Copyright © 1985-2007 by the Massachusetts Institute of Technology.
Export of software employing encryption from the United States of America may require a specific license from the United States Government. It is the responsibility of any person or organization contemplating export to obtain such a license before exporting.
WITHIN THAT CONSTRAINT, permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation, and that the name of M.I.T. not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. Furthermore if you modify this software you must label your software as modified software and not distribute it in such a fashion that it might be confused with the original MIT software. M.I.T. makes no representations about the suitability of this software for any purpose. It is provided “as is” without express or implied warranty.
Individual source code files are copyright MIT, Cygnus Support, Novell, OpenVision Technologies, Oracle, Red Hat, Sun Microsystems, FundsXpress, and others.
Project Athena, Athena, Athena MUSE, Discuss, Hesiod, Kerberos, Moira, and Zephyr are trademarks of the Massachusetts Institute of Technology (MIT). No commercial use of these trademarks may be made without prior written permission of MIT.
“Commercial use” means use of a name in a product or other for-profit manner. It does NOT prevent a commercial firm from referring to the MIT trademarks in order to convey information (although in doing so, recognition of their trademark status should be given).
The following copyright and permission notice applies to the
OpenVision Kerberos Administration system located in
kadmin/create, kadmin/dbutil, kadmin/passwd,
kadmin/server, lib/kadm5, and portions of
lib/rpc:
Copyright, OpenVision Technologies, Inc., 1996, All Rights ReservedWARNING: Retrieving the OpenVision Kerberos Administration system source code, as described below, indicates your acceptance of the following terms. If you do not agree to the following terms, do not retrieve the OpenVision Kerberos administration system.
You may freely use and distribute the Source Code and Object Code compiled from it, with or without modification, but this Source Code is provided to you “AS IS” EXCLUSIVE OF ANY WARRANTY, INCLUDING, WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, OR ANY OTHER WARRANTY, WHETHER EXPRESS OR IMPLIED. IN NO EVENT WILL OPENVISION HAVE ANY LIABILITY FOR ANY LOST PROFITS, LOSS OF DATA OR COSTS OF PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, OR FOR ANY SPECIAL, INDIRECT, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THIS AGREEMENT, INCLUDING, WITHOUT LIMITATION, THOSE RESULTING FROM THE USE OF THE SOURCE CODE, OR THE FAILURE OF THE SOURCE CODE TO PERFORM, OR FOR ANY OTHER REASON.
OpenVision retains all copyrights in the donated Source Code. OpenVision also retains copyright to derivative works of the Source Code, whether created by OpenVision or by a third party. The OpenVision copyright notice must be preserved if derivative works are made based on the donated Source Code.
OpenVision Technologies, Inc. has donated this Kerberos Administration system to MIT for inclusion in the standard Kerberos 5 distribution. This donation underscores our commitment to continuing Kerberos technology development and our gratitude for the valuable work which has been performed by MIT and the Kerberos community.
Portions contributed by Matt Crawford <crawdad@fnal.gov> were work
performed at Fermi National Accelerator Laboratory, which is operated
by Universities Research Association, Inc., under contract
DE-AC02-76CHO3000 with the U.S. Department of Energy.
Portions of src/lib/crypto have the following copyright:
Copyright © 1998 by the FundsXpress, INC.All rights reserved.
Export of this software from the United States of America may require a specific license from the United States Government. It is the responsibility of any person or organization contemplating export to obtain such a license before exporting.
WITHIN THAT CONSTRAINT, permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation, and that the name of FundsXpress. not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. FundsXpress makes no representations about the suitability of this software for any purpose. It is provided “as is” without express or implied warranty.
THIS SOFTWARE IS PROVIDED “AS IS” AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
The implementation of the Yarrow pseudo-random number generator
in src/lib/crypto/yarrow has the following copyright:
Copyright 2000 by Zero-Knowledge Systems, Inc.Permission to use, copy, modify, distribute, and sell this software and its documentation for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation, and that the name of Zero-Knowledge Systems, Inc. not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. Zero-Knowledge Systems, Inc. makes no representations about the suitability of this software for any purpose. It is provided “as is” without express or implied warranty.
ZERO-KNOWLEDGE SYSTEMS, INC. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL ZERO-KNOWLEDGE SYSTEMS, INC. BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTUOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
The implementation of the AES encryption algorithm in
src/lib/crypto/aes has the following copyright:
Copyright © 2001, Dr Brian Gladman<brg@gladman.uk.net>, Worcester, UK.
All rights reserved.LICENSE TERMS
The free distribution and use of this software in both source and binary form is allowed (with or without changes) provided that:
- distributions of this source code include the above copyright notice, this list of conditions and the following disclaimer;
- distributions in binary form include the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other associated materials;
- the copyright holder's name is not used to endorse products built using this software without specific written permission.
DISCLAIMER
This software is provided 'as is' with no explcit or implied warranties in respect of any properties, including, but not limited to, correctness and fitness for purpose.
Portions contributed by Red Hat, including the pre-authentication plug-in framework, contain the following copyright:
Copyright © 2006 Red Hat, Inc.
Portions copyright © 2006 Massachusetts Institute of Technology
All Rights Reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
- Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
- Neither the name of Red Hat, Inc., nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
The implementations of GSSAPI mechglue in GSSAPI-SPNEGO in
src/lib/gssapi, including the following files:
lib/gssapi/generic/gssapi_err_generic.et
lib/gssapi/mechglue/g_accept_sec_context.c
lib/gssapi/mechglue/g_acquire_cred.c
lib/gssapi/mechglue/g_canon_name.c
lib/gssapi/mechglue/g_compare_name.c
lib/gssapi/mechglue/g_context_time.c
lib/gssapi/mechglue/g_delete_sec_context.c
lib/gssapi/mechglue/g_dsp_name.c
lib/gssapi/mechglue/g_dsp_status.c
lib/gssapi/mechglue/g_dup_name.c
lib/gssapi/mechglue/g_exp_sec_context.c
lib/gssapi/mechglue/g_export_name.c
lib/gssapi/mechglue/g_glue.c
lib/gssapi/mechglue/g_imp_name.c
lib/gssapi/mechglue/g_imp_sec_context.c
lib/gssapi/mechglue/g_init_sec_context.c
lib/gssapi/mechglue/g_initialize.c
lib/gssapi/mechglue/g_inquire_context.c
lib/gssapi/mechglue/g_inquire_cred.c
lib/gssapi/mechglue/g_inquire_names.c
lib/gssapi/mechglue/g_process_context.c
lib/gssapi/mechglue/g_rel_buffer.c
lib/gssapi/mechglue/g_rel_cred.c
lib/gssapi/mechglue/g_rel_name.c
lib/gssapi/mechglue/g_rel_oid_set.c
lib/gssapi/mechglue/g_seal.c
lib/gssapi/mechglue/g_sign.c
lib/gssapi/mechglue/g_store_cred.c
lib/gssapi/mechglue/g_unseal.c
lib/gssapi/mechglue/g_userok.c
lib/gssapi/mechglue/g_utils.c
lib/gssapi/mechglue/g_verify.c
lib/gssapi/mechglue/gssd_pname_to_uid.c
lib/gssapi/mechglue/mglueP.h
lib/gssapi/mechglue/oid_ops.c
lib/gssapi/spnego/gssapiP_spnego.h
lib/gssapi/spnego/spnego_mech.c
are subject to the following license:
Copyright © 2004 Sun Microsystems, Inc.Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Kerberos V5 includes documentation and software developed at the University of California at Berkeley, which includes this copyright notice:
Copyright © 1983 Regents of the University of California.
All rights reserved.Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
- Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
- Neither the name of the University nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Portions contributed by Novell, Inc., including the LDAP database backend, are subject to the following license:
Copyright (c) 2004-2005, Novell, Inc. All rights reserved.Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
- Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
- The copyright holder's name is not used to endorse or promote products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Portions funded by Sandia National Laboratory and developed by the University of Michigan's Center for Information Technology Integration, including the PKINIT implementation, are subject to the following license:
COPYRIGHT © 2006-2007
THE REGENTS OF THE UNIVERSITY OF MICHIGAN
ALL RIGHTS RESERVEDPermission is granted to use, copy, create derivative works and redistribute this software and such derivative works for any purpose, so long as the name of The University of Michigan is not used in any advertising or publicity pertaining to the use of distribution of this software without specific, written prior authorization. If the above copyright notice or any other identification of the University of Michigan is included in any copy of any portion of this software, then the disclaimer below must also be included.
THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
The pkcs11.h file included in the PKINIT code has the following license:
Copyright 2006 g10 Code GmbH Copyright 2006 Andreas Jellinghaus
This file is free software; as a special exception the author gives unlimited permission to copy and/or distribute it, with or without modifications, as long as this notice is preserved.
This file is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY, to the extent permitted by law; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Permission is granted to make and distribute verbatim copies of this manual provided the copyright notices and this permission notice are preserved on all copies.
Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.
Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions.
Kerberos V5 is based on the Kerberos authentication system developed at MIT. Under Kerberos, a client (generally either a user or a service) sends a request for a ticket to the Key Distribution Center (KDC). The KDC creates a ticket-granting ticket (TGT) for the client, encrypts it using the client's password as the key, and sends the encrypted TGT back to the client. The client then attempts to decrypt the TGT, using its password. If the client successfully decrypts the TGT (i.e., if the client gave the correct password), it keeps the decrypted TGT, which indicates proof of the client's identity.
