Master of Science

thesisCloud infrastructures have massively increased access to latent compute resources al- lowing for computations that were previously out of reach to be performed efficiently and cheaply. Due to the multi-user nature of clouds, this wealth of resources has been "siloed" into discrete isolated segments to ensure privacy and control over the resources by their current owner. Modern clouds have evolved beyond basic resource sharing, and have become platforms of modern development. Clouds are now home to rich ecosystems of services provided by third parties, or the cloud itself. However, clouds employ a rigid access control model that limits how cloud users can access these third-party services. With XNet, we aim to make cloud access control systems more flexible and dynamic by model- ing cloud access control as an object-based capability system. In this model, cloud users create and exchange "capabilities" to resources that permit them to use those resources as long as they continue to possess a capability to them. This model has collaborative policy definition at its core, allowing cloud users to more safely provide services to other users, and use services provided to them. We have implemented our model, and have integrated it into the popular OpenStack cloud system. Further, we have modified the existing Galaxy scientific workflow system to support our model, greatly enhancing the security guaranteed to users of the Galaxy system