Policy Conflict Analysis Using Free Variable Tableaux for Access Control in Web Services Environments

Web Services technologies are now an active research area. By integrating individual existing web systems the technology enables the provision of advanced and sophisticated services, such as allowing users to use different types of resources and services simultaneously in a simple procedure. However the management and maintenance of a large number of Web Services is not easy and, in particular, needs appropriate authorization policies to be defined so as to realize reliable and secure Web Services. The required authorization policies can be quite complex, resulting in unintended conflicts, which could result in information leaks or prevent access to information needed. This paper proposes an approach using free variable tableaux for detecting conflicts resulting from the combination of various kinds of authorization and constraint policies used in Web Services environments. The method not only enables static detection of policy conflicts such as modality and static constraint conflicts but also yields information that is helpful for correcting the policies.