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sarthurdev committed Jan 11, 2024
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Expand Up @@ -7,16 +7,16 @@ Quick Start
This chapter will guide you on how to get up to speed quickly using your new
VyOS system. It will show you a very basic configuration example that will
provide a :ref:`nat` gateway for a device with two network interfaces
(`eth0` and `eth1`).
(``eth0`` and ``eth1``).

.. _quick-start-configuration-mode:

Configuration Mode
##################

By default, VyOS is in operational mode, and the command prompt displays a `$`.
To configure VyOS, you will need to enter configuration mode, resulting in the
command prompt displaying a `#`, as demonstrated below:
By default, VyOS is in operational mode, and the command prompt displays
a ``$``. To configure VyOS, you will need to enter configuration mode, resulting
in the command prompt displaying a ``#``, as demonstrated below:

.. code-block:: none
Expand All @@ -43,10 +43,10 @@ the following command:
Interface Configuration
#######################

* Your outside/WAN interface will be `eth0`. It will receive its interface
* Your outside/WAN interface will be ``eth0``. It will receive its interface
address via DHCP.
* Your internal/LAN interface will be `eth1`. It will use a static IP address
of `192.168.0.1/24`.
* Your internal/LAN interface will be ``eth1``. It will use a static IP address
of ``192.168.0.1/24``.

After switching to :ref:`quick-start-configuration-mode` issue the following
commands:
Expand Down Expand Up @@ -81,11 +81,11 @@ The following settings will configure DHCP and DNS services on
your internal/LAN network, where VyOS will act as the default gateway and
DNS server.

* The default gateway and DNS recursor address will be `192.168.0.1/24`
* The address range `192.168.0.2/24 - 192.168.0.8/24` will be reserved for
* The default gateway and DNS recursor address will be ``192.168.0.1/24``
* The address range ``192.168.0.2/24 - 192.168.0.8/24`` will be reserved for
static assignments
* DHCP clients will be assigned IP addresses within the range of
`192.168.0.9 - 192.168.0.254` and have a domain name of `internal-network`
``192.168.0.9 - 192.168.0.254`` and have a domain name of ``internal-network``
* DHCP leases will hold for one day (86400 seconds)
* VyOS will serve as a full DNS recursor, replacing the need to utilize Google,
Cloudflare, or other public DNS servers (which is good for privacy)
Expand Down Expand Up @@ -118,68 +118,205 @@ network via IP masquerade.
set nat source rule 100 source address '192.168.0.0/24'
set nat source rule 100 translation address masquerade
Firewall
########

.. note:: Starting from VyOS 1.4-rolling-202308040557, a new firewall
structure can be found on all vyos instalations. Documentation for most
of the new firewall CLI can be found in the `firewall
<https://docs.vyos.io/en/latest/configuration/firewall/general.html>`_
chapter. The legacy firewall is still available for versions before
1.4-rolling-202308040557 and can be found in the :ref:`legacy-firewall`
chapter. The examples in this section use the new firewall configuration
commands.

Add a set of firewall policies for our outside/WAN interface.

This configuration creates a proper stateful firewall that blocks all traffic
which was not initiated from the internal/LAN side first.

.. code-block:: none
set firewall ipv4 forward filter default-action 'drop'
set firewall ipv4 forward filter rule 10 action 'accept'
set firewall ipv4 forward filter rule 10 state established 'enable'
set firewall ipv4 forward filter rule 10 state related 'enable'
set firewall ipv4 forward filter rule 20 action 'drop'
set firewall ipv4 forward filter rule 20 state invalid 'enable'
set firewall ipv4 forward filter rule 30 inbound-interface name 'eth1'
set firewall ipv4 forward filter rule 30 action 'accept'
set firewall ipv4 input filter default-action drop
set firewall ipv4 input filter rule 10 action 'accept'
set firewall ipv4 input filter rule 10 state established 'enable'
set firewall ipv4 input filter rule 10 state related 'enable'
set firewall ipv4 input filter rule 20 action 'drop'
set firewall ipv4 input filter rule 20 state invalid 'enable'
A new firewall structure—which uses the ``nftables`` backend, rather
than ``iptables``—is available on all installations starting from
VyOS ``1.4-rolling-202308040557``. The firewall supports creation of distinct,
interlinked chains for each `Netfilter hook
<https://wiki.nftables.org/wiki-nftables/index.php/Netfilter_hooks>`_
and allows for more granular control over the packet filtering process.

