Example ldap samba iptable ruleset

#! /bin/sh
# /etc/iptables.bak

# Let's save typing & confusion with variables
IPTABLES=/sbin/iptables

# Flush active rules and custom tables
$IPTABLES --flush
$IPTABLES --delete-chain

# set the defaults so that by-default incoming packets are dropped, unless explicitly allowed;
# for a desktop workstation, we'll let lots of (unpredictable) outgoing packets go freely.
$IPTABLES -P INPUT DROP
$IPTABLES -P FORWARD DROP
$IPTABLES -P OUTPUT ACCEPT

# INBOUND POLICY
# ==============
# of course, accepting loopback is a good idea
$IPTABLES -A INPUT -i lo -j ACCEPT 

#   (Applies to packets entering our network interface from the network, 
#   and addressed to this host.)

$IPTABLES -A INPUT -m state --state INVALID -j DROP 
$IPTABLES -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT 

# ssh incoming, including non-standard port (if needed)
$IPTABLES -A INPUT -p tcp -m state --state NEW --dport 22 -j ACCEPT 
#$IPTABLES -A INPUT -p tcp -m state --state NEW --dport 222 -j ACCEPT

# samba (smbd and nmbd) ports
$IPTABLES -A INPUT -p udp -m udp --dport 137 -j ACCEPT
$IPTABLES -A INPUT -p udp -m udp --dport 138 -j ACCEPT
$IPTABLES -A INPUT -p tcp -m state --state NEW --dport 139 -j ACCEPT
$IPTABLES -A INPUT -p tcp -m state --state NEW --dport 445 -j ACCEPT

# LDAP incoming query port
$IPTABLES -A INPUT -p tcp -m state --state NEW --dport 389 -j ACCEPT

# nagios (5666); monitor time (123), allow snmp (161)
$IPTABLES -A INPUT -p tcp -m state --state NEW --dport 5666 -j ACCEPT
$IPTABLES -A INPUT -p udp -m udp --dport 123 -j ACCEPT
$IPTABLES -A INPUT -p udp -m udp --dport 161 -j ACCEPT

# amanda tape-backups; we reach out and tape things from this machine
$IPTABLES -A INPUT -p udp -m state --state NEW -m udp --dport 10080 -j ACCEPT
$IPTABLES -A INPUT -p tcp -m state --state NEW --dport 10082 -j ACCEPT
$IPTABLES -A INPUT -p tcp -m state --state NEW --dport 10083 -j ACCEPT


# OUTBOUND POLICY
# ===============
# of course, accepting loopback is a good idea
$IPTABLES -A OUTPUT -o lo -j ACCEPT

#   (Applies to packets sent to the network interface from local processes)

$IPTABLES -A OUTPUT -j ACCEPT

Invoke and make these rules effective:

hostname ~ # sh /etc/iptables.bak

Resulting active rules:

hostname ~ # iptables -L

Chain INPUT (policy DROP)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere
DROP       all  --  anywhere             anywhere            state INVALID
ACCEPT     all  --  anywhere             anywhere            state RELATED,ESTABLISHED
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:ssh
ACCEPT     udp  --  anywhere             anywhere            udp dpt:netbios-ns
ACCEPT     udp  --  anywhere             anywhere            udp dpt:netbios-dgm
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:netbios-ssn
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:microsoft-ds
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:ldap
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:5666
ACCEPT     udp  --  anywhere             anywhere            udp dpt:ntp
ACCEPT     udp  --  anywhere             anywhere            udp dpt:snmp
ACCEPT     udp  --  anywhere             anywhere            udp dpt:amanda
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:amandaidx
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:amidxtape

Chain FORWARD (policy DROP)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere
ACCEPT     all  --  anywhere             anywhere

REMEMBER! If you like the ruleset, and want it to be in-effect the next time you start iptables (ie after a reboot), then you must:

hostname ~ # rc-update add iptables default
* iptables added to runlevel default

hostname ~ # /etc/init.d/iptables save
* Saving iptables state ...