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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> | |
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15 | #include <crypto/hash_info.h> |
16 | #include <crypto/sha2.h> | |
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17 | #include <uapi/linux/fsverity.h> |
18 | ||
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19 | /* |
20 | * Largest digest size among all hash algorithms supported by fs-verity. | |
21 | * Currently assumed to be <= size of fsverity_descriptor::root_hash. | |
22 | */ | |
23 | #define FS_VERITY_MAX_DIGEST_SIZE SHA512_DIGEST_SIZE | |
24 | ||
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25 | /* Verity operations for filesystems */ |
26 | struct fsverity_operations { | |
27 | ||
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28 | /** |
29 | * Begin enabling verity on the given file. | |
30 | * | |
31 | * @filp: a readonly file descriptor for the file | |
32 | * | |
33 | * The filesystem must do any needed filesystem-specific preparations | |
34 | * for enabling verity, e.g. evicting inline data. It also must return | |
35 | * -EBUSY if verity is already being enabled on the given file. | |
36 | * | |
37 | * i_rwsem is held for write. | |
38 | * | |
39 | * Return: 0 on success, -errno on failure | |
40 | */ | |
41 | int (*begin_enable_verity)(struct file *filp); | |
42 | ||
43 | /** | |
44 | * End enabling verity on the given file. | |
45 | * | |
46 | * @filp: a readonly file descriptor for the file | |
47 | * @desc: the verity descriptor to write, or NULL on failure | |
48 | * @desc_size: size of verity descriptor, or 0 on failure | |
49 | * @merkle_tree_size: total bytes the Merkle tree took up | |
50 | * | |
51 | * If desc == NULL, then enabling verity failed and the filesystem only | |
52 | * must do any necessary cleanups. Else, it must also store the given | |
53 | * verity descriptor to a fs-specific location associated with the inode | |
54 | * and do any fs-specific actions needed to mark the inode as a verity | |
55 | * inode, e.g. setting a bit in the on-disk inode. The filesystem is | |
56 | * also responsible for setting the S_VERITY flag in the VFS inode. | |
57 | * | |
58 | * i_rwsem is held for write, but it may have been dropped between | |
59 | * ->begin_enable_verity() and ->end_enable_verity(). | |
60 | * | |
61 | * Return: 0 on success, -errno on failure | |
62 | */ | |
63 | int (*end_enable_verity)(struct file *filp, const void *desc, | |
64 | size_t desc_size, u64 merkle_tree_size); | |
65 | ||
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66 | /** |
67 | * Get the verity descriptor of the given inode. | |
68 | * | |
69 | * @inode: an inode with the S_VERITY flag set | |
70 | * @buf: buffer in which to place the verity descriptor | |
71 | * @bufsize: size of @buf, or 0 to retrieve the size only | |
72 | * | |
73 | * If bufsize == 0, then the size of the verity descriptor is returned. | |
74 | * Otherwise the verity descriptor is written to 'buf' and its actual | |
75 | * size is returned; -ERANGE is returned if it's too large. This may be | |
76 | * called by multiple processes concurrently on the same inode. | |
77 | * | |
78 | * Return: the size on success, -errno on failure | |
79 | */ | |
80 | int (*get_verity_descriptor)(struct inode *inode, void *buf, | |
81 | size_t bufsize); | |
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82 | |
83 | /** | |
84 | * Read a Merkle tree page of the given inode. | |
85 | * | |
86 | * @inode: the inode | |
87 | * @index: 0-based index of the page within the Merkle tree | |
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88 | * @num_ra_pages: The number of Merkle tree pages that should be |
89 | * prefetched starting at @index if the page at @index | |
90 | * isn't already cached. Implementations may ignore this | |
91 | * argument; it's only a performance optimization. | |
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92 | * |
93 | * This can be called at any time on an open verity file, as well as | |
94 | * between ->begin_enable_verity() and ->end_enable_verity(). It may be | |
95 | * called by multiple processes concurrently, even with the same page. | |
96 | * | |
97 | * Note that this must retrieve a *page*, not necessarily a *block*. | |
98 | * | |
99 | * Return: the page on success, ERR_PTR() on failure | |
100 | */ | |
101 | struct page *(*read_merkle_tree_page)(struct inode *inode, | |
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102 | pgoff_t index, |
103 | unsigned long num_ra_pages); | |
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104 | |
105 | /** | |
106 | * Write a Merkle tree block to the given inode. | |
107 | * | |
108 | * @inode: the inode for which the Merkle tree is being built | |
109 | * @buf: block to write | |
110 | * @index: 0-based index of the block within the Merkle tree | |
111 | * @log_blocksize: log base 2 of the Merkle tree block size | |
112 | * | |
113 | * This is only called between ->begin_enable_verity() and | |
114 | * ->end_enable_verity(). | |
115 | * | |
116 | * Return: 0 on success, -errno on failure | |
117 | */ | |
118 | int (*write_merkle_tree_block)(struct inode *inode, const void *buf, | |
119 | u64 index, int log_blocksize); | |
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120 | }; |
121 | ||
122 | #ifdef CONFIG_FS_VERITY | |
123 | ||
124 | static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) | |
125 | { | |
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126 | /* |
