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

[Jarkko Sakkinen]

On Fri, May 06, 2016 at 09:14:43AM +0200, Pavel Machek wrote:
> 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.)

Somehow that email from Ingo dissolved to my inbox :( Anyway, I gave
now my response.

For my part I'll create a second revision of the patch set and update the
documentation so that it has reasonable explanation about root of trust
SGX.

> -- 
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

/Jarkko