linux-kernel - Re: [PATCH v14 19/19] x86/sgx: Driver documentation

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Date:   Mon, 15 Oct 2018 22:54:36 +0200
From:   Pavel Machek <pavel@....cz>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     x86@...nel.org, platform-driver-x86@...r.kernel.org,
        dave.hansen@...el.com, sean.j.christopherson@...el.com,
        nhorman@...hat.com, npmccallum@...hat.com, serge.ayoun@...el.com,
        shay.katz-zamir@...el.com, linux-sgx@...r.kernel.org,
        andriy.shevchenko@...ux.intel.com,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v14 19/19] x86/sgx: Driver documentation

On Tue 2018-09-25 16:06:56, Jarkko Sakkinen wrote:
> Documentation of the features of the Software Guard eXtensions used
> by the Linux kernel and basic design choices for the core and driver
> and functionality.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

> --- /dev/null
> +++ b/Documentation/x86/intel_sgx.rst
> @@ -0,0 +1,185 @@
> +===================
> +Intel(R) SGX driver
> +===================
> +
> +Introduction
> +============
> +
> +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.
> +In a way you can think that SGX provides inverted sandbox. It protects the
> +application from a malicious host.

Well, recently hardware had some problems keeping its
promises. So... what about rowhammer, meltdown and spectre?

Which ones apply, which ones do not, and on what cpu generations?

> +Overview of SGX
> +===============
> +
> +SGX has a set of data structures to maintain information about the enclaves and
> +their security properties. BIOS reserves a fixed size region of physical memory
> +for these structures by setting Processor Reserved Memory Range Registers
> +(PRMRR).
> +
> +This memory range is protected from outside access by the CPU and all the data
> +coming in and out of the CPU package is encrypted by a key that is generated for
> +each boot cycle.

Encryption, that sounds nice, but it is hard to do right. If SGX
protected code changes single bit in its memory, how many bits will be
changed in physical RAM?

Can we get security people to look at this and perhaps tells us what
properties it has?

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

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