Impersonation with NTLM

Discussion in 'ASP .Net Security' started by Thomas Mueller-Lynch, Feb 6, 2004.

  1. I want to use impersonation within a second thread of an httpwebrequest.
    While configuring IIS with basic authentication everything works fine.
    Changing to Intergrated Windows Authentication the thread (which should return a secure web-page) returns the http status code 401.

    My web.config looks like:
    <identity impersonate="true"/><authentication mode="Windows" />

    My Testpage looks like:

    dim url as String = "https://server/secure/index.html"
    dim Req as HttpWebRequest = DirectCast(WebRequest.Create(url), HttpWebRequest)

    Req.Method = "GET"
    Req.ContentType = "application/x-www-form-urlencoded;charset=iso-8859-1"
    Req.PreAuthenticate = true

    if Request.ServerVariables("AUTH_TYPE") = "Basic"
    Req.Credentials = new System.Net.NetworkCredential(Request.ServerVariables("AUTH_USER"),Request.ServerVariables("AUTH_PASSWORD"))
    Req.Credentials = CredentialCache.DefaultCredentials
    ' Should impersonate the user in case of NTLM, shouldn't it???
    end if

    dim Resp as HttpWebResponse = DirectCast(req.GetResponse(),HttpWebResponse)
    dim Reader as StreamReader

    Reader = new StreamReader(Resp.GetResponseStream())

    while Reader.Peek() > -1
    strLine = Reader.ReadLine()
    end while


    The included thread should impersonate the logged-on user (NTLM or Basic).

    What did I do wrong?

    Thomas Mueller-Lynch, Feb 6, 2004
    1. Advertisements

  2. Thomas Mueller-Lynch

    Paul Glavich Guest

    At a guess, you are trying to do a "double hop" in that, you have used
    windows auth/NTLM to logon to your web app, then that same security token to
    go to another web site on another machine. Using NTLM, you cannot
    impersonate a user, then use that impersonation to authenticate to another
    machine (this is the double hop). Basic works because the credentials are
    propagated in clear text as part of the Http header. NTLM used a security
    token and cannot propagate the same token and be valid.

    Kerberos can do it, but you still need to mark the user account as
    "Delegateable". (Win2000+)
    - Paul Glavich

    return a secure web-page) returns the http status code 401.
    Paul Glavich, Feb 9, 2004
    1. Advertisements

  3. Thomas Mueller-Lynch

    Paul Glavich Guest

    It may still be suffering the "double hop" syndrome if it thinks that the
    page you are trying to access (even though its on the same machine) is on
    another machine. when you specify the "host" part of the URL is it as you
    specified below (ie. https://server/....) or does it contain periods (eg.

    Also, try it without using SSL (ie. http://server/....) to see what happens.
    Paul Glavich, Feb 10, 2004
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.