Tag: whitelist

ConfigServer firewall is a popular Linux firewall security suite. It is easy to install, flexible to configure and secure with extra checks.
CSF is generally considered a more advanced firewall as there are more configuration options compared to other firewalls, while still being simple enough to install and configure that even novice administrators can use it. Some of the MANY functions of CSF are given below:-

Daemon process that checks for login authentication failures for:

Courier imap, Dovecot, uw-imap, Kerio
openSSH
cPanel, WHM, Webmail (cPanel servers only)
Pure-ftpd, vsftpd, Proftpd
Password protected web pages (htpasswd)
Mod_security failures (v1 and v2)
Suhosin failures
Exim SMTP AUTH
Custom login failures with separate log file and regular expression matching

SSH login notification
SU login notification
SYN Flood protection
Ping of death protection
Port Scan tracking and blocking
IPv6 Support with ip6tables
…lots more!

Removing Your Current Firewall
To prevent any conflicts in operation we will need to remove your current firewall. The most common software firewalls on our dedicated servers are APF and CSF, so we have provided instructions on how to remove APF below. If you are using a different software firewall be sure to follow that programs uninstall directions before continuing. After completing the uninstall continue with the CSF installation below.
Using Yum to Remove APF
If it was installed via yum, which is most likely, you will first need to identify the name of your APF package:
rpm -qa |grep -i apf
In this case:
[root@host ~]# rpm -qa | grep apf
apf-9.6_5-1
In order to remove that package, and get your server ready for CSF installation, run the following command:
[root@host ~]# rpm -e apf-9.6_5-1
If you see this:
[root@host ~ ]# rpm -e apf-9.6_5-1
error: Failed dependencies:
apf >= 9.6_5-1 is needed by (installed) bfd-1.2-1.noarch
It means you have BFD installed, and it will need to be removed before you can proceed to removing APF:
[root@host ~ ]# rpm -e bfd-1.2-1.noarch
Then attempt to remove apf again:
[root@host ~ ]# rpm -e apf-9.6_5-1
Any further dependency errors can be handled in the same way as long as you are aware of what you are removing. If you have any questions or get stuck at any point feel free to contact me here.
Removing Source Installed APF
This can be a bit trickier, and if you are not sure what you’re doing you may want to contact me . If you are confident and wish to proceed you will find a list of commands below that you can use to remove APF if it is installed in the most common CentOS directories.
Stopping APF and iptables clears all of the rules from your firewall and ensures that removing the APF installation won’t cause access problems:
[root@host ~ ]# /etc/init.d/iptables stop

[root@host ~ ]# /etc/init.d/apf stop
Remove all of the APF related files:
[root@host ~ ]# rm -Rfv /etc/apf
[root@host ~ ]# rm -fv /etc/cron.daily/fw
[root@host ~ ]# rm -fv /etc/init.d/apf
Remove APF from the list of programs that start at boot:
[root@host ~ ]# chkconfig apf off

Installing CSF

So, login to your server via ssh and let’s start CSF installation by retrieving the package files using wget command:

# wget http://configserver.com/free/csf.tgz

Unpack the archive:

# tar xfvz csf.tgz
Navigate to the uncomperssed csf directory:

# cd csf

Check CSF will work on your server
CSF provides a test script. We can check whether CSF works with your Server or not prior to installing it.

#perl csftest.pl

Testing ip_tables/iptable_filter…OK
Testing ipt_LOG…OK
Testing ipt_multiport/xt_multiport…OK
Testing ipt_REJECT…OK
Testing ipt_state/xt_state…OK
Testing ipt_limit/xt_limit…OK
Testing ipt_recent…OK
Testing xt_connlimit…OK
Testing ipt_owner/xt_owner…OK
Testing iptable_nat/ipt_REDIRECT…OK
Testing iptable_nat/ipt_DNAT…OK

RESULT: csf should function on this server

If you get this output, you can proceed to installation. Otherwise you need to enable each missing modules and then install csf.

Run the installer:
Now there founr installation scripts
install.cpanel.sh For cPanel
install.directadmin.sh
install.generic.sh
install.sh

csf installation for cPanel and DirectAdmin is preconfigured to work on those servers with all the standard ports open.. So install as per your requirement.

#sh install.sh

csf auto-configures your SSH port on installation where it’s running on a non-standard port. CSF also auto-whitelists your connected IP address where possible on installation.
Configuration

By default CSF is in Test mode. So you need to disable the test mode once you configured the firewall correctly. Then only the lfd daemon starts.

