Compartmentation policies for Android apps:A combinatorial optimization approach

Some smartphone platforms such as Android have a distinctive message passing system that allows for sophisticated interactions among app components, both within and across app boundaries. This gives rise to various security and privacy risks, including not only intentional collusion attacks via permission re-delegation but also inadvertent disclosure of information and service misuse through confused deputy attacks. In this paper, we revisit the perils of app coexistence in the same platform and propose a risk mitigation mechanism based on segregating apps into isolated groups following classical security compartmentation principles. Compartments can be implemented using lightweight approaches such as Inter-Component Communication (ICC) firewalling or through virtualization, effectively fencing off each group of apps. We then leverage recent works on quantified risk metrics for Android apps to couch compartmentation as a combinatorial optimization problem akin to the classical bin packing or knapsack problems. We study a number of simple yet effective numerical optimization heuristics, showing that very good compartmentation solutions can be obtained for the problem sizes expected in current’s mobile environments

Security Code Smells in Android ICC

Android Inter-Component Communication (ICC) is complex, largely unconstrained, and hard for developers to understand. As a consequence, ICC is a common source of security vulnerability in Android apps. To promote secure programming practices, we have reviewed related research, and identified avoidable ICC vulnerabilities in Android-run devices and the security code smells that indicate their presence. We explain the vulnerabilities and their corresponding smells, and we discuss how they can be eliminated or mitigated during development. We present a lightweight static analysis tool on top of Android Lint that analyzes the code under development and provides just-in-time feedback within the IDE about the presence of such smells in the code. Moreover, with the help of this tool we study the prevalence of security code smells in more than 700 open-source apps, and manually inspect around 15% of the apps to assess the extent to which identifying such smells uncovers ICC security vulnerabilities.Comment: Accepted on 28 Nov 2018, Empirical Software Engineering Journal (EMSE), 201

The Android Platform Security Model

Android is the most widely deployed end-user focused operating system. With its growing set of use cases encompassing communication, navigation, media consumption, entertainment, finance, health, and access to sensors, actuators, cameras, or microphones, its underlying security model needs to address a host of practical threats in a wide variety of scenarios while being useful to non-security experts. The model needs to strike a difficult balance between security, privacy, and usability for end users, assurances for app developers, and system performance under tight hardware constraints. While many of the underlying design principles have implicitly informed the overall system architecture, access control mechanisms, and mitigation techniques, the Android security model has previously not been formally published. This paper aims to both document the abstract model and discuss its implications. Based on a definition of the threat model and Android ecosystem context in which it operates, we analyze how the different security measures in past and current Android implementations work together to mitigate these threats. There are some special cases in applying the security model, and we discuss such deliberate deviations from the abstract model