Biblio

In Infrastructure-as-a-Service clouds, there exist many virtual machines (VMs) that are not used for a long time. For such VMs, many vulnerabilities are often found in installed software while VMs are suspended. If security updates are applied to such VMs after the VMs are resumed, the VMs easily suffer from attacks via the Internet. To solve this problem, offline update of VMs has been proposed, but some approaches have to permit cloud administrators to resume users' VMs. The others are applicable only to completely stopped VMs and often corrupt virtual disks if they are applied to suspended VMs. In addition, it is sometimes difficult to accurately emulate security updates offline. In this paper, we propose OUassister, which enables consistent offline update of suspended VMs. OUassister emulates security updates of VMs offline in a non-intrusive manner and applies the emulation results to the VMs online. This separation prevents virtual disks of even suspended VMs from being corrupted. For more accurate emulation of security updates, OUassister provides an emulation environment using a technique called VM introspection. Using this environment, it automatically extracts updated files and executed scripts. We have implemented OUassister in Xen and confirmed that the time for critical online update was largely reduced.

Infrastructure-as-a-Service clouds provide out-of-band remote management for users to access their virtual machines (VMs). Out-of-band remote management is a method for indirectly accessing VMs via their virtual devices. While virtual devices running in the virtualized system are managed by cloud operators, not all cloud operators are always trusted in clouds. To prevent information leakage from virtual devices and tampering with their I/O data, several systems have been proposed by trusting the hypervisor in the virtualized system. However, they have various issues on security and management. This paper proposes VSBypass, which enables secure out-of-band remote management outside the virtualized system using a technique called transparent passthrough. VSBypass runs the entire virtualized system in an outer VM using nested virtualization. Then it intercepts I/O requests of out-of-band remote management and processes those requests in shadow devices, which run outside the virtualized system. We have implemented VSBypass in Xen for the virtual serial console and GUI remote access. We confirmed that information leakage was prevented and that the performance was comparable to that in traditional out-of-band remote management.