###
### The mangle chains are arranged as follows.
###
-### The PREROUTING hook simply invokes in-classify and out-classify chains as
-### subroutines. These will tail-call appropriate classification chains.
+### The INPUT and FORWARD hooks simply invoke in-classify and out-classify
+### chains as subroutines. These will tail-call appropriate classification
+### chains.
###
### The in-classify chain is responsible for both source address
### classification and verifying that the packet arrived from the correct
### goes to bad-source-address, which logs a message and drops the packet.
### The default interface is special. If no explicit matches are found, it
### dispatches to in-default which forbids a few obviously evil things and
-### finally dispatches to mark-from-untrusted.
+### finally dispatches to mark-from-DEFAULT (usually `untrusted').
###
### The out-classify is simpler because it doesn't care about the interface.
### It simply checks each network range in turn, dispatching to mark-to-CLASS
-### on a match or mark-to-DEFAULT (probably untrusted) if there is no match.
+### on a match or mark-to-DEFAULT (probably `untrusted') if there is no
+### match.
clearchain mangle:in-classify mangle:in-default mangle:out-classify
clearchain mangle:local-source
## over the loopback interface, I shouldn't see a packet from me over any
## other interface. Except that I will if I sent a broadcast or multicast.
## Allow the broadcasts, and remember not to trust them. There are no
-## broadcast addresses in IPv6 (only link-local multicast)m so we don't have
+## broadcast addresses in IPv6 (only link-local multicast) so we don't have
## to worry about that.
run iptables -t mangle -A local-source -j RETURN \
-m addrtype --dst-type BROADCAST
## 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
-## class.
+## class. We also build a table mapping interface names to numbers (since
+## the names are so unhelpful).
seen=:
+ifq=0
+ifmap=""
for iface in $host_ifaces_<::>FWHOST; do
ifname=${iface%=*}
case $seen in *:$ifname:*) continue ;; esac
seen=$seen$ifname:
+ addword ifmap $ifname=$ifq
+ ifq=$(( $ifq + 1 ))
clearchain mangle:in-$ifname
run ip46tables -t mangle -A in-classify -i $ifname -g in-$ifname
done
-## Now populate the `in-IFACE' and `out-classify' chains. We iterate over
-## the available networks and add addresses to the appropriate chains. Also,
-## build up a map of which interfaces receive from which address ranged so
-## that we can finish the chains off properly later. This contains entries
-## of the form IFACE=:ADDR:ADDR:...:
-ifnets=""
+## We do a first pass over nets first, and then the interfaces which those
+## networks reach. During this pass, we populate the `out-classify' chains,
+## and we also build some lists so that we can do later passes over
+## interfaces first and then reaching networks. This is complicated by
+## interface names being unhelpful.
+##
+## Here are the variables we maintain.
+##
+## ifmap A list of entries IFACE=N mapping interface names to
+## numbers.
+##
+## ifnets_N A space-separated list of networks reaching interface
+## number N. This is used for building the matching
+## chains.
+##
+## ifaddrs_N A bang-separated list of address ranges reaching
+## interface number N. This is used for filtering out
+## known networks if the default network reaches the
+## interface.
for net in $allnets; do
- ## Determine the addresses and class for this network, and populate the
- ## `out-classify' chains.
- eval addr=\$net_inet_$net addr6=\$net_inet6_$net class=\$net_class_$net
- case $class in virtual) continue ;; esac
- trace "$net : $class"
- for a in $addr; do
- run iptables -t mangle -A out-classify -g mark-to-$class -d $a
+ ## Work through the interfaces that this network reaches.
+ for iface in $(net_interfaces FWHOST $net); do
+ case $iface in -) break ;; esac
+
+ ## Find a sequence number for this interface.
+ q=nil
+ for i in $ifmap; do
+ case "$i" in "$iface"=*) q=${i##*=}; break ;; esac
+ done
+ case $q in
+ nil)
+ echo >&2 "$0 INTERNAL ERROR: missing interface \`$iface'!"
