Re: One question about trusted key of keyring in Linux kernel.

From: Jarkko Sakkinen
Date: Wed Dec 11 2019 - 12:24:07 EST


On Mon, Dec 09, 2019 at 12:31:53PM -0800, James Bottomley wrote:
> On Mon, 2019-12-09 at 21:47 +0200, Jarkko Sakkinen wrote:
> > On Mon, Dec 02, 2019 at 10:55:32AM -0800, James Bottomley wrote:
> > > blob but it looks like we need to fix the API. I suppose the good
> > > news is given this failure that we have the opportunity to rewrite
> > > the API since no-one else can have used it for anything because of
> > > this. The
> >
> > I did successfully run this test when I wrote it 5 years ago:
> >
> > https://github.com/jsakkine-intel/tpm2-scripts/blob/master/keyctl-smo
> > ke.sh
> >
> > Given that there is API a way must be found that backwards
> > compatibility
> > is not broken. New format is fine but it must co-exist.
>
> The old API is unsupportable in the combination of policy + auth as I
> already explained. The kernel doesn't have access to the nonces to
> generate the HMAC because the session was created by the user and the
> API has no way to pass them in (plus passing them in would be a huge
> security failure if we tried). Given that Shirley appears to be the
> first person ever to try this, I don't think the old API has grown any
> policy users so its safe to remove it. If we get a complaint, we can
> discuss adding it back.

It works within limits so it can be definitely be maintained for
backwards compatibility.

Also, you are making a claim of the users that we cannot verify.

Finally, the new feature neither handles sessions. You claim that
it could be added later. I have to deny that because until session
handling is there we have no ways to be sure about that.

I see your point but this needs more consideration. It does not
make sense to rush.

/Jarkko