Duo Single Sign-On for Stack Overflow for Teams

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 Stack Overflow for Teams 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 Stack Overflow for Teams.

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 Stack Overflow for Teams. Duo checks the user, device, and network against an application's policy before allowing access to the application.

Configure Single Sign-On

Before configuring Stack Overflow for Teams with Duo SSO using Security Assertion Markup Language (SAML) 2.0 authentication you'll first need to configure a working authentication source.

Once you have your SSO authentication source working, continue to the next step of creating the Stack Overflow for Teams application in Duo.

Create the Stack Overflow for Teams Application in Duo

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

2. Locate the entry for Stack Overflow for Teams with the "SSO" label in the catalog. Click the + Add button to start configuring Stack Overflow for Teams. See Protecting Applications for more information about protecting applications with Duo and additional application options. You'll need the information on the Stack Overflow for Teams 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. Stack Overflow for Teams uses the Mail attribute and Display name attribute when authenticating. We've mapped these attributes to external authentication source attributes as follows:

   Default Attribute	Active Directory	SAML IdP
   <Email Address>	mail	Email
   <Display Name>	display_name	displayName

   If you are using non-standard attributes for your authentication source, check the Custom attributes box and enter the name of the attributes 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 Stack Overflow for Teams 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 Stack Overflow for Teams 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 Stack Overflow for Teams for SSO

1. Log into your Stack Overflow for Teams account as an administrator.

2. In the sidebar menu, navigate to Admin settings → Authentication. The "Authentication" page opens.

3. Click the Single sign-on (SSO) radio button.

4. Copy the Assertion Consumer Service URL and paste it into the Duo Admin Panel Assertion Consumer Service URL field, under "Service Provider".

   

5. In the Duo Admin Panel under "Metadata", copy the Issuer URL and paste it into the Stack Overflow for Teams Issuer field.

6. Return to the Duo Admin Panel. Copy the Single sign-on Service Url and paste it into the Stack Overflow for Teams Single sign-on Service Url field.

   

7. In Stack Overflow for Teams, click the Single sign-on Service Protocol Binding drop-down menu and select urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST.

8. Copy the Assertion Consumer Service URL and paste it into the Audience Restriction field.

9. Type DisplayName into the Display Name Assertion field.

10. Type Email into the Email Address Assertion field.

11. Leave the Job Title Assertion and Department Assertion fields empty.

12. Make sure the following checkboxes are not checked:

    • Don't user Subject/NameID as User Identifier

    • Enforce 80 byte maximum RelayState length?

    • Verify the SubjectConfirmation element on a SAML Response?

    • Automatically update certificates periodically

13. Return to the Duo Admin Panel. Under "Downloads", click Copy certificate and paste the certificate text into the Stack Overflow for Teams Identity Provider Certificates field, including the -----BEGIN CERTIFICATE----- and -----END CERTIFICATE----- lines.

14. In Stack Overflow for Teams, click Validate certificate.

15. Click Authenticate and enable SSO. You will be automatically redirected to Duo Single Sign-On to authenticate your configuration.

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

Learn more about Stack Overflow for Teams SSO at the Stack Overflow for Teams Help Center.

Using SSO

You can log on to Stack Overflow for Teams by navigating to your Stack Overflow for Teams SSO page e.g., https://stackoverflowteams.com/c/your-site/. Click Log in with SSO 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 Stack Overflow for Teams to complete the login process.

* Universal Prompt experience shown.

You can also log into Stack Overflow for Teams using Duo Central, our cloud-hosted portal which allows users to access all of their applications in one spot. Link to Stack Overflow for Teams 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 Stack Overflow for Teams.

Congratulations! Your Stack Overflow for Teams 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 Stack Overflow for Teams and your other Duo Single Sign-On SAML applications, be sure to apply a shared "Remembered Devices" policy to your SAML applications.

Automated Provisioning

You may be able to create, manage, and delete users and groups in this application automatically from Duo using SCIM 2.0 provisioning. See Automated Provisioning to learn how.

Troubleshooting

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