Google Cloud Kubernetes Engine
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      Default Service Account Used

      Ensure that no Kubernetes cluster nodes are using the default service account

      Risk Level: Low

      Description

      This plugin ensures that the Kubernetes cluster nodes are not using the default service account. All GKE cluster nodes use an IAM service account. By default, the nodes are associated with the default service account. This account has broad access scopes, granting more than the required permissions.

      About the Service

      Google Cloud Kubernetes Engine:

      The Google Cloud Kubernetes Engine is a Kubernetes-based service that includes a control plane, nodes that house pods, and Google Cloud services. It aids in the modernization of your programmes by offering a platform for deploying, managing, and scaling containerized applications. The Google Cloud Console or kubectl can be used to interact with this Google Cloud Kubernetes Engine. To know more, read here. 

      Impact

      The default service account has a broad access scope that could be exploited in the event of a node compromise. This jeopardizes the safety and efficiency of the cluster and the data stored. By using a different service account with minimal privileges, you can reduce the risks of attacks and data leaks. This also ensures that the principle of least privilege is not violated.

      Steps to Reproduce

      Using GCP Console-

      1. Log In to your GCP Console.
      2. From the top navigation bar, select the GCP project you want to investigate.
      3. From the navigation panel on the left side of the console, go to Kubernetes Engine and select Clusters. You can use this link here to navigate directly if you’re already logged in.
      4. Select the cluster you want to investigate from the list of clusters displayed and go to the NODES tab of the selected cluster.
      5. Under the Node pools section, select the node pool you want to verify from the list of node pools displayed in the table.
      6. In the Security section, check which Service account is being used. If it says default then the current service account being used is not recommended.
      7. Repeat steps 5 and 6 for all the node pools present in the selected cluster.
      8. Repeat steps 4 to 7 for all the clusters you want to investigate in the selected project.
      9. If you have multiple projects that you want to investigate, repeat steps 2-8 for each project in your GCP console.

      Steps for Remediation

      Determine whether or not you truly require the default service account to be used. If not, make the necessary changes using the steps given below.
      NOTE: This feature cannot be changed once the node pool is made. Hence, to enable it, we must re-create the node pool.

      Using GCP Console-

      1. Log In to your GCP Console.
      2. From the top navigation bar, select the GCP project you want to investigate.
      3. From the navigation panel on the left side of the console, go to Kubernetes Engine and select Clusters. You can use this link here to navigate directly if you’re already logged in.
      4. Select the cluster you want to reconfigure from the list of clusters displayed and go to the NODES tab of the selected cluster.  (In case you aren’t sure which node pool needs to be configured, follow the steps to reproduce listed above to determine which to choose.)
      5. Under the Node pools section, select the node pool you want to verify from the list of node pools displayed in the table and note down all the configuration details.
      6. Go back to the configuration page of the selected cluster and click on the ADD NODE POOL button.
      7. Enter and configure the desired details according to the configuration settings of the node pool you are re-creating.
      8. In the Security tab, change the service account to your desired account from the drop down list provided.
      9. Click CREATE to create the new node pool.
      10. You can now delete the original node pool to avoid unwanted expenses. Click on the node pool and select the DELETE button from the top navigation bar and press DELETE in the pop up box to confirm the deletion.
      11. Repeat steps 5 to 10  for all the node pools that you want to reconfigure in the selected cluster.
      12. Repeat steps 4 to 11 for all the clusters you want to reconfigure in the selected project.
      13. If you have multiple projects, repeat steps 2-12 for each project in your GCP console.