[RH8 - IPTABLES] firewall vraagje

[Mujo]

Allereerst excuus voor de brede layout, ik kon het zo gauw niet
smaller krijgen.

Ik ben sinds 2 dagen aan het rommelen met een nieuwe firewall, dit
keer met iptables onder RedHat 8. Het is flink wennen ten opzichte van een
simpel ipchains tooltje wat ik eerst op RH 6.2 altijd gebruikte.

Het timmert echter alles ZO goed dicht dat het me niet lukt om ports open
te krijgen voor de buitenwereld. Ik wil graag dat mensen bij mijn
ip (via DHCP toegewezen) kunnen op port 2222 bijvoorbeeld voor SecureSHell (SSH).
Ik heb Quicknet als ISP, en die gooien de wat lagere poorten dicht,
vandaar dat de daemon van OpenSSH nu op 2222 draait.
Ergens bijna onderaan in dit script staat een stukje tussen een
aantal ###'s bij de INPUT-chain. Ik snap niet goed waarom dat
(en de daemon draaiende op port 2222) niet voldoende zijn om van BUITENAF
bij mijn ip op port 2222 te kunnen secureshellen.
Ik heb sterk de indruk dat er ergens een rule of chain is die het toch verbied
of een flag die verkeerd staat...

Ik ben al blij dat ik het voor al het interne verkeer werkend heb gekregen, en
ik ben het nog overal aan het aanpassen, dus let niet op engels en nederlandse
tekst die door elkaar heen wordt gebruikt (ben bezig met vertaling).
Suggesties ter verbetering zijn
natuurlijk altijd superwelkom. Bijvoorbeeld als er stomme definities in staan die
de firewall 'gevaarlijk' maken.

Hier volgt dus script (ja het is een rommeltje) wat nu redelijk werkt:

code:

#!/bin/sh
#
###########################################################################
# Firewall 1.0                                                       #
#                                                                         #
# Een IPTABLES firewall met IP Masquerade support                         #
# voor Linux 2.4.x kernels.                                               #
###########################################################################

FWVERSIE=1.0    
echo -e "\nBezig met laden van firewall - versie $FWVERSIE...\n"

###########################################################################
# De locatie van de iptables en andere shell programma's,                 #
# meestal in /sbin. Bij handmatig compilen van iptables is de             #
# standaard locatie /usr/local/sbin.                                      #
# (gebruik "whereis iptables" om goede directory te vinden)               #
###########################################################################

IPTABLES=/sbin/iptables
#IPTABLES=/usr/local/sbin/iptables
LSMOD=/sbin/lsmod
DEPMOD=/sbin/depmod
INSMOD=/sbin/insmod
GREP=/bin/grep
AWK=/bin/awk
SED=/bin/sed
IFCONFIG=/sbin/ifconfig

###########################################################################
# Externe en Interne interfaces van het netwerk                           #
#                                                                         #
# Het Externe netwerk is waar NAT gebeurd.                                #
# Het Interne netwerk is bij voorkeur een RFC1918 private adres.          #
# Verander EXTIF in "ppp0" als het een modem betreft.                     #
###########################################################################

EXTIF="eth0"
INTIF="eth1"
echo " Externe Interface:  $EXTIF"
echo " Interne Interface:  $INTIF"
echo " ---"

