RE: Resource sets and resource string semantics

["Platt, Darren" <dplatt@securant.com>]

I'm not sure when an attribute authority would be creating assertions which
contain a URL.  It is my understanding that the attribute authority is used
for storing attributes about users which can be queried for use in policy
decisions, such as department, role, group, contract status,...  It seems
that the types of assertions you mention are about policy (currently being
defined by the XACML effort), and are the kinds of things that a PDP would
take as input or be configured with directly.

Regards,

Darren


> -----Original Message-----
> From: Edwards, Nigel [mailto:Nigel_Edwards@hp.com]
> Sent: Tuesday, May 15, 2001 11:07 AM
> To: 'Platt, Darren'; 'Philip Hallam-Baker'; 'Hal Lockhart';
> security-services@lists.oasis-open.org
> Subject: RE: Resource sets and resource string semantics
> 
> 
> I think it would be useful to allow Attribute Authorities to issue
> assertions containing strings of the form
> http://www.hp.com/* 
> 
> This being the case I believe we need to agree on the semantics of
> such assertions (to be consumed by PDPs). I would like to separate 
> this from discussion of PDP/PEP interaction, although I agree
> it is important that is fixed too.
> 
> I would like to see more powerful ways of expressing sets of
> resources than the simple example above. However, I note that
> some feel that regular expressions and the like are
> too onerous for SAML at this time. Perhaps this can be picked
> up in SAMLv2.
> 
> Nigel.
> 
> > -----Original Message-----
> > From: Platt, Darren [mailto:dplatt@securant.com]
> > Sent: 15 May 2001 02:20
> > To: 'Philip Hallam-Baker'; 'Edwards, Nigel'; 'Hal Lockhart';
> > security-services@lists.oasis-open.org
> > Subject: RE: Resource sets and resource string semantics
> > 
> > 
> > > PEP: Can Alice access http://www.hp.com/finance/fred.xls 
> > > PDP: Yes, and Alice can access http://www.hp.com/*
> > 
> > I don't think we should be passing policy back with the 
> authorization
> > decision. 
> > 
> > 
> > > Note that another possibility is that the PEP is not a file 
> > > system. If the
> > > access control policy or permissions/whathaveyou are 
> embedded in the
> > > resource the PEP may be asking a question of the form 'Does 
> > > Alice have the
> > > Role X' or 'Does Alice have any resources in the set ..../*'
> > 
> > It is my understanding that the consensus of the TC was that 
> > a PDP did not
> > know how to make decisions, and would therefore not interact 
> > in this way.
> > This seems to be a PDP/PEP combination.
> > 
> > Regards,
> > 
> > Darren
> > 
> > 
> > 
> > 
> > > -----Original Message-----
> > > From: Philip Hallam-Baker [mailto:pbaker@verisign.com]
> > > Sent: Friday, May 04, 2001 12:24 PM
> > > To: 'Edwards, Nigel'; 'Hal Lockhart';
> > > security-services@lists.oasis-open.org
> > > Subject: RE: Resource sets and resource string semantics
> > > 
> > > 
> > > 
> > > All resources on the HP web site ???
> > > 
> > > How about http://www.hp.com/*
> > > 
> > > or if we want to avoid any possibility of collision 
> (although * is a
> > > reserved URI character):
> > > 
> > > http://www.hp.com/ *
> > > 
> > > Or we could use an XPATH statement - maybe Eve can fill us in???
> > > 
> > > The way I would see the conversation going is:
> > > 
> > > PEP: Can Alice access http://www.hp.com/finance/fred.xls 
> > > PDP: Yes, and Alice can access http://www.hp.com/*
> > > 
> > > PEP: Can Alice access http://www.hp.com/finance/mary.xls
> > > PEP-Cache: Yes
> > > 
> > > I don't like the idea of unconstrained wildcard matching etc. 
> > > However simple
> > > hierarchical partitioning is probably enough for what we 
> > > need. After all the
