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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> | |
5d0f0e57 | 15 | #include <linux/mm.h> |
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16 | #include <crypto/hash_info.h> |
17 | #include <crypto/sha2.h> | |
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18 | #include <uapi/linux/fsverity.h> |
19 | ||
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20 | /* |
21 | * Largest digest size among all hash algorithms supported by fs-verity. | |
22 | * Currently assumed to be <= size of fsverity_descriptor::root_hash. | |
23 | */ | |
24 | #define FS_VERITY_MAX_DIGEST_SIZE SHA512_DIGEST_SIZE | |
25 | ||
38622010 BB |
26 | /* Arbitrary limit to bound the kmalloc() size. Can be changed. */ |
27 | #define FS_VERITY_MAX_DESCRIPTOR_SIZE 16384 | |
28 | ||
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29 | /* Verity operations for filesystems */ |
30 | struct fsverity_operations { | |
31 | ||
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32 | /** |
33 | * Begin enabling verity on the given file. | |
34 | * | |
35 | * @filp: a readonly file descriptor for the file | |
36 | * | |
37 | * The filesystem must do any needed filesystem-specific preparations | |
38 | * for enabling verity, e.g. evicting inline data. It also must return | |
39 | * -EBUSY if verity is already being enabled on the given file. | |
40 | * | |
41 | * i_rwsem is held for write. | |
42 | * | |
43 | * Return: 0 on success, -errno on failure | |
44 | */ | |
45 | int (*begin_enable_verity)(struct file *filp); | |
46 | ||
47 | /** | |
48 | * End enabling verity on the given file. | |
49 | * | |
50 | * @filp: a readonly file descriptor for the file | |
51 | * @desc: the verity descriptor to write, or NULL on failure | |
52 | * @desc_size: size of verity descriptor, or 0 on failure | |
53 | * @merkle_tree_size: total bytes the Merkle tree took up | |
54 | * | |
55 | * If desc == NULL, then enabling verity failed and the filesystem only | |
56 | * must do any necessary cleanups. Else, it must also store the given | |
57 | * verity descriptor to a fs-specific location associated with the inode | |
58 | * and do any fs-specific actions needed to mark the inode as a verity | |
59 | * inode, e.g. setting a bit in the on-disk inode. The filesystem is | |
60 | * also responsible for setting the S_VERITY flag in the VFS inode. | |
61 | * | |
62 | * i_rwsem is held for write, but it may have been dropped between | |
63 | * ->begin_enable_verity() and ->end_enable_verity(). | |
64 | * | |
65 | * Return: 0 on success, -errno on failure | |
66 | */ | |
67 | int (*end_enable_verity)(struct file *filp, const void *desc, | |
68 | size_t desc_size, u64 merkle_tree_size); | |
69 | ||
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70 | /** |
71 | * Get the verity descriptor of the given inode. | |
72 | * | |
73 | * @inode: an inode with the S_VERITY flag set | |
74 | * @buf: buffer in which to place the verity descriptor | |
75 | * @bufsize: size of @buf, or 0 to retrieve the size only | |
76 | * | |
77 | * If bufsize == 0, then the size of the verity descriptor is returned. | |
78 | * Otherwise the verity descriptor is written to 'buf' and its actual | |
79 | * size is returned; -ERANGE is returned if it's too large. This may be | |
80 | * called by multiple processes concurrently on the same inode. | |
81 | * | |
82 | * Return: the size on success, -errno on failure | |
83 | */ | |
84 | int (*get_verity_descriptor)(struct inode *inode, void *buf, | |
85 | size_t bufsize); | |
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86 | |
87 | /** | |
88 | * Read a Merkle tree page of the given inode. | |
89 | * | |
90 | * @inode: the inode | |
91 | * @index: 0-based index of the page within the Merkle tree | |
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92 | * @num_ra_pages: The number of Merkle tree pages that should be |
93 | * prefetched starting at @index if the page at @index | |
94 | * isn't already cached. Implementations may ignore this | |
95 | * argument; it's only a performance optimization. | |
8a1d0f9c | 96 | * |
56124d6c | 97 | * This can be called at any time on an open verity file. It may be |
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98 | * called by multiple processes concurrently, even with the same page. |
99 | * | |
100 | * Note that this must retrieve a *page*, not necessarily a *block*. | |
101 | * | |
102 | * Return: the page on success, ERR_PTR() on failure | |
103 | */ | |
104 | struct page *(*read_merkle_tree_page)(struct inode *inode, | |
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105 | pgoff_t index, |
106 | unsigned long num_ra_pages); | |
