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Non-encrypted confidential information - EFS

Description​

The AWS Elastic File System (EFS) service is encrypted with a default KMS key. Best practices recommend encrypting EFS instances using Customer Managed Keys (CMKs) to reduce risk of exposure and give full control of encrypted information.

Impact​

Obtain confidential information from file system

Recommendation​

Enable the EFS encryption using a KMS Customer Managed Key (CMK)

Threat​

Anonymous attacker with local access to one or more EFS instances

Expected Remediation Time​

⌚ 20 minutes.

Score​

Default score using CVSS 3.1. It may change depending on the context of the vulnerability.

Base​

  • Attack vector: N
  • Attack complexity: H
  • Privileges required: N
  • User interaction: N
  • Scope: U
  • Confidentiality: L
  • Integrity: N
  • Availability: N

Temporal​

  • Exploit code madurity: P
  • Remediation level: O
  • Report confidence: C

Result​

  • Vector string: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N/E:P/RL:O/RC:C
  • Score:
    • Base: 3.7
    • Temporal: 3.4
  • Severity:
    • Base: Low
    • Temporal: Low

Code Examples​

Compliant code​

The resource has encryption correctly configured with a KMS Key

Resources:
  FileSystemResource:
    Type: 'AWS::EFS::FileSystem'
    Properties:
      AvailabilityZoneName: us-east-1a
      BackupPolicy:
        Status: ENABLED
      Encrypted: true
      KMS_Key: ${encrypted_key}

Non compliant code​

The resource does not have encryption correctly set up

Resources:
  FileSystemResource:
    Type: 'AWS::EFS::FileSystem'
    Properties:
      AvailabilityZoneName: us-east-1a
      BackupPolicy:
        Status: ENABLED
      Encrypted: false

Terraform example

resource "aws_efs_file_system" "enabled" {
  creation_token = "example"
  encrypted      = false
}

Using the AWS CLI, the following command checks if the EFS file systems are encrypted

$ aws efs describe-file-systems
      --region us-east-1
      --file-system-id {fs_id}
      --query 'FileSystems[*].Encrypted'

If the command output returns false, the file system is unencrypted.

Details​

https://docs.bridgecrew.io/docs/bc_aws_general_104

Requirements​

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