUM
31 struct fscrypt_context_v1 {
32 u8 version; /* FSCRYPT_CONTEXT_V1 */
33 u8 contents_encryption_mode;
34 u8 filenames_encryption_mode;
36 u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
37 u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
40 struct fscrypt_context_v2 {
41 u8 version; /* FSCRYPT_CONTEXT_V2 */
42 u8 contents_encryption_mode;
43 u8 filenames_encryption_mode;
46 u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
47 u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
51 * fscrypt_context - the encryption context of an inode
53 * This is the on-disk equivalent of an fscrypt_policy, stored alongside each
54 * encrypted file usually in a hidden extended attribute. It contains the
55 * fields from the fscrypt_policy, in order to identify the encryption algorithm
56 * and key with which the file is encrypted. It also contains a nonce that was
57 * randomly generated by fscrypt itself; this is used as KDF input or as a tweak
58 * to cause different files to be encrypted differently.
60 union fscrypt_context {
62 struct fscrypt_context_v1 v1;
63 struct fscrypt_context_v2 v2;
67 * Return the size expected for the given fscrypt_context based on its version
68 * number, or 0 if the context version is unrecognized.
70 static inline int fscrypt_context_size(const union fscrypt_context *ctx)
72 switch (ctx->version) {
73 case FSCRYPT_CONTEXT_V1:
74 BUILD_BUG_ON(sizeof(ctx->v1) != 28);
75 return sizeof(ctx->v1);
76 case FSCRYPT_CONTEXT_V2:
77 BUILD_BUG_ON(sizeof(ctx->v2) != 40);
78 return sizeof(ctx->v2);
83 /* Check whether an fscrypt_context has a recognized version number and size */
84 static inline bool fscrypt_context_is_valid(const union fscrypt_context *ctx,
87 return ctx_size >= 1 && ctx_size == fscrypt_context_size(ctx);
90 /* Retrieve the context's nonce, assuming the context was already validated */
91 static inline const u8 *fscrypt_context_nonce(const union fscrypt_context *ctx)
93 switch (ctx->version) {
94 case FSCRYPT_CONTEXT_V1:
96 case FSCRYPT_CONTEXT_V2:
103 union fscrypt_policy {
105 struct fscrypt_policy_v1 v1;
106 struct fscrypt_policy_v2 v2;
110 * Return the size expected for the given fscrypt_policy based on its version
111 * number, or 0 if the policy version is unrecognized.
113 static inline int fscrypt_policy_size(const union fscrypt_policy *policy)
115 switch (policy->version) {
116 case FSCRYPT_POLICY_V1:
117 return sizeof(policy->v1);
118 case FSCRYPT_POLICY_V2:
119 return sizeof(policy->v2);
124 /* Return the contents encryption mode of a valid encryption policy */
126 fscrypt_policy_contents_mode(const union fscrypt_policy *policy)
128 switch (policy->version) {
129 case FSCRYPT_POLICY_V1:
130 return policy->v1.contents_encryption_mode;
131 case FSCRYPT_POLICY_V2:
132 return policy->v2.contents_encryption_mode;
137 /* Return the filenames encryption mode of a valid encryption policy */
139 fscrypt_policy_fnames_mode(const union fscrypt_policy *policy)
141 switch (policy->version) {
142 case FSCRYPT_POLICY_V1:
143 return policy->v1.filenames_encryption_mode;
144 case FSCRYPT_POLICY_V2:
145 return policy->v2.filenames_encryption_mode;
150 /* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */
152 fscrypt_policy_flags(const union fscrypt_policy *policy)
154 switch (policy->version) {
155 case FSCRYPT_POLICY_V1:
156 return policy->v1.flags;
157 case FSCRYPT_POLICY_V2:
158 return policy->v2.flags;
164 * For encrypted symlinks, the ciphertext length is stored at the beginning
165 * of the string in little-endian format.
167 struct fscrypt_symlink_data {
169 char encrypted_path[1];
173 * struct fscrypt_prepared_key - a key prepared for actual encryption/decryption
174 * @tfm: crypto API transform object
175 * @blk_key: key for blk-crypto
177 * Normally only one of the fields will be non-NULL.
