Difference between revisions of "SCG WS Apache"

Revision as of 13:17, 4 April 2016

This article is part of the OWASP Secure Configuration Guide.

Back to the OWASP Secure Configuration Guide ToC:
   https://www.owasp.org/index.php/Secure_Configuration_Guide
Back to the OWASP Secure Configuration Guide Project:
   https://www.owasp.org/index.php/OWASP_Secure_Configuration_Guide

1 Summary
2 Important Files of Apache Server
3 Apache Server Information Leakage
- 3.1 Server Token Directive
- 3.2 Server Signature
4 Operating System Privileges for Apache
5 Access Control List in Apache
6 Apache Features
7 Apache Module Configuration
8 SSL / TLS Configuration
9 Attack Migigation
- 9.1 DOS
- 9.2 Buffer Overflow
10 References

NEEDS TO BE REVIEWED, SEE REFERENCES BELOW FOR ANY QUERIES!

Summary

The Apache HTTP Server Project is a collaborative software development effort aimed at creating a robust, commercial-grade, featureful, and freely-available source code implementation of an HTTP (Web) server. The project is jointly managed by a group of volunteers located around the world, using the Internet and the Web to communicate, plan, and develop the server and its related documentation. This project is part of the Apache Software Foundation. In addition, hundreds of users have contributed ideas, code, and documentation to the project. This file is intended to briefly describe the history of the Apache HTTP Server and recognize the many contributors.

Important Files of Apache Server

Apache Global Server Configuration Files

Debian

/etc/apache2/apache2.conf

RHEL / Red Hat / CentOS / Fedora Linux

/etc/httpd/conf/httpd.conf

FreeBSD

/usr/local/etc/apache2X/httpd.conf

Note:X represents the version number

Apache Module Files

Debian

/etc/apache2/mods-enabled

RHEL / Red Hat / CentOS / Fedora Linux

/etc/httpd/conf/conf.d

Apache Port Configuration File

Debian

/etc/apache2/ports.conf

RHEL / Red Hat / CentOS / Fedora Linux

/etc/httpd/conf/conf.d

Apache Error Files

Debian

/var/log/apache2/error.log

RHEL / Red Hat / CentOS / Fedora Linux

var/log/httpd/error_log

FreeBSD

/var/log/httpd-error.log

Apache Server Information Leakage

Server Token Directive

Description

This Directive Controls wheather Server response field is sent back to clients includes a description of Generic OS Type of the Server.

Server: Apache/2.2.14 (Unix) mod_ssl/2.2.14 OpenSSL/0.9.8e-fips-rhel5

This allows attackers to identify web servers details greatly and increases the efficiency of any attack,as security vulnerabilities are dependent upon specific software versions.

How to test

In order to test for ServerToken configuration, one should check the Apache configuration file.

Misconfiguration

ServerTokens Full

Remediation

Configure the ServerTokens directive in the Apache configuration to value of Prod or ProductOnly. This tells Apache to only return "Apache" in the Server header, returned on every page request.

ServerTokens Prod
or
ServerTokens ProductOnly

Server Signature

Description

This Apache directive allows the configuration of a trailing footer line under server-generated documents.

How to test

In order to test for ServerSignature configuration, one should check the Apache configuration file.

Misconfiguration

ServerSignature On

Remediation

Configure the ServerSingature directive in the Apache configuration to value of "Off". This tell Apache not to display the server version on error pages, or other pages it generates.

 ServerSignature On

Operating System Privileges for Apache

Run Apache with least privilege user

Description

Apache typically is started with root privileges in order to listen on port 80 and 443. One of the best ways to reduce your exposure to attack when running a web server is to create a unique, unprivileged userid and group for the web daemon to execute. The “nobody” or “daemon” userid & group that come default on Unix variants should NOT be used to run the web server as these principals are commonly used by other daemon services. Instead, create a user and group that are exclusively used by the web service so as to not give unnecessary access to other services. The userid used for the apache user should be a unique value between 1 and 499 as these lower values are reserved for the special system accounts. A more secure alternative is to bind Apache web service to an unprivileged port so it is not necessary to start Apache as root.

How to test

Ensure the apache account is unique and has been created with a UID between1-499 with the apache group and configured in the Apache Configuration File.

Misconfiguration

Remediation

If the Apache user and group does exist, create the account and group as a unique system account.

