Security Basics mailing list archives
RE: Windows Remote Desktop
From: "Depp, Dennis M." <deppdm () ornl gov>
Date: Fri, 16 Jan 2004 20:07:24 -0500
Is it possible to gain access to a certificate without having admin privs on the box? Denny -----Original Message----- From: Shawn Jackson [mailto:sjackson () horizonusa com] Sent: Thursday, January 15, 2004 7:05 PM To: Depp, Dennis M.; jamesworld () intelligencia com Cc: Michael Gale; security-basics () securityfocus com Subject: RE: Windows Remote Desktop If you get a hold of the certificate the server presents to the clients and match your server configuration to match the target server the certificate can remain valid and it won't be flagged by the client. I've done this with some servers on a few 'crunch time' occasions. Shawn Jackson Systems Administrator Horizon USA 1190 Trademark Dr #107 Reno NV 89521 www.horizonusa.com Email: sjackson () horizonusa com Phone: (775) 858-2338 (800) 325-1199 x338 -----Original Message----- From: Depp, Dennis M. [mailto:deppdm () ornl gov] Sent: Thursday, January 15, 2004 3:06 PM To: Shawn Jackson; jamesworld () intelligencia com Cc: Michael Gale; security-basics () securityfocus com Subject: RE: Windows Remote Desktop Https would not be subject to a MiM attack using the method I described. This is because a third party is willing to vouch for the identity of the server. This is done through the ssl certificate. If my browser/client trusts the third party, then they can also trust the server. If I attempt a MiM attack, the client should notify me there is a problem with the server. This prevents the MiM attack. Denny -----Original Message----- From: Shawn Jackson [mailto:sjackson () horizonusa com] Sent: Thursday, January 15, 2004 4:51 PM To: Depp, Dennis M.; jamesworld () intelligencia com Cc: Michael Gale; security-basics () securityfocus com Subject: RE: Windows Remote Desktop Well if you use that example everything is subject to a MiM attack. You could do that with websites, application servers, network programs, etc. With Citrix you can setup a HTTP gateway, protect it with SSL/HTTPS then use the Citrix ICA encryption on top of that, only give the Cert to client you wish to have access to the gateway. That is how Citrix can be more secure then RDP. If you are not using a separate system for your http gateway you mitigate the risk of a MiM attack. Additionally you can create ICA Client packages that have all the required information hard coded, this makes it hard for the user to change the server information and harder for it to connect to a 'wrong' server. The TSAC (Terminal Services Advanced Client) has a web TS interface; you can protect that the same way using SSL and certificates and only allow known people to access it. I've personally never used TSAC in this way, but I believe it's possible. The older NT 4 Terminal Service edition used Citrix ICA protocols. RDP5 is a Microsoft only protocol and was created mostly from scratch. A good comparison of the protocols is at http://www.purenetworking.net/RDPvsICA.htm. Everything is possible in the world of security; you can't protect yourself 100% no matter how hard you try. The only thing we as security processionals can do is try and decrease/mitigate the risk as much as possible. I agree that use of RDP/ICA can open up a hole into your network. But you can mitigate the risk of a RDP/ICA connection with planning, thoroughness and foresight. Shawn Jackson Systems Administrator Horizon USA 1190 Trademark Dr #107 Reno NV 89521 www.horizonusa.com Email: sjackson () horizonusa com Phone: (775) 858-2338 (800) 325-1199 x338 -----Original Message----- From: Depp, Dennis M. [mailto:deppdm () ornl gov] Sent: Thursday, January 15, 2004 1:14 PM To: Shawn Jackson; jamesworld () intelligencia com Cc: Michael Gale; security-basics () securityfocus com Subject: RE: Windows Remote Desktop Shawn, I still fail to see the difference between Citrix and RDP as far as security goes. RDP like Citrix can be configured on the server side. As for the MiM attack. Theoretically I can setup an machine and have it masquerade as your Citrix server. When you logon to my machine you enter your Username and Password. I pass this information on to your Citrix server and I have compromised your data. This is possible because no authentication is done at the client to ensure your machine is authentic. This is true for both the HTTP interface/gateway