4.2. Configuring SSSD to use LDAP and require TLS authentication

Procédure

1. Install the requisite packages:

   # dnf -y install openldap-clients sssd sssd-ldap oddjob-mkhomedir

2. Switch the authentication provider to sssd:

   # authselect select sssd with-mkhomedir

3. Copy the core-dirsrv.ca.pem file containing the root CA signing certificate chain from the Certificate Authority that issued the OpenLDAP server’s SSL/TLS certificate into the /etc/openldap/certs folder.

   # cp core-dirsrv.ca.pem /etc/openldap/certs

4. Add the URL and suffix of your LDAP server to the /etc/openldap/ldap.conf file:

   URI ldap://ldap-server.example.com/
   BASE dc=example,dc=com

5. In the /etc/openldap/ldap.conf file, add a line pointing the TLS_CACERT parameter to /etc/openldap/certs/core-dirsrv.ca.pem:

   # 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

6. In the /etc/sssd/sssd.conf file, add your environment values to the ldap_uri and ldap_search_base parameters and set the ldap_id_use_start_tls to True:

   [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
   …

7. In /etc/sssd/sssd.conf, specify the TLS authentication requirement by modifying the ldap_tls_cacert and ldap_tls_reqcert values in the [domain] section:

   …
   cache_credentials = True
   ldap_tls_cacert = /etc/openldap/certs/core-dirsrv.ca.pem
   ldap_tls_reqcert = hard
   …

8. Change the permissions on the /etc/sssd/sssd.conf file:

   # chmod 600 /etc/sssd/sssd.conf

9. Restart and enable the SSSD service and the oddjobd daemon:

   # systemctl restart sssd oddjobd
   # systemctl enable sssd oddjobd

10. (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 to communicate using these protocols:

    # update-crypto-policies --set LEGACY

    For more details, see the Strong crypto defaults in RHEL 8 and deprecation of weak crypto algorithms Knowledgebase article on the Red Hat Customer Portal and the update-crypto-policies(8) man page.