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Subject: Re: [xacml] BTG comment
Hi Doron To answer your question, it is because your solution is too simplistic and does not answer the following questions 1. Which users are allowed to set the attribute Emergency=true? Could a cleaner or a member of the public? Or only doctors in the emergency ward? 2. Does the PEP always provide the Emergency attribute to the PDP regardless of its value? 3. How is the Emergency set to Untrue? Who is allowed to do this. The BTG profile I am proposing answers all these questions and provides a mechanism for PDP policy rules to be created for 1 and 3 above. In other words, it allows for controlled emergencies with policies to dictate who can and who cannot notify them regards David On 21/03/2011 14:34, Doron Grinstein wrote: > I agree. The PEP provides an attribute Emergency="true" (set by user > action). Glass is broken. Period. > > Why make things complicated? > > Doron Grinstein > CEO > BiTKOO > > > > On Mar 21, 2011, at 7:23 AM, "Rich.Levinson" <rich.levinson@oracle.com > <mailto:rich.levinson@oracle.com>> wrote: > >> Hi Erik, >> >> I do not disagree with your assumed example that has the PDP and >> StateDB conspire >> to reduce the bank account balance before the transaction has been >> executed. If you >> are suggesting that I am making a suggestion along those lines, then >> you are mistaken. >> >> In the RSA 2008 Interop, when a doctor from an external facility made >> a request to >> see a patient record, the doctor was denied access. However, the >> doctor then >> "declared an emergency", and was able to obtain an emergency-override >> attribute, >> which was then submitted with a follow-up request and access was allowed. >> >> Although not specified, the act of the doctor "declaring the >> emergency" means that >> the doctor as an authorized user of StateDB was able to change the >> state of the >> situation and thus an attribute became available that was not >> previously enabled. >> >> In theory, now the PDP could look for the emergency access attribute >> and the PIP >> could obtain it from StateDB, which could not have been done before >> the doctor >> declared the emergency. >> >> I have not fully reviewed Paul's email that refers to David's >> proposal. However, >> I was under the impression that in David's proposal, the first request >> resulted >> in the generation of an obligation, which from my perspective would inform >> the PEP that a situation now existed that is being denied, but that >> there is >> an option to override, if some external action is taken to enable the >> override. >> >> Whether or how any state changes take place in the external StateDB at >> this >> point is beyond the scope of the XACML specs, and any presumptions as >> to what anyone would propose to do at this point is purely in the realm of >> conjecture and the creation of strawmen, such as an academic question of >> what would one's opinion be of a PEP that reduced the bank balance before >> the transaction was attempted. >> >> From my perspective the discussion has solved the problem by informing >> the world outside of XACML that a situation exists that is being denied, >> but could be permitted if someone in authority were to grant a particular >> privilege. >> >> Thanks, >> Rich >> >> >> Erik Rissanen wrote: >>> Hi Rich, >>> >>> What I meant with my comment, and which I think is what Paul is also >>> objecting to, is that it might not be a good idea to let the >>> request/response protocol itself drive the state changes in the >>> "StateDB". >>> >>> With "letting the request/response protocol drive the state changes >>> in the StateDB" I mean roughly that the stateDB would be associated >>> with triggers, which, when they see particular attribute values in a >>> request and particular decision, the would change the state of some >>> attribute in the StateDB. For instance, if an incoming request to the >>> PDP says action-id = "BTG" and the response says "Permit", then the >>> attribute "btg-in-process" would be set to true. This would be done >>> within the StateDB/PDP combo, without involvement of the PEP. >>> >>> This would have two undesirable characteristics: >>> >>> 1. It is harder to understand the behavior of the PDP since it is no >>> longer idempotent from the perspective of the PEP. >>> >>> 2. From a more fundamental level, from the point of view of the use >>> cases, it is doubtful whether it makes sense to have a trigger like >>> this since the fact that a PDP has permitted something is not the >>> primary event which matters. Rather it is usually the enforcement >>> action in the PEP