Access and information flow control to secure mobile web service compositions in resource constrained environments

The growing use of mobile web services such as electronic health records systems and applications like twitter, Facebook has increased interest in robust mechanisms for ensuring security for such information sharing services. Common security mechanisms such as access control and information flow control are either restrictive or weak in that they prevent applications from sharing data usefully, and/or allow private information leaks when used independently. Typically, when services are composed there is a resource that some or all of the services involved in the composition need to share. However, during service composition security problems arise because the resulting service is made up of different services from different security domains. A key issue that arises and that we address in this thesis is that of enforcing secure information flow control during service composition to prevent illegal access and propagation of information between the participating services. This thesis describes a model that combines access control and information flow control in one framework. We specifically consider a case study of an e-health service application, and consider how constraints like location and context dependencies impact on authentication and authorization. Furthermore, we consider how data sharing applications such as the e-health service application handle issues of unauthorized users and insecure propagation of information in resource constrained environments¹. Our framework addresses this issue of illegitimate information access and propagation by making use of the concept of program dependence graphs (PDGs). Program dependence graphs use path conditions as necessary conditions for secure information flow control. The advantage of this approach to securing information sharing is that, information is only propagated if the criteria for data sharing are verified. Our solution proposes or offers good performance, fast authentication taking into account bandwidth limitations. A security analysis shows the theoretical improvements our scheme offers. Results obtained confirm that the framework accommodates the CIA-triad (which is the confidentiality, integrity and availability model designed to guide policies of information security) of our work and can be used to motivate further research work in this field

An investigation of interoperability issues between authorisation systems within web services

The existing authorisation systems within the context of Web Services mainly apply two access control approaches – Role-Based Access Control (RBAC) and Attribute-Based Access Control (ABAC). The RBAC approach links an authenticated Web Service Requester to its specific access control permission through roles, but RBAC is not flexible enough to cater for some cases where extra attribute information is needed in addition to the identity. By contrast, the ABAC approach has more flexibility, as it allows a Web Service Requester to submit necessary credentials containing extra attribute information that can fulfil the policies declared by a Web Service Provider, which aims to protect the sensitive resources/services.RBAC and ABAC can only help to establish a unilateral trust relationship between two Web Services to enable a Web Service Provider to make an access control decision. Unfortunately, the nature of Web Services presents a high probability that two Web Services may not know each other. Therefore, successful authorisation may fail, if the Web Service Requester does not trust the Web Service Provider.Trust Negotiation (TN) is also an access control approach, which can provide a bilateral trust relationship between two unknown entities, so it sometimes can enable authorisation success in situations where success is not possible through RBAC or ABAC approaches. However, interoperability issues will arise between authorisation systems within Web Services, where a bilateral trust-based authorisation solution is applied. In addition, a lack of a unified approach that can address the interoperability issues remains as a research problem. This research aims to explore possible factors causing the lack of interoperability first, and then to explore an approach that can address the interoperability issues. The main contributions of this research are an improved interoperability model illustrating interoperability issues at different layers of abstraction, and a novel interoperability-solution design along with an improved TN protocol as an example of utilising this design to provide interoperability between authorisation systems within Web Services

DACA: arquitetura para implementação de mecanismos dinâmicos de controlo de acesso em camadas de negócio

