Unlocking Microsoft Teams Extensibility - Enabling Single Sign-On (SSO) in Microsoft Teams Tabs

Single Sign-On (SSO) is a crucial feature for delivering seamless user experiences in custom Teams Tabs. By enabling SSO, users can access your app’s functionality without needing to sign in multiple times, leveraging their Microsoft 365 credentials for secure and efficient authentication. In this blog post, we’ll explore how SSO works and provide a step-by-step guide to implement it in a Teams Tab using Teams Toolkit.

How Does SSO Work in Teams?

SSO in Teams relies on Azure Active Directory (AAD) to authenticate users and provide access tokens for secure communication with your app. Here's an overview of how it works:

1. User Authentication:

   • The user signs in to Microsoft Teams using their Microsoft 365 credentials.

2. Token Exchange:

   • Teams uses its AAD app registration to request an access token for your app.

3. Token Passing:

   • The access token is passed to your Teams Tab as a part of the microsoftTeams.authentication flow.

4. Backend Validation:

   • Your app’s backend validates the token with Microsoft Identity Platform to ensure authenticity.

5. Data Access:

   • Once validated, the token is used to access secured APIs like Microsoft Graph or your custom backend services.

Setting Up SSO in Teams Tabs

1. Create an Azure AD App Registration

1. Log in to the Azure Portal.
2. Navigate to Azure Active Directory > App registrations.
3. Click New registration and fill in the required details:
   • Name: Enter a name for your app (e.g., TeamsTabSSO).
   • Supported account types: Choose "Accounts in this organizational directory only."
   • Redirect URI: Add a Web platform redirect URI: https://<your-app-domain>/auth-end. This will be used during the authentication flow.
4. Click Register.

2. Configure API Permissions

1. In your app registration, navigate to API permissions > Add a permission.
2. Select Microsoft Graph, then choose the permissions your app needs (e.g., User.Read, Mail.Read).
3. Grant admin consent for your organization.

3. Enable Teams Toolkit SSO Integration

Teams Toolkit simplifies the integration of SSO. Follow these steps:

1. Open your Teams app project in Visual Studio Code.
2. Run the following command to enable SSO:

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   teamsfx add capability auth

   This updates your project with the necessary AAD configuration files.
3. Open the manifest.json file and verify the following entries:

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   {
     "webApplicationInfo": {
       "id": "<client-id-from-aad>",
       "resource": "https://<your-app-domain>"
     }
   }

4. Configure your local environment by running:

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   teamsfx provision

4. Implement Authentication in Your Tab

Use the Teams JavaScript SDK to handle token retrieval and authentication.

Example Code:

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microsoftTeams.authentication.getAuthToken({
  successCallback: (token) => {
    console.log("Token retrieved:", token);
    // Send the token to your backend for validation
  },
  failureCallback: (error) => {
    console.error("Failed to retrieve token:", error);
  }
});

5. Validate the Token in Your Backend

Set up your backend to validate the token using the Microsoft Identity library.

Example in Node.js:

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const jwt = require("jsonwebtoken");
const jwksClient = require("jwks-rsa");

const client = jwksClient({
  jwksUri: "https://login.microsoftonline.com/<tenant-id>/discovery/v2.0/keys"
});

function verifyToken(token) {
  const decoded = jwt.decode(token, { complete: true });
  const kid = decoded.header.kid;

  client.getSigningKey(kid, (err, key) => {
    const signingKey = key.publicKey || key.rsaPublicKey;
    jwt.verify(token, signingKey, (err, payload) => {
      if (err) {
        console.error("Token verification failed", err);
      } else {
        console.log("Token is valid", payload);
      }
    });
  });
}

6. Test Your Tab Locally

Use Teams Toolkit’s local debugging feature to test the SSO flow:

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teamsfx preview

Additionally, tools like Dev Tunnels or ngrok can help you expose your local environment to the internet for debugging. This is especially useful for validating SSO redirects and token exchanges with Azure AD.

Best Practices for SSO in Teams Tabs

• Use HTTPS: Always use secure connections to protect tokens during transmission.
• Token Refresh: Implement token refresh logic to avoid authentication interruptions.
• Scopes Minimization: Request only the permissions your app truly needs to minimize security risks.
• Error Handling: Gracefully handle authentication errors to improve user experience.

Conclusion

Implementing SSO in Microsoft Teams Tabs enhances the user experience by eliminating redundant sign-ins and providing secure, seamless access to your app. With Teams Toolkit and Azure AD, you can quickly enable SSO and focus on delivering value to your users. Ready to unlock the potential of SSO in your Teams Tab? Start building today!