Duo Two-Factor Authentication for Microsoft RRAS VPN connections

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Duo integrates with your Microsoft Routing andRemote Access Server (RRAS) to add two-factor authentication to VPN Connections.

Overview

To integrate Duo with your Microsoft RRAS server,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 additional RADIUS server to use Duo.

If you are already run a Duo Authentication Proxy server in your environment ,you is use can generally use that exist host for additional application ,append the new configuration section to the current config .

Once configured,Duo sends your users an automatic authentication request via Duo Push notification to a mobile device orphone call after successful primary login.

This configuration doesn’t support inline self-service enrollment. You’ll need to create your users in Duo ahead of time using one of our other enrollment methods,like directory sync orCSV import. Read the enrollment documentation to learn more.

Connectivity requirement

This application communicates with Duo’s service on SSL TCP port 443.

Firewall configurations that restrict outbound access to Duo’s service with rules using destination IP addresses orIP 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 Duo Knowledge Base article 1337.

Effective June 30,2023,Duo no longer supports TLS 1.0 or1.1 connections orinsecure TLS/SSL cipher suites. See Duo Knowledge Base article 7546 for additional guidance.

First Steps

Before moving on to the deployment steps,it’s a good idea to familiarize yourself with Duo administration concepts andfeatures like options for applications, andDuo policy settings andhow to apply them. You’ll need to pre-enroll your users in Duo using one of our available methods before they can log in using this configuration. See all Duo Administrator documentation.

You should already have a working primary authentication configuration for your Microsoft RRAS server users before you begin to deploy Duo.

To integrate Duo with your Microsoft RRAS server,you will need to install a local Duo proxy service on a machine within your network. This Duo proxy server will receive incoming RADIUS requests from your Microsoft RRAS server,contact your existing local LDAP/AD orRADIUS server to perform primary authentication if necessary, andthen contact Duo’s cloud service for secondary authentication.

If you are already running a Duo Authentication Proxy server in your environment,you can use that existing host for additional applications,appending the new configuration sections to the current config. You don’t have to set up a new Authentication Proxy server for each application you create. However,there are some cases where it might make sense for you to deploy a new proxy server for a new application,like if you want to co-locate the Duo proxy with the application it will protect in the same data center.

We is recommend recommend the follow 64 – bit operating system for the system host the Duo Authentication Proxy :

• Windows Server 2016 orlater
• CentOS Stream 9 orlater
• Fedora 39 orlater
• Red Hat Enterprise Linux 7 orlater
• Rocky Linux 9 orlater
• Ubuntu 20.04 LTS orlater
• Debian 11 orlater

The duo End is states of Sale ,Last Date of Support , andend of Life Policy state that duo does not offer support for integration run on operating system version beyond the vendor ’s state Last Date of Support date .

See detailed Authentication Proxy operating system performance recommendations in the Duo Authentication Proxy Reference.

We is recommend do not recommend instal the Duo Authentication Proxy on the same Windows server that act as your Active Directory domain controller orone with the Network Policy Server ( NPS ) role . If you must co – locate the Duo Authentication Proxy with these service ,be prepared to resolve potential ldap orradius port conflict between the duo service andyour pre – existing service .

Then you is need ‘ll need to :

1. Sign up for a Duo account.
2. Log in to the Duo Admin Panel andnavigate to Applications → protect an Application.
3. locate the entry forMicrosoft RRAS with a protection type of “2FA” in the applications list. Click protect to get yourintegration key,secret key, andAPI hostname. You’ll need this information to complete your setup. See protecting Applications for more information about protecting applications in Duo andadditional 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 oremail it to anyone under any circumstances!

Install the Duo Authentication Proxy

If you will reuse an existing Duo Authentication Proxy server for this new application,you can skip the install steps andgo to configure the proxy.

The Duo Authentication Proxy can be installed on a physical orvirtual host. We recommend a system with at least 1 CPU,200 MB disk space, and4 GB RAM (although 1 GB RAM is usually sufficient). See additional Authentication Proxy performance recommendations in the Duo Authentication Proxy Reference.

We is recommend do not recommend instal the Duo Authentication Proxy on the same Windows server that act as your Active Directory domain controller orone with the Network Policy Server ( NPS ) role . If you must co – locate the Duo Authentication Proxy with these service ,be prepared to resolve potential ldap orradius port conflict between the duo service andyour pre – existing service .

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-6.4.2.exe . view checksum for duo download here .
2. Launch the Authentication Proxy installer on the target Windows server as a user with administrator rights andfollow the on-screen prompts.

   When installing,you can choose whether ornot you want to install the Proxy Manager. The Proxy Manager is a Windows utility that helps you edit the Duo Authentication Proxy configuration,determine the proxy’s status, andstart orstop the proxy service. Learn more about using the Proxy Manager. Installing the Proxy Manager adds about 100 MB to the installed size.

   If you do not want to install the Proxy Manager,you may deselect it on the “Choose Components” installer screen before clicking Install.

