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I'm trying to get a list of buckets in a project, using python like this:

from google.cloud import storage

storage_client = storage.Client(project='[project-id]')
bucket = storage_client.get_bucket([bucket-name])

blobs = bucket.list_blobs()

for blob in blobs:
    print(blob.name)

But i get an error:

[service-account-ID]-compute@developer.gserviceaccount.com does not have storage.buckets.get access to [bucket-name]

Anyways if i try using gsutil (using the same service account):

gsutil ls gs://[bucket-name]

I can get the list of objects in the bucket... So i dont understand what is happening, any clue about what should i do?

Dimitri
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2 Answers2

27

GCP has the concept of roles and permissions. A role is something like Storage Admin (roles/storage.admin) and a permission is something like storage.buckets.get. Roles are made up of one or more permissions. Permissions are always granted by applying a role to a principal (user, service account, or group) -- that is, you cannot assign a permission directly to a principal.

The error you're seeing is because the permission storage.buckets.get is missing from the service account -- that is, none of the role(s) applied to the service account grant the storage.buckets.get permission. You can list the objects of a bucket (storage.objects.list permission) without the ability to list buckets (storage.buckets.get permission).

Therefore you need to assign a role such as roles/storage.admin that has the storage.buckets.get permission. You can also create a Custom Role with just that permission if you want to operate with a least-privilege model.

Garrett
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12

To add to the top answer, note that the role roles/storage.legacyBucketReader has the storage.buckets.get permission too. (See https://cloud.google.com/iam/docs/permissions-reference)

So to add that service account to that role:

gsutil iam ch serviceAccount:john.doe@example.com:legacyBucketReader gs://ex-bucket
Andrew Schulman
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JohnFlux
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