HOWTO: OPNsense and Wireguard to AirVPN

[Sj0rs 2]

This HOWTO describes how to connect to AirVPN with a Wireguard VPN tunnel from OPNsense.
This is the first draft of this howto, i might add (more) screenshots later on.
 

• Version: 0.1
• Date: 20231029

What we are going to achieve

1. We'll create a single Wireguard VPN Tunnel, IPv4 Only.
2. Traffic to the tunnel will be NATted

Requirements

1. OPNsense firewall is up-and-running and updated. This howto is based on version 23.7.7_1
2. You have basic knowledge on using OPNsense i.e. firewall rules, NAT, routing, gateways and aliases.
3. AirVPN Premium Access

Step 1. Information gathering
We'll grab some info that we need to configure the Wireguard Tunnel.

1. Go to the Client Area.
2. Got to VPN Devices.
3. Add a device or edit your existing device.
4. Note your Public Key and IPv4 under the heading "Wireguard"
5. Go back to the Client Aerea.
6. Go to Config Generator
7. Select "router" under "Choose your OS"
8. Select "Wireguard under "Choose protocols"
9. Select your country under "By Countries". I selected Netherlands
10. Scroll way down and download your config.

This is an example of a Wireguard config:
(the keys and IP are random and will not work, use your own)
 

[Interface]
Address = 10.45.95.123/32
PrivateKey = X72xgdx23XDomnSXmcy#S4Jc#9Y5G*vU$wg^n499yn6
MTU = 1320
DNS = 10.128.0.1

[Peer]
PublicKey = VTSQ77Uk4^&RY4h%S$#9h8PR2T&xyya&yPTtk6oD^m$
PresharedKey = b7&&7bntmCS5q%&4J*mSKBAUvV4XEqHerwscvbappXQ
Endpoint = nl3.vpn.airdns.org:1637
AllowedIPs = 0.0.0.0/0
PersistentKeepalive = 15

Step 2. Create the Tunnel configuration
Peer configuration:

1. in OPNsense go to VPN|Wireguard|Settings|Peers.
2. Create a peer with the following information:
   1. Name: wg_airvpn_<country code>. mine is called wg_airvpn_nl
   2. Public key: <PublicKey under heading [Peer] of your generated WG Config>
   3. Pre-shared key <presharedKey under heading [Peer] of your generated WG Config>
   4. Allowed IP's: 0.0.0.0/0
   5. Endpoint Address: <Endpoint under heading [Peer] of your generated WG Config>
   6. Endpoint port: 1637 (default port)
   7. Keepalive interval: 15 (default interval)

Instance configuration:

1. in OPNsense go to VPN|Wireguard|Settings|Instances
2. Create an instance with the following information:
   1. Enable Advanced Mode.
   2. Name: <Endpoint Name i.e. nl.vpn.airdns.org>
   3. Public Key: <Public Key as noted with step 1.4>
   4. Private Key: <PrivateKey under heading [Interface] of your generated WG Config>
   5. Listen Port: 1637
   6. MTU: 1320
   7. Tunnel Address: <Address including /32 under harding [Interface] of your generated WG Config>
   8. Peers: <select peer that you created with step 2.2>
   9. Disable routes: Enabled.

Step 3. Make an exception on your WAN interface

1. in OPNsense go to Firewall|Rules
2. Select your WAN interface, mine is called WAN_PPPOE
3. Create a Pass rule for IPv4/UDP port 1647 to your WAN-address.

Step 4. Assign Wireguard Interface

1. in OPNsense go to Interfaces|Assignments
2. You'll find a "wg1(Wireguard - nl.vpn.airdns.org)" (or similiar) interface.
3. bind it to an interface with a name of your choice. mine is called WAN_WG1 as is is the first site-to-site Wireguard tunnel on my WAN interface.

Step 5. Create a gateway.
Remember we disabled the routes for the WG instance configuration? Because of that we need to create a gateway.

1. In OPNsense go to System|Gateways|Single
2. Add a Gateway with the following information:
   1. Name: WAN_WG_GW
   2. Description: Interface WAN_WG1 Gateway
   3. Interface: Select WAN_WG1 as created in step 4.
   4. Address Family: IPv4
   5. IP address: Dynamic (leave empty)
   6. Far Gateway: Enabled (this i am not sure of but for now i'm happy it works)
   7. Disable Gateway Monitoring: enabled

Step 6. Aliases
We set up some aliases. This will make it more easy to redirect some hosts or networks to the Wireguard tunnel.

