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2.4.1 Ensure that encryption is enabled for EFS file systems

Warning! Audit Deprecated

This audit has been deprecated and will be removed in a future update.

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Information

EFS data should be encrypted at rest using AWS KMS (Key Management Service).

Rationale:

Data should be encrypted at rest to reduce the risk of a data breach via direct access to the storage device.

NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.

Solution

It is important to note that EFS file system data at rest encryption must be turned on when creating the file system.
If an EFS file system has been created without data at rest encryption enabled then you must create another EFS file system with the correct configuration and transfer the data.
Steps to create an EFS file system with data encrypted at rest:
From Console:

Login to the AWS Management Console and Navigate to Elastic File System (EFS) dashboard.

Select File Systems from the left navigation panel.

Click Create File System button from the dashboard top menu to start the file system setup process.

On the Configure file system access configuration page, perform the following actions.

Choose the right VPC from the VPC dropdown list.

Within Create mount targets section, select the checkboxes for all of the Availability Zones (AZs) within the selected VPC. These will be your mount targets.

Click Next step to continue.

Perform the following on the Configure optional settings page.

Create tags to describe your new file system.

Choose performance mode based on your requirements.

Check Enable encryption checkbox and choose aws/elasticfilesystem from Select KMS master key dropdown list to enable encryption for the new file system using the default master key provided and managed by AWS KMS.

Click Next step to continue.

Review the file system configuration details on the review and create page and then click Create File System to create your new AWS EFS file system.

Copy the data from the old unencrypted EFS file system onto the newly create encrypted file system.

Remove the unencrypted file system as soon as your data migration to the newly create encrypted file system is completed.

Change the AWS region from the navigation bar and repeat the entire process for other aws regions.

From CLI:

Run describe-file-systems command to describe the configuration information available for the selected (unencrypted) file system (see Audit section to identify the right resource):

aws efs describe-file-systems --region <region> --file-system-id <file-system-id from audit section step 2 output>

The command output should return the requested configuration information.

To provision a new AWS EFS file system, you need to generate a universally unique identifier (UUID) in order to create the token required by the create-file-system command. To create the required token, you can use a randomly generated UUID from 'https://www.uuidgenerator.net'.

Run create-file-system command using the unique token created at the previous step.

aws efs create-file-system --region <region> --creation-token <Token (randomly generated UUID from step 3)> --performance-mode generalPurpose --encrypted

The command output should return the new file system configuration metadata.

Run create-mount-target command using the newly created EFS file system ID returned at the previous step as identifier and the ID of the Availability Zone (AZ) that will represent the mount target:

aws efs create-mount-target --region <region> --file-system-id <file-system-id> --subnet-id <subnet-id>

The command output should return the new mount target metadata.

Now you can mount your file system from an EC2 instance.

Copy the data from the old unencrypted EFS file system onto the newly create encrypted file system.

Remove the unencrypted file system as soon as your data migration to the newly create encrypted file system is completed.

aws efs delete-file-system --region <region> --file-system-id <unencrypted-file-system-id>

Change the AWS region by updating the --region and repeat the entire process for other aws regions.

Default Value:

EFS file system data is encrypted at rest by default when creating a file system via the Console. Encryption at rest is not enabled by default when creating a new file system using the AWS CLI, API, and SDKs.

See Also

https://workbench.cisecurity.org/benchmarks/14207

Item Details

References: CSCv7|14.8

Plugin: amazon_aws

Control ID: cb0d3fa295174e0bf43754213569a36acd354b05886467fd170bcc6f3a2a0e63