The firewall begins with the base ``filter`` tables you define for each of the
``forward``, ``input``, and ``output`` Netfiter hooks. Each of these tables is
populated with rules that are processed in order and can jump to other chains
for more granular filtering.

Configure Firewall Groups
-------------------------

To make firewall configuration easier, we can create groups of interfaces,
networks, addresses, ports, and domains that describe different parts of
our network. We can then use them for filtering within our firewall rulesets,
allowing for more concise and readable configuration.

In this case, we will create two interface groups—a ``WAN`` group for our
interfaces connected to the public internet and a ``LAN`` group for the
interfaces connected to our internal network. Additionally, we will create a
network group, ``NET-INSIDE-v4``, that contains our internal subnet.

.. code-block:: none
set firewall group interface-group WAN interface eth0
set firewall group interface-group LAN interface eth1
set firewall group network-group NET-INSIDE-v4 network '192.168.0.0/24'
Configure Stateful Packet Filtering
-----------------------------------

With the new firewall structure, we have have a lot of flexibility in how we
group and order our rules, as shown by the two alternative approaches below.

Option 1: Common Chain
^^^^^^^^^^^^^^^^^^^^^^

We can create a common chain for stateful connection filtering of multiple
interfaces (or multiple netfilter hooks on one interface). Those individual
chains can then jump to the common chain for stateful connection filtering,
returning to the original chain for further rule processing if no action is
taken on the packet.

The chain we will create is called ``CONN_FILTER`` and has three rules:

- A default action of ``return``, which returns the packet back to the original
chain if no action is taken.
- A rule to ``accept`` packets from established and related connections.
- A rule to ``drop`` packets from invalid connections.

.. code-block:: none
set firewall ipv4 name CONN_FILTER default-action 'return'
set firewall ipv4 name CONN_FILTER rule 10 action 'accept'
set firewall ipv4 name CONN_FILTER rule 10 state established
set firewall ipv4 name CONN_FILTER rule 10 state related
set firewall ipv4 name CONN_FILTER rule 20 action 'drop'
set firewall ipv4 name CONN_FILTER rule 20 state invalid
Then, we can jump to the common chain from both the ``forward`` and ``input``
hooks as the first filtering rule in the respective chains:

.. code-block:: none
set firewall ipv4 forward filter rule 10 action 'jump'
set firewall ipv4 forward filter rule 10 jump-target CONN_FILTER
set firewall ipv4 input filter rule 10 action 'jump'
set firewall ipv4 input filter rule 10 jump-target CONN_FILTER
Option 2: Per-Hook Chain
^^^^^^^^^^^^^^^^^^^^^^^^

Alternatively, instead of configuring the ``CONN_FILTER`` chain described above,
you can take the more traditional stateful connection filtering approach by
creating rules on each hook's chain:

.. code-block:: none
set firewall ipv4 forward filter rule 5 action 'accept'
set firewall ipv4 forward filter rule 5 state established
set firewall ipv4 forward filter rule 5 state related
set firewall ipv4 forward filter rule 10 action 'drop'
set firewall ipv4 forward filter rule 10 state invalid
set firewall ipv4 input filter rule 5 action 'accept'
set firewall ipv4 input filter rule 5 state established
set firewall ipv4 input filter rule 5 state related
set firewall ipv4 input filter rule 10 action 'drop'
set firewall ipv4 input filter rule 10 state invalid
Block Incoming Traffic
----------------------

Now that we have configured stateful connection filtering to allow traffic from
established and related connections, we can block all other incoming traffic
addressed to our local network.

Create a new chain (``OUTSIDE-IN``) which will drop all traffic that is not
explicity allowed at some point in the chain. Then, we can jump to that chain
from the ``forward`` hook when traffic is coming from the ``WAN`` interface
group and is addressed to our local network.

.. code-block:: none
set firewall ipv4 name OUTSIDE-IN default-action 'drop'
set firewall ipv4 forward filter rule 100 action jump
set firewall ipv4 forward filter rule 100 jump-target OUTSIDE-IN
set firewall ipv4 forward filter rule 100 inbound-interface group WAN
set firewall ipv4 forward filter rule 100 destination group network-group NET-INSIDE-v4
We should also block all traffic destinated to the router itself that isn't
explicitly allowed at some point in the chain for the ``input`` hook. As
we've already configured stateful packet filtering above, we only need to
set the default action to ``drop``:

.. code-block:: none
set firewall ipv4 input filter default-action 'drop'
Allow Management Access
---------------------------

We can now configure access to the router itself, allowing SSH
access from the inside/LAN network and rate limiting SSH access from the
outside/WAN network.

