Securing Your Ubuntu Server: A Comprehensive Guide to DNS over HTTPS (DoH)

DNS over HTTPS (DoH) enhances the privacy and security of your DNS queries by encrypting them over HTTPS. This prevents your ISP and potential eavesdroppers from seeing which websites you're visiting. This guide will walk you through configuring DoH on your Ubuntu server, covering various methods and considerations.

Why Use DNS over HTTPS on Your Ubuntu Server?

Traditional DNS queries are sent in plain text, making them vulnerable to interception and manipulation. DoH mitigates these risks by:

Increased Privacy: Your DNS queries are encrypted, hiding your browsing activity from your ISP and others on the network.
Improved Security: Encryption protects against DNS spoofing and other attacks that could redirect you to malicious websites.
Enhanced Censorship Resistance: DoH can make it more difficult for entities to censor websites by intercepting DNS requests.

Choosing a DoH Resolver

Several reputable DoH resolvers are available. Popular choices include:

Cloudflare (1.1.1.1): Known for its speed and privacy focus. Uses https://cloudflare-dns.com/
Google Public DNS (8.8.8.8): A widely used and reliable option.
Quad9 (9.9.9.9): Prioritizes security and privacy, blocking known malicious domains.

The best choice depends on your priorities. Consider factors such as speed, privacy policies, and security features when making your selection.

Configuring DoH on Your Ubuntu Server: Different Approaches

1. System-wide Configuration (Recommended for most users):

This method changes the system's default DNS settings, affecting all applications and users on the server.

Using NetworkManager (for desktop environments):

If you're using a desktop environment with NetworkManager, you can typically configure DoH through the graphical interface. Look for DNS settings within your network connection configuration.

Editing `/etc/resolv.conf` (Not recommended for most users):

Warning: Directly editing `/etc/resolv.conf` is generally discouraged as it's often managed dynamically by other system services. Changes made here might be overwritten.

Using systemd-resolved (recommended):

systemd-resolved is a modern DNS resolver included in most recent Ubuntu versions. To configure it for DoH, add the following lines to the file `/etc/systemd/resolved.conf`:


[Resolve]
DNS=2606:4700:4700::1111,2606:4700:4700::1001 # Example for Cloudflare
#DNS=8.8.8.8 # Example for Google
#DNS=9.9.9.9 # Example for Quad9
DNSOverHTTPS=yes

Replace the example DNS addresses with your chosen resolver. After saving the changes, restart the service:

sudo systemctl restart systemd-resolved

2. Application-Specific Configuration:

Some applications allow you to specify custom DNS settings. Check your application's documentation for instructions on how to configure DoH.

3. Using a DNS Proxy:

You can use a DNS proxy server to handle all DNS queries and encrypt them using DoH. This approach offers greater flexibility but adds complexity.

Verification and Troubleshooting

After configuring DoH, verify that it's working correctly. You can use tools like dig or online DoH checkers to test your DNS resolution.

If you encounter issues, check your configuration files for errors. Ensure the chosen DoH resolver is reachable and that the necessary services are running. Consult the documentation for your chosen resolver and configuration method.

Conclusion

Implementing DNS over HTTPS on your Ubuntu server significantly enhances security and privacy. By following the steps outlined in this guide, you can effectively protect your DNS queries from interception and manipulation.