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Citrix Gateway

Last Updated: December 5th, 2019

Duo integrates with your Citrix Gateway to add two-factor authentication to VPN logins. Duo Security supports inline self-service enrollment and Duo Prompt when logging on using a web browser. For Citrix Receiver or Workspace client connections, Duo Security supports passcodes, phone, and push authentication.

If your users need the ability to reset passwords from the Citrix Gateway, please use the Citrix Gateway Alternate Instructions. Learn more about the differences between the two Citrix Gateway deployment configurations.

Overview

To add Duo two-factor authentication to your Citrix Gateway you'll configure two RADIUS authentication policies — one that provides Duo's interactive enrollment and authentication prompts to browser-based Gateway logins, and a second one that responds to Receiver or Workspace client logins with an automatic authentication request via push notification to a mobile device or a phone call.

Citrix Gateway was formerly known as NetScaler Gateway. These instructions apply to both products.

Connectivity Requirements

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.

 

First Steps

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:

  • Windows Server 2008 R2 or later (Server 2016 or 2019 recommended)
  • CentOS 7 or later
  • Red Hat Enterprise Linux 7 or later
  • Ubuntu 16.04 or later
  • Debian 7 or later.

Then you'll need to:

  1. Sign up for a Duo account.
  2. Log in to the Duo Admin Panel and navigate to Applications.
  3. Click Protect an Application and locate Citrix NetScaler in the applications list. Click Protect this Application to get your integration key, secret key, and API hostname. See Getting Started for help.
Treat your secret key like a password

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!

Install the Duo Authentication Proxy

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).

  1. Download the most recent Authentication Proxy for Windows from https://dl.duosecurity.com/duoauthproxy-latest.exe. Note that the actual filename will reflect the version e.g. duoauthproxy-3.2.1.exe. View checksums for Duo downloads here.
  2. Launch the Authentication Proxy installer on the target Windows server as a user with administrator rights and follow the on-screen prompts.
  1. Ensure that Perl, Python 2.6 or 2.7 (including development headers and libraries), 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 python-devel libffi-devel perl zlib-devel

    On Debian-derived systems, install these dependencies by running (as root):

    $ apt-get install build-essential python-dev libffi-dev perl zlib1g-dev
  2. 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-3.2.1-src.tgz. View checksums for Duo downloads here.

  3. Extract the Authentication Proxy files and build it as follows:

    $ tar xzf duoauthproxy-latest-src.tgz
    $ cd duoauthproxy-version-src
    $ make
  4. 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 /opt/duoauthproxy/uninstall.

Configure the Proxy

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:

Platform Default Configuration Path
Windows (64-bit) C:\Program Files (x86)\Duo Security Authentication Proxy\conf\authproxy.cfg
Windows (32-bit) C:\Program Files\Duo Security Authentication Proxy\conf\authproxy.cfg
Linux /opt/duoauthproxy/conf/authproxy.cfg

The configuration file is formatted as a simple INI file. Section headings appear as:

[section]

Individual properties beneath a section appear as:

name=value

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.

Configure the Proxy for Your Primary Authenticator

In this step, you'll set up the Proxy's primary authenticator — the system which will validate users' existing passwords. In most cases, this means configuring the Proxy to communicate with Active Directory or RADIUS.

Active Directory

To use Active Directory/LDAP as your primary authenticator, add an [ad_client] section to the top of your config file. Add the following properties to the section:

Required

host

The hostname or IP address of your domain controller.

service_account_username

The username of a domain account that has permission to bind to your directory and perform searches. We recommend creating a service account that has read-only access.

service_account_password

The password corresponding to service_account_username. If you're on Windows and would like to encrypt this password, see Encrypting Passwords in the full Authentication Proxy documentation.

search_dn

The LDAP distinguished name (DN) of an Active Directory container or organizational unit (OU) containing all of the users you wish to permit to log in. For example:

search_dn=DC=example,DC=com

Optional

host_2

The hostname or IP address of a secondary/fallback domain controller. You can add additional domain controllers as host_3, host_4, etc.

security_group_dn

To further restrict access, specify the LDAP distinguished name (DN) of a security group that contains the users who should be able to log in. Other users will not pass primary authentication. For example:

security_group_dn=CN=DuoVPNUsers,OU=Groups,DC=example,DC=com

For example:

[ad_client]
host=1.2.3.4
host_2=1.2.3.5
service_account_username=duoservice
service_account_password=password1
search_dn=DC=example,DC=com
security_group_dn=CN=DuoVPNUsers,OU=Groups,DC=example,DC=com

For advanced Active Directory configuration, see the full Authentication Proxy documentation.

