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>
18 #define CONST_STRLEN(str) (sizeof(str) - 1)
20 #define FS_KEY_DERIVATION_NONCE_SIZE 16
22 #define FSCRYPT_MIN_KEY_SIZE 16
24 #define FSCRYPT_CONTEXT_V1 1
25 #define FSCRYPT_CONTEXT_V2 2
27 struct fscrypt_context_v1 {
28 u8 version; /* FSCRYPT_CONTEXT_V1 */
29 u8 contents_encryption_mode;
30 u8 filenames_encryption_mode;
32 u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
33 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
36 struct fscrypt_context_v2 {
37 u8 version; /* FSCRYPT_CONTEXT_V2 */
38 u8 contents_encryption_mode;
39 u8 filenames_encryption_mode;
42 u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
43 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
47 * fscrypt_context - the encryption context of an inode
49 * This is the on-disk equivalent of an fscrypt_policy, stored alongside each
50 * encrypted file usually in a hidden extended attribute. It contains the
51 * fields from the fscrypt_policy, in order to identify the encryption algorithm
52 * and key with which the file is encrypted. It also contains a nonce that was
53 * randomly generated by fscrypt itself; this is used as KDF input or as a tweak
54 * to cause different files to be encrypted differently.
56 union fscrypt_context {
58 struct fscrypt_context_v1 v1;
59 struct fscrypt_context_v2 v2;
63 * Return the size expected for the given fscrypt_context based on its version
64 * number, or 0 if the context version is unrecognized.
66 static inline int fscrypt_context_size(const union fscrypt_context *ctx)
68 switch (ctx->version) {
69 case FSCRYPT_CONTEXT_V1:
70 BUILD_BUG_ON(sizeof(ctx->v1) != 28);
71 return sizeof(ctx->v1);
72 case FSCRYPT_CONTEXT_V2:
73 BUILD_BUG_ON(sizeof(ctx->v2) != 40);
74 return sizeof(ctx->v2);
79 /* Check whether an fscrypt_context has a recognized version number and size */
80 static inline bool fscrypt_context_is_valid(const union fscrypt_context *ctx,
83 return ctx_size >= 1 && ctx_size == fscrypt_context_size(ctx);
86 /* Retrieve the context's nonce, assuming the context was already validated */
87 static inline const u8 *fscrypt_context_nonce(const union fscrypt_context *ctx)
89 switch (ctx->version) {
90 case FSCRYPT_CONTEXT_V1:
92 case FSCRYPT_CONTEXT_V2:
100 union fscrypt_policy {
102 struct fscrypt_policy_v1 v1;
103 struct fscrypt_policy_v2 v2;
107 * Return the size expected for the given fscrypt_policy based on its version
108 * number, or 0 if the policy version is unrecognized.
110 static inline int fscrypt_policy_size(const union fscrypt_policy *policy)
112 switch (policy->version) {
113 case FSCRYPT_POLICY_V1:
114 return sizeof(policy->v1);
115 case FSCRYPT_POLICY_V2:
116 return sizeof(policy->v2);
121 /* Return the contents encryption mode of a valid encryption policy */
123 fscrypt_policy_contents_mode(const union fscrypt_policy *policy)
125 switch (policy->version) {
126 case FSCRYPT_POLICY_V1:
127 return policy->v1.contents_encryption_mode;
128 case FSCRYPT_POLICY_V2:
129 return policy->v2.contents_encryption_mode;
134 /* Return the filenames encryption mode of a valid encryption policy */
136 fscrypt_policy_fnames_mode(const union fscrypt_policy *policy)
138 switch (policy->version) {
139 case FSCRYPT_POLICY_V1:
140 return policy->v1.filenames_encryption_mode;
141 case FSCRYPT_POLICY_V2:
142 return policy->v2.filenames_encryption_mode;
147 /* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */
149 fscrypt_policy_flags(const union fscrypt_policy *policy)
151 switch (policy->version) {
152 case FSCRYPT_POLICY_V1:
153 return policy->v1.flags;
154 case FSCRYPT_POLICY_V2:
155 return policy->v2.flags;
161 * For encrypted symlinks, the ciphertext length is stored at the beginning
162 * of the string in little-endian format.
164 struct fscrypt_symlink_data {
166 char encrypted_path[1];
170 * fscrypt_info - the "encryption key" for an inode
172 * When an encrypted file's key is made available, an instance of this struct is
173 * allocated and stored in ->i_crypt_info. Once created, it remains until the
176 struct fscrypt_info {
178 /* The actual crypto transform used for encryption and decryption */
179 struct crypto_skcipher *ci_ctfm;
181 /* True if the key should be freed when this fscrypt_info is freed */
185 * Encryption mode used for this inode. It corresponds to either the
186 * contents or filenames encryption mode, depending on the inode type.
