title: symfony2 get firewall name on login page
body: <p>I'd want to use a login page to access different firewalls, so I need to get information about the firewall I'm logging in.
  In my controller I'd use</p>
  
  <pre><code>$this-&gt;container-&gt;get('security.context')-&gt;getToken()-&gt;getProviderKey()
  </code></pre>
  
  <p>but as an anonymous user I don't have access to getProviderKey method.
  I could also parse</p>
  
  <pre><code>_security.xxx.target_path 
  </code></pre>
  
  <p>to get xxx firewall but I'm looking for a more general solution if it exists at all.<br />
  Any idea?</p>