ProK's Blog: Apache Server Configuration (CentOS/Redhat)

What is Apache ?

Apache is the most popular web server on the internet. It is used to serve more than half of all active websites on the globe. It is an open source web application program for deploying web servers. Apache is developed and maintained by an open community of developers under the Apache Software Foundation. Most commonly used on a UNIX-like (usually Linux), the software is available for a variety of operating system besides UNIX, including Microsoft Windows.

Installing Apache Server

Before starting the installation procedure, ensure that the host system must have a FQDN (Fully Qualified Domain Name) hostname.

To check the existing hostname of the system, the following command is used:

Now, To Install the Apache Web Server with its documentation and a collection of their relative utilities, the following command is used:

By default in CentOS Operating System, Apache installed in the directory at “/etc/httpd”.

The default directory structure of the installed apache is follows:

There are a number of plain text files and sub-directories in /etc/httpd directory.

Here we have a need to familiar with the useful files & directories under this.

We are starting with one by one & proceed further to understand it thoroughly.

“logs” File:- This is the symbolic link for the Default Log file of the Apache Server which is at /var/www/httpd/ directory.

“modules” File:- This is the symbolic link for the Apache modules installed directory which is at /usr/lib64/httpd/modules/ location. Here, all the Apache Modules are stored.

“run” File:- This is the symbolic link for the Directory containing the process id file of the Apache Server which is at /var/run/httpd/ location.

“Conf” Directory: - This directory contains the main configuration files of the Apache Web Server like httpd.conf file.

Here, one thing that needs to be known is that some of the directives are enabled by default in the Apache Web Server configuration after installation in httpd.conf file.

These directives are described below:

ServerTokens: - This directive is responsible for sending information like OS type, configured modules etc. to the requesting clients. By default is is set to OS which replies back the results like:

ServerRoot: - This directive tells us the location of directory where server keeps all the configurations and log files. By default, the ServerRoot is as:

PidFile: - This directive tells us the location where server records its Process ID (PID).

Timeout: - This directive is defined in seconds. This is the amount of time server waits for the receipts and transmissions during the communication process.

IfModule: - This directive is used as the set of conditional containers which contains the details of a module. This container gets active only when the specified module gets loaded.

The example of this directive is as below:-

Listen: - This directive used to define the specific port and IP on which the server accept the requests. The example format of this directive is as below:-

Include: - This directive is responsible for including the directory containing configuration files.

Virtual Host: - Apache Server can host multiple websites on a single server. This task can be achieved by creating multiple Virtual Hosts or Vhosts. The configuration file for these Vhosts varies depending upon the different Linux operating systems.

Types of Virtual Host: - There are two types of Vhost configuration.

Name Based Virtual Host: - Name Based Virtual hosting is used for hosting multiple websites on single IP address.

An example of Name Based Virtual Hosting is:

IP Based Virtual Host: - IP Based Virtual Hosting is used for hosting multiple websites on multiple different IP’s.

An example of IP Based Virtual Hosting is:

Here, one important thing to know is that the vhost includes some list of directives that are used for hosting a website. The detailed explanation of these directives is as follows.

ServerAdmin: - This directive contains the administrative email id of the domain.

ServerName: - This directive contains the Domain name or Server hostname.

DocumentRoot: - This directive is used to point the directory of the domain where the related web content files of the domain is stored.

ErrorLog: - This directive contains the path of the log file where the error logs are stored.

Here, we see an example of vhost working over http as:

Apache Web Server Configuration over SSL

In this section, we will see the configuration needed for Securing the Apache Web Server.

Here we need to understand that the Virtual host contains many directives which are used for running the website on SSL. We will look on some of them now.

SSLEngine: - This directive is used to enable or disable SSL for the particular Vhost or Domain. It value can be On or Off.

SSLCertificateFile: - This directive contains the exact path of the certificate file of the domain and binds it with the domain too.

SSLCertificateKey: - This directive contains the exact path of the certificate key of the included certificate and binds it with the domain.

An example of vhost using SSL configuration to work over https connection is as follows:

Self-Signed Certificate:- Here we need to discuss one more thing related to SSL as sometimes, if a user wants to use self signed certificate for SSL connections so the following steps needs to be follow to generate the self signed certificate.

Step 1 :- First install or upgrade the package called “openSSL”.

Step 2:- Now, create a Self-Signed SSL Certificate. First, let's create a new directory where we

can store the private key and certificate.

Generate a new certificate and a private key to protect it.