# Specify your Static IP address here or let the script take care of it 
# for you.
#
#   If you prefer to use STATIC addresses in your firewalls, un-# out the
#   static example below and # out the dynamic line.  If you don't care,
#   just leave this section alone.
#
#   If you have a DYNAMIC IP address, the ruleset already takes care of
#   this for you.  Please note that the different single and double quote 
#   characters and the script MATTER.
#
#
#   DHCP users:
#   -----------
#   If you get your TCP/IP address via DHCP, **you will need ** to enable the 
#   #ed out command below underneath the PPP section AND replace the word 
#   "eth0" with the name of your EXTERNAL Internet connection (ppp0, ippp0, 
#   etc) on the lines for "ppp-ip" and "extip".  You should also note that the 
#   DHCP server can and will change IP addresses on you.  To deal with this, 
#   users should configure their DHCP client to re-run the rc.firewall ruleset 
#   everytime the DHCP lease is renewed.
#
#     NOTE #1:  Some DHCP clients like the original "pump" (the newer
#               versions have been fixed) did NOT have the ability to run 
#               scripts after a lease-renew.  Because of this, you need to 
#               replace it with something like "dhcpcd" or "dhclient".
#
#     NOTE #2:  The syntax for "dhcpcd" has changed in recent versions.
#
#               Older versions used syntax like:
#                         dhcpcd -c /etc/rc.d/rc.firewall eth0
#
#               Newer versions execute a file called /etc/dhcpc/dhcpcd-eth0.exe
#
#     NOTE #3:  For Pump users, put the following line in /etc/pump.conf:
#
#                   script /etc/rc.d/rc.firewall
#
#   PPP users:
#   ----------
#   If you aren't already aware, the /etc/ppp/ip-up script is always run when 
#   a PPP connection comes up.  Because of this, we can make the ruleset go and 
#   get the new PPP IP address and update the strong firewall ruleset.
#
#   If the /etc/ppp/ip-up file already exists, you should edit it and add a line
#   containing "/etc/rc.d/rc.firewall" near the end of the file.
#
#   If you don't already have a /etc/ppp/ip-up sccript, you need to create the 
#   following link to run the /etc/rc.d/rc.firewall script.
#
#       ln -s /etc/rc.d/rc.firewall /etc/ppp/ip-up
#
#   * You then want to enable the #ed out shell command below *
#
#
# Determine the external IP automatically:
# ----------------------------------------
#
#  The following line will determine your external IP address.  This
#  line is somewhat complex and confusing but it will also work for
#  all NON-English Linux distributions:
#
EXTIP="`$IFCONFIG $EXTIF | $AWK \
 /$EXTIF/'{next}//{split($0,a,":");split(a[2],a," ");print a[1];exit}'`"

###########################################################################
# Voor gebruikers met een STATIC IP adres:                                #
#                                                                         #
#    plaats een # voor de EXTIP-regel hierboven en haal de # weg voor de  #
#    EXTIP-regel hieronder.                                               #
###########################################################################

#EXTIP="your.static.PPP.address"
echo "  Extern IP: $EXTIP"
echo "  ---"

###########################################################################
# Toewijzen van interne TCP/IP netwerk en IP-adressen                     #
###########################################################################

INTNET="192.168.1.0/24"
INTIP="192.168.1.1/24"
PRIVPORTS="0:1013"
UNPRIVPORTS="1024:65535"
ALLPORTS="0:65535"
ANYWHERE="0.0.0.0/0"
UNIVERSE="0.0.0.0/0"
echo "  Interne Netwerk: $INTNET"
echo "  Intern IP:       $INTIP"
echo "  ---"

##########################################################################
# Na deze regel hoeft niets geedit te worden voor MASQ-testen            #
##########################################################################

# Kijken of alle modules alle benodigde depencencies hebben           
echo "  - Controleren of alle kernel-modules in orde zijn"
$DEPMOD -a
echo -en "    Bezig met laden van kernel modules: "

# With the new IPTABLES code, the core MASQ functionality is now either
# modular or compiled into the kernel.  This HOWTO shows ALL IPTABLES
# options as MODULES.  If your kernel is compiled correctly, there is
# NO need to load the kernel modules manually.  
#
#  NOTE: The following items are listed ONLY for informational reasons.
#        There is no reason to manual load these modules unless your
#        kernel is either mis-configured or you intentionally disabled
#        the kernel module autoloader.
#
# Upon the commands of starting up IP Masq on the server, the
# following kernel modules will be automatically loaded:
#
# NOTE:  Only load the IP MASQ modules you need.  All current IP MASQ 
#        modules are shown below but are commented out from loading.

#Load the main body of the IPTABLES module - "ip_tables"
#  - Loaded automatically when the "iptables" command is invoked
#
#  - Loaded manually to clean up kernel auto-loading timing issues
#
echo -en "ip_tables, "
#
#Verify the module isn't loaded.  If it is, skip it
#
if [ -z "` $LSMOD | $GREP ip_tables | $AWK {'print $1'} `" ]; then
   $INSMOD ip_tables
fi


#Load the IPTABLES filtering module - "iptable_filter" 
#
#  - Loaded automatically when filter policies are activated


#Load the stateful connection tracking framework - "ip_conntrack"
#
# The conntrack  module in itself does nothing without other specific 
# conntrack modules being loaded afterwards such as the "ip_conntrack_ftp"
# module
#
#  - This module is loaded automatically when MASQ functionality is 
#    enabled 
#
#  - Loaded manually to clean up kernel auto-loading timing issues
#
echo -en "ip_conntrack, "
#
#Verify the module isn't loaded.  If it is, skip it
#
if [ -z "` $LSMOD | $GREP ip_conntrack | $AWK {'print $1'} `" ]; then
   $INSMOD ip_conntrack
fi


