mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-06 02:50:43 +00:00
74836ecbc5
Address several issues with the calling convention and documentation of fsverity_get_digest(): - Make it provide the hash algorithm as either a FS_VERITY_HASH_ALG_* value or HASH_ALGO_* value, at the caller's choice, rather than only a HASH_ALGO_* value as it did before. This allows callers to work with the fsverity native algorithm numbers if they want to. HASH_ALGO_* is what IMA uses, but other users (e.g. overlayfs) should use FS_VERITY_HASH_ALG_* to match fsverity-utils and the fsverity UAPI. - Make it return the digest size so that it doesn't need to be looked up separately. Use the return value for this, since 0 works nicely for the "file doesn't have fsverity enabled" case. This also makes it clear that no other errors are possible. - Rename the 'digest' parameter to 'raw_digest' and clearly document that it is only useful in combination with the algorithm ID. This hopefully clears up a point of confusion. - Export it to modules, since overlayfs will need it for checking the fsverity digests of lowerdata files (https://lore.kernel.org/r/dd294a44e8f401e6b5140029d8355f88748cd8fd.1686565330.git.alexl@redhat.com). Acked-by: Mimi Zohar <zohar@linux.ibm.com> # for the IMA piece Link: https://lore.kernel.org/r/20230612190047.59755-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
102 lines
3.2 KiB
C
102 lines
3.2 KiB
C
// 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
|
|
* @raw_digest: (out) the raw file digest
|
|
* @alg: (out) the digest's algorithm, as a FS_VERITY_HASH_ALG_* value
|
|
* @halg: (out) the digest's algorithm, as a HASH_ALGO_* value
|
|
*
|
|
* Retrieves the fsverity digest of the given file. The file must have been
|
|
* opened at least once since the inode was last loaded into the inode cache;
|
|
* otherwise this function will not recognize when fsverity is enabled.
|
|
*
|
|
* The file's fsverity digest consists of @raw_digest in combination with either
|
|
* @alg or @halg. (The caller can choose which one of @alg or @halg to use.)
|
|
*
|
|
* IMPORTANT: Callers *must* make use of one of the two algorithm IDs, since
|
|
* @raw_digest is meaningless without knowing which algorithm it uses! fsverity
|
|
* provides no security guarantee for users who ignore the algorithm ID, even if
|
|
* they use the digest size (since algorithms can share the same digest size).
|
|
*
|
|
* Return: The size of the raw digest in bytes, or 0 if the file doesn't have
|
|
* fsverity enabled.
|
|
*/
|
|
int fsverity_get_digest(struct inode *inode,
|
|
u8 raw_digest[FS_VERITY_MAX_DIGEST_SIZE],
|
|
u8 *alg, enum hash_algo *halg)
|
|
{
|
|
const struct fsverity_info *vi;
|
|
const struct fsverity_hash_alg *hash_alg;
|
|
|
|
vi = fsverity_get_info(inode);
|
|
if (!vi)
|
|
return 0; /* not a verity file */
|
|
|
|
hash_alg = vi->tree_params.hash_alg;
|
|
memcpy(raw_digest, vi->file_digest, hash_alg->digest_size);
|
|
if (alg)
|
|
*alg = hash_alg - fsverity_hash_algs;
|
|
if (halg)
|
|
*halg = hash_alg->algo_id;
|
|
return hash_alg->digest_size;
|
|
}
|
|
EXPORT_SYMBOL_GPL(fsverity_get_digest);
|