179 struct fscrypt_prepared_key {
180 struct crypto_skcipher *tfm;
181 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
182 struct fscrypt_blk_crypto_key *blk_key;
187 * fscrypt_info - the "encryption key" for an inode
189 * When an encrypted file's key is made available, an instance of this struct is
190 * allocated and stored in ->i_crypt_info. Once created, it remains until the
193 struct fscrypt_info {
195 /* The key in a form prepared for actual encryption/decryption */
196 struct fscrypt_prepared_key ci_enc_key;
198 /* True if ci_enc_key should be freed when this fscrypt_info is freed */
201 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
203 * True if this inode will use inline encryption (blk-crypto) instead of
204 * the traditional filesystem-layer encryption.
210 * Encryption mode used for this inode. It corresponds to either the
211 * contents or filenames encryption mode, depending on the inode type.
213 struct fscrypt_mode *ci_mode;
215 /* Back-pointer to the inode */
216 struct inode *ci_inode;
219 * The master key with which this inode was unlocked (decrypted). This
220 * will be NULL if the master key was found in a process-subscribed
221 * keyring rather than in the filesystem-level keyring.
223 struct fscrypt_master_key *ci_master_key;
226 * Link in list of inodes that were unlocked with the master key.
227 * Only used when ->ci_master_key is set.
229 struct list_head ci_master_key_link;
232 * If non-NULL, then encryption is done using the master key directly
233 * and ci_enc_key will equal ci_direct_key->dk_key.
235 struct fscrypt_direct_key *ci_direct_key;
238 * This inode's hash key for filenames. This is a 128-bit SipHash-2-4
239 * key. This is only set for directories that use a keyed dirhash over
240 * the plaintext filenames -- currently just casefolded directories.
242 siphash_key_t ci_dirhash_key;
243 bool ci_dirhash_key_initialized;
245 /* The encryption policy used by this inode */
246 union fscrypt_policy ci_policy;
248 /* This inode's nonce, copied from the fscrypt_context */
249 u8 ci_nonce[FSCRYPT_FILE_NONCE_SIZE];
251 /* Hashed inode number. Only set for IV_INO_LBLK_32 */
258 } fscrypt_direction_t;
261 extern struct kmem_cache *fscrypt_info_cachep;
262 int fscrypt_initialize(unsigned int cop_flags);
263 int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
264 u64 lblk_num, struct page *src_page,
265 struct page *dest_page, unsigned int len,
266 unsigned int offs, gfp_t gfp_flags);
267 struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags);
269 void __printf(3, 4) __cold
270 fscrypt_msg(const struct inode *inode, const char *level, const char *fmt, ...);
272 #define fscrypt_warn(inode, fmt, ...) \
273 fscrypt_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
274 #define fscrypt_err(inode, fmt, ...) \
275 fscrypt_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
277 #define FSCRYPT_MAX_IV_SIZE 32
281 /* logical block number within the file */
284 /* per-file nonce; only set in DIRECT_KEY mode */
285 u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
287 u8 raw[FSCRYPT_MAX_IV_SIZE];
288 __le64 dun[FSCRYPT_MAX_IV_SIZE / sizeof(__le64)];
291 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
292 const struct fscrypt_info *ci);
295 int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname,
296 u8 *out, unsigned int olen);
297 bool fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
298 u32 orig_len, u32 max_len,
299 u32 *encrypted_len_ret);
300 extern const struct dentry_operations fscrypt_d_ops;
304 struct fscrypt_hkdf {
305 struct crypto_shash *hmac_tfm;
308 int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
309 unsigned int master_key_size);
312 * The list of contexts in which fscrypt uses HKDF. These values are used as
313 * the first byte of the HKDF application-specific info string to guarantee that
314 * info strings are never repeated between contexts. This ensures that all HKDF
315 * outputs are unique and cryptographically isolated, i.e. knowledge of one
316 * output doesn't reveal another.
318 #define HKDF_CONTEXT_KEY_IDENTIFIER 1 /* info=<empty> */
319 #define HKDF_CONTEXT_PER_FILE_ENC_KEY 2 /* info=file_nonce */
320 #define HKDF_CONTEXT_DIRECT_KEY 3 /* info=mode_num */
321 #define HKDF_CONTEXT_IV_INO_LBLK_64_KEY 4 /* info=mode_num||fs_uuid */
322 #define HKDF_CONTEXT_DIRHASH_KEY 5 /* info=file_nonce */
323 #define HKDF_CONTEXT_IV_INO_LBLK_32_KEY 6 /* info=mode_num||fs_uuid */
324 #define HKDF_CONTEXT_INODE_HASH_KEY 7 /* info=<empty> */
326 int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
327 const u8 *info, unsigned int infolen,
328 u8 *okm, unsigned int okmlen);
330 void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf);
333 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
334 int fscrypt_select_encryption_impl(struct fscrypt_info *ci);
337 fscrypt_using_inline_encryption(const struct fscrypt_info *ci)
339 return ci->ci_inlinecrypt;
342 int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
344 const struct fscrypt_info *ci);
346 void fscrypt_destroy_inline_crypt_key(struct fscrypt_prepared_key *prep_key);
349 * Check whether the crypto transform or blk-crypto key has been allocated in
350 * @prep_key, depending on which encryption implementation the file will use.