#Load the FTP tracking mechanism for full FTP tracking
#
# Enabled by default -- insert a "#" on the next line to deactivate
#
echo -e "ip_conntrack_ftp, "
#
#Verify the module isn't loaded.  If it is, skip it
#
if [ -z "` $LSMOD | $GREP ip_conntrack_ftp | $AWK {'print $1'} `" ]; then
   $INSMOD ip_conntrack_ftp
fi


#Load the IRC tracking mechanism for full IRC tracking
#
# Enabled by default -- insert a "#" on the next line to deactivate
#
echo -en "                             ip_conntrack_irc, "
#
#Verify the module isn't loaded.  If it is, skip it
#
if [ -z "` $LSMOD | $GREP ip_conntrack_irc | $AWK {'print $1'} `" ]; then
   $INSMOD ip_conntrack_irc
fi


#Load the general IPTABLES NAT code - "iptable_nat"
#  - Loaded automatically when MASQ functionality is turned on
# 
#  - Loaded manually to clean up kernel auto-loading timing issues
#
echo -en "iptable_nat, "
#
#Verify the module isn't loaded.  If it is, skip it
#
if [ -z "` $LSMOD | $GREP iptable_nat | $AWK {'print $1'} `" ]; then
   $INSMOD iptable_nat
fi


#Loads the FTP NAT functionality into the core IPTABLES code
# Required to support non-PASV FTP.
#
# Enabled by default -- insert a "#" on the next line to deactivate
#
echo -e "ip_nat_ftp"
#
#Verify the module isn't loaded.  If it is, skip it
#
if [ -z "` $LSMOD | $GREP ip_nat_ftp | $AWK {'print $1'} `" ]; then
   $INSMOD ip_nat_ftp
fi

echo "  ---"

# Just to be complete, here is a list of the remaining kernel modules 
# and their function.  Please note that several modules should be only
# loaded by the correct master kernel module for proper operation.
# --------------------------------------------------------------------
#
#    ipt_mark       - this target marks a given packet for future action.
#                     This automatically loads the ipt_MARK module
#
#    ipt_tcpmss     - this target allows to manipulate the TCP MSS
#                     option for braindead remote firewalls.
#                     This automatically loads the ipt_TCPMSS module
#
#    ipt_limit      - this target allows for packets to be limited to
#                     to many hits per sec/min/hr
#
#    ipt_multiport  - this match allows for targets within a range
#                     of port numbers vs. listing each port individually
#
#    ipt_state      - this match allows to catch packets with various
#                     IP and TCP flags set/unset
#
#    ipt_unclean    - this match allows to catch packets that have invalid
#                     IP/TCP flags set
#
#    iptable_filter - this module allows for packets to be DROPped, 
#                     REJECTed, or LOGged.  This module automatically 
#                     loads the following modules:
#
#                     ipt_LOG - this target allows for packets to be 
#                               logged
#
#                     ipt_REJECT - this target DROPs the packet and returns 
#                                  a configurable ICMP packet back to the 
#                                  sender.
# 
#    iptable_mangle - this target allows for packets to be manipulated
#                     for things like the TCPMSS option, etc.


#CRITICAL:  Enable IP forwarding since it is disabled by default since
#
#           Redhat Users:  you may try changing the options in
#                          /etc/sysconfig/network from:
#
#                       FORWARD_IPV4=false
#                             to
#                       FORWARD_IPV4=true
#
echo "  Enabling forwarding.."
echo "1" > /proc/sys/net/ipv4/ip_forward


# Dynamic IP users:
#
#   If you get your IP address dynamically from SLIP, PPP, or DHCP, 
#   enable the following option.  This enables dynamic-address hacking
#   which makes the life with Diald and similar programs much easier.
#
echo "  Enabling DynamicAddr.."
echo "1" > /proc/sys/net/ipv4/ip_dynaddr

echo "  ---"