which matters for the state change. >>> >>> This latter point is perhaps easier to understand in the context of a >>> simple banking example: an application access is made to withdraw >>> $100 from an account. The PEP intercepts this and asks the PDP. The >>> PDP has a policy which, among others, requires that the balance of >>> the account >= $100. The balance of the account is in this example an >>> attribute maintained in the "StateDB". Let's say the balance equals >>> $200 so the PDP permits the action. >>> >>> Now at this stage, it would not make sense to reduce the balance of >>> the account by a StateDB trigger since the transaction has not been >>> completed. It has just been permitted. There may be other reasons for >>> the transaction to be aborted or rolled back, and we would gain >>> nothing by involving the PDP and the StateDB in this. >>> >>> I have not analyzed the BTG case in detail, but it appears similar to >>> me, that is, it makes more sense to change the state in the PEP >>> and/or application. >>> >>> And I have not come up with any good use case or example where this >>> kind of StateDB and triggers would make sense. >>> >>> Best regards, >>> Erik >>> >>> On 2011-03-18 23:23, Rich.Levinson wrote: >>>> Hi Paul, >>>> >>>> I am not sure I understand the objections you are raising. I have >>>> put comments >>>> inline below, trying to respond to the points you have made. >>>> >>>> As I have indicated in prev emails, I believe the proposal is using >>>> standard mechanisms >>>> and not introducing any "state" to the PDP, other than the implicit >>>> state of the request >>>> context which already exists, nor is it doing anything significantly >>>> different from techniques >>>> we have already used in the RSA 2008 Interop, where we had policies for >>>> emergency conditions based on an emergency-override attribute that a >>>> subject >>>> could obtain thru some external mechanism from a trusted authority >>>> that could >>>> then be submitted with the request. If you are interested the >>>> details of that Interop >>>> are in the XACML Repository: >>>> http://www.oasis-open.org/committees/document.php?document_id=28030&wg_abbrev=xacml >>>> <http://www.oasis-open.org/committees/document.php?document_id=28030&wg_abbrev=xacml> >>>> >>>> (In the doc description of the zip file at the above URL, it is item >>>> #2 that contains >>>> the specification with details of requests and responses and >>>> policies in section 2.2.4 >>>> that describes the "Emergency Access Use Case".) >>>> >>>> Thanks, >>>> Rich >>>> >>>> Tyson, Paul H wrote: >>>>> Erik seems to appreciate my objection to David's BTG proposal, which has >>>>> nothing to do with stateful or stateless PDPs, but with my desire to >>>>> restrict (or at least not to sanction) the use of the request/response >>>>> mechanism to directly change attribute values in the request context. >>>>> >>>> In the proposed approach, there is only one request context, which >>>> is initially populated by >>>> the request from the PEP. It can subsequently have "additional" >>>> attributes set during Policy >>>> evaluation if a referenced attribute is not present and the PDP >>>> calls out to a PIP to supply >>>> the attribute. >>>> >>>> The response does not get created until policy evaluation has >>>> completed, and once created, >>>> the request context is no longer used for anything. >>>> >>>> i.e. I don't understand what you mean when you refer to your "desire >>>> not to sanction the use >>>> of the request/response mechanism to directly change attribute >>>> values". That is not what is >>>> happening here. The original attributes are left intact. Additional >>>> attributes may be "read" >>>> from a PIP. >>>>> If one wants to analyze the request context one should only have to look >>>>> at how the PIP is implemented (and of course the attribute instances >>>>> conveyed by the original request). Introducing a distinguished >>>>> action-id value or specialized attribute id that has the power to modify >>>>> the request context makes it harder to analyze. The only virtue of this >>>>> approach is convenience, and it seems a slim virtue at that. It should >>>>> be possible to set up a 3rd-party service that can communicate with the >>>>> PEP and PIP as necessary to set and retrieve BTG state. >>>>> >>>> I think that is exactly what the proposal is. The "StateDB" would >>>> generally sit behind a PIP and >>>> the Policy can request the BTG state attribute, or the PEP can get >>>> it in advance and send it in. >>>>> The patient's medical condition, whether or not the building is on fire, >>>>> and the client's bank account history are