Re: [PATCH 1/4] fs-verity: define a function to return the integrity protected file digest

[Lakshmi Ramasubramanian]

Hi Mimi,

On 11/29/2021 6:19 PM, Eric Biggers wrote:
> Generally looks fine.  A few nits below:
>
> On Mon, Nov 29, 2021 at 12:00:54PM -0500, Mimi Zohar wrote:
> > Define a function named fsverity_measure() to return the verity file digest
> > and the associated hash algorithm (enum hash_algo).
> >
> > Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
> > ---
> >   fs/verity/fsverity_private.h |  6 -----
> >   fs/verity/measure.c          | 49 ++++++++++++++++++++++++++++++++++++
> >   include/linux/fsverity.h     | 17 +++++++++++++
> >   3 files changed, 66 insertions(+), 6 deletions(-)
> >
> > diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h
> > index a7920434bae5..54c5f0993541 100644
> > --- a/fs/verity/fsverity_private.h
> > +++ b/fs/verity/fsverity_private.h
> > @@ -26,12 +26,6 @@ struct ahash_request;
> >    */
> >   #define FS_VERITY_MAX_LEVELS		8
> >   
> > -/*
> > - * Largest digest size among all hash algorithms supported by fs-verity.
> > - * Currently assumed to be <= size of fsverity_descriptor::root_hash.
> > - */
> > -#define FS_VERITY_MAX_DIGEST_SIZE	SHA512_DIGEST_SIZE
>
> The include of sha2.h should be removed from this file.
>
> > +/**
> > + * fsverity_measure() - get a verity file's digest
nit: The function name seems to suggest it is measuring the fs-verity 
file's digest. Since it is reading the file's digest: 
fsverity_read_digest() or fsverity_read_measure()?

 -lakshmi

> > + * @inode: inode to get digest of
> > + * @digest: pointer to the digest
> > + * @alg: pointer to the hash algorithm enumeration
>
> It should be made clear that @digest and @alg are output, for example:
>
>   * @digest: (out) pointer to the digest
>   * @alg: (out) pointer to the hash algorithm enumeration
>
> > + * Return the file hash algorithm, digest size, and digest of an fsverity
> > + * protected file.
>
> The digest size is implied, not returned.
>
> > +
> > +		if (!strcmp(hash_alg->name, hash_algo_name[i])) {
>
> As the kernel test robot pointed out, this creates a dependency on
> CRYPTO_HASH_INFO.  So FS_VERITY will need to select CRYPTO_HASH_INFO.
>
> - Eric