A Multi-Tenant RBAC Model for Collaborative Cloud Services

Most cloud services are built with multi-tenancy which enables data and configuration segregation upon shared infrastructures. In this setting, a tenant temporarily uses a piece of virtually dedicated software, platform, or infrastructure. To fully benefit from the cloud, tenants are seeking to build controlled and secure collaboration with each other. In this paper, we propose a Multi-Tenant Role-Based Access Control (MT-RBAC) model family which aims to provide fine-grained authorization in collaborative cloud environments by building trust relations among tenants. With an established trust relation in MT-RBAC, the trustee can precisely authorize cross-tenant accesses to the truster's resources consistent with constraints over the trust relation and other components designated by the truster. The users in the trustee may restrictively inherit permissions from the truster so that multi-tenant collaboration is securely enabled. Using SUN's XACML library, we prototype MT-RBAC models on a novel Authorization as a Service (AaaS) platform with the Joyent commercial cloud system. The performance and scalability metrics are evaluated with respect to an open source cloud storage system. The results show that our prototype incurs only 0.016 second authorization delay for end users on average and is scalable in cloud environments.