RADIUS

To use RADIUS as your primary authenticator, add a [radius_client] section to the top of your config file. Then add the following properties to the section:

Required

host

The IP address of your RADIUS server. You can add backup servers with host_2, host_3, etc.

secret

A secret to be shared between the Authentication Proxy and your existing RADIUS server. If you're on Windows and would like to encrypt this secret, see Encrypting Passwords in the full Authentication Proxy documentation.

Optional

port

The authentication port on your RADIUS server. Use port_2, port_3, etc. to specify ports for the backup servers.

Default:1812

pass_through_all

If this option is set to true, all RADIUS attributes set by the primary authentication server will be copied into RADIUS responses sent by the proxy.

Default: false

For example:

[radius_client]
host=1.2.3.4
secret=radiusclientsecret

In addition, make sure that the RADIUS server is configured to accept authentication requests from the Authentication Proxy.

For advanced RADIUS configuration, see the full Authentication Proxy documentation.

Configure the Proxy for Your Citrix Gateway

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 [radius_server_iframe2].

type Either citrix_netscaler or citrix_netscaler_rfwebui:
citrix_netscaler Use citrix_netscaler when with the Default, Green Bubbles, or X1 themes.
citrix_netscaler_rfwebui Use citrix_netscaler_rfwebui with the the RFWebUI theme. Requires Authentication Proxy v3.1.0 and NS build 12.1-51.16 or later.

Select the value that corresponds to your Gateway virtual server's theme. If you customized the theme, use the value that matches the theme you used for customization.

api_host Your API hostname (i.e. api-XXXXXXXX.duosecurity.com)
ikey Your Duo Citrix NetScaler integration key
skey Your Duo Citrix NetScaler secret key
failmode Either safe or secure:
failmode Description
safe In the event that Duo's service cannot be contacted, users' authentication attempts will be permitted if primary authentication succeeds. (Default)
secure In the event that Duo's service cannot be contacted, all users' authentication attempts will be rejected.
client

The mechanism that the Authentication Proxy should use to perform primary authentication. This should correspond with the "client" section you created earlier.

ad_client Use Active Directory for primary authentication. Make sure you have an [ad_client] section configured.
radius_client Use RADIUS for primary authentication. Make sure you have a [radius_client] section configured.

This parameter is optional if you only have one "client" section. If you have multiple, each "server" section should specify which "client" to use.

radius_ip_1 The IP address of your (first) Citrix Gateway or NetScaler
radius_secret_1 A secret to be shared between the proxy and your (first) Citrix Gateway or NetScaler
radius_ip_X (Optional) IP addresses of additional Citrix Gateways or NetScalers (specified as radius_ip_2, radius_ip_3, etc.)
radius_secret_X (Optional) Secrets shared with additional Citrix Gateways or NetScalers (specified as radius_secret_2, radius_secret_3, etc.)
port

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.

Default: 1812

Configure the Proxy for Citrix Receiver or Workspace Client

After that, you need to set up the Authentication Proxy to work with Citrix Receiver or Workspace client. Create a [radius_server_auto] section and add the properties listed below. If you've already set up the Duo Authentication Proxy for a different RADIUS Auto application, append a number to the section header to make it unique, like [radius_server_auto2].

api_host Your API hostname (i.e. api-XXXXXXXX.duosecurity.com)
ikey Your Duo Citrix NetScaler integration key
skey Your Duo Citrix NetScaler secret key
failmode Either safe or secure:
failmode Description
safe In the event that Duo's service cannot be contacted, users' authentication attempts will be permitted if primary authentication succeeds. (Default)
secure In the event that Duo's service cannot be contacted, all users' authentication attempts will be rejected.
client

The mechanism that the Authentication Proxy should use to perform primary authentication. This should correspond with the "client" section you created earlier.

ad_client Use Active Directory for primary authentication. Make sure you have an [ad_client] section configured.
radius_client Use RADIUS for primary authentication. Make sure you have a [radius_client] section configured.

