hGuard: A Framework to Measure Hypervisor Critical Files

Virtualization has been widely adopted in current computer systems. A key part of virtualization is a hyper visor, which virtualizes physical resources to be shared among multiple guest virtual machines (VMs). Configuration files and security policy files used by the hyper visor control VMs' behavior. If these critical files are tampered with, all the VMs that run on the same hyper visor will be affected. This paper presents hGuard, a framework to measure hyper visor critical files. Each time a critical file is updated, its hash is stored into a non-volatile storage of the trusted chip. When a critical file is loaded into memory, a measurement module computes its hash and a validation module checks its integrity by comparing this hash with that stored in the non-volatile storage. Only if they are the same could the files be used and continuous operation will be allowed. The experiment shows that hGuard can detect illegal modification of hyper visor critical files.