Commit | Line | Data |
---|---|---|
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 | |
fb7845a8 MW |
73 | run ip46tables -t mangle -A bad-destination-address \ |
74 | -j MARK --set-mark $BAD_DEST | |
75 | run ip46tables -t mangle -A bad-destination-address -j ACCEPT | |
44f95827 | 76 | for i in $inchains; do |
fb7845a8 | 77 | run ip46tables -A $i -m mark --mark $BAD_DEST -g bad-destination-address |
44f95827 MW |
78 | done |
79 | ||
bfdc045d MW |
80 | ## Packets over the loopback interface are automatically trusted. All manner |
81 | ## of weird stuff happens on lo, and it's best not to second-guess it. | |
0291d6d5 | 82 | run ip46tables -t mangle -A in-classify -i lo -j ACCEPT |
bfdc045d | 83 | |
429f4314 MW |
84 | ## Local broadcast and link-local multicast packets sometimes have bizarre |
85 | ## addresses. Don't block them just because of this. | |
bfdc045d MW |
86 | run iptables -t mangle -A in-classify -j RETURN \ |
87 | -s 0.0.0.0 -d 255.255.255.255 \ | |
429f4314 MW |
88 | -p udp |
89 | run iptables -t mangle -A in-classify -j RETURN \ | |
90 | -s 0.0.0.0 -d 224.0.0.0/24 \ | |
91 | -p udp | |
bfdc045d MW |
92 | |
93 | ## Since packets with source and destination addresses both local will go | |
94 | ## over the loopback interface, I shouldn't see a packet from me over any | |
95 | ## other interface. Except that I will if I sent a broadcast or multicast. | |
d5214471 MW |
96 | ## Allow the broadcasts, and remember not to trust them. There are no |
97 | ## broadcast addresses in IPv6 (only link-local multicast)m so we don't have | |
98 | ## to worry about that. | |
bfdc045d MW |
99 | run iptables -t mangle -A local-source -j RETURN \ |
100 | -m addrtype --dst-type BROADCAST | |
101 | run iptables -t mangle -A local-source -j RETURN \ | |
102 | -m addrtype --dst-type MULTICAST | |
0291d6d5 MW |
103 | run ip6tables -t mangle -A local-source -j RETURN \ |
104 | -d ff00::/8 | |
105 | run ip46tables -t mangle -A local-source -g bad-source-address | |
bfdc045d MW |
106 | run iptables -t mangle -A in-classify -j local-source \ |
107 | -m addrtype --src-type LOCAL | |
0291d6d5 MW |
108 | for addr in $host_6addrs; do |
109 | run ip6tables -t mangle -A in-classify -j local-source \ | |
110 | -s $addr | |
111 | done | |
bfdc045d MW |
112 | |
113 | m4_divert(41)m4_dnl | |
114 | ## Define the important networks. | |
115 | for pass in 1 2; do | |
116 | netclassindex=0 | |
117 | m4_divert(42)m4_dnl | |
118 | done | |
119 | ||
120 | m4_divert(46)m4_dnl | |
44f95827 MW |
121 | ## Special IPv4 source addresses. Forbid broadcast and multicast sources. |
122 | ## Mark the special zero address and link-local addresses as such. (This | |
123 | ## also matches class-E addresses, which are probably permanently invalid.) | |
124 | for i in 0.0.0.0 169.254.0.0/16; do | |
125 | run iptables -t mangle -A in-classify -g mark-from-link -s $i | |
126 | done | |
127 | run iptables -t mangle -A in-classify -g bad-source-address \ | |
128 | -s 224.0.0.0/3 | |
129 | run iptables -t mangle -A in-classify -g bad-source-address \ | |
130 | -m addrtype --src-type BROADCAST \ | |
131 | ||
132 | ## Special IPv6 addresses. Format multicast sources, and mark zero and | |
133 | ## link local addresses. | |
134 | for i in :: fe80::/10; do | |
135 | run ip6tables -t mangle -A in-classify -g mark-from-link -s $i | |
136 | done | |
137 | run ip6tables -t mangle -A in-classify -g bad-source-address \ | |
138 | -s ff00::/8 | |
139 | ||
140 | ## Special IPv4 destination addresses. The zero address is invalid; mark | |
141 | ## link-local and recognized broadcast addresses as link-local. We leave | |
142 | ## multicast for later. | |
143 | for i in 0.0.0.0 240.0.0.0/4; do | |
144 | run iptables -t mangle -A out-classify -g bad-destination-address -d $i | |
145 | done | |
146 | run iptables -t mangle -A out-classify -g mark-to-link -d 169.254.0.0/16 | |
147 | run iptables -t mangle -A out-classify -g mark-to-link \ | |
148 | -m addrtype --dst-type BROADCAST | |
149 | ||
150 | ## Special IPv6 destination addressses. The zero address is again invalid; | |
151 | ## mark link local addresses. We do multicast later. | |
152 | run ip6tables -t mangle -A out-classify -g bad-destination-address \ | |
153 | -d :: | |
154 | run ip6tables -t mangle -A out-classify -g mark-to-link -d fe80::/10 | |
155 | ||
156 | ## Now deal with multicast. Link-local multicast is detected as being | |
157 | ## link-local, so that we can prevent it being forwarded correctly. | |
158 | clearchain mangle:out-classify-mcast | |
159 | run iptables -t mangle -A out-classify-mcast -g mark-to-link \ | |
160 | -d 224.0.0.0/24 | |
161 | for i in 0 1 2 3 4 5 6 7 8 9 a b c d e f; do | |
162 | run ip6tables -t mangle -A out-classify-mcast -g mark-to-link \ | |
163 | -d ff${i}2::/16 | |
164 | done | |
165 | run ip46tables -t mangle -A out-classify-mcast -g mark-to-mcast | |
166 | run iptables -t mangle -A out-classify -g out-classify-mcast \ | |
167 | -d 224.0.0.0/4 | |
168 | run ip6tables -t mangle -A out-classify -g out-classify-mcast \ | |
169 | -d ff00::/8 | |
170 | ||
beb4f0ee MW |
171 | ## Build the input classification chains. There's one chain `in-IFACE' for |
172 | ## each local interface. This chain does a further dispatch on the source | |
173 | ## address to the appropriate `mark-from-CLASS' chain for the source network | |
174 | ## class. | |
175 | seen=: | |
176 | for iface in $host_ifaces_<::>FWHOST; do | |
177 | ifname=${iface%=*} | |
178 | case $seen in *:$ifname:*) continue ;; esac | |
179 | seen=$seen$ifname: | |
180 | clearchain mangle:in-$ifname | |
181 | run ip46tables -t mangle -A in-classify -i $ifname -g in-$ifname | |
182 | done | |
183 | ||
184 | ## Now populate the `in-IFACE' and `out-classify' chains. We iterate over | |
185 | ## the available networks and add addresses to the appropriate chains. Also, | |
186 | ## build up a map of which interfaces receive from which address ranged so | |
187 | ## that we can finish the chains off properly later. This contains entries | |
188 | ## of the form IFACE=:ADDR:ADDR:...: | |
189 | ifnets="" | |
bfdc045d | 190 | for net in $allnets; do |
beb4f0ee MW |
191 | |
192 | ## Determine the addresses and class for this network, and populate the | |
193 | ## `out-classify' chains. | |
194 | eval addr=\$net_inet_$net addr6=\$net_inet6_$net class=\$net_class_$net | |
195 | case $class in virtual) continue ;; esac | |
196 | trace "$net : $class" | |
197 | for a in $addr; do | |
198 | run iptables -t mangle -A out-classify -g mark-to-$class -d $a | |
3a68f688 | 199 | done |
beb4f0ee MW |
200 | for a in $addr6; do |
201 | run ip6tables -t mangle -A out-classify -g mark-to-$class -d $a | |
3a68f688 | 202 | done |
beb4f0ee MW |
203 | |
204 | ## Now work through the interfaces. | |
205 | for iface in $(net_interfaces FWHOST $net); do | |
206 | nets="" | |
207 | case $iface in | |
208 | ||
209 | -) | |
210 | ## A special `no interface' marker: we should not receive packets | |
211 | ## from this network at all. | |
212 | continue | |
213 | ;; | |
214 | ||
215 | *-+) | |
216 | ## A special marker indicating a collection of point-to-point | |
217 | ## interfaces. We should match an address to a particular interface. | |
218 | ## Later, we'll cap this chain off by rejecting all other traffic. | |
219 | eval hosts=\$net_hosts_$net | |
220 | for host in $hosts; do | |
221 | eval ha=\$host_inet_$host ha6=\$host_inet6_$host | |
222 | trace "$host : $class -> $iface" | |
223 | for a in $ha; do | |
224 | run iptables -t mangle -A in-$iface \ | |
225 | -i ${iface%+}$host -s $a -g mark-from-$class | |
226 | nets=$nets$a: | |
227 | done | |
228 | for a in $ha6; do | |
229 | run ip6tables -t mangle -A in-$iface \ | |
230 | -i ${iface%+}$host -s $a -g mark-from-$class | |
231 | nets=$nets$a: | |
232 | done | |
233 | done | |
234 | ;; | |
235 | ||
236 | *) | |
237 | ## A normal interface. Classify incoming traffic according to the | |
238 | ## source address. | |
239 | trace "$net : $class -> $iface" | |
