[[linux:firewall]]
Trace: • sidebar • sidebar • sidebar
Show page
AdminRecent ChangesSitemap

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision 		Previous revision
Next revision Both sides next revision
linux:firewall [2008/04/28 19:03]
greebo 		linux:firewall [2013/04/05 15:08]
zagi
Line 1: Line 1:
-[[iptables| GO HERE! ]]+[[linux:firewall6|Linux IPV6 firewall]]\\ 
 +[[linux:firewall_blocktor| how to block TOR network in realtime]]\\  
 +[[http://www.fs-security.com/|FS security]]\\ 
 + 
 +<code bash |> 
 + 
 +#!/bin/bash 
 +echo "*************" 
 +echo "* Running $0" 
 +echo "*************" 
 +echo "* http://tnt.aufbix.org/ linux firewall script" 
 + 
 +echo 
 +echo  "It was sad music. But it waved its sadness like a battle flag." 
 +echo  " It said the universe had done all it could, but you were still alive." 
 +echo 
 +echo " Discworld" 
 + 
 +TNX_IDIOT="yes" 
 + 
 +echo " how iptables work in linux kernel" 
 +echo 
 +echo ">-[prerouting]-> + >-[forward]-> + >-[postrouting]->" 
 +echo " | |" 
 +echo " [input] >--->[output]" 
 + 
 +# path to iptables and iproute2 files 
 +IPTB="/sbin/iptables" 
 +IP="/sbin/ip" 
 + 
 +# name of our Internet and intranet interfaces 
 +# use INTRANET="eth1+" or INTERNET="eth0+" 
 +# if you have more ifaces (example: eth0:0)  towards Intranet/Internet 
 +# 
 +# WAN Interface 
 +INTERNET="eth0" 
 +# ADSL - INTERNET="ppp0" 
 +# 
 +# LAN Interface 
 +INTRANET="eth1" 
 +   
 +# what IPs are used in intranet 
 +LAN="192.168.6.0/24" 
 +   
 +# what is our static  IP (if we have one) 
 +GW_IP="X.X.X.X" 
 +   
 +# what TCP ports/services we allow (and FORWARD) from Internet 
 +# use " " as delimiter 
 +TCP_PORTS="25 53 80" 
 + 
 +# what UDP ports/services we allow (and FORWARD) from Internet 
 +# use "," as delimiter 
 +UDP_PORTS="53,123" 
 + 
 +# which ports we forward into our intranet 
 +# use "," as delimiter 
 +FWD_TCP_PORTS="1214,6346" 
 +   
 +# set to 1 if we you have intranet 
 +WE_HAVE_INTRANET="0" 
 + 
 +#  
 +TRUSTED_HOSTS="193.77.1.1/32 \ 
 +212.93.224.0/19 \ 
 +212.18.32.0/24" 
 + 
 +# enable IP forwarding (routing!) 
 +echo "0" > /proc/sys/net/ipv4/ip_forward 
 + 
 +# enable PMTU (mss/mtu discovery) 
 +echo "1" > /proc/sys/net/ipv4/tcp_mtu_probing 
 + 
 +# first we flush the tables and policy 
 +$IPTB -F 
 +$IPTB -X 
 +$IPTB -F INPUT 
 +$IPTB -F FORWARD 
 +$IPTB -F OUTPUT 
 + 
 +$IPTB -t nat -F 
 + 
 +# new chain for SSH and HTTP access 
 +$IPTB -N ssh-access 
 +$IPTB -N http-access 
 + 
 +# port redirection (transparent proxy) 
 +# redirect all outgoing traffic that is NOT for the GW to local (GW) ports 
 +# DNS (53/tcp and 53/udp) and SMTP (25/tcp) 
 +#$IPTB -t nat -A PREROUTING -i ! $INTERNET -p tcp -s $LAN -d ! $LAN --dport 53 -j REDIRECT 
 +#$IPTB -t nat -A PREROUTING -i ! $INTERNET -p udp -s $LAN -d ! $LAN --dport 53 -j REDIRECT 
 +#$IPTB -t nat -A PREROUTING -i ! $INTERNET -p tcp -s $LAN -d ! $LAN --dport 25 -j REDIRECT --to-ports 25 
 + 
 +# INPUT TABLE 
 +$IPTB -P INPUT DROP 
 + 
 +# statefull firewall makes most hits 
 +$IPTB -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT 
 + 
 +# move all SSH and HTTP traffic to apropriate chains 
 +$IPTB -A INPUT -p tcp -m state --syn --state NEW --dport 22 -j ssh-access 
 +$IPTB -A INPUT -p tcp -m state --syn --state NEW --dport 80 -j http-access 
 + 
 +# ssh chain 
 +for sshhostese in $TRUSTED_HOSTS; 
 +        do 
 +        $IPTB -A ssh-access -s $sshhostese -j ACCEPT 
 +        done 
 + # Connection limit for SSH connections (1 connection per minute PER source IP) 
 + # - usefull against ssh scanners if you MUST open SSH for every IP! 
