Elasticsearch Error: SSL/TLS handshake failure - Common Causes & Fixes

Brief Explanation

The SSL/TLS handshake failure error in Elasticsearch occurs when there's a problem establishing a secure connection between Elasticsearch nodes or between a client and the Elasticsearch cluster. This error indicates that the SSL/TLS negotiation process failed to complete successfully.

Common Causes

1. Mismatched SSL/TLS versions
2. Expired or invalid SSL certificates
3. Incorrect certificate authority (CA) configuration
4. Hostname verification failures
5. Incompatible cipher suites
6. Firewall or network issues blocking SSL/TLS traffic

Troubleshooting and Resolution Steps

1. Verify SSL/TLS versions:

   • Ensure all nodes and clients are using compatible SSL/TLS versions
   • Check Elasticsearch configuration for ssl.supported_protocols setting

2. Check certificate validity:

   • Verify that certificates are not expired
   • Ensure certificates are issued by a trusted CA
   • Check that the certificate's Common Name (CN) or Subject Alternative Name (SAN) matches the hostname

3. Review CA configuration:

   • Confirm that the correct CA certificates are configured in Elasticsearch
   • Verify the CA chain is complete and valid

4. Address hostname verification:

   • Ensure DNS resolution is correct for all nodes
   • Check that certificate hostnames match the actual hostnames or IPs of the nodes

5. Verify cipher suite compatibility:

   • Review and align cipher suites across all nodes and clients
   • Check Elasticsearch configuration for ssl.cipher_suites setting

6. Investigate network issues:

   • Confirm that firewalls allow SSL/TLS traffic on required ports
   • Check for any network connectivity issues between nodes

7. Enable debug logging:

   • Set logging level to DEBUG for org.elasticsearch.security in log4j2.properties
   • Analyze logs for detailed SSL/TLS handshake information

8. Use OpenSSL for testing:

   • Run openssl s_client -connect hostname:port to test SSL/TLS connectivity
   • Analyze the output for specific handshake failures

Best Practices

• Regularly update and rotate SSL certificates
• Use strong cipher suites and disable weak protocols
• Implement proper certificate management and distribution processes
• Conduct regular security audits of your Elasticsearch cluster
• Keep Elasticsearch and its dependencies up to date

Frequently Asked Questions

Q: How can I test if my SSL certificate is valid for Elasticsearch?
A: You can use the openssl command to verify your certificate. Run openssl x509 -in your_cert.pem -text -noout to display certificate details and check its validity period and other information.

Q: What should I do if I'm getting SSL handshake errors after upgrading Elasticsearch?
A: After upgrading, ensure that all nodes are using compatible SSL/TLS versions and cipher suites. Review the Elasticsearch upgrade documentation for any security-related changes and update your configurations accordingly.

Q: Can mismatched Java versions cause SSL/TLS handshake failures in Elasticsearch?
A: Yes, different Java versions may support different SSL/TLS protocols and cipher suites. Ensure all nodes are running the same Java version, preferably the one recommended for your Elasticsearch version.

Q: How do I enable SSL debug logging in Elasticsearch?
A: Add -Djavax.net.debug=ssl,handshake to your Elasticsearch JVM options. This will provide detailed SSL/TLS handshake information in the logs.

Q: Is it possible to use self-signed certificates with Elasticsearch?
A: Yes, you can use self-signed certificates, but it's not recommended for production environments. If you must use them, ensure all nodes and clients trust the self-signed CA, and be aware of the security implications.