In the realm of web server management, ensuring the security and reliability of your local network websites is paramount. One effective way to achieve this is by using Caddy, a powerful and user-friendly web server, with self-signed SSL certificates. In this blog post, we'll guide you through the process of configuring Caddy to serve a specific domain, such as yourdomain.com, with a self-signed certificate. This setup is ideal for local network environments where you need the security of HTTPS without the need for external certificate authorities.

Why Choose Caddy?

Caddy stands out for its simplicity and automatic HTTPS configuration. It's an excellent choice for both beginners and experienced server administrators. Caddy handles much of the heavy lifting, making the setup process smoother compared to other web servers.

Generating a Self-Signed SSL Certificate

The first step involves creating a self-signed SSL certificate for your domain. This can be done using OpenSSL with the following command:

openssl req -x509 -newkey rsa:4096 -sha256 -days 365 -nodes -keyout yourdomain.com.key -out yourdomain.com.crt -subj "/CN=yourdomain.com"

This command generates a certificate and key pair valid for 365 days, specifically for yourdomain.com.

Configuring the Caddyfile

Next, you'll need to edit your Caddyfile, the primary configuration file for Caddy. Here's a simple setup:

yourdomain.com {
    root * /path/to/website
    file_server
    tls yourdomain.com.crt yourdomain.com.key
}

Replace /path/to/website with the actual directory where your website's files are located.

Handling Permissions and Security

Ensure the SSL key file is securely stored and has the appropriate permissions. It should be readable by the Caddy server process, but not by unauthorized users.

Addressing Permission and Ownership Issues in Caddy Configuration

A common challenge when setting up a web server like Caddy, especially with self-signed SSL certificates, is managing file permissions and ownership correctly. Misconfigurations in this area can lead to service startup failures. An example error message, as shown in server logs, might look like this:

Nov 14 14:26:22 caddy[887070]: Error: loading initial config: loading new config: loading http app module: provision http: getting tls app: loading tls app module: provision tls: loading certificates: open /path/to/your/certs/yourdomain.com.key: permission denied

This message indicates that Caddy is unable to read the SSL key file due to insufficient permissions. Here's how to address this issue:

Understanding File Permissions and Ownership

  • File Permissions: SSL certificate files are sensitive and should have strict permissions to prevent unauthorized access. Typically, these files should be readable only by the user account under which the web server (Caddy) is running.
  • Ownership: The user and group ownership of these files should be set to the user account that runs the Caddy server process.

Resolving Permission Issues

  1. Check Current Permissions: Use ls -l /path/to/your/certs/yourdomain.com.key to view the current permissions of the SSL key file.
  2. Change Ownership: If Caddy runs as a specific user (e.g., caddy or www-data), change the file's ownership to this user. Use sudo chown caddy:caddy /path/to/your/certs/yourdomain.com.key.
  3. Adjust Permissions: Modify the file permissions so that they are restrictive, yet accessible by the Caddy process. A common setting is 640, which allows the owner to read and write, and the group to read. Adjust with sudo chmod 640 /path/to/your/certs/yourdomain.com.key.

Additional Considerations

  • Service User: Confirm the user account under which the Caddy service runs. This is often caddy or www-data, but may vary.
  • Security Practices: Always maintain strict permissions for SSL keys and certificates. Loose permissions can expose your server to security risks.
  • SELinux Contexts: If you're on a SELinux-enabled system (like CentOS or RHEL), ensure the correct SELinux contexts are applied to the certificate files.

Running and Testing Caddy

After configuring, start Caddy with your new Caddyfile. Access your site via https://yourdomain.com from a browser within your local network. Remember, browsers will warn you about the self-signed certificate's security; this is expected and normal for local testing environments.

Conclusion

Using Caddy with self-signed certificates for local network environments provides a secure and practical solution for testing and development purposes. It combines the ease of use of Caddy with the security benefits of HTTPS, making it an ideal choice for local web server setups.