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This file documents how to install the RELEASE release of PRODUCT.

Copyright
*********

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Introduction
************

What is Kerberos and How Does it Work?
======================================

PRODUCT 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.

Why Should I use Kerberos?
==========================

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, PRODUCT from COMPANY will play a vital role in the security of your network.

Please Read the Documentation
=============================

As with any software package that uses a centrallized database, the installation procedure is somewhat involved, and requires forethought and planning.  COMPANY has attempted to make this PRODUCT Installation Guide as concise as possible, rather than making it an exhaustive description of the details of Kerberos.

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Overview of This Guide
======================

The next chapter describes the decisions you need to make before installing PRODUCT.

Chapter three provided instructions for building the Kerberos sources.

Chapter four describes installation procedures for each class of Kerberos machines:

 1. Key Distribution Centers (KDCs).

      A. The Master KDC.

      B. Slave KDCs.

 2. UNIX client machines

 3. UNIX application server machines

Note that a machine can be both a client machine and an application server.

Chapter five describes procedure for updating previous installations of PRODUCT.

Chapter six describes our problem reporting system.

Realm Configuration Decisions
*****************************

Before installing PRODUCT, it is necessary to consider the following issues:

  * The name of your Kerberos realm (or the name of each realm, if you need more than one).

  * How you will map your hostnames onto Kerberos realms.

  * Which ports your KDC and and kadmin (database access) services will use.

  * How many slave KDCs you need and where they should be located.

  * The hostnames of your master and slave KDCs.

  * How frequently you will propagate the database from the master KDC to the slave KDCs.

  * Whether you need backward compatibility with Kerberos V4.

Kerberos Realms
===============

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 SECONDDOMAIN would be in the Kerberos realm SECONDREALM.

If you need multiple Kerberos realms, COMPANY recommends that you use descriptive names which end with your domain name, such as BOSTON.SECONDREALM and HOUSTON.SECONDREALM.

Mapping Hostnames onto Kerberos Realms
======================================

     [file dnstxt.texinfo not included]

Ports for the KDC and Admin Services
====================================

The default ports used by Kerberos are port DefaultPort for the KDC (Kerberos V4 used port DefaultSecondPort.  If
necessary, you can run on both ports for backward compatibility.)  and port DefaultKadmindPort 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 PRODUCT programs, refer to the ``Configuring Your Firewall to Work With PRODUCT'' section of the PRODUCT System Administrator's Guide.

Slave KDCs
==========

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:

  * Have at least one slave KDC as a backup, for when the master KDC is down, is being upgraded, or is otherwise unavailable.

  * If your network is split such that a network outage is likely to cause a network partition (some segment or segments of the network to become cut off or isolated from other segments), have a slave KDC accessible to each segment.

  * If possible, have at least one slave KDC in a different building from the master, in case of power outages, fires, or other localized disasters.

Hostnames for the Master and Slave KDCs
=======================================

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Database Propagation
====================

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.

Building PRODUCT
****************

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Installing PRODUCT
******************

The sections of this chapter describe procedures for installing PRODUCT on:

 1. The KDCs

 2. UNIX client machines

 3. UNIX Application Servers

Installing KDCs
===============

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.

COMPANY 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.

Install the Master KDC
----------------------

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.

Edit the Configuration Files
............................

Modify the configuration files, /etc/krb5.conf and ROOTDIR/var/krb5kdc/kdc.conf to reflect the correct information (such as the hostnames and realm name) for your realm. COMPANY 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 PRODUCT System Administrator's Guide sections on configuration files.

krb5.conf
.........

     [file krb5conf.texinfo not included]

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 = PRIMARYREALM

     [realms]
         PRIMARYREALM = {
         	kdc = KDCSERVER.PRIMARYDOMAIN
         	kdc = KDCSLAVE1.PRIMARYDOMAIN
         	kdc = KDCSLAVE2.PRIMARYDOMAIN
         	admin_server = KDCSERVER.PRIMARYDOMAIN
         {

     [logging]
         kdc = FILE:/var/log/krb5kdc.log
         admin_server = FILE:/var/log/kadmin.log
         default = FILE:/var/log/krb5lib.log

kdc.conf
........

