OpenSearch/docs/reference/security/securing-communications/tls-ldap.asciidoc

[role="xpack"]
[[tls-ldap]]
==== Encrypting communications between {es} and LDAP

To protect the user credentials that are sent for authentication in an LDAP 
realm, it's highly recommended to encrypt communications between {es} and your 
LDAP server. Connecting via SSL/TLS ensures that the identity of the LDAP server 
is authenticated before {security} transmits the user credentials and the 
contents of the connection are encrypted. Clients and nodes that connect via 
TLS to the LDAP server need to have the LDAP server's certificate or the 
server's root CA certificate installed in their keystore or truststore. 

For more information, see <<configuring-ldap-realm>>. 

. Configure the realm's TLS settings on each node to trust certificates signed 
by the CA that signed your LDAP server certificates. The following example 
demonstrates how to trust a CA certificate, `cacert.pem`, located within the 
{xpack} configuration directory:
+
--
[source,shell]
--------------------------------------------------
xpack:
  security:
    authc:
      realms:
        ldap:
          ldap1:
            order: 0
            url: "ldaps://ldap.example.com:636"
            ssl:
              certificate_authorities: [ "ES_PATH_CONF/cacert.pem" ]
--------------------------------------------------

The CA certificate must be a PEM encoded.

NOTE: You can also specify the individual server certificates rather than the CA
certificate, but this is only recommended if you have a single LDAP server or 
the certificates are self-signed.

--

. Set the `url` attribute in the realm configuration to specify the LDAPS
protocol and the secure port number. For example, `url: ldaps://ldap.example.com:636`.

. Restart {es}.

NOTE: By default, when you configure {security} to connect to an LDAP server
      using SSL/TLS, {security} attempts to verify the hostname or IP address
      specified with the `url` attribute in the realm configuration with the
      values in the certificate. If the values in the certificate and realm
      configuration do not match, {security} does not allow a connection to the
      LDAP server. This is done to protect against man-in-the-middle attacks. If
      necessary, you can disable this behavior by setting the
      `ssl.verification_mode` property to `certificate`.