1 /* SPDX-License-Identifier: GPL-2.0 */
3 * fscrypt.h: declarations for per-file encryption
5 * Filesystems that implement per-file encryption must include this header
8 * Copyright (C) 2015, Google, Inc.
10 * Written by Michael Halcrow, 2015.
11 * Modified by Jaegeuk Kim, 2015.
13 #ifndef _LINUX_FSCRYPT_H
14 #define _LINUX_FSCRYPT_H
18 #include <linux/slab.h>
19 #include <uapi/linux/fscrypt.h>
21 #define FS_CRYPTO_BLOCK_SIZE 16
32 const struct qstr *usr_fname;
33 struct fscrypt_str disk_name;
36 struct fscrypt_str crypto_buf;
37 bool is_ciphertext_name;
40 #define FSTR_INIT(n, l) { .name = n, .len = l }
41 #define FSTR_TO_QSTR(f) QSTR_INIT((f)->name, (f)->len)
42 #define fname_name(p) ((p)->disk_name.name)
43 #define fname_len(p) ((p)->disk_name.len)
45 /* Maximum value for the third parameter of fscrypt_operations.set_context(). */
46 #define FSCRYPT_SET_CONTEXT_MAX_SIZE 28
48 #ifdef CONFIG_FS_ENCRYPTION
50 * fscrypt superblock flags
52 #define FS_CFLG_OWN_PAGES (1U << 1)
55 * crypto operations for filesystems
57 struct fscrypt_operations {
59 const char *key_prefix;
60 int (*get_context)(struct inode *, void *, size_t);
61 int (*set_context)(struct inode *, const void *, size_t, void *);
62 bool (*dummy_context)(struct inode *);
63 bool (*empty_dir)(struct inode *);
64 unsigned int max_namelen;
72 struct work_struct work;
74 struct list_head free_list; /* Free list */
79 static inline bool fscrypt_has_encryption_key(const struct inode *inode)
81 /* pairs with cmpxchg_release() in fscrypt_get_encryption_info() */
82 return READ_ONCE(inode->i_crypt_info) != NULL;
85 static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
87 return inode->i_sb->s_cop->dummy_context &&
88 inode->i_sb->s_cop->dummy_context(inode);
92 * When d_splice_alias() moves a directory's encrypted alias to its decrypted
93 * alias as a result of the encryption key being added, DCACHE_ENCRYPTED_NAME
94 * must be cleared. Note that we don't have to support arbitrary moves of this
95 * flag because fscrypt doesn't allow encrypted aliases to be the source or
96 * target of a rename().
98 static inline void fscrypt_handle_d_move(struct dentry *dentry)
100 dentry->d_flags &= ~DCACHE_ENCRYPTED_NAME;
104 extern void fscrypt_enqueue_decrypt_work(struct work_struct *);
105 extern struct fscrypt_ctx *fscrypt_get_ctx(gfp_t);
106 extern void fscrypt_release_ctx(struct fscrypt_ctx *);
108 extern struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
112 extern int fscrypt_encrypt_block_inplace(const struct inode *inode,
113 struct page *page, unsigned int len,
114 unsigned int offs, u64 lblk_num,
117 extern int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len,
119 extern int fscrypt_decrypt_block_inplace(const struct inode *inode,
120 struct page *page, unsigned int len,
121 unsigned int offs, u64 lblk_num);
123 static inline bool fscrypt_is_bounce_page(struct page *page)
125 return page->mapping == NULL;
128 static inline struct page *fscrypt_pagecache_page(struct page *bounce_page)
130 return (struct page *)page_private(bounce_page);
133 extern void fscrypt_free_bounce_page(struct page *bounce_page);
136 extern int fscrypt_ioctl_set_policy(struct file *, const void __user *);
137 extern int fscrypt_ioctl_get_policy(struct file *, void __user *);
138 extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
139 extern int fscrypt_inherit_context(struct inode *, struct inode *,
142 extern void fscrypt_sb_free(struct super_block *sb);
143 extern int fscrypt_ioctl_add_key(struct file *filp, void __user *arg);
