aboutsummaryrefslogtreecommitdiff
path: root/include/linux/fscrypt.h
blob: f622f7460ed8c6463871bad6c8713ace10a14614 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
/* SPDX-License-Identifier: GPL-2.0 */
/*
 * fscrypt.h: declarations for per-file encryption
 *
 * Filesystems that implement per-file encryption must include this header
 * file.
 *
 * Copyright (C) 2015, Google, Inc.
 *
 * Written by Michael Halcrow, 2015.
 * Modified by Jaegeuk Kim, 2015.
 */
#ifndef _LINUX_FSCRYPT_H
#define _LINUX_FSCRYPT_H

#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <uapi/linux/fscrypt.h>

#define FS_CRYPTO_BLOCK_SIZE		16

struct fscrypt_ctx;
struct fscrypt_info;

struct fscrypt_str {
	unsigned char *name;
	u32 len;
};

struct fscrypt_name {
	const struct qstr *usr_fname;
	struct fscrypt_str disk_name;
	u32 hash;
	u32 minor_hash;
	struct fscrypt_str crypto_buf;
	bool is_ciphertext_name;
};

#define FSTR_INIT(n, l)		{ .name = n, .len = l }
#define FSTR_TO_QSTR(f)		QSTR_INIT((f)->name, (f)->len)
#define fname_name(p)		((p)->disk_name.name)
#define fname_len(p)		((p)->disk_name.len)

/* Maximum value for the third parameter of fscrypt_operations.set_context(). */
#define FSCRYPT_SET_CONTEXT_MAX_SIZE	40

#ifdef CONFIG_FS_ENCRYPTION
/*
 * fscrypt superblock flags
 */
#define FS_CFLG_OWN_PAGES (1U << 1)

/*
 * crypto operations for filesystems
 */
struct fscrypt_operations {
	unsigned int flags;
	const char *key_prefix;
	int (*get_context)(struct inode *, void *, size_t);
	int (*set_context)(struct inode *, const void *, size_t, void *);
	bool (*dummy_context)(struct inode *);
	bool (*empty_dir)(struct inode *);
	unsigned int max_namelen;
};

/* Decryption work */
struct fscrypt_ctx {
	union {
		struct {
			struct bio *bio;
			struct work_struct work;
		};
		struct list_head free_list;	/* Free list */
	};
	u8 flags;				/* Flags */
};

static inline bool fscrypt_has_encryption_key(const struct inode *inode)
{
	/* pairs with cmpxchg_release() in fscrypt_get_encryption_info() */
	return READ_ONCE(inode->i_crypt_info) != NULL;
}

static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
{
	return inode->i_sb->s_cop->dummy_context &&
		inode->i_sb->s_cop->dummy_context(inode);
}

/*
 * When d_splice_alias() moves a directory's encrypted alias to its decrypted
 * alias as a result of the encryption key being added, DCACHE_ENCRYPTED_NAME
 * must be cleared.  Note that we don't have to support arbitrary moves of this
 * flag because fscrypt doesn't allow encrypted aliases to be the source or
 * target of a rename().
 */
static inline void fscrypt_handle_d_move(struct dentry *dentry)
{
	dentry->d_flags &= ~DCACHE_ENCRYPTED_NAME;
}

/* crypto.c */
extern void fscrypt_enqueue_decrypt_work(struct work_struct *);
extern struct fscrypt_ctx *fscrypt_get_ctx(gfp_t);
extern void fscrypt_release_ctx(struct fscrypt_ctx *);

extern struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
						     unsigned int len,
						     unsigned int offs,
						     gfp_t gfp_flags);
extern int fscrypt_encrypt_block_inplace(const struct inode *inode,
					 struct page *page, unsigned int len,
					 unsigned int offs, u64 lblk_num,
					 gfp_t gfp_flags);

extern int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len,
					    unsigned int offs);
extern int fscrypt_decrypt_block_inplace(const struct inode *inode,
					 struct page *page, unsigned int len,
					 unsigned int offs, u64 lblk_num);

static inline bool fscrypt_is_bounce_page(struct page *page)
{
	return page->mapping == NULL;
}

static inline struct page *fscrypt_pagecache_page(struct page *bounce_page)
{
	return (struct page *)page_private(bounce_page);
}

extern void fscrypt_free_bounce_page(struct page *bounce_page);

/* policy.c */
extern int fscrypt_ioctl_set_policy(struct file *, const void __user *);
extern int fscrypt_ioctl_get_policy(struct file *, void __user *);
extern int fscrypt_ioctl_get_policy_ex(struct file *, void __user *);
extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
extern int fscrypt_inherit_context(struct inode *, struct inode *,
					void *, bool);
/* keyring.c */
extern void fscrypt_sb_free(struct super_block *sb);
extern int fscrypt_ioctl_add_key(struct file *filp, void __user *arg);
extern int fscrypt_ioctl_remove_key(struct file *filp, void __user *arg);
extern int fscrypt_ioctl_remove_key_all_users(struct file *filp,
					      void __user *arg);
extern int fscrypt_ioctl_get_key_status(struct file *filp, void __user *arg);

/* keysetup.c */
extern int fscrypt_get_encryption_info(struct inode *);
extern void fscrypt_put_encryption_info(struct inode *);
extern void fscrypt_free_inode(struct inode *);
extern int fscrypt_drop_inode(struct inode *inode);

/* fname.c */
extern int fscrypt_setup_filename(struct inode *, const struct qstr *,
				int lookup, struct fscrypt_name *);

static inline void fscrypt_free_filename(struct fscrypt_name *fname)
{
	kfree(fname->crypto_buf.name);
}

extern int fscrypt_fname_alloc_buffer(const struct inode *, u32,
				struct fscrypt_str *);
extern void fscrypt_fname_free_buffer(struct fscrypt_str *);
extern int fscrypt_fname_disk_to_usr(struct inode *, u32, u32,
			const struct fscrypt_str *, struct fscrypt_str *);

#define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE	32

/* Extracts the second-to-last ciphertext block; see explanation below */
#define FSCRYPT_FNAME_DIGEST(name, len)	\
	((name) + round_down((len) - FS_CRYPTO_BLOCK_SIZE - 1, \
			     FS_CRYPTO_BLOCK_SIZE))

#define FSCRYPT_FNAME_DIGEST_SIZE	FS_CRYPTO_BLOCK_SIZE

/**
 * fscrypt_digested_name - alternate identifier for an on-disk filename
 *
 * When userspace lists an encrypted directory without access to the key,
 * filenames whose ciphertext is longer than FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE
 * bytes are shown in this abbreviated form (base64-encoded) rather than as the
 * full ciphertext (base64-encoded).  This is necessary to allow supporting
 * filenames up to NAME_MAX bytes, since base64 encoding expands the length.
 *
 * To make it possible for filesystems to still find the correct directory entry
 * despite not knowing the full on-disk name, we encode any filesystem-specific
 * 'hash' and/or 'minor_hash' which the filesystem may need for its lookups,
 * followed by the second-to-last ciphertext block of the filename.  Due to the
 * use of the CBC-CTS encryption mode, the second-to-last ciphertext block
 * depends on the full plaintext.  (Note that ciphertext stealing causes the
 * last two blocks to appear "flipped".)  This makes accidental collisions very
 * unlikely: just a 1 in 2^128 chance for two filenames to collide even if they
 * share the same filesystem-specific hashes.
 *
 * However, this scheme isn't immune to intentional collisions, which can be
 * created by anyone able to create arbitrary plaintext filenames and view them
 * without the key.  Making the "digest" be a real cryptographic hash like
 * SHA-256 over the full ciphertext would prevent this, although it would be
 * less efficient and harder to implement, especially since the filesystem would
 * need to calculate it for each directory entry examined during a search.
 */
struct fscrypt_digested_name {
	u32 hash;
	u32 minor_hash;
	u8 digest[FSCRYPT_FNAME_DIGEST_SIZE];
};

/**
 * fscrypt_match_name() - test whether the given name matches a directory entry
 * @fname: the name being searched for
 * @de_name: the name from the directory entry
 * @de_name_len: the length of @de_name in bytes
 *
 * Normally @fname->disk_name will be set, and in that case we simply compare
 * that to the name stored in the directory entry.  The only exception is that
 * if we don't have the key for an encrypted directory and a filename in it is
 * very long, then we won't have the full disk_name and we'll instead need to
 * match against the fscrypt_digested_name.
 *
 * Return: %true if the name matches, otherwise %false.
 */
static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
				      const u8 *de_name, u32 de_name_len)
{
	if (unlikely(!fname->disk_name.name)) {
		const struct fscrypt_digested_name *n =
			(const void *)fname->crypto_buf.name;
		if (WARN_ON_ONCE(fname->usr_fname->name[0] != '_'))
			return false;
		if (de_name_len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE)
			return false;
		return !memcmp(FSCRYPT_FNAME_DIGEST(de_name, de_name_len),
			       n->digest, FSCRYPT_FNAME_DIGEST_SIZE);
	}

	if (de_name_len != fname->disk_name.len)
		return false;
	return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len);
}

