Practical attacks on security and privacy through a low-cost Android device

As adoption of smartphones and tablets increases, and budget device offerings become increasingly affordable, the vision of bringing universal connectivity to the developing world is becoming more and more viable. Nonetheless, it is important to consider the diverse use-cases for smartphones and tablets today, particularly where a user may only have access to a single connected device. In many regions, banking and other important services can be accessed from mobile connected devices, expanding the reach of these services. This paper highlights the practical risks of one such lowcost computing device, highlighting the ease with which a very recent (manufacturered September 2015) Android-based internet tablet, designed for the developing world, can be completely compromised by an attacker. The weaknesses identified allow an attacker to gain full root access and persistent malicious code execution capabilities. We consider the implications of these attacks, and the ease with which these attacks may be carried out, and highlight the difficulty in effectively mitigating these weaknesses as a user, even on a recently manufactured device

An Historical Analysis of the SEAndroid Policy Evolution

Android adopted SELinux's mandatory access control (MAC) mechanisms in 2013. Since then, billions of Android devices have benefited from mandatory access control security policies. These policies are expressed in a variety of rules, maintained by Google and extended by Android OEMs. Over the years, the rules have grown to be quite complex, making it challenging to properly understand or configure these policies. In this paper, we perform a measurement study on the SEAndroid repository to understand the evolution of these policies. We propose a new metric to measure the complexity of the policy by expanding policy rules, with their abstraction features such as macros and groups, into primitive "boxes", which we then use to show that the complexity of the SEAndroid policies has been growing exponentially over time. By analyzing the Git commits, snapshot by snapshot, we are also able to analyze the "age" of policy rules, the trend of changes, and the contributor composition. We also look at hallmark events in Android's history, such as the "Stagefright" vulnerability in Android's media facilities, pointing out how these events led to changes in the MAC policies. The growing complexity of Android's mandatory policies suggests that we will eventually hit the limits of our ability to understand these policies, requiring new tools and techniques.Comment: 16 pages, 11 figures, published in ACSAC '1

FINE-GRAINED ACCESS CONTROL ON ANDROID COMPONENT

The pervasiveness of Android devices in today’s interconnected world emphasizes the importance of mobile security in protecting user privacy and digital assets. Android’s current security model primarily enforces application-level mechanisms, which fail to address component-level (e.g., Activity, Service, and Content Provider) security concerns. Consequently, third-party code may exploit an application’s permissions, and security features like MDM or BYOD face limitations in their implementation. To address these concerns, we propose a novel Android component context-aware access control mechanism that enforces layered security at multiple Exception Levels (ELs), including EL0, EL1, and EL3. This approach effectively restricts component privileges and controls resource access as needed. Our solution comprises Flasa at EL0, extending SELinux policies for inter-component interactions and SQLite content control; Compac, spanning EL0 and EL1, which enforces component-level permission controls through Android runtime and kernel modifications; and TzNfc, leveraging TrustZone technologies to secure third-party services and limit system privileges via Trusted Execution Environment (TEE). Our evaluations demonstrate the effectiveness of our proposed solution in containing component privileges, controlling inter-component interactions and protecting component level resource access. This enhanced solution, complementing Android’s existing security architecture, provides a more comprehensive approach to Android security, benefiting users, developers, and the broader mobile ecosystem

Cross-vendor Security Analysis of Android Unix Domain Sockets

The Android operating system is currently the most popular mobile operating system in the world. Android is based on Linux and therefore inherits its features including its Inter-process Communication (IPC) mechanisms. These mechanisms are used by processes to communicate with one another and are extensively used in Android. Although the Android-specific IPC mechanisms have been studied extensively, Unix domain sockets have not been studied as much despite playing a crucial role in the IPC of highly privileged system daemons. In this thesis, we propose SAUSAGE, an efficient novel static analysis framework to study the security properties of these sockets. SAUSAGE considers access control policies implemented in the Android security model as well as authentication checks implemented by the daemon binaries. It is a fully static large-scale analysis framework specifically designed to analyze Unix domain socket usage in Android system daemons. We use this framework to analyze 200 Android images across eight popular smartphone vendors spanning Android versions 7-9. As a result, we uncover multiple access control misconfigurations and insecure authentication checks introduced by vendor customization. Our notable findings include a permission bypass in highly privileged Qualcomm system daemons and a vendor-specific daemon exposing an unprotected socket that allows an untrusted app to set the scheduling priority of other processes running on the system

