Virtual Machine (VM) Security in Cloud Infrastructures

1. Dynamic VM Creation and Security Challenges

• Cloud-based infrastructures allow the creation of VMs almost instantly and in large quantities.
• Managing security becomes difficult because:
  • VMs are created and destroyed frequently throughout the day.
  • Each VM might have different configurations (CPUs, memory, storage, operating systems).

2. Variability of Virtual Machine Configurations

• VMs can vary in:
  • Number and capabilities of CPUs
  • Amount of memory
  • Amount of storage
  • Operating system versions (e.g., Windows, Linux)
• Despite variations, VMs must follow the same security best practices as physical devices.

3. VM-Specific Security Vulnerabilities

• VMs are vulnerable to traditional and VM-specific attacks, including:
  • Local privilege escalation
  • Command injection
  • Information disclosure

4. VM Isolation and VM Escape

• Normally, a VM is isolated with its own:
  • CPU
  • Memory
  • Storage
  • Other resources
• VM Escape:
  • A critical vulnerability where an attacker moves from one VM to another on the same hypervisor.
  • Risks include gaining access to tens or hundreds of VMs managed by one hypervisor.

Example: Pwn2Own 2017 VM Escape Attack

• Attackers exploited:
  • A bug in the Microsoft Edge JavaScript engine.
  • Gained access to the browser’s sandbox.
  • Exploited a vulnerability in the Windows 10 kernel.
  • Leveraged a hardware simulation bug in VMware to move between VMs.
• Impact: Highlighted the need for rapid patching and hypervisor hardening.

5. Resource Reuse Concerns

• Hypervisor Role:
  • Manages allocation of physical resources (memory, CPU, storage) among multiple VMs.
• Over-allocation Example:
  • Physical host has 4 GB RAM but allocates 2 GB each to 3 VMs (total 6 GB).
  • Relies on hypervisor's efficiency to manage memory usage dynamically.

Security Risk in Resource Sharing

• If the hypervisor mismanages memory:
  • A memory segment used by one VM could be accessible by another VM.
  • Could lead to data leakage across VMs.
• Solution:
  • Hypervisor updates and patches to fix memory management issues.