Control: 4.3 Ensure 'Block Project-wide SSH keys' is enabled for VM instances

Description

It is recommended to use Instance specific SSH key(s) instead of using common/shared project-wide SSH key(s) to access Instances.

Project-wide SSH keys are stored in Compute/Project-meta-data. Project wide SSH keys can be used to login into all the instances within project. Using project-wide SSH keys eases the SSH key management but if compromised, poses the security risk which can impact all the instances within project. It is recommended to use Instance specific SSH keys which can limit the attack surface if the SSH keys are compromised.

Remediation

From Console

1. Go to the VM instances page by visiting: https://console.cloud.google.com/compute/instances. It will list all the instances in your project.
2. Click on the name of the Impacted instance
3. Click Edit in the toolbar
4. Under SSH Keys, go to the Block project-wide SSH keys checkbox
5. To block users with project-wide SSH keys from connecting to this instance, select Block project-wide SSH keys
6. Click Save at the bottom of the page
7. Repeat steps for every impacted Instance

From Command Line

To block project-wide public SSH keys, set the metadata value to TRUE:

gcloud compute instances add-metadata <INSTANCE_NAME> --metadata block- project-ssh-keys=TRUE

Default Value

By Default Block Project-wide SSH keys is not enabled.