CODEWITHSUNDEEP
google-cloud-platformgoogle-compute-enginegoogle-cloud-iam
Josh
Josh

Reputation: 2869

GCP limit service account to have conditional access to a single instance

I'd like to set up an instance schedule and apparently this requires the service account to have compute.instances.start/stop permissions. The only way to do this is to enable the service account to have admin privileges which adds a whole host of (in my case) unnecessary permissions that come associated with the role.

So I'd like to keep the default role as "Compute Engine Service Agent" and add the admin role with a condition that it only applies to a single VM. So I tried setting the condition as:

resource.type == "compute.googleapis.com/Instance"
resource.name == "//compute.googleapis.com/projects/<project>/zones/<zone>/instances/<name>"

however I still get an IAM error when I try to apply the schedule. Should this approach work, and what format does 'name' need to be?

Also what are the security risks of setting an unconditional role here? The documentation basically says "set it" without any further qualification.

EDIT: This condition (above) doesn't seem to scope correctly at all, all VMs show that my service account has the admin role. It's like the resource.name is ignored.

I can correctly set this role, scoped to a single VM, using the "Permissions" tab on the Compute Engine Instances page, but still two questions:

  1. It seems like the Compute Admin (beta) conditions aren't sufficient, even though they contain instance start/stop. v1 does work though, when set via instance permissions. What's the difference?
  2. How can I set the condition correctly as an IAM rule, rather than manually per instance?

Upvotes: 1

Views: 1150

Answers (1)

Gabriel Robledo Ahumada
Gabriel Robledo Ahumada

Reputation: 1691

A better approach would be to create a custom role with just the start/stop permissions and then bind that role to the Compute Engine Service Agent service account.

To create the custom role:

gcloud iam roles create Scheduler --project=$YOUR_PROJECT_ID \
    --title=Scheduler \
    --description="Schedule a VM instance to start/stop" \
    --permissions=compute.instances.start,compute.instances.stop

And to bind the custom role to the Compute Engine Service Agent:

gcloud projects add-iam-policy-binding $PROJECT_ID \
    --member="serviceAccount:[email protected]" \
    --role="projects/$PROJECT_ID/roles/Scheduler"

This way you avoid the conditional part and just grant the start/stop permissions as I believe was your original intention.

Upvotes: 2

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