Ensure S3 bucket encryption 'kms_master_key_id' is not empty or null

Description:

Amazon S3 provides a variety of no, or low, cost encryption options to protect data at rest.

Rationale:

Encrypting data at rest reduces the likelihood that it is unintentionally exposed and can nullify the impact of disclosure if the encryption remains unbroken.

Amazon S3 buckets with default bucket encryption using SSE-KMS cannot be used as destination buckets for Amazon S3 server access logging. Only SSE-S3 default encryption is supported for server access log destination buckets.

From Console:

1. Login to AWS Management Console and open the Amazon S3 console using https://console.aws.amazon.com/s3/
2. Select a Bucket.
3. Click on 'Properties'.
4. Click edit on 'Default Encryption'.
5. Select either 'AES-256', 'AWS-KMS', 'SSE-KMS' or 'SSE-S3'.
6. Click 'Save'
7. Repeat for all the buckets in your AWS account lacking encryption.

From Command Line:

Run either

aws s3api put-bucket-encryption --bucket --server-side-encryption-configuration '{"Rules": [{"ApplyServerSideEncryptionByDefault": {"SSEAlgorithm": "AES256"}}]}'

or

aws s3api put-bucket-encryption --bucket --server-side-encryption-configuration '{"Rules": [{"ApplyServerSideEncryptionByDefault": {"SSEAlgorithm": "aws:kms","KMSMasterKeyID": "aws/s3"}}]}'

Note: the KMSMasterKeyID can be set to the master key of your choosing; aws/s3 is an AWS preconfigured default.