Hi I just want to know how can I match XACML 3.0 Request from the PEP against the Policies stored in policy store using PDP. How I will evaluate particular request against the multiple policies stored in policy store.
XACML request is matched with the "Target" element of the policies that are stored in PDP policy store. Once target element is matched for policies, Those matched policies (applicable policies) are evaluated (rules of the policies) according to the policy order and results are combined according to the policy combining algorithm of the policy store. If PEP wants to know that; what PEP policies are matched for given XACML request, PEP can send the XACML request with "ReturnPolicyIdList" attribute as "true".
<Request xmlns="urn:oasis:names:tc:xacml:3.0:core:schema:wd-17" CombinedDecision="false" ReturnPolicyIdList="true">
Then XACML response would returns the matched policies in the XACML response.
In addition to Asela's answer, I'd like to add that a "policy store" is implementation-specific.
The way Asela describes it essentially means that the policy store acts a policy set with a combining algorithm and no target.
Adding my experience of using WSO2 Identity Server as a PDP
So you can add multiple policy files in IS. But you have to give ranking to each policy file.
So what i think is, those policies get validated in the order of ranking which we provide and for whichever policy the target element gets matched first get evaluated first.
Related
I basically want to use Authzforce in a multi-tenant system.
Right now, I have a single root policy that has a few PolicySetIdReference elements that point to other policy sets (per organization) but I noticed that it tries to resolve every reference element and queries the database (I set up my own version of the MongoDbBasedRefProvider). I am worried that I would needlessly load every other policy for other organizations.
<PolicySet PolicySetId="ROOT" ....>
<PolicySetIdReference>ID-for-org-1</PolicySetIdReference>
<PolicySetIdReference>ID-for-org-2</PolicySetIdReference>
</PolicySet>
Am I able to make the root policy provider check some condition(based on org) so that the policies that I check are significantly smaller? In the example above, i only want to retrieve the one for ID-for-org-1
For full multi-tenancy, I recommend to have one PDP instance per tenant, i.e. dispatch the request to a specific PdpEngine instance based on the tenant (org) ID, e.g. via a String-to-PdpEngine map or whatever, just a suggestion.
If you still want to use the same PDP engine for all tenants (i.e. handling policies for all), make sure you do all these:
Use the first-applicable policy combining algorithm in the ROOT policy (so that the evaluation stops at the first applicable policyset within).
Make sure there is a tenant/org ID attribute present in XACML requests.
Define a XACML Target in each org policyset with a Match (equal) on this tenant/org ID attribute, to make sure the policyset applies (is evaluated) only if the tenant/org-id matches.
Implement and enable a Decision Cache on the PDP.
Our requirement is that i have to separate xacml policy file from default registry called wso2Registry.
so , i am trying to do this scenario using wso2-Governance Registry
but i cant get succeded on this
is anythings other then i have to do to seprate xacml policy based on Tenent so that one tenent cant see other Tenent Xacml policy file not even super tenent
I think your requirement is to isolate the entitlement(XACML) policy. You don't need a separate WSO2 G-Reg instances to do that. In default you it will save the policy at following path for all the tenant, and all the tenants have their own registry space. Therefore any other tenant/ super tenant cannot access them. /_system/governance/repository/identity/entitlement/policy/pap
I have the following scenario:
in a business workflow many decisions regarding different arguments must be taken.
eg: first check user roles, then do some business logic, then check business permission, ecc...
my question is:
assuming that on the PDP there are many policies for each of that arguments,
should the PEP do a single (big) xacml request to the PDP, containing all the attributes (eg: user roles, buisiness attributes, ecc)?
or
should the PEP do multiple (short) xacml request to the PDP, containing just one kind of attributes (eg: first call with user roles, second with business attributes, ecc..) ?
thank you
The PEP should never be aware of how many policies the PDP has let alone how they are structured. In addition, you should have one request per authorization question. If you have multiple use cases e.g.
create transaction
view transaction
print transaction
approve transaction
then you should do 4 independent XACML requests. 1 XACML request = 1 authorization request. If you created a single XACML request with a huge number of attributes, you wouldn't actually be asking 4 separate questions but rather a weird mix whereby you might be permitted if any of the provided attributes triggered a Permit (and of course that all depends on the policies and combining algorithms you have).
To save on roundtrip time (transport cost...), you can use the Multiple Decision Profile of XACML (MDP) whereby you can ask in one go:
Can the user create, view, print, approve transaction X?
The Axiomatics Policy Server implements the Multiple Decision Profile. You can read this blog post to understand how to create the request.
HTH,
David.
I am beginner for creating XACML 3.0 policies. In my case we have multiple actions for a single resource.The permissions of a single resource will be depend upon Role.Here in my case resource in the sense like "Name" and "Actions" in the sense "Read,Create,Update,Delete".
Please suggest me the best way of creating policy?
You can use policy editors to create XACML policies. There are some policy editors that are available free. If you are using WSO2 identity Server, You can find the policy editors in the management console to create the XACML policies. You can find more details about them from here. Also According to the your scenario, let me give few suggestion of creating a XACML policy
First identify the entities and their mapping.. Just think as following
Policy is going to create for Resource -- foo
Foo resource has actions -- Read,Create,Update,Delete
All actions can be preformed by role -- admin
Read action can be preformed by role -- role1
Update,Create action can be preformed by role - role2
Identify the target for policy --> This can be the entity that policy is written for, Here it is the resource; i.e "foo"
Define rules policy rule. There can be three rules (if want , we can write them in even one rule)
All action --> admin
Read action ---> role1
Update,Create -- role2
(Optional) Define the last rule as denied to avoid any other access to foo resource
I am attaching UI view of the Identity Server simple policy editor that is used to create the above scenario..(deny rule would be auto generated in this editor). once you have the template and idea, It is easy even to modify the policy using XML and see try out.
