#!/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"
				;;
			*)
				error "Unrecognized argument: ${1}"
				return ${EXIT_ERROR}
				;;
		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_custom_chains
	firewall_connection_tracking
	firewall_tcp_clamp_mss

	# Add policies for every zone.
	firewall_localhost_create_chains

	local zone
	for zone in $(zones_get_all); do
		# Create all needed chains for the zone.
		firewall_zone_create_chains ${zone}

		# After the chains that are always available have been
		# created, we will add a custom policy to every single
		# zone.

		policy_zone_add ${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_custom_chains() {
	log INFO "Creating CUSTOM* chains..."

	# These chains are intened to be filled with
	# rules by the user. They are processed at the very
	# beginning so it is possible to overwrite everything.

	iptables_chain_create CUSTOMINPUT
	iptables -A INPUT -j CUSTOMINPUT

	iptables_chain_create CUSTOMFORWARD
	iptables -A FORWARD -j CUSTOMFORWARD

	iptables_chain_create CUSTOMOUTPUT
	iptables -A OUTPUT -j CUSTOMOUTPUT

	iptables_chain_create -4 -t nat CUSTOMPREROUTING
	iptables -4 -t nat -A PREROUTING -j CUSTOMPREROUTING

	iptables_chain_create -4 -t nat CUSTOMPOSTROUTING
	iptables -4 -t nat -A POSTROUTING -j CUSTOMPOSTROUTING

	iptables_chain_create -4 -t nat CUSTOMOUTPUT
	iptables -4 -t nat -A OUTPUT -j CUSTOMOUTPUT
}

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() {
	# Do nothing if this has been disabled.
	enabled FIREWALL_CLAMP_PATH_MTU || return ${EXIT_OK}

	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_localhost_create_chains() {
	log DEBUG "Creating firewall chains for localhost..."

	# Accept everything on lo
	iptables -A INPUT  -i lo -m state --state NEW -j ACCEPT
	iptables -A OUTPUT -o lo -m state --state NEW -j ACCEPT
}

function firewall_zone_create_chains() {
	local zone=${1}
	assert isset zone

	log DEBUG "Creating firewall chains for zone '${zone}'."

	local chain_prefix="ZONE_${zone^^}"

	# Create filter chains.
	iptables_chain_create "${chain_prefix}_INPUT"
	iptables -A INPUT   -i ${zone} -j "${chain_prefix}_INPUT"

	iptables_chain_create "${chain_prefix}_OUTPUT"
	iptables -A OUTPUT  -o ${zone} -j "${chain_prefix}_OUTPUT"

	# Custom rules.
	iptables_chain_create "${chain_prefix}_CUSTOM"

	# Intrusion Prevention System.
	iptables_chain_create "${chain_prefix}_IPS"

	# Create a chain for each other zone.
	# This leaves us with n^2 chains. Duh.

	local other_zone other_chain_prefix
	for other_zone in $(zones_get_all); do
		other_chain_prefix="${chain_prefix}_${other_zone^^}"
		iptables_chain_create ${other_chain_prefix}

		# Connect the chain with the FORWARD chain.
		iptables -A FORWARD -i ${zone} -o ${other_zone} \
			-j "${other_chain_prefix}"

		# Handle custom rules.
		iptables -A ${other_chain_prefix} -j "${chain_prefix}_CUSTOM"

		# Link IPS.
		iptables -A ${other_chain_prefix} -j "${chain_prefix}_IPS"

		# Rules.
		iptables_chain_create "${other_chain_prefix}_RULES"
		iptables -A ${other_chain_prefix} -j "${other_chain_prefix}_RULES"

		# Policy.
		iptables_chain_create "${other_chain_prefix}_POLICY"
		iptables -A ${other_chain_prefix} -j "${other_chain_prefix}_POLICY"
	done

	## Create mangle chain.
	#iptables_chain_create -t mangle ${chain_prefix}
	#iptables -t mangle -A PREROUTING  -i ${zone} -j ${chain_prefix}
	#iptables -t mangle -A POSTROUTING -o ${zone} -j ${chain_prefix}

