Citrix Secure Gateway via https-only
Configuring a Citrix Secure Gateway (CSG) server is simple, but provides a powerful solution to access resource from remote locations. CSG is an application installed on a DMZ server. Mostly I also configure the Citrix WebInterface on the same server. The CSG instance listens on TCP/443 and the WI instance listens on TCP/80. To improve the user friendliness of the solution you have to configure a redirect. This redirect changes the protocol from the unsecure http protocol to the secure https protocol. It also redirect the user to the correct login portal, like redirecting http://portal.booches.nl to https://portal.booches.nl/Citrix/XenApp/auth/login.aspx. The HTML code for the redirect is:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
<meta http-equiv="Refresh" content="1 ;URL=https://portal.booches.nl/Citrix/XenApp/auth/login.aspx" />
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Citrix Secure Gateway-Booches</title>
Please click <a href=’https://portal.booches.nl/Citrix/XenApp/auth/login.aspx’>here</a> if you are not automatically redirected.
This configuration requires you to allow the http and https protocols from the internet to the server. When accessing the login page the remote user connects to the CSG instance over https and the CSG instance connects to the WI instance over http. A customer noticed that a user could change the login URL from https to the unsecure http. This means that the remote user connects directly to the WI instance and bypasses the CSG instance. This behavior is not allowed and also unsecure, because username and password are sent clear text over the internet.
I wanted to change this behavior so the user isn’t allowed to connect over http to the login page, but the default redirect from http to https should still be allowed. I looked at solutions on the internet to redirect all IIS traffic from http to https, but this introduced some problems and errors. In the end I simply configured IP Address and Domain Restriction on the /Citrix/XenApp virtual directory. Only the CSG instance needs to connect to the WI instance, so the IP restrictions only allow the localhost and the server IP address. I also changed the default behavior to deny all unspecified clients.
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