Check if httponly cookie exists in Javascript

Question

As the question says can you find out if a cookie exists within Javascript if it is a HttpOnly? I don't need to access the information inside of it, just know it has one.

A little more information on the situation is that there was originally a web server which used a cookie as an authentication token, and it was set to httponly as it was not used by the client so it added to the security.

However now there is a change needed where the client needs to know if it has the cookie (as the site can work without the user being logged in, but if they are logged in (the auth cookie would exist) the site needs to display certain things and hide others.

There are other security precautions in place on the web server so there is no harm in the scenario where the client has an incorrect auth cookie, but the site makes it look like they are logged in, as it would delete the cookie and reject the user.

Answer 1

You can indirectly check to see if it exists by trying to set it to a value with javascript if it can't be set, then the HTTP Only Cookie must be there (or the user is blocking cookies).

function doesHttpOnlyCookieExist(cookiename) {
  var d = new Date();
  d.setTime(d.getTime() + (1000));
  var expires = "expires=" + d.toUTCString();

  document.cookie = cookiename + "=new_value;path=/;" + expires;
  if (document.cookie.indexOf(cookiename + '=') == -1) {
    return true;
  } else {
    return false;
  }
}