The TGT, which expires at a specified time, permits the client to obtain additional tickets, which give permission for specific services. The requesting and granting of these additional tickets is user-transparent.
Since Kerberos negotiates authenticated, and optionally encrypted, communications between two points anywhere on the Internet, it provides a layer of security that is not dependent on which side of a firewall either client is on. Since studies have shown that half of the computer security breaches in industry happen from inside firewalls, Kerberos V5 from MIT will play a vital role in the security of your network.
As with any software package that uses a centrallized database, the installation procedure is somewhat involved, and requires forethought and planning. MIT has attempted to make this Kerberos V5 Installation Guide as concise as possible, rather than making it an exhaustive description of the details of Kerberos. Consequently, everything in this guide appears because MIT believes that it is important. Please read and follow these instructions carefully.
This document is one piece of the document set for Kerberos V5. The documents, and their intended audiences, are:
The next chapter describes the decisions you need to make before installing Kerberos V5.
Chapter three provided instructions for building the Kerberos sources.
Chapter four describes installation procedures for each class of Kerberos machines:
Note that a machine can be both a client machine and an application server.
Chapter five describes procedure for updating previous installations of Kerberos V5.
Chapter six describes our problem reporting system.
Before installing Kerberos V5, it is necessary to consider the following issues:
Although your Kerberos realm can be any ASCII string, convention is to make it the same as your domain name, in upper-case letters. For example, hosts in the domain example.com would be in the Kerberos realm EXAMPLE.COM.
If you need multiple Kerberos realms, MIT recommends that you use descriptive names which end with your domain name, such as BOSTON.EXAMPLE.COM and HOUSTON.EXAMPLE.COM.
Mapping hostnames onto Kerberos realms is done in one of two ways.
The first mechanism, which has been in use for years in MIT-based
Kerberos distributions, works through a set of rules in
the krb5.conf configuration file. (See krb5.conf.) You can
specify mappings for an entire domain or subdomain, and/or on a
hostname-by-hostname basis. Since greater specificity takes precedence,
you would do this by specifying the mappings for a given domain or
subdomain and listing the exceptions.
The second mechanism works by looking up the information in special
TXT records in the Domain Name Service. This is currently not
used by default because security holes could result if the DNS TXT
records were spoofed. If this mechanism is enabled on the client,
it will try to look up a TXT record for the DNS name formed by
putting the prefix _kerberos in front of the hostname in question.
If that record is not found, it will try using _kerberos and the
host's domain name, then its parent domain, and so forth. So for the
hostname BOSTON.ENGINEERING.FOOBAR.COM, the names looked up would be:
_kerberos.boston.engineering.foobar.com
_kerberos.engineering.foobar.com
_kerberos.foobar.com
_kerberos.com
The value of the first TXT record found is taken as the realm name. (Obviously, this doesn't work all that well if a host and a subdomain have the same name, and different realms. For example, if all the hosts in the ENGINEERING.FOOBAR.COM domain are in the ENGINEERING.FOOBAR.COM realm, but a host named ENGINEERING.FOOBAR.COM is for some reason in another realm. In that case, you would set up TXT records for all hosts, rather than relying on the fallback to the domain name.)
Even if you do not choose to use this mechanism within your site, you may wish to set it up anyway, for use when interacting with other sites.
The default ports used by Kerberos are port 88 for the
KDC1 and
port 749 for the admin server. You can, however,
choose to run on other ports, as long as they are specified in each
host's /etc/services and krb5.conf files, and the
kdc.conf file on each KDC. For a more thorough treatment of
port numbers used by the Kerberos V5 programs, refer to the
“Configuring Your Firewall to Work With Kerberos V5” section of
the Kerberos V5 System Administrator's Guide.
Slave KDCs provide an additional source of Kerberos ticket-granting services in the event of inaccessibility of the master KDC. The number of slave KDCs you need and the decision of where to place them, both physically and logically, depends on the specifics of your network.
All of the Kerberos authentication on your network requires that each client be able to contact a KDC. Therefore, you need to anticipate any likely reason a KDC might be unavailable and have a slave KDC to take up the slack.
Some considerations include:
MIT recommends that your KDCs have a predefined set of
CNAME records (DNS hostname aliases), such as kerberos
for the master KDC and
kerberos-1, kerberos-2, ... for the
slave KDCs. This way, if you need to swap a machine, you only need to
change a DNS entry, rather than having to change hostnames.
A new mechanism for locating KDCs of a realm through DNS has been added
to the MIT Kerberos V5 distribution. A relatively new
record type called SRV has been added to DNS. Looked up by a
service name and a domain name, these records indicate the hostname and
port number to contact for that service, optionally with weighting and
prioritization. (See RFC 2782 if you want more information. You can
follow the example below for straightforward cases.)
The use with Kerberos is fairly straightforward. The domain name used in the SRV record name is the domain-style Kerberos realm name. (It is possible to have Kerberos realm names that are not DNS-style names, but we don't recommend it for Internet use, and our code does not support it well.) Several different Kerberos-related service names are used:
_kerberos._udp_kerberos._tcp_kerberos-master._udpIf you have only one KDC, or for whatever reason there is no accessible
KDC that would get database changes faster than the others, you do not
need to define this entry.
_kerberos-adm._tcpkadmin program and related utilities. For now, you
will also need the admin_server entry in krb5.conf.
(See krb5.conf.)
_kpasswd._udp_kerberos-iv._udpBe aware, however, that the DNS SRV specification requires that the hostnames listed be the canonical names, not aliases. So, for example, you might include the following records in your (BIND-style) zone file:
$ORIGIN foobar.com.
_kerberos TXT "FOOBAR.COM"
kerberos CNAME daisy
kerberos-1 CNAME use-the-force-luke
kerberos-2 CNAME bunny-rabbit
_kerberos._udp SRV 0 0 88 daisy
SRV 0 0 88 use-the-force-luke
SRV 0 0 88 bunny-rabbit
_kerberos-master._udp SRV 0 0 88 daisy
_kerberos-adm._tcp SRV 0 0 749 daisy
_kpasswd._udp SRV 0 0 464 daisy
As with the DNS-based mechanism for determining the Kerberos realm of a
host, we recommend distributing the information this way for use by
other sites that may want to interact with yours using Kerberos, even if
you don't immediately make use of it within your own site. If you
anticipate installing a very large number of machines on which it will
be hard to update the Kerberos configuration files, you may wish to do
all of your Kerberos service lookups via DNS and not put the information
(except for admin_server as noted above) in future versions of
your krb5.conf files at all. Eventually, we hope to phase out
the listing of server hostnames in the client-side configuration files;
making preparations now will make the transition easier in the future.
The Kerberos database resides on the master KDC, and must be propagated regularly (usually by a cron job) to the slave KDCs. In deciding how frequently the propagation should happen, you will need to balance the amount of time the propagation takes against the maximum reasonable amount of time a user should have to wait for a password change to take effect.
If the propagation time is longer than this maximum reasonable time (e.g., you have a particularly large database, you have a lot of slaves, or you experience frequent network delays), you may wish to cut down on your propagation delay by performing the propagation in parallel. To do this, have the master KDC propagate the database to one set of slaves, and then have each of these slaves propagate the database to additional slaves.
Kerberos V5 uses a configuration system built using the Free Software Foundation's autoconf program. This system makes Kerberos V5 much simpler to build and reduces the amount of effort required in porting Kerberos V5 to a new platform.
Below is a brief overview of the organization of the complete source directory. More detailed descriptions follow.
The Kerberos release provides certain UNIX utilities, modified to use Kerberos authentication. In the appl/bsd directory are the Berkeley utilities login, rlogin, rsh, and rcp, as well as the associated daemons kshd and klogind. The login program obtains ticket-granting tickets for users upon login; the other utilities provide authenticated Unix network services.
The appl directory also contains Kerberized telnet and ftp programs, as well as sample Kerberos application client and server programs.
This directory contains the code for several user-oriented programs.
kdestroy before logging out.
su program that is
meant to securely change the real and effective user ID to that of the
target user and to create a new security context.
There are two manual pages in this directory. One is an introduction
to the Kerberos system. The other describes the .k5login file
which allows users to give access with their UID to other users
authenticated by the Kerberos system.
This directory contains the include files needed to build the Kerberos system.
In this directory is the code for the utilities kadmin,
kadmin.local, kdb5_util, and ktutil.
ktutil is the Kerberos keytab file maintenance utility from
which a Kerberos administrator can read, write, or edit entries in a
Kerberos V5 keytab or Kerberos V4 srvtab. kadmin and
kadmin.local are command-line interfaces to the Kerberos V5 KADM5
administration system. kadmin.local runs on the master KDC and
does not use Kerberos to authenticate to the database, while
kadmin uses Kerberos authentication and an encrypted RPC. The
two provide identical functionalities, which allow administrators to
modify the database of Kerberos principals. kdb5_util allows
administrators to perform low-level maintenance procedures on Kerberos
and the KADM5 database. With this utility, databases can be created,
destroyed, or dumped to and loaded from ASCII files. It can also be
used to create master key stash files.
This directory contains the code for the krb5kdc daemon, the
Kerberos Authentication Service and Key Distribution Center.
This directory contains the code for krb524, a service that
converts Kerberos V5 credentials into Kerberos V4 credentials suitable
for use with applications that for whatever reason do not use V5
directly.
