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