“/etc/csf/csf.conf” is the main CSF configuration file.
TCP_IN/TCP_OUT/UDP_IN/UDP_OUT = : These are the ports you want to leave open for your server to operate. If you change the default SSH port make sure to add it here. Also add any other services you might have running such as Shoutcast or game servers. All the ports not mentioed here will be blocked.

LF_DSHIELD = 0: Change this option to 86400. This is an automatic updated list of known attacking IPs. Enabling this will stop them from being able to connect to your server.

Spam Protection Alerts
If you want to add some spam protection, CSF can help. Look in the configuration for the following:

LF_SCRIPT_ALERT = 0 change this to 1. This will send an email alert to the system administrator when the limit configured below is reached within an hour.

LF_SCRIPT_LIMIT = 100 change this to 250. This will alert you when any scripts sends out 250 email messages in an hour.
Providing all the configuration options for CSF here is beyond the scope of the article. Please refer to this README from csf for more details

Note:

If you have installed CSF on cPanel/WHM, it also installs WHM plugin to manage CSF. You can access it from

WHM >> Home >> Plugins >> CnfigServer Firewall
Now TEST all your services to make sure everything is working – SSH, FTP, http. After you do a few quick tests go back into the Firewall Configuration page.

TESTING = 1 change this to 0 and click Change at the bottom. Then Restart csf+lfd using below commands

#csf -r
Or
#/etc/init.d/csf restart

That’s it, the firewall is successfully installed and running!!
Common commands:-

To block an IP Permenently
#csf -d IP

To allow or whitelist IP permenently.
#csf -a IP

To temporary block IP
#csf -td IP

To temporary allow an IP
#csf -ta IP

To check an IP is blocked in firewall
#iptables -nL | grep IP
or
# csf -g IP

To find Reason for block.

#grep IP /var/log/lfd.log

To remove a permanent block
#csf -dr IP

To remove IP from allow list
#csf -ar IP

To disable csf
#csf -x

To enable CSF
#csf -e

To restart
#csf -r
CSF is an increasingly popular alternative to the stock firewalls on some servers. Should you require any other help , please contact me.

IPTABLES complete cheatlist

By wahab

On November 17, 2011

In Cpanel and WHM, Linux server, Plesk

Please note that the iptables rules are stored in the /etc/sysconfig/iptables file. If you view this file, you’ll see all the default rules.

1. Delete Existing Rules

Before you start building new set of rules, you might want to clean-up all the default rules, and existing rules. Use the iptables flush command as shown below to do this.

iptables -F
(or)
iptables –flush
service iptables save

2. Set Default Chain Policies

The default chain policy is ACCEPT. Change this to DROP for all INPUT, FORWARD, and OUTPUT chains as shown below.

iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT DROP

When you make both INPUT, and OUTPUT chain’s default policy as DROP, for every firewall rule requirement you have, you should define two rules. i.e one for incoming andone for outgoing.
Change default policy for INPUT/OUTPUT/FORWARD to ACCEPT. All inbound connections will be allowed

iptables -P INPUT ACCEPT
iptables -P OUTPUT ACCEPT
iptables -P FORWARD ACCEPT

3.Block an IP for inbound connection

iptables -A INPUT -s 192.168.1.5 -j DROP
iptables -A INPUT -i eth0 -p tcp -s “$BLOCK_THIS_IP” -j DROP
4.Allow an IP for inbound connection

iptables -A INPUT -s 192.168.1.5 -j ACCEPT

5.Block outbound IP address

iptables -A OUTPUT -d <IP> -j DROP

6.Block outbound PORT

iptables -A OUTPUT -p tcp –dport <PORT> -j DROP

7.Block outbound IP:PORT

iptables -A OUTPUT -p tcp -d <IP> –dport <PORT> -j DROP

8.Allow port 2222 for inbound tcp connections

iptables -A INPUT -p tcp –dport 2222 -j ACCEPT

9.White list an IP

iptables -A INPUT -i eth0 -s <IP> -j ACCEPT

10.Open port 5666

iptables -I INPUT -p tcp -m tcp –dport 5666 -j ACCEPT
11.Allow ALL Incoming SSH

The following rules allow ALL incoming ssh connections on eth0 interface.

iptables -A INPUT -i eth0 -p tcp –dport 22 -m state –state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp –sport 22 -m state –state ESTABLISHED -j ACCEPT

12.Allow Incoming SSH only from a Sepcific Network

The following rules allow incoming ssh connections only from 192.168.100.X network.

iptables -A INPUT -i eth0 -p tcp -s 192.168.100.0/24 –dport 22 -m state –state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp –sport 22 -m state –state ESTABLISHED -j ACCEPT

In the above example, instead of /24, you can also use the full subnet mask. i.e “192.168.100.0/255.255.255.0″.