The lib directory contain 10 subdirectories as well as some definition and glue files. The crypto subdirectory contains the Kerberos V5 encryption library. The des425 subdirectory exports the Kerberos V4 encryption API, and translates these functions into calls to the Kerberos V5 encryption API. The gssapi library contains the Generic Security Services API, which is a library of commands to be used in secure client-server communication. The kadm5 directory contains the libraries for the KADM5 administration utilities. The Kerberos 5 database libraries are contained in kdb. The directories krb4 and krb5 contain the Kerberos 4 and Kerberos 5 APIs, respectively. The rpc directory contains the API for the Kerberos Remote Procedure Call protocol.
This directory contains several template files. The prototype.h
and prototype.c files contain the MIT copyright message and a
placeholder for the title and description of the file.
prototype.h also has a short template for writing ifdef
and ifndef preprocessor statements. The getopt.c file
provides a template for writing code that will parse the options with
which a program was called.
This directory contains code which allows for the propagation of the
Kerberos principal database from the master KDC to slave KDCs over an
encrypted, secure channel. kprop is the program which actually
propagates the database dump file. kpropd is the Kerberos V5
slave KDC update server which accepts connections from the kprop
program. kslave_update is a script that takes the name of a
slave server, and propagates the database to that server if the
database has been modified since the last dump or if the database has
been dumped since the last propagation.
This directory contains several utility programs and libraries. The
programs used to configure and build the code, such as autoconf,
lndir, kbuild, reconf, and makedepend,
are in this directory. The profile directory contains most of the
functions which parse the Kerberos configuration files (krb5.conf
and kdc.conf). Also in this directory are the Kerberos error table
library and utilities (et), the Sub-system library and utilities
(ss), database utilities (db2), pseudo-terminal utilities
(pty), bug-reporting program send-pr, and a generic
support library support used by several of our other libraries.
In order to build Kerberos V5, you will need approximately 60-70 megabytes of disk space. The exact amount will vary depending on the platform and whether the distribution is compiled with debugging symbol tables or not.
Your C compiler must conform to ANSI C (ISO/IEC 9899:1990, “c89”). Some operating systems do not have an ANSI C compiler, or their default compiler requires extra command-line options to enable ANSI C conformance.
If you wish to keep a separate build tree, which contains the compiled *.o file and executables, separate from your source tree, you will need a make program which supports VPATH, or you will need to use a tool such as lndir to produce a symbolic link tree for your build tree.
The first step in each of these build procedures is to unpack the source distribution. The Kerberos V5 distribution comes in a tar file, generally named krb5-1.6.tar, which contains a compressed tar file consisting of the sources for all of Kerberos (generally krb5-1.6.tar.gz) and a PGP signature for this source tree (generally krb5-1.6.tar.gz.asc). MIT highly recommends that you verify the integrity of the source code using this signature.
Unpack the compressed tar file in some directory, such as /u1/krb5-1.6. (In the rest of this document, we will assume that you have chosen to unpack the Kerberos V5 source distribution in this directory. Note that the tarfiles will by default all unpack into the ./krb5-1.6 directory, so that if your current directory is /u1 when you unpack the tarfiles, you will get /u1/krb5-1.6/src, etc.)
You have a number of different options in how to build Kerberos. If you only need to build Kerberos for one platform, using a single directory tree which contains both the source files and the object files is the simplest. However, if you need to maintain Kerberos for a large number of platforms, you will probably want to use separate build trees for each platform. We recommend that you look at OS Incompatibilities, for notes that we have on particular operating systems.
If you don't want separate build trees for each architecture, then use the following abbreviated procedure.
cd /u1/krb5-1.6/src
./configure
make
That's it!
If you wish to keep separate build directories for each platform, you can do so using the following procedure. (Note, this requires that your make program support VPATH. GNU's make will provide this functionality, for example.) If your make program does not support this, see the next section.
For example, if you wish to create a build directory for pmax binaries
you might use the following procedure:
mkdir /u1/krb5-1.6/pmax
cd /u1/krb5-1.6/pmax
../src/configure
make
If you wish to keep separate build directories for each platform, and you do not have access to a make program which supports VPATH, all is not lost. You can use the lndir program to create symbolic link trees in your build directory.
For example, if you wish to create a build directory for solaris binaries you might use the following procedure:
mkdir /u1/krb5-1.6/solaris
cd /u1/krb5-1.6/solaris
/u1/krb5-1.6/src/util/lndir `pwd`/../src
./configure
make
You must give an absolute pathname to lndir because it has a bug that makes it fail for relative pathnames. Note that this version differs from the latest version as distributed and installed by the XConsortium with X11R6. Either version should be acceptable.
Once you have built Kerberos, you should install the binaries. You can do this by running:
% make install
If you want to install the binaries into a destination directory that is not their final destination, which may be convenient if you want to build a binary distribution to be deployed on multiple hosts, you may use:
% make install DESTDIR=/path/to/destdir
This will install the binaries under DESTDIR/PREFIX, e.g., the
user programs will install into DESTDIR/PREFIX/bin, the
libraries into DESTDIR/PREFIX/lib, etc.
Note that if you want to test the build (see Testing the Build),
you usually do not need to do a make install first.
Some implementations of make allow multiple commands to be run in parallel, for faster builds. We test our Makefiles in parallel builds with GNU make only; they may not be compatible with other parallel build implementations.
The Kerberos V5 distribution comes with built-in regression tests. To run them, simply type the following command while in the top-level build directory (i.e., the directory where you sent typed make to start building Kerberos; see Doing the Build.):
% make check
However, there are several prerequisites that must be satisfied first:
--with-tcl to configure to
tell it the location of the Tcl configuration script. (See
See Options to Configure.)
Some of the built-in regression tests are setup to use the DejaGnu framework for running tests. These tests tend to be more comprehensive than the normal built-in tests as they setup test servers and test client/server activities.
DejaGnu may be found wherever GNU software is archived.
Most of the tests are setup to run as a non-privileged user. For some
of the krb-root tests to work properly, either (a) the user running the
tests must not have a .k5login file in the home directory or (b) the
.k5login file must contain an entry for <username>@KRBTEST.COM.
There are two series of tests (rlogind and telnetd) which
require the ability to rlogin as root to the local
machine. Admittedly, this does require the use of a .rhosts file
or some authenticated means. 2
If you cannot obtain root access to your machine, all the other tests will still run. Note however, with DejaGnu 1.2, the "untested testcases" will cause the testsuite to exit with a non-zero exit status which make will consider a failure of the testing process. Do not worry about this, as these tests are the last run when make check is executed from the top level of the build tree. This problem does not exist with DejaGnu 1.3.
Regression tests for the KADM5 system, including the GSS-RPC, KADM5
client and server libraries, and kpasswd, are also included in this
release. Each set of KADM5 tests is contained in a sub-directory called
unit-test directly below the system being tested. For example,
lib/rpc/unit-test contains the tests for GSS-RPC. The tests are all
based on DejaGnu (but they are not actually called part of "The DejaGnu
tests," whose naming predates the inclusion of the KADM5 system). In
addition, they require the Tool Command Language (TCL) header files and
libraries to be available during compilation and some of the tests also
require Perl in order to operate. If all of these resources are not
available during configuration, the KADM5 tests will not run. The TCL
installation directory can be specified with the --with-tcl
configure option. (See See Options to Configure.) The runtest and
perl programs must be in the current execution path.
If you install DejaGnu, TCL, or Perl after configuring and building
Kerberos and then want to run the KADM5 tests, you will need to
re-configure the tree and run make at the top level again to make
sure all the proper programs are built. To save time, you actually only
need to reconfigure and build in the directories src/kadmin/testing,
src/lib/rpc, src/lib/kadm5.
There are a number of options to configure which you can use to control how the Kerberos distribution is built. The following table lists the most commonly used options to Kerberos V5's configure program.
--help--prefix=PREFIX--exec-prefix=EXECPREFIX--localstatedir=LOCALSTATEDIRLOCALSTATEDIR/krb5kdc, which is by default
PREFIX/var/krb5kdc.
CC=COMPILERCOMPILER as the C compiler.
CFLAGS=FLAGSFLAGS as the default set of C compiler flags.
Note that if you use the native Ultrix compiler on a
DECstation you are likely to lose if you pass no flags to cc; md4.c
takes an estimated 3,469 billion years to compile if you provide neither
the -g flag nor the -O flag to cc.
CPPFLAGS=CPPOPTSCPPOPTS as the default set of C preprocessor flags. The most
common use of this option is to select certain #define's for use
with the operating system's include files.
LD=LINKERLINKER as the default loader if it should be different from C
compiler as specified above.
LDFLAGS=LDOPTS--with-krb4--with-krb4=KRB4DIRKRB4DIR specifies where the V4 header files should be found
(KRB4DIR/include) as well as where the V4 Kerberos library should
be found (KRB4DIR/lib).
--without-krb4--with-netlib[=libs]-lnsl and
-lsocket. If your operating system has a broken resolver library
(see Solaris versions 2.0 through 2.3) or fails to pass the tests in
src/tests/resolv you will need to use this option.
--with-tcl=TCLPATHTCLPATH specifies where the Tcl
header file (TCLPATH/include/tcl.h as well as where the Tcl
library should be found (TCLPATH/lib).
