Single sign-on (SSO) with 3rd party IDPs

Single Sign-On (SSO) is a crucial feature that enables users to authenticate once and gain access to multiple applications or systems without having to log in again. SSO works by using a centralized authentication system, typically through a third-party Identity Provider (IDP) like Google, Microsoft, Okta, or others.

In this guide, we will go through how to implement SSO using a third-party IDP to authenticate users.

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Step 1: Choose a Third-Party Identity Provider (IDP)

Popular third-party identity providers for SSO include:

• Google Identity Platform
• Microsoft Azure Active Directory (Azure AD)
• Okta
• Auth0
• Ping Identity

Each IDP will have its specific setup process, but the general principles are similar.

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Step 2: Register Your Application with the IDP

Before integrating SSO, you need to register your application with the chosen IDP to obtain the necessary credentials (Client ID, Client Secret, etc.).

Google Identity Platform Example:

1. Go to Google Cloud Console:
   Open Google Cloud Console.
2. Create a New Project:
   Create a new project (or use an existing project).
3. Enable the “Google Identity Platform” API:
   Go to the APIs & Services > Library and enable the Google Identity Platform.
4. Create OAuth 2.0 Credentials:
   • Navigate to APIs & Services > Credentials.
   • Click Create Credentials and select OAuth 2.0 Client ID.
   • Choose the appropriate application type (Web application, Mobile app, etc.).
   • Set up Authorized Redirect URIs for your application (This is the endpoint where Google will redirect users after authentication).
   • Save your credentials, which will include a Client ID and Client Secret.

For Other IDPs (e.g., Okta, Auth0):

• The process will be similar: create an application in the provider’s dashboard, configure the OAuth2 or OpenID Connect (OIDC) settings, and generate your Client ID and Client Secret.

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Step 3: Integrate SSO in Your Application

Now that you have your credentials from the IDP, it’s time to integrate the SSO functionality into your application.

General Steps for Integration:

1. Install SDK/Library:
   Most IDPs offer SDKs or libraries to simplify integration. You can find SDKs for various platforms like JavaScript, Python, Java, etc. For example:
   • Google: Google provides a Google API Client Library.
   • Okta: Okta offers an Okta SDK.
   • Auth0: Auth0 provides Auth0 SDKs.
2. Configure Redirect URIs:
   When users attempt to sign in, they’ll be redirected to the IDP’s login page. After a successful login, the IDP will send a response to the Redirect URI you registered during setup.
3. Handle Authentication Request: Redirect users to the IDP’s login page using OAuth 2.0 or OpenID Connect. This request includes parameters such as:
   • client_id: Your application’s Client ID.redirect_uri: The URI to send the user back to after login.response_type: Usually, this will be code (for authorization code flow).scope: Define the scope of access you need (e.g., email, profile).
   Example (Google OAuth 2.0):
   <a href="https://accounts.google.com/o/oauth2/v2/auth?client_id=YOUR_CLIENT_ID&redirect_uri=YOUR_REDIRECT_URI&response_type=code&scope=email profile">Login with Google</a>
4. Receive and Exchange the Authorization Code:
   After successful authentication, the IDP will redirect the user back to the redirect_uri with an authorization code. Exchange the authorization code for an access token and optionally a refresh token. This token will be used to authenticate requests. Example (Exchange code for token using Python and requests library):
   import requests def exchange_code_for_token(code): url = "https://oauth2.googleapis.com/token" payload = { 'code': code, 'client_id': 'YOUR_CLIENT_ID', 'client_secret': 'YOUR_CLIENT_SECRET', 'redirect_uri': 'YOUR_REDIRECT_URI', 'grant_type': 'authorization_code' } response = requests.post(url, data=payload) token_data = response.json() access_token = token_data['access_token'] return access_token
5. Access User Data Using the Token:
   Once you have the access token, you can use it to retrieve user information (email, profile data, etc.) from the IDP. Example (Google user info): pythonCopyEditdef get_user_info(access_token): url = "https://www.googleapis.com/oauth2/v2/userinfo" headers = {'Authorization': f'Bearer {access_token}'} response = requests.get(url, headers=headers) user_info = response.json() return user_info
6. Store User Information:
   Once the user’s information is retrieved, store it in your application’s database or session for subsequent use.

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Step 4: Implement Logout Functionality

To fully implement SSO, you also need to handle logging out users. When users log out, they should be logged out of both your application and the IDP.

Example (Google Logout URL):

Google provides a single logout URL that you can use to log users out of both your application and Google:

<a href="https://accounts.google.com/Logout">Logout</a>

Other IDPs, like Okta and Auth0, provide similar mechanisms to log out users across applications.

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Step 5: Configure Security

When implementing SSO with third-party IDPs, security is paramount. Consider the following best practices:

1. Use HTTPS:
   Always ensure your application uses HTTPS to protect sensitive data (like tokens) during the authentication process.
2. Validate Tokens:
   Always validate the tokens (ID token, access token) you receive from the IDP to ensure they are legitimate and have not been tampered with. This can be done using the IDP’s public keys or by using their SDK.
3. Use Refresh Tokens:
   To avoid forcing users to log in repeatedly, use refresh tokens to obtain new access tokens when they expire. Store refresh tokens securely.
4. OAuth Scopes:
   Only request the minimum scopes necessary for your application to function (e.g., just email, profile, etc.).
5. Session Management:
   Ensure you manage user sessions properly and securely. Store session data in secure cookies and implement session expiration.

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Step 6: Test and Debug the Integration

Test the SSO integration by logging in with the third-party IDP. Verify the following:

• The login page appears correctly.
• After authentication, the user is redirected back to your application.
• The user’s information (e.g., email, name) is retrieved correctly.
• The logout functionality works as expected.
• Security features, such as token validation and session management, are functioning properly.