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opensense-docs/source/manual/how-tos/sslvpn_instance_s2s.rst
2023-06-29 19:09:02 +02:00

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=================================
Setup SSL VPN site to site tunnel
=================================
Site to site VPNs connect two locations with static public IP addresses and allow
traffic to be routed between the two networks. This is most commonly used to
connect an organization's branch offices back to its main office, so branch users
can access network resources in the main office.
.. contents:: Index
----------------
Before you start
----------------
Before starting with the configuration of an OpenVPN SSL tunnel you need to have a
working OPNsense installation with a unique LAN IP subnet for each side of your
connection (your local network needs to be different than that of the remote
network).
.. Note::
For the sample we will use a private IP for our WAN connection.
This requires us to disable the default block rule on WAN to allow private traffic.
To do so, go to :menuselection:`Interfaces --> [WAN]` and uncheck "Block private networks".
*(Don't forget to save and apply)*
.. image:: images/block_private_networks.png
--------------------------------
Network topology
--------------------------------
The schema below describes the situation we are implementing. Two networks (A,B) and a transit network (10.10.8.0/24)
to peer both firewalls. We will create a tunnel network :code:`10.1.8.0/24` between both sites.
.. nwdiag::
:scale: 100%
nwdiag {
span_width = 90;
node_width = 180;
network A {
address = "10.0.8.0/24";
pclana [label="PC Site A\n10.0.8.20",shape="cisco.pc"];
fwa [shape = "cisco.firewall", address="10.0.8.1/24"];
}
network Ext {
address = "10.10.8.0/24";
label = "Tunnel net 10.1.8.0/24";
fwa [shape = "cisco.firewall", address="10.10.8.1/24"];
fwb [shape = "cisco.firewall", address="10.10.8.2/24"];
}
network B {
address = "192.168.8.0/24"
fwb [shape = "cisco.firewall", address="192.168.8.20"];
pclanb [label="PC Site B\n192.168.8.20",shape="cisco.pc"];
}
}
--------------------------------
Preparations
--------------------------------
.....................
Trust
.....................
In order to setup a tunnel on both ends, we need to configure certificates to warrant trust between both machines.
We have chosen to setup the server on "Site B", so we start with Trust configuration there.
* First we need an **Authority** which we are going to create in :menuselection:`System --> Trust --> Authorities`
* Select `Create an internal Certificate Authority`
* Choose cryptographic settings and a lifetime (you may want to increase the default as after this time you do need to redistribute certificates to both server and client).
* Add descriptive information for this CA (`Descriptive name`, `City`, `Email`, ..`)
* Set the `Common Name` to something descriptive for this certificate, like "Office-ovpn"
* Next generate a **Certficate** for the server using :menuselection:`System --> Trust --> Certificates`
* Select `Create an internal Certificate`
* Choose the just created authority in `Certificate authority`
* Add descriptive information for this CA (`Descriptive name`, whereabouts are copied from the CA)
* Set Type to `Server`
* Choose cryptographic settings, lifetime determines the validaty of the server certificate (you do need to track this yourself), it's allow to choose a longer period here
* Set the `Common Name` to the fqdn of this machine.
* As the client (Site A) will also need a **Certificate**, we need to create a certificate, also using :menuselection:`System --> Trust --> Certificates`
* Select `Create an internal Certificate`
* Choose the just created authority in `Certificate authority`
* Add descriptive information for this CA (`Descriptive name`, whereabouts are copied from the CA)
* Set Type to `Server`
* Choose cryptographic settings, lifetime determines the validaty of the server certificate (you do need to track this yourself), it's allow to choose a longer period here
* Set the `Common Name` to username the other end will use for identification. For this example we use :code:`test-client`
.. Note::
It's a best practice to offer each user it's own certificate using the same common name as the username, although
it is also possible to clients to share a certificate. When adding a certificate from the user manager the CN is automatically
set to its name. In this example we will only authenticate using the certificate, no additional user or password will be required.
.....................
Static keys
.....................
We create a static key and define it's use in :menuselection:`VPN --> OpenVPN --> Instances --> Static Keys`, for this example
select `auth` as mode and click the gear button to generate one. Provide a description for this key.
..........................................
Prepare Site A
..........................................
* Copy the public part of the certificate authority to the firewall at Site a (use the download button and copy the contents into a new CA on this host)
* Copy the public and private part of the client certificate into a new one on Site A
* Copy the contents of the static key to a new entry and select the same type
------------------------------------
Create a server instance (Site B)
------------------------------------
Now the generic setup is done, we can configure a new server type instance via :menuselection:`VPN --> OpenVPN --> Instances`
===============================================================
======================= =======================================
Property site B
======================= =======================================
Role Server
Description MyServer
Protocol UDP (IPv4)
Port number 1194
Bind address 10.10.8.1 :sup:`1`
Server (IPv4) 10.1.8.0/24 (the tunnel network used)
Certificate choose the prepared server certificate
TLS static key choose the prepared static key
Local Network 192.168.8.0/24
Remote Network 10.0.8.0/24 :sup:`2`
======================= =======================================
.. admonition:: Note :sup:`1`
Leave empty to bind to all addresses assigned to this machine or use a loopback address combined with a port forward when
the external address is not static.
.. admonition:: Note :sup:`2`
The network(s) served by this openvpn instance, after startup routes will be created. In order to bind
the network to the correct client a `Client Specific Overwrite` is also needed.
Hit the apply button when the instance is configured and add a client specific overwrite in :menuselection:`VPN --> OpenVPN --> Client Specific Overrides`
===============================================================
======================= =======================================
Property site B
======================= =======================================
Servers leave empty or select our server
Common name test-client
Remote Network 10.0.8.0/24 :sup:`1`
======================= =======================================
.. admonition:: Note :sup:`1`
The remote network bound to this common name, without this entry the traffic will not be routed between hosts.
Next go to :menuselection:`Firewall --> Rules --> WAN` and add a rule to allow traffic on port :code:`1494/UDP` from the other
host. At minimum we should add a rule similar to this one:
===============================================================
======================= =======================================
Property site B
======================= =======================================
Interface WAN
Protocol UDP
Destination port range 1194
======================= =======================================
Finally we are going to allow traffic on the tunnel itself by adding a rule to :menuselection:`Firewall --> Rules --> OpenVPN`,
for this example we keep it simple and add one to allow all, in which case we can save the defaults when adding a rule.
------------------------------------
Create a client instance (Site A)
------------------------------------
With the server in place it's time to setup the client on OPNsense, for this we go to :menuselection:`VPN --> OpenVPN --> Instances`
and add a new instance using the following settings.
===============================================================
======================= =======================================
Property site A
======================= =======================================
Role Client
Description MyClient
Protocol UDP (IPv4)
Remote 10.10.8.1
Certificate choose the prepared client certificate
TLS static key choose the prepared static key
Remote Network 192.168.8.0/24
======================= =======================================
--------------------------------
Test connectivity
--------------------------------
Use the :menuselection:`VPN: OpenVPN: Connection Status` page to watch the status of both server and client, when
passing traffic over the link on both ends the counters should increase.
Now try to ping from Site A (:code:`10.0.8.20`) to Site B (:code:`192.168.8.20`).