[PATCH] SoC: cros_ec_codec: switch to library API for SHA-256

[Tzung-Bi Shih]

On Fri, May 15, 2020 at 12:26 AM Benson Leung <bleung at google.com> wrote:
> On Thu, May 14, 2020 at 06:18:47PM +0200, Ard Biesheuvel wrote:
> > The CrOS EC codec driver uses SHA-256 explicitly, and not in a
> > performance critical manner, so there is really no point in using
> > the dynamic SHASH crypto API here. Let's switch to the library API
> > instead.

Pardon me if I don't understand it precisely.  What is the difference
between the two APIs?  Suppose it should calculate the same SHA256
hash with the same binary blob after switching to library API?

> > Looking at the code, I was wondering if the SHA-256 is really required
> > here? It looks like it is using it as some kind of fingerprint to decide
> > whether the provided file is identical to the one that has already been
> > loaded. If this is the case, we should probably just use CRC32 instead.

No, the binary blob carries data and possibly code.  We are not only
using the hash as a fingerprint but also an integrity check.

> > Also, do we really need to wipe the context struct? Is there any security
> > sensitive data in there?

No, not necessary as far as I know.