FreeIPA

FreeIPA is an open-source Identity, Policy and Audit (IPA) suite, sponsored by Red Hat, which provides services similar to Microsoft's Active Directory

Manual configuration as IPA client

Make sure your clocks are synchronized. Kerberos will not work otherwise. NTP is recommended.

Instead of using ipa-client-install script for automated client configuration and enrollment, the following sections describe a manual procedure for enrolling the client client.example.com to the FreeIPA server ipaserver.example.com in the example.com domain.

Configure SSSD and Kerberos

Follow the LDAP auth instructions to setup SSSD. Use a SSSD configuration similar to the following, substituting the requisite fields:

/etc/sssd/sssd.conf

[sssd]
config_file_version = 2
services = nss, pam, sudo, ssh
domains = EXAMPLE.COM
#debug_level = 9

[domain/EXAMPLE.COM]
#debug_level = 9
cache_credentials = true
krb5_store_password_if_offline = true
id_provider = ipa
auth_provider = ipa
access_provider = ipa
chpass_provider = ipa
#ipa_domain=example.com  # Optional if you set SRV records in DNS
#ipa_server=ipaserver.example.com  # Optional if you set SRV records in DNS
ipa_hostname=client.example.com

Configure pam in similar way to LDAP, replacing pam_ldap.so with pam_sss.so.

Create an /etc/krb5.conf file for your domain:

/etc/krb5.conf

[libdefaults]
        default_realm = EXAMPLE.COM
        dns_lookup_realm = false
        dns_lookup_kdc = false
        rdns = false
        ticket_lifetime = 24h
        forwardable = yes
        #allow_weak_crypto = yes  # Only if absolutely necessary. Currently FreeIPA supports strong crypto.

[realms]
        EXAMPLE.COM = {
                admin_server = freeipaserver.example.com
                kdc = freeipaserver.example.com:749
                default_admin = example.com
        }

[domain_realm]
        example.com = EXAMPLE.COM
        .example.com = EXAMPLE.COM

[logging]
        default = FILE:/var/log/krb5libs.log
        kdc = FILE:/var/log/krb5kdc.log
        admin_server = FILE:/var/log/kadmin.log

Enroll the client

On FreeIPA server, add the client to the IPA server (From Fedora documentation^{[dead link 2023-04-23 ⓘ]}):

1. Login and request and admin session

   $ kinit admin

2. Create a host entry

   $ ipa host-add --force --ip-address=192.168.166.31 client.example.com

   if the host does not have a static IP, use

   $ ipa host-add client.example.com

3. Set the client to be managed by IPA

   $ ipa host-add-managedby --hosts=ipaserver.example.com client.example.com

4. Generate keytab for the client

   # ipa-getkeytab -s ipaserver.example.com  -p host/client.example.com -k /tmp/client1.keytab

Install the keytab on the client:

$ scp user@ipaserver.example.com:/tmp/client1.keytab krb5.keytab
# mv krb5.keytab /etc/krb5.keytab

SSH integration

authorized_keys

You can configure SSHD to fetch users SSH public key from the LDAP directory by uncommenting those lines in /etc/ssh/sshd_config:

AuthorizedKeysCommand /usr/bin/sss_ssh_authorizedkeys
AuthorizedKeysCommandUser nobody

Then restart sshd.service.

You can add your ssh key to your FreeIPA user account through the web interface or use the -sshpubkey='ssh-rsa AAAA...' argument to the ipa user-mod or ipa user-create commands.

Test it:

$ sudo -u nobody sss_ssh_authorizedkeys <username>

You should see your ssh public key on standard output and no error message on standard error.

known_hosts

You can configure SSH to fetch hosts public key information from their directory entries in FreeIPA by adding those lines in /etc/ssh/ssh_config:

GlobalKnownHostsFile /var/lib/sss/pubconf/known_hosts
ProxyCommand /usr/bin/sss_ssh_knownhostsproxy -p %p %h

Kerberos/GSS API Authentication

You can enabled Kerberos / GSS API Authentication for the SSH Client to FreeIPA member hosts by uncommenting and changing the following lines in /etc/ssh/ssh_config:

GSSAPIAuthentication yes
GSSAPIDelegateCredentials yes

See also

• Wikipedia:FreeIPA
• Manually Configuring a Linux Client^{[dead link 2023-04-23 ⓘ]} from the FreeIPA user guide
• Freeipa30_SSSD_OpenSSH_integration.pdf^{[dead link 2023-07-30 ⓘ]}