Received error "Not Authorized to access this resource/api" when trying to use Google Directory API and Service Account Authentication

Question

I'm really struggling with trying to use Service Account authentication to use the Google Directory API (Admin SDK).

Using client based three legged OAuth this works (tested here - https://developers.google.com/admin-sdk/directory/v1/reference/members/insert) but there's a problem with the permission delegation to the service account I am using. Under the Google Apps administration, I enabled using APIs and added the service account to the list of allowed OAuth clients as instructed.

Here is the code:

import httplib2
import sys

from apiclient.discovery import build
from oauth2client.client import SignedJwtAssertionCredentials

credentials = SignedJwtAssertionCredentials(
    '<KEY>@developer.gserviceaccount.com',
    '<KEY DATA>',
    scope='https://www.googleapis.com/auth/apps.groups.settings https://www.googleapis.com/auth/admin.directory.group https://www.googleapis.com/auth/admin.directory.group.member'
)
http = httplib2.Http()
http = credentials.authorize(http)

service = build("admin", "directory_v1", http=http)
groups = service.groups()
g = groups.get(groupKey="<GROUP NAME>").execute()

Eventually, I get the following error:

apiclient.errors.HttpError: <HttpError 403 when requesting https://www.googleapis.com/admin/directory/v1/groups/<GROUP NAME>?alt=json returned "Not Authorized to access this resource/api">

I tried using the following API as well:

service = build("groupssettings", "v1", http=http)

But this returns an error as well - "Backend Error".

Answer 1

Even though you're using a Service Account you still need to act on behalf of a Google Apps user in the instance that has the proper admin permissions. Try doing:

credentials = SignedJwtAssertionCredentials(
  '<KEY>@developer.gserviceaccount.com',
  '<KEY DATA>',
  scope='https://www.googleapis.com/auth/apps.groups.settings https://www.googleapis.com/auth/admin.directory.group https://www.googleapis.com/auth/admin.directory.group.member',
  sub='[email protected]'
)

where [email protected] is a super administrator in your Google Apps account.