Rethinking Permission Enforcement Mechanism on Mobile Systems

摘要

To protect sensitive resources from unauthorized use, modern mobile systems, such as Android and iOS, design a permission-based access control model. However, current model could not enforce fine-grained control over the dynamic permission use contexts, causing two severe security problems. First, any code package in an application could use the granted permissions, inducing attackers to embed malicious payloads into benign apps. Second, the permissions granted to a benign application may be utilized by an attacker through vulnerable application interactions. Although ad hoc solutions have been proposed, none could systematically solve these two issues within a unified framework. This paper presents the first such framework to provide context-sensitive permission enforcement that regulates permission use policies according to system-wide application contexts, which cover both intra-application context and inter-application context. We build a prototype system on Android, named FineDroid, to track such context during the application execution. To flexibly regulate the context-sensitive permission rules, FineDroid features a policy framework that could express generic application contexts. We demonstrate the benefits of FineDroid by instantiating several security extensions based on the policy framework, for three potential users: end users, administrators, and developers. Furthermore, FineDroid is showed to introduce a minor overhead.