~mdw / firewall / blame
| Commit | Line | Data |
|---|---|---|
| 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 -------------------------------------------------- |