AUDACIOUS: User-Driven Access Control with Unmodified Operating Systems

User-driven access control improves the coarse-grained access control of current operating systems (particularly in the mobile space) that provide only all-or-nothing access to a resource such as the camera or the current location. By granting appropriate permissions only in response to explicit user actions (for example, pressing a camera button), userdriven access control better aligns application actions with user expectations. Prior work on user-driven access control has relied in essential ways on operating system (OS) modifications to provide applications with uncompromisable access control gadgets, distinguished user interface (UI) elements that can grant access permissions. This work presents a design, implementation, and evaluation of user-driven access control that works with no OS modifications, thus making deployability and incremental adoption of the model more feasible. We develop (1) a userlevel trusted library for access control gadgets, (2) static analyses to prevent malicious creation of UI events, illegal flows of sensitive information, and circumvention of our library, and (3) dynamic analyses to ensure users are not tricked into granting permissions. In addition to providing the original user-driven access control guarantees, we use static information flow to limit where results derived from sensitive sources may flow in an application. Our implementation targets Android applications. We port open-source applications that need interesting resource permissions to use our system. We determine in what ways user-driven access control in general and our implementation in particular are good matches for real applications. We demonstrate that our system is secure against a variety of attacks that malware on Android could otherwise mount.