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 <crypto/hash.h>
17 #define CONST_STRLEN(str) (sizeof(str) - 1)
19 #define FS_KEY_DERIVATION_NONCE_SIZE 16
21 #define FSCRYPT_MIN_KEY_SIZE 16
23 #define FSCRYPT_CONTEXT_V1 1
24 #define FSCRYPT_CONTEXT_V2 2
26 struct fscrypt_context_v1 {
27 u8 version; /* FSCRYPT_CONTEXT_V1 */
28 u8 contents_encryption_mode;
29 u8 filenames_encryption_mode;
31 u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
32 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
35 struct fscrypt_context_v2 {
36 u8 version; /* FSCRYPT_CONTEXT_V2 */
37 u8 contents_encryption_mode;
38 u8 filenames_encryption_mode;
41 u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
42 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
46 * fscrypt_context - the encryption context of an inode
48 * This is the on-disk equivalent of an fscrypt_policy, stored alongside each
49 * encrypted file usually in a hidden extended attribute. It contains the
50 * fields from the fscrypt_policy, in order to identify the encryption algorithm
51 * and key with which the file is encrypted. It also contains a nonce that was
52 * randomly generated by fscrypt itself; this is used as KDF input or as a tweak
53 * to cause different files to be encrypted differently.
55 union fscrypt_context {
57 struct fscrypt_context_v1 v1;
58 struct fscrypt_context_v2 v2;
62 * Return the size expected for the given fscrypt_context based on its version
63 * number, or 0 if the context version is unrecognized.
65 static inline int fscrypt_context_size(const union fscrypt_context *ctx)
67 switch (ctx->version) {
68 case FSCRYPT_CONTEXT_V1:
69 BUILD_BUG_ON(sizeof(ctx->v1) != 28);
70 return sizeof(ctx->v1);
71 case FSCRYPT_CONTEXT_V2:
72 BUILD_BUG_ON(sizeof(ctx->v2) != 40);
73 return sizeof(ctx->v2);
79 union fscrypt_policy {
81 struct fscrypt_policy_v1 v1;
82 struct fscrypt_policy_v2 v2;
86 * Return the size expected for the given fscrypt_policy based on its version
87 * number, or 0 if the policy version is unrecognized.
89 static inline int fscrypt_policy_size(const union fscrypt_policy *policy)
91 switch (policy->version) {
92 case FSCRYPT_POLICY_V1:
93 return sizeof(policy->v1);
94 case FSCRYPT_POLICY_V2:
95 return sizeof(policy->v2);
100 /* Return the contents encryption mode of a valid encryption policy */
102 fscrypt_policy_contents_mode(const union fscrypt_policy *policy)
104 switch (policy->version) {
105 case FSCRYPT_POLICY_V1:
106 return policy->v1.contents_encryption_mode;
107 case FSCRYPT_POLICY_V2:
108 return policy->v2.contents_encryption_mode;
113 /* Return the filenames encryption mode of a valid encryption policy */
115 fscrypt_policy_fnames_mode(const union fscrypt_policy *policy)
117 switch (policy->version) {
118 case FSCRYPT_POLICY_V1:
119 return policy->v1.filenames_encryption_mode;
120 case FSCRYPT_POLICY_V2:
121 return policy->v2.filenames_encryption_mode;
126 /* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */
128 fscrypt_policy_flags(const union fscrypt_policy *policy)
130 switch (policy->version) {
131 case FSCRYPT_POLICY_V1:
132 return policy->v1.flags;
133 case FSCRYPT_POLICY_V2:
134 return policy->v2.flags;
140 * For encrypted symlinks, the ciphertext length is stored at the beginning
141 * of the string in little-endian format.
143 struct fscrypt_symlink_data {
145 char encrypted_path[1];
149 * fscrypt_info - the "encryption key" for an inode
151 * When an encrypted file's key is made available, an instance of this struct is
152 * allocated and stored in ->i_crypt_info. Once created, it remains until the
155 struct fscrypt_info {
157 /* The actual crypto transform used for encryption and decryption */
158 struct crypto_skcipher *ci_ctfm;
160 /* True if the key should be freed when this fscrypt_info is freed */
164 * Encryption mode used for this inode. It corresponds to either the
165 * contents or filenames encryption mode, depending on the inode type.
