The Bozteck Blog

We’ve had a lot of request for the ability to automatically reconnect to computers when they are rebooted.  A majority of the requests were resolved with the implementation of the background scanner and the actions that can be performed when the scanner detects that the computer is alive.

To take this a step further, we’ve modified the ping window that happens when you right-click a computer and choose “Ping Computer”.  Instead of just opening a command window with the standard ping command running, we’ve designed our own.  We’ve done this in order to bring you an exciting new feature - automatically running commands or connecting when a computer responds for X number of consecutive pings.

Here’s a quick video showing how: http://screencast.com/t/CqJI7YhE

Download the latest version here!

Introduction

Bozteck VENM Console can deploy UltraVNC with session level encryption enabled. This is recommended in network environments where you fear that your VNC session may be “sniffed” from the network and replayed back without your knowledge. The risk of someone successfully doing this on your LAN is very low as it does require a moderately high level of “hacker skill”. Some networks, however, need extra protection even against low risk attacks such as this.

This document will explain the principles behind the VENM supported UltraVNC encryption as well as how to deploy and enable it from the console. The skill level to use this information successful varies. If you simply accept the safe defaults, the skill level required is low. If you choose to make modifications such as creating a custom rc4.key file, the skill level required is much higher.

This document is for Admins who want to customize the encryption, get to know how it works at a lower level, or are having DSM errors when connecting to an encrypted server. Anyone else can skim through or read this document as they wish.

Basic Principles

vncviewer.exe –> {RC4.KEY} ===> (Network) ===> {RC4.KEY} ==> [msrc4plugin_noreg.dsm] –> winvnc.exe

There are two key files that are fundamental to UltraVNC session level encryption and they are “msrc4plugin_noreg.dsm” and “rc4.key”. These will be refered to as the DSM and KEY files respectively through the rest of this document.

When a vncviewer.exe file wants to talk to an UltraVNC server that is set to use encryption, it starts by looking for it’s copy of the KEY file. If found, it encrypts it’s connection attempt using the data in the KEY file. It, then, sends a connection request to the remote server using this encrypted mode of communication that would seem like garbage to anything else on the network.

On the other end, the server hears a connection being requested. Because it is also configured to require encryption, it consults it’s copy of the KEY file and uses the data in the KEY file to decrypt the communication request coming from the viewer. If the keys match up, the data is correctly deciphered and the two commence communication in this encrypted tunnel.

If the keys do not match, the connection attempt is rejected and the viewer presents an error to the user stating that possible reasons could include the failure to find a DSM file and a few other suggestions. The error message is vague but it pretty much just means that either:

• The remote server is not configured for encryption but you are sending an encrypted request
• The server is configured to require encryption but you are sending an unencrypted request
• Both ends are configured for encryption but the KEY files do not match

More About the KEY and DSM Files (Server End)

The DSM file is a plug-in to the winvnc.exe service file. For reference, the winvnc.exe is the actual server executable for UltraVNC that is deployed to the remote computers and installed as a service. The DSM file must reside in the same folder as the winvnc.exe file. Don’t worry too much about that because the Bozteck VNC Deployment Tool does that work for you. When the DSM file is in the same folder as the winvnc.exe file and the configuration for the server has been properly set, the server will attempt to encrypt communication for any client that attempts to connect to it.

The KEY file also must reside in the same folder as the winvnc.exe file. The Deployment Tool also make sure that this happens as long as you do not modify things too much. If you simply tell the Profile Editor to enable encryption, it takes the KEY file that is located in c:\fastpush\vnc7\ultra and copies it to your Deployment Profile’s folder for easy deployment every time that you push that profile out to a computer.

Because this KEY file must match the KEY file on the Viewer end, it is best practice to only use one KEY file for your entire network. You do not gain sufficient security advantage by using multiple KEY files to make up for the headache required to keep them all straight and matched up. If you choose to generate a new KEY file, you must push that new KEY file out to each and every computer on your network that has encryption enabled to ensure proper connectivity.