> > > admin will probably organize directories so that the 
> wildcards match
> > > cleanly.
> > > 
> > > 
> > > Note that another possibility is that the PEP is not a file 
> > > system. If the
> > > access control policy or permissions/whathaveyou are 
> embedded in the
> > > resource the PEP may be asking a question of the form 'Does 
> > > Alice have the
> > > Role X' or 'Does Alice have any resources in the set ..../*'
> > > 
> > > 	Phill
> > > 
> > > Phillip Hallam-Baker FBCS C.Eng.
> > > Principal Scientist
> > > VeriSign Inc.
> > > pbaker@verisign.com
> > > 781 245 6996 x227
> > > 
> > > 
> > > > -----Original Message-----
> > > > From: Edwards, Nigel [mailto:Nigel_Edwards@hp.com]
> > > > Sent: Friday, May 04, 2001 2:29 PM
> > > > To: 'Hal Lockhart'; Edwards, Nigel;
> > > > security-services@lists.oasis-open.org
> > > > Subject: RE: Resource sets and resource string semantics
> > > > 
> > > > 
> > > > Hi Hal,
> > > > I should have made it more clear that I am worring 
> about the kind
> > > > of interaction that make take place between an 
> Attribute Authority
> > > > and a PDP, rather than a PDP and a PEP.
> > > > 
> > > > Sorry about that,
> > > > Nigel.
> > > > 
> > > > > -----Original Message-----
> > > > > From: Hal Lockhart [mailto:hal.lockhart@entegrity.com]
> > > > > Sent: 04 May 2001 16:56
> > > > > To: 'Edwards, Nigel'; security-services@lists.oasis-open.org
> > > > > Subject: RE: Resource sets and resource string semantics
> > > > > 
> > > > > 
> > > > > Nigel,
> > > > >  
> > > > > > The intent of this assertion is to specify authorizations 
> > > > associated
> > > > > > with Alice's account.
> > > > > > 
> > > > > > Suppose I want to issue an assertion allowing Alice to 
> > > access all
> > > > > > resources on a large web site with a dynamic resource set,
> > > > > > e.g. http://www.hp.com/ 
> > > > > > 
> > > > > > Clearly it is not possible to enumerate the entire 
> > > > resource set. So
> > > > > > how do we handle this case?
> > > > > > 
> > > > > > It occurs to me that some may feel that this sort of 
> > > > > assertion should
> > > > > > be considered by XACML, rather than SAML. I guess 
> one possible
> > > > > > resolution is to leave it to XACML.
> > > > > 
> > > > > I don't understand the use case you have in mind. SAML is 
> > > > not a policy
> > > > > provisioning protocol. What sort of request might Alice have 
> > > > > made to suggest
> > > > > to the PEP that she might want to access all of www.hp.com? 
> > > > > In the normal
> > > > > case, there will be thousands of pages she can access and 
> > > > > thousands she
> > > > > cannot. Even with a really general language to express 
> > > > > resources, e.g. reg
> > > > > exp, It's going to be a long list.
> > > > > 
> > > > > It sounds to me that what you really ought to do is operate a 
> > > > > PDP, which
> > > > > receives Attribute Assertions (and perhaps Authorization 
> > > > > Assertions) and
> > > > > makes a decision whether to allow access. A PEP is supposed 
> > > > > to be quite
> > > > > simple.
> > > > > 
> > > > > > A related issue is the semantics of resource strings. I 
> > > believe we
> > > > > > need to define what these are. Suppose one of the 
> > > > > <Resource> elements
> > > > > > contains the following: http://www.hp.com/ 
> > > > > > 
> > > > > > What are the semantics: the home page or everything 
> under it? 
> > > > > > In my opinion
> > > > > > serious security issues will arise if the asserting party 
> > > > > and relying
> > > > > > party apply different semantics.
> > > > > 
> > > > > Certainly this is something that the specification should 
> > > > > make unambigious.
> > > > > 
> > > > > Hal
> > > > > 
> > > > > 
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