Debian / Shorewall / Webmin / FWLogwatch / DNSMasq / MRTG

An OpenSource Protection system with intrusion detection, logging, traffic graphs, DMZ and web based logs, charts and control interface.

Constructed on a Sun UltraSparc5 hardware platform with 5 nic interfaces used as:

Ethernet 0 Primary Internet Connection 75.26.146.82/28

Ethernet 1 DMZ (#1) 172.168.2.1/28

DMZ Machines 172.168.2.2 75.26.146.86/28

172.168.2.3 75.26.146.87/28

Ethernet 2 DMZ (#2) Unused

Ethernet 3 Secondary Internet Connection (Unused)

Ethernet 4 Local Network 192.168.0.6/24

The system is built upon the Debian Linux operating system using the “Etch” build and is compiled for a basic network structure with the latest stable PERL and OpenSSL modules. Hardening of the system AFTER it is up and running is seriously recommended.

Operating mode options that drove the system configuration and design

The system was conceived because in my work I was consistently faced with the requirement of helping small / midsize businesses provide Web based services to both the outside world over the “Big Bad Internet” as well as the internal user base.

The .net based software I was providing required consistent web name convention, as the web.config files reference the machine name to identify the instance(s). IP Addressing for the web server is not an option unless routable addresses are used both internally and externally. Common security practice makes that impractical.

Most commercial firewall systems were either not effective enough, or flexible enough or simple enough to configure…. Or they were just too bloody expensive. Thus was this system born. The following configurations are easily accommodated:

Internet Connection Options

1. Static address provided by network services to the internet. (As Supplied)

2. Secondary Internet Connection

a. Bonding available

3. PPPOE DSL Connection, either Static or Dynamic addressing

4. Cable Modem dynamic or static ip address

5. Firewall can provide Classic DNS Server Services

6. Firewall can provide classic Mail Transfer Services of SMTP/POP/Imap. Available both internally and externally

7. PPTP and IPSec VPN Server available (Not installed or configured as Shipped)

8. Firewall system uses distributed internet NTP Pool system for system time.

9. LDAP/KERBEROS and Active Directory integration is possible. (Not installed or configured as shipped)

DMZ Options

1. SNAT One to One mapping of Non-Routable addresses to Routable IP Addresses. (Requires that the subnet is large enough to have addresses for both the Firewall and the Servers within the DMZ)[ As Supplied]

2. DNAT Port Forwarding of a single IP address to the DMZ server(s) based upon function. The limitation is that there can only be one server of any particular internet service (web server/mail server/telnet server) etc.

3. Dynamic mapping of address space based upon a pool of routable addresses

4. Multiple DMZ Zones using any of the above methods.

Local Network Options

1. Firewall is accessed using a single static address and provides no internal services

2. Firewall provides internal DNS services based upon external “Canonical” Root server based address resolution with injection of naming modification for access of DMZ machines from inside the Local Network.

3. Firewall can provide internal DHCP services (To be able to broadcast the dns address for internal users that advertise the dmz machine(s)

4. Firewall can provide mail services for the internal network, or can interface with the existing internal mail system.

5. Mail Filtering and AntiVirus services are also available for the internal or external mail systems. (Not installed or configured as shipped)

System as Shipped

Default Network:

The network can be configured using the Webmin | Networking | Network Graphic interface. The addresses are configured in the /etc/network/interfaces file, (See Appendix A);

Access to the Control Interface:

In order to make the system ‘User Friendly (er)’ we employ the Webmin interface to access all of the control interfaces for the System, Firewall, Routing and Usage Graphing.

The system will not allow access from either the DMZ or the Internet. In order to access the Webmin system a LOCAL NETWORK connection must be used. Direct your Browser to https://192.168.0.6:10000

And log in with the root login and password.

The first time you log in, you will be questioned about the website certificate:

(Firefox version)

(IE 7 Version)

(In order to NOT see this again in IE… Goto the Certificate Error button and Accept the certificate)

And after installing the certificate, you should see ...

(IE7 version)

Here you can access the Firewall configuration, the Network settings and see bandwidth usage.

You can upload and download files to the system via the browser interface on the “Others” Tab, Add or remove software from the system via the “System” Tab and set up Web and FTP services on the box using the Servers Tab.

PPPOE Client is available via the ADSL Client tag, (But not installed or configured). VPN services are also available.

Accessing the Firewall Logs

Reporting on the Firewall system is available via the system logs, but also via webpage from the FWLogwatch program. To see the FWLogwatch output, open another browser window at:

http://192.168.0.6:888

At the login screen, DO NOT ENTER ANYTHING! Just hit return!

