Intermittent Authorization Header Issue with AWS Amplify

The intermittent issue you're experiencing with missing Authorization headers in your React application using AWS Amplify is a concerning problem that can indeed lead to 403 Forbidden errors when accessing protected API Gateway endpoints. This type of issue can be challenging to diagnose due to its sporadic nature. However, there are several potential causes and solutions to consider:

1. Token Expiration and Refresh: Ensure that your Amplify configuration is set up to properly handle token expiration and refresh. The issue might occur if there's a race condition between token expiration and the API request. Make sure you're using the latest version of Amplify libraries, as older versions may have had issues with token refresh timing.

2. Network Conditions: Intermittent network issues could potentially interfere with token retrieval or refresh. Ensure your application has proper error handling and retry mechanisms for network failures.

3. Amplify Configuration: Double-check your Amplify configuration to ensure it's correctly set up for your Cognito User Pool and API Gateway. Incorrect configuration could lead to sporadic authentication issues.

4. Custom Interceptors: If you're using custom interceptors or modifying the default Amplify behavior, ensure these are not interfering with the header attachment process.

5. Browser Storage: Verify that browser storage (localStorage or sessionStorage) is not being cleared unexpectedly, which could lead to loss of authentication tokens.

6. API Gateway Configuration: Review your API Gateway settings to ensure the Cognito authorizer is correctly configured and that there are no issues with the integration between API Gateway and Cognito.

7. Logging and Monitoring: Implement detailed logging on both the client-side and server-side to capture more information about when and why these 403 errors occur. You can use AWS X-Ray in conjunction with CloudWatch to gain deeper insights into the request flow and identify where the authorization is failing.

8. Token Validation: Ensure that the tokens being sent are valid and not malformed. You might want to implement additional client-side checks before sending requests.

To further diagnose and resolve this issue:

1. Implement more comprehensive error handling and logging in your React application to capture details about the requests that fail.

2. Use browser developer tools to monitor network requests and inspect the headers being sent.

3. Implement server-side logging in your Lambda functions to track incoming requests and their headers.

4. Consider using AWS X-Ray to trace requests through your application stack and identify where the authorization is failing.

5. If the issue persists, you may want to consider implementing a custom credentials provider or exploring alternative authentication flows that Amplify supports, such as using OIDC or SAML providers, which might provide more stability in your specific use case.

Remember to test thoroughly after making any changes to ensure that the fix doesn't introduce new issues and resolves the intermittent nature of the problem.

Sources
6 New AWS Amplify Launches for Frontend Developers | Front-End Web & Mobile
New in AWS Amplify: Integrate with SQL databases, OIDC/SAML providers, and the AWS CDK | Front-End Web & Mobile
Community | Solving Problems You Can't See: How AWS X-Ray and CloudWatch Provide User-Level Observability in Serverless Microservices Applications

Hi,

I'd would strongly suggest you to read this recent issue stream and see if their solution is also applicable to your use case : https://github.com/aws-amplify/amplify-js/issues/13489

Best,

Didier