xref: /linux/fs/crypto/fscrypt_private.h (revision 79790b6818e96c58fe2bffee1b418c16e64e7b80)
1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3  * fscrypt_private.h
4  *
5  * Copyright (C) 2015, Google, Inc.
6  *
7  * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
8  * Heavily modified since then.
9  */
10 
11 #ifndef _FSCRYPT_PRIVATE_H
12 #define _FSCRYPT_PRIVATE_H
13 
14 #include <linux/fscrypt.h>
15 #include <linux/siphash.h>
16 #include <crypto/hash.h>
17 #include <linux/blk-crypto.h>
18 
19 #define CONST_STRLEN(str)	(sizeof(str) - 1)
20 
21 #define FSCRYPT_FILE_NONCE_SIZE	16
22 
23 /*
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.
27  */
28 #define FSCRYPT_MIN_KEY_SIZE	16
29 
30 #define FSCRYPT_CONTEXT_V1	1
31 #define FSCRYPT_CONTEXT_V2	2
32 
33 /* Keep this in sync with include/uapi/linux/fscrypt.h */
34 #define FSCRYPT_MODE_MAX	FSCRYPT_MODE_AES_256_HCTR2
35 
36 struct fscrypt_context_v1 {
37 	u8 version; /* FSCRYPT_CONTEXT_V1 */
38 	u8 contents_encryption_mode;
39 	u8 filenames_encryption_mode;
40 	u8 flags;
41 	u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
42 	u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
43 };
44 
45 struct fscrypt_context_v2 {
46 	u8 version; /* FSCRYPT_CONTEXT_V2 */
47 	u8 contents_encryption_mode;
48 	u8 filenames_encryption_mode;
49 	u8 flags;
50 	u8 log2_data_unit_size;
51 	u8 __reserved[3];
52 	u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
53 	u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
54 };
55 
56 /*
57  * fscrypt_context - the encryption context of an inode
58  *
59  * This is the on-disk equivalent of an fscrypt_policy, stored alongside each
60  * encrypted file usually in a hidden extended attribute.  It contains the
61  * fields from the fscrypt_policy, in order to identify the encryption algorithm
62  * and key with which the file is encrypted.  It also contains a nonce that was
63  * randomly generated by fscrypt itself; this is used as KDF input or as a tweak
64  * to cause different files to be encrypted differently.
65  */
66 union fscrypt_context {
67 	u8 version;
68 	struct fscrypt_context_v1 v1;
69 	struct fscrypt_context_v2 v2;
70 };
71 
72 /*
73  * Return the size expected for the given fscrypt_context based on its version
74  * number, or 0 if the context version is unrecognized.
75  */
fscrypt_context_size(const union fscrypt_context * ctx)76 static inline int fscrypt_context_size(const union fscrypt_context *ctx)
77 {
78 	switch (ctx->version) {
79 	case FSCRYPT_CONTEXT_V1:
80 		BUILD_BUG_ON(sizeof(ctx->v1) != 28);
81 		return sizeof(ctx->v1);
82 	case FSCRYPT_CONTEXT_V2:
83 		BUILD_BUG_ON(sizeof(ctx->v2) != 40);
84 		return sizeof(ctx->v2);
85 	}
86 	return 0;
87 }
88 
89 /* Check whether an fscrypt_context has a recognized version number and size */
fscrypt_context_is_valid(const union fscrypt_context * ctx,int ctx_size)90 static inline bool fscrypt_context_is_valid(const union fscrypt_context *ctx,
91 					    int ctx_size)
92 {
93 	return ctx_size >= 1 && ctx_size == fscrypt_context_size(ctx);
94 }
95 
96 /* Retrieve the context's nonce, assuming the context was already validated */
fscrypt_context_nonce(const union fscrypt_context * ctx)97 static inline const u8 *fscrypt_context_nonce(const union fscrypt_context *ctx)
98 {
99 	switch (ctx->version) {
100 	case FSCRYPT_CONTEXT_V1:
101 		return ctx->v1.nonce;
102 	case FSCRYPT_CONTEXT_V2:
103 		return ctx->v2.nonce;
104 	}
105 	WARN_ON_ONCE(1);
106 	return NULL;
107 }
108 
109 union fscrypt_policy {
110 	u8 version;
111 	struct fscrypt_policy_v1 v1;
112 	struct fscrypt_policy_v2 v2;
113 };
114 
115 /*
116  * Return the size expected for the given fscrypt_policy based on its version
117  * number, or 0 if the policy version is unrecognized.