all things that are outside >>>>> the scope of XACML. Information about them should come into the XACML >>>>> system in the normal ways: either from a trusted source via the PEP, or >>>>> a PIP. >>>>> >>>> I don't believe there is anything in this proposal at variance with >>>> this. All information is coming >>>> in normal ways thru trusted PEP or PIP. >>>> >>>>> Regards, >>>>> --Paul >>>>> >>>>> -----Original Message----- >>>>> From: Davis, John M. [mailto:Mike.Davis@va.gov] >>>>> Sent: Friday, March 18, 2011 13:34 >>>>> To: Rich.Levinson; Erik Rissanen; David Chadwick >>>>> Cc:xacml@lists.oasis-open.org <mailto:xacml@lists.oasis-open.org> >>>>> Subject: RE: [xacml] BTG comment >>>>> >>>>> I think we are agreed. The attributes of the StateDB can refer to both >>>>> the policy set and the attribute used to evaluate the request, eg. >>>>> "Normal Healthcare Rules", or "BTG Rules" plus "Normal Healthcare >>>>> attributes" or "BTG Attributes". The implication is that the user >>>>> request would include the requester purpose of use (setting the state), >>>>> and associated attributes which combined with existing attributes about >>>>> the (from various sources) relative to that POU allows for decision. >>>>> User asserted information, and in particular purpose of use, is >>>>> included in the XSPA profiles of XACML, SAML and WS-Trust as a mandatory >>>>> attribute. >>>>> >>>>> Regards, Mike Davis, CISSP >>>>> Department of Veterans Affairs >>>>> Office of Health Information >>>>> Security Architect >>>>> 760-632-0294 >>>>> >>>>> >>>>> -----Original Message----- >>>>> From: Rich.Levinson [mailto:rich.levinson@oracle.com] >>>>> Sent: Friday, March 18, 2011 10:13 AM >>>>> To: Erik Rissanen; David Chadwick >>>>> Cc:xacml@lists.oasis-open.org <mailto:xacml@lists.oasis-open.org> >>>>> Subject: Re: [xacml] BTG comment >>>>> >>>>> Hi Erik, Paul, Mike, Hal, and David, >>>>> >>>>> I believe David's position: >>>>> http://lists.oasis-open.org/archives/xacml/201103/msg00017.html >>>>> >>>>> is consistent with the position I recommended: >>>>> http://lists.oasis-open.org/archives/xacml/201102/msg00042.html >>>>> and originally, when this discussion began last year: >>>>> http://lists.oasis-open.org/archives/xacml/201011/msg00040.html >>>>> >>>>> >>>>> so, I think David and I are pretty much in agreement on the concepts >>>>> at this point. >>>>> >>>>> The bottom line is that any "state" that is evaluated by the PDP >>>>> policies >>>>> is contained in the request context in attributes. Who maintains those >>>>> attributes and how they get into the request context is dependent on >>>>> the system designers, and the Policy designers. But the PDP, itself, >>>>> should not require any changes from XACML 2.0 or 3.0 to implement >>>>> this. >>>>> >>>>> From my perspective, "StateDB" is nothing more than an attribute >>>>> repository, whose attributes can be referenced in Policy statements. >>>>> >>>>> Also, from my perspective, a "profile" might be useful, but is not >>>>> required >>>>> for anyone to use this system design strategy with either XACML 2.0 or >>>>> XACML 3.0. >>>>> >>>>> Thanks, >>>>> Rich >>>>> >>>>> >>>>> Erik Rissanen wrote: >>>>> >>>>>> Paul, all, >>>>>> >>>>>> I am not sure if there is a motivation for it, but there would be a >>>>>> need for an XACML state component if the desired behavior is that >>>>>> "state is changed when an access decision says Permit" (Or deny). This >>>>>> >>>>> >>>>> >>>>>> is distinct from "state is changed when an access to a resources is >>>>>> performed". >>>>>> >>>>>> In the bank case, clearly it should be the latter case, that is, the >>>>>> PEP enforces the Permit, by which the banking application will change >>>>>> the amount in the account. >>>>>> >>>>>> I cannot think if a specific real world example of the case where the >>>>>> decision by the PDP itself would cause a state change. >>>>>> >>>>>> Also It might be useful from a purely practical implementation point >>>>>> of view though. Not sure. Anybody? >>>>>> >>>>>> Best regards, >>>>>> Erik >>>>>> >>>>>> On 2011-03-15 21:42, Tyson, Paul H wrote: >>>>>> >>>>>>> The 3rd example differs from the previous 2 in that the XACML request >>>>>>> >>>>> is >>>>> >>>>>>> simultaneously *changing* the request context and requesting >>>>>>> >>>>> permission >>>>> >>>>>>> to perform an action. >>>>>>> >>>>>>> Nothing in the XACML spec prevents this (as far as I can see), but it >>>>>>> overloads the request message unnecessarily. I would not want to >>>>>>> sanction this behavior in an official profile. I believe it >>>>>>> >>>>> simplifies >>>>> >>>>>>> analysis to assume that the request/response sequence is