and the ICA client. The same also holds true for the RDP protocol. (Which I believe has a lot of Citrix components in it.) I still don't want end users accessing their home workstation via RDP, Citrix, PCAnywhere, VNC or any other protocol. This creates another portal into my network for virii and worms. Denny -----Original Message----- From: Shawn Jackson [mailto:sjackson () horizonusa com] Sent: Thursday, January 15, 2004 3:52 PM To: Depp, Dennis M.; jamesworld () intelligencia com Cc: Michael Gale; security-basics () securityfocus com Subject: RE: Windows Remote Desktop Citrix ICA defaults to the setting on the server side, so if you configured your server with *some* security then a 'basic default' is not the case. Personally I separate raw data (Files, Databases, etc) and interactive 'streaming' data. Raw data is a file/component in transit on the wire that can be sniffed and recompiled, while streaming data can't be recompiled into anything but can be sifted through for information. Capturing interface information from even an unencrypted RDP connection is difficult. Setup three workstations on a hub then setup VNC server on 1 and the viewer on the 2nd. From the 3rd workstation use SNORT and sniff the traffic between the two. Have another person play with the viewer to give you something too look at. To my understanding Citrix is only at risk of a MiM attack when using the HTTP interface/gateway and not the ICA client. If I'm incorrect please supply a link to information about this attack. Also I don't believe you can use SSL with XP RDP and that's Terminal Services. Personally I can justify the need of using RDP to my workstation at home, but then again I know that system and its security. I setup and maintain that network and servers so I can be reasonably sure that my connection is clean and my systems are not at risk. Would I personally let my users have RDP access to their workstations at home, nope. My reasoning for this is that they could be violating the company policy (browsing bad sites, playing games, listening to their MP3 collection, etc) and we can't see it. Would I let our IT/IS guys, yep. I'm not worried about people taking data offsite because everyone has USB drives already. I'm also not *too* worried about virii or hackers; it's that it just walks too fine a line with our security policy. But then again, if them have a business need... My 2,000,000 cents! :-) Shawn Jackson Systems Administrator Horizon USA 1190 Trademark Dr #107 Reno NV 89521 www.horizonusa.com Email: sjackson () horizonusa com Phone: (775) 858-2338 (800) 325-1199 x338 -----Original Message----- From: Depp, Dennis M. [mailto:deppdm () ornl gov] Sent: Thursday, January 15, 2004 10:29 AM To: Shawn Jackson; jamesworld () intelligencia com Cc: Michael Gale; security-basics () securityfocus com Subject: RE: Windows Remote Desktop Two statements I don't agree with: 1) "Additionally no actual 'data' is transferred through the RDP connection, it's just interface information (mouse movement, button clicks, typing) and screen refreshes. Now if you were using the resource mapping then data would traverse the RDP connection and would be subject to its encryption." Data is sent over the wire concerning keystrokes, mouse movements and screen refresh data. Obviously this information, particularly keystrokes can provide data to a hacker. However all information set via RDP is encrypted the default is 56-bit with the capacity to use 128-bit RC4. Even when using local resources, the data is still encrypted with 128-bit security. 2) "All in all I think that PCAnywhere and Citrix have more secure RDP/VNC like interfaces" The default security setting in Citrix is basic (no encryption) PCAnywhere maybe better, I'm not sure. Both Citrix and RDP are vulnerable to MiM attacks. Citrix does have the capability to use SSL but this is comprable to Microsoft's VPN solution. Denny -----Original Message----- From: Shawn Jackson [mailto:sjackson () horizonusa com] Sent: Wednesday, January 14, 2004 6:36 PM To: jamesworld () intelligencia com Cc: Michael Gale; security-basics () securityfocus com Subject: RE: Windows Remote Desktop Well transferring data outside a company is easier then pie these days. With everything from encrypted email to USB drives it's hard to use that as a sole point 'ban' RDP to offsite resources. Unless you're running at high level security i.e. Military, Extremely