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

Laurence Lundblade <lgl@island-resort.com> Wed, 13 November 2019 18:07 UTC

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From: Laurence Lundblade <lgl@island-resort.com>
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Date: Wed, 13 Nov 2019 10:07:02 -0800
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Cc: "Smith, Ned" <ned.smith@intel.com>, "Oliver, Ian (Nokia - FI/Espoo)" <ian.oliver@nokia-bell-labs.com>, "Nancy Cam-Winget (ncamwing)" <ncamwing@cisco.com>, "rats@ietf.org" <rats@ietf.org>, Henk Birkholz <henk.birkholz@sit.fraunhofer.de>
To: Dave Thaler <dthaler@microsoft.com>
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Subject: Re: [Rats] Call for adoption (after draft rename) for Yang module draft
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My version of technology bases for attestation is something like this:

Router/Netconf World
Millions of devices. Currently TPM oriented. Long possible transition to EAT. YANG used to create very specific fine-grained interactions. No privacy issues.

Web Browser World
Billions of devices. Current attestation use is primarily WebAuthN / FIDO. JWT is used heavily for authentication so would be more EAT oriented, but TPM attestation is supported in FIDO. Larger use of attestation may evolve. Fine-grained interactions are with WebAPIs (Javascript) (sort of parallel to YANG for routers). Big privacy issues.

Mobile App World
Billions of devices. Main attestation use is Android’s Keystore. This is EAT-like, but based on X.509. Fine grained interactions are Android APIs. I may be out of date, but so far IoS doesn’t do attestation. Privacy issues vary by app.

IoT World
Billions of devices most likely going to trillions. Attestation is a critical enabling feature in this world. There are lots of protocols and formats involved. TPMs are too expensive for many of these, but are probably in use somewhere. No privacy issues for a large portion of this world.

The router world is the smallest, but it is “well represented” because this is the IETF.

I see EAT as applicable to all these worlds, where the YANG module is just for the smallish router world. So I mostly agree with Dave about proportions, however this is the IETF where YANG modules are created.  (Maybe I should go join the W3C world and work on attestations APIs for browsers after RATS is done).

LL



> On Nov 11, 2019, at 5:43 PM, Dave Thaler <dthaler@microsoft.com> wrote:
> 
> 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 <rats-bounces@ietf.org> On Behalf Of Smith, Ned
> Sent: Monday, November 11, 2019 10:12 AM
> To: Oliver, Ian (Nokia - FI/Espoo) <ian.oliver@nokia-bell-labs.com>om>; Laurence Lundblade <lgl@island-resort.com>om>; Nancy Cam-Winget (ncamwing) <ncamwing@cisco.com>
> Cc: rats@ietf.org; Henk Birkholz <henk.birkholz@sit.fraunhofer.de>
> 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)" <rats-bounces@ietf.org <mailto:rats-bounces@ietf.org> on behalf of ian.oliver@nokia-bell-labs.com <mailto:ian.oliver@nokia-bell-labs.com>> 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
> 
> +358 50 483 6237
> 
>  
> From: Laurence Lundblade <lgl@island-resort.com <mailto:lgl@island-resort.com>>
> Sent: 11 November 2019 00:44
> To: Nancy Cam-Winget (ncamwing) <ncamwing@cisco.com <mailto:ncamwing@cisco.com>>
> Cc: Henk Birkholz <henk.birkholz@sit.fraunhofer.de <mailto:henk.birkholz@sit.fraunhofer.de>>; rats@ietf..org <mailto:rats@ietf..org> <rats@ietf.org <mailto:rats@ietf.org>>
> 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) <ncamwing@cisco.com <mailto:ncamwing@cisco.com>> 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
>