/* bio.c */
extern void fscrypt_decrypt_bio(struct bio *);
extern void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx,
					struct bio *bio);
extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t,
				 unsigned int);

/* hooks.c */
extern int fscrypt_file_open(struct inode *inode, struct file *filp);
extern int __fscrypt_prepare_link(struct inode *inode, struct inode *dir,
				  struct dentry *dentry);
extern int __fscrypt_prepare_rename(struct inode *old_dir,
				    struct dentry *old_dentry,
				    struct inode *new_dir,
				    struct dentry *new_dentry,
				    unsigned int flags);
extern int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry,
				    struct fscrypt_name *fname);
extern int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len,
				     unsigned int max_len,
				     struct fscrypt_str *disk_link);
extern int __fscrypt_encrypt_symlink(struct inode *inode, const char *target,
				     unsigned int len,
				     struct fscrypt_str *disk_link);
extern const char *fscrypt_get_symlink(struct inode *inode, const void *caddr,
				       unsigned int max_size,
				       struct delayed_call *done);
static inline void fscrypt_set_ops(struct super_block *sb,
				   const struct fscrypt_operations *s_cop)
{
	sb->s_cop = s_cop;
}
#else  /* !CONFIG_FS_ENCRYPTION */

static inline bool fscrypt_has_encryption_key(const struct inode *inode)
{
	return false;
}

static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
{
	return false;
}

static inline void fscrypt_handle_d_move(struct dentry *dentry)
{
}

/* crypto.c */
static inline void fscrypt_enqueue_decrypt_work(struct work_struct *work)
{
}

static inline struct fscrypt_ctx *fscrypt_get_ctx(gfp_t gfp_flags)
{
	return ERR_PTR(-EOPNOTSUPP);
}

static inline void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
{
	return;
}

static inline struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
							    unsigned int len,
							    unsigned int offs,
							    gfp_t gfp_flags)
{
	return ERR_PTR(-EOPNOTSUPP);
}

static inline int fscrypt_encrypt_block_inplace(const struct inode *inode,
						struct page *page,
						unsigned int len,
						unsigned int offs, u64 lblk_num,
						gfp_t gfp_flags)
{
	return -EOPNOTSUPP;
}

static inline int fscrypt_decrypt_pagecache_blocks(struct page *page,
						   unsigned int len,
						   unsigned int offs)
{
	return -EOPNOTSUPP;
}

static inline int fscrypt_decrypt_block_inplace(const struct inode *inode,
						struct page *page,
						unsigned int len,
						unsigned int offs, u64 lblk_num)
{
	return -EOPNOTSUPP;
}

static inline bool fscrypt_is_bounce_page(struct page *page)
{
	return false;
}

static inline struct page *fscrypt_pagecache_page(struct page *bounce_page)
{
	WARN_ON_ONCE(1);
	return ERR_PTR(-EINVAL);
}

static inline void fscrypt_free_bounce_page(struct page *bounce_page)
{
}

/* policy.c */
static inline int fscrypt_ioctl_set_policy(struct file *filp,
					   const void __user *arg)
{
	return -EOPNOTSUPP;
}

static inline int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
{
	return -EOPNOTSUPP;
}

static inline int fscrypt_ioctl_get_policy_ex(struct file *filp,
					      void __user *arg)
{
	return -EOPNOTSUPP;
}

static inline int fscrypt_has_permitted_context(struct inode *parent,
						struct inode *child)
{
	return 0;
}

static inline int fscrypt_inherit_context(struct inode *parent,
					  struct inode *child,
					  void *fs_data, bool preload)
{
	return -EOPNOTSUPP;
}