1. in OPNsense, go to Firewall|Aliases
2. Create host entries for the specific hosts you'll redirect
3. Create network entries for the specific network(s) you'll redirect.
4. Create a Network Group Entry with the host and network entries to group them together. My alias is called networkgroup_wireguard

Step 7. Create Outbound NAT for Wireguard.
(In my setup, i use Manual Outbound Rule Generation because i like to have control)

1. In OPNsense go to Firewall|NAT|Outbound
2. Create a new Outbound NAT rule with the following information:
   1. Interface: WAN_WG1
   2. TCP/IP version: IPv4
   3. Protocol: Any
   4. Source Address: <alias networkgroup_wireguard from step 6>
   5. Translation /target WAN_WG1 address
   6. Description: Wireguard VPN Outbound NAT rule

Step 8. Create Outbound Redirect rule.
In this example we create 2 rules on our LAN interface, one for redirecting to WG, the other to prevent leaks.

1. In OPNsense go to Firewall|Rules
2. Select your LAN interface
3. add an outbound Pass rule:
   1. Action: Pass
   2. Source: Networkgroup_wireguard
   3. Destination: Any (in my case i use an inverted network group called networkgroup_local where all my local vlans are grouped together)
   4. Gateway: WAN_WG1_GW (the gateway you created in step 5.)
4. Add an outbound block rule below that:
   1. Action: Block
   2. Source: Networkgroup_wireguard
   3. Destination: Any
   4. Gateway: default

Your WG VPN tunnel should now work. Test with https://ipleak.net

The following steps are more advanced and i'm still finetuning/experimenting with the settings. your experience may vary.

Step 9. Prevent VPN leakage
I'm new to OPNsense and i am not sure what the default setting is, but from my pfSense experience i know the following setting is important when you want to make sure your VPN does not leak when for instance the tunnel is down.

1. In OPNsense go to Firewall|Settings|Advanced
2. Under "Gateway Monitoring" enable "Skip Rules when gateway is down"

Step 10. MTU/MSS optimization
For now i have set thte MTU according to the default setting of AirVPN. I want it to be higher but for now i'm just happy it works.
My settings are as follows:

1. In the properties of the WAN_WG1 interface i set the MTU to 1320 and the MSS to 1280.
2. I created a normalize rule (Firewall|Settings|Normalization) with the following settings. this should enable me to clamp the MSS to 1280 for the wireguard group but leave the MSS to the desired setting (1452) as defined on my LAN interface for the rest of the hosts on my LAN;
   1. Interface: LAN
   2. Direction, Protocol: Any
   3. Source: networkgroup_wireguard
   4. Max MSS: 1280

 

[OpenSourcerer 1360]

Guides are always appreciated, thank you for the time you invested into it. Screenshots would be a blast.

[OPN-UserGuide 1]

Hey, pictures would make this post indeed so much better.

So, I have done it and posted below. Please note the following:

 

1. My OPNsense Firewall is "clean" I did a factory reset before conducting the steps and completing the guide.
2. For simplicity, I copy and pasted most of the Text but added it with the missing pictured and did fix where I believe it was necessary. All Credits for this goes to the original poster @Sj0rs
3. I configure OPNsense from the WAN interface. To do this, I did the following steps as a preparation before this guide.

Disclaimer

In general, DO NOT TRUST ME ! I'm not a security expert. I do not know what I'm doing here !

Preparation (not required if you access the firewall from LAN)

Some advice here… Opening the WAN interface to allow administration is not good ! I am doing this because the firewall sits in my private LAN, and I'm not doing any port forwarding on my main router ! If your firewall is connected directly to the internet, do not do this !
Again, in general, DO NOT TRUST ME ! I'm not a security expert. I do not know what I'm doing here !

Now that you know it…

1. Deselect "Block private networks" and "Block bogon networks" in Interfaces → WAN. After doing so: hit save and "Apply changes".


2. Select "Disable reply-to" in Firewall → Settings → Advanced. Hit save at the end.


3. Add incoming WAN rule to allow administration. Go to Firewall → Rules → WAN

Add a TCP rule from "WAN net" to "This Firewall" on HTTPs.

