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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 | ||
44f95827 MW |
68 | ## An unpleasant hack. We can't reject packets from the mangle table, so |
69 | ## we mark packets with a bad destination and then detect this in the | |
70 | ## filter table. | |
71 | clearchain mangle:bad-destination-address | |
72 | BAD_DEST=0xf6f377d2 | |
73 | ip46tables -t mangle -A bad-destination-address -j MARK --set-mark $BAD_DEST | |
74 | ip46tables -t mangle -A bad-destination-address -j ACCEPT | |
75 | for i in $inchains; do | |
76 | ip46tables -A $i -m mark --mark $BAD_DEST -g bad-destination-address | |
77 | done | |
78 | ||
bfdc045d MW |
79 | ## Packets over the loopback interface are automatically trusted. All manner |
80 | ## of weird stuff happens on lo, and it's best not to second-guess it. | |
0291d6d5 | 81 | run ip46tables -t mangle -A in-classify -i lo -j ACCEPT |
bfdc045d | 82 | |
429f4314 MW |
83 | ## Local broadcast and link-local multicast packets sometimes have bizarre |
84 | ## addresses. Don't block them just because of this. | |
bfdc045d MW |
85 | run iptables -t mangle -A in-classify -j RETURN \ |
86 | -s 0.0.0.0 -d 255.255.255.255 \ | |
429f4314 MW |
87 | -p udp |
88 | run iptables -t mangle -A in-classify -j RETURN \ | |
89 | -s 0.0.0.0 -d 224.0.0.0/24 \ | |
90 | -p udp | |
bfdc045d MW |
91 | |
92 | ## Since packets with source and destination addresses both local will go | |
93 | ## over the loopback interface, I shouldn't see a packet from me over any | |
94 | ## other interface. Except that I will if I sent a broadcast or multicast. | |
d5214471 MW |
95 | ## Allow the broadcasts, and remember not to trust them. There are no |
96 | ## broadcast addresses in IPv6 (only link-local multicast)m so we don't have | |
97 | ## to worry about that. | |
bfdc045d MW |
98 | run iptables -t mangle -A local-source -j RETURN \ |
99 | -m addrtype --dst-type BROADCAST | |
100 | run iptables -t mangle -A local-source -j RETURN \ | |
101 | -m addrtype --dst-type MULTICAST | |
0291d6d5 MW |
102 | run ip6tables -t mangle -A local-source -j RETURN \ |
103 | -d ff00::/8 | |
104 | run ip46tables -t mangle -A local-source -g bad-source-address | |
bfdc045d MW |
105 | run iptables -t mangle -A in-classify -j local-source \ |
106 | -m addrtype --src-type LOCAL | |
0291d6d5 MW |
107 | for addr in $host_6addrs; do |
108 | run ip6tables -t mangle -A in-classify -j local-source \ | |
109 | -s $addr | |
110 | done | |
bfdc045d MW |
111 | |
112 | m4_divert(41)m4_dnl | |
113 | ## Define the important networks. | |
114 | for pass in 1 2; do | |
115 | netclassindex=0 | |
116 | m4_divert(42)m4_dnl | |
117 | done | |
118 | ||
119 | m4_divert(46)m4_dnl | |
44f95827 MW |
120 | ## Special IPv4 source addresses. Forbid broadcast and multicast sources. |
121 | ## Mark the special zero address and link-local addresses as such. (This | |
122 | ## also matches class-E addresses, which are probably permanently invalid.) | |
123 | for i in 0.0.0.0 169.254.0.0/16; do | |
124 | run iptables -t mangle -A in-classify -g mark-from-link -s $i | |
125 | done | |
126 | run iptables -t mangle -A in-classify -g bad-source-address \ | |
127 | -s 224.0.0.0/3 | |
128 | run iptables -t mangle -A in-classify -g bad-source-address \ | |
129 | -m addrtype --src-type BROADCAST \ | |
130 | ||
131 | ## Special IPv6 addresses. Format multicast sources, and mark zero and | |
132 | ## link local addresses. | |
133 | for i in :: fe80::/10; do | |
134 | run ip6tables -t mangle -A in-classify -g mark-from-link -s $i | |
135 | done | |
136 | run ip6tables -t mangle -A in-classify -g bad-source-address \ | |
137 | -s ff00::/8 | |
138 | ||
139 | ## Special IPv4 destination addresses. The zero address is invalid; mark | |
140 | ## link-local and recognized broadcast addresses as link-local. We leave | |
141 | ## multicast for later. | |
142 | for i in 0.0.0.0 240.0.0.0/4; do | |
143 | run iptables -t mangle -A out-classify -g bad-destination-address -d $i | |
144 | done | |
145 | run iptables -t mangle -A out-classify -g mark-to-link -d 169.254.0.0/16 | |
