Two-Factor Authentication for Citrix Web Interface

Duo integrates with Citrix Web Interface to add two-factor authentication to the Citrix Web Interface.

Citrix Web Interface 5.4 is part of XenApp 6.5, which is an end of life product. See the Citrix Web Interface 5.4 FAQ for additional information. Consider updating to NetScaler Gateway and StoreFront for application delivery.

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 Web Interface users before you begin to deploy Duo.

To integrate Duo with your Citrix Web Interface, 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 2012 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:

Sign up for a Duo account.
Log in to the Duo Admin Panel and navigate to Applications.
Click Protect an Application and locate RADIUS in the applications list. Click Protect to get your integration key, secret key, and API hostname. You'll need this information to complete your setup. See Protecting Applications for more information about protecting applications in Duo and additional application options.

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).

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-4.0.2.exe. View checksums for Duo downloads here.
Launch the Authentication Proxy installer on the target Windows server as a user with administrator rights and follow the on-screen prompts.

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-4.0.2-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 /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 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 Duo Only Authentication

At the top of your authproxy.cfg, create a [duo_only_client] section. This section has no additional parameters to configure.

[duo_only_client]

When using the [duo_only_client] configuration, the Authentication Proxy will ignore primary credentials and perform Duo factor authentication only.

Configure the Proxy for Your Citrix Web Interface

Next, you need to set up the Authentication Proxy to work with your Citrix Web Interface. Create a [radius_server_duo_only] section and add the properties listed below. If you've already set up the Duo Authentication Proxy for a different RADIUS Duo-only application, append a number to the section header to make it unique, like [radius_server_duo_only2].

Required

ikey

Your integration key.

skey

Your secret key.

api_host

Your API hostname (e.g. "api-XXXXXXXX.duosecurity.com").

radius_ip_1

The IP address of your Citrix Web Interface.

radius_secret_1

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

client

The mechanism that the Authentication Proxy should use to perform primary authentication. This should correspond with a "client" section elsewhere in the config file.

duo_only_client

Do not perform primary authentication. Make sure you have a [duo_only_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.

Optional

port

The 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.

failmode

Either "safe" or "secure":

"safe"	In the event that Duo's service cannot be contacted, users' authentication attempts will be permitted if primary authentication succeeds. This is the default.
"secure"	In the event that Duo's service cannot be contacted, all users' authentication attempts will be rejected.

radius_ip_2

The IP address of your second Citrix Web Interface, if you have one. You can specify additional devices as as radius_ip_3, radius_ip_4, etc.

radius_secret_2

The secrets shared with your second Citrix Web Interface, if using one. You can specify secrets for additional devices as radius_secret_3, radius_secret_4, etc. If you're on Windows and would like to encrypt this secret, see Encrypting Passwords in the full Authentication Proxy documentation.

A completed config file for radius_server_duo_only with no primary authenticator should look something like:

[duo_only_client]
 
[radius_server_duo_only]
ikey=DIXXXXXXXXXXXXXXXXXX
skey=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
api_host=api-XXXXXXXX.duosecurity.com
failmode=safe
radius_ip_1=5.6.7.8
radius_secret_1=radiussecret1
port=1812

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 Citrix Web Interface

Configure Your Citrix Web Interface Server

Log in to the Citrix Web Interface Management Console.
Navigate to XenApp Web Sites and click on Authentication Methods.
Confirm that only Explicit is checked and click properties
Click on Two-Factor Authentication and select RADIUS for the Two-factor Setting.
Add a RADIUS server and enter the authentication proxy IP address as the server address and 1812 for the server port. Configure the Timeout to 60 seconds and save your configuration.
Create a new text file in the Citrix Web Interface \conf folder called radius_secret.txt.
Type the radius_secret from the authentication proxy configuration in the radius_secret.txt file.

(The location for this file is given by the RADIUS_SECRET_PATH configuration value in the web.config file (for sites hosted on IIS) or web.xml file (for sites hosted on Java application servers). The location given is relative to the \conf folder for sites hosted on IIS and relative to the /WEB_INF directory for sites hosted on Java application servers.) Typically the location will be similar to: C:\inetpub\wwwroot\Citrix\Xenapp\conf.
On the Citrix Web Interface server open the web.config (IIS Hosted) or web.xml (Java Apps) file and add the Citrix Web Interface IP address as the "RADIUS_NAS_IP_ADDRESS".

Test Your Setup

First enroll users by using the Duo Security's Bulk Enrollment feature. See our documentation for Bulk Enrollment in the Administration Guide.
Once users are enrolled, start Your Citrix Web Interface Client and enter your username and password.

In the "passcode" field you may enter a passcode or type in the name of a Duo factor:

push	Perform Duo Push authentication You can use Duo Push if you've installed and activate Duo Mobile on your device.
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.

If you wanted to use Duo Push (rather than a passcode) to authenticate, you would enter:

username: bob
password: password
passcode: push

You can also specify a number after the factor name if you have more than one device enrolled (as the automatic push or phone call goes to the first capable device attached to a user). So you can enter phone2 or push2 if you have two phones enrolled and you want the authentication request to go to the second phone.

Troubleshooting

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 our Citrix Knowledge Base articles or Community discussions. For further assistance, contact Support.

Documentation

Citrix - Web Interface

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