firewall: Add rule to clamp PMTU.

[people/ms/network.git] / functions.firewall

#!/bin/bash
###############################################################################
#                                                                             #
# IPFire.org - A linux based firewall                                         #
# Copyright (C) 2012  IPFire Network Development Team                         #
#                                                                             #
# This program is free software: you can redistribute it and/or modify        #
# it under the terms of the GNU General Public License as published by        #
# the Free Software Foundation, either version 3 of the License, or           #
# (at your option) any later version.                                         #
#                                                                             #
# This program is distributed in the hope that it will be useful,             #
# but WITHOUT ANY WARRANTY; without even the implied warranty of              #
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               #
# GNU General Public License for more details.                                #
#                                                                             #
# You should have received a copy of the GNU General Public License           #
# along with this program.  If not, see <http://www.gnu.org/licenses/>.       #
#                                                                             #
###############################################################################

# High-level function which will create a ruleset for the current firewall
# configuration and load it into the kernel.
function firewall_start() {
	# Test mode.
	local test="false"

	while [ $# -gt 0 ]; do
		case "${1}" in
			--test)
				test="true"
				;;
		esac
		shift
	done

	if enabled test; then
		log INFO "Test mode enabled."
		log INFO "The firewall ruleset will not be loaded."
	fi

	firewall_lock_acquire

	# Initialize an empty iptables ruleset.
	iptables_init DROP

	# Add default chains.
	firewall_tcp_state_flags
	firewall_connection_tracking
	firewall_tcp_clamp_mss

	# Add policies for every zone.
	policy_add_localhost

	local zone
	for zone in $(zones_get_all); do
		policy_add_zone ${zone}
	done

	# Load the new ruleset.
	iptables_load ${test}

	firewall_lock_release
}

function firewall_stop() {
	firewall_lock_acquire

	# Initialize an empty firewall ruleset
	# with default policy ACCEPT.
	iptables_init ACCEPT

	# Load it.
	iptables_load

	firewall_lock_release
}

function firewall_show() {
	# Shows the ruleset that is currently loaded.
	iptables_status

	return ${EXIT_OK}
}

function firewall_panic() {
	local admin_hosts="$@"

	firewall_lock_acquire

	# Drop all communications.
	iptables_init DROP

	# If an admin host is provided, some administrative
	# things will be allowed from there.
	local admin_host
	for admin_host in ${admin_hosts}; do
		iptables -A INPUT -s ${admin_host} -j ACCEPT
		iptables -A OUTPUT -d ${admin_host} -j ACCEPT
	done

	# Load it.
	iptables_load

	firewall_lock_release
}

function firewall_lock_acquire() {
	lock_acquire ${RUN_DIR}/.firewall_lock

	# Make sure the lock is released after the firewall
	# script has crashed or exited early.
	trap firewall_lock_release EXIT TERM KILL

	# Create a directory where we can put our
	# temporary data in the most secure way as possible.
	IPTABLES_TMPDIR=$(mktemp -d)
}

function firewall_lock_release() {
	if isset IPTABLES_TMPDIR; then
		# Remove all temporary data.
		rm -rf ${IPTABLES_TMPDIR}

		# Reset the tempdir variable.
		IPTABLES_TMPDIR=
	fi

	# Reset the trap.
	trap true EXIT TERM KILL

	lock_release ${RUN_DIR}/.firewall_lock
}

function firewall_tcp_state_flags() {
	log INFO "Creating TCP State Flags chain..."
	iptables_chain_create BADTCP_LOG
	iptables -A BADTCP_LOG -p tcp -j $(iptables_LOG "Illegal TCP state: ")
	iptables -A BADTCP_LOG -j DROP

	iptables_chain_create BADTCP
	iptables -A BADTCP -p tcp --tcp-flags ALL NONE -j BADTCP_LOG
	iptables -A BADTCP -p tcp --tcp-flags SYN,FIN SYN,FIN -j BADTCP_LOG
	iptables -A BADTCP -p tcp --tcp-flags SYN,RST SYN,RST -j BADTCP_LOG
	iptables -A BADTCP -p tcp --tcp-flags FIN,RST FIN,RST -j BADTCP_LOG
	iptables -A BADTCP -p tcp --tcp-flags ACK,FIN FIN     -j BADTCP_LOG
	iptables -A BADTCP -p tcp --tcp-flags ACK,PSH PSH     -j BADTCP_LOG
	iptables -A BADTCP -p tcp --tcp-flags ACK,URG URG     -j BADTCP_LOG

	iptables -A INPUT   -p tcp -j BADTCP
	iptables -A OUTPUT  -p tcp -j BADTCP
	iptables -A FORWARD -p tcp -j BADTCP
}

function firewall_tcp_clamp_mss() {
	log DEBUG "Adding rules to clamp MSS to path MTU..."
	iptables -t mangle -A FORWARD \
		-p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
}

function firewall_connection_tracking() {
	log INFO "Creating Connection Tracking chain..."
	iptables_chain_create CONNTRACK
	iptables -A CONNTRACK -m state --state ESTABLISHED,RELATED -j ACCEPT
	iptables -A CONNTRACK -m state --state INVALID -j $(iptables_LOG "INVALID packet: ")
	iptables -A CONNTRACK -m state --state INVALID -j DROP

	iptables -A INPUT   -j CONNTRACK
	iptables -A OUTPUT  -j CONNTRACK
	iptables -A FORWARD -j CONNTRACK
}

function firewall_import_rules() {
	local zone=${1}
	shift

	local protocol="ipv6"
	local table="filter"

	while [ $# -gt 0 ]; do
		case "${1}" in
			--table=*)
				table=$(cli_get_val ${1})
				;;
			--protocol=*)
				protocol=$(cli_get_val ${1})
				;;
		esac
	done

	assert isoneof protocol ipv4 ipv6
	assert isoneof table $(iptables_table ${protocol})

	# XXX TODO

	local src dst proto
	while read src dst proto; do
		case "${chain}" in
			filter)
				;;
			nat)
				;;
		esac
	done < ${FIREWALL_CONFIG_RULES}
}