1. Policy-Based Dynamic Negotiation for Grid Services Authorization Ionut Constandache, Daniel Olmedilla, Wolfgang Nejdl Semantic Web Policy Workshop, ISWC’05 Galway, Ireland, 7 th November 2005

2. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop2 Motivating Scenario (I) Grid Limitations

3. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop3 Policy-Driven Negotiation (I) Characteristics Both client and servers are semantically annotated with policies Annotations specify constraints and capabilities  access control requirements -which certificates must be presented to gain access to it -who is responsible for obtaining and presenting these certificates are used during a negotiation  to reason about and to communicate the need to see certain credentials from the other party  to determine whether requested credentials can be obtained and revealed. User involvement is drastically reduced in favor of automated interactions.

4. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop4 Policy-Driven Negotiation (& II) Example: Security & Privacy Step 1: Alice requests a service from Bob Step 5: Alice discloses her VISA card credential Step 4: Bob discloses his BBB credential Step 6: Bob grants access to the service Service BobAlice Step 2: Bob discloses his policy for the serviceStep 3: Alice discloses her policy for VISA

5. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop5 Policy-Driven Negotiation on the Grid (I) Example scenario With only one certificate to access the online repository The delegated certificate is used to retrieve the requested certificates Server informs the client about its access control policy

6. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop6 Policy-Driven Negotiation on the Grid (II) Enhanced Characteristics Distributed authorization mechanisms  Driven by policies, not hardcoded Bilateral policy specification Access is negotiated Dynamic credential fetching  Now possible to use discovery and scheduling services to locate the best available resources  Otherwise, impossible to predict before hand what exact service instances would be used and which certificates required Capability based authorization architecture  Instead of identity based No previous trust relationships required Monitoring and explanation of authorization decision

7. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop7 Policy-Driven Negotiation on the Grid (III) Implementation on Globus Toolkit 4.0 Directed integrated with the grid services paradigm Extension to GSI pluggable to any GT4.0 compliant grid service or client Only requirement: Java based grid services We use:  Custom PDP as part of the Client Call Interceptor -Redirects to a negotiation if required  Asynchronous negotiations are achieved through WS- Base Notification and WS-Topics CAS integration into negotiations API for easy integration within client code

8. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop8 Policy-Driven Negotiation on the Grid (& IV) Architecture Service wsdl file Service Deployment Descriptor

9. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop9 Conclusions & Future Work (I) Conclusions Main Features Self-describing resources for access requirements  Based on properties Dynamic negotiation for service authorization Automatic credential fetching Implementation in Java Extension of GSI in GT4.0 Backwards compatible

10. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop10 Conclusions & Future Work (& II) Further Work Study performance impact of negotiations And approaches to minimize the extra load  Limit number of iterations -E.g. 2 steps negotiations  Advertise policies before the service is invoked Improve credential repositories  Integration of TN in MyProxy Investigate the use of XACML  Delegation not yet supported but planned Use of traceable negotiations  E.g. monitoring or accounting

11. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop11 Questions? olmedilla@l3s.de - http://www.l3s.de/~olmedilla/ Thanks!

12. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop12 Implementation in GT4 Easy Integration with Current Grid Services Service - include one jar file containing the policy based trust negotiation engine - minor add-ons to the service wsdl file (import one wsdl file and extend one port type) and wsdd file (add one more provider and install a security descriptor) - have a resource (if not available) - re-deploy the service Client - use one jar file containing the policy based trust negotiation engine - invoke the service as usual / or call directly for a trust negotiation process - look for authorization exceptions and if one triggered by trust negotiation failure make simple calls to the negotiation engine

13. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop13 Integration into Globus Toolkit 4.0 (I) Grid Service Descriptor Descriptors: - grid service descriptor (wsdl file): TrustNegotiation.wsdl - defines the data types and functions for exchanging trust negotiation messages The grid service should extend the NotificationProducer port type (used for asynchronous communication with the client) and the TrustNegotiation port type(used for exposing the functions used by the client to push proofs/requirements to the grid service).

14. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop14 Integration into Globus Toolkit 4.0 (II) Grid Service Deployment Descriptor Descriptors: - grid service deployment descriptor (wsdd file): Rely on GT4.0 providers for notification usage and use a TrustNegotiationProvider implementing the logic for policy based dynamic negotiation Install a security descriptor specifying the use of a PDP for filtering client calls/managing authorization information.

15. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop15 Integration into Globus Toolkit 4.0 (& III) Requirements Resource: - the grid service should use a resource implementing TopicListAccessor - a topic would be added by TrustNegotiationProvider for trust negotiation (using this topic the service pushes proofs/requirements on the client side)

16. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop16 Client Service

17. Daniel Olmedilla Nov 7th, 2005Semantic Web Policy Workshop17 Client Factory Service Instance Service Resource Exposes a topic like TrustNegotiationTopic for asynchronous communication with the client. Notify the client when his requests are fulfilled or further requirements are imposed by the service 9. Notify the client about service policies and further requirements PDP specified in the Instance service descriptor that intercepts operation calls. It checks if operation invoked is authorized. Operations getNegotiationTopic() and trustNegotiate() are permitted by default and all the other operations are denied unless a trust negotiation process has succeeded. Have the instance service extend the standard port types Subscribe and GetMessage (used by notifications) and a port type which we provide TrustNegotiationProvider which is going to expose 2 operations getNegotiationTopic() and trustNegotiation(). Receive through them the client requests and proofs with regard to service authorization 5. Catch the exception 10. Operation executed on resource if the trust negotiation process was successful 3. Operation called on the resource 4. Client is not authorized to make the call throw an exception. 8. Client call trustNegotiation() operation for sending client policies and proofs 1. Requests create resource 2. Creates the resource 7. Register with TrustNegotiation Topic for notifications 6. Client call getNegotiationTopic() receive the QName of the negotiation topic.