This parameter is optional if you only have one "client" section. If you have multiple, each "server" section should specify which "client" to use.

radius_ip_1 The IP address of your (first) Citrix Gateway or NetScaler
radius_secret_1 A secret to be shared between the proxy and your (first) Citrix Gateway or NetScaler
radius_ip_X (Optional) IP addresses of additional Citrix Gateway or NetScalers (specified as radius_ip_2, radius_ip_3, etc.)
radius_secret_X (Optional) Secrets shared with additional Citrix Gateway or NetScalers (specified as radius_secret_2, radius_secret_3, etc.)
port

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.

Default: 1812

Note

The RADIUS port for the Citrix Receiver or Workspace client radius_server_auto section should not be the same RADIUS port used by the Gateway in the radius_server_iframe section of the authproxy.cfg file. For example, if port 1812 is specified for radius_server_iframe, you might use port 18120 for radius_server_auto.

A completed config file, using Active Directory as the primary authenticator, should look something like:

[ad_client]
host=1.2.3.4
service_account_username=duoservice
service_account_password=password1
search_dn=cn=Users,dc=example,dc=com
 
[radius_server_iframe]
type=citrix_netscaler
ikey=DIXXXXXXXXXXXXXXXXXX
skey=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
api_host=api-XXXXXXXX.duosecurity.com
failmode=safe
client=ad_client
radius_ip_1=5.6.7.8
radius_secret_1=thisisaradiussecret
port=1812
 
[radius_server_auto]
ikey=DIXXXXXXXXXXXXXXXXXX
skey=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
api_host=api-XXXXXXXX.duosecurity.com
failmode=safe
client=ad_client
radius_ip_1=5.6.7.8
radius_secret_1=thisisaradiussecret
port=18120

Make sure to save your configuration file when done.

Note

View video guides for proxy deployment at the Authentication Proxy Overview or see the Authentication Proxy Reference Guide for additional configuration options.

Start the Proxy

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.

Configure Your Citrix Gateway

Before starting, 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).

Learn more about customizing the Citrix Gateway User Portal.

When creating your Citrix Gateway custom theme, use one of these built-in themes as the base for your customizations.

  1. Log in to the Citrix NetScaler administrative interface.
  2. Navigate to NetScaler GatewayVirtual Servers in the left panel of the administrative interface.
  3. Select your existing NetScaler Gateway Virtual Server, and then click Edit.
  4. On the "VPN Virtual Server" page, click the plus sign (+) next to Authentication to add a new authentication policy.
  5. On the "Choose Type" page, select the RADIUS policy and Primary type from the drop-down menus and click Continue.

    Choose Type

  6. On the next "Choose Type" screen, click the plus sign (+) next to the "Policy Binding" → "Select Policy" box.

  7. On the "Create Authentication RADIUS Policy" page, enter a name for the policy (like CitrixWebPortal), and then click the plus sign (+) next to the "Server" box to create a new RADIUS server for Duo authentication for web browser clients.

  8. On the "Create Authentication RADIUS Server" page, enter the information for your Duo Authentication Proxy server:

    Name Duo CitrixWebPortal (or some descriptive name)
    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)
    Time-out (seconds) 60
    Secret Key The RADIUS secret shared with your Duo Authentication Proxy
    Confirm Secret Key The RADIUS secret shared with your Duo Authentication Proxy

    Create RADIUS server for iframe

  9. Click Create to add the Duo CitrixWebPortal RADIUS server and return to the "Create Authentication RADIUS Policy" page.

  10. Click the Expression Editor link on the "Create Authentication RADIUS Policy" page to add an expression with the following details:

    Expression Type General
    Flow Type REQ
    Protocol HTTP
    Qualifier HEADER
    Operator NOTCONTAINS
    Value* CitrixReceiver
    Header Name* User-Agent

    Expression for Web Browsers

  11. When the Server and Expression information is correct click Create to save the new CitrixWebPortal policy and return to the "Choose Type" page.

    Create Web Browser Authentication Policy

  12. On the "Choose Type" page, make sure the new RADIUS authentication policy you just created is selected. Set the Priority under "Binding Details" to 100 and click Bind.

    Bind Policy for Web Browsers

  13. Binding the new authentication policy returns you to the "VPN Virtual Server" page. Click the plus sign (+) next to Authentication again to add a second new authentication policy.

