1.\" Copyright (c) 2000 Kungliga Tekniska Högskolan 2.\" (Royal Institute of Technology, Stockholm, Sweden). 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 16.\" 3. Neither the name of the Institute nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" $Id$ 33.\" 34.Dd May 15, 2021 35.Dt KERBEROS 8 36.Os HEIMDAL 37.Sh NAME 38.Nm kerberos 39.Nd introduction to the Kerberos system 40.Sh DESCRIPTION 41Kerberos is a network authentication system. Its purpose is to 42securely authenticate users and services in an insecure network 43environment. 44.Pp 45This is done with a Kerberos server acting as a trusted third party, 46keeping a database with secret keys for all users and services 47(collectively called 48.Em principals ) . 49.Pp 50Each principal belongs to exactly one 51.Em realm , 52which is the administrative domain in Kerberos. A realm usually 53corresponds to an organisation, and the realm should normally be 54derived from that organisation's domain name. A realm is served by one 55or more Kerberos servers. 56.Pp 57The authentication process involves exchange of 58.Sq tickets 59and 60.Sq authenticators 61which together prove the principal's identity. 62.Pp 63When you login to the Kerberos system, either through the normal 64system login or with the 65.Xr kinit 1 66program, you acquire a 67.Em ticket granting ticket 68which allows you to get new tickets for other services, such as 69.Ic telnet 70or 71.Ic ftp , 72without giving your password. 73.Pp 74For more information on how Kerberos works, see the tutorial at 75.Lk https://kerberos.org/software/tutorial.html 76or the informal 77.Dq dialogue 78at 79.Lk https://web.mit.edu/kerberos/dialogue.html . 80.Pp 81For setup instructions see the Heimdal Texinfo manual. 82.Sh SEE ALSO 83.Xr ftp 1 , 84.Xr kdestroy 1 , 85.Xr kinit 1 , 86.Xr klist 1 , 87.Xr kpasswd 1 , 88.Xr telnet 1 89.Sh HISTORY 90The Kerberos authentication system was developed in the late 1980's as 91part of the Athena Project at the Massachusetts Institute of 92Technology. Versions one through three never reached outside MIT, but 93version 4 was (and still is) quite popular, especially in the academic 94community, but is also used in commercial products like the AFS 95filesystem. 96.Pp 97The problems with version 4 are that it has many limitations, the code 98was not too well written (since it had been developed over a long 99time), and it has a number of known security problems. To resolve many 100of these issues work on version five started, and resulted in IETF RFC 1011510 in 1993. IETF RFC 1510 was obsoleted in 2005 with IETF RFC 4120, 102also known as Kerberos clarifications. With the arrival of IETF RFC 1034120, the work on adding extensibility and internationalization have 104started (Kerberos extensions), and a new RFC will hopefully appear 105soon. 106.Pp 107This manual page is part of the 108.Nm Heimdal 109Kerberos 5 distribution, which has been in development at the Royal 110Institute of Technology in Stockholm, Sweden, since about 1997. 111