Configuring Kerberos with OpenLDAP back-end
===========================================


 1. Set up SSL on the OpenLDAP server and client to ensure secure
    communication when the KDC service and LDAP server are on different
    machines.  ``ldapi://`` can be used if the LDAP server and KDC
    service are running on the same machine.

    A. Setting up SSL on the OpenLDAP server:

      i) Get a CA certificate using OpenSSL tools
      ii) Configure OpenLDAP server for using SSL/TLS

          For the latter, you need to specify the location of CA
          certificate location in *slapd.conf* file.

          Refer to the following link for more information:
          http://www.openldap.org/doc/admin23/tls.html

    B. Setting up SSL on OpenLDAP client:

       i) For the KDC and Admin Server, you need to do the client-side
          configuration in ldap.conf.  For example::

              TLS_CACERT /etc/openldap/certs/cacert.pem

 2. Include the Kerberos schema file (kerberos.schema) in the
    configuration file (slapd.conf) on the LDAP Server, by providing
    the location where it is stored::

       include /etc/openldap/schema/kerberos.schema

 3. Choose DNs for the :ref:`krb5kdc(8)` and :ref:`kadmind(8)` servers
    to bind to the LDAP server, and create them if necessary. These DNs
    will be specified with the **ldap_kdc_dn** and **ldap_kadmind_dn**
    directives in :ref:`kdc.conf(5)`; their passwords can be stashed
    with "``kdb5_ldap_util stashsrvpw``" and the resulting file
    specified with the **ldap_service_password_file** directive.

 4. Choose a DN for the global Kerberos container entry (but do not
    create the entry at this time).  This DN will be specified with the
    **ldap_kerberos_container_dn** directive in :ref:`kdc.conf(5)`.
    Realm container entries will be created underneath this DN.
    Principal entries may exist either underneath the realm container
    (the default) or in separate trees referenced from the realm
    container.

 5. Configure the LDAP server ACLs to enable the KDC and kadmin server
    DNs to read and write the Kerberos data.

    Sample access control information::

       access to dn.base=""
           by * read

       access to dn.base="cn=Subschema"
           by * read

       access to attrs=userPassword,userPKCS12
           by self write
           by * auth

       access to attrs=shadowLastChange
           by self write
           by * read

       # Providing access to realm container
       access to dn.subtree= "cn=EXAMPLE.COM,cn=krbcontainer,dc=example,dc=com"
           by dn.exact="cn=kdc-service,dc=example,dc=com" read
           by dn.exact="cn=adm-service,dc=example,dc=com" write
           by * none

       # Providing access to principals, if not underneath realm container
       access to dn.subtree= "ou=users,dc=example,dc=com"
           by dn.exact="cn=kdc-service,dc=example,dc=com" read
           by dn.exact="cn=adm-service,dc=example,dc=com" write
           by * none

       access to *
           by * read

    If the locations of the container and principals or the DNs of
    the service objects for a realm are changed then this
    information should be updated.

 6. Start the LDAP server as follows::

       slapd -h "ldapi:/// ldaps:///"

 7. Modify the :ref:`kdc.conf(5)` file to include LDAP specific items
    listed below::

       realms
           database_module

       dbmodules
           db_library
           db_module_dir
           ldap_kdc_dn
           ldap_kadmind_dn
           ldap_service_password_file
           ldap_servers
           ldap_conns_per_server

 8. Create the realm using :ref:`kdb5_ldap_util(8)` (see
    :ref:`ldap_create_realm`)::

       kdb5_ldap_util -D cn=admin,dc=example,dc=com create -subtrees ou=users,dc=example,dc=com -r EXAMPLE.COM -s

    Use the **-subtrees** option if the principals are to exist in a
    separate subtree from the realm container.  Before executing the
    command, make sure that the subtree mentioned above
    ``(ou=users,dc=example,dc=com)`` exists.  If the principals will
    exist underneath the realm container, omit the **-subtrees** option
    and do not worry about creating the principal subtree.

    For more information, refer to the section :ref:`ops_on_ldap`.

    The realm object is created under the
    **ldap_kerberos_container_dn** specified in the configuration file.
    This operation will also create the Kerberos container, if not
    present already.  This will be used to store information related to
    all realms.

 9. Stash the password of the service object used by the KDC and
    Administration service to bind to the LDAP server using the
    :ref:`kdb5_ldap_util(8)` **stashsrvpw** command (see
    :ref:`stash_ldap`).  The object DN should be the same as
    **ldap_kdc_dn** and **ldap_kadmind_dn** values specified in the
    :ref:`kdc.conf(5)` file::

       kdb5_ldap_util -D cn=admin,dc=example,dc=com stashsrvpw -f /etc/kerberos/service.keyfile cn=krbadmin,dc=example,dc=com

 10. Add ``krbPrincipalName`` to the indexes in slapd.conf to speed up
     the access.

With the LDAP back end it is possible to provide aliases for principal
entries.  Currently we provide no mechanism provided for creating
aliases, so it must be done by direct manipulation of the LDAP
entries.

An entry with aliases contains multiple values of the
*krbPrincipalName* attribute.  Since LDAP attribute values are not
ordered, it is necessary to specify which principal name is canonical,
by using the *krbCanonicalName* attribute.  Therefore, to create
aliases for an entry, first set the *krbCanonicalName* attribute of
the entry to the canonical principal name (which should be identical
to the pre-existing *krbPrincipalName* value), and then add additional
*krbPrincipalName* attributes for the aliases.

Principal aliases are only returned by the KDC when the client
requests canonicalization.  Canonicalization is normally requested for
service principals; for client principals, an explicit flag is often
required (e.g., ``kinit -C``) and canonicalization is only performed
for initial ticket requests.

.. seealso:: :ref:`ldap_be_ubuntu`
