Implementing GCP Organization Policy Constraints

# Implementing GCP Organization Policy Constraints

## Overview

The GCP Organization Policy Service provides centralized and programmatic control over cloud resources. Organization policies configure constraints that restrict one or more Google Cloud services, enforced at organization, folder, or project levels. They improve security by blocking external IPs, requiring encryption, and minimizing unauthorized access. Changes can take up to 15 minutes to propagate.


## When to Use

- When deploying or configuring implementing gcp organization policy constraints capabilities in your environment
- When establishing security controls aligned to compliance requirements
- When building or improving security architecture for this domain
- When conducting security assessments that require this implementation

## Prerequisites

- GCP Organization with Organization Administrator role
- `gcloud` CLI configured and authenticated
- Terraform or gcloud for policy management
- Organization Policy Administrator IAM role (`roles/orgpolicy.policyAdmin`)

## Core Concepts

### Constraint Types

1. **List Constraints**: Allow or deny specific values (e.g., allowed regions)
2. **Boolean Constraints**: Enable or disable a capability (e.g., disable serial port access)
3. **Custom Constraints**: User-defined rules targeting specific resource fields (Preview)

### Policy Inheritance

Policies inherit from the lowest ancestor with an enforced policy. If no ancestor has a policy, Google's managed default behavior applies.

## Essential Security Constraints

### Restrict VM External IP Addresses

```bash
# Deny external IP addresses on all VMs
gcloud resource-manager org-policies set-policy \
  --organization=ORGANIZATION_ID \
  policy.yaml
```

policy.yaml:
```yaml
constraint: constraints/compute.vmExternalIpAccess
listPolicy:
  allValues: DENY
```