Commit | Line | Data |
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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 | |
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 | |
1264e917 MW |
174 | ## class. We also build a table mapping interface names to numbers (since |
175 | ## the names are so unhelpful). | |
beb4f0ee | 176 | seen=: |
1264e917 MW |
177 | ifq=0 |
178 | ifmap="" | |
beb4f0ee MW |
179 | for iface in $host_ifaces_<::>FWHOST; do |
180 | ifname=${iface%=*} | |
181 | case $seen in *:$ifname:*) continue ;; esac | |
182 | seen=$seen$ifname: | |
1264e917 MW |
183 | addword ifmap $ifname=$ifq |
184 | ifq=$(( $ifq + 1 )) | |
beb4f0ee MW |
185 | clearchain mangle:in-$ifname |
186 | run ip46tables -t mangle -A in-classify -i $ifname -g in-$ifname | |
187 | done | |
188 | ||
1264e917 MW |
189 | ## We do a first pass over nets first, and then the interfaces which those |
190 | ## networks reach. During this pass, we populate the `out-classify' chains, | |
191 | ## and we also build some lists so that we can do later passes over | |
192 | ## interfaces first and then reaching networks. This is complicated by | |
193 | ## interface names being unhelpful. | |
194 | ## | |
195 | ## Here are the variables we maintain. | |
196 | ## | |
197 | ## ifmap A list of entries IFACE=N mapping interface names to | |
198 | ## numbers. | |
199 | ## | |
200 | ## ifnets_N A space-separated list of networks reaching interface | |
201 | ## number N. This is used for building the matching | |
202 | ## chains. | |
203 | ## | |
204 | ## ifaddrs_N A bang-separated list of address ranges reaching | |
205 | ## interface number N. This is used for filtering out | |
206 | ## known networks if the default network reaches the | |
207 | ## interface. | |
bfdc045d | 208 | for net in $allnets; do |
beb4f0ee | 209 | |
1264e917 MW |
210 | ## Work through the interfaces that this network reaches. |
211 | for iface in $(net_interfaces FWHOST $net); do | |
212 | case $iface in -) break ;; esac | |
213 | ||
214 | ## Find a sequence number for this interface. | |
215 | q=nil | |
216 | for i in $ifmap; do | |
217 | case "$i" in "$iface"=*) q=${i##*=}; break ;; esac | |
218 | done | |
219 | case $q in | |
220 | nil) | |
221 | echo >&2 "$0 INTERNAL ERROR: missing interface \`$iface'!" | |
222 | exit 1 | |
223 | ;; | |
224 | esac | |
225 | ||
226 | ## Remember the reachability information. | |
227 | addword ifnets_$q $net | |
3a68f688 | 228 | done |
1264e917 MW |
229 | done |
230 | ||
231 | ## Build the `ifaddr_N' map and an `all-addresses' list. | |
232 | alladdrs=! | |
233 | trace "ifmap = $ifmap" | |
234 | for entry in $ifmap; do | |
235 | iface=${entry%=*} q=${entry##*=} | |
236 | eval nets=\$ifnets_$q | |
237 | trace "iface $iface [$q] = $nets" | |
238 | aa=! | |
239 | for n in $nets; do | |
240 | eval "addrs=\"\$net_inet_$n \$net_inet6_$n\"" | |
241 | trace "$iface $n addrs = $addrs" | |
242 | for a in $addrs; do | |
243 | case $aa in *!$a!*) ;; *) aa=$aa$a! ;; esac | |
244 | case $alladdrs in *!$a!*) ;; *) alladdrs=$alladdrs$a! ;; esac | |
245 | done | |
3a68f688 | 246 | done |
1264e917 MW |
247 | eval ifaddrs_$q=\$aa |
248 | trace "iface $q = $iface; nets = $nets; addrs = $aa" | |
249 | trace "alladdrs = $alladdrs" | |
250 | done | |
beb4f0ee | 251 | |
1264e917 MW |
252 | ## Populate the `out-classify' chain, matching networks. |
253 | prepare_to () { mode=goto fail=mark-to-$net_class_default; } | |
254 | matchnets -d mark-from : prepare_to out-classify "" 0 $allnets | |
beb4f0ee | 255 | |
1264e917 MW |
256 | ## A `finish' hook for rejecting known address ranges arriving on a |
257 | ## default-reachable interface. | |
258 | finish_from_default () { | |
259 | q=$1 chain=$2 | |
260 | eval addrs=\$ifaddrs_$q | |
261 | ||
262 | for n in $allnets; do | |
263 | eval addr=\$net_inet_$n addr6=\$net_inet6_$n | |
264 | for a in $addr; do | |
265 | case $a in !*) continue ;; esac | |
266 | case $addrs in *"!$a!"*) continue ;; esac | |
267 | run iptables -t mangle -A $chain -s $a -g bad-source-address | |
268 | done | |
269 | for a in $addr6; do | |
