SSL/TLS handshake failures can disrupt secure connections between clients and servers. In WHM cPanel, it's essential to address these issues promptly to maintain a secure and reliable web hosting environment. This knowledge base provides guidance on troubleshooting SSL handshake failures.

Understanding SSL Handshake Failures

What is an SSL Handshake?

The SSL handshake is a protocol used to establish secure communication between a client and server. It involves a series of steps, including encryption key exchange and authentication, to ensure a secure connection.

Common Causes of SSL Handshake Failures

1. Incorrect SSL Certificate Configuration: Mismatched or expired certificates can lead to handshake failures.

2. Outdated SSL/TLS Versions: Incompatible protocol versions between the client and server can cause handshake failures.

3. Firewall or Security Software Interference: Overzealous security settings can block the handshake process.

4. Incorrect Cipher Suites: Misconfigured cipher suites can lead to handshake failures.

Troubleshooting SSL Handshake Failures

Checking the SSL Certificate

1. Verify Certificate Validity:

   • Ensure that the SSL certificate is valid and has not expired.

2. Certificate Chain:

   • Check if the certificate chain is properly configured. All intermediate certificates should be in place.

SSL/TLS Protocol and Cipher Configuration

1. Update Protocols and Ciphers:

   • Ensure that both the client and server support compatible SSL/TLS versions and cipher suites.

2. WHM SSL/TLS Configuration:

   • In WHM, navigate to Home > Service Configuration > Manage Service SSL Certificates. Ensure the correct certificates are selected.

Firewall and Security Software

1. Whitelist Ports:

   • Ensure that the necessary ports (typically 443 for HTTPS) are open in the firewall.

2. Temporarily Disable Security Software:

   • Temporarily disable any security software or firewalls to check if they are causing the issue.

Log Analysis

1. Apache Error Logs:

   • Check the Apache error logs (/usr/local/apache/logs/error_log) for any SSL-related error messages.

2. cPanel Error Logs:

   • Review cPanel error logs for any SSL handshake-related entries.

Server Time and Date

1. Verify Time and Date:

   • Ensure that the server's system time and date are set correctly. SSL certificates are time-sensitive.

ModSecurity Rules

1. Disable ModSecurity Rules:

   • Temporarily disable ModSecurity rules to see if they are causing the handshake failures.

WHM Plugins and Extensions

1. Review Installed Plugins:

   • Check for any installed WHM plugins or extensions that might interfere with SSL handshakes.

Check for Updates

1. Update cPanel and WHM:

   • Ensure that cPanel and WHM are up to date to benefit from the latest security patches and updates.

Conclusion

Addressing SSL handshake failures is crucial for maintaining secure connections between clients and servers in WHM cPanel environments. By following the troubleshooting steps outlined in this knowledge base, you can diagnose and resolve SSL handshake issues efficiently. Regular monitoring and maintenance of SSL configurations will help ensure a secure and reliable web hosting environment.