+ exit 1
+ ;;
+ esac
+
+ ## Remember the reachability information.
+ addword ifnets_$q $net
done
- for a in $addr6; do
- run ip6tables -t mangle -A out-classify -g mark-to-$class -d $a
+done
+
+## Build the `ifaddr_N' map and an `all-addresses' list.
+alladdrs=!
+trace "ifmap = $ifmap"
+for entry in $ifmap; do
+ iface=${entry%=*} q=${entry##*=}
+ eval nets=\$ifnets_$q
+ aa=!
+ for n in $nets; do
+ eval "addrs=\"\$net_inet_$n \$net_inet6_$n\""
+ trace "$iface $n addrs = $addrs"
+ for a in $addrs; do
+ case $aa in *!$a!*) ;; *) aa=$aa$a! ;; esac
+ case $alladdrs in *!$a!*) ;; *) alladdrs=$alladdrs$a! ;; esac
+ done
done
+ eval ifaddrs_$q=\$aa
+ trace "iface $q = $iface; nets = $nets; addrs = $aa"
+done
+trace "alladdrs = $alladdrs"
- ## Now work through the interfaces.
- for iface in $(net_interfaces FWHOST $net); do
- nets=""
- case $iface in
+## Populate the `out-classify' chain, matching networks.
+prepare_to () { mode=goto fail=mark-to-$net_class_default; }
+matchnets -d mark-to : prepare_to out-classify "" 0 $allnets
- -)
- ## A special `no interface' marker: we should not receive packets
- ## from this network at all.
- continue
- ;;
+## A `finish' hook for rejecting known address ranges arriving on a
+## default-reachable interface.
+finish_from_default () {
+ q=$1 chain=$2
+ eval addrs=\$ifaddrs_$q
+
+ for n in $allnets; do
+ eval addr=\$net_inet_$n addr6=\$net_inet6_$n
+ for a in $addr; do
+ case $a in !*) continue ;; esac
+ case $addrs in *"!$a!"*) continue ;; esac
+ run iptables -t mangle -A $chain -s $a -g bad-source-address
+ done
+ for a in $addr6; do
+ case $a in !*) continue ;; esac
+ case $addrs in *"!$a!"*) continue ;; esac
+ run ip6tables -t mangle -A $chain -s $a -g bad-source-address
+ done
+ done
+ run ip46tables -t mangle -A $chain -g in-default
+}
+
+## A `prepare' hook for input classification. If the interface is
+## default-reachable, then we need to reject known address ranges before
+## dispatching to the default chain; otherwise just reject the packet.
+prepare_from () {
+ q=$1 flags=$2
+ case $flags in
+ *:default:*) mode=call finish="finish_from_default $q" ;;
+ *) mode=goto fail=bad-source-address ;;
+ esac
+}
- *-+)
- ## A special marker indicating a collection of point-to-point
- ## interfaces. We should match an address to a particular interface.
- ## Later, we'll cap this chain off by rejecting all other traffic.
- eval hosts=\$net_hosts_$net
+## Populate the `in-IFACE' chains.
+for entry in $ifmap; do
+ iface=${entry%=*} q=${entry##*=}
+ eval nets=\$ifnets_$q
+
+ case $iface in
+ *-+)
+ ## A special marker indicating a collection of point-to-point
+ ## interfaces. We should match an address to a particular interface.
+ chains=""
+ for net in $nets; do
+ eval hosts=\$net_hosts_$net class=\$net_class_$net
for host in $hosts; do
eval ha=\$host_inet_$host ha6=\$host_inet6_$host
trace "$host : $class -> $iface"
for a in $ha; do
run iptables -t mangle -A in-$iface \
-i ${iface%+}$host -s $a -g mark-from-$class
- nets=$nets$a:
done
for a in $ha6; do
run ip6tables -t mangle -A in-$iface \
-i ${iface%+}$host -s $a -g mark-from-$class
- nets=$nets$a:
done
done
- ;;
-
- *)
- ## A normal interface. Classify incoming traffic according to the
- ## source address.
