TweetFollow Us on Twitter

Review: VNC Over SSH: The next best thing to being there

Volume Number: 20 (2004)
Issue Number: 7
Column Tag: Review

Review: VNC Over SSH: The next best thing to being there

by Aaron Adams

Securely control a remote Mac with two pieces of free software

The ability to remotely control a machine can come in handy for a variety of reasons, whether the purpose is system administration, or helping a friend. Apple's most recent remote control offering, Remote Desktop 2.0, can be overkill when it comes to a simple one-to-one connection between machines. Most users won't need all the features included in Remote Desktop; it's intended for labs and other environments that require the management of large numbers of machines at once, not the remote control of a single machine. Freeware VNC, on the other hand, fits the one-to-one bill perfectly. VNC stands for Virtual Network Computing, and it allows a user to control a remote machine as if he were sitting at the desk in front of it.

VNC is certainly a useful tool for those who need something simpler than Remote Desktop. However, it's the wild wild web out there, and security is a major consideration. VNC was developed at a time when security wasn't the same priority as it is now, and the data transmitted between a VNC server and client is unencrypted. Passing login names and passwords, or other sensitive data, over the public Internet in the clear isn't a good idea, and neither is advertising the fact that a machine can be controlled via VNC by leaving its corresponding TCP port open. Is there some way to keep VNC traffic from prying eyes?

Yes! The solution comes in the form of another piece of freeware included with every Mac: Secure Shell. SSH is the encrypted replacement for plain-text telnet, a command line utility used frequently on the old text-based Internet, with a few added features thrown in for good measure, including the ability to encrypt traffic generated by other protocols. This process is called tunneling because the data travels inside an encrypted virtual pathway created by the communicating SSH pieces. To force VNC to use the tunnel, it has to be instructed to connect to the local machine at a certain port. SSH intercepts the traffic from the VNC client at that port, encrypts it, sends it to the SSH server at the other end of the connection, where it is decrypted and passed to the VNC server. Besides encryption, one other advantage of using SSH to tunnel other protocols is that a server only needs to expose a single port for SSH instead of an individual port for each service offered, such as additional ports for each possible VNC session. This prevents port scanners, and other miscreants, from discovering VNC on a target machine.

Making this encryption happen requires use of the *gasp!* command line! Most Mac users cringe at the thought of using the command line because it's so "un-Mac-like", but it's a powerful tool that's not very hard to learn, and quickly becomes an excellent exercise in abstract thinking. Don't shy away from encrypting VNC sessions because of Terminal fright.

On the remote machine...

Two things are required on the remote machine to prepare it to accept an encrypted VNC session: An SSH server and a VNC server. Enabling SSH on any Mac is as simple as going in to System Preferences, bringing the Sharing pane, and checking the box next to Remote Login. Make sure the connecting user has a username and password available on the remote box.

As for VNC, a great server is OSXvnc, available at popular download sites, such as Version Tracker or MacUpdate. OSXvnc is a straightforward application, and most of the options it presents are obvious and don't require an explanation. The two important things to point out are that, under the General tab, the port should be set to 5900 for the purposes of this tutorial, and that, under the Sharing tab, the Only allow local connections (SSH) box should be checked. Checking this box is important because it requires that the VNC session be encrypted via SSH and won't allow any unencrypted sessions to be established. It won't even let the VNC server advertise the usual VNC port. VNC remains totally hidden to the outside world.

OSXvnc has the option to require a password before the VNC session can be established. Providing a password is strongly recommended. A Startup item can also be configured that starts the server with the machine, and it includes a keepalive script that restarts the server should it close for some reason.

On the local machine...

Locally, a VNC client is needed to connect to the remote machine. VNC clients are a matter of personal preference, and again, popular download sites such as VersionTracker and MacUpdate have a selection.

And now for the part everyone has been dreading... the *gasp!* command line part! The following command serves to establish the tunnel between machines. Perhaps the best way to explain the command is to write it out and then dissect it piece by piece.

The following line needs to be entered in the Terminal:

    ssh -NfL 5900:127.0.0.1:5900 user@remote.host

    ssh - The command that starts the SSH client to create the tunnel.

    * Start SSH with these options:

    N Do not present the user with a command prompt on the remote machine after login is complete.

    f After the user authenticates, put the SSH process, and hence the tunnel, into the background to free up the local command prompt for other uses.

    L Forward a local port to a remote address, creating the tunnel.

    5900: - The port on the local machine where SSH will listen for traffic. This port can be anything >1025, but for this example 5900 has been chosen because it is the port typically used for VNC traffic.

