class AWS::S3::Request

def string_to_sign


CanonicalizedAmzHeaders + CanonicalizedResource;
date + "\n" +
content-type + "\n" +
content-md5 + "\n" +
HTTP-Verb + "\n" +
StringToSign =

From the S3 developer guide: 
def string_to_sign
  [
    http_method,
    headers.values_at('content-md5', 'content-type').join("\n"),
    signing_string_date,
    canonicalized_headers,
    canonicalized_resource,
  ].flatten.compact.join("\n")
end