 +$IPTB -A ssh-access -m hashlimit --hashlimit 1/minute --hashlimit-burst 1 --hashlimit-mode srcip --hashlimit-name ssh -j ACCEPT 
 +$IPTB -A ssh-access -j DROP 
 +# ssh 
 + 
 +# http 
 +for httphostese in $TRUSTED_HOSTS; 
 +        do 
 +        $IPTB -A http-access -s $httphostese -j ACCEPT 
 +        done 
 +# http 
 + 
 +# IPSEC 
 +#$IPTB -A INPUT -i $INTERNET -p udp --sport 500 --dport 500  -j ACCEPT 
 +#$IPTB -A INPUT -i $INTERNET -p 50 -j ACCEPT 
 +#$IPTB -A INPUT -i $INTERNET -p 51 -j ACCEPT 
 + 
 +# we allow all traffic from $INTRANET and localhost interfaces 
 +$IPTB -A INPUT -i $INTRANET -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT 
 +$IPTB -A INPUT -i lo  -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT 
 + 
 +$IPTB -A INPUT -m state --state INVALID -m limit --limit 1/minute -j LOG --log-prefix "packet not in conntrack> " 
 +$IPTB -A INPUT -m state --state INVALID -j DROP 
 + 
 +# 
 +$IPTB -A INPUT -i $INTERNET -m pkttype --pkt-type broadcast -j DROP 
 +$IPTB -A INPUT -i $INTERNET -m pkttype --pkt-type multicast -j DROP 
 +  
 +#FIN is set and ACK is not 
 +$IPTB -A INPUT -p tcp --tcp-flags ACK,FIN FIN -j LOG --log-prefix "FIN> " 
 +$IPTB -A INPUT -p tcp --tcp-flags ACK,FIN FIN -j DROP 
 + 
 +#PSH is set and ACK is not 
 +$IPTB -A INPUT -p tcp --tcp-flags ACK,PSH PSH -j LOG --log-prefix "PSH> " 
 +$IPTB -A INPUT -p tcp --tcp-flags ACK,PSH PSH -j DROP 
 + 
 +#URG is set and ACK is not 
 +$IPTB  -A INPUT -p tcp --tcp-flags ACK,URG URG -j LOG --log-prefix "URG> " 
 +$IPTB  -A INPUT -p tcp --tcp-flags ACK,URG URG -j DROP 
 + 
 +# Block portscans: 
 +$IPTB -A INPUT -p tcp --tcp-flags ALL ALL  -j LOG --log-prefix "XMAS scan> " 
 +$IPTB -A INPUT -p tcp --tcp-flags ALL ALL  -j DROP 
 + 
 +#no flag is set 
 +$IPTB -A INPUT -p tcp --tcp-flags ALL NONE -j LOG --log-prefix "NULL scan> " 
 +$IPTB -A INPUT -p tcp --tcp-flags ALL NONE -j DROP 
 + 
 +$IPTB -A INPUT -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j LOG --log-prefix "pscan> " 
 +$IPTB -A INPUT -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j DROP 
 + 
 +#SYN and FIN are both set 
 +$IPTB -A INPUT -p tcp --tcp-flags SYN,FIN SYN,FIN -j LOG --log-prefix "pscan 2> " 
 +$IPTB -A INPUT -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP 
 + 
 +#FIN and RST are both set 
 +$IPTB -A INPUT -p tcp --tcp-flags FIN,RST FIN,RST -j LOG --log-prefix "fin/rts flag>" 
 +$IPTB -A INPUT -p tcp --tcp-flags FIN,RST FIN,RST -j DROP 
 + 
 +$IPTB -A INPUT -f -j LOG --log-prefix "Lost FRAGMENT> " 
 +$IPTB -A INPUT -f -j DROP 
