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Re: RDP, can it be done safely?
From: Jeffrey Walton <noloader () gmail com>
Date: Thu, 10 Jun 2010 10:20:40 -0400

Hi Thor,

I only bring this up because I think one should consider
the ramifications of the “VPN first” model before assuming
it grants you some inherent security.
My experience in the enterprise and the work-at-home crowd has been:
(1) VPN into corpnet
(2) Land at a TS (users) or JumpBox (Admins)

I've read your reply a few times, so please forgive my ignorance: What
are you claiming? (1) There are technologies other than VPN? (2) Don't
use VPN? (3) Use Windows Firewall and IP filtering? (4) Use RDP over
HTTPS for single sign on? Again, my apologies.

However, when it comes to a network-level “least privilege”
standpoint, I think there are stark differences:  The VPN
endpoint typically will give the end user full-stack IP acces
 to resources unless otherwise specified.
In this respect, how is VPN any different than a user walking in to
the office, punching in, and signing on at the computer in their cube?

For the Admin, its allow VPN to TS or jumpbox. Then network security
applies. Or am I missing something in your statements?

RDP endpoints however only require the specified RDP port to access the host.
This is kind of Apples and Oranges.... The vpn GIVES acces to TCP/IP,
while rdp REQUIRES that 3389 be open on the host. Perhaps I misread
you.

Jeff

On Wed, Jun 9, 2010 at 11:58 PM, Thor (Hammer of God)
<Thor () hammerofgod com> wrote:

I request that you start thinking about RDS/TS/RDP as a “direct” technology.  Treating access via RDP as something 
that one must first VPN/RAS into a corpnet first in order to secure properly obscures what one might consider obvious:

If you require me to logon to your network via VPN first before I can subsequently connect to internal RDP resources, 
one might consider the VPN endpoint as the primary authentication point.  As such, one might logically conclude that 
since access was granted via the VPN, that internal access to RDP resources would be considered “safe.”  In this 
model, what is the difference between me authenticating to the VPN endpoint as opposed to me authenticating to an RDP 
endpoint?

Insofar as the authentication layer is concerned, there really isn’t a difference.  However, when it comes to a 
network-level “least privilege” standpoint, I think there are stark differences:  The VPN endpoint typically will 
give the end user full-stack IP access to resources unless otherwise specified.  RDP endpoints however only require 
the specified RDP port to access the host.  What happens after a successful connection to the host is up to the 
admin.   In the case of RDP via TSGateway, we find that one can deploy a server at the “connection-level” using 
client certificates – not only for encryption upon connection, but for validation TO connect in the first place.

To me, that is an important distinction.

VPN endpoint authentication might lead to the propensity for one to consider access to down-range resources as 
authorized.  I don’t think you should do that when you consider the capabilities an attacker has given an “open pipe” 
once authenticated versus an single protocol access to a machine you can tightly control.

I only bring this up because I think one should consider the ramifications of the “VPN first” model before assuming 
it grants you some inherent security.

t

 [SNIP]

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