Example:

# groupadd –r apache
# useradd apache -r -g apache -d /var/www -s /sbin/nologin

2. Configure the Apache user and group in the Apache configuration file.

User apache
Group apache

Restrict Shell Access for Apache User

Description

The Apache account must not be used as a regular login account, and should be assigned an invalid or nologin shell to ensure that the account cannot be used to login.

How to test

Misconfiguration

Check the apache login shell in the /etc/password file for Linux Systems.

# grep apache /etc/passwd

Remediation

The below command will configure the apache user with "nologin" restrictions.

#chsh -s /usr/sbin/nologin apache

Expected Output

Command to chec:
#cat/etc/passwd
Expected Output:
apache:x:48:48:Apache:/var/www:usr/sbin/nologin

Lock Apache user account

Description

The user account under which Apache runs, should have a valid password, but should be locked.

How to test

Misconfiguration

The below is the misconfiguration for an Apache user.

Command

# passwd -S apache

Expected Output:

apache P 09/07/2015 0 99999 7 -1

Remediation

# passwd -l apache

Validate the Configuration using the below command in Linux.

#passwd -S apache

Expected Output:

apache LK 2015-09-09 0 99999 7 -1

Apache Directory Ownership and Permissions

Description

All of the Apache Software directories and files installed should be owned by root user and root group.This will help in mitigate exploration severity and information disclosure.

Apache Web Document folders like "/var/www/html" need a designated group to allow web content to be updated.

How to test

Type the below command to check the User and Group associated with a file.The file varies in Between Debian,RHEL/CentOS/Fedora,FreeBSD.

Example:

# ls -l /usr/share/apache2

Misconfiguration

In the Below example the apache2 folder is owned by a user name "alice" and group "sysadmin" which can be considered as a misconfiguration.

drwxr-xr-x    6 alice sysadmin 4096 Sep  7 13:20 apache2

Remediation

The below command will set a Directory named "apache2" with root user and root group recursively.

#chown –R root:root /usr/local/apache2

Apache File Ownership and Permissions

Description

Setting the appropriate permissions on the Apache files and directories can help to prevent/mitigate exploitation severity and information disclosure.

Preventing execution of Apache binaries with limited permission will decrease the attack surface.

Permission of the Apache directories and files should be rwxr-xr-x and they can change if it is Apache binary or executable file.

How to test

Run the below command to check the file permissions.

#ls -l /var/www/html

Misconfiguration

Other than rwxr-xr-x would be considered as a mis configuration.

Remediation

Permission of the Apache directories and files should be rwxr-xr-x and they can change if it is Apache binary or executable file.

Access Control List in Apache

Restrict OS Root directory access using Allow,Deny Directive

Description

Apache will serve any file mapped from an URL to clients with efault configuration.

It is better to create a deny policy that will not allow access to Operating system directoories or files.

A small modification in the configuration will allow access to tthe required files.

The order of the directive is important as it provides for otherr Allow diectives to override the default deny.

How to test

1. Find the appropriate Apache configuration file in your Server. 2. Ensure there is a single Order directive and set the value to deny, allow 3. Ensure there is a Deny directive, and set the value to "from all". 4. Remove any Allow directives from the root <Directory> element.

Misconfiguration

<Directory />
 . . .
 Order allow,deny
 Allow from all
 . . .
</Directory>

Remediation

<Directory />
 . . .
 Order deny,allow
 Deny from all
 . . .
</Directory>

Restrict WebSite Content using Allow,Deny Directive

Description

Appropriate access to various files,directories, locations and virtual hosts that contains web site content can make attack surface strong.

Based up on the requirement you can provide allow access or you can deny.

How to test

1. Find the appropriate Apache configuration file in your Server.
2. Ensure there is a single Order directive and set the value to deny, allow
3. Ensure there is a Deny directive, and set the value to "from all".
4. Remove any Allow directives from the root <Directory> element.

MisConfiguration

<Directory "/var/www/html">
 . . .
 Order deny,allow
 Allow from all
</Directory>

Remediation

<Directory "/var/www/html/">
Order deny,allow
deny from all
allow from 172.16.5.0/24
</Directory>

AllowOverride Directive

Description

How to test

Misconfiguration

<Directory /var/www/html>
AllowOverride All
</Directory>

Remediation

<Directory /var/www/html>
AllowOverride None
</Directory>

Apache Features

Limit HTTP Request Methods

Description

Apache Server is capable of accepting and processing GET,HEAD,POST,OPTIONS,PUT,DELETE HTTP request methods. If we use <LimitExcept> directive then Apache will not process the unnecessary HTTP request methods. The primary security concerened is to disable the unnecessary HTTP request methods. Apache <LimitExcept> directive does not deny the TRACE request method.

