Configure SSL/TLS for self-managed Fleet Servers

If you’re running a self-managed cluster, configure Transport Layer Security (TLS) to encrypt traffic between Elastic Agents, Fleet Server, and other components in the Elastic Stack.

For the install settings specific to mutual TLS, as opposed to one-way TLS, refer to Elastic Agent deployment models with mutual TLS.

For a summary of flow by which TLS is established between components using either one-way or mutual TLS, refer to One-way and mutual TLS certifications flow.

Our hosted Elasticsearch Service on Elastic Cloud provides secure, encrypted connections out of the box!

Prerequisites

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Configure security and generate certificates for the Elastic Stack. For more information about securing the Elastic Stack, refer to Configure security for the Elastic Stack.

Elastic Agents require a PEM-formatted CA certificate to send encrypted data to Elasticsearch. If you followed the steps in Configure security for the Elastic Stack, your certificate will be in a p12 file. To convert it, use OpenSSL:

openssl pkcs12 -in path.p12 -out cert.crt -clcerts -nokeys
openssl pkcs12 -in path.p12 -out private.key -nocerts -nodes

Key passwords are not currently supported.

When you run Elastic Agent with the Elastic Defend integration, the TLS certificates used to connect to Fleet Server and Elasticsearch need to be generated using RSA. For a full list of available algorithms to use when configuring TLS or mTLS, see Configure SSL/TLS for standalone Elastic Agents. These settings are available for both standalone and Fleet-managed Elastic Agent.

Generate a custom certificate and private key for Fleet Server

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This section describes how to use the certutil tool provided by Elasticsearch, but you can use whatever process you typically use to generate PEM-formatted certificates.

Generate a certificate authority (CA). Skip this step if you want to use an existing CA.
```
./bin/elasticsearch-certutil ca --pem
```
This command creates a zip file that contains the CA certificate and key you’ll use to sign the Fleet Server certificate. Extract the zip file:

Store the files in a secure location.
Use the certificate authority to generate certificates for Fleet Server. For example:
```
./bin/elasticsearch-certutil cert \
  --name fleet-server \
  --ca-cert /path/to/ca/ca.crt \
  --ca-key /path/to/ca/ca.key \
  --dns your.host.name.here \
  --ip 192.0.2.1 \
  --pem
```
Where dns and ip specify the name and IP address of the Fleet Server. Run this command for each Fleet Server you plan to deploy.

This command creates a zip file that includes a .crt and .key file. Extract the zip file:

Store the files in a secure location. You’ll need these files later to encrypt traffic between Elastic Agents and Fleet Server.

Encrypt traffic between Elastic Agents, Fleet Server, and Elasticsearch

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Fleet Server needs a CA certificate or the CA fingerprint to connect securely to Elasticsearch. It also needs to expose a Fleet Server certificate so other Elastic Agents can connect to it securely.

For the steps in this section, imagine you have the following files:

`ca.crt`	The CA certificate to use to connect to Fleet Server. This is the CA used to generate a certificate and key for Fleet Server.
`fleet-server.crt`	The certificate you generated for Fleet Server.
`fleet-server.key`	The private key you generated for Fleet Server. If the `fleet-server.key` file is encrypted with a passphrase, the passphrase will need to be specified through a file.
`elasticsearch-ca.crt`	The CA certificate to use to connect to Elasticsearch. This is the CA used to generate certs for Elasticsearch (see Prerequisites). Note that the CA certificate’s SHA-256 fingerprint (hash) may be used instead of the `elasticsearch-ca.crt` file for securing connections to Elasticsearch.

To encrypt traffic between Elastic Agents, Fleet Server, and Elasticsearch:

Configure Fleet settings. These settings are applied to all Fleet-managed Elastic Agents.
In Kibana, open the main menu, then click Management > Fleet > Settings.
1. Under Fleet Server hosts, specify the URLs Elastic Agents will use to connect to Fleet Server. For example, https://192.0.2.1:8220, where 192.0.2.1 is the host IP where you will install Fleet Server.
  
