A Goal-oriented Approach to Grid Security Requirements Benjamin Aziz (STFC Rutherford Appleton Laboratory, UK) Joint work with Alvaro Arenas (STFC RAL, UK), Philippe Massonet (CETIC, Belgium) and Christophe Ponsard (CETIC, Belgium) UK e-Science All Hands Meeting (AHM 2008) W4: Information Assurance for the Grid: Crossing boundaries between stakeholders 10 September 2008, Edinburgh, U.K.

Motivation “We need more trust and security reasoning earlier in system development; at the requirement specification stage.” Analysis Requirements Specification Implementation Integration and Testing Operation and Maintenance Design Software Development Current trust and security Future trust and security

Objectives Extend a requirement engineering methodology with constructs for expressing trust relations and security policies Apply the extension to a Grid-based scenario Enhance an existing requirement engineering tool to support the new trust and security extensions

KAOS in a Nutshell KAOS (Knowledge Acquisition in autOmated Specifications) is a formal requirement engineering methodology consisting of several models including: –The Goal Model –The Operation Model –The Object Model –The Agent Model –The Anti-Goal Model Goals Requirements Operations Objects Agents Anti-Goals Anti- Requirements

Our Scenario: Grid-based Content Management (GCM) System Complex digital product VO VO has defined number of member organisations Product generation process is knowledge/content-intensive Product generation process is structured as a workflow Policies may be applied to control usage/access to resources along the workflow

The Goal/Operation Models for GCM System

The Agent/Operation/Object Models for GCM System

Trust and Security Requirements The previous models cannot express trust relations nor security policy requirements The Trust model introduces the following relations: –Ownership, Capability and Trust –Delegation –Distrust and Monitoring The Policy model introduces the policy relation

Ownership, Capability and Trust In our GCM system scenario: Trust TrustorEditor Goal[ContentReviewed] TrusteeReviewer DescriptionAgent Editor trusts Reviewer to enforce goal [ContentReviewed] ag G Owner(ag,G/Op) Op / ag G Capable(ag,G/Op) Op / G / ag1ag2 Trust(ag1,ag2,G/Op)

Delegation In our GCM system scenario: Delegation DelegatorReviewer OperationReview DelegateeAnotherReviewer PreConditionOwner(Reviewer,Review) DescriptionAgent Reviewer, owner of permission to execute operation Review, delegates such permission to agent AnotherReviewer G Op / ag1ag2 Delegation(ag1,ag2,G/Op) Owner(ag1,G/Op)

Monitoring and Distrust In our GCM system scenario: Distrust Dis-trustorReviewer OperationReview Dis-trusteeAnotherReviewer PreConditionMonitor(Reviewer,Review) DescriptionAgent Reviewer, monitoring operation Review, distrusts AnotherReviewer in its use of Review G Op / ag1ag2 Distrust(ag1,ag2,G/Op) Monitor(ag1,G/Op) ag G Monitor(ag,G/Op) Op /

Policies In our GCM system scenario: Policy SubjectReviewer OperationReview ObjectContent Formula (Reviewer,Review,Content)  ACL(Content) DescriptionAgent Reviewer, in applying operation Review to object Document, is constrained by the logical formula P Op ag Policy(ag,Op,Ob,F) Ob

Tool Support for Grid Security Requirements We are currently developing an Eclipse- based design tool for: –modelling trust requirements –deriving semi-automatically deployable policies from the Policy model: Rule-based XACML policies (ABAC) Process algebra-based policies (UCON)

Conclusion Many systems lack rigorous analysis of trust and security properties at the requirement specification stage We proposed one extension of the KAOS requirement engineering methodology to incorporate trust relations and security policies We applied the extension in the context of a Grid-based content management system

Future Work Investigate other trust and security relations, in particular, quantified trust We are planning to finish the tool development and produce a library of requirement patterns –E.g. The Chinese-walls security pattern Integrate the requirements into system design –Integrating KAOS with Event-B specification language

Thank You Questions?