implementing-gcp-organization-policy-constraints

name	implementing-gcp-organization-policy-constraints
description	Implements GCP Organization Policy constraints via gcloud and Terraform, such as restricting external IPs, resource locations, default service accounts, and service account keys, plus dry-run testing of policy impact before enforcement. Use when enforcing security guardrails across an org's resource hierarchy, or hardening GCP config at the org, folder, or project level.
domain	cybersecurity
subdomain	cloud-security
tags	["gcp","organization-policy","constraints","governance","compliance","cloud-security","resource-manager"]
version	1.0
author	mahipal
license	Apache-2.0
nist_csf	["PR.IR-01","ID.AM-08","GV.SC-06","DE.CM-01"]
mitre_attack	["T1078.004","T1530","T1537","T1580"]

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

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

policy.yaml:

constraint: constraints/compute.vmExternalIpAccess
listPolicy:
  allValues: DENY

Restrict Resource Locations

gcloud org-policies set-policy \
  --organization=ORGANIZATION_ID \
  location-policy.yaml

location-policy.yaml:

constraint: