4 * This is included by filesystems configured with encryption support.
7 #ifndef _LINUX_FSCRYPT_SUPP_H
8 #define _LINUX_FSCRYPT_SUPP_H
10 #include <linux/fscrypt_common.h>
13 extern struct kmem_cache
*fscrypt_info_cachep
;
14 extern struct fscrypt_ctx
*fscrypt_get_ctx(const struct inode
*, gfp_t
);
15 extern void fscrypt_release_ctx(struct fscrypt_ctx
*);
16 extern struct page
*fscrypt_encrypt_page(const struct inode
*, struct page
*,
17 unsigned int, unsigned int,
19 extern int fscrypt_decrypt_page(const struct inode
*, struct page
*, unsigned int,
21 extern void fscrypt_restore_control_page(struct page
*);
23 extern const struct dentry_operations fscrypt_d_ops
;
25 static inline void fscrypt_set_d_op(struct dentry
*dentry
)
27 d_set_d_op(dentry
, &fscrypt_d_ops
);
30 static inline void fscrypt_set_encrypted_dentry(struct dentry
*dentry
)
32 spin_lock(&dentry
->d_lock
);
33 dentry
->d_flags
|= DCACHE_ENCRYPTED_WITH_KEY
;
34 spin_unlock(&dentry
->d_lock
);
38 extern int fscrypt_ioctl_set_policy(struct file
*, const void __user
*);
39 extern int fscrypt_ioctl_get_policy(struct file
*, void __user
*);
40 extern int fscrypt_has_permitted_context(struct inode
*, struct inode
*);
41 extern int fscrypt_inherit_context(struct inode
*, struct inode
*,
44 extern int fscrypt_get_encryption_info(struct inode
*);
45 extern void fscrypt_put_encryption_info(struct inode
*, struct fscrypt_info
*);
48 extern int fscrypt_setup_filename(struct inode
*, const struct qstr
*,
49 int lookup
, struct fscrypt_name
*);
51 static inline void fscrypt_free_filename(struct fscrypt_name
*fname
)
53 kfree(fname
->crypto_buf
.name
);
56 extern u32
fscrypt_fname_encrypted_size(const struct inode
*, u32
);
57 extern int fscrypt_fname_alloc_buffer(const struct inode
*, u32
,
58 struct fscrypt_str
*);
59 extern void fscrypt_fname_free_buffer(struct fscrypt_str
*);
60 extern int fscrypt_fname_disk_to_usr(struct inode
*, u32
, u32
,
61 const struct fscrypt_str
*, struct fscrypt_str
*);
62 extern int fscrypt_fname_usr_to_disk(struct inode
*, const struct qstr
*,
63 struct fscrypt_str
*);
65 #define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE 32
67 /* Extracts the second-to-last ciphertext block; see explanation below */
68 #define FSCRYPT_FNAME_DIGEST(name, len) \
69 ((name) + round_down((len) - FS_CRYPTO_BLOCK_SIZE - 1, \
70 FS_CRYPTO_BLOCK_SIZE))
72 #define FSCRYPT_FNAME_DIGEST_SIZE FS_CRYPTO_BLOCK_SIZE
75 * fscrypt_digested_name - alternate identifier for an on-disk filename
77 * When userspace lists an encrypted directory without access to the key,
78 * filenames whose ciphertext is longer than FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE
79 * bytes are shown in this abbreviated form (base64-encoded) rather than as the
80 * full ciphertext (base64-encoded). This is necessary to allow supporting
81 * filenames up to NAME_MAX bytes, since base64 encoding expands the length.
83 * To make it possible for filesystems to still find the correct directory entry
84 * despite not knowing the full on-disk name, we encode any filesystem-specific
85 * 'hash' and/or 'minor_hash' which the filesystem may need for its lookups,
86 * followed by the second-to-last ciphertext block of the filename. Due to the
87 * use of the CBC-CTS encryption mode, the second-to-last ciphertext block
88 * depends on the full plaintext. (Note that ciphertext stealing causes the
89 * last two blocks to appear "flipped".) This makes accidental collisions very
90 * unlikely: just a 1 in 2^128 chance for two filenames to collide even if they
91 * share the same filesystem-specific hashes.
93 * However, this scheme isn't immune to intentional collisions, which can be
94 * created by anyone able to create arbitrary plaintext filenames and view them
95 * without the key. Making the "digest" be a real cryptographic hash like
96 * SHA-256 over the full ciphertext would prevent this, although it would be
97 * less efficient and harder to implement, especially since the filesystem would
98 * need to calculate it for each directory entry examined during a search.
100 struct fscrypt_digested_name
{
103 u8 digest
[FSCRYPT_FNAME_DIGEST_SIZE
];
107 * fscrypt_match_name() - test whether the given name matches a directory entry
108 * @fname: the name being searched for
109 * @de_name: the name from the directory entry
110 * @de_name_len: the length of @de_name in bytes
112 * Normally @fname->disk_name will be set, and in that case we simply compare
113 * that to the name stored in the directory entry. The only exception is that
114 * if we don't have the key for an encrypted directory and a filename in it is
115 * very long, then we won't have the full disk_name and we'll instead need to
116 * match against the fscrypt_digested_name.
118 * Return: %true if the name matches, otherwise %false.
120 static inline bool fscrypt_match_name(const struct fscrypt_name
*fname
,
121 const u8
*de_name
, u32 de_name_len
)
123 if (unlikely(!fname
->disk_name
.name
)) {
124 const struct fscrypt_digested_name
*n
=
125 (const void *)fname
->crypto_buf
.name
;
126 if (WARN_ON_ONCE(fname
->usr_fname
->name
[0] != '_'))
128 if (de_name_len
<= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE
)
130 return !memcmp(FSCRYPT_FNAME_DIGEST(de_name
, de_name_len
),
131 n
->digest
, FSCRYPT_FNAME_DIGEST_SIZE
);
134 if (de_name_len
!= fname
->disk_name
.len
)
136 return !memcmp(de_name
, fname
->disk_name
.name
, fname
->disk_name
.len
);
140 extern void fscrypt_decrypt_bio_pages(struct fscrypt_ctx
*, struct bio
*);
141 extern void fscrypt_pullback_bio_page(struct page
**, bool);
142 extern int fscrypt_zeroout_range(const struct inode
*, pgoff_t
, sector_t
,
145 #endif /* _LINUX_FSCRYPT_SUPP_H */