Precise alias analysis for static detection of web application vulnerabilities

The number and the importance of web applications have increased rapidly over the last years. At the same time, the quantity and impact of security vulnerabilities in such applications have grown as well. Since manual code reviews are time-consuming, error-prone and costly, the need for automated solutions has become evident. In this paper, we address the problem of vulnerable web applications by means of static source code analysis. To this end, we present a novel, precise alias analysis targeted at the unique reference semantics commonly found in scripting languages. Moreover, we enhance the quality and quantity of the generated vulnerability reports by employing a novel, iterative two-phase algorithm for fast and precise resolution of file inclusions.We integrated the presented concepts into Pixy~\cite{jovanovic06:pixy_short}, a high-precision static analysis tool aimed at detecting cross-site scripting vulnerabilities in PHP scripts. To demonstrate the effectiveness of our techniques, we analyzed three web applications and discovered 106 vulnerabilities. Both the high analysis speed as well as the low number of generated false positives show that our techniques can be used for conducting effective security audits.