We should introduce a configuration for the spark UI to omit X-Frame-Options from the response headers if explicitly set.
The X-Frame-Options header was introduced in org.apache.spark.ui.JettyUtils to prevent frame-related click-jacking vulnerabilities. This was addressed in:
The problem with this, is that we only allow the same origin or a singular host to present the UI with iframes. I propose we add a configuration that turns this off.
Use Case: Currently building a "portal UI" for all things related to a cluster. Embedding the spark UI in the portal is necessary because the cluster is in the cloud and can only be accessed via an SSH tunnel - as intended. (The reverse proxy configuration spark.ui.reverseProxy could be used to simplify connecting to all the workers, but this doesn't solve handling multiple, unrelated, UIs through a single tunnel.
Moreover, the host that our "portal UI" would reside on is not assigned a hostname and has an ephemeral IP address, so the ALLOW-FROM directive isn't useful in this case.
Lastly, the current design does not allow for different hosts to be configured, i.e. spark.ui.allowFramingFrom hostname1,hostname2 is not a valid config.
An alternative option would be to explore Content-Security-Policy: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy#frame-ancestors