  14. On the "Choose Type" page, select the RADIUS policy and Primary type from the drop-down menus and click Continue.

    Choose Type

  15. On the next "Choose Type" screen, click the Add Binding button.

  16. Click the plus sign (+) next to the "Policy Binding" → "Select Policy" box.

  17. On the "Create Authentication RADIUS Policy" page, enter a name for the policy (like CitrixReceiver), and then click the plus sign (+) next to the "Server" box to create a new RADIUS server for Duo authentication for Citrix Receiver or Workspace clients.

  18. On the "Create Authentication RADIUS Server" page, enter the information for your Duo Authentication Proxy server:

    Name Duo CitrixReceiver (or some descriptive name)
    Server Name or IP Address The hostname or IP address of your Duo Authentication Proxy server.
    Port The port configured for radius_server_auto on the Duo Authentication Proxy (18120 in the example)
    Time-out (seconds) 60
    Secret Key The RADIUS secret shared with your Duo Authentication Proxy
    Confirm Secret Key The RADIUS secret shared with your Duo Authentication Proxy
    Send Calling Station ID Check this box in order to send the IP address of Citrix Receiver or Workspace clients to Duo

    Create RADIUS server for auto

  19. Click Create to add the Duo CitrixReceiver RADIUS server and return to the "Create Authentication RADIUS Policy" page.

  20. Click the Expression Editor link on the "Create Authentication RADIUS Policy" page to add an expression with the following details:

    Expression Type General
    Flow Type REQ
    Protocol HTTP
    Qualifier HEADER
    Operator CONTAINS
    Value* CitrixReceiver
    Header Name* User-Agent

    Expression for Receiver

  21. When the Server and Expression information is correct click Create to save the new CitrixReceiver policy and return to the "Choose Type" page.

    Create Receiver Authentication Policy

  22. On the "Choose Type" page, make sure the new RADIUS authentication policy you just created is selected. Set the Priority under "Binding Details" to 110 and click Bind.

    Bind Policy for Receiver

  23. Verify that your new policies for Citrix Receiver or Workspace clients and browser clients are both listed and are bound in the correct order. Click Close to save the new policy configuration.

    Duo Primary RADIUS Authentication Policies

  24. Verify that you have two RADIUS policies for Primary Authentication. Remove any other non-Duo primary authentication policies (or increase the priority value so the NetScaler invokes Duo policies first) and click Done.

  25. Save all of the changes made to the running config.

  1. Log in to the Citrix NetScaler administrative interface.
  2. Navigate to NetScaler GatewayVirtual Servers in the left panel of the administrative interface.
  3. Select your existing NetScaler Gateway Virtual Server, and then click Edit.
  4. On the "VPN Virtual Server" page, click the plus sign (+) next to Basic Authentication to add a new authentication policy.
  5. On the "Choose Type" page, select the RADIUS policy and Primary type from the drop-down menus and click Continue.

    Choose Type

  6. On the next "Choose Type" screen, click the plus sign (+) next to the "Policy Binding" → "Select Policy" box.

  7. On the "Create Authentication RADIUS Policy" page, enter a name for the policy (like CitrixWebPortal), and then click the plus sign (+) next to the "Server" box to create a new RADIUS server for Duo authentication for web browser clients.

  8. On the "Create Authentication RADIUS Server" page, enter the information for your Duo Authentication Proxy server:

    Name Duo CitrixWebPortal (or some descriptive name)
    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)
    Time-out (seconds) 60
    Secret Key The RADIUS secret shared with your Duo Authentication Proxy
    Confirm Secret Key The RADIUS secret shared with your Duo Authentication Proxy

    Create RADIUS server for iframe

  9. Click Create to add the Duo CitrixWebPortal RADIUS server and return to the "Create Authentication RADIUS Policy" page.

  10. Click the Expression Editor link on the "Create Authentication RADIUS Policy" page to add an expression with the following details:

    Expression Type General
    Flow Type REQ
    Protocol HTTP
    Qualifier HEADER
    Operator NOTCONTAINS
    Value* CitrixReceiver
    Header Name* User-Agent

    Expression for Web Browsers

  11. When the Server and Expression information is correct click Create to save the new CitrixWebPortal policy and return to the "Choose Type" page.

    Create Web Browser Authentication Policy

  12. On the "Choose Type" page, make sure the new RADIUS authentication policy you just created is selected. Set the Priority under "Binding Details" to 100 and click Bind.