144 extern int fscrypt_ioctl_remove_key(struct file *filp, void __user *arg);
147 extern int fscrypt_get_encryption_info(struct inode *);
148 extern void fscrypt_put_encryption_info(struct inode *);
149 extern void fscrypt_free_inode(struct inode *);
150 extern int fscrypt_drop_inode(struct inode *inode);
153 extern int fscrypt_setup_filename(struct inode *, const struct qstr *,
154 int lookup, struct fscrypt_name *);
156 static inline void fscrypt_free_filename(struct fscrypt_name *fname)
158 kfree(fname->crypto_buf.name);
161 extern int fscrypt_fname_alloc_buffer(const struct inode *, u32,
162 struct fscrypt_str *);
163 extern void fscrypt_fname_free_buffer(struct fscrypt_str *);
164 extern int fscrypt_fname_disk_to_usr(struct inode *, u32, u32,
165 const struct fscrypt_str *, struct fscrypt_str *);
167 #define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE 32
169 /* Extracts the second-to-last ciphertext block; see explanation below */
170 #define FSCRYPT_FNAME_DIGEST(name, len) \
171 ((name) + round_down((len) - FS_CRYPTO_BLOCK_SIZE - 1, \
172 FS_CRYPTO_BLOCK_SIZE))
174 #define FSCRYPT_FNAME_DIGEST_SIZE FS_CRYPTO_BLOCK_SIZE
177 * fscrypt_digested_name - alternate identifier for an on-disk filename
179 * When userspace lists an encrypted directory without access to the key,
180 * filenames whose ciphertext is longer than FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE
181 * bytes are shown in this abbreviated form (base64-encoded) rather than as the
182 * full ciphertext (base64-encoded). This is necessary to allow supporting
183 * filenames up to NAME_MAX bytes, since base64 encoding expands the length.
185 * To make it possible for filesystems to still find the correct directory entry
186 * despite not knowing the full on-disk name, we encode any filesystem-specific
187 * 'hash' and/or 'minor_hash' which the filesystem may need for its lookups,
188 * followed by the second-to-last ciphertext block of the filename. Due to the
189 * use of the CBC-CTS encryption mode, the second-to-last ciphertext block
190 * depends on the full plaintext. (Note that ciphertext stealing causes the
191 * last two blocks to appear "flipped".) This makes accidental collisions very
192 * unlikely: just a 1 in 2^128 chance for two filenames to collide even if they
193 * share the same filesystem-specific hashes.
195 * However, this scheme isn't immune to intentional collisions, which can be
196 * created by anyone able to create arbitrary plaintext filenames and view them
197 * without the key. Making the "digest" be a real cryptographic hash like
198 * SHA-256 over the full ciphertext would prevent this, although it would be
199 * less efficient and harder to implement, especially since the filesystem would
200 * need to calculate it for each directory entry examined during a search.
202 struct fscrypt_digested_name {
205 u8 digest[FSCRYPT_FNAME_DIGEST_SIZE];
209 * fscrypt_match_name() - test whether the given name matches a directory entry
210 * @fname: the name being searched for
211 * @de_name: the name from the directory entry
212 * @de_name_len: the length of @de_name in bytes
214 * Normally @fname->disk_name will be set, and in that case we simply compare
215 * that to the name stored in the directory entry. The only exception is that
216 * if we don't have the key for an encrypted directory and a filename in it is
217 * very long, then we won't have the full disk_name and we'll instead need to
218 * match against the fscrypt_digested_name.
220 * Return: %true if the name matches, otherwise %false.
