Secure Apache Web Server – Practical Guide
1 Introduction
The Web
Server is a crucial part of web-based applications. Apache Web Server is
often placed at the edge of the network hence it becomes one of the
most vulnerable services to attack. Having default configuration supply
many sensitive information which may help hacker to prepare for an
attack the web server.
The
majority of web application attacks are through XSS, Info Leakage,
Session Management and PHP Injection attacks which is due to weak
programming code and failure to sanitize web application infrastructure.
According to the security vendor Cenzic, 96% of tested applications have vulnerabilities. Below chart from Cenzic shows the vulnerability trend report of 2013.
This
practical guide provides you the necessary skill set to secure Apache
Web Server. In this course, we will talk about how to Harden &
Secure Apache Web Server on Unix platform. Following are tested on
Apache 2.4.x and I don’t see any reason it won’t work with Apache 2.2.x.
- This assumes you have installed Apache on UNIX platform. If not, you can go through Installation guide. You can also refer very free video about how to Install Apache, MySQL & PHP.
- We will call Apache installation directory /opt/apache as $Web_Server throughout this course.
- You are advised to take a backup of existing configuration file before any modification.
1.1 Audience
This is designed for Middleware Administrator, Application Support, System Analyst, or anyone working or eager to learn Hardening & Security guidelines. Fair knowledge of Apache Web Server & UNIX command is mandatory. This is seven page guide, click on Next to proceed. You may navigate through table of contents at right hand side.
2 Information Leakage
In default Apache configuration you
would have many sensitive information disclosure, which can be used to
prepare for an attack. It’s one of the most critical tasks for
administrator to understand and secure them. As per report by Cenzic,
16% of vulnerability is found in Info leakage. We require some tool to examine HTTP Headers for verification. Let’s do this by install firebug add-on in Firefox.
- Click on Install Now
- Restart Firefox
- You can see firebug icon at right top bar
We will use this icon to open firebug console to view HTTP Headers information. There
are many online tools also available which helps to check in HTTP
header information. Below are some of them you can try out. http://tools.geekflare.com/seo/tool.php?id=check-headers
2.1 Remove Server Version Banner
I would say this is one of the first
things to consider, as you don’t want to expose what web server version
you are using. Exposing version means you are helping hacker to speedy
the reconnaissance process. Default configuration will expose Apache
Version and OS type as shown below.
Implementation:
- Go to $Web_Server/conf folder
- Modify httpd.conf by using vi editor
- Add following directive and save the httpd.conf
ServerTokens Prod
ServerSignature Off
ServerSignature will remove the version information from the page generated like 403, 404, 502, etc. by apache web server. ServerTokens will change Header to production only, i.e. Apache
Verification:
- Open Firefox
- Activate firebug by clicking firebug icon at top right side
- Click on Net tab
- Hit the URL in address bar
- Expand the GET request and you could see Server directive is just
showing Apache, which is much better than exposing version and OS type.
2.2 Disable directory browser listing
Disable directory listing in browser so
visitor doesn’t see what all file and folders you have under root or
sub-directory. Let’s test how does it look like in default settings.
- Go to $Web_Server/htdocs directory
- Create a folder and few files inside that
# mkdir test
# touch hi
# touch hello
Now, let’s try to access Apache by http://localhost/test
As you could see it reveals what all file/folders you have which is certainly you don’t want to expose.
Implementation:
- Go to $Web_Server/conf directory
- Open httpd.conf using vi
- Search for Directory and change Options directive to None or –Indexes
<Directory /opt/apache/htdocs>
Options None
Order allow,deny
Allow from all
</Directory>
(or)
<Directory /opt/apache/htdocs>
Options -Indexes
Order allow,deny
Allow from all
</Directory>
Note: if you have multiple Directory directives in your environment, you should consider doing the same for all.
Verification:
Now, let’s try to access Apache by http://localhost/test
As you could see, it displays forbidden error instead showing test folder listing.
