Chapter 4. Configuring SSSD to use LDAP and require TLS authentication
The System Security Services Daemon (SSSD) is a daemon that manages identity data retrieval and authentication on a Red Hat Enterprise Linux host. A system administrator can configure the host to use a standalone LDAP server as the user account database. The administrator can also specify the requirement that the connection with the LDAP server must be encrypted with a TLS certificate.
The SSSD configuration option to enforce TLS, ldap_id_use_start_tls, defaults to false. When using ldap:// without TLS for identity lookups, it can pose a risk for an attack vector, namely a man-in-the-middle (MITM) attack which could allow you to impersonate a user by altering, for example, the UID or GID of an object returned in an LDAP search.
Ensure that your setup operates in a trusted environment and decide if it is safe to use unencrypted communication for id_provider = ldap. Note id_provider = ad and id_provider = ipa are not affected as they use encrypted connections protected by SASL and GSSAPI.
If it is not safe to use unencrypted communication, you should enforce TLS by setting the ldap_id_use_start_tls option to true in the /etc/sssd/sssd.conf file.
4.1. An OpenLDAP client using SSSD to retrieve data from LDAP in an encrypted way
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 here.
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.
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