linux-kernel - Re: [RFC v2 0/6] Introduce TEE based Trusted Keys support

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Date:   Wed, 31 Jul 2019 19:53:08 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Janne Karhunen <janne.karhunen@...il.com>
Cc:     keyrings@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Jens Wiklander <jens.wiklander@...aro.org>,
        Jonathan Corbet <corbet@....net>, dhowells@...hat.com,
        jejb@...ux.ibm.com,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "tee-dev @ lists . linaro . org" <tee-dev@...ts.linaro.org>
Subject: Re: [RFC v2 0/6] Introduce TEE based Trusted Keys support

On Wed, 31 Jul 2019 at 16:33, Janne Karhunen <janne.karhunen@...il.com> wrote:
>
> On Wed, Jul 31, 2019 at 1:26 PM Sumit Garg <sumit.garg@...aro.org> wrote:
>
> > > Interesting, I wrote something similar and posted it to the lists a while back:
> > > https://github.com/jkrh/linux/commit/d77ea03afedcb5fd42234cd834da8f8a0809f6a6
> > >
> > > Since there are no generic 'TEEs' available,
> >
> > There is already a generic TEE interface driver available in kernel.
> > Have a look here: "Documentation/tee.txt".
>
> I guess my wording was wrong, tried to say that physical TEEs in the
> wild vary massively hardware wise. Generalizing these things is rough.
>

There are already well defined GlobalPlatform Standards to generalize
the TEE interface. One of them is GlobalPlatform TEE Client API [1]
which provides the basis for this TEE interface.

>
> > > I implemented the same
> > > thing as a generic protocol translator. The shared memory binding for
> > > instance already assumes fair amount about the TEE and how that is
> > > physically present in the system. Besides, the help from usage of shm
> > > is pretty limited due to the size of the keydata.
> > >
> >
> > If you look at patch #1 and #2, they add support to register kernel
> > memory buffer (keydata buffer in this case) with TEE to operate on. So
> > there isn't any limitation due to the size of the keydata.
>
> Ah, didn't mean that. Meant that the keydata is typically pretty small
> in size, so there is limited benefit from passing that in via shm if
> that complicates anything.
>

Ah, ok. Do you think of any better approach rather than to use SHM?

[1] https://globalplatform.org/specs-library/tee-client-api-specification/

-Sumit

>
> --
> Janne