188 struct fscrypt_mode *ci_mode;
190 /* Back-pointer to the inode */
191 struct inode *ci_inode;
194 * The master key with which this inode was unlocked (decrypted). This
195 * will be NULL if the master key was found in a process-subscribed
196 * keyring rather than in the filesystem-level keyring.
198 struct key *ci_master_key;
201 * Link in list of inodes that were unlocked with the master key.
202 * Only used when ->ci_master_key is set.
204 struct list_head ci_master_key_link;
207 * If non-NULL, then encryption is done using the master key directly
208 * and ci_ctfm will equal ci_direct_key->dk_ctfm.
210 struct fscrypt_direct_key *ci_direct_key;
213 * This inode's hash key for filenames. This is a 128-bit SipHash-2-4
214 * key. This is only set for directories that use a keyed dirhash over
215 * the plaintext filenames -- currently just casefolded directories.
217 siphash_key_t ci_dirhash_key;
218 bool ci_dirhash_key_initialized;
220 /* The encryption policy used by this inode */
221 union fscrypt_policy ci_policy;
223 /* This inode's nonce, copied from the fscrypt_context */
224 u8 ci_nonce[FS_KEY_DERIVATION_NONCE_SIZE];
226 /* Hashed inode number. Only set for IV_INO_LBLK_32 */
233 } fscrypt_direction_t;
236 extern struct kmem_cache *fscrypt_info_cachep;
237 int fscrypt_initialize(unsigned int cop_flags);
238 int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
239 u64 lblk_num, struct page *src_page,
240 struct page *dest_page, unsigned int len,
241 unsigned int offs, gfp_t gfp_flags);
242 struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags);
244 void __printf(3, 4) __cold
245 fscrypt_msg(const struct inode *inode, const char *level, const char *fmt, ...);
247 #define fscrypt_warn(inode, fmt, ...) \
248 fscrypt_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
249 #define fscrypt_err(inode, fmt, ...) \
250 fscrypt_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
252 #define FSCRYPT_MAX_IV_SIZE 32
256 /* logical block number within the file */
259 /* per-file nonce; only set in DIRECT_KEY mode */
260 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
262 u8 raw[FSCRYPT_MAX_IV_SIZE];
265 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
266 const struct fscrypt_info *ci);
269 int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname,
270 u8 *out, unsigned int olen);
271 bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
272 u32 max_len, u32 *encrypted_len_ret);
273 extern const struct dentry_operations fscrypt_d_ops;
277 struct fscrypt_hkdf {
278 struct crypto_shash *hmac_tfm;
281 int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
282 unsigned int master_key_size);
285 * The list of contexts in which fscrypt uses HKDF. These values are used as
286 * the first byte of the HKDF application-specific info string to guarantee that
287 * info strings are never repeated between contexts. This ensures that all HKDF
288 * outputs are unique and cryptographically isolated, i.e. knowledge of one
289 * output doesn't reveal another.
291 #define HKDF_CONTEXT_KEY_IDENTIFIER 1
292 #define HKDF_CONTEXT_PER_FILE_ENC_KEY 2
293 #define HKDF_CONTEXT_DIRECT_KEY 3
294 #define HKDF_CONTEXT_IV_INO_LBLK_64_KEY 4
295 #define HKDF_CONTEXT_DIRHASH_KEY 5
296 #define HKDF_CONTEXT_IV_INO_LBLK_32_KEY 6
297 #define HKDF_CONTEXT_INODE_HASH_KEY 7
299 int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
300 const u8 *info, unsigned int infolen,
301 u8 *okm, unsigned int okmlen);
303 void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf);
308 * fscrypt_master_key_secret - secret key material of an in-use master key
310 struct fscrypt_master_key_secret {
313 * For v2 policy keys: HKDF context keyed by this master key.
314 * For v1 policy keys: not set (hkdf.hmac_tfm == NULL).
316 struct fscrypt_hkdf hkdf;
318 /* Size of the raw key in bytes. Set even if ->raw isn't set. */
321 /* For v1 policy keys: the raw key. Wiped for v2 policy keys. */
322 u8 raw[FSCRYPT_MAX_KEY_SIZE];
324 } __randomize_layout;
327 * fscrypt_master_key - an in-use master key
329 * This represents a master encryption key which has been added to the
330 * filesystem and can be used to "unlock" the encrypted files which were
333 struct fscrypt_master_key {
336 * The secret key material. After FS_IOC_REMOVE_ENCRYPTION_KEY is
337 * executed, this is wiped and no new inodes can be unlocked with this
338 * key; however, there may still be inodes in ->mk_decrypted_inodes
339 * which could not be evicted. As long as some inodes still remain,
340 * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or
341 * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again.
343 * Locking: protected by key->sem (outer) and mk_secret_sem (inner).
