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5.6.7 Ensure Network Policy is Enabled and set as appropriate

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Information

Use Network Policy to restrict pod to pod traffic within a cluster and segregate workloads.

Rationale:

By default, all pod to pod traffic within a cluster is allowed. Network Policy creates a pod-level firewall that can be used to restrict traffic between sources. Pod traffic is restricted by having a Network Policy that selects it (through the use of labels). Once there is any Network Policy in a namespace selecting a particular pod, that pod will reject any connections that are not allowed by any Network Policy. Other pods in the namespace that are not selected by any Network Policy will continue to accept all traffic.

Network Policies are managed via the Kubernetes Network Policy API and enforced by a network plugin, simply creating the resource without a compatible network plugin to implement it will have no effect. GKE supports Network Policy enforcement through the use of Calico.

Solution

Using Google Cloud Console

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

Select the cluster for which Network policy is disabled

Click EDIT

Set 'Network policy for master' to 'Enabled'

Click SAVE

Once the cluster has updated, repeat steps 1-3

Set 'Network Policy for nodes' to 'Enabled'

Click SAVE.

Using Command Line

To enable Network Policy for an existing cluster, firstly enable the Network Policy add-on:

gcloud container clusters update [CLUSTER_NAME] \
 --zone [COMPUTE_ZONE] \
 --update-addons NetworkPolicy=ENABLED

Then, enable Network Policy:

gcloud container clusters update [CLUSTER_NAME] \
 --zone [COMPUTE_ZONE] \
 --enable-network-policy

Impact:

Network Policy requires the Network Policy add-on. This add-on is included automatically when a cluster with Network Policy is created, but for an existing cluster, needs to be added prior to enabling Network Policy.

Enabling/Disabling Network Policy causes a rolling update of all cluster nodes, similar to performing a cluster upgrade. This operation is long-running and will block other operations on the cluster (including delete) until it has run to completion.

If Network Policy is used, a cluster must have at least 2 nodes of type n1-standard-1 or higher. The recommended minimum size cluster to run Network Policy enforcement is 3 n1-standard-1 instances.

Enabling Network Policy enforcement consumes additional resources in nodes. Specifically, it increases the memory footprint of the kube-system process by approximately 128MB, and requires approximately 300 millicores of CPU.

Default Value:

By default, Network Policy is disabled.

See Also

https://workbench.cisecurity.org/files/2764

Item Details

References: CSCv7|9.2, CSCv7|9.4

Plugin: GCP

Control ID: fb604df80b0924fb5e1f52cc8b2b5dc9a0d0633ce5e41b5e3618bf5dc00be64e