- trace "$net : $class -> $iface"
- for a in $addr; do
- run iptables -t mangle -A in-$iface -g mark-from-$class -s $a
- nets=$nets$a:
- done
- for a in $addr6; do
- run ip6tables -t mangle -A in-$iface -g mark-from-$class -s $a
- nets=$nets$a:
- done
- case $net in default) nets=${nets}default: ;; esac
- ;;
- esac
-
- ## Record that this interface receives traffic from this network.
- unset nifnets
- foundp=nil
- for ifnet in $ifnets; do
- case $ifnet in
- $iface=*:$net:*) addword nifnets $ifnet; foundp=t ;;
- $iface=*) addword nifnets $ifnet$nets; foundp=t ;;
- *) addword nifnets $ifnet ;;
- esac
- done
- case $foundp in nil) addword nifnets $iface=:$nets ;; esac
- ifnets=$nifnets
-
- done
-done
-
-## Wrap up all of the `in-IFACE' chains. A chain which matches the `default'
-## net should have unmatched but known networks blocked off, and then chain
-## onto `in-default'. Other chains should just chain onto
-## `bad-source-address'.
-trace "ifnets = $ifnets"
-for ifnet in $ifnets; do
- iface=${ifnet%%=*} nets=${ifnet#*=}
- case $nets in
- *:default:*)
- for n in $allnets; do
- eval addr=\$net_inet_$n addr6=\$net_inet6_$n
- for a in $addr; do
- case $nets in *:$a:*) continue ;; esac
- nets=$nets$a
- run iptables -t mangle -A in-$iface -s $a -g bad-source-address
- done
- for a in $addr6; do
- case $nets in *:$a:*) continue ;; esac
- nets=$nets$a
- run ip6tables -t mangle -A in-$iface -s $a -g bad-source-address
- done
done
- run ip46tables -t mangle -A in-$iface -g in-default
+ run ip46tables -t mangle -A in-$iface -g bad-source-address
;;
*)
- run ip46tables -t mangle -A in-$iface -g bad-source-address
+ matchnets -s mark-from : "prepare_from $q" in-$iface "" 0 $nets
;;
esac
done
-## Fill in the black holes in the network.
+## Fill in the black holes in the network. Some of these might actually be
+## known networks, so don't fill those in again. See RFC5735 and RFC4291,
+## and their successors.
for addr in \
10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 \
127.0.0.0/8 \
192.0.2.0/24 198.51.100.0/24 203.0.113.0/24
do
+ case $alladdrs in *!$addr!*) continue ;; esac
run iptables -t mangle -A in-default -s $addr -g bad-source-address
done
for addr in \
fc00::/7 \
+ ::0:0/96 ::ffff:0:0/96 \
2001:db8::/32
do
+ case $alladdrs in *!$addr!*) continue ;; esac
run ip6tables -t mangle -A in-default -s $addr -g bad-source-address
done
run ip46tables -t mangle -A in-default -g mark-from-$net_class_default
m4_divert(92)m4_dnl
## Put the final default decision on the in-default chain, and attach the
-## classification chains to the PREROUTING hook.
+## classification chains to the INPUT and (maybe) FORWARD hooks.
for iface in $defaultifaces; do
run ip46tables -t mangle -A in-$iface -g in-default
done
-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
+chains="INPUT"
+case $forward in 1) chains="$chains FORWARD" ;; esac
+for c in $chains; do
+ run ip46tables -t mangle -A $c -j in-classify
+ run ip46tables -t mangle -A $c -j out-classify
+done
## Incoming stuff to or from a link-local address is OK.
run ip46tables -t mangle -A INPUT \
~mdw / firewall / blobdiff