Openssl req –x509 –nodes –days 365 –newkey rsa:2048 –keyout /etc/httpd/ssl/apache.key –out /etc/httpd/ssl/apache.crt

Following things need to understand on the above command:

· The Days flag specifies how long the certificate should remain valid. In the example, the

certificate will last for one year (365 Days).

· The keyout flag specifies the path to our generated key.

· The out flag specifies the path to our generated certificate.

During the execution of the command, some parameters will ask to fill like Country Name, State, Organization Name, etc. So, you should fill the desired parameters as asked.

Step 3:- Now, set the file permissions to protect your private key and certificate.

Step 4:- Now, these self signed certificates can be used to run the domain or server over https

Connection. An example of Virtual host of such SSL enabled domain is as below:

Apache Log Format

In this section, we will see the things related to the Apache Log Format. Apache logs provide detailed information that helps to detect common issues with apache server.

Here we use, mod_log_config module in order to enable the access log.

There are total of three directives available in Apache Config file with relation to the logs.

They are as follows:

TransferLog: Creating a log file.

LogFormat: Specifying a custom format.

CustomLog: Creating and formatting a log file.

TransferLog directive is available in the apache configuration file and it rotates virtual host log files as per set parameters.

Apache Web Server Hardening

Hardening of our web server is very important it means allowing others to see only the intended information & protecting our web server data and restricting their access.

These are common things that enhance our Apache Web Servers Security.

1. Hiding Apache version and OS information:

Apache displays its version and the name of the operating system in errors. It is shows as:

Apache/2.2.3 (CentOS) Server at 1.2.3.4 at Port 80

In order to prevent Apache web server to display this information, there are some directives which needs to be set as “off”. There is an option called “server signature” is available in the Apache Configuration file. By default, it is “on” so here we need to set it as “off” in httpd.conf file.

Also set “ServerTokens Prod” Directive which actually tells that the web server to return only apache and suppress the OS major and minor version.

2. Restricting Access to files outside the web root directory:

In this step we are trying to restrict the access of the files that are placed outside the web server root directory. For this, configuration needs to be done in httpd.conf file as:

Once the Access of the files outside to the web root directory get restricted, any visitor will not be able to access any file located on any other folder on your web server, they will get 404 return code.

3. Disable Directory Listing

Sometimes, the document root entry of the domain or server does not have any index file; by default the apache web server shows the list of all the directories present in the document root. In order to block or hide the content of the directory, feature could be turn off for a specific directory through “options directive” available in the Apache configuration file.

Integration with PHP module:-

In this section, we will see the integration of the Apache Server with PHP module. In order to run the PHP files over the server, we need to follow the below steps.

Step 1:- First, Install the php module packages from repository.

Need to select “Agree” for the installation during the above command execution and PHP will be installed on your Droplet.

Step 2:- Once the above command works, you should just Restart or Reload the Apache Service.

Step 3:- Add a new entry in the Virtual host file of the domain to which the php files need to be run.

Then the new Virtual host may looks like as below:

Step 3:- At last, we need to create a Test file in the root folder of the Domain and then check the file by opening it on to the Web Browser.

Virtual Hosting :-

Virtual hosting is a method for hosting multiple websites (domains) on a single server. You can host multiple websites on a single machine with a single IP using virtual hosting. All domains on that server will be sharing a single IP. Virtual hosting is very useful in shared web hosting environments, where hundreds of websites are hosted on a single server. All of the Virtual Host configurations for the different websites are created or stored in the /etc/httpd/con.d directory on Centos/Redhat.

Types of Virtual Hosting :-

Name based Virtual Hosting:- It is the type of virtual hosting which is defined on the basis of domain name. i.e. single ip is used to host multiple websites on a single web server. Let's create a virtual host file for the website www.example1.com.

First, let’s create a directory structure of the website www.example1.com

Add the following content to the index.html file.

After that, lets create a virtualhost configuration file for a website www.example1.com

Add the following content.

Save and close the file when you are finished.

Similarly, let’s create a directory structure of the website www.example2.com

Add the following content to the index.html file.

After that, let’s create another virtual host file for the website www.example2.com.

Add the following content.

In this way, the two Virtual host files are created for two domains.
Now restart the apache service.

Now edit the hosts file of the web server and add the entries of these two domain names as shown below:

After successful restart of apache service, open the domain name example1.com or example2.com on browser.

IP Based Virtual Hosting :- It is the type of virtual hosting which is defined on the basis of dedicated IP address. i.e. each website is assigned with a dedicated IP address. Let's create a virtual host file for the website www.example3.com.