What are the steps to configure a secure Elasticsearch cluster using TLS/SSL?

In today’s digital landscape, securing your data is paramount. A critical component of securing your Elasticsearch cluster is setting up TLS/SSL. When data is encrypted both at rest and in transit, you can ensure that only authorized users have access. This guide will walk you through the steps to configure your Elasticsearch cluster using TLS/SSL, providing a layer of security that is indispensable for safeguarding sensitive information.

Setting Up Your Elasticsearch Certificates

Before diving into the configuration, it’s essential to generate and manage your elastic certificates. Certificates are the backbone of TLS/SSL security, authenticating and encrypting the connection between nodes.

First, you will need a certificate authority (CA) to issue trusted certificates. You can either use a commercial CA or generate your own:

Generate CA Certificate:
- Use Elasticsearch’s certutil to generate a CA.
- Command:
```
./bin/elasticsearch-certutil ca
```
- Follow the on-screen instructions to generate the CA certificate and key.
Generate Node Certificates:
- With your CA ready, it’s time to issue node certificates.
- Command:
```
./bin/elasticsearch-certutil cert --ca elastic-stack-ca.p12
```
- This will generate certificate files for your nodes, including node.crt and node.key.

Ensure that each node in your cluster gets its own certificate, and distribute these files securely. Avoid shared paths or global permissions that could expose these sensitive files.

Configuring the Elasticsearch YML File

Once you have your certificates, the next step is to configure the elasticsearch.yml file to enable TLS/SSL. This configuration ensures that all nodes within the Elasticsearch cluster communicate securely.

Define the Paths for Certificates:

Open elasticsearch.yml and add the following lines:

xpack.security.enabled: true
xpack.security.transport.ssl.enabled: true
xpack.security.transport.ssl.verification_mode: full
xpack.security.transport.ssl.keystore.path: /path/to/node.p12
xpack.security.transport.ssl.truststore.path: /path/to/elastic-stack-ca.p12
xpack.security.http.ssl.enabled: true
xpack.security.http.ssl.keystore.path: /path/to/node.p12
xpack.security.http.ssl.truststore.path: /path/to/elastic-stack-ca.p12

Specify Passwords and Enable SSL:

If your certificate files are password-protected, include the passwords in elasticsearch.yml, or you can use the elasticsearch-keystore to securely store and use these passwords:

xpack.security.transport.ssl.keystore.secure_password: your_password
xpack.security.transport.ssl.truststore.secure_password: your_password
xpack.security.http.ssl.keystore.secure_password: your_password
xpack.security.http.ssl.truststore.secure_password: your_password

By configuring these settings, you’re enabling xpack security to handle the encryption and validation of data across your Elasticsearch nodes.

Enabling and Verifying Security Transport

It’s not enough to just configure your certificates; you must verify that the settings are correctly applied and working as intended. Here’s how you can do that:

Restart the Elasticsearch Nodes:
- After updating elasticsearch.yml, restart each node to apply the new settings:
```
sudo systemctl restart elasticsearch
```
Check the Cluster State:
- Use the following command to verify the SSL enabled status:
```
curl -X GET "https://your-node:9200/_cluster/health?pretty" -k -u user:password
```
- Look for the "status" field to confirm that the cluster is operating normally.
Examine Logs:
- Inspect the Elasticsearch logs for any SSL or certificate related errors. Log files are typically located at /var/log/elasticsearch/.
- Resolve any issues by rechecking your elasticsearch.yml configurations and certificate paths.

This section ensures that your security transport settings are correctly implemented, preventing unauthorized access and data breaches.

Integrating Kibana and Logstash

Securing your Elasticsearch cluster is crucial, but it’s equally important to integrate Kibana and Logstash with the same level of security. Kibana is the visualization tool, while Logstash is the data processing pipeline of the Elastic Stack.

Configure Kibana:

Open the kibana.yml file and add the SSL settings:

server.ssl.enabled: true
server.ssl.certificate: /path/to/kibana.crt
server.ssl.key: /path/to/kibana.key
elasticsearch.ssl.certificateAuthorities: [ "/path/to/elastic-stack-ca.crt" ]
elasticsearch.ssl.verificationMode: full

Restart Kibana to apply the new settings:
```
sudo systemctl restart kibana
```

Configure Logstash:
- Open logstash.yml and add the necessary SSL settings:
```
xpack.monitoring.elasticsearch.ssl.certificate_authority: /path/to/elastic-stack-ca.crt
xpack.monitoring.elasticsearch.ssl.verification_mode: full
```
- Additionally, ensure that your Logstash pipeline configuration files (.conf) have the ssl => true setting for Elasticsearch output plugins.
Verify Connections:
- Test the connection from Kibana and Logstash to Elasticsearch using their respective monitoring tools and logs.
- Ensure that all components are communicating securely over TLS/SSL.

By configuring Kibana and Logstash with SSL, you maintain a consistent security posture across the entire Elastic Stack.

Securing your Elasticsearch cluster with TLS/SSL is a comprehensive process that involves generating certificates, configuring settings across multiple configuration files, and verifying the secure transport of data. By following these steps, you can establish a robust security framework that protects your sensitive information from unauthorized access.

From generating your elastic certificates to configuring xpack security in the elasticsearch.yml file, and seamlessly integrating with Kibana and Logstash, you ensure that your data is encrypted and secure. Verifying that your SSL settings are enabled and functioning correctly is crucial for maintaining the integrity and confidentiality of your Elasticsearch operations.

In summary, securing your Elasticsearch cluster with TLS/SSL not only protects your data but also builds trust with users, knowing that their information is handled with the highest level of security. By taking these steps, you fortify your infrastructure against potential threats and enable a secure, reliable environment for your applications and users.