[isapros] Re: OT: Requiring client-side certs for RDP
- From: "Jim Harrison" <Jim@xxxxxxxxxxxx>
- To: <isapros@xxxxxxxxxxxxx>
- Date: Fri, 13 Jul 2007 11:32:59 -0700
No - TSG is RPC/HTTP.
I've had to work with the TSG group on ISA deployment a few times.
-----Original Message-----
From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] On
Behalf Of Thor (Hammer of God)
Sent: Friday, July 13, 2007 10:46 AM
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: OT: Requiring client-side certs for RDP
"TSG" that is...
t
> -----Original Message-----
> From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-
> bounce@xxxxxxxxxxxxx] On Behalf Of Thor (Hammer of God)
> Sent: Friday, July 13, 2007 10:44 AM
> To: isapros@xxxxxxxxxxxxx
> Subject: [isapros] Re: OT: Requiring client-side certs for RDP
>
> It is: TSD is RDP via HTTPS.
>
> The advantage is there, and in scenarios where one controls servers and
> workstations, it is a good thing. However, given the nature of RDP,
> there needs to be server-level enforcement mechanisms in place to
> obviate anonymous attacks.
>
> There are ways to increase security, but server enforced client
> certificates would be ideal.
>
> t
>
> > -----Original Message-----
> > From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-
> > bounce@xxxxxxxxxxxxx] On Behalf Of Thomas W Shinder
> > Sent: Friday, July 13, 2007 10:39 AM
> > To: isapros@xxxxxxxxxxxxx
> > Subject: [isapros] Re: OT: Requiring client-side certs for RDP
> >
> > I thought TSG was RDP/HTTP
> >
> > Also, the advantage of using RDP/TLS is that a TLS session is
> > established before credentials are sent.
> >
> > The author of the winsecurity.org article is well known for such
> gaffs.
> >
> > -----Original Message-----
> > From: "Jim Harrison"<Jim@xxxxxxxxxxxx>
> > Sent: 7/13/07 11:27:27 AM
> > To: "isapros@xxxxxxxxxxxxx"<isapros@xxxxxxxxxxxxx>
> > Subject: [isapros] Re: OT: Requiring client-side certs for RDP
> >
> > I just love it when "tribal knowledge" becomes "documented fact".
> > It's clear from the "article" that the author never tested any of the
> > configuration or application statements he makes.
> > Even the dialog for his "attempt authentication" screenshot clearly
> > states "Authentication will confirm the identity of the remote
> computer
> > to which you connect" - NOT "Authentication will confirm the identity
> > of
> > the user/machine **from which you connect**".
> >
> > In theory you *could* require user cert auth, but I don't know if
> the
> > TSG client will respond appropriately. Since TSG is "just" RPC/HTTP,
> > it's rpcrt4.dll that handles the translation between RPC and HTTP and
> > AFAIK, it only handles Basic and NTLM.
> >
> > Because TSG is RPC/HTTP, you can configure the /RPC vroot to require
> > user certs and thus impose this requirement on your connecting
> clients
> > to test this theory. Of course, if you also share this vroot with
> > Exchange RPC/HTTP you'll break OL connections, since they can't
> handle
> > cert auth.
> >
> > -----Original Message-----
> > From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-
> > bounce@xxxxxxxxxxxxx]
> > On Behalf Of Thor (Hammer of God)
> > Sent: Friday, July 13, 2007 9:29 AM
> > To: isapros@xxxxxxxxxxxxx
> > Subject: [isapros] OT: Requiring client-side certs for RDP
> >
> > Greets:
> >
> >
> >
> > Windows Server 2003 SP1 allows one to configure server-authentication
> > via certificate for RDP over TLS/SSL. The MSFT articles say things
> > like "the client must trust the certificate" etc in their
> > client-configuration notes, and other articles specify that you can
> > control access to RDP by issuing self signed certs and controlling
> > distribution.
> >
> >
> >
> > This presents the illusion that one can limit connections to RDP on a
> > Win2k3 server via this method. See:
> >
> > http://support.microsoft.com/kb/895433
> >
> > http://technet2.microsoft.com/windowsserver/en/Library/a92d8eb9-f53d-
> > 4e8
> > 6-ac9b-29fd6146977b1033.mspx
> >
> > http://www.windowsecurity.com/articles/Secure-remote-desktop-
> > connections
> > -TLS-SSL-based-authentication.html
> >
> >
> >
> > Win2k3 Terminal Services allows one to require security levels, but
> > only
> > provides "server" authentication - it does not allow you to require a
> > particular certification to be requested of the client (as IIS does).
> >
> >
> >
> > Snips from the windowsecurity article compound this perception:
> >
> > <snip>
> > The threat becomes even bigger, when the server running Microsoft
> > Windows Terminal Services is accessible from the Internet through an
> > RDP
> > connection on port 3389, even though you have an advanced firewall
> such
> > as ISA Server in front of it. A scenario that is common especially
> for
> > Microsoft Small Business Server users.
> >
> > The good news however, is that you can prevent these attacks. The
> > solution is certificate based computer authentication. If the
> computer
> > cannot authenticate itself by presenting a valid certificate to the
> > terminal server it is trying to connect to, then the RDP connection
> > will
> > be dropped before the user has a chance to attempt to log on.
> >
> > </snip>
> >
> >
> >
> > This is simply untrue. The client does not "present a valid
> > certificate" at all. It either trusts the server or not, and it is
> up
> > to the client to make that decision. While RDP clients 6 and below
> > only
> > allow "No auth, attempt, or require" which do provide the expected
> > behavior, updated or alternate clients (like Vista) allow you to
> > connect
> > anyway.
> >
> >
> >
> > This being said, does anyone know if the current longhorn/ts gateway
> > features will actually allow enforcement of client certificates such
> a
> > requiring client certs that are signed by particular authorities?
> >
> >
> >
> > Sorry for all the detail, but I wanted to avoid people saying "Sure,
> > just require TLS for RDP".
> >
> >
> >
> > t
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > All mail to and from this domain is GFI-scanned.
> >
> >
> >
All mail to and from this domain is GFI-scanned.
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