  For host settings, use the https protocol. DNS-based names are also allowed.
2. Under Outputs, search for the default output, then click the Edit icon in the Action column.
3. In the Hosts field, specify the Elasticsearch URLs where Elastic Agents will send data. For example, https://192.0.2.0:9200.
4. Specify either a CA certificate or CA fingerprint to connect securely Elasticsearch:

If you have a valid HEX encoded SHA-256 CA trusted fingerprint from root CA, specify it in the Elasticsearch CA trusted fingerprint field. To learn more, refer to the Elasticsearch security documentation.
Otherwise, under Advanced YAML configuration, set ssl.certificate_authorities and specify the CA certificate to use to connect to Elasticsearch. You can specify a list of file paths (if the files are available), or embed a certificate directly in the YAML configuration. If you specify file paths, the certificates must be available on the hosts running the Elastic Agents.

File path example:
```
ssl.certificate_authorities: ["/path/to/your/elasticsearch-ca.crt"] 
```
The path to the CA certificate on the Elastic Agent host.

Pasted certificate example:
```
ssl:
  certificate_authorities:
  - |
    -----BEGIN CERTIFICATE-----
    MIIDSjCCAjKgAwIBAgIVAKlphSqJclcni3P83gVsirxzuDuwMA0GCSqGSIb3DQEB
    CwUAMDQxMjAwBgNVBAMTKUVsYXN0aWMgQ2VydGlmaWNhdGUgVG9vbCBBdXRvZ2Vu
    ZXJhdGVkIENBMB4XDTIxMDYxNzAxMzIyOVoXDTI0MDYxNjAxMzIyOVowNDEyMDAG
    A1UEAxMpRWxhc3RpYyBDZXJ0aWZpY2F0ZSBUb29sIEF1dG9nZW5lcmF0ZWQgQ0Ew
    ggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQDOFgtVri7Msy2iR33nLrVO
    /M/6IyF72kFXup1E67TzetI22avOxNlq+HZTpZoWGV1I4RgxiQeN12FLuxxhd9nm
    rxfZEqpuIjvo6fvU9ifC03WjXg1opgdEb6JqH93RHKw0PYimxhQfFcwrKxFseHUx
    DeUNQgHkMQhDZgIfNgr9H/1X6qSU4h4LemyobKY3HDKY6pGsuBzsF4iOCtIitE9p
    sagiWR21l1gW/lNaEW2ICKhJXbaqbE/pis45/yyPI4Q1Jd1VqZv744ejnZJnpAx9
    mYSE5RqssMeV6Wlmu1xWljOPeerOVIKUfHY38y8GZwk7TNYAMajratG2dj+v9eAV
    AgMBAAGjUzBRMB0GA1UdDgQWBBSCNCjkb66eVsIaa+AouwUsxU4b6zAfBgNVHSME
    GDAWgBSCNCjkb66eVsIaa+AouwUsxU4b6zAPBgNVHRMBAf8EBTADAQH/MA0GCSqG
    SIb3DQEBCwUAA4IBAQBVSbRObxPwYFk0nqF+THQDG/JfpAP/R6g+tagFIBkATLTu
    zeZ6oJggWNSfgcBviTpXc6i1AT3V3iqzq9KZ5rfm9ckeJmjBd9gAcyqaeF/YpWEb
    ZAtbxfgPLI3jK+Sn8S9fI/4djEUl6F/kARpq5ljYHt9BKlBDyL2sHymQcrDC3pTZ
    hEOM4cDbyKHgt/rjcNhPRn/q8g3dDhBdzjlNzaCNH/kmqWpot9AwmhhfPTcf1VRc
    gxdg0CTQvQvuceEvIYYYVGh/cIsIhV2AyiNBzV5jJw5ztQoVyWvdqn3B1YpMP8oK
    +nadUcactH4gbsX+oXRULNC7Cdd9bp2G7sQc+aZm
    -----END CERTIFICATE-----
```
1. Install an Elastic Agent as a Fleet Server on the host and configure it to use TLS:
  1. If you don’t already have a Fleet Server service token, click the Agents tab in Fleet and follow the instructions to generate the service token now.
    
    The in-product installation steps are incomplete. Before running the install command, add the settings shown in the next step.
  2. From the directory where you extracted Fleet Server, run the install command and specify the certificates to use.
    
    The following command installs Elastic Agent as a service, enrolls it in the Fleet Server policy, and starts the service.
    
