Resolving 401 Unauthorized Issues in Ocelot After Migrating to .NET 8 with Custom Authentication Sc

Описание: Learn how to fix 401 Unauthorized errors in Ocelot after upgrading from .NET Core 3.1 to .NET 8 by implementing a custom no-authentication scheme for selective route authentication.
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This video is based on the question https://stackoverflow.com/q/79055186/ asked by the user 'Malik Haseeb' ( https://stackoverflow.com/u/10178045/ ) and on the answer https://stackoverflow.com/a/79066472/ provided by the user 'Malik Haseeb' ( https://stackoverflow.com/u/10178045/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

After migrating a microservice API Gateway from .NET Core 3.1 to .NET 8, a common problem arises: Ocelot starts returning 401 Unauthorized errors unexpectedly. This happens because the latest version of Ocelot applies authentication across all routes by default, unlike older versions.

Problem

The upgrade caused all routes proxied through Ocelot to require authentication, even those that previously didn't. This results in calls to endpoints (e.g., https://localhost:3000/swaggerfiles.json) failing with HTTP 401 errors.

The Root Cause

Ocelot v17+ (compatible with .NET 8) enforces authentication on all routes unless explicitly configured otherwise. The previous setup relied on a single HTTP authentication scheme, which now blocks some routes unintentionally.

Solution: Implement a Custom "No Authentication" Scheme

To regain fine-grained control over which routes require authentication, create a custom authentication scheme that bypasses authentication for selected routes.



Steps to Fix the 401 Unauthorized Error

1. Define a Custom Authentication Handler

Create a NoHttpAuthenticationHandler that always returns successful authentication without checking credentials.

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

2. Register the Custom Scheme in Startup.cs

Add this no-auth scheme alongside your existing authentication methods so Ocelot can selectively apply it.

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

3. Update Ocelot's Configuration for Routes That Don’t Require Authentication

In your ocelot.global.json or equivalent routing configuration file, specify the new scheme for routes that should bypass authentication.

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

4. Results

Selective Authentication: Routes needing authentication use your original scheme.

Unauthenticated Routes: Swagger or public endpoints use the NoHttpAuthentication scheme and don’t return 401.

Summary

When migrating to .NET 8 and updating Ocelot:

Ocelot applies authentication to all routes by default.

To avoid 401 unauthorized errors on public routes, implement a "no authentication" scheme.

Register this scheme and assign it selectively in your Ocelot route configuration.

This approach maintains security where needed but allows unauthenticated access where appropriate, restoring your gateway’s expected behavior.



Additional Tips

Always review your authentication settings after library upgrades.

Use explicit schemes in Ocelot config to control pipeline behavior.

Test routes individually to confirm which require authentication.