fscrypt_private.h

  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 <crypto/sha2.h>
 15#include <linux/fscrypt.h>
 16#include <linux/minmax.h>
 17#include <linux/siphash.h>
 18#include <linux/blk-crypto.h>
 19
 20#define CONST_STRLEN(str)	(sizeof(str) - 1)
 21
 22#define FSCRYPT_FILE_NONCE_SIZE	16
 23
 24/*
 25 * Minimum size of an fscrypt master key.  Note: a longer key will be required
 26 * if ciphers with a 256-bit security strength are used.  This is just the
 27 * absolute minimum, which applies when only 128-bit encryption is used.
 28 */
 29#define FSCRYPT_MIN_KEY_SIZE	16
 30
 31/* Maximum size of a raw fscrypt master key */
 32#define FSCRYPT_MAX_RAW_KEY_SIZE	64
 33
 34/* Maximum size of a hardware-wrapped fscrypt master key */
 35#define FSCRYPT_MAX_HW_WRAPPED_KEY_SIZE	BLK_CRYPTO_MAX_HW_WRAPPED_KEY_SIZE
 36
 37/* Maximum size of an fscrypt master key across both key types */
 38#define FSCRYPT_MAX_ANY_KEY_SIZE \
 39	MAX(FSCRYPT_MAX_RAW_KEY_SIZE, FSCRYPT_MAX_HW_WRAPPED_KEY_SIZE)
 40
 41/*
 42 * FSCRYPT_MAX_KEY_SIZE is defined in the UAPI header, but the addition of
 43 * hardware-wrapped keys has made it misleading as it's only for raw keys.
 44 * Don't use it in kernel code; use one of the above constants instead.
 45 */
 46#undef FSCRYPT_MAX_KEY_SIZE
 47
 48/*
 49 * This mask is passed as the third argument to the crypto_alloc_*() functions
 50 * to prevent fscrypt from using the Crypto API drivers for non-inline crypto
 51 * engines.  Those drivers have been problematic for fscrypt.  fscrypt users
 52 * have reported hangs and even incorrect en/decryption with these drivers.
 53 * Since going to the driver, off CPU, and back again is really slow, such
 54 * drivers can be over 50 times slower than the CPU-based code for fscrypt's
 55 * workload.  Even on platforms that lack AES instructions on the CPU, using the
 56 * offloads has been shown to be slower, even staying with AES.  (Of course,
 57 * Adiantum is faster still, and is the recommended option on such platforms...)
 58 *
 59 * Note that fscrypt also supports inline crypto engines.  Those don't use the
 60 * Crypto API and work much better than the old-style (non-inline) engines.
 61 */
 62#define FSCRYPT_CRYPTOAPI_MASK                            \
 63	(CRYPTO_ALG_ASYNC | CRYPTO_ALG_ALLOCATES_MEMORY | \
 64	 CRYPTO_ALG_KERN_DRIVER_ONLY)
 65
 66#define FSCRYPT_CONTEXT_V1	1
 67#define FSCRYPT_CONTEXT_V2	2
 68
 69/* Keep this in sync with include/uapi/linux/fscrypt.h */
 70#define FSCRYPT_MODE_MAX	FSCRYPT_MODE_AES_256_HCTR2
 71
 72struct fscrypt_context_v1 {
 73	u8 version; /* FSCRYPT_CONTEXT_V1 */
 74	u8 contents_encryption_mode;
 75	u8 filenames_encryption_mode;
 76	u8 flags;
 77	u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
 78	u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
 79};
 80
 81struct fscrypt_context_v2 {
 82	u8 version; /* FSCRYPT_CONTEXT_V2 */
 83	u8 contents_encryption_mode;
 84	u8 filenames_encryption_mode;
 85	u8 flags;
 86	u8 log2_data_unit_size;
 87	u8 __reserved[3];
 88	u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
 89	u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
 90};
 91
 92/*
 93 * fscrypt_context - the encryption context of an inode
 94 *
 95 * This is the on-disk equivalent of an fscrypt_policy, stored alongside each
 96 * encrypted file usually in a hidden extended attribute.  It contains the
 97 * fields from the fscrypt_policy, in order to identify the encryption algorithm
 98 * and key with which the file is encrypted.  It also contains a nonce that was
 99 * randomly generated by fscrypt itself; this is used as KDF input or as a tweak
100 * to cause different files to be encrypted differently.
