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      Instance Default Service Account Used

      Ensure that instances are not configured to use the default service account.

      Risk Level: Low

      Description

      By default, when a new GCP Compute Engine instance is created, the credentials provided by the default service account are assigned to it. The default service account has the editor role permissions. SentinelOne CNS recommends using a new service account instead of the default service account. This plugin ensures that compute instances are not configured to use the default service account. 

      About the Service

      Google Cloud Compute Engine:

      Google Cloud Compute Engine is a service that allows you to create Virtual Machines based on your preferences and run them on Google’s infrastructure. You can either use their predefined machines with certain default configurations or create your own custom Virtual Machine to meet your exact requirements. To know more, read here. 

      Impact

      If the instances are configured to use the default service account, then users can gain access to all the cloud services and storage buckets, giving them access to all the data in the Google Cloud project. This poses a serious threat as attackers can easily access the data thus compromising the security of the data.

      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 Compute Engine and select VM Instances. You can use this link (https://console.cloud.google.com/compute) to navigate directly if you’re already logged in.
      4. Select the VM instance you want to investigate from the list of instances and go to the Details tab to examine the details of the VM instance selected.
      5. Scroll down to the Service Account section. The VM instance is configured to use the default Compute Engine service account if the ID matches the pattern <gcp-project-number>-compute@developer.gserviceaccount.com.
      6. Repeat steps 4 and 5 for all the VM instances you want to investigate in the selected project.
      7. If you have multiple projects that you want to investigate, repeat steps 2 to 6 for each project in your GCP console.

      Steps for Remediation

      Determine whether or not you truly want to use the default service account. If not, follow the steps below to make the necessary changes.

      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 IAM & Admin and select Service Accounts. You can use this link (https://console.cloud.google.com/iam-admin/serviceaccounts)  to navigate directly if you’re already logged in.
      4. Click the CREATE SERVICE ACCOUNT option to start creating your service account. In the Service account details section of the page, provide a service account name and a short description about what the service account is for in the Service account description text-box. Then, click create and continue to proceed to the next sections.
      5. In the Grant this service account access to the project (optional) section, grant access to the GCP project by adding the necessary roles and then click continue.
      6. In the Grant users access to this service account (optional) section, add the required users in the Service account users role textbox to grant only those specific users the permissions to deploy jobs and VMs with this service account. Similarly, add the required users in the Service account admins role textbox to grant them permission to administer this service account. Then click DONE to finish creating the service account.


      7. From the navigation panel on the left side of the console, go to Compute Engine and select VM Instances. You can use this link (https://console.cloud.google.com/compute)  to navigate directly.
      8. Choose the virtual machine (VM) instance you want to change the settings for select the STOP button from the top navigation bar and confirm the action in the confirmation box.
      9. Now, click on the EDIT button on the top navigation bar to edit the required configurations of the VM instance.
      10. Scroll down to the Service account section and select the service account you just created from the drop-down list provided. Click Save to save the changes.
      11. Select the START button from the top navigation bar and confirm the action in the confirmation box. This VM instance is now successfully using the new GCP service account you created.
      12. Repeat steps 3 to 11 for all the VM instances you want to reconfigure in the selected project.
      13. If you have multiple projects, repeat steps 2 to 12 for each project in your GCP console.