146 | run iptables -t mangle -A out-classify -g mark-to-link \ | |
147 | -m addrtype --dst-type BROADCAST | |
148 | ||
149 | ## Special IPv6 destination addressses. The zero address is again invalid; | |
150 | ## mark link local addresses. We do multicast later. | |
151 | run ip6tables -t mangle -A out-classify -g bad-destination-address \ | |
152 | -d :: | |
153 | run ip6tables -t mangle -A out-classify -g mark-to-link -d fe80::/10 | |
154 | ||
155 | ## Now deal with multicast. Link-local multicast is detected as being | |
156 | ## link-local, so that we can prevent it being forwarded correctly. | |
157 | clearchain mangle:out-classify-mcast | |
158 | run iptables -t mangle -A out-classify-mcast -g mark-to-link \ | |
159 | -d 224.0.0.0/24 | |
160 | for i in 0 1 2 3 4 5 6 7 8 9 a b c d e f; do | |
161 | run ip6tables -t mangle -A out-classify-mcast -g mark-to-link \ | |
162 | -d ff${i}2::/16 | |
163 | done | |
164 | run ip46tables -t mangle -A out-classify-mcast -g mark-to-mcast | |
165 | run iptables -t mangle -A out-classify -g out-classify-mcast \ | |
166 | -d 224.0.0.0/4 | |
167 | run ip6tables -t mangle -A out-classify -g out-classify-mcast \ | |
168 | -d ff00::/8 | |
169 | ||
beb4f0ee MW |
170 | ## Build the input classification chains. There's one chain `in-IFACE' for |
171 | ## each local interface. This chain does a further dispatch on the source | |
172 | ## address to the appropriate `mark-from-CLASS' chain for the source network | |
173 | ## class. | |
174 | seen=: | |
175 | for iface in $host_ifaces_<::>FWHOST; do | |
176 | ifname=${iface%=*} | |
177 | case $seen in *:$ifname:*) continue ;; esac | |
178 | seen=$seen$ifname: | |
179 | clearchain mangle:in-$ifname | |
180 | run ip46tables -t mangle -A in-classify -i $ifname -g in-$ifname | |
181 | done | |
182 | ||
183 | ## Now populate the `in-IFACE' and `out-classify' chains. We iterate over | |
184 | ## the available networks and add addresses to the appropriate chains. Also, | |
185 | ## build up a map of which interfaces receive from which address ranged so | |
186 | ## that we can finish the chains off properly later. This contains entries | |
187 | ## of the form IFACE=:ADDR:ADDR:...: | |
188 | ifnets="" | |
bfdc045d | 189 | for net in $allnets; do |
beb4f0ee MW |
190 | |
191 | ## Determine the addresses and class for this network, and populate the | |
192 | ## `out-classify' chains. | |
193 | eval addr=\$net_inet_$net addr6=\$net_inet6_$net class=\$net_class_$net | |
194 | case $class in virtual) continue ;; esac | |
195 | trace "$net : $class" | |
196 | for a in $addr; do | |
197 | run iptables -t mangle -A out-classify -g mark-to-$class -d $a | |
3a68f688 | 198 | done |
beb4f0ee MW |
199 | for a in $addr6; do |
200 | run ip6tables -t mangle -A out-classify -g mark-to-$class -d $a | |
3a68f688 | 201 | done |
beb4f0ee MW |
202 | |
203 | ## Now work through the interfaces. | |
204 | for iface in $(net_interfaces FWHOST $net); do | |
205 | nets="" | |
206 | case $iface in | |
207 | ||
208 | -) | |
209 | ## A special `no interface' marker: we should not receive packets | |
210 | ## from this network at all. | |
211 | continue | |
212 | ;; | |
213 | ||
214 | *-+) | |
215 | ## A special marker indicating a collection of point-to-point | |
216 | ## interfaces. We should match an address to a particular interface. | |
217 | ## Later, we'll cap this chain off by rejecting all other traffic. | |
218 | eval hosts=\$net_hosts_$net | |
219 | for host in $hosts; do | |
220 | eval ha=\$host_inet_$host ha6=\$host_inet6_$host | |
221 | trace "$host : $class -> $iface" | |
222 | for a in $ha; do | |
223 | run iptables -t mangle -A in-$iface \ | |
224 | -i ${iface%+}$host -s $a -g mark-from-$class | |
225 | nets=$nets$a: | |
226 | done | |
227 | for a in $ha6; do | |
228 | run ip6tables -t mangle -A in-$iface \ | |
229 | -i ${iface%+}$host -s $a -g mark-from-$class | |
230 | nets=$nets$a: | |
231 | done | |
232 | done | |
233 | ;; | |
234 | ||
235 | *) | |
236 | ## A normal interface. Classify incoming traffic according to the | |
