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775bd287 | 1 | ### -*-sh-*- |
bfdc045d MW |
2 | ### |
3 | ### Initialization and finishing touches for firewall scripts | |
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(30)m4_dnl | |
25 | ###-------------------------------------------------------------------------- | |
26 | ### Clear existing firewall rules. | |
27 | ||
28 | ## The main chains: set policy to drop, and then clear the rules. For a | |
29 | ## while, incoming packets will be silently dropped, but we should have got | |
30 | ## everything going before anyone actually hits a timeout. | |
31 | for t in mangle filter; do | |
32 | for i in PREROUTING INPUT FORWARD OUTPUT POSTROUTING; do | |
0291d6d5 MW |
33 | run ip46tables -t $t -P $i DROP 2>/dev/null || : |
34 | run ip46tables -t $t -F $i 2>/dev/null || : | |
bfdc045d | 35 | done |
0291d6d5 MW |
36 | run ip46tables -t $t -F |
37 | run ip46tables -t $t -X | |
bfdc045d MW |
38 | done |
39 | ||
40 | m4_divert(32)m4_dnl | |
41 | ###-------------------------------------------------------------------------- | |
42 | ### Set safe IP options. | |
43 | ||
44 | ## Set forwarding options. Apparently setting ip_forward clobbers other | |
45 | ## settings, so put this first. | |
46 | setopt ip_forward $forward | |
47 | setdevopt forwarding $forward | |
48 | ||
49 | ## Set dynamic port allocation. | |
50 | setopt ip_local_port_range $open_port_min $open_port_max | |
51 | ||
52 | ## Deploy SYN-cookies if necessary. | |
53 | setopt tcp_syncookies 1 | |
54 | ||
c8d422ec MW |
55 | ## Allow broadcast and multicast ping, because it's a useful diagnostic tool. |
56 | setopt icmp_echo_ignore_broadcasts 0 | |
57 | ||
429f4314 MW |
58 | ## Turn off iptables filtering for bridges. We'll use ebtables if we need |
59 | ## to; but right now the model is that we do filtering at the borders, and | |
60 | ## are tolerant of things which are local. | |
61 | for filter in arptables iptables ip6tables; do | |
62 | run sysctl -q net/bridge/bridge-nf-call-$filter=0 | |
63 | done | |
64 | ||
bfdc045d MW |
65 | ## Turn on the reverse-path filter, and log weird things. |
66 | setdevopt rp_filter 1 | |
67 | setdevopt log_martians 1 | |
68 | ||
69 | ## Turn off things which can mess with our routing decisions. | |
70 | setdevopt accept_source_route 0 | |
71 | setdevopt accept_redirects 0 | |
72 | ||
73 | ## If we're maent to stop the firewall, then now is the time to do it. | |
74 | $exit_after_clearing | |
75 | ||
76 | m4_divert(34)m4_dnl | |
77 | ###-------------------------------------------------------------------------- | |
78 | ### Establish error chains. | |
79 | ||
0291d6d5 MW |
80 | errorchain forbidden REJECT |
81 | ## Generic `not allowed' chain. | |
bfdc045d | 82 | |
0291d6d5 MW |
83 | errorchain tcp-fragment REJECT |
84 | ## Chain for logging fragmented TCP segements. | |
bfdc045d MW |
85 | |
86 | errorchain bad-tcp REJECT -p tcp --reject-with tcp-reset | |
87 | ## Bad TCP segments (e.g., for unknown connections). Sends a TCP reset. | |
88 | ||
89 | errorchain mangle:bad-source-address DROP | |
0291d6d5 | 90 | errorchain bad-source-address DROP |
bfdc045d MW |
91 | ## Packet arrived on wrong interface for its source address. Drops the |
92 | ## packet, since there's nowhere sensible to send an error. | |
93 | ||
0291d6d5 MW |
94 | errorchain bad-destination-address REJECT |
95 | ## Packet arrived on non-loopback interface with loopback destination. | |
f381cc0a | 96 | |
bfdc045d MW |
97 | errorchain interesting ACCEPT |
98 | ## Not an error, just log interesting packets. | |
99 | ||
100 | m4_divert(36)m4_dnl | |
101 | ###-------------------------------------------------------------------------- | |
f381cc0a | 102 | ### Standard loopback stuff. |
bfdc045d | 103 | |
f381cc0a | 104 | ## Don't clobber local traffic |
0291d6d5 | 105 | run ip46tables -A INPUT -i lo -j ACCEPT |
bfdc045d | 106 | |
f381cc0a MW |
107 | ## We really shouldn't see packets destined for localhost on any interface |
108 | ## other than the loopback. | |
109 | run iptables -A INPUT -g bad-destination-address \ | |
110 | -d 127.0.0.0/8 | |
0291d6d5 MW |
111 | run ip6tables -A INPUT -g bad-destination-address \ |
112 | -d ::1 | |
113 | ||
114 | ## We shouldn't be asked to forward things with link-local addresses. | |
115 | run iptables -A FORWARD -g bad-source-address \ | |
116 | -s 169.254.0.0/16 | |
117 | run iptables -A FORWARD -g bad-destination-address \ | |
118 | -d 169.254.0.0/16 | |
119 | run ip6tables -A FORWARD -g bad-source-address \ | |
120 | -s fe80::/10 | |
121 | run ip6tables -A FORWARD -g bad-destination-address \ | |
122 | -d fe80::/10 | |
f381cc0a | 123 | |
429f4314 MW |
124 | ## Also, don't forward link-local broadcast or multicast. |
125 | run iptables -A FORWARD -g bad-destination-address \ | |
126 | -d 255.255.255.255 | |
127 | run iptables -A FORWARD -g bad-destination-address \ | |
128 | -m addrtype --dst-type BROADCAST | |
129 | run iptables -A FORWARD -g bad-destination-address \ | |
130 | -d 224.0.0.0/24 | |
131 | for x in 0 1 2 3 4 5 6 7 8 9 a b c d e f; do | |
132 | run ip6tables -A FORWARD -g bad-destination-address \ | |
133 | -d fe${x}2::/16 | |
134 | done | |
135 | ||
bfdc045d MW |
136 | m4_divert(90)m4_dnl |
137 | ###-------------------------------------------------------------------------- | |
138 | ### Finishing touches. | |
139 | ||
140 | m4_divert(94)m4_dnl | |
141 | ## Locally generated packets are all OK. | |
142 | run iptables -P OUTPUT ACCEPT | |
143 | ||
144 | ## Other incoming things are forbidden. | |
145 | for chain in INPUT FORWARD; do | |
146 | run iptables -A $chain -g forbidden | |
147 | done | |
148 | ||
149 | m4_divert(-1) | |
150 | ###----- That's all, folks -------------------------------------------------- |