     [file kdcconf.texinfo not included]

Create the Database
...................

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 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 PRIMARYREALM with the name of your Kerberos realm.

     shell% ROOTDIR/sbin/kdb5_util create -r PRIMARYREALM -s
     Initializing database 'ROOTDIR/var/krb5kdc/principal' for
     => realm 'PRIMARYREALM',
     master key name 'K/M@PRIMARYREALM'
     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 ROOTDIR/var/krb5kdc.)  If you do not want a stash file, run the above command without the -s option.

Add Administrators to the Acl File
..................................

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 DefaultAclFile.

     [file kadm5acl.texinfo not included]

Add Administrators to the Kerberos Database
...........................................

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 Add Administrators to the Acl File.)  In the following example, the administration principal admin/admin is created:

     shell% ROOTDIR/sbin/kadmin.local
     kadmin.local: addprinc admin/admin@PRIMARYREALM
     NOTICE: no policy specified for "admin/admin@PRIMARYREALM";
     assigning "default".
     Enter password for principal admin/admin@PRIMARYREALM:  <= Enter a password.
     Re-enter password for principal admin/admin@PRIMARYREALM:  <= Type it again.
     Principal "admin/admin@PRIMARYREALM" created.
     kadmin.local:

Create a kadmind Keytab (optional)
..................................

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% ROOTDIR/sbin/kadmin.local
     kadmin.local: ktadd -k ROOTDIR/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
 ROOTDIR/var/krb5kdc/kadm5.keytab. The filename you use must be the one specified in your kdc.conf file.

Start the Kerberos Daemons on the Master KDC
............................................

At this point, you are ready to start the Kerberos daemons on the Master KDC.  To do so, type:

     shell% ROOTDIR/sbin/krb5kdc
     shell% ROOTDIR/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.

Install the Slave KDCs
----------------------

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.

Create Host Keys for the Slave KDCs
...................................

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 KDCSERVER.PRIMARYDOMAIN, and you had two KDC slaves named KDCSLAVE1.PRIMARYDOMAIN and KDCSLAVE2.PRIMARYDOMAIN, you would type the following:

     shell% ROOTDIR/sbin/kadmin
     kadmin: addprinc -randkey host/KDCSERVER.PRIMARYDOMAIN
     NOTICE: no policy specified for "host/KDCSERVER.PRIMARYDOMAIN@PRIMARYREALM";
     assigning "default"
     Principal "host/KDCSERVER.PRIMARYDOMAIN@PRIMARYREALM" created.
     kadmin: addprinc -randkey host/KDCSLAVE1.PRIMARYDOMAIN
     NOTICE: no policy specified for "host/KDCSLAVE1.PRIMARYDOMAIN@PRIMARYREALM";
     assigning "default"
     Principal "host/KDCSLAVE1.PRIMARYDOMAIN@PRIMARYREALM" created.
     kadmin: addprinc -randkey host/KDCSLAVE2.PRIMARYDOMAIN
     NOTICE: no policy specified for "host/KDCSLAVE2.PRIMARYDOMAIN@PRIMARYREALM";
     assigning "default"
     Principal "host/KDCSLAVE2.PRIMARYDOMAIN@PRIMARYREALM" created.
     kadmin:

It is not actually necessary to have the master KDC server in the Kerberos database, but it can be handy if:

  * anyone will be logging into the machine as something other than root

  * you want to be able to swap the master KDC with one of the slaves if necessary.

Extract Host Keytabs for the KDCs
.................................

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 KDCSERVER.PRIMARYDOMAIN, you would execute the following command:

     kadmin: ktadd host/KDCSERVER.PRIMARYDOMAIN
     kadmin: Entry for principal host/KDCSERVER.PRIMARYDOMAIN@PRIMARYREALM 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.

Set Up the Slave KDCs for Database Propagation
..............................................

