Brief Explanation
The "SSLException: SSL handshake failed" error in Elasticsearch occurs when there's a problem establishing a secure SSL/TLS connection between Elasticsearch nodes or between a client and the Elasticsearch cluster. This error indicates that the SSL handshake process, which is crucial for setting up a secure communication channel, has failed.
Common Causes
- Mismatched SSL/TLS versions
- Expired or invalid SSL certificates
- Incorrect certificate configuration
- Hostname verification failures
- Incompatible cipher suites
- Firewall or network issues blocking SSL traffic
Troubleshooting and Resolution Steps
Verify SSL certificate validity:
- Check expiration dates
- Ensure certificates are issued by a trusted Certificate Authority (CA)
Confirm SSL/TLS version compatibility:
- Ensure all nodes and clients use compatible SSL/TLS versions
- Consider upgrading to the latest TLS version for better security
Review Elasticsearch SSL configuration:
- Check
elasticsearch.yml
for correct SSL settings - Verify paths to keystore and truststore files
- Check
Validate hostname verification:
- Ensure certificate Common Name (CN) or Subject Alternative Name (SAN) matches the hostname
Check network and firewall settings:
- Confirm SSL ports (usually 9200 for HTTP and 9300 for transport) are open
- Verify no firewall rules are blocking SSL traffic
Analyze Elasticsearch logs:
- Look for detailed SSL-related error messages
- Use debug logging for more information on SSL handshake process
Test SSL connection manually:
- Use tools like
openssl s_client
to test SSL handshake
- Use tools like
Update cipher suites if necessary:
- Ensure compatible and secure cipher suites are enabled
Best Practices
- Regularly update and rotate SSL certificates
- Use strong, industry-standard encryption algorithms
- Implement proper certificate management processes
- Monitor SSL certificate expiration dates
- Use tools like Certbot for automatic certificate renewal
- Implement mutual TLS (mTLS) for enhanced security when appropriate
Frequently Asked Questions
Q: How can I check if my SSL certificate is valid?
A: You can use the openssl
command to verify a certificate's validity. Run openssl x509 -in certificate.pem -text -noout
to view certificate details, including expiration date.
Q: What SSL/TLS version should I use with Elasticsearch?
A: It's recommended to use TLS 1.2 or higher. Elasticsearch 7.x and above support TLS 1.3, which provides better security and performance.
Q: Can SSL handshake failures be caused by clock synchronization issues?
A: Yes, if the system clocks are significantly out of sync, it can cause SSL handshake failures due to certificate validation issues. Ensure all systems have synchronized time, preferably using NTP.
Q: How do I enable debug logging for SSL in Elasticsearch?
A: Add logger.org.elasticsearch.xpack.security: DEBUG
to your log4j2.properties
file to enable detailed SSL-related logging.
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 these certificates explicitly.