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This sample Cloud Function code is designed to remove permissions from a Drive file where the file is visible across the entire domain. The Function is triggered against a Pub/Sub payload that contains Drive document metadata and sharing events that would prompt the Function to execute.

• GSuite and Google Drive
• Google Cloud Functions
• Google Cloud Pub/Sub

The scope of this package only pertains to parts 5 and 6 in the graphic below. For previous parts 1-4, please refer to this repository to get those elements set up.

• GSuite Admin console - Accessed from admin.google.com from a GSuite administrator account. Used to give API scopes to service accounts and set up security dashboarding and audit investigations.
• Google Cloud Platform (GCP) project - organizational unit within GCP that houses public cloud services such as VMs, logging and monitoring, data streaming, and serverless compute. “Projects” sit under an “Organization” that controls billing accounts and umbrella IAM policies for the domain.
• GCP Console - User interface to control GCP resources, accessed from console.cloud.google.com
• Service Account - an Identity and Access Management (IAM) role that is given specific permissions in order to fulfill an automated task, usually.
• Stackdriver - native logging, monitoring, and error reporting tool in GCP
• Pub/Sub (“Publisher/Subscriber”) - asynchronous, serverless messaging service, analogous to Apache Kafka. In this case, used to carry Stackdriver log entries to Cloud Functions.
• Cloud Functions - Serverless, autoscaling function-as-a-service that executes python or javascript code against a trigger, in this case, Pub/Sub messages

In this step, we will create a GCP project (unless you already created one using while setting up this Terraform repository) and we will give the GSuite administrator the Project Owner role.

So let's create the project by going to console.cloud.google.com and sign in using your GSuite administrator's email. We will refer to this email as {gsuite-admin-email} from now on. You will need a billing account to enable the APIs in later steps.

From the sidebar menu, go to IAM & admin and click IAM.

Click "Add"

Give {gsuite-admin-email} the Project Owner role.

Enable the following APIs in your GCP project:

• Admin SDK
• Google Drive
• Service Usage
• Resource Manager
• Stackdriver
• IAM
• IAM Service Account Credentials
• Token Service
• Pub/Sub
• Functions
• Compute Engine

Go back to IAM & admin and click Service Accounts.

Find the App Engine default service account. We will use {service-account-name} to reference it and it should end with "@appspot.gserviceaccount.com").

Create a JSON key and download the credential. We'll refer to this file as {credential-file}.

Give the service account domain-wide delegation, by first clicking Edit on the right-side options menu.

Click Show Domain-Wide Delegation and enable.

From the project dropdown at the top of the console, click the Organization that matches the domain you're working under and click IAM & admin.

Find the App Engine default service account and give it the “Service Account Token Creator” and "Project Editor" roles.

Log into the GSuite Admin console using {gsuite-admin-email}, then go to Security -> Advanced Settings -> Manage API Scopes

For {service-account-name}, set the following scopes by pasting the service account's Unique ID number, e.g., 100518674616449638338, in the name field and pasting this into the scopes field: https://www.googleapis.com/auth/admin.directory.user,https://www.googleapis.com/auth/drive,https://www.googleapis.com/auth/iam

You can retrieve this project's source code by running the following command: git clone https://github.com/google/cloud-function-edit-drive-permissions.git

You need to update the following variables in the main.py file:

• Line 36: Change {path-to-credential-file}
• Line 39: Change {gsuite-admin-email}
• Line 68: Change {OU} if you want some Organizational Units to be exempt

From here, package the files in your current directory into a Zip file. At a minimum, this should include main.py, requirements.txt, and {credential-file}

Upload this Zip into a bucket using Cloud Storage. We'll reference this bucket as {bucket-name}.

We will finally set up the Cloud Function that will strip domain-visibility from Drive documents.

Go to left menu and hit “Cloud Functions” then create a new Function.

Set Trigger to the Pub/Sub topic that is carrying the drive audit events. Again, this can be set up using this Terraform.

Set Source Code to be from ZIP from Cloud Storage and link to the right {bucket-name}.

Click Create

To observe what’s happening, feel free to look at Logging from Stackdriver.