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SonicWall SRA or SMA 100 Series SSL VPN with RADIUS and Duo Prompt

Last Updated: February 23rd, 2021

Duo integrates with your SonicWall SRA or SMA 100 Series SSL VPN to add two-factor authentication to browser VPN logins, complete with inline self-service enrollment and Duo Prompt.

If you are using SonicWall Mobile Connect client or SonicWall's Global VPN Client using IPsec then see the VPN Client Instructions to configure the SonicWall device to use Duo Security's push authentication. The Duo Prompt shown in browsers does not work with SonicWall client VPN applications.

Other types of SonicWall devices (such as the SMA 1000 series, NSA series, or Aventail) may also work with Duo's RADIUS Application.

The Duo web-based prompt is compatible with the following:

  • SRA firmware versions up to 8.5.x
  • SMA 100 series devices (SMA 200, SMA 400, and SMA 500v) with v9 firmware as of
  • SMA 100 series devices (SMA 200, SMA 400, and SMA 500v) with v10 firmware

The Duo web-based prompt does not support:

  • SMA 100 series devices with 9.0 firmwares before
  • SMA 100 series devices or upgraded SRA devices with 8.6.x firmwares
  • SMA 1000 series devices running v12+ firmwares.

Sonicwall introduced a new "Contemporary mode" for SMA in v10.2. This mode may prevent display of the Duo prompt. If you have issues with the v10 "Contemporary mode", access the "Classic mode" login page by changing the VPN login URL in your browser from https://<your SMA VPN portal>/spog/welcome to https://<your SMA VPN portal>/cgi-bin/welcome. There is no setting in the SMA config to force use of "Classic mode".

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 SonicWall SMA/SRA SSL VPN users before you begin to deploy Duo.

To integrate Duo with your SonicWall SMA/SRA SSL VPN, 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:

  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 SonicWALL SRA SSL VPN 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-5.2.2.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 Depending on your download method, the actual filename may reflect the version e.g. duoauthproxy-5.2.2-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:

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. 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:



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.

For example:


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


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:



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


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.



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



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:


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 SonicWALL SMA/SRA SSL VPN

Next, we'll set up the Authentication Proxy to work with your SonicWALL SMA/SRA SSL VPN. 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 sonicwall_sra

Your integration key.


Your secret key.


Your API hostname (e.g. "").


The IP address of your SonicWALL SMA/SRA SSL VPN.


A secret to be shared between the proxy and your SonicWALL SMA/SRA SSL VPN. If you're on Windows and would like to encrypt this secret, see Encrypting Passwords in the full Authentication Proxy documentation.


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.


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


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.



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.


Either "safe" or "secure":


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


In the event that Duo's service cannot be contacted, all users' authentication attempts will be rejected.


The IP address of your second SonicWALL SMA/SRA SSL VPN, if you have one. You can specify additional devices as as radius_ip_3, radius_ip_4, etc.


The secrets shared with your second SonicWALL SMA/SRA SSL VPN, 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, 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 Your SonicWall SRA SSL VPN

Configure the Portal Settings

You can add Duo authentication to an existing remote access portal, or you can create a new portal to use with Duo. However, the portal you choose to use with Duo should be dedicated for Duo authentication, with the Duo RADIUS domain you create later in this document bound to it. Follow these steps to create a new portal.

  1. Log in to the SonicWall administrative interface.
  2. In the left menu, navigate to Portals → Portals.
  3. Click on Add Portal.
  4. Navigate to the General tab.
  5. In the Portal Name field, enter "Duo-Portal".
  6. On the General tab, add the following to the end of the text in the Login Message box:

    <script src="https://API_HOSTNAME/frame/hosted/Duo-SonicWALL-SRA-v1.js"></script>

    Replace API_HOSTNAME with your API hostname (i.e.

  7. Select the Display custom login page check box.

  8. Select the Display login message on custom login page check box.

    Portal Setting

  9. Click on the Virtual Host tab.

  10. Enter your desired Virtual Host Domain Name and select a Virtual Host Certificate to secure the connection with SSL (see the SonicWALL administration guide for your device to learn how to import certificates).

    Portal Virtual Host Setting

  11. Click OK to save the settings.

Add a RADIUS Domain

  1. In the left menu of the SonicWall console, navigate to Portals → Domains.
  2. Click on Add Domain.
  3. Select Radius from the Authentication type dropdown.
  4. In the Domain Name field, "Duo-RADIUS" or another unique name.
  5. Under Primary Radius server, enter the following information:

    Radius server address The IP address of your Duo Authentication Proxy
    Radius server port 1812
    Secret password The RADIUS secret shared with your Duo Authentication Proxy
    Radius Timeout (Seconds) Increase to 60
  6. For the Portal name, select the portal(s) that should use this new RADIUS domain from the list.

    RADIUS Domain Add

  7. Click Submit to save the settings.

Update CSP for Duo

  1. Navigate to the SMA Internal Settings page at https://<your SMA IP or hostname>/cgi-bin/diagsettings.

  2. Scroll down to the "Content Security Policy Settings" setting and enter * as the "Content Security Policy URL". Separate multiple values in that field with a semi-colon (;) if necessary.

  3. Click Accept to save the settings.

Test Your Setup

To test your setup, go to the "Classic mode" version of the Duo-Portal URL for your SonicWall SRA VPN (i.e. https://<your SMA VPN portal>/cgi-bin/welcome). Make sure to select Duo Domain from the Domain drop down list.

After you complete primary authentication, the Duo enrollment/login prompt appears.

SonicWall SRA Authentication Prompt

Enable Hostname Whitelisting

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.


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 SonicWall SRA Frequently Asked Questions (FAQ) page or try searching our SonicWall SRA Knowledge Base articles or Community discussions. For further assistance, contact Support.

Network Diagram

  1. Primary authentication initiated to SonicWall SRA
  2. SonicWall SRA 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. SonicWall SRA access granted