101 */
102union fscrypt_context {
103	u8 version;
104	struct fscrypt_context_v1 v1;
105	struct fscrypt_context_v2 v2;
106};
107
108/*
109 * Return the size expected for the given fscrypt_context based on its version
110 * number, or 0 if the context version is unrecognized.
111 */
112static inline int fscrypt_context_size(const union fscrypt_context *ctx)
113{
114	switch (ctx->version) {
115	case FSCRYPT_CONTEXT_V1:
116		BUILD_BUG_ON(sizeof(ctx->v1) != 28);
117		return sizeof(ctx->v1);
118	case FSCRYPT_CONTEXT_V2:
119		BUILD_BUG_ON(sizeof(ctx->v2) != 40);
120		return sizeof(ctx->v2);
121	}
122	return 0;
123}
124
125/* Check whether an fscrypt_context has a recognized version number and size */
126static inline bool fscrypt_context_is_valid(const union fscrypt_context *ctx,
127					    int ctx_size)
128{
129	return ctx_size >= 1 && ctx_size == fscrypt_context_size(ctx);
130}
131
132/* Retrieve the context's nonce, assuming the context was already validated */
133static inline const u8 *fscrypt_context_nonce(const union fscrypt_context *ctx)
134{
135	switch (ctx->version) {
136	case FSCRYPT_CONTEXT_V1:
137		return ctx->v1.nonce;
138	case FSCRYPT_CONTEXT_V2:
139		return ctx->v2.nonce;
140	}
141	WARN_ON_ONCE(1);
142	return NULL;
143}
144
145union fscrypt_policy {
146	u8 version;
147	struct fscrypt_policy_v1 v1;
148	struct fscrypt_policy_v2 v2;
149};
150
151/*
152 * Return the size expected for the given fscrypt_policy based on its version
153 * number, or 0 if the policy version is unrecognized.
154 */
155static inline int fscrypt_policy_size(const union fscrypt_policy *policy)
156{
157	switch (policy->version) {
158	case FSCRYPT_POLICY_V1:
159		return sizeof(policy->v1);
160	case FSCRYPT_POLICY_V2:
161		return sizeof(policy->v2);
162	}
163	return 0;
164}
165
166/* Return the contents encryption mode of a valid encryption policy */
167static inline u8
168fscrypt_policy_contents_mode(const union fscrypt_policy *policy)
169{
170	switch (policy->version) {
171	case FSCRYPT_POLICY_V1:
172		return policy->v1.contents_encryption_mode;
173	case FSCRYPT_POLICY_V2:
174		return policy->v2.contents_encryption_mode;
175	}
176	BUG();
177}
178
179/* Return the filenames encryption mode of a valid encryption policy */
180static inline u8
181fscrypt_policy_fnames_mode(const union fscrypt_policy *policy)
182{
183	switch (policy->version) {
184	case FSCRYPT_POLICY_V1:
185		return policy->v1.filenames_encryption_mode;
186	case FSCRYPT_POLICY_V2:
187		return policy->v2.filenames_encryption_mode;
188	}
189	BUG();
190}
191
192/* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */
193static inline u8
194fscrypt_policy_flags(const union fscrypt_policy *policy)
195{
196	switch (policy->version) {
197	case FSCRYPT_POLICY_V1:
198		return policy->v1.flags;
199	case FSCRYPT_POLICY_V2:
200		return policy->v2.flags;
201	}
202	BUG();
203}
204
205static inline int
206fscrypt_policy_v2_du_bits(const struct fscrypt_policy_v2 *policy,
207			  const struct inode *inode)
208{
209	return policy->log2_data_unit_size ?: inode->i_blkbits;
210}
211
212static inline int
213fscrypt_policy_du_bits(const union fscrypt_policy *policy,
214		       const struct inode *inode)
215{
216	switch (policy->version) {
217	case FSCRYPT_POLICY_V1:
218		return inode->i_blkbits;
219	case FSCRYPT_POLICY_V2:
220		return fscrypt_policy_v2_du_bits(&policy->v2, inode);
221	}
222	BUG();
223}
224
225/*
226 * For encrypted symlinks, the ciphertext length is stored at the beginning
227 * of the string in little-endian format.
