On Properties of Policy-Based Specifications

The advent of large-scale, complex computing systems has dramatically increased the difficulties of securing accesses to systems' resources. To ensure confidentiality and integrity, the exploitation of access control mechanisms has thus become a crucial issue in the design of modern computing systems. Among the different access control approaches proposed in the last decades, the policy-based one permits to capture, by resorting to the concept of attribute, all systems' security-relevant information and to be, at the same time, sufficiently flexible and expressive to represent the other approaches. In this paper, we move a step further to understand the effectiveness of policy-based specifications by studying how they permit to enforce traditional security properties. To support system designers in developing and maintaining policy-based specifications, we formalise also some relevant properties regarding the structure of policies. By means of a case study from the banking domain, we present real instances of such properties and outline an approach towards their automatised verification.Comment: In Proceedings WWV 2015, arXiv:1508.0338

The Conflict Notion and its Static Detection: a Formal Survey

The notion of policy is widely used to enable a flexible control of many systems: access control, privacy, accountability, data base, service, contract , network configuration, and so on. One important feature is to be able to check these policies against contradictions before the enforcement step. This is the problem of the conflict detection which can be done at different steps and with different approaches. This paper presents a review of the principles for conflict detection in related security policy languages. The policy languages, the notions of conflict and the means to detect conflicts are various, hence it is difficult to compare the different principles. We propose an analysis and a comparison of the five static detection principles we found in reviewing more than forty papers of the literature. To make the comparison easier we develop a logical model with four syntactic types of systems covering most of the literature examples. We provide a semantic classification of the conflict notions and thus, we are able to relate the detection principles, the syntactic types and the semantic classification. Our comparison shows the exact link between logical consistency and the conflict notions, and that some detection principles are subject to weaknesses if not used with the right conditions

A Formal Approach to Specification, Analysis and Implementation of Policy-Based Systems

The design of modern computing systems largely exploits structured sets of declarative rules called policies. Their principled use permits controlling a wide variety of system aspects and achieving separation of concerns between the managing and functional parts of systems. These so-called policy-based systems are utilised within different application domains, from network management and autonomic computing to access control and emergency handling. The various policy-based proposals from the literature lack however a comprehensive methodology supporting the whole life-cycle of system development: specification, analysis and implementation. In this thesis we propose formally-defined tool-assisted methodologies for supporting the development of policy-based access control and autonomic computing systems. We first present FACPL, a formal language that defines a core, yet expressive syntax for the specification of attribute-based access control policies. On the base of its denotational semantics, we devise a constraint-based analysis approach that enables the automatic verification of different properties of interest on policies. We then present PSCEL, a FACPL-based formal language for the specification of autonomic computing systems. FACPL policies are employed to enforce authorisation controls and context-dependent adaptation strategies. To statically point out the effects of policies on system behaviours, we rely again on a constraint-based analysis approach and reason on progress properties of PSCEL systems. The implementation of the languages and their analyses provides us some practical software tools. The effectiveness of the proposed solutions is illustrated through real-world case studies from the e-Health and autonomic computing domains

Formal analysis of confidentiality conditions related to data leakage

The size of the financial risk, the social repercussions and the legal ramifications resulting from data leakage are of great concern. Some experts believe that poor system designs are to blame. The goal of this thesis is to use applied formal methods to verify that data leakage related confidentiality properties of system designs are satisfied. This thesis presents a practically applicable approach for using Banks's confidentiality framework, instantiated using the Circus notation. The thesis proposes a tool-chain for mechanizing the application of the framework and includes a custom tool and the Isabelle theorem prover that coordinate to verify a given system model. The practical applicability of the mechanization was evaluated by analysing a number of hand-crafted systems having literature related confidentiality requirements. Without any reliable tool for using BCF or any Circus tool that can be extended for the same purpose, it was necessary to build a custom tool. Further, a lack of literature related descriptive case studies on confidentiality in systems compelled us to use hand-written system specifications with literature related confidentiality requirements. The results of this study show that the tool-chain proposed in this thesis is practically applicable in terms of time required. Further, the efficiency of the proposed tool-chain has been shown by comparing the time taken for analysing a system both using the mechanised approach as well as the manual approach