CookieContainer does not store cookies for internationalized domain names

Question

I'm trying to perform authorization on a cyrillic domain using WebClient. Authorization goes through few stages with redirects between normal and punicode domains. The problem is HttpWebRequest can not store cookies in assigned CookieContaier if it was set by punycode domain. For example, this code will throw CookieException.

var cookie = new Cookie("test_cookie", "test_value", "/", ".xn----7sbcca6bi0ak9b0a6f.xn--p1ai");
var container = new CookieContainer().Add(cookie);

The problem is exacerbated by the fact that response that sets cookie redirects to another page, i.e. after WebClient.UploadValues(...) have been executed there's no cookie information in WebClient.ResponseHeaders.

Below is normal authorization process (using browser)

Method  Result  Received  Type       URL                                                        RedirectURL                                                Set-Cookie                                                                                                                                 
POST    302     1,18 K    text/html  http://xn----7sbcca6bi0ak9b0a6f.xn--p1ai/admin/login       http://xn----7sbcca6bi0ak9b0a6f.xn--p1ai/admin             sess_id=.......; expires=Mon, 06-Jun-2016 07:20:57 GMT; Max-Age=31536000; path=/; domain=.xn----7sbcca6bi0ak9b0a6f.xn--p1ai; httponly     
GET     302     722       text/html  http://xn----7sbcca6bi0ak9b0a6f.xn--p1ai/admin             /admin/orders                                                                                                                                                                                        
GET     200     200,00 K  text/html  http://xn----7sbcca6bi0ak9b0a6f.xn--p1ai/admin/orders                                                                                                                                                                                                            

Is there any workaround?

Answer 1

Are you sure the IDN is the problem?

The following code snippet (which is the same as yours, but with the second line split up to make it compile)

var cookie = new Cookie("test_cookie", "test_value", "/", ".xn----7sbcca6bi0ak9b0a6f.xn--p1ai");
var container = new CookieContainer();
container.Add(cookie);

container.GetCookies(new Uri("http://test.xn----7sbcca6bi0ak9b0a6f.xn--p1ai")).Dump();

does not throw a CookieException at all (run from LINQPad). Could the problem perhaps be in the name and/or value you are trying to set for the cookie? What is the exact message you get from the CookieException?