    Bind Policy for Web Browsers

  13. Binding the new authentication policy returns you to the "VPN Virtual Server" page. Click the plus sign (+) next to Authentication again to add a second new authentication policy.

  14. On the "Choose Type" page, select the RADIUS policy and Primary type from the drop-down menus and click Continue.

    Choose Type

  15. On the next "Choose Type" screen, click the Add Binding button.

  16. Click the plus sign (+) next to the "Policy Binding" → "Select Policy" box.

  17. On the "Create Authentication RADIUS Policy" page, enter a name for the policy (like CitrixReceiver), and then click the plus sign (+) next to the "Server" box to create a new RADIUS server for Duo authentication for Citrix Receiver or Workspace clients.

  18. On the "Create Authentication RADIUS Server" page, enter the information for your Duo Authentication Proxy server:

    Name CitrixReceiver (or some descriptive name)
    Server Name or IP Address The hostname or IP address of your Duo Authentication Proxy server.
    Port The port configured for radius_server_auto on the Duo Authentication Proxy (18120 in the example)
    Time-out (seconds) 60
    Secret Key The RADIUS secret shared with your Duo Authentication Proxy
    Confirm Secret Key The RADIUS secret shared with your Duo Authentication Proxy
    Send Calling Station ID Check this box in order to send the IP address of Citrix Receiver or Workspace clients to Duo (click > More to expose this option)

    Create RADIUS server for auto

  19. Click Create to add the CitrixReceiver RADIUS server and return to the "Create Authentication RADIUS Policy" page.

  20. Click the Expression Editor link on the "Create Authentication RADIUS Policy" page to add an expression with the following details:

    Expression Type General
    Flow Type REQ
    Protocol HTTP
    Qualifier HEADER
    Operator CONTAINS
    Value* CitrixReceiver
    Header Name* User-Agent

    Expression for Receiver

  21. When the Server and Expression information is correct click Create to save the new CitrixReceiver policy and return to the "Choose Type" page.

    Create Receiver Authentication Policy

  22. On the "Choose Type" page, make sure the new RADIUS authentication policy you just created is selected. Set the Priority under "Binding Details" to 110 and click Bind.

    Bind Policy for Receiver

  23. Verify that your new policies for Citrix Receiver or Workspace clients and browser clients are both listed and are bound in the correct order. Click Close to save the new policy configuration.

    Duo Primary RADIUS Authentication Policies

  24. Verify that you have two RADIUS policies for Primary Authentication. Remove any other non-Duo primary authentication policies (or increase the priority value so the NetScaler invokes Duo policies first) and click Done.

  25. Save all of the changes made to the running config.

  1. Log in to the Citrix Gateway administrative interface.
  2. Navigate to Citrix GatewayVirtual Servers in the left panel of the administrative interface.
  3. Select your existing Citrix Gateway Virtual Server, and then click Edit.
  4. On the "VPN Virtual Server" page, click the plus sign (+) next to Basic Authentication to add a new authentication policy.
  5. On the "Choose Type" page, select the RADIUS policy and Primary type from the drop-down menus and click Continue.

    Choose Type

  6. On the next "Choose Type" screen, click the plus sign (+) next to the "Policy Binding" → "Select Policy" box.

  7. On the "Create Authentication RADIUS Policy" page, enter a name for the policy (like CitrixWebPortal), and then click the plus sign (+) next to the "Server" box to create a new RADIUS server for Duo authentication for web browser clients.

  8. On the "Create Authentication RADIUS Server" page, enter the information for your Duo Authentication Proxy server:

    Name Duo CitrixWebPortal (or some descriptive name)
    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)
    Time-out (seconds) 60
    Secret Key The RADIUS secret shared with your Duo Authentication Proxy
    Confirm Secret Key The RADIUS secret shared with your Duo Authentication Proxy

    Create RADIUS server for iframe

  9. Click Create to add the Duo CitrixWebPortal RADIUS server and return to the "Create Authentication RADIUS Policy" page.

  10. Click the Expression Editor link on the "Create Authentication RADIUS Policy" page to add an expression with the following details:

    Expression Type General
    Flow Type REQ
    Protocol HTTP
    Qualifier HEADER
    Operator NOTCONTAINS
    Value* CitrixReceiver
    Header Name* User-Agent

    Expression for Web Browsers

  11. When the Server and Expression information is correct click Create to save the new CitrixWebPortal policy and return to the "Choose Type" page.

