Hypertext transfer protocol ( HTTP ) Apache Server

Apache is the most popular, secure, robust, reliable and powerful web server. Apache is used by more websites than all other web servers combined. RHEL6 includes Apache version 2.2

RHCE6 Exam objectives covered in this article

  • HTTP/HTTPS
  • Configure a virtual host.
  • Configure private directories.
  • Deploy a basic CGI application.
  • Configure group-managed content.

Installation of Apache  Two packages are required for Apache server

  • httpd
  • mod_ssl
  • elinks
httpd package install Apache web server.
mod_ssl is the additional package which required to create secure websites
elinks is the additional package for text based web browser.

If you have yum repository configured use following command to install Apache web server with additional package
 
# yum install –y httpd mod_ssl
yum-httpd
 
# yum install elinks
yum-elinks
Or you can do it in more simpler way by using groupinsatall. With following command you can install mandatory and all default packages.
 
# yum groupinstall "Web Server"
yum-groupinstall-httpd

If yum repository is not configured use rpm command to install necessary RPM. Mount installation disk of RHEL6 in media folder and move in Packages folder.
cd-media-packages

Run following command to install httpd
#rpm -ivh httpd* --nodeps --force
rpm-httpd

Run following command to install mod_ssl
#rpm -ivh mod_ssl* --nodeps --force
rpm-mod-ssl

Run following command to install elinks
#rpm -ivh elinks* --nodeps --force
rpm-elink

Verify that the packages were installed correctly
verfiy-rpm

Run following command to start service when the system boots
chkconfig-httpd-on

Start httpd service
arp-scok-add-fail

httpd service requires at least one active network connection, if it does not detect any active connection it will throw following message
Starting httpd: httpd: apr_sockaddr_info_get() failed for Server

httpd service try to resolve system IP with domain name. It will throw following error, If it fails to resolve.
httpd: Could not reliably determine the server's fully qualified domain name, using 127.0.0.1 for ServerName

In real world DNS Server are used to bind IP address with domain name. In LAB environment where we have limited systems , we can also use hosts file for this purpose.
Open /etc/sysconfig/network
etc-sysconfig-network

Change hostname to Server.example.com and save the file
sysconfig-entry

Reboot the system
reboot

Verify that hostname is changed
ipaddress-hostname-server

Before we update hosts file on server also verify the hostname and ip address of linuxclient
ipaddress-hostname-client

Now on server open /etc/hosts file
etc-hosts

Add entry for server and linuxclient system and save the file
hosts-entry

Verify the network card status
service-network-status

Now restart the httpd service
service-httpd-restart

Default versions of httpd create a generic web server service which is sufficient for most basic operations. Once httpd service is running start web browser and enter a URL http://localhost
apache-test-page-server

Same testing can be done form text based web browser ,If GUI is unavailable.
# elinks 127.0.0.1
elinks-localhost
We got Apache test page which confirm successful Apache configuration.
apache-test-page-command-line
Exit from the ELinks browser. Press Q, and when the Exit ELinks text menu appears, press Y to exit Elinks.

We have successfully installed Apache Web Server. So far its a generic web server service, to make it a regular and a secure web server, we need to configure it.

IPTABLES Firewall rules for web Server

Default installation of Apache web server use port 80 for HTTP traffic and 443 for HTTPS traffic.

You can create custom iptables rule to limit access to one or more networks or systems. For example following rules allows access to every computers on 192.168.1.0 network except one with IP address 192.168.1.25 over port 80.

-A INPUT -m state --state NEW -m tcp -p tcp -s 192.168.1.25 --dport 80 -j REJECT 
-A INPUT -m state --state NEW -m tcp -p tcp -s 192.168.1.0/24 --dport 80 -j ACCEPT
 
We have a well written article for IPTABLES firewall, use that to create custom firewall rules for web server. For this article create rules to allow all traffic on port 80 and 443.

#iptables -A INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT 
#iptables -A INPUT -m state --state NEW -m tcp -p tcp --dport 443 -j ACCEPT
 
iptables-httpd-rules

Save the firewall rules you have just created and restart the iptables service
# service iptables save 
# service iptables restart
iptables-save-restart
Until you change the value of DocumentRoot directive in httpd.conf file , Apache looks for web pages in default location /var/www/html directory.

To get your web server up and running, all you need to do is to transfer the web pages or websites in /var/www/html directory.

We will make two websites for testing. RHCE exam does not test your ability to make websites. Its only test your ability to configure and run web server. You can use most simple html web page for testing.

Make two directories mysite1 and mysite2 in /var/www/html folder
mkdir-mysite

Make a sample html page in both directories
cat-index-htm
Our sample websites are ready for use.

