Cis Azure Foundations 9.3.6

Ensure the 'Minimum TLS version' for storage accounts is set to 'Version 1.2'

Description

In some cases, Azure Storage sets the minimum TLS version to be version 1.0 by default. TLS 1.0 is a legacy version and has known vulnerabilities. This minimum TLS version can be configured to be later protocols such as TLS 1.2.

Rationale

TLS 1.0 has known vulnerabilities and has been replaced by later versions of the TLS protocol. Continued use of this legacy protocol affects the security of data in transit.

Impact

When set to TLS 1.2 all requests must leverage this version of the protocol. Applications leveraging legacy versions of the protocol will fail.

Audit Procedure

Audit from Azure Portal

1. Go to Storage Accounts.
2. For each storage account, under Settings, click Configuration.
3. Ensure that the Minimum TLS version is set to Version 1.2.

Audit from Azure CLI

Get a list of all storage accounts and their resource groups:

az storage account list | jq '.[] | {name, resourceGroup}'

Then query the minimumTLSVersion field:

az storage account show \
    --name <storage-account> \
    --resource-group <resource-group> \
    --query minimumTlsVersion \
    --output tsv

Audit from PowerShell

To get the minimum TLS version, run the following command:

(Get-AzStorageAccount -Name <STORAGEACCOUNTNAME> -ResourceGroupName <RESOURCEGROUPNAME>).MinimumTlsVersion

Expected Result

minimumTlsVersion should be TLS1_2 for all storage accounts.

Remediation

Remediate from Azure Portal

1. Go to Storage Accounts.
2. For each storage account, under Settings, click Configuration.
3. Set the Minimum TLS version to Version 1.2.
4. Click Save.

Remediate from Azure CLI

az storage account update \
    --name <storage-account> \
    --resource-group <resource-group> \
    --min-tls-version TLS1_2

Remediate from PowerShell

To set the minimum TLS version, run the following command:

Set-AzStorageAccount -AccountName <STORAGEACCOUNTNAME> `
                     -ResourceGroupName <RESOURCEGROUPNAME> `
                     -MinimumTlsVersion TLS1_2

Default Value

If a storage account is created through the portal, the MinimumTlsVersion property for that storage account will be set to TLS 1.2. If a storage account is created through PowerShell or CLI, the MinimumTlsVersion property for that storage account will not be set, and defaults to TLS 1.0.

References

1. https://learn.microsoft.com/en-us/azure/storage/common/transport-layer-security-configure-minimum-version
2. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-data-protection#dp-3-encrypt-sensitive-data-in-transit

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