Qubes OS is a security-focused Linux distribution that utilizes virtualization technology to compartmentalize the desktop environment into isolated compartments called Qubes. This unique architecture allows Qubes OS to offer unparalleled security by limiting the ability of malware to spread across the system and access sensitive data. In this post, we’ll explore som of the interesting features of Qubes OS and what sets it apart from other Linux distributions.
Security Through Isolation
One of the core principles of Qubes OS is security through isolation [[1]]. Whereas traditional operating systems run all apps on the same OS, Qubes OS uses virtual machines (VMs) to isolate apps and processes from each other. For example, you could have one VM just for web browsing, another for document editing, and another holding your personal files. This way, if your web browser gets compromised by malware, the infection is restricted to that one VM and can’t access anything else.
These VMs are seamlessly integrated using Qubes’ management infrastructure while keeping them securely isolated behind the scenes. This approach minimizes the potential attack surface by limiting what any one app can access across the system.
Disposable VMs
In addition to traditional VMs, Qubes OS introduced the concept of “Disposable VMs” [[2]]. These are lightweight VMs that are created on-demand for specific tasks and are automatically destroyed afterward.
For example, you could configure Qubes so that every new browser tab opens in its own disposable VM. This means even if you accidentally visit a malicious website, as soon as you close that tab, the disposable VM containing that website is immediately deleted. This makes browsing vastly more secure by preventing browser exploits from persisting across tabs or browser sessions.
TemplateVMs
Qubes takes a unique approach to installing apps with TemplateVMs [[3]]. Instead of installing apps directly into VMs, app templates are created. These TemplateVMs contain full installations of operating systems (e.g. Linux Mint, Ubuntu, Whonix) and apps.
VMs can then be created from templates that inherit all their software without needing to reinstall everything. For example, creating a new VM from the Whonix template would give you a VM with Whonix already pre-installed. This allows easily spinning up throwaway VMs with specific software stacks.
TemplateVMs centralize where updates are managed, avoiding the tedious updates for every individual VM. And their read-only nature maximizes security, acting as “golden images” that can’t be infected. Even if a VM is compromised, reverting back to the pristine template is trivial.
Split GPG
Qubes implements an intriguing special case of an HSM with its Split GPG feature [[4]]. Split GPG separates your GPG private key for drives encryption across two VMs - a vault VM that holds the encrypted private key and requires a password and another VM for decryption.
The benefit of this split is that no single VM contains the full private key making it useless if compromised. And physical access is still required to enter the password, preventing fully automated attacks. Overall, it presents a clever implementation to heighten protection for encryption keys.
Dom0
Dom0 is the privileged domain within Qubes [[5]]. It manages the hypervisor and controls VM operations like starting, stopping, and networking. Dom0 has access to view VMs but they cannot access it, providing strict isolation.
Dom0 runs a minimal Linux distribution with only necessary services. Minimizing exposed attack surface in dom0 enhances security, as fewer vectors exist for escape to the hypervisor. This domain separation limits potential bugs and config issues.
Anti-Evil Maid
Qubes implements defense mechanisms against “evil maid” attacks [[6]], where an attacker with physical access alters a system prior to booting. These attacks can bypass software protections.
Anti-evil maid uses verified boot to cryptographically ensure no tampering occurred before the OS loaded. And LUKS encryption secures disks transparently, preventing offline tampering. Together they ensure the sanctity of Qubes OS from external physical meddling.
Removable VMs
Qubes allows pairing a removable drive with a VM [[7]]. The paired VM will then only run when that removable media is attached to the system.
This gives flexibility to carry secured environments on a USB stick. The VM auto shuts down when removed protecting media detached. And VM state resets on re-insert enforcing one-time execution avoiding lateral movement.
Summary
Qubes OS offers uniquely strong security by leveraging virtualization to isolate apps and protect the OS. Disposable VMs offer single-use instances that vanish afterward limiting persistence. TemplateVMs simplify centralizing updates and reverting to clean systems. And Split GPG fragment keys across VMs requiring physical presence. These innovations demonstrate novel ways isolation and compartmentalization can strengthen security on the desktop.
References:
[1] https://www.qubes-os.org/intro/
[2] https://www.qubes-os.org/doc/disposablevm/
[3] https://www.qubes-os.org/doc/templates/
[4] https://www.qubes-os.org/doc/split-gpg/