/* keyring.c */
static inline void fscrypt_sb_free(struct super_block *sb)
{
}

static inline int fscrypt_ioctl_add_key(struct file *filp, void __user *arg)
{
	return -EOPNOTSUPP;
}

static inline int fscrypt_ioctl_remove_key(struct file *filp, void __user *arg)
{
	return -EOPNOTSUPP;
}

static inline int fscrypt_ioctl_remove_key_all_users(struct file *filp,
						     void __user *arg)
{
	return -EOPNOTSUPP;
}

static inline int fscrypt_ioctl_get_key_status(struct file *filp,
					       void __user *arg)
{
	return -EOPNOTSUPP;
}

/* keysetup.c */
static inline int fscrypt_get_encryption_info(struct inode *inode)
{
	return -EOPNOTSUPP;
}

static inline void fscrypt_put_encryption_info(struct inode *inode)
{
	return;
}

static inline void fscrypt_free_inode(struct inode *inode)
{
}

static inline int fscrypt_drop_inode(struct inode *inode)
{
	return 0;
}

 /* fname.c */
static inline int fscrypt_setup_filename(struct inode *dir,
					 const struct qstr *iname,
					 int lookup, struct fscrypt_name *fname)
{
	if (IS_ENCRYPTED(dir))
		return -EOPNOTSUPP;

	memset(fname, 0, sizeof(*fname));
	fname->usr_fname = iname;
	fname->disk_name.name = (unsigned char *)iname->name;
	fname->disk_name.len = iname->len;
	return 0;
}

static inline void fscrypt_free_filename(struct fscrypt_name *fname)
{
	return;
}

static inline int fscrypt_fname_alloc_buffer(const struct inode *inode,
					     u32 max_encrypted_len,
					     struct fscrypt_str *crypto_str)
{
	return -EOPNOTSUPP;
}

static inline void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
{
	return;
}

static inline int fscrypt_fname_disk_to_usr(struct inode *inode,
					    u32 hash, u32 minor_hash,
					    const struct fscrypt_str *iname,
					    struct fscrypt_str *oname)
{
	return -EOPNOTSUPP;
}

static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
				      const u8 *de_name, u32 de_name_len)
{
	/* Encryption support disabled; use standard comparison */
	if (de_name_len != fname->disk_name.len)
		return false;
	return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len);
}

/* bio.c */
static inline void fscrypt_decrypt_bio(struct bio *bio)
{
}

static inline void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx,
					       struct bio *bio)
{
}

static inline int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
					sector_t pblk, unsigned int len)
{
	return -EOPNOTSUPP;
}

/* hooks.c */

static inline int fscrypt_file_open(struct inode *inode, struct file *filp)
{
	if (IS_ENCRYPTED(inode))
		return -EOPNOTSUPP;
	return 0;
}

static inline int __fscrypt_prepare_link(struct inode *inode, struct inode *dir,
					 struct dentry *dentry)
{
	return -EOPNOTSUPP;
}

static inline int __fscrypt_prepare_rename(struct inode *old_dir,
					   struct dentry *old_dentry,
					   struct inode *new_dir,
					   struct dentry *new_dentry,
					   unsigned int flags)
{
	return -EOPNOTSUPP;
}

static inline int __fscrypt_prepare_lookup(struct inode *dir,
					   struct dentry *dentry,
					   struct fscrypt_name *fname)
{
	return -EOPNOTSUPP;
}

static inline int __fscrypt_prepare_symlink(struct inode *dir,
					    unsigned int len,
					    unsigned int max_len,
					    struct fscrypt_str *disk_link)
{
	return -EOPNOTSUPP;
}


static inline int __fscrypt_encrypt_symlink(struct inode *inode,
					    const char *target,
					    unsigned int len,
					    struct fscrypt_str *disk_link)
{
	return -EOPNOTSUPP;
}

static inline const char *fscrypt_get_symlink(struct inode *inode,
					      const void *caddr,
					      unsigned int max_size,
					      struct delayed_call *done)
{
	return ERR_PTR(-EOPNOTSUPP);
}

static inline void fscrypt_set_ops(struct super_block *sb,
				   const struct fscrypt_operations *s_cop)
{
}

