I have been running a four-M0n0wall VPN network for a while, using Pre-Shared
Key authentication. I really wanted to use RSA Signature authentication, but
the M0n0wall documentation is a bit sparse on how to do that. I have just
managed to get all my M0n0s working with RSA Signature authentication, so I
thought I would document how I did it. This is not the be-all-and-end-all of
certificate documentation, but it might help other folks get started.
Quick Start for RSA Signature Authentication
You will need to generate a certificate and a private key for each router.
You can do this with OpenSSL, and there are several tutorials on the web
about how to do this. A quicker way is to use the XCA program, from
Christian Hohnstaedt. It is available here
(http://sourceforge.net/projects/xca) as a *nix tarbal or a Windows exe file,
and is licensed under a BSD-like license.
First you need to create a Certification Authority (CA) key to use in signing
your certificates. Bring up XCA, and click on the "Private Keys" tab, then
click the "New Key" button. Give the key a name like "My Company Certificate
Authority". Keytype should be "RSA". The default keysize of 1024 is
probably about right.
Now click on the "Certificates" tab, and click the "New Certificate" button.
On the "Create x509 Certificate" page, select "Create a self signed
certificate with the serial 1". Click on the "Subject" tab. For "Internal
name" and "Common name", use something like "My Company Certificate
Authority". Fill in the other fields at the top of the page (Country code,
State or Province -- spelled out, by the way -- Locality, Organisation,
Organ. unit, E-mail address). Click on the "Extensions" tab. Set the type
to "Certification Authority". Uner "Key Identifier", select "Subject Key
Identifier". Click on the "Key Usage" tab and select "Certificate Sign".
Click the "OK" button.
Now that you have a certificate signing certificate, you can make certificates
for all of your routers.
In XCA, click on the "private keys" tab, then click the "New Key" button.
Give the key a name that lets you remember which router it goes to. Keytype
should be "RSA", and the default of 1024 bit keysize is probably about right.
Click the "Create" button. Do this for each router.
Click on the "Certificates" tab, then click the "New Certificate" button. On
the "Source" page, select "Use this Certificate for signing", and select your
CA certificate. (This value should be in the field by default.) On
the "Subject" page, enter the information for your router. I use the router
name as the Internal Name and Common Name. Click on the "Extensions" tab.
Set the type to "End Entity" and under "Key Identifier", select "Subject Key
Now comes the most important part. In the "subject alternative name" field,
put "IP:" followed by the IP address of the interface, for
example "IP:10.0.0.1". This must match the IP address of the interface that
the VPN goes over; if you have VPNs on the WAN interface, and VPNs to
internal routers on the LAN interface, you will need two separate
certificates. Click on "OK" to create your certificate. Repeat this for each
Now select each router certificate under the "Certificates" tab and click on
the "Export" button. Choose a file name. Select "PEM" for the export format
and click "OK".
Now click the "Private Keys" tab. Select the private key for each router, and
click on the "Export" button. Choose a file name. Select "PEM" for the
export format and click "OK". Keep in mind that the key files are the key to
the router's identity, so be sure to delete them as soon as your are done
setting up the routers.
It is probably best to get your VPN tunnel working in Pre-Shared Key mode
first, so you can get any kinks out of the other parameters, before you add
the additional complexity of certificates. Bring up the VPN:IPSEC:Edit
Tunnel page on your M0n0walls. If you already have the tunnel working in
Pre-Shared Key mode, you can bring them up side-by-side in two browser
windows, which will make things easier. Just be sure to move slowly and read
all the directions before you do anything, so you don't lose contact with the
remote M0n0wall before you get it set up.
Lets say your two routers are RouterA and RouterB. On RouterA, change
the "Authentication Method" to "RSA Signature". Bring up the RouterA
certificate in your favorite text editor. It should look something like
Copy it however your editor does that, and paste it into the "Certificate" box
on RouterA's page. Also paste it into the "Peer Certificate" box on
Now edit the RouterB certificate. Copy it and paste it into the "Certificate"
box on RouterB's page and the "Peer Certificate" box on RouterA's page.
Bring up the RouterA private key file in your editor. It should look
something like this:
-----BEGIN RSA PRIVATE KEY-----
-----END RSA PRIVATE KEY-----
Paste it into the "Key" field on RouterA's page. Edit the RouterB private key
file, and copy and paste it into the "Key" file on RouterB's page.
Click the "Save" button on each page.
You will now have an "Apply Changes" button at the top of each page. Here is
the critical part. As soon as you click either of the "Apply Changes"
buttons, you will lose contact with the remote router until the tunnel is
re-established. So the proper order is:
- Click "Apply Changes" on the remote router's page.
- Click "Apply Changes" on the local router's page.
The local router's page should refresh almost immediately. The remote router
will take a little longer, since the tunnel has to be re-established, but if
you did everything right, it should come up shortly. If the tunnel is slow
coming up, you may have to refresh the page if it times out. If something
got messed up, like you pasted the wrong certificate in the wrong box, or you
got the IP address wrong in the subject alternative key, you will have to
change both M0n0wall's back to Pre-Shared Key authentication (which will
involve physically going to where the remote router is, since you can't talk
to it any more) and start over.
Don't forget to delete the files you exported the private keys to when you are
done setting up!
Cross Design Group LLC