103 lines
2.8 KiB
C
103 lines
2.8 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Ioctl to get a verity file's digest
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*
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* Copyright 2019 Google LLC
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*/
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#include "fsverity_private.h"
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#include <linux/uaccess.h>
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/**
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* fsverity_ioctl_measure() - get a verity file's digest
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* @filp: file to get digest of
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* @_uarg: user pointer to fsverity_digest
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*
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* Retrieve the file digest that the kernel is enforcing for reads from a verity
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* file. See the "FS_IOC_MEASURE_VERITY" section of
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* Documentation/filesystems/fsverity.rst for the documentation.
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*
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* Return: 0 on success, -errno on failure
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*/
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int fsverity_ioctl_measure(struct file *filp, void __user *_uarg)
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{
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const struct inode *inode = file_inode(filp);
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struct fsverity_digest __user *uarg = _uarg;
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const struct fsverity_info *vi;
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const struct fsverity_hash_alg *hash_alg;
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struct fsverity_digest arg;
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vi = fsverity_get_info(inode);
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if (!vi)
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return -ENODATA; /* not a verity file */
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hash_alg = vi->tree_params.hash_alg;
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/*
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* The user specifies the digest_size their buffer has space for; we can
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* return the digest if it fits in the available space. We write back
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* the actual size, which may be shorter than the user-specified size.
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*/
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if (get_user(arg.digest_size, &uarg->digest_size))
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return -EFAULT;
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if (arg.digest_size < hash_alg->digest_size)
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return -EOVERFLOW;
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memset(&arg, 0, sizeof(arg));
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arg.digest_algorithm = hash_alg - fsverity_hash_algs;
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arg.digest_size = hash_alg->digest_size;
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if (copy_to_user(uarg, &arg, sizeof(arg)))
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return -EFAULT;
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if (copy_to_user(uarg->digest, vi->file_digest, hash_alg->digest_size))
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return -EFAULT;
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return 0;
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}
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EXPORT_SYMBOL_GPL(fsverity_ioctl_measure);
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/**
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* fsverity_get_digest() - get a verity file's digest
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* @inode: inode to get digest of
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* @digest: (out) pointer to the digest
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* @alg: (out) pointer to the hash algorithm enumeration
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*
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* Return the file hash algorithm and digest of an fsverity protected file.
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* Assumption: before calling fsverity_get_digest(), the file must have been
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* opened.
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*
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* Return: 0 on success, -errno on failure
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*/
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int fsverity_get_digest(struct inode *inode,
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u8 digest[FS_VERITY_MAX_DIGEST_SIZE],
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enum hash_algo *alg)
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{
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const struct fsverity_info *vi;
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const struct fsverity_hash_alg *hash_alg;
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int i;
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vi = fsverity_get_info(inode);
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if (!vi)
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return -ENODATA; /* not a verity file */
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hash_alg = vi->tree_params.hash_alg;
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memset(digest, 0, FS_VERITY_MAX_DIGEST_SIZE);
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/* convert the verity hash algorithm name to a hash_algo_name enum */
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i = match_string(hash_algo_name, HASH_ALGO__LAST, hash_alg->name);
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if (i < 0)
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return -EINVAL;
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*alg = i;
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if (WARN_ON_ONCE(hash_alg->digest_size != hash_digest_size[*alg]))
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return -EINVAL;
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memcpy(digest, vi->file_digest, hash_alg->digest_size);
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pr_debug("file digest %s:%*phN\n", hash_algo_name[*alg],
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hash_digest_size[*alg], digest);
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return 0;
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}
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