Here you can see and analyze the action of the firewall:

Greater and Lesser symbols allow ordering of the reports in classic windows fashion

The logwatch system holds the logs for 24 hours and then autocycles them. (This setting is adjustable) MAN Pages are available on the system for all of these modules. FWLogwatch is NOT available via Webmin.

Realtime Bandwidth monitoring is available on another web page…

http://192.168.0.6/mrtg

No Login … just bandwidth across the three currently active interfaces.

Local Network DNS services

For the local network, both and ‘Stub DNS’ and a DHCP Server are available via the DNSMasq program. This program is ONLY configurable via the config file /etc/dnsmasq.conf (See Appendix A)

IE7 View of your Monitor Console

Examples of different network topologies supported by firewall (not all inclusive)

1.    Single/Dual Intenet Connection. Firewall provided DNS and Local Network Address space
2.     Dual Internet Connections. Internet access, DNS, DHCP and Mail provided by Network Services

Appendix A

Network Interface Configuration File
/ETC/network/interfaces
<Begin File>
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug eth0
iface eth0 inet static
        address 75.26.146.82
        netmask 255.255.255.240
        network 75.26.146.80
        broadcast 75.26.146.95
        gateway 75.26.146.81
        # dns-* options are implemented by the resolvconf package, if installed
        dns-nameservers 4.2.2.2
        dns-search ghanks.com
auto eth1
iface eth1 inet static
        address 172.168.2.1
        netmask 255.255.255.240
        network 172.168.2.0
        broadcast 172.168.2.15
auto eth4
iface eth4 inet static
      address 192.168.0.6

        netmask 255.255.255.0
        network 192.168.0.0
        broadcast 192.168.0.255
<End of File>

DNSMASQ Configuration File
/ETC/dnsmasq.conf

<Begin File>
# Configuration file for dnsmasq.
#
# Format is one option per line, legal options are the same
# as the long options legal on the command line. See
# "/usr/sbin/dnsmasq --help" or "man 8 dnsmasq" for details.

# The following two options make you a better netizen, since they
# tell dnsmasq to filter out queries which the public DNS cannot
# answer, and which load the servers (especially the root servers)
# uneccessarily. If you have a dial-on-demand link they also stop
# these requests from bringing up the link uneccessarily.

# Never forward plain names (without a dot or domain part)
#domain-needed
# Never forward addresses in the non-routed address spaces.
#bogus-priv

# Uncomment this to filter useless windows-originated DNS requests
# which can trigger dial-on-demand links needlessly.
# Note that (amongst other things) this blocks all SRV requests,
# so don't use it if you use eg Kerberos.
# This option only affects forwarding, SRV records originating for
# dnsmasq (via srv-host= lines) are not suppressed by it.
#filterwin2k

# Change this line if you want dns to get its upstream servers from
# somewhere other that /etc/resolv.conf
#resolv-file=

# By default, dnsmasq will send queries to any of the upstream
# servers it knows about and tries to favour servers to are known
# to be up. Uncommenting this forces dnsmasq to try each query
# with each server strictly in the order they   appear   in
# /etc/resolv.conf
#strict-order

# If you don't want dnsmasq to read /etc/resolv.conf or any other
# file, getting its servers from this file instead (see below), then
# uncomment this
#no-resolv

# If you don't want dnsmasq to poll /etc/resolv.conf or other resolv
# files for changes and re-read them then uncomment this.
#no-poll

# Add other name servers here, with domain specs if they are for
# non-public domains.
#server=/localnet/192.168.0.1

# Add local-only domains here, queries in these domains are answered
# from /etc/hosts or DHCP only.
#local=/localnet/

# Add domains which you want to force to an IP address here.
# The example below send any host in doubleclick.net to a local
# webserver.
#address=/doubleclick.net/127.0.0.1

# If you want dnsmasq to change uid and gid to something other
# than the default, edit the following lines.
#user=
#group=

# If you want dnsmasq to listen for DHCP and DNS requests only on
# specified interfaces (and the loopback) give the name of the
# interface (eg eth0) here.
# Repeat the line for more than one interface.
interface=eth4
# Or you can specify which interface _not_ to listen on
#except-interface=
# Or which to listen on by address (remember to include 127.0.0.1 if
# you use this.)
#listen-address=
# If you want dnsmasq to provide only DNS service on an interface,
# configure it as shown above, and then use the following line to
# disable DHCP on it.
no-dhcp-interface=eth4

