local.m4: Protect the `untrusted' network from incoming requests.

Currently the untrusted network is vulnerable to incoming hostile IPv6
requests, and only protected from IPv4 by NAT.

I don't think it's especially useful to allow untrusted hosts to
provide externally facing services, so rather than deploy a new
network, I'm just going to change the policy for the existing one, and
forbid new connections and UDP traffic to untrusted hosts.  This
involves splitting out a separate network class for the external
Internet, which is now `scary'.

diff --git a/local.m4 b/local.m4
index 785a78b..b5cee43 100644 (file)
--- a/local.m4
+++ b/local.m4
@@ -112,10 +112,11 @@ m4_divert(-1)
 
 ## Define the available network classes.
 m4_divert(42)m4_dnl
-defnetclass untrusted  untrusted trusted             mcast
-defnetclass trusted    untrusted trusted safe noloop mcast
-defnetclass safe                 trusted safe noloop mcast
-defnetclass noloop               trusted safe        mcast
+defnetclass scary      scary           trusted             mcast
+defnetclass untrusted  scary untrusted trusted             mcast
+defnetclass trusted    scary untrusted trusted safe noloop mcast
+defnetclass safe                       trusted safe noloop mcast
+defnetclass noloop                     trusted safe        mcast
 
 defnetclass link
 defnetclass mcast
@@ -253,7 +254,7 @@ defnet vpn safe
 defnet anycast trusted
        addr 172.29.199.224/27 2001:ba8:1d9:0::/64
        via dmz unsafe safe untrusted jump colo vpn
-defnet default untrusted
+defnet default scary
        addr 62.49.204.144/28 2001:470:1f09:1b98::/64
        addr 212.13.198.64/28 2001:ba8:0:1d9::/64
        addr 2001:ba8:1d9::/48 #temporary
@@ -371,6 +372,16 @@ openports inbound
 run ip46tables -A inbound -j forbidden
 run ip46tables -A INPUT -m mark --mark $from_untrusted/$MASK_FROM -g inbound
 
+## Allow responses from the scary outside world into the untrusted net, but
+## don't let untrusted things run services.  [EXPERIMENTAL]
+case $forward in
+  1)
+    run ip46tables -A FORWARD -j ACCEPT \
+       -m mark --mark $(( $from_scary | $to_untrusted ))/$(( $MASK_FROM | $MASK_TO )) \
+       -m state --state ESTABLISHED,RELATED
+    ;;
+esac
+
 ## Otherwise process as indicated by the mark.
 for i in $inchains; do
   run ip46tables -A $i -m mark ! --mark 0/$MASK_MASK -j ACCEPT