Copyright (C) 1985-2001 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.
@hrule
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 Reserved WARNING: 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.
@hrule
Kerberos V5 includes documentation and software developed at the University of California at Berkeley, which includes this copyright notice:
Copyright (C) 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:
This product includes software developed by the University of California, Berkeley and its contributors.
@hrule
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. @pagealignmacro
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.
This document is one piece of the document set for Kerberos V5. The documents, and their intended audiences, are:
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.
The next chapter describes the decisions you need to make before installing Kerberos V5.
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.
The appendices give sample configuration files.
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 fubar.org would be in the Kerberos realm FUBAR.ORG.
If you need multiple Kerberos realms, MIT recommends that you use descriptive names which end with your domain name, such as BOSTON.FUBAR.ORG and HOUSTON.FUBAR.ORG.
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 section 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 Kerberos V5 System Administrator's Guide contains a thorough
description of the parts of the krb5.conf file and what may be
specified in each. A sample krb5.conf file appears in
section krb5.conf. You should be able to use this file, substituting the
relevant information for your Kerberos installation for the samples.
The second mechanism, recently introduced into the MIT code base but not
currently used by default, works by looking up the information in
special TXT records in the Domain Name Service. 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 up anyways, for use when interacting with other sites.
The default ports used by Kerberos are port 88 for the
KDC(1) 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-master._udp
_kerberos-adm._tcp
kadmin program and related utilities. For now, you will also
need the admin_server entry in krb5.conf.
_kpasswd._udp
Be 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.
Starting with the Beta 4 distribution, we are using a new configuration system, which was built using the Free Software Foundation's `autoconf' program. This system will hopefully make Kerberos V5 much simpler to build and reduce the amount of effort required in porting Kerberos V5 to a new platform.
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.
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 two compressed tar files. The first file, which is generally named `krb5-1.2.src.tar.gz', contains the sources for all of Kerberos except for the crypto library, which is found in the file `krb5-1.2.crypto.tar.gz'.
Both files should be unpacked in the same directory, such as `/u1/krb5-1.2'. (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 `./krb5-1.2' directory, so that if your current directory is `/u1' when you unpack the tarfiles, you will get `/u1/krb5-1.2/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 section Operating System 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/krb5-1.2/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/krb5-1.2/pmax
cd /u1/krb5-1.2/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/krb5-1.2/solaris
cd /u1/krb5-1.2/solaris
/u1/krb5-1.2/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.
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 section Doing the Build.):
% make check
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-privledged 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 section 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=LOCALSTATEDIR
LOCALSTATEDIR/krb5kdc, which is by default
PREFIX/var/krb5kdc.
--with-cc=COMPILER
COMPILER as the C compiler.
--with-ccopts=FLAGS
FLAGS 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'.
--with-cppopts=CPPOPTS
CPPOPTS 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.
--with-linker=LINKER
LINKER as the default loader if it should be different from C
compiler as specified above.
--with-ldopts=LDOPTS
--with-krb4
--with-krb4=KRB4DIR
KRB4DIR 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 section 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-vague-errors
--with-kdc-kdb-update
--with-tcl=TCLPATH
TCLPATH 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
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 --with-cc=suncc --with-ccopts=-O
There is one configuration file which you may wish to edit to control various compile-time parameters in the Kerberos distribution: `include/krb5/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 section Options to Configure.
DEFAULT_PROFILE_PATH
DEFAULT_KEYTAB_NAME
DEFAULT_KDC_ENCTYPE
KDCRCACHE
RCTMPDIR
DEFAULT_KDB_FILE
Shared 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 (aka SunOS 5.6) and Irix 6.5.
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, NetBSD 1.4.x (i386), and HP/UX 10.20.
Platforms for which there is shared library support but not significant testing include FreeBSD, OpenBSD, MacOS 10, AIX, Linux, 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 work arounds 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 any optimizer problems with the native compiler.
Alpha Tru64 4.0 will have some trouble compiling the some stdarg prototypes, since it defaults to K&R C. Use the `-std' or `-std1' flags to force ANSI behavior (e.g. `./configure --with-cc='cc -std1'').
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 compiler (c89) should work as long as you give it the `-D_HPUX_SOURCE' flag (i.e. `./configure --with-cc='c89 -D_HPUX_SOURCE''). This has only been tested recently for HPUX 10.20.
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 dnsand 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 dclNote 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
--with-ccopts=-i option to `configure'.
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' version 2.4, 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 section `Overview' in 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/krb5-1.2/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/krb5-1.2/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 section 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
(see section krb5.conf) and /usr/local/var/krb5kdc/kdc.conf
(see section 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.
Among the settings in your /etc/krb5.conf file, be sure to create
a [logging] stanza so that the KDC and kadmind will generate
logging output. For example:
[logging]
kdc = FILE:/var/log/krb5kdc.log
admin_server = FILE:/var/log/kadmin.log
default = FILE:/var/log/krb5lib.log
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 section 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.
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: @doubleleftarrow{ Type the master password.}
Re-enter KDC database master key to verify: @doubleleftarrow{ 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. The
filename should match the value you have set for "acl_file" in your
kdc.conf file. The default file name is `kadm5.acl'. The
format of the file is:
Kerberos principal permissions optional target principal
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.