 

Configure SELinux for web server

Use following command to check all associated SELinux Booleans with httpd
getsebool-httpd

Most of these options are self explained and relate to interactions with other services. for example httpd_enable_ftp_server allow Apache to act as an FTP server, which is out of scope for this article.
getsebool-httpd-list

Default enabled SELinux options
BooleansDescriptions
httpd_builtin_scriptingUsed to provide permission for php content
httpd_dbus_avahiSupports access from HTTP services
httpd_enable_cgiAllows HTTP services to execute GCI scripts
httpd_tty_commEnables communication with controlling terminals
httpd_unifiedSupports read/write/execute access by httpd_t files
httpd_enable_homedirs supports access to files from user home directories, default value is off. 

We will enable it later in this article. Default enabled options are sufficient to provide basic web services , you do not need to make any changes. But you need to configure SELinux contexts, user context is system_u and the type is http_sys_content_t.
Check the current context of the files
#ls -Z /var/www 
#ls -Z /var/www/html
ls-z

We need to set context of any newly created file or directory for the web server user to be able to access it.

Use the chcon command to change the context
#chcon -R -u system_u /var/www/html 
#chcon -R -t httpd_sys_content_t /var/www/html/

Verify that all the context fields have been changed correctly
#ls -Z /var/www/html
chcon
Test these websites form linuxclient system [make sure client system have elinks rpm installed]

elinks 192.168.1.1/mystie1/index.htm
start-elinks

Verify the site
elink-test

Close elinks
eixt-from-elink

On window client open browser and type 192.168.1.1/mysite2/index.htm
internet-explore

We have set up Apache web server with default configuration.
Back up the default httpd.conf file on a safe location.
mkdir-backup

Open the /etc/httpd/conf/httpd.conf
vi-httpd-conf

This is the main configuration file for httpd web service and completely usable right out of the box for generic web service.

This file is grouped in three sections and each section is well commented
  • Global environment directives that control the whole operation of Apache server process.
  • Directives that define the parameters of the main or default server, which responds to requests that are not handled by a virtual host. These directives also provide default values for the settings of all virtual hosts.
  • Settings for virtual hosts, which allow Web requests to be sent to different IP addresses or hostnames and have them handled by the same Apache server process.

To make navigation easier, turn on line number ESC Key + : +set nu + Enter Key
set-nu

Host-Based Security

If server have multiple IP address, you can limit the IP address and port on which the server can listen for incoming connection. By default server listen on port 80, but can be update as well.
default-listen

For example to limit server only to listen on IP address 192.168.1.1 with port 80 Set Listen Directive
Listen 192.168.1.1:80
listen-changed
Now Server will listen only on the 192.168.1.1 IP address on port 80 for incoming requests.

Apache also let you configure the hosts which should be allow to access to web server. 

<Directory> section allow you to specify the hosts base security.
ValueExampleDescriptions
Allow from all
Default value, allow access from all hosts
Allow from [IP Address]Allow from 192.168.1.10To allow only a specific IP or host
Allow from [Host name]Allow from linuxclientTo allow only specific host
Allow from [Network]Allow from .example.comTo allow only example.com network
Allow from [Network]192.168.1.0/24
192.168.1.0/255.255.255.0
To allow only from 192.168.1.0 network
Deny from all
Deny access from all hosts
Deny from [IP Address]Deny from 192.168.1.10To Deny only a specific IP or host
Deny from [Host name]Deny from linuxclientTo deny only specific host
Deny from [Network]Deny from .example.comTo deny only example.com network
Deny from [Network]192.168.1.0/24
192.168.1.0/255.255.255.0
To deny only from 192.168.1.0 network
For exam remember
  • If DNS service is unreliable use IP address.
  • When specify domain name to allow or deny from, make sure you include the leading dot[.]
  • When specify a subnet, there is no ending dot[.] at last octet.
  • Order play the most important role, when set allow or deny access.
  • If you set Order allow, deny Only those host names or IP addresses associated with allow directive are allowed access. All remaining hosts or IP address would be denied.
  • If you set Order deny, allow Only those host names or IP addresses associated with deny directive are denied access. All remaining hosts or IP address would be allowed.
Default value is Allow from all
default-allow-from-entry
In our LAB setup we have two clients linuxclient [192.168.1.10], and windowclient [192.168.1.20]. Lets allow access only to linuxclient system.
allow-from-entry

Save the file and restart the httpd service
httpd-service-restart

Try to access same websites again from both client systems. This time linuxclient system would be able to access web server as usual, but on windowsystem you will be denied
windowclient-error

 

User-Based Security

User based authentication provides a way to allow only certain users or group to access web server.

