Hi Vitaly,
On Mon, 2022-01-10 at 03:47 +0300, Vitaly Chikunov wrote:
> 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!
Mimi
>
> > +
> > + /* 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;
> > +}
