8.8. Enabling GSSAPI authentication and enforcing Kerberos authentication indicators for sudo on an IdM client

Procedure

1. Open the /etc/sssd/sssd.conf configuration file.

2. Add the following entries to the [domain/<domain_name>] section.

   [domain/<domain_name>]
   pam_gssapi_services = sudo, sudo-i
   pam_gssapi_indicators_map = sudo:pkinit, sudo-i:pkinit

3. Save and close the /etc/sssd/sssd.conf file.

4. Restart the SSSD service to load the configuration changes.

   [root@idmclient ~]# systemctl restart sssd

5. Determine if you have selected the sssd authselect profile:

   # authselect current
   Profile ID: sssd

6. Optional: Select the sssd authselect profile:

   # authselect select sssd

7. Enable GSSAPI authentication:

   # authselect enable-feature with-gssapi

8. Configure the system to authenticate only users with smart cards:

   # authselect with-smartcard-required

Verification

1. Log into the host as the idm_user account and authenticate with a smart card.

   [root@idmclient ~]# ssh -l idm_user@idm.example.com localhost
   PIN for smart_card

2. Verify that you have a ticket-granting ticket as the smart card user.

   [idm_user@idmclient ~]$ klist
   Ticket cache: KEYRING:persistent:1358900015:krb_cache_TObtNMd
   Default principal: idm_user@IDM.EXAMPLE.COM
   
   Valid starting       Expires              Service principal
   02/15/2021 16:29:48  02/16/2021 02:29:48  krbtgt/IDM.EXAMPLE.COM@IDM.EXAMPLE.COM
   	renew until 02/22/2021 16:29:44

3. Display which sudo rules the idm_user account is allowed to perform.

   [idm_user@idmclient ~]$ sudo -l
   Matching Defaults entries for idmuser on idmclient:
       !visiblepw, always_set_home, match_group_by_gid, always_query_group_plugin,
       env_reset, env_keep="COLORS DISPLAY HOSTNAME HISTSIZE KDEDIR LS_COLORS",
       env_keep+="MAIL PS1 PS2 QTDIR USERNAME LANG LC_ADDRESS LC_CTYPE",
       env_keep+="LC_COLLATE LC_IDENTIFICATION LC_MEASUREMENT LC_MESSAGES",
       env_keep+="LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE",
       env_keep+="LC_TIME LC_ALL LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY KRB5CCNAME",
       secure_path=/sbin\:/bin\:/usr/sbin\:/usr/bin
   
   User idm_user may run the following commands on idmclient:
       (root) /usr/sbin/reboot

4. Reboot the machine using sudo, without specifying a password.

   [idm_user@idmclient ~]$ sudo /usr/sbin/reboot