--enable-shared--enable-dns--enable-dns-for-kdc--enable-dns-for-realm--enable-kdc-replay-cache--with-system-etCPPFLAGS=-I/some/dir and
LDFLAGS=-L/some/other/dir options at configuration time as
well.
If this option is not given, a version supplied with the Kerberos
sources will be built and installed along with the rest of the
Kerberos tree, for Kerberos applications to link against.
--with-system-ssCPPFLAGS=-I/some/dir and
LDFLAGS=-L/some/other/dir options at configuration time as
well. See also the SS_LIB option.
If this option is not given, the ss library supplied with the
Kerberos sources will be compiled and linked into those programs that
need it; it will not be installed separately.
SS_LIB=libs...This option is ignored if --with-system-ss is not specified.
--with-system-dbIf this option is not given, a version supplied with the Kerberos
sources will be built and installed. (We are not updating this
version at this time because of licensing issues with newer versions
that we haven't investigated sufficiently yet.)
DB_HEADER=headername.hDB_LIB=libs...For example, in order to configure Kerberos on a Solaris machine using the suncc compiler with the optimizer turned on, run the configure script with the following options:
% ./configure CC=suncc CFLAGS=-O
For a slightly more complicated example, consider a system where several packages to be used by Kerberos are installed in /usr/foobar, including Berkeley DB 3.3, and an ss library that needs to link against the curses library. The configuration of Kerberos might be done thus:
% ./configure CPPFLAGS=-I/usr/foobar/include LDFLAGS=-L/usr/foobar/lib \
--with-system-et --with-system-ss --with-system-db \
SS_LIB='-lss -lcurses' \
DB_HEADER=db3/db_185.h DB_LIB=-ldb-3.3
In previous releases, --with- options were used to specify the
compiler and linker and their options.
There is one configuration file which you may wish to edit to control various compile-time parameters in the Kerberos distribution: include/stock/osconf.h. The list that follows is by no means complete, just some of the more interesting variables.
Please note: The former configuration file config.h no longer exists as its functionality has been merged into the auto-configuration process. See Options to Configure.
DEFAULT_PROFILE_PATHThe profile file format is no longer the same format as Kerberos V4's
krb.conf file.
DEFAULT_KEYTAB_NAMEDEFAULT_KDC_ENCTYPEKDCRCACHERCTMPDIRDEFAULT_KDB_FILEShared library support is provided for a few operating systems. There are restrictions as to which compiler to use when using shared libraries. In all cases, executables linked with the shared libraries in this build process will have built in the location of the libraries, therefore obliterating the need for special LD_LIBRARY_PATH, et al environment variables when using the programs. Except where noted, multiple versions of the libraries may be installed on the same system and continue to work.
Currently the supported platforms are Solaris 2.6-2.9 (aka SunOS 5.6-5.9), Irix 6.5, Redhat Linux, MacOS 8-10, and Microsoft Windows (using DLLs).
Shared library support has been tested on the following platforms but not exhaustively (they have been built but not necessarily tested in an installed state): Tru64 (aka Alpha OSF/1 or Digital Unix) 4.0, and HP/UX 10.20.
Platforms for which there is shared library support but not significant testing include FreeBSD, OpenBSD, AIX (4.3.3), Linux, NetBSD 1.4.x (i386), and SunOS 4.x.
To enable shared libraries on the above platforms, run the configure script with the option --enable-shared.
This section details operating system incompatibilities with Kerberos V5
which have been reported to the developers at MIT. If you find
additional incompatibilities, and/or discover workarounds to such
problems, please send a report via the krb5-send-pr program.
Thanks!
The AIX 3.2.5 linker dumps core trying to build a shared libkrb5.a produced with the GNU C compiler. The native AIX compiler works fine. This problem is fixed using the AIX 4.1 linker.
Using the native compiler, compiling with the -O compiler flag
causes the asn.1 library to be compiled incorrectly.
Using GCC version 2.6.3 or later instead of the native compiler will also work fine, both with or without optimization.
There used to be a bug when using the native compiler in compiling md4.c when compiled without either the -O or -g compiler options. We have changed the code and there is no problem under V2.1, but we do not have access to V2.0 to test and see if the problem would exist there. (We welcome feedback on this issue). There was never a problem in using GCC version 2.6.3.
In version 3.2 and beyond of the operating system, we have not seen this sort of problem with the native compiler.
The C compiler provided with Alpha OSF/1 V4.0 (a.k.a. Digital UNIX) defaults to an extended K&R C mode, not ANSI C. You need to provide the -std argument to the compiler (i.e., ./configure CC='cc -std') to enable extended ANSI C mode. More recent versions of the operating system, such as 5.0, seem to have C compilers which default to -std.
BSDI versions 1.0 and 1.1 reportedly has a bad sed which causes it to go into an infinite loop during the build. The work around is to use a sed from somewhere else, such as GNU. (This may be true for some versions of other systems derived from BSD 4.4, such as NetBSD and FreeBSD.)
The native (bundled) compiler for HPUX currently will not work, because it is not a full ANSI C compiler. The optional ANSI C compiler should work as long as you give it the -Ae flag (i.e. ./configure CC='cc -Ae'). This is equivalent to ./configure CC='c89 -D_HPUX_SOURCE', which was the previous recommendation. This has only been tested recently for HPUX 10.20.
You will need to configure with --disable-shared
--enable-static, because as of 1.4 we don't have support for HPUX
shared library finalization routines, nor the option (yet) to ignore
that lack of support (which means repeated
dlopen/dlclose cycles on the Kerberos libraries may not
be safe) and build the shared libraries anyways.
You will also need to configure the build tree with
--disable-thread-support if you are on HPUX 10 and do not have
the DCE development package installed, because that's where the
pthread.h header file is found. (We don't know if our code
will work with such a package installed, because according to some HP
documentation, their pthread.h has to be included before any
other header files, and our code doesn't do that.)
If you use GCC, it may work, but some versions of GCC have omitted
certain important preprocessor defines, like __STDC_EXT__ and
__hpux.
The gethostbyname() routine is broken; it does not return a fully
qualified domain name, even if you are using the Domain Name Service
routines. Since Kerberos V5 uses the fully qualified domain name as the
second component of a service principal (i.e,
host/tsx-11.mit.edu@ATHENA.MIT.EDU), this causes problems for servers
who try to figure out their own fully qualified domain name.
Workarounds:
hosts: files dns
and then in /etc/hosts, make sure there is a line with your workstation's IP address and hostname, with the fully qualified domain name first. Example:
18.172.1.4 dcl.mit.edu dcl
Note that making this change may cause other programs in your environment to break or behave differently.
You must compile Kerberos V5 without the UCB compatibility
libraries. This means that /usr/ucblib must not be in the
LD_LIBRARY_PATH environment variable when you compile it. Alternatively
you can use the -i option to cc, by using the specifying
CFLAGS=-i option to configure.
If you are compiling for a 64-bit execution environment, you may need
to configure with the option CFLAGS="-D_XOPEN_SOURCE=500
-D__EXTENSIONS__". This is not well tested; at MIT we work primarily
with the 32-bit execution environment.
Solaris 9 has a kernel race condition which causes the final output written to the slave side of a pty to be lost upon the final close() of the slave device. This causes the dejagnu-based tests to fail intermittently. A workaround exists, but requires some help from the scheduler, and the “make check” must be executed from a shell with elevated priority limits.
Run something like
priocntl -s -c FX -m 30 -p 30 -i pid nnnn
as root, where nnnn is the pid of the shell whose priority
limit you wish to raise.
Sun has released kernel patches for this race condition. Apply patch 117171-11 for sparc, or patch 117172-11 for x86. Later revisions of the patches should also work. It is not necessary to run “make check” from a shell with elevated priority limits once the patch has been applied.
If you are building in a tree separate from the source tree, the vendors version of make does not work properly with regards to VPATH. It also has problems with standard inference rules in 5.2 (not tested yet in 5.3) so one needs to use GNU's make.
Under 5.2, there is a bug in the optional System V -lsocket
library in which the routine gethostbyname() is broken. The
system supplied version in -lc appears to work though so one may
simply specify --with-netlib option to configure.
In 5.3, gethostbyname() is no longer present in -lsocket and
is no longer an issue.
The DEC MIPS platform currently will not support the native compiler, since the Ultrix compiler is not a full ANSI C compiler. You should use GCC instead.
(If you are not a developer, you can skip this section.)
In most of the Kerberos V5 source directories, there is a configure script which automatically determines the compilation environment and creates the proper Makefiles for a particular platform. These configure files are generated using autoconf, which can be found in the src/util/autoconf directory in the distribution.
Normal users will not need to worry about running autoconf; the distribution comes with the configure files already prebuilt. Developers who wish to modify the configure.in files should see Overview (The Autoconf Manual).
Note that in order to run autoconf, you must have GNU m4 in your path. Before you use the autoconf in the Kerberos V5 source tree, you may also need to run configure, and then run make in the src/util/autoconf directory in order to properly set up autoconf.
One tool which is provided for the convenience of developers can be
found in src/util/reconf. This program should be run while the
current directory is the top source directory. It will automatically
rebuild any configure files which need rebuilding. If you know
that you have made a change that will require that all the
configure files need to be rebuilt from scratch, specify the
--force option:
% cd /u1/krb5-1.6/src
% ./util/reconf --force
The developmental sources are a raw source tree (before it's been packaged for public release), without the pre-built configure files. In order to build from such a source tree, you must do:
% cd krb5/util/autoconf
% ./configure
% make
% cd ../..
