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my trouble (i think) is with the udp rules. I'm trying to follow this tutorial but there is something I'm not getting.
I have added this to a very vanilla rc.firewall (as generated by above):
Code:
SAMBA_SERVER="XX.X.X.XX" # //ruach
NETWORK="XX.X.X.0/24"
BROADCAST="X.X.X.0"
# to the UDP inbound chain
$IPT -A udp_indbound -p UDP -s $SAMBA_SERVER -d $NETWORK -m multiport --dports 137,138 -j ACCEPT
$IPT -A udp_indbound -p UDP -s $SAMBA_SERVER -d $NETWORK -m multiport --dports 139,445 -j ACCEPT
# to the input chain
$IPT -A INPUT -p udp -s $NETWORK -d $SAMBA_SERVER -m multiport --dports 137,138 -j ACCEPT
$IPT -A INPUT -p tcp -s $NETWORK -d $SAMBA_SERVER -m multiport --dports 139,445 -j ACCEPT
$IPT -A INPUT -p udp -s $NETWORK -d $BROADCAST --dport 137 -j ACCEPT
$IPT -A INPUT -p udp -d $SAMBA_SERVER -m multiport --dports 137,138 -j DROP
$IPT -A INPUT -p tcp -d $SAMBA_SERVER -m multiport --dports 139,445 -j DROP
# to the output chain
$IPT -A OUTPUT -s $SAMBA_SERVER -d $NETWORK -m state --state ESTABLISHED,RELATED -j ACCEPT
I can run the above from a script (rc.smbfwl) and 'findsmb' still sees the local samba server, but I can't make it work inside the rc.firewall script.
I am very _new_ and stupid at networking/firewalling etc. (feel free to point and laugh)
also if its useful, here is the whole rc.firewall script (with my modifications and removed some comments)
Code:
#!/bin/sh
#
###############################################################################
#
# Local Settings
#
# sysctl location. If set, it will use sysctl to adjust the kernel parameters.
# If this is set to the empty string (or is unset), the use of sysctl
# is disabled.
#!/bin/bash
SAMBA_SERVER="XX.X.X.15" # //ruach
NETWORK="XX.X.X.0/24" # Local area network
BROADCAST="XX.X.X.0" # Local area network Broadcast Address
SYSCTL="/sbin/sysctl -w"
# To echo the value directly to the /proc file instead
# SYSCTL=""
# IPTables Location - adjust if needed
IPT="/usr/sbin/iptables"
IPTS="/usr/sbin/iptables-save"
IPTR="/usr/sbin/iptables-restore"
# Internet Interface
INET_IFACE="eth0"
INET_WIFACE="wlan0"
# Localhost Interface
LO_IFACE="lo"
LO_IP="127.0.0.1"
# Save and Restore arguments handled here
if [ "$1" = "save" ]
then
echo -n "Saving firewall to /etc/sysconfig/iptables ... "
$IPTS > /etc/sysconfig/iptables
echo "done"
exit 0
elif [ "$1" = "restore" ]
then
echo -n "Restoring firewall from /etc/sysconfig/iptables ... "
$IPTR < /etc/sysconfig/iptables
echo "done"
exit 0
fi
###############################################################################
#
# Load Modules
#
echo "Loading kernel modules ..."
