Hybrid User-level Sandboxing of Third-party Android Apps.

ABSTRACTUsers of Android phones increasingly entrust personal information to third-party apps. However, recent studies reveal that many apps, even benign ones, could leak sensitive information without user awareness or consent. Previous solutions either require to modify the Android framework thus significantly impairing their practical deployment, or could be easily defeated by malicious apps using a native library. In this paper, we propose AppCage, a system that thoroughly confines the run-time behavior of third-party Android apps without requiring framework modifications or root privilege. AppCage leverages two complimentary user-level sandboxes to interpose and regulate an app's access to sensitive APIs. Specifically, dex sandbox hooks into the app's Dalvik virtual machine instance and redirects each sensitive framework API to a proxy which strictly enforces the user-defined policies, and native sandbox leverages software fault isolation to prevent the app's native libraries from directly accessing the protected APIs or subverting the dex sandbox. We have implemented a prototype of AppCage. Our evaluation shows that AppCage can successfully detect and block attempts to leak private information by third-party apps, and the performance overhead caused by AppCage is negligible for apps without native libraries and minor for apps with them.