CovertInspector: Identification of Shared Memory Covert Timing Channel in Multi-tenanted Cloud

Abstract

Memory deduplication improves the memory efficiency of common multi-tenanted cloud. Due to the cross-VM memory sharing, malicious users can mount covert channel attack to steal secret information. While this kind of attack does not break the normal restrictions, it is very hard to detect and defend. In the paper, we present the design, implementation and evaluation of CovertInspector--a VMM-based system to identify and eliminate a covert timing channel constructed on shared memory. Our proof-of-concept prototype is built on KVM and Kernel Samepage Merging (KSM), with minor modification to KVM hypervisor (about 300 LOC). Further evaluation shows that CovertInspector is able to fully identify and eliminate such kind of covert channel with tolerable impact to the performance of guest VMs.