% util/reconf
Then follow the instructions for building packaged source trees (above). To install the binaries into a binary tree, do:
% cd /u1/krb5-1.6/src
% make all
% make install DESTDIR=somewhere-else
The sections of this chapter describe procedures for installing Kerberos V5 on:
The Key Distribution Centers (KDCs) issue Kerberos tickets. Each KDC contains a copy of the Kerberos database. The master KDC contains the master copy of the database, which it propagates to the slave KDCs at regular intervals. All database changes (such as password changes) are made on the master KDC.
Slave KDCs provide Kerberos ticket-granting services, but not database administration. This allows clients to continue to obtain tickets when the master KDC is unavailable.
MIT recommends that you install all of your KDCs to be able to function as either the master or one of the slaves. This will enable you to easily switch your master KDC with one of the slaves if necessary. (See Switching Master and Slave KDCs.) This installation procedure is based on that recommendation.
This installation procedure will require you to go back and forth a couple of times between the master KDC and each of the slave KDCs. The first few steps must be done on the master KDC.
Modify the configuration files, /etc/krb5.conf and
/usr/local/var/krb5kdc/kdc.conf to reflect the correct
information (such as the hostnames and realm name) for your realm.
MIT recommends that you keep krb5.conf in /etc.
Most of the tags in the configuration have default values that will
work well for most sites. There are some tags in the krb5.conf
file whose values must be specified, and this section will explain
those as well as give an overview of all of the sections in both
configuration files. For more information on changing defaults with
the configuration files, see the Kerberos V5 System Administrator's
Guide sections on configuration files.
The krb5.conf file contains Kerberos configuration information,
including the locations of KDCs and admin servers for the Kerberos
realms of interest, defaults for the current realm and for Kerberos
applications, and mappings of hostnames onto Kerberos realms. Normally,
you should install your krb5.conf file in the directory
/etc. You can override the default location by setting the
environment variable KRB5_CONFIG.
The krb5.conf file is set up in the style of a Windows INI file.
Sections are headed by the section name, in square brackets. Each
section may contain zero or more relations, of the form:
foo = bar
or
fubar = {
foo = bar
baz = quux
}
Placing a `*' at the end of a line indicates that this is the final value for the tag. This means that neither the remainder of this configuration file nor any other configuration file will be checked for any other values for this tag.
For example, if you have the following lines:
foo = bar*
foo = baz
then the second value of foo (baz) would never be read.
The krb5.conf file may contain any or all of the following
sections:
If you are not using DNS TXT records, you must specify the
default_realm in the libdefaults section. If you are not
using DNS SRV records, you must include the kdc tag for each
realm in the realms section. To communicate with the kadmin
server in each realm, the admin_server tag must be set in the
realms section. If your domain name and realm name are not the
same, you must provide a translation in domain_realm. It is
also higly recommeneded that you create a [logging] stanza if
the computer will be functioning as a KDC so that the KDC and kadmind
will generate logging output.
An example krb5.conf file:
[libdefaults]
default_realm = ATHENA.MIT.EDU
[realms]
ATHENA.MIT.EDU = {
kdc = kerberos.mit.edu
kdc = kerberos-1.mit.edu
kdc = kerberos-2.mit.edu
admin_server = kerberos.mit.edu
{
[logging]
kdc = FILE:/var/log/krb5kdc.log
admin_server = FILE:/var/log/kadmin.log
default = FILE:/var/log/krb5lib.log
The kdc.conf file contains KDC configuration information,
including defaults used when issuing Kerberos tickets. Normally, you
should install your kdc.conf file in the directory
/usr/local/var/krb5kdc. You can override the default
location by setting the environment variable KRB5_KDC_PROFILE.
The kdc.conf file is set up in the same format as the
krb5.conf file. (See krb5.conf.) The kdc.conf file
may contain any or all of the following three sections:
You will use the kdb5_util command on the Master KDC to
create the Kerberos database and the optional stash file. The
stash file is a local copy of the master key that resides in
encrypted form on the KDC's local disk. The stash file is used to
authenticate the KDC to itself automatically before starting the
kadmind and krb5kdc daemons (e.g., as part of the
machine's boot sequence). The stash file, like the keytab file
(see See The Keytab File, for more information) is a potential
point-of-entry for a break-in,
and if compromised, would allow unrestricted access to the Kerberos
database. If you choose to install a stash file, it should be readable
only by root, and should exist only on the KDC's local disk. The file
should not be part of any backup of the machine, unless access to the
backup data is secured as tightly as access to the master password
itself.
If you choose not to install a stash file, the KDC will prompt you for the master key each time it starts up. This means that the KDC will not be able to start automatically, such as after a system reboot.
Note that kdb5_util will prompt you for the master key for the
Kerberos database. This key can be any string. A good key is one you
can remember, but that no one else can guess. Examples of bad keys are
words that can be found in a dictionary, any common or popular name,
especially a famous person (or cartoon character), your username in any
form (e.g., forward, backward, repeated twice, etc.), and any of
the sample keys that appear in this manual. One example of a key which
might be good if it did not appear in this manual is “MITiys4K5!”,
which represents the sentence “MIT is your source for Kerberos 5!”
(It's the first letter of each word, substituting the numeral “4” for
the word “for”, and includes the punctuation mark at the end.)
The following is an example of how to create a Kerberos database and
stash file on the master KDC, using the kdb5_util command. (The
line that begins with => is a continuation of the previous line.)
Replace ATHENA.MIT.EDU with the name of your Kerberos realm.
shell% /usr/local/sbin/kdb5_util create -r ATHENA.MIT.EDU -s
Initializing database '/usr/local/var/krb5kdc/principal' for
=> realm 'ATHENA.MIT.EDU',
master key name 'K/M@ATHENA.MIT.EDU'
You will be prompted for the database Master Password.
It is important that you NOT FORGET this password.
Enter KDC database master key: <= Type the master password.
Re-enter KDC database master key to verify: <= Type it again.
shell%
This will create five files in the directory specified in your
kdc.conf file: two Kerberos database files, principal.db,
and principal.ok; the Kerberos administrative database file,
principal.kadm5; the administrative database lock file,
principal.kadm5.lock; and the stash file, .k5stash. (The
default directory is /usr/local/var/krb5kdc.) If you do not
want a stash file, run the above command without the -s option.
Next, you need create an Access Control List (acl) file, and put the
Kerberos principal of at least one of the administrators into it. This
file is used by the kadmind daemon to control which principals
may view and make privileged modifications to the Kerberos database
files. The filename should match the value you have set for
“acl_file” in your kdc.conf file. The default file name is
/usr/local/var/krb5kdc/kadm5.acl.
The format of the file is:
Kerberos_principal permissions [target_principal] [restrictions]
The Kerberos principal (and optional target principal) can include the
“*” wildcard, so if you want any principal with the instance
“admin” to have full permissions on the database, you could use the
principal “*/admin@REALM” where “REALM” is your Kerberos
realm. target_principal can also include backreferences to
Kerberos_principal, in which "*number" matches the
component number in the Kerberos_principal.
Note: a common use of an admin instance is so you can grant
separate permissions (such as administrator access to the Kerberos
database) to a separate Kerberos principal. For example, the user
joeadmin might have a principal for his administrative
use, called joeadmin/admin. This way,
joeadmin would obtain joeadmin/admin
tickets only when he actually needs to use those permissions.
The permissions are represented by single letters; UPPER-CASE letters represent negative permissions. The permissions are:
The restrictions are a string of flags. Allowed restrictions are:
+ and - flags for the kadmin addprinc and
modprinc commands.
The above flags act as restrictions on any add or modify operation which is allowed due to that ACL line.
Here is an example of a kadm5.acl file. Note that order is
important; permissions are determined by the first matching entry.
*/admin@ATHENA.MIT.EDU *
joeadmin@ATHENA.MIT.EDU ADMCIL
joeadmin/*@ATHENA.MIT.EDU il */root@ATHENA.MIT.EDU
*@ATHENA.MIT.EDU cil *1/admin@ATHENA.MIT.EDU
*/*@ATHENA.MIT.EDU i
*/admin@EXAMPLE.COM * -maxlife 9h -postdateable
In the above file, any principal in the
ATHENA.MIT.EDU realm with an admin instance has all
administrative privileges. The user joeadmin
has all permissions with his admin instance,
joeadmin/admin@ATHENA.MIT.EDU (matches the first
line). He has no permissions at all with his null instance,
joeadmin@ATHENA.MIT.EDU (matches the second line).
His root instance has inquire and list permissions with any
other principal that has the instance root. Any principal
in ATHENA.MIT.EDU can inquire, list, or change the password of
their admin instance, but not any other admin instance.
Any principal in the realm ATHENA.MIT.EDU (except for
joeadmin@ATHENA.MIT.EDU, as mentioned above) has
inquire privileges. Finally, any principal with an admin instance
in EXAMPLE.COM has all permissions, but any principal that they
create or modify will not be able to get postdateable tickets or tickets
with a life of longer than 9 hours.
Next you need to add administrative principals to the Kerberos database.
