[ogsa-authn-bof] Shibboleth/Grid Namespace Convergence
Tom Scavo
trscavo at gmail.com
Wed Feb 7 11:33:22 CST 2007
Just a point of clarification with respect to the IdP...today campus
IdPs are able to assert eduPersonPrincipalName (which has the same
value across SPs), but many production IdPs are loathe to release
ePPN. Instead, to prevent collusion among SPs (and to protect
privacy), Internet2 is moving towards eduPersonTargetedID (ePTID).
Unlike ePPN, the value of ePTID is specific to the SP, that is, ePTID
is essentially a triple (see SAML2Core regarding the new persistent
identifier). So by default, collusion is prevented.
Moreover, I should point out that campus IdPs do not, and probably
will not (unless the CA is integrated with the IdP), assert
X509SubjectName. In the foreseeable future, t will be up to the Grid
to map ePTID to DN. Today we algorithmically map a campus identifier
to a DN. I think we will have to move to a persistent model
regardless of the DN properties we choose to adopt. The model I have
in mind is employed by myVocs today.
Tom
On 2/7/07, David Chadwick <d.w.chadwick at kent.ac.uk> wrote:
> Hi Von
>
> to answer your specific points:
>
> Von Welch wrote:
> >
> > David,
> >
> > I should have phrased requirement #1 as:
> >
> >> 1) The same user, identified by a given IdP, using the same
> >> GridShib-CA, MUST always map to the same DN in the Grid space
> >
> > In regards to dropping requirement #6, I think what you really want is
> > to change requirement #1 so that it looks like the following:
> >
> > The same user, identified by a given IdP, using *any* GridShib-CA, MUST
> > always map to the same DN.
> >
> > I have several concerns about this approach. I believe this means we
> > have to do one of the following:
> >
> > 1) Every GridShib-CA instance must have access to the same user
> > attributes and use the same transformation policy. This is tight
> > coordination that I don't believe is possible to guarantee.
>
> It is not unreasonable to assume that each IDP will have the same
> privacy policy for the set of GridShib CAs that provide access to the
> same set of grid applications. Thus the user's attribute set will be
> identical in each instance. Therefore it is reasonable to expect the
> same DN to be issued by each of these CAs.
>
>
> >
> > 2) The IdP must provide the DN to all instances of the GridShib-CA.
> > Again, global coordination that I don't see as possible.
>
> I think it is reasonable to expect that if the IDP releases the DN to
> one of the CAs, it will release it to all of them. I dont see why the
> IDP would treat members of the set differently do you, since the same
> user is accessing the same grid applications in each case.
>
>
> >
> > I also find it disconcerting to have two different CAs issuing DNs in
> > the same namespace in the event something goes wrong.
>
> I dont find that disconcerting at all. The same user should be entitled
> to have the same DN regardless of the CA. I repeat that CA's are not
> naming authorities, they are certification authorities that certify a
> user's DN that is issued by a naming authority.
>
> (I agree we could
> > move to a model of Issuer/DN for identity to resolve this.)
>
> In this case the CA becomes a naming authority.
>
> regards
>
> David
>
> >
> > Von
> >
> >
> > On Feb 7, 2007, at 7:35 AM, David Chadwick wrote:
> >
> >> Hi Von
> >>
> >> It seems to me that requirements 1) and 6) conflict. I support
> >> requirement 1) but not 6). If a user enters grid space via two
> >> different Shibbolised portals, he will always be redirected back to
> >> his IDP to authenticate, and ought to get the same grid DN from both
> >> portals. Requirement 1) implies this. Requirement 6) states this will
> >> not be the case. Hence I think you should drop requirement 6).
> >>
> >> regards
> >>
> >> David
> >>
> >>
> >> Von Welch wrote:
> >>> Nate,
> >>> Here's my current thinking on this. Let me start with what I see
> >>> as the requirements and then move on to what our plans are
> >>> currently. Note that our current implementation (0.3.0) of the
> >>> GridShib-CA does not implement this, but the plan is for the next
> >>> version to do so.
> >>> Requirements for a standard Grid profile follow. One could also
> >>> imagine profiles that support psuedonymity, but I assert that the
> >>> following profile is a standard mode of operation any Shib->Grid
> >>> translator SHOULD be able to support.
> >>> 1) The same user, identified by a given IdP, MUST always map to
> >>> the same DN in the Grid space
> >>> 2) Two different users MUST never map to the same DN in the Grid space
> >>> 3) Identifiers mapped from a given IdP MUST be mapped in such a
> >>> manner that prevents conflict with identifiers mapped from another
> >>> Idp. (Note that this implies that the same user, identified by two
> >>> different IdPs, will have two different DNs.)
> >>> 4) It SHOULD be discernible from a DN, which IdP asserted the
> >>> mapped identifier.
> >>> 5) DNs SHOULD contain a reasonable facsimile of the user's legal
> >>> name. (This motivation for this comes from the IGTF.)
> >>> 6) DNs created by two different instances of a GridShib-CA SHOULD
> >>> be done in such a manner as to prevent any conflict. This implies
> >>> the same user, from the same IdP going through two different
> >>> GridShib-CA instances will get two different DNs. The only exception
> >>> to this should be if both GridShib-CA instances are operated by the
> >>> same organization in some sort of replication scenario (the are
> >>> logically the same instance).
