USN-8867-1: Ceph vulnerability

It was discovered that the Ceph Object Gateway (RGW) SigV4 handler did not reject requests carrying x-amz-* headers that were absent from the signed header set. An attacker holding a presigned URL could possibly use this issue to attach arbitrary unsigned x-amz-* headers that RGW would honor, allowing them to escalate their privileges beyond what the URL's signer intended.