Configuring LDAP Auth for Linux
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As a central source of user information, the EmpowerID Virtual Directory Server (VDS) can be leveraged as an authentication or identity provider for Linux servers. By making a few configuration changes, organizations can give users single sign-on capabilities to one or more Linux machines without requiring those users have accounts on those machines. In this way, organizations can simplify the processes for managing Linux users as the need for creating and maintaining accounts across multiple systems is negated. With the EmpowerID VDS, this information can be fully managed from one locationāthe EmpowerID Identity Warehouse.
Configuring LDAP authentication for Linux involves making a few configuration changes on each Linux machine for which you want to enable the feature. These changes include the following:
- Installing the System Security Services Daemon (SSSD)
- Configuring NSS services for SSSD
- Editing the LDAP configuration file for your LDAP domain
- Modifying PAM files
- Creating a working SSSD configuration file
- Starting the SSSD service
Prerequisites
Before configuring LDAP authentication for your Linux servers, you should install the EmpowerID Virtual Directory server. For more information, see Installing and Configuring the EmpowerID Virtual Directory Server.
To configure LDAP Auth for Linux
This topic demonstrates how to configure LDAP authentication for Debian/Ubuntu and CentOS/RedHat distributions.
Log into the target Linux server as an administrative user and install SSSD for your particular Linux distribution.
Debian/Ubuntusudo apt-get install sssd sssd-tools
CentOS/RedHatsudo yum install sssd sssd-tools
Next, open the nsswitch.conf file and verify SSSD. Change the file as needed so that you see the following values:
Debian/Ubuntusudo vi /etc/nsswitch.conf passwd: compat sss group: compat sss shadow: compat sss ... services: db files sss
CentOS/RedHatsudo vi /etc/nsswitch.conf passwd: files sss group: files sss shadow: files sss ... services: files sss ...
Open the ldap.conf file and add the following to the end of the file to instruct SSSD to use the specified LDAP directory as the auth provider. This information consists of the mechanism for TLS, the URI and port for your LDAP server, as well as the search base.
Be sure to replaceĀ serverFQDN:port with the FQDN and port of your EmopowerID LDAP server.
Debian/Ubuntusudo vi /etc/ldap/ldap.conf TLS_CACERT /etc/ssl/certs/ca-certificates.crt URI ldaps://serverFQDN:port/ BASE o=empowerid
CentOS/RedHatsudo vi /etc/openldap/ldap.conf TLS_CACERT /etc/ssl/certs/ca-certificates.crt URI ldaps://serverFQDN:port/ BASE o=empowerid
Next, configure PAM files for SSSD. In Debian/Ubuntu, this involves multiple files, whereas in CentOS/RedHat, you edit a single PAM file.
The following examples include instructional comments. You can exclude these when altering your files.
Debian/Ubuntusudo vi /etc/pam.d/common-account # Add the following to the end of the file account [default-bad success=ok user_unknow=ignore] pam_sss.so sudo vi /etc/pam.d/common-auth # Add the following after pam_unix auth [success=1 default=ignore] pam_sss.so use_first_pass sudo vi /etc/pam.d/common-password # Add the following to the beginning of the Session section session required pam_mkhomedir.so umask=0022 skel=/etc/skel/ # Add the following after pam_unix.so session optional pam_sss.so
CentOS/RedHatcp /etc/pam.d/system-auth-ac /etc/pam.d/system-auth-ac.orig && cp /etc/pam.d/password-auth-ac /etc/pam.d/password-auth-ac.orig sudo vi /etc/pam.d/system-auth-ac # In the auth section, after pam_succedd_if add the following: auth sufficient pam_sss.so forward_pass # In the account section, after pam_succeed_if add the following: account [default=bad success=ok user_unknown=ignore] pam_sss.so # In the password section, after pam_unix add the following: password sufficient pam_sss.so use_authtok # At the beginning of the session section, ensure the following is present: session required pam_mkhomedir.so umask=0022 skel=/etc/skel/ # In the session section, after pam_unix add the following: session optional pam_sss.so cp -f /etc/pam.d/system-auth-ac /etc/pam.d/password-auth-ac
Create an sssd.config file and give the sudo user read and write permissions to it. The procedure is the same for each distribution discussed in this topic.
sudo vi /etc/sssd/sssd.conf sudo chmod 0600 /etc/sssd/sssd.conf
Open the sssd.conf file and add the following content to it. When doing so, replace serverFQDN:port with the FQDN and port of your EmpowerID LDAP server.
[sssd] config_file_version = 2 services = nss, pam domains = EmpowerID [nss] [pam] [domain/EmpowerID] # Debug and Enumeration should only be on for testing/troubleshooting # debug_level = 4 # enumerate = True case_sensitive = False auth_provider = ldap id_provider = ldap chpass_provider = ldap # Set access_provder to simple to allow everyone. # Alternately, use ldap and set ldap_access_filter below # access_provider = ldap access_provider = simple # Set LDAP servers here ldap_uri = ldaps://serverFQDN:port # Set the search bases ldap_search_base = o=empowerid ldap_user_search_base = cn=people,o=empowerid # bind credentials # Run sss_obfuscate to make the password less readable # ldap_default_bind_dn = cn=proxyuser,ou=Service Accounts,o=empowerid # ldap_default_authtok = p@$$word # ldap_default_authtok_type = password # Set any attribute mappings needed here ldap_user_object_class = eidPerson ldap_user_name = uid ldap_user_uid_number = uidNumber ldap_user_gid_number = gidNumber ldap_user_fullname = gecos ldap_user_home_directory = homeDirectory ldap_group_object_class = eidGroup ldap_group_name = cn # If access_provider = ldap above, set the filter here to allow access # EXAMPLE: Allow users in server1 allow group # ldap_access_filter = memberof=cn=server1 allow,ou=server access,o=empowerid # Only allow Linus Torvalds or Stallman access to this server # ldap_access_filter = (|(uid=ltorvalds)(uid=rms))
Turn off SELinux on CentOS and RedHat.
setenforce 0
Start the SSSD service.
Debian/Ubuntusudo service sssd start
CentOS/RedHatsudo systemctl start sssd