Образец настройки ipfw.Часть 2

Есть почтовый сервер с двумя подсетями (Интернет и локальная сеть) и кучей сервисов.

Нам необходимо, чтобы часть сервисов была видна в интернете, а другая только из локальной сети.

Шлюзом доступа в Интернет сервер не является. Управление им осуществляется по локальной сети.

Будем настраивать фаервол через конфигурационные файлы rc.conf и rc.firewall.

Описание сервисов из rc.conf убрано.

Итак

rc.conf:

# — sysinstall generated deltas — # Fri Nov  6 12:40:50 2009

# Created: Fri Nov  6 12:40:50 2009

# Enable network daemons for user convenience.

# Please make all changes to this file, not to /etc/defaults/rc.conf.

# This file now contains just the overrides from /etc/defaults/rc.conf.

#Шлюз по-умолчанию.

defaultrouter=»213.XX.XX.193″

#Имя сервера.

hostname=»exim.mizx.ru»

# Интерфейс локальной сети

ifconfig_bge1=»inet 10.10.10.203  netmask 255.255.255.0″

# Интерфейс Интернет сети

ifconfig_bge0=»inet 213.xx.xx.205  netmask 255.255.255.240″

# Включаем ipfw

firewall_enable=»YES»

# Назначаем тип фаервола как SIMPLE

firewall_type=»SIMPLE»

Если версия FreeBSD 5.x, необходимо перекомпилить ядро в опциями:

options IPFIREWALL

—  включает код IPFW в ядро

options IPFIREWALL_VERBOSE

— включает протоколирование пакетов

options IPFIREWALL_VERBOSE_LIMIT=10

— требуется для безопасности от DoS- атаки.

options IPDIVERT

— включает код NATD  в ядро (если требуется).

Теперь рассмотрим файл

/etc/rc.firewall

#!/bin/sh —

# Copyright (c) 1996  Poul-Henning Kamp

# All rights reserved.

#

# Redistribution and use in source and binary forms, with or without

# modification, are permitted provided that the following conditions

# are met:

# 1. Redistributions of source code must retain the above copyright

#    notice, this list of conditions and the following disclaimer.

# 2. Redistributions in binary form must reproduce the above copyright

#    notice, this list of conditions and the following disclaimer in the

#    documentation and/or other materials provided with the distribution.

#

# $FreeBSD: src/etc/rc.firewall,v 1.52.2.3.4.1 2009/04/15 03:14:26 kensmith Exp $

#

#

# Setup system for ipfw(4) firewall service.

#

# Suck in the configuration variables.

if [ -z «${source_rc_confs_defined}» ]; then

if [ -r /etc/defaults/rc.conf ]; then

. /etc/defaults/rc.conf

source_rc_confs

elif [ -r /etc/rc.conf ]; then

. /etc/rc.conf

fi

fi

############

# Define the firewall type in /etc/rc.conf.  Valid values are:

#   open        — will allow anyone in

#   client      — will try to protect just this machine

#

simple      — will try to protect a whole network

#   closed      — totally disables IP services except via lo0 interface

#   workstation — will try to protect just this machine using statefull

#    firewalling. See below for rc.conf variables used

#   UNKNOWN     — disables the loading of firewall rules.

#   filename    — will load the rules in the given filename (full path required)

#

# For «client» and «simple» the entries below should be customized

# appropriately.

############

#

# If you don’t know enough about packet filtering, we suggest that you

# take time to read this book:

#

# Building Internet Firewalls, 2nd Edition

# Brent Chapman and Elizabeth Zwicky

#

# O’Reilly & Associates, Inc

# ISBN 1-56592-871-7

# http://www.ora.com/

# http://www.oreilly.com/catalog/fire2/

#

# For a more advanced treatment of Internet Security read:

#

# Firewalls and Internet Security: Repelling the Wily Hacker, 2nd Edition

# William R. Cheswick, Steven M. Bellowin, Aviel D. Rubin

#

# Addison-Wesley / Prentice Hall

# ISBN 0-201-63466-X

# http://www.pearsonhighered.com/

# http://www.pearsonhighered.com/educator/academic/product/0,3110,020163466X,00.html

#

Правила для интерфейса lo

setup_loopback () {

############

# Only in rare cases do you want to change these rules

#

${fwcmd} add 100 pass all from any to any via lo0

${fwcmd} add 200 deny all from any to 127.0.0.0/8

${fwcmd} add 300 deny ip from 127.0.0.0/8 to any

}

# Определяем тип фаервола

if [ -n «${1}» ]; then

firewall_type=»${1}»

fi

############

# Set quiet mode if requested

#

case ${firewall_quiet} in

[Yy][Ee][Ss])

fwcmd=»/sbin/ipfw -q»

;;

*)

fwcmd=»/sbin/ipfw»

;;

esac

############

Сбрасываем правила

# Flush out the list before we begin.

#

${fwcmd} -f flush

#Загружаем правила lo

setup_loopback

############

# Network Address Translation.  All packets are passed to natd(8)

# before they encounter your remaining rules.  The firewall rules

# will then be run again on each packet after translation by natd

# starting at the rule number following the divert rule.

#

# For «simple» firewall type the divert rule should be put to a

# different place to not interfere with address-checking rules.

#

Ищем метку типа нашего фаервола

.

case ${firewall_type} in

[Oo][Pp][Ee][Nn]|[Cc][Ll][Ii][Ee][Nn][Tt])

case ${natd_enable} in

[Yy][Ee][Ss])

if [ -n «${natd_interface}» ]; then

${fwcmd} add 50 divert natd ip4 from any to any via ${natd_interface}

fi

;;

esac

case ${firewall_nat_enable} in

[Yy][Ee][Ss])

if [ -n «${firewall_nat_interface}» ]; then

if echo «${firewall_nat_interface}» | \r

grep -q -E ‘~~[0-9]+(.[0-9]+){0,3}$’; then

firewall_nat_flags=»ip ${firewall_nat_interface} ${firewall_nat_flags}»

else

firewall_nat_flags=»if ${firewall_nat_interface} ${firewall_nat_flags}»

fi

${fwcmd} nat 123 config log ${firewall_nat_flags}

${fwcmd} add 50 nat 123 ip4 from any to any via ${firewall_nat_interface}

fi

;;

esac

esac

############

# If you just configured ipfw in the kernel as a tool to solve network

# problems or you just want to disallow some particular kinds of traffic

# then you will want to change the default policy to open.  You can also

# do this as your only action by setting the firewall_type to «open».

#

# ${fwcmd} add 65000 pass all from any to any

# Prototype setups.

#

case ${firewall_type} in

[Oo][Pp][Ee][Nn])

${fwcmd} add 65000 pass all from any to any

;;

[Cc][Ll][Ii][Ee][Nn][Tt])

############

# This is a prototype setup that will protect your system somewhat

# against people from outside your own network.

#

# Configuration:

#  firewall_client_net:  Network address of local network.

############

# set this to your local network

net=»$firewall_client_net»

# Allow any traffic to or from my own net.

${fwcmd} add pass all from me to ${net}

${fwcmd} add pass all from ${net} to me

# Allow TCP through if setup succeeded

${fwcmd} add pass tcp from any to any established

# Allow IP fragments to pass through

${fwcmd} add pass all from any to any frag

# Allow setup of incoming email

${fwcmd} add pass tcp from any to me 25 setup

# Allow setup of outgoing TCP connections only

${fwcmd} add pass tcp from me to any setup

# Disallow setup of all other TCP connections

${fwcmd} add deny tcp from any to any setup

# Allow DNS queries out in the world

${fwcmd} add pass udp from me to any 53 keep-state

# Allow NTP queries out in the world

${fwcmd} add pass udp from me to any 123 keep-state

# Everything else is denied by default, unless the

# IPFIREWALL_DEFAULT_TO_ACCEPT option is set in your kernel

# config file.

;;

#Наш тип фаервола

[Ss][Ii][Mm][Pp][Ll][Ee])

############

# This is a prototype setup for a simple firewall.  Configure this

# machine as a DNS and NTP server, and point all the machines

# on the inside at this machine for those services.

#

# Configuration:

#  firewall_simple_iif:  Inside network interface.

#  firewall_simple_inet: Inside network address.

#  firewall_simple_oif:  Outside network interface.

#  firewall_simple_onet: Outside network address.

############

# set these to your outside interface network

#

Назначаем интерфейс и подсеть для интернет

oif=»213.xx.xx.205″

onet=»213.xx.xx.192/27″

# set these to your inside interface network

Назначаем интерфейс и подсеть для локальной сети

iif=»10.10.10.203″

inet=»10.10.10.0/24″

# Stop spoofing.

Не допускаем спуфинг

${fwcmd} add deny all from ${inet} to any in via ${oif}

${fwcmd} add deny all from ${onet} to any in via ${iif}

# Stop RFC1918 nets on the outside interface.

Запрещаем коннектиться

# к локальной сети через интерфейс интернета с известных диапазонов подсетей.

${fwcmd} add deny all from any to 10.0.0.0/8 via ${oif}

${fwcmd} add deny all from any to 172.16.0.0/12 via ${oif}

${fwcmd} add deny all from any to 192.168.0.0/16 via ${oif}

# Stop draft-manning-dsua-03.txt (1 May 2000) nets (includes RESERVED-1,

# DHCP auto-configuration, NET-TEST, MULTICAST (class D), and class E)

# on the outside interface.

Запрещаем NET-TEST, MULTICAST (class D), and class E)

# через интерфейс интернета.

${fwcmd} add deny all from any to 0.0.0.0/8 via ${oif}

${fwcmd} add deny all from any to 169.254.0.0/16 via ${oif}

${fwcmd} add deny all from any to 192.0.2.0/24 via ${oif}

${fwcmd} add deny all from any to 224.0.0.0/4 via ${oif}

${fwcmd} add deny all from any to 240.0.0.0/4 via ${oif}

# Network Address Translation.  This rule is placed here deliberately

# so that it does not interfere with the surrounding address-checking

# rules.  If for example one of your internal LAN machines had its IP

# address set to 192.0.2.1 then an incoming packet for it after being

# translated by natd(8) would match the `deny’ rule above.  Similarly

# an outgoing packet originated from it before being translated would

# match the `deny’ rule below.

# NAT  у нас отсутствует ( не нужен).

case ${natd_enable} in

[Yy][Ee][Ss])

if [ -n «${natd_interface}» ]; then

${fwcmd} add divert natd all from any to any via ${natd_interface}

fi

;;

esac

# Stop RFC1918 nets on the outside interface

## ${fwcmd} add deny all from 10.0.0.0/8 to any via ${oif}

## ${fwcmd} add deny all from 172.16.0.0/12 to any via ${oif}

## ${fwcmd} add deny all from 192.168.0.0/16 to any via ${oif}

# Stop draft-manning-dsua-03.txt (1 May 2000) nets (includes RESERVED-1,

# DHCP auto-configuration, NET-TEST, MULTICAST (class D), and class E)

# on the outside interface

## ${fwcmd} add deny all from 0.0.0.0/8 to any via ${oif}

## ${fwcmd} add deny all from 169.254.0.0/16 to any via ${oif}

## ${fwcmd} add deny all from 192.0.2.0/24 to any via ${oif}

## ${fwcmd} add deny all from 224.0.0.0/4 to any via ${oif}

## ${fwcmd} add deny all from 240.0.0.0/4 to any via ${oif}

# Ниже описаны правила нашего фаервола.

# Allow TCP through if setup succeeded

# Разрешаем прохождение TCP для установленных соединений

${fwcmd} add pass tcp from any to any established

# Allow IP fragments to pass through

# Разрешаем фрагментацию

${fwcmd} add pass all from any to any frag

# Allow setup of incoming email

# Разрешаем работу почты (SMTP,IMAP,POP3) через оба интерфейса.

${fwcmd} add pass tcp from any to me 25 setup

${fwcmd} add pass tcp from any to me 110 setup

${fwcmd} add pass tcp from any to me 143 setup

# Allow setup of incoming ftp

# Разрешаем работу ftp через оба  интерфейса.

${fwcmd} add pass tcp from any to me 21 setup

${fwcmd} add pass tcp from any to me 20 setup

#Allow all from 10.10.10.0/24

# Разрешаем подключаться из локальной сети к интерфейсу,

#подключенному к локальной сети и пингование.

${fwcmd} add pass tcp from ${inet} to ${iif} any setup

${fwcmd} add pass icmp from ${inet} to ${iif} in icmptypes 8

${fwcmd} add pass icmp from ${iif} to ${inet} out icmptypes 0

${fwcmd} add pass tcp from ${inet} to ${iif} 22 setup

# Allow access to our DNS

##

Разрешаем работу DNS  для обеих интерфейсов

${fwcmd} add pass udp from any to me 53

${fwcmd} add pass udp from ${oif} 53 to any

# Allow access to our WWW all address

# Разрешаем подключаться  к соответствующим портам 80,8080,8020

#к обеим интерфейсам.

${fwcmd} add pass tcp from any to me 80 setup

${fwcmd} add pass tcp from any to me 8080 setup

${fwcmd} add pass tcp from any to me 8020 setup

# Allow access to our WWW not all address

# Разрешаем подключаться  к соответствующим портам 8070,8025,8021,10000

#к локальному интерфейсу из локальной сети.

${fwcmd} add pass tcp from any to ${iif} 8070 setup

${fwcmd} add pass tcp from any to ${iif} 8025 setup

${fwcmd} add pass tcp from any to ${iif} 8021 setup

${fwcmd} add pass tcp from any to ${iif} 10000 setup

#Allow PING.

Разрешаем пинг из и в интернет

.