118  */
fscrypt_policy_size(const union fscrypt_policy * policy)119 static inline int fscrypt_policy_size(const union fscrypt_policy *policy)
120 {
121 	switch (policy->version) {
122 	case FSCRYPT_POLICY_V1:
123 		return sizeof(policy->v1);
124 	case FSCRYPT_POLICY_V2:
125 		return sizeof(policy->v2);
126 	}
127 	return 0;
128 }
129 
130 /* Return the contents encryption mode of a valid encryption policy */
131 static inline u8
fscrypt_policy_contents_mode(const union fscrypt_policy * policy)132 fscrypt_policy_contents_mode(const union fscrypt_policy *policy)
133 {
134 	switch (policy->version) {
135 	case FSCRYPT_POLICY_V1:
136 		return policy->v1.contents_encryption_mode;
137 	case FSCRYPT_POLICY_V2:
138 		return policy->v2.contents_encryption_mode;
139 	}
140 	BUG();
141 }
142 
143 /* Return the filenames encryption mode of a valid encryption policy */
144 static inline u8
fscrypt_policy_fnames_mode(const union fscrypt_policy * policy)145 fscrypt_policy_fnames_mode(const union fscrypt_policy *policy)
146 {
147 	switch (policy->version) {
148 	case FSCRYPT_POLICY_V1:
149 		return policy->v1.filenames_encryption_mode;
150 	case FSCRYPT_POLICY_V2:
151 		return policy->v2.filenames_encryption_mode;
152 	}
153 	BUG();
154 }
155 
156 /* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */
157 static inline u8
fscrypt_policy_flags(const union fscrypt_policy * policy)158 fscrypt_policy_flags(const union fscrypt_policy *policy)
159 {
160 	switch (policy->version) {
161 	case FSCRYPT_POLICY_V1:
162 		return policy->v1.flags;
163 	case FSCRYPT_POLICY_V2:
164 		return policy->v2.flags;
165 	}
166 	BUG();
167 }
168 
169 static inline int
fscrypt_policy_v2_du_bits(const struct fscrypt_policy_v2 * policy,const struct inode * inode)170 fscrypt_policy_v2_du_bits(const struct fscrypt_policy_v2 *policy,
171 			  const struct inode *inode)
172 {
173 	return policy->log2_data_unit_size ?: inode->i_blkbits;
174 }
175 
176 static inline int
fscrypt_policy_du_bits(const union fscrypt_policy * policy,const struct inode * inode)177 fscrypt_policy_du_bits(const union fscrypt_policy *policy,
178 		       const struct inode *inode)
179 {
180 	switch (policy->version) {
181 	case FSCRYPT_POLICY_V1:
182 		return inode->i_blkbits;
183 	case FSCRYPT_POLICY_V2:
184 		return fscrypt_policy_v2_du_bits(&policy->v2, inode);
185 	}
186 	BUG();
187 }
188 
189 /*
190  * For encrypted symlinks, the ciphertext length is stored at the beginning
191  * of the string in little-endian format.
192  */
193 struct fscrypt_symlink_data {
194 	__le16 len;
195 	char encrypted_path[];
196 } __packed;
197 
198 /**
199  * struct fscrypt_prepared_key - a key prepared for actual encryption/decryption
200  * @tfm: crypto API transform object
201  * @blk_key: key for blk-crypto
202  *
203  * Normally only one of the fields will be non-NULL.
204  */
205 struct fscrypt_prepared_key {
206 	struct crypto_skcipher *tfm;
207 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
208 	struct blk_crypto_key *blk_key;
209 #endif
210 };
211 
212 /*
213  * fscrypt_inode_info - the "encryption key" for an inode
214  *
215  * When an encrypted file's key is made available, an instance of this struct is
216  * allocated and stored in ->i_crypt_info.  Once created, it remains until the
217  * inode is evicted.
