Скачать или смотреть Resolving invalid_response Error in FastAPI with SAML Single Sign-On Integration

Learn how to fix the `invalid_response` error when integrating SAML SSO with FastAPI and Nginx. Step-by-step guide to configure Nginx and FastAPI for seamless authentication.
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This video is based on the question https://stackoverflow.com/q/76568592/ asked by the user 'Amogha Varsha' ( https://stackoverflow.com/u/9518629/ ) and on the answer https://stackoverflow.com/a/76581032/ provided by the user 'Amogha Varsha' ( https://stackoverflow.com/u/9518629/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving invalid_response Error in FastAPI with SAML Single Sign-On Integration

Integrating SAML Single Sign-On (SSO) with FastAPI can sometimes present challenges, especially when faced with errors like invalid_response. One common issue developers encounter is when the response is received at the wrong URL—specifically, the response is received at an internal address (https://containerip/) instead of the expected external server URL. This can lead to authentication failures and a frustrating development experience.

In this guide, we'll explore how to resolve this issue effectively, using a concrete example involving Nginx and FastAPI configurations. Let's walk through the solution step by step.

Understanding the Problem

When integrating FastAPI with SAML SSO, it’s crucial that the correct headers and properties are passed through your setup. The error ERROR:routers.auth:Errors occurred: ['invalid_response'] usually indicates that the SAML response is being routed incorrectly. This is often traced back to how your application and Nginx are set to communicate over HTTPS.

Key Issue

The primary issue arises when the application does not correctly recognize the external URLs when proxying requests. Instead of seeing the public-facing URL (https://myserverurl), it perceives the internal Docker container IP address (https://containerip/). To tackle this, we need to ensure that we accurately handle the headers that forward the original request information.

Solution Steps

Follow these steps to modify your FastAPI request handling and get the SAML SSO integration working correctly.

Step 1: Modify Nginx Configuration

First, ensure your Nginx configuration is set up to pass the correct headers to your FastAPI application. You’ve already set the proxy_set_header directives correctly, which is great. Here’s a snippet of what parts should look like:

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Step 2: Update FastAPI Request Preparation

Here’s the crux of the solution: updating your FastAPI function responsible for preparing the request data. Modify the prepare_fastapi_request function to instead use the forwarded host and port from the request headers.

Replace your existing function with this updated version:

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Step 3: Rerun Docker Container with Correct Parameters

Finally, ensure when you run your Docker container, you’re allowing proxy headers to be processed correctly. Here’s the command to start your FastAPI application inside Docker:

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Conclusion

With these adjustments, FastAPI should now receive the correct URL and port information through the forwarded headers, eliminating the invalid_response error. You should now be able to proceed with SAML SSO integration smoothly, allowing users to authenticate seamlessly through your FastAPI app.

Additional Tips

Always ensure that your Nginx SSL certificates and configurations are correct to avoid other security-related issues.

Review your application logs frequently to catch any unexpected errors or behavior during the authentication process.

By following this guide, you should be well on your way to a successful SAML SSO implementation with FastAPI. Happy coding!