The growing maturity of orchestration languages is contributing to the elaboration of cloud composite services, whose resources may be deployed over different distributed infrastructures. These composite services are subject to changes over time, that are typically required to support cloud properties, such as scalability and rapid elasticity. In particular, the migration of their elementary resources may be triggered by performance constraints. However, changes induced by this migration may introduce vulnerabilities that may compromise the resources, or even the whole cloud service. In that context, we propose an automated SMT 1 -based security framework for supporting the migration of resources in cloud composite services, and preventing the occurrence of new configuration vulnerabilities. We formalize the underlying security automation based on SMT solving, in order to assess the migrated resources and select adequate counter-measures, considering both endogenous and exogenous security mechanisms. We then evaluate its benefits and limits through large series of experiments based on a proof-ofconcept prototype implemented over the CVC4 commonly-used open-source solver. These experiments show a minimal overhead with regular operating systems deployed in cloud environments.

The large-scale deployment of cloud composite services distributed over heterogeneous environments poses new challenges in terms of security management. In particular, the migration of their resources is facilitated by recent advances in the area of virtualization techniques. This contributes to increase the dynamics of their configuration, and may induce vulnerabilities that could compromise the security of cloud resources, or even of the whole service. In addition, cloud providers may be reluctant to share precise information regarding the configuration of their infrastructures with cloud tenants that build and deploy cloud composite services. This makes the assessment of vulnerabilities difficult to be performed with only a partial view on the overall configuration.We therefore propose in this article an inter-cloud trusted third-party approach, called C3S-TTP, for supporting secure configurations in cloud composite services, more specifically during the migration of their resources. We describe the considered architecture, its main building blocks and their interactions based on an extended version of the TOSCA orchestration language. The trusted third party is capable to perform a precise and exhaustive vulnerability assessment, without requiring the cloud provider and the cloud tenant to share critical configuration information between each other. After designing and formalizing this third party solution, we perform large series of experiments based on a proof-of-concept prototype in order to quantify its benefits and limits.