# On systems which support it, dnsmasq binds the wildcard address,
# even when it is listening on only some interfaces. It then discards
# requests that it shouldn't reply to. This has the advantage of
# working even when interfaces come and go and change address. If you
# want dnsmasq to really bind only the interfaces it is listening on,
# uncomment this option. About the only time you may need this is when
# running another nameserver on the same machine.
#bind-interfaces

# If you don't want dnsmasq to read /etc/hosts, uncomment the
# following line.
#no-hosts
# or if you want it to read another file, as well as /etc/hosts, use
# this.
#addn-hosts=/etc/banner_add_hosts
# Set this (and domain: see below) if you want to have a domain
# automatically added to simple names in a hosts-file.
#expand-hosts

# Set the domain for dnsmasq. this is optional, but if it is set, it
# does the following things.
# 1) Allows DHCP hosts to have fully qualified domain names, as long
#     as the domain part matches this setting.
# 2) Sets the "domain" DHCP option thereby potentially setting the
#    domain of all systems configured by DHCP
# 3) Provides the domain part for "expand-hosts"
#domain=thekelleys.org.uk

# Uncomment this to enable the integrated DHCP server, you need
# to supply the range of addresses available for lease and optionally
# a lease time. If you have more than one network, you will need to
# repeat this for each network on which you want to supply DHCP
# service.
#dhcp-range=192.168.0.50,192.168.0.150,12h

# This is an example of a DHCP range where the netmask is given. This
# is needed for networks we reach the dnsmasq DHCP server via a relay
# agent. If you don't know what a DHCP relay agent is, you probably
# don't need to worry about this.
#dhcp-range=192.168.0.50,192.168.0.150,255.255.255.0,12h

# This is an example of a DHCP range with a network-id, so that
# some DHCP options may be set only for this network.
#dhcp-range=red,192.168.0.50,192.168.0.150

# Supply parameters for specified hosts using DHCP. There are lots
# of valid alternatives, so we will give examples of each. Note that
# IP addresses DO NOT have to be in the range given above, they just
# need to be on the same network. The order of the parameters in these
# do not matter, it's permissble to give name,adddress and MAC in any order

# Always allocate the host with ethernet address 11:22:33:44:55:66
# The IP address 192.168.0.60
#dhcp-host=11:22:33:44:55:66,192.168.0.60

# Always set the name of the host with hardware address
# 11:22:33:44:55:66 to be "fred"
#dhcp-host=11:22:33:44:55:66,fred

# Always give the host with ethernet address 11:22:33:44:55:66
# the name fred and IP address 192.168.0.60 and lease time 45 minutes
#dhcp-host=11:22:33:44:55:66,fred,192.168.0.60,45m

# Give the machine which says it's name is "bert" IP address
# 192.168.0.70 and an infinite lease
#dhcp-host=bert,192.168.0.70,infinite

# Always give the host with client identifier 01:02:02:04
# the IP address 192.168.0.60
#dhcp-host=id:01:02:02:04,192.168.0.60

# Always give the host with client identifier "marjorie"
# the IP address 192.168.0.60
#dhcp-host=id:marjorie,192.168.0.60

# Enable the address given for "judge" in /etc/hosts
# to be given to a machine presenting the name "judge" when
# it asks for a DHCP lease.
#dhcp-host=judge

# Never offer DHCP service to a machine whose ethernet
# address is 11:22:33:44:55:66
#dhcp-host=11:22:33:44:55:66,ignore

# Ignore any client-id presented by the machine with ethernet
# address 11:22:33:44:55:66. This is useful to prevent a machine
# being treated differently when running under different OS's or
# between PXE boot and OS boot.
#dhcp-host=11:22:33:44:55:66,id:*

# Send extra options which are tagged as "red" to
# the machine with ethernet address 11:22:33:44:55:66
#dhcp-host=11:22:33:44:55:66,net:red

# Send extra options which are tagged as "red" to
# any machine with ethernet address starting 11:22:33:
#dhcp-host=11:22:33:*:*:*,net:red

# Send extra options which are tagged as "red" to any machine whose
# DHCP vendorclass string includes the substring "Linux"
#dhcp-vendorclass=red,Linux

# Send extra options which are tagged as "red" to any machine one
# of whose DHCP userclass strings includes the substring "accounts"
#dhcp-userclass=red,accounts

# Send extra options which are tagged as "red" to any machine whose
# MAC address matches the pattern.
#dhcp-mac=red,00:60:8C:*:*:*

# If this line is uncommented, dnsmasq will read /etc/ethers and act
# on the ethernet-address/IP pairs found there just as if they had
# been given as --dhcp-host options. Useful if you keep
# MAC-address/host mappings there for other purposes.
#read-ethers

