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Two-Factor Authentication for CyberArk Privileged Account Security Solution

Last Updated: November 9th, 2020

Duo helps secure your CyberArk Privileged Account Security Solution with two-factor authentication for Password Vault logins. In this type of configuration, users receive an automatic push or phone callback during login. Users who need to use a passcode may append it to their password when logging in.

These instructions assume that you already have Active Directory authentication working with CyberArk Privileged Account Security Solution. Use Duo's LDAP proxy with CyberArk instead of RADIUS when you want to continue using LDAP group lookup to assign privileges in CyberArk Privileged Account Security.

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 LDAP authentication configuration for your CyberArk Privileged Account Security Solution environment users before you begin to deploy Duo.

To integrate Duo with your CyberArk Privileged Account Security Solution environment, you will need to install a local Duo proxy service on a machine within your network. This Duo proxy server will receive incoming LDAP requests from your CyberArk Privileged Account Security Solution environment, contact your existing local LDAP/AD server to perform primary authentication, and then contact Duo's cloud service for secondary authentication.

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:

  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 CyberArk Privileged Account Security LDAP/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).

  1. Download the most recent Authentication Proxy for Windows from Note that the actual filename will reflect the version e.g. duoauthproxy-5.5.0.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.

To perform a silent install on Windows, issue the following from an elevated command prompt after downloading the installer (replacing version with the actual version you downloaded):

duoauthproxy-version.exe /S
  1. 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 diffutils

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

    $ apt-get install build-essential libffi-dev perl zlib1g-dev
  2. Download the most recent Authentication Proxy for Unix from From the command line you can use curl or wget to download the file, like $ wget --content-disposition Depending on your download method, the actual filename may reflect the version e.g. duoauthproxy-5.5.0-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.

    The proxy listens for LDAP connections on ports 389 and 636 by default. Privileged ports below 1024 are reserved for the root user. Therefore, the proxy will not start if you choose any user account other than "root" to run under during installation.

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:

Operating System Authentication
Proxy Version
Windows v5.0.0 and later C:\Program Files\Duo Security Authentication Proxy\conf\authproxy.cfg
Windows v4.0.2 and earlier C:\Program Files (x86)\Duo Security Authentication Proxy\conf\authproxy.cfg
Linux All /opt/duoauthproxy/conf/authproxy.cfg

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.

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. The primary authentication source for Duo LDAP must be another LDAP directory. In most cases, this means configuring the Proxy to communicate with Active Directory.

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:



The hostname or IP address of your domain controller.


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.


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.


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:




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


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 as direct group members. Nested groups are not supported. Users who are not direct members of the specified group will not pass primary authentication. Example:


Starting with Authentication Proxy v3.2.0, the security_group_dn may be the DN of an AD user's primarygroup. Prior versions do not support primary groups.


LDAP attribute found on a user entry which will contain the submitted username. In most Active Directory configurations, it should not be necessary to change this option from the default value. OpenLDAP directories may use "uid" or another attribute for the username, which should be specified with this option.

Default: "sAMAccountName"

For example:


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

Configure the Proxy As a LDAP Server

Next, you need to set up the Authentication Proxy to handle LDAP authentication requests. Create an [ldap_server_auto] section and add the properties listed below. If you've already set up the Duo Authentication Proxy for a different LDAP application, append a number to the section header to make it unique, like [ldap_server_auto2].


api_host Your API hostname (i.e.
ikey Your integration key
skey Your secret key

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


Use Active Directory for primary authentication. Make sure you have an [ad_client] section configured. Neither [radius_client] nor [duo_only_client] are valid for use with [ldap_server_auto].

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

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.

(Optional) Path to PEM-formatted SSL/TLS server certificate. Both ssl_key_path and ssl_cert_path must be specified to listen for STARTTLS or LDAPS requests.


(Optional) Path to PEM-formatted SSL/TLS private key. Both ssl_key_path and ssl_cert_path must be specified to listen for STARTTLS or LDAPS requests.


