linux-kernel - Re: [intel-sgx-kernel-dev] [PATCH v11 13/13] intel

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Date:   Wed, 20 Jun 2018 10:23:49 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     X86 ML <x86@...nel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        nhorman@...hat.com, npmccallum@...hat.com,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        intel-sgx-kernel-dev@...ts.01.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Darren Hart <dvhart@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, andy@...radead.org
Subject: Re: [intel-sgx-kernel-dev] [PATCH v11 13/13] intel_sgx: in-kernel
 launch enclave

On Sun, Jun 10, 2018 at 10:17:13PM -0700, Andy Lutomirski wrote:
> > On Jun 9, 2018, at 10:39 PM, Andy Lutomirski <luto@...nel.org> wrote:
> >
> > On Fri, Jun 8, 2018 at 10:32 AM Jarkko Sakkinen
> > <jarkko.sakkinen@...ux.intel.com> wrote:
> >>
> >> The Launch Enclave (LE) generates cryptographic launch tokens for user
> >> enclaves. A launch token is used by EINIT to check whether the enclave
> >> is authorized to launch or not. By having its own launch enclave, Linux
> >> has full control of the enclave launch process.
> >>
> >> LE is wrapped into a user space proxy program that reads enclave
> >> signatures outputs launch tokens. The kernel-side glue code is
> >> implemented by using the user space helper framework.  The IPC between
> >> the LE proxy program and kernel is handled with an anonymous inode.
> >>
> >> The commit also adds enclave signing tool that is used by kbuild to
> >> measure and sign the launch enclave. CONFIG_INTEL_SGX_SIGNING_KEY points
> >> to a PEM-file for the 3072-bit RSA key that is used as the LE public key
> >> pair. The default location is:
> >>
> >>  drivers/platform/x86/intel_sgx/sgx_signing_key.pem
> >>
> >> If the default key does not exist kbuild will generate a random key and
> >> place it to this location. KBUILD_SGX_SIGN_PIN can be used to specify
> >> the passphrase for the LE public key.
> >
> > It seems to me that it might be more useful to just commit a key pair
> > into the kernel.  As far as I know, there is no security whatsoever
> > gained by keeping the private key private, so why not make
> > reproducible builds easier by simply fixing the key?
> 
> Having thought about this some more, I think that you should
> completely remove support for specifying a key. Provide a fixed key
> pair, hard code the cache, and call it a day. If you make the key
> configurable, every vendor that has any vendor keys (Debian, Ubuntu,
> Fedora, Red Hat, SuSE, Clear Linux, etc) will see that config option
> and set up their own key pair for no gain whatsoever.  Instead, it'll
> give some illusion of security and it'll slow down operations in a VM
> guest due to swapping out the values of the MSRs.  And, if the code to
> support a locked MSR that just happens to have the right value stays
> in the kernel, then we'll risk having vendors actually ship one
> distro's public key hash, and that will seriously suck.
> 
> I'm going to try to get this code working tomorrow.  I'll keep you
> posted on how that goes.  Can you point me to the userspace bits (i.e.
> something buildable that will run on a kernel with your patches
> applied)?

Sorry for some delay. I was on leave last week.

The SDK supports my driver starting from 2.1 release:

  https://github.com/intel/linux-sgx

SampleCode folder contains some trivial test code to run.

/Jarkko