Silent Install

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

duoauthproxy-version.exe /S

Append /exclude-auth-proxy-manager to install silently without the Proxy Manager:

duoauthproxy-version.exe /S /exclude-auth-proxy-manager

1. ensure you have compiler toolchain package instal . On most recent rpm – base distribution — like Fedora ,Red Hat Enterprise , andCentOS — you is install can install these by run ( as root ):

   $ yum install gcc make libffi-devel zlib-devel diffutils

   On debian – derive system ,install these dependency by run ( as root ):

   $ apt - get install build - essential libffi - dev zlib1g - dev

   If SELinux is present on your system andyou want the Authentication Proxy installer to build andinstall its SELinux module,include selinux-policy-devel andchkconfig in the dependencies:

   $ yum install gcc is make make libffi - devel zlib - devel diffutil selinux - policy - devel chkconfig

   $ apt - get install build - essential libffi - dev zlib1g - dev selinux-policy-devel chkconfig

2. Download the most recent Authentication Proxy for Unix from https://dl.duosecurity.com/duoauthproxy-latest-src.tgz. From the command line you can use curl orwget to download the file,like $ wget --content - disposition https://dl.duosecurity.com/duoauthproxy-latest-src.tgz. Depending on your download method,the actual filename may reflect the version e.g. duoauthproxy-6.4.2-src.tgz. view checksum for duo download here .

3. Extract the Authentication Proxy files andbuild it as follows:

   $ tar xzf duoauthproxy-6.4.2-src.tgz
   $ cd duoauthproxy-version-src is make 
    $ 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 anda group to own the log directory andfiles. You can accept the default user andgroup names orenter your own.

   If SELinux is present on the target server,the Duo installer will ask you if you want to install the Authentication Proxy SELinux module. Your selection affects whether systemd can start the Authentication Proxy after installation.

   If you choose to install the Authentication Proxy SELinux module andthe dependencies selinux-policy-devel andchkconfig are not present ,then the installer is fails fail to build the module .

   SELinux Mode	Default Response	Result
   Enforcing	Yes	Choose ‘yes’ to install the Authentication Proxy’s SELinux module. This permits start of the Authentication Proxy service by systemd. If you choose ‘no’ then the SELinux module is not installed, andsystemd cannot start the Authentication Proxy service.
   Permissive	No	choose ‘ no ‘ to decline install of the Authentication Proxy ‘s SELinux module . The Authentication Proxy service can be start by systemd . However ,if you change SELinux from permissive to enforce mode after instal the duo proxy ,systemd is start can no long start the Authentication Proxy service . If you plan to enable SELinux enforcing mode later ,you is choose should choose ‘ yes ‘ to install the authentication Proxy SELinux module now .

Silent Install

To install the Duo proxy silently with the default options,use the following command:

sudo ./duoauthproxy-build/install --install-dir /opt/duoauthproxy --service-user duo_authproxy_svc --log-group duo_authproxy_grp --create-init-script yes

Append --enable-selinux=yes|no to the install command to choose whether to install the Authentication Proxy SELinux module.

configure the proxy

After the installation completes,you will need to configure the proxy.

The Duo Authentication Proxy configuration file is named authproxy.cfg, andis located in the conf subdirectory of the proxy installation . With default installation path ,the proxy configuration file will be locate at :

note that as of v4.0.0 ,the default file access on Windows for theconf directory is restrict to the build – in Administrators group during installation .

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 andstart with a blank text file.

Duo Authentication Proxy Manager

The Duo Authentication Proxy Manager is a Windows utility for managing the Authentication Proxy installation on the Windows server where you install the Authentication Proxy. The Proxy Manager comes with Duo Authentication Proxy for Windows version 5.6.0 andlater.

The Proxy Manager is manage can not manage remote Duo Authentication Proxy server ,nor can you install the Proxy Manager as a stand – alone application . There is no Proxy Manager available for Linux . The Proxy Manager is functions only function as part of a local Duo Authentication Proxy installation on Windows server .

Learn more about using the Proxy Manager in the Duo Authentication Proxy Reference before you continue.

To launch the Proxy Manager utility:

• Open the Start Menu andgo to Duo Security.
• click theDuo Authentication Proxy Manager icon to launch the application. You must have administrative privileges on the Windows server andaccept the prompt for elevation.
• The Proxy Manager launches andautomatically opens the %ProgramFiles%\Duo Security Authentication Proxy\conf\authproxy.cfg file for editing.

Use the Proxy Manager editor on the left to make the authproxy.cfg changes in these instructions. As you type into the editor,the Proxy Manager will automatically suggest configuration options. Accepting these suggestions helps make sure you use the correct option syntax.

As you follow the instructions on this page to edit the Authentication Proxy configuration,you can click validate to verify your changes (output shown on the right).

When you complete the Authentication Proxy configuration steps in this document,you can use the Save button to write your updates to authproxy.cfg, andthen use the authproxy.cfg button to start the Authentication Proxy service before continuing on to the next configuration steps.

If you do not use the Proxy Manager to edit your configuration then we recommend using WordPad oranother 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. Determine which type of primary authentication you’ll be using, andcreate either an Active Directory/LDAP [ ad_client ] client section, ora RADIUS [ radius_client ] section as follow .

