File uploads getting blocked after introducing AWS WAF

Question

I recently setup WAF and POST upload requests (greater than ~10 GB, no issues for small files) are getting blocked. 413 is returned with the response shown below. ``` ERROR: The request could not be satisfied

413 ERROR

The request could not be satisfied.

Bad request. We can't connect to the server for this app or website at this time. There might be too much traffic or a configuration error. Try again later, or contact the app or website owner.
If you provide content to customers through CloudFront, you can find steps to troubleshoot and help prevent this error by reviewing the CloudFront documentation.

Generated by cloudfront (CloudFront)
Request ID: XXXXXXXXXXXXX==

``` The issue is I cannot find this request ID inside the WAF Logs. It looks like it is getting blocked before the waf rules, is that possible? I tried adding custom rules (with max priority) to pass everything through for this specific API but it's getting blocked even before it reaches there. Any idea why this happens ? Thanks

Answer

Could be related to WAF web cl rules: https://repost.aws/knowledge-center/waf-http-request-body-inspection#:~:text=Request%20bodies%20over%208%20KB%20are%20blocked.&text=When%20you%20configure%20a%20custom,is%20larger%20than%208%2C192%20bytes. Look into constraints about body size

File uploads getting blocked after introducing AWS WAF

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