Sensitive Work, National Security the movement of data offsite would be a secondary concern. The RDP encryption is 'in transit' protection and won't protect the resources. I personally never use the clipboard sharing, drive/printer mapping, etc. Access to those resources should be dictated by the company security policy and doesn't follow the 'security' of the protocol/connection. Seaming the connection is one-way (From Workstation or RDP Host) it hard to open a hole/exploit through an infected RDP host and use the RDP interface to your advantage. Additionally no actual 'data' is transferred through the RDP connection, it's just interface information (mouse movement, button clicks, typing) and screen refreshes. Now if you were using the resource mapping then data would traverse the RDP connection and would be subject to its encryption. All in all I think that PCAnywhere and Citrix have more secure RDP/VNC like interfaces but RDP is pretty secure by itself. Just as James stated, watch the local resource mapping. Shawn Jackson Systems Administrator Horizon USA 1190 Trademark Dr #107 Reno NV 89521 www.horizonusa.com Email: sjackson () horizonusa com Phone: (775) 858-2338 (800) 325-1199 x338 -----Original Message----- From: jamesworld () intelligencia com [mailto:jamesworld () intelligencia com] Sent: Wednesday, January 14, 2004 3:03 PM To: Shawn Jackson Cc: Michael Gale; security-basics () securityfocus com Subject: RE: Windows Remote Desktop Ahh,, but what about the option to connect local resources...... Drives Printers Serial Ports Smart Cards .... Talk about the ability to transfer company data out... What is protecting the actual data, MS RDP encryption which defaults to "medium" security by default. Again it comes back to.......What is the company policy? If it doesn't cover it, the policy needs to be updated. -James At 12:14 01/14/2004, Shawn Jackson wrote:
Eh' for 'Testing' I use a remote SSH server off my backbone. I do 'periodically' login to my remote XP workstation and do some work. Because only screen information is transmitted even if that system was hacked or infected with a virus it won't affect my network at work. My XP system doesn't sit directly on the Internet through; it goes through a Debian box running iptables. Shawn Jackson Systems Administrator Horizon USA 1190 Trademark Dr #107 Reno NV 89521 www.horizonusa.com Email: sjackson () horizonusa com Phone: (775) 858-2338 (800) 325-1199 x338 -----Original Message----- From: Michael Gale [mailto:michael () bluesuperman com] Sent: Tuesday, January 13, 2004 8:35 PM To: security-basics () securityfocus com Subject: Windows Remote Desktop Hello, I have a question, I have locked down a company network
allowing
only web browsing, SSH and FTP. Nothing else is need and soon SSH and FTP will be gone hopefully once the VPN is final. Right now a internal user is complaining about the fact their remote desktop connection to their home PC is no longer working. The justification is that a remote PC out side the network is needed
for
testing. At which point I gladly offered to setup a out side box for testing. :) Any ways the question I have is, do you feel that Remote Desktop (into WinXP) is a secure enough connection to allow it. I mind you that this is supposed to be a outbound connection only but you never know with windows. -- Hand over the Slackware CD's and back AWAY from the computer, your geek rights have been revoked !!! Michael Gale Slackware user :) Bluesuperman.com -----------------------------------------------------------------------
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Current thread:
- RE: Windows Remote Desktop, (continued)
- RE: Windows Remote Desktop Shawn Jackson (Jan 16)
- RE: Windows Remote Desktop Shawn Jackson (Jan 16)
- Re: Windows Remote Desktop Jamie Pratt (Jan 16)
- RE: Windows Remote Desktop Shawn Jackson (Jan 16)
- RE: Windows Remote Desktop Shawn Jackson (Jan 19)
- RE: Windows Remote Desktop Depp, Dennis M. (Jan 19)
- RE: Windows Remote Desktop Shawn Jackson (Jan 19)
- Re: Windows Remote Desktop erisk (Jan 20)
- Terminal Services Hardening >> was >> Re: Windows Remote Desktop jamesworld (Jan 20)
- RE: Windows Remote Desktop P Cannon (Jan 20)
- Re: Windows Remote Desktop erisk (Jan 20)
- RE: Windows Remote Desktop Depp, Dennis M. (Jan 19)
- RE: Windows Remote Desktop Depp, Dennis M. (Jan 20)
- RE: Windows Remote Desktop Shawn Jackson (Jan 20)