Step 1. Information gathering.

We'll grab some info that we need to configure the WireGuard Tunnel.

1. Go to the Client Area.
2. Got to VPN Devices.
3. Add a device or edit your existing device.
4. Note your Public Key and IPv4 under the heading "WireGuard"
5. Go back to the Client Area.
6. Go to Config Generator
7. Select "router" under "Choose your OS"
8. Select "WireGuard under "Choose protocols"
9. Select your country under "By Countries". I selected Netherlands
10. Scroll way down and download your config.

This is an example of a WireGuard config:
(the keys and IP are random and will not work, use your own)

[Interface]
Address = 10.10.10.10/32
PrivateKey = X72xgdx23XDomnSXmcy#S4Jc#9Y5G*vU$wg^n499yn6
MTU = 1320
DNS = 10.128.0.1

[Peer]
PublicKey = VTSQ77Uk4^&RY4h%S$#9h8PR2T&xyya&yPTtk6oD^m$
PresharedKey = b7&&7bntmCS5q%&4J*mSKBAUvV4XEqHerwscvbappXQ
Endpoint = nl3.vpn.airdns.org:1637
AllowedIPs = 0.0.0.0/0
PersistentKeepalive = 15

Step 2. Create the Tunnel configuration.

Pre Configuration — Install WireGuard plugin

0.1 Go to System → Firmware → Plugins and install the "os-wireguard" plugin.

Peer configuration:

1. in OPNsense go to VPN → WireGuard → Settings → Peers.
2. Create a peer with the following information:
   1. Name: wg_airvpn_<country code>. Mine is called wg_airvpn_nl
   2. Public key: <PublicKey under heading [Peer] of your generated WG Config>
   3. Pre-shared key <presharedKey under heading [Peer] of your generated WG Config>
   4. Allowed IP's: 0.0.0.0/0
   5. Endpoint Address: <Endpoint under heading [Peer] of your generated WG Config>
   6. Endpoint port: 1637 (default port)
   7. Keepalive interval: 15 (default interval)

Click "Save" and you should see the below

Instance configuration:

1. in OPNsense go to VPN → Wireguard → Settings → Instances
2. Create an instance with the following information:
   1. Enable Advanced Mode. (upper left corner)
   2. Name: <Endpoint Name i.e. nl.vpn.airdns.org>
   3. Public Key: <Public Key as noted with step 1.4>
   4. Private Key: <PrivateKey under heading [Interface] of your generated WG Config>
   5. Listen Port: 1637
   6. MTU: 1320
   7. Tunnel Address: <Address including /32 under harding [Interface] of your generated WG Config>
   8. Peers: <select peer that you created with step 2.2>
   9. Disable routes: Enabled.

Hit the "Save" button.


 

Enable WireGuard configuration

Go to VPN → Wireguard → Settings → General and click on "Enable WireGuard"



Hit "Apply"

Step 3. Make an exception on your WAN interface

1. in OPNsense go to Firewall → Rules → WAN
2. On the WAN interface, default is called WAN, create a Pass rule for IPv4/UDP port 1647 to your WAN-address.

Scroll down and hit "Save". It should look like this:



 

Step 4. Assign WireGuard Interface

 

 

 

1. in OPNsense go to Interfaces → Assignments
2. You'll find a "wg1(WireGuard - nl.vpn.airdns.org)" (or similar) interface.
3. bind it to an interface with a name of your choice. Mine is called WAN_WG1 as is the first site-to-site WireGuard tunnel on my WAN interface.

 

 

Click the "Add" button

 

 

Enable the Interface

Interfaces → Assignments → WAN_WG1

1. Enable: Enable the Interface.
2. Dynamic gateway policy: Selected (I found it's not working without this. Not sure why)

No further configuration required. Ensure the "Block private networks" and "Block bogon networks" options are not selected, as shown below.

 

 

Hit "Save" and "Apply changes".

Step 5. Create a gateway.

Remember, we disabled the routes for the WG instance configuration? Because of that, we need to create a gateway.

