linux-kernel - Re: [PATCH v17 18/23] platform/x86: Intel SGX driver

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Message-ID: <20181126221649.GE868@linux.intel.com>
Date:   Mon, 26 Nov 2018 14:16:49 -0800
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     "Dr. Greg" <greg@...ellic.com>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        linux-sgx@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>,
        "Christopherson, Sean J" <sean.j.christopherson@...el.com>,
        nhorman@...hat.com, npmccallum@...hat.com,
        "Ayoun, Serge" <serge.ayoun@...el.com>, shay.katz-zamir@...el.com,
        haitao.huang@...ux.intel.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Svahn, Kai" <kai.svahn@...el.com>, mark.shanahan@...el.com,
        Suresh Siddha <suresh.b.siddha@...el.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v17 18/23] platform/x86: Intel SGX driver

On Mon, Nov 26, 2018 at 05:00:39AM -0600, Dr. Greg wrote:
> We will be interested in your comments as to why the proposal is
> insufficient in the real world of FLC.
> 
> I believe the proposed architecture can be defended as being effective
> in the real world, as it allows the root user to use cryptographic
> protections of access to the PROVISION bit and to enclave execution in
> general.  On FLC that is the strongest guarantee that can be
> delivered.
> 
> When we speak of 'unauthorized' users I believe we are speaking in the
> parlance of discretionary access controls which has a much wider TCB
> scope then the cryptographic model we are proposing.  The model we
> propose allows the platform owner (root) to effectively implement the
> same level of security over the PROVISION bit that current locked
> platforms have, in a free and open fashion of course.
> 
> We can certainly attempt to explain our position further.

I think kernel controlled provision would in all cases lower the
mitigations of thread scenarios (at least what you've presented so far)
assuming that a compromissed kernel could be detected fairly quickly,
wouldn't it?

Even without SGX, having a compromissed kernel, you can anyhow stealth
your malware in many ways.

/Jarkko