RGW DoS attack with empty HTTP header in S3 object copy

Ceph is a distributed object, block, and file storage platform. In versions up to and including 19.2.3, using the argument `x-amz-copy-source` to put an object and specifying an empty string as its content leads to the RGW daemon crashing, resulting in a DoS attack. As of time of publication, no known patched versions exist.