| 1 | ### -*-sh-*- |
| 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 ip46tables -t $t -P $i DROP 2>/dev/null || : |
| 34 | run ip46tables -t $t -F $i 2>/dev/null || : |
| 35 | done |
| 36 | run ip46tables -t $t -F |
| 37 | run ip46tables -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 |
| 71 | ## Generic `not allowed' chain. |
| 72 | |
| 73 | errorchain tcp-fragment REJECT |
| 74 | ## Chain for logging fragmented TCP segements. |
| 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 |
| 80 | errorchain 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 | |
| 84 | errorchain bad-destination-address REJECT |
| 85 | ## Packet arrived on non-loopback interface with loopback destination. |
| 86 | |
| 87 | errorchain interesting ACCEPT |
| 88 | ## Not an error, just log interesting packets. |
| 89 | |
| 90 | m4_divert(36)m4_dnl |
| 91 | ###-------------------------------------------------------------------------- |
| 92 | ### Standard loopback stuff. |
| 93 | |
| 94 | ## Don't clobber local traffic |
| 95 | run ip46tables -A INPUT -i lo -j ACCEPT |
| 96 | |
| 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 |
| 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 |
| 113 | |
| 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 -------------------------------------------------- |