1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * fs-verity: read-only file-based authenticity protection
4 *
5 * This header declares the interface between the fs/verity/ support layer and
6 * filesystems that support fs-verity.
7 *
8 * Copyright 2019 Google LLC
9 */
10
11 #ifndef _LINUX_FSVERITY_H
12 #define _LINUX_FSVERITY_H
13
14 #include <linux/fs.h>
15 #include <uapi/linux/fsverity.h>
16
17 /* Verity operations for filesystems */
18 struct fsverity_operations {
19
20 /**
21 * Begin enabling verity on the given file.
22 *
23 * @filp: a readonly file descriptor for the file
24 *
25 * The filesystem must do any needed filesystem-specific preparations
26 * for enabling verity, e.g. evicting inline data. It also must return
27 * -EBUSY if verity is already being enabled on the given file.
28 *
29 * i_rwsem is held for write.
30 *
31 * Return: 0 on success, -errno on failure
32 */
33 int (*begin_enable_verity)(struct file *filp);
34
35 /**
36 * End enabling verity on the given file.
37 *
38 * @filp: a readonly file descriptor for the file
39 * @desc: the verity descriptor to write, or NULL on failure
40 * @desc_size: size of verity descriptor, or 0 on failure
41 * @merkle_tree_size: total bytes the Merkle tree took up
42 *
43 * If desc == NULL, then enabling verity failed and the filesystem only
44 * must do any necessary cleanups. Else, it must also store the given
45 * verity descriptor to a fs-specific location associated with the inode
46 * and do any fs-specific actions needed to mark the inode as a verity
47 * inode, e.g. setting a bit in the on-disk inode. The filesystem is
48 * also responsible for setting the S_VERITY flag in the VFS inode.
49 *
50 * i_rwsem is held for write, but it may have been dropped between
51 * ->begin_enable_verity() and ->end_enable_verity().
52 *
53 * Return: 0 on success, -errno on failure
54 */
55 int (*end_enable_verity)(struct file *filp, const void *desc,
56 size_t desc_size, u64 merkle_tree_size);
57
58 /**
59 * Get the verity descriptor of the given inode.
60 *
61 * @inode: an inode with the S_VERITY flag set
62 * @buf: buffer in which to place the verity descriptor
63 * @bufsize: size of @buf, or 0 to retrieve the size only
64 *
65 * If bufsize == 0, then the size of the verity descriptor is returned.
66 * Otherwise the verity descriptor is written to 'buf' and its actual
67 * size is returned; -ERANGE is returned if it's too large. This may be
68 * called by multiple processes concurrently on the same inode.
69 *
70 * Return: the size on success, -errno on failure
71 */
72 int (*get_verity_descriptor)(struct inode *inode, void *buf,
73 size_t bufsize);
74
75 /**
76 * Read a Merkle tree page of the given inode.
77 *
78 * @inode: the inode
79 * @index: 0-based index of the page within the Merkle tree
80 *
81 * This can be called at any time on an open verity file, as well as
82 * between ->begin_enable_verity() and ->end_enable_verity(). It may be
83 * called by multiple processes concurrently, even with the same page.
84 *
85 * Note that this must retrieve a *page*, not necessarily a *block*.
86 *
87 * Return: the page on success, ERR_PTR() on failure
88 */
89 struct page *(*read_merkle_tree_page)(struct inode *inode,
90 pgoff_t index);
91
92 /**
93 * Write a Merkle tree block to the given inode.
94 *
95 * @inode: the inode for which the Merkle tree is being built
96 * @buf: block to write
97 * @index: 0-based index of the block within the Merkle tree
98 * @log_blocksize: log base 2 of the Merkle tree block size
99 *
100 * This is only called between ->begin_enable_verity() and
101 * ->end_enable_verity().
102 *
103 * Return: 0 on success, -errno on failure
104 */
105 int (*write_merkle_tree_block)(struct inode *inode, const void *buf,
106 u64 index, int log_blocksize);
107 };
108
109 #ifdef CONFIG_FS_VERITY
110
111 static inline struct fsverity_info *fsverity_get_info(const struct inode *inode)
112 {
113 /* pairs with the cmpxchg() in fsverity_set_info() */
114 return READ_ONCE(inode->i_verity_info);
115 }
116
117 /* enable.c */
118
119 extern int fsverity_ioctl_enable(struct file *filp, const void __user *arg);
120
121 /* measure.c */
122
123 extern int fsverity_ioctl_measure(struct file *filp, void __user *arg);
124
125 /* open.c */
126
127 extern int fsverity_file_open(struct inode *inode, struct file *filp);
128 extern int fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr);
129 extern void fsverity_cleanup_inode(struct inode *inode);
130
131 /* verify.c */
132
133 extern bool fsverity_verify_page(struct page *page);
134 extern void fsverity_verify_bio(struct bio *bio);
135 extern void fsverity_enqueue_verify_work(struct work_struct *work);
136
137 #else /* !CONFIG_FS_VERITY */
138
139 static inline struct fsverity_info *fsverity_get_info(const struct inode *inode)
140 {
141 return NULL;
142 }
143
144 /* enable.c */
145
146 static inline int fsverity_ioctl_enable(struct file *filp,
147 const void __user *arg)
148 {
149 return -EOPNOTSUPP;
150 }
151
152 /* measure.c */
153
154 static inline int fsverity_ioctl_measure(struct file *filp, void __user *arg)
155 {
156 return -EOPNOTSUPP;
157 }
158
159 /* open.c */
160
161 static inline int fsverity_file_open(struct inode *inode, struct file *filp)
162 {
163 return IS_VERITY(inode) ? -EOPNOTSUPP : 0;
164 }
165
166 static inline int fsverity_prepare_setattr(struct dentry *dentry,
167 struct iattr *attr)
168 {
169 return IS_VERITY(d_inode(dentry)) ? -EOPNOTSUPP : 0;
170 }
171
172 static inline void fsverity_cleanup_inode(struct inode *inode)
173 {
174 }
175
176 /* verify.c */
177
178 static inline bool fsverity_verify_page(struct page *page)
179 {
180 WARN_ON(1);
181 return false;
182 }
183
184 static inline void fsverity_verify_bio(struct bio *bio)
185 {
186 WARN_ON(1);
187 }
188
189 static inline void fsverity_enqueue_verify_work(struct work_struct *work)
190 {
191 WARN_ON(1);
192 }
193
194 #endif /* !CONFIG_FS_VERITY */
195
196 /**
197 * fsverity_active() - do reads from the inode need to go through fs-verity?
198 *
199 * This checks whether ->i_verity_info has been set.
200 *
201 * Filesystems call this from ->readpages() to check whether the pages need to
202 * be verified or not. Don't use IS_VERITY() for this purpose; it's subject to
203 * a race condition where the file is being read concurrently with
204 * FS_IOC_ENABLE_VERITY completing. (S_VERITY is set before ->i_verity_info.)
205 */
206 static inline bool fsverity_active(const struct inode *inode)
207 {
208 return fsverity_get_info(inode) != NULL;
209 }
210
211 #endif /* _LINUX_FSVERITY_H */