5.6.5 Ensure clusters are created with Private Nodes

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Information

Disable public IP addresses for cluster nodes, so that they only have private IP addresses. Private Nodes are nodes with no public IP addresses.

Rationale:

Disabling public IP addresses on cluster nodes restricts access to only internal networks, forcing attackers to obtain local network access before attempting to compromise the underlying Kubernetes hosts.

Impact:

To enable Private Nodes, the cluster has to also be configured with a private master IP range and IP Aliasing enabled.

Private Nodes do not have outbound access to the public internet. If you want to provide outbound Internet access for your private nodes, you can use Cloud NAT or you can manage your own NAT gateway.

To access Google Cloud APIs and services from private nodes, Private Google Access needs to be set on Kubernetes Engine Cluster Subnets.

Solution

Once a cluster is created without enabling Private Nodes, it cannot be remediated. Rather the cluster must be recreated.
Using Google Cloud Console

Go to Kubernetes Engine by visiting https://console.cloud.google.com/kubernetes/list

Click CREATE CLUSTER

Configure the cluster as desired then click 'Availability, networking, security, and additional features'

Under 'Network Security' ensure the 'Private cluster' checkbox is checked

Configure other settings as required

Click CREATE.

Using Command Line
To create a cluster with Private Nodes enabled, include the --enable-private-nodes flag within the cluster create command:

gcloud container clusters create [CLUSTER_NAME] \
--enable-private-nodes

Setting this flag also requires the setting of --enable-ip-alias and --master-ipv4-cidr=[MASTER_CIDR_RANGE].

Default Value:

By default, Private Nodes are disabled.

See Also

https://workbench.cisecurity.org/files/4135