#############################################################################
#
# Enable Stronger IP forwarding and Masquerading
#
#  NOTE:  In IPTABLES speak, IP Masquerading is a form of SourceNAT or SNAT.
#
#  NOTE #2:  The following is an example for an internal LAN address in the
#            192.168.1.x network with a 255.255.255.0 or a "24" bit subnet 
#            mask connecting to the Internet on external interface "eth0".  
#            This example will MASQ internal traffic out to the Internet 
#            but not allow non-initiated traffic into your internal network.
#
#            
#         ** Please change the above network numbers, subnet mask, and your 
#         *** Internet connection interface name to match your setup
#         

#Clearing any previous configuration
#
#  Unless specified, the defaults for INPUT, OUTPUT, and FORWARD to DROP.
#
#    You CANNOT change this to REJECT as it isn't a vaild setting for a
#    policy.  If you want REJECT, you must explictly REJECT at the end
#    of a giving INPUT, OUTPUT, or FORWARD chain
#
echo "  Clearing any existing rules and setting default policy to DROP.."
$IPTABLES -P INPUT DROP  
$IPTABLES -F INPUT 
$IPTABLES -P OUTPUT DROP  
$IPTABLES -F OUTPUT 
$IPTABLES -P FORWARD DROP  
$IPTABLES -F FORWARD 
$IPTABLES -F -t nat

#Not needed and it will only load the unneeded kernel module
#$IPTABLES -F -t mangle
#
# Flush the user chain.. if it exists
if [ -n "`$IPTABLES -L | $GREP drop-and-log-it`" ]; then
   $IPTABLES -F drop-and-log-it
fi
#
# Delete all User-specified chains
$IPTABLES -X
#
# Reset all IPTABLES counters
$IPTABLES -Z


#Configuring specific CHAINS for later use in the ruleset
#
#  NOTE:  Some users prefer to have their firewall silently
#         "DROP" packets while others prefer to use "REJECT"
#         to send ICMP error messages back to the remote 
#         machine.  The default is "REJECT" but feel free to
#         change this below.
#
# NOTE: Without the --log-level set to "info", every single
#       firewall hit will goto ALL vtys.  This is a very big
#       pain.
#
echo "  Creating a DROP chain.."
$IPTABLES -N drop-and-log-it
$IPTABLES -A drop-and-log-it -j LOG --log-level info 
$IPTABLES -A drop-and-log-it -j DROP

echo -e "\n   - Loading INPUT rulesets"


#######################################################################
# INPUT: Incoming traffic from various interfaces.  All rulesets are 
#        already flushed and set to a default policy of DROP. 
#

# loopback interfaces are valid.
#
$IPTABLES -A INPUT -i lo -s $UNIVERSE -d $UNIVERSE -j ACCEPT


# local interface, local machines, going anywhere is valid
#
$IPTABLES -A INPUT -i $INTIF -s $INTNET -d $UNIVERSE -j ACCEPT


# remote interface, claiming to be local machines, IP spoofing, get lost
#
$IPTABLES -A INPUT -i $EXTIF -s $INTNET -d $UNIVERSE -j drop-and-log-it


# external interface, from any source, for ICMP traffic is valid
#
#  If you would like your machine to "ping" from the Internet, 
#  enable this next line
#
#$IPTABLES -A INPUT -i $EXTIF -p ICMP -s $UNIVERSE -d $EXTIP -j ACCEPT


# remote interface, any source, going to permanent PPP address is valid
#
#$IPTABLES -A INPUT -i $EXTIF -s $UNIVERSE -d $EXTIP -j ACCEPT


###################
###################
###################
# SSH GEDEELTE VAN MUJO
$IPTABLES -A INPUT -i $EXTIF -p tcp \
 -s $ANYWHERE -d $EXTIP \ --sport $ALLPORTS --dport 2222 -j ACCEPT 
###################
###################
###################


# Allow any related traffic coming back to the MASQ server in
#
$IPTABLES -A INPUT -i $EXTIF -s $UNIVERSE -d $EXTIP -m state --state \
 ESTABLISHED,RELATED -j ACCEPT


# ----- Begin OPTIONAL Section -----
#

# DHCPd - Enable the following lines if you run an INTERNAL DHCPd server
#
#$IPTABLES -A INPUT -i $INTIF -p tcp --sport 68 --dport 67 -j ACCEPT
#$IPTABLES -A INPUT -i $INTIF -p udp --sport 68 --dport 67 -j ACCEPT

# HTTPd - Enable the following lines if you run an EXTERNAL WWW server
#
#echo -e "      - Allowing EXTERNAL access to the WWW server"
#$IPTABLES -A INPUT -i $EXTIF -m state --state NEW,ESTABLISHED,RELATED \
# -p tcp -s $UNIVERSE -d $EXTIP --dport 80 -j ACCEPT