 + 
 +$IPTB -A INPUT -p tcp --tcp-flags ALL SYN,FIN -j LOG --log-prefix "SYNFIN-SCAN>" 
 +$IPTB -A INPUT -p tcp --tcp-flags ALL SYN,FIN -j DROP 
 + 
 +$IPTB -A INPUT -p tcp --tcp-flags ALL URG,PSH,FIN -j LOG --log-prefix "NMAP-XMAS-SCAN>" 
 +$IPTB -A INPUT -p tcp --tcp-flags ALL URG,PSH,FIN -j DROP 
 + 
 +$IPTB -A INPUT -p tcp --tcp-flags ALL FIN -j LOG --log-prefix "FIN-SCAN>" 
 +$IPTB -A INPUT -p tcp --tcp-flags ALL FIN -j DROP 
 + 
 +$IPTB -A INPUT -p tcp --tcp-flags ALL URG,PSH,SYN,FIN -j LOG --log-prefix "NMAP-ID>" 
 +$IPTB -A INPUT -p tcp --tcp-flags ALL URG,PSH,SYN,FIN -j DROP 
 + 
 +#SYN and RST are both set 
 +$IPTB -A INPUT -p tcp --tcp-flags SYN,RST SYN,RST -j LOG --log-prefix "SYN-RST> " 
 +$IPTB -A INPUT -p tcp --tcp-flags SYN,RST SYN,RST -j DROP 
 + 
 +# what we allow from Internet - TCP ports 
 +for i in $TCP_PORTS 
 + do 
 + $IPTB -A INPUT -p tcp -m state --syn --state NEW  --dport $i -j ACCEPT 
 +        done 
 + 
 +# what we allow from Internet - UDP ports 
 +$IPTB -A INPUT -p udp -m multiport --dport $UDP_PORTS -j ACCEPT 
 + 
 +# identd requests 
 +$IPTB -A INPUT -p tcp --dport 113 -j REJECT --reject-with tcp-reset 
 + 
 +# traceroute (udp - IOS, Uni*es) 
 +$IPTB -A INPUT -p udp -m limit --limit 3/second  --sport 32769:65535 --dport 33434:33523 -j ACCEPT 
 + 
 +# Log and drop ICMP fragments (shouldn not happen at all, but often used for DoS) 
 +$IPTB -A INPUT -i $INTERNET --fragment -p icmp -j LOG --log-prefix "Fragmented incoming ICMP> " 
 +$IPTB -A INPUT -i $INTERNET --fragment -p icmp -m hashlimit --hashlimit 10/second --hashlimit-burst 1 --hashlimit-mode srcip --hashlimit-name icmp-frag -j ACCEPT 
 + 
 +# thou shall NOT block ALL ICMP, but only allow usefull ICMP types to pass trough 
 +# echo-reply 
 +#$IPTB -A INPUT -p icmp --icmp-type 0 -m hashlimit --hashlimit 10/second --hashlimit-burst 1 --hashlimit-mode srcip --hashlimit-name icmp0 -j ACCEPT 
 +$IPTB -A INPUT -p icmp --icmp-type 3 -m hashlimit --hashlimit 10/second --hashlimit-burst 1 --hashlimit-mode srcip --hashlimit-name icmp3 -j ACCEPT 
 +#$IPTB -A INPUT -p icmp --icmp-type 4 -m hashlimit --hashlimit 10/second --hashlimit-burst 1 --hashlimit-mode srcip --hashlimit-name icmp4 -j ACCEPT 
 +$IPTB -A INPUT -p icmp --icmp-type 11 -m hashlimit --hashlimit 10/second --hashlimit-burst 1 --hashlimit-mode srcip --hashlimit-name icmp11 -j ACCEPT 
 +$IPTB -A INPUT -p icmp --icmp-type 12 -m hashlimit --hashlimit 10/second --hashlimit-burst 1 --hashlimit-mode srcip --hashlimit-name icmp12 -j ACCEPT 
 +#icmp-traceroute 