By default, the UltraVNC Server is installed to either “C:\Program Files\orl\vnc” or “C:\Program Files\ultravnc” depending on the version of UltraVNC you are using. If you choose to distribute the KEY file using some method other than a VNC Push from VENM, it must in somehow make it’s way into that path on the remote computer end. Again, the VNC Push from VENM does this for you.

More About the KEY and DSM Files (Viewer End)

The KEY file is required to be in the same folder as the vncviewer.exe file. This KEY file must be an exact copy of the KEY file that is located at the server end as described above. By default, VENM uses the vncviewer.exe located in “C:\Program Files\Bozteck\VNCScan Console .NET” or whatever location you have installed VENM to.

You have the ability to customize the location of your vncviewer.exe file using either the main preferences (Support Files section), group properties (VNC Settings section), or the computer properties (VNC Settings section). If you choose to modify the location of the vncviewer.exe file, you need to make sure that a copy of your RC4.KEY file is moved with it.

Creating Custom KEYs

The Profile Editor has a button in the “Customs” section that allows you to generate a new key. This is an advanced level function and should never really need to be done in normal circumstances. To my knowledge, there has never been a tool released that allows someone to decrypt an encrypted UltraVNC stream for later playback. You should only need to generate a custom key if this is ever done. The KEY file does not control who can access you server. It only controls the way that the session is encrypted. You will still need to authenticate with the remote server using your password even if the KEY files match up.

If you do choose to create a custom KEY file, pressing this button is the easiest way to make sure that everything is placed in the correct locations for easy deployment. You may need to manually copy the new KEY file to the location where your vncviewer.exe resides, however. The newly generated key is always placed in c:\fastpush\vnc7\ultra.

Conclusion

I hope that this was a good in-depth overview of how the UltraVNC encryption works and how it interacts within the Bozteck VNCScan Enterprise Network Manager (VENM).

I just wanted to put out a quick blog post to let you know about a couple of new updates.

First, the VNCScan 2009.2.10 package has been updated to deploy the UltraVNC version 1.0.5.3 server and contains the latest 1.0.5.4 version of their viewer. You can download it here.

I also wanted to point out that we’ve updated the link for the recommended TCPIP.SYS patcher for Vista. The link is on the download page or you can just click here.

Important Information

There has been a serious integer overflow vulnerability found in the UltraVNC viewer with versions 1.0.5.3 and earlier. There is more information about this vulnerability at Core Security.

Notice that this is for the viewer only. The server is not affected by this bug.

Solution

The easiest way to upgrade the viewer is to upgrade to the latest release of VENM Console. This version uses the patched viewer and is safe.

Alternatively, you can manually update your vncviewer.exe by performing the following steps:

1. Download the zipped viewer here
2. Unzip the vncviewer.exe into the following places:

• “C:\Program Files\Bozteck\VNCScan Console .Net”
• “C:\fastpush\vnc7\ultra”

Thank You,

Steve Bostedor
Bozteck VENM Support
http://www.vncscan.com

Introduction

Bozteck VENM Console makes it very easy to deploy many versions of the VNC (Virtual Network Computing) remote control software to desktops and servers on your network.

With VENM, you simply create a template of settings called a Deployment Profile, select some computers, and choose to deploy VNC to them from the toolbar. Using the settings in your Deployment Profile, VNC is copied onto the remote computers, the services are installed and started, and you are ready to remote control the desktops!

Security and Authentication

Because this tool is copying files to secured ares of the hard disk over the network, you do need to know the credentials of a valid Administrator level user for the remote computer(s). If the computers are joined to a domain, you can typically use the domain administrator account.

If the computer is not a member of an Active Directory domain, you simply use the local administrator username and password. You will see in the instructions below how to specify this using the %HOST% variable.

You can enter and save these login credentials in the group properties if you’d like. You can do this by right-clicking a group and choosing to view it’s properties. You can save them in the section called “Remote Login Settings”. You can also simply enter them in every time that you choose to deploy a computer.

Firewalls

Files are being transferred over the network and commands to start and stop services are traveling about. This requires that any firewalls be adjusted to allow for this.

The deployment process requires that TCP port 445 is open on each computer. In addition, it would be a good idea to allow TCP and UDP ports 138 and 139. These are the standard Windows filesharing ports.

