Advanced Clientless VPN access with Citrix Gateway

Clientless VPN sees a way of providing remote access to the corporate’s intranet resources through Citrix Gateway without a VPN client application at the client machine. Clientless VPN provides remote access to enterprise web-applications, portals, and other resources using a web browser at the client’s end. Advanced clientless VPN solution eliminates the following limitations pertaining to clientless VPN:

  • Relative URLs cannot be identified at times.

  • Relative URLs generated dynamically cannot be identified.

The advanced clientless VPN identifies the absolute URL and host names and rewrites them in a new and unique manner instead of trying to rewrite relative URLs present in the HTTP-responses/Web-Pages. SharePoint no longer needs to use the default folder for rewriting URLs and a custom SharePoint access is supported.

Prerequisites

The following are the prerequisites to configure the advanced clientless VPN.

  1. WildCard Server Certificate - VPN virtual server requires a wildcard server certificate. If the server is hosted with https://vpn.com, then the server certificate must have entries for (vpn.com and .vpn.com) as part of certificates CN or SAN (where CN=common name, SAN= Subject Alternative Name). The process of binding this certificate remains the same on Citrix Gateway.

  2. WildCard DNS entry - s The clients (web browsers) must resolve the Advanced clientless VPN app’s FQDN. While setting up the Citrix Gateway server, you would have configured a DNS entry to resolve vpn.com. Configure a subdomain for ‘.’ so that ‘.vpn.com’now resolves to vpn.com as well.

Configure Advanced Clientless VPN access

To configure Advanced Clientless VPN access using the command line interface, at the command prompt, type:

set vpn parameter -clientlessVpnMode ON
set vpn parameter -advancedClientlessVpnMode ENABLED

If a session action is bound to the virtual server, you must enable the Advanced Clientless VPN Mode option for that session action as well.

Example:

set vpn sessionaction SessionActionName -advancedclientlessvpn ENABLED

To configure Advanced Clientless VPN access using the Citrix ADC GUI:

  1. In the NetScaler GUI, navigate to Configuration> Citrix NetScaler> Global Settings.

  2. On the Global Settings page, click Change Global Settings, and then select the Client Experience tab.

  3. On the Client Experience tab, from the Clientless Access list, click On.

  4. On the Client Experience tab, from the Advanced Clientless VPN Mode list, click Enabled.

    Note:

    • If a session action is bound to the virtual server, you must enable the Advanced Clientless VPN Mode option for that session action as well from the Client Experience tab in the Configure Citrix Gateway Session Profile page.
    • You can select the Override Global option to override the global settings.

Setting the advanced clientless VPN

You can configure the Advanced clientless VPN feature at a session level as well.

Caveats

The advanced clientless VPN is aimed at providing access to Enterprise Web apps. Such apps have only one FQDN for every kind of resource they need (JavaScript, css, images, and so on). Since we encode the complete FQDN of internal apps into a single-octet (clientless VPN), we lose out on the subdomain relationship. As a result, whenever an Enterprise WebApp is configured with CORS, sometimes you might notice issues while accessing it over the advanced clientless VPN.