Installing a WebKDC

These are supplemental installation instructions for installing a WebKDC. Each site running WebAuth only needs one WebKDC for the entire site, so normally users do not need to follow these steps. They are here only for site WebAuth administrators.

It is important to always keep in mind that the security of the entire WebAuth system depends on the security of the WebKDC. A compromise of the WebKDC system would allow an attacker to steal usernames and passwords for anyone using the login server and to be able to forge arbitrary authentication credentials and use them to contact WebAuth servers. This system should be locked down as tightly as possible and proactively monitored for security.

We also recommend giving the WebKDC and WebLogin server its own separate domain name. This will generally require giving it a separate IP address unless you can use wildcard SSL/TLS certificates, but it's useful to separate the cookies used by the WebLogin server from cookies used by applications. This is particularly important if you use Active Directory as your KDC and do ticket delegation. Active Directory Kerberos tickets can be fairly large, and the combination of WebKDC cookies, WebAuth proxy cookies, credential cookies, and id cookies can result in a Cookie header that's longer than the HTTP protocol permits.

Follow the standard WebAuth installation instructions as given in the INSTALL file at the top of the source tree, but also pass the flags --enable-mod_webkdc, --disable-mod_webauth, and --disable-mod_webauthldap to ./configure. This will install only the WebKDC module, and it will also install the Perl bindings (into the site_perl directory for the first version of Perl found on your path).
You'll need to install the following Perl modules from CPAN:
```
    HTML::Template
    libwww (LWP)
    Crypt::SSLeay (for LWP https support)
    URI
    XML::Parser
```
You'll probably also want to install and configure mod_fastcgi as well, though it's not a requirement. If you decide to install it, you'll need to configure it like so:
```
    FastCGIConfig -initial-env LD_LIBRARY_PATH
    LoadModule fastcgi_module modules/mod_fastcgi.so
    <Directory "/usr/local/share/weblogin">
        AllowOverride All
        Options Indexes FollowSymlinks +ExecCGI
        AddHandler fastcgi-script .fcgi
        Order allow,deny
        Allow from all
    </Directory>
```
This assumes the WebLogin scripts and templates are installed into /usr/local/share/weblogin, which is the default installation location. You can put them anywhere; just adjust the path above and the paths in Apache configuration options below accordingly.
Add Apache directives for the WebKDC. The basic set is:
```
    LoadModule webkdc_module modules/mod_webkdc.so
    WebKdcServiceTokenLifetime 30d
    WebKdcKeyring conf/webkdc/keyring
    WebKdcKeytab conf/webkdc/keytab
    WebKdcTokenAcl conf/webkdc/token.acl
```
If you are testing a beta release, please also add:
```
    WebKdcDebug on
```
so that your server will generate more complete logs if anything goes wrong. This may also be useful if this is the first time you've installed a WebKdc. You'll also want to set LogLevel to debug:
```
    LogLevel debug
```

Set up a script aliases to run the login CGI service by adding the following lines to your Apache configuration:

    ScriptAlias /login "/usr/local/share/weblogin/login.fcgi"
    ScriptAlias /logout "/usr/local/share/weblogin/logout.fcgi"
    Alias /images "/usr/local/share/weblogin/generic/images/"
    Alias /help.html \
        "/usr/local/share/weblogin/generic/templates/help.html"

You may want to add the first two only inside a VirtualHost block that requires SSL to ensure that they are only accessible over SSL.

Set up a <VirtualHost> directive using SSL for the WebKDC service. Inside that directive, set a handler for the URL /webkdc-service. In other words, use a configuration block like:
```
    <VirtualHost _default_:443>
       SSLEngine on
       ...
       <Location /webkdc-service>
          SetHandler webkdc
       </Location>
       ...
    </VirtualHost>
```

Create the conf/webkdc directory.

    cd <apache-root>
    mkdir -p conf/webkdc

Install the WebKDC files used by the login server, the portion that runs on the regular SSL port. cd to the root of the WebAuth source tree and then run:
```
    make install
```
This will install Perl modules into the site_perl directory of whatever Perl was found by configure.
If the path and URL in <site-perl>/WebKDC/Config.pm are not correct for your site (see docs/weblogin-config for the defaults), create /etc/webkdc/webkdc.conf and in it put lines like:
```
    $KEYRING_PATH = "../conf/webkdc/keyring";
    $URL = "https://localhost/webkdc-service/";
```
changing the values to what is appropriate for your site. If you follow the default recommendations on where to place the keyring and CGI scripts, you shouldn't have to change anything. There are other settings you can change; see doc/weblogin-config for all the details.
Install a keytab for the WebKDC. This keytab must be for the same identity as is mentioned in the WebAuthWebKdcPrincipal configuration option in the Apache configuration of individual WebAuth servers. The keytab should for the identity service/webkdc, and should be installed in <apache-root>/conf/webkdc/keytab or in whatever path the Apache configuration option WebKdcKeyring references.

(Note that you can use some other identity if you prefer, as this is part of the WebAuth module configuration. You'll just then have to configure all of your systems using the WebAuth module to use whatever other identity you chose.)
Create a file named token.acl in <apache-root>/conf/webkdc. This file specifies which tokens various server identities are allowed to create. There is an example file in conf/token.acl, so for an initial configuration, do:
```
    cp conf/token.acl <apache-root>/conf/webkdc/
```
uncomment the first line, and change the ACL pattern to match your realm. This will allow any server with a webauth/* keytab to get an id token (which identifies a user but conveys no other privileges). This is a good place to start. See the mod_webkdc manual for more.
Restart the Apache web server. You should now have a working WebKDC and login server, which you can point a WebAuth server at. You will need to install a regular WebAuth server following the instructions in INSTALL to be able to test your WebKDC.

If you want to use let clients use SPNEGO to authenticate to the WebLogin front-end with fallback to standard password authentication, see the separate install-spengo documentation.

Last modified Thursday, 02-Mar-2006 05:22:12 PM

STANFORD UNIVERSITY

INFORMATION TECHNOLOGY SERVICES

Installing a WebKDC