353 fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
354 const struct fscrypt_info *ci)
357 * The two smp_load_acquire()'s here pair with the smp_store_release()'s
358 * in fscrypt_prepare_inline_crypt_key() and fscrypt_prepare_key().
359 * I.e., in some cases (namely, if this prep_key is a per-mode
360 * encryption key) another task can publish blk_key or tfm concurrently,
361 * executing a RELEASE barrier. We need to use smp_load_acquire() here
362 * to safely ACQUIRE the memory the other task published.
364 if (fscrypt_using_inline_encryption(ci))
365 return smp_load_acquire(&prep_key->blk_key) != NULL;
366 return smp_load_acquire(&prep_key->tfm) != NULL;
369 #else /* CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
371 static inline int fscrypt_select_encryption_impl(struct fscrypt_info *ci)
377 fscrypt_using_inline_encryption(const struct fscrypt_info *ci)
383 fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
385 const struct fscrypt_info *ci)
392 fscrypt_destroy_inline_crypt_key(struct fscrypt_prepared_key *prep_key)
397 fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
398 const struct fscrypt_info *ci)
400 return smp_load_acquire(&prep_key->tfm) != NULL;
402 #endif /* !CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
407 * fscrypt_master_key_secret - secret key material of an in-use master key
409 struct fscrypt_master_key_secret {
412 * For v2 policy keys: HKDF context keyed by this master key.
413 * For v1 policy keys: not set (hkdf.hmac_tfm == NULL).
415 struct fscrypt_hkdf hkdf;
417 /* Size of the raw key in bytes. Set even if ->raw isn't set. */
420 /* For v1 policy keys: the raw key. Wiped for v2 policy keys. */
421 u8 raw[FSCRYPT_MAX_KEY_SIZE];
423 } __randomize_layout;
426 * fscrypt_master_key - an in-use master key
428 * This represents a master encryption key which has been added to the
429 * filesystem and can be used to "unlock" the encrypted files which were
432 struct fscrypt_master_key {
435 * Back-pointer to the super_block of the filesystem to which this
436 * master key has been added. Only valid if ->mk_active_refs > 0.
438 struct super_block *mk_sb;
441 * Link in ->mk_sb->s_master_keys->key_hashtable.
442 * Only valid if ->mk_active_refs > 0.
444 struct hlist_node mk_node;
446 /* Semaphore that protects ->mk_secret and ->mk_users */
447 struct rw_semaphore mk_sem;
450 * Active and structural reference counts. An active ref guarantees
451 * that the struct continues to exist, continues to be in the keyring
452 * ->mk_sb->s_master_keys, and that any embedded subkeys (e.g.
453 * ->mk_direct_keys) that have been prepared continue to exist.
454 * A structural ref only guarantees that the struct continues to exist.
456 * There is one active ref associated with ->mk_secret being present,
457 * and one active ref for each inode in ->mk_decrypted_inodes.
459 * There is one structural ref associated with the active refcount being
460 * nonzero. Finding a key in the keyring also takes a structural ref,
461 * which is then held temporarily while the key is operated on.
463 refcount_t mk_active_refs;
464 refcount_t mk_struct_refs;
466 struct rcu_head mk_rcu_head;
469 * The secret key material. After FS_IOC_REMOVE_ENCRYPTION_KEY is
470 * executed, this is wiped and no new inodes can be unlocked with this
471 * key; however, there may still be inodes in ->mk_decrypted_inodes
472 * which could not be evicted. As long as some inodes still remain,
473 * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or
474 * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again.
476 * While ->mk_secret is present, one ref in ->mk_active_refs is held.
478 * Locking: protected by ->mk_sem. The manipulation of ->mk_active_refs
479 * associated with this field is protected by ->mk_sem as well.
481 struct fscrypt_master_key_secret mk_secret;
484 * For v1 policy keys: an arbitrary key descriptor which was assigned by
485 * userspace (->descriptor).
