Nutzerdefinierte Restriktion delegierter Privilegien im Grid-Computing

This thesis analyses current Grid infrastructures regarding the implemented mechanisms for the delegation of user rights. The results of this analysis are subsequently employed to design an approach for the user-based restriction of delegated rights. Finally, a prototypical implementation of the approach based on a current Grid middleware package is presented. The Grid computing approach pursues the vision of inter-institutional computing and storage infrastructures using standardized access mechanisms. In the future, Grid infrastructures are envisioned to be enhanced by interconnecting existing computing environments with scientific instruments to simplify access to experimental and observational data for postprocessing. The core of Grid infrastructures is Grid middleware, which establishes an abstraction layer between the Grid and individual resources. Grid middlewares —in addition to providing standard interfaces— implement mechanisms to monitor participating systems and provide information about them. Furthermore, load-balancing between resources as well as accounting and billing functionalities are commonly provided. Due to their distributed nature and the availability of substantial resources, Grid infrastructures are attractive attack targets. To guarantee stable and reliable operation, advanced security mechanisms are implemented to establish mandatory encryption of communication connections and mutual authentication of users and services. The utilization of indirectly accessed resources by users requires the employment of delegation mechanisms. Current Grid infrastructures base their delegation functionality on proxy certificates which enable services to act in the users’ name and with the complete scope of their rights. To protect users, the lifetime of proxy certificates is limited. Should they be compromised however, a succesful attacker may act with the complete scope of the user’s right. Current Grid infrastructures offer no mechanisms to restrict the delegated rights. As a direct consequence of these shortcomings, disciplines with high security requirements are subject to tight restrictions in using inter-institutional Grid infrastructures. This in particular affects communities in the biological and medical disciplines which are subjected to strict data privacy regulations when working with personal data. Besides this, abuse of rights can cause negative repercussions for users when significant amounts of resources are consumed as resource usage is typically accounted and the user may be invoiced for it.