Providing Active Directory authentication via Kerberos protocol in Apache

Before Getting Started
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You will need to have hands-on experiences with UNIX, Apache, and Kerberos before continuing on this article.
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In this example, I will be using Tao Linux 1.0 as the Linux distribution base.� Tao Linux is one of several projects to build a free Linux distribution from the source used in the Red Hat Enterprise product line.� For more information about Tao Linux, please visit their web site at http://taolinux.org.
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Tao Linux ships with Apache 2 and Kerberos 5.� Please check with the User Guide for package installation.
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Download the latest version of mod_auth_kerb from http://modauthkerb.sourceforge.net.� We will be using this module to provide Kerberos protocol support in Apache.
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Step 1
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Uncompress mod_auth_krb and�follow the README file to install the module to your Apache's modules directory.
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# zcat mod_auth_kerb-5.0-rc4.tar.gz | tar xvf -
# cd mod_auth_kerb-5.0-rc4.tar.gz
# ./configure --with-krb4=no --with-krb5=/usr/kerberos
# make
# make install
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Step 2
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Append this line�to the�Apache configuration file.� The default location for the configuration file�is�/etc/httpd/conf/httpd.conf.
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LoadModule auth_kerb_module modules/mod_auth_kerb.so
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Step 3
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Create a Kerberos keytab file and make it readable by all.� This will be the key entry for the module that you installed in step 1.��The format of the file is�HTTP/replace_your_web_server_full_hostname_here@ACTIVE_DIRECTORY_FULL_DOMAIN_NAME
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# echo HTTP/intranet.example.com@EXAMPLE.COM > /path/auth_kerb.keytab
# chmod ugo+r /path/auth_kerb.keytab
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Step 4
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Configure the Kerberos configuration file.� The default location for the configuration file�is /etc/krb5.conf.� Please see template below.� Replace EXAMPLE.COM with your Active Directory domain's FQDN and dc-01/dc-02.example.com with your domain controllers' FQDN.
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[libdefaults]
�ticket_lifetime = 24000
�default_realm = EXAMPLE.COM
�dns_lookup_realm = false
�dns_lookup_kdc = false
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[realms]
�EXAMPLE.COM = {
� kdc = dc-01.example.com:88
� kdc = dc-02.example.com:88
�}
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[domain_realm]
�.example.com = EXAMPLE.COM
�example.com = EXAMPLE.COM
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[appdefaults]
�pam = {
�� debug = false
�� ticket_lifetime = 36000
�� renew_lifetime = 36000
�� forwardable = true
�� krb4_convert = false
�}
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Step 5
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Create an .htaccess file�and set up a basic authentication.� Please see template below.� Replace /path/auth_kerb.keytab with the location of the keytab file and�EXAMPLE.COM with your Active Directory domain's FQDN.
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AuthName "Kerberos Login"
AuthType Kerberos
Krb5Keytab /path/auth_kerb.keytab
KrbAuthRealm EXAMPLE.COM
KrbMethodNegotiate off
KrbSaveCredentials off
KrbVerifyKDC off
Require valid-user
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Step 6
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Restart Apache daemon.
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# service httpd restart
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Notes
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It is recommended that you tunnel basic password authentication via SSL in Apache using mod_ssl so the password will not be exposed in plain text format.
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Questions and Answers
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1) How do I test the Kerberos configuration file that I set up in step 4?
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A: Execute "kinit valid_AD_account_username" and "klist" (without quotes). �For example:
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# kinit jdoe
Password for jdoe@EXAMPLE.COM: XXXXXXXX
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# Klist
Ticket cache: FILE/tmp/krb5cc_999
Default principal: jdoe@EXAMPLE.COM
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Valid starting���� Expires����������� Service principal
04/15/04 18:00:00� 04/16/04 18:00:00� krbtgt/EXAMPLE.COM@EXAMPLE.COM
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Kerberos 4 ticket cache: /tmp/tkt999
Klist: You have no tickets cached
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Don't forget to execute "kdestroy" (without quotes) to clear out�the ticket file.

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