Add feature for "rbacBindingConfig" to google_container_cluster resource

[vinovee]

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Description

GKE API reference has RBACBindingConfig defined to allow the users to restrict ClusterRoleBindings. This attribute supports enableInsecureBindingSystem(Un)authenticated - Setting this to true will allow any ClusterRoleBinding and RoleBinding with subjects system:anonymous or system:unauthenticated.

The enableInsecureBindingSystemUnauthenticated is set to true by default in the API. This must be controlled by terraform to disable the unauthenticated binding. As this feature is currently not supported in terraform provider, it sets to true on API by default. Not desired configuration.

This is one of the security threat - TA0004.T1098.006 - Privilege Escalation - Account Manipulation: Additional Container Cluster Roles

GIVEN GKE Cluster
AND principal requests io.k8s.authorization.rbac.v1.rolebindings.create
AND one of the following conditions is true
response.metadata.kubectl.kubernetes.io/last-applied-configuration =
""kind":"Group","name":"system:unauthenticated""
response.metadata.kubectl.kubernetes.io/last-applied-configuration =
""kind":"Group","name":"system:anonymous""
WHEN request is successful
THEN Unauthenticated or anonymous kubectl client has permissions assigned
THEN TA0004.T1098.006 - Privilege Escalation - Account Manipulation: Additional Container Cluster Roles

New or Affected Resource(s)

google_container_clusters

Potential Terraform Configuration

rbac_binding_config{
  ## either one is desired, but not both
  enable_insecure_binding_system_unauthenticated = bool #false/true
  enable_insecure_binding_system_authenticated = bool #false/true
}

References

No response

b/417319811

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