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. Refer to
the Kerberos V5 Administrator's Guide or the Kerberos V5 User's
Guide for more detailed explanations of principals and
instances.
The permissions (acls) recognized in the acl file are the following:
To give the principal */admin@ATHENA.MIT.EDU permission to
change all of the database permissions on any principal permissions, you
would place the following line in the file:
*/admin@ATHENA.MIT.EDU *
To give the principal joeadmin@ATHENA.MIT.EDU
permission to add, list, and inquire about any principal that has the
instance "root", you would add the following line to the acl file:
joeadmin@ATHENA.MIT.EDU ali */root@ATHENA.MIT.EDU
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 section 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
WARNING: no policy specified for "admin/admin@ATHENA.MIT.EDU";
defaulting to no policy.
Enter password for principal admin/admin@ATHENA.MIT.EDU: @doubleleftarrow{ Enter a password.}
Re-enter password for principal admin/admin@ATHENA.MIT.EDU: @doubleleftarrow{ Type it again.}
Principal "admin/admin@ATHENA.MIT.EDU" created.
kadmin.local:
The kadmind keytab is the key that kadmind will use to decrypt
administrators' Kerberos tickets to determine whether or not it should
give them 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@ATHENA.MIT.EDU with
kvno 3, encryption type DES-CBC-CRC added to keytab
WRFILE:/usr/local/var/krb5kdc/kadm5.keytab.
Entry for principal kadmin/changepw@ATHENA.MIT.EDU with
kvno 3, encryption type DES-CBC-CRC 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 See section 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 WARNING: no policy specified for "host/kerberos.mit.edu@ATHENA.MIT.EDU"; defaulting to no policy. Principal "host/kerberos.mit.edu@ATHENA.MIT.EDU" created. kadmin: addprinc -randkey host/kerberos-1.mit.edu WARNING: no policy specified for "host/kerberos-1.mit.edu@ATHENA.MIT.EDU"; defaulting to no policy. Principal "host/kerberos-1.mit.edu@ATHENA.MIT.EDU" created. kadmin: addprinc -randkey host/kerberos-2.mit.edu WARNING: no policy specified for "host/kerberos-2.mit.edu@ATHENA.MIT.EDU"; defaulting to no policy. 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 -R "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 section 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: @doubleleftarrow{ 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 section 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 section Start the Kerberos Daemons on the Master KDC.)
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 section 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 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 (section 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 section 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. 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 dump format in releases prior to 1.2.2 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. We expect to add other, faster encryption algorithms at some point in the future.
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.
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 session keys; it will instead issue only single-DES session keys, even if other services are already capable of using triple-DES. So if you make sure your application server software is updated before adding a triple-DES 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 by default until you have updated a lot of
your application servers, and then change the default to include
triple-DES. 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.
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.
Bug reports that include proposed fixes are especially welcome. If you include proposed fixes, please send them using either context diffs (`diff -c') or unified diffs (`diff -u').
@vfill
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.
@vfill
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.
Here is an example krb5.conf file:
[libdefaults]
ticket_lifetime = 600
default_realm = ATHENA.MIT.EDU
default_tkt_enctypes = des3-hmac-sha1 des-cbc-crc
default_tgs_enctypes = des3-hmac-sha1 des-cbc-crc
[realms]
ATHENA.MIT.EDU = {
kdc = kerberos.mit.edu:88
kdc = kerberos-1.mit.edu:88
kdc = kerberos-2.mit.edu:88
admin_server = kerberos.mit.edu:749
default_domain = mit.edu
}
[domain_realm]
.mit.edu = ATHENA.MIT.EDU
mit.edu = ATHENA.MIT.EDU
For the KDCs, add a section onto the end of the krb5.conf file
telling how logging information should be stored, as in the following
example:
[logging]
kdc = FILE:/var/log/krb5kdc.log
admin_server = FILE:/var/log/kadmin.log
default = FILE:/var/log/krb5lib.log
@vfill
Here's an example of a kdc.conf file:
[kdcdefaults]
kdc_ports = 88,750
[realms]
ATHENA.MIT.EDU = {
database_name = /usr/local/var/krb5kdc/principal
admin_keytab = /usr/local/var/krb5kdc/kadm5.keytab
acl_file = /usr/local/var/krb5kdc/kadm5.acl
dict_file = /usr/local/var/krb5kdc/kadm5.dict
key_stash_file = /usr/local/var/krb5kdc/.k5.ATHENA.MIT.EDU
kadmind_port = 749
max_life = 10h 0m 0s
max_renewable_life = 7d 0h 0m 0s
master_key_type = des3-hmac-sha1
supported_enctypes = des3-hmac-sha1:normal des-cbc-crc:normal
}
To add Kerberos V4 support, add des-cbc-crc:v4 to the
supported_enctypes line.
Currently, Kerberos V5 supports only DES and triple-DES encryption.
The encoding types include
des-cbc-crc and des3-cbc-sha1. The salt is
additional information encoded within the key that tells what kind of
key it is. The only salts that you will be likely to encounter are:
kinit, and then only with des-cbc-crc
encryption
Support for additional encryption types is planned in the future.
This document was generated on 15 November 2002 using texi2html 1.56k.