Control: 1.9 Ensure that Cloud KMS cryptokeys are not anonymously or publicly accessible

Description

It is recommended that the IAM policy on Cloud KMS cryptokeys should restrict anonymous and/or public access.

Granting permissions to allUsers or allAuthenticatedUsers allows anyone to access the dataset. Such access might not be desirable if sensitive data is stored at the location. In this case, ensure that anonymous and/or public access to a Cloud KMS cryptokey is not allowed.

Remediation

From Command Line

List all Cloud KMS Cryptokeys.

gcloud kms keys list --keyring=[key_ring_name] --location=global --format=json | jq '.[].name'

Remove IAM policy binding for a KMS key to remove access to allUsers and allAuthenticatedUsers using the below command.

gcloud kms keys remove-iam-policy-binding [key_name] --keyring=[key_ring_name] --location=global --member='allAuthenticatedUsers' --role='[role]' 
gcloud kms keys remove-iam-policy-binding [key_name] --keyring=[key_ring_name] --location=global --member='allUsers' --role='[role]'

Default Value

By default Cloud KMS does not allow access to allUsers or allAuthenticatedUsers.

Usage

Run the control in your terminal:

powerpipe control run gcp_compliance.control.cis_v200_1_9

Snapshot and share results via Turbot Pipes:

powerpipe login
powerpipe control run gcp_compliance.control.cis_v200_1_9 --share

SQL

This control uses a named query:

with public_keys as (
  select
    distinct self_link
  from
    gcp_kms_key,
    jsonb_array_elements(iam_policy -> 'bindings') as b
  where
    b -> 'members' ?| array['allAuthenticatedUsers', 'allUsers']
)
select
  k.self_link as resource,
  case
    when p.self_link is null then 'ok'
    else 'alarm'
  end as status,
  case
    when p.self_link is null then title || ' in ' || k.key_ring_name || ' key ring not publicly accessible.'
    else title || ' in ' || k.key_ring_name || ' key ring publicly accessible.'
  end as reason
  
  , location as location, project as project
from
  gcp_kms_key k
left join public_keys p on k.self_link = p.self_link;