First, create a new dedicated chain (``VyOS_MANAGEMENT``) for management
access, which returns to the parent chain if no action is taken. Add a rule
to accept traffic from the ``LAN`` interface group:

.. code-block:: none
set firewall ipv4 name VyOS_MANAGEMENT default-action 'return'
Configure a rule on the ``input`` hook filter to jump to the ``VyOS_MANAGEMENT``
chain when new connections are addressed to port 22 (SSH) on the router itself:

.. code-block:: none
set firewall ipv4 input filter rule 20 action jump
set firewall ipv4 input filter rule 20 jump-target VyOS_MANAGEMENT
set firewall ipv4 input filter rule 20 destination port 22
set firewall ipv4 input filter rule 20 protocol tcp
Finally, configure the ``VyOS_MANAGEMENT`` chain to accept connection from the
``LAN`` interface group while limiting requests coming from the ``WAN``
interface group to 4 per minute:

.. code-block:: none
set firewall ipv4 name VyOS_MANAGEMENT rule 15 action 'accept'
set firewall ipv4 name VyOS_MANAGEMENT rule 15 inbound-interface group 'LAN'
set firewall ipv4 name VyOS_MANAGEMENT rule 20 action 'drop'
set firewall ipv4 name VyOS_MANAGEMENT rule 20 recent count 4
set firewall ipv4 name VyOS_MANAGEMENT rule 20 recent time minute
set firewall ipv4 name VyOS_MANAGEMENT rule 20 state new
set firewall ipv4 name VyOS_MANAGEMENT rule 20 inbound-interface group 'WAN'
set firewall ipv4 name VyOS_MANAGEMENT rule 21 action 'accept'
set firewall ipv4 name VyOS_MANAGEMENT rule 21 state new
set firewall ipv4 name VyOS_MANAGEMENT rule 21 inbound-interface group 'WAN'
Allow Access to Services
------------------------

Here we're allowing the router to respond to pings. Then, we can allow access to
the DNS recursor we configured earlier, accepting traffic bound for port 53 from
all hosts on the ``NET-INSIDE-v4`` network:

.. code-block:: none
set firewall ipv4 input filter rule 30 action 'accept'
set firewall ipv4 input filter rule 30 icmp type-name 'echo-request'
set firewall ipv4 input filter rule 30 protocol 'icmp'
set firewall ipv4 input filter rule 30 state new 'enable'
set firewall ipv4 input filter rule 30 state new
If you wanted to enable SSH access to your firewall from the outside/WAN
interface, you could create some additional rules to allow that kind of
traffic.
set firewall ipv4 input filter rule 40 action 'accept'
set firewall ipv4 input filter rule 40 destination port '53'
set firewall ipv4 input filter rule 40 protocol 'tcp_udp'
set firewall ipv4 input filter rule 40 source group network-group NET-INSIDE-v4
These rules allow SSH traffic and rate limit it to 4 requests per minute. This
blocks brute-forcing attempts:
Finally, we can now configure access to the services running on this router,
allowing all connections coming from localhost:

.. code-block:: none
set firewall ipv4 input filter rule 40 action 'drop'
set firewall ipv4 input filter rule 40 inbound-interface name 'eth0'
set firewall ipv4 input filter rule 40 destination port '22'
set firewall ipv4 input filter rule 40 protocol 'tcp'
set firewall ipv4 input filter rule 40 recent count '4'
set firewall ipv4 input filter rule 40 recent time 'minute'
set firewall ipv4 input filter rule 40 state new 'enable'
set firewall ipv4 input filter rule 41 action 'accept'
set firewall ipv4 input filter rule 41 destination port '22'
set firewall ipv4 input filter rule 41 protocol 'tcp'
set firewall ipv4 input filter rule 41 state new 'enable'
set firewall ipv4 input filter rule 50 action 'accept'
set firewall ipv4 input filter rule 50 source address 127.0.0.0/8
Commit changes, save the configuration, and exit configuration mode:

Expand All @@ -192,14 +329,13 @@ Commit changes, save the configuration, and exit configuration mode:
vyos@vyos# exit
vyos@vyos$
Hardening
#########

Especially if you are allowing SSH remote access from the outside/WAN
interface, there are a few additional configuration steps that should be taken.

Replace the default `vyos` system user:
Replace the default ``vyos`` system user:

.. code-block:: none
Expand Down

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