> >>> Currently Shibboleth identifiers are scoped to the issuing IdP. This
> >>> makes some of the requirements above easier to meet. If this
> >>> changes, it will require the addition of a IdP identifier to the DN
> >>> given below. See the following URL for a discussion of this: http://
> >>> bugzilla.globus.org/bugzilla/show_bug.cgi?id=4888
> >>> Our plan is for the GridShib-CA to issue DNs which look like the
> >>> following:
> >>> /DC=edu/DC=uiuc/DC=ncsa/DC=gridshib-ca/O=User Certificate/CN=<ePTID>/
> >>> <displayName>
> >>> The DC components serve to uniquely identify the GridShib-CA
> >>> instance in question and meet requirement #6.
> >>> Where <ePTID> is the eduPerson Targeted ID and <displayName> is the
> >>> displayName attribute, both as provided by the IdP.
> >>> ePTID is used because it has a persistence quality lacked by ePPN
> >>> (i.e. it is guaranteed never to be reassigned). This serves to meet
> >>> requirements #1-#4.
> >>> displayName provides the facsimile of the user's legal name
> >>> (requirement #5).
> >>> That said, we expect some institutions may have problems providing
> >>> ePTID, so we expect to be able to fall back to ePPN, recognizing
> >>> that doesn't guarantee meeting requirement #2 as ePPN could, in
> >>> theory be re-assigned, and doesn't meet requirement #5 as ePPN looks
> >>> more like an email address than a legal name.
> >>> Comments welcome.
> >>> Von
> >>> On Feb 5, 2007, at 10:26 PM, Nate Klingenstein wrote:
> >>>> OGSA-Authn BoFfers,
> >>>>
> >>>> At our meeting in North Carolina, I flagged the translation of names
> >>>> from the grid world to the institutional world and vice versa as
> >>>> being an important topic for discussion in the next several months.
> >>>> We need to begin to document current practices so that a path towards
> >>>> convergence can be identified.
> >>>>
> >>>> I'd like to give a brief background for those on the list who aren't
> >>>> heavily steeped in this problem. The various Shibboleth-grid
> >>>> integration projects out there all want to bootstrap grid
> >>>> authentication (and sometimes authorization) by use of institutional
> >>>> authentication. This authentication generally results in a unique
> >>>> identifier for the user which differs in form from that used on the
> >>>> grid, and potentially in semantic meaning as well.
> >>>>
> >>>> There is a lot of different types of identifiers. If a campus is
> >>>> using LDAP, the user will also have a DN associated with their entry,
> >>>> but this directory DN is rarely used as an identifier in practice and
> >>>> usually won't correspond to those issued in x.509 certificates
> >>>> anyway. Local practices for primary identifier vary based on local
> >>>> needs, and many institutions don't use LDAP at all.
> >>>> eduPersonPrincipalName, which takes the form of name at domain, has
> >>>> proven the most ubiquitous and successful in inter-realm deployment
> >>>> thus far.
> >>>>
> >>>> The critical step is translation of the identifier that results from
> >>>> campus authentication to a grid-usable credential(and, potentially,
> >>>> vice-versa for callbacks). This bootstrap can be performed in many
> >>>> ways at many different points. Differences in practice could lead to
> >>>> non-interoperability and general confusion for grid SP's and campus
> >>>> IdP's alike.
> >>>>
> >>>> There are several projects out there that have bridged this gap in
> >>>> creative ways, such as SHEBANGS, SLCS, and GridShib. I'd like to
> >>>> invite each project to take some time within the next month to
> >>>> describe in a brief document how they linked Shibboleth
> >>>> authentication to the grid as a first step. If there's a willingness
> >>>> to document additional passing of authorization or attribute
> >>>> information, I think that would be useful as well.
> >>>>
> >>>> Cheers,
> >>>> Nate.
> >>>> _______________________________________________
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> >>>>
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> >>
> >> --
> >> *****************************************************************
> >> David W. Chadwick, BSc PhD
> >> Professor of Information Systems Security
> >> The Computing Laboratory, University of Kent, Canterbury, CT2 7NF
> >> Skype Name: davidwchadwick
> >> Tel: +44 1227 82 3221
> >> Fax +44 1227 762 811
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> >> Email: D.W.Chadwick at kent.ac.uk
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> >>
> >> *****************************************************************
> >>
> >
> >
>
> --
>
> *****************************************************************
> David W. Chadwick, BSc PhD
> Professor of Information Systems Security
> The Computing Laboratory, University of Kent, Canterbury, CT2 7NF
> Skype Name: davidwchadwick
> Tel: +44 1227 82 3221
> Fax +44 1227 762 811
> Mobile: +44 77 96 44 7184
> Email: D.W.Chadwick at kent.ac.uk
> Home Page: http://www.cs.kent.ac.uk/people/staff/dwc8/index.html
> Research Web site: http://sec.cs.kent.ac.uk
> Entrust key validation string: MLJ9-DU5T-HV8J
> PGP Key ID is 0xBC238DE5
>
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