Cis Azure Foundations 9.3.1.3

Ensure 'Allow storage account key access' for Azure Storage Accounts is 'Disabled'

Description

Every secure request to an Azure Storage account must be authorized. By default, requests can be authorized with either Microsoft Entra credentials or by using the account access key for Shared Key authorization.

Rationale

Microsoft Entra ID provides superior security and ease of use compared to Shared Key and is recommended by Microsoft. To require clients to use Microsoft Entra ID for authorizing requests, you can disallow requests to the storage account that are authorized with Shared Key.

Impact

When you disallow Shared Key authorization for a storage account, any requests to the account that are authorized with Shared Key, including shared access signatures (SAS), will be denied. Client applications that currently access the storage account using the Shared Key will no longer function.

Audit Procedure

Audit from Azure Portal

1. Go to Storage accounts.
2. Click on a storage account.
3. Under Settings, click Configuration.
4. Under Allow storage account key access, ensure that the radio button next to Disabled is selected.
5. Repeat steps 1-4 for each storage account.

Audit from Azure CLI

Run the following command to list storage accounts:

az storage account list

For each storage account, run the following command:

az storage account show --resource-group <resource-group> --name <storage-account>

Ensure that allowSharedKeyAccess is set to false.

Audit from PowerShell

Run the following command to list storage accounts:

Get-AzStorageAccount

Run the following command to get the storage account in a resource group with a given name:

$storageAccount = Get-AzStorageAccount -ResourceGroupName <resource-group> -Name <storage-account>

Run the following command to get the shared key access setting for the storage account:

$storageAccount.allowSharedKeyAccess

Ensure that the command returns False.

Expected Result

allowSharedKeyAccess should be set to false for all storage accounts.

Remediation

Remediate from Azure Portal

1. Go to Storage accounts.
2. Click on a storage account.
3. Under Settings, click Configuration.
4. Under Allow storage account key access, click the radio button next to Disabled.
5. Click Save.
6. Repeat steps 1-5 for each storage account requiring remediation.

Remediate from Azure CLI

For each storage account requiring remediation, run the following command to disallow shared key authorization:

az storage account update --resource-group <resource-group> --name <storage-account> --allow-shared-key-access false

Remediate from PowerShell

For each storage account requiring remediation, run the following command to disallow shared key authorization:

Set-AzStorageAccount -ResourceGroupName <resource-group> -Name <storage-account> -AllowSharedKeyAccess $false

Default Value

The AllowSharedKeyAccess property of a storage account is not set by default and does not return a value until you explicitly set it. The storage account permits requests that are authorized with the Shared Key when the property value is null or when it is true.

References

1. https://learn.microsoft.com/en-us/azure/storage/common/shared-key-authorization-prevent
2. https://learn.microsoft.com/en-us/cli/azure/storage/account
3. https://learn.microsoft.com/en-us/powershell/module/az.storage/get-azstorageaccount
4. https://learn.microsoft.com/en-us/powershell/module/az.storage/set-azstorageaccount

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