# core netfilter module
/sbin/modprobe ip_tables
# the stateful connection tracking module
/sbin/modprobe ip_conntrack
# The ftp nat module is required for non-PASV ftp support
/sbin/modprobe ip_nat_ftp
# the module for full ftp connection tracking
/sbin/modprobe ip_conntrack_ftp
# the module for full irc connection tracking
/sbin/modprobe ip_conntrack_irc
###############################################################################
#
# Kernel Parameter Configuration
#
# See http://ipsysctl-tutorial.frozentux.net/chunkyhtml/index.html
# for a detailed tutorial on sysctl and the various settings
# available.
# This enables dynamic address hacking.
# This may help if you have a dynamic IP address \(e.g. slip, ppp, dhcp\).
if [ "$SYSCTL" = "" ]
then
echo "1" > /proc/sys/net/ipv4/ip_dynaddr
else
$SYSCTL net.ipv4.ip_dynaddr="1"
fi
# This enables SYN flood protection.
if [ "$SYSCTL" = "" ]
then
echo "1" > /proc/sys/net/ipv4/tcp_syncookies
else
$SYSCTL net.ipv4.tcp_syncookies="1"
fi
if [ "$SYSCTL" = "" ]
then
echo "1" > /proc/sys/net/ipv4/conf/all/rp_filter
else
$SYSCTL net.ipv4.conf.all.rp_filter="1"
fi
# The following kernel settings were suggested by Alex Weeks. Thanks!
# This kernel parameter instructs the kernel to ignore all ICMP
# echo requests sent to the broadcast address. This prevents
# a number of smurfs and similar DoS nasty attacks.
if [ "$SYSCTL" = "" ]
then
echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
else
$SYSCTL net.ipv4.icmp_echo_ignore_broadcasts="1"
fi
# This option can be used to accept or refuse source routed
# packets. It is usually on by default, but is generally
# considered a security risk. This option turns it off.
if [ "$SYSCTL" = "" ]
then
echo "0" > /proc/sys/net/ipv4/conf/all/accept_source_route
else
$SYSCTL net.ipv4.conf.all.accept_source_route="0"
fi
# However, we'll ensure the secure_redirects option is on instead.
# This option accepts only from gateways in the default gateways list.
if [ "$SYSCTL" = "" ]
then
echo "1" > /proc/sys/net/ipv4/conf/all/secure_redirects
else
$SYSCTL net.ipv4.conf.all.secure_redirects="1"
fi
# This option logs packets from impossible addresses.
if [ "$SYSCTL" = "" ]
then
echo "1" > /proc/sys/net/ipv4/conf/all/log_martians
else
$SYSCTL net.ipv4.conf.all.log_martians="1"
fi
###############################################################################
#
# Flush Any Existing Rules or Chains
#
echo "Flushing Tables ..."
# Reset Default Policies
$IPT -P INPUT ACCEPT
$IPT -P FORWARD ACCEPT
$IPT -P OUTPUT ACCEPT
$IPT -t nat -P PREROUTING ACCEPT
$IPT -t nat -P POSTROUTING ACCEPT
$IPT -t nat -P OUTPUT ACCEPT
$IPT -t mangle -P PREROUTING ACCEPT
$IPT -t mangle -P OUTPUT ACCEPT
# Flush all rules
$IPT -F
$IPT -t nat -F
$IPT -t mangle -F
# Erase all non-default chains
$IPT -X
$IPT -t nat -X
$IPT -t mangle -X
if [ "$1" = "stop" ]
then
echo "Firewall completely flushed! Now running with no firewall."
exit 0
fi
###############################################################################
#
# Rules Configuration
#
###############################################################################
#
# Filter Table
#
###############################################################################
# Set Policies
$IPT -P INPUT DROP
$IPT -P OUTPUT DROP
$IPT -P FORWARD DROP
###############################################################################
#
# User-Specified Chains
#
# Create user chains to reduce the number of rules each packet
# must traverse.
echo "Create and populate custom rule chains ..."