Specify the DN of the service account used to authenticate from CyberArk Privileged Account Security Solution to the Authentication Proxy (the account configured as the BindUserName for the LDAP directory in CyberArk). Multi-factor authentication is not required for this user. This setting is needed because CyberArk Privileged Account Security Solution first connects to the Authentication Proxy as the service account user, disconnects, and then authenticates the user who is logging in with a separate LDAP connection. All other accounts will require Duo authentication.


Set this value to 'false'. This setting, when combined with the exempt_ou_1 setting above, ensures that the CyberArk Privileged Account Security Solution service account's initial bind to the Authentication Proxy does not require two-factor authentication, but all other account logins via LDAP do.

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



Make sure to save your configuration file when done.


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.

Authentication Proxy v5.1.0 and later includes the authproxyctl executable, which shows the connectivity tool output when starting the service. The installer adds the Authentication Proxy C:\Program Files\Duo Security Authentication Proxy\bin to your system path automatically, so you should not need to specify the full path to authproxyctl to run it.

From an administrator command prompt run:

authproxyctl start

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

To stop and restart the Authentication Proxy using authproxyctl, from an administrator command prompt run:

authproxyctl restart

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 the LDAP Directory in CyberArk Privileged Account Security Solution

Configure Password Vault Web Access

  1. Log on to Password Vault Web Access via your browser as the predefined Administrator user. This is typically accessed at https://yourvaultserver/PasswordVault.

  2. Click on ADMINISTRATION at the top to navigate to the "System Configuration" page. Then, click on LDAP Integration in the "Component Settings" table.

  3. Go to LDAPDirectoriesthe AD directory currently used for Privileged Account Security access. Verify that the BindUserName is set to the full DN of the service account user (e.g. CN=ServiceAcct,CN=users,DC=example,DC=com) and that it matches the exempt_ou_1 value you configured in the ldap_server_auto section of your Duo proxy server's authproxy.cfg file earlier .

  4. Go to LDAPDirectoriesthe AD directory currently used for Privileged Account Security accessHosts. Right-click Hosts and select Add Host.

  5. In the Properties table, the required information about the Duo LDAP proxy host (example shows adding Duo Authentication Proxy host to the "Duo LDAP" existing directory with the IP using LDAP/389):


    The IP address or fully-qualified DNS host name of your Duo Authentication Proxy server.


    Duo Authentication Proxy server port for incoming LDAP requests. Default port is '389' for CLEAR and STARTTLS and '636' for LDAPS.

    If using STARTTLS or LDAPS then the ssl_cert_path and ssl_key_path options must be configured in the Authentication Proxy LDAP configuration above.


    Select No for LDAP or Yes for LDAPS and STARTTLS.

  6. Right-click the new Duo LDAP Proxy host in the "Hosts" tree and select Move Up. Repeat until the Duo host is the first one in the list.

  7. Click Apply in the upper left, and then click OK.

    CyberArk LDAP Integration Host

For additional information please refer to the "LDAP Authentication" section in the "CyberArk Privileged Account Security Installation Guide".

Test Your Setup

Navigate to the Privileged Account Security web login page and click the LDAP directory option to which you added the Duo LDAP proxy host.

CyberArk LDAP Logon

Enter your Active Directory username and password. 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 initial authentication attempt is rejected and you'll receive a text message with Duo passcodes. You can then try to log on again, authenticating 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 and you want the Duo Push or phone call request to go to your second phone instead.


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

Next Steps

To further secure access to the CyberArk Privileged Account Security Solution, you can remove any LDAP hosts that aren't Duo LDAP proxy hosts or disable alternate authentication methods. See the "Authenticating to the Privileged Account Security Solution" section in the "CyberArk Privileged Account Security Installation Guide" for guidance.

Network Diagram

CyberArk Privileged Account Security LDAP Network Diagram

  1. Primary authentication initiated to CyberArk Privileged Account Security
  2. CyberArk Privileged Account Security sends authentication request to Duo Security’s authentication proxy
  3. Primary authentication using Active Directory
  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. CyberArk Privileged Account Security access granted