 +$IPTB -A INPUT -p icmp --icmp-type 30 -m hashlimit --hashlimit 10/second --hashlimit-burst 1 --hashlimit-mode srcip --hashlimit-name icmp30 -j ACCEPT 
 +# echo-request 
 +$IPTB -A INPUT -p icmp --icmp-type 8 -m hashlimit --hashlimit 10/second --hashlimit-burst 1 --hashlimit-mode srcip --hashlimit-name icmp8 -j ACCEPT 
 + 
 +# if the default policy is not DROP then we must use this 
 +#$IPTB -A INPUT -p icmp -j DROP 
 +   
 +# FORWARD TABLE 
 +$IPTB -P FORWARD DROP 
 +   
 +# port forwarding 
 +#$IPTB -A FORWARD -p tcp -i $INTERNET -m multiport --dport $FWD_TCP_PORTS -j ACCEPT 
 + 
 +# START / port forwarding 
 +# list forwarder ports in separate command lines 
 +#$IPTB -t nat -A PREROUTING -p tcp -i $INTERNET --dport 1214  -j DNAT --to 192.168.1.10 
 +#$IPTB -t nat -A PREROUTING -p tcp -i $INTERNET --dport 6346  -j DNAT --to 192.168.1.10 
 +# END / port forwarding  
 + 
 +# statefull firewall 
 +#$IPTB -A FORWARD -m state --state INVALID -j LOG --log-prefix "INVALID: " 
 +$IPTB -A FORWARD -m state --state INVALID -j DROP 
 +$IPTB -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT 
 +$IPTB -A FORWARD -m state --state NEW -i ! $INTERNET -j ACCEPT 
 + 
 +$IPTB -A FORWARD -m pkttype --pkt-type broadcast -j DROP 
 +$IPTB -A FORWARD -m pkttype --pkt-type multicast -j DROP 
 +   
 +# NAT (IP masquerading) 
 +#$IPTB -t nat -A POSTROUTING -o $INTERNET -j MASQUERADE 
 + 
 +# NAT but to certain IP (if we have multiple Internet IPs) 
 +$IPTB -t nat -A POSTROUTING -o $INTERNET -s $LAN -j SNAT --to-source $GW_IP 
 + 
 +# ADSL (PPPoE connections) 
 +#$IPTB -I FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu 
 +$IPTB -I FORWARD -o $INTERNET -p tcp --tcp-flags SYN,RST SYN -m tcpmss --mss 1400:1536 -j TCPMSS --clamp-mss-to-pmtu 
 + 
 +# we allow only access to network cards (NIC) that have their MAC addresses listed 
 +# in "valid-macs" file 
 +#for mac in `cat valid-macs`; do $IPTB -I FORWARD -m mac --mac-source $mac -j fwfilter ; done 
 + 
 +# OUTPUT 
 +$IPTB -P OUTPUT DROP 
 + 
 +# only allow NEW and related connections out 
 +$IPTB -A OUTPUT -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT 
 +   
 +# list the rules 
 +$IPTB -L -v -n --line 
 +$IPTB -t nat -L -v -n --line 
 +   
 +echo $WE_HAVE_INTRANET > /proc/sys/net/ipv4/ip_forward 
 + 
 +</code>
linux/firewall.txt · Last modified: 2019/04/15 10:18 by zagi
Show pageOld revisions
Media ManagerBack to top
CC Attribution-Share Alike 4.0 International
Driven by DokuWiki Recent changes RSS feed Valid CSS Valid XHTML 1.0 ipv6 ready