1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * fscrypt_supp.h
4 *
5 * Do not include this file directly. Use fscrypt.h instead!
6 */
7 #ifndef _LINUX_FSCRYPT_H
8 #error "Incorrect include of linux/fscrypt_supp.h!"
9 #endif
10
11 #ifndef _LINUX_FSCRYPT_SUPP_H
12 #define _LINUX_FSCRYPT_SUPP_H
13
14 #include <linux/mm.h>
15 #include <linux/slab.h>
16
17 /*
18 * fscrypt superblock flags
19 */
20 #define FS_CFLG_OWN_PAGES (1U << 1)
21
22 /*
23 * crypto operations for filesystems
24 */
25 struct fscrypt_operations {
26 unsigned int flags;
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;
33 };
34
35 struct fscrypt_ctx {
36 union {
37 struct {
38 struct page *bounce_page; /* Ciphertext page */
39 struct page *control_page; /* Original page */
40 } w;
41 struct {
42 struct bio *bio;
43 struct work_struct work;
44 } r;
45 struct list_head free_list; /* Free list */
46 };
47 u8 flags; /* Flags */
48 };
49
fscrypt_has_encryption_key(const struct inode * inode)50 static inline bool fscrypt_has_encryption_key(const struct inode *inode)
51 {
52 return (inode->i_crypt_info != NULL);
53 }
54
fscrypt_dummy_context_enabled(struct inode * inode)55 static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
56 {
57 return inode->i_sb->s_cop->dummy_context &&
58 inode->i_sb->s_cop->dummy_context(inode);
59 }
60
61 /**
62 * fscrypt_is_nokey_name() - test whether a dentry is a no-key name
63 * @dentry: the dentry to check
64 *
65 * This returns true if the dentry is a no-key dentry. A no-key dentry is a
66 * dentry that was created in an encrypted directory that hasn't had its
67 * encryption key added yet. Such dentries may be either positive or negative.
68 *
69 * When a filesystem is asked to create a new filename in an encrypted directory
70 * and the new filename's dentry is a no-key dentry, it must fail the operation
71 * with ENOKEY. This includes ->create(), ->mkdir(), ->mknod(), ->symlink(),
72 * ->rename(), and ->link(). (However, ->rename() and ->link() are already
73 * handled by fscrypt_prepare_rename() and fscrypt_prepare_link().)
74 *
75 * This is necessary because creating a filename requires the directory's
76 * encryption key, but just checking for the key on the directory inode during
77 * the final filesystem operation doesn't guarantee that the key was available
78 * during the preceding dentry lookup. And the key must have already been
79 * available during the dentry lookup in order for it to have been checked
80 * whether the filename already exists in the directory and for the new file's
81 * dentry not to be invalidated due to it incorrectly having the no-key flag.
82 *
83 * Return: %true if the dentry is a no-key name
84 */
fscrypt_is_nokey_name(const struct dentry * dentry)85 static inline bool fscrypt_is_nokey_name(const struct dentry *dentry)
86 {
87 return dentry->d_flags & DCACHE_ENCRYPTED_NAME;
88 }
89
90 /* crypto.c */
91 extern void fscrypt_enqueue_decrypt_work(struct work_struct *);
92 extern struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *, gfp_t);
93 extern void fscrypt_release_ctx(struct fscrypt_ctx *);
94 extern struct page *fscrypt_encrypt_page(const struct inode *, struct page *,
95 unsigned int, unsigned int,
96 u64, gfp_t);
97 extern int fscrypt_decrypt_page(const struct inode *, struct page *, unsigned int,
98 unsigned int, u64);
99
fscrypt_control_page(struct page * page)100 static inline struct page *fscrypt_control_page(struct page *page)
101 {
102 return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
103 }
104
105 extern void fscrypt_restore_control_page(struct page *);
106
107 /* policy.c */
108 extern int fscrypt_ioctl_set_policy(struct file *, const void __user *);
109 extern int fscrypt_ioctl_get_policy(struct file *, void __user *);
110 extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
111 extern int fscrypt_inherit_context(struct inode *, struct inode *,
112 void *, bool);
113 /* keyinfo.c */
114 extern int fscrypt_get_encryption_info(struct inode *);
115 extern void fscrypt_put_encryption_info(struct inode *);
116
117 /* fname.c */
118 extern int fscrypt_setup_filename(struct inode *, const struct qstr *,
119 int lookup, struct fscrypt_name *);
120
fscrypt_free_filename(struct fscrypt_name * fname)121 static inline void fscrypt_free_filename(struct fscrypt_name *fname)
122 {
123 kfree(fname->crypto_buf.name);
124 }
125
126 extern int fscrypt_fname_alloc_buffer(const struct inode *, u32,
127 struct fscrypt_str *);
128 extern void fscrypt_fname_free_buffer(struct fscrypt_str *);
129 extern int fscrypt_fname_disk_to_usr(struct inode *, u32, u32,
130 const struct fscrypt_str *, struct fscrypt_str *);
131
132 #define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE 32
133
134 /* Extracts the second-to-last ciphertext block; see explanation below */
135 #define FSCRYPT_FNAME_DIGEST(name, len) \
136 ((name) + round_down((len) - FS_CRYPTO_BLOCK_SIZE - 1, \
137 FS_CRYPTO_BLOCK_SIZE))
138
139 #define FSCRYPT_FNAME_DIGEST_SIZE FS_CRYPTO_BLOCK_SIZE
140
141 /**
142 * fscrypt_digested_name - alternate identifier for an on-disk filename
143 *
144 * When userspace lists an encrypted directory without access to the key,
145 * filenames whose ciphertext is longer than FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE
146 * bytes are shown in this abbreviated form (base64-encoded) rather than as the
147 * full ciphertext (base64-encoded). This is necessary to allow supporting
148 * filenames up to NAME_MAX bytes, since base64 encoding expands the length.
