Amazon CloudFront
Developer Guide (API Version 2016-09-29)

Restricting Access Using Crossdomain.xml

The Adobe Flash Media Server crossdomain.xml file specifies which domains can access media files in a particular domain. CloudFront supplies a default file that allows all domains to access the media files in your RTMP distribution, and you cannot change this behavior. If you include a more restrictive crossdomain.xml file in your Amazon S3 bucket, CloudFront ignores it.