OAuth2 authentication flow consists of four main steps: Authorization, Token Request, Token Response, and Resource Access. In Angular applications, integration can be achieved using libraries like angular-oauth2-oidc.
1. Authorization: User is redirected to the authorization server (e.g., Google) from the Angular app. The user grants permission for the app to access their data.
Example URL:
https://accounts.google.com/o/oauth2/v2/auth?client_id=CLIENT_ID&redirect_uri=REDIRECT_URI&response_type=code&scope=SCOPES
2. Token Request: After successful authorization, the server redirects back to the Angular app with an authorization code. The app exchanges this code for an access token by making a POST request to the token endpoint.
Example POST request:
POST /token HTTP/1.1
Host: oauth2.googleapis.com
Content-Type: application/x-www-form-urlencoded
code=AUTHORIZATION_CODE&client_id=CLIENT_ID&client_secret=CLIENT_SECRET&redirect_uri=REDIRECT_URI&grant_type=authorization_code
3. Token Response: The server responds with an access token and optionally a refresh token. These tokens are stored securely in the Angular app (e.g., HttpOnly cookies).
4. Resource Access: The Angular app uses the access token to make API requests on behalf of the user. The token is included as a Bearer token in the Authorization header of each request.