222 static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
223 const u8 *de_name, u32 de_name_len)
225 if (unlikely(!fname->disk_name.name)) {
226 const struct fscrypt_digested_name *n =
227 (const void *)fname->crypto_buf.name;
228 if (WARN_ON_ONCE(fname->usr_fname->name[0] != '_'))
230 if (de_name_len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE)
232 return !memcmp(FSCRYPT_FNAME_DIGEST(de_name, de_name_len),
233 n->digest, FSCRYPT_FNAME_DIGEST_SIZE);
236 if (de_name_len != fname->disk_name.len)
238 return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len);
242 extern void fscrypt_decrypt_bio(struct bio *);
243 extern void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx,
245 extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t,
249 extern int fscrypt_file_open(struct inode *inode, struct file *filp);
250 extern int __fscrypt_prepare_link(struct inode *inode, struct inode *dir,
251 struct dentry *dentry);
252 extern int __fscrypt_prepare_rename(struct inode *old_dir,
253 struct dentry *old_dentry,
254 struct inode *new_dir,
255 struct dentry *new_dentry,
257 extern int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry,
258 struct fscrypt_name *fname);
259 extern int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len,
260 unsigned int max_len,
261 struct fscrypt_str *disk_link);
262 extern int __fscrypt_encrypt_symlink(struct inode *inode, const char *target,
264 struct fscrypt_str *disk_link);
265 extern const char *fscrypt_get_symlink(struct inode *inode, const void *caddr,
266 unsigned int max_size,
267 struct delayed_call *done);
268 static inline void fscrypt_set_ops(struct super_block *sb,
269 const struct fscrypt_operations *s_cop)
273 #else /* !CONFIG_FS_ENCRYPTION */
275 static inline bool fscrypt_has_encryption_key(const struct inode *inode)
280 static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
285 static inline void fscrypt_handle_d_move(struct dentry *dentry)
290 static inline void fscrypt_enqueue_decrypt_work(struct work_struct *work)
294 static inline struct fscrypt_ctx *fscrypt_get_ctx(gfp_t gfp_flags)
296 return ERR_PTR(-EOPNOTSUPP);
299 static inline void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
304 static inline struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
309 return ERR_PTR(-EOPNOTSUPP);
312 static inline int fscrypt_encrypt_block_inplace(const struct inode *inode,
315 unsigned int offs, u64 lblk_num,
321 static inline int fscrypt_decrypt_pagecache_blocks(struct page *page,
328 static inline int fscrypt_decrypt_block_inplace(const struct inode *inode,
331 unsigned int offs, u64 lblk_num)
336 static inline bool fscrypt_is_bounce_page(struct page *page)
341 static inline struct page *fscrypt_pagecache_page(struct page *bounce_page)
344 return ERR_PTR(-EINVAL);
347 static inline void fscrypt_free_bounce_page(struct page *bounce_page)
352 static inline int fscrypt_ioctl_set_policy(struct file *filp,
353 const void __user *arg)
358 static inline int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
363 static inline int fscrypt_has_permitted_context(struct inode *parent,
369 static inline int fscrypt_inherit_context(struct inode *parent,
371 void *fs_data, bool preload)
377 static inline void fscrypt_sb_free(struct super_block *sb)
381 static inline int fscrypt_ioctl_add_key(struct file *filp, void __user *arg)
386 static inline int fscrypt_ioctl_remove_key(struct file *filp, void __user *arg)
392 static inline int fscrypt_get_encryption_info(struct inode *inode)
397 static inline void fscrypt_put_encryption_info(struct inode *inode)
402 static inline void fscrypt_free_inode(struct inode *inode)
406 static inline int fscrypt_drop_inode(struct inode *inode)
412 static inline int fscrypt_setup_filename(struct inode *dir,
413 const struct qstr *iname,
414 int lookup, struct fscrypt_name *fname)
416 if (IS_ENCRYPTED(dir))
419 memset(fname, 0, sizeof(*fname));
420 fname->usr_fname = iname;
421 fname->disk_name.name = (unsigned char *)iname->name;
422 fname->disk_name.len = iname->len;
426 static inline void fscrypt_free_filename(struct fscrypt_name *fname)
431 static inline int fscrypt_fname_alloc_buffer(const struct inode *inode,
432 u32 max_encrypted_len,
433 struct fscrypt_str *crypto_str)
438 static inline void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
443 static inline int fscrypt_fname_disk_to_usr(struct inode *inode,
444 u32 hash, u32 minor_hash,
445 const struct fscrypt_str *iname,
446 struct fscrypt_str *oname)
451 static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
452 const u8 *de_name, u32 de_name_len)
454 /* Encryption support disabled; use standard comparison */
455 if (de_name_len != fname->disk_name.len)
457 return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len);
461 static inline void fscrypt_decrypt_bio(struct bio *bio)
465 static inline void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx,
470 static inline int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
471 sector_t pblk, unsigned int len)
478 static inline int fscrypt_file_open(struct inode *inode, struct file *filp)
480 if (IS_ENCRYPTED(inode))
485 static inline int __fscrypt_prepare_link(struct inode *inode, struct inode *dir,
486 struct dentry *dentry)
491 static inline int __fscrypt_prepare_rename(struct inode *old_dir,
492 struct dentry *old_dentry,
493 struct inode *new_dir,
494 struct dentry *new_dentry,
500 static inline int __fscrypt_prepare_lookup(struct inode *dir,
501 struct dentry *dentry,
502 struct fscrypt_name *fname)
507 static inline int __fscrypt_prepare_symlink(struct inode *dir,
509 unsigned int max_len,
510 struct fscrypt_str *disk_link)
516 static inline int __fscrypt_encrypt_symlink(struct inode *inode,
519 struct fscrypt_str *disk_link)
524 static inline const char *fscrypt_get_symlink(struct inode *inode,
526 unsigned int max_size,
527 struct delayed_call *done)
529 return ERR_PTR(-EOPNOTSUPP);
532 static inline void fscrypt_set_ops(struct super_block *sb,
533 const struct fscrypt_operations *s_cop)
537 #endif /* !CONFIG_FS_ENCRYPTION */
540 * fscrypt_require_key - require an inode's encryption key
541 * @inode: the inode we need the key for
543 * If the inode is encrypted, set up its encryption key if not already done.
