| 1 | ### -*-sh-*- |
| 2 | ### |
| 3 | ### ICMP filtering 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(50)m4_dnl |
| 25 | ###-------------------------------------------------------------------------- |
| 26 | ### ICMP filtering. |
| 27 | |
| 28 | clearchain check-icmp |
| 29 | |
| 30 | ## Ping needs inspecting on a host-by-host basis. |
| 31 | for type in echo-request echo-reply; do |
| 32 | run iptables -A check-icmp -p icmp --icmp-type $type -j RETURN |
| 33 | done |
| 34 | |
| 35 | ## Certainly don't allow ping to broadcast addresses. |
| 36 | run iptables -A check-icmp -g forbidden \ |
| 37 | -p icmp --icmp-type echo-request \ |
| 38 | -m addrtype --dst-type BROADCAST |
| 39 | |
| 40 | m4_divert(58)m4_dnl |
| 41 | ## Other ICMP is basically benign, we claim. |
| 42 | run iptables -A check-icmp -j ACCEPT |
| 43 | |
| 44 | ## Done. |
| 45 | for i in INPUT FORWARD; do |
| 46 | run iptables -A $i -p icmp -j check-icmp |
| 47 | done |
| 48 | |
| 49 | m4_divert(-1) |
| 50 | ###----- That's all, folks -------------------------------------------------- |