2.3 Etag
It allows remote attackers to obtain
sensitive information like inode number, multipart MIME boundary and
child process through Etag header. To prevent this vulnerability, let’s
implement it as below. This is required to fix for PCI compliance.
Implementation:
- Go to $Web_Server/conf directory
- Add following directive and save the httpd.conf
FileETag None
Verification:
- Open Firefox and access your application
- Check HTTP response headers in firebug, you should not see Etag at all.
3 Authorization
3.1 Run Apache from non-privileged account
Default apache configuration is to run
as nobody or daemon. It’s good to use a separate non-privileged user for
Apache. The idea here is to protect other services running in case of
any security hole.
Implementation:
- Create a user and group called apache
#groupadd apache
# useradd –G apache apache
- Change apache installation directory ownership to newly created non-privileged user
# chown –R apache:apache /opt/apache
- Go to $Web_Server/conf
- Modify httpd.conf using vi
- Search for User & Group Directive and change as non-privileged account apache
User apache
Group apache
- Save the httpd.conf
- Restart Apache
Verification:
grep for running http process and ensure it’s running with apache user
# ps –ef |grep http
Note:
You could see one process is running with root. That’s because Apache
is listening on port 80 and it has to be started with root. We will talk
about how to change port number later in this course.
3.2 Protect binary and configuration directory permission
By default, permission for binary and
configuration is 755 that mean any user on server can view the
configuration. You can disallow other user to get into conf and bin
folder.
Implementation:
- Go to $Web_Server directory
- Change permission of bin and conf folder
# chown –R 750 bin conf
Verification: 
3.3 System Settings Protection
In default installation, users can
override apache configuration using .htaccess. if you want to stop users
changing your apache server settings, you can add AllowOverride to None
as shown below. This must be done at root level.
Implementation:
- Go to $Web_Server/conf directory
- Open httpd.conf using vi
- Search for Directory at root level
<Directory />
Options -Indexes
AllowOverride None
</Directory>
- Save the httpd.conf
- Restart Apache
3.4 HTTP Request Methods
HTTP 1.1 protocol support many request
methods which may not be required and some of them are having potential
risk. Typically you may just need GET, HEAD, POST request methods in web
application, which can be configured in respective Directory directive.
Default apache configuration support OPTIONS, GET, HEAD, POST, PUT,
DELETE, TRACE, CONNECT method in HTTP 1.1 protocol.
Implementation:
- Go to $Web_Server/conf directory
- Open httpd.conf using vi
- Search for Directory and add following
<LimitExcept GET POST HEAD>
deny from all
</LimitExcept>
4 Web Application Security
Apache web server misconfiguration or
not hardened properly can exploit web application. It’s critical to
harden your web server configuration.
4.1 Cookies
4.1.1 Disable Trace HTTP Request
By default Trace method is enabled in
Apache web server. Having this enabled can allow Cross Site Tracing
attack and potentially giving an option to hacker to steal cookie
information. Let’s see how it looks like in default configuration.
- Do a telnet web server IP with listen port
- Make a TRACE request as shown below
#telnet localhost 80
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
TRACE / HTTP/1.1 Host: test
HTTP/1.1 200 OK
Date: Sat, 31 Aug 2013 02:13:24 GMT
Server: Apache
Transfer-Encoding: chunked
Content-Type: message/http 20
TRACE / HTTP/1.1
Host: test 0
Connection closed by foreign host.
#
As you could see in above TRACE request it has responded my query. Let’s disable it and test it.
Implementation:
- Go to $Web_Server/conf directory
- Add following directive and save the httpd.conf
TraceEnable off
Verification:
- Do a telnet web server IP with listen port and make a TRACE request as shown below
#telnet localhost 80
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
TRACE / HTTP/1.1 Host: test
HTTP/1.1 405 Method Not Allowed
Date: Sat, 31 Aug 2013 02:18:27 GMT
Server: Apache Allow:
Content-Length: 223
Content-Type: text/html; charset=iso-8859-1 <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>405 Method Not Allowed</title> </head><body> <h1>Method Not Allowed</h1>
<p>The requested method TRACE is not allowed for the URL /.</p> </body></html>
Connection closed by foreign host.
