Adhesive Media Stuff - Configuring a VPN on FreeBSD using pipsecd

This is a mirror of a pipsecd document from adhesivemedia. When the server went down, I pulled this out of the google cache. This isnt my work.

I've had to setup two secure VPN's between FreeBSD boxes now. The first time I didn't document my steps -- figuring I'd remember :) -- which I didn't. I just finished setting up the second one and as it happened I also noticed several posts to c.u.b.f.m asking about setting up secure VPN's using FreeBSD so I thought I'd write up what I did. So, here it is:

A VPN (virtual private network) allows you to treat two physically separate networks as though they were on the same network. At least that's how I understand it. What's cool about this is that it allows my home network and my office network to appear to be one contiguous network allowing me to work from one or the other without a lot of differences.

I'm going to use the following fictitious networks to illustrate my steps. Below we have two separate networks whose gateways (or routers, or firewall/natd boxes ,etc.) are gw1 and gw2. Our goal is to make it appear to the machines on either LAN that it is one seamless network. Additionally we want any data that is transferred between the two networks to be secure (encrypted). We do that by setting up a secure tunnel.

(Note: In my case, gw1 is 3.4 and gw2 is 4.0. I believe there are other ways to do this using an all 4.0 solution, but that doesn' work for me) 
        ___________                                     ___________
        |         |                                     |         |
10.0.0.1-   gw1   -111.111.111.111 <---> 222.222.222.222-   gw2   -10.1.0.1
  (LAN) |         |   (Internet)           (Internet)   |         |  (LAN)
        |_________|                                     |_________| 
             |                                               | 
          10.2.0.1 <------------ encrypted -------------> 10.2.0.2
          (tunnel)                                        (tunnel)
Steps:
  1. Make sure that you have at least one tunnel device compiled into the kernel on both gw1 and gw2. In particular you want to make sure your kernel config has the following:
    pseudo-device tun 1
    If you're going to have multiple vpns (perhaps the office server will provide vpns for multiple employee's home networks) then you should increase 1 to something larger. Build the new kernel, install it, and make the devices.

  2. Install the pipsecd port on both machines. FreeBSD-3.4 will also install OpenSSL, 4.0 won't since it's already there. Nothing special needs to be done besides a "make install".

  3. On gw1 create /usr/local/etc/rc.d/pipsecd.sh with the following: 
    #!/bin/sh

/usr/local/sbin/pipsecd &
#
# For some reason 4.0 complains if we access the tun device
# to soon after calling pipsecd.  Sleeping for a bit fixes that.
#
sleep 3
/sbin/ifconfig tun0 10.2.0.1 10.2.0.2 netmask 255.255.255.0
/sbin/route add -net 10.1.0.0 -netmask 255.255.255.0 10.2.0.2

  4. On gw2 create /usr/local/etc/rc.d/pipsecd.sh with the following: 
    #!/bin/sh

/usr/local/sbin/pipsecd &
#
# For some reason 4.0 complains if we access the tun device
# to soon after calling pipsecd.  Sleeping for a bit fixes that.
#
sleep 3
/sbin/ifconfig tun0 10.2.0.2 10.2.0.1 netmask 255.255.255.0
/sbin/route add -net 10.0.0.0 -netmask 255.255.255.0 10.2.0.1

  5. On gw1 create /usr/local/etc/ipsec/pipsecd.conf with the following. 'CCCCC', 'DDDDD', 'AAAAA', 'BBBBB' can be changed to any string of characters consisting of valid hex (ie. 0123456789ABCDEF) as long as you change them in both files. 
    sa ipesp spi=1000 auth=hmac-md5-96 akey=CCCCC enc=blowfish_cbc ekey=AAAAA dest=222.222.222.222
sa ipesp spi=1000 auth=hmac-md5-96 akey=DDDDD enc=blowfish_cbc ekey=BBBBB
if /dev/tun0 local_spi=1000 remote_spi=1000

  6. On gw2 create /usr/local/etc/ipsec/pipsecd.conf with the following: 
    sa ipesp spi=1000 auth=hmac-md5-96 akey=CCCCC enc=blowfish_cbc ekey=AAAAA
sa ipesp spi=1000 auth=hmac-md5-96 akey=DDDDD enc=blowfish_cbc ekey=BBBBB dest=111.111.111.111
if /dev/tun0 local_spi=1000 remote_spi=1000

  7. That's it. Now, on both machines, start pipsecd by typing (as root):
    sh /usr/local/etc/rc.d/pipsecd.sh
  8. At this point machines on either LAN should be able to connect to machines on the other LAN -- that is, host 10.0.0.2 should be able to ping 10.1.0.2 provided that they are both on.

    For some reason the gateways themselves will not be able to talk to each other. When I setup my first VPN they could, but I must have changed something by accident and now they can't. But it's not that big of a deal because you shouldn't be connecting from/to your gateways very much anyway.


Notes: