Duo Single Sign-On for Proton VPN

Overview

As business applications move from on-premises to cloud hosted solutions, users experience password fatigue due to disparate logons for different applications. Single sign-on (SSO) technologies seek to unify identities across systems and reduce the number of different credentials a user has to remember or input to gain access to resources.

While SSO is convenient for users, it presents new security challenges. If a user's primary password is compromised, attackers may be able to gain access to multiple resources. In addition, as sensitive information makes its way to cloud-hosted services it is even more important to secure access by implementing two-factor authentication and zero-trust policies.

About Duo Single Sign-On

Duo Single Sign-On is our cloud-hosted SSO product which layers Duo's strong authentication and flexible policy engine on top of Proton VPN logins. Duo Single Sign-On acts as an identity provider (IdP), authenticating your users using existing on-premises Active Directory (AD) or another SSO IdP. Duo SSO prompts users for two-factor authentication and performs endpoint assessment and verification before permitting access to Proton VPN.

Duo Single Sign-On is available in Duo Premier, Duo Advantage, and Duo Essentials plans, which also include the ability to define policies that enforce unique controls for each individual SSO application. For example, you can require that Salesforce users complete two-factor authentication at every login, but only once every seven days when accessing Proton VPN. Duo checks the user, device, and network against an application's policy before allowing access to the application.

Configure Single Sign-On

Before configuring Proton VPN with Duo SSO using Security Assertion Markup Language (SAML) 2.0 authentication you'll first need to enable Duo Single Sign-On for your Duo account and configure a working authentication source.

Once you have your SSO authentication source working, continue to the next step of creating the Proton VPN application in Duo.

Create the Proton VPN Application in Duo

1. Log in to the Duo Admin Panel and navigate to Applications → Protect an Application.

2. Locate the entry for Proton VPN with a protection type of "2FA with SSO hosted by Duo (Single Sign-On)" in the applications list. Click Protect to the far-right to start configuring Proton VPN. See Protecting Applications for more information about protecting applications with Duo and additional application options. You'll need the information on the Proton VPN page under Metadata later.

3. No users can log in to new applications until you grant access. Update the User access setting to grant access to this application to users in selected Duo groups, or to all users. Learn more about user access to applications. If you do not change this setting now, be sure to update it so that your test user has access before you test your setup.

4. Proton VPN uses the Mail attribute when authenticating. We've mapped the <Email Address> bridge attribute to Duo Single Sign-On supported authentication source attributes as follows:

   Bridge Attribute	Active Directory	SAML IdP
   <Email Address>	mail	Email

   If you are using a non-standard email attribute for your authentication source, check the Custom attributes box and enter the name of the attribute you wish to use instead.

5. You can adjust additional settings for your new SAML application at this time — like changing the application's name from the default value, enabling self-service, or assigning a group policy.

6. Keep the Duo Admin Panel tab open. You will come back to it later.

Duo Universal Prompt

The Duo Universal Prompt provides a simplified and accessible Duo login experience for web-based applications, offering a redesigned visual interface with security and usability enhancements.

Universal Prompt	Traditional Prompt

The Duo Proton VPN application supports the Universal Prompt by default, so there's no additional action required on your part to start using the newest authentication experience.

Activate Universal Prompt

Activation of the Universal Prompt is a per-application change. Activating it for one application does not change the login experience for your other Duo applications. Universal Prompt is already activated for new Proton VPN applications at creation.

The "Universal Prompt" area of the application details page shows that this application's status is "Activation complete", with these activation control options:

• Show traditional prompt: Your users experience Duo's traditional prompt via redirect when logging in to this application.
• Show new Universal Prompt: (Default) Your users experience the Universal Prompt via redirect when logging in to this application.

The application's Universal Prompt status shows "Activation complete" both here and on the Universal Prompt Update Progress report.

For the time being, you may change this setting to Show traditional prompt to use the legacy experience. Keep in mind that support for the traditional Duo prompt ended for the majority of applications in March 2024. This option will be removed in the future.

Universal Update Progress

Click the See Update Progress link to view the Universal Prompt Update Progress report. This report shows the update availability and migration progress for all your Duo applications. You can also activate the new prompt experience for multiple supported applications from the report page instead of visiting the individual details pages for each application.