#
As you could see in above TRACE request
it has blocked my request with HTTP 405 Method Not Allowed. Now, this
web server doesn’t allow TRACE request and help in blocking Cross Site
Tracing attack.
4.1.2 Set cookie with HttpOnly and Secure flag
You can mitigate most of the common
Cross Site Scripting attack using HttpOnly and Secure flag in cookie.
Without having HttpOnly and Secure, it is possible to steal or
manipulate web application session and cookies and it’s dangerous.
Implementation:
- Ensure mod_headers.so is enabled in your httpd.conf
- Go to $Web_Server/conf directory
- Add following directive and save the httpd.conf
Header edit Set-Cookie ^(.*)$ $1;HttpOnly;Secure
Verification:
- Open Firefox and access your application
- Check HTTP response headers in firebug, you should see Set-Cookie is flagged with HttpOnly and Secure as shown below.
4.2 Clickjacking Attack
Clickjacking is well known web application vulnerabilities. You can refer my previous post Secure Your Web Site from Clickjacking Attack.
Implementation:
- Ensure mod_headers.so is enabled in your httpd.conf
- Go to $Web_Server/conf directory
- Add following directive and save the httpd.conf
Header always append X-Frame-Options SAMEORIGIN
Verification:
- Open Firefox and access your application
- Check HTTP response headers in firebug, you should see X-Frame-Options as shown below.
4.3 Server Side Include
Server Side Include (SSI) has a risk in
increasing load on the server. If you have shared environment and heavy
traffic web applications you should consider disable SSI by adding
Includes in Options directive. SSI attack allows the exploitation of a
web application by injecting scripts in HTML pages or executing codes
remotely.
Implementation:
- Go to $Web_Server/conf directory
- Open httpd.conf using vi
- Search for Directory and add Includes in Options directive
<Directory /opt/apache/htdocs>
Options –Indexes -Includes
Order allow,deny
Allow from all
</Directory>
Note: if you have multiple Directory directives in your environment, you should consider doing the same for all.
4.4 X-XSS Protection
Cross Site Scripting (XSS) protection
can be bypassed in many browsers. You can force apply this protection
for web application if it was disabled by the user. This is used by
majority of giant web companies like Facebook, twitter, Google, etc.
Implementation:
- Go to $Web_Server/conf directory
- Open httpd.conf using vi and add following Header directive
Header set X-XSS-Protection “1; mode=block”
Verification:
- Open Firefox and access your application
- Check HTTP response headers in firebug, you should see XSS Protection is enabled and mode is blocked.
4.5 Disable HTTP 1.0 Protocol
When we talk about security, we should
protect as much we can. So why do we use older HTTP version of protocol,
let’s disable them as well. HTTP 1.0 has security weakness related to
session hijacking. We can disable this by using mod_rewrite module.
Implementation:
- Ensure to load mod_rewrite module in httpd.conf file
- Enable RewriteEngine directive as following and add Rewrite condition to allow only HTTP 1.1
RewriteEngine On
RewriteCond %{THE_REQUEST} !HTTP/1.1$
RewriteRule .* - [F]
4.6 Timeout value configuration
By default Apache timed-out value is
300 seconds, which can be victim of Slow Loris attack and DoS. To
mitigate this you can lower the timeout value to maybe 60 seconds.
Implementation:
- Go to $Web_Server/conf directory
- Open httpd.conf using vi
- Add following in httpd.conf
Timeout 60
5 SSL
Having SSL is additional layer of
security you are adding into Web Application. However, default SSL
configuration leads to certain vulnerabilities and you should consider
tweaking those configurations. We
require some tool to verify SSL settings. There are many available
however, I would use SSL-Scan free tool. You can download from http://sourceforge.net/projects/sslscan/
5.1 SSL Key
Breaching SSL key is hard, but not
impossible. Its just matter of computational power and time. As you
might know using a 2009-era PC cracking away for around 73 days you can reverse engineer a 512-bit key.
