lab/sec/ex-4_iptables.adoc

= Iptables with shorewall!
Apostolos rootApostolos@swarmlab.io
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:description: Intro and Install
:keywords: sec, tcpdump
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:toc-title: Πίνακας περιεχομένων
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[[cheat-Docker]]
== Install swarmlab-sec (Home PC)

HowTo: See http://docs.swarmlab.io/lab/sec/sec.adoc.html


.NOTE
[NOTE]
====
Assuming you're already logged in
====



== shorewall


**Shorewall** is an open source firewall tool for Linux that builds upon the Netfilter (iptables/ipchains) system built into the Linux kernel, making it easier to manage more complex configuration schemes by providing a higher level of abstraction for describing rules using text files. 

https://en.wikipedia.org/wiki/Shorewall[More: wikipedia]


=== Installation

Shorewall is already installed on swarmlab-sec. 


== Basic Two-Interface Firewall


image::basics.png[Basic Two-Interface Firewall]



.connect to master first
[NOTE]
====

Assuming you're already logged in master!

master is now our Firewall/Router

swarmlab-sec login 
====


== Shorewall Concepts

The configuration files for Shorewall are contained in the directory /etc/shorewall 

=== zones — Shorewall zone declaration file

The /etc/shorewall/zones file declares your network zones. You specify the hosts in each zone through entries in /etc/shorewall/interfaces 


./etc/shorewall/zones
[source,bash]
----
#ZONE   TYPE     OPTIONS                 IN_OPTIONS              OUT_OPTIONS
fw      firewall
net     ipv4
loc     ipv4
----

=== interfaces — Shorewall interfaces file

The interfaces file serves to define the firewall's network interfaces to Shorewall. 

./etc/shorewall/interfaces
[source,bash]
----
#ZONE       INTERFACE       BROADCAST      OPTIONS
net         eth0                           dhcp,routefilter
loc         eth1            detect
----


=== policy — Shorewall policy file

This file defines the high-level policy for connections between zone


./etc/shorewall/policy
[source,bash]
----
#SOURCE    DEST        POLICY      LOGLEVEL    LIMIT
loc        net         ACCEPT
net        all         DROP        info
all        all         REJECT      info
----


=== rules — Shorewall rules file

Entries in this file govern connection establishment by defining exceptions to the policies


./etc/shorewall/rules
[source,bash]
----
#ACTION    SOURCE    DEST               PROTO     DPORT
ACCEPT     $FW       net                udp       53
ACCEPT     net       $FW         	udp       53
ACCEPT     $FW       net                tcp       80
ACCEPT     net       $FW         	tcp       80
----


=== Compile then Execute

Shorewall uses a "compile" then "execute" approach. The Shorewall configuration compiler reads the configuration files and generates a shell script. Errors in the compilation step cause the script to be discarded and the command to be aborted. If the compilation step doesn't find any errors then the shell script is executed.



./sbin/shorewall
[source,bash]
----
/sbin/shorewall start
/sbin/shorewall stop
/sbin/shorewall clear
----



.NOTE
[NOTE]
====
The 'compiled' scripts are placed by default in the directory /var/lib/shorewall and are named to correspond to the command being executed. For example, the command /sbin/shorewall start will generate a script named /var/lib/shorewall/.start and, if the compilation is error free, that script will then be executed. If the script executes successfully, it then copies itself to /var/lib/shorewall/firewall. When an /sbin/shorewall stop or /sbin/shorewall clear command is subsequently executed, /var/lib/shorewall/firewall is run to perform the requested operation.

The AUTOMAKE option in /etc/shorewall/shorewall.conf may be set to automatically generate a new script when one of the configuration files is changed. When no file has changed since the last compilation, the /sbin/shorewall start, /sbin/shorewall reload and /sbin/shorewall restart commands will simply execute the current /var/lib/shorewall/firewall script.
====







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'''

.Reminder
[NOTE]
====
:hardbreaks:
Caminante, no hay camino, 
se hace camino al andar.

Wanderer, there is no path, 
the path is made by walking.

*Antonio Machado* Campos de Castilla
====