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775bd287 | 1 | ### -*-sh-*- |
bfdc045d | 2 | ### |
20106bbb | 3 | ### Classify packets according to source and destination networks. |
bfdc045d MW |
4 | ### |
5 | ### (c) 2008 Mark Wooding | |
6 | ### | |
7 | ||
8 | ###----- Licensing notice --------------------------------------------------- | |
9 | ### | |
10 | ### This program is free software; you can redistribute it and/or modify | |
11 | ### it under the terms of the GNU General Public License as published by | |
12 | ### the Free Software Foundation; either version 2 of the License, or | |
13 | ### (at your option) any later version. | |
14 | ### | |
15 | ### This program is distributed in the hope that it will be useful, | |
16 | ### but WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | ### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
18 | ### GNU General Public License for more details. | |
19 | ### | |
20 | ### You should have received a copy of the GNU General Public License | |
21 | ### along with this program; if not, write to the Free Software Foundation, | |
22 | ### Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
23 | ||
24 | m4_divert(40)m4_dnl | |
25 | ###-------------------------------------------------------------------------- | |
26 | ### Address classification. | |
27 | ### | |
28 | ### The objective of address classification is to work out what kind of | |
29 | ### networks a packet is travelling between, in order to make filtering | |
30 | ### decisions easier. | |
31 | ### | |
32 | ### Address classification is done in the mangle table, by attaching | |
33 | ### appropriate marks to the packet. We split the Internet into a number of | |
34 | ### address classes, and make forwarding decisions based on the classes of | |
35 | ### the source and destination addresses. | |
36 | ### | |
37 | ### The mark word is split into three fields: the FROM and TO fields simply | |
38 | ### record the source and destination classes numerically; the MASK field is | |
39 | ### used to determine whether forwarding should occur. There is a mask bit | |
40 | ### for each address class. Source classification sets mask bits according | |
41 | ### to the forwarding policy for the source address class. Destination | |
42 | ### classification clears all of the mask bits except for the one | |
43 | ### corresponding to the actual destination class. Therefore, forwarding is | |
44 | ### permitted if and only if the mask bits are not all zero. | |
45 | ### | |
46 | ### The mangle chains are arranged as follows. | |
47 | ### | |
48 | ### The PREROUTING hook simply invokes in-classify and out-classify chains as | |
49 | ### subroutines. These will tail-call appropriate classification chains. | |
50 | ### | |
51 | ### The in-classify chain is responsible for both source address | |
52 | ### classification and verifying that the packet arrived from the correct | |
53 | ### interface. It does an initial dispatch on the source interface, to | |
54 | ### in-IFACE. The in-IFACE chain dispatches to mark-from-CLASS when it | |
55 | ### recognizes an address belonging to the CLASS; if no matches succeed, it | |
56 | ### goes to bad-source-address, which logs a message and drops the packet. | |
57 | ### The default interface is special. If no explicit matches are found, it | |
58 | ### dispatches to in-default which forbids a few obviously evil things and | |
59 | ### finally dispatches to mark-from-untrusted. | |
60 | ### | |
61 | ### The out-classify is simpler because it doesn't care about the interface. | |
62 | ### It simply checks each network range in turn, dispatching to mark-to-CLASS | |
63 | ### on a match or mark-to-DEFAULT (probably untrusted) if there is no match. | |
64 | ||
65 | clearchain mangle:in-classify mangle:in-default mangle:out-classify | |
66 | clearchain mangle:local-source | |
67 | ||
68 | ## Packets over the loopback interface are automatically trusted. All manner | |
69 | ## of weird stuff happens on lo, and it's best not to second-guess it. | |
0291d6d5 | 70 | run ip46tables -t mangle -A in-classify -i lo -j ACCEPT |
bfdc045d | 71 | |
429f4314 MW |
72 | ## Local broadcast and link-local multicast packets sometimes have bizarre |
73 | ## addresses. Don't block them just because of this. | |
bfdc045d MW |