(You must add at least one now.) To do this, use kadmin.local
on the master KDC. The administrative principals you create
should be the ones you added to the ACL file. (See See Add Administrators to the Acl File.) In the following example, the
administration principal admin/admin is created:
shell% /usr/local/sbin/kadmin.local
kadmin.local: addprinc admin/admin@ATHENA.MIT.EDU
NOTICE: no policy specified for "admin/admin@ATHENA.MIT.EDU";
assigning "default".
Enter password for principal admin/admin@ATHENA.MIT.EDU: <= Enter a password.
Re-enter password for principal admin/admin@ATHENA.MIT.EDU: <= Type it again.
Principal "admin/admin@ATHENA.MIT.EDU" created.
kadmin.local:
The kadmind keytab is the key that the legacy admininstration daemons
kadmind4 and v5passwdd will use to decrypt
administrators' or clients' Kerberos tickets to determine whether or
not they should have access to the database. You need to create the
kadmin keytab with entries for the principals kadmin/admin and
kadmin/changepw. (These principals are placed in the Kerberos
database automatically when you create it.) To create the kadmin
keytab, run kadmin.local and use the ktadd command, as
in the following example. (The line beginning with => is a
continuation of the previous line.):
shell% /usr/local/sbin/kadmin.local
kadmin.local: ktadd -k /usr/local/var/krb5kdc/kadm5.keytab
=> kadmin/admin kadmin/changepw
Entry for principal kadmin/admin with kvno 5, encryption
type Triple DES cbc mode with HMAC/sha1 added to keytab
WRFILE:/usr/local/var/krb5kdc/kadm5.keytab.
Entry for principal kadmin/admin with kvno 5, encryption type DES cbc mode
with CRC-32 added to keytab
WRFILE:/usr/local/var/krb5kdc/kadm5.keytab.
Entry for principal kadmin/changepw with kvno 5, encryption
type Triple DES cbc mode with HMAC/sha1 added to keytab
WRFILE:/usr/local/var/krb5kdc/kadm5.keytab.
Entry for principal kadmin/changepw with kvno 5,
encryption type DES cbc mode with CRC-32 added to keytab
WRFILE:/usr/local/var/krb5kdc/kadm5.keytab.
kadmin.local: quit
shell%
As specified in the -k argument, ktadd will save the
extracted keytab as
/usr/local/var/krb5kdc/kadm5.keytab.
The filename you use must be the one specified in your kdc.conf
file.
At this point, you are ready to start the Kerberos daemons on the Master KDC. To do so, type:
shell% /usr/local/sbin/krb5kdc
shell% /usr/local/sbin/kadmind
Each daemon will fork and run in the background. Assuming you want
these daemons to start up automatically at boot time, you can add them
to the KDC's /etc/rc or /etc/inittab file. You need to
have a stash file in order to do this.
You can verify that they started properly by checking for their startup
messages in the logging locations you defined in /etc/krb5.conf.
(See Edit the Configuration Files.) For example:
shell% tail /var/log/krb5kdc.log
Dec 02 12:35:47 beeblebrox krb5kdc[3187](info): commencing operation
shell% tail /var/log/kadmin.log
Dec 02 12:35:52 beeblebrox kadmind[3189](info): starting
Any errors the daemons encounter while starting will also be listed in the logging output.
You are now ready to start configuring the slave KDCs. Assuming you are setting the KDCs up so that you can easily switch the master KDC with one of the slaves, you should perform each of these steps on the master KDC as well as the slave KDCs, unless these instructions specify otherwise.
Each KDC needs a host principal in the Kerberos database. You can enter
these from any host, once the kadmind daemon is running. For
example, if your master KDC were called
kerberos.mit.edu, and you had two KDC slaves
named kerberos-1.mit.edu and
kerberos-2.mit.edu, you would type the following:
shell% /usr/local/sbin/kadmin
kadmin: addprinc -randkey host/kerberos.mit.edu
NOTICE: no policy specified for "host/kerberos.mit.edu@ATHENA.MIT.EDU";
assigning "default"
Principal "host/kerberos.mit.edu@ATHENA.MIT.EDU" created.
kadmin: addprinc -randkey host/kerberos-1.mit.edu
NOTICE: no policy specified for "host/kerberos-1.mit.edu@ATHENA.MIT.EDU";
assigning "default"
Principal "host/kerberos-1.mit.edu@ATHENA.MIT.EDU" created.
kadmin: addprinc -randkey host/kerberos-2.mit.edu
NOTICE: no policy specified for "host/kerberos-2.mit.edu@ATHENA.MIT.EDU";
assigning "default"
Principal "host/kerberos-2.mit.edu@ATHENA.MIT.EDU" created.
kadmin:
It is not actually necessary to have the master KDC server in the Kerberos database, but it can be handy if:
Each KDC (including the master) needs a keytab to decrypt tickets. Ideally, you should extract each keytab locally on its own KDC. If this is not feasible, you should use an encrypted session to send them across the network. To extract a keytab on a KDC called kerberos.mit.edu, you would execute the following command:
kadmin: ktadd host/kerberos.mit.edu
kadmin: Entry for principal host/kerberos.mit.edu@ATHENA.MIT.EDU with
kvno 1, encryption type DES-CBC-CRC added to keytab
WRFILE:/etc/krb5.keytab.
kadmin:
Note that the principal must exist in the Kerberos database in order to extract the keytab.
The database is propagated from the master KDC to the slave KDCs via the
kpropd daemon. To set up propagation, create a file on each KDC,
named /usr/local/var/krb5kdc/kpropd.acl, containing the
principals for each of the KDCs.
For example, if the master KDC were
kerberos.mit.edu, the slave KDCs were
kerberos-1.mit.edu and
kerberos-2.mit.edu, and the realm were
ATHENA.MIT.EDU, then the file's contents would be:
host/kerberos.mit.edu@ATHENA.MIT.EDU
host/kerberos-1.mit.edu@ATHENA.MIT.EDU
host/kerberos-2.mit.edu@ATHENA.MIT.EDU
Then, add the following lines to /etc/inetd.conf file on each KDC
(the line beginnng with => is a continuation of the previous
line):
krb5_prop stream tcp nowait root /usr/local/sbin/kpropd kpropd
eklogin stream tcp nowait root /usr/local/sbin/klogind
=> klogind -k -c -e
The first line sets up the kpropd database propagation daemon.
The second line sets up the eklogin daemon, allowing
Kerberos-authenticated, encrypted rlogin to the KDC.
You also need to add the following lines to /etc/services on each
KDC:
kerberos 88/udp kdc # Kerberos authentication (udp)
kerberos 88/tcp kdc # Kerberos authentication (tcp)
krb5_prop 754/tcp # Kerberos slave propagation
kerberos-adm 749/tcp # Kerberos 5 admin/changepw (tcp)
kerberos-adm 749/udp # Kerberos 5 admin/changepw (udp)
eklogin 2105/tcp # Kerberos encrypted rlogin
Now that the slave KDCs are able to accept database propagation, you'll need to propagate the database to each of them.
First, create a dump of the database on the master KDC, as follows:
shell% /usr/local/sbin/kdb5_util dump /usr/local/var/krb5kdc/slave_datatrans
shell%
Next, you need to manually propagate the database to each slave KDC, as in the following example. (The lines beginning with => are continuations of the previous line.):
/usr/local/sbin/kprop -f /usr/local/var/krb5kdc/slave_datatrans
=> kerberos-1.mit.edu
/usr/local/sbin/kprop -f /usr/local/var/krb5kdc/slave_datatrans
=> kerberos-2.mit.edu
You will need a script to dump and propagate the database. The following is an example of a bourne shell script that will do this. (Note that the line that begins with => is a continuation of the previous line. Remember that you need to replace /usr/local with the name of the directory in which you installed Kerberos V5.)
#!/bin/sh
kdclist = "kerberos-1.mit.edu kerberos-2.mit.edu"
/usr/local/sbin/kdb5_util "dump
=> /usr/local/var/krb5kdc/slave_datatrans"
for kdc in $kdclist
do
/usr/local/sbin/kprop -f /usr/local/var/krb5kdc/slave_datatrans $kdc
done
You will need to set up a cron job to run this script at the intervals you decided on earlier (See Database Propagation.)
Now that the slave KDCs have copies of the Kerberos database, you can
create stash files for them and start the krb5kdc daemon.
Create stash files, by issuing the following commands on each slave KDC:
shell% kdb5_util stash
kdb5_util: Cannot find/read stored master key while reading master key
kdb5_util: Warning: proceeding without master key
Enter KDC database master key: <= Enter the database master key.
shell%
As mentioned above, the stash file is necessary for your KDCs to be able authenticate to themselves, such as when they reboot. You could run your KDCs without stash files, but you would then need to type in the Kerberos database master key by hand every time you start a KDC daemon.
The final step in configuing your slave KDCs is to run the KDC daemon:
shell% /usr/local/sbin/krb5kdc
As with the master KDC, you will probably want to add this command to
the KDCs' /etc/rc or /etc/inittab files, so they will
start the krb5kdc daemon automatically at boot time.
Once your KDCs are set up and running, you are ready to use
kadmin to load principals for your users, hosts, and other
services into the Kerberos database. This procedure is described fully in the
“Adding or Modifying Principals” section of the Kerberos V5 System
Administrator's Guide. (See Create Host Keys for the Slave KDCs, for a
brief description.) The keytab is generated by running kadmin
and issuing the ktadd command.