Improving the Policy Specification for Practical Access Control Systems

Access control systems play a crucial role in protecting the security of information systems by ensuring that only authorized users are granted access to sensitive resources, and the protection is only as good as the access control policies. For enabling a security administrator to express her desired policy conveniently, it is paramount that a policy specification is expressive, comprehensible, and free of inconsistencies. In this dissertation, we study the policy specifications for three practical access control systems (i.e., obligation systems, firewalls, and Security-Enhanced Linux in Android) and improve their expressiveness, comprehensibility, and consistency. First, we improve the expressiveness of obligation policies for handling different types of obligations. We propose a language for specifying obligations as well as an architecture for handling access control policies with these obligations, by extending XACML (i.e., the de facto standard for specifying access control policies). We also implement our design into a prototype system named ExtXACML to handle various obligations. Second, we improve the comprehensibility of firewall policies enabling administrators to better understand and manage the policies. We introduce the tri-modularized design of firewall policies for elevating them from monolithic to modular. To support legacy firewall policies, we also define a five-step process and present algorithms for converting them into their modularized form. Finally, we improve the consistency of Security-Enhanced Linux in Android (SEAndroid) policies for reducing the attack surface in Android systems. We propose a systematic approach as well as a semiautomatic tool for uncovering three classes of policy misconfigurations. We also analyze SEAndroid policies from four Android versions and seven Android phone vendors, and in all of them we observe examples of potential policy misconfigurations

Towards Modular and Flexible Access Control on Smart Mobile Devices

Smart mobile devices, such as smartphones and tablets, have become an integral part of our daily personal and professional lives. These devices are connected to a wide variety of Internet services and host a vast amount of applications, which access, store and process security- and privacy-sensitive data. A rich set of sensors, ranging from microphones and cameras to location and acceleration sensors, allows these applications and their back end services to reason about user behavior. Further, enterprise administrators integrate smart mobile devices into their IT infrastructures to enable comfortable work on the go. Unsurprisingly, this abundance of available high-quality information has made smart mobile devices an interesting target for attackers, and the number of malicious and privacy-intrusive applications has steadily been rising. Detection and mitigation of such malicious behavior are in focus of mobile security research today. In particular, the Android operating system has received special attention by both academia and industry due to its popularity and open-source character. Related work has scrutinized its security architecture, analyzed attack vectors and vulnerabilities and proposed a wide variety of security extensions. While these extensions have diverse goals, many of them constitute modifications of the Android operating system and extend its default permission-based access control model. However, they are not generic and only address specific security and privacy concerns. The goal of this dissertation is to provide generic and extensible system-centric access control architectures, which can serve as a solid foundation for the instantiation of use-case specific security extensions. In doing so, we enable security researchers, enterprise administrators and end users to design, deploy and distribute security extensions without further modification of the underlying operating system. To achieve this goal, we first analyze the mobile device ecosystem and discuss how Android's security architecture aims to address its inherent threats. We proceed to survey related work on Android security, focusing on system-centric security extensions, and derive a set of generic requirements for extensible access control architectures targeting smart mobile devices. We then present two extensible access control architectures, which address these requirements by providing policy-based and programmable interfaces for the instantiation of use-case specific security solutions. By implementing a set of practical use-cases, ranging from context-aware access control, dynamic application behavior analysis to isolation of security domains we demonstrate the advantages of system-centric access control architectures over application-layer approaches. Finally, we conclude this dissertation by discussing an alternative approach, which is based on application-layer deputies and can be deployed whenever practical limitations prohibit the deployment of system-centric solutions