title: Retrieve existing resource data using AWS Cloudformation
body: <p>I need to retrieve existing data/properties of a given resource by using an AWS Cloudformation template. Is it possible? If it is how can I do it?</p>
  <p>Example 1:</p>
  <ul>
  <li>Output: Security Group ID which allows traffic on port 22</li>
  </ul>
  <p>Example 2:</p>
  <ul>
  <li>Output: Instance ID which use default VPC</li>
  </ul>