Setup SSL VPN Road Warrior

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Road Warriors are remote users who need secure access to the companies infrastructure. OPNsense uses OpenVPN for its SSL VPN Road Warrior setup and offers OTP (One Time Password) integration with standard tokens and Googles Authenticator.

Tip

Did you know that OPNsense offers two-factor authentication throughout the entire system? See for more information: Two-factor authentication

The main advantages of using SSL VPN for Road Warriors instead of IPsec are:

  • Easy setup on almost all mobile clients using OPNsense’s Client Configuration Export.
  • Fine grained access control by using multiple servers or Client Specific Overrides.
  • No issues with NAT without NAT-T

With this how-to we’ll show you how to configure OPNsense’s SSL VPN for road warriors and give you configuration examples for:

  • Two Factor Authentication (2FA)
  • Multi Factor Authentication ( Client Certificate + Password + OTP )
  • Client configuration on Windows, OSX, iOS and Android

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 the Interfaces->[WAN] and uncheck “Block private networks”. (Dont forget to save and apply)

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Sample Setup

For the sample configuration we configure OPNsense

Company Network with Remote Client

Company Network

Hostname fw1
WAN IP 172.18.0.129
LAN IP 192.168.1.1/24
LAN DHCP Range 192.168.1.100-192.168.1.200
SSL VPN Clients 10.10.0.0/24

Step 0 - Preparation

For our example we will use two factor authentication (2FA) and multi factor authentication. So before we start with the SSL VPN configuration we will need an TOTP server and a valid signing certificate authority.

For completeness of this how-to we will also prepare a user.

Configure TOTP server

To configure a Time based One Time Password server go to System->Access->Servers and click on Add server in the top right corner of the form.

Tip

You can also use the quick-search to jump right into the the Access Server configuration. Try it by typing Ac… and see for yourself:

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Now first change the Type to Local + Timebased One time Password Enter a Descriptive name such as TOTP VPN Access Server

For our example we leave everything else default as we will be using Google’s Authenticator and the defaults are correct for that.

When using other tokens you may need to change the Token length.

Click Save to add the new server.

Add Certificate Authority

The VPN server needs a certificate authority to sign client or server certificates.

To setup a new certificate authority go to System->Trust->Authorities and click on add or import ca in the top right corner of the form.

For our example we will use the following setting:

Descriptive name SSL VPN CA
Method Create an internal Certificate Authority
Key length (bits) 4096
Digest Algorithm SHA512
Lifetime (days) 365
Country Code : NL
State or Province : ZH
City : Middelharnis
Organization : OPNsense
Email Address : spam@opnsense.org
Common Name : internal-sslvpn-ca

Click Save to add the new Certificate Authority.

Create a Certificate

After creating the Authority we will also need a certificate. To create a new certificate, go to System->Trust->Certificates and click add or import certificate in the upper right corner of the form.

Fill in the form with (leave the rest default):

Method Create an internal Certificate
Descriptive name SSLVPN Server Certificate
Certificate authority SSL VPN CA
Type Server Certificate
Key length (bits) 4096
Digest Algorithm SHA512
Lifetime (days) 365
Country Code : NL
State or Province : ZH
City : Middelharnis
Organization : OPNsense
Email Address : spam@opnsense.org
Common Name : SSLVPN Server Certificate

Click Save to create the certificate.

Adding a User

To add a new user go to System->Access->Users and click on the plus sign in the lower right corner of the form.

Creating a user will be done in two steps, the first one is adding a basic user with a username, password, TOTP seed and user certificate. The second step (after saving) will be to activate the generated OTP seed with a Google Authenticator compatible app.

For the first step we enter:

Username Donald
Password (2x) S3cr3tP@ssw0rd
Full name Donald Duck
Certificate True
OTP seed True
Click Save and you will be redirected to create the User Certificate. Fill in the Certificate form with the following for our example (leave anything not listed on its presented defaults):
Method Create an internal Certificate
Descriptive Name Leave default (Donald)
Certificate authority SSL VPN CA
Type Client Certificate
Key length 4096
Digest Algorithm SHA512

Click Save and you will be redirected to the User page. Now we will activate your newly created seed with your Google Authenticator compatible app. To do so click in the Click to unhide button in the OTP QR code row and you will get a QR code to scan with your smartphone. See also: Configure 2FA TOTP & Google Authenticator


Step 1 - Add SSL Server

Adding a new SSL VPN server is relatively simple. We’ll start by adding one that uses our two factor authentication. This setup offers a good protection and it is easy to setup on the clients as each client can use the same configuration.

Go to VPN->OpenVPN->Servers and click on add server in to top right corner of the form.

For our example will use the following settings:

Note

The setting Hardware Crypto is not used for new systems equipped with AESNI, when the aesni module is loaded it will be used automatically.

