linux-kernel - Re: [PATCH v1 00/15] Add support for Nitro Enclaves

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Message-ID: <602565db-d9a6-149a-0e1a-fe9c14a90ce7@amazon.com>
Date:   Fri, 24 Apr 2020 21:11:52 +0200
From:   Alexander Graf <graf@...zon.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        "Paraschiv, Andra-Irina" <andraprs@...zon.com>,
        <linux-kernel@...r.kernel.org>
CC:     Anthony Liguori <aliguori@...zon.com>,
        Benjamin Herrenschmidt <benh@...zon.com>,
        Colm MacCarthaigh <colmmacc@...zon.com>,
        Bjoern Doebel <doebel@...zon.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Frank van der Linden <fllinden@...zon.com>,
        Martin Pohlack <mpohlack@...zon.de>,
        Matt Wilson <msw@...zon.com>, Balbir Singh <sblbir@...zon.com>,
        Stewart Smith <trawets@...zon.com>,
        Uwe Dannowski <uwed@...zon.de>, <kvm@...r.kernel.org>,
        <ne-devel-upstream@...zon.com>
Subject: Re: [PATCH v1 00/15] Add support for Nitro Enclaves


On 24.04.20 18:27, Paolo Bonzini wrote:
> 
> On 24/04/20 14:56, Alexander Graf wrote:
>> Yes, that part is not documented in the patch set, correct. I would
>> personally just make an example user space binary the documentation for
>> now. Later we will publish a proper device specification outside of the
>> Linux ecosystem which will describe the register layout and image
>> loading semantics in verbatim, so that other OSs can implement the
>> driver too.
> 
> But this is not part of the device specification, it's part of the child
> enclave view.  And in my opinion, understanding the way the child
> enclave is programmed is very important to understand if Linux should at
> all support this new device.

Oh, absolutely. All of the "how do I load an enclave image, run it and 
interact with it" bits need to be explained.

What I was saying above is that maybe code is easier to transfer that 
than a .txt file that gets lost somewhere in the Documentation directory :).

I'm more than happy to hear of other suggestions though.

> 
>> To answer the question though, the target file is in a newly invented
>> file format called "EIF" and it needs to be loaded at offset 0x800000 of
>> the address space donated to the enclave.
> 
> What is this EIF?

It's just a very dumb container format that has a trivial header, a 
section with the bzImage and one to many sections of initramfs.

As mentioned earlier in this thread, it really is just "-kernel" and 
"-initrd", packed into a single binary for transmission to the host.

> 
> * a new Linux kernel format?  If so, are there patches in flight to
> compile Linux in this new format (and I would be surprised if they were
> accepted, since we already have PVH as a standard way to boot
> uncompressed Linux kernels)?
> 
> * a userspace binary (the CPL3 that Andra was referring to)?  In that
> case what is the rationale to prefer it over a statically linked ELF binary?
> 
> * something completely different like WebAssembly?
> 
> Again, I cannot provide a sensible review without explaining how to use
> all this.  I understand that Amazon needs to do part of the design
> behind closed doors, but this seems to have the resulted in issues that
> reminds me of Intel's SGX misadventures. If Amazon has designed NE in a
> way that is incompatible with open standards, it's up to Amazon to fix

Oh, if there's anything that conflicts with open standards here, I would 
love to hear it immediately. I do not believe in security by obscurity  :).


Alex



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