lacework-global-236
1.6 Ensure That IAM Users Are Not Assigned the Service Account User or Service Account Token Creator Roles at Project Level (Manual)
note
This rule has been changed to manual, see Manual Rules for CIS GCP 1.3.0 for details.
Profile Applicability
• Level 1
Description
It is recommended to assign the Service Account User (iam.serviceAccountUser)
and Service Account Token Creator (iam.serviceAccountTokenCreator)
roles to a user for a specific service account rather than assigning the role to a user at project level.
Rationale
A service account is a special Google account that belongs to an application or a virtual machine (VM), instead of to an individual end-user. Application/VM-Instance uses the service account to call the service's Google API so that users aren't directly involved. In addition to being an identity, a service account is a resource that has IAM policies attached to it. These policies determine who can use the service account.
Users with IAM roles to update the App Engine and Compute Engine instances (such as App Engine Deployer or Compute Instance Admin) can effectively run code as the service accounts used to run these instances, and indirectly gain access to all the resources for which the service accounts have access. Similarly, SSH access to a Compute Engine instance may also provide the ability to execute code as that instance/Service account.
Based on business needs, there could be multiple user-managed service accounts configured for a project. Granting the iam.serviceAccountUser
or iam.serviceAccountTokenCreator
roles to a user for a project gives the user access to all service accounts in the project, including service accounts that may be created in the future. This can result in elevation of privileges by using service accounts and corresponding Compute Engine instances
.
In order to implement least privileges
best practices, IAM users should not be assigned the Service Account User
or Service Account Token Creator
roles at the project level. Instead, these roles should be assigned to a user for a specific service account, giving that user access to the service account. The Service Account User
allows a user to bind a service account to a long-running job service, whereas the Service Account Token Creator
role allows a user to directly impersonate (or assert) the identity of a service account.
Impact
After revoking Service Account User
or Service Account Token Creator
roles at the project level from all impacted user account(s), these roles should be assigned to a user(s) for specific service account(s) according to business needs.
Audit
From Console:
Go to the IAM page in the GCP Console by visiting https://console.cloud.google.com/iam-admin/iam
Click on the filter table text bar, Type
Role: Service Account User
.Ensure no user is listed as a result of the filter.
Click on the filter table text bar, Type
Role: Service Account Token Creator
.Ensure no user is listed as a result of the filter.
From Command Line:
To ensure IAM users are not assigned Service Account User role at the project level:
gcloud projects get-iam-policy PROJECT_ID --format json | jq '.bindings[].role' | grep "roles/iam.serviceAccountUser"
gcloud projects get-iam-policy PROJECT_ID --format json | jq '.bindings[].role' | grep "roles/iam.serviceAccountTokenCreator"
These commands should not return any output.
Remediation
From Console:
Go to the IAM page in the GCP Console by visiting: https://console.cloud.google.com/iam-admin/iam.
Click on the filter table text bar. Type
Role: Service Account User
Click the
Delete Bin
icon in front of the roleService Account User
for every user listed as a result of a filter.Click on the filter table text bar. Type
Role: Service Account Token Creator
Click the
Delete Bin
icon in front of the roleService Account Token Creator
for every user listed as a result of a filter.
From Command Line:
- Using a text editor, remove the bindings with the
roles/iam.serviceAccountUser
orroles/iam.serviceAccountTokenCreator
.
For example, you can use the iam.json file shown below as follows:
{
"bindings": [
{
"members": [
"serviceAccount:our-project-123@appspot.gserviceaccount.com",
],
"role": "roles/appengine.appViewer"
},
{
"members": [
"user:email1@gmail.com"
],
"role": "roles/owner"
},
{
"members": [
"serviceAccount:our-project-123@appspot.gserviceaccount.com",
"serviceAccount:123456789012-compute@developer.gserviceaccount.com"
],
"role": "roles/editor"
}
],
"etag": "BwUjMhCsNvY="
}
- Update the project's IAM policy:
gcloud projects set-iam-policy PROJECT_ID iam.json
References
https://cloud.google.com/iam/docs/service-accounts
https://cloud.google.com/iam/docs/granting-roles-to-service-accounts
https://cloud.google.com/iam/docs/understanding-roles
https://cloud.google.com/iam/docs/granting-changing-revoking-access
https://console.cloud.google.com/iam-admin/iam
Additional Information
To assign the role roles/iam.serviceAccountUser
or roles/iam.serviceAccountTokenCreator
to a user role on a service account instead of a project:
Go to https://console.cloud.google.com/projectselector/iam-admin/serviceaccounts
Select
Target Project
Select
target service account
. ClickPermissions
on the top bar. It will open permission pane on right side of the pageAdd desired members with
Service Account User
orService Account Token Creator
role.