kerberos.5 (2010 09)

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
yourself 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 Ker-
beros system.
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 Kerberos
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
command 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.
Kerberos supports the following encryption types:
des-cbc-crc DES CBC mode with CRC-32.
des-cbc-md4 DES CBC mode with RSA-MD4.
des-cbc-md5 DES CBC mode with RSA-MD5.
des DES CBC mode with RSA-MD5. Alias to des-cbc-md5.
des-cbc-raw DES CBC mode RAW.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1