problems with DotNetOpenAuth OAuth2 Client for Google - asp.net-mvc

Question

I have an ASP.NET MVC 4 application.
Yesterday my users started to complain they cannot login using their Google accounts. After lots of googling I found this: DotNetOpenAuth.GoogleOAuth2. I followed the instructions.
I created Client ID for web applications in Google console.
In AuthConfig.RegisterAuth() I have:
var client = new DotNetOpenAuth.GoogleOAuth2.GoogleOAuth2Client(googleClientID, googleClientSecret);
var extraData = new Dictionary<string, object>();
OAuthWebSecurity.RegisterClient(client, "Google", extraData);
In AccountController, I have something like this:
public ActionResult ExternalLoginCallback(string returnUrl)
{
DotNetOpenAuth.GoogleOAuth2.GoogleOAuth2Client.RewriteRequest();
AuthenticationResult result = OAuthWebSecurity.VerifyAuthentication(Url.Action("ExternalLoginCallback", new { ReturnUrl = returnUrl }));
if (!result.IsSuccessful)
{
return RedirectToAction("ExternalLoginFailure");
}
if (OAuthWebSecurity.Login(result.Provider, result.ProviderUserId, createPersistentCookie: false))
{
// here I have some logic where is user sent when login was successfull
return RedirectToLocal(returnUrl);
}
if (User.Identity.IsAuthenticated)
{
// If the current user is logged in add the new account
OAuthWebSecurity.CreateOrUpdateAccount(result.Provider, result.ProviderUserId, User.Identity.Name);
return RedirectToLocal(returnUrl);
}
else
{
// User is new, ask for their desired membership name
string loginData = OAuthWebSecurity.SerializeProviderUserId(result.Provider, result.ProviderUserId);
// some logic
return View("ExternalLoginConfirmation", new RegisterExternalLoginModel { UserName = username, ExternalLoginData = loginData, EncryptedEmail = encryptedEmail });
}
}
I have two problems:
Before the change, the result.UserName contained the users email. Now it contains name. But I need email. Except for this, registration works fine.
My biggest problem - existing users cannot log in using their google account. The code goes to "// User is new, ask for their desired membership name" for them. The ProviderUserId I get now is different for the same email address.
Thanks a lot for any advice.

Answer 1

Can you configure this library to pass additional parameters to the Google authorization service? If so, you should pass 'openid.realm=$your_app_openid2_realm' (if your app was configured for OpenID2 before, it most likely asserted a 'realm' value in its requests, you should use the same value).
In this case, you'll receive two identifiers from Google. The new one (which is compatible with profile URLs and overall more Google APIs) and the old one (returned as openid_id).