Caddy Certificate Renewal Failed On OPNsense: Debugging

Hey guys! Running into certificate renewal issues with Caddy on OPNsense can be a real headache. This article breaks down a specific problem encountered with the os-caddy plugin, where a wildcard DNS certificate from Cloudflare failed to renew. We'll explore the symptoms, potential causes, and how to troubleshoot this kind of issue effectively.

Understanding the Issue

The core problem? A wildcard DNS certificate, managed through Cloudflare, expired without being automatically renewed by the os-caddy plugin on OPNsense. Despite having the Cloudflare API key configured correctly and showing as active, the certificate renewal process simply didn't kick in. What makes it even more frustrating is the complete absence of any relevant logs, leaving you in the dark about what went wrong.

Key Symptoms

• Certificate Expiry: The wildcard DNS certificate expired.
• Cloudflare Setup: Cloudflare API key is active and correctly configured.
• Missing Logs: No entries in Caddy logs, even with debug mode enabled. This includes startup or shutdown messages.
• Reboot Ineffective: Rebooting the system doesn't trigger the renewal process.

Diagnosing the Root Cause

When facing a silent failure like this, it's crucial to systematically investigate potential causes. Here’s a breakdown of areas to check:

1. Cloudflare API Key Permissions

• Verify Permissions: While the API key might be active, double-check that it has the necessary permissions to manage DNS records. Specifically, it needs the ability to edit DNS records for the domain in question. Insufficient permissions are a common culprit.
• Re-enter the Key: Sometimes, re-entering the API key (even if it hasn't changed) can resolve underlying issues with how the key is stored or accessed by the plugin. This ensures that the plugin is definitely using the correct and valid key.

2. Caddy Configuration (Caddyfile)

• Syntax Errors: Even minor syntax errors in your Caddyfile can prevent Caddy from starting or renewing certificates. Use Caddy's built-in syntax checker (if available through the OPNsense plugin) or an online Caddyfile validator to ensure your configuration is valid.
• Domain Configuration: Ensure the domain names in your Caddyfile match exactly with what you have configured in Cloudflare. Pay special attention to wildcard domains and any potential typos. Mismatched domain names will prevent Caddy from correctly requesting and renewing certificates.
• DNS Challenge Configuration: Double-check the DNS challenge configuration within your Caddyfile. If you're using Cloudflare, ensure the correct DNS provider is specified and that any required parameters (like the API key reference) are accurate.

3. OPNsense Plugin Issues

• Plugin Version: Ensure you're running the latest version of the os-caddy plugin. Older versions may have bugs or compatibility issues that prevent certificate renewal.
• Plugin Reinstallation: Try reinstalling the plugin. This can resolve corrupted files or configuration issues that might be preventing the renewal process from starting.
• OPNsense Updates: Make sure your OPNsense system is up to date. Sometimes, underlying system updates can affect plugin functionality.

4. Firewall Rules

• Outbound Access: Confirm that your OPNsense firewall allows outbound access on port 443 (HTTPS) to Let's Encrypt's servers and Cloudflare's API endpoints. Blocking these connections will prevent Caddy from completing the certificate renewal process.
• DNS Resolution: Verify that your OPNsense system can resolve external DNS names correctly. Caddy needs to resolve Let's Encrypt and Cloudflare domains to obtain and manage certificates.

5. Caddy Process Status

• Check Process: Even if the service appears to be running, the Caddy process itself might have crashed or be in a bad state. Use the command line to check the status of the Caddy process and restart it manually if necessary.
• Memory Issues: In some cases, resource constraints (like memory limitations) can cause Caddy to fail silently. Monitor your system's resource usage to ensure Caddy has enough memory to operate correctly.

Troubleshooting Steps

Given the lack of logs, a methodical approach is key:

1. Verbose Logging: Even if the Caddy log is set to debug, try increasing the verbosity of the logs further (if possible through the plugin's configuration). Sometimes, more detailed logs can reveal hidden errors.
2. Manual Renewal Attempt: If the plugin provides a way to manually trigger certificate renewal, try using that option. This can help isolate whether the problem is with the automated renewal process or with Caddy's ability to obtain certificates in general.
3. Simplify Caddyfile: Temporarily simplify your Caddyfile to the bare minimum required for certificate renewal. This can help rule out complex configurations as the source of the problem.
4. Check System Time: Ensure the system time on your OPNsense firewall is accurate. Incorrect system time can cause issues with certificate validation.
5. Examine the Output of opnsense-revert: reverting to a previous version may offer insights from older logs that are more descriptive. If the system was previously working, compare the current configurations with those in a functional state.

Addressing the Empty Logs Issue

The most perplexing aspect of this issue is the complete absence of Caddy logs. Here are some potential reasons and solutions:

• Incorrect Log Path: Double-check that the log path configured in the os-caddy plugin is correct and that the log file exists and is writable by the Caddy process.
• Logging Configuration: Verify that the logging configuration within the Caddyfile (if any) is not overriding the plugin's logging settings. In some cases, a misconfigured Caddyfile can prevent logs from being written to the expected location.
• Permissions Issues: Ensure that the Caddy process has the necessary permissions to write to the log file. This might involve adjusting file ownership or permissions on the log file itself.
• System Logging Issues: In rare cases, there might be an issue with the underlying system logging infrastructure on OPNsense. Check the system logs for any errors related to logging services.

Example Scenario and Solution

Let's say you've checked all the configurations and everything seems correct. The issue might be with the Cloudflare API key permissions. Here’s how you'd address it:

1. Log in to Cloudflare: Access your Cloudflare account.
2. Navigate to API Tokens: Find the API token you're using for Caddy.
3. Edit the Token: Review the permissions assigned to the token. Ensure it has, at a minimum, Zone.DNS:Edit permission for the zone (domain) for which you're requesting the certificate.
4. Save Changes: Save the changes to the API token.
5. Update OPNsense: Re-enter the updated (or the same) API key in the os-caddy plugin configuration on OPNsense.
6. Trigger Renewal: Attempt a manual certificate renewal through the plugin.
7. Monitor Logs: Check the Caddy logs (if they start working) for any errors during the renewal process.

Conclusion

Troubleshooting Caddy certificate renewal issues on OPNsense requires a systematic approach, especially when logs are missing. By meticulously checking configurations, permissions, and system settings, you can identify the root cause and restore automatic certificate renewal. Don't get discouraged. Start with the basics and work your way through each potential issue. You've got this!

For additional insights on Caddy and Let's Encrypt integration, check out the official Let's Encrypt website for comprehensive documentation and support resources.