Ensure S3 bucket encryption 'kms_master_key_id' is not empty or null - Terraform Version 1.x

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.

From Console:

1. Login to AWS Management Console and open the Amazon S3 console using https://console.aws.amazon.com/s3/
2. Select the Check box next to the Bucket.
3. Click on 'Properties'.
4. Click on Default Encryption.
5. Select either AES-256 or AWS-KMS
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 <bucket name> --server-side-encryption-configuration '{"Rules": [{"ApplyServerSideEncryptionByDefault": {"SSEAlgorithm": "AES256"}}]}'

or

aws s3api put-bucket-encryption --bucket <bucket name> --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.