Deserialization Gadget Chains are not a Pathological Problem in Android:an In-Depth Study of Java Gadget Chains in AOSP

Abstract: Inter-app communication is a mandatory and security-critical functionality of operating systems, such as Android. On the application level, Android implements this facility through Intents, which can also transfer non-primitive objects using Java's Serializable API. However, the Serializable API has a long history of deserialization vulnerabilities, specifically deserialization gadget chains. Research endeavors have been heavily directed towards the detection of deserialization gadget chains on the Java platform. Yet, there is little knowledge about the existence of gadget chains within the Android platform. We aim to close this gap by searching gadget chains in the Android SDK, Android's official development libraries, as well as frequently used third-party libraries. To handle this large dataset, we design a gadget chain detection tool optimized for soundness and efficiency. In a benchmark on the full Ysoserial dataset, it achieves similarly sound results to the state-of-the-art in significantly less time. Using our tool, we first show that the Android SDK contains almost the same trampoline gadgets as the Java Class Library. We also find that one can trigger Java native serialization through Android's Parcel API. Yet, running our tool on the Android SDK and 1,200 Android dependencies, in combination with a comprehensive sink dataset, yields no security-critical gadget chains. This result opposes the general notion of Java deserialization gadget chains being a widespread problem. Instead, the issue appears to be more nuanced, and we provide a perspective on where to direct further research.