cis-aws-foundations-4-5

name	cis-aws-foundations-4.5
description	Ensure CloudTrail logs are encrypted at rest using KMS CMKs
category	cis-logging
version	7.0.0
author	cyberstrike-official
tags	["cis","aws","logging","cloudtrail","kms","encryption","sse-kms","cmk"]
cis_id	4.5
cis_benchmark	CIS AWS Foundations Benchmark v7.0.0
tech_stack	["aws"]
cwe_ids	[]
chains_with	["cis-aws-foundations-4.1","cis-aws-foundations-4.6"]
prerequisites	[]
severity_boost	{}

Ensure CloudTrail logs are encrypted at rest using KMS CMKs

Description

AWS CloudTrail is a web service that records AWS API calls for an account and makes those logs available to users and resources in accordance with IAM policies. AWS Key Management Service (KMS) is a managed service that helps create and control the encryption keys used to encrypt account data, and uses Hardware Security Modules (HSMs) to protect the security of encryption keys. CloudTrail logs can be configured to leverage server side encryption (SSE) and KMS customer-created master keys (CMK) to further protect CloudTrail logs. It is recommended that CloudTrail be configured to use SSE-KMS.

Rationale

Configuring CloudTrail to use SSE-KMS provides additional confidentiality controls on log data, as a given user must have S3 read permission on the corresponding log bucket and must be granted decrypt permission by the CMK policy.

Impact

Customer-created keys incur an additional cost. See https://aws.amazon.com/kms/pricing/ for more information.

Audit Procedure

Using AWS Console

1. Sign in to the AWS Management Console and open the CloudTrail console at https://console.aws.amazon.com/cloudtrail.
2. In the left navigation pane, choose Trails.
3. Select a trail.
4. In the General details section, select Edit to edit the trail configuration.
5. Ensure the box at Log file SSE-KMS encryption is checked and that a valid AWS KMS alias of a KMS key is entered in the respective text box.

Using AWS CLI

1. Run the following command:

aws cloudtrail describe-trails

2. For each trail listed, SSE-KMS is enabled if the trail has a KmsKeyId property defined.

Expected Result

All CloudTrail trails have a KmsKeyId property defined, indicating SSE-KMS encryption is enabled.

Remediation

Using AWS Console

1. Sign in to the AWS Management Console and open the CloudTrail console at https://console.aws.amazon.com/cloudtrail.
2. In the left navigation pane, choose Trails.
3. Click on a trail.
4. Under the S3 section, click the edit button (pencil icon).
5. Click .