Duo integrates with your on-premises Citrix Gateway to add two-factor authentication to remote access logins by utilizing the Advanced Authentication Policy framework. Duo Security supports inline self-service enrollment and Duo Prompt when logging on to the Citrix Gateway.
To add Duo two-factor authentication to your Citrix Gateway you'll configure the Duo Authentication Proxy as a secondary RADIUS authentication server.
Citrix Gateway was formerly known as NetScaler Gateway. These instructions apply to both products.
Before starting, make sure that Duo is compatible with your Citrix Gateway device. Log on to your Citrix Gateway via the web interface and verify that your Citrix Gateway firmware is version 12.1-51.16 or later and your Citrix Receiver or Citrix Workspace clients support 12.1 or later. Also verify that your Citrix Gateway is licensed for Advanced Authentication Policy. If not, refer to our Basic Authentication instructions.
This application communicates with Duo's service on TCP port 443. Firewall configurations that restrict outbound access to Duo's service with rules using destination IP addresses or IP address ranges aren't recommended, since these may change over time to maintain our service's high availability. If your organization requires IP-based rules, please review this Duo KB article.
Before moving on to the deployment steps, it's a good idea to familiarize yourself with Duo administration concepts and features like options for applications, available methods for enrolling Duo users, and Duo policy settings and how to apply them. See all Duo Administrator documentation.
You should already have a working primary authentication configuration for your Citrix Gateway users before you begin to deploy Duo.
To integrate Duo with your Citrix Gateway, you will need to install a local proxy service on a machine within your network. This Duo proxy server also acts as a RADIUS server — there's usually no need to deploy a separate RADIUS server to use Duo.
Next, locate (or set up) a system on which you will install the Duo Authentication Proxy. The proxy supports these operating systems:
Then you'll need to:
The security of your Duo application is tied to the security of your secret key (skey). Secure it as you would any sensitive credential. Don't share it with unauthorized individuals or email it to anyone under any circumstances!
The Duo Authentication Proxy can be installed on a physical or virtual host. We recommend a system with at least 1 CPU, 200 MB disk space, and 4 GB RAM (although 1 GB RAM is usually sufficient).
Ensure that Perl and a compiler toolchain are installed. On most recent RPM-based distributions — like Fedora, RedHat Enterprise, and CentOS — you can install these by running (as root):
$ yum install gcc make libffi-devel perl zlib-devel
On Debian-derived systems, install these dependencies by running (as root):
$ apt-get install build-essential libffi-dev perl zlib1g-dev
Download the most recent Authentication Proxy for Unix from https://dl.duosecurity.com/duoauthproxy-latest-src.tgz. Depending on your download method, the actual filename may reflect the version e.g. duoauthproxy-5.0.1-src.tgz. View checksums for Duo downloads here.
Extract the Authentication Proxy files and build it as follows:
$ tar xzf duoauthproxy-latest-src.tgz $ cd duoauthproxy-version-src $ make
Install the authentication proxy (as root):
$ cd duoauthproxy-build $ ./install
Follow the prompts to complete the installation. The installer creates a user to run the proxy service and a group to own the log directory and files. You can accept the default user and group names or enter your own.
If you ever need to uninstall the proxy, run
After the installation completes, you will need to configure the proxy.
The Duo Authentication Proxy configuration file is named authproxy.cfg, and is located in the conf subdirectory of the proxy installation. With default installation paths, the proxy configuration file will be located at:
|Windows||v5.0.0 and later||
|Windows||v4.0.2 and earlier||
Note that as of v4.0.0, the default file access on Windows for the `conf` directory is restricted to the built-in Administrators group during installation.
The configuration file is formatted as a simple INI file. Section headings appear as:
Individual properties beneath a section appear as:
The Authentication Proxy may include an existing authproxy.cfg with some example content. For the purposes of these instructions, however, you should delete the existing content and start with a blank text file. We recommend using WordPad or another text editor instead of Notepad when editing the config file on Windows.
At the top of your authproxy.cfg, create a
[duo_only_client] section. This section has no additional parameters to configure.
When using the
[duo_only_client] configuration, the Authentication Proxy will ignore primary credentials and perform Duo factor authentication only.
Next, you need to set up the Authentication Proxy to work with your Citrix Gateway or NetScaler. Create a
[radius_server_iframe] section and add the properties listed below. If you've already set up the Duo Authentication Proxy for a different RADIUS iframe application, append a number to the section header to make it unique, like
Your API hostname (i.e.
||Your Duo Citrix NetScaler integration key|
||Your Duo Citrix NetScaler secret key|
The mechanism that the Authentication Proxy should use to perform primary authentication. This should correspond with the "client" section you created earlier.