167 struct fscrypt_mode *ci_mode;
169 /* Back-pointer to the inode */
170 struct inode *ci_inode;
173 * The master key with which this inode was unlocked (decrypted). This
174 * will be NULL if the master key was found in a process-subscribed
175 * keyring rather than in the filesystem-level keyring.
177 struct key *ci_master_key;
180 * Link in list of inodes that were unlocked with the master key.
181 * Only used when ->ci_master_key is set.
183 struct list_head ci_master_key_link;
186 * If non-NULL, then encryption is done using the master key directly
187 * and ci_ctfm will equal ci_direct_key->dk_ctfm.
189 struct fscrypt_direct_key *ci_direct_key;
191 /* The encryption policy used by this inode */
192 union fscrypt_policy ci_policy;
194 /* This inode's nonce, copied from the fscrypt_context */
195 u8 ci_nonce[FS_KEY_DERIVATION_NONCE_SIZE];
201 } fscrypt_direction_t;
204 extern struct kmem_cache *fscrypt_info_cachep;
205 extern int fscrypt_initialize(unsigned int cop_flags);
206 extern int fscrypt_crypt_block(const struct inode *inode,
207 fscrypt_direction_t rw, u64 lblk_num,
208 struct page *src_page, struct page *dest_page,
209 unsigned int len, unsigned int offs,
211 extern struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags);
213 extern void __printf(3, 4) __cold
214 fscrypt_msg(const struct inode *inode, const char *level, const char *fmt, ...);
216 #define fscrypt_warn(inode, fmt, ...) \
217 fscrypt_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
218 #define fscrypt_err(inode, fmt, ...) \
219 fscrypt_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
221 #define FSCRYPT_MAX_IV_SIZE 32
225 /* logical block number within the file */
228 /* per-file nonce; only set in DIRECT_KEY mode */
229 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
231 u8 raw[FSCRYPT_MAX_IV_SIZE];
234 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
235 const struct fscrypt_info *ci);
238 extern int fscrypt_fname_encrypt(const struct inode *inode,
239 const struct qstr *iname,
240 u8 *out, unsigned int olen);
241 extern bool fscrypt_fname_encrypted_size(const struct inode *inode,
242 u32 orig_len, u32 max_len,
243 u32 *encrypted_len_ret);
244 extern const struct dentry_operations fscrypt_d_ops;
248 struct fscrypt_hkdf {
249 struct crypto_shash *hmac_tfm;
252 extern int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
253 unsigned int master_key_size);
256 * The list of contexts in which fscrypt uses HKDF. These values are used as
257 * the first byte of the HKDF application-specific info string to guarantee that
258 * info strings are never repeated between contexts. This ensures that all HKDF
259 * outputs are unique and cryptographically isolated, i.e. knowledge of one
260 * output doesn't reveal another.
262 #define HKDF_CONTEXT_KEY_IDENTIFIER 1
263 #define HKDF_CONTEXT_PER_FILE_KEY 2
264 #define HKDF_CONTEXT_DIRECT_KEY 3
265 #define HKDF_CONTEXT_IV_INO_LBLK_64_KEY 4
267 extern int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
268 const u8 *info, unsigned int infolen,
269 u8 *okm, unsigned int okmlen);
271 extern void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf);
276 * fscrypt_master_key_secret - secret key material of an in-use master key
278 struct fscrypt_master_key_secret {
281 * For v2 policy keys: HKDF context keyed by this master key.
282 * For v1 policy keys: not set (hkdf.hmac_tfm == NULL).
284 struct fscrypt_hkdf hkdf;
286 /* Size of the raw key in bytes. Set even if ->raw isn't set. */
289 /* For v1 policy keys: the raw key. Wiped for v2 policy keys. */
290 u8 raw[FSCRYPT_MAX_KEY_SIZE];
292 } __randomize_layout;
295 * fscrypt_master_key - an in-use master key
297 * This represents a master encryption key which has been added to the
298 * filesystem and can be used to "unlock" the encrypted files which were
301 struct fscrypt_master_key {
304 * The secret key material. After FS_IOC_REMOVE_ENCRYPTION_KEY is
305 * executed, this is wiped and no new inodes can be unlocked with this
306 * key; however, there may still be inodes in ->mk_decrypted_inodes
307 * which could not be evicted. As long as some inodes still remain,
308 * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or
309 * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again.
311 * Locking: protected by key->sem (outer) and mk_secret_sem (inner).
