Cis Azure Storage 17.2.2

17.2.2 Ensure that 'Public Network Access' is 'Disabled' for storage accounts (Automated)

Description

Disallowing public network access for a storage account overrides the public access settings for individual containers in that storage account for Azure Resource Manager Deployment Model storage accounts. Azure Storage accounts that use the classic deployment model will be retired on August 31, 2024.

Rationale

The default network configuration for a storage account permits a user with appropriate permissions to configure public network access to containers and blobs in a storage account. Keep in mind that public access to a container is always turned off by default and must be explicitly configured to permit anonymous requests. It grants read-only access to these resources without sharing the account key, and without requiring a shared access signature. It is recommended not to provide public network access to storage accounts until, and unless, it is strongly desired. A shared access signature token or Azure AD RBAC should be used for providing controlled and timed access to blob containers.

Impact

Access will have to be managed using shared access signatures or via Azure AD RBAC.

For classic storage accounts (to be retired on August 31, 2024), each container in the account must be configured to block anonymous access. Either configure all containers or to configure at the storage account level, migrate to the Azure Resource Manager deployment model.

Audit Procedure

Audit from Azure Portal

1. Go to Storage Accounts.
2. For each storage account, under the Security + networking section, click Networking.
3. Ensure the Public network access setting is set to Disabled.

Audit from Azure CLI

Ensure publicNetworkAccess is Disabled:

az storage account show --name <storage-account> --resource-group <resource-group> --query "{publicNetworkAccess:publicNetworkAccess}"

Audit from PowerShell

For each Storage Account, ensure PublicNetworkAccess is Disabled:

Get-AzStorageAccount -Name <storage account name> -ResourceGroupName <resource group name> |select PublicNetworkAccess

Audit from Azure Policy

If referencing a digital copy of this Benchmark, clicking a Policy ID will open a link to the associated Policy definition in Azure. If referencing a printed copy, you can search Policy IDs from this URL: https://portal.azure.com/#view/Microsoft_Azure_Policy/PolicyMenuBlade/~/Definitions

• Policy ID: b2982f36-99f2-4db5-8eff-283140c09693
• Name: 'Storage accounts should disable public network access'

Expected Result

The Public network access setting is set to Disabled for each storage account. In Azure CLI, publicNetworkAccess returns Disabled. In PowerShell, PublicNetworkAccess returns Disabled. The Azure Policy 'Storage accounts should disable public network access' shows compliant.

Remediation

Remediate from Azure Portal

First, follow Microsoft documentation and create shared access signature tokens for your blob containers. Then,

1. Go to Storage Accounts.
2. For each storage account, under the Security + networking section, click Networking.
3. Set Public network access to Disabled.
4. Click Save.

Remediate from Azure CLI

Set 'Public Network Access' to Disabled on the storage account:

az storage account update --name <storage-account> --resource-group <resource-group> --public-network-access Disabled

Remediate from PowerShell

For each Storage Account, run the following to set the PublicNetworkAccess setting to Disabled:

Set-AzStorageAccount -ResourceGroupName <resource group name> -Name <storage account name> -PublicNetworkAccess Disabled

Default Value

By default, Public Network Access is set to Enabled from all networks for the Storage Account.

References

1. https://docs.microsoft.com/en-us/azure/storage/blobs/storage-manage-access-to-resources
2. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-governance-strategy#gs-2-define-and-implement-enterprise-segmentationseparation-of-duties-strategy
3. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-network-security#ns-2-secure-cloud-native-services-with-network-controls
4. https://docs.microsoft.com/en-us/azure/storage/blobs/assign-azure-role-data-access
5. https://learn.microsoft.com/en-us/azure/storage/common/storage-network-security?tabs=azure-portal

Additional Information

This recommendation is based on the Common Reference Recommendation Ensure public network access is Disabled, from the Common Reference Recommendations > Networking > Virtual Networks (VNets) section.

Profile

Level 1 | Automated