Re: [Rats] [Iotops] 802.1AR device identity

Michael Richardson <mcr+ietf@sandelman.ca> Sun, 14 March 2021 01:34 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Eliot Lear <lear=40cisco.com@dmarc.ietf.org>, "rats\@ietf.org" <rats@ietf.org>, iotops@ietf.org
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Date: Sat, 13 Mar 2021 20:34:41 -0500
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Subject: Re: [Rats] [Iotops] 802.1AR device identity
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Eliot Lear <lear=40cisco.com@dmarc.ietf.org> wrote:
    > Yeah, this is an issue that comes up from time to time.  How
    > “immutable” should that iDevID be?

I take the approach that the IDevID that was shipped from the factory can not
be replaced without a device recall.

(It could be that there are modes where another IDevID can be installed, but
the original would not be removed.  Whether this is an LDevID or IDevID is
open to intepretation)

    > I’ve had this thought in two
    > different contexts: What if the signature algorithm, CA, or private key
    > used to protect the iDevID has been compromised?

Then, the device is broken.
I think you would certainly agree that this can be the only answer if the
software signing key is compromised, right?

    > Can one recover with an update?
    > What if there are attributes in the cert that I want to
    > dink and share with the deployment?

Please define "dink" for me.  I know of only one definition from the school yard.
Does this mean remove? replace?

    > I’d like to take that latter case off the table, but then we need to
    > seriously think about RATS or SUIT providing a standard protected TLV
    > list that deployments could receive through a standard interface.
    > These are attestations of a form, but they’re not really measurements,
    > as has been previously discussed here.

Can you give me an example of one of these attributes?
This sounds like the FIDO situation, from section 6.3 of (my) the usecase
document:

   According to [fidotechnote] FIDO uses attestation to make claims
   about the kind of device which is be used to enroll.  Keypairs are
   generated on a per-device _model_ basis, with a certificate having a
   trust chain that leads back to a well-known root certificate.  It is
   expected that as many as 100,000 devices in a production run would
   have the same public and private key pair.  One assumes that this is
   stored in a tamper-proof TPM so it is relatively difficult to get
   this key out.  The use of this key attests to the the device type,
   and the kind of protections for keys that the relying party may
   assume, not to the identity of the end user.


--
Michael Richardson <mcr+IETF@sandelman.ca>   . o O ( IPv6 IøT consulting )
           Sandelman Software Works Inc, Ottawa and Worldwide