Fixing 401 Error on Angular-NestJs: Refresh Token Issues with Auth0

Описание: Learn how to resolve the `401 Error` in your Angular-NestJs application when refreshing tokens using Auth0 for authentication.
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This video is based on the question https://stackoverflow.com/q/78191663/ asked by the user 'Marc Fernandez' ( https://stackoverflow.com/u/4789347/ ) and on the answer https://stackoverflow.com/a/78198720/ provided by the user 'Marc Fernandez' ( https://stackoverflow.com/u/4789347/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving the 401 Error when Refreshing Tokens in Angular-NestJs with Auth0

When building web applications, authentication can often present challenges, especially when incorporating different technologies together. Recently, a common issue has emerged for developers using Angular as the frontend and NestJs as the backend, particularly while implementing Auth0 for user authentication. The problem arises when attempting to refresh the token after the initial request, resulting in a frustrating 401 Unauthorized error from NestJs.

In this guide, we will explore why this issue occurs and how to effectively fix it, ensuring your users can enjoy seamless authentication without interruptions.

Understanding the Issue

The 401 Unauthorized error indicates that the server cannot verify the credentials provided in the request. This situation typically occurs when an invalid or expired authentication token is used. In the scenario described, the user successfully logs in, and the Angular application initiates a successful token request to the NestJs API. However, upon refreshing the page and attempting to use the same token, the application returns a 401 error.

Factors to Consider:

Initial Login vs. Token Refresh: The initial token request might work perfectly, yet subsequent requests fail if the token is improperly configured.

JWT and Passport: The backend relies on JSON Web Tokens (JWT) for authentication, processed through the Passport.js middleware.

Interceptor configuration: Angular uses interceptors to modify HTTP requests, and improper configurations can lead to the errors encountered.

Solution to the 401 Error

The solution to this problem centers around the Angular interceptor responsible for handling API request headers. By configuring the interceptor correctly, we can ensure the server properly validates any refreshed tokens.

Step-by-Step Guide to Fixing the Issue

Locate the Interceptor:

Find the interceptor in your Angular application that adds the token to your HTTP requests. This is typically a class implementing the HttpInterceptor interface.

Modify the Interceptor Configuration:

Add an issuer parameter to the token being sent in the headers. This configuration must correspond with what the NestJs backend expects when validating tokens.

Example Code Snippet:

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

Testing:

After modifying the interceptor, retest the application by logging in and refreshing the page to see if the repeated requests succeed without returning a 401 error.

Conclusion

By adding the correct issuer parameter to your Angular interceptor, you can ensure that your NestJs backend properly validates refreshed tokens. This solution enables seamless user experiences without authentication interruptions, allowing your applications to run smoothly.

If you encounter more authentication-related issues, take time to review both your frontend and backend configurations as they need to align perfectly for optimal functionality. Happy coding!