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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 | ||
55 | ## Turn on the reverse-path filter, and log weird things. | |
56 | setdevopt rp_filter 1 | |
57 | setdevopt log_martians 1 | |
58 | ||
59 | ## Turn off things which can mess with our routing decisions. | |
60 | setdevopt accept_source_route 0 | |
61 | setdevopt accept_redirects 0 | |
62 | ||
63 | ## If we're maent to stop the firewall, then now is the time to do it. | |
64 | $exit_after_clearing | |
65 | ||
66 | m4_divert(34)m4_dnl | |
67 | ###-------------------------------------------------------------------------- | |
68 | ### Establish error chains. | |
69 | ||
0291d6d5 MW |
70 | errorchain forbidden REJECT |
71 | ## Generic `not allowed' chain. | |
bfdc045d | 72 | |
0291d6d5 MW |
73 | errorchain tcp-fragment REJECT |
74 | ## Chain for logging fragmented TCP segements. | |
bfdc045d MW |
75 | |
76 | errorchain bad-tcp REJECT -p tcp --reject-with tcp-reset | |
77 | ## Bad TCP segments (e.g., for unknown connections). Sends a TCP reset. | |
78 | ||
79 | errorchain mangle:bad-source-address DROP | |
0291d6d5 | 80 | errorchain bad-source-address DROP |
bfdc045d MW |
81 | ## Packet arrived on wrong interface for its source address. Drops the |
82 | ## packet, since there's nowhere sensible to send an error. | |
83 | ||
0291d6d5 MW |
84 | errorchain bad-destination-address REJECT |
85 | ## Packet arrived on non-loopback interface with loopback destination. | |
f381cc0a | 86 | |
bfdc045d MW |
87 | errorchain interesting ACCEPT |
88 | ## Not an error, just log interesting packets. | |
89 | ||
90 | m4_divert(36)m4_dnl | |
91 | ###-------------------------------------------------------------------------- | |
f381cc0a | 92 | ### Standard loopback stuff. |
bfdc045d | 93 | |
f381cc0a | 94 | ## Don't clobber local traffic |
0291d6d5 | 95 | run ip46tables -A INPUT -i lo -j ACCEPT |
bfdc045d | 96 | |
f381cc0a MW |
97 | ## We really shouldn't see packets destined for localhost on any interface |
98 | ## other than the loopback. | |
99 | run iptables -A INPUT -g bad-destination-address \ | |
100 | -d 127.0.0.0/8 | |
0291d6d5 MW |
101 | run ip6tables -A INPUT -g bad-destination-address \ |
102 | -d ::1 | |
103 | ||
104 | ## We shouldn't be asked to forward things with link-local addresses. | |
105 | run iptables -A FORWARD -g bad-source-address \ | |
106 | -s 169.254.0.0/16 | |
107 | run iptables -A FORWARD -g bad-destination-address \ | |
108 | -d 169.254.0.0/16 | |
109 | run ip6tables -A FORWARD -g bad-source-address \ | |
110 | -s fe80::/10 | |
111 | run ip6tables -A FORWARD -g bad-destination-address \ | |
112 | -d fe80::/10 | |
f381cc0a | 113 | |
bfdc045d MW |
114 | m4_divert(90)m4_dnl |
115 | ###-------------------------------------------------------------------------- | |
116 | ### Finishing touches. | |
117 | ||
118 | m4_divert(94)m4_dnl | |
119 | ## Locally generated packets are all OK. | |
120 | run iptables -P OUTPUT ACCEPT | |
121 | ||
122 | ## Other incoming things are forbidden. | |
123 | for chain in INPUT FORWARD; do | |
124 | run iptables -A $chain -g forbidden | |
125 | done | |
126 | ||
127 | m4_divert(-1) | |
128 | ###----- That's all, folks -------------------------------------------------- |