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5.6.3 Ensure Control Plane Authorized Networks is Enabled

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Information

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

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.

Solution

Using Google Cloud Console:

 - Go to Kubernetes Engine by visiting

https://console.cloud.google.com/kubernetes/list

 - Select Kubernetes clusters for which Control Plane Authorized Networks is disabled
 - Within the Details pane, under the Networking heading, click on the pencil icon named Edit control plane authorised networks.
 - Check the box next to Enable control plane authorised networks.
 - Click SAVE CHANGES.

Using Command Line:

To enable Control Plane Authorized Networks for an existing cluster, run the following command:

gcloud container clusters update <cluster_name> --zone <compute_zone> --enable-master-authorized-networks

Along with this, you can list authorized networks using the --master-authorized-networks flag which contains a list of up to 20 external networks that are allowed to connect to your cluster's control plane through HTTPS. You provide these networks as a comma-separated list of addresses in CIDR notation (such as 90.90.100.0/24 ).

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.

See Also

https://workbench.cisecurity.org/benchmarks/16093

Item Details

References: CSCv7|14.6

Plugin: GCP

Control ID: ce11984c4460cd8357c6be37a2362c7aba5b2dc500e3d33fb8513f73e201a459