linux-kernel - Re: [PATCH v33 12/21] x86/sgx: Allow a limited use of ATTRIBUTE.PROVISIONKEY for attestation

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Date:   Tue, 30 Jun 2020 10:49:56 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>, x86@...nel.org,
        linux-sgx@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Jethro Beekman <jethro@...tanix.com>,
        Andy Lutomirski <luto@...nel.org>, akpm@...ux-foundation.org,
        andriy.shevchenko@...ux.intel.com, asapek@...gle.com,
        cedric.xing@...el.com, chenalexchen@...gle.com,
        conradparker@...gle.com, cyhanish@...gle.com,
        dave.hansen@...el.com, haitao.huang@...el.com,
        josh@...htriplett.org, kai.huang@...el.com, kai.svahn@...el.com,
        kmoy@...gle.com, ludloff@...gle.com, nhorman@...hat.com,
        npmccallum@...hat.com, puiterwijk@...hat.com, rientjes@...gle.com,
        tglx@...utronix.de, yaozhangx@...gle.com
Subject: Re: [PATCH v33 12/21] x86/sgx: Allow a limited use of
 ATTRIBUTE.PROVISIONKEY for attestation

On Mon, Jun 29, 2020 at 03:04:00PM -0700, Sean Christopherson wrote:
> > I don't see this acronym resolved anywhere in the whole patchset.
> 
> Quoting Enclave.

Yah, pls add it somewhere.

> /dev/sgx/provision is root-only by default, the expectation is that the admin
> will configure the system to grant only specific enclaves access to the
> PROVISION_KEY.

Uuh, I don't like "the expectation is" - the reality happens to turn
differently, more often than not.

> In this series, access is fairly binary, i.e. there's no additional kernel
> infrastructure to help userspace make per-enclave decisions.  There have been
> more than a few proposals on how to extend the kernel to help provide better
> granularity, e.g. LSM hooks, but it was generally agreed to punt that stuff
> to post-upstreaming to keep things "simple" once we went far enough down
> various paths to ensure we weren't painting ourselves into a corner.

So this all sounds to me like we should not upstream /dev/sgx/provision
now but delay it until the infrastructure for that has been made more
concrete. We can always add it then. Changing it after the fact -
if we have to and for whatever reason - would be a lot harder for a
user-visible interface which someone has started using already.

So I'd leave  that out from the initial patchset.

> If you want super gory details, Intel's whitepaper on attestation in cloud
> environments is a good starting point[*], but I don't recommended doing much
> more than skimming unless you really like attestation stuff or are
> masochistic, which IMO amount to the same thing :-)

No thanks. :)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette