Date: Thu, 10 Jun 2010 05:44:27 -0400
From: Larry Seltzer <larry@...ryseltzer.com>
To: "Thor (Hammer of God)" <Thor@...merofgod.com>
Cc: "full-disclosure@...ts.grok.org.uk" <full-disclosure@...ts.grok.org.uk>,
	Daniel Sichel <daniels@...derosatel.com>
Subject: Re: RDP, can it be done safely?

All right, I guess you've got a point. I reflexively say VPN at times like
this because the very few reported RDP attacks I've seen have been MITM
attacks of the sort that VPNs effectively block. But a client
certificate/TLS implementation accomplishes the same thing and all you have
to open is the RDP port.

On Wed, Jun 9, 2010 at 11:58 PM, Thor (Hammer of God)
<Thor@...merofgod.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
>
>
>
> *From:* full-disclosure-bounces@...ts.grok.org.uk [mailto:
> full-disclosure-bounces@...ts.grok.org.uk] *On Behalf Of *Larry Seltzer
> *Sent:* Wednesday, June 09, 2010 2:20 PM
> *To:* noloader@...il.com; Daniel Sichel
>
> *Cc:* full-disclosure@...ts.grok.org.uk
> *Subject:* Re: [Full-disclosure] RDP, can it be done safely?
>
>
>
> See http://technet.microsoft.com/en-us/library/cc782610(WS.10).aspx
>
>
>
> If you connect through a VPN it should be as secure as anything else you’re
> going to consider.
>
>
>
> *From:* full-disclosure-bounces@...ts.grok.org.uk [mailto:
> full-disclosure-bounces@...ts.grok.org.uk] *On Behalf Of *Jeffrey Walton
> *Sent:* Wednesday, June 09, 2010 5:04 PM
> *To:* Daniel Sichel
> *Cc:* full-disclosure@...ts.grok.org.uk
> *Subject:* Re: [Full-disclosure] RDP, can it be done safely?
>
>
>
> Hi Dan,
>
>
>
> Where are the users located (local LAN or from an untrusted network such as
> the Internet)?
>
>
>
> If I recall correctly, RDP encryption is "turned on" from a GPO setting
> that applies to the host/server, and not just RDP [or was it strong
> encryption?] (corrections, please). So you can get a secure RDP connection
> at the cost of possibly breaking other functionality.
>
> You might find it easier to use another remote access solution.
>
>
> Jeff
>
>
>
> On Wed, Jun 9, 2010 at 4:35 PM, Daniel Sichel <daniels@...derosatel.com>
> wrote:
>
> We have a boneheaded group of software developers who even in this day and
> age eschew the client server model of software for the easier dumber run it
> from the console school of design. So I have this idiotic Windows accounting
> application that MUST run on an application server, cannot be run from a
> client.  Rather than have my accounting department log in directly to the
> physical box, I would like to have them use some flavor of terminal services
> on my Windows server. My question therefore is, can I turn on RDP safely,
> without exposing my Windows server to risk of exploitation?
>
> Thanks for any help you can give.
>
> Dan S.
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