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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 $open_port_max | |
51 | ||
52 | ## Deploy SYN-cookies if necessary. | |
53 | setopt tcp_syncookies 1 | |
54 | ||
c8d422ec MW |
55 | ## Allow broadcast and multicast ping, because it's a useful diagnostic tool. |
56 | setopt icmp_echo_ignore_broadcasts 0 | |
57 | ||
429f4314 MW |
58 | ## Turn off iptables filtering for bridges. We'll use ebtables if we need |
59 | ## to; but right now the model is that we do filtering at the borders, and | |
60 | ## are tolerant of things which are local. | |
6d47692a MW |
61 | if [ -x /sbin/brctl ]; then |
62 | modprobe bridge || : | |
63 | if [ -d /proc/sys/net/bridge ]; then | |
64 | for filter in arptables iptables ip6tables; do | |
65 | run sysctl -q net.bridge.bridge-nf-call-$filter=0 | |
66 | done | |
67 | fi | |
68 | fi | |
429f4314 | 69 | |
bfdc045d | 70 | ## Turn on the reverse-path filter, and log weird things. |
a0ade6f1 MW |
71 | setdevopt rp_filter $rp_filter |
72 | setdevopt log_martians $log_martians | |
bfdc045d MW |
73 | |
74 | ## Turn off things which can mess with our routing decisions. | |
75 | setdevopt accept_source_route 0 | |
76 | setdevopt accept_redirects 0 | |
77 | ||
78 | ## If we're maent to stop the firewall, then now is the time to do it. | |
79 | $exit_after_clearing | |
80 | ||
81 | m4_divert(34)m4_dnl | |
82 | ###-------------------------------------------------------------------------- | |
83 | ### Establish error chains. | |
84 | ||
0291d6d5 MW |
85 | errorchain forbidden REJECT |
86 | ## Generic `not allowed' chain. | |
bfdc045d | 87 | |
0291d6d5 MW |
88 | errorchain tcp-fragment REJECT |
89 | ## Chain for logging fragmented TCP segements. | |
bfdc045d MW |
90 | |
91 | errorchain bad-tcp REJECT -p tcp --reject-with tcp-reset | |
92 | ## Bad TCP segments (e.g., for unknown connections). Sends a TCP reset. | |
93 | ||
94 | errorchain mangle:bad-source-address DROP | |
0291d6d5 | 95 | errorchain bad-source-address DROP |
bfdc045d MW |
96 | ## Packet arrived on wrong interface for its source address. Drops the |
97 | ## packet, since there's nowhere sensible to send an error. | |
98 | ||
0291d6d5 MW |
99 | errorchain bad-destination-address REJECT |
100 | ## Packet arrived on non-loopback interface with loopback destination. | |
f381cc0a | 101 | |
bfdc045d MW |
102 | errorchain interesting ACCEPT |
103 | ## Not an error, just log interesting packets. | |
104 | ||
105 | m4_divert(36)m4_dnl | |
106 | ###-------------------------------------------------------------------------- | |
f543dab7 | 107 | ### Standard filtering. |
bfdc045d | 108 | |
f381cc0a | 109 | ## Don't clobber local traffic |
0291d6d5 | 110 | run ip46tables -A INPUT -i lo -j ACCEPT |
bfdc045d | 111 | |
f381cc0a MW |
112 | ## We really shouldn't see packets destined for localhost on any interface |
113 | ## other than the loopback. | |
114 | run iptables -A INPUT -g bad-destination-address \ | |
115 | -d 127.0.0.0/8 | |
0291d6d5 MW |
116 | run ip6tables -A INPUT -g bad-destination-address \ |
117 | -d ::1 | |
118 | ||
119 | ## We shouldn't be asked to forward things with link-local addresses. | |
120 | run iptables -A FORWARD -g bad-source-address \ | |
121 | -s 169.254.0.0/16 | |
122 | run iptables -A FORWARD -g bad-destination-address \ | |
123 | -d 169.254.0.0/16 | |
124 | run ip6tables -A FORWARD -g bad-source-address \ | |
125 | -s fe80::/10 | |
126 | run ip6tables -A FORWARD -g bad-destination-address \ | |
127 | -d fe80::/10 | |
f381cc0a | 128 | |
429f4314 MW |
129 | ## Also, don't forward link-local broadcast or multicast. |
130 | run iptables -A FORWARD -g bad-destination-address \ | |
131 | -d 255.255.255.255 | |
132 | run iptables -A FORWARD -g bad-destination-address \ | |
133 | -m addrtype --dst-type BROADCAST | |
134 | run iptables -A FORWARD -g bad-destination-address \ | |
135 | -d 224.0.0.0/24 | |
136 | for x in 0 1 2 3 4 5 6 7 8 9 a b c d e f; do | |
137 | run ip6tables -A FORWARD -g bad-destination-address \ | |
138 | -d fe${x}2::/16 | |
139 | done | |
140 | ||
f543dab7 MW |
141 | ## Add a hook for fail2ban. |
142 | clearchain fail2ban | |
143 | run ip46tables -A INPUT -j fail2ban | |
144 | ||
bfdc045d MW |
145 | m4_divert(90)m4_dnl |
146 | ###-------------------------------------------------------------------------- | |
147 | ### Finishing touches. | |
148 | ||
149 | m4_divert(94)m4_dnl | |
150 | ## Locally generated packets are all OK. | |
c1c877c2 | 151 | run ip46tables -P OUTPUT ACCEPT |
bfdc045d MW |
152 | |
153 | ## Other incoming things are forbidden. | |
154 | for chain in INPUT FORWARD; do | |
c1c877c2 | 155 | run ip46tables -A $chain -g forbidden |
bfdc045d MW |
156 | done |
157 | ||
158 | m4_divert(-1) | |
159 | ###----- That's all, folks -------------------------------------------------- |