# Create a chain to filter INVALID packets
$IPT -N bad_packets
# Create another chain to filter bad tcp packets
$IPT -N bad_tcp_packets
# Create separate chains for icmp, tcp (incoming and outgoing),
# and incoming udp packets.
$IPT -N icmp_packets
# Used for UDP packets inbound from the Internet
$IPT -N udp_inbound
# Used to block outbound UDP services from internal network
# Default to allow all
$IPT -N udp_outbound
# Used to allow inbound services if desired
# Default fail except for established sessions
$IPT -N tcp_inbound
# Used to block outbound services from internal network
# Default to allow all
$IPT -N tcp_outbound
###############################################################################
#
# Populate User Chains
#
# bad_packets chain
#
# Drop INVALID packets immediately
$IPT -A bad_packets -p ALL -m state --state INVALID -j LOG \
--log-prefix "Invalid packet: "
$IPT -A bad_packets -p ALL -m state --state INVALID -j DROP
# Then check the tcp packets for additional problems
$IPT -A bad_packets -p tcp -j bad_tcp_packets
# All good, so return
$IPT -A bad_packets -p ALL -j RETURN
# bad_tcp_packets chain
$IPT -A bad_tcp_packets -p tcp ! --syn -m state --state NEW -j LOG \
--log-prefix "New not syn: "
$IPT -A bad_tcp_packets -p tcp ! --syn -m state --state NEW -j DROP
$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL NONE -j LOG \
--log-prefix "Stealth scan: "
$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL NONE -j DROP
$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL ALL -j LOG \
--log-prefix "Stealth scan: "
$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL ALL -j DROP
$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL FIN,URG,PSH -j LOG \
--log-prefix "Stealth scan: "
$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL FIN,URG,PSH -j DROP
$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j LOG \
--log-prefix "Stealth scan: "
$IPT -A bad_tcp_packets -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j DROP
$IPT -A bad_tcp_packets -p tcp --tcp-flags SYN,RST SYN,RST -j LOG \
--log-prefix "Stealth scan: "
$IPT -A bad_tcp_packets -p tcp --tcp-flags SYN,RST SYN,RST -j DROP
$IPT -A bad_tcp_packets -p tcp --tcp-flags SYN,FIN SYN,FIN -j LOG \
--log-prefix "Stealth scan: "
$IPT -A bad_tcp_packets -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP
# All good, so return
$IPT -A bad_tcp_packets -p tcp -j RETURN
# icmp_packets chain
# ICMP packets should fit in a Layer 2 frame, thus they should
# never be fragmented. Fragmented ICMP packets are a typical sign
# of a denial of service attack.
$IPT -A icmp_packets --fragment -p ICMP -j LOG \
--log-prefix "ICMP Fragment: "
$IPT -A icmp_packets --fragment -p ICMP -j DROP
# By default, however, drop pings without logging. Blaster
$IPT -A icmp_packets -p ICMP -s 0/0 --icmp-type 8 -j DROP
# Time Exceeded
$IPT -A icmp_packets -p ICMP -s 0/0 --icmp-type 11 -j ACCEPT
# Not matched, so return so it will be logged
$IPT -A icmp_packets -p ICMP -j RETURN
# TCP & UDP
# Identify ports at:
# http://www.chebucto.ns.ca/~rakerman/port-table.html
# http://www.iana.org/assignments/port-numbers
# udp_inbound chain
#
# Drop netbios calls
# chatter from Windows systems.
#$IPT -A udp_inbound -p UDP -s 0/0 --destination-port 137 -j DROP
#$IPT -A udp_inbound -p UDP -s 0/0 --destination-port 138 -j DROP
$IPT -A udp_indbound -p UDP -s $SAMBA_SERVER -d $NETWORK -m multiport --dports 137,138 -j ACCEPT
$IPT -A udp_indbound -p UDP -s $SAMBA_SERVER -d $NETWORK -m multiport --dports 139,445 -j ACCEPT
#$IPT -A INPUT -i lo -j ACCEPT
#$IPT -A OUTPUT -o lo -j ACCEPT
# Dynamic Address
# If DHCP, the initial request is a broadcast. The response
# doesn't exactly match the outbound packet. This explicitly
# allow the DHCP ports to alleviate this problem.
# If you receive your dynamic address by a different means, you
# can probably comment this line.
$IPT -A udp_inbound -p UDP -s 0/0 --source-port 67 --destination-port 68 -j ACCEPT
# Not matched, so return for logging
$IPT -A udp_inbound -p UDP -j RETURN
# udp_outbound chain
#
# This chain is used with a private network to prevent forwarding for
# UDP requests on specific protocols. Applied to the FORWARD rule from
# the internal network. Ends with an ACCEPT
# No match, so ACCEPT
$IPT -A udp_outbound -p UDP -s 0/0 -j ACCEPT
# tcp_inbound chain
#
# This chain is used to allow inbound connections to the
# system/gateway. Use with care. It defaults to none.
# It's applied on INPUT from the external or Internet interface.
# Not matched, so return so it will be logged
$IPT -A tcp_inbound -p TCP -j RETURN
# tcp_outbound chain
#
# This chain is used with a private network to prevent forwarding for
# requests on specific protocols. Applied to the FORWARD rule from
# the internal network. Ends with an ACCEPT
# No match, so ACCEPT
$IPT -A tcp_outbound -p TCP -s 0/0 -j ACCEPT
###############################################################################
#
# INPUT Chain
#
echo "Process INPUT chain ..."