74 | run iptables -t mangle -A in-classify -j RETURN \ |
75 | -s 0.0.0.0 -d 255.255.255.255 \ | |
429f4314 MW |
76 | -p udp |
77 | run iptables -t mangle -A in-classify -j RETURN \ | |
78 | -s 0.0.0.0 -d 224.0.0.0/24 \ | |
79 | -p udp | |
bfdc045d MW |
80 | |
81 | ## Since packets with source and destination addresses both local will go | |
82 | ## over the loopback interface, I shouldn't see a packet from me over any | |
83 | ## other interface. Except that I will if I sent a broadcast or multicast. | |
d5214471 MW |
84 | ## Allow the broadcasts, and remember not to trust them. There are no |
85 | ## broadcast addresses in IPv6 (only link-local multicast)m so we don't have | |
86 | ## to worry about that. | |
bfdc045d MW |
87 | run iptables -t mangle -A local-source -j RETURN \ |
88 | -m addrtype --dst-type BROADCAST | |
89 | run iptables -t mangle -A local-source -j RETURN \ | |
90 | -m addrtype --dst-type MULTICAST | |
0291d6d5 MW |
91 | run ip6tables -t mangle -A local-source -j RETURN \ |
92 | -d ff00::/8 | |
93 | run ip46tables -t mangle -A local-source -g bad-source-address | |
bfdc045d MW |
94 | run iptables -t mangle -A in-classify -j local-source \ |
95 | -m addrtype --src-type LOCAL | |
0291d6d5 MW |
96 | for addr in $host_6addrs; do |
97 | run ip6tables -t mangle -A in-classify -j local-source \ | |
98 | -s $addr | |
99 | done | |
bfdc045d | 100 | |
d5214471 MW |
101 | ## It's not valid to have a multicast address as a packet source: multicast |
102 | ## routing is done away from the source, so a multicast address would make | |
103 | ## this impossible to do. So discard these packets. Also discard class-E | |
104 | ## IPv4 addresses, since they aren't assigned. | |
105 | run iptables -t mangle -A in-classify -g bad-source-address \ | |
106 | -s 224.0.0.0/3 | |
107 | run ip6tables -t mangle -A in-classify -g bad-source-address \ | |
108 | -s ff00::/8 | |
109 | ||
bfdc045d MW |
110 | m4_divert(41)m4_dnl |
111 | ## Define the important networks. | |
112 | for pass in 1 2; do | |
113 | netclassindex=0 | |
114 | m4_divert(42)m4_dnl | |
115 | done | |
116 | ||
117 | m4_divert(46)m4_dnl | |
beb4f0ee MW |
118 | ## Build the input classification chains. There's one chain `in-IFACE' for |
119 | ## each local interface. This chain does a further dispatch on the source | |
120 | ## address to the appropriate `mark-from-CLASS' chain for the source network | |
121 | ## class. | |
122 | seen=: | |
123 | for iface in $host_ifaces_<::>FWHOST; do | |
124 | ifname=${iface%=*} | |
125 | case $seen in *:$ifname:*) continue ;; esac | |
126 | seen=$seen$ifname: | |
127 | clearchain mangle:in-$ifname | |
128 | run ip46tables -t mangle -A in-classify -i $ifname -g in-$ifname | |
129 | done | |
130 | ||
131 | ## Now populate the `in-IFACE' and `out-classify' chains. We iterate over | |
132 | ## the available networks and add addresses to the appropriate chains. Also, | |
133 | ## build up a map of which interfaces receive from which address ranged so | |
134 | ## that we can finish the chains off properly later. This contains entries | |
135 | ## of the form IFACE=:ADDR:ADDR:...: | |
136 | ifnets="" | |
bfdc045d | 137 | for net in $allnets; do |
beb4f0ee MW |
138 | |
139 | ## Determine the addresses and class for this network, and populate the | |
140 | ## `out-classify' chains. | |
141 | eval addr=\$net_inet_$net addr6=\$net_inet6_$net class=\$net_class_$net | |
142 | case $class in virtual) continue ;; esac | |
143 | trace "$net : $class" | |
144 | for a in $addr; do | |
145 | run iptables -t mangle -A out-classify -g mark-to-$class -d $a | |
3a68f688 | 146 | done |
beb4f0ee MW |
147 | for a in $addr6; do |
148 | run ip6tables -t mangle -A out-classify -g mark-to-$class -d $a | |
3a68f688 | 149 | done |
beb4f0ee MW |
150 | |
151 | ## Now work through the interfaces. | |
152 | for iface in $(net_interfaces FWHOST $net); do | |
153 | nets="" | |
154 | case $iface in | |
155 | ||
156 | -) | |
157 | ## A special `no interface' marker: we should not receive packets | |
158 | ## from this network at all. | |
159 | continue | |
160 | ;; | |
161 | ||
162 | *-+) | |
163 | ## A special marker indicating a collection of point-to-point | |
164 | ## interfaces. We should match an address to a particular interface. | |
165 | ## Later, we'll cap this chain off by rejecting all other traffic. | |
166 | eval hosts=\$net_hosts_$net | |
167 | for host in $hosts; do | |
168 | eval ha=\$host_inet_$host ha6=\$host_inet6_$host | |
169 | trace "$host : $class -> $iface" | |
170 | for a in $ha; do | |
171 | run iptables -t mangle -A in-$iface \ | |
172 | -i ${iface%+}$host -s $a -g mark-from-$class | |
173 | nets=$nets$a: | |
174 | done | |
175 | for a in $ha6; do | |
176 | run ip6tables -t mangle -A in-$iface \ | |
177 | -i ${iface%+}$host -s $a -g mark-from-$class | |
178 | nets=$nets$a: | |
179 | done | |
180 | done | |
181 | ;; | |
182 | ||
183 | *) | |
184 | ## A normal interface. Classify incoming traffic according to the | |
185 | ## source address. | |
186 | trace "$net : $class -> $iface" | |
187 | for a in $addr; do | |
188 | run iptables -t mangle -A in-$iface -g mark-from-$class -s $a | |
189 | nets=$nets$a: | |
190 | done | |
191 | for a in $addr6; do | |
192 | run ip6tables -t mangle -A in-$iface -g mark-from-$class -s $a | |
193 | nets=$nets$a: | |
194 | done | |
195 | case $net in default) nets=${nets}default: ;; esac | |
196 | ;; | |
197 | esac | |
198 | ||
199 | ## Record that this interface receives traffic from this network. | |
200 | unset nifnets | |
201 | foundp=nil | |
202 | for ifnet in $ifnets; do | |
203 | case $ifnet in | |
204 | $iface=*:$net:*) addword nifnets $ifnet; foundp=t ;; | |
205 | $iface=*) addword nifnets $ifnet$nets; foundp=t ;; | |
206 | *) addword nifnets $ifnet ;; | |
207 | esac | |
208 | done | |
209 | case $foundp in nil) addword nifnets $iface=:$nets ;; esac | |
210 | ifnets=$nifnets | |
211 | ||
212 | done | |
213 | done | |
214 | ||
215 | ## Wrap up all of the `in-IFACE' chains. A chain which matches the `default' | |
216 | ## net should have unmatched but known networks blocked off, and then chain | |
217 | ## onto `in-default'. Other chains should just chain onto | |
218 | ## `bad-source-address'. | |
219 | trace "ifnets = $ifnets" | |
220 | for ifnet in $ifnets; do | |
221 | iface=${ifnet%%=*} nets=${ifnet#*=} | |
222 | case $nets in | |
223 | *:default:*) | |
224 | for n in $allnets; do | |
225 | eval addr=\$net_inet_$n addr6=\$net_inet6_$n | |
226 | for a in $addr; do | |
227 | case $nets in *:$a:*) continue ;; esac | |
228 | nets=$nets$a | |
229 | run iptables -t mangle -A in-$iface -s $a -g bad-source-address | |
230 | done | |
231 | for a in $addr6; do | |
232 | case $nets in *:$a:*) continue ;; esac | |
233 | nets=$nets$a | |
234 | run ip6tables -t mangle -A in-$iface -s $a -g bad-source-address | |
235 | done | |
3a68f688 | 236 | done |
beb4f0ee MW |
237 | run ip46tables -t mangle -A in-$iface -g in-default |
238 | ;; | |
239 | *) | |
240 | run ip46tables -t mangle -A in-$iface -g bad-source-address | |
0291d6d5 MW |
241 | ;; |
242 | esac | |
243 | done | |
bfdc045d MW |
244 | |
245 | ## Fill in the black holes in the network. | |
246 | for addr in \ | |
247 | 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 \ | |
677ef44e MW |
248 | 127.0.0.0/8 \ |
249 | 192.0.2.0/24 198.51.100.0/24 203.0.113.0/24 | |
bfdc045d MW |
250 | do |
251 | run iptables -t mangle -A in-default -s $addr -g bad-source-address | |
252 | done | |
0291d6d5 MW |
253 | for addr in \ |
254 | fc00::/7 \ | |
255 | 2001:0db8::/32 | |
256 | do | |
257 | run ip6tables -t mangle -A in-default -s $addr -g bad-source-address | |
258 | done | |
beb4f0ee | 259 | run ip46tables -t mangle -A in-default -g mark-from-$net_class_default |
bfdc045d MW |
260 | |
261 | m4_divert(92)m4_dnl | |
262 | ## Put the final default decision on the in-default chain, and attach the | |
263 | ## classification chains to the PREROUTING hook. | |
3a68f688 | 264 | for iface in $defaultifaces; do |
beb4f0ee | 265 | run ip46tables -t mangle -A in-$iface -g in-default |
3a68f688 | 266 | done |
beb4f0ee | 267 | run ip46tables -t mangle -A out-classify -g mark-to-$net_class_default |
0291d6d5 MW |
268 | run ip46tables -t mangle -A PREROUTING -j in-classify |
269 | run ip46tables -t mangle -A PREROUTING -j out-classify | |
bfdc045d MW |
270 | |
271 | ## Now it's safe to let stuff through. | |
272 | for i in PREROUTING INPUT FORWARD OUTPUT POSTROUTING; do | |
0291d6d5 | 273 | run ip46tables -t mangle -P $i ACCEPT |
bfdc045d MW |
274 | done |
275 | ||
276 | m4_divert(-1) | |
277 | ###----- That's all, folks -------------------------------------------------- |