Sophos SG/XG Firewalls use OpenVPN to create Site To Site SSL VPN tunnels, but the configuration file is specific to Sophos firewalls. This can be converted to a normal ovpn file though.

Here is how you can manually convert the APC configuration file into an OVPN file.

Take now of these things in your apc file:

Block 1 is the client certificate:

-----BEGIN CERTIFICATE-----

-----BEGIN CERTIFICATE-----

Block 2 is the CA certificate:

-----BEGIN CERTIFICATE-----

-----BEGIN CERTIFICATE-----

Block 3 is the private key:

-----BEGIN PRIVATE KEY-----

-----END PRIVATE KEY-----

Block 4: there is also a username and password:

Just above the private key is the user:

Just below the private key is the password:

So now here is the ovpn file:

client
dev tun
proto tcp
remote insert hostname or IP of the firewall here 443
route remote_host 255.255.255.255 net_gateway
resolv-retry infinite
nobind
persist-key
persist-tun
auth-user-pass
cipher AES-128-CBC
auth SHA256
comp-lzo
route-delay 4
verb 3
reneg-sec 0
<cert>

Insert certificate here from Block 1

</cert>

<ca>

Insert certificate here from Block 2

</ca>

<key>

Insert private key from Block 3

</key>

Here is a short test with OpenVPN client on Windows. The password has to be inserted manually, but normally the tunnel gets initiated from a firewall/network appliance, in that case you should be able to insert username and password in the command line.