Firewall ACLs

[punto]

Hi I have installed ISPconfig and must say think it is a fantastic application , thankyou so much to the developers.

I was wondering if it is possible to configure the ISPconfig firewall so that you can limit ssh access to certain IP addresses?

With my other linux server I have an explicit REJECT in /etc/sysconfig/iptables for port 22 and then just add an ACCEPT in for the source IP addresses I want to accept and it works well.

-A RH-Firewall-1-INPUT -p tcp -m tcp -s 172.16.8.35 --dport 22 --syn -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 22 --syn -j REJECT

Where is the script or config file for the ISPconfig firewall? Can I manually edit the script without breaking anything? I dont like having ssh access open to anyone.

Thanks in advance

Matt.

[till]

The script is:

/etc/Bastille/bastille-firewall.cfg

You will have to change the master file too:

/root/ispconfig/isp/conf/bastille-firewall.cfg.master

Then run:

/etc/init.d/bastille-firewall restart

[punto]

Great, thanks Till.

Regards

Matt

[punto]

Originally Posted by till

The script is:

/etc/Bastille/bastille-firewall.cfg

You will have to change the master file too:

/root/ispconfig/isp/conf/bastille-firewall.cfg.master

Then run:

/etc/init.d/bastille-firewall restart

I found that I wasnt able to add ACLs directly to the bastille-firewall.cfg script.

After doing some reading, here is my how-to and hopefully others will find it useful:

In this case I want to restrict ssh access to only one IP address (you can configure it for any number depending on your needs)

I order to restrict access to certain source IPs for certain protocols, using the Bastille-firewall setup you need to firstly create a new directory under /etc/Bastille. This directory needs to be called firewall.d

#cd /etc/Bastille
#mkdir firewall.d

You then need to create a new file within the newly created directory called post-rule-setup.sh

#cd firewall.d
#vi post-rule-setup.sh


This is the file where any IPTABLES rules can be entered. When you restart bastille.cfg the script is read and the rules applied. A knowledge of IPTABLES is required but once you get the hang of it, it is easy enough.
So in my case I want to allow ssh access to only 123.34.56.789 and deny it to ALL other IP addresses, so my post-rule-setup.sh file will look like this:

/sbin/iptables -I INPUT -p tcp -m tcp -s 123.34.56.789 --dport 22 --syn -j ACCEPT
/sbin/iptables -I INPUT -p tcp -m tcp --dport 22 --syn -j REJECT


The first line accepts ssh (tcp port 22) connections only from 123.34.56.789 and the second line denies ALL other source IP addresses. If there is no match in this case 123.34.56.789 then all traffic bound for port 22 will be denied.

Ok now we have our rule we need to restart bastille.cfg

#/etc/init.d/bastille-firewall restart

A successfully read script will yield the following

Setting up IP spoofing protection... done.
Allowing traffic from trusted interfaces... done.
Setting up chains for public/internal interface traffic... done.
Setting up general rules... done.
Setting up outbound rules... done

The last line is the one we are interested in. If your IPTABLES rules are not understood or written incorrectly then you will get the following output when you restart bastille.cfg

Setting up IP spoofing protection... done.
Allowing traffic from trusted interfaces... done.
Setting up chains for public/internal interface traffic... done.
Setting up general rules... done.
Setting up outbound rules..../post-rule-setup.sh: line 5: -I: command not found
done

You will need to go back into your post-rule-setup.sh and modify it.

You can specify a subnet simply by using for example 192.168.0.0/24 notation in your rule set

Cheers

Matt

[falko]

That's a great solution.

[tijn_tux]

Thnx for the mini-howto ! works perfect!

[punto]

Glad you found it useful

[rdutton]

Thanks punto for you explanation.

Just something extra in case people came across the same problem I did..

In additional to the file "post-rule-setup.sh" you can also add a file called "pre-chain-split.sh" in the same directory. Any commands you put in "pre-chain-split.sh" will be executed BEFORE the standard firewall rules.

This is useful when you want to allow packets through which are normally dropped due to preceding firewall rules.

e.g. I added rules to allow samba just for my home IP address:

iptables -A INPUT -s [OK_REMOTE_IP] -p udp -m multiport --destination-ports 445,135,136,137,138,139 -j ACCEPT
iptables -A INPUT -s [OK_REMOTE_IP] -p tcp -m multiport --destination-ports 445,135,136,137,138,139 -j ACCEPT
iptables -A OUTPUT -s [OK_REMOTE_IP] -p udp -m multiport --destination-ports 445,135,136,137,138,139 -j ACCEPT
iptables -A OUTPUT -s [OK_REMOTE_IP] -p tcp -m multiport --destination-ports 445,135,136,137,138,139 -j ACCEPT

There is 4 rules to account for the variations of UDP/TCP and INPUT/OUTPUT chains.

The iptables commands explained:
-A Which chain to append the rule to
-s The source address(es)
-p protocol (udp/tcp for samba)
-m Modules to load (in this case multiport)
--destination-ports The parameter to the mulitport module specifying the samba ports.
-j Jump to another chain. In this case ACCEPT

[IKShadow]

Strange it does not work at my linux box


I made following rule:

/sbin/iptables -I INPUT -p tcp -m tcp -s 213.143.90.139 --dport 22 --syn -j ACCEPT
/sbin/iptables -I INPUT -p tcp -m tcp --dport 22 --syn -j REJECT

213.143.90.139 is PC from which i want to access my linux box.
(Later on i would copy/paste first line for few other IP's )

When I restart firewall everything seems ok:

krneki:/etc/Bastille/firewall.d # /etc/init.d/bastille-firewall restart
Setting up IP spoofing protection... done.
Allowing traffic from trusted interfaces... done.
Setting up chains for public/internal interface traffic... done.
Setting up general rules... done.
Setting up outbound rules... done.

But after it I cant SSH to my linux box.

[falko]

Originally Posted by IKShadow

213.143.90.139 is PC from which i want to access my linux box.
(Later on i would copy/paste first line for few other IP's )

Are both systems in the same local network?