Set up transport TLS

Self-Managed

Configuring TLS between nodes is the basic security setup to prevent unauthorized nodes from accessing to your Elasticsearch cluster, and it's required by multi-node clusters. Production mode clusters will not start if you do not enable TLS.

This document focuses on the manual configuration of TLS for Elasticsearch transport protocol in self-managed environments. Use this approach if you want to provide your own TLS certificates, generate them with Elastic’s tools, or have full control over the configuration. Alternatively, Elasticsearch can automatically generate and configure HTTPS certificates for you.

In this guide, you will learn how to:

• Generate or provide security certificates.
• Configure your Elasticsearch nodes to use the generated certificate for the transport layer.

Refer to Transport TLS/SSL settings for the complete list of available settings in Elasticsearch.

You can add as many nodes as you want in a cluster but they must be able to communicate with each other. The communication between nodes in a cluster is handled by the transport module. To secure your cluster, you must ensure that internode communications are encrypted and verified, which is achieved with mutual TLS.

In a secured cluster, Elasticsearch nodes use certificates to identify themselves when communicating with other nodes.

The cluster must validate the authenticity of these certificates. The recommended approach is to trust a specific certificate authority (CA). When nodes are added to your cluster they must use a certificate signed by the same CA.

For the transport layer, we recommend using a separate, dedicated CA instead of an existing, possibly shared CA so that node membership is tightly controlled.

When you manually set up transport TLS, you can choose from the following CA options:

• Use the elasticsearch-certutil tool to generate a CA unique to your cluster (recommended)
• Provide certificates from an external CA

You can use the elasticsearch-certutil tool to generate a CA for your cluster. Using elasticsearch-certutil guarantees that your certificates meet Elasticsearch certificate requirements and security best practices.

1. Before starting Elasticsearch, generate the CA:

   1. Use the elasticsearch-certutil tool on any single node to generate a CA for your cluster.

   ./bin/elasticsearch-certutil ca
   		

   2. When prompted, accept the default file name, which is elastic-stack-ca.p12. This file contains the public certificate for your CA and the private key used to sign certificates for each node.
   3. Enter a password for your CA. You can choose to leave the password blank if you’re not deploying to a production environment.

2. Generate the certificate:

   1. On any single node, generate a certificate and private key for the nodes in your cluster. Include the elastic-stack-ca.p12 output file that you generated in the previous step.

      ./bin/elasticsearch-certutil cert --ca elastic-stack-ca.p12
      		

      1. The --ca flag must contain the name of the CA file used to sign your certificates. The default file name from the elasticsearch-certutil tool is elastic-stack-ca.p12.

   2. Enter the password for your CA, or press Enter if you did not configure one in the previous step.

   3. Create a password for the certificate and accept the default file name.

      The output file is a keystore named elastic-certificates.p12. This file contains a node certificate, node key, and CA certificate.

You might choose to use an external CA to generate transport certificates for node-to-node connections. An external CA is any CA that is not managed using elasticsearch-certutil.

Transport connections between Elasticsearch nodes are security-critical and you must protect them carefully. Malicious actors who can observe or interfere with unencrypted node-to-node transport traffic can read or modify cluster data. A malicious actor who can establish a transport connection might be able to invoke system-internal APIs, including APIs that read or modify cluster data.

Carefully review Using an external certificate authority to secure node-to-node connections to ensure that your certificates meet the security requirements for transport connections.

The transport networking layer is used for internal communication between nodes in a cluster. When security features are enabled, you must use TLS to ensure that communication between the nodes is encrypted.

Now that you’ve obtained your certificates, you’ll update your cluster to use these files.

These steps assume that you generated a CA and certificates using elasticsearch-certutil. The xpack.security.transport.ssl settings that you need to set differ if you're using a certificate generated with an external CA. Refer to Transport TLS/SSL settings for a full list of available settings.

Complete the following steps for each node in your cluster. To join the same cluster, all nodes must share the same cluster.name value.

1. Place the certificate or keystore file that you obtained in the $ES_PATH_CONF directory on every node in your cluster. If you generated a CA using elasticsearch-certutil, then this file is named elastic-certificates.p12.

2. Open the $ES_PATH_CONF/elasticsearch.yml file and make the following changes:

   1. Add the cluster-name setting and enter a name for your cluster:

      cluster.name: my-cluster
      		

   2. Add the node.name setting and enter a name for the node. The node name defaults to the hostname of the machine when Elasticsearch starts.

      node.name: node-1
      		

   3. Add the following settings to enable internode communication and provide access to the node’s certificate.

      Because you are using the same elastic-certificates.p12 file on every node in your cluster, set the verification mode to certificate:

      xpack.security.transport.ssl.enabled: true
      xpack.security.transport.ssl.verification_mode: certificate
      xpack.security.transport.ssl.client_authentication: required
      xpack.security.transport.ssl.keystore.path: elastic-certificates.p12
      xpack.security.transport.ssl.truststore.path: elastic-certificates.p12
      		

      1. If you want to use hostname verification, set the verification mode to full. You should generate a different certificate for each host that matches the DNS or IP address. See the xpack.security.transport.ssl.verification_mode parameter in TLS settings.

3. If you entered a password when creating the node certificate, run the following commands to store the password in the Elasticsearch keystore:

   ./bin/elasticsearch-keystore add xpack.security.transport.ssl.keystore.secure_password
   		

   ./bin/elasticsearch-keystore add xpack.security.transport.ssl.truststore.secure_password
   		

4. Complete the previous steps for each node in your cluster.

5. On every node in your cluster, start Elasticsearch. The method for starting and stopping Elasticsearch varies depending on how you installed it.

   For example, if you installed Elasticsearch with an archive distribution (tar.gz or .zip), you can enter Ctrl+C on the command line to stop Elasticsearch.

   Warning

   You must perform a full cluster restart. Nodes that are configured to use TLS for transport cannot communicate with nodes that use unencrypted transport connection (and vice-versa).

Congratulations! You’ve encrypted communications between the nodes in your cluster and can pass the TLS bootstrap check.

To add another layer of security, set up HTTP TLS to encrypt client communications with both Elasticsearch and Kibana.

For other tasks related with TLS encryption in self-managed deployments, refer to Manage TLS encryption in self-managed deployments.