The deployment script will open any additional ports required by VNC for you.

Step-By-Step

Select The Deployment Editor

Choose to create a new profile

Fill in the desired settings
Note: only version and password are required
Choose to Deploy VNC from the ToolBar

Overview

Bozteck VENM Console includes a powerful remote screen capturing feature. This feature does not require that VNC or any other remote screen sharing software be installed in order to work. There are a few system requirements on the remote computer end, however.

Those requirements are as follows:

• UnFirewalled ports 443 (TCP) and 139 (UDP, TCP)
• Remote Registry service running
• Administrative priviledges on the remote computer
• Windows 2000, XP, Vista, or Windows 7

Because of these requirements, it is “best practice” to use this feature on computers that are on your LAN or within reach of your VPN. For security reasons, it is not advisable to use this feature over the open Internet.

You can supply the Administrator level access required to make this feature work in either the main VNCScan preferences, the group properties, or the computer properties. The choice depends upon the scope that you wish to apply.

Feature Set

• Resizable - You can resize the thumbnail by adjusting the slider in the toolbar
• Adjustable Interval - You can adjust the interval using a dropdown box of predefined timings or type in your own number. The intervals are measured in minutes. You can enter a decimal number to take snapshots in times less than one minute. If you manually enter a timing, it is applied when you press .
• Archive Screen Captures - You can archive your screen captures for later viewing. The location of these archives can be changed by clicking on the “Folders” button on the toolbar.
• Connect to VNC - You can connect to VNC right from the thumbnail. The connection options are taken from the computer entry settings in VNCScan.

What To Look Out For

• The “Please Wait Screen” - This screen is the start image for a new screen capture session. It is normal for it to still be visible even after the progress bar has cycled a couple of times. If it is still the only image being displayed for a computer even after the progress bar has cycled more than three times, you may want to check the permissions settings for the computer.

  You can test this out by attempting to access the c$ share of the remote computer. You can do this by clicking on your Start button and choosing “Run”. In the textbox, type \\\c$ (where is the name or IP address of the remote computer).

• Black Screen Capture - This is shown if the remote computer is sitting at the login screen and nobody is logged into the computer.

Video Example

Download video

New in version 2009.1.21, the remote screen captures work on Vista desktops as well as XP. More about this in the release notes.

Overview

New in 2009, Bozteck includes background service scanning and alerting to it’s powerful Enterprise Network Manager. This paper is a brief explanation of how it works and how to best take advantage of this new feature.

Usage and Benefits

Background scanning allows you to see an accurate view of what computers are running the VNC and RDP services as well as what computers are currently pingable on your network. You set the amount of time between scans in the main program preferences and then let VENM fo the rest!

The powerful alerting features keep you up to date on what is happening even when you’re away from your desk. Each of these actions can be set in the group properties and overridden by the computer properties. Below is an overview of available alerting and actions.

• When a computer goes offline
  • Send an email to a designated address
  • Run a local custom command such as “PING -t %HOST%” or any other command that you have created using the Custom Commands feature in VENM.
• When a computer comes back online
  • Send an email to a designated address
  • Auto-connect to VNC once the VNC service has been detected
  • Run a script remotely on the computer once Windows has been fully loaded. This is a powerful way to schedule a script if the computer is currently not online.

How It Works

There is a decision tree method being employed for determining if a computer should be probed in the background. This decision tree is explained in the following bullet points.

• Scanning is enabled in the program preferences
  • Scanning is enabled in the group settings
    • Computer is inheriting settings from the group
      • Scan the computer according to group settings
    • Computer is overriding group settings
      • Services are selected in the computer settings
        • Scan the selected services
      • Services are NOT selected in the computer settings
        • Skip this computer in the group scan
  • Scanning is NOT enabled in the group settings
    • Skip the entire group from background scanning
• Scanning is disabled in the program preferences
  • Do no background scans at all

Conclusion

We’re excited about these new features in the VENM Console and will continue to build upon them. We would love to hear your feedback about this! Let us know what you think at feedback@vncscan.com