So the higher key length you have, the more complex it becomes to break
SSL key. Majority of giant Web Companies use 2048 bit key, as below so
why don’t we?
- Outlook.com
- Microsoft.com
- Live.com
- Skype.com
- Apple.com
- Yahoo.com
- Bing.com
- Hotmail.com
- Twitter.com
Implementation:
- You can use openssl to generate CSR with 2048 bit as below.
- Generate self-signed certificate
openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout localhost.key -out localhost.crt
- Generate new CSR and private key
openssl req -out localhost.csr -new -newkey rsa:2048 -nodes -keyout localhost.key
- Add Personal Cert, Signer Cert and Key file in httpd-ssl.conf file under below directive
SSLCertificateFile # Personal Certificate
SSLCertificateKeyFile # Key File
SSLCACertificateFile # Signer Cert file
Verification:
Execute sslscan utility with following parameter. Change localhost to your actual domain name.
sslscan localhost | grep –i key
- As you can see current ssl key is 2048 bit, which is stronger.
5.2 SSL Cipher
SSL Cipher is an encryption algorithm,
which is used as a key between two computers over the Internet. Data
encryption is the process of converting plain text into secret ciphered
codes. It’s based on your web server SSL Cipher configuration the data
encryption will take place. So it’s important to configure SSL Cipher,
which is stronger and not vulnerable. Let’s validate the Cipher accepted
in current SSL configuration. We will use sslscan utility to validate as below command. Change localhost to your actual domain name.
sslscan –no-failed localhost
As you could see above, in current configuration DHE, AES, EDH, RC4
cipher is accepted. Now if you are performing penetration test or PCI
compliance test, your report will say RC4 Cipher detected. Lately, it
was found that RC4 is weak cipher and to pass certain security test, you
must not accept RC4 or any weak cipher. You should also ensure not to
accept any cipher, which is less than 128 bits.
Implementation:
- Go to $Web_Server/conf/extra folder
- Modify SSLCipherSuite directive in httpd-ssl.conf as below to reject RC4
SSLCipherSuite HIGH:!MEDIUM:!aNULL:!MD5:!RC4
- Save the configuration file and restart apache server
Note: if you have many weak cipher in your SSL auditing report, you can easily reject them adding ! at beginning. For ex – to reject RC4: !RC4 Verification: Again, we will use sslscan utility to validate as below command. Change localhost to your actual domain name.
sslscan –no-failed localhost
So
now we don’t see RC4 anymore as accepted Cipher. It’s good to reject
any low, medium, null or vulnerable cipher to keep yourself tension free
from getting attacked. You can also scan your domain against Qualys SSL Labs to check if you have weak or vulnerable cipher in your environment.
5.3 Disable SSL v2
SSL v2 has many security flaws and if
you are working towards penetration test or PCI compliance then you are
expected to close security finding to disable SSL v2. Any SSL v2
communication may be vulnerable to Man-in-The-Middle attack that could
allow data tempering or disclosure. Let’s implement apache web server to
accept only latest SSL v3 and reject SSL v2 connection request.
Implementation:
- Go to $Web_Server/conf/extra folder
- Modify SSLProtocol directive in httpd-ssl.conf as below to accept only SSL v3 and TLS v1
SSLProtocol –ALL +SSLv3 +TLSv1
Verification:
Let’s use sslscan utility to validate as below command. Change localhost to your actual domain name.
sslscan –no-failed localhost
As you could see above, accepted is only SSLv3 and TLSv1, which is safe from SSLv2 vulnerabilities.
