Modern websites are powered by JavaScript, a flexible dynamic scripting language that executes in client browsers. A common paradigm in such websites is to include third-party JavaScript code in the form of libraries or advertisements. If this code were malicious, it could read sensitive information from the page or write to the location bar, thus redirecting the user to a malicious page, from which the entire machine could be compromised. We present an information-flow based approach for inferring the effects that a piece of JavaScript has on the website in order to ensure that key security properties are not violated. To handle dynamically loaded and generated JavaScript, we propose a framework for staging information flow properties. Our framework propagates information flow through the currently known code in order to compute a minimal set of syntactic residual checks that are performed on the remaining code when it is dynamically loaded. We have implemented a prototype framework for staging information flow. We describe our techniques for handling some difficult features of JavaScript and evaluate our system's performance on a variety of large realworld websites. Our experiments show that static information flow is feasible and efficient for JavaScript, and that our technique allows the enforcement of information-flow policies with almost no run-time overhead.

We present Dependent JavaScript (DJS), a statically typed dialect of the imperative, object-oriented, dynamic language. DJS supports the particularly challenging features such as run-time type-tests, higher-order functions, extensible objects, prototype inheritance, and arrays through a combination of nested refinement types, strong updates to the heap, and heap unrolling to precisely track prototype hierarchies. With our implementation of DJS, we demonstrate that the type system is expressive enough to reason about a variety of tricky idioms found in small examples drawn from several sources, including the popular book JavaScript: The Good Parts and the SunSpider benchmark suite.

Abstract. Proving software free of security bugs is hard. Languages that ensure that programs correctly enforce their security policies would help, but, to date, no security-typed language has the ability to verify the enforcement of the kinds of policies used in practice-dynamic, stateful policies which address a range of concerns including forms of access control and information flow tracking. This paper presents FINE, a new source-level security-typed language that, through the use of a simple module system and dependent, refinement, and affine types, checks the enforcement of dynamic security policies applied to real software. FINE is proven sound. A prototype implementation of the compiler and several example programs are available from http://research.microsoft.com/fine.

Direct manipulation interfaces provide intuitive and interactive features to a broad range of users, but they often exhibit two limitations: the built-in features cannot possibly cover all use cases, and the internal representation of the content is not readily exposed. We believe that if direct manipulation interfaces were to (a) use general-purpose programs as the representation format, and (b) expose those programs to the user, then experts could customize these systems in powerful new ways and non-experts could enjoy some of the benefits of programmable systems.In recent work, we presented a prototype SVG editor called SKETCH-N-SKETCH that offered a step towards this vision. In that system, the user wrote a program in a general-purpose lambda-calculus to generate a graphic design and could then directly manipulate the output to indirectly change design parameters (i.e. constant literals) in the program in real-time during the manipulation. Unfortunately, the burden of programming the desired relationships rested entirely on the user.In this paper, we design and implement new features for SKETCH-N-SKETCH that assist in the programming process itself. Like typical direct manipulation systems, our extended SKETCH-N-SKETCH now provides GUI-based tools for drawing shapes, relating shapes to each other, and grouping shapes together. Unlike typical systems, however, each tool carries out the user's intention by transforming their general-purpose program. This novel, semi-automated programming workflow allows the user to rapidly create highlevel, reusable abstractions in the program while at the same time retaining direct manipulation capabilities. In future work, our approach may be extended with more graphic design features or realized for other application domains.

Modern websites are powered by JavaScript, a flexible dynamic scripting language that executes in client browsers. A common paradigm in such websites is to include third-party JavaScript code in the form of libraries or advertisements. If this code were malicious, it could read sensitive information from the page or write to the location bar, thus redirecting the user to a malicious page, from which the entire machine could be compromised. We present an information-flow based approach for inferring the effects that a piece of JavaScript has on the website in order to ensure that key security properties are not violated. To handle dynamically loaded and generated JavaScript, we propose a framework for staging information flow properties. Our framework propagates information flow through the currently known code in order to compute a minimal set of syntactic residual checks that are performed on the remaining code when it is dynamically loaded. We have implemented a prototype framework for staging information flow. We describe our techniques for handling some difficult features of JavaScript and evaluate our system's performance on a variety of large realworld websites. Our experiments show that static information flow is feasible and efficient for JavaScript, and that our technique allows the enforcement of information-flow policies with almost no run-time overhead.