218  */
219 struct fscrypt_inode_info {
220 
221 	/* The key in a form prepared for actual encryption/decryption */
222 	struct fscrypt_prepared_key ci_enc_key;
223 
224 	/* True if ci_enc_key should be freed when this struct is freed */
225 	u8 ci_owns_key : 1;
226 
227 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
228 	/*
229 	 * True if this inode will use inline encryption (blk-crypto) instead of
230 	 * the traditional filesystem-layer encryption.
231 	 */
232 	u8 ci_inlinecrypt : 1;
233 #endif
234 
235 	/* True if ci_dirhash_key is initialized */
236 	u8 ci_dirhash_key_initialized : 1;
237 
238 	/*
239 	 * log2 of the data unit size (granularity of contents encryption) of
240 	 * this file.  This is computable from ci_policy and ci_inode but is
241 	 * cached here for efficiency.  Only used for regular files.
242 	 */
243 	u8 ci_data_unit_bits;
244 
245 	/* Cached value: log2 of number of data units per FS block */
246 	u8 ci_data_units_per_block_bits;
247 
248 	/* Hashed inode number.  Only set for IV_INO_LBLK_32 */
249 	u32 ci_hashed_ino;
250 
251 	/*
252 	 * Encryption mode used for this inode.  It corresponds to either the
253 	 * contents or filenames encryption mode, depending on the inode type.
254 	 */
255 	struct fscrypt_mode *ci_mode;
256 
257 	/* Back-pointer to the inode */
258 	struct inode *ci_inode;
259 
260 	/*
261 	 * The master key with which this inode was unlocked (decrypted).  This
262 	 * will be NULL if the master key was found in a process-subscribed
263 	 * keyring rather than in the filesystem-level keyring.
264 	 */
265 	struct fscrypt_master_key *ci_master_key;
266 
267 	/*
268 	 * Link in list of inodes that were unlocked with the master key.
269 	 * Only used when ->ci_master_key is set.
270 	 */
271 	struct list_head ci_master_key_link;
272 
273 	/*
274 	 * If non-NULL, then encryption is done using the master key directly
275 	 * and ci_enc_key will equal ci_direct_key->dk_key.
276 	 */
277 	struct fscrypt_direct_key *ci_direct_key;
278 
279 	/*
280 	 * This inode's hash key for filenames.  This is a 128-bit SipHash-2-4
281 	 * key.  This is only set for directories that use a keyed dirhash over
282 	 * the plaintext filenames -- currently just casefolded directories.
283 	 */
284 	siphash_key_t ci_dirhash_key;
285 
286 	/* The encryption policy used by this inode */
287 	union fscrypt_policy ci_policy;
288 
289 	/* This inode's nonce, copied from the fscrypt_context */
290 	u8 ci_nonce[FSCRYPT_FILE_NONCE_SIZE];
291 };
292 
293 typedef enum {
294 	FS_DECRYPT = 0,
295 	FS_ENCRYPT,
296 } fscrypt_direction_t;
297 
298 /* crypto.c */
299 extern struct kmem_cache *fscrypt_inode_info_cachep;
300 int fscrypt_initialize(struct super_block *sb);
301 int fscrypt_crypt_data_unit(const struct fscrypt_inode_info *ci,
302 			    fscrypt_direction_t rw, u64 index,
303 			    struct page *src_page, struct page *dest_page,
304 			    unsigned int len, unsigned int offs,
305 			    gfp_t gfp_flags);
306 struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags);
307 
308 void __printf(3, 4) __cold
309 fscrypt_msg(const struct inode *inode, const char *level, const char *fmt, ...);
310 
311 #define fscrypt_warn(inode, fmt, ...)		\
312 	fscrypt_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
313 #define fscrypt_err(inode, fmt, ...)		\
314 	fscrypt_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
315 
316 #define FSCRYPT_MAX_IV_SIZE	32
317 
318 union fscrypt_iv {
319 	struct {
320 		/* zero-based index of data unit within the file */
321 		__le64 index;
322 
323 		/* per-file nonce; only set in DIRECT_KEY mode */
324 		u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
325 	};
326 	u8 raw[FSCRYPT_MAX_IV_SIZE];
327 	__le64 dun[FSCRYPT_MAX_IV_SIZE / sizeof(__le64)];
328 };
329 
330 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 index,
331 			 const struct fscrypt_inode_info *ci);
332 
333 /*
334  * Return the number of bits used by the maximum file data unit index that is
335  * possible on the given filesystem, using the given log2 data unit size.
