Online padding oracle

gistfile1.cs

//Class implements ICBCOracle
public class OnlineCBCOracle : ICBCOracle
{
    public bool RequestOracle(byte[] cipher)
    {
	const string BASE_URL = "ORACLE_URL?er=";
	string urlData = Helpers.ConvertByteArrayToHexString(cipher);
	WebClient wc = new WebClient();
 
	try
	{
		wc.DownloadData(BASE_URL + urlData);
	}
	catch (WebException e)
	{
        	//Invalid padding
        	if (e.Message.Contains("403"))
                	return false;
 
        	//Valid padding, but wrong mac
        	if (e.Message.Contains("404"))
                	return true;
	}
	//Failed, the oracle is not up!
	return false;
    }
}