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bfdc045d MW |
1 | ### -*-m4-*- |
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 | |
33 | run iptables -t $t -P $i DROP 2>/dev/null || : | |
34 | run iptables -t $t -F $i 2>/dev/null || : | |
35 | done | |
36 | run iptables -t $t -F | |
37 | run iptables -t $t -X | |
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 | ||
70 | errorchain forbidden REJECT --reject-with icmp-host-prohibited | |
71 | ## Generic `not allowed' chain. Rejects with ICMP host-prohibited. | |
72 | ||
73 | errorchain tcp-fragment REJECT --reject-with icmp-host-prohibited | |
74 | ## Chain for logging fragmented TCP segements. Rejects with ICMP | |
75 | ## host-prohibited. | |
76 | ||
77 | errorchain bad-tcp REJECT -p tcp --reject-with tcp-reset | |
78 | ## Bad TCP segments (e.g., for unknown connections). Sends a TCP reset. | |
79 | ||
80 | errorchain mangle:bad-source-address DROP | |
81 | ## Packet arrived on wrong interface for its source address. Drops the | |
82 | ## packet, since there's nowhere sensible to send an error. | |
83 | ||
f381cc0a MW |
84 | errorchain bad-destination-address REJECT --reject-with icmp-host-prohibited |
85 | ## Packet arrived on non-loopback interface with loopback destination. Sends | |
86 | ## a rude note back. | |
87 | ||
bfdc045d MW |
88 | errorchain interesting ACCEPT |
89 | ## Not an error, just log interesting packets. | |
90 | ||
91 | m4_divert(36)m4_dnl | |
92 | ###-------------------------------------------------------------------------- | |
f381cc0a | 93 | ### Standard loopback stuff. |
bfdc045d | 94 | |
f381cc0a | 95 | ## Don't clobber local traffic |
bfdc045d MW |
96 | run iptables -A INPUT -i lo -j ACCEPT |
97 | ||
f381cc0a MW |
98 | ## We really shouldn't see packets destined for localhost on any interface |
99 | ## other than the loopback. | |
100 | run iptables -A INPUT -g bad-destination-address \ | |
101 | -d 127.0.0.0/8 | |
102 | ||
bfdc045d MW |
103 | m4_divert(90)m4_dnl |
104 | ###-------------------------------------------------------------------------- | |
105 | ### Finishing touches. | |
106 | ||
107 | m4_divert(94)m4_dnl | |
108 | ## Locally generated packets are all OK. | |
109 | run iptables -P OUTPUT ACCEPT | |
110 | ||
111 | ## Other incoming things are forbidden. | |
112 | for chain in INPUT FORWARD; do | |
113 | run iptables -A $chain -g forbidden | |
114 | done | |
115 | ||
116 | m4_divert(-1) | |
117 | ###----- That's all, folks -------------------------------------------------- |