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 ROOTDIR/var/krb5kdc/kpropd.acl, containing the principals for each of the KDCs. For example, if the master KDC were KDCSERVER.PRIMARYDOMAIN, the slave KDCs were KDCSLAVE1.PRIMARYDOMAIN and KDCSLAVE2.PRIMARYDOMAIN, and the realm were PRIMARYREALM, then the file's contents would be:

     host/KDCSERVER.PRIMARYDOMAIN@PRIMARYREALM
     host/KDCSLAVE1.PRIMARYDOMAIN@PRIMARYREALM
     host/KDCSLAVE2.PRIMARYDOMAIN@PRIMARYREALM

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 ROOTDIR/sbin/kpropd kpropd
     eklogin   stream tcp nowait root ROOTDIR/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

Back on the Master KDC
----------------------

Now that the slave KDCs are able to accept database propagation, you'll need to propagate the database to each of them.

Propagate the Database to Each Slave KDC
........................................

First, create a dump of the database on the master KDC, as follows:

     shell% ROOTDIR/sbin/kdb5_util dump ROOTDIR/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.):

     ROOTDIR/sbin/kprop -f ROOTDIR/var/krb5kdc/slave_datatrans
     => KDCSLAVE1.PRIMARYDOMAIN
     ROOTDIR/sbin/kprop -f ROOTDIR/var/krb5kdc/slave_datatrans
     => KDCSLAVE2.PRIMARYDOMAIN

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 ROOTDIR with the name of the directory in which you installed PRODUCT.)

     #!/bin/sh

     kdclist = "KDCSLAVE1.PRIMARYDOMAIN KDCSLAVE2.PRIMARYDOMAIN"

     ROOTDIR/sbin/kdb5_util "dump
     => ROOTDIR/var/krb5kdc/slave_datatrans"

     for kdc in $kdclist
     do
     ROOTDIR/sbin/kprop -f ROOTDIR/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.)

Finish Installing the Slave KDCs
--------------------------------

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 on the Slave KDCs
....................................

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.

Start the krb5kdc Daemon on Each KDC
....................................

The final step in configuing your slave KDCs is to run the KDC daemon:

     shell% ROOTDIR/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.

Add Kerberos Principals to the Database
---------------------------------------

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 PRODUCT 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.

Limit Access to the KDCs
------------------------

To limit the possibility that your Kerberos database could be compromised, COMPANY 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.

COMPANY 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 ROOTDIR/sbin/kpropd  kpropd
     eklogin   stream tcp nowait root ROOTDIR/sbin/klogind
     => klogind -5 -c -e

Switching Master and Slave KDCs
-------------------------------

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:

 1. Kill the kadmind process.

 2. Disable the cron job that propagates the database.

 3. Run your database propagation script manually, to ensure that the slaves all have the latest copy of the database.  (see Propagate the Database to Each Slave KDC.)  If there is a need to preserve per-principal policy information from the database, you should do a ``kdb5_util dump -ov'' in order to preserve that information and propogate that dump file securely by some means to the slave so that its database has the correct state of the per-principal policy information.

On the new master KDC:

 1. Create a database keytab.  (see Create a kadmind Keytab (optional).)

 2. Start the kadmind daemon.  (see Start the Kerberos Daemons.)

 3. Set up the cron job to propagate the database.  (see Propagate the Database to Each Slave KDC.)

 4. Switch the CNAMEs of the old and new master KDCs.  (If you don't do this, you'll need to change the krb5.conf file on every client machine in your Kerberos realm.)

Installing and Configuring UNIX Client Machines
===============================================

Client machine installation is much more straightforward than installation of the KDCs.

Client Programs
---------------

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 ROOTDIR/bin, except for login.krb5 which is in ROOTDIR/sbin.

You will probably want to have your users put ROOTDIR/bin ahead of /bin and /usr/bin in their paths, so they will by default get the PRODUCT versions of rlogin, telnet, ftp, rcp, and rsh.

COMPANY 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.

Client Machine Configuration Files
----------------------------------

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 PRODUCT, 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      DefaultPort/udp    kdc    # Kerberos V5 KDC
     kerberos      DefaultPort/tcp    kdc    # Kerberos V5 KDC
     klogin        DefaultKloginPort/tcp          # Kerberos authenticated rlogin
     kshell        DefaultKshellPort/tcp   cmd    # and remote shell
     kerberos-adm  DefaultKadmindPort/tcp          # Kerberos 5 admin/changepw
     kerberos-adm  DefaultKadmindPort/udp          # Kerberos 5 admin/changepw
     krb5_prop     DefaultKrbPropPort/tcp          # Kerberos slave propagation
     eklogin       DefaultEkloginPort/tcp         # Kerberos auth. & encrypted rlogin
     krb524        DefaultKrb524Port/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.

