Re: [EAT] [EXTERNAL] Re: [Rats] Attestation BoF charter updates?

"Smith, Ned" <ned.smith@intel.com> Tue, 16 October 2018 13:52 UTC

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From: "Smith, Ned" <ned.smith@intel.com>
To: Hannes Tschofenig <Hannes.Tschofenig@arm.com>, Henk Birkholz <henk.birkholz@sit.fraunhofer.de>, "rats@ietf.org" <rats@ietf.org>, "Jeremy O'Donoghue" <jodonogh@qti.qualcomm.com>, Denis <denis.ietf@free.fr>
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Thread-Topic: [EAT] [EXTERNAL] Re: [Rats] Attestation BoF charter updates?
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Date: Tue, 16 Oct 2018 13:51:57 +0000
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Subject: Re: [EAT] [EXTERNAL] Re: [Rats] Attestation BoF charter updates?
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Agree with Hannes that identity discussion can lead to confusion as identity is often highly dependent on some sort of context (domain of interpretation). 

In order to have productive conversation about attestation and identity, it may be important to understand that attestation semantics sets the context for identity. 

* Attestation attributes have trust semantics (and trust semantics are interpreted through the eyes of the verifier). Identity attributes may also have trust semantics (in addition to identity semantics) hence can be regarded as playing a role in both identity and attestation. Since RATS should be interested primarily in trust semantics, it makes sense to understand, discuss and consider identity in terms of its trust semantics. Hence identity attributes are only interesting to RATS if they are useful for evaluating trust semantics.

* In a closed ecosystem, the trust characteristics and properties may be implied because there often exists out-of-band processes that ensure the characteristics are applied (for example, if an IT organization sets a policy that all asymmetric keys are to be hardened using a smartcard, they can apply a deployment process where the IT professional verifies the smartcard is used during enrollment.) But in a non-closed ecosystem, there isn't an assumption that out-of-band processes exist. Attestation attempts to make explicit what otherwise is implicit and therefore subject to misinterpretation if the verifier, relying party and attester are not part of the same closed ecosystem. Implicit attestation therefore can lead to semantic confusion if we're not careful. Therefore, the rigor of treating implicit attestation claims (assertions assumed to exist but not explicitly named) should nevertheless be defined explicitly. Then, if there is a need for implicit attestation, the specifications that describe them can describe them in terms of an explicit definition. 

* In the context of asserting trust characteristics, the verifier needs to know that a set of characteristics applies to the instance of the endpoint being evaluated (aka the attester). (Otherwise a MITM could supply characteristics that may be valid, but don’t apply to the specific instance). Consequently, it makes sense to consider that *attestation* keys are needed to authenticate the endpoint being evaluated. This doesn't imply an identity key couldn't double as an attestation key. But if it does, we care about its relevance to the attester endpoint.

-Ned

On 10/15/18, 6:49 PM, "Hannes Tschofenig" <Hannes.Tschofenig@arm.com> wrote:

    Here are my 5 cents on the term 'identity'.
    
    I have been working on identity management for many years (partially because of my OAuth co-chair role) and I have noticed that the use of the term "identity" tends to confuse more than it helps (even more so when the term is applied to devices and software rather than humans).
    
    I believe we could get away with describing what we want without ever using the term.
    
    In this context I would argue that we are about identifying different components, such as hardware and software.
    
    Ciao
    Hannes
    
    -----Original Message-----
    From: EAT <eat-bounces@ietf.org> On Behalf Of Smith, Ned
    Sent: Monday, October 15, 2018 9:00 AM
    To: Henk Birkholz <henk.birkholz@sit.fraunhofer.de>de>; rats@ietf.org; Jeremy O'Donoghue <jodonogh@qti.qualcomm.com>om>; Denis <denis.ietf@free.fr>
    Cc: eat@ietf.org
    Subject: Re: [EAT] [EXTERNAL] Re: [Rats] Attestation BoF charter updates?
    
    I agree with Henk's observation that there is opportunity to find common ground on identity as identity can be a collection of attributes, that if signed, becomes a set of verifiable claims (about identity attributes). Attestation has a similar structure in that it consists of a set of attributes, that if signed becomes a set of verifiable claims. The main difference between identity and attestation attributes is whether the attribute semantically relate to trust (vs. identity). For example, claims of security certification compliance resonates as attestation.
    
    It may be possible to combine a set of attestation attributes in such a way that the combination uniquely identifies an entity. But that doesn't make it an identity system per se and shouldn't cause a conflict in charter goals with respect to other identity focused efforts in IETF.
    
    Also, inclusion of attributes that don't have semantics that reasonably relate to trust should not be of interest to a working group focused on attestation.
    
    -Ned
    
    On 10/15/18, 3:53 PM, "EAT on behalf of Henk Birkholz" <eat-bounces@ietf.org on behalf of henk.birkholz@sit.fraunhofer.de> wrote:
    
        Hi Jeremy & Denis,
    
        all these points of view have merit, I think.
    
        Please have a look at these quotes:
    
        > knowing the provenance of the device
    
        > having the entity creator/manufacturer provide a set of claims which can be verified
    
        > to know the characteristics of a device by issuing to the device a public key certificate which will only be issued to the device if it fulfills an expected set of functionalities.
    
        To me, these descriptions seem to have different intents, scope or
        audience and require most certainly different work-flows, but
        semantically and in consequence representation-wise they also seem quite
        related.
    
