Date: Tue, 16 Apr 2002 11:22:54 -0700 From: James O'Rourke <jamesworourke@hotmail.com> To: <freebsd-ipfw@freebsd.org> Subject: Strange gateway issues Message-ID: <B8E1BA0E.140D%jamesworourke@hotmail.com>
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Hi,
I'm using a freebsd box as a gateway for an internal network.
Configuration is like so:
<---Internet ---->x.x.x.x (dynamic) FreeBSD 192.168.0.1 <------ LAN ------>
------>
------>
My problem is when I connect to certain sites from inside the lan I get now
reponse. My.yahoo.com is an example. After doing some packet sniffing, I
notice that everything is as normal on making a connection with SYN, SYN
ACK, ACK, ACK PSH all going through. When I make the GET request I get no
response from my.yahoo.com for some reason. However, this does not occur
when connecting from the gateway box. I thought this may have something to
do with cookies however that doesn't make sense to me.
I'm using natd & ipfw and they are correctly configured from what I can see.
It can't be a firewall problem or else surely I wouldn't be able to receive
on the gateway box. The packets are exactly the same coming from inside the
LAN as from the gateway box until I send the GET package - I receive nothing
back. The other thing is that sometimes the my.yahoo.com will work but then
I can't access the links from my page.
This one really has got me beat - well almost. Any suggestions. (copy of
firewall script and natd.conf below:
----------------------------------
rc.firewall.current
#!/bin/sh
# Originally found at http://www.bsdtoday.com/2000/December/Features359.html
# By Peter Brezny
# Modifications done to support dynamic IP and default OS X configuration
# Available at: http://www3.sympatico.ca/dccote/firewall.html
#
# Simple stateful network firewall rules for IPFW with NAT v. 1.01
# See bottom of file for instructions and description of rules
# Created 20001206206 by Peter Brezny, pbrezny@purplecat.net (with a great
# deal of help from freebsd-security@freebsd.org). Specific questions
# about the use of ipfw should be directed to freebsd-ipfw@freebsd.org or
# more general security questions to freebsd-security@freebsd.org.
# Use this script at your own risk.
#
# if you don't know the a.b.c.0/xx notation for ip networks the ipsubnet
# calculator can help you. /usr/ports/net/ipsc-0.4.2
#
###########################
# Note: This does not apply to Mac OS X
#
# Brief Installation instructions
#
# Name this script /etc/rc.firewall.current
# Edit /etc/rc.conf to include
# gateway_enable="YES"
# firewall_enable="YES"
# firewall_script="/etc/rc.firewall.current"
# natd_enable="YES"
# natd_interface="***" #replace with your external ifX
# natd_flags="-dynamic"
# Make sure your kernel is configured to handle ipfw and natd
# See the FreeBSD handbook on how to do this.
#
############################
# Make sure logging is enabled (disabled by default)
if [ `/usr/sbin/sysctl -n net.inet.ip.fw.verbose` == 0 ] ; then
/usr/sbin/sysctl -w net.inet.ip.fw.verbose=1
fi
#
# Define your variables
#
#
fwcmd="/sbin/ipfw" # leave as is if using ipfw
oif="ppp0" # set to outside interface name (for DSL pppoe0 in 10.0.x,
ppp0 in 10.1.x)
# set following line to outside ip address
# or leave as is for dynamic IP address)
oip=`/sbin/ifconfig $oif| grep inet | awk '{ print $2 }'`;
onwr="$oip/8" #set to outside network range
iif="en1" #set to internal interface name
inwr="192.168.0.0/16" #set to internal network range
iip="192.168.0.1" #set to internal ip address
mail="207.69.200.246" # mail server sometimes requires 113
ns1=207.69.188.185 #set to primary name server best if = oif
ns2=207.69.188.186 #set to primary name server best if = oif
ntp=17.254.0.27 #set to ip of NTP server or leave as is
ntp1=17.254.0.31 #set to ip of NTP server or leave as is
ntp2=17.254.0.26 #set to ip of NTP server or leave as is
###
# Rules with descriptions
#
# Basic rules: there is no need to modify anything in this first
section.
# This is the bare minimum to block simple spoofing.
###
#
# Force a flush of the current firewall rules before we reload
$fwcmd -f flush
# Allow your loop back to work
$fwcmd add allow all from any to any via lo0
# Prevent spoofing of your loopback
$fwcmd add deny log all from any to 127.0.0.0/8
# Allow DNS traffic from internet to query your DNS (for reverse
# lookups etc).
# (Seems to be necessary to put it here to make sure lookups are allowed
ASAP)
# $fwcmd add allow udp from any 53 to $ns1 53 via $oif (Good with dynamic
rules)
# $fwcmd add allow udp from any 53 to $ns2 53 via $oif (Good with dynamic
rules)
$fwcmd add allow udp from any 53 to $oip via $oif
$fwcmd add allow udp from $oip to any 53 via $oif
#
# Stop spoofing of your internal network range
$fwcmd add deny log ip from $inwr to any in via $oif
#
# Stop spoofing from inside your private ip range
$fwcmd add deny log ip from not $inwr to any in via $iif
# Stop from gnutella - out of hand
$fwcmd add deny log tcp from any to $oip 6346
#
# Stop private networks (RFC1918) from entering the outside interface.
$fwcmd add deny log ip from 192.168.0.0/16 to any in via $oif
$fwcmd add deny log ip from 172.16.0.0/12 to any in via $oif
$fwcmd add deny log ip from 10.0.0.0/8 to any in via $oif
$fwcmd add deny log ip from any to 192.168.0.0/16 in via $oif
$fwcmd add deny log ip from any to 172.16.0.0/12 in via $oif
$fwcmd add deny log ip from any to 10.0.0.0/8 in via $oif
#
# Stop draft-manning-dsua-01.txt nets on the outside interface
$fwcmd add deny log all from 0.0.0.0/8 to any in via $oif
$fwcmd add deny log all from 169.254.0.0/16 to any in via $oif
$fwcmd add deny log all from 192.0.2.0/24 to any in via $oif
$fwcmd add deny log all from 224.0.0.0/4 to any in via $oif
$fwcmd add deny log all from 240.0.0.0/4 to any in via $oif
$fwcmd add deny log all from any to 0.0.0.0/8 in via $oif
$fwcmd add deny log all from any to 169.254.0.0/16 in via $oif
$fwcmd add deny log all from any to 192.0.2.0/24 in via $oif
$fwcmd add deny log all from any to 224.0.0.0/4 in via $oif
$fwcmd add deny log all from any to 240.0.0.0/4 in via $oif
#
###
# User rules: Some of the rules below are dependent on your
configuration.
# They might require some adjustments. They are emphasized with the
# word "ADJUST".
###
# ADJUST: If you use NATD (for your 192.168.0.1 interface for instance)
# you must uncomment the following:
# Divert all packets through natd
$fwcmd add divert natd all from any to any via $oif
#
# Allow all established connections to persist (setup required
# for new connections).
$fwcmd add allow tcp from any to any established
#
# ADJUST: Allow incoming requests to reach the various services.
# To allow multiple services you may list them separated
# by a coma, for example ...to $oip 22,25,110,80 setup
# If you have an internal interface (e.g. if you do not run NATd)
# uncomment the second line to enable AppleTalk on it.
# $fwcmd add allow tcp from any to $oip 22 setup
$fwcmd add allow tcp from any to $oip 21,22,80,548 setup
# $fwcmd add allow tcp from any to $iip 548 setup via $oif
#
# NOTE: you may have to change your client to passive or active mode
# to get ftp to work once enabled, only ssh, ftp and appletalk enabled by
default.
# 21:ftp enabled by default
# 22:ssh enabled by default
# 23:telnet
# 25:smtp
# 110:pop
# 143:imap
# 80:http
# 443:ssl
# 548:appleshare enabled by default
#
# Allow icmp packets for diagnostic purposes (ping traceroute)
# you may wish to leave commented out.
$fwcmd add allow icmp from any to any
#
# Allow required ICMP
$fwcmd add allow icmp from any to any icmptypes 3,4,11,12
#
# Allow time update traffic
$fwcmd add allow udp from $ntp to $oip
$fwcmd add allow udp from $ntp1 to $oip
$fwcmd add allow udp from $ntp2 to $oip
# Politely and quickly rejects AUTH requests (e.g. email and ftp)
$fwcmd add reset tcp from $mail to $oip 113
#
# Checks packets against dynamic rule set below.
# $fwcmd add check-state (Does not work in OS X)
#
# Allow any traffic from firewall ip to any going out the
# external interface
# $fwcmd add allow ip from $oip to any keep-state out via $oif (Does not
work in OS X)
$fwcmd add allow ip from $oip to any out via $oif
#
# Allow any traffic from local network to any passing through the
# internal interface
# $fwcmd add allow ip from $inwr to any keep-state via $iif (Does not
work in OS X)
$fwcmd add allow ip from $inwr to any via $iif
#
# Deny everything else
$fwcmd add 65435 deny log ip from any to any
#
#####################################################
#
# End firewall script.
---------------------
natd.conf
interface ppp0
dynamic yes
use_sockets yes
same_ports yes
----------------------
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