1 /* SPDX-License-Identifier: GPL-2.0 */
5 * Do not include this file directly. Use fscrypt.h instead!
7 #ifndef _LINUX_FSCRYPT_H
8 #error "Incorrect include of linux/fscrypt_supp.h!"
11 #ifndef _LINUX_FSCRYPT_SUPP_H
12 #define _LINUX_FSCRYPT_SUPP_H
15 #include <linux/slab.h>
18 * fscrypt superblock flags
20 #define FS_CFLG_OWN_PAGES (1U << 1)
23 * crypto operations for filesystems
25 struct fscrypt_operations
{
27 const char *key_prefix
;
28 int (*get_context
)(struct inode
*, void *, size_t);
29 int (*set_context
)(struct inode
*, const void *, size_t, void *);
30 bool (*dummy_context
)(struct inode
*);
31 bool (*empty_dir
)(struct inode
*);
32 unsigned int max_namelen
;
38 struct page
*bounce_page
; /* Ciphertext page */
39 struct page
*control_page
; /* Original page */
43 struct work_struct work
;
45 struct list_head free_list
; /* Free list */
50 static inline bool fscrypt_has_encryption_key(const struct inode
*inode
)
52 return (inode
->i_crypt_info
!= NULL
);
55 static inline bool fscrypt_dummy_context_enabled(struct inode
*inode
)
57 return inode
->i_sb
->s_cop
->dummy_context
&&
58 inode
->i_sb
->s_cop
->dummy_context(inode
);
62 extern void fscrypt_enqueue_decrypt_work(struct work_struct
*);
63 extern struct fscrypt_ctx
*fscrypt_get_ctx(const struct inode
*, gfp_t
);
64 extern void fscrypt_release_ctx(struct fscrypt_ctx
*);
65 extern struct page
*fscrypt_encrypt_page(const struct inode
*, struct page
*,
66 unsigned int, unsigned int,
68 extern int fscrypt_decrypt_page(const struct inode
*, struct page
*, unsigned int,
71 static inline struct page
*fscrypt_control_page(struct page
*page
)
73 return ((struct fscrypt_ctx
*)page_private(page
))->w
.control_page
;
76 extern void fscrypt_restore_control_page(struct page
*);
79 extern int fscrypt_ioctl_set_policy(struct file
*, const void __user
*);
80 extern int fscrypt_ioctl_get_policy(struct file
*, void __user
*);
81 extern int fscrypt_has_permitted_context(struct inode
*, struct inode
*);
82 extern int fscrypt_inherit_context(struct inode
*, struct inode
*,
85 extern int fscrypt_get_encryption_info(struct inode
*);
86 extern void fscrypt_put_encryption_info(struct inode
*);
89 extern int fscrypt_setup_filename(struct inode
*, const struct qstr
*,
90 int lookup
, struct fscrypt_name
*);
92 static inline void fscrypt_free_filename(struct fscrypt_name
*fname
)
94 kfree(fname
->crypto_buf
.name
);
97 extern int fscrypt_fname_alloc_buffer(const struct inode
*, u32
,
98 struct fscrypt_str
*);
99 extern void fscrypt_fname_free_buffer(struct fscrypt_str
*);
100 extern int fscrypt_fname_disk_to_usr(struct inode
*, u32
, u32
,
101 const struct fscrypt_str
*, struct fscrypt_str
*);
103 #define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE 32
105 /* Extracts the second-to-last ciphertext block; see explanation below */
106 #define FSCRYPT_FNAME_DIGEST(name, len) \
107 ((name) + round_down((len) - FS_CRYPTO_BLOCK_SIZE - 1, \
108 FS_CRYPTO_BLOCK_SIZE))
110 #define FSCRYPT_FNAME_DIGEST_SIZE FS_CRYPTO_BLOCK_SIZE
113 * fscrypt_digested_name - alternate identifier for an on-disk filename
115 * When userspace lists an encrypted directory without access to the key,
116 * filenames whose ciphertext is longer than FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE
117 * bytes are shown in this abbreviated form (base64-encoded) rather than as the
118 * full ciphertext (base64-encoded). This is necessary to allow supporting
119 * filenames up to NAME_MAX bytes, since base64 encoding expands the length.