228 */
229struct fscrypt_symlink_data {
230	__le16 len;
231	char encrypted_path[];
232} __packed;
233
234/**
235 * struct fscrypt_prepared_key - a key prepared for actual encryption/decryption
236 * @tfm: crypto API transform object
237 * @blk_key: key for blk-crypto
238 *
239 * Normally only one of the fields will be non-NULL.
240 */
241struct fscrypt_prepared_key {
242	struct crypto_sync_skcipher *tfm;
243#ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
244	struct blk_crypto_key *blk_key;
245#endif
246};
247
248/*
249 * fscrypt_inode_info - the "encryption key" for an inode
250 *
251 * When an encrypted file's key is made available, an instance of this struct is
252 * allocated and a pointer to it is stored in the file's in-memory inode.  Once
253 * created, it remains until the inode is evicted.
254 */
255struct fscrypt_inode_info {
256
257	/* The key in a form prepared for actual encryption/decryption */
258	struct fscrypt_prepared_key ci_enc_key;
259
260	/* True if ci_enc_key should be freed when this struct is freed */
261	u8 ci_owns_key : 1;
262
263#ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
264	/*
265	 * True if this inode will use inline encryption (blk-crypto) instead of
266	 * the traditional filesystem-layer encryption.
267	 */
268	u8 ci_inlinecrypt : 1;
269#endif
270
271	/* True if ci_dirhash_key is initialized */
272	u8 ci_dirhash_key_initialized : 1;
273
274	/*
275	 * log2 of the data unit size (granularity of contents encryption) of
276	 * this file.  This is computable from ci_policy and ci_inode but is
277	 * cached here for efficiency.  Only used for regular files.
278	 */
279	u8 ci_data_unit_bits;
280
281	/* Cached value: log2 of number of data units per FS block */
282	u8 ci_data_units_per_block_bits;
283
284	/* Hashed inode number.  Only set for IV_INO_LBLK_32 */
285	u32 ci_hashed_ino;
286
287	/*
288	 * Encryption mode used for this inode.  It corresponds to either the
289	 * contents or filenames encryption mode, depending on the inode type.
290	 */
291	struct fscrypt_mode *ci_mode;
292
293	/* Back-pointer to the inode */
294	struct inode *ci_inode;
295
296	/*
297	 * The master key with which this inode was unlocked (decrypted).  This
298	 * will be NULL if the master key was found in a process-subscribed
299	 * keyring rather than in the filesystem-level keyring.
300	 */
301	struct fscrypt_master_key *ci_master_key;
302
303	/*
304	 * Link in list of inodes that were unlocked with the master key.
305	 * Only used when ->ci_master_key is set.
306	 */
307	struct list_head ci_master_key_link;
308
309	/*
310	 * If non-NULL, then encryption is done using the master key directly
311	 * and ci_enc_key will equal ci_direct_key->dk_key.
312	 */
313	struct fscrypt_direct_key *ci_direct_key;
314
315	/*
316	 * This inode's hash key for filenames.  This is a 128-bit SipHash-2-4
317	 * key.  This is only set for directories that use a keyed dirhash over
318	 * the plaintext filenames -- currently just casefolded directories.
319	 */
320	siphash_key_t ci_dirhash_key;
321
322	/* The encryption policy used by this inode */
323	union fscrypt_policy ci_policy;
324
325	/* This inode's nonce, copied from the fscrypt_context */
326	u8 ci_nonce[FSCRYPT_FILE_NONCE_SIZE];
327};
328
329typedef enum {
330	FS_DECRYPT = 0,
331	FS_ENCRYPT,
332} fscrypt_direction_t;
333
334/* crypto.c */
335extern struct kmem_cache *fscrypt_inode_info_cachep;
336int fscrypt_initialize(struct super_block *sb);
337int fscrypt_crypt_data_unit(const struct fscrypt_inode_info *ci,
338			    fscrypt_direction_t rw, u64 index,
339			    struct page *src_page, struct page *dest_page,
340			    unsigned int len, unsigned int offs);
341struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags);
342
343void __printf(3, 4) __cold
344fscrypt_msg(const struct inode *inode, const char *level, const char *fmt, ...);
345
346#define fscrypt_warn(inode, fmt, ...)		\
347	fscrypt_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
348#define fscrypt_err(inode, fmt, ...)		\
349	fscrypt_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
350
351#define FSCRYPT_MAX_IV_SIZE	32
352
353union fscrypt_iv {
354	struct {
355		/* zero-based index of data unit within the file */
356		__le64 index;
357
358		/* per-file nonce; only set in DIRECT_KEY mode */
359		u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
360	};
361	u8 raw[FSCRYPT_MAX_IV_SIZE];
362	__le64 dun[FSCRYPT_MAX_IV_SIZE / sizeof(__le64)];
363};
364
365void fscrypt_generate_iv(union fscrypt_iv *iv, u64 index,
366			 const struct fscrypt_inode_info *ci);
367
368/*
369 * Return the number of bits used by the maximum file data unit index that is
370 * possible on the given filesystem, using the given log2 data unit size.