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107 | |
108 | /** | |
109 | * Write a Merkle tree block to the given inode. | |
110 | * | |
111 | * @inode: the inode for which the Merkle tree is being built | |
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112 | * @buf: the Merkle tree block to write |
113 | * @pos: the position of the block in the Merkle tree (in bytes) | |
114 | * @size: the Merkle tree block size (in bytes) | |
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115 | * |
116 | * This is only called between ->begin_enable_verity() and | |
117 | * ->end_enable_verity(). | |
118 | * | |
119 | * Return: 0 on success, -errno on failure | |
120 | */ | |
121 | int (*write_merkle_tree_block)(struct inode *inode, const void *buf, | |
72ea15f0 | 122 | u64 pos, unsigned int size); |
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123 | }; |
124 | ||
125 | #ifdef CONFIG_FS_VERITY | |
126 | ||
127 | static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) | |
128 | { | |
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129 | /* |
130 | * Pairs with the cmpxchg_release() in fsverity_set_info(). | |
131 | * I.e., another task may publish ->i_verity_info concurrently, | |
132 | * executing a RELEASE barrier. We need to use smp_load_acquire() here | |
133 | * to safely ACQUIRE the memory the other task published. | |
134 | */ | |
135 | return smp_load_acquire(&inode->i_verity_info); | |
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136 | } |
137 | ||
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138 | /* enable.c */ |
139 | ||
9cd6b593 | 140 | int fsverity_ioctl_enable(struct file *filp, const void __user *arg); |
3fda4c61 | 141 | |
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142 | /* measure.c */ |
143 | ||
9cd6b593 | 144 | int fsverity_ioctl_measure(struct file *filp, void __user *arg); |
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145 | int fsverity_get_digest(struct inode *inode, |
146 | u8 digest[FS_VERITY_MAX_DIGEST_SIZE], | |
147 | enum hash_algo *alg); | |
4dd893d8 | 148 | |
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149 | /* open.c */ |
150 | ||
a6528a96 | 151 | int __fsverity_file_open(struct inode *inode, struct file *filp); |
01d90c07 | 152 | int __fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr); |
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153 | void __fsverity_cleanup_inode(struct inode *inode); |
154 | ||
155 | /** | |
156 | * fsverity_cleanup_inode() - free the inode's verity info, if present | |
157 | * @inode: an inode being evicted | |
158 | * | |
159 | * Filesystems must call this on inode eviction to free ->i_verity_info. | |
160 | */ | |
161 | static inline void fsverity_cleanup_inode(struct inode *inode) | |
162 | { | |
163 | if (inode->i_verity_info) | |
164 | __fsverity_cleanup_inode(inode); | |
165 | } | |
fd2d1acf | 166 | |
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167 | /* read_metadata.c */ |
168 | ||
169 | int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg); | |
170 | ||
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171 | /* verify.c */ |
172 | ||
5d0f0e57 | 173 | bool fsverity_verify_blocks(struct folio *folio, size_t len, size_t offset); |
9cd6b593 EB |
174 | void fsverity_verify_bio(struct bio *bio); |
175 | void fsverity_enqueue_verify_work(struct work_struct *work); | |
8a1d0f9c | 176 | |
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177 | #else /* !CONFIG_FS_VERITY */ |
178 | ||
179 | static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) | |
180 | { | |
181 | return NULL; | |
182 | } | |
183 | ||
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184 | /* enable.c */ |
185 | ||
186 | static inline int fsverity_ioctl_enable(struct file *filp, | |
187 | const void __user *arg) | |
188 | { | |
189 | return -EOPNOTSUPP; | |
190 | } | |
191 | ||
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192 | /* measure.c */ |
193 | ||
194 | static inline int fsverity_ioctl_measure(struct file *filp, void __user *arg) | |
195 | { | |
196 | return -EOPNOTSUPP; | |
197 | } | |
198 | ||
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199 | static inline int fsverity_get_digest(struct inode *inode, |
200 | u8 digest[FS_VERITY_MAX_DIGEST_SIZE], | |
201 | enum hash_algo *alg) | |
202 | { | |
203 | return -EOPNOTSUPP; | |
204 | } | |
205 | ||
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206 | /* open.c */ |
207 | ||
a6528a96 | 208 | static inline int __fsverity_file_open(struct inode *inode, struct file *filp) |
fd2d1acf | 209 | { |
a6528a96 | 210 | return -EOPNOTSUPP; |
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211 | } |
212 | ||
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213 | static inline int __fsverity_prepare_setattr(struct dentry *dentry, |