#
# ----- End OPTIONAL Section -----



# Catch all rule, all other incoming is denied and logged. 
#
$IPTABLES -A INPUT -s $UNIVERSE -d $UNIVERSE -j drop-and-log-it


echo -e "   - Loading OUTPUT rulesets"

#######################################################################
# OUTPUT: Outgoing traffic from various interfaces.  All rulesets are 
#         already flushed and set to a default policy of DROP. 
#

# loopback interface is valid.
#
$IPTABLES -A OUTPUT -o lo -s $UNIVERSE -d $UNIVERSE -j ACCEPT


# local interfaces, any source going to local net is valid
#
$IPTABLES -A OUTPUT -o $INTIF -s $EXTIP -d $INTNET -j ACCEPT


# local interface, any source going to local net is valid
#
$IPTABLES -A OUTPUT -o $INTIF -s $INTIP -d $INTNET -j ACCEPT


# outgoing to local net on remote interface, stuffed routing, deny
#
$IPTABLES -A OUTPUT -o $EXTIF -s $UNIVERSE -d $INTNET -j drop-and-log-it


# anything else outgoing on remote interface is valid
#
$IPTABLES -A OUTPUT -o $EXTIF -s $EXTIP -d $UNIVERSE -j ACCEPT


# ----- Begin OPTIONAL Section -----
#

# DHCPd - Enable the following lines if you run an INTERNAL DHCPd server
#         - Remove BOTH #s all the #s if you need this functionality.
#
#$IPTABLES -A OUTPUT -o $INTIF -p tcp -s $INTIP --sport 67 \
# -d 255.255.255.255 --dport 68 -j ACCEPT
#$IPTABLES -A OUTPUT -o $INTIF -p udp -s $INTIP --sport 67 \
# -d 255.255.255.255 --dport 68 -j ACCEPT

#
# ----- End OPTIONAL Section -----

# Catch all rule, all other outgoing is denied and logged. 
#
$IPTABLES -A OUTPUT -s $UNIVERSE -d $UNIVERSE -j drop-and-log-it


echo -e "   - Loading FORWARD rulesets"

#######################################################################
# FORWARD: Enable Forwarding and thus IPMASQ
#

echo "     - FWD: Allow all connections OUT and only existing/related IN"
$IPTABLES -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED \
 -j ACCEPT
$IPTABLES -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT

# Catch all rule, all other forwarding is denied and logged. 
#
$IPTABLES -A FORWARD -j drop-and-log-it


echo "     - NAT: Enabling SNAT (MASQUERADE) functionality on $EXTIF"
#
#More liberal form
#$IPTABLES -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE
#
#Stricter form
$IPTABLES -t nat -A POSTROUTING -o $EXTIF -j SNAT --to $EXTIP


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


echo -e "\nKlaar.\n"

[ProZa|IA]

###################
# SSH GEDEELTE VAN MUJO
$IPTABLES -A INPUT -i $EXTINF -p tcp \
-s $ANYWHERE -d $EXTIP \ --sport $ALLPORTS --dport 2222 -j ACCEPT
###################

Ik heb de rest niet nagekeken, maar verander je ssh verhaal eens in dit:

$IPTABLES -A INPUT -i $EXTINF -p tcp \
-s $ANYWHERE -d $EXTIP --sport $ALLPORTS --dport 2222 -j ACCEPT

die backslash achter je $EXTIP moet weg tenzij je na die backslash op de volgende regel verder gaat

[Mujo]

Dat EXTINF naar EXTIF had ik al verandert, maar je quote was me voor.
Was een typootje dat me opeens opviel.

/edit:
Ah geweldig
Ik had
$IPTABLES -A INPUT -i $EXTINF -s $ANYWHERE -d $EXTIP -j ACCEPT
al even geprobeerd om te kijken of het uberhaupt wel lukte, en dat deed het opeens!
Maar ik zet dan wel heel veel open, dus nu maar effe dichtimmeren op jouw manier.
Dat van die backslashes wist ik niet.

/edit2:
perfect! top! die regel van jou werkt ook prima, dus idd met die backslash en
dan daarna niks meer, maar op volgende regel. Sjanks!

[ProZa|IA]

Ah die typo was me nog niet opgevallen

Als ie af is post hem dan nog maar eens, dan kunnen de knappe koppen zich er ook eens over buigen