371 */
372static inline int
373fscrypt_max_file_dun_bits(const struct super_block *sb, int du_bits)
374{
375	return fls64(sb->s_maxbytes - 1) - du_bits;
376}
377
378/* fname.c */
379bool __fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
380				    u32 orig_len, u32 max_len,
381				    u32 *encrypted_len_ret);
382
383/* hkdf.c */
384void fscrypt_init_hkdf(struct hmac_sha512_key *hkdf, const u8 *master_key,
385		       unsigned int master_key_size);
386
387/*
388 * The list of contexts in which fscrypt uses HKDF.  These values are used as
389 * the first byte of the HKDF application-specific info string to guarantee that
390 * info strings are never repeated between contexts.  This ensures that all HKDF
391 * outputs are unique and cryptographically isolated, i.e. knowledge of one
392 * output doesn't reveal another.
393 */
394#define HKDF_CONTEXT_KEY_IDENTIFIER_FOR_RAW_KEY	1 /* info=<empty>	*/
395#define HKDF_CONTEXT_PER_FILE_ENC_KEY	2 /* info=file_nonce		*/
396#define HKDF_CONTEXT_DIRECT_KEY		3 /* info=mode_num		*/
397#define HKDF_CONTEXT_IV_INO_LBLK_64_KEY	4 /* info=mode_num||fs_uuid	*/
398#define HKDF_CONTEXT_DIRHASH_KEY	5 /* info=file_nonce		*/
399#define HKDF_CONTEXT_IV_INO_LBLK_32_KEY	6 /* info=mode_num||fs_uuid	*/
400#define HKDF_CONTEXT_INODE_HASH_KEY	7 /* info=<empty>		*/
401#define HKDF_CONTEXT_KEY_IDENTIFIER_FOR_HW_WRAPPED_KEY \
402					8 /* info=<empty>		*/
403
404void fscrypt_hkdf_expand(const struct hmac_sha512_key *hkdf, u8 context,
405			 const u8 *info, unsigned int infolen,
406			 u8 *okm, unsigned int okmlen);
407
408/* inline_crypt.c */
409#ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
410int fscrypt_select_encryption_impl(struct fscrypt_inode_info *ci,
411				   bool is_hw_wrapped_key);
412
413static inline bool
414fscrypt_using_inline_encryption(const struct fscrypt_inode_info *ci)
415{
416	return ci->ci_inlinecrypt;
417}
418
419int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
420				     const u8 *key_bytes, size_t key_size,
421				     bool is_hw_wrapped,
422				     const struct fscrypt_inode_info *ci);
423
424void fscrypt_destroy_inline_crypt_key(struct super_block *sb,
425				      struct fscrypt_prepared_key *prep_key);
426
427int fscrypt_derive_sw_secret(struct super_block *sb,
428			     const u8 *wrapped_key, size_t wrapped_key_size,
429			     u8 sw_secret[BLK_CRYPTO_SW_SECRET_SIZE]);
430
431/*
432 * Check whether the crypto transform or blk-crypto key has been allocated in
433 * @prep_key, depending on which encryption implementation the file will use.
434 */
435static inline bool
436fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
437			const struct fscrypt_inode_info *ci)
438{
439	/*
440	 * The two smp_load_acquire()'s here pair with the smp_store_release()'s
441	 * in fscrypt_prepare_inline_crypt_key() and fscrypt_prepare_key().
442	 * I.e., in some cases (namely, if this prep_key is a per-mode
443	 * encryption key) another task can publish blk_key or tfm concurrently,
444	 * executing a RELEASE barrier.  We need to use smp_load_acquire() here
445	 * to safely ACQUIRE the memory the other task published.