idempotent >>>>>>> >>>>> with >>>>> >>>>>>> respect to the request context. >>>>>>> >>>>>>> Nothing prevents an implementation from using other communication >>>>>>> channels to modify the environment to cause a change in the >>>>>>> >>>>> evaluation >>>>> >>>>>>> context. In the bank account examples, it would seem a very poor >>>>>>> >>>>> design >>>>> >>>>>>> to make the XACML system update account information--surely that >>>>>>> >>>>> happens >>>>> >>>>>>> outside of the XACML system. Each time a request is received, it >>>>>>> evaluates with new values for withdrawal amount and frequency. Why >>>>>>> shouldn't the same design principle apply to a BTG attribute? >>>>>>> >>>>>>> I raised this and other concerns in my note of 22 February 2011: >>>>>>> http://lists.oasis-open.org/archives/xacml/201102/msg00037.html. >>>>>>> >>>>>>> Regards, >>>>>>> --Paul >>>>>>> >>>>>>> -----Original Message----- >>>>>>> From: David Chadwick [mailto:d.w.chadwick@kent.ac.uk] >>>>>>> Sent: Tuesday, March 15, 2011 15:10 >>>>>>> To: Davis, John M. >>>>>>> Cc:xacml@lists.oasis-open.org <mailto:xacml@lists.oasis-open.org> >>>>>>> Subject: Re: [xacml] BTG comment >>>>>>> >>>>>>> <<<first 2 examples omitted - pht>>> >>>>>>> >>>>>>> All you need is the >>>>>>> >>>>>>>> value of the current attribute for retry count. No change of state. >>>>>>>> However, if you link this to a system change that says the user must >>>>>>>> >>>>>>> now >>>>>>> >>>>>>>> authenticate by providing "Mothers maiden name" and other personally >>>>>>>> known information, then the policy state has changed from "Normal >>>>>>>> authentication used" to "Alternate authentication used". In other >>>>>>>> >>>>>>> words >>>>>>> >>>>>>>> access policies may change under alternate (can only reset >>>>>>>> >>>>> password). >>>>> >>>>>>>> 3*. BTG*. Here we require the system to go from a "Normal" access to >>>>>>>> >>>>> a >>>>> >>>>>>>> new rule set "BTG" which would have new expectations of system >>>>>>>> >>>>>>> Again we can have a fixed policy with the following condition >>>>>>> >>>>> attached >>>>> >>>>>>> to a rule >>>>>>> >>>>>>> If BTG = True then grant access >>>>>>> >>>>>>> We can have the following fixed rules as well >>>>>>> >>>>>>> If Action=BTG and .... then grant with obligation set BTG to True in >>>>>>> StateDB. >>>>>>> >>>>>>> If Action=ResetBTG and .... then grant with obligation set BTG to >>>>>>> >>>>> False >>>>> >>>>>>> in StateDB >>>>>>> >>>>>>> regards >>>>>>> >>>>>>> david >>>>>>> >>>>>>> >>>>>>> >>>>>>>> performance caused by changing the policy set referenced by the PAP. >>>>>>>> >>>>>>> For >>>>>>> >>>>>>>> example, the rule set for patient privacy might be much different >>>>>>>> >>>>> for >>>>> >>>>>>>> normal "treatment" than for "emergency" where imminent harm or death >>>>>>>> >>>>>>> was >>>>>>> >>>>>>>> involved. >>>>>>>> >>>>>>>> Regards, Mike Davis, CISSP >>>>>>>> Department of Veterans Affairs >>>>>>>> Office of Health Information >>>>>>>> Security Architect >>>>>>>> 760-632-0294 >>>>>>>> >>>>>>>> >>>>>>>> -----Original Message----- >>>>>>>> From: David Chadwick [mailto:d.w.chadwick@kent.ac.uk] >>>>>>>> Sent: Monday, March 14, 2011 10:20 AM >>>>>>>> To:xacml@lists.oasis-open.org <mailto:xacml@lists.oasis-open.org> >>>>>>>> Subject: Re: [xacml] BTG comment >>>>>>>> >>>>>>>> Hal, Erik >>>>>>>> >>>>>>>> is some sort of consensus arising that we need an entity in the >>>>>>>> >>>>> XACML >>>>> >>>>>>>> model (call it a StateDB for now) that holds the state of the system >>>>>>>> >>>>>>> in >>>>>>> >>>>>>>> the form of one or more attributes, whose values can be changed. >>>>>>>> >>>>> When >>>>> >>>>>>> an >>>>>>> >>>>>>>> attribute value changes this represents a state change of the >>>>>>>> >>>>> system. >>>>> >>>>>>>> The PDP is and remains stateless. >>>>>>>> >>>>>>>> The request context carries the current state of the system to the >>>>>>>> >>>>>>> PDP. >>>>>>> >>>>>>>> A component of the XACML system (might be a PIP, or it might be >>>>>>>> something new) picks up the current state of the system from the >>>>>>>> >>>>>>> StateDB >>>>>>> >>>>>>>> and inserts these attributes into the request context for passing to >>>>>>>> >>>>>>> the >>>>>>> >>>>>>>> PDP. >>>>>>>> >>>>>>>> When certain authz decision requests are granted (or denied) this >>>>>>>> >>>>>>> might >>>>>>> >>>>>>>> cause a change in the state of the system. A new component is needed >>>>>>>> which updates the StateDB when this occurs. >>>>>>>> >>>>>>>> This type of state based system is more generic than BTG, and can >>>>>>>> incorporate BTG as one of its use cases. You can for example use >>>>>>>> >>>>> this >>>>> >>>>>>>> type of state