cis-gke-v170-5-6-3

name	cis-gke-v170-5.6.3
description	Ensure Control Plane Authorized Networks is Enabled (Automated)
category	cis-gke
version	1.7.0
author	cyberstrike-official
tags	["cis","gke","kubernetes","gcp","networking","authorized-networks","control-plane","access-control"]
cis_id	5.6.3
cis_benchmark	CIS Google Kubernetes Engine (GKE) Benchmark v1.7.0
tech_stack	["kubernetes","gcp","gke"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

5.6.3 Ensure Control Plane Authorized Networks is Enabled (Automated)

Profile Applicability

• Level 2

Description

Enable Control Plane Authorized Networks to restrict access to the cluster's control plane to only an allowlist of authorized IPs.

Rationale

Authorized networks are a way of specifying a restricted range of IP addresses that are permitted to access your cluster's control plane. Kubernetes Engine uses both Transport Layer Security (TLS) and authentication to provide secure access to your cluster's control plane from the public internet. This provides you the flexibility to administer your cluster from anywhere; however, you might want to further restrict access to a set of IP addresses that you control. You can set this restriction by specifying an authorized network.

Control Plane Authorized Networks blocks untrusted IP addresses. Google Cloud Platform IPs (such as traffic from Compute Engine VMs) can reach your master through HTTPS provided that they have the necessary Kubernetes credentials.

Restricting access to an authorized network can provide additional security benefits for your container cluster, including:

• Better protection from outsider attacks: Authorized networks provide an additional layer of security by limiting external, non-GCP access to a specific set of addresses you designate, such as those that originate from your premises. This helps protect access to your cluster in the case of a vulnerability in the cluster's authentication or authorization mechanism.
• Better protection from insider attacks: Authorized networks help protect your cluster from accidental leaks of master certificates from your company's premises. Leaked certificates used from outside GCP and outside the authorized IP ranges (for example, from addresses outside your company) are still denied access.

Impact

When implementing Control Plane Authorized Networks, be careful to ensure all desired networks are on the allowlist to prevent inadvertently blocking external access to your cluster's control plane.

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 cluster to open the Details page and make sure 'Master authorized networks' is set to 'Enabled'.

Using Command Line:

To check Master Authorized Networks status for an existing cluster, run the following command:

gcloud container clusters update $CLUSTER_NAME --zone $COMPUTE_ZONE --enable-master-authorized-networks