We propose a novel technique for statically verifying the strings generated by a program. The verification is conducted by encoding the program in Monadic Second-order Logic (M2L). We use M2L to describe constraints among program variables and to abstract built-in string operations. Once we encode a program in M2L, a theorem prover for M2L, such as MONA, can automatically check if a string generated by the program satisfies a given specification, and if not, exhibit a counterexample. With this approach, we can naturally encode relationships among strings, accounting also for cases in which a program manipulates strings using indices. In addition, our string analysis is path sensitive in that it accounts for the effects of string and Boolean comparisons, as well as regular-expression matches.We have implemented our string analysis algorithm, and used it to augment an industrial security analysis for Web applications by automatically detecting and verifying sanitizers-methods that eliminate malicious patterns from untrusted strings, making these strings safe to use in security-sensitive operations. On the 8 benchmarks we analyzed, our string analyzer discovered 128 previously unknown sanitizers, compared to 71 sanitizers detected by a previously presented string analysis. ACM Reference Format:Tateishi, T., Pistoia, M., and Tripp, O. 2013. Path-and index-sensitive string analysis based on monadic second-order logic.

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In modern software systems, programs are obtained by dynamically assembling components. This has made it necessary to subject component providers to access-control restrictions. What permissions should be granted to each component? Too few permissions may cause run-time authorization failures, too many constitute a security hole. We have designed and implemented a composite algorithm for precise static permission analysis for Java and the CLR. Unlike previous work, the analysis is modular and fully integrated with a novel slicing-based string analysis that is used to statically compute the string values defining a permission and disambiguate permission propagation paths. The results of our research prototype on production-level Java code support the effectiveness, practicality, and precision of our techniques, and show outstanding improvement over previous work.

SUMMARYThe emergence of Web 2.0 technologies such as Ajax and Mashup has revealed the weakness of the same-origin policy [1], the current de facto standard for the Web browser security model. We propose a new browser security model to allow fine-grained access control in the clientside Web applications for secure mashup and user-generated contents. We propose a browser security model that is based on information-flow-based access control (IBAC) to overcome the dynamic nature of the client-side Web applications and to accurately determine the privilege of scripts in the event-driven programming model.

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