AWS OU SCP Terraform Module

Module initially comes from Trussworks and is adjusted to reflect Appsilon custom policies, like require_ec2_tags i.e.

Supports two main use cases:

• Combines multiple Service Control Policy (SCP) statements - combining multiple policy statements into a single policy allows more than 5 policies to be be applied to a single Organizational Unit (OU).
• Alternatively, creates a "Deny All Access" Service Control Policy.

Alternatively, enables creation of a "Deny All Access" Service Control Policy.

Policy options (listed by sid) are:

• Deny leaving AWS Organizations (DenyLeavingOrgs)
• Deny creating IAM users or access keys (DenyCreatingIAMUsers)
• Deny deleting KMS Keys (DenyDeletingKMSKeys)
• Deny deleting Route53 Hosted Zones (DenyDeletingRoute53Zones)
• Deny deleting VPC Flow logs, Cloudwatch log groups, and Cloudwatch log streams (DenyDeletingCloudwatchLogs)
• Deny root account (DenyRootAccount)
• Protect S3 Buckets (ProtectS3Buckets)
• Deny S3 Buckets Public Access (DenyS3BucketsPublicAccess)
• Protect IAM Roles (ProtectIAMRoles)
• Restrict Regional Operations (LimitRegions)
• Require S3 encryption (DenyIncorrectEncryptionHeader + DenyUnEncryptedObjectUploads)

Usage for combined policy statements

To include a policy in your combined policy block, set it to true. Otherwise omit the policy variable.

module "github_terraform_aws_ou_scp" {
  source = "appsilon/ou-scp/aws"
  target =  aws_organizations_organizational_unit.my_ou

  # don't allow all accounts to be able to leave the org
  deny_leaving_orgs             = true
  # applies to accounts that are not managing IAM users
  deny_creating_iam_users       = true
  # don't allow deleting KMS keys
  deny_deleting_kms_keys        = true
  # don't allow deleting Route53 zones
  deny_deleting_route53_zones   = true
  # don't allow deleting CloudWatch logs
  deny_deleting_cloudwatch_logs = true
  # don't allow access to the root user
  deny_root_account             = true

  protect_s3_buckets            = true
  # protect terraform statefile bucket
  protect_s3_bucket_resources   = [
    "arn:aws:s3:::prod-terraform-state-us-west-2",
    "arn:aws:s3:::prod-terraform-state-us-west-2/*"
  ]

  # don't allow public access to bucket
  deny_s3_buckets_public_access = true
  deny_s3_bucket_public_access_resources = [
    "arn:aws:s3:::log-delivery-august-2020"
  ]

  protect_iam_roles             = true
  # - protect OrganizationAccountAccessRole
  protect_iam_role_resources     = [
    "arn:aws:iam::*:role/OrganizationAccountAccessRole"
  ]

  # restrict region-specific operations to us-west-2
  limit_regions                 = true
  # - restrict region-specific operations to us-west-2
  allowed_regions               = ["us-west-2"]

  # require s3 objects be encrypted
  require_s3_encryption = true

  # SCP policy tags
  tags = {
    managed_by = "terraform"
  }
}

Usage for a policy which denies all access

module "github_terraform_aws_ou_scp" {
  source = "appsilon/ou-scp/aws"
  target =  aws_organizations_organizational_unit.my_ou

  # don't allow any access at all
  deny_all=true
}

Requirements

Name	Version
terraform	>= 1.0.0
aws	>= 3.45.0

Providers

Name	Version
aws	3.45.0

Modules

No modules.

Resources

Name	Type
aws_organizations_policy.generated	resource
aws_organizations_policy_attachment.generated	resource
aws_iam_policy_document.combined_policy_block	data source
aws_iam_policy_document.deny_all_access	data source

Inputs

Name	Description	Type	Default	Required
allowed_regions	AWS Regions allowed for use (for use with the restrict regions SCP)	list(string)	[ "" ]	no
deny_all	If false, create a combined policy. If true, deny all access	bool	false	no
deny_creating_iam_users	DenyCreatingIAMUsers in the OU policy.	bool	false	no
deny_deleting_cloudwatch_logs	DenyDeletingCloudwatchLogs in the OU policy.	bool	false	no
deny_deleting_kms_keys	DenyDeletingKMSKeys in the OU policy.	bool	false	no
deny_deleting_route53_zones	DenyDeletingRoute53Zones in the OU policy.	bool	false	no
deny_leaving_orgs	DenyLeavingOrgs in the OU policy.	bool	false	no
deny_root_account	DenyRootAccount in the OU policy.	bool	false	no
deny_s3_bucket_public_access_resources	S3 bucket resource ARNs to block public access	list(string)	[ "" ]	no
deny_s3_buckets_public_access	DenyS3BucketsPublicAccess in the OU policy.	bool	false	no
limit_regions	LimitRegions in the OU policy.	bool	false	no
protect_iam_role_resources	IAM role resource ARNs to protect from modification and deletion	list(string)	[ "" ]	no
protect_iam_roles	ProtectIAMRoles in the OU policy.	bool	false	no
protect_s3_bucket_resources	S3 bucket resource ARNs to protect from bucket and object deletion	list(string)	[ "" ]	no
protect_s3_buckets	ProtectS3Buckets in the OU policy.	bool	false	no
require_ec2_tags	RequireTagsForEC2InstancesAndVolumes in the OU policy	bool	false	no
require_s3_encryption	DenyIncorrectEncryptionHeader and DenyUnEncryptedObjectUploads in the OU policy	bool	false	no
tags	Tags applied to the SCP policy	map(string)	{}	no
target	OU resource to attach SCP	object({ name = string id = string })	n/a	yes

Outputs

No outputs.

Developer Setup

Install dependencies (macOS)

brew install pre-commit go terraform terraform-docs
pre-commit install --install-hooks