This Moodle filter recognises cloudfront URLs from the URL defined in the filter settings and replaces them with signed URLs.
See http://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/private-content-signed-urls.html for full details
Simply place the filter files in ./filter/cloudfront_signurl
In the filter settings you will need to define the URL for the cloudfront distribution along with the Key Pair ID and private key file to use for the signing process.
At present only canned policies are supported.