7.b) Explain the security risks posed by shared images and management OS.
Answer:
Security risks posed by shared images
Image sharing is critical for the IaaS cloud delivery model. For example, a user of AWS has the option to choose between
- Amazon Machine Images (AMIs) accessible through the Quick Start.
- Community AMI menus of the EC2 service
Many of the images analyzed by a recent report allowed a user to undelete files, recover credentials, private keys, or other types of sensitive information with little effort and using standard tools.
A software vulnerability audit revealed that 98% of the Windows AMIs and 58% of Linux AMIs audited had critical vulnerabilities.
Security risks:
- Backdoors and leftover credentials.
- Unsolicited connections.
- Malware.
Security risks posed by a management OS
A virtual machine monitor, or hypervisor, is considerably smaller than an operating system, e.g., the Xen VMM has ~ 60,000 lines of code.
The Trusted Computer Base (TCB) of a cloud computing environment includes not only the hypervisor but also the management OS.
The management OS supports administrative tools, live migration, device drivers, and device emulators.
In Xen the management operating system runs in Dom0; it manages the building of all user domains, a process consisting of several steps:
- Allocate memory in the Dom0 address space and load the kernel of the guest operating system from the secondary storage.
- Allocate memory for the new VM and use foreign mapping to load the kernel to the new VM.
- Set up the initial page tables for the new VM.
- Release the foreign mapping on the new VM memory, set up the virtual CPU registers and launch the new VM.
