linux-kernel - Re: [PATCH v5 11/11] intel

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Message-ID: <20171120224623.hpx7zcorrwo4ivhh@linux.intel.com>
Date:   Tue, 21 Nov 2017 00:46:23 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Borislav Petkov <bp@...en8.de>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v5 11/11] intel_sgx: driver documentation

On Wed, Nov 15, 2017 at 12:54:12PM +0100, Peter Zijlstra wrote:
> On Tue, Nov 14, 2017 at 10:49:48PM +0200, Jarkko Sakkinen wrote:
> > In these cases IA32_FEATURE_CONTROL[17] would be zeroed before locking
> > the feature control, which would mean that the kernel could not write
> > new values with wrmsr for the root key hash.
> 
> > The question is whether we want to allow this or not. If the answer is
> > no, a check can be added to the driver initialization code whether 17 is
> > set, and if not, it driver would fail to initialize.
> 
> That has my vote; I would not trust a firmware/BIOS key.

Please note that it does not have a key to look inside the enclave. The
enclave is protected by two means:

1. The CPU asserts the memory accesses to it.
2. The CPU encrypts/decrypts in L1 in order to protect from physical
   attacks and peripherals that have potential spy the bus.

/Jarkko