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

.. versionadded:: Jewel

You can delegate the Ceph Object Gateway authentication to an LDAP server.

How it works
============

The Ceph Object Gateway extracts the users LDAP credentials from a token. A
search filter is constructed with the user name. The Ceph Object Gateway uses
the configured service account to search the directory for a matching entry. If
an entry is found, the Ceph Object Gateway attempts to bind to the found
distinguished name with the password from the token. If the credentials are
valid, the bind will succeed, and the Ceph Object Gateway will grant access and
radosgw-user will be created with the provided username.

You can limit the allowed users by setting the base for the search to a
specific organizational unit or by specifying a custom search filter, for
example requiring specific group membership, custom object classes, or
attributes.

The LDAP credentials must be available on the server to perform the LDAP
authentication. Make sure to set the ``rgw`` log level low enough to hide the
base-64-encoded credentials / access tokens.

Requirements
============

- **LDAP or Active Directory:** A running LDAP instance accessible by the Ceph
  Object Gateway
- **Service account:** LDAP credentials to be used by the Ceph Object Gateway
  with search permissions
- **User account:** At least one user account in the LDAP directory
- **Do not overlap LDAP and local users:** You should not use the same user
  names for local users and for users being authenticated by using LDAP. The
  Ceph Object Gateway cannot distinguish them and it treats them as the same
  user.

Sanity checks
=============

Use the ``ldapsearch`` utility to verify the service account or the LDAP connection:

::

  # ldapsearch -x -D "uid=ceph,ou=system,dc=example,dc=com" -W \
  -H ldaps://example.com -b "ou=users,dc=example,dc=com" 'uid=*' dn

.. note:: Make sure to use the same LDAP parameters like in the Ceph configuration file to
          eliminate possible problems.

Configuring the Ceph Object Gateway to use LDAP authentication
==============================================================

The following parameters in the Ceph configuration file are related to the LDAP
authentication:

- ``rgw_s3_auth_use_ldap``: Set this to ``true`` to enable S3 authentication with LDAP
- ``rgw_ldap_uri``:  Specifies the LDAP server to use. Make sure to use the
  ``ldaps://<fqdn>:<port>`` parameter to not transmit clear text credentials
  over the wire.
- ``rgw_ldap_binddn``: The Distinguished Name (DN) of the service account used
  by the Ceph Object Gateway
- ``rgw_ldap_secret``: Path to file containing credentials for ``rgw_ldap_binddn``
- ``rgw_ldap_searchdn``: Specifies the base in the directory information tree
  for searching users. This might be your users organizational unit or some
  more specific Organizational Unit (OU).
- ``rgw_ldap_dnattr``: The attribute being used in the constructed search
  filter to match a username. Depending on your Directory Information Tree
  (DIT) this would probably be ``uid`` or ``cn``. The generated filter string
  will be, e.g., ``cn=some_username``.
- ``rgw_ldap_searchfilter``: If not specified, the Ceph Object Gateway
  automatically constructs the search filter with the ``rgw_ldap_dnattr``
  setting. Use this parameter to narrow the list of allowed users in very
  flexible ways. Consult the *Using a custom search filter to limit user access
  section* for details

Using a custom search filter to limit user access
=================================================

There are two ways to use the ``rgw_search_filter`` parameter:

Specifying a partial filter to further limit the constructed search filter
--------------------------------------------------------------------------

An example for a partial filter:

::

  "objectclass=inetorgperson"

The Ceph Object Gateway will generate the search filter as usual with the
user name from the token and the value of ``rgw_ldap_dnattr``. The constructed
filter is then combined with the partial filter from the ``rgw_search_filter``
attribute. Depending on the user name and the settings the final search filter
might become:

::

  "(&(uid=hari)(objectclass=inetorgperson))"

So user ``hari`` will only be granted access if he is found in the LDAP
directory, has an object class of ``inetorgperson``, and did specify a valid
password.

Specifying a complete filter
----------------------------

A complete filter must contain a ``@USERNAME@`` token which will be substituted
with the user name during the authentication attempt. The ``rgw_ldap_dnattr``
parameter is not used anymore in this case. For example, to limit valid users
to a specific group, use the following filter:

::

  "(&(uid=@USERNAME@)(memberOf=cn=ceph-users,ou=groups,dc=mycompany,dc=com))"

.. note:: Using the ``memberOf`` attribute in LDAP searches requires server side
          support from you specific LDAP server implementation.

Generating an access token for LDAP authentication
==================================================

The ``radosgw-token`` utility generates the access token based on the LDAP
user name and password. It will output a base-64 encoded string which is the
access token.

::

  # export RGW_ACCESS_KEY_ID="<username>"
  # export RGW_SECRET_ACCESS_KEY="<password>"
  # radosgw-token --encode

.. important:: The access token is a base-64 encoded JSON struct and contains
               the LDAP credentials as a clear text.

Alternatively, users can also generate the token manually by base-64-encoding
this JSON snippet, if they do not have the ``radosgw-token`` tool installed.

::

  {
    "RGW_TOKEN": {
      "version": 1,
      "type": "ldap",
      "id": "your_username",
      "key": "your_clear_text_password_here"
    }
  }

Using the access token
======================

Use your favorite S3 client and specify the token as the access key in your
client or environment variables.

::

  # export AWS_ACCESS_KEY_ID=<base64-encoded token generated by radosgw-token>
  # export AWS_SECRET_ACCESS_KEY="" # define this with an empty string, otherwise tools might complain about missing env variables.

.. important:: The access token is a base-64 encoded JSON struct and contains
               the LDAP credentials as a clear text. DO NOT share it unless
               you want to share your clear text password!
