[Firehol-support] SMTP/Telnet Problem

Thu Nov 29 10:35:39 GMT 2007

Hi

I’ve been running with an unchanged Firehol config for a couple of years but
have suddenly come across a problem trying to send email to one particular
server.  To try to identify the cause of the problem I’ve run telnet to that
server on port 25.  this is what I get in the log: (I’ve overwritten my IP
addresses to protect the innocent)

Nov 29 10:08:25 mail kernel: OUT-unknown:IN= OUT=eth1 SRC=public_ip
DST=77.75.72.32 LEN=60 TOS=0x10 PREC=0x00 TTL=64 ID=39033 DF PROTO=TCP
SPT=54822 DPT=25 WINDOW=5840 RES=0x00 SYN URGP=0 

Nov 29 10:08:28 mail kernel: OUT-unknown:IN= OUT=eth1 SRC=public_ip
DST=77.75.72.32 LEN=60 TOS=0x10 PREC=0x00 TTL=64 ID=39034 DF PROTO=TCP
SPT=54822 DPT=25 WINDOW=5840 RES=0x00 SYN URGP=0

This doesn’t happen when I telnet to other SMTP servers and I can connect
perfectly OK when Firehol is switched off.

Any ideas on what might be wrong here?

The complete config is :

#

FIREHOL_LOG_LEVEL=error

# $Id: lan-gateway.conf,v 1.1 2003/10/12 13:43:42 ktsaou Exp $

#

# Configuration file for a LAN router with one ethernet interface (eth0)

# for the LAN and a PPP interface for connecting to the Internet.

#

# The LAN works with private IP addresses.

#

# This script will also setup a transparent cache for all the PCs on the

# local LAN.

#
----------------------------------------------------------------------------

# CUSTOM SERVICES

#
----------------------------------------------------------------------------

# See the section "Adding Services" in the documentation

# Example service x, listening on port TCP/z

# > server_x_ports="tcp/z"

# > client_x_ports="default"

#

#
----------------------------------------------------------------------------

# STOP UDP 2222 MESSAGES FLOODING SYSLOG

#
----------------------------------------------------------------------------

server_office_ports="udp/2222"

client_office_ports="any"

#
----------------------------------------------------------------------------

# NETWORK DEFINITIONS - Normally, only these are to be touched by you.

#
----------------------------------------------------------------------------

# You can define anything you like, assuming you are using it later.

# --- HOME ---

# The definition of our HOME LAN.

HOME_MYIP="home_ip"                        # The IP on our HOME LAN

HOME_MYIF="eth0"                  # The HOME LAN interface

HOME_BCAST="home_ip"         # The HOME LAN broadcast

HOME_LAN="home_ip/24"                     # The HOME LAN

HOME_SERVICES="all"

# Do we run a DHCP server on the HOME LAN?

HOME_DHCP=1                                    # Set to 0 to disable

# --- PUBLIC ---

# The definition of our PUBLIC interface.

PUBLIC_MYIP="public_ip"                                  # Leave empty for
dynamic IP

PUBLIC_MYIF="eth1"                # The public interface

PUBLIC_SERVICES="smtp ftp imap pptp"

# Is the PPP interface a DIAL-ON-DEMAND?

DIAL_ON_DEMAND=0               # Set to 0 to disable

# --- TRUSTED ---

# Hosts in the internet I trust for accessing private services

# Empty these to disable.

TRUSTED_IPS=""

TRUSTED_SERVICES=""

# --- TRANSPARENT CACHE ---

# Run a transparent cache?

SQUID_PORT=""                       # Leave empty to disable SQUID

SQUID_USERS=""                     # Users to be excluded from the cache

SQUID_EXCLUDE=""                 # Web Server IPs to be excluded from the
cache

# --- BLACKLIST ---

# A space-separated list of IPs to be blocked.

blacklist=""