6 Mod Security
Mod Security is an open-source Web
Application Firewall, which you can use with Apache. It comes as a
module which you have to compile and install. If you can’t afford
commercial web application firewall, this would be good choice to go for
it. Mod Security says: In order to provide generic web applications
protection, the Core Rules use the following techniques:
- HTTP Protection – detecting violations of the HTTP protocol and a locally defined usage policy
- Real-time Blacklist Lookups – utilizes 3rd Party IP Reputation
- Web-based Malware Detection – identifies malicious web content by check against the Google Safe Browsing API.
- HTTP Denial of Service Protections – defense against HTTP Flooding and Slow HTTP DoS Attacks.
- Common Web Attacks Protection – detecting common web application security attack
- Automation Detection – Detecting bots, crawlers, scanners and other surface malicious activity
- Integration with AV Scanning for File Uploads – detects malicious files uploaded through the web application.
- Tracking Sensitive Data – Tracks Credit Card usage and blocks leakages.
- Trojan Protection – Detecting access to Trojans horses.
- Identification of Application Defects – alerts on application misconfigurations.
- Error Detection and Hiding – Disguising error messages sent by the server.
6.1 Download & Installation
Following prerequisites must be
installed on server where you wish to use Mod Security with Apache. If
any one of these doesn’t exist then Mod Security compilation will fail.
You may use yum install on Linux or Centos to install these packages.
- apache 2.x or higher
- libpcre package
- libxml2 package
- liblua package
- libcurl package
- libapr and libapr-util package
- mod_unique_id module bundled with Apache web server
Now, let’s download the latest stable version of Mod Security 2.7.5 from http://www.modsecurity.org/download/
- Transfer downloaded file to /opt/apache
- Extract modsecurity-apache_2.7.5.tar.gz
# gunzip –c modsecurity-apache_2.7.5.tar.gz | tar xvf –
- Go to extracted folder modsecurity-apache_2.7.5
# cd modsecurity-apache_2.7.5
- Run the configure script including apxs path to existing Apache
# ./configure –with-apxs=/opt/apache/bin/apxs
- Compile & install with make script
# make
#make install
- Once installation is done, you would see mod_security2.so in modules folder under /opt/apache as shown below
Now this concludes, you have installed Mod Security module in existing Apache web server.
6.2 Configuration
In order to use Mod security feature with Apache, we have to load mod security module in httpd.conf. mod_unique_id
module is pre-requisite for Mod Security. This module provides an
environment variable with a unique identifier for each request, which is
tracked and used by Mod Security.
- Add following line to load module for Mod Security in httpd.conf and save the configuration file
LoadModule unique_id_module modules/mod_unique_id.so
LoadModule security2_module modules/mod_security2.so
- Restart apache web server
Mod Security is now installed! Next
thing you have to do is to install Mod Security core rule to take a full
advantage of its feature. Latest Core Rule can be downloaded from
following link, which is free. https://github.com/SpiderLabs/owasp-modsecurity-crs/zipball/master
- Copy downloaded core rule zip to /opt/apache/conf folder
- Unzip core rule file, you should see the extracted folder as shown below
- You may wish to rename the folder to something short and easy to remember. In this example, I will rename to crs.
- Go to crs folder and rename modsecurity_crs10_setup.conf.example to modsecurity_crs10_setup.conf
Now, let’s enable these rules to get it working with Apache web server.
- Add following in httpd.conf
<IfModule security2_module>
Include conf/crs/modsecurity_crs_10_setup.conf
Include conf/crs/base_rules/*.conf
</IfModule>
In above configuration, we are loading Mod Security main configuration file modsecurity_crs_10_setup.conf and base rules base_rules/*.conf provided by Mod Security Core Rules to protect web applications.
- Restart apache web server
You have successfully configured Mod Security with Apache!
Well done. Now, Apache Web server is protected with Mod Security web application firewall.
