From: Mark Wooding <mdw@distorted.org.uk>
Date: Mon, 12 Mar 2012 00:16:27 +0000 (+0000)
Subject: Merge branch 'master' into emergency
X-Git-Url: https://git.distorted.org.uk/~mdw/firewall/commitdiff_plain/50982adee2bcdcfdb7cd53bd672c12f1ecca79f0?hp=c8dab9d26762658a6ba0b34c5598b589ae2652d3

Merge branch 'master' into emergency

* master:
  Overhaul address classification for link-local and non-unicast addresses.
  functions.m4: Publish the per-class forwarding bitmasks.
  functions.m4: The mark-{from,to}-* rules no longer own the packet marks.
  classify.m4: Use canonical forms for IPv6 addresses.
  local.m4: Actually use the IPv6 fragmentation forbidding filter.
  Extend proper ICMP handling to IPv6.
  bookends.m4: Optimize checking for forwarding IPv6 link-local multicast.
  vampire.m4: Extend services to untrusted hosts over IPv6.
  Introduce variable for expected input chains.
---

diff --git a/bookends.m4 b/bookends.m4
index 69a721e..a0731d2 100644
--- a/bookends.m4
+++ b/bookends.m4
@@ -111,6 +111,10 @@ case $host_type_<::>FWHOST in
 esac
 setopt ip_forward $forward
 setdevopt forwarding $forward
+case $forward in
+  0) inchains="INPUT" ;;
+  1) inchains="INPUT FORWARD" ;;
+esac
 
 ## Set dynamic port allocation.
 setopt ip_local_port_range $open_port_min $open_port_max
@@ -207,10 +211,12 @@ case $forward in
 	    -m addrtype --dst-type BROADCAST
     run iptables -A FORWARD -g bad-destination-address \
 	    -d 224.0.0.0/24
+    clearchain check-fwd-multi
     for x in 0 1 2 3 4 5 6 7 8 9 a b c d e f; do
-      run ip6tables -A FORWARD -g bad-destination-address \
-	    -d fe${x}2::/16
+      run ip6tables -A check-fwd-multi -g bad-destination-address \
+	    -d ff${x}2::/16
     done
+    ip6tables -A FORWARD -j check-fwd-multi -d ff00::/8
     ;;
 esac
 
diff --git a/classify.m4 b/classify.m4
index 16a92c9..59ac3d9 100644
--- a/classify.m4
+++ b/classify.m4
@@ -65,6 +65,17 @@ m4_divert(40)m4_dnl
 clearchain mangle:in-classify mangle:in-default mangle:out-classify
 clearchain mangle:local-source
 
+## An unpleasant hack.  We can't reject packets from the mangle table, so
+## we mark packets with a bad destination and then detect this in the
+## filter table.
+clearchain mangle:bad-destination-address
+BAD_DEST=0xf6f377d2
+ip46tables -t mangle -A bad-destination-address -j MARK --set-mark $BAD_DEST
+ip46tables -t mangle -A bad-destination-address -j ACCEPT
+for i in $inchains; do
+  ip46tables -A $i -m mark --mark $BAD_DEST -g bad-destination-address
+done
+
 ## Packets over the loopback interface are automatically trusted.  All manner
 ## of weird stuff happens on lo, and it's best not to second-guess it.
 run ip46tables -t mangle -A in-classify -i lo -j ACCEPT
@@ -98,15 +109,6 @@ for addr in $host_6addrs; do
 	  -s $addr
 done
 
