Bilingual Problems: Studying the Security Risks Incurred by Native Extensions in Scripting Languages
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Scripting languages are continuously gaining popularity due to their ease of use and the flourishing software ecosystems that surround them. These languages offer crash and memory safety by design, hence developers do not need to understand and prevent most low-level security issues plaguing languages like C. However, scripting languages often allow native extensions, which are a way for custom C/C++ code to be invoked directly from the high-level language. While this feature promises several benefits such as increased performance or the reuse of legacy code, it can also break the guarantees provided by the language, e.g., crash-safety. In this work, we first provide a comparative analysis of the security risks of the existing native extension API in three popular scripting languages. Additionally, we discuss a novel methodology for studying vulnerabilities caused by misuse of the native extension API. We then perform an in-depth study of npm, an ecosystem which appears to be the most exposed to threats introduced by native extensions. We show that vulnerabilities in extensions can be exploited in their embedding library by producing a hard crash in 30 npm packages, simply by invoking their API. Moreover, we identify five open-source web applications in which such exploits can be deployed remotely. Finally, we provide a set of recommendations for language designers, users and for the research community.
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