336  */
337 static inline int
fscrypt_max_file_dun_bits(const struct super_block * sb,int du_bits)338 fscrypt_max_file_dun_bits(const struct super_block *sb, int du_bits)
339 {
340 	return fls64(sb->s_maxbytes - 1) - du_bits;
341 }
342 
343 /* fname.c */
344 bool __fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
345 				    u32 orig_len, u32 max_len,
346 				    u32 *encrypted_len_ret);
347 
348 /* hkdf.c */
349 struct fscrypt_hkdf {
350 	struct crypto_shash *hmac_tfm;
351 };
352 
353 int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
354 		      unsigned int master_key_size);
355 
356 /*
357  * The list of contexts in which fscrypt uses HKDF.  These values are used as
358  * the first byte of the HKDF application-specific info string to guarantee that
359  * info strings are never repeated between contexts.  This ensures that all HKDF
360  * outputs are unique and cryptographically isolated, i.e. knowledge of one
361  * output doesn't reveal another.
362  */
363 #define HKDF_CONTEXT_KEY_IDENTIFIER	1 /* info=<empty>		*/
364 #define HKDF_CONTEXT_PER_FILE_ENC_KEY	2 /* info=file_nonce		*/
365 #define HKDF_CONTEXT_DIRECT_KEY		3 /* info=mode_num		*/
366 #define HKDF_CONTEXT_IV_INO_LBLK_64_KEY	4 /* info=mode_num||fs_uuid	*/
367 #define HKDF_CONTEXT_DIRHASH_KEY	5 /* info=file_nonce		*/
368 #define HKDF_CONTEXT_IV_INO_LBLK_32_KEY	6 /* info=mode_num||fs_uuid	*/
369 #define HKDF_CONTEXT_INODE_HASH_KEY	7 /* info=<empty>		*/
370 
371 int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
372 			const u8 *info, unsigned int infolen,
373 			u8 *okm, unsigned int okmlen);
374 
375 void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf);
376 
377 /* inline_crypt.c */
378 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
379 int fscrypt_select_encryption_impl(struct fscrypt_inode_info *ci);
380 
381 static inline bool
fscrypt_using_inline_encryption(const struct fscrypt_inode_info * ci)382 fscrypt_using_inline_encryption(const struct fscrypt_inode_info *ci)
383 {
384 	return ci->ci_inlinecrypt;
385 }
386 
387 int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
388 				     const u8 *raw_key,
389 				     const struct fscrypt_inode_info *ci);
390 
391 void fscrypt_destroy_inline_crypt_key(struct super_block *sb,
392 				      struct fscrypt_prepared_key *prep_key);
393 
394 /*
395  * Check whether the crypto transform or blk-crypto key has been allocated in
396  * @prep_key, depending on which encryption implementation the file will use.
397  */
398 static inline bool
fscrypt_is_key_prepared(struct fscrypt_prepared_key * prep_key,const struct fscrypt_inode_info * ci)399 fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
400 			const struct fscrypt_inode_info *ci)
401 {
402 	/*
403 	 * The two smp_load_acquire()'s here pair with the smp_store_release()'s
404 	 * in fscrypt_prepare_inline_crypt_key() and fscrypt_prepare_key().
405 	 * I.e., in some cases (namely, if this prep_key is a per-mode
406 	 * encryption key) another task can publish blk_key or tfm concurrently,
407 	 * executing a RELEASE barrier.  We need to use smp_load_acquire() here
408 	 * to safely ACQUIRE the memory the other task published.