Doutoramento em Ciências da ComputaçãoAccess control is a software engineering challenge in database applications. Currently, there is no satisfactory solution to dynamically implement evolving fine-grained access control mechanisms (FGACM) on business tiers of relational database applications. To tackle this access control gap, we propose an architecture, herein referred to as Dynamic Access Control Architecture (DACA). DACA allows FGACM to be dynamically built and updated at runtime in accordance with the established fine-grained access control policies (FGACP). DACA explores and makes use of Call Level Interfaces (CLI) features to implement FGACM on business tiers. Among the features, we emphasize their performance and their multiple access modes to data residing on relational databases. The different access modes of CLI are wrapped by typed objects driven by FGACM, which are built and updated at runtime. Programmers prescind of traditional access modes of CLI and start using the ones dynamically implemented and updated. DACA comprises three main components: Policy Server (repository of metadata for FGACM), Dynamic Access Control Component (DACC) (business tier component responsible for implementing FGACM) and Policy Manager (broker between DACC and Policy Server). Unlike current approaches, DACA is not dependent on any particular access control model or on any access control policy, this way promoting its applicability to a wide range of different situations. In order to validate DACA, a solution based on Java, Java Database Connectivity (JDBC) and SQL Server was devised and implemented. Two evaluations were carried out. The first one evaluates DACA capability to implement and update FGACM dynamically, at runtime, and, the second one assesses DACA performance against a standard use of JDBC without any FGACM. The collected results show that DACA is an effective approach for implementing evolving FGACM on business tiers based on Call Level Interfaces, in this case JDBC.Controlo de acesso é um desafio para a engenharia de software nas aplicações de bases de dados. Atualmente, não há uma solução satisfatória para a implementação dinâmica de mecanismos finos e evolutivos de controlo de acesso (FGACM) ao nível das camadas de negócio de aplicações de bases de dados relacionais. Para solucionar esta lacuna, propomos uma arquitetura, aqui referida como Arquitetura Dinâmica de Controlo de Acesso (DACA). DACA permite que FGACM sejam dinamicamente construídos e atualizados em tempo de execução de acordo com as políticas finas de controlo de acesso (FGACP) estabelecidas. DACA explora e utiliza as características das Call Level Interfaces (CLI) para implementar FGACM ao nível das camadas de negócio. De entre as características das CLI, destacamos o seu desempenho e os diversos modos para acesso a dados armazenados em bases de dados relacionais. Na DACA, os diversos modos de acesso das CLI são envolvidos por objetos tipados derivados de FGACM, que são construídos e atualizados em tempo de execução. Os programadores prescindem dos modos tradicionais de acesso das CLI e passam a utilizar os dinamicamente construídos e atualizados. DACA compreende três componentes principais: Policy Server (repositório de meta-data dos FGACM), Dynamic Access Control Component (componente da camada de negócio que é responsável pela implementação dos FGACM) e Policy Manager (broker entre DACC e Policy Server). Ao contrário das soluções atuais, DACA não é dependente de qualquer modelo de controlo de acesso ou de qualquer política de controlo de acesso, promovendo assim a sua aplicabilidade a muitas e diversificadas situações. Com o intuito de validar DACA, foi concebida e desenvolvida uma solução baseada em Java, Java Database Connectivity (JDBC) e SQL Server. Foram efetuadas duas avaliações. A primeira avalia DACA quanto à sua capacidade para dinamicamente, em tempo de execução, implementar e atualizar FGACM e, a segunda, avalia o desempenho de DACA contra uma solução sem FGACM que utiliza o JDBC normalizado. Os resultados recolhidos mostram que DACA é uma solução válida para implementar FGACM evolutivos em camadas de negócio baseadas em CLI

ACConv -- An Access Control Model for Conversational Web Services

With organizations increasingly depending on Web services to build complex applications, security and privacy concerns including the protection of access control policies are becoming a serious issue. Ideally, service providers would like to make sure that clients have knowledge of only portions of the access control policy relevant to their interactions to the extent to which they are entrusted by the Web service and without restricting the client’s choices in terms of which operations to execute. We propose ACConv, a novel model for access control in Web services that is suitable when interactions between the client and the Web service are conversational and long-running. The conversation-based access control model proposed in this article allows service providers to limit how much knowledge clients have about the credentials specified in their access policies. This is achieved while reducing the number of times credentials are asked from clients and minimizing the risk that clients drop out of a conversation with the Web service before reaching a final state due to the lack of necessary credentials. Clients are requested to provide credentials, and hence are entrusted with part of the Web service access control policies, only for some specific granted conversations which are decided based on: (1) a level of trust that the Web service provider has vis-à-vis the client, (2) the operation that the client is about to invoke, and (3) meaningful conversations which represent conversations that lead to a final state from the current one. We have implemented the proposed approach in a software prototype and conducted extensive experiments to show its effectiveness