Databases, Systems & Networks

We all are very familiar with Apache web server, it is a very popular web server to host your web files or your website on the web. Here are some links which can help you to configure Apache web server on your Linux box.

Here in this tutorial, I’ll cover some main tips to secure your web server. Before you apply these changes in your web server, you should have some basics of the Apache server.

• Document root Directory: /var/www/html or /var/www
• Main Configuration file: /etc/httpd/conf/httpd.conf (RHEL/CentOS/Fedora) and /etc/apache/apache2.conf(Debian/Ubuntu).
• Default HTTP Port: 80 TCP
• Default HTTPS Port: 443 TCP
• Test your Configuration file settings and syntax: httpd -t
• Access Log files of Web Server: /var/log/httpd/access_log
• Error Log files of Web Server: /var/log/httpd/error_log

1. How to hide Apache Version and OS Identity from Errors

When you install Apache with source or any other package installers like yum, it displays the version of your Apache web server installed on your server with the Operating system name of your server in Errors. It also shows the information about Apache modules installed in your server.

Show-Apache-Version

In above picture, you can see that Apache is showing its version with the OS installed in your server. This can be a major security threat to your web server as well as your Linux box too. To prevent Apache to not to display these information to the world, we need to make some changes in Apache main configuration file.

Open configuration file with vim editor and search for “ServerSignature“, its by default On. We need to Off these server signature and the second line “ServerTokens Prod” tells Apache to return only Apache as product in the server response header on the every page request, It suppress the OS, major and minor version info.

# vim /etc/httpd/conf/httpd.conf (RHEL/CentOS/Fedora)
# vim /etc/apache/apache2.conf (Debian/Ubuntu)

ServerSignature Off
ServerTokens Prod

# service httpd restart (RHEL/CentOS/Fedora)
# service apache2 restart (Debian/Ubuntu)

2. Disable Directory Listing

By default Apache list all the content of Document root directory in the absence of index file. Please see the image below.

Apache-Directory-Listing

<Directory /var/www/html>
    Options -Indexes
</Directory>

Hide-Apache-Directory-Listing

Lire la suite…

Question: Whenever Apache2 web server returns error pages (e.g., 404 not found, 403 access forbidden pages), it shows web server signature (e.g., Apache version number and operating system info) at the bottom of the pages. Also, when Apache2 web server serves any PHP pages, it reveals PHP version info. How can I turn off these web server signatures in Apache2 web server?

Revealing web server signature with server/PHP version info can be a security risk as you are essentially telling attackers known vulnerabilities of your system. Thus it is recommended you disable all web server signatures as part of server hardening process.

Disable Apache Web Server Signature

Disabling Apache web server signature can be achieved by editing Apache config file.

On Debian, Ubuntu or Linux Mint:

$ sudo vi /etc/apache2/apache2.conf

On CentOS, Fedora, RHEL or Arch Linux:

$ sudo vi /etc/httpd/conf/httpd.conf

Add the following two lines at the end of Apache config file.

Then restart web server to activate the change:

$ sudo service apache2 restart (Debian, Ubuntu or Linux Mint)
$ sudo service httpd restart (CentOS/RHEL 6)
$ sudo systemctl restart httpd.service (Fedora, CentOS/RHEL 7, Arch Linux)

The first line ‘ServerSignature Off‘ makes Apache2 web server hide Apache version info on any error pages.

However, without the second line ‘ServerTokens Prod‘, Apache server will still include a detailed server token in HTTP response headers, which reveals Apache version number.

What the second line ‘ServerTokens Prod‘ does is to suppress a server token in HTTP response headers to a bare minimal.

So with both lines in place, Apache will not reveal Apache version info in either web pages or HTTP response headers.

Hide PHP Version

Another potential security threat is PHP version info leak in HTTP response headers. By default, Apache web server includes PHP version info via « X-Powered-By » field in HTTP response headers. If you want to hide PHP version in HTTP headers, open php.ini file with a text editor, look for « expose_php = On », and change it to « expose_php = Off ».

On Debian, Ubuntu, or Linux Mint:

$ sudo vi /etc/php5/apache2/php.ini

On CentOS, Fedora, RHEL or Arch Linux:

$ sudo vi /etc/php.ini

expose_php = Off

Finally, restart Apache2 web server to reload updated PHP config file.

Now you will no longer see « X-Powered-By » field in HTTP response headers.

MySQL secure SSH

When users want to have a secure connection to their MySQL server, they often rely on VPN or SSH tunnels. Yet another option for securing MySQL connections is to enable SSL wrapper on an MySQL server. Each of these approaches has its own pros and cons. For example, in highly dynamic environments where a lot of short-lived MySQL connections occur, VPN or SSH tunnels may be a better choice than SSL as the latter involves expensive per-connection SSL handshake computation. On the other hand, for those applications with relatively few long-running MySQL connections, SSL based encryption can be reasonable. Since MySQL server already comes with built-in SSL support, you do not need to implement a separate security layer like VPN or SSH tunnel, which has their own maintenance overhead.

