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Subject: Re: [PATCH v1 00/15] Add support for Nitro Enclaves
To:     Alexander Graf <graf@amazon.com>,
        "Paraschiv, Andra-Irina" <andraprs@amazon.com>,
        linux-kernel@vger.kernel.org
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        Colm MacCarthaigh <colmmacc@amazon.com>,
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        Frank van der Linden <fllinden@amazon.com>,
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        Stewart Smith <trawets@amazon.com>,
        Uwe Dannowski <uwed@amazon.de>, kvm@vger.kernel.org,
        ne-devel-upstream@amazon.com
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From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <bed6e250-9de5-d719-623b-b72db78ebcb9@redhat.com>
Date:   Thu, 30 Apr 2020 13:58:14 +0200
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On 30/04/20 13:47, Alexander Graf wrote:
>>
>> So the issue would be that a firmware image provided by the parent could
>> be tampered with by something malicious running in the parent enclave?
> 
> You have to have a root of trust somewhere. That root then checks and
> attests everything it runs. What exactly would you attest for with a
> flat address space model?
> 
> So the issue is that the enclave code can not trust its own integrity if
> it doesn't have anything at a higher level attesting it. The way this is
> usually solved on bare metal systems is that you trust your CPU which
> then checks the firmware integrity (Boot Guard). Where would you put
> that check in a VM model?

In the enclave device driver, I would just limit the attestation to the
firmware image

So yeah it wouldn't be a mode where ne_load_image is not invoked and
the enclave starts in real mode at 0xffffff0.  You would still need
"load image" functionality.

> How close would it be to a normal VM then? And
> if it's not, what's the point of sticking to such terrible legacy boot
> paths?

The point is that there's already two plausible loaders for the kernel
(bzImage and ELF), so I'd like to decouple the loader and the image.

Paolo