linux-kernel - Re: [PATCH 3/4] tpm: seal/unseal for TPM 2.0

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Message-ID: <20151013194915.GB3669@intel.com>
Date:	Tue, 13 Oct 2015 22:49:15 +0300
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	peterhuewe@....de, gregkh@...uxfoundation.org,
	akpm@...ux-foundation.org, mjg59@...f.ucam.org,
	Marcel Selhorst <tpmdd@...horst.net>,
	David Safford <safford@...ibm.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	David Howells <dhowells@...hat.com>,
	"open list:KEYS-TRUSTED" <linux-security-module@...r.kernel.org>,
	"open list:KEYS-TRUSTED" <keyrings@...r.kernel.org>
Subject: Re: [PATCH 3/4] tpm: seal/unseal for TPM 2.0

On Tue, Oct 13, 2015 at 11:34:42AM -0600, Jason Gunthorpe wrote:
> On Fri, Oct 02, 2015 at 11:38:17AM +0300, Jarkko Sakkinen wrote:
> > Added tpm_trusted_seal() and tpm_trusted_unseal() API for sealing
> > trusted keys.
> > 
> > This patch implements basic sealing and unsealing functionality for
> > TPM 2.0:
> 
> We really need to stop using chip id's as a handle - the caller should
> be using a pointer, it is just a horrible API, and the TPM_ANY_NUM
> business is awful too.. TPM's are stateful devices!

Eventually this needs to be refactored out. I don't see it in the scope
of these patches or as high priority ATM.

> Is it feasible to introduce new APIs with a saner scheme?
> 
> The api layering also seems really weird to me. At a minimum the
> tpm_seal_trusted should be called within key_seal, but really, should
> key_seal be migrated into the TPM core? I'm not sure it makes alot of
> sense to have a tpm_seal_trusted which uses the high level key structs
> when other tpm functions are all low level RPC wrappers...

I think tpm_seal() inside trusted.c is not a very good API. It takes the
ad hoc version of the structs given to key_seal from stack. I don't see
a problem here.

My viewpoint has been that key_seal/unseal in trusted.c should be
refactored out and TPM1 implementations seal/unseal should be moved to
the TPM subsystem. There's so little amount of in-kernel low-level TPM
code that IMHO it makes sense to keep in one place (as are all the other
TPM utility functions).

I can work on the TPM1 migration when we have the basic TPM2 stuff in
place.

> Jason

/Jakrkko
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