based system to >>>>>>>> - support withdrawals from a credit card machine up to a daily >>>>>>>> >>>>> limit, >>>>> >>>>>>>> - block a user's account after 3 concurrent denies, >>>>>>>> - implement BTG by setting the glass to broken when a user is >>>>>>>> >>>>> granted >>>>> >>>>>>>> permission to break the glass >>>>>>>> >>>>>>>> Does this also answer Mike's suggestion that BTG is an example of >>>>>>>> something more generic? >>>>>>>> >>>>>>>> regards >>>>>>>> >>>>>>>> David >>>>>>>> >>>>>>>> >>>>>>>> On 24/02/2011 17:48, Erik Rissanen wrote: >>>>>>>> >>>>>>>>> Hal, >>>>>>>>> >>>>>>>>> Yes, I agree that a special entity with the explicit purpose of >>>>>>>>> maintaining authorization state would be something good to add. >>>>>>>>> >>>>> It's >>>>> >>>>>>>>> not unusual for real world access control needs to depend on >>>>>>>>> >>>>> state, >>>>> >>>>>>>>> which may be itself affected by an access decision. XACML should >>>>>>>>> support this, but not in the PDP itself. >>>>>>>>> >>>>>>>>> Erik >>>>>>>>> >>>>>>>>> >>>>>>>>> On 02/24/2011 06:04 PM, Hal Lockhart wrote: >>>>>>>>> >>>>>>>>>> When we say that the PDP is stateless, what is meant is that no >>>>>>>>>> >>>>>>> state >>>>>>> >>>>>>>>>> is carried by the server from one decision to the next. Policy >>>>>>>>>> decisions are purely a function of policies in force and the >>>>>>>>>> >>>>>>> content >>>>>>> >>>>>>>>>> of the request context. >>>>>>>>>> I agree with the general view that this is a valuable property >>>>>>>>>> >>>>>>> which >>>>>>> >>>>>>>>>> not should be lightly changed across the board. However, I am >>>>>>>>>> >>>>>>> keeping >>>>>>> >>>>>>>>>> an open mind on the desirability of explicitly defining entities >>>>>>>>>> within the access control architecture which do maintain state. >>>>>>>>>> For example, the RBAC profile as it currently exists implies some >>>>>>>>>> kind of stateful mechanism to keep track which dynamic roles have >>>>>>>>>> been enabled. The exact mechanism was deliberately not specified >>>>>>>>>> >>>>> as >>>>> >>>>>>>>>> it was recognized that many designs were possible. >>>>>>>>>> Hal >>>>>>>>>> >>>>>>>>>> -----Original Message----- >>>>>>>>>> *From:* Rich.Levinson >>>>>>>>>> *Sent:* Wednesday, February 23, 2011 11:57 AM >>>>>>>>>> *To:* Davis, John M. >>>>>>>>>> *Cc:*erik@axiomatics.com <mailto:erik@axiomatics.com>;xacml@lists.oasis-open.org <mailto:xacml@lists.oasis-open.org> >>>>>>>>>> *Subject:* Re: [xacml] BTG comment [WAS: [xacml] Proposed Agenda >>>>>>>>>> 10 February 2011 TC Meeting] >>>>>>>>>> >>>>>>>>>> Hi Mike, Erik, Paul, and David, >>>>>>>>>> >>>>>>>>>> Here's my two cents on what I've taken from the emails on this >>>>>>>>>> thread, David's BTG profile and protocol description. >>>>>>>>>> >>>>>>>>>> I agree w Erik's statement that the XACML model does not have >>>>>>>>>> state built in, and that there is not yet a compelling reason to >>>>>>>>>> add it. >>>>>>>>>> >>>>>>>>>> However, my interpretation of "state" is wrt the Policy >>>>>>>>>> >>>>>>> definitions. >>>>>>> >>>>>>>>>> i.e. the Policy defns themselves are "static". >>>>>>>>>> >>>>>>>>>> However, for "Policy evaluation", the "state" is the >>>>>>>>>> >>>>>>> RequestContext, >>>>>>> >>>>>>>>>> namely whatever values are in the Attributes in the RequestContext >>>>>>>>>> at Policy evaluation time may be regarded as the "state". >>>>>>>>>> >>>>>>>>>> So, for "BTG", what I see as the essential ingredient is the defn >>>>>>>>>> >>>>>>> of >>>>>>> >>>>>>>>>> a BTG-State Attribute, that can be supplied by the PEP, or some >>>>>>>>>> PIP that supplies it to an attribute finder during policy >>>>>>>>>> >>>>>>> evaluation. >>>>>>> >>>>>>>>>> Testing the attribute would be triggered by its presence in a >>>>>>>>>> >>>>>>> Policy >>>>>>> >>>>>>>>>> with it MustBePresent xml attribute set to true, and the Policy >>>>>>>>>> should be defined, so that the BTG-State Attribute is not tested >>>>>>>>>> unless the request is not permitted without it. >>>>>>>>>> >>>>>>>>>> This is equivalent to what we did in the RSA-2008 Interop, where >>>>>>>>>> the "BTG-State" attribute was "hl7:pea-001", which would allow an >>>>>>>>>> external user access, where they would otherwise be denied. >>>>>>>>>> i.e. the presence of hl7:pea-001 effectively changed the "state" >>>>>>>>>> of Policy evaluation, which enabled BTG logic to be applied. >>>>>>>>>> >>>>>>>>>> With respect to David's documents, I basically agree with the >>>>>>>>>> approach, except for statements like in the protocol descr step 8, >>>>>>>>>> where it says: "The PDP sets the relevant BTG-state variable >>>>>>>>>> to true ...". >>>>>>>>>> >>>>>>>>>> I think it is fine to return an