linux-kernel - Re: [PATCH 0/6] Intel Secure Guard Extensions

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Date:	Mon, 2 May 2016 11:37:52 -0400
From:	"Austin S. Hemmelgarn" <ahferroin7@...il.com>
To:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	Pavel Machek <pavel@....cz>
Cc:	gregkh@...uxfoundation.org, Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...e.de>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	"open list:STAGING SUBSYSTEM" <devel@...verdev.osuosl.org>,
	Ingo Molnar <mingo@...nel.org>,
	Kristen Carlson Accardi <kristen@...ux.intel.com>,
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	Mathias Krause <minipli@...glemail.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Wan Zongshun <Vincent.Wan@....com>
Subject: Re: [PATCH 0/6] Intel Secure Guard Extensions

On 2016-04-29 16:17, Jarkko Sakkinen wrote:
> On Tue, Apr 26, 2016 at 09:00:10PM +0200, Pavel Machek wrote:
>> On Mon 2016-04-25 20:34:07, Jarkko Sakkinen wrote:
>>> Intel(R) SGX is a set of CPU instructions that can be used by
>>> applications to set aside private regions of code and data.  The code
>>> outside the enclave is disallowed to access the memory inside the
>>> enclave by the CPU access control.
>>>
>>> The firmware uses PRMRR registers to reserve an area of physical memory
>>> called Enclave Page Cache (EPC). There is a hardware unit in the
>>> processor called Memory Encryption Engine. The MEE encrypts and decrypts
>>> the EPC pages as they enter and leave the processor package.
>>
>> What are non-evil use cases for this?
>
> I'm not sure what you mean by non-evil.
>
I would think that this should be pretty straightforward.  Pretty much 
every security technology integrated in every computer in existence has 
the potential to be used by malware for various purposes.  Based on a 
cursory look at SGX, it is pretty easy to figure out how to use this to 
hide arbitrary code from virus scanners and the OS itself unless you 
have some way to force everything to be a debug enclave, which entirely 
defeats the stated purpose of the extensions.  I can see this being 
useful for tight embedded systems.  On a desktop which I have full 
control of physical access to though, it's something I'd immediately 
turn off, because the risk of misuse is so significant (I've done so on 
my new Thinkpad L560 too, although that's mostly because Linux doesn't 
support it yet).