Building call graphs for embedded client-side code in dynamic web applications

Abstract

When developing and maintaining a software system, programmers often rely on IDEs to provide editor services such as syntax highlighting, auto-completion, and "jump to declaration". In dynamic web applications, such tool support is currently limited to either the server-side code or to hand-written or generated client-side code. Our goal is to build a call graph for providing editor services on client-side code while it is still embedded as string literals within server-side code. First, we symbolically execute the server-side code to identify all possible client-side code variations. Subsequently, we parse the generated client-side code with all its variations into a VarDOM that compactly represents all DOM variations for further analysis. Based on the VarDOM, we build conditional call graphs for embedded HTML, CSS, and JS. Our empirical evaluation on real-world web applications show that our analysis achieves 100% precision in identifying call-graph edges. 62% of the edges cross PHP strings, and 17% of them cross files - in both situations, navigation without tool support is tedious and error prone.