In exam you can use following options to configure user based authentication.
OptionsDescriptions
AuthTypeDefines the authentication method
AuthNameComment for the users
AuthUserFileFile used to define username and password
AuthGroupFileFile used to define groups
RequireSpecifies the users or groups that can log in

Open httpd.conf file again
vi-httpd-conf


In last practice we have restricted all hosts except one
allow-from-entry

Before we do this exercise lets allow all hosts to access the web server.
default-allow-from-entry

In < directory > section add following and save the file
AuthType Basic
AuthName “Password Restricted Area”
AuthUserFile /etc/httpd/userauthfile
Require user rhceuser01
require-user1

Use htpasswd command to create a userauthfile, that will be holds user accounts.
# htpasswd -cm /etc/httpd/userauthfile rhceuser01
useradd-rhceuser01

-c Create new file and populates it with first user and password.
-m Passwords will be encrypted in MD5 before saving

Do not use -c options for creating subsequent users, otherwise it will completely override the file. Use -c option only first time for first user, from second users do not use -c option.

Restart the web server
service-httpd-restart

Try again to access same sites from client, this time it will ask for user name and password
ask-for-pass

If you cancel or use wrong user name and password, access would be denied
auth-require

Use correct user name and password
type-pass

Upon successful authentication access would be granted
sucess-get

Secure web server with .htaccess file

In previous exercise we have secured entire sites. However in real life you want to allow certain parts of site publicly accessible, while other by only authenticated users. For this we will use .htaccess file.

Open /etc/httpd/conf/httpd.conf file again
vi-httpd-conf

Change AllowOverride directive value to authconfig
allow-override-none

In previous example we did user base authentication

Remove that and save the file
allow-override-authconfig

Make a directory and file under mysite1

mkdir /var/www/html/mysite1/salary
mkdir-salary
Suppose that salary folder contains the salary sheet of employees and we want to allow only hr group to access it.

Create a .htaccess file in the salary folder
#vi /var/www/html/mysite1/salary/.htaccess
vi-htaccess

Add followings and save the file
AuthType Basic
AuthName “Password Restricted Area”
AuthGroupFile /etc/httpd/rhcegroupfile
Require group hr
htaccess-entry
Now only users from hr group, defined in /etc/httpd/rhcegroupfile can assess this.

Create few more accounts
useradd-hruser

Create rhcegroupfile, this file will hold entry for groups
vi-rhcegroup

Add user accounts in hr group and save file
rhcegroup-entry

Update the SELinux context of .htaccess file
chcon-htaccess

Restart the web server
httpd-service-restart

Try again to access site for client, access to other parts of site are allowed except salary
mysite-homepage

To access salary folder you need to provide user name and password
htaccess-ask-pass

Upon successful authentication access would be granted
salary-sheet-htm

Configure public_html folder in user home directory

httpd.conf file includes a commented directive UserDir public_html just under the default UserDir disable , when it's enabled, it allows users to browse and access the public_html directory within their home folder.

Open /etc/httpd/conf/httpd.conf file
vi-httpd-conf

Comment the default directive
userdir-disable

Uncomment the UserDir public_html directive and save the file
userdir-public-html

Now anyone will have access to web pages that a user puts in his ~/public_html directory. This option can be useful if you want each user to share files over the Web. For this option you need to make users home directory executable for world. You also need to make public_html readable and executable. By default this option is disable because this requires a bit of security compromise. So unless you need to be able to share content out of a users home directory, do not enable this option. If you have to enable it in real world, take all caution in setting up this option.

Create a new normal user
useradd-rh-user1


Make public_html folder under his home folder and create a test file in public_html folder
mkdir-public-html


Change file permission
chmod-public-html


Enable SELinux Boolean associated with home directory
set-bool-http-enable-homedir

Restart the web server
httpd-service-restart

Access it from client system by typing 192.168.1.1/~rh_user1/index.htm
access-home-dir

How to create virtual hosts

Virtual host feature of Apache allows you to define multiple web sites on single IP address. For Virtual hosts configuration following options are required
NameVirtualHostHostname or IP address of the virtual host
ServerAdminEmail address of the webmaster
DocumentRootLocation of the directory, which holds virtual host files
ServerNameURL of the virtual host
ErrorLogLocation for the error log
CustomLogLocation for a custom log

Suppose that we want to host a new website example.com in virtual host.

