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LDAP Single Sign-On
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=======================================
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To use the single sign-on feature, your web server must provide an authentication
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mechanism for LDAP. The only authentication mechanism used in development
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was mod_auth_sspi for Apache/Windows, but so long as the web server's LDAP
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authentication mechanism is configured to provide the $_SERVER variable
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$_SERVER['REMOTE_USER'] or $_SERVER['REDIRECT_REMOTE_USER'] corresponding
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directly to a user's LDAP user name, this should work all the same. This
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will require some sort of LDAP authentication mechanism; mod_auth_sspi is
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available here: http://mod-auth-sspi.sourceforge.net/, while mod_ntlm is
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available here: http://modntlm.sourceforge.net/, and mod_auth_ntlm_winbind is
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available here: http://samba.org/ftp/unpacked/lorikeet/mod_auth_ntlm_winbind/.
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If a Linux distribution is being used, Apache authentication modules are likely
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available within the distro's package manager.
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Unless an administrator wishes to require that all visitors be authenticated,
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NTLM and/or basic authentication should be set up only on the path
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user/login/sso, which will authentify the visitor but not deny access to view
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the site if the visitor is not authenticated. An administrator may wish to
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require LDAP authentication to view any portion of the site; this can be
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achieved by changing the location directive below to "/". An administrator may
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also wish to automatically log in visitors to Drupal; this can be achieved by
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checking "Turn on automated single sign-on" in the modules' configuration page.
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An example of an Apache configuration for a named virtualhost configuration
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using mod_auth_sspi on Windows is as follows:
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httpd.conf:
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_______________________________________________________________________________
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_______________________________________________________________________________
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# Virtual hosts
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Include conf/extra/httpd-vhosts.conf
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# Pass NTLM authentication to Apache
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LoadModule sspi_auth_module modules/mod_auth_sspi.so
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<IfModule !mod_auth_sspi.c>
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LoadModule sspi_auth_module modules/mod_auth_sspi.so
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</IfModule>
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_______________________________________________________________________________
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_______________________________________________________________________________
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httpd-vhosts.conf:
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_______________________________________________________________________________
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_______________________________________________________________________________
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NameVirtualHost example.com
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<VirtualHost example.com>
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DocumentRoot "D:/www/example.com/htdocs"
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ServerName example.com
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<directory "D:/www/example.com/htdocs">
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Options Indexes FollowSymLinks MultiViews
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AllowOverride All
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Order Allow,Deny
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Allow from all
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</directory>
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<Location /user/login/sso>
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AuthType SSPI
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AuthName "Example.com - Login using your LDAP user name and password"
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SSPIAuth On
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SSPIAuthoritative On
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### The domain used to authenticate with LDAP; this should match the domain
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### configured in the LDAP integration configuration within Drupal
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SSPIDomain ad.example.com
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SSPIOmitDomain On
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SSPIOfferBasic On
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Require valid-user
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#SSPIBasicPreferred On
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#SSPIofferSSPI off
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</Location>
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</VirtualHost>
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_______________________________________________________________________________
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_______________________________________________________________________________
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After enabling and configuring an LDAP authentication module within Apache,
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visit user/login/sso in the Drupal installation on example.com. With or without
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the ldap sso feature enabled, the browser should prompt for a user name and
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password if using Internet Explorer 8 or a non-Microsoft browser. Internet
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Explorer 7 by default will pass NTLM authentication credentials to local
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websites, and IE8 and Firefox can be configured to do this as well.
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If prompted for credentials on that path, enter a valid LDAP user name,
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omitting the domain if "SSPIOmitDomain On" is configured, as well as a password.
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If the credentials are correct, or if NTLM credentials are passed automatically
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by the browser and successfully authenticated, a Drupal 404 "Page not found"
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message will be displayed if the module is not enabled; an "access is denied"
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message will be displayed if the module is enabled and the browser is already
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logged in; and if the ldap_sso module is fully configured and there is no
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existing session, the browser will display the message "You have been
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successfully authenticated" after redirecting to the sites' home page if you
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have checked "Notify user of successful authentication".
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