OAuth2 Authorization Flow with Postman Tutorial

Welcome to the short tutorial. This tutorial covers how to test an OAuth2 authorization flow using Postman, utilizing the Imgur API as an example. This process holds for any application implementing this authorization flow.

Overview

• OAuth2 Authorization Code Grant Flow: A widespread method for authorizing using OAuth2.
• Major Providers: Facebook and Google use this method.
• **Flow Explanation: **
  1. Application redirects to Authorization Server: Provides a redirection URL.
  2. User Authentication: User authenticates on the authorization server.
  3. Authorization Request: User approves application's request to access information.
  4. Receive Authorization Code: Application receives an authorization code.
  5. Request Access Token: Application requests an access token using the authorization code.
  6. Access Protected Resources: Access resources using the obtained access token.

Testing OAuth2 Flow with Postman

1. **Endpoint Access Issue: **

   • Accessing an endpoint without an OAuth2 token results in an error (access denied).
   • Postman can handle this using its authorization capabilities.

2. **Postman Setup: **

   • Open a new tab in Postman.
   • Under the Authorization tab, select OAuth2.
   • Click to get a new token which opens a new pop-up window.

3. **App Registration: **

   • Register your application with the API provider (e.g., Imgur).
   • Provide a callback URL in Postman and register application.
   • Obtain Client ID and Client Secret.

4. **Postman Configuration: **

   • Enter Client ID and Client Secret in Postman.
   • Provide Authorization URL and Token URL.
   • Request token, log in, and grant permission.

5. **Receiving Tokens: **

   • Receive an access token and a refresh token.
   • The access token is added to the request header either manually or automatically.

6. **Make Authenticated Requests: **

   • Add the access token to the header or as a URL parameter.
   • Make a request to verify authentication using the provided token.

Final Notes

• **Headers vs URL Parameters: **
  • Tokens can be added to headers or as URL parameters, depending on the application.
• **Advantages of Using Postman: **
  • Allows testing OAuth2 authorization without writing client code.
• **Feedback and Questions: **
  • Leave a comment for queries and check descriptions for additional tips.

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