RE: [tpmdd-devel] [PATCH 4/4] keys, trusted: seal/unseal with TPM 2.0 chips

From: "Fuchs, Andreas" <andreas.fuchs@sit.fraunhofer.de>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: "tpmdd-devel@lists.sourceforge.net" 
	<tpmdd-devel@lists.sourceforge.net>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	David Howells <dhowells@redhat.com>,
	"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
	"open list:KEYS-TRUSTED" <linux-security-module@vger.kernel.org>,
	"open list:KEYS-TRUSTED" <keyrings@vger.kernel.org>,
	James Morris <james.l.morris@oracle.com>,
	"David Safford" <safford@us.ibm.com>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	"josh@joshtripplet.org" <josh@joshtripplet.org>,
	"richard.l.maliszewski@intel.com"
	<richard.l.maliszewski@intel.com>,
	"monty.wiseman@intel.com" <monty.wiseman@intel.com>
Subject: RE: [tpmdd-devel] [PATCH 4/4] keys,	trusted: seal/unseal with TPM 2.0 chips
Date: Mon, 5 Oct 2015 13:36:18 +0000	[thread overview]
Message-ID: <9F48E1A823B03B4790B7E6E69430724D9D7AEBD5@EXCH2010A.sit.fraunhofer.de> (raw)
In-Reply-To: <20151005131733.GA4459@intel.com>

> > Regarding the in-kernel "minimal resource manager": AFAIK there is
> > already a tpm-mutex inside the kernel. We could use that mutex and
> > then have the algorithm:
> >
> > [SNIP]
> 
> I don't care about one purpose hacks. Second, I don't care about pseudo
> code (at least not for "too big things"). It has tendency to mask
> unexpected details. If you want to propose something, please go through
> the patch process.
> 
> > We don't need anything more fancy than this. And it should even
> > guarantee that the old values are still present after mutex_release,
> > so (opposed to a full-blown resource-manager) we do not need to keep
> > track and rewrite virtual handles inside the user-space commands.
> >
> > IMHO, this should be lightweight enough even for the most embedded of
> > applications, since the 2*2k blobs are only allocated on demand...
> 
> It's still unnecessary functionality and increases the kernel image size
> and every hack requires maintenance. It would probably end up needing
> compilation flag as there exists efforts like:
> 
> https://tiny.wiki.kernel.org/
> 
> My simple and stupid solution does not *prevent* adding better
> synchronization. I would go with that and implement access broker
> properly and not for just one use case later on.

Unfortunately, I'm not able to write up some code for this myself atm.
Other priorities unfortunately.

I was just pointing out, that the proposed patch will not fit in with
the current approach in TSS2.0, before this user-facing kernel API is
set in stone and _corrected_ new syscalls need to be added later.

Also, the pseudo-code proposal should be a proper minimal access broker
that should solve most accesses to TPM transient objects down the road. 
Session-brokering is a different beast of course.

Cheers,
Andreas