6.3 Getting Started
Lets get it started with some of the
important configuration in Mod Security to harden & secure web
applications. In this section, we will do all configuration modification
in /opt/apache/conf/crs/modsecurity_crs_10_setup.conf We will refer /opt/apache/conf/crs/modsecurity_crs_10_setup.conf as setup.conf in this section for example purpose. It’s important to understand what are the OWASP rules are provided in free. There are two types of rules provided by OWASP.
Base Rules – these rules are heavily tested and probably false alarm ratio is less.
Experimental Rules –
these rules are for experimental purpose and you may have high false
alarm. It’s important to configure, test and implement in UAT before
using these in production environment.
Optional Rules
– these optional rules may not be suitable for the entire environment.
Based on your requirement you may use them. If you are looking for CSRF,
User tracking, Session hijacking, etc. protection then you may consider
using optional rules. We have
base, optional and experimental rules after extracting downloaded crs
zip file from OWASP download page. These rules configuration file is
available in crs/base_rules, crs/optional_rules and
crs/experimental_rules folder. Let’s get familiar with some of the base rules.
- modsecurity_crs_20_protocol_violations.conf:This
rule is protecting from Protocol vulnerabilities like response
splitting, request smuggling, using non-allowed protocol (HTTP 1.0).
- modsecurity_crs_21_protocol_anomalies.conf:This is to protect from request, which is missing with Host, Accept, User-Agent in header.
- modsecurity_crs_23_request_limits.conf:This rule has dependency on application specific like request size, upload size, length of parameter, etc.
- modsecurity_crs_30_http_policy.conf:This is to configure and protect allowed or disallowed method like CONNECT, TRACE, PUT, DELETE, etc.
- modsecurity_crs_35_bad_robots.conf:Detect malicious robots
- modsecurity_crs_40_generic_attacks.conf:This is to protect from OS command injection, remote file inclusion, etc.
- modsecurity_crs_41_sql_injection_attacks.conf:This rule to protect SQL and blind SQL inject request.
- modsecurity_crs_41_xss_attacks.conf:Protection from Cross Site Scripting request.
- modsecurity_crs_42_tight_security.conf:Directory traversal detection and protection.
- modsecurity_crs_45_trojans.conf:This rule to detect generic file management output, uploading of http backdoor page, known signature.
- modsecurity_crs_47_common_exceptions.conf:This
is used as an exception mechanism to remove common false positives that
may be encountered suck as Apache internal dummy connection, SSL
pinger, etc.
6.3.1 Logging
Logging is one of the first things to
configure so you can have logs created for what Mod Security is doing.
There are two types of logging available; Debug & Audit log.
Debug Log: this is to duplicate the Apache error, warning and notice messages from the error log.
Audit Log: this is to write the transaction logs that are marked by Mod Security rule Mod
Security gives you flexibility to configure Audit, Debug or both
logging. By default configuration will write both logs. However, you can
change based on your requirement. Log is controlled in SecDefaultAction
directive. Let’s look at default logging configuration in setup.conf
SecDefaultAction “phase:1,deny,log”
To log Debug, Audit log – use “log” To log only audit log – use “nolog,auditlog” To log only debug log – use “log,noauditlog” You
can specify the Audit Log location to be stored which is controlled by
SecAuditLog directive. Let’s write audit log into
/opt/apache/logs/modsec_audit.log by adding as shown below.
Implementation:
- Add SecAuditLog directive in setup.conf and restart Apache Web Server
SecAuditLog /opt/apache/logs/modsec_audit.log
- After restart, you should see modsec_audit.log getting generated as shown below.
6.3.2 Enable Rule Engine
By default Engine Rule is Off that
means if you don’t enable Rule Engine you are not utilizing all the
advantages of Mod Security. Rule Engine enabling or disabling is
controlled by SecRuleEngine directive.
Implementation:
- Add SecRuleEngine directive in setup.conf and restart Apache Web Server
SecRuleEngine On
There are three values for SecRuleEngine:
- On – to enable Rule Engine
- Off – to disable Rule Engine
- DetectionOnly – enable Rule Engine but never executes any actions like block, deny, drop, allow, proxy or redirect
Once Rule Engine is on – Mod Security is ready to protect with some of the common attack types.