-## It's not valid to have a multicast address as a packet source: multicast
-## routing is done away from the source, so a multicast address would make
-## this impossible to do.  So discard these packets.  Also discard class-E
-## IPv4 addresses, since they aren't assigned.
-run iptables -t mangle -A in-classify -g bad-source-address \
-	-s 224.0.0.0/3
-run ip6tables -t mangle -A in-classify -g bad-source-address \
-	-s ff00::/8
-
 m4_divert(41)m4_dnl
 ## Define the important networks.
 for pass in 1 2; do
@@ -115,6 +117,56 @@ m4_divert(42)m4_dnl
 done
 
 m4_divert(46)m4_dnl
+## Special IPv4 source addresses.  Forbid broadcast and multicast sources.
+## Mark the special zero address and link-local addresses as such.  (This
+## also matches class-E addresses, which are probably permanently invalid.)
+for i in 0.0.0.0 169.254.0.0/16; do
+  run iptables -t mangle -A in-classify -g mark-from-link -s $i
+done
+run iptables -t mangle -A in-classify -g bad-source-address \
+	-s 224.0.0.0/3
+run iptables -t mangle -A in-classify -g bad-source-address \
+	-m addrtype --src-type BROADCAST \
+
+## Special IPv6 addresses.  Format multicast sources, and mark zero and
+## link local addresses.
+for i in :: fe80::/10; do
+  run ip6tables -t mangle -A in-classify -g mark-from-link -s $i
+done
+run ip6tables -t mangle -A in-classify -g bad-source-address \
+	-s ff00::/8
+
+## Special IPv4 destination addresses.  The zero address is invalid; mark
+## link-local and recognized broadcast addresses as link-local.  We leave
+## multicast for later.
+for i in 0.0.0.0 240.0.0.0/4; do
+  run iptables -t mangle -A out-classify -g bad-destination-address -d $i
+done
+run iptables -t mangle -A out-classify -g mark-to-link -d 169.254.0.0/16
+run iptables -t mangle -A out-classify -g mark-to-link \
+	-m addrtype --dst-type BROADCAST
+
+## Special IPv6 destination addressses.  The zero address is again invalid;
+## mark link local addresses.  We do multicast later.
+run ip6tables -t mangle -A out-classify -g bad-destination-address \
+	-d ::
+run ip6tables -t mangle -A out-classify -g mark-to-link -d fe80::/10
+
+## Now deal with multicast.  Link-local multicast is detected as being
+## link-local, so that we can prevent it being forwarded correctly.
+clearchain mangle:out-classify-mcast
+run iptables -t mangle -A out-classify-mcast -g mark-to-link \
+	-d 224.0.0.0/24
+for i in 0 1 2 3 4 5 6 7 8 9 a b c d e f; do
+  run ip6tables -t mangle -A out-classify-mcast -g mark-to-link \
+	  -d ff${i}2::/16
+done
+run ip46tables -t mangle -A out-classify-mcast -g mark-to-mcast
+run iptables -t mangle -A out-classify -g out-classify-mcast \
+	-d 224.0.0.0/4
+run ip6tables -t mangle -A out-classify -g out-classify-mcast \
+	-d ff00::/8
+
 ## Build the input classification chains.  There's one chain `in-IFACE' for
 ## each local interface.  This chain does a further dispatch on the source
 ## address to the appropriate `mark-from-CLASS' chain for the source network
@@ -252,7 +304,7 @@ do
 done
 for addr in \
 	fc00::/7 \
-	2001:0db8::/32
+	2001:db8::/32
 do
   run ip6tables -t mangle -A in-default -s $addr -g bad-source-address
 done
@@ -268,6 +320,14 @@ run ip46tables -t mangle -A out-classify -g mark-to-$net_class_default
 run ip46tables -t mangle -A PREROUTING -j in-classify
 run ip46tables -t mangle -A PREROUTING -j out-classify
 
