1 /*
2 * fscrypt_supp.h
3 *
4 * Do not include this file directly. Use fscrypt.h instead!
5 */
6 #ifndef _LINUX_FSCRYPT_H
7 #error "Incorrect include of linux/fscrypt_supp.h!"
8 #endif
9
10 #ifndef _LINUX_FSCRYPT_SUPP_H
11 #define _LINUX_FSCRYPT_SUPP_H
12
13 /* crypto.c */
14 extern struct kmem_cache *fscrypt_info_cachep;
15 extern struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *, gfp_t);
16 extern void fscrypt_release_ctx(struct fscrypt_ctx *);
17 extern struct page *fscrypt_encrypt_page(const struct inode *, struct page *,
18 unsigned int, unsigned int,
19 u64, gfp_t);
20 extern int fscrypt_decrypt_page(const struct inode *, struct page *, unsigned int,
21 unsigned int, u64);
22 extern void fscrypt_restore_control_page(struct page *);
23
24 extern const struct dentry_operations fscrypt_d_ops;
25
fscrypt_set_d_op(struct dentry * dentry)26 static inline void fscrypt_set_d_op(struct dentry *dentry)
27 {
28 d_set_d_op(dentry, &fscrypt_d_ops);
29 }
30
fscrypt_set_encrypted_dentry(struct dentry * dentry)31 static inline void fscrypt_set_encrypted_dentry(struct dentry *dentry)
32 {
33 spin_lock(&dentry->d_lock);
34 dentry->d_flags |= DCACHE_ENCRYPTED_WITH_KEY;
35 spin_unlock(&dentry->d_lock);
36 }
37
38 /* policy.c */
39 extern int fscrypt_ioctl_set_policy(struct file *, const void __user *);
40 extern int fscrypt_ioctl_get_policy(struct file *, void __user *);
41 extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
42 extern int fscrypt_inherit_context(struct inode *, struct inode *,
43 void *, bool);
44 /* keyinfo.c */
45 extern int fscrypt_get_encryption_info(struct inode *);
46 extern void fscrypt_put_encryption_info(struct inode *, struct fscrypt_info *);
47
48 /* fname.c */
49 extern int fscrypt_setup_filename(struct inode *, const struct qstr *,
50 int lookup, struct fscrypt_name *);
51
fscrypt_free_filename(struct fscrypt_name * fname)52 static inline void fscrypt_free_filename(struct fscrypt_name *fname)
53 {
54 kfree(fname->crypto_buf.name);
55 }
56
57 extern u32 fscrypt_fname_encrypted_size(const struct inode *, u32);
58 extern int fscrypt_fname_alloc_buffer(const struct inode *, u32,
59 struct fscrypt_str *);
60 extern void fscrypt_fname_free_buffer(struct fscrypt_str *);
61 extern int fscrypt_fname_disk_to_usr(struct inode *, u32, u32,
62 const struct fscrypt_str *, struct fscrypt_str *);
63 extern int fscrypt_fname_usr_to_disk(struct inode *, const struct qstr *,
64 struct fscrypt_str *);
65
66 #define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE 32
67
68 /* Extracts the second-to-last ciphertext block; see explanation below */
69 #define FSCRYPT_FNAME_DIGEST(name, len) \
70 ((name) + round_down((len) - FS_CRYPTO_BLOCK_SIZE - 1, \
71 FS_CRYPTO_BLOCK_SIZE))
72
73 #define FSCRYPT_FNAME_DIGEST_SIZE FS_CRYPTO_BLOCK_SIZE
74
75 /**
76 * fscrypt_digested_name - alternate identifier for an on-disk filename
77 *
78 * When userspace lists an encrypted directory without access to the key,
79 * filenames whose ciphertext is longer than FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE
80 * bytes are shown in this abbreviated form (base64-encoded) rather than as the
81 * full ciphertext (base64-encoded). This is necessary to allow supporting
82 * filenames up to NAME_MAX bytes, since base64 encoding expands the length.
83 *
84 * To make it possible for filesystems to still find the correct directory entry
85 * despite not knowing the full on-disk name, we encode any filesystem-specific
86 * 'hash' and/or 'minor_hash' which the filesystem may need for its lookups,
87 * followed by the second-to-last ciphertext block of the filename. Due to the
88 * use of the CBC-CTS encryption mode, the second-to-last ciphertext block
89 * depends on the full plaintext. (Note that ciphertext stealing causes the
90 * last two blocks to appear "flipped".) This makes collisions very unlikely:
91 * just a 1 in 2^128 chance for two filenames to collide even if they share the
92 * same filesystem-specific hashes.
93 *
94 * This scheme isn't strictly immune to intentional collisions because it's
95 * basically like a CBC-MAC, which isn't secure on variable-length inputs.
96 * However, generating a CBC-MAC collision requires the ability to choose
97 * arbitrary ciphertext, which won't normally be possible with filename
98 * encryption since it would require write access to the raw disk.
99 *
100 * Taking a real cryptographic hash like SHA-256 over the full ciphertext would
101 * be better in theory but would be less efficient and more complicated to
102 * implement, especially since the filesystem would need to calculate it for
103 * each directory entry examined during a search.
104 */
105 struct fscrypt_digested_name {
106 u32 hash;
107 u32 minor_hash;
108 u8 digest[FSCRYPT_FNAME_DIGEST_SIZE];
109 };
110
111 /**
112 * fscrypt_match_name() - test whether the given name matches a directory entry
113 * @fname: the name being searched for
114 * @de_name: the name from the directory entry
115 * @de_name_len: the length of @de_name in bytes
116 *
117 * Normally @fname->disk_name will be set, and in that case we simply compare
118 * that to the name stored in the directory entry. The only exception is that
119 * if we don't have the key for an encrypted directory and a filename in it is
120 * very long, then we won't have the full disk_name and we'll instead need to
121 * match against the fscrypt_digested_name.
122 *
123 * Return: %true if the name matches, otherwise %false.
124 */
fscrypt_match_name(const struct fscrypt_name * fname,const u8 * de_name,u32 de_name_len)125 static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
126 const u8 *de_name, u32 de_name_len)
127 {
128 if (unlikely(!fname->disk_name.name)) {
129 const struct fscrypt_digested_name *n =
130 (const void *)fname->crypto_buf.name;
131 if (WARN_ON_ONCE(fname->usr_fname->name[0] != '_'))
132 return false;
133 if (de_name_len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE)
134 return false;
135 return !memcmp(FSCRYPT_FNAME_DIGEST(de_name, de_name_len),
136 n->digest, FSCRYPT_FNAME_DIGEST_SIZE);
137 }
138
139 if (de_name_len != fname->disk_name.len)
140 return false;
141 return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len);
142 }
143
144 /* bio.c */
145 extern void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *, struct bio *);
146 extern void fscrypt_pullback_bio_page(struct page **, bool);
147 extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t,
148 unsigned int);
149
150 /* hooks.c */
151 extern int fscrypt_file_open(struct inode *inode, struct file *filp);
152 extern int __fscrypt_prepare_link(struct inode *inode, struct inode *dir);
153 extern int __fscrypt_prepare_rename(struct inode *old_dir,
154 struct dentry *old_dentry,
155 struct inode *new_dir,
156 struct dentry *new_dentry,
157 unsigned int flags);
158 extern int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry);
159
160 #endif /* _LINUX_FSCRYPT_SUPP_H */
161