Re: [Rats] Propose a new event-log-type in CHARRA

Michael Richardson <mcr+ietf@sandelman.ca> Fri, 28 August 2020 20:37 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: "Panwei \(William\)" <william.panwei@huawei.com>, "rats\@ietf.org" <rats@ietf.org>
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Date: Fri, 28 Aug 2020 16:37:00 -0400
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Subject: Re: [Rats] Propose a new event-log-type in CHARRA
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Panwei (William) <william.panwei@huawei.com> wrote:
    > When the device boots, it needs to load/execute a lot of files, but the
    > order in which these files are loaded/executed is not deterministic or
    > hard to keep fixed, so it's difficult to give an accurate reference
    > value.

    > The method to overcome this difficulty is below:
    > 1. The Attester measures each file before execution, extends the hash
    > value of the file into PCR, and records the measurement information of
    > the file in the log.

Does the Attester measure the files in a deterministic order?

    > 2. When doing the remote attestation, the Attester sends the final
    > values of the PCRs and the detailed logs to the Verifier.

I remember this discussion.

    > 3. The Verifier has a list of reference values for all files. It
    > compares the hash value of each file recorded in the log with the
    > corresponding reference value. If all files' hash values match with
    > their reference values, then the Verifier extends the hash values one
    > by one according to the order recorded in the log, gets the final
    > value, and compares the final value with the PCR value sent by the
    > Attester.

Why not impose some canonical ordering (even alphabetical) to how the files
are recorded into the PCR, regardless of the order they are executed?

--
Michael Richardson <mcr+IETF@sandelman.ca>ca>, Sandelman Software Works
 -= IPv6 IoT consulting =-