${fwcmd} add deny icmp from any to ${oif} in icmptypes 8

${fwcmd} add pass icmp from ${oif} to any out icmptypes 8

${fwcmd} add pass icmp from any to ${oif} in icmptypes 0

# Reject&Log all setup of incoming connections from the outside

${fwcmd} add deny log tcp from any to any in via ${oif} setup

# Allow setup of any other TCP connection

## ${fwcmd} add pass tcp from any to any setup

#

Allow DNS queries out in the world ( Для уже установленных соединений).

${fwcmd} add pass udp from me to any 53 keep-state

# Allow NTP queries out in the world

## ${fwcmd} add pass udp from me to any 123 keep-state

##

Для  всех, уже установленных соединений.

${fwcmd} add pass tcp from me to any  keep-state

# Everything else is denied by default, unless the

# IPFIREWALL_DEFAULT_TO_ACCEPT option is set in your kernel

# config file.

;;

[Ww][Oo][Rr][Kk][Ss][Tt][Aa][Tt][Ii][Oo][Nn])

# Configuration:

#  firewall_myservices:  List of TCP ports on which this host

#      offers services.

#  firewall_allowservices: List of IPs which has access to

#     $firewall_myservices.

#  firewall_trusted:  List of IPs which has full access

#     to this host. Be very carefull

#     when setting this. This option can

#     seriously degrade the level of

#     protection provided by the firewall.

#  firewall_logdeny:  Boolean (YES/NO) specifying if the

#     default denied packets should be

#     logged (in /var/log/security).

#  firewall_nologports:  List of TCP/UDP ports for which

#     denied incomming packets are not

#     logged.

# Allow packets for which a state has been built.

${fwcmd} add check-state

# For services permitted below.

${fwcmd} add pass tcp  from me to any established

# Allow any connection out, adding state for each.

${fwcmd} add pass tcp  from me to any setup keep-state

${fwcmd} add pass udp  from me to any       keep-state

${fwcmd} add pass icmp from me to any       keep-state

# Allow DHCP.

${fwcmd} add pass udp  from 0.0.0.0 68 to 255.255.255.255 67 out

${fwcmd} add pass udp  from any 67     to me 68 in

${fwcmd} add pass udp  from any 67     to 255.255.255.255 68 in

# Some servers will ping the IP while trying to decide if it’s

# still in use.

${fwcmd} add pass icmp from any to any icmptype 8

# Allow «mandatory» ICMP in.

${fwcmd} add pass icmp from any to any icmptype 3,4,11

# Add permits for this workstations published services below

# Only IPs and nets in firewall_allowservices is allowed in.

# If you really wish to let anyone use services on your

# workstation, then set «firewall_allowservices=’any'» in /etc/rc.conf

#

# Note: We don’t use keep-state as that would allow DoS of

#       our statetable.

#       You can add ‘keep-state’ to the lines for slightly

#       better performance if you fell that DoS of your

#       workstation won’t be a problem.

#

for i in ${firewall_allowservices} ; do

for j in ${firewall_myservices} ; do

${fwcmd} add pass tcp from $i to me $j

done

done

# Allow all connections from trusted IPs.

# Playing with the content of firewall_trusted could seriously

# degrade the level of protection provided by the firewall.

for i in ${firewall_trusted} ; do

${fwcmd} add pass ip from $i to me

done

${fwcmd} add 65000 count ip from any to any

# Drop packets to ports where we don’t want logging

for i in ${firewall_nologports} ; do

${fwcmd} add deny { tcp or udp } from any to any $i in

done

# Broadcasts and muticasts

${fwcmd} add deny ip  from any to 255.255.255.255

${fwcmd} add deny ip  from any to 224.0.0.0/24 in # XXX

# Noise from routers

${fwcmd} add deny udp from any to any 520 in

# Noise from webbrowsing.

# The statefull filter is a bit agressive, and will cause some

#  connection teardowns to be logged.

${fwcmd} add deny tcp from any 80,443 to any 1024-65535 in

# Deny and (if wanted) log the rest unconditionally.

log=»»

if [ ${firewall_logdeny:-x} = «YES» -o ${firewall_logdeny:-x} = «yes» ] ; then

log=»log logamount 500″ # The default of 100 is too low.

sysctl net.inet.ip.fw.verbose=1 >/dev/null

fi

${fwcmd} add deny $log ip from any to any

;;

[Cc][Ll][Oo][Ss][Ee][Dd])

${fwcmd} add 65000 deny ip from any to any

;;

[Uu][Nn][Kk][Nn][Oo][Ww][Nn])

;;

*)

if [ -r «${firewall_type}» ]; then

${fwcmd} ${firewall_flags} ${firewall_type}

fi

;;

esac

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