	## Quality of Service
	#iptables_chain_create -t mangle "${chain_prefix}_QOS_INC"
	#iptables -t mangle -A ${chain_prefix} -i ${zone} -j "${chain_prefix}_QOS_INC"
	#iptables_chain_create -t mangle "${chain_prefix}_QOS_OUT"
	#iptables -t mangle -A ${chain_prefix} -o ${zone} -j "${chain_prefix}_QOS_OUT"

	# Create NAT chain.
	iptables_chain_create -4 -t nat ${chain_prefix}
	iptables -4 -t nat -A PREROUTING  -i ${zone} -j ${chain_prefix}
	iptables -4 -t nat -A POSTROUTING -o ${zone} -j ${chain_prefix}

	# Network Address Translation
	iptables_chain_create -4 -t nat "${chain_prefix}_DNAT"
	iptables -4 -t nat -A PREROUTING  -i ${zone} -j "${chain_prefix}_DNAT"
	iptables_chain_create -4 -t nat "${chain_prefix}_SNAT"
	iptables -4 -t nat -A POSTROUTING -o ${zone} -j "${chain_prefix}_SNAT"

	# UPnP
	iptables_chain_create -4 -t nat "${chain_prefix}_UPNP"
	iptables -4 -t nat -A ${chain_prefix} -j "${chain_prefix}_UPNP"

	return ${EXIT_OK}
}

function firewall_parse_rules() {
	local file=${1}
	assert isset file
	shift

	# End if no rule file exists.
	[ -r "${file}" ] || return ${EXIT_OK}

	local cmd

	local ${FIREWALL_RULES_CONFIG_PARAMS}
	local line
	while read -r line; do
		# Skip empty lines.
		[ -n "${line}" ] || continue

		# Skip commented lines.
		[ "${line:0:1}" = "#" ] && continue

		# Parse the rule.
		_firewall_parse_rule_line ${line}
		if [ $? -ne ${EXIT_OK} ]; then
			log WARNING "Skipping invalid line: ${line}"
			continue
		fi

		cmd="iptables $@"

		# Source IP address/net.
		if isset src; then
			list_append cmd "-s ${src}"
		fi

		# Destination IP address/net.
		if isset dst; then
			list_append cmd "-d ${dst}"
		fi

		# Protocol.
		if isset proto; then
			list_append cmd "-p ${proto}"

			if list_match ${proto} ${FIREWALL_PROTOCOLS_SUPPORTING_PORTS}; then
				if isset sport; then
					list_append cmd "--sport ${sport}"
				fi

				if isset dport; then
					list_append cmd "--dport ${dport}"
				fi
			fi
		fi

		# Always append the action.
		list_append cmd "-j ${action}"

		# Execute command.
		${cmd}
	done < ${file}
}

function _firewall_parse_rule_line() {
	local arg

	# Clear all values.
	for arg in ${FIREWALL_RULES_CONFIG_PARAMS}; do
		assign "${arg}" ""
	done

	local key val
	while read -r arg; do
		key=$(cli_get_key ${arg})

		if ! listmatch "${key}" ${FIREWALL_RULES_CONFIG_PARAMS}; then
			log WARNING "Unrecognized argument: ${arg}"
			return ${EXIT_ERROR}
		fi

		val=$(cli_get_val ${arg})
		assign "${key}" "${val}"
	done <<< "$(args $@)"

	# action must always be set.
	if ! isset action; then
		log WARNING "'action' is not set: $@"
		return ${EXIT_ERROR}
	fi

	for arg in src dst; do
		isset ${arg} || continue

		# Check for valid IP addresses.
		if ! ip_is_valid ${!arg}; then
			log WARNING "Invalid IP address for '${arg}=${!arg}': $@"
			return ${EXIT_ERROR}
		fi
	done

	if isset proto; then
		# Make lowercase.
		proto=${proto,,}

		if ! list_match "${proto}" ${FIREWALL_SUPPORTED_PROTOCOLS}; then
			log WARNING "Unsupported protocol type 'proto=${proto}': $@"
			return ${EXIT_ERROR}
		fi
	fi

	for arg in sport dport; do
		isset ${arg} || continue

		# Check if port is valid.
		if ! isinteger ${arg}; then
			log WARNING "Invalid port '${arg}=${!arg}': $@"
			return ${EXIT_ERROR}
		fi
	done

	return ${EXIT_OK}
}