#
----------------------------------------------------------------------------

# HELPERS

#
----------------------------------------------------------------------------

# Block all traffic from/to certain IPs

if [ ! -z "${blacklist}" ]

then

            blacklist full "${blacklist}"

fi

# Setup a transparent squid, only if SQUID_PORT is set.

if [ ! -z "${SQUID_PORT}" ]

then

            transparent_squid "${SQUID_PORT}" "${SQUID_USERS}"            \

              inface "${HOME_MYIF}" src "${HOME_LAN}"                 \

              `test ! -z "${SQUID_EXCLUDE}" && echo "dst not
'${SQUID_EXCLUDE}'"`

fi

#
----------------------------------------------------------------------------

# NETWORK ADDRESS TRANSLATION

#
----------------------------------------------------------------------------

# Change the source/destination of packets...

# Should we do SNAT or MASQUERADE?

# If there is a PUBLIC_MYIP defined, we should do SNAT, otherwise MASQ.

#

if [ ! -z "${PUBLIC_MYIP}" ]

then

            snat to "${PUBLIC_MYIP}"
\

                        outface "${PUBLIC_MYIF}"
\

                        src "${HOME_LAN}" dst not "${UNROUTABLE_IPS}"

else

            masquerade "${PUBLIC_MYIF}"

fi

# To have some public service hit an internal machine, do this:

# (the example redirects external port TCP/26 to internal IP 10.0.0.2 port
25)

#

# > dnat to 10.0.0.2:25
\

# >       inface "${PUBLIC_MYIF}"
\

# >       src not "${HOME_LAN} ${UNROUTABLE_IPS}"
\

# >       proto tcp dport 26

#

# For each such statement, the router at the end has to support it.

#
----------------------------------------------------------------------------

# PROTECT SELF

#
----------------------------------------------------------------------------

# Protect the firewall host...

# --- HOME ---

# Protect us from the HOME LAN

interface "${HOME_MYIF}" home src "${HOME_LAN}" dst "${HOME_MYIP}
${HOME_BCAST}"

            policy reject

            server "${HOME_SERVICES}" accept

            client all accept

# DHCP needs 0.0.0.0/255.255.255.255 access.

if [ ${HOME_DHCP} -eq 1 ]

then

            interface "${HOME_MYIF}" dhcp

                        server dhcp accept

                server office drop

fi

# --- PUBLIC ---

# Protect us from the PUBLIC

interface "${PUBLIC_MYIF}" internet
\

            src not "${UNROUTABLE_IPS}"
\

            `test ! -z "${PUBLIC_MYIP}" && echo "dst '${PUBLIC_MYIP}'"`

            protection strong

            policy drop

            # Are there any trusted PCs/services?

            if [ ! -z "${TRUSTED_PCS}" -a ! -z "${TRUSTED_SERVICES}" ]

            then

                        server "${TRUSTED_SERVICES}" accept src
"${TRUSTED_PCS}"

            fi

            server "${PUBLIC_SERVICES}" accept

            server custom rvw tcp/some_port default accept

            client all accept

# DIAL-ON-DEMAND needs this in case there is a PUBLIC_MYIP defined.

if [ ${DIAL_ON_DEMAND} -eq 1 ]

then

            interface "${PUBLIC_MYIF}" dialup

                        client all accept

fi

#
----------------------------------------------------------------------------

# PROTECT ROUTING

#
----------------------------------------------------------------------------

# Protect the LAN...

# Route traffic for the clients on the LAN

router internet2lan inface "${PUBLIC_MYIF}" outface "${HOME_MYIF}"      \

            src not "${UNROUTABLE_IPS}" dst "${HOME_LAN}"

            # route all client traffic

            client all accept

            # For the dnat example above, this is needed:

            # > server smtp accept dst 10.0.0.2

#---------------------------------------------------------------------------
-

# SET LOG OPTIONS

#
---------------------------------------------------------------------------

#FIREHOL_LOG_LEVEL="error"

FIREHOL_LOG_FREQUENCY="1/minute"

FIREHOL_LOG_BURST="5"

****************************************************
Richard Williams
email: HYPERLINK
"mailto:richard at everything4it.co.uk"richard at everything4it.co.uk 
mobile: 07981 734697

web: HYPERLINK
"http://www.everything4it.co.uk"http://www.everything4it.co.uk 
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21:11

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