Description: 

SMB (Server Message Block) channel encryption for Azure File Shares ensures that data transmitted over the SMB protocol is encrypted, preventing unauthorized access or tampering. Setting the encryption to AES-256-GCM or higher ensures that the data transfer between clients and Azure File Shares is protected with strong encryption algorithms, which is crucial for maintaining confidentiality and integrity.

Rationale: 

AES-256-GCM provides one of the highest levels of security for data in transit and is a recommended encryption standard for SMB communication. Using strong encryption standards like AES-256-GCM helps prevent data breaches and protects against eavesdropping or tampering. Ensuring that SMB channel encryption is configured to AES-256-GCM or higher meets compliance requirements for organizations that need to adhere to stringent security and data protection regulations like SOC 2, HIPAA, and GDPR.

Impact: 

Enabling SMB channel encryption with AES-256-GCM or higher ensures that all data transmitted to and from the Azure File Shares is protected with strong encryption. However, enabling encryption may slightly impact performance due to the computational overhead of encryption, though the benefits of enhanced security outweigh this impact in most cases.

Default Value:

 By default, SMB channel encryption is not enabled for Azure File Shares. It must be explicitly configured to use AES-256-GCM or higher.

Pre-requisites:

  • Azure account: Ensure you have appropriate permissions to configure SMB settings on Azure File Shares.

  • Azure Storage Account with SMB File Shares: Ensure the storage account and SMB file shares exist.

  • Permissions: You need appropriate permissions, such as Owner or Contributor role, to modify the SMB file share settings.

  • Supported SMB Protocol Versions: Ensure that the storage account supports SMB 3.0 or higher (SMB 3.0 is required for encryption features).

Remediation:

Audit:

To check if SMB channel encryption is set to AES-256-GCM or higher for your Azure File Shares:

  1. Sign in to the Azure portal using an account with appropriate permissions.

  2. Navigate to the Azure Storage Account.

  3. Check SMB encryption settings:

    • In the Settings section, click on File shares.

    • Select a file share and go to the Configuration tab.

    • Verify that SMB encryption is enabled and set to AES-256-GCM or higher.

Automated Implementation:

To ensure that SMB channel encryption is enabled with AES-256-GCM or higher for all Azure File Shares, you can use Azure Policy.

  1. Create a custom Azure Policy to enforce SMB encryption:

    • Go to the Azure portal.

    • Navigate to Policy and click on Definitions.

    • Create a new Custom Policy with the following content:

{
  "properties": {
    "displayName": "Ensure SMB Channel Encryption is Set to AES-256-GCM or Higher for File Shares",
    "policyType": "Custom",
    "mode": "All",
    "description": "This policy ensures that SMB channel encryption is set to AES-256-GCM or higher for all Azure file shares.",
    "parameters": {},
    "metadata": {
      "version": "1.0.0",
      "category": "Storage"
    },
    "policyRule": {
      "if": {
        "field": "Microsoft.Storage/storageAccounts/fileServices.protocolSettings.smbEncryption",
        "notEquals": "AES-256-GCM"
      },
      "then": {
        "effect": "deny"
      }
    }
  }
}


  1. Assign the policy:

    • After creating the custom policy, assign it to the relevant subscriptions or resource groups to ensure that SMB channel encryption is set to AES-256-GCM or higher for all file shares.

Backout Plan:

To disable SMB channel encryption or revert to a lower encryption setting:

  1. Sign in to the Azure portal with appropriate permissions.

  2. Navigate to the Azure Storage Account.

  3. Go to File Share settings:

    • In the Settings section, click on File shares and select the file share.

  4. Disable or Change Encryption:

    • Modify the SMB encryption settings to a lower standard or disable encryption if necessary. Note that disabling encryption will reduce the security of the data in transit.

If the setting was enforced via Azure Policy, modify or remove the policy to allow a different encryption setting or no encryption.

References: