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==================
OVS IPsec Tutorial
==================

This document provides a step-by-step guide for running IPsec tunnel in Open
vSwitch. A more detailed description on OVS IPsec tunnel and its
configuration modes can be found in :doc:`/howto/ipsec`.

Requirements
------------

OVS IPsec tunnel requires Linux kernel (>= v3.10.0) and OVS out-of-tree kernel
module. The compatible IKE daemons are LibreSwan (>= v3.23) and StrongSwan
(>= v5.3.5).

.. _install-ovs-ipsec:

Installing OVS and IPsec Packages
---------------------------------

OVS IPsec has .deb and .rpm packages. You should use the right package
based on your Linux distribution. This tutorial uses Ubuntu 16.04 and Fedora 27
as examples.

Ubuntu
~~~~~~

1. Follow :doc:`/intro/install/debian` to build debian packages.

   .. note::

     If you have already installed OVS, then you only need to install
     openvswitch-pki_*.deb and openvswitch-ipsec_*.deb in the following step.
     If your kernel version is below v4.13.0, update your kernel to v4.13.0 or
     above.

2. Install the related packages::

       $ apt-get install dkms strongswan
       $ dpkg -i libopenvswitch_*.deb openvswitch-common_*.deb \
             openvswitch-switch_*.deb openvswitch-datapath-dkms_*.deb \
             python-openvswitch_*.deb openvswitch-pki_*.deb \
             openvswitch-ipsec_*.deb

   If the installation is successful, you should be able to see the
   ovs-monitor-ipsec daemon is running in your system.

Fedora
~~~~~~

1. Follow :doc:`/intro/install/fedora` to build RPM packages.

2. Install the related packages::

       $ dnf install python2-openvswitch libreswan \
                     "kernel-devel-uname-r == $(uname -r)"
       $ rpm -i openvswitch-*.rpm openvswitch-kmod-*.rpm \
                openvswitch-openvswitch-ipsec-*.rpm

3. Install firewall rules to allow ESP and IKE traffic::

       $ iptables -A IN_FedoraServer_allow -p esp -j ACCEPT
       $ iptables -A IN_FedoraServer_allow -p udp --dport 500 -j ACCEPT

4. Run the openvswitch-ipsec service::

       $ systemctl start openvswitch-ipsec.service

   .. note::

     The SELinux policies might prevent openvswitch-ipsec.service to access
     certain resources. You can configure SELinux to remove such restrictions.

Configuring IPsec tunnel
------------------------

Suppose you want to build IPsec tunnel between two hosts. Assume `host_1`'s
external IP is 1.1.1.1, and `host_2`'s external IP is 2.2.2.2. Make sure
`host_1` and `host_2` can ping each other via these external IPs.

0. Set up some variables to make life easier.  On both hosts, set ``ip_1`` and
   ``ip_2`` variables, e.g.::

     $ ip_1=1.1.1.1
     $ ip_2=2.2.2.2

1. Set up OVS bridges in both hosts.

   In `host_1`::

       $ ovs-vsctl add-br br-ipsec
       $ ip addr add 192.0.0.1/24 dev br-ipsec
       $ ip link set br-ipsec up

   In `host_2`::

       $ ovs-vsctl add-br br-ipsec
       $ ip addr add 192.0.0.2/24 dev br-ipsec
       $ ip link set br-ipsec up

2. Set up IPsec tunnel.

   There are three authentication methods. You can choose one to set up your
   IPsec tunnel.

   a) Using pre-shared key:

      In `host_1`::

          $ ovs-vsctl add-port br-ipsec tun -- \
                      set interface tun type=gre \
                                    options:remote_ip=$ip_2 \
                                    options:psk=swordfish

      In `host_2`::

          $ ovs-vsctl add-port br-ipsec tun -- \
                      set interface tun type=gre \
                                    options:remote_ip=$ip_1 \
                                    options:psk=swordfish

      .. note::

        Pre-shared key (PSK) based authentication is easy to set up but less
        secure compared with other authentication methods. You should use it
        cautiously in production systems.

   b) Using self-signed certificate:

      Generate self-signed certificate in both `host_1` and `host_2`. Then copy
      the certificate of `host_1` to `host_2` and the certificate of `host_2`
      to `host_1`.

      In `host_1`::

          $ ovs-pki req -u host_1
          $ ovs-pki self-sign host_1
          $ scp host_1-cert.pem $ip_2:/etc/keys/host_1-cert.pem

      In `host_2`::

          $ ovs-pki req -u host_2
          $ ovs-pki self-sign host_2
          $ scp host_2-cert.pem $ip_1:/etc/keys/host_2-cert.pem

      .. note::

        If you use StrongSwan as IKE daemon, please move the host certificates
        to /etc/ipsec.d/certs/ and private key to /etc/ipsec.d/private/ so that
        StrongSwan has permission to access those files.

      Configure IPsec tunnel to use self-signed certificates.

      In `host_1`::

          $ ovs-vsctl set Open_vSwitch . \
                     other_config:certificate=/etc/keys/host_1-cert.pem \
                     other_config:private_key=/etc/keys/host_1-privkey.pem
          $ ovs-vsctl add-port br-ipsec tun -- \
                      set interface tun type=gre \
                             options:remote_ip=$ip_2 \
                             options:remote_cert=/etc/keys/host_2-cert.pem

      In `host_2`::

          $ ovs-vsctl set Open_vSwitch . \
                     other_config:certificate=/etc/keys/host_2-cert.pem \
                     other_config:private_key=/etc/keys/host_2-privkey.pem
          $ ovs-vsctl add-port br-ipsec tun -- \
                      set interface tun type=gre \
                             options:remote_ip=$ip_1 \
                             options:remote_cert=/etc/keys/host_1-cert.pem

      .. note::

        The confidentiality of the private key is very critical.  Don't copy it
        to places where it might be compromised.  (The certificate need not be
        kept confidential.)

   c) Using CA-signed certificate:

      First you need to establish a public key infrastructure (PKI). Suppose
      you choose `host_1` to host PKI.

      In `host_1`::

          $ ovs-pki init

      Generate certificate requests and copy the certificate request of
      `host_2` to `host_1`.

      In `host_1`::

          $ ovs-pki req -u host_1

      In `host_2`::

          $ ovs-pki req -u host_2
          $ scp host_2-req.pem $ip_1:/etc/keys/host_2-req.pem

      Sign the certificate requests with the CA key. Copy `host_2`'s signed
      certificate and the CA certificate to `host_2`.

      In `host_1`::

          $ ovs-pki sign host_1 switch
          $ ovs-pki sign host_2 switch
          $ scp host_2-cert.pem $ip_2:/etc/keys/host_2-cert.pem
          $ scp /var/lib/openvswitch/pki/switchca/cacert.pem \
                    $ip_2:/etc/keys/cacert.pem

      .. note::

        If you use StrongSwan as IKE daemon, please move the host certificates
        to /etc/ipsec.d/certs/, CA certificate to /etc/ipsec.d/cacerts/, and
        private key to /etc/ipsec.d/private/ so that StrongSwan has permission
        to access those files.

      Configure IPsec tunnel to use CA-signed certificate.

      In `host_1`::

          $ ovs-vsctl set Open_vSwitch . \
                  other_config:certificate=/etc/keys/host_1-cert.pem \
                  other_config:private_key=/etc/keys/host_1-privkey.pem \
                  other_config:ca_cert=/etc/keys/cacert.pem
          $ ovs-vsctl add-port br-ipsec tun -- \
                   set interface tun type=gre \
                                 options:remote_ip=$ip_2 \
                                 options:remote_name=host_2

      In `host_2`::

          $ ovs-vsctl set Open_vSwitch . \
                  other_config:certificate=/etc/keys/host_2-cert.pem \
                  other_config:private_key=/etc/keys/host_2-privkey.pem \
                  other_config:ca_cert=/etc/keys/cacert.pem
          $ ovs-vsctl add-port br-ipsec tun -- \
                   set interface tun type=gre \
                                 options:remote_ip=$ip_1 \
                                 options:remote_name=host_1

      .. note::

        remote_name is the common name (CN) of the signed-certificate.  It must
        match the name given as the argument to the ``ovs-pki sign command``.
        It ensures that only certificate with the expected CN can be
        authenticated; otherwise, any certificate signed by the CA would be
        accepted.

3. Test IPsec tunnel.

   Now you should have an IPsec GRE tunnel running between two hosts. To verify
   it, in `host_1`::

       $ ping 192.0.0.2 &
       $ tcpdump -ni any net $ip_2

   You should be able to see that ESP packets are being sent from `host_1` to
   `host_2`.

Troubleshooting
---------------

The ``ovs-monitor-ipsec`` daemon manages and monitors the IPsec tunnel state.
Use the following ``ovs-appctl`` command to view ``ovs-monitor-ipsec`` internal
representation of tunnel configuration::

    $ ovs-appctl -t ovs-monitor-ipsec tunnels/show

If there is misconfiguration, then ``ovs-appctl`` should indicate why.
For example::

   Interface name: gre0 v5 (CONFIGURED) <--- Should be set to CONFIGURED.
                                             Otherwise, error message will
                                             be provided
   Tunnel Type:    gre
   Local IP:       %defaultroute
   Remote IP:      2.2.2.2
   SKB mark:       None
   Local cert:     None
   Local name:     None
   Local key:      None
   Remote cert:    None
   Remote name:    None
   CA cert:        None
   PSK:            swordfish
   Ofport:         1          <--- Whether ovs-vswitchd has assigned Ofport
                                   number to this Tunnel Port
   CFM state:      Up         <--- Whether CFM declared this tunnel healthy
   Kernel policies installed:
   ...                          <--- IPsec policies for this OVS tunnel in
                                     Linux Kernel installed by strongSwan
   Kernel security associations installed:
   ...                          <--- IPsec security associations for this OVS
                                     tunnel in Linux Kernel installed by
                                     strongswan
   IPsec connections that are active:
   ...                          <--- IPsec "connections" for this OVS
                                     tunnel

If you don't see any active connections, try to run the following command to
refresh the ``ovs-monitor-ipsec`` daemon::

    $ ovs-appctl -t ovs-monitor-ipsec refresh

You can also check the logs of the ``ovs-monitor-ipsec`` daemon and the IKE
daemon to locate issues. ``ovs-monitor-ipsec`` outputs log messages to
/var/log/openvswitch/ovs-monitor-ipsec.log.

Bug Reporting
-------------

If you think you may have found a bug with security implications, like

1. IPsec protected tunnel accepted packets that came unencrypted; OR
2. IPsec protected tunnel allowed packets to leave unencrypted;

Then report such bugs according to :doc:`/internals/security`.

If bug does not have security implications, then report it according to
instructions in :doc:`/internals/bugs`.

If you have suggestions to improve this tutorial, please send a email to
ovs-discuss@openvswitch.org.
