Why Am I Getting 401 Unauthorized Response?

Question

I have the following C# code I'm trying to use to get a response from a url I can go to manually.

        static void Main(string[] args)
        {
            Uri theRequestUriString = new Uri("<<<my_url>>>");
            var request = WebRequest.Create(theRequestUriString);
            request.UseDefaultCredentials = true;
            WebProxy myproxy = new WebProxy("<<<my_proxy>>>:<<<my_port>>>", true);
            request.Proxy = myproxy;
            request.Timeout = Convert.ToInt32(TimeSpan.FromMinutes(5).TotalMilliseconds);
            request.Credentials = CredentialCache.DefaultCredentials;

            string textResponse;
            var resp = request.GetResponse();//*****401 error here*****
            using (var sr = new StreamReader(resp.GetResponseStream()))
            {
                textResponse = sr.ReadToEnd().Trim();
            }

        }

System.Net.WebException: 'The remote server returned an error: (401) Unauthorized.'

I can go there manually but get a 401 Unauthorized if I try to use this code. Shouldn't the CredentialCache take care of that? I'm using Visual Studio locally if that is not the case.

If the url is instead https://www.yahoo.com then this works just fine.

First rule of "*why isn't my http request working*" questions. Get it working in Postman first. Second rule, then use Ffiddler to work out the difference between postman and C# code — TheGeneral, Feb 02 '21 at 03:58
401 is a server response. Something about your request doesn't satisfy the server's requirements so it deems you not to be authorised. To further exapnd on why we can't just give you a solution: I could write a server application with something like this: `if (today == Friday && (priceOfCookiesAtStarBucks > 100 || weather == Rainy)) { return 401; }`. If you called my API, you would get a 401 response if those conditions were met. — ProgrammingLlama, Feb 02 '21 at 04:16
Cookies should never be so expensive but I really like the example. — Mark McGown, Feb 02 '21 at 04:58

score 0 · Answer 1 · answered Feb 02 '21 at 04:36

In your code

request.Credentials = CredentialCache.DefaultCredentials

means you are using NTLM for auth.

Windows authentication (formerly named NTLM, and also referred to as Windows NT Challenge/Response authentication) is a secure form of authentication because the user name and password are hashed before being sent across the network. When you enable Windows authentication, the client browser sends a strongly hashed version of the password in a cryptographic exchange with your Web server.

Why Am I Getting 401 Unauthorized Response?

1 Answers1