PubSub Topics Should Be Encrypted Using CMEK

Using Console

To remediate the misconfiguration “PubSub Topics Should Be Encrypted Using CMEK” for GCP using GCP console, you can follow the below steps:

Login to your GCP console.
Navigate to the Pub/Sub page from the left-hand side menu.
Select the topic that you want to encrypt using CMEK.
Click on the “Edit” button present at the top of the page.
Scroll down to the “Encryption” section.
Click on the “Enable encryption” checkbox.
Select the “Customer-managed key” option from the dropdown.
Choose the CMEK key that you want to use for encryption from the “Key name” dropdown.
Click on the “Save” button to save the changes.

Once you have completed these steps, your Pub/Sub topic will be encrypted using the selected CMEK key.

Using CLI

To remediate the misconfiguration in GCP using GCP CLI, follow these steps:

Open the Cloud Shell in the GCP Console.
Set the project where the Pub/Sub topic is located:

gcloud config set project [PROJECT_ID]

Retrieve the list of Pub/Sub topics in the project:

gcloud pubsub topics list

For each topic that does not have encryption enabled, enable encryption using the following command:

gcloud alpha pubsub topics update [TOPIC_NAME] --update-attribute=encryption_key_name=projects/[PROJECT_ID]/locations/[LOCATION]/keyRings/[KEYRING_NAME]/cryptoKeys/[KEY_NAME]

Replace [TOPIC_NAME] with the name of the Pub/Sub topic that needs to be encrypted, and replace [PROJECT_ID], [LOCATION], [KEYRING_NAME], and [KEY_NAME] with the appropriate values for your project.

Verify that the encryption has been enabled for the topic by running the following command:

gcloud alpha pubsub topics describe [TOPIC_NAME]

The output should include the following line:

encryptionKeyName: projects/[PROJECT_ID]/locations/[LOCATION]/keyRings/[KEYRING_NAME]/cryptoKeys/[KEY_NAME]

This indicates that the topic is now encrypted using a customer-managed encryption key (CMEK).

Using Python

To remediate the misconfiguration where PubSub topics should be encrypted using CMEK in GCP using Python, you can follow these step-by-step instructions:

First, ensure that you have the necessary permissions to create a new key ring and key in the Cloud KMS service.
Next, you will need to create a new key ring and key in the Cloud KMS service. You can do this using the following Python code:

from google.cloud import kms_v1
from google.cloud.kms_v1 import enums

client = kms_v1.KeyManagementServiceClient()

# Replace [PROJECT_ID] with your GCP project ID
parent = client.location_path('[PROJECT_ID]', 'global')

# Replace [KEY_RING_ID] with a unique ID for your key ring
key_ring_id = '[KEY_RING_ID]'

# Create the key ring
key_ring = client.create_key_ring(parent, key_ring_id, {})

# Replace [KEY_ID] with a unique ID for your key
key_id = '[KEY_ID]'

# Create the key
purpose = enums.CryptoKey.CryptoKeyPurpose.ENCRYPT_DECRYPT
crypto_key = {'purpose': purpose, 'next_rotation_time': '2022-01-01T00:00:00Z'}
key = client.create_crypto_key(key_ring.name, key_id, crypto_key)

Once you have created the key ring and key, you can use it to encrypt your PubSub topics. You can do this using the following Python code:

from google.cloud import pubsub_v1
from google.cloud.pubsub_v1 import types

# Replace [PROJECT_ID] with your GCP project ID
project_id = '[PROJECT_ID]'

# Replace [TOPIC_ID] with the ID of your PubSub topic
topic_id = '[TOPIC_ID]'

# Replace [KEY_RING_ID] with the ID of your key ring
key_ring_id = '[KEY_RING_ID]'

# Replace [KEY_ID] with the ID of your key
key_id = '[KEY_ID]'

# Create the topic client
publisher = pubsub_v1.PublisherClient()

# Create the topic name
topic_name = 'projects/{project_id}/topics/{topic_id}'.format(
    project_id=project_id,
    topic_id=topic_id,
)

# Create the encryption key
key_name = client.crypto_key_path(project_id, key_ring_id, key_id)
key = types.Key(
    version=1,
    key=client.encrypt(key_name, b'')[1]
)

# Create the topic with encryption enabled
topic = publisher.create_topic(
    request={
        'name': topic_name,
        'kms_key_name': key_name,
        'message_storage_policy': {
            'allowed_persistence_regions': ['us-central1'],
        },
    },
)

print('Topic created: {}'.format(topic))

Finally, you can verify that your PubSub topic is encrypted using CMEK by checking the topic details in the GCP Console or by using the following Python code:

# Replace [PROJECT_ID] with your GCP project ID
project_id = '[PROJECT_ID]'

# Replace [TOPIC_ID] with the ID of your PubSub topic
topic_id = '[TOPIC_ID]'

# Get the topic client
publisher = pubsub_v1.PublisherClient()

# Get the topic name
topic_name = 'projects/{project_id}/topics/{topic_id}'.format(
    project_id=project_id,
    topic_id=topic_id,
)

# Get the topic details
topic = publisher.get_topic(request={'topic': topic_name})

# Check if encryption is enabled
if topic.encryption_config.kms_key_name:
    print('Encryption is enabled with key: {}'.format(topic.encryption_config.kms_key_name))
else:
    print('Encryption is not enabled')

These steps will help you remediate the misconfiguration where PubSub topics should be encrypted using CMEK in GCP using Python.

Using Terraform

# KMS key used as CMEK for the Pub/Sub topic
resource "google_kms_key_ring" "pubsub_key_ring" {
  name     = "PUBSUB_KEY_RING_NAME"      # replace with your key ring name
  location = "KMS_LOCATION"              # e.g. "us-central1"
  project  = "PROJECT_ID"                # replace with your GCP project ID
}

resource "google_kms_crypto_key" "pubsub_cmek" {
  name     = "PUBSUB_CMEK_KEY_NAME"      # replace with your KMS crypto key name
  key_ring = google_kms_key_ring.pubsub_key_ring.id
}

# Grant Pub/Sub service account permission to use the CMEK
# Replace PROJECT_NUMBER with your numeric project ID
data "google_project" "current" {
  project_id = "PROJECT_ID"
}

resource "google_kms_crypto_key_iam_member" "pubsub_cmek_user" {
  crypto_key_id = google_kms_crypto_key.pubsub_cmek.id
  role          = "roles/cloudkms.cryptoKeyEncrypterDecrypter"
  member        = "serviceAccount:service-${data.google_project.current.number}@gcp-sa-pubsub.iam.gserviceaccount.com"
}

# Pub/Sub topic encrypted with CMEK
resource "google_pubsub_topic" "topic" {
  name    = "PUBSUB_TOPIC_NAME"          # replace with your topic name
  project = "PROJECT_ID"                 # replace with your GCP project ID

  kms_key_name = google_kms_crypto_key.pubsub_cmek.id
}

Changing or adding kms_key_name on an existing google_pubsub_topic forces replacement of the topic, which may cause a brief outage and loss of unacknowledged messages during the recreate.To verify, terraform plan should show the google_pubsub_topic either being created with kms_key_name = google_kms_crypto_key.pubsub_cmek.id or updated by replacing the existing topic to set that kms_key_name.

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