ipsec: Add block rules to avoid conntrack entries

If an IPsec VPN connections is not established, there are
rare cases when packets are supposed to be sent through
that said tunnel and incorrectly handled.

Those packets are sent to the default gateway an entry
for this connection is created in the connection tracking
table (usually only happens to UDP). All following packets
are sent the same route even after the tunnel has been
brought up. That leads to SIP phones not being able to
register among other things.

This patch adds firewall rules that these packets are
rejected. That will sent a notification to the client
that the tunnel is not up and avoid the connection to
be added to the connection tracking table.

Apart from a small performance penalty there should
be no other side-effects.

Fixes: #10908
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
Cc: tomvend@rymes.com
Cc: daniel.weismueller@ipfire.org
Cc: morlix@morlix.de
Reviewed-by: Timo Eissler <timo.eissler@ipfire.org>

diff --git a/config/firewall/ipsec-block b/config/firewall/ipsec-block
new file mode 100644 (file)
index 0000000..9fa8e1a
--- /dev/null
+++ b/config/firewall/ipsec-block
@@ -0,0 +1,59 @@
+#!/bin/bash
+###############################################################################
+#                                                                             #
+# IPFire.org - A linux based firewall                                         #
+# Copyright (C) 2015 IPFire 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/>.       #
+#                                                                             #
+###############################################################################
+
+VPN_CONFIG="/var/ipfire/vpn/config"
+
+block_subnet() {
+       local subnet="${1}"
+
+       # Don't block a wildcard subnet
+       if [ "${subnet}" = "0.0.0.0/0" ] || [ "${subnet}" = "0.0.0.0/0.0.0.0" ]; then
+               return 0
+       fi
+
+       iptables -A IPSECBLOCK -d "${subnet}" -j REJECT --reject-with icmp-net-unreachable
+}
+
+block_ipsec() {
+       # Flush all exists rules
+       iptables -F IPSECBLOCK
+
+       local id status name lefthost type ctype unknown1 unknown2 unknown3
+       local leftsubnets unknown4 righthost rightsubnets rest
+       while IFS="," read -r id status name lefthost type ctype unkown1 unknown2 unknown3 \
+                       leftsubnets unknown4 righthost rightsubnets rest; do
+               # Check if the connection is enabled
+               [ "${status}" = "on" ] || continue
+
+               # Check if this a net-to-net connection
+               [ "${type}" = "net" ] || continue
+
+               # Split multiple subnets
+               rightsubnets="${rightsubnets//\|/ }"
+
+               local rightsubnet
+               for rightsubnet in ${rightsubnets}; do
+                       block_subnet "${rightsubnet}"
+               done
+       done < "${VPN_CONFIG}"
+}
+
+block_ipsec || exit $?

diff --git a/config/rootfiles/common/stage2 b/config/rootfiles/common/stage2
index 90e28d9c4c26cc7f404ae5766b4088de30215198..4021cafad68643d9ea6bf089d0d7e1452e622cb2 100644 (file)
--- a/config/rootfiles/common/stage2
+++ b/config/rootfiles/common/stage2
@@ -73,6 +73,7 @@ run
 #usr/lib
 usr/lib/firewall
 usr/lib/firewall/firewall-lib.pl
+usr/lib/firewall/ipsec-block
 usr/lib/firewall/rules.pl
 #usr/lib/libgcc_s.so
 usr/lib/libgcc_s.so.1

diff --git a/config/rootfiles/common/x86_64/stage2 b/config/rootfiles/common/x86_64/stage2
index 0ac9ab55ac418421f6b24b1c6b6131aed017085b..531daaadd39c80d5c0ebf2e9a3de6cd916591e7d 100644 (file)
--- a/config/rootfiles/common/x86_64/stage2
+++ b/config/rootfiles/common/x86_64/stage2
@@ -74,6 +74,7 @@ run
 #usr/lib
 usr/lib/firewall
 usr/lib/firewall/firewall-lib.pl
+usr/lib/firewall/ipsec-block
 usr/lib/firewall/rules.pl
 #usr/lib/libgcc_s.so
 usr/lib/libgcc_s.so.1

diff --git a/lfs/stage2 b/lfs/stage2
index 3244fa36fa79afc8b946a100173c9ce9784ee5c9..ec5d1170d972eb587045e954ae27bcaff3d1fbe9 100644 (file)
--- a/lfs/stage2
+++ b/lfs/stage2
@@ -114,6 +114,8 @@ endif
                /usr/lib/firewall/rules.pl
        install -m 644 $(DIR_SRC)/config/firewall/firewall-lib.pl \
                /usr/lib/firewall/firewall-lib.pl
+       install -m 755 $(DIR_SRC)/config/firewall/ipsec-block \
+               /usr/lib/firewall/ipsec-block
 
        # Nobody user
        -mkdir -p /home/nobody

diff --git a/src/initscripts/init.d/firewall b/src/initscripts/init.d/firewall
index 8ca02bc9d1932b4530556d5baf29ef0053eb090d..2d462d786d1bf31cb82756d164cac4f7d6bf6abd 100644 (file)
--- a/src/initscripts/init.d/firewall
+++ b/src/initscripts/init.d/firewall
@@ -115,6 +115,11 @@ iptables_init() {
        iptables -A INPUT -j GUARDIAN
        iptables -A FORWARD -j GUARDIAN
 
+       # Block non-established IPsec networks
+       iptables -N IPSECBLOCK
+       iptables -A FORWARD -m policy --dir out --pol none -j IPSECBLOCK
+       iptables -A OUTPUT  -m policy --dir out --pol none -j IPSECBLOCK
+
        # Block OpenVPN transfer networks
        iptables -N OVPNBLOCK
        iptables -A INPUT   -i tun+ -j OVPNBLOCK
@@ -270,6 +275,9 @@ iptables_init() {
        iptables -t nat -N REDNAT
        iptables -t nat -A POSTROUTING -j REDNAT
 
+       # Populate IPsec block chain
+       /usr/lib/firewall/ipsec-block
+
        # Apply OpenVPN firewall rules
        /usr/local/bin/openvpnctrl --firewall-rules
 

diff --git a/src/misc-progs/ipsecctrl.c b/src/misc-progs/ipsecctrl.c
index e99202d9fa33cb5ab35121d09ff59f9ed633fd10..7499e94c9a7f384e6d0fd809203d32163cb84e96 100644 (file)
--- a/src/misc-progs/ipsecctrl.c
+++ b/src/misc-progs/ipsecctrl.c
@@ -144,6 +144,9 @@ void turn_connection_on(char *name, char *type) {
                 "/usr/sbin/ipsec down %s >/dev/null", name);
         safe_system(command);
 
+       // Reload the IPsec block chain
+       safe_system("/usr/lib/firewall/ipsec-block >/dev/null");
+
        // Reload the configuration into the daemon (#10339).
        ipsec_reload();
 
@@ -302,6 +305,7 @@ int main(int argc, char *argv[]) {
 
         // start the system
         if ((argc == 2) && strcmp(argv[1], "S") == 0) {
+               safe_system("/usr/lib/firewall/ipsec-block >/dev/null");
                safe_system("/usr/sbin/ipsec restart >/dev/null");
                 exit(0);
         }