Originally, I asked "How do you write a policy that requires a subject be granted access to a requested permission, where the set of allowed permissions is in an external attribute store. Can you reference an external set of permissions in a policy?" The second question has been answered in the affirmative, so I'm revising the question a bit to focus on the "how".
Can someone provide a xacml policy snippet (or even pseudo-xacml) that requires a role attribute id (will be provided by the request) to be within a set of roles which are identified by another attribute id (managed by external attribute store).
For the sake of providing a starting point, the following is an example from http://docs.oasis-open.org/xacml/2.0/XACML-2.0-OS-ALL.zip. In this case, the role is inline.
<Subject>
<SubjectMatch MatchId="urn:oasis:names:tc:xacml:1.0:function:string-equal">
<AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">administrator</AttributeValue>
<SubjectAttributeDesignator AttributeId="urn:oasis:names:tc:xacml:2.0:example:attribute:role"
DataType="http://www.w3.org/2001/XMLSchema#string"/>
</SubjectMatch>
</Subject>
Yes, policies can be written to reference attributes that come from an external attribute store.
However, where the attributes actually come from is usually not specified in the policy itself, other than perhaps by a naming pattern in the attribute ID. In the XACML PDP reference architecture, it's the responsibility of the request context handler to resolve attribute IDs and produce values for the PDP.
It goes something like this: While evaluating a request against a set of policies, the PDP encounters an attributeID in a policy rule that it needs to form a decision about the request. The PDP asks the request context handler to get the value of that attributeID "from whereever" - the PDP doesn't care where it comes from. The request context handler may look for the attribute in the attributes provided with the request, or in any number of external attribute providers, such as LDAP or AD or SAML or plain old databases. The request handler might recognize naming patterns (like, namespace prefixes) in the attributeID to know where to obtain it.
You want your attributeIDs to be specific enough to know what they are and what they mean, but not so specific that all of your policies break when you move your attribute provider to a different machine. Policies should be configuration independent.
Ultimately, where the request handler looks for attributes is a matter of configuration of the request handler / PDP server, and will vary by product vendor.
Update: To answer the 2nd revision to this question
You would write your policy to perform a comparison between the attribute value(s) provided in the request and a list of values provided by an external source.
Keep in mind that an attribute designator returns a list of values, since the request could contain multiple attribute values for the same attributeID. You can accommodate that by either by wrapping the attribute designator in a "one-and-only" reduction function, or by using a many-to-many cross product match function that will test every member of list1 for a match in list2.
Unless you have a specific design requirement that the request is only allowed to contain one role attribute, it's best to avoid the "one-and-only" reduction since it really limits your options.
Your Xacml 2.0 policy could look something like this: (forgive syntax errors, my Xacml 2.0 is a little rusty)
<Policy [...] RuleCombiningAlgorithm="deny-unless-permit">
<Rule [...]>
<Effect>Permit</Effect>
<Condition>
<Apply FunctionId=”urn:oasis:names:tc:xacml:1.0:function:string-at-least-one-member-of”>
<SubjectAttributeDesignator
AttributeId="urn:oasis:names:tc:xacml:2.0:example:attribute:role"
DataType="http://www.w3.org/2001/XMLSchema#string"/>
<SubjectAttributeDesignator
AttributeId="list-of-acceptable-roles-from-external-provider-attribute-id"
DataType="http://www.w3.org/2001/XMLSchema#string"/>
</Apply>
</Condition>
</Rule>
</Policy>
The Xacml function "at-least-one-member-of" takes two lists as parameters. For every item in the first list, it tests to see if that item exists in the second list. It returns true as soon as it finds at least one match.
The attribute "...example:attribute:role" from your example is the attribute you're expecting to be provided in the request. If you want to enforce that the attribute must be provided in the request, you can set MustBePresent="true" in the attribute designator.
The "list-of-acceptable-roles..." attribute is an attribute id that your PDP context handler recognizes and retrieves from some external provider. What prefix or pattern the context handler looks for and which provider it fetches from is a matter of PDP configuration.
Ideally, the naming pattern on the attribute id indicates a conceptual domain or namespace the id is associated with, but the id does not explicitly indicate the physical location or provider of the attribute value(s). For longer app lifetime with lower maintenance costs, you want to be able to change your provider implementation details without having to rewrite all of your policies.
You can have vendor-specific attribute ids that will probably only come from a single provider, you can have application-specific attribute ids that could be supplied by multiple providers but only make sense for a particular application, and you can have generic or standardized attribute ids that could come from multiple providers and be used in multiple applications. The Oasis standards body and domain-specific profiles are a good starting point for finding standardized attribute ids and their semantics or getting ideas on how to organize your own app specific ids.
Depending on your PDP and context handler implementation, it may also possible to use the "Issuer" field as a way to constrain the list of providers for an attribute. The Xacml spec doesn't say much about use of the Issuer field, but the same goals of decoupling policy from provider implementation details still holds.