cis-azure-storage-17.1.3

DevOps & Security

Ensure that Storage Account Access Keys are Periodically Regenerated

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17.1.3 Ensure that Storage Account Access Keys are Periodically Regenerated (Manual)

Description

For increased security, regenerate storage account access keys periodically.

Rationale

When a storage account is created, Azure generates two 512-bit storage access keys which are used for authentication when the storage account is accessed. Rotating these keys periodically ensures that any inadvertent access or exposure does not result from the compromise of these keys.

Cryptographic key rotation periods will vary depending on your organization's security requirements and the type of data which is being stored in the Storage Account. For example, PCI DSS mandates that cryptographic keys be replaced or rotated 'regularly,' and advises that keys for static data stores be rotated every 'few months.'

For the purposes of this recommendation, 90 days will prescribed for the reminder. Review and adjustment of the 90 day period is recommended, and may even be necessary. Your organization's security requirements should dictate the appropriate setting.

Impact

Regenerating access keys can affect services in Azure as well as the organization's applications that are dependent on the storage account. All clients who use the access key to access the storage account must be updated to use the new key.

Audit Procedure

Audit from Azure Portal

Go to Storage Accounts.
For each Storage Account, under Security + networking, go to Access keys.
Review the date and days in the Last rotated field for each key.

If the Last rotated field indicates a number or days greater than 90 [or greater than your organization's period of validity], the key should be rotated.

Audit from Azure CLI

Get a list of storage accounts

az storage account list --subscription <subscription-id>

Make a note of id, name and resourceGroup.

For every storage account make sure that key is regenerated in past 90 days.

az monitor activity-log list --namespace Microsoft.Storage --offset 90d --query "[?contains(authorization.action, 'regenerateKey')]" --resource-id <resource id>

The output should contain:

"authorization"/"scope": <your_storage_account> AND "authorization"/"action": "Microsoft.Storage/storageAccounts/regeneratekey/action" AND "status"/"localizedValue": "Succeeded" "status"/"Value": "Succeeded"

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: 044985bb-afe1-42cd-8a36-9d5d42424537
Name: 'Storage account keys should not be expired'

Expected Result

The Last rotated field for each access key shows a date within the last 90 days. The Azure CLI activity log contains successful regenerateKey actions within the last 90 days for each storage account. The Azure Policy 'Storage account keys should not be expired' shows compliant for all storage accounts.

Remediation

Remediate from Azure Portal

Go to Storage Accounts.
For each Storage Account with outdated keys, under Security + networking, go to Access keys.
Click Rotate key next to the outdated key, then click Yes to the prompt confirming that you want to regenerate the access key.

After Azure regenerates the Access Key, you can confirm that Access keys reflects a Last rotated date of (0 days ago).