PublishInternal was authorised by IAM policy alone, with its resource
built from the body accountId and the URL cluster. The control-plane
role grants it on "*", so any control-plane VM session, any tenant
holding eks:*, or static system credentials could publish cluster
state, bootstrap and add-on reports for another cluster or account.
PublishInternal now passes the existing internal-route gate: the caller
must be a control-plane instance-role session that is a member of the
URL cluster in the body account. The gate and the handler decode the
body through one shared decoder, so the account checked is the account
the subject is built from. Every unauthorised target returns the same
AccessDenied, and invalid account or cluster names are treated as not
found. Valid publishes keep their subjects and payload bytes.
joshsiv-mulga
ee13be9501