+## Incoming stuff to or from a link-local address is OK.
+run ip46tables -t mangle -A INPUT \
+	-m mark --mark $to_link/$MASK_TO \
+	-j MARK --or-mark $fwd_link
+run ip46tables -t mangle -A INPUT \
+	-m mark --mark $from_link/$MASK_FROM \
+	-j MARK --or-mark $fwd_link
+
 ## Now it's safe to let stuff through.
 for i in PREROUTING INPUT FORWARD OUTPUT POSTROUTING; do
   run ip46tables -t mangle -P $i ACCEPT
diff --git a/functions.m4 b/functions.m4
index b78dcbe..0ebba30 100644
--- a/functions.m4
+++ b/functions.m4
@@ -393,30 +393,30 @@ defnetclass () {
       trace "netclass $name = $netclassindex"
       eval from_$name=$(( $netclassindex << $BIT_FROM ))
       eval to_$name=$(( $netclassindex << $BIT_TO ))
-      eval _mask_$name=$(( 1 << ($netclassindex + $BIT_MASK) ))
+      eval fwd_$name=$(( 1 << ($netclassindex + $BIT_MASK) ))
       nets="$nets $name"
       ;;
     2)
 
-      ## Pass 2.  Compute the actual from and to values.  We're a little bit
-      ## clever during source classification, and set the TO field to
-      ## all-bits-one, so that destination classification needs only a single
-      ## AND operation.
-      from=$(( ($netclassindex << $BIT_FROM) + (0xf << $BIT_TO) ))
+      ## Pass 2.  Compute the actual from and to values.  This is fiddly:
+      ## we want to preserve the other flags.
+      from=$(( ($netclassindex << $BIT_FROM) ))
+      frommask=$(( $MASK_FROM | $MASK_MASK ))
       for net; do
-	eval bit=\$_mask_$net
+	eval bit=\$fwd_$net
 	from=$(( $from + $bit ))
       done
-      to=$(( ($netclassindex << $BIT_TO) + \
-	     (0xf << $BIT_FROM) + \
-	     (1 << ($netclassindex + $BIT_MASK)) ))
-      trace "from $name --> set $(printf %x $from)"
-      trace "  to $name --> and $(printf %x $from)"
+      to=$(( ($netclassindex << $BIT_TO) ))
+      tomask=$(( $MASK_MASK ^ (1 << ($netclassindex + $BIT_MASK)) ))
+      trace "from $name --> set $(printf %08x/%08x $from $frommask)"
+      trace "  to $name --> and $(printf %08x/%08x $to $tomask)"
 
       ## Now establish the mark-from-NAME and mark-to-NAME chains.
       clearchain mangle:mark-from-$name mangle:mark-to-$name
-      run ip46tables -t mangle -A mark-from-$name -j MARK --set-mark $from
-      run ip46tables -t mangle -A mark-to-$name -j MARK --and-mark $to
+      run ip46tables -t mangle -A mark-from-$name -j MARK \
+	      --set-xmark $from/$frommask
+      run ip46tables -t mangle -A mark-to-$name -j MARK \
+	      --set-xmark $to/$tomask
       ;;
   esac
   netclassindex=$(( $netclassindex + 1 ))
diff --git a/icmp.m4 b/icmp.m4
index 3de0483..93c2973 100644
--- a/icmp.m4
+++ b/icmp.m4
@@ -30,21 +30,15 @@ clearchain check-icmp
 ## Ping needs inspecting on a host-by-host basis.
 for type in echo-request echo-reply; do
   run iptables -A check-icmp -p icmp --icmp-type $type -j RETURN
+  run ip6tables -A check-icmp -p icmpv6 --icmpv6-type $type -j RETURN
 done
 
-## Certainly don't allow ping to broadcast addresses.
-run iptables -A check-icmp -g forbidden \
-	-p icmp --icmp-type echo-request \
-	-m addrtype --dst-type BROADCAST
-
 m4_divert(58)m4_dnl
 ## Other ICMP is basically benign, we claim.
-run iptables -A check-icmp -j ACCEPT
+run ip46tables -A check-icmp -j ACCEPT
 
