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Subject: Re: [security-services] comment on saml-loa-authncontext-profile: remove 800-63 schemas

Bob, thanks for the comments.

I fully agree that defining how SAML can carry assurance level URIs in isolation, without the other components of a full assurance program (such as IAFs or InCommon) being in place, isn't useful.

Some questions on the InCommon bronze and silver profiles

1) can you point me to the corresponding URIs?

The AC class mechanism would have us (or InCommon) jump through the hoop of defining a set of class schemas that then linked to the profiles through the <Documentation> kluge ..

2) Is linking to the profiles, directly or indirectly, the right thing? Should we not link to appropriate sections of the InCommon framework docs, i.e. to ensure that the profiles are interpreted in the context of the full IAAF?

3) I cant find any info on how the IAQs are expressed on the wire. As attributes?



[1] - http://www.incommonfederation.org/docs/assurance/InC_Bronze-Silver_IAP_1.0_Final.pdf

RL 'Bob' Morgan wrote:

Sections 3 and 4 of saml-loa-authncontext-profile-02 define a profile for expressing LoA based on NIST 800-63.  I think I understand the motivation for having this material in the document, but I think it's a mistake and should be removed.  I argue that if assurance concepts are going to be useful to the community, assurance profiles have to be defined and supported by organizational programs designed for that purpose, not just technical specs.

NIST 800-63 was originally written to support the US E-Authentication program by specifying technical requirements based on OMB-04-04, which defined the infamous 4 levels in business terms.  800-63 is a great document, but it was explicitly just a part of an assurance program. E-Auth incorporated the technical material in 800-63 into a framework that included:

 * taking some elements where 800-63 says "you can do it this way or that
   way" or "methods might be developed to control this factor" and
   providing the necessary additional definition;

 * an auditor-friendly checklist of assessment criteria;

 * an assessment process, including people to answer questions about
   interpretation of the elements, and procedures resulting in assignment
   of level values;

 * assessment processes for relying parties to help them determine their
   LoA requirements;

 * operational specs supporting LoA, including defining how to express the
   levels as values of a SAML attribute.

E-Auth is no more.  But this approach has been carried on by the Liberty IAEG, and by the InCommon Federation Identity Assurance program (http://incommonfederation.org/assurance).  In the InCommon program we have followed the E-Auth model, including a framework with processes for assessment, auditable checklists, and URIs that are assigned representing assurance profiles (which may be used as values in this SAML authncontext profile at some point).

NIST continues to work on revising 800-63, but it is not operating an assurance program.  If I have a question about interpreting whether some practice in my IdP meets a provision of 800-63, as far as I know there's no way to ask NIST that question.  You can't hand 800-63 to an auditor and ask them to audit against it.  NIST doesn't review organizations' claims to meet 800-63 provisions.  Nor has NIST defined representations of the 4 levels in protocols such as SAML.

I don't think the SSTC intends, via the publication of this profile with these defined 800-63-based schemas, to create an assurance program.  As one example, when the next version of 800-63 comes out, presumably the TC would be obliged to create a new set of URIs referring to that version. That's not hard, but it would raise questions about transition procedures, equivalence between the two versions, etc.  The TC could leave these questions for someone else to answer, but then have we really done the world a favor by defining these schemas in the first place?

It might be argued: these schemas are no different than a profile like urn:oasis:names:tc:SAML:2.0:ac:classes:Kerberos from saml-authn-context, which is just out there, anyone can use it, it creates no questions, needs no program.  And I'd respond: exactly; it has none of those features, and it has essentially *no* value in helping sites implement policies that meet the assurance needs of inter-organizational federation.  We can treat assurance the same way, ie as just a reference to a technical spec, but I think this would be profoundly misleading, and would set a very bad precedent.

If we agreed to take out the NIST 800-63 material, then the question is
whether to replace it with something that would be more suitable, or just
not include an example in this doc.  I think it would be OK to have the
doc not include an example.  Alternatively a dummy example could be
included, eg with a http://www.example.com/assurance/foo URI.  If we want
to include a real example, I offer two possibilities.  Probably the more
appropriate would be schema for the Liberty IAF 1.0.  I can't tell from
the LIAF material whether there are URIs assigned for the various levels.
Maybe someone knows.  The other possibility would be the InCommon IAF.
InCommon unfortunately hasn't started using SAML 2.0 yet, so this would be
a little speculative, but if people thought it was the best choice we
could push on it.

(Just to mention:  the OpenID PAPE spec has more or less the same feature,
ie a way of sending NIST 800-63 values.  This is also a mistake, in my

 - RL "Bob"

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Paul Madsen
e:paulmadsen @ ntt-at.com

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