# Send options to hosts which ask for a DHCP lease.
# See RFC 2132 for details of available options.
# Note that all the common settings, such as netmask and
# broadcast address, DNS server and default route, are given
# sane defaults by dnsmasq. You very likely will not need any
# any dhcp-options. If you use Windows clients and Samba, there
# are some options which are recommended, they are detailed at the
# end of this section.
# For reference, the common options are:
# subnet mask - 1
# default router - 3
# DNS server - 6
# broadcast address - 28

# Override the default route supplied by dnsmasq, which assumes the
# router is the same machine as the one running dnsmasq.
#dhcp-option=3,1.2.3.4

# Set the NTP time server addresses to 192.168.0.4 and 10.10.0.5
#dhcp-option=42,192.168.0.4,10.10.0.5

# Set the NTP time server address to be the same machine as
# is running dnsmasq
#dhcp-option=42,0.0.0.0

# Set the NIS domain name to "welly"
#dhcp-option=40,welly

# Set the default time-to-live to 50
#dhcp-option=23,50

# Set the "all subnets are local" flag
#dhcp-option=27,1

# Send the etherboot magic flag and then etherboot options (a string).
#dhcp-option=128,e4:45:74:68:00:00
#dhcp-option=129,NIC=eepro100

# Specify an option which will only be sent to the "red" network
# (see dhcp-range for the declaration of the "red" network)
#dhcp-option=red,42,192.168.1.1

# The following DHCP options set up dnsmasq in the same way as is specified
# for the ISC dhcpcd in
# http://www.samba.org/samba/ftp/docs/textdocs/DHCP-Server-Configuration.txt
# adapted for a typical dnsmasq installation where the host running
# dnsmasq is also the host running samba.
# you may want to uncomment them if you use Windows clients and Samba.
#dhcp-option=19,0           # option ip-forwarding off
#dhcp-option=44,0.0.0.0     # set netbios-over-TCP/IP nameserver(s) aka WINS serv
er(s)
#dhcp-option=45,0.0.0.0     # netbios datagram distribution server
#dhcp-option=46,8           # netbios node type
#dhcp-option=47             # empty netbios scope.

# Send RFC-3397 DNS domain search DHCP option. WARNING: Your DHCP client
# probably doesn't support this......
#dhcp-option=119,eng.apple.com,marketing.apple.com

# Send RFC-3442 classless static routes (note the netmask encoding)
#dhcp-option=121,192.168.1.0/24,1.2.3.4,10.0.0.0/8,5.6.7.8

# Send encapsulated vendor-class specific options. The vendor-class
# is sent as DHCP option 60, and all the options marked with the
# vendor class are send encapsulated in DHCP option 43. The meaning of
# the options is defined by the vendor-class. This example sets the
# mtftp address to 0.0.0.0 for PXEClients
#dhcp-option=vendor:PXEClient,1,0.0.0.0

# Set the boot filename and tftpd server name and address
# for BOOTP. You will only need this is you want to
# boot machines over the network.
#dhcp-boot=/var/ftpd/pxelinux.0,boothost,192.168.0.3

# Set the limit on DHCP leases, the default is 150
#dhcp-lease-max=150

# The DHCP server needs somewhere on disk to keep its lease database.
# This defaults to a sane location, but if you want to change it, use
# the line below.
#dhcp-leasefile=/var/lib/misc/dnsmasq.leases

# Set the DHCP server to authoritative mode. In this mode it will barge in
# and take over the lease for any client which broadcasts on the network,
# whether it has a record of the lease or not. This avoids long timeouts
# when a machine wakes up on a new network. DO NOT enable this if there's
# the slighest chance that you might end up accidentally configuring a DHCP
# server for your campus/company accidentally. The ISC server uses the same
# the same option, and this URL provides more information:
# http://www.isc.org/index.pl?/sw/dhcp/authoritative.php
#dhcp-authoritative

# Run an executable when a DHCP lease is created or destroyed.
# The arguments sent to the script are "add" or "del",
# then the MAC address, the IP address and finally the hostname
# if there is one.
#dhcp-script=/bin/echo

# Set the cachesize here.
#cache-size=150

# If you want to disable negative caching, uncomment this.
#no-negcache

# Normally responses which come form /etc/hosts and the DHCP lease
# file have Time-To-Live set as zero, which conventionally means
# do not cache further. If you are happy to trade lower load on the
# server for potentially stale date, you can set a time-to-live (in
# seconds) here.
#local-ttl=