Enable Proton VPN for SSO

1. Log into your Proton VPN account as an administrator.

2. In the sidebar menu, click Single sign-on. The "Single sign-on" page opens.

3. Under "SAML authentication", click Configure SAML. The "Add domain" pop-up window opens.

4. Enter your domain into the Allowed domain field and then click Add domain. The "Verify domain" pop-up window opens.

   Note: If your email address is user@example.com, then your domain is example.com.

5. Add the DNS TXT record to your domain in your DNS provider.

   Note: It can take up to 48 hours for your domain to be verified. You can still go to the next step and configure SAML, but you will not be able to test your configuration until your domain is verified.

6. In the "Verify domain" pop-up window, click Continue. The "Enter endpoints into your identity provider" pop-up window opens.

7. Click Continue. The "Enter SAML metadata" pop-up window opens.

8. Click the Text fields radio button.

9. Return to the Duo Admin Panel. Under "Metadata", copy the Single sign-on URL and paste it into the Proton VPN Single sign-on URL field.

10. Return to the Duo Admin Panel. Copy the Single sign-on Entity ID and paste it into the Proton VPN Single sign-on Entity ID field.

    

11. Return to the Duo Admin Panel. Under "Downloads", click Copy certificate and paste the certificate text into the Proton VPN Public certificate (X.509) field, including the -----BEGIN CERTIFICATE----- and -----END CERTIFICATE----- lines.

12. In Proton VPN, click Done. The "Enter SAML metadata" pop-up window closes and you return to the "Single sign-on" page.

13. Return to the Duo Admin Panel. Scroll down to the bottom of the page and click Save.

14. Return to Proton VPN. Under the Allowed Domain field, make sure there is a green checkmark with the message "Domain ownership verified". Your domain must be verified before going to the next step.

15. In Proton VPN, scroll down and click Test SAML configuration. The "Test SAML configuration" pop-up window opens.

16. Enter your email address username into the Email field. Your domain is automatically populated.

    Note: If your email address is user@example.com, then your username is user.

17. Click Test. You will be redirected to Duo Single Sign-On to test your SAML configuration.

18. After the test passes, you will be automatically redirected back to Proton VPN with The "It works!" pop-up window open. Click Done.

Learn more about Proton VPN SSO at Proton VPN Support.

Using SSO

You can log on to Proton VPN by navigating to your Proton VPN SSO page e.g., https://account.protonvpn.com. In the "Sign in" box, enter your email address and click Continue. In the "Sign in to your organization" box, click Sign in to be redirected to Duo Single Sign-On to begin authentication.

Active Directory Login

With Active Directory as the Duo SSO authentication source, enter the primary username (email address) on the Duo SSO login page and click or tap Next.

Enter the AD primary password and click or tap Log in to continue.

Enable Duo Passwordless to log in to Duo SSO backed by Active Directory authentication without entering a password in the future.

SAML Login

The SAML login experience depends on your Duo SSO routing rules configuration.

With another SAML identity provider as the only enabled Duo SSO authentication source and the default routing rule in place, Duo SSO immediately redirects the login attempt to that SAML IdP for primary authentication. Users do not see the Duo SSO primary login screen.

If you have multiple enabled SAML authentication sources or custom routing rules in place, then users enter their primary username (email address) on the Duo SSO login page and then will be redirected to the correct external SAML identity provider.

Duo Authentication

Successful verification of your primary credentials by Active Directory or a SAML IdP redirects back to Duo. Complete Duo two-factor authentication when prompted and then you'll return to Proton VPN to complete the login process.

* Universal Prompt experience shown.

You can also log into Proton VPN using Duo Central, our cloud-hosted portal which allows users to access all of their applications in one spot. Link to Proton VPN in Duo Central by adding it as an application tile. Once the tile has been added, log into Duo Central and click the tile for IdP-initiated authentication to Proton VPN.

Congratulations! Your Proton VPN users now authenticate using Duo Single Sign-On.

See the full user login experience, including expired password reset (available for Active Directory authentication sources) in the Duo End User Guide for SSO.

Grant Access to Users

If you did not already grant user access to the Duo users you want to use this application be sure to do that before inviting or requiring them to log in with Duo.

Enable Remembered Devices

To minimize additional Duo two-factor prompts when switching between Proton VPN and your other Duo Single Sign-On SAML applications, be sure to apply a shared "Remembered Devices" policy to your SAML applications.

Troubleshooting

Need some help? Try searching our Knowledge Base articles or Community discussions. For further assistance, contact Support.