To limit the possibility that your Kerberos database could be compromised, MIT recommends that each KDC be a dedicated host, with limited access. If your KDC is also a file server, FTP server, Web server, or even just a client machine, someone who obtained root access through a security hole in any of those areas could gain access to the Kerberos database.
MIT recommends that your KDCs use the following
/etc/inetd.conf file. (Note: each line beginning with =>
is a continuation of the previous line.):
#
# Configuration file for inetd(1M). See inetd.conf(4).
#
# To re-configure the running inetd process, edit this file, then
# send the inetd process a SIGHUP.
#
# Syntax for socket-based Internet services:
# <service_name> <socket_type> <proto> <flags> <user>
=> <server_pathname> <args>
#
# Syntax for TLI-based Internet services:
#
# <service_name> tli <proto> <flags> <user> <server_pathname> <args>
#
# Ftp and telnet are standard Internet services.
#
# This machine is a secure Kerberos Key Distribution Center (KDC).
# Services are limited.
#
#
# Time service is used for clock synchronization.
#
time stream tcp nowait root internal
time dgram udp wait root internal
#
# Limited Kerberos services
#
krb5_prop stream tcp nowait root /usr/local/sbin/kpropd kpropd
eklogin stream tcp nowait root /usr/local/sbin/klogind
=> klogind -5 -c -e
You may occasionally want to use one of your slave KDCs as the master. This might happen if you are upgrading the master KDC, or if your master KDC has a disk crash.
Assuming you have configured all of your KDCs to be able to function as either the master KDC or a slave KDC (as this document recommends), all you need to do to make the changeover is:
If the master KDC is still running, do the following on the old master KDC:
kadmind process.
On the new master KDC:
kadmind daemon. (See Start the Kerberos Daemons.)
krb5.conf file on every client
machine in your Kerberos realm.)
Client machine installation is much more straightforward than installation of the KDCs.
The Kerberized client programs are login.krb5, rlogin,
telnet, ftp, rcp, rsh, kinit,
klist, kdestroy, kpasswd, ksu, and
krb524init. All of these programs are in the directory
/usr/local/bin, except for login.krb5 which is in
/usr/local/sbin.
You will probably want to have your users put /usr/local/bin
ahead of /bin and /usr/bin in their paths, so they will by
default get the Kerberos V5 versions of rlogin,
telnet, ftp, rcp, and rsh.
MIT recommends that you use login.krb5 in place of
/bin/login to give your users a single-sign-on system. You will
need to make sure your users know to use their Kerberos passwords when
they log in.
You will also need to educate your users to use the ticket management
programs kinit,
klist, kdestroy, and to use the Kerberos programs
ksu, and kpasswd in place of their non-Kerberos
counterparts
su, passwd, and rdist.
Each machine running Kerberos must have a /etc/krb5.conf file.
(See krb5.conf.)
Also, for most UNIX systems, you must add the appropriate Kerberos
services to each client machine's /etc/services file. If you are
using the default configuration for Kerberos V5, you should be able
to just insert the following code:
#
# Note --- if you are using Kerberos V4 and you either:
#
# (a) haven't converted all your master or slave KDCs to V5, or
#
# (b) are worried about inter-realm interoperability with other KDC's
# that are still using V4
#
# you will need to switch the "kerberos" service to port 750 and create a
# "kerberos-sec" service on port 88.
#
kerberos 88/udp kdc # Kerberos V5 KDC
kerberos 88/tcp kdc # Kerberos V5 KDC
klogin 543/tcp # Kerberos authenticated rlogin
kshell 544/tcp cmd # and remote shell
kerberos-adm 749/tcp # Kerberos 5 admin/changepw
kerberos-adm 749/udp # Kerberos 5 admin/changepw
krb5_prop 754/tcp # Kerberos slave propagation
eklogin 2105/tcp # Kerberos auth. & encrypted rlogin
krb524 4444/tcp # Kerberos 5 to 4 ticket translator
As described in the comments in the above code, if your master
KDC or any of your slave KDCs is running Kerberos V4, (or if you will be
authenticating to any Kerberos V4 KDCs in another realm) you will need
to switch the port number for kerberos to 750 and create a
kerberos-sec service (tcp and udp) on port 88, so the Kerberos
V4 KDC(s) will continue to work properly.
To install Kerberos V5 on Mac OS X and Mac OS X Server, follow the
directions for generic Unix-based OS's, except for the
/etc/services updates described above.
Mac OS X and Mac OS X Server use a database called NetInfo to store
the contents of files normally found in /etc. Instead of
modifying /etc/services, you should run the following commands
to add the Kerberos service entries to NetInfo:
$ niutil -create . /services/kerberos
$ niutil -createprop . /services/kerberos name kerberos kdc
$ niutil -createprop . /services/kerberos port 750
$ niutil -createprop . /services/kerberos protocol tcp udp
$ niutil -create . /services/krbupdate
$ niutil -createprop . /services/krbupdate name krbupdate kreg
$ niutil -createprop . /services/krbupdate port 760
$ niutil -createprop . /services/krbupdate protocol tcp
$ niutil -create . /services/kpasswd
$ niutil -createprop . /services/kpasswd name kpasswd kpwd
$ niutil -createprop . /services/kpasswd port 761
$ niutil -createprop . /services/kpasswd protocol tcp
$ niutil -create . /services/klogin
$ niutil -createprop . /services/klogin port 543
$ niutil -createprop . /services/klogin protocol tcp
$ niutil -create . /services/eklogin
$ niutil -createprop . /services/eklogin port 2105
$ niutil -createprop . /services/eklogin protocol tcp
$ niutil -create . /services/kshell
$ niutil -createprop . /services/kshell name kshell krcmd
$ niutil -createprop . /services/kshell port 544
$ niutil -createprop . /services/kshell protocol tcp
In addition to adding services to NetInfo, you must also modify the resolver configuration in NetInfo so that the machine resolves its own hostname as a FQDN (fully qualified domain name). By default, Mac OS X and Mac OS X Server machines query NetInfo to resolve hostnames before falling back to DNS. Because NetInfo has an unqualified name for all the machines in the NetInfo database, the machine's own hostname will resolve to an unqualified name. Kerberos needs a FQDN to look up keys in the machine's keytab file.
Fortunately, you can change the lookupd caching order to query
DNS first. Run the following NetInfo commands and reboot the machine:
$ niutil -create . /locations/lookupd/hosts
$ niutil -createprop . /locations/lookupd/hosts LookupOrder CacheAgent DNSAgent
NIAgent NILAgent
Once you have rebooted, you can verify that the resolver now behaves correctly. Compile the Kerberos 5 distribution and run:
$ cd .../src/tests/resolve
$ ./resolve
This will tell you whether or not your machine returns FQDNs on name lookups. If the test still fails, you can also try turning off DNS caching. Run the following commands and reboot:
$ niutil -create . /locations/lookupd/hosts
$ niutil -createprop . /locations/lookupd/hosts LookupOrder DNSAgent
CacheAgent NIAgent NILAgent
The remainder of the setup of a Mac OS X client machine or application server should be the same as for other UNIX-based systems.
An application server is a host that provides one or more services over the network. Application servers can be “secure” or “insecure.” A “secure” host is set up to require authentication from every client connecting to it. An “insecure” host will still provide Kerberos authentication, but will also allow unauthenticated clients to connect.
If you have Kerberos V5 installed on all of your client machines, MIT recommends that you make your hosts secure, to take advantage of the security that Kerberos authentication affords. However, if you have some clients that do not have Kerberos V5 installed, you can run an insecure server, and still take advantage of Kerberos V5's single sign-on capability.
Just as Kerberos V5 provided its own Kerberos-enhanced versions of
client UNIX network programs, Kerberos V5 also provides
Kerberos-enhanced versions of server UNIX network daemons. These are
ftpd, klogind, kshd, and telnetd.
These programs are installed in the directory
/usr/local/sbin. You may want to add this directory to
root's path.
For a secure server, make the following changes to
/etc/inetd.conf:
Find and comment out any lines for the services ftp,
telnet, shell, login, and exec.
Add the following lines. (Note: each line beginning with => is a continuation of the previous line.)
klogin stream tcp nowait root /usr/local/sbin/klogind
=> klogind -k -c
eklogin stream tcp nowait root /usr/local/sbin/klogind
=> klogind -k -c -e
kshell stream tcp nowait root /usr/local/sbin/kshd
=> kshd -k -c -A
ftp stream tcp nowait root /usr/local/sbin/ftpd
=> ftpd -a
telnet stream tcp nowait root /usr/local/sbin/telnetd
=> telnetd -a valid
For an insecure server, make the following changes instead to
/etc/inetd.conf:
Find and comment out any lines for the services ftp and
telnet.
Add the following lines. (Note: each line beginning with => is a continuation of the previous line.)
klogin stream tcp nowait root /usr/local/sbin/klogind
=> klogind -k -c
eklogin stream tcp nowait root /usr/local/sbin/klogind
=> klogind -k -c -e
kshell stream tcp nowait root /usr/local/sbin/kshd
=> kshd -k -c -A
ftp stream tcp nowait root /usr/local/sbin/ftpd
=> ftpd
telnet stream tcp nowait root /usr/local/sbin/telnetd
=> telnetd -a none
All Kerberos server machines need a keytab file, called
/etc/krb5.keytab, to authenticate to the KDC. The keytab file is
an encrypted, local, on-disk copy of the host's key. The keytab file,
like the stash file (Create the Database) is a potential
point-of-entry for a break-in, and if compromised, would allow
unrestricted access to its host. The keytab file should be readable
only by root, and should exist only on the machine's local disk. The
file should not be part of any backup of the machine, unless access to
the backup data is secured as tightly as access to the machine's root
password itself.