#endif	/* !CONFIG_FS_ENCRYPTION */

/**
 * fscrypt_require_key - require an inode's encryption key
 * @inode: the inode we need the key for
 *
 * If the inode is encrypted, set up its encryption key if not already done.
 * Then require that the key be present and return -ENOKEY otherwise.
 *
 * No locks are needed, and the key will live as long as the struct inode --- so
 * it won't go away from under you.
 *
 * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
 * if a problem occurred while setting up the encryption key.
 */
static inline int fscrypt_require_key(struct inode *inode)
{
	if (IS_ENCRYPTED(inode)) {
		int err = fscrypt_get_encryption_info(inode);

		if (err)
			return err;
		if (!fscrypt_has_encryption_key(inode))
			return -ENOKEY;
	}
	return 0;
}

/**
 * fscrypt_prepare_link - prepare to link an inode into a possibly-encrypted directory
 * @old_dentry: an existing dentry for the inode being linked
 * @dir: the target directory
 * @dentry: negative dentry for the target filename
 *
 * A new link can only be added to an encrypted directory if the directory's
 * encryption key is available --- since otherwise we'd have no way to encrypt
 * the filename.  Therefore, we first set up the directory's encryption key (if
 * not already done) and return an error if it's unavailable.
 *
 * We also verify that the link will not violate the constraint that all files
 * in an encrypted directory tree use the same encryption policy.
 *
 * Return: 0 on success, -ENOKEY if the directory's encryption key is missing,
 * -EXDEV if the link would result in an inconsistent encryption policy, or
 * another -errno code.
 */
static inline int fscrypt_prepare_link(struct dentry *old_dentry,
				       struct inode *dir,
				       struct dentry *dentry)
{
	if (IS_ENCRYPTED(dir))
		return __fscrypt_prepare_link(d_inode(old_dentry), dir, dentry);
	return 0;
}

/**
 * fscrypt_prepare_rename - prepare for a rename between possibly-encrypted directories
 * @old_dir: source directory
 * @old_dentry: dentry for source file
 * @new_dir: target directory
 * @new_dentry: dentry for target location (may be negative unless exchanging)
 * @flags: rename flags (we care at least about %RENAME_EXCHANGE)
 *
 * Prepare for ->rename() where the source and/or target directories may be
 * encrypted.  A new link can only be added to an encrypted directory if the
 * directory's encryption key is available --- since otherwise we'd have no way
 * to encrypt the filename.  A rename to an existing name, on the other hand,
 * *is* cryptographically possible without the key.  However, we take the more
 * conservative approach and just forbid all no-key renames.
 *
 * We also verify that the rename will not violate the constraint that all files
 * in an encrypted directory tree use the same encryption policy.
 *
 * Return: 0 on success, -ENOKEY if an encryption key is missing, -EXDEV if the
 * rename would cause inconsistent encryption policies, or another -errno code.
 */
static inline int fscrypt_prepare_rename(struct inode *old_dir,
					 struct dentry *old_dentry,
					 struct inode *new_dir,
					 struct dentry *new_dentry,
					 unsigned int flags)
{
	if (IS_ENCRYPTED(old_dir) || IS_ENCRYPTED(new_dir))
		return __fscrypt_prepare_rename(old_dir, old_dentry,
						new_dir, new_dentry, flags);
	return 0;
}

/**
 * fscrypt_prepare_lookup - prepare to lookup a name in a possibly-encrypted directory
 * @dir: directory being searched
 * @dentry: filename being looked up
 * @fname: (output) the name to use to search the on-disk directory
 *
 * Prepare for ->lookup() in a directory which may be encrypted by determining
 * the name that will actually be used to search the directory on-disk.  Lookups
 * can be done with or without the directory's encryption key; without the key,
 * filenames are presented in encrypted form.  Therefore, we'll try to set up
 * the directory's encryption key, but even without it the lookup can continue.
 *
 * This also installs a custom ->d_revalidate() method which will invalidate the
 * dentry if it was created without the key and the key is later added.
 *
 * Return: 0 on success; -ENOENT if key is unavailable but the filename isn't a
 * correctly formed encoded ciphertext name, so a negative dentry should be
 * created; or another -errno code.
 */
static inline int fscrypt_prepare_lookup(struct inode *dir,
					 struct dentry *dentry,
					 struct fscrypt_name *fname)
{
	if (IS_ENCRYPTED(dir))
		return __fscrypt_prepare_lookup(dir, dentry, fname);

	memset(fname, 0, sizeof(*fname));
	fname->usr_fname = &dentry->d_name;
	fname->disk_name.name = (unsigned char *)dentry->d_name.name;
	fname->disk_name.len = dentry->d_name.len;
	return 0;
}

