=================== LDAP Authentication

Presto can be configured to enable frontend LDAP authentication over HTTPS for clients, such as the :ref:cli_ldap, or the JDBC and ODBC drivers. At present only simple LDAP authentication mechanism involving username and password is supported. The Presto client sends a username and password to the coordinator and coordinator validates these credentials using an external LDAP service.

To enable LDAP authentication for Presto, configuration changes are made on the Presto coordinator. No changes are required to the worker configuration; only the communication from the clients to the coordinator is authenticated. However, if you want to secure the communication between Presto nodes with SSL/TLS configure :doc:/security/internal-communication.

Presto Server Configuration

Environment Configuration ^^^^^^^^^^^^^^^^^^^^^^^^^

.. _ldap_server:

Secure LDAP


Presto requires Secure LDAP (LDAPS), so make sure you have TLS
enabled on your LDAP server.

TLS Configuration on Presto Coordinator

You need to import the LDAP server's TLS certificate to the default Java truststore of the Presto coordinator to secure TLS connection. You can use the following example keytool command to import the certificate ldap_server.crt, to the truststore on the coordinator.

.. code-block:: none

$ keytool -import -keystore <JAVA_HOME>/jre/lib/security/cacerts -trustcacerts -alias ldap_server -file ldap_server.crt

In addition to this, access to the Presto coordinator should be through HTTPS. You can do it by creating a :ref:server_java_keystore on the coordinator.

Presto Coordinator Node Configuration ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

You must make the following changes to the environment prior to configuring the Presto coordinator to use LDAP authentication and HTTPS.

:ref:ldap_server
:ref:server_java_keystore

You also need to make changes to the Presto configuration files. LDAP authentication is configured on the coordinator in two parts. The first part is to enable HTTPS support and password authentication in the coordinator's config.properties file. The second part is to configure LDAP as the password authenticator plugin.

Server Config Properties


The following is an example of the required properties that need to be added
to the coordinator's ``config.properties`` file:

.. code-block:: none

    http-server.authentication.type=PASSWORD

    http-server.https.enabled=true
    http-server.https.port=8443

    http-server.https.keystore.path=/etc/presto_keystore.jks
    http-server.https.keystore.key=keystore_password

======================================================= ======================================================
Property                                                Description
======================================================= ======================================================
``http-server.authentication.type``                     Enable password authentication for the Presto
                                                        coordinator. Must be set to ``PASSWORD``.
``http-server.https.enabled``                           Enables HTTPS access for the Presto coordinator.
                                                        Should be set to ``true``. Default value is
                                                        ``false``.
``http-server.https.port``                              HTTPS server port.
``http-server.http2.enabled``                           Enables HTTP2 server on the worker.
``http-server.https.keystore.path``                     The location of the Java Keystore file that will be
                                                        used to secure TLS.
``http-server.https.keystore.key``                      The password for the keystore. This must match the
                                                        password you specified when creating the keystore.
``http-server.authentication.allow-forwarded-https``    Enable treating forwarded HTTPS requests over HTTP as secure.
                                                        Requires the ``X-Forwarded-Proto`` header to be set to ``https`` on forwarded requests.
                                                        Default value is ``false``.
======================================================= ======================================================

Password Authenticator Configuration

Password authentication needs to be configured to use LDAP. Create an etc/password-authenticator.properties file on the coordinator. Example:

.. code-block:: none

password-authenticator.name=ldap
ldap.url=ldaps://ldap-server:636
ldap.user-bind-pattern=<Refer below for usage>

======================================================= ====================================================== Property Description ======================================================= ====================================================== ldap.url The url to the LDAP server. The url scheme must be ldaps:// since Presto allows only Secure LDAP. ldap.user-bind-pattern This property can be used to specify the LDAP user bind string for password authentication. This property must contain the pattern ${USER} which will be replaced by the actual username during the password authentication. Example: ${USER}@corp.example.com. ======================================================= ======================================================

Based on the LDAP server implementation type, the property ldap.user-bind-pattern can be used as described below.

Active Directory

.. code-block:: none

ldap.user-bind-pattern=${USER}@<domain_name_of_the_server>

Example:

.. code-block:: none

ldap.user-bind-pattern=${USER}@corp.example.com

OpenLDAP

.. code-block:: none

ldap.user-bind-pattern=uid=${USER},<distinguished_name_of_the_user>

Example:

.. code-block:: none

ldap.user-bind-pattern=uid=${USER},OU=America,DC=corp,DC=example,DC=com

Authorization based on LDAP Group Membership


You can further restrict the set of users allowed to connect to the Presto
coordinator based on their group membership by setting the optional
``ldap.group-auth-pattern`` and ``ldap.user-base-dn`` properties in addition
to the basic LDAP authentication properties.

======================================================= ======================================================
Property                                                Description
======================================================= ======================================================
``ldap.user-base-dn``                                   The base LDAP distinguished name for the user
                                                        who tries to connect to the server.
                                                        Example: ``OU=America,DC=corp,DC=example,DC=com``
``ldap.group-auth-pattern``                             This property is used to specify the LDAP query for
                                                        the LDAP group membership authorization. This query
                                                        will be executed against the LDAP server and if
                                                        successful, the user will be authorized.
                                                        This property must contain a pattern ``${USER}``
                                                        which will be replaced by the actual username in
                                                        the group authorization search query.
                                                        See samples below.
======================================================= ======================================================

Based on the LDAP server implementation type, the property
``ldap.group-auth-pattern`` can be used as described below.

