Information flows as a permission mechanism

This paper proposes Flow Permissions, an extension to the Android permission mechanism. Unlike the existing permission mechanism, our permission mechanism contains semantic information based on information flows. Flow Permissions allow users to examine and grant per-app information flows within an application e.g., a permission for reading the phone number and sending it over the network) as well as cross-app information flows across multiple applications e.g., a permission for reading the phone number and sending it to another application already installed on the user's phone). Our goal with Flow Permissions is to provide visibility into the holistic behavior of the applications installed on a user's phone. In order to support Flow Permissions on Android, we have developed a static analysis engine that detects flows within an Android application. We have also modified Android's existing permission mechanism and installation procedure to support Flow Permissions. We evaluate our prototype with 2,992 popular applications and 1,047 malicious applications and show that our design is practical and effective in deriving Flow Permissions. We validate our cross-app flow generation and installation procedure on a Galaxy Nexus smartphone.