544 * Then require that the key be present and return -ENOKEY otherwise.
546 * No locks are needed, and the key will live as long as the struct inode --- so
547 * it won't go away from under you.
549 * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
550 * if a problem occurred while setting up the encryption key.
552 static inline int fscrypt_require_key(struct inode *inode)
554 if (IS_ENCRYPTED(inode)) {
555 int err = fscrypt_get_encryption_info(inode);
559 if (!fscrypt_has_encryption_key(inode))
566 * fscrypt_prepare_link - prepare to link an inode into a possibly-encrypted directory
567 * @old_dentry: an existing dentry for the inode being linked
568 * @dir: the target directory
569 * @dentry: negative dentry for the target filename
571 * A new link can only be added to an encrypted directory if the directory's
572 * encryption key is available --- since otherwise we'd have no way to encrypt
573 * the filename. Therefore, we first set up the directory's encryption key (if
574 * not already done) and return an error if it's unavailable.
576 * We also verify that the link will not violate the constraint that all files
577 * in an encrypted directory tree use the same encryption policy.
579 * Return: 0 on success, -ENOKEY if the directory's encryption key is missing,
580 * -EXDEV if the link would result in an inconsistent encryption policy, or
581 * another -errno code.
583 static inline int fscrypt_prepare_link(struct dentry *old_dentry,
585 struct dentry *dentry)
587 if (IS_ENCRYPTED(dir))
588 return __fscrypt_prepare_link(d_inode(old_dentry), dir, dentry);
593 * fscrypt_prepare_rename - prepare for a rename between possibly-encrypted directories
594 * @old_dir: source directory
595 * @old_dentry: dentry for source file
596 * @new_dir: target directory
597 * @new_dentry: dentry for target location (may be negative unless exchanging)
598 * @flags: rename flags (we care at least about %RENAME_EXCHANGE)
600 * Prepare for ->rename() where the source and/or target directories may be
601 * encrypted. A new link can only be added to an encrypted directory if the
602 * directory's encryption key is available --- since otherwise we'd have no way
603 * to encrypt the filename. A rename to an existing name, on the other hand,
604 * *is* cryptographically possible without the key. However, we take the more
605 * conservative approach and just forbid all no-key renames.
607 * We also verify that the rename will not violate the constraint that all files
608 * in an encrypted directory tree use the same encryption policy.
610 * Return: 0 on success, -ENOKEY if an encryption key is missing, -EXDEV if the
611 * rename would cause inconsistent encryption policies, or another -errno code.
613 static inline int fscrypt_prepare_rename(struct inode *old_dir,
614 struct dentry *old_dentry,
615 struct inode *new_dir,
616 struct dentry *new_dentry,
619 if (IS_ENCRYPTED(old_dir) || IS_ENCRYPTED(new_dir))
620 return __fscrypt_prepare_rename(old_dir, old_dentry,
621 new_dir, new_dentry, flags);
626 * fscrypt_prepare_lookup - prepare to lookup a name in a possibly-encrypted directory
627 * @dir: directory being searched
628 * @dentry: filename being looked up
629 * @fname: (output) the name to use to search the on-disk directory
631 * Prepare for ->lookup() in a directory which may be encrypted by determining
632 * the name that will actually be used to search the directory on-disk. Lookups
633 * can be done with or without the directory's encryption key; without the key,
634 * filenames are presented in encrypted form. Therefore, we'll try to set up
635 * the directory's encryption key, but even without it the lookup can continue.
637 * This also installs a custom ->d_revalidate() method which will invalidate the
638 * dentry if it was created without the key and the key is later added.
640 * Return: 0 on success; -ENOENT if key is unavailable but the filename isn't a
641 * correctly formed encoded ciphertext name, so a negative dentry should be
642 * created; or another -errno code.
