Cis Gke V180 5.6.2

5.6.2 Ensure use of VPC-native clusters (Automated)

Profile Applicability

• Level 1

Description

Create Alias IPs for the node network CIDR range in order to subsequently configure IP-based policies and firewalling for pods. A cluster that uses Alias IPs is called a VPC-native cluster.

Rationale

Using Alias IPs has several benefits:

• Pod IPs are reserved within the network ahead of time, which prevents conflict with other compute resources.
• The networking layer can perform anti-spoofing checks to ensure that egress traffic is not sent with arbitrary source IPs.
• Firewall controls for Pods can be applied separately from their nodes.
• Alias IPs allow Pods to directly access hosted services without using a NAT gateway.

Impact

You cannot currently migrate an existing cluster that uses routes for Pod routing to a cluster that uses Alias IPs.

Cluster IPs for internal services remain only available from within the cluster. If you want to access a Kubernetes Service from within the VPC, but from outside of the cluster, use an internal load balancer.

Audit

Using Google Cloud Console:

1. Go to Kubernetes Engine by visiting: https://console.cloud.google.com/kubernetes/list.
2. From the list of clusters, click on the desired cluster to open the Details page. Under the 'Networking' section, make sure 'VPC-native traffic routing' is set to 'Enabled'.

Using Command Line: To check Alias IP is enabled for an existing cluster, first define 2 variables Cluster Name and Zone and then run the following command:

gcloud container clusters describe $CLUSTER_NAME --zone $COMPUTE_ZONE --format json | jq '.ipAllocationPolicy.useIpAliases'

The output of the above command should return

{
  "useIpAliases": true
}

if VPC-native (using alias IP) is enabled. If VPC-native (using alias IP) is disabled, the above command will return null ({ }).

Remediation

Alias IPs cannot be enabled on an existing cluster. To create a new cluster using Alias IPs, follow the instructions below. Using Google Cloud Console: If using Standard configuration mode:

1. Go to Kubernetes Engine by visiting: https://console.cloud.google.com/kubernetes/list.
2. Click CREATE CLUSTER, and select Standard configuration mode.
3. Configure your cluster as desired, then, click Networking under CLUSTER in the navigation pane.
4. In the 'VPC-native' section, leave 'Enable VPC-native (using alias IP)' selected.
5. Click CREATE.

Using Command Line To enable Alias IP on a new cluster, run the following command:

gcloud container clusters create <cluster_name> --zone <compute_zone> --enable-ip-alias

Default Value

By default, VPC-native (using alias IP) is enabled when you create a new cluster. The exception is clusters created before GKE version 1.21.0-gke.1500 (September 2021) using the gcloud CLI without --enable-ip-alias."

References

1. https://cloud.google.com/kubernetes-engine/docs/how-to/alias-ips
2. https://cloud.google.com/kubernetes-engine/docs/concepts/alias-ips

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