237 | ## source address. | |
238 | trace "$net : $class -> $iface" | |
239 | for a in $addr; do | |
240 | run iptables -t mangle -A in-$iface -g mark-from-$class -s $a | |
241 | nets=$nets$a: | |
242 | done | |
243 | for a in $addr6; do | |
244 | run ip6tables -t mangle -A in-$iface -g mark-from-$class -s $a | |
245 | nets=$nets$a: | |
246 | done | |
247 | case $net in default) nets=${nets}default: ;; esac | |
248 | ;; | |
249 | esac | |
250 | ||
251 | ## Record that this interface receives traffic from this network. | |
252 | unset nifnets | |
253 | foundp=nil | |
254 | for ifnet in $ifnets; do | |
255 | case $ifnet in | |
256 | $iface=*:$net:*) addword nifnets $ifnet; foundp=t ;; | |
257 | $iface=*) addword nifnets $ifnet$nets; foundp=t ;; | |
258 | *) addword nifnets $ifnet ;; | |
259 | esac | |
260 | done | |
261 | case $foundp in nil) addword nifnets $iface=:$nets ;; esac | |
262 | ifnets=$nifnets | |
263 | ||
264 | done | |
265 | done | |
266 | ||
267 | ## Wrap up all of the `in-IFACE' chains. A chain which matches the `default' | |
268 | ## net should have unmatched but known networks blocked off, and then chain | |
269 | ## onto `in-default'. Other chains should just chain onto | |
270 | ## `bad-source-address'. | |
271 | trace "ifnets = $ifnets" | |
272 | for ifnet in $ifnets; do | |
273 | iface=${ifnet%%=*} nets=${ifnet#*=} | |
274 | case $nets in | |
275 | *:default:*) | |
276 | for n in $allnets; do | |
277 | eval addr=\$net_inet_$n addr6=\$net_inet6_$n | |
278 | for a in $addr; do | |
279 | case $nets in *:$a:*) continue ;; esac | |
280 | nets=$nets$a | |
281 | run iptables -t mangle -A in-$iface -s $a -g bad-source-address | |
282 | done | |
283 | for a in $addr6; do | |
284 | case $nets in *:$a:*) continue ;; esac | |
285 | nets=$nets$a | |
286 | run ip6tables -t mangle -A in-$iface -s $a -g bad-source-address | |
287 | done | |
3a68f688 | 288 | done |
beb4f0ee MW |
289 | run ip46tables -t mangle -A in-$iface -g in-default |
290 | ;; | |
291 | *) | |
292 | run ip46tables -t mangle -A in-$iface -g bad-source-address | |
0291d6d5 MW |
293 | ;; |
294 | esac | |
295 | done | |
bfdc045d MW |
296 | |
297 | ## Fill in the black holes in the network. | |
298 | for addr in \ | |
299 | 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 \ | |
677ef44e MW |
300 | 127.0.0.0/8 \ |
301 | 192.0.2.0/24 198.51.100.0/24 203.0.113.0/24 | |
bfdc045d MW |
302 | do |
303 | run iptables -t mangle -A in-default -s $addr -g bad-source-address | |
304 | done | |
0291d6d5 MW |
305 | for addr in \ |
306 | fc00::/7 \ | |
2f863436 | 307 | 2001:db8::/32 |
0291d6d5 MW |
308 | do |
309 | run ip6tables -t mangle -A in-default -s $addr -g bad-source-address | |
310 | done | |
beb4f0ee | 311 | run ip46tables -t mangle -A in-default -g mark-from-$net_class_default |
bfdc045d MW |
312 | |
313 | m4_divert(92)m4_dnl | |
314 | ## Put the final default decision on the in-default chain, and attach the | |
315 | ## classification chains to the PREROUTING hook. | |
3a68f688 | 316 | for iface in $defaultifaces; do |
beb4f0ee | 317 | run ip46tables -t mangle -A in-$iface -g in-default |
3a68f688 | 318 | done |
beb4f0ee | 319 | run ip46tables -t mangle -A out-classify -g mark-to-$net_class_default |
0291d6d5 MW |
320 | run ip46tables -t mangle -A PREROUTING -j in-classify |
321 | run ip46tables -t mangle -A PREROUTING -j out-classify | |
bfdc045d | 322 | |
44f95827 MW |
323 | ## Incoming stuff to or from a link-local address is OK. |
324 | run ip46tables -t mangle -A INPUT \ | |
325 | -m mark --mark $to_link/$MASK_TO \ | |
326 | -j MARK --or-mark $fwd_link | |
327 | run ip46tables -t mangle -A INPUT \ | |
328 | -m mark --mark $from_link/$MASK_FROM \ | |
329 | -j MARK --or-mark $fwd_link | |
330 | ||
bfdc045d MW |
331 | ## Now it's safe to let stuff through. |
332 | for i in PREROUTING INPUT FORWARD OUTPUT POSTROUTING; do | |
0291d6d5 | 333 | run ip46tables -t mangle -P $i ACCEPT |
bfdc045d MW |
334 | done |
335 | ||
336 | m4_divert(-1) | |
337 | ###----- That's all, folks -------------------------------------------------- |