240 | for a in $addr; do | |
241 | run iptables -t mangle -A in-$iface -g mark-from-$class -s $a | |
242 | nets=$nets$a: | |
243 | done | |
244 | for a in $addr6; do | |
245 | run ip6tables -t mangle -A in-$iface -g mark-from-$class -s $a | |
246 | nets=$nets$a: | |
247 | done | |
248 | case $net in default) nets=${nets}default: ;; esac | |
249 | ;; | |
250 | esac | |
251 | ||
252 | ## Record that this interface receives traffic from this network. | |
253 | unset nifnets | |
254 | foundp=nil | |
255 | for ifnet in $ifnets; do | |
256 | case $ifnet in | |
257 | $iface=*:$net:*) addword nifnets $ifnet; foundp=t ;; | |
258 | $iface=*) addword nifnets $ifnet$nets; foundp=t ;; | |
259 | *) addword nifnets $ifnet ;; | |
260 | esac | |
261 | done | |
262 | case $foundp in nil) addword nifnets $iface=:$nets ;; esac | |
263 | ifnets=$nifnets | |
264 | ||
265 | done | |
266 | done | |
267 | ||
268 | ## Wrap up all of the `in-IFACE' chains. A chain which matches the `default' | |
269 | ## net should have unmatched but known networks blocked off, and then chain | |
270 | ## onto `in-default'. Other chains should just chain onto | |
271 | ## `bad-source-address'. | |
272 | trace "ifnets = $ifnets" | |
273 | for ifnet in $ifnets; do | |
274 | iface=${ifnet%%=*} nets=${ifnet#*=} | |
275 | case $nets in | |
276 | *:default:*) | |
277 | for n in $allnets; do | |
278 | eval addr=\$net_inet_$n addr6=\$net_inet6_$n | |
279 | for a in $addr; do | |
280 | case $nets in *:$a:*) continue ;; esac | |
281 | nets=$nets$a | |
282 | run iptables -t mangle -A in-$iface -s $a -g bad-source-address | |
283 | done | |
284 | for a in $addr6; do | |
285 | case $nets in *:$a:*) continue ;; esac | |
286 | nets=$nets$a | |
287 | run ip6tables -t mangle -A in-$iface -s $a -g bad-source-address | |
288 | done | |
3a68f688 | 289 | done |
beb4f0ee MW |
290 | run ip46tables -t mangle -A in-$iface -g in-default |
291 | ;; | |
292 | *) | |
293 | run ip46tables -t mangle -A in-$iface -g bad-source-address | |
0291d6d5 MW |
294 | ;; |
295 | esac | |
296 | done | |
bfdc045d MW |
297 | |
298 | ## Fill in the black holes in the network. | |
299 | for addr in \ | |
300 | 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 \ | |
677ef44e MW |
301 | 127.0.0.0/8 \ |
302 | 192.0.2.0/24 198.51.100.0/24 203.0.113.0/24 | |
bfdc045d MW |
303 | do |
304 | run iptables -t mangle -A in-default -s $addr -g bad-source-address | |
305 | done | |
0291d6d5 MW |
306 | for addr in \ |
307 | fc00::/7 \ | |
2f863436 | 308 | 2001:db8::/32 |
0291d6d5 MW |
309 | do |
310 | run ip6tables -t mangle -A in-default -s $addr -g bad-source-address | |
311 | done | |
beb4f0ee | 312 | run ip46tables -t mangle -A in-default -g mark-from-$net_class_default |
bfdc045d MW |
313 | |
314 | m4_divert(92)m4_dnl | |
315 | ## Put the final default decision on the in-default chain, and attach the | |
316 | ## classification chains to the PREROUTING hook. | |
3a68f688 | 317 | for iface in $defaultifaces; do |
beb4f0ee | 318 | run ip46tables -t mangle -A in-$iface -g in-default |
3a68f688 | 319 | done |
beb4f0ee | 320 | run ip46tables -t mangle -A out-classify -g mark-to-$net_class_default |
0291d6d5 MW |
321 | run ip46tables -t mangle -A PREROUTING -j in-classify |
322 | run ip46tables -t mangle -A PREROUTING -j out-classify | |
bfdc045d | 323 | |
44f95827 MW |
324 | ## Incoming stuff to or from a link-local address is OK. |
325 | run ip46tables -t mangle -A INPUT \ | |
326 | -m mark --mark $to_link/$MASK_TO \ | |
327 | -j MARK --or-mark $fwd_link | |
328 | run ip46tables -t mangle -A INPUT \ | |
329 | -m mark --mark $from_link/$MASK_FROM \ | |
330 | -j MARK --or-mark $fwd_link | |
331 | ||
bfdc045d MW |
332 | ## Now it's safe to let stuff through. |
333 | for i in PREROUTING INPUT FORWARD OUTPUT POSTROUTING; do | |
0291d6d5 | 334 | run ip46tables -t mangle -P $i ACCEPT |
bfdc045d MW |
335 | done |
336 | ||
337 | m4_divert(-1) | |
338 | ###----- That's all, folks -------------------------------------------------- |