Click here to Skip to main content
15,867,453 members
Please Sign up or sign in to vote.
1.00/5 (2 votes)
See more:
In C# the copyTo() and the readToEnd() and the LoadXML() methods are also vulnerable to a DDoS attack because of its need to read all the way to the end of the line which is usually designated by a character. If that character does not exist the funtion will proceed to keep reading and copying data until all the resources are consumed and an error is thrown.

as per WhiteHat scan this statement is received. How can prevent From denial-of-service attack for these methods. Is there any alternate method? Or what are the points which can take care.

This below method is:

private static bool IsResponseError(string response, out int errorCode, out string errorMessage)
{
errorCode = 0;
errorMessage = null;
var retVal = false;

if (String.IsNullOrWhiteSpace(response)) return false;
var xmlDocument = new XmlDocument();

try
{
xmlDocument.LoadXml(response); //This Is Vulnerable.
}
catch
{
// if you are here, the string is not XML which is the case for Authenticate; if successful, the token returned is a string, not xml
return false;
}

if (xmlDocument.DocumentElement != null)
{
//XmlNode errorElement = xmlDocument.DocumentElement.SelectSingleNode("//ERRORCODE");
var errorElement = GetErrorNode(xmlDocument);

if (errorElement != null)
{
try
{
retVal = true;
errorCode = int.Parse(errorElement.InnerText);
if (Errors.ContainsKey(errorCode))
errorMessage = Errors[errorCode];
else
{
errorCode = 99999;
errorMessage = "Unknown error message: " + errorElement.InnerText;
}
}
catch
{
errorCode = 99999;
errorMessage = "Unknown error message: " + errorElement.InnerText;
}
}
}

return retVal;
}

What I have tried:

For LoadXml(), i got the solution to prevent from vulnerability..
BUt Fro CopyTo() & readToEnd() method.... I need the solution.
Posted
Updated 14-Jul-17 4:41am
Comments
Richard MacCutchan 13-Jul-17 10:07am    
I would be interested to see your explanation of exactly how these commands are vulnerable to DDOS.
gggustafson 13-Jul-17 10:59am    
I too would like an answer to Richard's question.

1 solution

If you're referring to the DoS (NB: Not DDoS, which is a different thing altogether!) and XXE vulnerabilities, the problem and solutions are described in this MSDN Magazine article: XML Denial of Service Attacks and Defenses[^]

In short:
public static XmlDocument LoadUntrustedXml(string input)
{
    var settings = new XmlReaderSettings
    {
        DtdProcessing = DtdProcessing.Prohibit,
        MaxCharactersFromEntities = 1024,
        XmlResolver = null,
    };
    
    using (var stringReader = new StringReader(input))
    using (var xmlReader = XmlReader.Create(stringReader, settings))
    {
        var result = new XmlDocument();
        result.Load(xmlReader);
        return result;
    }
}
 
Share this answer
 

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)



CodeProject, 20 Bay Street, 11th Floor Toronto, Ontario, Canada M5J 2N8 +1 (416) 849-8900