446	 */
447	if (fscrypt_using_inline_encryption(ci))
448		return smp_load_acquire(&prep_key->blk_key) != NULL;
449	return smp_load_acquire(&prep_key->tfm) != NULL;
450}
451
452#else /* CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
453
454static inline int fscrypt_select_encryption_impl(struct fscrypt_inode_info *ci,
455						 bool is_hw_wrapped_key)
456{
457	return 0;
458}
459
460static inline bool
461fscrypt_using_inline_encryption(const struct fscrypt_inode_info *ci)
462{
463	return false;
464}
465
466static inline int
467fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
468				 const u8 *key_bytes, size_t key_size,
469				 bool is_hw_wrapped,
470				 const struct fscrypt_inode_info *ci)
471{
472	WARN_ON_ONCE(1);
473	return -EOPNOTSUPP;
474}
475
476static inline void
477fscrypt_destroy_inline_crypt_key(struct super_block *sb,
478				 struct fscrypt_prepared_key *prep_key)
479{
480}
481
482static inline int
483fscrypt_derive_sw_secret(struct super_block *sb,
484			 const u8 *wrapped_key, size_t wrapped_key_size,
485			 u8 sw_secret[BLK_CRYPTO_SW_SECRET_SIZE])
486{
487	fscrypt_warn(NULL, "kernel doesn't support hardware-wrapped keys");
488	return -EOPNOTSUPP;
489}
490
491static inline bool
492fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
493			const struct fscrypt_inode_info *ci)
494{
495	return smp_load_acquire(&prep_key->tfm) != NULL;
496}
497#endif /* !CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
498
499/* keyring.c */
500
501/*
502 * fscrypt_master_key_secret - secret key material of an in-use master key
503 */
504struct fscrypt_master_key_secret {
505
506	/*
507	 * The KDF with which subkeys of this key can be derived.
508	 *
509	 * For v1 policy keys, this isn't applicable and won't be set.
510	 * Otherwise, this KDF will be keyed by this master key if
511	 * ->is_hw_wrapped=false, or by the "software secret" that hardware
512	 * derived from this master key if ->is_hw_wrapped=true.
513	 */
514	struct hmac_sha512_key	hkdf;
515
516	/*
517	 * True if this key is a hardware-wrapped key; false if this key is a
518	 * raw key (i.e. a "software key").  For v1 policy keys this will always
519	 * be false, as v1 policy support is a legacy feature which doesn't
520	 * support newer functionality such as hardware-wrapped keys.
521	 */
522	bool			is_hw_wrapped;
523
524	/*
525	 * Size of the key in bytes.  This remains set even if ->bytes was
526	 * zeroized due to no longer being needed.  I.e. we still remember the
527	 * size of the key even if we don't need to remember the key itself.
528	 */
529	u32			size;
530
531	/*
532	 * The bytes of the key, when still needed.  This can be either a raw
533	 * key or a hardware-wrapped key, as indicated by ->is_hw_wrapped.  In
534	 * the case of a raw, v2 policy key, there is no need to remember the
535	 * actual key separately from ->hkdf so this field will be zeroized as
536	 * soon as ->hkdf is initialized.
537	 */
538	u8			bytes[FSCRYPT_MAX_ANY_KEY_SIZE];
539
540} __randomize_layout;
541
542/*
543 * fscrypt_master_key - an in-use master key
544 *
545 * This represents a master encryption key which has been added to the
546 * filesystem.  There are three high-level states that a key can be in:
547 *
548 * FSCRYPT_KEY_STATUS_PRESENT
549 *	Key is fully usable; it can be used to unlock inodes that are encrypted
550 *	with it (this includes being able to create new inodes).  ->mk_present
551 *	indicates whether the key is in this state.  ->mk_secret exists, the key
552 *	is in the keyring, and ->mk_active_refs > 0 due to ->mk_present.
553 *
554 * FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED
555 *	Removal of this key has been initiated, but some inodes that were
556 *	unlocked with it are still in-use.  Like ABSENT, ->mk_secret is wiped,
557 *	and the key can no longer be used to unlock inodes.  Unlike ABSENT, the
558 *	key is still in the keyring; ->mk_decrypted_inodes is nonempty; and
559 *	->mk_active_refs > 0, being equal to the size of ->mk_decrypted_inodes.
