Static Detection of Unsafe Component Loadings

Dynamic loading of software components is a commonly used mechanism to achieve better flexibility and modularity in software. For an application’s runtime safety, it is important for the application to load only its intended components. However, programming mistakes may lead to failures to load a component, or even worse, to load a malicious component. Recent work has shown that these errors are both prevalent and severe, sometimes leading to remote code execution attacks. The work is based on dynamic analysis by monitoring and analyzing runtime component loadings. Although simple and effective in detecting real errors, it suffers from limited code coverage and may miss important vulnerabilities. Thus, it is desirable to develop effective techniques to detect all possible unsafe component loadings. This paper presents the first static binary analysis aiming at detecting all possible loading-related errors. The key challenge is how to scalably and precisely compute what components may be loaded at relevant program locations. Our main insight is that this information is often determined locally from the component loading call sites. This motivates us to design a demand-driven analysis, working backward starting from the relevant call sites. In particular, for a given call site c, we first compute its context-sensitive executable slices, one for each execution context. Then we emulate the slices to obtain the set of components possibly loaded at c. This novel combination of slicing and emulation achieves good scalability and precision by avoiding expensive symbolic analysis. We implemented our technique and evaluated its effectiveness against the existing dynamic technique on nine popular Windows applications. Results show that our tool has better coverage and is precise—it is able to detect many more unsafe loadings. It is also scalable and able to analyze all nine applications within minutes.