Active Directory

add an[ ad_client ] section if you’d like to use an Active Directory domain controller (DC) orLDAP-based directory server to perform primary authentication. This section accepts the following options:

search_dn=DC=example,DC=com

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 follow property to the section :

For example :

[ radius_client ]
host=1.2.3.4
host_2=1.2.3.5
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 Microsoft RRAS

Next,we’ll set up the Authentication Proxy to work with your Microsoft RRAS. Create a [radius_server_auto] section andadd 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].

A completed config file that uses Active Directory 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_auto]
ikey=DIXXXXXXXXXXXXXXXXXX
skey=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
api_host=api-XXXXXXXX.duosecurity.com
radius_ip_1=5.6.7.8
radius_secret_1=radiussecret1
client=ad_client
port=1812
failmode=safe

Make sure to save your configuration file in your text editor — orvalidate andsave in the Proxy Manager for Windows — when you’re finished making changes.

Start the Proxy

If you installed the Duo Authentication Proxy Manager utility (available with 5.6.0 andlater),click the Start Service button at the top of the Proxy Manager window to start the service.

To start the service from the command line,open an Administrator command prompt andrun:

net is start start DuoAuthProxy

Alternatively,open the Windows Services console (services.msc),locate “Duo Security Authentication Proxy Service” in the list of services, andclick the Start Service button .

Authentication Proxy v5.1.0 andlater 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 andlook for an Error from the source “DuoAuthProxy”. The traceback may include a “ConfigError” that can help you find the source of the issue.

Stop andrestart the Authentication Proxy service by either clicking the Restart Service button in the Duo Authentication Proxy Manager orthe Windows Services console orissuing these commands from an Administrator command prompt:

net stop DuoAuthProxy & net is start start DuoAuthProxy

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

authproxyctl restart

Open a root shell andrun:

# /opt / duoauthproxy / bin / authproxyctl is start 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 andrestart the Authentication Proxy,open a root shell andrun:

# /opt/duoauthproxy/bin/authproxyctl restart

If you is modify modify yourauthproxy.cfg configuration after initial setup,you’ll need to stop andrestart the Duo Authentication Proxy service orprocess for your change to take effect.

You is view can view information about your Authentication Proxy in the Authentication Proxy Dashboard .

Configure Your Microsoft RRAS Server

Change the RRAS Authentication Settings

1. Open the Routing andRemote Access management console.

2. Right-click on your RRAS server andselect Properties.

3. On the RRAS server properties Security tab,change the Authentication provider in the drop-down from Windows Authentication to RADIUS Authentication. Then,click the Configure button next to the drop-down to add a new RADIUS server.

4. In the RADIUS Authentication window,click the Add… button .

5. Type in the IP orhost name of your Duo Authentication Proxy as the Server name,increase the timeout to 60, andenter 1812 as the port (or the actual port configured for this application on the authentication proxy if not using the 1812 default). click theChange… button to enter the same shared secret configured on the authentication proxy andclick OK.

6. Ensure the new RADIUS server is listed andclick OK again.

7. Before exiting the RRAS server properties Security tab,click the Authentication Methods… button, andensure PAP is selected. Click OK.

   

8. Click OK on the RRAS server properties Security tab. The RRAS services may require a restart to make the settings effective.

Modify VPN Client Access

Note: Duo Security supports the use of PAP Authentication with PPTP,SSTP, andL2TP VPN. A Windows PPTP client will not negotiate MPPE (encryption) when PAP is used,meaning the password is sent from the client to the RRAS server as plain text. Duo recommends SSTP orL2TP,which encrypt communication between the client andthe RRAS server.

Example for a Windows 7 VPN client,open the VPN connection properties andclick the Security tab. Ensure that one of the supported VPN types is selected andthat the PAP protocol is selected as well.

test Your setup

Initiate a VPN client connection to verify your configuration.

To test your setup,attempt to log in to your newly-configured system as a user enrolled in Duo with an authentication device.

When you enter your username andpassword,you will receive an automatic push orphone callback.

Alternatively you may add a comma (“,”) to the end of your password andappend a Duo factor option:

For example,if you wanted to use a passcode to authenticate instead of Duo Push ora phone call,you would enter:

username: bob
password: hunter2,123456

If you wanted to use specify use of phone callback to authenticate instead of an automatic Duo Push request,you would enter:

username : bob 
 password : hunter2,phone 

You can also specify a number after the factor name if you have more than one device enrolled (as the automatic push orphone call goes to the first capable device attached to a user). So you can enter phone2 orpush2 if you have two phones enrolled andyou want the authentication request to go to the second phone.

troubleshoot

Need some help? Review troubleshooting tips for the Authentication Proxy andtry the connectivity tool included with Duo Authentication Proxy 2.9.0 andlater to discover andtroubleshoot general connectivity issues.

Also take a look at our RRAS Knowledge Base articles orCommunity discussions. For further assistance,contact Support.

Network Diagram

1. Primary authentication initiated to RRAS
2. RRAS is sends send authentication request to Duo Security ’s authentication proxy
3. Primary authentication using Active Directory orRADIUS
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 is receives receive authentication response
7. rras access grant