    If you’re using DEB or RPM, or already have the Elastic Agent installed, use the enroll command along with the following options, then start the service as described in Start Elastic Agent.
    
    sudo ./elastic-agent install \ --url=https://192.0.2.1:8220 \ --fleet-server-es=https://192.0.2.0:9200 \ --fleet-server-service-token=AAEBAWVsYXm0aWMvZmxlZXQtc2XydmVyL3Rva2VuLTE2MjM4OTAztDU1OTQ6dllfVW1mYnFTVjJwTC2ZQ0EtVnVZQQ \ --fleet-server-policy=fleet-server-policy \ --fleet-server-es-ca=/path/to/elasticsearch-ca.crt \ --certificate-authorities=/path/to/ca.crt \ --fleet-server-cert=/path/to/fleet-server.crt \ --fleet-server-cert-key=/path/to/fleet-server.key \ --fleet-server-port=8220 \ --elastic-agent-cert=/tmp/fleet-server.crt \ --elastic-agent-cert-key=/tmp/fleet-server.key \ --fleet-server-es-cert=/tmp/fleet-server.crt \ --fleet-server-es-cert-key=/tmp/fleet-server.key \ --fleet-server-client-auth=required
    
    Where:
    
    url
    
    Fleet Server URL.
    
    fleet-server-es
    
    Elasticsearch URL
    
    fleet-server-service-token
    
    Service token to use to communicate with Elasticsearch.
    
    fleet-server-policy
    
    The specific policy that Fleet Server will use.
    
    fleet-server-es-ca
    
    CA certificate that the current Fleet Server uses to connect to Elasticsearch.
    
    certificate-authorities
    
    List of paths to PEM-encoded CA certificate files that should be trusted for the other Elastic Agents to connect to this Fleet Server
    
    fleet-server-cert
    
    The path for the PEM-encoded certificate (or certificate chain) which is associated with the fleet-server-cert-key to expose this Fleet Server HTTPS endpoint to the other Elastic Agents
    
    fleet-server-cert-key
    
    Private key to use to expose this Fleet Server HTTPS endpoint to the other Elastic Agents
    
    elastic-agent-cert
    
    The certificate to use as the client certificate for Elastic Agent’s connections to Fleet Server.
    
    elastic-agent-cert-key
    
    The path to the private key to use as for Elastic Agent’s connections to Fleet Server.
    
    fleet-server-es-cert
    
    The path to the client certificate that Fleet Server will use when connecting to Elasticsearch.
    
    fleet-server-es-cert-key
    
    The path to the private key that Fleet Server will use when connecting to Elasticsearch.
    
    fleet-server-client-auth
    
    One of none, optional, or required. Defaults to none. Fleet Server’s client_authentication option for client mTLS connections. If optional or required is specified, client certificates are verified using CAs specified in the --certificate-authorities flag.
    
    Note that additionally an optional passphrase for the private key may be specified with:
    
    fleet-server-cert-key-passphrase
    
    Passphrase file used to decrypt Fleet Server’s private key.
    
    What happens if you enroll Fleet Server without specifying certificates?
    
    If the certificates are managed by your organization and installed at the system level, they will be used to encrypt traffic between Elastic Agents, Fleet Server, and Elasticsearch.
    
    If system-level certificates don’t exist, Fleet Server automatically generates self-signed certificates. Traffic between Fleet Server and Elastic Agents over HTTPS is encrypted, but the certificate chain cannot be verified. Any Elastic Agents enrolling in Fleet Server will need to pass the --insecure flag to acknowledge that the certificate chain is not verified.
    
    Allowing Fleet Server to generate self-signed certificates is useful to get things running for development, but not recommended in a production environment.
2. Install your Elastic Agents and enroll them in Fleet.
  
  Elastic Agents connecting to a secured Fleet Server need to pass in the CA certificate used by the Fleet Server. The CA certificate used by Elasticsearch is already specified in the agent policy because it’s set under Fleet settings in Kibana. You do not need to pass it on the command line.
  
  The following command installs Elastic Agent as a service, enrolls it in the agent policy associated with the specified token, and starts the service.
```
sudo elastic-agent install --url=https://192.0.2.1:8220 \
  --enrollment-token=<string> \
  --certificate-authorities=/path/to/ca.crt
```
  Where:
  
  url
  
  Fleet Server URL to use to enroll the Elastic Agent into Fleet.
  
  enrollment-token
  
  The enrollment token for the policy that will be applied to the Elastic Agent.
  
  certificate-authorities
  
  CA certificate to use to connect to Fleet Server. This is the CA used to generate a certificate and key for Fleet Server.
  
  Don’t have an enrollment token? On the Agents tab in Fleet, click Add agent. Under Enroll and start the Elastic Agent, follow the in-product installation steps, making sure that you add the --certificate-authorities option before you run the command.

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