Cis Azure Foundations 9.3.1.1

Ensure 'Enable key rotation reminders' is enabled for each Storage Account

Description

Access Keys authenticate application access requests to data contained in Storage Accounts. A periodic rotation of these keys is recommended to ensure that potentially compromised keys cannot result in a long-term exploitable credential. The "Rotation Reminder" is an automatic reminder feature for a manual procedure.

Rationale

Reminders such as those generated by this recommendation will help maintain a regular and healthy cadence for activities which improve the overall efficacy of a security program.

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 be 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

This recommendation only creates a periodic reminder to regenerate access keys. Regenerating access keys can affect services in Azure as well as the organization's applications that are dependent on the storage account. All clients that use the access key to access the storage account must be updated to use the new key.

Audit Procedure

Audit from Azure Portal

1. Go to Storage Accounts
2. For each Storage Account, under Security + networking, go to Access keys
3. If the button Edit rotation reminder is displayed, the Storage Account is compliant. Click Edit rotation reminder and review the Remind me every field for a desirable periodic setting that fits your security program's needs. If the button Set rotation reminder is displayed, the Storage Account is not compliant.

Audit from PowerShell

$rgName = <resource group name for the storage>
$accountName = <storage account name>
$account = Get-AzStorageAccount -ResourceGroupName $rgName -Name $accountName

Write-Output $accountName ->
Write-Output "Expiration Reminder set to:
$($account.KeyPolicy.KeyExpirationPeriodInDays) Days"
Write-Output "Key1 Last Rotated:
$($account.KeyCreationTime.Key1.ToShortDateString())"
Write-Output "Key2 Last Rotated:
$($account.KeyCreationTime.Key2.ToShortDateString())"

Key rotation is recommended if the creation date for any key is empty. If the reminder is set, the period in days will be returned. The recommended period is 90 days.

Expected Result

The Edit rotation reminder button should be displayed (not Set rotation reminder), and the rotation period should be set to 90 days or less.

Remediation

Remediate from Azure Portal

1. Go to Storage Accounts
2. For each Storage Account that is not compliant, under Security + networking, go to Access keys
3. Click Set rotation reminder
4. Check Enable key rotation reminders
5. In the Send reminders field select Custom, then set the Remind me every field to 90 and the period drop down to Days
6. Click Save

Remediate from PowerShell

$rgName = <resource group name for the storage>
$accountName = <storage account name>
$account = Get-AzStorageAccount -ResourceGroupName $rgName -Name $accountName
if ($account.KeyCreationTime.Key1 -eq $null -or $account.KeyCreationTime.Key2 -eq $null){
      Write-output ("You must regenerate both keys at least once before setting expiration policy")
} else {
      $account = Set-AzStorageAccount -ResourceGroupName $rgName -Name $accountName -KeyExpirationPeriodInDay 90
}
$account.KeyPolicy.KeyExpirationPeriodInDays

Default Value

By default, Key rotation reminders are not configured.

References

1. https://learn.microsoft.com/en-us/azure/storage/common/storage-account-keys-manage
2. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-privileged-access#pa-1-separate-and-limit-highly-privilegedadministrative-users
3. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-identity-management#im-3-manage-application-identities-securely-and-automatically
4. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-governance-strategy#gs-6-define-and-implement-identity-and-privileged-access-strategy
5. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-identity-management#im-8-restrict-the-exposure-of-credentials-and-secrets
6. https://www.pcidssguide.com/pci-dss-key-rotation-requirements/
7. https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57pt1r5.pdf

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