Mimi,
On Sun, Jan 09, 2022 at 01:55:13PM -0500, Mimi Zohar wrote:
> Define a function named fsverity_get_digest() to return the verity file
> digest and the associated hash algorithm (enum hash_algo).
>
> Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
> ---
> fs/verity/Kconfig | 1 +
> fs/verity/fsverity_private.h | 7 -------
> fs/verity/measure.c | 40 ++++++++++++++++++++++++++++++++++++
> include/linux/fsverity.h | 18 ++++++++++++++++
> 4 files changed, 59 insertions(+), 7 deletions(-)
>
> diff --git a/fs/verity/measure.c b/fs/verity/measure.c
> index f0d7b30c62db..52906b2e5811 100644
> --- a/fs/verity/measure.c
> +++ b/fs/verity/measure.c
> @@ -57,3 +57,43 @@ int fsverity_ioctl_measure(struct file *filp, void __user *_uarg)
> 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.
> + *
> + * 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);
> + *alg = HASH_ALGO__LAST;
Perhaps this line is redundant (*alg is overwritten later) and would
needlessly mangle output value in case of -EINVAL while it's being
untouched on -ENODATA.
Thanks,
> +
> + /* convert hash algorithm to hash_algo_name */
> + i = match_string(hash_algo_name, HASH_ALGO__LAST, hash_alg->name);
> + if (i < 0)
> + return -EINVAL;
> + *alg = i;
> +
> + 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;
> +}
