HP-UX Reference (11i v3 07/02) - 5 Miscellaneous Topics (vol 9)

k
Kerberos(5) Kerberos(5)
NAME
Kerberos - introduction to the Kerberos system
DESCRIPTION
The Kerberos system authenticates individual users in a network environment. After authenticating your-
self to Kerberos, you can use network utilities such as
rlogin, rcp, and remsh without having to
present passwords to the remote hosts and without having to edit and use
.rhosts files. Note that these
utilities will work without passwords only if the remote machines you deal with support the Kerberos sys-
tem.
If you enter your username and the remote machine is not a Kerberos system, you will get the following
message:
Principal unknown (Kerberos) you haven’t been registered as a Ker-
beros user
.
You will have to see your system administrator when the above message is encountered.
A Kerberos name usually contains three parts. The first is the primary, which is usually a user’s or
service’s name. The second is the instance, which in the case of a user is usually null. Some users may
have privileged instances, such as "root" or "admin". In the case of a service, the instance is the fully
qualified name of the machine on which it runs; that is, there can be an
rlogin service running on the
machine ABC, which is different from the
rlogin service running on the machine XYZ. The third part of
a Kerberos name is the realm. The realm corresponds to the Kerberos service providing authentication for
the principal.
When writing a Kerberos name, the principal name is separated from the instance (if not null) by a slash
(/), and the realm (if not the local realm) follows, preceded by an @ sign. The following are examples of
valid Kerberos names:
david
jennifer/admin
[e-mail]
cbrown/[e-mail]
When you authenticate yourself with Kerberos, you get an initial Kerberos ticket. A Kerberos ticket is an
encrypted protocol message that provides authentication. Kerberos uses this ticket for network utilities
such as
rlogin and rcp. The ticket transactions are done transparently, so you do not have to worry
about their management.
Note, however, that tickets will expire. Privileged tickets, such as those with the instance "root", expire
within a few minutes, while tickets that carry more ordinary privileges may be valid for several hours or a
day, depending on the Kerberos server configuration. If your login session extends beyond the lifetime
limit, you will have to re-authenticate yourself to Kerberos to get new tickets. Use the
kinit command to
re-authenticate yourself.
If you use the
kinit command to get your tickets, make sure you use the kdestroy
command to des-
troy your tickets before you end your login session. You should put the
kdestroy
command in your
.logout file so that your tickets will be destroyed automatically when you logout. For more information
about the kinit and kdestroy commands, see kinit(1) and kdestroy(1).
Kerberos tickets can be forwarded. In order to forward tickets, you must request forwardable tickets when
you use the kinit command. Once you have forwardable tickets, most Kerberos programs have a com-
mand line option to forward them to the remote host.
Currently, Kerberos support is available for the following network services: rlogin, remsh, rcp, tel-
net
, ftp, and ssh.
AUTHOR
Kerberos was developed by the Massachusetts Institute of Technology by Steve Miller, MIT Project
Athena/Digital Equipment Corporation, and Clifford Neuman, MIT Project Athena.
SEE ALSO
kdestroy(1), kinit(1), klist(1), kpasswd(1), libkrb5(3), krb5.conf(4).
218 Hewlett-Packard Company − 1 − HP-UX 11i Version 3: February 2007