Information flow analysis for a dynamically typed language with staged metaprogramming

Web applications written in JavaScript are regularly used for dealing with sensitive or personal data. Consequently, reasoning about their security properties has become an important problem, which is made very difficult by the highly dynamic nature of the language, particularly its support for runtime code generation via eval. In order to deal with this, we propose to investigate security analyses for languages with more principled forms of dynamic code generation. To this end, we present a static information flow analysis for a dynamically typed functional language with prototype-based inheritance and staged metaprogramming. We prove its soundness, implement it and test it on various examples designed to show its relevance to proving security properties, such as noninterference, in JavaScript. To demonstrate the applicability of the analysis, we also present a general method for transforming a program using eval into one using staged metaprogramming. To our knowledge, this is the first fully static information flow analysis for a language with staged metaprogramming, and the first formal soundness proof of a CFA-based information flow analysis for a functional programming language

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

The Transitivity of Trust Problem in the Interaction of Android Applications

Mobile phones have developed into complex platforms with large numbers of installed applications and a wide range of sensitive data. Application security policies limit the permissions of each installed application. As applications may interact, restricting single applications may create a false sense of security for the end users while data may still leave the mobile phone through other applications. Instead, the information flow needs to be policed for the composite system of applications in a transparent and usable manner. In this paper, we propose to employ static analysis based on the software architecture and focused data flow analysis to scalably detect information flows between components. Specifically, we aim to reveal transitivity of trust problems in multi-component mobile platforms. We demonstrate the feasibility of our approach with Android applications, although the generalization of the analysis to similar composition-based architectures, such as Service-oriented Architecture, can also be explored in the future

SafeWeb: A Middleware for Securing Ruby-Based Web Applications

Web applications in many domains such as healthcare and finance must process sensitive data, while complying with legal policies regarding the release of different classes of data to different parties. Currently, software bugs may lead to irreversible disclosure of confidential data in multi-tier web applications. An open challenge is how developers can guarantee these web applications only ever release sensitive data to authorised users without costly, recurring security audits. Our solution is to provide a trusted middleware that acts as a “safety net” to event-based enterprise web applications by preventing harmful data disclosure before it happens. We describe the design and implementation of SafeWeb, a Ruby-based middleware that associates data with security labels and transparently tracks their propagation at different granularities across a multi-tier web architecture with storage and complex event processing. For efficiency, maintainability and ease-of-use, SafeWeb exploits the dynamic features of the Ruby programming language to achieve label propagation and data flow enforcement. We evaluate SafeWeb by reporting our experience of implementing a web-based cancer treatment application and deploying it as part of the UK National Health Service (NHS)

CamFlow: Managed Data-sharing for Cloud Services

A model of cloud services is emerging whereby a few trusted providers manage the underlying hardware and communications whereas many companies build on this infrastructure to offer higher level, cloud-hosted PaaS services and/or SaaS applications. From the start, strong isolation between cloud tenants was seen to be of paramount importance, provided first by virtual machines (VM) and later by containers, which share the operating system (OS) kernel. Increasingly it is the case that applications also require facilities to effect isolation and protection of data managed by those applications. They also require flexible data sharing with other applications, often across the traditional cloud-isolation boundaries; for example, when government provides many related services for its citizens on a common platform. Similar considerations apply to the end-users of applications. But in particular, the incorporation of cloud services within `Internet of Things' architectures is driving the requirements for both protection and cross-application data sharing. These concerns relate to the management of data. Traditional access control is application and principal/role specific, applied at policy enforcement points, after which there is no subsequent control over where data flows; a crucial issue once data has left its owner's control by cloud-hosted applications and within cloud-services. Information Flow Control (IFC), in addition, offers system-wide, end-to-end, flow control based on the properties of the data. We discuss the potential of cloud-deployed IFC for enforcing owners' dataflow policy with regard to protection and sharing, as well as safeguarding against malicious or buggy software. In addition, the audit log associated with IFC provides transparency, giving configurable system-wide visibility over data flows. [...]Comment: 14 pages, 8 figure