487 * For v2 policy keys: a cryptographic hash of this key (->identifier).
489 struct fscrypt_key_specifier mk_spec;
492 * Keyring which contains a key of type 'key_type_fscrypt_user' for each
493 * user who has added this key. Normally each key will be added by just
494 * one user, but it's possible that multiple users share a key, and in
495 * that case we need to keep track of those users so that one user can't
496 * remove the key before the others want it removed too.
498 * This is NULL for v1 policy keys; those can only be added by root.
500 * Locking: protected by ->mk_sem. (We don't just rely on the keyrings
501 * subsystem semaphore ->mk_users->sem, as we need support for atomic
502 * search+insert along with proper synchronization with ->mk_secret.)
504 struct key *mk_users;
507 * List of inodes that were unlocked using this key. This allows the
508 * inodes to be evicted efficiently if the key is removed.
510 struct list_head mk_decrypted_inodes;
511 spinlock_t mk_decrypted_inodes_lock;
514 * Per-mode encryption keys for the various types of encryption policies
515 * that use them. Allocated and derived on-demand.
517 struct fscrypt_prepared_key mk_direct_keys[FSCRYPT_MODE_MAX + 1];
518 struct fscrypt_prepared_key mk_iv_ino_lblk_64_keys[FSCRYPT_MODE_MAX + 1];
519 struct fscrypt_prepared_key mk_iv_ino_lblk_32_keys[FSCRYPT_MODE_MAX + 1];
521 /* Hash key for inode numbers. Initialized only when needed. */
522 siphash_key_t mk_ino_hash_key;
523 bool mk_ino_hash_key_initialized;
525 } __randomize_layout;
528 is_master_key_secret_present(const struct fscrypt_master_key_secret *secret)
531 * The READ_ONCE() is only necessary for fscrypt_drop_inode().
532 * fscrypt_drop_inode() runs in atomic context, so it can't take the key
533 * semaphore and thus 'secret' can change concurrently which would be a
534 * data race. But fscrypt_drop_inode() only need to know whether the
535 * secret *was* present at the time of check, so READ_ONCE() suffices.
537 return READ_ONCE(secret->size) != 0;
540 static inline const char *master_key_spec_type(
541 const struct fscrypt_key_specifier *spec)
543 switch (spec->type) {
544 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
546 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
552 static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
554 switch (spec->type) {
555 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
556 return FSCRYPT_KEY_DESCRIPTOR_SIZE;
557 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
558 return FSCRYPT_KEY_IDENTIFIER_SIZE;
563 void fscrypt_put_master_key(struct fscrypt_master_key *mk);
565 void fscrypt_put_master_key_activeref(struct fscrypt_master_key *mk);
567 struct fscrypt_master_key *
568 fscrypt_find_master_key(struct super_block *sb,
569 const struct fscrypt_key_specifier *mk_spec);
571 int fscrypt_add_test_dummy_key(struct super_block *sb,
572 struct fscrypt_key_specifier *key_spec);
574 int fscrypt_verify_key_added(struct super_block *sb,
575 const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
577 int __init fscrypt_init_keyring(void);
581 struct fscrypt_mode {
582 const char *friendly_name;
583 const char *cipher_str;
584 int keysize; /* key size in bytes */
585 int security_strength; /* security strength in bytes */
586 int ivsize; /* IV size in bytes */
587 int logged_impl_name;
588 enum blk_crypto_mode_num blk_crypto_mode;
591 extern struct fscrypt_mode fscrypt_modes[];
593 int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key,
594 const u8 *raw_key, const struct fscrypt_info *ci);
596 void fscrypt_destroy_prepared_key(struct fscrypt_prepared_key *prep_key);
598 int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key);
600 int fscrypt_derive_dirhash_key(struct fscrypt_info *ci,
601 const struct fscrypt_master_key *mk);
603 void fscrypt_hash_inode_number(struct fscrypt_info *ci,
604 const struct fscrypt_master_key *mk);
608 void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
610 int fscrypt_setup_v1_file_key(struct fscrypt_info *ci,
611 const u8 *raw_master_key);
613 int fscrypt_setup_v1_file_key_via_subscribed_keyrings(struct fscrypt_info *ci);
617 bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
618 const union fscrypt_policy *policy2);
619 bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
620 const struct inode *inode);
621 int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
622 const union fscrypt_context *ctx_u,
624 const union fscrypt_policy *fscrypt_policy_to_inherit(struct inode *dir);
626 #endif /* _FSCRYPT_PRIVATE_H */