ASP.NET MVC Anti Forgery Token Insecure

Question

I can actually see the verification token key generated by MVC3 framework in plain text when making a request to the server without ssl.

This key is stored in a cookie called: _RequestVerificationToken_Lw__

In mixed security environment it is actually possible to see this token in plain text sent to the server on the initial request to the non ssl site. This token is also static for the duration of the user's session. Then what's the use of having this token when it can easily be stolen by an attacker, because the cookie gets thrown around in plain text.

Shouldn't this cookie be marked as secure and never to be sent across in plain text? Or at the very least be regenerated on every request such that the secure information doesn't leak out of the ssl channel?

I'm talking about this block in MVC 3 AntiForgeryWorker class

private string GetAntiForgeryTokenAndSetCookie(HttpContextBase httpContext, string salt, string domain, string path)
{
  string forgeryTokenName = AntiForgeryData.GetAntiForgeryTokenName(httpContext.Request.ApplicationPath);
  AntiForgeryData token = (AntiForgeryData) null;
  HttpCookie httpCookie = httpContext.Request.Cookies[forgeryTokenName];
  if (httpCookie != null)
  {
    try
    {
      token = this.Serializer.Deserialize(httpCookie.Value);
    }
    catch (HttpAntiForgeryException ex)
    {
    }
  }
  if (token == null)
  {
    token = AntiForgeryData.NewToken();
    string str = this.Serializer.Serialize(token);
    HttpCookie cookie = new HttpCookie(forgeryTokenName, str)
    {
      HttpOnly = true,
      Domain = domain
    };
    if (!string.IsNullOrEmpty(path))
      cookie.Path = path;
    httpContext.Response.Cookies.Set(cookie); //Ma, Why isn't this marked as "SECURE"
  }
  return this.Serializer.Serialize(new AntiForgeryData(token)
  {
    Salt = salt,
    Username = AntiForgeryData.GetUsername(httpContext.User)
  });
}

Answer 1

That's quite the inflammatory question title you have there.

The built-in MVC anti-forgery functionality is as secure as the application is configured to be. All cookies written to Response.Cookies will be automatically marked with the "secure" modifier if <httpCookies requireSSL="true" /> is set in Web.config (see MSDN docs). MVC's anti-forgery cookie also gets this behavior if this switch is set.

Combine this with other functionality like setting the HSTS header in your responses, and you're essentially providing a guarantee that the browser will never send sensitive data over plaintext channels.

Additionally, the anti-forgery system does allow storing custom data in the tokens, and you can receive a callback to verify the custom data when the token is validated. See AntiForgeryConfig.AdditionalDataProvider for more information.