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1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* | |
ed45e201 | 3 | * Ioctl to get a verity file's digest |
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4 | * |
5 | * Copyright 2019 Google LLC | |
6 | */ | |
7 | ||
8 | #include "fsverity_private.h" | |
9 | ||
10 | #include <linux/uaccess.h> | |
11 | ||
12 | /** | |
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13 | * fsverity_ioctl_measure() - get a verity file's digest |
14 | * @filp: file to get digest of | |
6377a38b | 15 | * @_uarg: user pointer to fsverity_digest |
4dd893d8 | 16 | * |
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17 | * Retrieve the file digest that the kernel is enforcing for reads from a verity |
18 | * file. See the "FS_IOC_MEASURE_VERITY" section of | |
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19 | * Documentation/filesystems/fsverity.rst for the documentation. |
20 | * | |
21 | * Return: 0 on success, -errno on failure | |
22 | */ | |
23 | int fsverity_ioctl_measure(struct file *filp, void __user *_uarg) | |
24 | { | |
25 | const struct inode *inode = file_inode(filp); | |
26 | struct fsverity_digest __user *uarg = _uarg; | |
27 | const struct fsverity_info *vi; | |
28 | const struct fsverity_hash_alg *hash_alg; | |
29 | struct fsverity_digest arg; | |
30 | ||
31 | vi = fsverity_get_info(inode); | |
32 | if (!vi) | |
33 | return -ENODATA; /* not a verity file */ | |
34 | hash_alg = vi->tree_params.hash_alg; | |
35 | ||
36 | /* | |
37 | * The user specifies the digest_size their buffer has space for; we can | |
38 | * return the digest if it fits in the available space. We write back | |
39 | * the actual size, which may be shorter than the user-specified size. | |
40 | */ | |
41 | ||
42 | if (get_user(arg.digest_size, &uarg->digest_size)) | |
43 | return -EFAULT; | |
44 | if (arg.digest_size < hash_alg->digest_size) | |
45 | return -EOVERFLOW; | |
46 | ||
47 | memset(&arg, 0, sizeof(arg)); | |
48 | arg.digest_algorithm = hash_alg - fsverity_hash_algs; | |
49 | arg.digest_size = hash_alg->digest_size; | |
50 | ||
51 | if (copy_to_user(uarg, &arg, sizeof(arg))) | |
52 | return -EFAULT; | |
53 | ||
ed45e201 | 54 | if (copy_to_user(uarg->digest, vi->file_digest, hash_alg->digest_size)) |
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55 | return -EFAULT; |
56 | ||
57 | return 0; | |
58 | } | |
59 | EXPORT_SYMBOL_GPL(fsverity_ioctl_measure); |