Cis Azure Compute 20.5

Ensure 'Enable Data Access Authentication Mode' is 'Checked'

Description

Data Access Authentication Mode provides a method of uploading or exporting Virtual Machine Disks.

Rationale

Enabling data access authentication mode adds a layer of protection using an Entra ID role to further restrict users from creating and using Secure Access Signature (SAS) tokens for exporting a detached managed disk or virtual machine state. Users will need the Data operator for managed disk role within Entra ID in order to download a VHD or VM Guest state using a secure URL.

Impact

To apply this setting, the virtual machine to which the disk or disks are attached will need to be powered down and have its disk detached. Users without the Data operator for managed disk role within Entra ID will not be able to export VHD or VM guest state using the secure download URL.

The following restrictions apply and must be considered when determining if this recommendation is appropriate for your environment:

• VHDs can't be uploaded to empty snapshots.
• Azure Backup doesn't currently support disks secured with Microsoft Entra ID.
• Azure Site Recovery doesn't currently support disks secured with Microsoft Entra ID.

Audit Procedure

Using Azure Portal

Part A. Select the Virtual Machine to Evaluate

1. Using the search bar, search for and open the Virtual Machines service.
2. Click on the name of the Virtual Machine to be audited.

Part B. Evaluate each Virtual Machine Disk individually

1. From the selected Virtual Machine resource window, expand the Settings menu item and click Disks.
2. For each disk, click the name of the disk to open the disk resource window.
3. From the selected Disk resource window, expand the Settings menu item, and click Disk Export.

Ensure that Enable Data Access Authentication Mode is checked.

Repeat Part B for each Disk attached to a VM. Repeat Parts A and B to evaluate all Disks in all VMs.

Using Azure PowerShell

Run the following command for each disk:

Get-AzDisk -ResourceGroupName <resource_group_name> -DiskName <disk_name>

Ensure the DataAccessAuthMode setting displays AzureActiveDirectory next to it.

Using Azure CLI

Run the following command for each disk:

az disk show --disk-name <disk_name> --resource-group <resource_group_name>

Ensure the dataAccessAuthMode setting is set to AzureActiveDirectory.

Expected Result

The dataAccessAuthMode setting should be set to AzureActiveDirectory for all VM disks.

Remediation

Using Azure Portal

Part A. Select the Virtual Machine to Remediate

1. Using the search bar, search for and open the Virtual Machines service.
2. Click on the name of the Virtual Machine to be remediated.

Part B. Remediate each Virtual Machine Disk individually

1. From the selected Virtual Machine resource window, expand the Settings menu item and click Disks.
2. For each disk, click the name of the disk to open the disk resource window.
3. From the selected Disk resource window, expand the Settings menu item, and click Disk Export.

check the checkbox next to Enable Data Access Authentication Mode.

Repeat Part B for each Disk attached to a VM. Repeat Parts A and B to remediate all Disks in all VMs.

Using Azure PowerShell

Ensure that each disk is detached from its associated Virtual Machine before proceeding. Once detached, run the following for each disk:

$disk = Get-AzDisk -ResourceGroupName <resource_group_name> -DiskName <disk_name>
$disk.DataAccessAuthMode = 'AzureActiveDirectory'
Update-AzDisk -ResourceGroup <resource_group_name> -DiskName $disk.Name -Disk $disk

Using Azure CLI

Ensure that each disk is detached from its associated Virtual Machine before proceeding. Once detached, run the following for each disk:

az disk update --name <disk_name> --resource-group <resource_group_name> --data-access-auth-mode AzureActiveDirectory

Default Value

By default, Data Access Authentication Mode is Disabled.

References

1. https://learn.microsoft.com/en-us/azure/virtual-machines/linux/download-vhd?tabs=azure-portal#secure-downloads-and-uploads-with-microsoft-entra-id
2. https://learn.microsoft.com/en-us/azure/virtual-machines/windows/download-vhd?tabs=azure-portal#secure-downloads-and-uploads-with-microsoft-entra-id

Profile

Level 1 | Automated