# Allow all on localhost interface
$IPT -A INPUT -p ALL -i $LO_IFACE -j ACCEPT
# Drop bad packets
$IPT -A INPUT -p ALL -j bad_packets
# DOCSIS compliant cable modems
# Drop them without logging.
$IPT -A INPUT -p ALL -d 224.0.0.1 -j DROP
# The rule to accept the packets.
# $IPT -A INPUT -p ALL -d 224.0.0.1 -j ACCEPT
# Inbound Internet Packet Rules
# Accept Established Connections
$IPT -A INPUT -p ALL -i $INET_IFACE -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPT -A INPUT -p ALL -i $INET_WIFACE -m state --state ESTABLISHED,RELATED -j ACCEPT
# Route the rest to the appropriate user chain
$IPT -A INPUT -p TCP -i $INET_IFACE -j tcp_inbound
$IPT -A INPUT -p UDP -i $INET_IFACE -j udp_inbound
$IPT -A INPUT -p ICMP -i $INET_IFACE -j icmp_packets
$IPT -A INPUT -p TCP -i $INET_WIFACE -j tcp_inbound
$IPT -A INPUT -p UDP -i $INET_WIFACE -j udp_inbound
$IPT -A INPUT -p ICMP -i $INET_WIFACE -j icmp_packets
# added 7-12-07
$IPT -A INPUT -p udp -s $NETWORK -d $SAMBA_SERVER -m multiport --dports 137,138 -j ACCEPT
$IPT -A INPUT -p tcp -s $NETWORK -d $SAMBA_SERVER -m multiport --dports 139,445 -j ACCEPT
$IPT -A INPUT -p udp -s $NETWORK -d $BROADCAST --dport 137 -j ACCEPT
$IPT -A INPUT -p udp -d $SAMBA_SERVER -m multiport --dports 137,138 -j DROP
$IPT -A INPUT -p tcp -d $SAMBA_SERVER -m multiport --dports 139,445 -j DROP
# Drop without logging broadcasts that get this far.
# Cuts down on log clutter.
# Comment this line if testing new rules that impact
# broadcast protocols.
$IPT -A INPUT -m pkttype --pkt-type broadcast -j DROP
# Log packets that still don't match
$IPT -A INPUT -m limit --limit 3/minute --limit-burst 3 -j LOG --log-prefix "INPUT packet died: "
###############################################################################
#
# FORWARD Chain
#
echo "Process FORWARD chain ..."
# Used if forwarding for a private network
###############################################################################
#
# OUTPUT Chain
#
echo "Process OUTPUT chain ..."
# Generally trust the firewall on output
# However, invalid icmp packets need to be dropped
# to prevent a possible exploit.
$IPT -A OUTPUT -m state -p icmp --state INVALID -j DROP
# Localhost
$IPT -A OUTPUT -p ALL -s $LO_IP -j ACCEPT
$IPT -A OUTPUT -p ALL -o $LO_IFACE -j ACCEPT
# To internet
$IPT -A OUTPUT -p ALL -o $INET_IFACE -j ACCEPT
$IPT -A OUTPUT -p ALL -o $INET_WIFACE -j ACCEPT
$IPT -A OUTPUT -s $SAMBA_SERVER -d $NETWORK -m state --state ESTABLISHED,RELATED -j ACCEPT
# Log packets that still don't match
$IPT -A OUTPUT -m limit --limit 3/minute --limit-burst 3 -j LOG \
--log-prefix "OUTPUT packet died: "
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