Brief Explanation
An SSL Handshake Error in Logstash occurs when there's a problem establishing a secure SSL/TLS connection between Logstash and another service or component. This error indicates that the SSL/TLS negotiation process failed, preventing encrypted communication.
Common Causes
- Mismatched SSL/TLS versions
- Invalid or expired SSL certificates
- Incorrect certificate authority (CA) configuration
- Hostname verification failures
- Firewall or network issues blocking SSL/TLS traffic
Troubleshooting and Resolution Steps
Verify SSL/TLS versions:
- Ensure both Logstash and the remote service support compatible SSL/TLS versions
- Update to the latest versions if possible
Check certificate validity:
- Verify that the SSL certificates are valid and not expired
- Ensure the certificate's Common Name (CN) or Subject Alternative Name (SAN) matches the hostname
Review CA configuration:
- Confirm that the correct CA certificates are installed and configured in Logstash
- Verify the trust chain is complete and valid
Enable hostname verification:
- Set
ssl_verify_mode
tofull
in your Logstash configuration - Ensure the hostname in the certificate matches the connection hostname
- Set
Investigate network issues:
- Check firewall rules to allow SSL/TLS traffic on required ports
- Verify network connectivity between Logstash and the remote service
Enable debug logging:
- Set
log.level: debug
inlogstash.yml
- Analyze the debug logs for detailed SSL/TLS negotiation information
- Set
Use OpenSSL for testing:
- Run
openssl s_client -connect host:port
to test SSL/TLS connectivity - Analyze the output for any certificate or handshake issues
- Run
Best Practices
- Regularly update Logstash and related components to ensure up-to-date SSL/TLS support
- Use strong cipher suites and disable outdated SSL/TLS versions
- Implement proper certificate management, including timely renewals
- Use hostname verification to prevent man-in-the-middle attacks
- Monitor SSL/TLS connections and set up alerts for certificate expiration
Frequently Asked Questions
Q: How can I check if my SSL certificate is valid?
A: You can use the OpenSSL command line tool: openssl x509 -in certificate.pem -text -noout
. This will display the certificate details, including validity dates and subject information.
Q: What SSL/TLS versions should I use with Logstash?
A: It's recommended to use TLS 1.2 or higher. Avoid using SSL 3.0 and TLS 1.0 as they have known vulnerabilities.
Q: How do I enable debug logging for SSL/TLS in Logstash?
A: Set log.level: debug
in your logstash.yml
file. You can also add --log.level=debug
to your Logstash command line arguments.
Q: Can I use self-signed certificates with Logstash?
A: Yes, but it's not recommended for production environments. If you must use self-signed certificates, ensure you properly configure the trust store in Logstash to recognize the certificate.
Q: How often should I rotate my SSL certificates?
A: Best practice is to rotate SSL certificates annually or more frequently. Many organizations opt for automated certificate management with shorter lifespans, such as 90 days, to enhance security.