    Create Web Browser Authentication Policy

  12. On the "Choose Type" page, make sure the new RADIUS authentication policy you just created is selected. Set the Priority under "Binding Details" to 100 and click Bind.

    Bind Policy for Web Browsers

  13. Binding the new authentication policy returns you to the "VPN Virtual Server" page. Click the plus sign (+) next to Authentication again to add a second new authentication policy.

  14. On the "Choose Type" page, select the RADIUS policy and Primary type from the drop-down menus and click Continue.

    Choose Type

  15. On the next "Choose Type" screen, click the Add Binding button.

  16. Click the plus sign (+) next to the "Policy Binding" → "Select Policy" box.

  17. On the "Create Authentication RADIUS Policy" page, enter a name for the policy (like CitrixReceiver), and then click the plus sign (+) next to the "Server" box to create a new RADIUS server for Duo authentication for Citrix Receiver or Workspace clients.

  18. On the "Create Authentication RADIUS Server" page, enter the information for your Duo Authentication Proxy server:

    Name CitrixReceiver (or some descriptive name)
    Server Name or IP Address The hostname or IP address of your Duo Authentication Proxy server.
    Port The port configured for radius_server_auto on the Duo Authentication Proxy (18120 in the example)
    Time-out (seconds) 60
    Secret Key The RADIUS secret shared with your Duo Authentication Proxy
    Confirm Secret Key The RADIUS secret shared with your Duo Authentication Proxy
    Send Calling Station ID Check this box in order to send the IP address of Citrix Receiver or Workspace clients to Duo (click > More to expose this option)

    Create RADIUS server for auto

  19. Click Create to add the CitrixReceiver RADIUS server and return to the "Create Authentication RADIUS Policy" page.

  20. Click the Expression Editor link on the "Create Authentication RADIUS Policy" page to add an expression with the following details:

    Expression Type General
    Flow Type REQ
    Protocol HTTP
    Qualifier HEADER
    Operator CONTAINS
    Value* CitrixReceiver
    Header Name* User-Agent

    Expression for Receiver

  21. When the Server and Expression information is correct click Create to save the new CitrixReceiver policy and return to the "Choose Type" page.

    Create Receiver Authentication Policy

  22. On the "Choose Type" page, make sure the new RADIUS authentication policy you just created is selected. Set the Priority under "Binding Details" to 110 and click Bind.

    Bind Policy for Receiver

  23. Verify that your new policies for Citrix Receiver or Workspace clients and browser clients are both listed and are bound in the correct order. Click Close to save the new policy configuration.

    Duo Primary RADIUS Authentication Policies

  24. Verify that you have two RADIUS policies for Primary Authentication. Remove any other non-Duo primary authentication policies (or increase the priority value so the NetScaler invokes Duo policies first) and click Done.

  25. Save all of the changes made to the running config.

Test Your Setup

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.

Citrix Gateway Authentication Prompt

To test your setup with Citrix Receiver or Workspace client, attempt to log in to your newly-configured system. When you enter your username and password, you will receive an automatic push or phone callback. Alternatively you can add a comma (",") to the end of your password, followed by a Duo passcode.

For example, given a username 'bob', with password 'password123' and a Duo passcode '123456', you would enter:

username: bob
password: password123,123456

In addition, you may also enter the name of an out-of-band factor in lieu of a passcode. You may choose from the following factor names:

push Perform Duo Push authentication
You can use Duo Push if you've installed Duo Mobile and added your account to it
phone Perform phone callback authentication
sms Send a new batch of SMS passcodes
Your authentication attempt will be denied. You can then authenticate with one of the newly-delivered passcodes.

Returning to the previous example, if you wanted to use Duo Push (rather than a passcode) to authenticate, you would enter:

username: bob
password: password123,push

You can also specify a number after the factor name if you have more than one device enrolled. So you can enter phone2 or push2 if you have two phones enrolled.

Troubleshooting

Need some help? 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.

Network Diagram

  1. Primary authentication initiated to Citrix Gateway
  2. Citrix Gateway send authentication request to Duo Security’s authentication proxy
  3. Primary authentication using Active Directory or RADIUS
  4. Duo authentication proxy connection established to Duo Security over TCP port 443
  5. Secondary authentication via Duo Security’s service
  6. Duo authentication proxy receives authentication response
  7. Citrix Gateway access granted