560 *
561 *	This state transitions to ABSENT if ->mk_decrypted_inodes becomes empty,
562 *	or to PRESENT if FS_IOC_ADD_ENCRYPTION_KEY is called again for this key.
563 *
564 * FSCRYPT_KEY_STATUS_ABSENT
565 *	Key is fully removed.  The key is no longer in the keyring,
566 *	->mk_decrypted_inodes is empty, ->mk_active_refs == 0, ->mk_secret is
567 *	wiped, and the key can no longer be used to unlock inodes.
568 */
569struct fscrypt_master_key {
570
571	/*
572	 * Link in ->s_master_keys->key_hashtable.
573	 * Only valid if ->mk_active_refs > 0.
574	 */
575	struct hlist_node			mk_node;
576
577	/* Semaphore that protects ->mk_secret, ->mk_users, and ->mk_present */
578	struct rw_semaphore			mk_sem;
579
580	/*
581	 * Active and structural reference counts.  An active ref guarantees
582	 * that the struct continues to exist, continues to be in the keyring
583	 * ->s_master_keys, and that any embedded subkeys (e.g.
584	 * ->mk_direct_keys) that have been prepared continue to exist.
585	 * A structural ref only guarantees that the struct continues to exist.
586	 *
587	 * There is one active ref associated with ->mk_present being true, and
588	 * one active ref for each inode in ->mk_decrypted_inodes.
589	 *
590	 * There is one structural ref associated with the active refcount being
591	 * nonzero.  Finding a key in the keyring also takes a structural ref,
592	 * which is then held temporarily while the key is operated on.
593	 */
594	refcount_t				mk_active_refs;
595	refcount_t				mk_struct_refs;
596
597	struct rcu_head				mk_rcu_head;
598
599	/*
600	 * The secret key material.  Wiped as soon as it is no longer needed;
601	 * for details, see the fscrypt_master_key struct comment.
602	 *
603	 * Locking: protected by ->mk_sem.
604	 */
605	struct fscrypt_master_key_secret	mk_secret;
606
607	/*
608	 * For v1 policy keys: an arbitrary key descriptor which was assigned by
609	 * userspace (->descriptor).
610	 *
611	 * For v2 policy keys: a cryptographic hash of this key (->identifier).
612	 */
613	struct fscrypt_key_specifier		mk_spec;
614
615	/*
616	 * Keyring which contains a key of type 'key_type_fscrypt_user' for each
617	 * user who has added this key.  Normally each key will be added by just
618	 * one user, but it's possible that multiple users share a key, and in
619	 * that case we need to keep track of those users so that one user can't
620	 * remove the key before the others want it removed too.
621	 *
622	 * This is NULL for v1 policy keys; those can only be added by root.
623	 *
624	 * Locking: protected by ->mk_sem.  (We don't just rely on the keyrings
625	 * subsystem semaphore ->mk_users->sem, as we need support for atomic
626	 * search+insert along with proper synchronization with other fields.)
627	 */
628	struct key		*mk_users;
629
630	/*
631	 * List of inodes that were unlocked using this key.  This allows the
632	 * inodes to be evicted efficiently if the key is removed.
633	 */
634	struct list_head	mk_decrypted_inodes;
635	spinlock_t		mk_decrypted_inodes_lock;
636
637	/*
638	 * Per-mode encryption keys for the various types of encryption policies
639	 * that use them.  Allocated and derived on-demand.
640	 */
641	struct fscrypt_prepared_key mk_direct_keys[FSCRYPT_MODE_MAX + 1];
642	struct fscrypt_prepared_key mk_iv_ino_lblk_64_keys[FSCRYPT_MODE_MAX + 1];
643	struct fscrypt_prepared_key mk_iv_ino_lblk_32_keys[FSCRYPT_MODE_MAX + 1];
644
645	/* Hash key for inode numbers.  Initialized only when needed. */
646	siphash_key_t		mk_ino_hash_key;
647	bool			mk_ino_hash_key_initialized;
648
649	/*
650	 * Whether this key is in the "present" state, i.e. fully usable.  For
651	 * details, see the fscrypt_master_key struct comment.
652	 *
653	 * Locking: protected by ->mk_sem, but can be read locklessly using
654	 * READ_ONCE().  Writers must use WRITE_ONCE() when concurrent readers
655	 * are possible.