        If you think of an identity document as a set of claims (potentially
        including a public key), that is signed and that can match one or more
        things, maybe all three types highlighted above are actually covered by
        the same identity document concept?
    
        With respect to identity documents, I think it is safe so say that we
        can find common ground here rather easily. That said, the way how these
        identity documents come into existence, when and how they are deployed
        on the thing or associated with multiple things is another question. We
        most certainly do not want to end up with a "signing fool" that does not
        add value to the level of confidence (I am quoting Ned Smith here).
    
        This has to be fleshed out explicitly for each scenario and the parts
        that are reused in every scenario should get special attention in the
        upcoming RATS architecture draft.
    
        Identifying claims aggregated in an identity document most certainly can
        include device characteristics, public key(s), or claims about the
        intended functions and capabilities of the thing. Claims can even
        originate from Claimants that are not the thing itself, but external
        entities providing an assertion (e.g. these things are CC-certified).
    
        All different composites of identifying claims have a specific shared
        intend in this context though, I think: expressing Attestation
        Provenance (again - one for one or more things of the same kind). And
        all of them originate from Claimants and therefore use a root of trust
        of measurement, I think.
    
        That said, establishing trustworthy knowledge about attestation
        provenance is only the first step and provides the foundation for more
        complex attestation procedures. In any case, this seem to be required by
        every scenario that was highlighted so far and therefore will most
        certainly be covered in a deliverable.
    
        IHTH,
    
        Henk
    
    
        On 10/15/2018 12:22 PM, Jeremy O'Donoghue wrote:
        > On 12 Oct 2018, at 14:33, Denis <denis.ietf@free.fr
        > <mailto:denis.ietf@free.fr>> wrote:
        >> The "Problem Statement" continues as follows:
        >>
        >> (2) Today, there is no common, standard way for Relying Parties to
        >> know the provenance and characteristics of a device (e.g., an end-user
        >> device,
        >> platform or endpoint, servers, IoT devices, device subsystems and
        >> sub-modules) that may be requesting services.
        >>
        >> Knowing the provenance of the device is not always necessary. What is
        >> important is to know that a specific set of functions is (securely)
        >> supported by the device.
        >> There already exists a common way to know the characteristics of a
        >> device by issuing to the device a public key certificate which will
        >> only be issued to the device
        >> if it fulfills an expected set of functionalities. In such a case a
        >> syntax for a trusted claim sets**is not needed.
        >>
        > This is indeed a possible way to address the problem, but suffers from
        > challenges which come down to:
        >
        > - Who issues such certificates. An option is that there is some form of
        > security certification behind this issuance otherwise it is of very
        > limited value.
        > - In order to capture the wide variety of different devices (I prefer
        > "entity" here as it is more general than "device"), many different forms
        > of such certificates would be required. This ends up being much the same
        > thing as a set of claims.
        >
        > Given the multiplicity of entities for which attestation might be
        > useful, it seems to me that having the entity creator/manufacturer
        > provide a set of claims which can be verified is more flexible than
        > requiring a certificate. It seems likely to me that where a formal
        > security certification is needed there will be a certificate issued by
        > the Certifying Body as one of the claims about an entity, but I can
        > think of many cases (supply chain management, to take just one example)
        > where provenance is by far the most useful information.
        >
        > I'm not in favour of changes to the charter in this direction.
        >>
        >> The simplest cases should also be part of the framework.
        >>
        >> Note: I personally appreciate that privacy is an aspect that
        >> will/should be taken into consideration.
        >>
        >> Denis
        >>
        >>> As with the earlier draft, there are many references to verify and
        >>> verifier in the lead up to the deliverable but no deliverables describing
        >>> verification rules. I'd like to see rules in one of these documents and
        >>> think it worth citing in the deliverables. Are bindings to certificate
        >>> management protocols out of scope?
        >>>
        >>> On 10/11/18, 9:49 AM, "RATS on behalf of Henk Birkholz"
        >>> <rats-bounces@ietf.org on behalf of henk.birkholz@sit.fraunhofer.de>  wrote:
        >>>
        >>>> Hi all,
        >>>>
        >>>> sorry for the delay. Please find an updated charter proposal here:
        >>>>
        >>>>> https://github.com/ietf-rats/charter/blob/RC2/ietf-rats-charter.md
        >>>> The BoF proponents tried to merge all comments and proposals on
        >>>> keystores, existing solutions, provenance & device characteristics, etc
        >>>> that were raised on the list - and align them in homogeneous fashion.
        >>>>
        >>>> This draft is intended to focus the discussion and improve the wording.
        >>>>
        >>>> Viele Grüße,
        >>>>
        >>>> Henk
        >>>>
        >>>> On 10/06/2018 08:23 AM, Laurence Lundblade wrote:
        >>>>> Hi Henk,
        >>>>>
        >>>>> Bangkok IETF is getting close, will you be able to update the charter
        >>>>> for the attestation BoF to properly include EAT?  I sent you some text
        >>>>> that just needs to be pasted along with some comments. It doesn’t look
        >>>>> like there’s been any updates.
        >>>>>
        >>>>> LL
        >>>>>
        >>>> _______________________________________________
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        >>>> RATS@ietf.org
        >>>> https://www.ietf.org/mailman/listinfo/rats
        >>> _______________________________________________
        >>> EAT mailing list
        >>> EAT@ietf.org
        >>> https://www.ietf.org/mailman/listinfo/eat
        >>
        >>
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