Before configuring ActiVPN OCSP Stapling with a secure NAT, ensure these are met:
A functional ActiVPN server installation.
A configured NAT environment (e.g., router or firewall).
OpenSSL installed on the ActiVPN server.
Access to the ActiVPN server's configuration files.
A domain name pointing to your server's public IP address.
Enable OCSP Stapling in OpenVPN: Edit your ActiVPN server's OpenVPN configuration file (e.g., server.conf). Add or modify the following lines:
tls-version-min 1.2
tls-cipher TLS-ECDHE-RSA-WITH-AES-256-GCM-SHA384:TLS-ECDHE-ECDSA-WITH-AES-256-GCM-SHA384:TLS-DHE-RSA-WITH-AES-256-GCM-SHA384
ssl-cert-verify script
Configure the Verification Script: Create the ssl-cert-verify script (e.g., /etc/openvpn/verify-script.sh). This script handles OCSP stapling verification.
#!/bin/bash
# OCSP Stapling Verification Script
# Add your OCSP verification logic here
exit 0 # Accept all certificates for now (replace with actual verification)
Make the script executable: chmod +x /etc/openvpn/verify-script.sh
Generate OCSP Stapling Information: This step involves fetching the OCSP response and configuring the server to serve it. This usually requires configuring your web server (e.g., Apache or Nginx) to handle OCSP stapling for the ActiVPN server's certificate.
Firewall Configuration: Ensure your firewall allows UDP traffic on the ActiVPN port (default 1194). If using TCP, allow TCP traffic instead. Configure NAT rules to forward this traffic to the internal IP address of the ActiVPN server.
DNS Records: Create an A record that resolves your domain name to your server's public IP. This is crucial for clients to connect using a domain name instead of a raw IP.
Client Configuration: Configure your ActiVPN client to use the same TLS settings as the server.
Connection Test: Connect to the ActiVPN server.
Log Analysis: Examine the ActiVPN server logs for OCSP stapling related messages. Successful stapling will show OCSP responses being served. Client logs may also indicate successful certificate validation.
Firewall Misconfiguration: Incorrect firewall rules can block ActiVPN traffic. Double-check your NAT and firewall settings.
DNS Resolution Issues: Ensure your domain name resolves correctly to the server's IP. Use nslookup or dig to verify.
Certificate Problems: Ensure the ActiVPN server's certificate is valid and trusted by clients. Expired or untrusted certificates will cause connection failures.
MTU Issues: Incorrect MTU settings can lead to packet fragmentation and performance problems. Adjust the mssfix option in the OpenVPN configuration if needed.
Verify OpenVPN is installed and configured.
Confirm NAT is correctly configured on your router/firewall.
Ensure the ActiVPN server's certificate is valid.
Check that OCSP stapling is enabled in the OpenVPN configuration.
Test the ActiVPN connection from a client device.
Review ActiVPN server and client logs for errors.
Document your configuration for future reference.