How to test

Misconfiguration

By default all the HTTP request methods are accepted by Apache Server.

Remediation


<Directory "/usr/local/apache2/cgi-bin">
 . . .
 # Limit HTTP methods
	<LimitExcept GET POST OPTIONS>
			deny from all
	</LimitExcept>
</Directory>

Disable HTTP Trace Method

Description

HTTP Trace Method is enabled by default on the Apache Web Server. This method intended for diagnostics purposes.

How to test

Method 1: 1. Locate the Apache configuration files and included configuration files. 2. Verify there is a single TraceEnable directive configured with a value of off.

Method 2: Telnet on the port your web server is running and request for “TRACE / HTTP/1.0” if you get a positive reply it means TRACE is enabled on your system. The output of a server with TRACE enabled will look like:

Misconfiguration

Below is an example of MisConfiguration.

TraceEnable on

Remediation

1.Locate the main Apache configuration file such as httpd.conf. 2.Add a TraceEnable directive to the server level configuration with a value of off as shown

TraceEnable off

HTTP Protocol Version

Description

Many attacks in the process of enumeration they use Vulnerability Scanners,Automated Programs and other fingerprinting tools to send abnormal HTTP protocol version to check how Web Server responds and it is very important that we need to deny these requests.

How to test

1.Locate the Apache configuration files and included configuration files.
2.Verify that below module is loaded.

mod_rewrite.so

Misconfiguration

By default this module is not loaded.So we need to load the module.

Remediation

Method1:
While compiling the Apache for installation we can enable this module and then install it.

#./configure --enable-rewrite

If the Apache is installed with default parameter then we can also use the below Method
Method2:
1.Locate the Apache configuration files and included configuration files.
2.Add the following line to the Configuration file.

LoadModule rewrite_module modules/mod_rewrite.so

3.Add/change the RewriteEngine directive to the configuration as shown.

RewriteEngine On
RewriteCond %{THE_REQUEST} !HTTP/1\.1$ 
RewriteRule .* - [F]

Restrict access to .htaccess files

Description

The following configuration prevent .htaccess and .htpasswd files from being viewed by Web clients.

How to test

Verify the below recommended configuration is present in the Apache config file and make sure they are not commented out.

Misconfiguration

Below is the Misconfiguration

<FilesMatch "^\.ht">
Order allow
</FilesMatch>

Remediation

1.Locate the Apache configuration files and included configuration files. 2.Add the following line to the Configuration file.

<FilesMatch "^\.ht">
Order allow,deny
Deny from all
Satisfy All
</FilesMatch>

Restrict file extensions

Description

There are many files that are often left within the web server document root that could provide an attacker with sensitive information. Most often these files are mistakenly left behind after installation, trouble-shooting, or backing up files before editing. We use FilesMatch directive to restrict access to only those file extensions that are appropriate for the web server.

How to test

Verify the below recommended configuration is present in the Apache config file and make sure they are not commented out.

Misconfiguration

Block all files by default, unless specifically allowed.

<FilesMatch "^.*$">
Order Deny,Allow
Deny from all
</FilesMatch>

Remediation

1.Locate the Apache configuration files and included configuration files.
2.Add the following line to the Configuration file so that Web Server Allow files with specifically approved file extensions such as "css,htm,html,js,pdf,txt,xml,xsl"

<FilesMatch "^.*\.(css|html?|js|pdf|txt|xml|xsl|gif|ico|jpe?g|png)$">
Order Deny,Allow
Allow from all
</FilesMatch>

Note: File extensions should be matched carefully and should be changed based upon the reqruiement.

Remove Default HTML Page

Description

All of the Web Servers comes with a default page which is not required .

How to test

Review all pre-installed web pages and remove content which is not required from root directory of the Web Server.

Misconfiguration

Post installation of the Web Server if the below items exits in Server then that is considered as a Misconfiguration. 1.Default Index Pages
2.Welcome Page
3.Apache User Manul
4.Server Information Handlers and Status Handlers.

Remediation

1.Remove the default index pages like ( index.html,default.html)
2.Remove the Welcome pages.
3.Remove the Apache User manuals.
4.Remove any Server Information Handlers and Status Handlers with configuration.

@@ Line 75: / Line 75: @@
 ==== Misconfiguration ====
-<pre>ServerSignature Off</pre>
+<pre>ServerSignature On</pre>
 ==== Remediation ====