# If you want dnsmasq to detect attempts by Verisign to send queries
# to unregistered .com and .net hosts to its sitefinder service and
# have dnsmasq instead return the correct NXDOMAIN response, uncomment
# this line. You can add similar lines to do the same for other
# registries which have implemented wildcard A records.
#bogus-nxdomain=64.94.110.11

# If you want to fix up DNS results from upstream servers, use the
# alias option. This only works for IPv4.
# This alias makes a result of 1.2.3.4 appear as 5.6.7.8
#alias=1.2.3.4,5.6.7.8
# and this maps 1.2.3.x to 5.6.7.x
#alias=1.2.3.0,5.6.7.0,255.255.255.0

# Change these lines if you want dnsmasq to serve MX records.

# Return an MX record named "maildomain.com" with target
# servermachine.com and preference 50
#mx-host=maildomain.com,servermachine.com,50

# Set the default target for MX records created using the localmx option.
#mx-target=servermachine.com

# Return an MX record pointing to the mx-target for all local
# machines.
#localmx

# Return an MX record pointing to itself for all local machines.
#selfmx

# Change the following lines if you want dnsmasq to serve SRV
# records. These are useful if you want to serve ldap requests for
# Active Directory and other windows-originated DNS requests.
# See RFC 2782.
# You may add multiple srv-host lines.
# The fields are <name>,<target>,<port>,<priority>,<weight>
# If the domain part if missing from the name (so that is just has the
# service and protocol sections) then the domain given by the domain=
# config option is used. (Note that expand-hosts does not need to be
# set for this to work.)

# A SRV record sending LDAP for the example.com domain to
# ldapserver.example.com port 289
#srv-host=_ldap._tcp.example.com,ldapserver.example.com,389

# A SRV record sending LDAP for the example.com domain to
# ldapserver.example.com port 289 (using domain=)
#domain=example.com
#srv-host=_ldap._tcp,ldapserver.example.com,389

# Two SRV records for LDAP, each with different priorities
#srv-host=_ldap._tcp.example.com,ldapserver.example.com,389,1
#srv-host=_ldap._tcp.example.com,ldapserver.example.com,389,2

# A SRV record indicating that there is no LDAP server for the domain
# example.com
#srv-host=_ldap._tcp.example.com

# Change the following lines to enable dnsmasq to serve TXT records.
# These are used for things like SPF and zeroconf. (Note that the
# domain-name expansion done for SRV records _does_not
# occur for TXT records.)

#Example SPF.
#txt-record=example.com,v=spf1 a -all

#Example zeroconf
# records. These are useful if you want to serve ldap requests for
# Active Directory and other windows-originated DNS requests.
# See RFC 2782.
# You may add multiple srv-host lines.
# The fields are <name>,<target>,<port>,<priority>,<weight>
# If the domain part if missing from the name (so that is just has the
# service and protocol sections) then the domain given by the domain=
# config option is used. (Note that expand-hosts does not need to be
# set for this to work.)

# A SRV record sending LDAP for the example.com domain to
# ldapserver.example.com port 289
#srv-host=_ldap._tcp.example.com,ldapserver.example.com,389

# A SRV record sending LDAP for the example.com domain to
# ldapserver.example.com port 289 (using domain=)
#domain=example.com
#srv-host=_ldap._tcp,ldapserver.example.com,389

# Two SRV records for LDAP, each with different priorities
#srv-host=_ldap._tcp.example.com,ldapserver.example.com,389,1
#srv-host=_ldap._tcp.example.com,ldapserver.example.com,389,2

# A SRV record indicating that there is no LDAP server for the domain
# example.com
#srv-host=_ldap._tcp.example.com

# Change the following lines to enable dnsmasq to serve TXT records.
# These are used for things like SPF and zeroconf. (Note that the
# domain-name expansion done for SRV records _does_not
# occur for TXT records.)

#Example SPF.
#txt-record=example.com,v=spf1 a -all

#Example zeroconf
#txt-record=_http._tcp.example.com,name=value,paper=A4

# For debugging purposes, log each DNS query as it passes through
# dnsmasq.
#log-queries

# Include a another lot of configuration options.
#conf-file=/etc/dnsmasq.more.conf
#conf-dir=/etc/dnsmasq.d
<End of File>

As Shipped, the system is configured to provide STUB dns services only to the local network, without providing DHCP services for the local network (Which assumes another server is providing local addresses).

The SYSTEM DNS reference server is specified in the /etc/resolv.conf file
The internet services supervisor is the extended function openbsd-inetd. To reset the networking functions, call the command “/etc/init.d/openbsd-inetd restart”

Greg Hanks Design

Better living thru Handcrafted Technology