409 	 */
410 	if (fscrypt_using_inline_encryption(ci))
411 		return smp_load_acquire(&prep_key->blk_key) != NULL;
412 	return smp_load_acquire(&prep_key->tfm) != NULL;
413 }
414 
415 #else /* CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
416 
fscrypt_select_encryption_impl(struct fscrypt_inode_info * ci)417 static inline int fscrypt_select_encryption_impl(struct fscrypt_inode_info *ci)
418 {
419 	return 0;
420 }
421 
422 static inline bool
fscrypt_using_inline_encryption(const struct fscrypt_inode_info * ci)423 fscrypt_using_inline_encryption(const struct fscrypt_inode_info *ci)
424 {
425 	return false;
426 }
427 
428 static inline int
fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key * prep_key,const u8 * raw_key,const struct fscrypt_inode_info * ci)429 fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
430 				 const u8 *raw_key,
431 				 const struct fscrypt_inode_info *ci)
432 {
433 	WARN_ON_ONCE(1);
434 	return -EOPNOTSUPP;
435 }
436 
437 static inline void
fscrypt_destroy_inline_crypt_key(struct super_block * sb,struct fscrypt_prepared_key * prep_key)438 fscrypt_destroy_inline_crypt_key(struct super_block *sb,
439 				 struct fscrypt_prepared_key *prep_key)
440 {
441 }
442 
443 static inline bool
fscrypt_is_key_prepared(struct fscrypt_prepared_key * prep_key,const struct fscrypt_inode_info * ci)444 fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
445 			const struct fscrypt_inode_info *ci)
446 {
447 	return smp_load_acquire(&prep_key->tfm) != NULL;
448 }
449 #endif /* !CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
450 
451 /* keyring.c */
452 
453 /*
454  * fscrypt_master_key_secret - secret key material of an in-use master key
455  */
456 struct fscrypt_master_key_secret {
457 
458 	/*
459 	 * For v2 policy keys: HKDF context keyed by this master key.
460 	 * For v1 policy keys: not set (hkdf.hmac_tfm == NULL).
461 	 */
462 	struct fscrypt_hkdf	hkdf;
463 
464 	/*
465 	 * Size of the raw key in bytes.  This remains set even if ->raw was
466 	 * zeroized due to no longer being needed.  I.e. we still remember the
467 	 * size of the key even if we don't need to remember the key itself.
468 	 */
469 	u32			size;
470 
471 	/* For v1 policy keys: the raw key.  Wiped for v2 policy keys. */
472 	u8			raw[FSCRYPT_MAX_KEY_SIZE];
473 
474 } __randomize_layout;
475 
476 /*
477  * fscrypt_master_key - an in-use master key
478  *
479  * This represents a master encryption key which has been added to the
480  * filesystem.  There are three high-level states that a key can be in:
481  *
482  * FSCRYPT_KEY_STATUS_PRESENT
483  *	Key is fully usable; it can be used to unlock inodes that are encrypted
484  *	with it (this includes being able to create new inodes).  ->mk_present
485  *	indicates whether the key is in this state.  ->mk_secret exists, the key
486  *	is in the keyring, and ->mk_active_refs > 0 due to ->mk_present.
487  *
488  * FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED
489  *	Removal of this key has been initiated, but some inodes that were
490  *	unlocked with it are still in-use.  Like ABSENT, ->mk_secret is wiped,
491  *	and the key can no longer be used to unlock inodes.  Unlike ABSENT, the
492  *	key is still in the keyring; ->mk_decrypted_inodes is nonempty; and
493  *	->mk_active_refs > 0, being equal to the size of ->mk_decrypted_inodes.
494  *
495  *	This state transitions to ABSENT if ->mk_decrypted_inodes becomes empty,
496  *	or to PRESENT if FS_IOC_ADD_ENCRYPTION_KEY is called again for this key.
497  *
498  * FSCRYPT_KEY_STATUS_ABSENT
499  *	Key is fully removed.  The key is no longer in the keyring,
500  *	->mk_decrypted_inodes is empty, ->mk_active_refs == 0, ->mk_secret is
501  *	wiped, and the key can no longer be used to unlock inodes.
502  */
503 struct fscrypt_master_key {
504 
505 	/*
506 	 * Link in ->s_master_keys->key_hashtable.
507 	 * Only valid if ->mk_active_refs > 0.
