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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 */
25struct 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
35struct 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
50static inline bool fscrypt_has_encryption_key(const struct inode *inode)
51{
52 return (inode->i_crypt_info != NULL);
53}
54
55static 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/* crypto.c */
62extern void fscrypt_enqueue_decrypt_work(struct work_struct *);
63extern struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *, gfp_t);
64extern void fscrypt_release_ctx(struct fscrypt_ctx *);
65extern struct page *fscrypt_encrypt_page(const struct inode *, struct page *,
66 unsigned int, unsigned int,
67 u64, gfp_t);
68extern int fscrypt_decrypt_page(const struct inode *, struct page *, unsigned int,
69 unsigned int, u64);
70
71static inline struct page *fscrypt_control_page(struct page *page)
72{
73 return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
74}
75
76extern void fscrypt_restore_control_page(struct page *);
77
78/* policy.c */
79extern int fscrypt_ioctl_set_policy(struct file *, const void __user *);
80extern int fscrypt_ioctl_get_policy(struct file *, void __user *);
81extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
82extern int fscrypt_inherit_context(struct inode *, struct inode *,
83 void *, bool);
84/* keyinfo.c */
85extern int fscrypt_get_encryption_info(struct inode *);
86extern void fscrypt_put_encryption_info(struct inode *);
87
88/* fname.c */
89extern int fscrypt_setup_filename(struct inode *, const struct qstr *,
90 int lookup, struct fscrypt_name *);
91
92static inline void fscrypt_free_filename(struct fscrypt_name *fname)
93{
94 kfree(fname->crypto_buf.name);
95}
96
97extern int fscrypt_fname_alloc_buffer(const struct inode *, u32,
98 struct fscrypt_str *);
99extern void fscrypt_fname_free_buffer(struct fscrypt_str *);
100extern int fscrypt_fname_disk_to_usr(struct inode *, u32, u32,
101 const struct fscrypt_str *, struct fscrypt_str *);
102
103#define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE 32
104
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))
109
110#define FSCRYPT_FNAME_DIGEST_SIZE FS_CRYPTO_BLOCK_SIZE
111
112/**
113 * fscrypt_digested_name - alternate identifier for an on-disk filename
114 *
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.
120 *
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.
130 *
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.
137 */
138struct fscrypt_digested_name {
139 u32 hash;
140 u32 minor_hash;
141 u8 digest[FSCRYPT_FNAME_DIGEST_SIZE];
142};
143
144/**
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
149 *
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.
155 *
156 * Return: %true if the name matches, otherwise %false.
157 */
158static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
159 const u8 *de_name, u32 de_name_len)
160{
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] != '_'))
165 return false;
166 if (de_name_len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE)
167 return false;
168 return !memcmp(FSCRYPT_FNAME_DIGEST(de_name, de_name_len),
169 n->digest, FSCRYPT_FNAME_DIGEST_SIZE);
170 }
171
172 if (de_name_len != fname->disk_name.len)
173 return false;
174 return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len);
175}
176
177/* bio.c */
178extern void fscrypt_decrypt_bio(struct bio *);
179extern void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx,
180 struct bio *bio);
181extern void fscrypt_pullback_bio_page(struct page **, bool);
182extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t,
183 unsigned int);
184
185/* hooks.c */
186extern int fscrypt_file_open(struct inode *inode, struct file *filp);
187extern int __fscrypt_prepare_link(struct inode *inode, struct inode *dir);
188extern int __fscrypt_prepare_rename(struct inode *old_dir,
189 struct dentry *old_dentry,
190 struct inode *new_dir,
191 struct dentry *new_dentry,
192 unsigned int flags);
193extern int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry);
194extern int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len,
195 unsigned int max_len,
196 struct fscrypt_str *disk_link);
197extern int __fscrypt_encrypt_symlink(struct inode *inode, const char *target,
198 unsigned int len,
199 struct fscrypt_str *disk_link);
200extern const char *fscrypt_get_symlink(struct inode *inode, const void *caddr,
201 unsigned int max_size,
202 struct delayed_call *done);
203
204#endif /* _LINUX_FSCRYPT_SUPP_H */