Massimiliano Masi

Formalisation and implementation of the XACML access control mechanism

We propose a formal account of XACML, an OASIS standard adhering to the Policy Based Access Control model for the specification and enforcement of access control policies. To clarify all ambiguous and intricate aspects of XACML, we provide it with a more manageable alternative syntax and with a solid semantic ground. This lays the basis for developing tools and methodologies which allow software engineers to easily and precisely regulate access to resources using policies. To demonstrate feasibility and effectiveness of our approach, we provide a software tool, supporting the specification and evaluation of policies and access requests, whose implementation fully relies on our formal development.

On Secure Implementation of an IHE XUA-Based Protocol for Authenticating Healthcare Professionals

The importance of the Electronic Health Record (EHR) has been addressed in recent years by governments and institutions.Many large scale projects have been funded with the aim to allow healthcare professionals to consult patients data. Properties such as confidentiality, authentication and authorization are the key for the success for these projects. The Integrating the Healthcare Enterprise (IHE) initiative promotes the coordinated use of established standards for authenticated and secure EHR exchanges among clinics and hospitals. In particular, the IHE integration profile named XUA permits to attest user identities by relying on SAML assertions, i.e. XML documents containing authentication statements. In this paper, we provide a formal model for the secure issuance of such an assertion. We first specify the scenario using the process calculus COWS and then analyse it using the model checker CMC. Our analysis reveals a potential flaw in the XUA profile when using a SAML assertion in an unprotected network. We then suggest a solution for this flaw, and model check and implement this solution to show that it is secure and feasible.

A Rigorous Framework for Specification, Analysis and Enforcement of Access Control Policies

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.

On a Formal and User-friendly Linguistic Approach to Access Control of Electronic Health Data

The importance of the exchange of Electronic Health Records (EHRs) between hospitals has been recognized by governments and institutions. Due to the sensitivity of data exchanged, only mature standards and implementations can be chosen to operate. This exchange process is of course under the control of the patient, who decides who has the rights to access her personal healthcare data and who has not, by giving her personal privacy consent. Patients’ privacy consent is regulated by local legislations, which can vary frequently from region to region. The technology implementing such privacy aspects must be highly adaptable, often resulting in complex security scenarios that cannot be easily managed by patients and software designers. To overcome such security problems, we advocate the use of a linguistic approach that relies on languages for expressing policies with solid mathematical foundations. Our approach bases on FACPL, a policy language we have intentionally designed by taking inspiration from OASIS XACML, the de-facto standard used in all projects covering secure EHRs transmission protected by patients’ privacy consent. FACPL can express policies similar to those expressible by XACML but, differently from XACML, it has an intuitive syntax, a formal semantics and easy to use software tools supporting policy development and enforcement. In this paper, we present the potentialities of our approach and outline ongoing work.

Security Analysis of Standards-Driven Communication Protocols for Healthcare Scenarios

The importance of the Electronic Health Record (EHR), that stores all healthcare-related data belonging to a patient, has been recognised in recent years by governments, institutions and industry. Initiatives like the Integrating the Healthcare Enterprise (IHE) have been developed for the definition of standard methodologies for secure and interoperable EHR exchanges among clinics and hospitals. Using the requisites specified by these initiatives, many large scale projects have been set up for enabling healthcare professionals to handle patients’ EHRs. The success of applications developed in these contexts crucially depends on ensuring such security properties as confidentiality, authentication, and authorization. In this paper, we first propose a communication protocol, based on the IHE specifications, for authenticating healthcare professionals and assuring patients’ safety. By means of a formal analysis carried out by using the specification language COWS and the model checker CMC, we reveal a security flaw in the protocol thus demonstrating that to simply adopt the international standards does not guarantee the absence of such type of flaws. We then propose how to emend the IHE specifications and modify the protocol accordingly. Finally, we show how to tailor our protocol for application to more critical scenarios with no assumptions on the communication channels. To demonstrate feasibility and effectiveness of our protocols we have fully implemented them.

On the Usage of SAML Delegate Assertions in an Healthcare Scenario with Federated Communities

The importance of the Electronic Health Record (EHR) has been addressed in recent years by governments and institutions. Many large scale projects have been funded with the aim to allow healthcare professionals to consult patients data in different organizations. Concepts like interoperability, security and confidentiality are the key for the success for these projects. The Integrating the Healthcare Enterprise (IHE) initiative promotes the coordinated use of established standards for authenticated and secure EHR exchange amongst clinics and hospitals or even regions. For these scenarios, the problem of having authenticated transactions is crucial, in order to provide a form of authorization while accessing patient healthcare information. The IHE initiative addresses the problem by mean of SAML assertions, i.e. XML documents containing authentication statements. In this paper, we focus on the problem of propagating the authentication information of healthcare professionals amongst hospitals or regions (in the IHE jargon, communities) by relying on the delegation mechanism introduced by SAML.

Developing and Enforcing Policies for Access Control, Resource Usage, and Adaptation - A Practical Approach

Policy-based software architectures are nowadays widely exploited to regulate different aspects of systems’ behavior, such as access control, resource usage, and adaptation. Several languages and technologies have been proposed as, e.g., the standard XACML. However, developing real-world systems using such approaches is still a tricky task, being them complex and error-prone. To overcome such difficulties, we advocate the use of FACPL, a formal policy language inspired to but simpler than XACML. FACPL has an intuitive syntax, a mathematical semantics and easy-to-use software tools supporting policy development and enforcement. We illustrate potentialities and effectiveness of our approach through a case study from the Cloud computing domain.

e-Health for Rural Areas in Developing Countries: Lessons from the Sebokeng Experience

We report the experience gained in an e-Health project in the Gauteng province, in South Africa. A Proof-of-Concept of the project has been already installed in 3 clinics in the Sebokeng township. The project is now going to be applied to 300 clinics in the whole province. This extension of the Proof-of-Concept can however give rise to security flaws because of the inclusion of rural areas with unreliable Internet connection. We address this problem and propose a safe solution.