149 *
150 * To make it possible for filesystems to still find the correct directory entry
151 * despite not knowing the full on-disk name, we encode any filesystem-specific
152 * 'hash' and/or 'minor_hash' which the filesystem may need for its lookups,
153 * followed by the second-to-last ciphertext block of the filename. Due to the
154 * use of the CBC-CTS encryption mode, the second-to-last ciphertext block
155 * depends on the full plaintext. (Note that ciphertext stealing causes the
156 * last two blocks to appear "flipped".) This makes accidental collisions very
157 * unlikely: just a 1 in 2^128 chance for two filenames to collide even if they
158 * share the same filesystem-specific hashes.
159 *
160 * However, this scheme isn't immune to intentional collisions, which can be
161 * created by anyone able to create arbitrary plaintext filenames and view them
162 * without the key. Making the "digest" be a real cryptographic hash like
163 * SHA-256 over the full ciphertext would prevent this, although it would be
164 * less efficient and harder to implement, especially since the filesystem would
165 * need to calculate it for each directory entry examined during a search.
166 */
167 struct fscrypt_digested_name {
168 u32 hash;
169 u32 minor_hash;
170 u8 digest[FSCRYPT_FNAME_DIGEST_SIZE];
171 };
172
173 /**
174 * fscrypt_match_name() - test whether the given name matches a directory entry
175 * @fname: the name being searched for
176 * @de_name: the name from the directory entry
177 * @de_name_len: the length of @de_name in bytes
178 *
179 * Normally @fname->disk_name will be set, and in that case we simply compare
180 * that to the name stored in the directory entry. The only exception is that
181 * if we don't have the key for an encrypted directory and a filename in it is
182 * very long, then we won't have the full disk_name and we'll instead need to
183 * match against the fscrypt_digested_name.
184 *
185 * Return: %true if the name matches, otherwise %false.
186 */
fscrypt_match_name(const struct fscrypt_name * fname,const u8 * de_name,u32 de_name_len)187 static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
188 const u8 *de_name, u32 de_name_len)
189 {
190 if (unlikely(!fname->disk_name.name)) {
191 const struct fscrypt_digested_name *n =
192 (const void *)fname->crypto_buf.name;
193 if (WARN_ON_ONCE(fname->usr_fname->name[0] != '_'))
194 return false;
195 if (de_name_len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE)
196 return false;
197 return !memcmp(FSCRYPT_FNAME_DIGEST(de_name, de_name_len),
198 n->digest, FSCRYPT_FNAME_DIGEST_SIZE);
199 }
200
201 if (de_name_len != fname->disk_name.len)
202 return false;
203 return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len);
204 }
205
206 /* bio.c */
207 extern void fscrypt_decrypt_bio(struct bio *);
208 extern void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx,
209 struct bio *bio);
210 extern void fscrypt_pullback_bio_page(struct page **, bool);
211 extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t,
212 unsigned int);
213
214 /* hooks.c */
215 extern int fscrypt_file_open(struct inode *inode, struct file *filp);
216 extern int __fscrypt_prepare_link(struct inode *inode, struct inode *dir,
217 struct dentry *dentry);
218 extern int __fscrypt_prepare_rename(struct inode *old_dir,
219 struct dentry *old_dentry,
220 struct inode *new_dir,
221 struct dentry *new_dentry,
222 unsigned int flags);
223 extern int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry,
224 struct fscrypt_name *fname);
225 extern int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len,
226 unsigned int max_len,
227 struct fscrypt_str *disk_link);
228 extern int __fscrypt_encrypt_symlink(struct inode *inode, const char *target,
229 unsigned int len,
230 struct fscrypt_str *disk_link);
231 extern const char *fscrypt_get_symlink(struct inode *inode, const void *caddr,
232 unsigned int max_size,
233 struct delayed_call *done);
234 int fscrypt_symlink_getattr(const struct path *path, struct kstat *stat);
235
236 #endif /* _LINUX_FSCRYPT_SUPP_H */
237