Consume https REST API developed in C#

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Hi All,

We have done integrated our application with one third party. We are consuming their Rest API developed in Java from C# application.

They have disabled all the protocols in the server other than TSL1.2(i.e. SSL2, TSL1.0, TSL1.1)

When we call the Rest API we are getting the error. Please find below my code

What I have tried:

string response;
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls|SecurityProtocolType.Ssl3;
        ServicePointManager.ServerCertificateValidationCallback = delegate(object obj, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors) { return true; };
        WebClient client = new WebClient();
        string credentials;
      
        credentials = Convert.ToBase64String(Encoding.ASCII.GetBytes("gujarat_ws_client" + ":" + "guj@r@t_C|ient"));
        client.Headers.Add("Authorization", "Basic Z3VqYXJhdF93c19jbGllbnQ6Z3VqQHJAdF9DfGllbnQ=");                                             
        try
        {
            
            var strEaushadhiURI = "https://xxx.com/";

            System.Net.ServicePointManager.ServerCertificateValidationCallback = (object se, System.Security.Cryptography.X509Certificates.X509Certificate cert, System.Security.Cryptography.X509Certificates.X509Chain chain, System.Net.Security.SslPolicyErrors sslerror) => true;
            response = client.DownloadString(new Uri(strEaushadhiURI + "/AMH/" + txtVoucherNumber.Text.Trim()));
            System.Net.ServicePointManager.ServerCertificateValidationCallback = null;
            TextBox1.Text = response;
        }
        catch (Exception ex)
        {
            TextBox1.Text = ex.Message;
        }

But I am getting error :

The remote server returned an error: (401) Unauthorized.

Posted 30-Jul-18 3:40am

Suman Zalodiya

Updated 31-Jul-18 18:34pm

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Gerry Schmitz · Answer 1 · 2018-07-31T15:09:00

Solution 1

The "certificate" is to insure the server is "valid / secure"; it has nothing to do with your "authority" to gain access to said server.

You are simply not "signing in" properly; implying an "account and password" or security token is required for access.

Posted 31-Jul-18 15:09pm

Gerry Schmitz

Nima Shayesteh · Answer 2 · 2018-07-31T18:35:00

I had the same problem and it was because of my request headers.
I will put a sample code for you :

httpWReq.UserAgent = "Apache-HttpClient/4.2.1";
httpWReq.Accept = "text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2";
httpWReq.ContentType = "text/plain";
httpWReq.Headers.Add("Authorization", "Basic " + Convert.ToBase64String(authBytes));
httpWReq.Headers.Add("Signature", CanonicalReq);
httpWReq.Headers.Add("SignedHeaders", "host");
/* httpWReq.Headers.Add("content-Type", "text/plain")*/
//user agent
httpWReq.ProtocolVersion = HttpVersion.Version11;
httpWReq.Method = "GET";

All the best.