X-Git-Url: https://git.distorted.org.uk/~mdw/firewall/blobdiff_plain/ade2c052e531ae5d80657164affb459f5f879d5e..b5aae78272ca6d750b101ab73e7907e63d10c9ee:/local.m4

diff --git a/local.m4 b/local.m4
index b9fa700..2d880b9 100644
--- a/local.m4
+++ b/local.m4
@@ -38,6 +38,14 @@ m4_divert(-1)m4_dnl
 m4_divert(46)m4_dnl
 ## Networks and routing.
 
+defiface $if_dmz \
+	trusted:62.49.204.144/28 \
+	trusted:172.29.199.0/25 \
+	untrusted:default
+defiface $if_trusted \
+	trusted:172.29.199.0/25 \
+	untrusted:default
+defiface $if_safe safe:172.29.199.192/26
 defiface $if_untrusted \
 	untrusted:172.29.198.0/25
 defvpn $if_vpn safe 172.29.199.128/27 \
@@ -46,48 +54,53 @@ defvpn $if_vpn safe 172.29.199.128/27 \
 defiface $if_iodine untrusted:172.29.198.128/28
 defiface $if_its_mz safe:172.29.199.160/30
 defiface $if_its_pi safe:192.168.0.0/24
-defiface $if_trusted \
-	trusted:172.29.199.0/26 \
-	safe:172.29.199.64/27 \
-	untrusted:default
+
+## Default NTP servers.
+ntp_servers="158.152.1.76 158.152.1.204 194.159.253.2 195.173.57.232"
 
 m4_divert(60)m4_dnl
 ###--------------------------------------------------------------------------
 ### Special forwarding exemptions.
 
+## Only allow these packets if they're not fragmented.  (Don't trust safe
+## hosts's fragment reassembly to be robust against malicious fragments.)
+## There's a hideous bug in iptables 1.4.11.1 which botches the meaning of
+## `! -f', so we do the negation using early return from a subchain.
+clearchain fwd-spec-nofrag
+run iptables -A fwd-spec-nofrag -j RETURN --fragment
+run ip6tables -A fwd-spec-nofrag -j RETURN \
+	-m ipv6header --soft --header frag
+run iptables -A FORWARD -j fwd-spec-nofrag
+
 ## Allow ping from safe/noloop to untrusted networks.
-run iptables -A FORWARD -j ACCEPT \
-	-p icmp ! -f --icmp-type echo-request \
+run iptables -A fwd-spec-nofrag -j ACCEPT \
+	-p icmp --icmp-type echo-request \
 	-m mark --mark $to_untrusted/$MASK_TO
-run iptables -A FORWARD -j ACCEPT \
-	-p icmp ! -f --icmp-type echo-reply \
+run iptables -A fwd-spec-nofrag -j ACCEPT \
+	-p icmp --icmp-type echo-reply \
 	-m mark --mark $from_untrusted/$MASK_FROM \
 	-m state --state ESTABLISHED
-run ip6tables -A FORWARD -j ACCEPT \
+run ip6tables -A fwd-spec-nofrag -j ACCEPT \
 	-p ipv6-icmp --icmpv6-type echo-request \
-	-m ipv6header --soft ! --header frag \
 	-m mark --mark $to_untrusted/$MASK_TO
-run ip6tables -A FORWARD -j ACCEPT \
+run ip6tables -A fwd-spec-nofrag -j ACCEPT \
 	-p ipv6-icmp --icmpv6-type echo-reply \
-	-m ipv6header --soft ! --header frag \
 	-m mark --mark $from_untrusted/$MASK_FROM \
 	-m state --state ESTABLISHED
 
 ## Allow SSH from safe/noloop to untrusted networks.
-run iptables -A FORWARD -j ACCEPT \
-	-p tcp ! -f --destination-port $port_ssh \
+run iptables -A fwd-spec-nofrag -j ACCEPT \
+	-p tcp --destination-port $port_ssh \
 	-m mark --mark $to_untrusted/$MASK_TO
-run iptables -A FORWARD -j ACCEPT \
-	-p tcp ! -f --source-port $port_ssh \
+run iptables -A fwd-spec-nofrag -j ACCEPT \
+	-p tcp --source-port $port_ssh \
 	-m mark --mark $from_untrusted/$MASK_FROM \
 	-m state --state ESTABLISHED
-run ip6tables -A FORWARD -j ACCEPT \
+run ip6tables -A fwd-spec-nofrag -j ACCEPT \
 	-p tcp --destination-port $port_ssh \
-	-m ipv6header --soft ! --header frag \
 	-m mark --mark $to_untrusted/$MASK_TO
-run ip6tables -A FORWARD -j ACCEPT \
+run ip6tables -A fwd-spec-nofrag -j ACCEPT \
 	-p tcp --source-port $port_ssh \
-	-m ipv6header --soft ! --header frag \
 	-m mark --mark $from_untrusted/$MASK_FROM \
 	-m state --state ESTABLISHED
 
@@ -125,6 +138,22 @@ run iptables -A inbound -j ACCEPT \
 	-s 172.29.198.0/23 \
 	-p udp --source-port $port_bootpc --destination-port $port_bootps
 
+## Incoming multicast on a network interface associated with a trusted
+## network is OK, since it must have originated there (or been forwarded, but
+## we don't do that yet).
+for i in $(echo $if_trusted $if_dmz $if_safe | sed 'y/,/ /'); do
+  echo $i
+done | {
+  seen=:
+  while read i; do
+    case "$seen" in *:$i:*) continue ;; esac
+    seen=$seen$i:
+    run iptables -A inbound -j ACCEPT \
+	-s 0.0.0.0 -d 224.0.0.0/24 \
+	-i $i
+  done
+}
+
 ## Allow incoming ping.  This is the only ICMP left.
 run ip46tables -A inbound -j ACCEPT -p icmp