508 	 */
509 	struct hlist_node			mk_node;
510 
511 	/* Semaphore that protects ->mk_secret, ->mk_users, and ->mk_present */
512 	struct rw_semaphore			mk_sem;
513 
514 	/*
515 	 * Active and structural reference counts.  An active ref guarantees
516 	 * that the struct continues to exist, continues to be in the keyring
517 	 * ->s_master_keys, and that any embedded subkeys (e.g.
518 	 * ->mk_direct_keys) that have been prepared continue to exist.
519 	 * A structural ref only guarantees that the struct continues to exist.
520 	 *
521 	 * There is one active ref associated with ->mk_present being true, and
522 	 * one active ref for each inode in ->mk_decrypted_inodes.
523 	 *
524 	 * There is one structural ref associated with the active refcount being
525 	 * nonzero.  Finding a key in the keyring also takes a structural ref,
526 	 * which is then held temporarily while the key is operated on.
527 	 */
528 	refcount_t				mk_active_refs;
529 	refcount_t				mk_struct_refs;
530 
531 	struct rcu_head				mk_rcu_head;
532 
533 	/*
534 	 * The secret key material.  Wiped as soon as it is no longer needed;
535 	 * for details, see the fscrypt_master_key struct comment.
536 	 *
537 	 * Locking: protected by ->mk_sem.
538 	 */
539 	struct fscrypt_master_key_secret	mk_secret;
540 
541 	/*
542 	 * For v1 policy keys: an arbitrary key descriptor which was assigned by
543 	 * userspace (->descriptor).
544 	 *
545 	 * For v2 policy keys: a cryptographic hash of this key (->identifier).
546 	 */
547 	struct fscrypt_key_specifier		mk_spec;
548 
549 	/*
550 	 * Keyring which contains a key of type 'key_type_fscrypt_user' for each
551 	 * user who has added this key.  Normally each key will be added by just
552 	 * one user, but it's possible that multiple users share a key, and in
553 	 * that case we need to keep track of those users so that one user can't
554 	 * remove the key before the others want it removed too.
555 	 *
556 	 * This is NULL for v1 policy keys; those can only be added by root.
557 	 *
558 	 * Locking: protected by ->mk_sem.  (We don't just rely on the keyrings
559 	 * subsystem semaphore ->mk_users->sem, as we need support for atomic
560 	 * search+insert along with proper synchronization with other fields.)
561 	 */
562 	struct key		*mk_users;
563 
564 	/*
565 	 * List of inodes that were unlocked using this key.  This allows the
566 	 * inodes to be evicted efficiently if the key is removed.
567 	 */
568 	struct list_head	mk_decrypted_inodes;
569 	spinlock_t		mk_decrypted_inodes_lock;
570 
571 	/*
572 	 * Per-mode encryption keys for the various types of encryption policies
573 	 * that use them.  Allocated and derived on-demand.
574 	 */
575 	struct fscrypt_prepared_key mk_direct_keys[FSCRYPT_MODE_MAX + 1];
576 	struct fscrypt_prepared_key mk_iv_ino_lblk_64_keys[FSCRYPT_MODE_MAX + 1];
577 	struct fscrypt_prepared_key mk_iv_ino_lblk_32_keys[FSCRYPT_MODE_MAX + 1];
578 
579 	/* Hash key for inode numbers.  Initialized only when needed. */
580 	siphash_key_t		mk_ino_hash_key;
581 	bool			mk_ino_hash_key_initialized;
582 
583 	/*
584 	 * Whether this key is in the "present" state, i.e. fully usable.  For
585 	 * details, see the fscrypt_master_key struct comment.
586 	 *
587 	 * Locking: protected by ->mk_sem, but can be read locklessly using
588 	 * READ_ONCE().  Writers must use WRITE_ONCE() when concurrent readers
589 	 * are possible.
590 	 */
591 	bool			mk_present;
592 
593 } __randomize_layout;
594 
master_key_spec_type(const struct fscrypt_key_specifier * spec)595 static inline const char *master_key_spec_type(
596 				const struct fscrypt_key_specifier *spec)
597 {
598 	switch (spec->type) {
599 	case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
600 		return "descriptor";
601 	case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
602 		return "identifier";
603 	}
604 	return "[unknown]";
605 }
606 
master_key_spec_len(const struct fscrypt_key_specifier * spec)607 static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
608 {
609 	switch (spec->type) {
610 	case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
611 		return FSCRYPT_KEY_DESCRIPTOR_SIZE;
612 	case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
613 		return FSCRYPT_KEY_IDENTIFIER_SIZE;
614 	}
615 	return 0;
616 }
617 
618 void fscrypt_put_master_key(struct fscrypt_master_key *mk);
619 
620 void fscrypt_put_master_key_activeref(struct super_block *sb,
621 				      struct fscrypt_master_key *mk);
622 
623 struct fscrypt_master_key *
624 fscrypt_find_master_key(struct super_block *sb,
625 			const struct fscrypt_key_specifier *mk_spec);
626 
627 int fscrypt_get_test_dummy_key_identifier(
628 			  u8 key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
629 
630 int fscrypt_add_test_dummy_key(struct super_block *sb,
631 			       struct fscrypt_key_specifier *key_spec);
632 
633 int fscrypt_verify_key_added(struct super_block *sb,
634 			     const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
635 
636 int __init fscrypt_init_keyring(void);
637 
638 /* keysetup.c */
639 
640 struct fscrypt_mode {
641 	const char *friendly_name;
642 	const char *cipher_str;
643 	int keysize;		/* key size in bytes */
644 	int security_strength;	/* security strength in bytes */
645 	int ivsize;		/* IV size in bytes */
646 	int logged_cryptoapi_impl;
647 	int logged_blk_crypto_native;
648 	int logged_blk_crypto_fallback;
649 	enum blk_crypto_mode_num blk_crypto_mode;
650 };
651 
652 extern struct fscrypt_mode fscrypt_modes[];
653 
654 int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key,
655 			const u8 *raw_key, const struct fscrypt_inode_info *ci);
656 
657 void fscrypt_destroy_prepared_key(struct super_block *sb,
658 				  struct fscrypt_prepared_key *prep_key);
659 
660 int fscrypt_set_per_file_enc_key(struct fscrypt_inode_info *ci,
661 				 const u8 *raw_key);
662 
663 int fscrypt_derive_dirhash_key(struct fscrypt_inode_info *ci,
664 			       const struct fscrypt_master_key *mk);
665 
666 void fscrypt_hash_inode_number(struct fscrypt_inode_info *ci,
667 			       const struct fscrypt_master_key *mk);
668 
669 int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported);
670 
671 /**
672  * fscrypt_require_key() - require an inode's encryption key
673  * @inode: the inode we need the key for
674  *
675  * If the inode is encrypted, set up its encryption key if not already done.
676  * Then require that the key be present and return -ENOKEY otherwise.
677  *
678  * No locks are needed, and the key will live as long as the struct inode --- so
679  * it won't go away from under you.
680  *
681  * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
682  * if a problem occurred while setting up the encryption key.
683  */
fscrypt_require_key(struct inode * inode)684 static inline int fscrypt_require_key(struct inode *inode)
685 {
686 	if (IS_ENCRYPTED(inode)) {
687 		int err = fscrypt_get_encryption_info(inode, false);
688 
689 		if (err)
690 			return err;
691 		if (!fscrypt_has_encryption_key(inode))
692 			return -ENOKEY;
693 	}
694 	return 0;
695 }
696 
697 /* keysetup_v1.c */
698 
699 void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
700 
701 int fscrypt_setup_v1_file_key(struct fscrypt_inode_info *ci,
702 			      const u8 *raw_master_key);
703 
704 int fscrypt_setup_v1_file_key_via_subscribed_keyrings(
705 				struct fscrypt_inode_info *ci);
706 
707 /* policy.c */
708 
709 bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
710 			    const union fscrypt_policy *policy2);
711 int fscrypt_policy_to_key_spec(const union fscrypt_policy *policy,
712 			       struct fscrypt_key_specifier *key_spec);
713 const union fscrypt_policy *fscrypt_get_dummy_policy(struct super_block *sb);
714 bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
715 			      const struct inode *inode);
716 int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
717 				const union fscrypt_context *ctx_u,
718 				int ctx_size);
719 const union fscrypt_policy *fscrypt_policy_to_inherit(struct inode *dir);
720 
721 #endif /* _FSCRYPT_PRIVATE_H */
722