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Re: [Openvpn-devel] Re: OpenVPN Protocol

  • Subject: Re: [Openvpn-devel] Re: OpenVPN Protocol
  • From: James Yonan <jim@xxxxxxxxx>
  • Date: Sat, 3 Sep 2005 11:21:27 -0600 (MDT)

On Sat, 3 Sep 2005, Gervasio Bernal wrote:

> Lars Gullik BjÃnnes <larsbj <at> gullik.net> writes:
> > 
> > Gervasio Bernal <gervasiobernal <at> speedy.com.ar> writes:
> > 
> > | First of all, I will explain what we are trying to develop. Basically, our 
> idea 
> > | is to make OpenVPN works at kernel level, not at user level, and use the 
> linux 
> > | cryptoapi instead of openssl.
> > 
> > Just a question.
> > 
> > Why do you want to do this? Performance or something else?
> > 
> > To me running in userspace is one of the really good things about
> > OpenVPN.
> > 
> You are right!, running in userspace is a great thing because it facilitates the 
> portability, but you lose performance. Obviously, if we run it at kernel level 
> we will lose that portability, but we will win performance.

You also lose the security of running the OpenVPN process outside the 
kernel as user/group nobody and chrooted to a sandbox.

If someone finds a remote code injection vulnerability, you are much worse 
off than you would be if you were running as an unprivileged process, 
chrooted to a sandbox, because now every remote compromise is a full root 

There are also stability issues -- what if there is a crash or assertion 
failure?  Running in kernel space, you will bring down the entire machine.
When alpha & beta testing new features, it's important to be able to 
convince users to test the new code, to help stabilize it.  People are 
going to be less likely to test code that might crash their whole machine 
as opposed to code which will only bring down a single process.

As far as performance is concerned, you will gain the time it normally 
takes to switch between user and kernel space.  But this time may be small 
in relation to the much higher cost of crypto operations.

The big question in my mind is whether this possibly small increase in 
performance will justify the loss of portability, and some level 
of stability and security.


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