/**
 * fscrypt_prepare_setattr - prepare to change a possibly-encrypted inode's attributes
 * @dentry: dentry through which the inode is being changed
 * @attr: attributes to change
 *
 * Prepare for ->setattr() on a possibly-encrypted inode.  On an encrypted file,
 * most attribute changes are allowed even without the encryption key.  However,
 * without the encryption key we do have to forbid truncates.  This is needed
 * because the size being truncated to may not be a multiple of the filesystem
 * block size, and in that case we'd have to decrypt the final block, zero the
 * portion past i_size, and re-encrypt it.  (We *could* allow truncating to a
 * filesystem block boundary, but it's simpler to just forbid all truncates ---
 * and we already forbid all other contents modifications without the key.)
 *
 * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
 * if a problem occurred while setting up the encryption key.
 */
static inline int fscrypt_prepare_setattr(struct dentry *dentry,
					  struct iattr *attr)
{
	if (attr->ia_valid & ATTR_SIZE)
		return fscrypt_require_key(d_inode(dentry));
	return 0;
}

/**
 * fscrypt_prepare_symlink - prepare to create a possibly-encrypted symlink
 * @dir: directory in which the symlink is being created
 * @target: plaintext symlink target
 * @len: length of @target excluding null terminator
 * @max_len: space the filesystem has available to store the symlink target
 * @disk_link: (out) the on-disk symlink target being prepared
 *
 * This function computes the size the symlink target will require on-disk,
 * stores it in @disk_link->len, and validates it against @max_len.  An
 * encrypted symlink may be longer than the original.
 *
 * Additionally, @disk_link->name is set to @target if the symlink will be
 * unencrypted, but left NULL if the symlink will be encrypted.  For encrypted
 * symlinks, the filesystem must call fscrypt_encrypt_symlink() to create the
 * on-disk target later.  (The reason for the two-step process is that some
 * filesystems need to know the size of the symlink target before creating the
 * inode, e.g. to determine whether it will be a "fast" or "slow" symlink.)
 *
 * Return: 0 on success, -ENAMETOOLONG if the symlink target is too long,
 * -ENOKEY if the encryption key is missing, or another -errno code if a problem
 * occurred while setting up the encryption key.
 */
static inline int fscrypt_prepare_symlink(struct inode *dir,
					  const char *target,
					  unsigned int len,
					  unsigned int max_len,
					  struct fscrypt_str *disk_link)
{
	if (IS_ENCRYPTED(dir) || fscrypt_dummy_context_enabled(dir))
		return __fscrypt_prepare_symlink(dir, len, max_len, disk_link);

	disk_link->name = (unsigned char *)target;
	disk_link->len = len + 1;
	if (disk_link->len > max_len)
		return -ENAMETOOLONG;
	return 0;
}

/**
 * fscrypt_encrypt_symlink - encrypt the symlink target if needed
 * @inode: symlink inode
 * @target: plaintext symlink target
 * @len: length of @target excluding null terminator
 * @disk_link: (in/out) the on-disk symlink target being prepared
 *
 * If the symlink target needs to be encrypted, then this function encrypts it
 * into @disk_link->name.  fscrypt_prepare_symlink() must have been called
 * previously to compute @disk_link->len.  If the filesystem did not allocate a
 * buffer for @disk_link->name after calling fscrypt_prepare_link(), then one
 * will be kmalloc()'ed and the filesystem will be responsible for freeing it.
 *
 * Return: 0 on success, -errno on failure
 */
static inline int fscrypt_encrypt_symlink(struct inode *inode,
					  const char *target,
					  unsigned int len,
					  struct fscrypt_str *disk_link)
{
	if (IS_ENCRYPTED(inode))
		return __fscrypt_encrypt_symlink(inode, target, len, disk_link);
	return 0;
}

/* If *pagep is a bounce page, free it and set *pagep to the pagecache page */
static inline void fscrypt_finalize_bounce_page(struct page **pagep)
{
	struct page *page = *pagep;

	if (fscrypt_is_bounce_page(page)) {
		*pagep = fscrypt_pagecache_page(page);
		fscrypt_free_bounce_page(page);
	}
}

#endif	/* _LINUX_FSCRYPT_H */