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

From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: James Bottomley <jejb@linux.ibm.com>
Cc: "Zhao, Shirley" <shirley.zhao@intel.com>,
	Mimi Zohar <zohar@linux.ibm.com>,
	Jonathan Corbet <corbet@lwn.net>,
	"linux-integrity@vger.kernel.org"
	<linux-integrity@vger.kernel.org>,
	"keyrings@vger.kernel.org" <keyrings@vger.kernel.org>,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	'Mauro Carvalho Chehab' <mchehab+samsung@kernel.org>,
	"Zhu, Bing" <bing.zhu@intel.com>,
	"Chen, Luhai" <luhai.chen@intel.com>
Subject: Re: One question about trusted key of keyring in Linux kernel.
Date: Wed, 11 Dec 2019 19:23:59 +0200	[thread overview]
Message-ID: <20191211172345.GB4516@linux.intel.com> (raw)
In-Reply-To: <1575923513.31378.22.camel@linux.ibm.com>

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