344 * The reason for two locks is that key->sem also protects modifying
345 * mk_users, which ranks it above the semaphore for the keyring key
346 * type, which is in turn above page faults (via keyring_read). But
347 * sometimes filesystems call fscrypt_get_encryption_info() from within
348 * a transaction, which ranks it below page faults. So we need a
349 * separate lock which protects mk_secret but not also mk_users.
351 struct fscrypt_master_key_secret mk_secret;
352 struct rw_semaphore mk_secret_sem;
355 * For v1 policy keys: an arbitrary key descriptor which was assigned by
356 * userspace (->descriptor).
358 * For v2 policy keys: a cryptographic hash of this key (->identifier).
360 struct fscrypt_key_specifier mk_spec;
363 * Keyring which contains a key of type 'key_type_fscrypt_user' for each
364 * user who has added this key. Normally each key will be added by just
365 * one user, but it's possible that multiple users share a key, and in
366 * that case we need to keep track of those users so that one user can't
367 * remove the key before the others want it removed too.
369 * This is NULL for v1 policy keys; those can only be added by root.
371 * Locking: in addition to this keyrings own semaphore, this is
372 * protected by the master key's key->sem, so we can do atomic
373 * search+insert. It can also be searched without taking any locks, but
374 * in that case the returned key may have already been removed.
376 struct key *mk_users;
379 * Length of ->mk_decrypted_inodes, plus one if mk_secret is present.
380 * Once this goes to 0, the master key is removed from ->s_master_keys.
381 * The 'struct fscrypt_master_key' will continue to live as long as the
382 * 'struct key' whose payload it is, but we won't let this reference
385 refcount_t mk_refcount;
388 * List of inodes that were unlocked using this key. This allows the
389 * inodes to be evicted efficiently if the key is removed.
391 struct list_head mk_decrypted_inodes;
392 spinlock_t mk_decrypted_inodes_lock;
395 * Per-mode encryption keys for the various types of encryption policies
396 * that use them. Allocated and derived on-demand.
398 struct crypto_skcipher *mk_direct_keys[__FSCRYPT_MODE_MAX + 1];
399 struct crypto_skcipher *mk_iv_ino_lblk_64_keys[__FSCRYPT_MODE_MAX + 1];
400 struct crypto_skcipher *mk_iv_ino_lblk_32_keys[__FSCRYPT_MODE_MAX + 1];
402 /* Hash key for inode numbers. Initialized only when needed. */
403 siphash_key_t mk_ino_hash_key;
404 bool mk_ino_hash_key_initialized;
406 } __randomize_layout;
409 is_master_key_secret_present(const struct fscrypt_master_key_secret *secret)
412 * The READ_ONCE() is only necessary for fscrypt_drop_inode() and
413 * fscrypt_key_describe(). These run in atomic context, so they can't
414 * take ->mk_secret_sem and thus 'secret' can change concurrently which
415 * would be a data race. But they only need to know whether the secret
416 * *was* present at the time of check, so READ_ONCE() suffices.
418 return READ_ONCE(secret->size) != 0;
421 static inline const char *master_key_spec_type(
422 const struct fscrypt_key_specifier *spec)
424 switch (spec->type) {
425 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
427 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
433 static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
435 switch (spec->type) {
436 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
437 return FSCRYPT_KEY_DESCRIPTOR_SIZE;
438 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
439 return FSCRYPT_KEY_IDENTIFIER_SIZE;
445 fscrypt_find_master_key(struct super_block *sb,
446 const struct fscrypt_key_specifier *mk_spec);
448 int fscrypt_add_test_dummy_key(struct super_block *sb,
449 struct fscrypt_key_specifier *key_spec);
451 int fscrypt_verify_key_added(struct super_block *sb,
452 const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
454 int __init fscrypt_init_keyring(void);
458 struct fscrypt_mode {
459 const char *friendly_name;
460 const char *cipher_str;
463 int logged_impl_name;
466 extern struct fscrypt_mode fscrypt_modes[];
468 struct crypto_skcipher *fscrypt_allocate_skcipher(struct fscrypt_mode *mode,
470 const struct inode *inode);
472 int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key);
474 int fscrypt_derive_dirhash_key(struct fscrypt_info *ci,
475 const struct fscrypt_master_key *mk);
479 void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
481 int fscrypt_setup_v1_file_key(struct fscrypt_info *ci,
482 const u8 *raw_master_key);
484 int fscrypt_setup_v1_file_key_via_subscribed_keyrings(struct fscrypt_info *ci);
488 bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
489 const union fscrypt_policy *policy2);
490 bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
491 const struct inode *inode);
492 int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
493 const union fscrypt_context *ctx_u,
496 #endif /* _FSCRYPT_PRIVATE_H */