 

1. In OPNsense go to System → Gateways → Single
2. Add a Gateway with the following information:
   1. Name: WAN_WG_GW
   2. Description: Interface WAN_WG1 Gateway
   3. Interface: Select WAN_WG1 as created in step 4.
   4. Address Family: IPv4
   5. IP address: Dynamic (leave empty)
   6. Far Gateway: Enabled (this I am not sure of, but for now I'm happy it works)
   7. Disable Gateway Monitoring: enabled

 

 

Hit the "Save" button.

 

Step 6. Aliases

I did not use aliases in my setup. I use the default LAN network group.

 

Step 7. Create Outbound NAT for WireGuard.

(In my setup, I use Manual Outbound Rule Generation because I like to have control)

 

1. In OPNsense go to Firewall → NAT → Outbound
2. Click "Manual outbound NAT rule generation" then "Save" then "Apply changes".

 

1. Create a new Outbound NAT rule with the following information:
   1. Interface: WAN_WG1
   2. TCP/IP version: IPv4
   3. Protocol: Any
   4. Source Address: LAN net (or use alias)
   5. Translation /target WAN_WG1 address
   6. Description: WireGuard VPN Outbound NAT rule

 

 

 

Click the "Save" button and then the "Apply changes" button.

 

 

Step 8. Create Outbound Redirect rule.

In this example we create 2 rules on our LAN interface, one for redirecting to WG, the other to prevent leaks.

1. In OPNsense go to Firewall → Rules → LAN
2. add an outbound Pass rule:
   1. Action: Pass
   2. Source: LAN net (or use alias)
   3. Destination: Any
   4. Gateway: WAN_WG_GW (the gateway you created in step 5.)

 

 

Hit the "Save" button.

 

1. Add an outbound block rule below that:
   1. Action: Block
   2. Source: LAN net
   3. Destination: Any
   4. Gateway: default

 

 

 

Hit the "Save"  button and then the "Apply changes" button.

 

You need to disable the existing Default rules by clicking on the green arrow then "apply changes" again. (I have removed them as we do not need them anyway)

 

 

Step 9. Prevent DNS leaks

1. Create an alias to use all available AirVPN servers. Firewall → Aliases
2. Click add
3. Enable: selected
4. Name: VPN_DNS
5. Content: 10.4.0.1 128.0.1 10.5.0.1 10.7.0.1

Click Save
 

1. Create NAT port forward rule. Firewall → NAT → Port Forward
2. Click Add
3. Interface: LAN
4. TCP/IP Version: IPv4
5. Protocol: TCP/UP (DNS traffic is usually UDP, but I thought it's better to do it like this)
6. Source: LAN net
7. Destination: This Firewall
8. Destination port range: DNS
9. Redirect target IP: VPN_DNS (the alias we created in 9.1)
10. Redirect target port: DNS
11. NAT reflection: Disable
12. Filter rule association: None

Hit "Save", then "Apply changes".





Your WG VPN tunnel should now work. Test with https://ipleak.net
 

Step 10. Port forwarding (Optional)

If you need port forwarding for something, make sure It's configured in your AirVPN Member settings !
 

1. Firewall → Rules → WAN_WG1 →  Add
2. Action: Pass
3. Interface: WAN_WG1
4. Direction: In
5. Protocol: select your protocol
6. Source: any (or if you can define it, do this here)
7. Destination: Single host or Network and the IP of the device
8. Destination port range: select the port (range)
9. reply-to: WAN_WG1_GW (this is very Important!)

Hit "Save", then "Apply changes".
 

1. Firewall → NAT→ Port Forward →  Add
2. Interface: WAN_WG1
3. Protocol: Same as in 10.5
4. Destination: WAN_WG1 address
5. Destination port range: Same as in 10.8
6. Redirect target IP: Same as in 10.7
7. Redirect target port: Same as in 10.8

Hit "Save", then "Apply changes".

That's it for port forwarding. Test the setting.
 

Let me know if something is not correct or clear.

 

END of the Guide... Everything below here can be ignored. It seems the board software adds all the pictures I have added again to the bottom of the post, so ignore everything below here ! Thanks

 

Edited ... by OPN-UserGuide
Update #6. Added port forwarding

[kaymio 7]

Thank you for this HowTo. Seems to work great, though running just a few minutes and only checked for leaks.

Did you put this in a Network Security Forum to get it checked?

What would be needed to also enable IPv6?