In order to generate a keytab for a host, the host must have a principal
in the Kerberos database. The procedure for adding hosts to the
database is described fully in the “Adding or Modifying Principals”
section of the Kerberos V5 System Administrator's Guide.
See Create Host Keys for the Slave KDCs. for a brief description.)
The keytab is generated by running kadmin and issuing the
ktadd command.
For example, to generate a keytab file to allow the host
trillium.mit.edu to authenticate for the services
host, ftp, and pop, the administrator
joeadmin would issue the command (on
trillium.mit.edu):
trillium% /usr/local/sbin/kadmin
kadmin5: ktadd host/trillium.mit.edu ftp/trillium.mit.edu
=> pop/trillium.mit.edu
kadmin: Entry for principal host/trillium.mit.edu@ATHENA.MIT.EDU with
kvno 3, encryption type DES-CBC-CRC added to keytab
WRFILE:/etc/krb5.keytab.
kadmin: Entry for principal ftp/trillium.mit.edu@ATHENA.MIT.EDU with
kvno 3, encryption type DES-CBC-CRC added to keytab
WRFILE:/etc/krb5.keytab.
kadmin: Entry for principal pop/trillium.mit.edu@ATHENA.MIT.EDU with
kvno 3, encryption type DES-CBC-CRC added to keytab
WRFILE:/etc/krb5.keytab.
kadmin5: quit
trillium%
If you generate the keytab file on another host, you need to get a copy
of the keytab file onto the destination host (trillium, in the
above example) without sending it unencrypted over the network. If you
have installed the Kerberos V5 client programs, you can use
encrypted rcp.
Kerberos V5 can protect your host from certain types of break-ins, but it is possible to install Kerberos V5 and still leave your host vulnerable to attack. Obviously an installation guide is not the place to try to include an exhaustive list of countermeasures for every possible attack, but it is worth noting some of the larger holes and how to close them.
As stated earlier in this section, MIT recommends that on a
secure host, you disable the standard ftp, login,
telnet, shell, and exec services in
/etc/inetd.conf. We also recommend that secure hosts have an empty
/etc/hosts.equiv file and that there not be a .rhosts file
in root's home directory. You can grant Kerberos-authenticated
root access to specific Kerberos principals by placing those principals
in the file .k5login in root's home directory.
We recommend that backups of secure machines exclude the keytab file
(/etc/krb5.keytab). If this is not possible, the backups should
at least be done locally, rather than over a network, and the backup
tapes should be physically secured.
Finally, the keytab file and any programs run by root, including the Kerberos V5 binaries, should be kept on local disk. The keytab file should be readable only by root.
If you already have an existing Kerberos database that you created with
a prior release of Kerberos 5, you can upgrade it to work with the
current release with the kdb5_util command. It is only
necessary to perform this dump/undump procedure if you were running a
krb5-1.0.x KDC and are migrating to a krb5-1.1.x or newer KDC or if you
were running a krb5-1.1.x KDC and are migrating to a krb5-1.2.x or newer
KDC. The process for upgrading a Master KDC involves the following
steps:
kdb5_util's “dump” command:
shell% cd /usr/local/var/krb5kdc
shell% kdb5_util dump old-kdb-dump
shell% kdb5_util dump -ov old-kdb-dump.ov
shell%
kdb5_util's “load” command:
shell% cd /usr/local/var/krb5kdc
shell% kdb5_util load old-kdb-dump
shell% kdb5_util load -update old-kdb-dump.ov
shell%
The “dump -ov” and “load -update” commands are necessary in order to preserve per-principal policy information, since the default dump format filters out that information. If you omit those steps, the loaded database database will lose the policy information for each principal that has a policy.
To update a Slave KDC, you must stop the old server processes on the Slave KDC, install the new server binaries, reload the most recent slave dump file, and re-start the server processes.
Beginning with the 1.2 release from MIT, Kerberos includes a stronger encryption algorithm called “triple DES” – essentially, three applications of the basic DES encryption algorithm, greatly increasing the resistance to a brute-force search for the key by an attacker. This algorithm is more secure, but encryption is much slower.
Release 1.1 had some support for triple-DES service keys, but with release 1.2 we have added support for user keys and session keys as well. Release 1.0 had very little support for multiple cryptosystems, and some of that software may not function properly in an environment using triple-DES as well as plain DES.
In the 1.3 release from MIT, Kerberos also includes the RC4 encryption alogorithm, a stream cipher symmetric key algorithm developed in 1987 by Ronald Rivest at RSA Data Security. Please note that RC4 is not part of the IETF standard.
Because of the way the MIT Kerberos database is structured, the KDC will assume that a service supports only those encryption types for which keys are found in the database. Thus, if a service has only a single-DES key in the database, the KDC will not issue tickets for that service that use triple-DES or RC4 session keys; it will instead issue only single-DES session keys, even if other services are already capable of using triple-DES or RC4. So if you make sure your application server software is updated before adding a triple-DES or RC4 key for the service, clients should be able to talk to services at all times during the updating process.
Normally, the listed supported_enctypes in kdc.conf are
all used when a new key is generated. You can control this with
command-line flags to kadmin and kadmin.local. You may
want to exclude triple-DES and RC4 by default until you have updated a
lot of your application servers, and then change the default to include
triple-DES and RC4. We recommend that you always include
des-cbc-crc in the default list.
In any complex software, there will be bugs. If you have successfully
built and installed Kerberos V5, please use the krb5-send-pr
program to fill out a Problem Report should you encounter any errors in
our software.
Bug reports that include proposed fixes are especially welcome. If you do include fixes, please send them using either context diffs or unified diffs (using diff -c or diff -u, respectively). Please be careful when using “cut and paste” or other such means to copy a patch into a bug report; depending on the system being used, that can result in converting TAB characters into spaces, which makes applying the patches more difficult.
The krb5-send-pr program is installed in the directory
/usr/local/sbin.
The krb5-send-pr program enters the problem report into our
Problem Report Management System (PRMS), which automatically assigns it
to the engineer best able to help you with problems in the assigned
category.
The krb5-send-pr program will try to intelligently fill in as
many fields as it can. You need to choose the category,
class, severity, and priority of the problem, as well
as giving us as much information as you can about its exact nature.
The PR category will be one of:
krb5-admin krb5-appl krb5-build krb5-clients
krb5-doc krb5-kdc krb5-libs krb5-misc
pty telnet test
Choose the category that best describes the area under which your problem falls.
The class can be sw-bug, doc-bug, change-request, or support. The first two are exactly as their names imply. Use change-request when the software is behaving according to specifications, but you want to request changes in some feature or behavior. The support class is intended for more general questions about building or using Kerberos V5.
The severity of the problem indicates the problem's impact on the usability of Kerberos V5. If a problem is critical, that means the product, component or concept is completely non-operational, or some essential functionality is missing, and no workaround is known. A serious problem is one in which the product, component or concept is not working properly or significant functionality is missing. Problems that would otherwise be considered critical are rated serious when a workaround is known. A non-critical problem is one that is indeed a problem, but one that is having a minimal effect on your ability to use Kerberos V5. E.g., The product, component or concept is working in general, but lacks features, has irritating behavior, does something wrong, or doesn't match its documentation. The default severity is serious.
The priority indicates how urgent this particular problem is in relation to your work. Note that low priority does not imply low importance. A priority of high means a solution is needed as soon as possible. A priority of medium means the problem should be solved no later than the next release. A priority of low means the problem should be solved in a future release, but it is not important to your work how soon this happens. The default priority is medium.
Note that a given severity does not necessarily imply a given priority. For example, a non-critical problem might still have a high priority if you are faced with a hard deadline. Conversely, a serious problem might have a low priority if the feature it is disabling is one that you do not need.
It is important that you fill in the release field and tell us what changes you have made, if any.
A sample filled-out form from a company named “Toasters, Inc.” might look like this:
To: krb5-bugs@mit.edu
Subject: misspelled "Kerberos" in title of installation guide
From: jcb
Reply-To: jcb
Cc:
X-send-pr-version: 3.99
>Submitter-Id: mit
>Originator: Jeffrey C. Gilman Bigler
>Organization:
mit
>Confidential: no
>Synopsis: Misspelled "Kerberos" in title of installation guide
>Severity: non-critical
>Priority: low
>Category: krb5-doc
>Class: doc-bug
>Release: 1.0-development
>Environment:
<machine, os, target, libraries (multiple lines)>
System: ULTRIX imbrium 4.2 0 RISC
Machine: mips
>Description:
Misspelled "Kerberos" in title of "Kerboros V5 Installation Guide"
>How-To-Repeat:
N/A
>Fix:
Correct the spelling.
If the krb5-send-pr program does not work for you, or if you did
not get far enough in the process to have an installed and working
krb5-send-pr, you can generate your own form, using the above as
an example.
[1] Kerberos V4 used port 750. If necessary, you can run on both ports for backward compatibility.
[2] If you are fortunate enough to have a previous version of Kerberos V5 or V4 installed, and the Kerberos rlogin is first in your path, you can setup .k5login or .klogin respectively to allow you access.