Presentation on theme: "Automatic XACML requests generation for policy testing"— Presentation transcript:
1Automatic XACML requests generation for policy testing Antonia Bertolino, Said Daoudagh,Francesca Lonetti, Eda MarchettiIstituto di Scienza e Tecnologiedell’Informazione “A. Faedo”Consiglio Nazionale delle Ricerche
2Agenda Access control policies and XACML language Why a testing methodology?An empirical evaluationConclusions and future worksX-CREATE Demo
3Access Control Policies Data and resources must be protected against unauthorized, malicious or improper usage or modificationPoliciesspecificationDataResources- -
4Testing the Policy Implementation PoliciesSUTverdictrequestPDPrequestrequestrequestTest SuitereplyOraclePDP (Policy Decision Point): evaluates the requests against the access control policies
5XACML Policy Structure XACML (eXtensible Access Control Markup Language)The XACML Policy elements:PolicySetPolicyTargetSubjectsResourcesActionsEnvironmentsRulesEsample of Policy<Policy><Target><Subject>Mario Rossi</Subject><Resource>personal id</Resource><Action>read</Action></Target></Policy>Example of request<Request></Request>
6X-CREATE Testing Framework XaCml REquests derivAtion for TEstingImplements several testing strategy:Preliminary XPT (XML Partition Testing)Incremental XPTSimple CombinatorialHierarchical SimpleHierarchical IncrementalInstantiatedRequestPoliciesspecificationRequeststructure
7Preliminary XPT Main Idea Deriving once and for all a universally valid generic test suite of conforming requests by applying:A variant of the Category Partition methodologyThe Boundary Conditions methodologyRequeststructureXACMLContextSchemaConformingtest suite
9An ExampleExample of request structure<Request><Subject> </Subject><Resource> </Resource><Action> </Action></Request>Issue: The maximum number of structurally different intermediate requests is of310 * 21 =
10118098!!!! Too Much!!! Testing objectives: New methodology for request structures generation (Incremental XPT)New stopping criterion for test requests executionNew specific test strategy satisfying the stopping criterion (Simple Combinatorial)
11Incremental XPT 36 = 729 request stuctures: one value for the <AttributeValue>zero to minOccurs and maxOccurs of the ResourceContent element and those of the contained <Any> element because not used in test values generation
12Filling request structures with values Take values from the policy under test for elements and attributes.SubjectSetResourceSetActionSetEnvironmentSetAn entity is a combination of 4 values taken from these sets (n-wise approach is used)
14Complete TableFor robustness and negative testing random values for elements and attributes are addedAttributeIdData TypeAttribute ValueSubjectSetSubjectidstringMario RossiS1s2ResourceSetResourceidpersonal idR1r2ActionSetActionidreadA1a2EnvironmentSetE1e2
15How many entities?Avoiding duplication derive all combinations of subject entities, resource entities, action entities and environment entities by applying:the pair-wise combination (PW)the three-wise combination (TW)apply the four-wise combination (FW)Note: The number of combinations is limited and strictly depends on the policy considered
16Examples <Subject>s2</Subject> Example of request <Subject>Mario Rossi</Subject><Subject>s2</Subject><Resource>p2</Resource><Action>read</Action><Enviroment>e2</Enviroment></Request>Example of request<Request><Subject>Mario Rossi</Subject><Resource>personal id</Resource><Action>read</Action></Request>Example of request<Request><Subject>s2</Subject><Resource>personal id</Resource><Action>a2</Action></Request>
17Simple CombinatorialIdea: derive as many requests as the possible combinations of the values of the subjects, resources, actions and environment of the XACML policy.The number of combinations could be also be used as a stopping criterion for the test case generation in XPT
18Incremental XPT vs. Simple Combinatorial Research questions: 1st Match TSEff: adopting the proposed stopping criterion, is the fault detection of the Simple Combinatorial strategy similar to that of the Incremental XPT one? 2nd MatchTSDecr: is it possible to reduce the test suites maintaining the same level of fault detection? 3rd MatchTSIncr: is it possible to increase the Incremental XPT fault detection?
19Rules of comparison Evaluation of the test strategies effectiveness: Define a set of XACML policiesApply mutation to each policy to introduce faultsExecute each set of test cases on the policy and its mutantsEstablish the winner according in each match
20XPT v.s. Simple Combinatorial Simple cobinatorialIncremental XPTXPT v.s. Simple Combinatorial1st Match TSEff:The same number of requests for each policythe effectiveness of the Incremental XPT is generally higher than that of the Simple Combinatorial strategyIn two cases the fault detection of the Simple Combinatorial is higher than that of Incremental XPT
21Deep AnalysisIncremental XPT is the winner when the access decision of the policy rules depends concurrently on the values of more than one subject or resource or action or environment entitySimple Combinatorial is the winner when the policies are very simple and the satisfiability of the policy rules depends on the combinations of a single subject, resource, action and environment entity
222nd Match TSDecr: from the first request ahead till we reached the maximum reachable percentage of fault detectionSimple Combinatorial is the winnerNote: For XPT usually the maximum reachable percentage is reached with almost half of the available requests =>the stopping criterion is a good upper bound
23XPT v.s. Simple Combinatorial 3rd Match TSIncr: the loss in the fault detection effectiveness due to the stopping criterionExecute the full pull of available requestspercentage of mutants killed could be increased a lotCalculate the minimum # requests for the maximum fault detection effectivenessin most of the cases the loss of fault detection effectiveness isaround 15%.
24Preliminary Conclusions and Future Works A good fault detection percentage of the Incremental XPT testing strategy due to the variability of the structures of the generated requestsIt is possible to reduce the number of requestsThe high variability of the Incremental XPT strategy can limit its performance when policies are very simpleHomework:Generalize the resultsConsider further mutation operatorsConceive new test strategy generating requests containing all the possible combinations of more than one subject, resource, action and environment entity.