From d052f3435f85d5b61ace87e158f77b7f37080395 Mon Sep 17 00:00:00 2001
From: Mark Wooding <mdw@distorted.org.uk>
Date: Sat, 8 Mar 2014 14:51:24 +0000
Subject: [PATCH] functions.m4, radius.m4: BCP38 filtering for outbound
 traffic.

---
 functions.m4 | 44 ++++++++++++++++++++++++++++++++++++++++++++
 radius.m4    |  6 ++++++
 2 files changed, 50 insertions(+)

diff --git a/functions.m4 b/functions.m4
index 1cd0db5..c0b90ed 100644
--- a/functions.m4
+++ b/functions.m4
@@ -349,6 +349,50 @@ openports () {
   run ip46tables -A $chain -p udp -g interesting --destination-port $1:$2
 }
 
+bcp38_setup=:
+bcp38 () {
+  ipv=$1 ifname=$2; shift 2
+  ## Add rules for BCP38 egress filtering for IP version IPV (either 4 or 6).
+  ## IFNAME is the outgoing interface; the remaining arguments are network
+  ## prefixes.
+
+  ## Sort out which command we're using
+  case $ipv in
+    4) ipt=iptables ;;
+    6) ipt=ip6tables ;;
+    *) echo >&2 "Unknown IP version $ipv"; exit 1 ;;
+  esac
+
+  ## If we've not set up the error chain then do that.
+  case $bcp38_setup in
+    :)
+      errorchain bcp38 DROP
+      clearchain bcp38-check
+      ip46tables -A bcp38-check -g bcp38
+      ;;
+  esac
+
+  ## Stitch our egress filter into the outbound chains if we haven't done
+  ## that yet.  Do this for both IP versions: if we're only ever given
+  ## IPv6 addresses for a particular interface then we assume that IPv4
+  ## packets aren't allowed on it at all.
+  case $bcp38_setup in
+    *:$ifname:*) ;;
+    *)
+      run ip46tables -A OUTPUT -j bcp38-check -o $ifname
+      case $forward in
+	1) run ip46tables -A FORWARD -j bcp38-check -o $ifname ;;
+      esac
+      bcp38_setup=$bcp38_setup$ifname:
+      ;;
+  esac
+
+  ## Finally, add in our allowed networks.
+  for i in "$@"; do
+    run $ipt -I bcp38-check -j RETURN -s $i
+  done
+}
+
 m4_divert(20)m4_dnl
 ###--------------------------------------------------------------------------
 ### Packet classification.
diff --git a/radius.m4 b/radius.m4
index b8481bb..090249c 100644
--- a/radius.m4
+++ b/radius.m4
@@ -57,6 +57,12 @@ iptables -A fwd-spec-nofrag -j ACCEPT \
 	-m mark --mark $from_untrusted/$MASK_FROM \
 	-m state --state ESTABLISHED
 
+## BCP38 filtering.  Note that addresses here are seen before NAT is applied.
+bcp38 4 ppp0 62.49.204.144/28 172.29.198.0/23
+bcp38 6 t6-he \
+	2001:470:1f08:1b98::2 2001:470:1f09:1b98::/64 \
+	2001:470:9740::/48
+
 ## NAT for RFC1918 addresses.
 for i in PREROUTING OUTPUT POSTROUTING; do
   run iptables -t nat -P $i ACCEPT 2>/dev/null || :
-- 
2.11.0