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From:   Dionna Amalie Glaze <dionnaglaze@google.com>
Date:   Tue, 8 Aug 2023 11:48:57 -0700
Message-ID: <CAAH4kHYJrKPgWXn7+G_sZXoAs8fq2sDEyT-tyECPthdaaoXyDw@mail.gmail.com>
Subject: Re: [PATCH 0/4] keys: Introduce a keys frontend for attestation reports
To:     James Bottomley <James.Bottomley@hansenpartnership.com>
Cc:     Dan Williams <dan.j.williams@intel.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@linux.intel.com>, dhowells@redhat.com,
        Brijesh Singh <brijesh.singh@amd.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Borislav Petkov <bp@alien8.de>,
        Jarkko Sakkinen <jarkko@kernel.org>,
        Samuel Ortiz <sameo@rivosinc.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-coco@lists.linux.dev, keyrings@vger.kernel.org,
        x86@kernel.org, linux-kernel@vger.kernel.org
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> Isn't this more runtime attestation?  In which case you wouldn't use
> the boot report.  I assume someone somewhere is hacking the TPM-TLS
> protocol to also do RTMRs, but it strikes me we could just use a vTPM
> and the existing protocols.
>
> Even if you don't do anything as complex as TPM-TLS (and continuing
> runtime attestation), you can still make TLS conditioned on a private
> key released after a successful boot time attestation.  Since the boot
> evidence never changes, there's not much point doing it on each
> connection, so relying on a private key conditioned on boot evidence is
> just as good.
>
> James
>

The TPM quote will need to be bound to the VM instance, so there will
still be a hardware attestation in there that incorporates the user's
challenge.
Anything less than that is subject to replay attacks, no? Am I missing
a clever trick?

-- 
-Dionna Glaze, PhD (she/her)