DocFlow: Extracting Taint Specifications from Software Documentation

Security practitioners routinely use static analysis to detect security problems and privacy violations in Android apps. The soundness of these analyses depends on how the platform is modelled and the list of sensitive methods. Collecting these methods often becomes impractical given the number of methods available, the pace at which the Android platform is updated, and the proprietary libraries Google releases on each new version. Despite the constant evolution of the Android platform, app developers cope with all these new features thanks to the documentation that comes with each new Android release. In this work, we take advantage of the rich documentation provided by platforms like Android and propose DocFlow, a framework to generate taint specifications for a platform, directly from its documentation. DocFlow models the semantics of API methods using their documentation to detect sensitive methods (sources and sinks) and assigns them semantic labels. Our approach does not require access to source code, enabling the analysis of proprietary libraries for which the code is unavailable. We evaluate DocFlow using Android platform packages and closed-source Google Play Services libraries. Our results show that our framework detects sensitive methods with high precision, adapts to new API versions, and can be easily extended to detect other method types. Our approach provides evidence that Android documentation encodes rich semantic information to categorise sensitive methods, removing the need to analyse source code or perform feature extraction.