Access control systems are widely used means for the protection of computing systems. They are defined in terms of access control policies regulating the access to system resources. In this paper, we introduce a formally-defined, fully-implemented framework for specification, analysis and enforcement of attribute-based access control policies. The framework rests on FACPL, a language with a compact, yet expressive, syntax for specification of real-world access control policies and with a rigorously defined denotational semantics. The framework enables the automated verification of properties regarding both the authorisations enforced by single policies and the relationships among multiple policies. Effectiveness and performance of the analysis rely on a semantic-preserving representation of FACPL policies in terms of SMT formulae and on the use of efficient SMT solvers. Our analysis approach explicitly addresses some crucial aspects of policy evaluation, such as missing attributes, erroneous values and obligations, which are instead overlooked in other proposals. The framework is supported by Java-based tools, among which an Eclipse-based IDE offering a tailored development and analysis environment for FACPL policies and a Java library for policy enforcement. We illustrate the framework and its formal ingredients by means of an e-Health case study, while its effectiveness is assessed by means of performance stress tests and experiments on a well-established benchmark.

A Cloud federation is a collaboration of organizations sharing data hosted on their private cloud infrastructures in order to exploit a common business opportunity. However, the adoption of cloud federations is hindered by member organizations' concerns on sharing their data with potentially competing organizations. For cloud federations to be viable, federated organizations' privacy concerns should be alleviated by providing mechanisms that allow organizations to control which users from other federated organizations can access which data. We propose the architecture of a novel identity and access management system part of FaaS, a cloud federation service developed by the H2020 SUNFISH project. Our system allows federated organizations to enforce attribute-based access control policies on their data in a privacy-preserving fashion. Users are granted access to federated data when their identity attributes match the policies, but without revealing their attributes in clear. The architecture relies on two novel technologies, blockchain and Intel SGX hardware platform to guarantee integrity of the policy evaluation process.

Cloud federation is a novel concept that has been drawing attention from research and industry. However, there is a lack of solid proposal that can be widely adopted in practice to guarantee adequate governance of federations, especially in the Public Sector contexts due to legal requirements. In this paper, we propose an innovative governance approach that ensures distributed and democratic control in cloud federations. Starting from FaaS, a recent cloud federation proposal, we propose a blockchain infrastructure for the federation registry that implements the proposed governance approach.

Cloud federation is an emergent cloud-computing paradigm where partner organisations share data and services hosted on their own cloud platforms. In this context, it is crucial to enforce access control policies that satisfy data protection and privacy requirements of partner organisations. However, due to the distributed nature of cloud federations, the access control system alone does not guarantee that its deployed components cannot be circumvented while processing access requests. In order to promote accountability and reliability of a distributed access control system, we present a decentralised runtime monitoring architecture based on blockchain technology.