SSSD/Kerberos/LDAP Authentication

Install Required Packages

1. RHEL6: Install the following packages.
   1. # yum install sssd krb5-workstation samba-common authconfig oddjob oddjob-mkhomedir openldap-clients ipa-client sssd-common krb5-devel
2. RHEL7: Install the following packages
   1. # yum install sssd krb5-workstation samba-common authconfig oddjob oddjob-mkhomedir openldap-clients sssd-libwbclient sssd-tools ipa-client sssd-common krb5-devel
3. UBUNTU: Install the following packages
   1. $ sudo apt-get install krb5-user krb5-config samba sssd ntp nscd libpam-sss libnss-sss sssd-tools sssd-ad libpam-modules

Configure Kerberos

1. Gather the list of KDCs for the realm, the KDCs are bold italic.
   1. # nslookup -type=SRV _kerberos._tcp.<domain.com>

      1. Output of previous command:

         Server: <ip address>

         Address: <ip address>#53

         
         _kerberos._tcp.<domain in lowercase> service = 0 100 88 dc1.<domain.com>.

         _kerberos._tcp.<domain in lowercase> service = 0 100 88 dc2.<domain.com>.

         _kerberos._tcp.<domain in lowercase> service = 0 100 88 dc3.<domain.com>.

         _kerberos._tcp.<domain in lowercase> service = 0 100 88 dc4.<domain.com>.

2. Create a backup of the /etc/krb5.conf file.
   1. # cp -p /etc/krb5.conf{,.bak}
   2. Modify the /etc/krb5.conf file as follows, changes are bold italic.

      1. [logging]

         default = FILE:/var/log/krb5libs.log

         kdc = FILE:/var/log/krb5kdc.log

         admin_server = FILE:/var/log/kadmind.log

         
         [libdefaults]

         default_realm = <DOMAIN.COM>

         dns_lookup_realm = false

         dns_lookup_kdc = false

         ticket_lifetime = 24h

         renew_lifetime = 7d

         forwardable = true

         
         [realms]

         <DOMAIN.COM> = {

         kdc = dc1.<DOMAIN.COM>

         kdc = dc2.<DOMAIN.COM>

         kdc = dc3.<DOMAIN.COM>

         kdc = dc4.<DOMAIN.COM>

         admin_server = <DOMAIN.COM>

         }

         
         [domain_realm]

         .<domain.com> = <DOMAIN.COM>

         <domain.com> = <DOMAIN.COM>

Configure Samba

1. Create a backup of the /etc/samba/smb.conf file.
   1. # cp -p /etc/samba/smb.conf{,.bak}
2. Modify the /etc/samba/smb.conf file as follows, changes are are in bold italic.

   1. [global]

             workgroup = <DOMAIN>

      ;      server string = Samba Server Version %v

              .

              .

      ;      security = user

      ;      passdb backend = tdbsam

              .

              .

             client signing = yes

             client use spnego = yes

             kerberos method = secrets and keytab

             security = ads

             passdb backend = tdbsam

             realm = <DOMAIN.COM>

              .

              .

      ;      load printers = yes

      ;      cups options = raw

              .

              .

      ;[printers]

      ;      comment = All Printers

      ;      path = /var/spool/samba

      ;      browseable = no

      ;      guest ok = no

      ;      writable = no

      ;      printable = yes

3. Verify the Samba configuration.
   1. # testparm
4. The output should be similar to

   1. [global]

             workgroup = <DOMAIN>

             realm = <DOMAIN.COM>

             security = ADS

             kerberos method = secrets and keytab

             log file = /var/log/samba/log.%m

             max log size = 50

             client signing = required

             idmap config * : backend = tdb

             
      [homes]

             comment = Home Directories

             read only = No

             browseable = No

Kerberos Ticket

1. Obtain and verify a new ticket using the new Kerberos configuration.
   1. # kinit <admin account>
      1. Enter the password.
2. Verify the ticket
   1. ;# klist
      1. The output should be similar to:

         1. Ticket cache: FILE:/tmp/krb5cc_0

            Default principal: <admin account>@<DOMAIN.COM>

            
            Valid starting     Expires            Service principal

            03/31/16 07:17:39  03/31/16 17:17:35  krbtgt/<DOMAIN.COM>@<DOMAIN.COM>

                     renew until 04/07/16 07:17:39

Register Server with Active Directory

1. Join AD and obtain a keytab
   1. # net ads join -k createcomputer="Computer-Groups/Servers/Linux"
2. Verify the keytab
   1. # klist -k

      1. The output should be similar to:

         Keytab name: FILE:/etc/krb5.keytab

         KVNO Principal

         ---- --------------------------------------------------------------------------

            2 host/<servername.domain.com@DOMAIN.COM>

            2 host/<servername.domain.com@DOMAIN.COM>

            2 host/<servername.domain.com@DOMAIN.COM>

            2 host/<servername.domain.com@DOMAIN.COM>

            2 host/<servername.domain.com@DOMAIN.COM>

            2 host/<SERVERNAME@DOMAIN.COM>

            2 host/<SERVERNAME@DOMAIN.COM>

            2 host/<SERVERNAME@DOMAIN.COM>

            2 host/<SERVERNAME@DOMAIN.COM>

            2 host/<SERVERNAME@DOMAIN.COM>

            2 <SERVERNAME$@DOMAIN.COM>

            2 <SERVERNAME$@DOMAIN.COM>

            2 <SERVERNAME$@DOMAIN.COM>

            2 <SERVERNAME$@DOMAIN.COM>

            2 <SERVERNAME$@DOMAIN.COM>

3. Obtain a Kerberos ticket using keytab in capitals.

# kinit -k <server name>$

4. Verify the new default principal, it will have changed from <admin account> to <server name>

1. klist