โฟลว์รหัสอนุญาตสิทธิ์ด้วย OIDC

Welcome! In this lesson, we'll combine the secure Authorization Code Flow from OAuth2 with OpenID Connect (OIDC). This allows an application to not only get permission to access resources (OAuth2) but also to verify the user's identity (OIDC).

Think of it as getting both a key to a safe and a valid ID card for the person holding the key, all in one go!

When using the Authorization Code Flow with OIDC, your application (the Client) starts by sending an authorization request to the Authorization Server. This request is similar to OAuth2 but includes specific OIDC parameters.

• response_type=code: Specifies we want an Authorization Code.
• scope=openid ...: Crucially, includes the openid scope to signal an OIDC request.
• nonce: A unique string to prevent replay attacks (optional but recommended).

The openid scope is the magic flag that tells the Authorization Server you're performing an OpenID Connect request, not just a plain OAuth2 request.

Without openid in your request's scope, the Authorization Server will treat it as a standard OAuth2 flow and will not issue an ID Token.

You can combine openid with other standard OAuth2 scopes like profile, email, or custom scopes.

While openid is mandatory, other OIDC-specific scopes allow you to request more user information:

• profile: Access to default profile claims (name, family name, gender, picture, etc.).
• email: Access to the user's email address and verification status.
• address: Access to the user's postal address.
• phone: Access to the user's phone number and verification status.

These claims are then included in the ID Token or accessible via the UserInfo Endpoint.

After your app sends the authorization request, the user is redirected to the Authorization Server. They log in (if needed) and are prompted to consent to your app's requested scopes.

If the user approves, the Authorization Server redirects the user back to your app's registered redirect URI, including the Authorization Code in the URL query parameters.

Now, your application (running on a server, for confidential clients) takes the received Authorization Code and exchanges it directly with the Authorization Server's token endpoint.

This is a back-channel request, meaning it happens directly between your server and the Authorization Server, not through the user's browser.

Crucially, this exchange now returns three important pieces of information:

• Access Token
• Refresh Token (if requested)
• ID Token

The ID Token is a JSON Web Token (JWT) that contains claims about the authenticated user. It's signed by the Authorization Server, allowing your application to verify its authenticity.

Unlike the Access Token (which is for resource access), the ID Token is specifically for identity verification. It tells your application *who* the user is, not *what* they can do.

Once your application receives the tokens:

• ID Token: You can decode and validate the ID Token to confirm the user's identity and retrieve basic profile information (claims). This is often used for user login sessions.
• Access Token: This token is then used to make requests to protected Resource Servers (APIs) on behalf of the user, granting access to specific resources based on the requested scopes.

Here's a simplified conceptual look at the server-side token exchange. In a real application, you'd use an OIDC client library.

Consider an application implementing the OpenID Connect Authorization Code Flow.

Which of the following parameters is essential in the initial authorization request to ensure an ID Token is returned?

Great job! You've learned how the secure Authorization Code Flow is extended by OpenID Connect to provide both authorization and identity.

• We use response_type=code and include the openid scope.
• The Authorization Server returns an Authorization Code.
• This code is exchanged for an Access Token (for resource access) and an ID Token (for user identity).
• The ID Token is a JWT carrying user claims, signed by the Authorization Server.

This flow is highly recommended for confidential clients like web applications.