packages: BCP38 support for openwrt

This adds firewall support for blocking common invalid address
ranges, using ipset.

bcp38/Makefile

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+#
+# Copyright (C) 2014 OpenWrt.org
+#
+# This is free software, licensed under the GNU General Public License v2.
+# See /LICENSE for more information.
+# Please note this is not an officially released version of bcp38
+
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=bcp38
+PKG_VERSION:=4
+PKG_RELEASE:=1
+
+include $(INCLUDE_DIR)/package.mk
+
+define Package/bcp38
+  SECTION:=net
+  CATEGORY:=Network
+  SUBMENU:=Routing and Redirection
+  TITLE:=BCP38 compliance 
+  URL:=http://www.github.com/dtaht/bcp38
+  MAINTAINER:=Dave Taht <d+bcp38@taht.net>
+  DEPENDS:=+ipset
+endef
+
+define Package/bcp38/description
+ bcp38 implements rfc bcp 38 for home routers.
+endef
+
+define Package/bcp38/conffiles
+/etc/config/bcp38
+endef
+
+define Build/Prepare
+endef
+
+define Build/Configure
+endef
+
+define Build/Compile
+endef
+
+define Package/bcp38/install
+	$(INSTALL_DIR) $(1)/etc/config
+	$(INSTALL_CONF) ./files/bcp38.config $(1)/etc/config/bcp38
+	$(INSTALL_DIR) $(1)/usr/lib/bcp38
+	$(INSTALL_BIN) ./files/run.sh $(1)/usr/lib/bcp38/run.sh
+	$(INSTALL_DIR) $(1)/etc/uci-defaults
+	$(INSTALL_BIN) ./files/bcp38.defaults $(1)/etc/uci-defaults/bcp38
+endef
+
+define Package/bcp38/postinst
+#!/bin/sh
+[ -x /etc/uci-defaults/bcp38 ] && /etc/uci-defaults/bcp38 || exit 0
+endef
+
+define Package/bcp38/postrm
+#!/bin/sh
+uci delete firewall.bcp38
+uci commit
+endef
+
+$(eval $(call BuildPackage,bcp38))

bcp38/files/bcp38.config

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+config bcp38
+	option enabled 1
+	option interface 'ge00'
+	option detect_upstream 1
+	list match '127.0.0.0/8'
+	list match '0.0.0.0/8'       # RFC 1700
+	list match '240.0.0.0/4'     # RFC 5745
+	list match '192.0.2.0/24'    # RFC 5737
+	list match '198.51.100.0/24' # RFC 5737
+	list match '203.0.113.0/24'  # RFC 5737
+	list match '192.168.0.0/16'  # RFC 1918
+	list match '10.0.0.0/8'      # RFC 1918
+	list match '172.16.0.0/12'   # RFC 1918
+	list match '169.254.0.0/16'  # RFC 3927
+
+# 	list nomatch '172.26.0.0/21' # Example of something not to match
+#	There is a dhcp trigger to do this for the netmask of a 
+#	double natted connection needed
+
+#	I will argue that this level of indirection doesn't scale
+# 	very well - see how to block china as an example
+#	http://www.okean.com/china.txt

bcp38/files/bcp38.defaults

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+#!/bin/sh
+
+uci -q batch <<-EOT
+	delete firewall.bcp38
+	set firewall.bcp38=include
+	set firewall.bcp38.type=script
+	set firewall.bcp38.path=/usr/lib/bcp38/run.sh
+	set firewall.bcp38.family=IPv4
+	set firewall.bcp38.reload=1
+	commit firewall
+EOT
+
+exit 0

bcp38/files/run.sh

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+#!/bin/sh
+
+STOP=$1
+IPSET_NAME=bcp38-ipv4
+IPTABLES_CHAIN=BCP38
+
+. /lib/functions.sh
+
+config_load bcp38
+
+add_bcp38_rule()
+{
+	local subnet="$1"
+	local action="$2"
+
+	if [ "$action" == "nomatch" ]; then
+		ipset add "$IPSET_NAME" "$subnet" nomatch
+	else
+		ipset add "$IPSET_NAME" "$subnet"
+	fi
+}
+
+detect_upstream()
+{
+	local interface="$1"
+
+	subnets=$(ip route show dev "$interface"  | grep 'scope link' | awk '{print $1}')
+	for subnet in $subnets; do
+		# ipset test doesn't work for subnets, so strip out the subnet part
+		# and test for that; add as exception if there's a match
+		addr=$(echo $subnet | sed 's|/[0-9]\+$||')
+		ipset test "$IPSET_NAME" $addr 2>/dev/null && add_bcp38_rule $subnet nomatch
+	done
+}
+
+run() {
+    	local section="$1"
+    	local enabled
+	local interface
+	local detect_upstream
+	config_get_bool enabled "$section" enabled 0
+	config_get interface "$section" interface
+	config_get detect_upstream "$section" detect_upstream
+
+	if [ "$enabled" -eq "1" -a -n "$interface" -a -z "$STOP" ] ; then
+		setup_ipset
+		setup_iptables "$interface"
+		config_list_foreach "$section" match add_bcp38_rule match
+		config_list_foreach "$section" nomatch add_bcp38_rule nomatch
+		[ "$detect_upstream" -eq "1" ] && detect_upstream "$interface"
+	fi
+	exit 0
+}
+
+setup_ipset()
+{
+	ipset create "$IPSET_NAME" hash:net family ipv4
+	ipset flush "$IPSET_NAME"
+}
+
+setup_iptables()
+{
+	local interface="$1"
+	iptables -N "$IPTABLES_CHAIN" 2>/dev/null
+	iptables -F "$IPTABLES_CHAIN" 2>/dev/null
+
+	iptables -I output_rule -j "$IPTABLES_CHAIN"
+	iptables -I input_rule -j "$IPTABLES_CHAIN"
+	iptables -I forwarding_rule -j "$IPTABLES_CHAIN"
+
+	# always accept DHCP traffic
+	iptables -A "$IPTABLES_CHAIN" -p udp --dport 67:68 --sport 67:68 -j RETURN
+	iptables -A "$IPTABLES_CHAIN" -o "$interface" -m set --match-set "$IPSET_NAME" dst -j REJECT --reject-with icmp-net-unreachable
+	iptables -A "$IPTABLES_CHAIN" -i "$interface" -m set --match-set "$IPSET_NAME" src -j DROP
+}
+
+destroy_ipset()
+{
+	ipset flush "$IPSET_NAME" 2>/dev/null
+	ipset destroy "$IPSET_NAME" 2>/dev/null
+}
+
+destroy_iptables()
+{
+	iptables -D output_rule -j "$IPTABLES_CHAIN" 2>/dev/null
+	iptables -D input_rule -j "$IPTABLES_CHAIN" 2>/dev/null
+	iptables -D forwarding_rule -j "$IPTABLES_CHAIN" 2>/dev/null
+	iptables -F "$IPTABLES_CHAIN" 2>/dev/null
+	iptables -X "$IPTABLES_CHAIN" 2>/dev/null
+}
+
+destroy_iptables
+destroy_ipset
+config_foreach run bcp38
+
+exit 0