Re: [Rats] Call for adoption (after draft rename) for Yang module draft

[Dave Thaler <[e-mail]>]

As far as I can understand from draft-birkholz-rats-basic-yang-module-01 and
draft-fedorkow-rats-network-device-attestation-01, they break down the use case
space as follows:

                        Requirements?
         +--------------+---------------+---------++---------------
         |  RoT         | Host Firewall | Privacy ||   Solution
         |  Type        |   Enabled     | Needed  ||    Pieces
         +--------------+---------------+---------++---------------
      1  |  SGX         | No            | No      ||
      2  |  SGX         | No            | Yes     ||
      3  |  SGX         | Yes           | No      ||
      4  |  SGX         | Yes           | Yes     ||
      5  |  TrustZone   | No            | No      ||
      6  |  TrustZone   | No            | Yes     ||
      7  |  TrustZone   | Yes           | No      ||
      8  |  TrustZone   | Yes           | Yes     ||
      9  |  TPM         | No            | No      || draft-birkholz-rats-basic-yang-module-01
     10  |  TPM         | No            | Yes     ||
     11  |  TPM         | Yes           | No      ||
     12  |  TPM         | Yes           | Yes     ||
     13  |SecureElement | No            | No      ||
     14  |SecureElement | No            | Yes     ||
     15  |SecureElement | Yes           | No      ||
     16  |SecureElement | Yes           | Yes     ||
     17  | Firmware     | No            | No      ||
     18  | Firmware     | No            | Yes     ||
     19  | Firmware     | Yes           | No      ||
     20  | Firmware     | Yes           | Yes     ||
     ... |   ...        |               |         ||

And draft-fedorkow-rats-network-device-attestation-01 further scopes itself down
by only being applicable to cases with "embedded" apps only = Yes, and where
the security policy is only an Exact match against reference values = Yes.
I believe that the yang draft doesn't have those two restrictions, from my reading.
However, the point is that both drafts are VERY narrow, and in the table shown above,
only address 1 out of 20 possibilies in that space.

In contrast, the TEEP WG decided that it was not interested in narrow scopings
(specifically something Global Platform specific), but instead wanted one general solution.

If the RATS WG spends effort on something that only addresses a single row out of 20+ rows,
then do we expect 19+ other solutions to also be done in the WG?  Or could we work on things
that are broader and happen to also work for row 9?

I've seen others commenting on the fact that the YANG module only supports TPMs and not
other things (EATs etc), which would just add support for a couple more rows, but still not
be general.

Personally, I would much rather see the WG spend effort on things that really are generic,
i.e., work with or without host firewalls, work with multiple RoT/TEE types, etc., rather
than seeing an explosion of point solutions.

Dave

From: RATS <[e-mail]> On Behalf Of Smith, Ned
Sent: Monday, November 11, 2019 10:12 AM
To: Oliver, Ian (Nokia - FI/Espoo) <[e-mail]>; Laurence Lundblade <[e-mail]>; Nancy Cam-Winget (ncamwing) <[e-mail]>
Cc: [e-mail]; Henk Birkholz <[e-mail]>
Subject: Re: [Rats] Call for adoption (after draft rename) for Yang module draft

Right. This implies the RATS “token” should support existing “binary” formats as an encapsulation (signed by a second TA where the TPM is a first TA) or as a conveyance (unsigned?) token. Possibly, the only added value of the latter is a tag that identifies it as a TPM binary format?


On 11/10/19, 23:21 PM, "RATS on behalf of Oliver, Ian (Nokia - FI/Espoo)" <[e-mail]<mailto:[e-mail]> on behalf of [e-mail]<mailto:[e-mail]>> wrote:

> Remote TPM attestations are useful and necessary the short run, but are of very limited capability. I believe that > EAT will replace TPM attestations in the long run (maybe decades) because they are far more expressive. I know > others believe that too.

I would disagree with the statement of "short run" ... TPM is practically the only existing standardised (hardware, software, firmware, measurement - x86 only etc) hardware root of trust in common use, ie: practically all x86 machines,  The attestation mechanisms provided are going to be around for a very long time.

From telco experience, 30 years ago we said SS7 would only be around in the short term.

> Thus, I am opposed to adoption with the current TPM-only draft. I’d be OK with the current draft and a promise > to add EAT to it.

Agree

Ian


--

Dr. Ian Oliver

Cybersecurity Research

Distinguished Member of Technical Staff

Nokia Bell Labs

[phone]

________________________________
From: Laurence Lundblade <[e-mail]<mailto:[e-mail]>>
Sent: 11 November 2019 00:44
To: Nancy Cam-Winget (ncamwing) <[e-mail]<mailto:[e-mail]>>
Cc: Henk Birkholz <[e-mail]<mailto:[e-mail]>>; rats@ietf..org<mailto:rats@ietf..org> <[e-mail]<mailto:[e-mail]>>
Subject: Re: [Rats] Call for adoption (after draft rename) for Yang module draft


On Nov 10, 2019, at 2:20 PM, Nancy Cam-Winget (ncamwing) <[e-mail]<mailto:[e-mail]>> wrote:

So, Laurence, are you still OK with the adoption of the current draft with a rename for now?
Thanks, Nancy

I think the value add to the larger RATS effort of adding EAT support to this YANG protocol is really high. It a core thing to do that helps bring together the two attestation worlds and make the TPM and EAT work here less like ships in the night.

Remote TPM attestations are useful and necessary the short run, but are of very limited capability. I believe that EAT will replace TPM attestations in the long run (maybe decades) because they are far more expressive. I know others believe that too.

If we don’t include EAT in the YANG mode it is sort of like defining HTTP to only convey HTML to the exclusion of PDF. We’re defining an attestation protocol that can only move one kind of attestation even though we have consensus on what the other one looks like.

It seems relatively simple to add EAT support (or promise to add EAT support). Pretty sure I heard Henk agree to add it.

Thus, I am opposed to adoption with the current TPM-only draft. I’d be OK with the current draft and a promise to add EAT to it.

LL