312 * The reason for two locks is that key->sem also protects modifying
313 * mk_users, which ranks it above the semaphore for the keyring key
314 * type, which is in turn above page faults (via keyring_read). But
315 * sometimes filesystems call fscrypt_get_encryption_info() from within
316 * a transaction, which ranks it below page faults. So we need a
317 * separate lock which protects mk_secret but not also mk_users.
319 struct fscrypt_master_key_secret mk_secret;
320 struct rw_semaphore mk_secret_sem;
323 * For v1 policy keys: an arbitrary key descriptor which was assigned by
324 * userspace (->descriptor).
326 * For v2 policy keys: a cryptographic hash of this key (->identifier).
328 struct fscrypt_key_specifier mk_spec;
331 * Keyring which contains a key of type 'key_type_fscrypt_user' for each
332 * user who has added this key. Normally each key will be added by just
333 * one user, but it's possible that multiple users share a key, and in
334 * that case we need to keep track of those users so that one user can't
335 * remove the key before the others want it removed too.
337 * This is NULL for v1 policy keys; those can only be added by root.
339 * Locking: in addition to this keyrings own semaphore, this is
340 * protected by the master key's key->sem, so we can do atomic
341 * search+insert. It can also be searched without taking any locks, but
342 * in that case the returned key may have already been removed.
344 struct key *mk_users;
347 * Length of ->mk_decrypted_inodes, plus one if mk_secret is present.
348 * Once this goes to 0, the master key is removed from ->s_master_keys.
349 * The 'struct fscrypt_master_key' will continue to live as long as the
350 * 'struct key' whose payload it is, but we won't let this reference
353 refcount_t mk_refcount;
356 * List of inodes that were unlocked using this key. This allows the
357 * inodes to be evicted efficiently if the key is removed.
359 struct list_head mk_decrypted_inodes;
360 spinlock_t mk_decrypted_inodes_lock;
362 /* Crypto API transforms for DIRECT_KEY policies, allocated on-demand */
363 struct crypto_skcipher *mk_direct_tfms[__FSCRYPT_MODE_MAX + 1];
366 * Crypto API transforms for filesystem-layer implementation of
367 * IV_INO_LBLK_64 policies, allocated on-demand.
369 struct crypto_skcipher *mk_iv_ino_lblk_64_tfms[__FSCRYPT_MODE_MAX + 1];
371 } __randomize_layout;
374 is_master_key_secret_present(const struct fscrypt_master_key_secret *secret)
377 * The READ_ONCE() is only necessary for fscrypt_drop_inode() and
378 * fscrypt_key_describe(). These run in atomic context, so they can't
379 * take ->mk_secret_sem and thus 'secret' can change concurrently which
380 * would be a data race. But they only need to know whether the secret
381 * *was* present at the time of check, so READ_ONCE() suffices.
383 return READ_ONCE(secret->size) != 0;
386 static inline const char *master_key_spec_type(
387 const struct fscrypt_key_specifier *spec)
389 switch (spec->type) {
390 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
392 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
398 static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
400 switch (spec->type) {
401 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
402 return FSCRYPT_KEY_DESCRIPTOR_SIZE;
403 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
404 return FSCRYPT_KEY_IDENTIFIER_SIZE;
410 fscrypt_find_master_key(struct super_block *sb,
411 const struct fscrypt_key_specifier *mk_spec);
413 extern int fscrypt_verify_key_added(struct super_block *sb,
414 const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
416 extern int __init fscrypt_init_keyring(void);
420 struct fscrypt_mode {
421 const char *friendly_name;
422 const char *cipher_str;
425 int logged_impl_name;
428 extern struct fscrypt_mode fscrypt_modes[];
430 extern struct crypto_skcipher *
431 fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key,
432 const struct inode *inode);
434 extern int fscrypt_set_derived_key(struct fscrypt_info *ci,
435 const u8 *derived_key);
439 extern void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
441 extern int fscrypt_setup_v1_file_key(struct fscrypt_info *ci,
442 const u8 *raw_master_key);
444 extern int fscrypt_setup_v1_file_key_via_subscribed_keyrings(
445 struct fscrypt_info *ci);
448 extern bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
449 const union fscrypt_policy *policy2);
450 extern bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
451 const struct inode *inode);
452 extern int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
453 const union fscrypt_context *ctx_u,
456 #endif /* _FSCRYPT_PRIVATE_H */