How can i authenticate via OpenLDAP using SSSD on Ubuntu 20.04? Well, this guide will take you through how to install and configure SSSD for LDAP authentication on Ubuntu 20.04. SSSD (System Security Services Daemon) is a system service to access remote directories and authentication mechanisms such as an LDAP directory, an Identity Management (IdM) or Active Directory (AD) domain, or a Kerberos realm.
Configure SSSD for LDAP Authentication on Ubuntu 20.04
Assuming you already have a running OpenLDAP server, proceed with this guide to learn how to install and configure SSSD for LDAP authentication.
Run System Update
Ensure that your system package cache is up-to-date.
apt update
Install SSSD on Ubuntu 20.04
To install SSSD and other required SSSD tools on Ubuntu 20.04, run the command below;
apt install sssd libpam-sss libnss-sss
Configure SSSD for OpenLDAP Authentication on Ubuntu 20.04
Create SSSD configuration file
SSSD do not ship with any configuration file by default. As such, you need to create your configuration file that defines your LDAP authentication specifics.
vim /etc/sssd/sssd.conf
Below is our sample configuration options;
[sssd] services = nss, pam config_file_version = 2 domains = default [nss] [pam] offline_credentials_expiration = 60 [domain/default] ldap_id_use_start_tls = True cache_credentials = True ldap_search_base = dc=ldapmaster,dc=kifarunix-demo,dc=com id_provider = ldap auth_provider = ldap chpass_provider = ldap access_provider = ldap ldap_uri = ldap://ldapmaster.kifarunix-demo.com ldap_default_bind_dn = cn=readonly,ou=system,dc=ldapmaster,dc=kifarunix-demo,dc=com ldap_default_authtok = [email protected] ldap_tls_reqcert = demand ldap_tls_cacert = /etc/ssl/certs/ldapcacert.crt ldap_tls_cacertdir = /etc/ssl/certs ldap_search_timeout = 50 ldap_network_timeout = 60 ldap_access_order = filter ldap_access_filter = (objectClass=posixAccount)
Check the highlighted lines above and replace their values appropriately.
For a comprehensive description of options used above, refer to man sssd.conf and man sssd-ldap.
Once you are done with your configurations, save and exit the file.
Install OpenLDAP Server CA Certificate on Ubuntu 20.04 LDAP client
SSSD authentication can only work over an encrypted communication channel. Therefore, your OpenLDAP server must be configured SSL/TLS.
If you have done this already, download the CA certificate from the LDAP server to the LDAP client by executing the command below;
openssl s_client -connect ldapmaster.kifarunix-demo.com:636 -showcerts < /dev/null | openssl x509 -text | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p'
if you are downloading the certificates from an OpenLDAP server listening on STARTTLS (port 389/{tcp,udp}), use the command below instead;
openssl s_client -connect ldapmaster.kifarunix-demo.com:389 -starttls ldap -showcerts < /dev/null | openssl x509 -text | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p'
Copy the certificate part;
-----BEGIN CERTIFICATE----- MIIDvzCCAqegAwIBAgIUc8imlOVhEej453dXtvacn7krg1MwDQYJKoZIhvcNAQEL BQAwbzELMAkGA1UEBhMCS0UxDDAKBgNVBAgMA05haTEMMAoGA1UEBwwDTWFpMRww GgYDVQQKDBNEZWZhdWx0IENvbXBhbnkgTHRkMSYwJAYDVQQDDB1sZGFwbWFzdGVy ... ... ExJaMa6cJkIFmepJ6wGvk33DiLRZrAKT2/11yswYm16mdpUynmx6pZvZizjxkq+c hegnowyEG4db/NktY44v2ryIQdEclnKmhk23vmhgZxl1IUgev2tc//JWPE9dXuP8 Uy7ivNi2PL6mBwxMpyi0zTopqTXSvi54APm48dd0JPsGLTIgPMc1WvaN7TsUeIBs Igf9K1e9M0Q+j2XEsTeCYVU/v0Jt0kER0+V/NM0IrDOX+6kRz6DNsZrwcMEf5Yvp ARWZ -----END CERTIFICATE-----
As per our SSSD configuration, the LDAP CA certificate file is stored as /etc/ssl/certs/cacert.crt. Therefore, copy the certificate above and place it in this file;
vim /etc/ssl/certs/ldapcacert.crt
-----BEGIN CERTIFICATE-----
MIIDvzCCAqegAwIBAgIUc8imlOVhEej453dXtvacn7krg1MwDQYJKoZIhvcNAQEL
BQAwbzELMAkGA1UEBhMCS0UxDDAKBgNVBAgMA05haTEMMAoGA1UEBwwDTWFpMRww
GgYDVQQKDBNEZWZhdWx0IENvbXBhbnkgTHRkMSYwJAYDVQQDDB1sZGFwbWFzdGVy
...
...
ExJaMa6cJkIFmepJ6wGvk33DiLRZrAKT2/11yswYm16mdpUynmx6pZvZizjxkq+c
hegnowyEG4db/NktY44v2ryIQdEclnKmhk23vmhgZxl1IUgev2tc//JWPE9dXuP8
Uy7ivNi2PL6mBwxMpyi0zTopqTXSvi54APm48dd0JPsGLTIgPMc1WvaN7TsUeIBs
Igf9K1e9M0Q+j2XEsTeCYVU/v0Jt0kER0+V/NM0IrDOX+6kRz6DNsZrwcMEf5Yvp
ARWZ
-----END CERTIFICATE-----Verify the validity of the certificate;
openssl s_client -connect ldapmaster.kifarunix-demo.com:389 -CAfile /etc/ssl/certs/cacert.crt
If you get, Verification: OK or Verify return code: 0 (ok) on the command output, then you are all set.
