OpenVPN between Mikrotik and OpenWRT

This is a page full of details, for the intro and how to set up Windows and Linux clients, see OpenVPN.

I am writing this while testing with three virtual machines on a Mac. Once I have the steps down, I will be transferring everything over to a Buffalo WZR WiFi access point running OpenWRT 14.xx and a Mikrotik RB750 running RouterOS 5.27.

I am running my virtual machines on VirtualBox. I use images downloaded from OpenWRT and Mikrotik and install them into very minimal setups. This is handy, they boot FAST and I don't risk cutting myself off from the remote end as I do tests and experiment.

The main reasons I chose to use OpenVPN over other options (today) are:

1. I can directly route packets so I don't need to mess with NAT at one end as with PPTP
2. My endpoint is hiding behind several layers of access points and routers that I don't control. OpenVPN works fine in this case.

The virtual network

Plover (Macintosh)
   192.168.56.1

    LAN (This will be the LAN in my house)

   192.168.56.101
VM1 = Router #1, OpenWRT Barrier Breaker
     76.0.0.1

     Internet

     76.0.0.2
VM2 = Router #2, Mikrotik RouterOS 6.23
    192.168.2.1

    REMOTE LAN (this will be the CDS OFFICE LAN)

   192.168.2.2
VM3 = Remote Debian server

Creating the certificate and key files

Using easy-rsa DID NOT WORK. I don't know why. I used the instructions on this page: http://wiki.mikrotik.com/wiki/Manual:Create_Certificates#Generate_certificates_with_dOpenSSL

I used "CDS Wireless CA" for the ca.crt CN and "CDS Wireless" for the client and server certificate CN.

# server
openssl genrsa -des3 -out ca.key 4096
openssl req -new -x509 -days 3650 -key ca.key -out ca.crt
openssl genrsa -des3 -out server.key 4096
openssl req -new -key server.key -out server.csr
openssl x509 -req -days 3650 -in server.csr -CA ca.crt -CAkey ca.key -set_serial 01 -out server.crt

# client
CLIENT="rb433"
openssl genrsa -des3 -out $CLIENT.key 4096
openssl req -new -key $CLIENT.key -out $CLIENT.csr
openssl x509 -req -days 3650 -in $CLIENT.csr -CA ca.crt -CAkey ca.key -set_serial 01 -out $CLIENT.crt

The OpenWRT router

Refer to http://wiki.openwrt.org/doc/howto/vpn.openvpn I am not going to copy all the instructions here, just go look at that page now.

ssh [email protected]
opkg update
opkg install openvpn-openssl
mkdir /etc/openvpn
mv /tmp/openwrt.* /tmp/ca.crt /etc/openvpn

A Debian client

When I could not get the OpenWRT and Mikrotik devices to talk, I backed off on the OpenWrt side and used the Debian Server as an OpenVPN client.

The Mikrotik router

Refer to same Mikrotik page as mentioned above, http://wiki.mikrotik.com/wiki/OpenVPN

Import the three files transferred in the "create" section above.

/certificate
import file-name=cdswireless.crt
import file-name=cdswireless.key
import file-name=ca.crt
set 0 name=cdswireless
set 1 name=ca

# This will let you have many OpenVPN clients
/ip pool add name=ovpn-pool ranges=10.10.10.2-10.10.10.50

/ppp profile 
add change-tcp-mss=default local-address=10.8.0.1 \
name="ovpn_profile" only-one=default remote-address=ovpn-pool \
use-compression=default use-encryption=required use-vj-compression=default
/ppp secret 
add caller-id="" comment="" disabled=no limit-bytes-in=0 \
limit-bytes-out=0 name="ovpn" password="password" routes="" service=any

# If you don't already have these defined, 
/ip address
add address=192.168.4.253/24 comment="Management LAN" interface=ether1 network=192.168.4.0
add address=192.168.2.1/24 comment="CDS LAN" interface=ether2 network=192.168.2.0
add address=172.16.1.1/24 comment=Internet interface=ether3 network=172.16.1.0

/ip route
# This is how we really reach the Internet
add distance=1 gateway=192.168.4.254
add dst-address=10.8.0.0/24 gateway=10.8.0.1 comment="OVPN"

I think when I "enable" this then port 1194 should light up? Hopefully on the Internet interface since that's where the OpenVPN client attempting to connect.

/interface ovpn-server server 
set auth=sha1,md5 certificate=cdswireless \
cipher=blowfish128,aes128,aes192,aes256 default-profile=ovpn_profile \
enabled=yes keepalive-timeout=disabled max-mtu=1500 mode=ip netmask=27 \
port=1194 require-client-certificate=no

# I have the firewall turned off for testing right now.
# When I activate the firewall I will need this
/ip firewall filter 
add action=accept chain=input comment="OpenVPN" disabled=no dst-port=1194 protocol=udp

The "remote" server

I have a generic Debian server installed already in a VirtualBox machine, so I used it as the far end of my network to allow me to test connectivity through the two routers.

Tests

Start the client

/etc/init.d/openvpn start
cat /tmp/openvpn.log
ifconfig tun0

Make sure you can reach each of the routers and the Debian server from the Mac, and that you can reach each of the routers and the Mac from the Debian server.