Obligation as the Profile >>>>>>>>>> >>>>>>> describes, >>>>>>> >>>>>>>>>> and that this be used as the basis of the User obtaining a >>>>>>>>>> "BTG-State" Attribute, which can be submitted in the >>>>>>>>>> follow-up request. I think the presence of this attribute >>>>>>>>>> is sufficient "state" for the Policy to evaluate properly. >>>>>>>>>> >>>>>>>>>> Thanks, >>>>>>>>>> Rich >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Davis, John M. wrote: >>>>>>>>>> >>>>>>>>>>> I still think BTG is a subset of a more general use case. >>>>>>>>>>> >>>>>>>>>>> Following along with the obligation, my impression was that this >>>>>>>>>>> >>>>>>>> must be followed with an ageement to abide by the obligation >>>>>>>> constraints, e.g. a "promise". The promise could act to tell the PDP >>>>>>>> >>>>>>> to >>>>>>> >>>>>>>> change the policy set (in this case to BTG). With the "state" change >>>>>>>> >>>>>>> the >>>>>>> >>>>>>>> decision is now correct. >>>>>>>> >>>>>>>>>>> Mike Davis >>>>>>>>>>> >>>>>>>>>>> ----- Original Message ----- >>>>>>>>>>> From: Erik Rissanen<erik@axiomatics.com <mailto:erik@axiomatics.com>> >>>>>>>>>>> To:xacml@lists.oasis-open.org<xacml@lists.oasis-open.org <mailto:xacml@lists.oasis-open.org>> >>>>>>>>>>> Sent: Wed Feb 23 04:42:41 2011 >>>>>>>>>>> Subject: Re: [xacml] BTG comment [WAS: [xacml] Proposed Agenda >>>>>>>>>>> 10 February 2011 TC Meeting] >>>>>>>>>>> >>>>>>>>>>> Hi Paul and Mike, >>>>>>>>>>> >>>>>>>>>>> I agree, but isn't this exactly what David is proposing? That is >>>>>>>>>>> >>>>>>> how I >>>>>>> >>>>>>>>>>> understand it, at least for the "PEP state" mode. The other >>>>>>>>>>> >>>>>>> alternative >>>>>>> >>>>>>>>>>> with the PDP maintaining state is something I don't think is a >>>>>>>>>>> >>>>>>> good >>>>>>> >>>>>>>> idea. >>>>>>>> >>>>>>>>>>> To make David's proposal better, it needs: >>>>>>>>>>> >>>>>>>>>>> - Drop the PDP state approach since this goes against the >>>>>>>>>>> >>>>>>> capability of >>>>>>> >>>>>>>>>>> the XACML model which does not have a state built in. >>>>>>>>>>> >>>>>>>>>>> - Define identifiers for at least the BTG obligation/advice >>>>>>>>>>> >>>>>>> (advice is >>>>>>> >>>>>>>>>>> better, but for XACML 2.0 an obligation needs to be used), the >>>>>>>>>>> >>>>>>> action-id >>>>>>> >>>>>>>>>>> for breaking glass (as well as giving some kind of direction of >>>>>>>>>>> >>>>>>> what the >>>>>>> >>>>>>>>>>> BTG request should look like in relation to resources being >>>>>>>>>>> >>>>>>> accessed). >>>>>>> >>>>>>>>>>> - It would be nice with a full, worked through example. >>>>>>>>>>> >>>>>>>>>>> Best regards, >>>>>>>>>>> Erik >>>>>>>>>>> >>>>>>>>>>> On 2011-02-23 05:06, Davis, John M. wrote: >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>>> Concur with Paul's analysis. We also see BTG as a state change. >>>>>>>>>>>> >>>>>>>>>>>> Regards, Mike Davis, CISSP >>>>>>>>>>>> Department of Veterans Affairs >>>>>>>>>>>> Office of Health Information >>>>>>>>>>>> Security Architect >>>>>>>>>>>> 760-632-0294 >>>>>>>>>>>> >>>>>>>>>>>> -----Original Message----- >>>>>>>>>>>> From: Tyson, Paul H [mailto:PTyson@bellhelicopter.textron.com] >>>>>>>>>>>> Sent: Tuesday, February 22, 2011 7:48 AM >>>>>>>>>>>> To: DavidChadwick;xacml@lists.oasis-open.org <mailto:xacml@lists.oasis-open.org> >>>>>>>>>>>> Subject: [xacml] BTG comment [WAS: [xacml] Proposed Agenda 10 >>>>>>>>>>>> >>>>>>> February >>>>>>> >>>>>>>>>>>> 2011 TC Meeting] >>>>>>>>>>>> >>>>>>>>>>>> I have some reservations about David's BTG proposal, primarily >>>>>>>>>>>> >>>>>>> because >>>>>>> >>>>>>>>>>>> the semantics are not well specified, and because it muddies the >>>>>>>>>>>> distinction between what should happen within the XACML system, >>>>>>>>>>>> >>>>>>> and >>>>>>> >>>>>>>> what >>>>>>>> >>>>>>>>>>>> should happen outside of XACML. >>>>>>>>>>>> >>>>>>>>>>>> Obligations, as currently defined, require the PEP to take some >>>>>>>>>>>> >>>>>>> action >>>>>>> >>>>>>>>>>>> prior to executing or acting on the PDP's decision for a >>>>>>>>>>>> >>>>>>> particular >>>>>>> >>>>>>>>>>>> request. The proposed BTG obligation is entirely different: it >>>>>>>>>>>> >>>>>>> says >>>>>>> >>>>>>>>>>>> "you can't have access, but you can break the glass if you >>>>>>>>>>>> >>>>>>> choose". We >>>>>>> >>>>>>>>>>>> added Advice in XACML 3 to accommodate this sort of >>>>>>>>>>>> message-passing--messages which may or may not have anything to >>>>>>>>>>>> >>>>>>> do with >>>>>>> >>>>>>>>>>>> the original request or the decision. I don't think the TC >>>>>>>>>>>> >>>>> should >>>>> >>>>>>>>>>>> encourage the use of Obligations for anything other than what >>>>>>>>>>>> >>>>>>> they are: >>>>>>> >>>>>>>>>>>> an obligation to discharge certain actions regarding the PDP's >>>>>>>>>>>> >>>>>>>> decision. >>>>>>>> >>>>>>>>>>>> This is the only way to assure predictable system behavior--or >>>>>>>>>>>> >>>>> to >>>>> >>>>>>>> detect >>>>>>>> >>>>>>>>>>>> a faulty system. >>>>>>>>>>>> >>>>>>>>>>>> As we discussed on the last call, the scope and definition of >>>>>>>>>>>> >>>>>>> "glass" >>>>>>> >>>>>>>>>>>> should be specified. If not, we are just standardizing some >>>>>>>>>>>> >>>>>>> features of >>>>>>> >>>>>>>>>>>> the request/response protocol without knowing what effect these >>>>>>>>>>>> >>>>>>>> features >>>>>>>> >>>>>>>>>>>> have, either on the PDP or the PEP. Does the glass cover a >>>>>>>>>>>> >>>>>>> specific >>>>>>> >>>>>>>>>>>> request, a specific class of subjects, a class of resources, or >>>>>>>>>>>> >>>>>>> what? >>>>>>> >>>>>>>>>>>> Or is glass-condition just another attribute in the request >>>>>>>>>>>> >>>>>>> context, >>>>>>> >>>>>>>>>>>> whose effective meaning is given by the policy rules? >>>>>>>>>>>> >>>>>>>>>>>> However you define glass-condition, it will have to be >>>>>>>>>>>> >>>>>>> implemented as a >>>>>>> >>>>>>>>>>>> XACML attribute in the request context, or as some extra-xacml >>>>>>>>>>>> functionality. Either way, you are now using the XACML request >>>>>>>>>>>> mechanism to change the policy evaluation state directly. While >>>>>>>>>>>> >>>>>>> this >>>>>>> >>>>>>>>>>>> isn't prohibited by the standard, it makes it harder to reason >>>>>>>>>>>> >>>>>>>> about the >>>>>>>> >>>>>>>>>>>> behavior of the system. >>>>>>>>>>>> >>>>>>>>>>>> David's "BreakTheGlass" action-id is egregious in that it is not >>>>>>>>>>>> >>>>>>> just a >>>>>>> >>>>>>>>>>>> request for permission to do something (outside the XACML >>>>>>>>>>>> >>>>>>>> system)--it is >>>>>>>> >>>>>>>>>>>> a directive to change the state of the policy evaluation with >>>>>>>>>>>> >>>>>>> regard to >>>>>>> >>>>>>>>>>>> a particular (non-XACML) resource, subject, or action. Now, if >>>>>>>>>>>> >>>>>>> state is >>>>>>> >>>>>>>>>>>> maintained in PEP, you could say this is a normal request, but >>>>>>>>>>>> nevertheless it has muddied the distinction between requests for >>>>>>>>>>>> permission to do something (outside of XACML) and directives to >>>>>>>>>>>> >>>>>>> do >>>>>>> >>>>>>>>>>>> something "inside" of XACML. >>>>>>>>>>>> >>>>>>>>>>>> I would favor one of two alternative approaches (or some >>>>>>>>>>>> >>>>>>> combination): >>>>>>> >>>>>>>>>>>> 1. Simply return an Obligation (along with a Permit decision) if >>>>>>>>>>>> >>>>>>> the >>>>>>> >>>>>>>>>>>> requestor is authorized to "break the glass". The PEP would be >>>>>>>>>>>> >>>>>>> obliged >>>>>>> >>>>>>>>>>>> to display the list of consequences associated with accessing >>>>>>>>>>>> >>>>> the >>>>> >>>>>>>>>>>> resource, and the user could choose to accept the consequences >>>>>>>>>>>> >>>>>>> and see >>>>>>> >>>>>>>>>>>> the resource, or cancel the request. The consequences could >>>>>>>>>>>> >>>>>>> include >>>>>>> >>>>>>>>>>>> changing the state of the system to allow access to other >>>>>>>>>>>> >>>>>>> resources, or >>>>>>> >>>>>>>>>>>> allow other people to see the same resource, or whatever the >>>>>>>>>>>> >>>>>>> business >>>>>>> >>>>>>>>>>>> meaning of "break the glass" carries in a specific application. >>>>>>>>>>>> >>>>>>> The >>>>>>> >>>>>>>>>>>> obligations would be discharged outside the XACML system. (I'm >>>>>>>>>>>> >>>>>>> not sure >>>>>>> >>>>>>>>>>>> that this approach really warrants a standard profile, unless we >>>>>>>>>>>> >>>>>>> just >>>>>>> >>>>>>>>>>>> want to provide a distinguished obligation id value for BTG.) >>>>>>>>>>>> >>>>>>>>>>>> 2. Write policies specifically to allow "break-the-glass" >>>>>>>>>>>> >>>>> actions >>>>> >>>>>>> to >>>>>>> >>>>>>>>>>>> certain subjects in certain conditions. The PEP would request >>>>>>>>>>>> permission to break the glass, and if allowed would use some >>>>>>>>>>>> >>>>>>> non-XACML >>>>>>> >>>>>>>>>>>> mechanism to change the policy evaluation state. Obligations >>>>>>>>>>>> >>>>>>> could be >>>>>>> >>>>>>>>>>>> returned with the decision to advise user of the consequences. >>>>>>>>>>>> >>>>>>> Then the >>>>>>> >>>>>>>>>>>> application would request access to the desired resource. (Again >>>>>>>>>>>> >>>>>>> I >>>>>>> >>>>>>>>>>>> question whether this is worthy of standardization, unless we >>>>>>>>>>>> >>>>>>> want to >>>>>>> >>>>>>>>>>>> name a distinguished "break-the-glass" action id.) >>>>>>>>>>>> >>>>>>>>>>>> Either of these approaches would meet the BTG use case without >>>>>>>>>>>> >>>>>>> altering >>>>>>> >>>>>>>>>>>> the semantics or conventional