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3.3. Configuring a Kerberos 5 Client
Setting up a Kerberos 5 client is less involved than setting up a server. At a minimum, install the client packages and provide each client with a valid
krb5.conf configuration file. While
slogin are the preferred method of remotely logging in to client systems, Kerberized versions of
rlogin are still available, though deploying them requires that a few more configuration changes be made.
Be sure that time synchronization is in place between the Kerberos client and the KDC. Refer to Section 3.2, “Configuring a Kerberos 5 Server”
for more information. In addition, verify that DNS is working properly on the Kerberos client before configuring the Kerberos client programs.
krb5-workstation packages on all of the client machines. Supply a valid
/etc/krb5.conf file for each client (usually this can be the same
krb5.conf file used by the KDC).
Before a workstation in the realm can use Kerberos to authenticate users who connect using
ssh or Kerberized
rlogin, it must have its own host principal in the Kerberos database. The
klogind server programs all need access to the keys for the host service's principal. Additionally, in order to use the kerberized
rlogin services, that workstation must have the
xinetd package installed.
kadmin, add a host principal for the workstation on the KDC. The instance in this case is the hostname of the workstation. Use the
-randkey option for the
addprinc command to create the principal and assign it a random key:
addprinc -randkey host/server.example.com
Now that the principal has been created, keys can be extracted for the workstation by running
kadmin on the workstation itself, and using the
ktadd command within
ktadd -k /etc/krb5.keytab host/server.example.com
Table 3.3. Common Kerberized Services
||OpenSSH uses GSS-API to authenticate users to servers if the client's and server's configuration both have
GSSAPIAuthentication enabled. If the client also has
GSSAPIDelegateCredentials enabled, the user's credentials are made available on the remote system.
|rsh and rlogin
||To use the kerberized versions of
||To use kerberized Telnet,
krb5-telnet must be enabled.
||To provide FTP access, create and extract a key for the principal with a root of
ftp. Be certain to set the instance to the fully qualified hostname of the FTP server, then enable
To use a kerberized IMAP server, the
cyrus-imap package uses Kerberos 5 if it also has the
cyrus-sasl-gssapi package installed. The
cyrus-sasl-gssapi package contains the Cyrus SASL plugins which support GSS-API authentication. Cyrus IMAP should function properly with Kerberos as long as the
cyrus user is able to find the proper key in
/etc/krb5.keytab, and the root for the principal is set to
imap (created with
An alternative to
cyrus-imap can be found in the
dovecot package, which is also included in Red Hat Enterprise Linux. This package contains an IMAP server but does not, to date, support GSS-API and Kerberos.
||To use a kerberized CVS server,
gserver uses a principal with a root of
cvs and is otherwise identical to the CVS