passing NTLM authentication proxy

Question

I have a legacy HTTP client application developed with VB on .NET Framework 2.0 long ago. Recently a new proxy server was introduced into our network and the VB app started meeting "407 Proxy Authentication Required" error.

The proxy requires NTLM authentication and the program didn't consider it.

After googling some web resources, I wrote the following code.

Dim proxy As New System.Net.WebProxy("http://my.proxy.com:81")
proxy.Credentials = System.Net.CredentialCache.DefaultCredentials
proxy.UseDefaultCredentials = true
webreq.Proxy = proxy

But I'm still seeing 407 error. User is logging into Windows domain.

I tried some different (but similar) ways but don't succeed.

Can anyone point what I may be missing?

Is there any possibility that any security policy setting may prevent this from working?

I can contact the network administrator but he is not familiar with application development and I don't know what I should ask him, neither.

Any help would be appreciated.

MarkWalls MarkWalls · Accepted Answer · 2013-06-04T15:33:15

I am hunting for a solution to this as well. Perhaps it is security related: Are they in the Intranet security zone? http://www.codinghorror.com/blog/2005/04/aspnet-ntlm-authentication---is-it-worth-it.html

I found this at: http://bytes.com/topic/net/answers/544841-ntlm-authentication-how It is a start, but they are having problems as well.

public string SendRequest()
        // run the request and return a string response
        {
            string FinalResponse = "";
            string Cookie = "";

            NameValueCollection collHeader = new NameValueCollection();

            HttpWebResponse webresponse;

             HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URI);

             request.KeepAlive = true;
            request.Timeout = 10000;
            request.Method = "POST";
            request.AllowAutoRedirect = false;
            request.Proxy = WebProxy.GetDefaultProxy();

            string addr = "http://" + ProxyServer + ":" + String.Format("{0:D}", ProxyPort);
            Uri u = new Uri(addr);

            CredentialCache wrCache = new CredentialCache();
            wrCache.Add(u, "Negotiate", System.Net.CredentialCache.DefaultNetworkCredentials);

            request.Proxy.Credentials = wrCache;

            try
            {
                byte[] bytes = Encoding.ASCII.GetBytes(Request);
                request.ContentLength = bytes.Length;

                Stream oStreamOut = request.GetRequestStream();
                oStreamOut.Write(bytes, 0, bytes.Length);
                oStreamOut.Close();

                webresponse = (HttpWebResponse)request.GetResponse();
                if (null == webresponse)
                {
                    FinalResponse = "No Response from " + URI;
                }
                else
                {
                    Encoding enc = System.Text.Encoding.GetEncoding(1252);
                    StreamReader rdr = new StreamReader(webresponse.GetResponseStream(),enc);
                    FinalResponse = rdr.ReadToEnd();
                }

            }//End of Try Block

            catch (WebException e)
            {
                // some kind of error..
                if (407 == (int)e.Status)
                {
                }

                throw CatchHttpExceptions(FinalResponse = e.Message);
            }
            catch (System.Exception e)
            {
                throw new Exception(FinalResponse = e.Message);
            }
            finally
            {
                // BaseHttp = null;
            }
            return FinalResponse;
        } //End of SendRequestTo method

passing NTLM authentication proxy

1 Answers