The implementation of SSL in an MySQL server encrypts all data going back and forth between a server and a client, thereby preventing potential eavesdropping or data sniffing in wide area networks or within data centers. In addition, SSL also provides identify verification by means of SSL certificates, which can protect users against possible phishing attacks.

In this article, we will show you how to enable SSL on MySQL server. Note that the same procedure is also applicable to MariaDB server.

Creating Server SSL Certificate and Private Key

We have to create an SSL certificate and private key for an MySQL server, which will be used when connecting to the server over SSL.

First, create a temporary working directory where we will keep the key and certificate files.

$ sudo mkdir ~/cert
$ cd ~/cert

Make sure that OpenSSL is installed on your system where an MySQL server is running. Normally all Linux distributions have OpenSSL installed by default. To check if OpenSSL is installed, use the following command.

$ openssl version
OpenSSL 1.0.1f 6 Jan 2014

Now go ahead and create the CA private key and certificate. The following commands will create ca-key.pem and ca-cert.pem.

$ openssl genrsa 2048 > ca-key.pem
$ openssl req -sha1 -new -x509 -nodes -days 3650 -key ca-key.pem > ca-cert.pem

The second command will ask you several questions. It does not matter what you put in these field. Just fill out those fields.

The next step is to create a private key for the server.

$ openssl req -sha1 -newkey rsa:2048 -days 730 -nodes -keyout server-key.pem > server-req.pem

This command will ask several questions again, and you can put the same answers which you have provided in the previous step.

Next, export the server’s private key to RSA-type key with this command below.

$ openssl rsa -in server-key.pem -out server-key.pem

Finally, generate a server certificate using the CA certificate.

$ openssl x509 -sha1 -req -in server-req.pem -days 730 -CA ca-cert.pem -CAkey ca-key.pem -set_serial 01 > server-cert.pem

Lire la suite…

sudo su
mkdir /tmp/.psad
cd /tmp/.psad
wget http://cipherdyne.org/psad/download/psad-2.4.3.tar.gz
tar -zxvf psad-2.4.3.tar.gz
cd psad-2.4.3
./install.pl 
cd /tmp
rm -R .psad
exit

vi /etc/psad/psad.conf

iptables -A INPUT -j LOG
iptables -A FORWARD -j LOG
ip6tables -A INPUT -j LOG
ip6tables -A FORWARD -j LOG

psad -R
psad --sig-update
psad -H

psad --Status

Lire la suite…

If you are running the Apache Web Server or your web hosting provider running Apache based web server, you can use .htaccess configuration file to restrict access to your website. This could be a very important issue from security stand point of view especially if your server is being attacked or hacked from any specific or range of IP addresses.

Now, restricting access method works in two ways. First, you can restrict access to certain IP addresses and allow others. Second, you can restrict access to everyone but few IP addresses only. On this post, I will focus on both method and will try to explain as much as I can.

Restrict Certain IP Addresses

If you want to restrict specific IP addresses from accessing your site, you can use the following lines on your .htaccess file.

order deny,allow
deny from 123.4.5.6
deny from 654.3.2.1
allow from all

These lines above will block “123.4.5.6” and “654.3.2.1” IP addresses from accessing your site. You can add as many IP addresses as you want on this “deny from” list. One interesting fact is, Apache web server gives you lot more flexibility in terms of blocking IP addresses. Take a look at the following lines.

order deny,allow
deny from 123.4.5.
allow from all

If you observe it carefully, you will see that the fourth set of digit is missing on this IP address. It means, if any IP address that matches the first three set of digits will be blocked. So basically anyone with IP address like “123.4.5.1” or “123.4.5.244” won’t be able to access your site as in both IP address matches with the first three (123.4.5.) sets of digits blocked by the Apache web server.

Allow Specific IP Addresses

Think of about a site that you built for a very specific purpose and for very few people, where you do not want everyone to show up. Apache allows you to do that as well.

For an example, lets assume that you built a site that you want one of your friend to be able to access and his IP address is “123.4.5.12”. Simply write the following line on your .htaccess file and you are good to go.

order allow,deny
allow from 123.4.5.12
deny from all

In this case Apache will block all IP addresses except your friends IP address. This is as simple as it can get and I hope you got the basic idea.

Note: On all of my example I used either “allow from all” or “deny from all” at the bottom, this is very important. You must declare either one of these line based on your requirement or things might get little more complicated.

Also remember that all blocked IP addresses would be forwarded or shown an “403 Forbidden” error message. You can definitely customize this message as well but that’s something I will talk about in another post.

Source: iftekhar.net