This paper proposed an Authorization Model for Cloud Computing. The proposed model aims to extend the UCONABC ongoing authorization model, providing resilience to the reevaluation of usage policies. Resilience means providing the model with the ability to deal with some individual user authorization attributes exceeding, while the SLA for the respective consumption service is under the contracted amount. The proposed architecture is based on a computing cloud composed of several types of services, providers, and consumers, and each of these may be exchanging data between different services (SaaS, PaaS, and IaaS). An intermediating (federated) environment is used, aiming to ease the interaction between entities using the cloud computing and to offer a PaaS that is UCONABC security oriented with ongoing authorizations. The experiments made with a proof-of-concept prototype show a set of measurements for an application scenario (e-commerce) and allows for the identification of exception conditions in the authorization reevaluation.