 ## Done.
-for i in INPUT FORWARD; do
-  run iptables -A $i -p icmp -j check-icmp
-done
+for i in $inchains; do run ip46tables -A $i -p icmp -j check-icmp; done
 
 m4_divert(-1)
 ###----- That's all, folks --------------------------------------------------
diff --git a/local.m4 b/local.m4
index 4385223..c479ed8 100644
--- a/local.m4
+++ b/local.m4
@@ -35,10 +35,12 @@ m4_divert(-1)
 
 ## Define the available network classes.
 m4_divert(42)m4_dnl
-defnetclass untrusted untrusted trusted
-defnetclass trusted untrusted trusted safe noloop
-defnetclass safe trusted safe noloop
-defnetclass noloop trusted safe
+defnetclass untrusted untrusted trusted mcast
+defnetclass trusted untrusted trusted safe noloop mcast
+defnetclass safe trusted safe noloop mcast
+defnetclass noloop trusted safe mcast
+defnetclass link
+defnetclass mcast
 m4_divert(-1)
 
 m4_divert(26)m4_dnl
@@ -162,7 +164,7 @@ case $forward in
     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
+    run ip46tables -A FORWARD -j fwd-spec-nofrag
 
     ## Allow ping from safe/noloop to untrusted networks.
     run iptables -A fwd-spec-nofrag -j ACCEPT \
@@ -173,10 +175,10 @@ case $forward in
 	    -m mark --mark $from_untrusted/$MASK_FROM \
 	    -m state --state ESTABLISHED
     run ip6tables -A fwd-spec-nofrag -j ACCEPT \
-	    -p ipv6-icmp --icmpv6-type echo-request \
+	    -p icmpv6 --icmpv6-type echo-request \
 	    -m mark --mark $to_untrusted/$MASK_TO
     run ip6tables -A fwd-spec-nofrag -j ACCEPT \
-	    -p ipv6-icmp --icmpv6-type echo-reply \
+	    -p icmpv6 --icmpv6-type echo-reply \
 	    -m mark --mark $from_untrusted/$MASK_FROM \
 	    -m state --state ESTABLISHED
 
@@ -237,22 +239,6 @@ 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).
-seen=:-:
-for net in $allnets; do
-  eval class=\$net_class_$net
-  case $class in trusted) ;; *) continue ;; esac
-  for iface in $(net_interfaces FWHOST $net); do
-    case "$seen" in *:$iface:*) continue ;; esac
-    seen=$seen$iface:
-    run iptables -A inbound -j ACCEPT \
-	-s 0.0.0.0 -d 224.0.0.0/24 \
-	-i $iface
-  done
-done
-
 ## Allow incoming ping.  This is the only ICMP left.
 run ip46tables -A inbound -j ACCEPT -p icmp
 
@@ -265,12 +251,9 @@ run ip46tables -A inbound -j forbidden
 run ip46tables -A INPUT -m mark --mark $from_untrusted/$MASK_FROM -g inbound
 
 ## Otherwise process as indicated by the mark.
-run ip46tables -A INPUT -m mark ! --mark 0/$MASK_MASK -j ACCEPT
-case $forward in
-  1)
-    run ip46tables -A FORWARD -m mark ! --mark 0/$MASK_MASK -j ACCEPT
-    ;;
-esac
+for i in $inchains; do
+  run ip46tables -A $i -m mark ! --mark 0/$MASK_MASK -j ACCEPT
+done
 
 m4_divert(-1)
 ###----- That's all, folks --------------------------------------------------
diff --git a/vampire.m4 b/vampire.m4
index 4e00a49..acd2008 100644
--- a/vampire.m4
+++ b/vampire.m4
@@ -48,8 +48,8 @@ allowservices inbound udp \
 
 ## Extend some services to local untrusted hosts.
 clearchain inbound-untrusted
-run iptables -A inbound -j inbound-untrusted \
-	-s 172.29.198.0/24
+run iptables -A inbound -j inbound-untrusted -s $net_inet_untrusted
+run ip6tables -A inbound -j inbound-untrusted -s $net_inet6_untrusted
 
 allowservices inbound-untrusted tcp \
 	dns \