    127.0.0.1 - The address of the machine that is the ultimate destination for the connection. This particular IP is a loopback address because in this case, the VNC client will be connecting to the same machine the SSH server is running on. Due to an SSH oddity, localhost is not valid here, you must use the loopback IP.

    :5900 - The port where the VNC server is listening on the remote machine. Again, 5900 is typically the port VNC uses.

    user - The username allowed SSH access on the remote machine.

    @ "at".

    remote.host - The hostname or IP address of the remote machine running the SSH server.

Fill in the variables with the correct values to establish an SSH tunnel for VNC. After pressing enter, a prompt requesting a password will appear. This is the SSH password for the user on the remote machine.

On the local machine, start the VNC client. Where it asks for a server, enter localhost. (Previous instructions said localhost could not be used at the command line because of an SSH weirdness, but it can be used with the VNC client. Just know that localhost is the same thing as 127.0.0.1. They are both a designator for the local machine.) Where it asks for a port, enter 5900, or if it asks for a display, enter display 0. Click the connect button, and enter the password for the VNC server. Congratulations, it's a tunnel!


Aaron Adams is a LAN administrator, a self-employed Macintosh consultant in Dayton, Ohio, and a former star of Apple's "Switch" ad campaign. He can be reached via e-mail at adamsa@mac.com.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

VueScan 9.5.09 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Airmail 2.1 - Powerful, minimal email cl...
Airmail 2 is a new mail client designed for OS X 10.10 Yosemite with fast performance and intuitive interaction. Support for iCloud, MS Exchange, Gmail, Google Apps, IMAP, POP3, Yahoo!, AOL, Outlook.... Read more
Logitech Control Center 3.9.2 - Keyboard...
Logitech Control Center (LCC) is designed to support OS X and allows you to take full advantage of your Logitech keyboard, mouse, or trackball. With the LCC you can: Browse the Internet using... Read more
Adobe Acrobat Pro 15.007.20033 - Powerfu...
Acrobat Pro DC is available only as a part of Adobe Creative Cloud, and can only be installed and/or updated through Adobe's Creative Cloud app. Adobe Acrobat Pro DC with Adobe Document Cloud... Read more
CleanMyMac 3.0.1 - Delete files that was...
CleanMyMac makes space for the things you love. Sporting a range of ingenious new features, CleanMyMac lets you safely and intelligently scan and clean your entire system, delete large, unused files... Read more
Evernote 6.0.10 - Create searchable note...
Evernote allows you to easily capture information in any environment using whatever device or platform you find most convenient, and makes this information accessible and searchable at anytime, from... Read more
CleanApp 5.0.1 - Application deinstaller...
CleanApp is an application deinstaller and archiver.... Your hard drive gets fuller day by day, but do you know why? CleanApp 5 provides you with insights how to reclaim disk space. There are... Read more
Quicken 2015 2.5.0 - Complete personal f...
Quicken 2015 helps you manage all your personal finances in one place, so you can see where you're spending and where you can save. Quicken automatically categorizes your financial transactions,... Read more
Tonality Pro 1.1.4 - Professional-grade...
Tonality Pro gives you the power to create stunning and dramatic black & white images. This is a complete monochrome image editor with more than 150 one-click style presets, totally unique... Read more
Adobe Photoshop CC 2014 15.2.2 - Profess...
Photoshop CC 2015 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Photoshop customer). Photoshop CS6 is still available for purchase (... Read more