214 | struct iattr *attr) | |
c1d9b584 | 215 | { |
01d90c07 | 216 | return -EOPNOTSUPP; |
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217 | } |
218 | ||
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219 | static inline void fsverity_cleanup_inode(struct inode *inode) |
220 | { | |
221 | } | |
222 | ||
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223 | /* read_metadata.c */ |
224 | ||
225 | static inline int fsverity_ioctl_read_metadata(struct file *filp, | |
226 | const void __user *uarg) | |
227 | { | |
228 | return -EOPNOTSUPP; | |
229 | } | |
230 | ||
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231 | /* verify.c */ |
232 | ||
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233 | static inline bool fsverity_verify_blocks(struct folio *folio, size_t len, |
234 | size_t offset) | |
8a1d0f9c | 235 | { |
8eb8af4b | 236 | WARN_ON_ONCE(1); |
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237 | return false; |
238 | } | |
239 | ||
240 | static inline void fsverity_verify_bio(struct bio *bio) | |
241 | { | |
8eb8af4b | 242 | WARN_ON_ONCE(1); |
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243 | } |
244 | ||
245 | static inline void fsverity_enqueue_verify_work(struct work_struct *work) | |
246 | { | |
8eb8af4b | 247 | WARN_ON_ONCE(1); |
8a1d0f9c EB |
248 | } |
249 | ||
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250 | #endif /* !CONFIG_FS_VERITY */ |
251 | ||
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252 | static inline bool fsverity_verify_folio(struct folio *folio) |
253 | { | |
254 | return fsverity_verify_blocks(folio, folio_size(folio), 0); | |
255 | } | |
256 | ||
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257 | static inline bool fsverity_verify_page(struct page *page) |
258 | { | |
5d0f0e57 | 259 | return fsverity_verify_blocks(page_folio(page), PAGE_SIZE, 0); |
5306892a EB |
260 | } |
261 | ||
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262 | /** |
263 | * fsverity_active() - do reads from the inode need to go through fs-verity? | |
6377a38b | 264 | * @inode: inode to check |
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265 | * |
266 | * This checks whether ->i_verity_info has been set. | |
267 | * | |
704528d8 | 268 | * Filesystems call this from ->readahead() to check whether the pages need to |
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269 | * be verified or not. Don't use IS_VERITY() for this purpose; it's subject to |
270 | * a race condition where the file is being read concurrently with | |
271 | * FS_IOC_ENABLE_VERITY completing. (S_VERITY is set before ->i_verity_info.) | |
6377a38b EB |
272 | * |
273 | * Return: true if reads need to go through fs-verity, otherwise false | |
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274 | */ |
275 | static inline bool fsverity_active(const struct inode *inode) | |
276 | { | |
277 | return fsverity_get_info(inode) != NULL; | |
278 | } | |
279 | ||
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280 | /** |
281 | * fsverity_file_open() - prepare to open a verity file | |
282 | * @inode: the inode being opened | |
283 | * @filp: the struct file being set up | |
284 | * | |
285 | * When opening a verity file, deny the open if it is for writing. Otherwise, | |
286 | * set up the inode's ->i_verity_info if not already done. | |
287 | * | |
288 | * When combined with fscrypt, this must be called after fscrypt_file_open(). | |
289 | * Otherwise, we won't have the key set up to decrypt the verity metadata. | |
290 | * | |
291 | * Return: 0 on success, -errno on failure | |
292 | */ | |
293 | static inline int fsverity_file_open(struct inode *inode, struct file *filp) | |
294 | { | |
295 | if (IS_VERITY(inode)) | |
296 | return __fsverity_file_open(inode, filp); | |
297 | return 0; | |
298 | } | |
299 | ||
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300 | /** |
301 | * fsverity_prepare_setattr() - prepare to change a verity inode's attributes | |
302 | * @dentry: dentry through which the inode is being changed | |
303 | * @attr: attributes to change | |
304 | * | |
305 | * Verity files are immutable, so deny truncates. This isn't covered by the | |
306 | * open-time check because sys_truncate() takes a path, not a file descriptor. | |
307 | * | |
308 | * Return: 0 on success, -errno on failure | |
309 | */ | |
310 | static inline int fsverity_prepare_setattr(struct dentry *dentry, | |
311 | struct iattr *attr) | |
312 | { | |
313 | if (IS_VERITY(d_inode(dentry))) | |
314 | return __fsverity_prepare_setattr(dentry, attr); | |
315 | return 0; | |
316 | } | |
317 | ||
fd2d1acf | 318 | #endif /* _LINUX_FSVERITY_H */ |