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

From: Pavel Machek
Date: Fri May 06 2016 - 03:14:52 EST

On Fri 2016-05-06 01:52:04, Jarkko Sakkinen wrote:
> On Mon, May 02, 2016 at 11:37:52AM -0400, Austin S. Hemmelgarn wrote:
> > 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).
> The code in enclave binary is in clear text so it does not really
> allow you to completely hide any code. It's a signed binary, not
> encypted binary.

Umm. Now you are evil.

Yes, the code that starts in the enclave may not be encrypted, but I'm
pretty sure the enclave will download some more code from remote
server after attestation... x86 or some kind of interpretted code.

(But of course we already know that the technology is evil, as only
Intel can use it, see Ingo's reply.)
(cesky, pictures)