Encrypting Azure Files

Azure Storage offers encryption for data at rest and in transit. This document focuses on the encryption of data within Azure Files shares.

Data Encryption at Rest

Azure Files automatically encrypts all data stored in a share when it's persisted to disk. This encryption is enabled by default for all new and existing storage accounts.

How it Works

Azure Storage uses 256-bit AES encryption. Data is encrypted on a per-disk basis using individual encryption keys. These keys are themselves protected by a master key stored securely in Azure Key Vault. The encryption process is transparent to clients accessing the data.

Key Management

Azure Storage offers two primary models for managing the encryption keys:

• Microsoft-Managed Keys: By default, Azure Storage manages the encryption keys for you. This is the simplest option and requires no configuration.
• Customer-Managed Keys (CMK): You can choose to use your own encryption keys stored in Azure Key Vault. This provides greater control over key rotation and access policies. To enable CMK:
  1. Ensure you have an Azure Key Vault resource.
  2. Grant the storage account's identity appropriate permissions to your Key Vault (e.g., "Get", "Wrap Key", "Unwrap Key").
  3. In your storage account's settings, navigate to the "Encryption" section and select "Customer-managed keys".
  4. Choose your Key Vault and the specific key to use.

Enabling Encryption for Existing Storage Accounts

Encryption at rest is enabled by default for all storage accounts. If you have an older account where encryption might not have been enabled, you can enable it through the Azure portal or Azure CLI.

# Example using Azure CLI to enable encryption for an existing account
az storage account update --name mystorageaccount --resource-group myresourcegroup --encryption true --key-source Microsoft.Storage

Data Encryption in Transit

Azure Files supports encryption in transit using two primary methods:

• SMB Encryption: For SMB 3.0 and later, you can enable SMB encryption. This encrypts the data as it travels between the client and the Azure Files endpoint. This is particularly important for sensitive data and when using public endpoints.
• HTTPS/TLS: When accessing Azure Files using the REST API (e.g., via Azure CLI or SDKs), the connection is secured by default using HTTPS, which provides TLS encryption.

Enabling SMB Encryption

SMB encryption can be enabled at the share level or for the entire storage account.

For optimal security, it's recommended to enable SMB 3.0+ encryption for all file shares that handle sensitive data.

Using Azure Portal

Navigate to your storage account, select "File shares", choose a specific share, and look for the "Encryption" or "SMB settings" option.

Using Azure CLI

# Example to enable SMB 3.0 encryption for a file share
az storage share update --account-name mystorageaccount --name myshare --smb-encryption true

Security Best Practices

• Always use HTTPS for REST API access.
• Enable SMB 3.0+ encryption for sensitive data accessed over SMB.
• Consider using Customer-Managed Keys for enhanced control over encryption keys, especially in regulated environments.
• Regularly rotate your encryption keys if using CMK.
• Implement proper access control (RBAC, Share Access Signatures) to limit who can access your file shares.

For more detailed information on specific configurations and advanced scenarios, please refer to the official Azure Storage documentation.