656	 */
657	bool			mk_present;
658
659} __randomize_layout;
660
661static inline const char *master_key_spec_type(
662				const struct fscrypt_key_specifier *spec)
663{
664	switch (spec->type) {
665	case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
666		return "descriptor";
667	case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
668		return "identifier";
669	}
670	return "[unknown]";
671}
672
673static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
674{
675	switch (spec->type) {
676	case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
677		return FSCRYPT_KEY_DESCRIPTOR_SIZE;
678	case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
679		return FSCRYPT_KEY_IDENTIFIER_SIZE;
680	}
681	return 0;
682}
683
684void fscrypt_put_master_key(struct fscrypt_master_key *mk);
685
686void fscrypt_put_master_key_activeref(struct super_block *sb,
687				      struct fscrypt_master_key *mk);
688
689struct fscrypt_master_key *
690fscrypt_find_master_key(struct super_block *sb,
691			const struct fscrypt_key_specifier *mk_spec);
692
693void fscrypt_get_test_dummy_key_identifier(
694			  u8 key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
695
696int fscrypt_add_test_dummy_key(struct super_block *sb,
697			       struct fscrypt_key_specifier *key_spec);
698
699int fscrypt_verify_key_added(struct super_block *sb,
700			     const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
701
702int __init fscrypt_init_keyring(void);
703
704/* keysetup.c */
705
706struct fscrypt_mode {
707	const char *friendly_name;
708	const char *cipher_str;
709	int keysize;		/* key size in bytes */
710	int security_strength;	/* security strength in bytes */
711	int ivsize;		/* IV size in bytes */
712	int logged_cryptoapi_impl;
713	int logged_blk_crypto_native;
714	int logged_blk_crypto_fallback;
715	enum blk_crypto_mode_num blk_crypto_mode;
716};
717
718extern struct fscrypt_mode fscrypt_modes[];
719
720int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key,
721			const u8 *raw_key, const struct fscrypt_inode_info *ci);
722
723void fscrypt_destroy_prepared_key(struct super_block *sb,
724				  struct fscrypt_prepared_key *prep_key);
725
726int fscrypt_set_per_file_enc_key(struct fscrypt_inode_info *ci,
727				 const u8 *raw_key);
728
729void fscrypt_derive_dirhash_key(struct fscrypt_inode_info *ci,
730				const struct fscrypt_master_key *mk);
731
732void fscrypt_hash_inode_number(struct fscrypt_inode_info *ci,
733			       const struct fscrypt_master_key *mk);
734
735int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported);
736
737/**
738 * fscrypt_require_key() - require an inode's encryption key
739 * @inode: the inode we need the key for
740 *
741 * If the inode is encrypted, set up its encryption key if not already done.
742 * Then require that the key be present and return -ENOKEY otherwise.
743 *
744 * No locks are needed, and the key will live as long as the struct inode --- so
745 * it won't go away from under you.
746 *
747 * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
748 * if a problem occurred while setting up the encryption key.
749 */
750static inline int fscrypt_require_key(struct inode *inode)
751{
752	if (IS_ENCRYPTED(inode)) {
753		int err = fscrypt_get_encryption_info(inode, false);
754
755		if (err)
756			return err;
757		if (!fscrypt_has_encryption_key(inode))
758			return -ENOKEY;
759	}
760	return 0;
761}
762
763/* keysetup_v1.c */
764
765void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
766
767int fscrypt_setup_v1_file_key(struct fscrypt_inode_info *ci,
768			      const u8 *raw_master_key);
769
770int fscrypt_setup_v1_file_key_via_subscribed_keyrings(
771				struct fscrypt_inode_info *ci);
772
773/* policy.c */
774
775bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
776			    const union fscrypt_policy *policy2);
777int fscrypt_policy_to_key_spec(const union fscrypt_policy *policy,
778			       struct fscrypt_key_specifier *key_spec);
779const union fscrypt_policy *fscrypt_get_dummy_policy(struct super_block *sb);
780bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
781			      const struct inode *inode);
782int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
783				const union fscrypt_context *ctx_u,
784				int ctx_size);
785const union fscrypt_policy *fscrypt_policy_to_inherit(struct inode *dir);
786
787#endif /* _FSCRYPT_PRIVATE_H */