WAVE Personal Calendar Now Connects You...
WAVE Calendar, by e-sites, has added an interesting new feature: real life personal assistants. The e-sites webpage has been redesigned so personal assistants can apply to work directly with WAVE. [Read more] | Read more »
Find Your Vacation Home With Dwellable
Dwellable is a new travel app that helps you to find rental homes for your vacation, allowing you to swipe your way through listings from over 15,000 destinations worldwide. [Read more] | Read more »
Play Endless Golf in Flick Golf Free...
Full Fat has released a new update for Flick Golf! Free. The ‘Eliminator’ update brings a whole new way to play with its endless round. [Read more] | Read more »
The Enchanted Cave 2 (Games)
The Enchanted Cave 2 2.1 Device: iOS Universal Category: Games Price: $2.99, Version: 2.1 (iTunes) Description: Delve into a strange cave with a seemingly endless supply of treasure, strategically choosing your battles to gather as... | Read more »
Crystal Siege is on Sale With a New Univ...
Crystal Siege,  FDG Entertainment's RPG  Tower Defense game, has gone universal in its latest update. [Read more] | Read more »
Platforming Action RPG Swordigo is Curre...
Touch Foo's 2D action-platformer, Swordigo, is free for a limited time on the App Store. Now you can run, jump, and slash your way through adventure for absolutely nothing. [Read more] | Read more »
Watch This Homerun Slides into Home on t...
Eyes Wide Games has launched their one-touch baseball game, Watch This Homerun, for the Apple Watch. [Read more] | Read more »
Disney Celebrates May 4th With Galaxy Si...
For Star Wars Day, May 4, join Disney Interactive and Lucasfilm as they celebrate with a whole lot of in=-app sales for their Star Wars apps. [Read more] | Read more »
Oh My Pixel! We Go Hands-on With The Kni...
I recently had a chance to play around with the upcoming Knights of Pen & Paper 2 from Paradox Interactive. I was a huge fan of the first game, so I had a lot of expectations going into it - and I wasn't disappointed. The game has gotten some... | Read more »
Throw Out Your Stylus and Sketch With Pe...
Penpoint Drawing, by Damin Liu,  is a new creative drawing app that uses your finger as your stylus. [Read more] | Read more »

Price Scanner via MacPrices.net

Save up to $300 on a new Mac, $30 on an iPad,...
Purchase a new Mac or iPad at The Apple Store for Education and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free,... Read more
iPad-Based iLynn Program Provides A Private U...
Lynn University of Boca Raton, Florida has announced that its innovative iPad-powered online bachelor’s degree program will be called iLynn. Beginning in fall 2015, Lynn U. says the new program will... Read more
iPad mini 4 Rumors Begin To Gel
First, I’ve been really hoping there will even be an iPad mini 4 at all. The smallest iPad has reportedly been hit pretty hard by iPhone 6 Plus cannibalization, along with getting caught in the... Read more
Mac Pros on sale for up to $260 off MSRP
B&H Photo has Mac Pros on sale for up to $260 off MSRP. Shipping is free, and B&H charges sales tax in NY only: - 3.7GHz 4-core Mac Pro: $2799, $200 off MSRP - 3.5GHz 6-core Mac Pro: $3719.99... Read more
Save up to $600 with Apple refurbished Mac Pr...
The Apple Store is offering Apple Certified Refurbished Mac Pros for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The... Read more
iMacs on sale for up to $205 off MSRP, NY tax...
B&H Photo has 21″ and 27″ iMacs on sale for up to $205 off MSRP including free shipping plus NY sales tax only: - 21″ 1.4GHz iMac: $999 $100 off - 21″ 2.7GHz iMac: $1189 $110 off - 21″ 2.9GHz... Read more
12-inch 1.1GHz Silver MacBook in stock today
B&H Photo has the new 12″ 1.1GHz Silver MacBook in stock today for $1299 including free shipping plus NY sales tax only. Act now if you’re interested, since we don’t expect B&H to have this... Read more
iPad Air 2s on sale for up to $50 off, NY tax...
B&H Photo has iPad Air 2s on sale for up to $64 off MSRP including free shipping plus NY sales tax only: - 16GB iPad Air 2 WiFi: $469 $30 off - 64GB iPad Air 2 WiFi: $549.99 $50 off - 128GB iPad... Read more
Check Apple prices on any device with the iTr...
MacPrices is proud to offer readers a free iOS app (iPhones, iPads, & iPod touch) and Android app (Google Play and Amazon App Store) called iTracx, which allows you to glance at today’s lowest... Read more
Sale! New 13-inch 256GB MacBook Air for $1099...
B&H Photo has the new 2015 13″ 1.6GHz/256GB MacBook Air on sale for $1099.99 including free shipping plus NY tax only. Their price is $100 off MSRP. Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Senior Identity Architect - *Apple* Pay - A...
Changing the world is all in a day039s work at Apple . If you love innovation, here039s your chance to make a career of it. You039ll work hard. But the job comes with Read more
Hardware Systems Integration Engineer - *App...
Changing the world is all in a day039s work at Apple . If you love innovation, here039s your chance to make a career of it. You039ll work hard. But the job comes with Read more
Senior Identity Architect - *Apple* Pay - A...
Changing the world is all in a day039s work at Apple . If you love innovation, here039s your chance to make a career of it. You039ll work hard. But the job comes with Read more
Hardware Systems Integration Engineer - *App...
Changing the world is all in a day039s work at Apple . If you love innovation, here039s your chance to make a career of it. You039ll work hard. But the job comes with Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.