Cloudtrail should be encrypted at rest to secure access to sensitive trail data

Explanation

Cloudtrail logs should be encrypted at rest to secure the sensitive data. Cloudtrail logs record all activity that occurs in the the account through API calls and would be one of the first places to look when reacting to a breach.

Possible Impact

Data can be freely read if compromised

Suggested Resolution

Enable encryption at rest

Insecure Example

The following example will fail the aws-cloudtrail-enable-at-rest-encryption check.

resource "aws_cloudtrail" "bad_example" {
  is_multi_region_trail = true

  event_selector {
    read_write_type           = "All"
    include_management_events = true

    data_resource {
      type = "AWS::S3::Object"
      values = ["${data.aws_s3_bucket.important-bucket.arn}/"]
    }
  }
}

Secure Example

The following example will pass the aws-cloudtrail-enable-at-rest-encryption check.

resource "aws_cloudtrail" "good_example" {
  is_multi_region_trail = true
  enable_log_file_validation = true
  kms_key_id = var.kms_id

  event_selector {
    read_write_type           = "All"
    include_management_events = true

    data_resource {
      type = "AWS::S3::Object"
      values = ["${data.aws_s3_bucket.important-bucket.arn}/"]
    }
  }
}

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