Shane Bracher


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Shane Bracher

  1. 1. Enabling Security Testing from Specification to Code Shane Bracher and Padmanabhan Krishnan Fifth International Conference on Integrated Formal Methods (IFM 2005) 29 November – 2 December 2005 Eindhoven, The Netherlands
  2. 2. Problem Statement <ul><li>Formal models: </li></ul><ul><ul><li>Usually created for verifying key properties. </li></ul></ul><ul><ul><li>The more abstract, the easier to verify. </li></ul></ul><ul><ul><li>But for testing , they are too far removed from the implementation. </li></ul></ul><ul><li>Possible testing approaches: </li></ul><ul><ul><li>Exhaustive testing – all possible behaviour. </li></ul></ul><ul><ul><li>Bounded exhaustive testing – all possible behaviour to a certain depth. </li></ul></ul><ul><ul><li>Fault injection testing – reaction under faulty environments. </li></ul></ul><ul><ul><li>Model based testing – aims to reduce the testing effort. </li></ul></ul>
  3. 3. Objective <ul><li>We have a formal model of a protocol. </li></ul><ul><li>We want to use this model to derive test sequences. </li></ul><ul><li>In particular, we are interested in testing the security properties. </li></ul><ul><li>How can we use model based techniques to automatically generate test sequences for testing the security properties of protocols? </li></ul><ul><li>Test sequences generated from: </li></ul><ul><ul><li>the formal model are too abstract. (too far from the implementation) </li></ul></ul><ul><ul><li>the implementation are too concrete. (not reusable) </li></ul></ul>
  4. 4. Methodology <ul><li>Translate the “high-level” formal specification into an intermediary model: </li></ul><ul><ul><li>less abstract </li></ul></ul><ul><ul><li>closer to an implementation </li></ul></ul><ul><li>Now we can generate test sequences from the intermediary model (which was derived from the formal model). </li></ul><ul><li>For testing the security properties: </li></ul><ul><ul><li>The security goals are already stated in the high-level model. </li></ul></ul><ul><ul><li>We can specify these goals within the intermediary model as annotations . </li></ul></ul>
  5. 5. “Bridging the gap” High Level Protocol Specification Language (HLPSL) Bandera Intermediate Representation (BIR) Bogor Model Checking Framework
  6. 6. Case Study <ul><li>Internet Open Trading Protocol (IOTP) </li></ul><ul><li>Objectives of case study: </li></ul><ul><ul><li>Verify the ability to translate a high-level model into an intermediary model. </li></ul></ul><ul><ul><li>Using annotations, determine the possibility of deriving test sequences from the intermediary model. </li></ul></ul>
  7. 7. Internet Open Trading Protocol Merchant (M) Payment Processor (P) Delivery Agent (D) Offer BrandList, Offer Select, Offer Pay, Offer, Sig_M(Pay) Offer, Pay, Merchant, Sig_C(Pay) Receipt, Sig_P(Pay, Receipt, Offer) Sig_P(Pay, Receipt, Offer), Pay, Receipt, Offer Data, Sig_D(Data) Customer (C)
  8. 8. Intermediary Model <ul><li>record (|Customer|) extends (|Role|) { </li></ul><ul><li>(|Agent|) /|Customer.C| ; /* All agents */ </li></ul><ul><li>(|PublicKey|) /|Customer.Kc| ; /* All keys */ </li></ul><ul><li>(|Channel|) /|Customer.SND_CM| ; /* All channels */ </li></ul><ul><li>/* snipped */ </li></ul><ul><li>loc loc1: live { [|brandlist|] , [|offer|] , [|select|] } </li></ul><ul><li>when [|this|] . /|Customer.RCV_CM| .read do invisible { </li></ul><ul><li>[|brandlist|] := ( (|BrandList|) ) [|this|] . /|Customer.RCV_CM| . /|Channel.payload| [ 0 ]; </li></ul><ul><li>[|offer|] := ( (|Offer|) ) [|this|] . /|Customer.RCV_CM| . /|Channel.payload| [ 1 ]; </li></ul><ul><li>[|this|] . /|Customer.RCV_CM| .read := false ; </li></ul><ul><li>[|select|] := new (|Select|) ; </li></ul><ul><li>[|this|] . /|Customer.SND_CM| . /|Channel.payload| [ 0 ] := [|select|] ; </li></ul><ul><li>[|this|] . /|Customer.SND_CM| . /|Channel.payload| [ 1 ] := [|offer|] ; </li></ul><ul><li>[|this|] . /|Customer.SND_CM| .read := true ; </li></ul><ul><li>} </li></ul><ul><li>goto loc2; </li></ul>
  9. 9. Deriving Test Sequences <ul><li>Security properties tested: </li></ul><ul><ul><li>Authentication – Customer authenticates Merchant on Pay. </li></ul></ul><ul><ul><li>Secrecy – Pay is to remain secret from the Delivery Agent (hypothetical). </li></ul></ul><ul><li>Sessions: </li></ul><ul><ul><li>Authentic Customer – Authentic Merchant </li></ul></ul><ul><ul><li>Authentic Customer – Intruder acting as Merchant </li></ul></ul><ul><ul><li>Intruder acting as Customer – Authentic Merchant </li></ul></ul><ul><li>Test sequences produced as counter examples. </li></ul><ul><ul><li>But to get a counter example, we need a violation to occur. </li></ul></ul><ul><ul><li>Solution: negate the security goals. </li></ul></ul>
  10. 10. Results <ul><li>Concurrent sessions: </li></ul><ul><ul><li>480 test sequences returned. </li></ul></ul><ul><ul><li>Reason: violation found in large number of interleavings. </li></ul></ul><ul><ul><li>Too many for the Bogor Counter Example Environment to display. </li></ul></ul><ul><li>Therefore, it was necessary to identify a sufficiently simple interleaving in order for a test sequence trace to be returned. </li></ul>
  11. 11. Conclusion <ul><li>Demonstrated the practicability of using an intermediary model for automatically deriving test sequences for testing the security properties of protocols. </li></ul><ul><li>The derived test sequences are both suitable and reusable for testers to apply to a working protocol implementation. </li></ul>
  12. 12. Thank you for your attention. <ul><li>Shane Bracher [email_address] </li></ul><ul><li>Padmanabhan Krishnan [email_address] </li></ul><ul><li>Centre for Software Assurance School of Information Technology, Bond University Gold Coast, Queensland, 4229, AUSTRALIA </li></ul><ul><li> </li></ul>