Make new directory which will hold our new site
mkdir-webdata

Make a sample file in new site
mkdir-webdata-cat-sample-file

Update SELinux context
chchon-webdata

Open main configuration file again
vi-httpd-conf

By default NameVirtualHost directive is disabled
namehost-commented

Enable it
namehost-uncomment

At the end of file in virtual host section add following lines and save the file
<VirtualHost *:80>
ServerAdmin webmaster@example.com
DocumentRoot /webdata/example.com
ServerName example.com
ErrorLog logs/example.com-error_log
CustomLog logs/example.com-access_log common
</VirtualHost>
virtual-host-entry
If you have DNS server configured update the zone files, otherwise update the hosts files . 
On server open the /etc/hosts file
etc-hosts

Add entry for new virtual host site and save the file
host-entry-server

Restart the httpd service
httpd-service-restart

On linuxclient system you also need to update the hosts file before testing. Open hosts file
vi-etc-host-linuxclient


Add entry for new virtual host site and save the file
hosts-entry-linuxclient

Now use elinks command to browse new site
elink-example-com

Test page confirms that we have successfully configured virtual host.
virtual-host-testing-client

How to deploy a basic CGI application

In this section we will deploy a basic CGI application. RHCE exam objective "Deploy a basic CGI application", does not test your programming skills, so you need not to worry about programming language. You only need to know the method.

Create a directory to hold your web application:
# mkdir /var/www/webapp
mkdir-webapp

Make a new sample perl file
vi-hello-pl

Add following in file and save the file. [This will make a sample perl script to print hello, world. Based on Apache manual]
#!/usr/bin/perl
print "Content-type: text/html\n\n";
print "Hello, World!";
hello-pl-entry

Update file permission and SELinux context
chmod-chcon-webapp

Open configuration file
vi-httpd-conf 

At end of file add following and save the file
ScriptAlias /webapp "/var/www/webapp"
<Directory "/var/www/webapp/">
Options ExecCGI FollowSymLinks
Order allow,deny
Allow from all
</Directory>
cgi-bin-entry

Restart the web server
httpd-service-restart

On client now you can access this CGI application.
webapp-testing

 

Configure secure virtual host

In this last section of tutorial we will configure a secure virtual host with self signed certificate. Make a directory to host our secure site
mkdir-secure-host1

Make a sample index.htm file in it
cat-secure-index

Change file permission and Update SELinux context
chcon-secure

Open main configuration file /etc/httpd/conf.d/ssl.conf
vi-ssl-conf

Make sure Listen Directive remain on
listen-443

Add new Directive NameVirtualHost *:443 just above the <VirtualHost _default_:443> and replace _default_ with * in <VirtualHost _default_:443> tag.Uncomment the DocumentRoot and ServerName directives.
namevirtualhost
 Change the value of directives and save the file

ssl-uncomment-documentroot
Move in certificate holder directory /etc/pki/tls/certs and use genkey command to generate new certificate and private key for secure site
genkey

Select Next and press enter on Keypair generation window
keypair-next

During the exam always choose minimum available key size. Even smaller key size can take up to several minutes and in exam every minute is precious. Select 512 and move to Next tab and press enter
choose-key-size

Wait while key generates
genrating-key

Select No and press enter on Generate CSR window
genrate-crs

Keep default details and select Next and press Enter
details-for-certificate

We have sucessfully created the certificate ,now we to update the hosts file on server
host1-host-entry


Restart the httpd service
httpd-service-restart

On client updated the hosts file
linuxclient-host1-entry-host-file


To test secure site open the web browser and type https://host1.example.com/index.htm in URL
untursted-connection

You will see Untrusted connection screen Unless you purchase an actual certificate from a certificate authority (CA) such as VeriSign and Thawte. For RHCE exam we do not need third party certificate, as we have self signed certificate. Click on I Understand the Risks and Click on Add Exception
add-exception


Click on confirm security exception
confirm-security

Test page confirms that we have successfully configured the secure virtual host
secure-test-page
To test secure sites form elinks test based browser we need to comment two standard directives


open /etc/elinks.conf file
linuxclient-vi-elinks-conf

You need to comment these directives
linuxclient-elinks-conf-uncommented

Comment them and save the file
linuxclient-elinks-conf-commented


Now you can access secure sites form elinks as well
linuxclient-elinks-test-host-index

Test page confirms our secure web hosting
linuxclient-elinks-test-page

When you restarts the httpd service, restart process actually stop the service from running before starting it again. This process hardly take few seconds that is ok for exam purpose but in real life where thousands of people are hitting your site, you can't afford any outage even its in seconds. In that situation you can use reload option which allows the main configuration to reread without the actually bringing service down.
#service httpd reload

One more important option which should know for real world is graceful
#service httpd graceful
 
This option reread the new configuration file without disconnecting any currently connected users. Only drawback of this option is that the currently active connections use the old configuration file until they terminate their connection and reconnect.
One more cool options is configtest, when used , service parses the main config file for any errors and reports back if something is found. It's your helping hand during the exam to detect any syntax errors in configuration file.
 
# service httpd configtest 
Syntax OK 

If this command detect any syntax related error it return with that, otherwise it return with Syntax ok.

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