Next, open the /etc/ldap/ldap.conf and replace the value of TLS_CACERT with the path to the CA certificate created above.
vim /etc/ldap/ldap.conf
... # TLS certificates (needed for GnuTLS) #TLS_CACERT /etc/ssl/certs/ca-certificates.crt TLS_CACERT /etc/ssl/certs/ldapcacert.crt
Save and close the configuration file.
Set Proper Permissions on SSSD configurations
After that, assign the root user read/write access to /etc/sssd/.
chmod 600 -R /etc/sssd
Restart SSSD service
systemctl restart sssd
Check the status of SSSD to ensure that it is running.
systemctl status sssd
● sssd.service - System Security Services Daemon
Loaded: loaded (/lib/systemd/system/sssd.service; enabled; vendor preset: enabled)
Active: active (running) since Fri 2020-05-08 11:38:21 EAT; 6s ago
Main PID: 7004 (sssd)
Tasks: 4 (limit: 2319)
Memory: 34.0M
CGroup: /system.slice/sssd.service
├─7004 /usr/sbin/sssd -i --logger=files
├─7020 /usr/libexec/sssd/sssd_be --domain default --uid 0 --gid 0 --logger=files
├─7021 /usr/libexec/sssd/sssd_nss --uid 0 --gid 0 --logger=files
└─7022 /usr/libexec/sssd/sssd_pam --uid 0 --gid 0 --logger=files
May 08 11:38:20 koromicha systemd[1]: Starting System Security Services Daemon...
May 08 11:38:20 koromicha sssd[7004]: Starting up
May 08 11:38:21 koromicha sssd[be[7020]: Starting up
May 08 11:38:21 koromicha sssd[7021]: Starting up
May 08 11:38:21 koromicha sssd[7022]: Starting up
May 08 11:38:21 koromicha systemd[1]: Started System Security Services Daemon.Enable SSSD to run on system boot;
systemctl enable sssd
Configure Auto-Home Directory Creation
To enable automatic creation of user’s home directory on first login, you need to configure the PAM modules (pam_mkhomedir.so) as shown below.
Open the /etc/pam.d/common-session configuration file and edit is ad follows;
vim /etc/pam.d/common-session
Add the line below just below the line, session optional pam_sss.so.
session required pam_mkhomedir.so skel=/etc/skel/ umask=0022
... # The pam_umask module will set the umask according to the system default in # /etc/login.defs and user settings, solving the problem of different # umask settings with different shells, display managers, remote sessions etc. # See "man pam_umask". session optional pam_umask.so # and here are more per-package modules (the "Additional" block) session required pam_unix.so session optional pam_sss.so session required pam_mkhomedir.so skel=/etc/skel/ umask=0022 session optional pam_systemd.so # end of pam-auth-update config ...
Save and exit the configuration file.
Verify SSSD OpenLDAP authentication
The installation and configuration of SSSD is done. To verify that you can login, try to authenticate against your LDAP server.
In this guide, we have two users, janedoe and johndoe, created on our OpenLDAP Server for demo purposes.
ldapsearch -H ldapi:/// -Y EXTERNAL -b "ou=people,dc=ldapmaster,dc=kifarunix-demo,dc=com" dn -LLL -Q
dn: ou=people,dc=ldapmaster,dc=kifarunix-demo,dc=com dn: uid=janedoe,ou=people,dc=ldapmaster,dc=kifarunix-demo,dc=com dn: uid=johndoe,ou=people,dc=ldapmaster,dc=kifarunix-demo,dc=com
These information about the users above should now be printable on the Ubuntu 20.04 ldap client.
[email protected]:~# id johndoe
uid=10000(johndoe) gid=10000(johndoe) groups=10000(johndoe)
[email protected]:~# id janedoe
uid=10010(janedoe) gid=10010(janedoe) groups=10010(janedoe)
To demo the SSSD LDAP authentication, we will use both SSH and GUI based authentication;
Verify SSH Authentication via OpenLDAP SSSD
ssh [email protected]
The authenticity of host 'ubuntu20 (192.168.58.19)' can't be established. ECDSA key fingerprint is SHA256:gN94vPFvyZ3Rdeb/+7R+0QJy9S4MdWmgJyEShIG9YgE. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added 'ubuntu20' (ECDSA) to the list of known hosts. [email protected]'s password: Creating directory '/home/johndoe'. Welcome to Ubuntu 20.04 LTS (GNU/Linux 5.4.0-29-generic x86_64) * Documentation: https://help.ubuntu.com * Management: https://landscape.canonical.com * Support: https://ubuntu.com/advantage * Ubuntu 20.04 LTS is out, raising the bar on performance, security, and optimisation for Intel, AMD, Nvidia, ARM64 and Z15 as well as AWS, Azure and Google Cloud. https://ubuntu.com/blog/ubuntu-20-04-lts-arrives 13 updates can be installed immediately. 9 of these updates are security updates. To see these additional updates run: apt list --upgradable The programs included with the Ubuntu system are free software; the exact distribution terms for each program are described in the individual files in /usr/share/doc/*/copyright. Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by applicable law. [email protected]:~$
Verify GUI authentication via OpenLDAP SSSD
Reboot your Ubuntu 20.04 desktop after SSSD setup and and verify authentication.
Once it boots, on the GDM login interface, click Not listed to enter your OpenLDAP username and password.
Upon successful login, you land on Ubuntu 20.04 desktop.
And there you go. You have successfully installed and configured SSSD for LDAP Authentication on Ubuntu 20.04.
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