644 static inline int fscrypt_prepare_lookup(struct inode *dir,
645 struct dentry *dentry,
646 struct fscrypt_name *fname)
648 if (IS_ENCRYPTED(dir))
649 return __fscrypt_prepare_lookup(dir, dentry, fname);
651 memset(fname, 0, sizeof(*fname));
652 fname->usr_fname = &dentry->d_name;
653 fname->disk_name.name = (unsigned char *)dentry->d_name.name;
654 fname->disk_name.len = dentry->d_name.len;
659 * fscrypt_prepare_setattr - prepare to change a possibly-encrypted inode's attributes
660 * @dentry: dentry through which the inode is being changed
661 * @attr: attributes to change
663 * Prepare for ->setattr() on a possibly-encrypted inode. On an encrypted file,
664 * most attribute changes are allowed even without the encryption key. However,
665 * without the encryption key we do have to forbid truncates. This is needed
666 * because the size being truncated to may not be a multiple of the filesystem
667 * block size, and in that case we'd have to decrypt the final block, zero the
668 * portion past i_size, and re-encrypt it. (We *could* allow truncating to a
669 * filesystem block boundary, but it's simpler to just forbid all truncates ---
670 * and we already forbid all other contents modifications without the key.)
672 * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
673 * if a problem occurred while setting up the encryption key.
675 static inline int fscrypt_prepare_setattr(struct dentry *dentry,
678 if (attr->ia_valid & ATTR_SIZE)
679 return fscrypt_require_key(d_inode(dentry));
684 * fscrypt_prepare_symlink - prepare to create a possibly-encrypted symlink
685 * @dir: directory in which the symlink is being created
686 * @target: plaintext symlink target
687 * @len: length of @target excluding null terminator
688 * @max_len: space the filesystem has available to store the symlink target
689 * @disk_link: (out) the on-disk symlink target being prepared
691 * This function computes the size the symlink target will require on-disk,
692 * stores it in @disk_link->len, and validates it against @max_len. An
693 * encrypted symlink may be longer than the original.
695 * Additionally, @disk_link->name is set to @target if the symlink will be
696 * unencrypted, but left NULL if the symlink will be encrypted. For encrypted
697 * symlinks, the filesystem must call fscrypt_encrypt_symlink() to create the
698 * on-disk target later. (The reason for the two-step process is that some
699 * filesystems need to know the size of the symlink target before creating the
700 * inode, e.g. to determine whether it will be a "fast" or "slow" symlink.)
702 * Return: 0 on success, -ENAMETOOLONG if the symlink target is too long,
703 * -ENOKEY if the encryption key is missing, or another -errno code if a problem
704 * occurred while setting up the encryption key.
706 static inline int fscrypt_prepare_symlink(struct inode *dir,
709 unsigned int max_len,
710 struct fscrypt_str *disk_link)
712 if (IS_ENCRYPTED(dir) || fscrypt_dummy_context_enabled(dir))
713 return __fscrypt_prepare_symlink(dir, len, max_len, disk_link);
715 disk_link->name = (unsigned char *)target;
716 disk_link->len = len + 1;
717 if (disk_link->len > max_len)
718 return -ENAMETOOLONG;
723 * fscrypt_encrypt_symlink - encrypt the symlink target if needed
724 * @inode: symlink inode
725 * @target: plaintext symlink target
726 * @len: length of @target excluding null terminator
727 * @disk_link: (in/out) the on-disk symlink target being prepared
729 * If the symlink target needs to be encrypted, then this function encrypts it
730 * into @disk_link->name. fscrypt_prepare_symlink() must have been called
731 * previously to compute @disk_link->len. If the filesystem did not allocate a
732 * buffer for @disk_link->name after calling fscrypt_prepare_link(), then one
733 * will be kmalloc()'ed and the filesystem will be responsible for freeing it.
735 * Return: 0 on success, -errno on failure
737 static inline int fscrypt_encrypt_symlink(struct inode *inode,
740 struct fscrypt_str *disk_link)
742 if (IS_ENCRYPTED(inode))
743 return __fscrypt_encrypt_symlink(inode, target, len, disk_link);
747 /* If *pagep is a bounce page, free it and set *pagep to the pagecache page */
748 static inline void fscrypt_finalize_bounce_page(struct page **pagep)
750 struct page *page = *pagep;
752 if (fscrypt_is_bounce_page(page)) {
753 *pagep = fscrypt_pagecache_page(page);
754 fscrypt_free_bounce_page(page);
758 #endif /* _LINUX_FSCRYPT_H */