121 * To make it possible for filesystems to still find the correct directory entry
122 * despite not knowing the full on-disk name, we encode any filesystem-specific
123 * 'hash' and/or 'minor_hash' which the filesystem may need for its lookups,
124 * followed by the second-to-last ciphertext block of the filename. Due to the
125 * use of the CBC-CTS encryption mode, the second-to-last ciphertext block
126 * depends on the full plaintext. (Note that ciphertext stealing causes the
127 * last two blocks to appear "flipped".) This makes accidental collisions very
128 * unlikely: just a 1 in 2^128 chance for two filenames to collide even if they
129 * share the same filesystem-specific hashes.
131 * However, this scheme isn't immune to intentional collisions, which can be
132 * created by anyone able to create arbitrary plaintext filenames and view them
133 * without the key. Making the "digest" be a real cryptographic hash like
134 * SHA-256 over the full ciphertext would prevent this, although it would be
135 * less efficient and harder to implement, especially since the filesystem would
136 * need to calculate it for each directory entry examined during a search.
138 struct fscrypt_digested_name
{
141 u8 digest
[FSCRYPT_FNAME_DIGEST_SIZE
];
145 * fscrypt_match_name() - test whether the given name matches a directory entry
146 * @fname: the name being searched for
147 * @de_name: the name from the directory entry
148 * @de_name_len: the length of @de_name in bytes
150 * Normally @fname->disk_name will be set, and in that case we simply compare
151 * that to the name stored in the directory entry. The only exception is that
152 * if we don't have the key for an encrypted directory and a filename in it is
153 * very long, then we won't have the full disk_name and we'll instead need to
154 * match against the fscrypt_digested_name.
156 * Return: %true if the name matches, otherwise %false.
158 static inline bool fscrypt_match_name(const struct fscrypt_name
*fname
,
159 const u8
*de_name
, u32 de_name_len
)
161 if (unlikely(!fname
->disk_name
.name
)) {
162 const struct fscrypt_digested_name
*n
=
163 (const void *)fname
->crypto_buf
.name
;
164 if (WARN_ON_ONCE(fname
->usr_fname
->name
[0] != '_'))
166 if (de_name_len
<= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE
)
168 return !memcmp(FSCRYPT_FNAME_DIGEST(de_name
, de_name_len
),
169 n
->digest
, FSCRYPT_FNAME_DIGEST_SIZE
);
172 if (de_name_len
!= fname
->disk_name
.len
)
174 return !memcmp(de_name
, fname
->disk_name
.name
, fname
->disk_name
.len
);
178 extern void fscrypt_decrypt_bio(struct bio
*);
179 extern void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx
*ctx
,
181 extern void fscrypt_pullback_bio_page(struct page
**, bool);
182 extern int fscrypt_zeroout_range(const struct inode
*, pgoff_t
, sector_t
,
186 extern int fscrypt_file_open(struct inode
*inode
, struct file
*filp
);
187 extern int __fscrypt_prepare_link(struct inode
*inode
, struct inode
*dir
);
188 extern int __fscrypt_prepare_rename(struct inode
*old_dir
,
189 struct dentry
*old_dentry
,
190 struct inode
*new_dir
,
191 struct dentry
*new_dentry
,
193 extern int __fscrypt_prepare_lookup(struct inode
*dir
, struct dentry
*dentry
);
194 extern int __fscrypt_prepare_symlink(struct inode
*dir
, unsigned int len
,
195 unsigned int max_len
,
196 struct fscrypt_str
*disk_link
);
197 extern int __fscrypt_encrypt_symlink(struct inode
*inode
, const char *target
,
199 struct fscrypt_str
*disk_link
);
200 extern const char *fscrypt_get_symlink(struct inode
*inode
, const void *caddr
,
201 unsigned int max_size
,
202 struct delayed_call
*done
);
204 #endif /* _LINUX_FSCRYPT_SUPP_H */