Solving the 401 Unauthorized Issue in .NET Web API Core JWT Authentication

Learn how to troubleshoot and fix the `401 Unauthorized` error when integrating JWT authentication in your .NET Web API Core application.
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This video is based on the question https://stackoverflow.com/q/72275178/ asked by the user 'Hammas_Stack' ( https://stackoverflow.com/u/10303682/ ) and on the answer https://stackoverflow.com/a/72293139/ provided by the user 'Hammas' ( https://stackoverflow.com/u/6612831/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting JWT Authentication Issues in .NET Web API Core

As you're embarking on your journey of creating Web APIs with .NET, encountering issues with authentication is not uncommon. A particularly frustrating situation is when you successfully authenticate a user and receive a JSON Web Token (JWT), but upon attempting to access restricted resources, you are met with a 401 Unauthorized response. Let’s delve into this problem and explore how to fix it.

The Problem

Imagine this scenario: You set up your Web API, implemented JWT authentication, and can successfully log in with valid credentials. You receive a bearer token, but when trying to use this token to access protected endpoints, you continuously get a 401 Unauthorized error. This can lead to confusion and frustration for developers who just want to get their APIs working smoothly.

Identifying the Cause

One common misconfiguration that leads to this issue is the way the security scheme is defined in your Swagger setup. Specifically, if the security type is set to SecuritySchemeType.ApiKey instead of SecuritySchemeType.Http, it can block the proper authentication flow.

Key Points to Check

Correct Security Definition: Your security scheme should properly reflect the use of JWT.

Token Passing: Ensure that the token is being sent with requests to secured endpoints.

HTTP Headers: Confirm that the token is included in the authorization header as expected.

Solution

To resolve the 401 Unauthorized issue caused by incorrect security scheme configurations in your Swagger setup, you need to make a minor adjustment in your Program.cs file.

Step-by-Step Fix

Locate Your Swagger Configuration:
Find the section of your Program.cs file where you have defined your OpenApiSecurityScheme. It should look something like this:

[[See Video to Reveal this Text or Code Snippet]]

Change the Security Type:
Modify the Type from SecuritySchemeType.ApiKey to SecuritySchemeType.Http. Your updated security scheme should resemble the following:

[[See Video to Reveal this Text or Code Snippet]]

This change indicates that you are using the HTTP standard for bearer tokens, which is what JWT authentication relies upon.

Rebuild and Test:
After making this change, rebuild your application and try to authenticate again via Swagger UI or Postman. You should now receive a successful response when accessing protected endpoints with the JWT token.

Conclusion

By adjusting the security scheme type in your Swagger configuration, you can resolve the frustrating 401 Unauthorized response that occurs when using JWT authentication in your .NET Web API. Remember, careful attention to the configuration details can save you a lot of time and trouble.

Keep experimenting, and don't hesitate to reach out to the developer community if you run into further issues!

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