API Gateway - Missing Authentication Token

Hi,

You may want to read this article to debug your implementation: https://repost.aws/knowledge-center/api-gateway-authentication-token-errors

Or this corresponding video: https://www.youtube.com/watch?v=dTxuhpEFQbk

Probably, it boils down to the fact that your requests do not provide the right Sigv4 signatures of your requests: https://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-authenticating-requests.html

Unless the API Gateway is public (is it your case?), the SigV4 must be provided in the http(sI request headers. BTW, I do not recommend to compute the SigV4 yourself but to use AWS SDK for Api Gateway that will compute them for you.

Best,

Didier

The "Missing Authentication Token" error you're encountering with API Gateway is a common issue that can occur for several reasons. This error typically indicates that the API Gateway cannot properly authenticate or authorize the incoming request. Here are some potential causes and solutions:

1. Incorrect API endpoint: Ensure you're using the correct and complete URL for your API. The error often occurs when trying to access a resource or method that doesn't exist.

2. HTTP method mismatch: Verify that you're using the correct HTTP method (GET, POST, PUT, DELETE, etc.) for the API resource you're trying to access.

3. Missing or incorrect API key: If your API requires an API key, make sure you're including it correctly in your request headers.

4. Authorization issues: If your API uses IAM, Lambda, or JWT authorizers, ensure that the necessary credentials or tokens are properly included in your request.

5. CORS configuration: For browser-based applications, check if CORS (Cross-Origin Resource Sharing) is properly configured on your API.

6. SSL/TLS certificate issues: While you mentioned resolving a certificate issue by turning off your VPN, it's worth double-checking that there are no remaining SSL/TLS related problems.

To troubleshoot further:

1. Double-check your API's configuration in the API Gateway console.
2. Review your client-side code to ensure all necessary headers and authentication information are included.
3. Test your API using tools like Postman or curl to isolate whether the issue is client-side or server-side.
4. Check the API Gateway logs and CloudWatch metrics for more detailed error information.

If the issue persists, you may need to customize the gateway response for this error type to provide more informative error messages, which can help in diagnosing the root cause.
Sources
Gateway responses for REST APIs in API Gateway - Amazon API Gateway
Amazon API Gateway important notes - Amazon API Gateway