Fine-Grained Access Control for HTML5-Based Mobile Applications in Android

HTML5-based mobile applications are becoming more and more popular because they can run on different platforms. Several newly introduced mobile OS natively support HTML5-based applications. For those that do not provide native sup-port, such as Android, iOS, and Windows Phone, developers can develop HTML5-based applications using middlewares, such as PhoneGap [17]. In these platforms, programs are loaded into a web component, called WebView, which can render HTML5 pages and execute JavaScript code. In order for the program to access the system resources, which are isolated from the content inside WebView due to its sand-box, bridges need to be built between JavaScript and the native code (e.g. Java code in Android). Unfortunately, such bridges break the existing protection that was origi-nally built into WebView. In this paper, we study the potential risks of HTML5-based applications, and investigate how the existing mobile systems ’ access control supports these applications. We fo-cus on Android and the PhoneGap middleware. However, our ideas can be applied to other platforms. Our studies indicate that Android does not provide an adequate access control for this kind of applications. We propose a fine-grained access control mechanism for the bridge in Android system. We have implemented our scheme in Android and have evaluated its effectiveness and performance. 1

Dynamic Scoping for Browser Based Access Control System

We have inorganically increased the use of web applications to the point of using them for almost everything and making them an essential part of our everyday lives. As a result, the enhancement of privacy and security policies for the web applications is becoming increasingly essential. The importance and stateless nature of the web infrastructure made the web a preferred target of attacks. The current web access control system is a reason behind the victory of attacks. The current web consists of two major components, the browser and the server, where the effective access control system needs to be implemented. In terms of an access control system, the current web has adopted the inadequate same origin policy and same session policy for the browser and server, respectively. The current web access control system policies are sufficient for the earlier day\u27s web, which became inadequate to address the protection needs of today\u27s web. In order to protect the web application from un-trusted contents, we provide an enhanced browser based access control system by enabling the dynamic scoping. Our security model for the browser will allow the client and trusted web application contents to share a common library and protect web contents from each other, while they still get executed at different trust levels. We have implemented a working model of an enhanced browser based access control system in Java, under the Lobo browser

Practical dynamic information flow control

Over the years, computer systems and applications have grown significantly complex while handling a plethora of private and sensitive user information. The complexity of these applications is often assisted by a set of (un)intentional bugs with both malicious and non-malicious intent leading to information leaks. Information flow control has been studied extensively as an approach to mitigate such information leaks. The technique works by enforcing the security property of non-interference using a specified set of security policies. A vast majority of existing work in this area is based on static analyses. However, some of the applications, especially on the Web, are developed using dynamic languages like JavaScript that make the static analyses techniques stale and ineffective. As a result, there has been a growing interest in recent years to develop dynamic information flow analysis techniques. In spite of the advances in the field, dynamic information flow analysis has not been at the helm of information flow security in dynamic settings like the Web; the prime reason being that the analysis techniques and the security property related to them (non-interference) either over-approximate or are too restrictive in most cases. Concretely, the analysis techniques gen- erate a lot of false positives, do not allow legitimate release of sensitive information, support only static and rigid security policies or are not general enough to be applied to real-world applications. This thesis focuses on improving the usability of dynamic information flow techniques by presenting mechanisms that can enhance the precision and permissiveness of the analyses. It begins by presenting a sound improvement and enhancement of the permissive-upgrade strategy, a strategy widely used to enforce dynamic information flow control, which improves the strategy’s permissiveness and makes it generic in applicability. The thesis, then, presents a sound and precise control scope analysis for handling complex features like unstructured control flow and exceptions in higher-order languages. Although non-interference is a desired property for enforcing information flow control, there are program instances that require legitimate release of some parts of the secret data to provide the required functionality. Towards this end, this thesis develops a sound approach to bound information leaks dynamically while allowing information release in accordance to a pre-specified budget. The thesis concludes by applying these techniques to an information flow control-enabled Web browser and explores a policy specification mechanism that allows flexible and useful information flow policies to be specified for Web applications.Seit Jahren werden Computersysteme und -Anwendungen immer komplexer und verarbeiten eine Unmenge private und sensible Daten. Die Komplexität der Anwendungen trägt neben der Existenz von (un)gewollt eingefügten Software Fehlern zur Weitergabe dieser sensiblen Informationen bei. Information Flow Control (IFC, zu Deutsch Informations-Fluss-Analyse) Mechanismen sind Gegenstand intensiver Forschung um diesem Problem entgegen zu wirken. Grundsätzlich basieren diese Ansätze auf der Anwendung von vordefinierten Sicherheitsregeln, die die Unbeeinflussbarkeit (engl. non-interference) garantieren. Der überwiegende Teil dieser Techniken nutzt statische Analyse zur Erzeugung der Regeln. Dem gegenüber steht die Tatsache, dass Anwendun- gen, insbesondere im Bereich Web-Anwendungen, in dynamischen Sprachen wie JavaScript entwickelt werden, wodurch rein statische Analysen unzureichend sind. Dynamische Methoden auf der anderen Seite approximieren das Verhalten einer Anwendung und können daher die grundlegende non-interference nicht garantieren. Sie tendieren dazu besonders restriktive Regeln zu erzeugen, wodurch auch der rechtmäßige Zugriff auf Information verweigert wird. Beide Ansätze sind daher nicht zur Anwendung auf Systeme in der realen Welt geeignet. Das Ziel dieser Arbeit besteht darin die Benutzbarkeit von dynamischen IFC Mechanismen zu verbessern indem Techniken entwickelt werden, die die Genauigkeit und Toleranz steigern. Die Arbeit präsentiert eine korrekte (engl. ’sound’) Erweiterung der permissive-upgrade Strategie (eine Standardstrategie für dynamische IFC), die die Toleranz der Strategie verbessert und sie weithin anwendbar macht. Darüber hinaus präsentiere ich eine neue dynamische IFC Analyse, die auch komplexe Funktionen, wie unstruktierte Kontrollflüsse und Exceptions in Hochsprachen, abbildet. Obwohl Unbeeinflussbarkeit eine wünschenswerte Eigenschaft ist, gibt es Anwendungen, die rechtmäßigen Zugang zu sensiblen Daten benötigen um ihre Funktion zu erfüllen. Um dies zu ermöglichen präsentiert diese Arbeit einen Ansatz, der die ungewollte Weitergabe von Information quantifiziert und anhand eines vordefinierten Grenzwertes freigibt. Diese Techniken wurden in einen Web-Browser integriert, welcher es erlaubt die Definition von flexiblen und nützlichen Informations-flussregeln für Web Anwendungen umzusetzen.RS3 - DF