[talk] VPNs: Choosing between OpenVPN and L2TP/IPsec

Christos Zoulas christos at zoulas.com
Sun Apr 19 20:42:09 EDT 2015

On Apr 19,  7:39pm, ike at blackskyresearch.net ("Isaac (.ike) Levy") wrote:
-- Subject: Re: [talk] VPNs: Choosing between OpenVPN and L2TP/IPsec

| Christos, I don't mean to put you on the spot, but I figure you're a
| great person to thoughtfully comment on the relative security of IPSec
| itself these days?
| Problems like these worry me,
| http://www.mail-archive.com/cryptography@metzdowd.com/msg12325.html

I've read this article and I agree with all its points. While I agree,
I don't see many alternatives out there -- you mentioned most of them
(and nobody has published an exploit that I know of).

| To me, it IPSec seems ripe for a very serious design flaw to come to
| light in coming years- and at the least, all the fuss surrounding it-
| and it's relative complexity- bothers me more.

What makes things worse is that the "roadwarrior" configuration
everyone uses utilizes a common shared secret (which makes things
easier to abuse and to break since now you only have to find the
username and password) and also needs a wildcard match since we
don't know a-priori the address of the client endpoint. This is
explained here (ENABLE_WILDCARD_MATCH explanation about shared
secret problems):


I would not feel comfortable deploying that configuration to customer
connections (unless I only had one customer), but this is what I use
for home (where I am the only customer). Others don't seem to mind,
and sell such tunnels for a few bucks a month... It is the ease of
stealing ones credentials from those tunnels that compelled me
to deploy my own.

I think that the OpenVPN solution is easier to deploy. I chose to
use IPSEC+L2TP mostly because I wanted to have a kernel supported,
standards compliant tunnel solution on NetBSD working.


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