6.3.3 Common Attack Type Protection
Now web server is ready to protect with
common attack types like XSS, SQL Injection, Protocol Violation, etc.
as we have installed Core Rule and turned on Rule Engine. Let’s test few
of them.
XSS Attack:-
- Open Firefox and access your application and put <script> tag at the end or URL as shown below
- Monitor the modsec_audit.log in apache/logs folder
As you can see Mod Security blocks request as it contains <script> tag which is the root of XSS attack.
Directory Traversal Attack:- Directory
traversal attacks can create lot of damage by taking advantage of this
vulnerabilities and access system related file. Ex – /etc/passwd,
.htaccess, etc.
- Open Firefox and access your application with directory traversal
- Monitor the modsec_audit.log in apache/logs folder
http://localhost/?../.../boot
- As you can see Mod Security blocks request as it contains directory traversal.
6.3.4 Change Server Banner
Earlier in this guide, you learnt how
to remove Apache and OS type, version help of ServerTokens directive.
Let’s go one step ahead, how about keeping server name whatever you
wish? It’s possible with SecServerSignature directive in Mod Security.
You see it’s an interesting.
Note: in order to use
Mod Security to manipulate Server Banner from header, you must set
ServerTokesn to Full in httpd.conf of Apache web server.
Implementation:
- Add SecServerSignature directive with your desired server name in setup.conf and restart Apache Web Server
SecServerSignature YourServerName
Ex:
[/opt/apache/conf/crs] #grep SecServer modsecurity_crs_10_setup.conf
SecServerSignature chandank.com
[/opt/apache/conf/crs] #
Verification:
- Open Firefox and access your application
- Check HTTP response headers in firebug, you should see Server banner is changed now as shown below.
7 General Configuration
We will talk about some of the general configuration as best practice.
7.1 Configure Listen
When you have multiple interface and
IP’s on single server, it’s recommended to have Listen directive
configured with absolute IP and Port number. When you leave apache
configuration to Listen on all IP’s with some port number, it may create
problem in forwarding HTTP request to some other web server. This is
quite common in shared environment.
Implementation:
- Configure Listen directive in httpd.conf with absolute IP and port as shown example below
Listen 10.10.10.1:80
7.2 Access Logging
It’s essential to configure access log
properly in your web server. Some of the important parameter to capture
in log would be the time taken to serve the request, SESSION ID. By
default apache is not configured to capture these data. You got to
configure them manually as following.
Implementation:
- To capture time taken to serve the request and SESSION ID in access log
- Add %T & %sessionID in httpd.conf under LogFormat directive
LogFormat "%h %l %u %t "%{sessionID}C" "%r" %>s %b %T" common
You can refer http://httpd.apache.org/docs/2.2/mod/mod_log_config.html for complete list of parameter supported in LogFormat directive in Apache Web Server.
7.3 Disable Loading unwanted modules
If you have compiled and installed with
all modules then there are high chances you will have many modules
loaded in Apache, which may not be required. Best practice is to
configure Apache with required modules in your web applications.
Following modules are having security concerns and you might be
interested to disable in httpd.conf of Apache Web Server. WebDAV (Web-based Distributed Authoring and Versioning) This
module allows remote clients to manipulate files on the server and
subject to various denial-of-service attacks. To disable comment
following in httpd.conf
#LoadModule dav_module modules/mod_dav.so
#LoadModule dav_fs_module modules/mod_dav_fs.so
#Include conf/extra/httpd-dav.conf
Info Module The
mod_info module can leak sensitive information using .htaccess once
this module is loaded. To disable comment following in httpd.conf
#LoadModule info_module modules/mod_info.so
Reference: This wouldn’t be possible without guidance from following link:
I hope this practical guide has helped you in securing your
Apache Web Server. If you liked this, please help to share with your friends.