13. Allow Incoming HTTP and HTTPS

The following rules allow all incoming web traffic. i.e HTTP traffic to port 80.

iptables -A INPUT -i eth0 -p tcp –dport 80 -m state –state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp –sport 80 -m state –state ESTABLISHED -j ACCEPT

The following rules allow all incoming secure web traffic. i.e HTTPS traffic to port 443.

iptables -A INPUT -i eth0 -p tcp –dport 443 -m state –state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp –sport 443 -m state –state ESTABLISHED -j ACCEPT

14.Combine Multiple Rules Together using MultiPorts

When you are allowing incoming connections from outside world to multiple ports, instead of writing individual rules for each and every port, you can combine them together using the multiport extension as shown below.

The following example allows all incoming SSH, HTTP and HTTPS traffic.

iptables -A INPUT -i eth0 -p tcp -m multiport –dports 22,80,443 -m state –state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp -m multiport –sports 22,80,443 -m state –state ESTABLISHED -j ACCEPT

15.Allow Outgoing SSH

The following rules allow outgoing ssh connection. i.e When you ssh from inside to an outside server.

iptables -A OUTPUT -o eth0 -p tcp –dport 22 -m state –state NEW,ESTABLISHED -j ACCEPT
iptables -A INPUT -i eth0 -p tcp –sport 22 -m state –state ESTABLISHED -j ACCEPT

Please note that this is slightly different than the incoming rule. i.e We allow both the NEW and ESTABLISHED state on the OUTPUT chain, and only ESTABLISHED state on the INPUT chain. For the incoming rule, it is vice versa.

16.Allow Outgoing SSH only to a Specific Network

The following rules allow outgoing ssh connection only to a specific network. i.e You an ssh only to 192.168.100.0/24 network from the inside.

iptables -A OUTPUT -o eth0 -p tcp -d 192.168.100.0/24 –dport 22 -m state –state NEW,ESTABLISHED -j ACCEPT
iptables -A INPUT -i eth0 -p tcp –sport 22 -m state –state ESTABLISHED -j ACCEPT

17.Allow Ping from Outside to Inside

The following rules allow outside users to be able to ping your servers.
iptables -A OUTPUT -p icmp –icmp-type echo-request -j ACCEPT
iptables -A INPUT -p icmp –icmp-type echo-reply -j ACCEPT
19.Allow Loopback Access

You should allow full loopback access on your servers. i.e access using 127.0.0.1

iptables -A INPUT -i lo -j ACCEPT
iptables -A OUTPUT -o lo -j ACCEPT

20. Allow MySQL connection only from a specific network

iptables -A INPUT -i eth0 -p tcp -s 192.168.100.0/24 –dport 3306 -m state –state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp –sport 3306 -m state –state ESTABLISHED -j ACCEPT

21.Prevent DoS Attack

The following iptables rule will help you prevent the Denial of Service (DoS) attack on your webserver.

iptables -A INPUT -p tcp –dport 80 -m limit –limit 25/minute –limit-burst 1000 -j ACCEPT
In the above example:
-m limit: This uses the limit iptables extension

–limit 25/minute: This limits only maximum of 25 connection per minute. Change this value based on your specific requirement
–limit-burst 1000: This value indicates that the limit/minute will be enforced only after the total number of connection have reached the limit-burst level.

22.Port forwarding using IPTables

Forward port 80 from IP address to another IP

iptables -t nat -A PREROUTING -i eth0 -p tcp –dport 80 -j DNAT –to <DESTIP>:80
iptables -t nat -A POSTROUTING -p tcp –dst <DESTIP> –dport 80 -j SNAT –to <SRCIP>
iptables -t nat -A OUTPUT –dst <SRC> -p tcp –dport 80 -j DNAT –to <DESTIP>:80

Removing the above rules
iptables -t nat -D PREROUTING -i eth0 -p tcp –dport 80 -j DNAT –to <DESTIP>:80
iptables -t nat -D POSTROUTING -p tcp –dst <DESTIP> –dport 80 -j SNAT –to <SRCIP>
iptables -t nat -d OUTPUT –dst <SRC> -p tcp –dport 80 -j DNAT –to <DESTIP>:80

23.List all the rules in the iptables

iptables -L

24.Check an IP in the rule

iptables -nL | grep <IP>

25.Save the current iptables rules

iptables-save > File_name

26.Restore iptable rules from the file

iptables-restore < File_name

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Tag: whitelist

Installing and managing firewall using ConfigServer Firewall (CSF)

IPTABLES complete cheatlist