Hybrid security analysis of web JavaScript code via dynamic partial evaluation

Abstract

This paper addresses the problem of detecting JavaScript security vulnerabilities in the client side of Web applications. Such vulnerabilities are becoming a source of growing concern due to the rapid migration of server-side business logic to the client side, combined with new JavaScript-backed Web technologies, such as AJAX and HTML5. Detection of client-side vulnerabilities is challenging given the dynamic and event-driven nature of JavaScript. We present a hybrid form of JavaScript analysis, which augments static analysis with (semi-)concrete information by applying partial evaluation to JavaScript functions according to dynamic data recorded by the Web crawler. The dynamic component rewrites the program per the enclosing HTML environment, and the static component then explores all possible behaviors of the partially evaluated program (while treating user-controlled aspects of the environment conservatively).