Mac OS X Configuration
......................

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.

UNIX Application Servers
========================

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 PRODUCT installed on all of your client machines, COMPANY 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 PRODUCT installed, you can run an insecure server, and still take advantage of PRODUCT's single sign-on capability.

Server Programs
---------------

Just as PRODUCT provided its own Kerberos-enhanced versions of client UNIX network programs, PRODUCT also provides Kerberos-enhanced versions of server UNIX network daemons.  These are ftpd, klogind, kshd, and telnetd. These programs are installed in the directory ROOTDIR/sbin.  You may want to add this directory to root's path.

Server Configuration Files
--------------------------

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  ROOTDIR/sbin/klogind
     => klogind -k -c
     eklogin stream  tcp  nowait  root  ROOTDIR/sbin/klogind
     => klogind -k -c -e
     kshell  stream  tcp  nowait  root  ROOTDIR/sbin/kshd
     => kshd -k -c -A
     ftp     stream  tcp  nowait  root  ROOTDIR/sbin/ftpd
     => ftpd -a
     telnet  stream  tcp  nowait  root  ROOTDIR/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  ROOTDIR/sbin/klogind
     => klogind -k -c
     eklogin stream  tcp  nowait  root  ROOTDIR/sbin/klogind
     => klogind -k -c -e
     kshell  stream  tcp  nowait  root  ROOTDIR/sbin/kshd
     => kshd -k -c -A
     ftp     stream  tcp  nowait  root  ROOTDIR/sbin/ftpd
     => ftpd
     telnet  stream  tcp  nowait  root  ROOTDIR/sbin/telnetd
     => telnetd -a none

The Keytab File
---------------

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 PRODUCT 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.PRIMARYDOMAIN to authenticate for the services host, ftp, and pop, the administrator ADMINUSER would issue the command (on trillium.PRIMARYDOMAIN):

     trillium% ROOTDIR/sbin/kadmin
     kadmin5: ktadd host/trillium.PRIMARYDOMAIN ftp/trillium.PRIMARYDOMAIN
     => pop/trillium.PRIMARYDOMAIN
     kadmin: Entry for principal host/trillium.PRIMARYDOMAIN@PRIMARYREALM with
     kvno 3, encryption type DES-CBC-CRC added to keytab
     WRFILE:/etc/krb5.keytab.
     kadmin: Entry for principal ftp/trillium.PRIMARYDOMAIN@PRIMARYREALM with
     kvno 3, encryption type DES-CBC-CRC added to keytab
     WRFILE:/etc/krb5.keytab.
     kadmin: Entry for principal pop/trillium.PRIMARYDOMAIN@PRIMARYREALM 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 PRODUCT client programs, you can use encrypted rcp.

Some Advice about Secure Hosts
------------------------------

PRODUCT can protect your host from certain types of break-ins, but it is possible to install PRODUCT 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, COMPANY 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 PRODUCT binaries, should be kept on local disk.  The keytab file should be readable only by root.

Upgrading Existing PRODUCT Installations
****************************************

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:

 1. Stop your current KDC and administration server processes, if any.

 2. Dump your existing Kerberos database to an ASCII file with kdb5_util's ``dump'' command:

          shell% cd ROOTDIR/var/krb5kdc
          shell% kdb5_util dump old-kdb-dump
          shell% kdb5_util dump -ov old-kdb-dump.ov
          shell%

 3. Create a new Master KDC installation (see Install the Master KDC.).  If you have a stash file for your current database, choose any new master password but then copy your existing stash file to the location specified by your kdc.conf; if you do not have a stash file for your current database, you must choose the same master password.

 4. Load your old Kerberos database into the new system with kdb5_util's ``load'' command:

          shell% cd ROOTDIR/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.

Upgrading to Triple-DES Encryption Keys
=======================================

Beginning with the 1.2 release from COMPANY, 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 COMPANY, 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.

Bug Reports for PRODUCT
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