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System Administration Guide: Security Services

ProcedureHow to Establish Direct Cross-Realm Authentication

The example in this procedure uses two realms, ENG.EAST.EXAMPLE.COM and SALES.WEST.EXAMPLE.COM. Cross-realm authentication will be established in both directions. This procedure must be completed on the master KDC in both realms.

Before You Begin

The master KDC for each realm must be configured. To fully test the authentication process, several Kerberos clients must be configured.

  1. Become superuser on one of the master KDC servers.

  2. Create ticket-granting ticket service principals for the two realms.

    You must log in with one of the admin principal names that was created when you configured the master KDC.


    # /usr/sbin/kadmin -p kws/admin
Enter password: <Type kws/admin password>
kadmin: addprinc krbtgt/ENG.EAST.EXAMPLE.COM@SALES.WEST.EXAMPLE.COM
Enter password for principal 
  krgtgt/ENG.EAST.EXAMPLE.COM@SALES.WEST.EXAMPLE.COM: <Type the password>
kadmin: addprinc krbtgt/SALES.WEST.EXAMPLE.COM@ENG.EAST.EXAMPLE.COM
Enter password for principal 
  krgtgt/SALES.WEST.EXAMPLE.COM@ENG.EAST.EXAMPLE.COM: <Type the password>
kadmin: quit
    Note –

    The password that is specified for each service principal must be identical in both KDCs. Thus, the password for the service principal krbtgt/ENG.EAST.EXAMPLE.COM@SALES.WEST.EXAMPLE.COM must be the same in both realms.

  3. Add entries in the Kerberos configuration file to define the direct path to the remote realm.

    This example shows the clients in the ENG.EAST.EXAMPLE.COM realm. You would need to swap the realm names to get the appropriate definitions in the SALES.WEST.EXAMPLE.COM realm.


    # cat /etc/krb5/krb5.conf
[libdefaults]
 .
 .
[capaths]
    ENG.EAST.EXAMPLE.COM = {
        SALES.WEST.EXAMPLE.COM = .
    }

    SALES.WEST.EXAMPLE.COM = {
         ENG.EAST.EXAMPLE.COM = .
    }

  4. Copy the Kerberos configuration file to all clients in the current realm.

    For cross-realm authentication to work, all systems (including slave KDCs and other servers) must have the new version of the Kerberos configuration file (/etc/krb5/krb5.conf) installed.

  5. Repeat all of these steps for the second realm.