Server Mode Remote Access (User Auth)
Backend for authentication TOTP VPN Access Server
Protocol UDP
Device Mode tun
Interface WAN
Local port 1194
Description My SSL VPN Server
TLS Authentication Leave both on enabled (checked)
Peer Certificate Revocation List N/A
Server Certificate SSLVPN Server Certificate (CA: SSL VPN CA)
DH Parameters Length 4096
Encryption algorithm AES-256-CBC (256-bit)
Auth Digest Algorithm SHA512 (512-bit)
Hardware Crypto No Hardware Crypto Acceleration
Certificate Depth One (Client+Server)
IPv4 Tunnel Network 10.10.0.0/24
IPv6 Tunnel Network Leave Empty
Redirect Gateway Leave Unchecked
IPv4 Local Network/s 192.168.1.0/24
IPv6 Local Network/s Leave Empty
IPv4 Remote Network/s Leave Empty
IPv6 Remote Network/s Leave Empty
Concurrent connections Leave Empty
Compression Enabled with Adaptive Compression
Type-of-Service Leave Unchecked
Duplicate Connections Leave Unchecked
Disable IPv6 Checked
Dynamic IP Leave Unchecked
Address Pool Leave Checked
Topology Leave Unchecked
DNS Default Domain Leave Unchecked
DNS Servers Leave Unchecked
Force DNS cache update Leave Unchecked
NTP Servers Leave Unchecked
NetBIOS Options Leave Unchecked
Client Management Port Leave Unchecked
Renegotiate time 0

Note

Renegotiate time is used to renegotiate data channel key after n seconds (default=3600).When using a one time password, be advised that your connection will automatically drop because your password is not valid anymore.Set to 0 to disable, remember to change your client when changed later.

Click Save to add the new server.

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Step 2 - Firewall Rules

To allow SSL VPN client connections, we should allow access to the OpenVPN server port on the WAN interface. When using multiple servers we need to open up each port.

For our configuration we only use one server accessible on udp port 1194.

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Next we also need to allow traffic from the VPN clients to our LAN interface. For our example we will allow client to access anything on our local area network, however you may decide just to allow traffic to one or more servers.

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Step 3 - Export Client Configuration

Mac OSX & Windows

For Mac OSX & Windows users we recommend using Viscosity from Sparklabs (https://www.sparklabs.com/viscosity/). Viscosity is very easy to setup and use and works well on both platforms.

Go to VPN->OpenVPN->Client Export and select the newly created VPN server from the list. Leave everything default and Download the Viscosity Bundle from the list of export options under Client Install Packages.

Now on your Mac or Windows PC unpack the bundle and import the Viscosity.visc file. Double clicking it should be enough to get it imported. When asked for an application to open the file with search and select Viscosity.

Some sample screenshots (Mac OSX):

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Import Configuration

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Connect & login

In the password field enter your TOTP token first followed by your password.

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Connected

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Android

For Android users we recommend using OpenVPN for Android (https://play.google.com/store/apps/details?id=de.blinkt.openvpn) from Arne Schwabe.

Go to VPN->OpenVPN->Client Export and select the newly created VPN server from the list. Leave everything default and Download the inline Android configuration from the list of export options under Client Install Packages.

Import the hostname-udp-1194-ios-config.ovpn file into OpenVPN for Android. Clicking on the file should be enough to get it imported. When asked for an application to open the file with, select OpenVPN for Android.


iOS

For iOS users we recommend using OpenVPN Connect (https://itunes.apple.com/us/app/openvpn-connect/id590379981) from OpenVPN Technologies.

Go to VPN->OpenVPN->Client Export and select the newly created VPN server from the list. Leave everything default and Download the inline OpenVPN Connect configuration from the list of export options under Client Install Packages.

Import the hostname-udp-1194-andoroid-config.ovpn file into OpenVPN Connect. Clicking on the file should be enough to get it imported. When asked for an application to open the file with, select OpenVPN Connect.


Step 4 - Multi Factor Authentication

For two factor authentication you need the factors username/password and a token. OPNsense supports another layer, namely a user certificate. This means that every user will be uniquely identified by the user certificate. In this case the multi factors are:

  • User certificate
  • Username/Password
  • Token (TOTP)

Go to VPN->OpenVPN->Servers and click on the pencil icon next to the server we just created to change the 2FA to multi factor authentication.

Now change Server Mode to Remote Access (SSL/TLS + User Auth) and leave everything else unchanged. Click Save on the bottom of the form.

Now when you go to the client exporter, you will see that each user is listed separately. In our case we see Donald listed. Exporting and importing this configuration works exactly the same as before, the only difference is that each user requires a User certificate and therefore their own configuration.

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