usage of XACML. >>>>>>>>>>>> >>>>>>>>>>>> Regards, >>>>>>>>>>>> --Paul >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> -----Original Message----- >>>>>>>>>>>>> From: David Chadwick [mailto:d.w.chadwick@kent.ac.uk] >>>>>>>>>>>>> Sent: Thursday, February 10, 2011 05:22 >>>>>>>>>>>>> To:xacml@lists.oasis-open.org >>>>>>>>>>>>> Subject: Re: [xacml] Proposed Agenda 10 February 2011 TC >>>>>>>>>>>>> Meeting >>>>>>>>>>>>> >>>>>>>>>>>>> Dear All, >>>>>>>>>>>>> >>>>>>>>>>>>> in preparation for this evening's call, I attach a revised >>>>>>>>>>>>> >>>>>>> version of >>>>>>> >>>>>>>>>>>>> the BTG profile for you consideration >>>>>>>>>>>>> >>>>>>>>>>>>> regards >>>>>>>>>>>>> >>>>>>>>>>>>> David >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>> <snip> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>> --------------------------------------------------------------------- >>>>>>> >>>>>>>>>>>> To unsubscribe from this mail list, you must leave the OASIS TC >>>>>>>>>>>> >>>>>>> that >>>>>>> >>>>>>>>>>>> generates this mail. Follow this link to all your TCs in OASIS >>>>>>>>>>>> >>>>>>> at: >>>>>>> >>>>>>> https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups. >>>>>>> >>>>>>>>>>>> php >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>> --------------------------------------------------------------------- >>>>>>> >>>>>>>>>>>> To unsubscribe from this mail list, you must leave the OASIS TC >>>>>>>>>>>> >>>>>>> that >>>>>>> >>>>>>>>>>>> generates this mail. Follow this link to all your TCs in OASIS >>>>>>>>>>>> >>>>>>> at: >>>>>>> >>>>>>> https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups. >>>>>>> >>>>>>>>>>>> php >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>> >>>>>>> --------------------------------------------------------------------- >>>>>>> >>>>>>>>>>> To unsubscribe from this mail list, you must leave the OASIS TC >>>>>>>>>>> >>>>>>> that >>>>>>> >>>>>>>>>>> generates this mail. Follow this link to all your TCs in OASIS >>>>>>>>>>> >>>>> at: >>>>> >>>>>>>>>>> >>>>>>> https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.p >>>>>>> >>>>>>>>>>> hp >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>> -- >>>>>>>> >>>>>>>> ***************************************************************** >>>>>>>> David W. Chadwick, BSc PhD >>>>>>>> Professor of Information Systems Security School of Computing, >>>>>>>> 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@kent.ac.uk <mailto:D.W.Chadwick@kent.ac.uk> >>>>>>>> Home Page:http://www.cs.kent.ac.uk/people/staff/dwc8/index.html >>>>>>>> Research Web site: >>>>>>>> >>>>>>> http://www.cs.kent.ac.uk/research/groups/iss/index.html >>>>>>> >>>>>>>> Entrust key validation string: MLJ9-DU5T-HV8J PGP Key ID is >>>>>>>> >>>>> 0xBC238DE5 >>>>> >>>>>>>> ***************************************************************** >>>>>>>> >>>>>>>> >>>>>>>> >>>>> --------------------------------------------------------------------- >>>>> >>>>>>>> To unsubscribe from this mail list, you must leave the OASIS TC that >>>>>>>> generates this mail. Follow this link to all your TCs in OASIS at: >>>>>>>> >>>>>>>> >>>>> https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php >>>>> >>>>>> --------------------------------------------------------------------- >>>>>> To unsubscribe from this mail list, you must leave the OASIS TC that >>>>>> generates this mail. Follow this link to all your TCs in OASIS at: >>>>>> https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php >>>>>> >>>>> >>>>> --------------------------------------------------------------------- >>>>> To unsubscribe from this mail list, you must leave the OASIS TC that >>>>> generates this mail. Follow this link to all your TCs in OASIS at: >>>>> https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php >>>>> >>>>> >>>>> --------------------------------------------------------------------- >>>>> To unsubscribe from this mail list, you must leave the OASIS TC that >>>>> generates this mail. Follow this link to all your TCs in OASIS at: >>>>> https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php >>>>> >>>>> >>> -- ***************************************************************** David W. Chadwick, BSc PhD Professor of Information Systems Security School of Computing, 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@kent.ac.uk Home Page: http://www.cs.kent.ac.uk/people/staff/dwc8/index.html Research Web site: http://www.cs.kent.ac.uk/research/groups/iss/index.html Entrust key validation string: MLJ9-DU5T-HV8J PGP Key ID is 0xBC238DE5 *****************************************************************
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