Chapter 3. Configuring SSSD to use LDAP and require TLS authentication
3.1. An OpenLDAP client using SSSD to retrieve data from LDAP in an encrypted way
The System Security Services Daemon (SSSD) is a daemon that manages identity data retrieval and authentication on a RHEL 8 host. A system administrator can configure the SSSD on the host to use a standalone LDAP server database as the user account database. Examples of an LDAP server include the OpenLDAP server and the Red Hat 389 Directory Server. In this chapter, the scenario also includes the requirement that the connection with the LDAP server must be encrypted with a TLS certificate.
The authentication method of the LDAP objects can be either a Kerberos password or an LDAP password. Note that the questions of authentication and authorization of the LDAP objects are not addressed in this chapter.
Configuring SSSD with LDAP is a complex procedure requiring a high level of expertise in SSSD and LDAP. Consider using an integrated and automated solution such as Active Directory or Red Hat Identity Management (IdM) instead. For details about IdM, see Planning Identity Management.
3.2. Configuring SSSD to use LDAP and require TLS authentication
Complete this procedure to configure your Red Hat Enterprise Linux (RHEL) system as an OpenLDAP client and to specify the following client configuration:
- The RHEL system uses an OpenLDAP server as the user account database.
- The RHEL system uses the System Security Services Daemon (SSSD) as the service responsible for retrieving the user data.
- The RHEL system uses a TLS certificate to encrypt the connection with the OpenLDAP server.
You can alternatively use the steps in this procedure to configure your RHEL system as a client of the Red Hat 389 Directory Server.
- The OpenLDAP server is installed.
- On the host you want to become a client of the OpenLDAP server, you have root credentials.
On the host you want to become a client of the OpenLDAP server, the
/etc/sssd/sssd.conffile has been created and configured to specify
You have the TLS certificate of the OpenLDAP server stored in a
Install the requisite packages:
# dnf -y install openldap-clients sssd sssd-ldap oddjob-mkhomedir
Switch the authentication provider to
# authselect select sssd with-mkhomedir
core-dirsrv.ca.pemfile containing the LDAP server certificate into the
Add the URL and suffix of your LDAP server to the
URI ldap://ldap-server.example.com/ BASE dc=example,dc=com
/etc/openldap/ldap.conf, specify the location of the OpenLDAP server certificate by adding a line pointing the TLS_CACERT parameter to
# When no CA certificates are specified the Shared System Certificates # are in use. In order to have these available along with the ones specified # by TLS_CACERTDIR one has to include them explicitly: TLS_CACERT /etc/openldap/certs/core-dirsrv.ca.pem
/etc/sssd/sssd.conffile, add your environment values to the
[domain/default] id_provider = ldap autofs_provider = ldap auth_provider = ldap chpass_provider = ldap ldap_uri = ldap://ldap-server.example.com/ ldap_search_base = dc=example,dc=com ldap_id_use_start_tls = True cache_credentials = True ldap_tls_cacertdir = /etc/openldap/certs ldap_tls_reqcert = allow [sssd] services = nss, pam, autofs domains = default [nss] homedir_substring = /home …
/etc/sssd/sssd.conf, specify the TLS authentication requirement by modifying the
ldap_tls_reqcertvalues in the
… cache_credentials = True ldap_tls_cacert = /etc/openldap/certs/core-dirsrv.ca.pem ldap_tls_reqcert = hard …
Change the permissions on the
# chmod 600 /etc/sssd/sssd.conf
Restart and enable SSSD:
# systemctl restart sssd oddjobd # systemctl enable sssd oddjobd
(Optional) If your LDAP server uses the deprecated TLS 1.0 or TLS 1.1 protocols, switch the system-wide cryptographic policy on the client system to the LEGACY level to allow RHEL 8 to communicate using these protocols:
# update-crypto-policies --set LEGACY
For more details, see the Deprecated Functionality section in the RHEL 8.0 Release Notes.
Verify login by using the
idcommand and specifying an LDAP user:
# id ldap_user uid=17388(ldap_user) gid=45367(sysadmins) groups=45367(sysadmins),25395(engineers),10(wheel),1202200000(admins)
The system administrator can now query users from LDAP using the
id command. The command returns a correct user ID and group membership.