270 | case $a in !*) continue ;; esac | |
271 | case $addrs in *"!$a!"*) continue ;; esac | |
272 | run ip6tables -t mangle -A $chain -s $a -g bad-source-address | |
273 | done | |
274 | done | |
275 | run ip46tables -t mangle -A $chain -g in-default | |
276 | } | |
277 | ||
278 | ## A `prepare' hook for input classification. If the interface is | |
279 | ## default-reachable, then we need to reject known address ranges before | |
280 | ## dispatching to the default chain; otherwise just reject the packet. | |
281 | prepare_from () { | |
282 | q=$1 flags=$2 | |
283 | case $flags in | |
284 | *:default:*) mode=call finish="finish_from_default $q" ;; | |
285 | *) mode=goto fail=bad-source-address ;; | |
286 | esac | |
287 | } | |
beb4f0ee | 288 | |
1264e917 MW |
289 | ## Populate the `in-IFACE' chains. |
290 | for entry in $ifmap; do | |
291 | iface=${entry%=*} q=${entry##*=} | |
292 | eval nets=\$ifnets_$q | |
293 | ||
294 | case $iface in | |
295 | *-+) | |
296 | ## A special marker indicating a collection of point-to-point | |
297 | ## interfaces. We should match an address to a particular interface. | |
298 | chains="" | |
299 | for net in $nets; do | |
beb4f0ee MW |
300 | eval hosts=\$net_hosts_$net |
301 | for host in $hosts; do | |
302 | eval ha=\$host_inet_$host ha6=\$host_inet6_$host | |
303 | trace "$host : $class -> $iface" | |
304 | for a in $ha; do | |
305 | run iptables -t mangle -A in-$iface \ | |
306 | -i ${iface%+}$host -s $a -g mark-from-$class | |
beb4f0ee MW |
307 | done |
308 | for a in $ha6; do | |
309 | run ip6tables -t mangle -A in-$iface \ | |
310 | -i ${iface%+}$host -s $a -g mark-from-$class | |
beb4f0ee MW |
311 | done |
312 | done | |
3a68f688 | 313 | done |
1264e917 | 314 | run ip46tables -t mangle -A in-$iface -g bad-source-address |
beb4f0ee MW |
315 | ;; |
316 | *) | |
1264e917 | 317 | matchnets -s mark-from : "prepare_from $q" in-$iface "" 0 $nets |
0291d6d5 MW |
318 | ;; |
319 | esac | |
320 | done | |
bfdc045d | 321 | |
1264e917 MW |
322 | ## Fill in the black holes in the network. Some of these might actually be |
323 | ## known networks, so don't fill those in again. | |
bfdc045d MW |
324 | for addr in \ |
325 | 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 \ | |
677ef44e MW |
326 | 127.0.0.0/8 \ |
327 | 192.0.2.0/24 198.51.100.0/24 203.0.113.0/24 | |
bfdc045d | 328 | do |
1264e917 | 329 | case $alladdrs in *!$addr!*) continue ;; esac |
bfdc045d MW |
330 | run iptables -t mangle -A in-default -s $addr -g bad-source-address |
331 | done | |
0291d6d5 MW |
332 | for addr in \ |
333 | fc00::/7 \ | |
2f863436 | 334 | 2001:db8::/32 |
0291d6d5 | 335 | do |
1264e917 | 336 | case $alladdrs in *!$addr!*) continue ;; esac |
0291d6d5 MW |
337 | run ip6tables -t mangle -A in-default -s $addr -g bad-source-address |
338 | done | |
beb4f0ee | 339 | run ip46tables -t mangle -A in-default -g mark-from-$net_class_default |
bfdc045d MW |
340 | |
341 | m4_divert(92)m4_dnl | |
342 | ## Put the final default decision on the in-default chain, and attach the | |
343 | ## classification chains to the PREROUTING hook. | |
3a68f688 | 344 | for iface in $defaultifaces; do |
beb4f0ee | 345 | run ip46tables -t mangle -A in-$iface -g in-default |
3a68f688 | 346 | done |
0291d6d5 MW |
347 | run ip46tables -t mangle -A PREROUTING -j in-classify |
348 | run ip46tables -t mangle -A PREROUTING -j out-classify | |
bfdc045d | 349 | |
44f95827 MW |
350 | ## Incoming stuff to or from a link-local address is OK. |
351 | run ip46tables -t mangle -A INPUT \ | |
352 | -m mark --mark $to_link/$MASK_TO \ | |
353 | -j MARK --or-mark $fwd_link | |
354 | run ip46tables -t mangle -A INPUT \ | |
355 | -m mark --mark $from_link/$MASK_FROM \ | |
356 | -j MARK --or-mark $fwd_link | |
357 | ||
bfdc045d MW |
358 | ## Now it's safe to let stuff through. |
359 | for i in PREROUTING INPUT FORWARD OUTPUT POSTROUTING; do | |
0291d6d5 | 360 | run ip46tables -t mangle -P $i ACCEPT |
bfdc045d MW |
361 | done |
362 | ||
363 | m4_divert(-1) | |
364 | ###----- That's all, folks -------------------------------------------------- |