This parameter is optional if you only have one "client" section. If you have multiple, each "server" section should specify which "client" to use.
||The IP address of your (first) Citrix Gateway or NetScaler|
||A secret to be shared between the proxy and your (first) Citrix Gateway or NetScaler|
||(Optional) IP addresses of additional Citrix Gateways or NetScalers (specified as radius_ip_2, radius_ip_3, etc.)|
||(Optional) Secrets shared with additional Citrix Gateways or NetScalers (specified as radius_secret_2, radius_secret_3, etc.)|
Port on which to listen for incoming RADIUS Access Requests. If you have multiple RADIUS server sections you should use a unique port for each one.
A completed config file, using duo_only_client so the NetScaler is the primary authenticator, should look something like:
[duo_only_client] [radius_server_iframe] type=citrix_netscaler_rfwebui ikey=DIXXXXXXXXXXXXXXXXXX skey=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX api_host=api-XXXXXXXX.duosecurity.com failmode=safe client=duo_only_client radius_ip_1=126.96.36.199 radius_secret_1=thisisaradiussecret port=1812
Make sure to save your configuration file when done.
Open an Administrator command prompt and run:
net start DuoAuthProxy
Alternatively, open the Windows Services console (services.msc), locate "Duo Security Authentication Proxy Service" in the list of services, and click the Start Service button.
If the service starts successfully, Authentication Proxy service output is written to the authproxy.log file, which can be found in the log subdirectory.
If you see an error saying that the "service could not be started", open the Application Event Viewer and look for an Error from the source "DuoAuthProxy". The traceback may include a "ConfigError" that can help you find the source of the issue.
Stop and restart the Authentication Proxy service by either clicking the Restart Service button in the Windows Services console or issuing these commands from an Administrator command prompt:
net stop DuoAuthProxy & net start DuoAuthProxy
Open a root shell and run:
# /opt/duoauthproxy/bin/authproxyctl start
To ensure the proxy started successfully, run:
# /opt/duoauthproxy/bin/authproxyctl status
Authentication Proxy service output is written to the authproxy.log file, which can be found in the log subdirectory.
To stop and restart the Authentication Proxy, open a root shell and run:
# /opt/duoauthproxy/bin/authproxyctl restart
If you modify your
authproxy.cfg configuration after initial setup, you'll need to stop and restart the Duo Authentication Proxy service or process for your change to take effect.
Before integrating with Duo, make sure your Citrix Gateway has a working Virtual Server with your preferred primary factor.
Additionally, check your Citrix Gateway web portal theme. The inline, browser-based Duo Prompt is compatible with the "Default" (aka "Caxton"), "Green Bubbles", "X1", and "RFWebUI" NetScaler themes (as well as custom themes based on one of those built-in themes).
When creating your Citrix Gateway custom theme, use one of these built-in themes as the base for your customizations.
On the "Create Authentication RADIUS Server" page, enter the information for your Duo Authentication Proxy server:
|Server Name or IP Address||The hostname or IP address of your Duo Authentication Proxy server.|
|Port||The port configured for radius_server_iframe on the Duo Authentication Proxy (1812 in the example)|
|Secret Key||The RADIUS secret shared with your Duo Authentication Proxy|
|Confirm Secret Key||The RADIUS secret shared with your Duo Authentication Proxy|
Click Create to add the RADIUS_DuoAuthenticationProxy RADIUS server and return to the "RADIUS Actions" page.
If you have no existing policy for your primary authentication click Add to add your primary authentication server. In this example primary authentication is done via an LDAP server.
Click Add to add your secondary authentication RADIUS Duo Authentication Proxy server.
Name the Policy Label and click Continue.
Select RADIUS_DuoAuthenticationProxy as your Policy.
Name the Authentication Virtual Server nFactor_Duo, select Non Addressable as your "IP Address Type" and click OK.
Choose or import the certicate for this virtual server.
Click No Authentication Policy and select your primary authentication server as the Policy.
Leave the "GoTo Expression" as NEXT and select RADIUS_DuoAuthenticationProxy as your "Next Factor" and click Bind.
Name the Authentication Profile nFactor_Duo and select nFactor_Duo as your Authentication Virtual Server.
Select nFactor_Duo as your "Authentication Profile".
Save all of the changes made to the running config.
To test your setup, browse to the URL you normally use to log in to your Citrix Gateway. After you complete primary authentication, the Duo enrollment/login prompt appears.
If you plan to permit use of WebAuthn authentication methods (security keys, U2F tokens, or Touch ID), Duo recommends enabling hostname whitelisting for this application and any others that show the inline Duo Prompt before onboarding your end-users.
To test your setup with the Citrix Receiver or Workspace app, complete primary authentication. The Duo enrollment/login prompt appears.
Need some help? Review troubleshooting tips for the Authentication Proxy and try the connectivity tool included with Duo Authentication Proxy 2.9.0 and later to discover and troubleshoot general connectivity issues.
Also take a look at the Citrix Gateway or NetScaler Frequently Asked Questions (FAQ) page or try searching our Citrix NetScaler Knowledge Base articles or Community discussions. For further assistance, contact Support.