X-Git-Url: https://git.distorted.org.uk/~mdw/firewall/blobdiff_plain/bfdc045deb6149808d309b4ac3c292d9c57a8b38..b44f44040943cad5ac2c02159024e7b0392ce4f8:/bookends.m4

diff --git a/bookends.m4 b/bookends.m4
index f99066c..ed5dcc7 100644
--- a/bookends.m4
+++ b/bookends.m4
@@ -1,4 +1,4 @@
-### -*-m4-*-
+### -*-sh-*-
 ###
 ### Initialization and finishing touches for firewall scripts
 ###
@@ -30,11 +30,11 @@ m4_divert(30)m4_dnl
 ## everything going before anyone actually hits a timeout.
 for t in mangle filter; do
   for i in PREROUTING INPUT FORWARD OUTPUT POSTROUTING; do
-    run iptables -t $t -P $i DROP 2>/dev/null || :
-    run iptables -t $t -F $i 2>/dev/null || :
+    run ip46tables -t $t -P $i DROP 2>/dev/null || :
+    run ip46tables -t $t -F $i 2>/dev/null || :
   done
-  run iptables -t $t -F
-  run iptables -t $t -X
+  run ip46tables -t $t -F
+  run ip46tables -t $t -X
 done
 
 m4_divert(32)m4_dnl
@@ -52,9 +52,24 @@ setopt ip_local_port_range $open_port_min $open_port_max
 ## Deploy SYN-cookies if necessary.
 setopt tcp_syncookies 1
 
+## Allow broadcast and multicast ping, because it's a useful diagnostic tool.
+setopt icmp_echo_ignore_broadcasts 0
+
+## Turn off iptables filtering for bridges.  We'll use ebtables if we need
+## to; but right now the model is that we do filtering at the borders, and
+## are tolerant of things which are local.
+if [ -x /sbin/brctl ]; then
+  modprobe bridge || :
+  if [ -d /proc/sys/net/bridge ]; then
+    for filter in arptables iptables ip6tables; do
+      run sysctl -q net.bridge.bridge-nf-call-$filter=0
+    done
+  fi
+fi
+
 ## Turn on the reverse-path filter, and log weird things.
-setdevopt rp_filter 1
-setdevopt log_martians 1
+setdevopt rp_filter $rp_filter
+setdevopt log_martians $log_martians
 
 ## Turn off things which can mess with our routing decisions.
 setdevopt accept_source_route 0
@@ -67,28 +82,61 @@ m4_divert(34)m4_dnl
 ###--------------------------------------------------------------------------
 ### Establish error chains.
 
-errorchain forbidden REJECT --reject-with icmp-host-prohibited
-## Generic `not allowed' chain.  Rejects with ICMP host-prohibited.
+errorchain forbidden REJECT
+## Generic `not allowed' chain.
 
-errorchain tcp-fragment REJECT --reject-with icmp-host-prohibited
-## Chain for logging fragmented TCP segements.  Rejects with ICMP
-## host-prohibited.
+errorchain tcp-fragment REJECT
+## Chain for logging fragmented TCP segements.
 
 errorchain bad-tcp REJECT -p tcp --reject-with tcp-reset
 ## Bad TCP segments (e.g., for unknown connections).  Sends a TCP reset.
 
 errorchain mangle:bad-source-address DROP
+errorchain bad-source-address DROP
 ## Packet arrived on wrong interface for its source address.  Drops the
 ## packet, since there's nowhere sensible to send an error.
 
+errorchain bad-destination-address REJECT
+## Packet arrived on non-loopback interface with loopback destination.
+
 errorchain interesting ACCEPT
 ## Not an error, just log interesting packets.
 
 m4_divert(36)m4_dnl
 ###--------------------------------------------------------------------------
-### Don't clobber local traffic.
-
-run iptables -A INPUT -i lo -j ACCEPT
+### Standard loopback stuff.
+
+## Don't clobber local traffic
+run ip46tables -A INPUT -i lo -j ACCEPT
+
+## We really shouldn't see packets destined for localhost on any interface
+## other than the loopback.
+run iptables -A INPUT -g bad-destination-address \
+	-d 127.0.0.0/8
+run ip6tables -A INPUT -g bad-destination-address \
+	-d ::1
+
+## We shouldn't be asked to forward things with link-local addresses.
+run iptables -A FORWARD -g bad-source-address \
+	-s 169.254.0.0/16
+run iptables -A FORWARD -g bad-destination-address \
+	-d 169.254.0.0/16
+run ip6tables -A FORWARD -g bad-source-address \
+	-s fe80::/10
+run ip6tables -A FORWARD -g bad-destination-address \
+	-d fe80::/10
+
+## Also, don't forward link-local broadcast or multicast.
+run iptables -A FORWARD -g bad-destination-address \
+	-d 255.255.255.255
+run iptables -A FORWARD -g bad-destination-address \
+	-m addrtype --dst-type BROADCAST
+run iptables -A FORWARD -g bad-destination-address \
+	-d 224.0.0.0/24
+for x in 0 1 2 3 4 5 6 7 8 9 a b c d e f; do
+  run ip6tables -A FORWARD -g bad-destination-address \
+	-d fe${x}2::/16
+done
 
 m4_divert(90)m4_dnl
 ###--------------------------------------------------------------------------
@@ -96,11 +144,11 @@ m4_divert(90)m4_dnl
 
 m4_divert(94)m4_dnl
 ## Locally generated packets are all OK.
-run iptables -P OUTPUT ACCEPT
+run ip46tables -P OUTPUT ACCEPT
 
 ## Other incoming things are forbidden.
 for chain in INPUT FORWARD; do
-  run iptables -A $chain -g forbidden
+  run ip46tables -A $chain -g forbidden
 done
 
 m4_divert(-1)