Use server_hostname (#496)

Author: slozier

Src/IronPython.Modules/_socket.cs

@@ -2438,6 +2438,7 @@ public class ssl {
             private readonly CodeContext _context;
             private readonly RemoteCertificateValidationCallback _callback;
             private Exception _validationFailure;
+            internal string _serverHostName;
 
             public ssl(CodeContext context, PythonSocket.socket sock, string keyfile=null, string certfile=null, X509Certificate2Collection certs=null) {
                 _context = context;
@@ -2640,7 +2641,7 @@ public void do_handshake() {
                         if (_cert != null) {
                             collection.Add(_cert);
                         }
-                        _sslStream.AuthenticateAsClient(_socket._hostName, collection, enabledSslProtocols, false);
+                        _sslStream.AuthenticateAsClient(_serverHostName ?? _socket._hostName, collection, enabledSslProtocols, false);
                     }
                 } catch (AuthenticationException e) {
                     ((IDisposable)_socket._socket).Dispose();

Src/IronPython.Modules/_ssl.cs

@@ -197,7 +197,7 @@ public void load_verify_locations(CodeContext context, [DefaultParameterValue(nu
             }
 
             public object _wrap_socket(CodeContext context, [DefaultParameterValue(null)] PythonSocket.socket sock, [DefaultParameterValue(false)] bool server_side, [DefaultParameterValue(null)] string server_hostname, [DefaultParameterValue(null)] object ssl_sock) {
-                return new PythonSocket.ssl(context, sock, server_side, null, _cafile, verify_mode, protocol | options, null, _cert_store);
+                return new PythonSocket.ssl(context, sock, server_side, null, _cafile, verify_mode, protocol | options, null, _cert_store) { _serverHostName = server_hostname };
             }
         }