Active Directory
****************

.. code-block:: none

    ldap.group-auth-pattern=(&(objectClass=<objectclass_of_user>)(sAMAccountName=${USER})(memberof=<dn_of_the_authorized_group>))

Example:

.. code-block:: none

    ldap.group-auth-pattern=(&(objectClass=person)(sAMAccountName=${USER})(memberof=CN=AuthorizedGroup,OU=Asia,DC=corp,DC=example,DC=com))

OpenLDAP
********

.. code-block:: none

    ldap.group-auth-pattern=(&(objectClass=<objectclass_of_user>)(uid=${USER})(memberof=<dn_of_the_authorized_group>))

Example:

.. code-block:: none

    ldap.group-auth-pattern=(&(objectClass=inetOrgPerson)(uid=${USER})(memberof=CN=AuthorizedGroup,OU=Asia,DC=corp,DC=example,DC=com))

For OpenLDAP, for this query to work, make sure you enable the
``memberOf`` `overlay <http://www.openldap.org/doc/admin24/overlays.html>`_.

You can also use this property for scenarios where you want to authorize a user
based on complex group authorization search queries. For example, if you want to
authorize a user belonging to any one of multiple groups (in OpenLDAP), this
property may be set as follows:

.. code-block:: none

    ldap.group-auth-pattern=(&(|(memberOf=CN=normal_group,DC=corp,DC=com)(memberOf=CN=another_group,DC=com))(objectClass=inetOrgPerson)(uid=${USER}))

.. _cli_ldap:

Presto CLI
----------

Environment Configuration
^^^^^^^^^^^^^^^^^^^^^^^^^

TLS Configuration
~~~~~~~~~~~~~~~~~

Access to the Presto coordinator should be through HTTPS when using LDAP
authentication. The Presto CLI can use either a :ref:`Java Keystore
<server_java_keystore>` file or :ref:`Java Truststore <cli_java_truststore>`
for its TLS configuration.

If you are using keystore file, it can be copied to the client machine and used
for its TLS configuration. If you are using truststore, you can either use
default java truststores or create a custom truststore on the CLI. We do not
recommend using self-signed certificates in production.

Presto CLI Execution
^^^^^^^^^^^^^^^^^^^^

In addition to the options that are required when connecting to a Presto
coordinator that does not require LDAP authentication, invoking the CLI
with LDAP support enabled requires a number of additional command line
options. You can either use ``--keystore-*`` or ``--truststore-*`` properties
to secure TLS connection. The simplest way to invoke the CLI is with a
wrapper script.

.. code-block:: none

    #!/bin/bash

    ./presto \
    --server https://presto-coordinator.example.com:8443 \
    --keystore-path /tmp/presto.jks \
    --keystore-password password \
    --truststore-path /tmp/presto_truststore.jks \
    --truststore-password password \
    --catalog <catalog> \
    --schema <schema> \
    --user <LDAP user> \
    --password

=============================== =========================================================================
Option                          Description
=============================== =========================================================================
``--server``                    The address and port of the Presto coordinator.  The port must
                                be set to the port the Presto coordinator is listening for HTTPS
                                connections on. Presto CLI does not support using ``http`` scheme for
                                the url when using LDAP authentication.
``--keystore-path``             The location of the Java Keystore file that will be used
                                to secure TLS.
``--keystore-password``         The password for the keystore. This must match the
                                password you specified when creating the keystore.
``--truststore-path``           The location of the Java Truststore file that will be used
                                to secure TLS.
``--truststore-password``       The password for the truststore. This must match the
                                password you specified when creating the truststore.
``--user``                      The LDAP username. For Active Directory this should be your
                                ``sAMAccountName`` and for OpenLDAP this should be the ``uid`` of
                                the user. This is the username which will be
                                used to replace the ``${USER}`` placeholder pattern in the properties
                                specified in ``config.properties``.
``--password``                  Prompts for a password for the ``user``.
=============================== =========================================================================

Troubleshooting
---------------

Java Keystore File Verification
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Verify the password for a keystore file and view its contents using
:ref:`troubleshooting_keystore`.

SSL Debugging for Presto CLI
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

If you encounter any SSL related errors when running Presto CLI, you can run CLI using ``-Djavax.net.debug=ssl``
parameter for debugging. You should use the Presto CLI executable jar to enable this. Eg:

.. code-block:: none

    java -Djavax.net.debug=ssl \
    -jar \
    presto-cli-<version>-executable.jar \
    --server https://coordinator:8443 \
    <other_cli_arguments>

Common SSL errors
~~~~~~~~~~~~~~~~~

java.security.cert.CertificateException: No subject alternative names present
*****************************************************************************

This error is seen when the Presto coordinator’s certificate is invalid and does not have the IP you provide
in the ``--server`` argument of the CLI. You will have to regenerate the coordinator's SSL certificate
with the appropriate :abbr:`SAN (Subject Alternative Name)` added.

Adding a SAN to this certificate is required in cases where ``https://`` uses IP address in the URL rather
than the domain contained in the coordinator's certificate, and the certificate does not contain the
:abbr:`SAN (Subject Alternative Name)` parameter with the matching IP address as an alternative attribute.

No console from which to read password
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

If you use the command line options ``--user`` and ``--password`` along with
supplying the query statements to execute using ``--file`` or ``--execute`` command line options as below -

.. code-block:: none

    ./presto \
    --server https://presto-coordinator.example.com:8443 \
    --execute "select * from tpch.tiny.nation"
    --user <LDAP user> \
    --password

    OR

    ./presto \
    --server https://presto-coordinator.example.com:8443 \
    --file input_queries.txt
    --user <LDAP user> \
    --password > output.txt

The following error might be displayed:

.. code-block:: none

    java.lang.RuntimeException: No console from which to read password

To avoid this error, export the password using the ``PRESTO_PASSWORD`` environment variable:

.. code-block:: none

    export PRESTO_PASSWORD=<password>