Mod_Security .. Intro

Mod_Security 2.5

Need for a Webserver Security Module

It is pretty difficult to secure application softwares. Common targets are Open Source software like PHPNuke. An attacker can easily find out vulnerabilities in the code.

If your application is vulnerable to SQL injection, invoking the URL above may very well delete all user data from your application.
You can use mod_rewrite to avoid this attack. it is very easy to detect the words drop and table, and then redirect the client away from the original URL. A determined attacker could simply invoke the same URL as above but use the POST method instead of GET. Since POST variables are not considered in the normal processing of most modules, the attack would go through.

To prevent the drop table SQL injection attack with mod_security, add the following to your Apache configuration:

SecFilter drop[[:space:]]table

The only parameter is a regular expression to be applied to the incoming request. This seems achievable with mod_rewrite, but the difference here is that mod_security will detect and prevent attacks performed using either GET or POST.

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Suhosin ..

What is Suhosin?

Suhosin is an advanced protection system for PHP installations.

Designed to protect servers and users from known and unknown flaws in PHP applications and the PHP core.

Suhosin comes in two independent parts:-

The first part is a small patch against the PHP core, that implements a few low-level protections against bufferoverflows or format string vulnerabilities .

The second part is a powerful PHP extension that implements all the other protections.

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Package Management(Yum and RPM)?

RPM Package Manager (RPM)

The RPM Package Manager (RPM) is a powerful command line driven package management system capable of installing, uninstalling, verifying, querying, and updating computer software packages. Each software package consists of an archive of files along with information about the package like its version, a description, and the like. There is also a library API, permitting advanced developers to manage such transactions from programming languages such as C or Python.

RPM is free software, released under the GNU GPL.

RPM is a core component of many Linux distributions, such as Red Hat Enterprise Linux, the Fedora Project, SUSE Linux Enterprise, openSUSE, CentOS, Mandriva Linux, and many others.

It is also used on many other operating systems as well, and the RPM format is part of the Linux Standard Base.
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Brief intro about mod_userdir | open_basedir

mod_userdir

It is an Apache module that allows you to create a separate website for each user on a server. These sites can all be accessed by going to,

http://servername.com/~username

Eg:- http://example.com/~user/

The module is installed on most Apache setups by default, but isnt necessarily always enabled. Most mass-hosted cPanel servers make extensive use of it for a variety of reasons.

Apaches mod_userdir allows users to view their sites by entering a tilde(~) and their username as the URL on a specific host. For example http://test.cpanel.net/~test will bring up the user Tests domain

How To Enable

1. To access the Server Setup Menu, click on Server Setup, on the main screen of your WebHost Manager interface. Then, click on Tweak Security.

2. Click on Configure in the mod_userdir Tweak section.

3. Click on the Checkbox next to Enable mod_userdir Protection to enable mod_userdir Protection.

4. Click on a checkbox next to a domains name to allow them to access their domain using ~username, if necessary.

5. Enter the name of any user you wish to be able access the domain using ~username, other than the domains owner, in the blank field next to the domains name, if necessary.

6. Click on Save.

Disadvantage

The disadvantage of this feature is that any bandwidth usage used by the site will be put on the domain it is accessed under .

Mod_userdir protection prevents access to a domain through domain.com/~user. You may however want to disable it on specific virtual hosts (generally shared SSL hosts).

open_basedir

Enable open_basedir

Set open_basedir to only allow access to required portions of the filesystem, like your web sites documents and any shared libraries.

You can set open_basedir in the php.ini file:

; Set open_basedir to the

open_basedir = /var/www/foo.bar/:/usr/local/php/

The setting can also be applied in apaches httpd.conf file, or an .htaccess file:

# Set open_basedir to a safe location

php_value open_basedir /var/www/foo.bar/:/usr/local/php

WHM

Steps :

1. To access the PHP open_basedir Tweak feature, click on Security, on the main screen of your WebHost Manager interface.

2. Then click on Security Center.

3. Then click on PHP open_basedir Tweak.

4. Click on Configure in the PHPs open_basedir section.

5. Click on the check box next to Enable PHP open_basedir Protection to enable Enable PHP open_basedir Protection.

6. Click on a check box next to a domain name to allow them to open files outside of their home directory with PHP, if necessary.

7. Click on Save.
Plesk : If you’re using Plesk hosting control panel, you may need to manually edit Apache configuration file of vhost.conf and vhost_ssl.conf, and add in or edit the following php_admin_value open_basedir lines to the following:

<Directory /full/path/to/the/directory/httpdocs>

php_admin_value open_basedir none

</Directory>

<Directory /full/path/to/the/directory/httpdocs>

php_admin_value open_basedir /full/path/to/dir:/full/path/to/directory/httpdocs:/tmp

</Directory>
Note: For SSL hosts in the vhost_ssl.conf file, the Directory path will end with httpsdocs instead of httpdocs

Disable Manually

Open up the httpd.conf file, and search for the lines that starts with the following characters:

php_admin_value open_basedir ..

Replace the whole line under the virtual host for the domain user account

php_admin_value open_basedir none.

Add Additional Directories
You can also opt to allow your PHP scripts to access additional directory instead without disabling the protection.For example, to add /new_directory to the allow list.

php_admin_value open_basedir /home/user_account/:/usr/lib/php:/usr/local/lib/php:/tmp

php_admin_value open_basedir /home/user_account/:/usr/lib/php:/usr/local/lib/php:/tmp:/new_directory

Restart the Apache after finished editing

Article Authored by Ajith KK

Author, Ajith KK, is a Systems Engineer with SupportPRO. Ajith specializes in L1 and L2 Linux/Windows administration. SupportPRO offers 24X7 technical support services to Web hosting companies and service providers.

If you require help, contact SupportPRO Server Admin

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