127 | * Pairs with the cmpxchg_release() in fsverity_set_info(). | |
128 | * I.e., another task may publish ->i_verity_info concurrently, | |
129 | * executing a RELEASE barrier. We need to use smp_load_acquire() here | |
130 | * to safely ACQUIRE the memory the other task published. | |
131 | */ | |
132 | return smp_load_acquire(&inode->i_verity_info); | |
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133 | } |
134 | ||
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135 | /* enable.c */ |
136 | ||
9cd6b593 | 137 | int fsverity_ioctl_enable(struct file *filp, const void __user *arg); |
3fda4c61 | 138 | |
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139 | /* measure.c */ |
140 | ||
9cd6b593 | 141 | int fsverity_ioctl_measure(struct file *filp, void __user *arg); |
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142 | int fsverity_get_digest(struct inode *inode, |
143 | u8 digest[FS_VERITY_MAX_DIGEST_SIZE], | |
144 | enum hash_algo *alg); | |
4dd893d8 | 145 | |
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146 | /* open.c */ |
147 | ||
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148 | int fsverity_file_open(struct inode *inode, struct file *filp); |
149 | int fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr); | |
150 | void fsverity_cleanup_inode(struct inode *inode); | |
fd2d1acf | 151 | |
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152 | /* read_metadata.c */ |
153 | ||
154 | int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg); | |
155 | ||
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156 | /* verify.c */ |
157 | ||
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158 | bool fsverity_verify_page(struct page *page); |
159 | void fsverity_verify_bio(struct bio *bio); | |
160 | void fsverity_enqueue_verify_work(struct work_struct *work); | |
8a1d0f9c | 161 | |
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162 | #else /* !CONFIG_FS_VERITY */ |
163 | ||
164 | static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) | |
165 | { | |
166 | return NULL; | |
167 | } | |
168 | ||
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169 | /* enable.c */ |
170 | ||
171 | static inline int fsverity_ioctl_enable(struct file *filp, | |
172 | const void __user *arg) | |
173 | { | |
174 | return -EOPNOTSUPP; | |
175 | } | |
176 | ||
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177 | /* measure.c */ |
178 | ||
179 | static inline int fsverity_ioctl_measure(struct file *filp, void __user *arg) | |
180 | { | |
181 | return -EOPNOTSUPP; | |
182 | } | |
183 | ||
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184 | static inline int fsverity_get_digest(struct inode *inode, |
185 | u8 digest[FS_VERITY_MAX_DIGEST_SIZE], | |
186 | enum hash_algo *alg) | |
187 | { | |
188 | return -EOPNOTSUPP; | |
189 | } | |
190 | ||
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191 | /* open.c */ |
192 | ||
193 | static inline int fsverity_file_open(struct inode *inode, struct file *filp) | |
194 | { | |
195 | return IS_VERITY(inode) ? -EOPNOTSUPP : 0; | |
196 | } | |
197 | ||
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198 | static inline int fsverity_prepare_setattr(struct dentry *dentry, |
199 | struct iattr *attr) | |
200 | { | |
201 | return IS_VERITY(d_inode(dentry)) ? -EOPNOTSUPP : 0; | |
202 | } | |
203 | ||
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204 | static inline void fsverity_cleanup_inode(struct inode *inode) |
205 | { | |
206 | } | |
207 | ||
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208 | /* read_metadata.c */ |
209 | ||
210 | static inline int fsverity_ioctl_read_metadata(struct file *filp, | |
211 | const void __user *uarg) | |
212 | { | |
213 | return -EOPNOTSUPP; | |
214 | } | |
215 | ||
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216 | /* verify.c */ |
217 | ||
218 | static inline bool fsverity_verify_page(struct page *page) | |
219 | { | |
220 | WARN_ON(1); | |
221 | return false; | |
222 | } | |
223 | ||
224 | static inline void fsverity_verify_bio(struct bio *bio) | |
225 | { | |
226 | WARN_ON(1); | |
227 | } | |
228 | ||
229 | static inline void fsverity_enqueue_verify_work(struct work_struct *work) | |
230 | { | |
231 | WARN_ON(1); | |
232 | } | |
233 | ||
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234 | #endif /* !CONFIG_FS_VERITY */ |
235 | ||
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236 | /** |
237 | * fsverity_active() - do reads from the inode need to go through fs-verity? | |
6377a38b | 238 | * @inode: inode to check |
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239 | * |
240 | * This checks whether ->i_verity_info has been set. | |
241 | * | |
704528d8 | 242 | * Filesystems call this from ->readahead() to check whether the pages need to |
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243 | * be verified or not. Don't use IS_VERITY() for this purpose; it's subject to |
244 | * a race condition where the file is being read concurrently with | |
245 | * FS_IOC_ENABLE_VERITY completing. (S_VERITY is set before ->i_verity_info.) | |
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246 | * |
247 | * Return: true if reads need to go through fs-verity, otherwise false | |
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248 | */ |
249 | static inline bool fsverity_active(const struct inode *inode) | |
250 | { | |
251 | return fsverity_get_info(inode) != NULL; | |
252 | } | |
253 | ||
fd2d1acf | 254 | #endif /* _LINUX_FSVERITY_H */ |