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1 | /* |
2 | * fscrypt_supp.h | |
3 | * | |
4 | * This is included by filesystems configured with encryption support. | |
5 | */ | |
6 | ||
7 | #ifndef _LINUX_FSCRYPT_SUPP_H | |
8 | #define _LINUX_FSCRYPT_SUPP_H | |
9 | ||
10 | #include <linux/fscrypt_common.h> | |
11 | ||
12 | /* crypto.c */ | |
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, | |
18 | u64, gfp_t); | |
19 | extern int fscrypt_decrypt_page(const struct inode *, struct page *, unsigned int, | |
20 | unsigned int, u64); | |
21 | extern void fscrypt_restore_control_page(struct page *); | |
22 | ||
23 | extern const struct dentry_operations fscrypt_d_ops; | |
24 | ||
25 | static inline void fscrypt_set_d_op(struct dentry *dentry) | |
26 | { | |
27 | d_set_d_op(dentry, &fscrypt_d_ops); | |
28 | } | |
29 | ||
30 | static inline void fscrypt_set_encrypted_dentry(struct dentry *dentry) | |
31 | { | |
32 | spin_lock(&dentry->d_lock); | |
33 | dentry->d_flags |= DCACHE_ENCRYPTED_WITH_KEY; | |
34 | spin_unlock(&dentry->d_lock); | |
35 | } | |
36 | ||
37 | /* policy.c */ | |
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 *, | |
42 | void *, bool); | |
43 | /* keyinfo.c */ | |
44 | extern int fscrypt_get_encryption_info(struct inode *); | |
45 | extern void fscrypt_put_encryption_info(struct inode *, struct fscrypt_info *); | |
46 | ||
47 | /* fname.c */ | |
48 | extern int fscrypt_setup_filename(struct inode *, const struct qstr *, | |
49 | int lookup, struct fscrypt_name *); | |
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50 | |
51 | static inline void fscrypt_free_filename(struct fscrypt_name *fname) | |
52 | { | |
53 | kfree(fname->crypto_buf.name); | |
54 | } | |
55 | ||
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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 *); | |
64 | ||
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65 | #define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE 32 |
66 | ||
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)) | |
71 | ||
72 | #define FSCRYPT_FNAME_DIGEST_SIZE FS_CRYPTO_BLOCK_SIZE | |
73 | ||
74 | /** | |
75 | * fscrypt_digested_name - alternate identifier for an on-disk filename | |
76 | * | |
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. | |
82 | * | |
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 | |
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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. | |
17159420 | 92 | * |
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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. | |
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99 | */ |
100 | struct fscrypt_digested_name { | |
101 | u32 hash; | |
102 | u32 minor_hash; | |
103 | u8 digest[FSCRYPT_FNAME_DIGEST_SIZE]; | |
104 | }; | |
105 | ||
106 | /** | |
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 | |
111 | * | |
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. | |
117 | * | |
118 | * Return: %true if the name matches, otherwise %false. | |
119 | */ | |
120 | static inline bool fscrypt_match_name(const struct fscrypt_name *fname, | |
121 | const u8 *de_name, u32 de_name_len) | |
122 | { | |
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] != '_')) | |
127 | return false; | |
128 | if (de_name_len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE) | |
129 | return false; | |
130 | return !memcmp(FSCRYPT_FNAME_DIGEST(de_name, de_name_len), | |
131 | n->digest, FSCRYPT_FNAME_DIGEST_SIZE); | |
132 | } | |
133 | ||
134 | if (de_name_len != fname->disk_name.len) | |
135 | return false; | |
136 | return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len); | |
137 | } | |
138 | ||
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139 | /* bio.c */ |
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, | |
143 | unsigned int); | |
144 | ||
145 | #endif /* _LINUX_FSCRYPT_SUPP_H */ |