Control: 4.13 Ensure Storage logging is Enabled for Blob Service for 'Read', 'Write', and 'Delete' requests

Description

The Storage Blob service provides scalable, cost-efficient object storage in the cloud. Storage Logging happens server-side and allows details for both successful and failed requests to be recorded in the storage account. These logs allow users to see the details of read, write, and delete operations against the blobs. Storage Logging log entries contain the following information about individual requests: timing information such as start time, end-to-end latency, and server latency; authentication details; concurrency information; and the sizes of the request and response messages.

Storage Analytics logs contain detailed information about successful and failed requests to a storage service. This information can be used to monitor each individual request to a storage service for increased security or diagnostics. Requests are logged on a best-effort basis.

Storage Analytics logging is not enabled by default for your storage account.

Remediation

From Azure Portal

Go to Storage Accounts.
For each storage account, under Monitoring, click Diagnostics settings.
Select the blob tab indented below the storage account.
To create a new diagnostic setting, click + Add diagnostic setting. To update an existing diagnostic setting, click Edit setting on the diagnostic setting.
Check the boxes next to StorageRead, StorageWrite, and StorageDelete.
Select an appropriate destination.
Click Save.

From Azure CLI

Use the below command to enable the Storage Logging for Blob service.

az storage logging update --account-name <storageAccountName> --account-key <storageAccountKey> --services b --log rwd --retention 90

Default Value

By default, storage account blob service logging is disabled for read, write, and delete operations.

Usage

Run the control in your terminal:

powerpipe control run azure_compliance.control.cis_v300_4_13

Snapshot and share results via Turbot Pipes:

powerpipe login
powerpipe control run azure_compliance.control.cis_v300_4_13 --share

SQL

This control uses a named query:

with blob_logs as (
  select
    a.id,
    a.name,
    log ->> 'category' as category,
    (log ->> 'enabled')::boolean as enabled
  from
    azure_storage_account a,
    jsonb_array_elements(a.default_blob_diagnostic_settings) as b,
    jsonb_array_elements(b -> 'properties' -> 'logs') as log
  where
    log ->> 'category' in ('StorageRead', 'StorageWrite', 'StorageDelete')
),
log_status as (
  select
    id,
    name,
    max(case when category = 'StorageRead' then (enabled::int) else 0 end) = 1 as read_enabled,
    max(case when category = 'StorageWrite' then (enabled::int) else 0 end) = 1 as write_enabled,
    max(case when category = 'StorageDelete' then (enabled::int) else 0 end) = 1 as delete_enabled
  from blob_logs
  group by id, name
)
select
  sa.id as resource,
  case
    when lower(sku_tier) = 'premium' and kind in ('StorageV2', 'FileStorage') then 'skip'
    when default_blob_diagnostic_settings is null then 'alarm'
    when ls.read_enabled and ls.write_enabled and ls.delete_enabled then 'ok'
    else 'alarm'
  end as status,
  case
    when lower(sku_tier) = 'premium' and kind in ('StorageV2', 'FileStorage') then sa.name || ' is premium ' || kind || ' storage account.'
    when default_blob_diagnostic_settings is null then sa.name || ' blob service logging disabled for read, write, delete requests.'
    when ls.read_enabled and ls.write_enabled and ls.delete_enabled then sa.name || ' blob service logging enabled for read, write, delete requests.'
    else sa.name || ' blob service logging missing for: ' ||
      trim(both ', ' from
        case when not ls.read_enabled then 'read, ' else '' end ||
        case when not ls.write_enabled then 'write, ' else '' end ||
        case when not ls.delete_enabled then 'delete, ' else '' end
      ) || ' requests.'
  end as reason
  
  , sa.resource_group as resource_group
  , sub.display_name as subscription
from
  azure_storage_account sa
  left join log_status as ls on ls.id = sa.id
  left join azure_subscription sub on sub.subscription_id = sa.subscription_id