How does Kubernetes RBAC decide whether a request is allowed, and can you write an explicit deny rule?
RBAC is default-deny and purely additive: a request is denied unless some Role/RoleBinding or ClusterRole/ClusterRoleBinding explicitly grants it, and there is no such thing as an explicit deny rule. Every applicable binding's permissions are unioned together, so restricting access means removing a grant (or removing the subject from a binding), not adding a deny statement on top of an existing grant, an approach that works cleanly for grant-based access but has no mechanism for "allow everything except X" within RBAC itself.