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Home :: Web Servers :: Apache

mod_security on ApachePublished: Thursday, November 10th, 2011 by Chris Ciufo

ModSecurity is a web application firewall for the Apache web server. In addition toproviding logging capabilities, ModSecurity can monitor the HTTP traffic in real timein order to detect attacks. ModSecurity also operates as a web intrusion detectiontool, allowing you to react to suspicious events that take place at your web systems.

Contents

Installing ModSecurityUbuntu / DebianCentOS / Fedora

OWASP ModSecurity Core Rule SetUbuntu / DebianCentOS / Fedora

Configuring ModSecurityUsing a Basic RulesetUsing Symbolic Links

More Information

Installing ModSecurityBefore you install ModSecurity, you'll want to have a LAMP stack set up on yourLinode. For instructions, see the LAMP Guides.

Ubuntu / Debian

To install ModSecurity on a Linode running Ubuntu or Debian, enter the followingcommands, one by one:

sudo apt-get install libxml2 libxml2-dev libxml2-utilssudo apt-get install libaprutil1 libaprutil1-devsudo apt-get install libapache-mod-security

ModSecurity is now installed on your Linode.

CentOS / Fedora

To install ModSecurity on a Linode running CentOS or Fedora, perform the followingsteps:

Install the GCC compiler and the dependancies by entering the followingcommands, one by one:

sudo yum install gcc makesudo yum install libxml2 libxml2-devel httpd-devel pcre-devel curl-devel

1.

You'll need to install mod_security from source as there is no maintained2.

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package CentOS or Fedora yet. Grab the mod_security package and install itby entering the following commands, one by one:

cd /usr/srcwget http://www.modsecurity.org/download/modsecurity-apache_2.6.2.tar.gztar xzf modsecurity-apache_2.6.2.tar.gzcd modsecurity-apache_2.6.2./configuremake installcp modsecurity.conf-recommended /etc/httpd/conf.d/modsecurity.conf

Now you'll need to modify your Apache configuration to load the ModSecuritymodule. Find the LoadModule section in httpd.conf and add this line to theend:

File: /etc/httpd/conf/httpd.conf

LoadModule security2_module modules/mod_security2.so

3.

Restart Apache by entering the following command:

sudo /etc/init.d/httpd restart

4.

ModSecurity is now installed on your Linode.

OWASP ModSecurity Core Rule SetFor a base configuration, we are going to use the OWASP core rule set. This sectionexplains how to download the latest tarball and move it into place on your Linode.

Ubuntu / Debian

To grab the latest tarball on a Linode running Ubuntu or Debian, enter the followingcommands, one by one:

cd /etc/apache2wget http://downloads.sourceforge.net/project/mod-security/modsecurity-crs/0-CURRENtar xzf modsecurity-crs_2.2.5.tar.gzmv modsecurity-crs_2.2.5 modsecurity-crscd modsecurity-crs

The OWASP core rule set is now in place on your Linode.

CentOS / Fedora

To grab the latest tarball on a Linode running CentOS or Fedora, enter the followingcommands, one by one:

cd /etc/httpd/confwget http://downloads.sourceforge.net/project/mod-security/modsecurity-crs/0-CURRENtar xzf modsecurity-crs_2.2.5.tar.gzmv modsecurity-crs_2.2.5 modsecurity-crscd modsecurity-crs

The OWASP core rule set is now in place on your Linode.

Configuring ModSecurity

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You'll want to use the modsecurity_10_crs_config, so let's copy that from theexample:

cp modsecurity_crs_10_config.conf.example modsecurity_crs_10_config.conf

There are five rules directories:

activated_rulesbase_rulesexperimental_rulesoptional_rulesslr_rules

NoteThe activated_rules directory will be empty in case you wantedto symlink the configuration files for the rules you wish to useinto that directory.

There are two ways to configure ModSecurity: use a basic ruleset, or use symboliclinks. The following sections explain how to use both methods.

Using a Basic Ruleset

If you want to get started with a basic ruleset and would rather not bother withsymbolically linking configuration files, perform the following steps:

Modify your httpd.conf file as shown below:

File: /etc/apache2/httpd.conf (Debian / Ubuntu)

<IfModule security2_module> Include modsecurity-crs/*.conf Include modsecurity-crs/base_rules/*.conf</IfModule>

File: /etc/httpd/conf/httpd.conf (CentOS / Fedora)

<IfModule security2_module> Include modsecurity-crs/*.conf Include modsecurity-crs/base_rules/*.conf</IfModule>

1.

In the modsecurity_crs_20_protocol_violations.conf file, rename theREQBODY_ERROR variable to REQBODY_PROCESSOR_ERROR.

2.

Restart Apache for the updates to take effect:

Debian / Ubuntu:

/etc/init.d/apache2 restart

CentOS / Fedora:

/etc/init.d/httpd restart

3.

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You have successfully configured ModSecurity.

Using Symbolic Links

If you would rather symbolically link those configuration files to the activated_rulesdirectory, perform the following steps:

Edit the Apache configuration file so IfModule looks like this:

File: /etc/apache2/httpd.conf (Debian / Ubuntu)

<IfModule security2_module> Include modsecurity-crs/modsecurity_crs_10_config.conf Include modsecurity-crs/activated_rules/*.conf</IfModule>

File: /etc/httpd/conf/httpd.conf (CentOS / Fedora)

<IfModule security2_module> Include modsecurity-crs/modsecurity_crs_10_config.conf Include modsecurity-crs/activated_rules/*.conf</IfModule>

1.

Create the symbolic links before restarting Apache. A few examples are shownbelow.

To copy all the base_rules over to activated_rules:

for f in `ls base_rules/` ; do ln -s /usr/local/apache/conf/crs

To copy the comment spam rules from the optional_rulesdirectory to the activated_rules directory:

for f in `ls optional_rules/ | grep comment_spam` ; do sudo ln

2.

Restart Apache for the updates to take effect:

Debian / Ubuntu:

/etc/init.d/apache2 restart

CentOS / Fedora:

/etc/init.d/httpd restart

3.

You have successfully configured ModSecurity.

More InformationYou may wish to consult the following resources for additional information on thistopic. While these are provided in the hope that they will be useful, please note thatwe cannot vouch for the accuracy or timeliness of externally hosted materials.

ModSecurity Home PageModSecurity WikiOWASP Home Page

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OWASP ModSecurity Core Rule Set Wiki

This guide is licensed under a Creative Commons Attribution-NoDerivs 3.0 United StatesLicense.

Last edited by Matthew Cone on Tuesday, August 14th, 2012 (r3011).

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