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

calibre 3.1.1 - Complete e-book library...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital librarian... Read more
Sparkle Pro 2.2 - $79.99
Sparkle Pro will change your mind if you thought building websites wasn't for you. Sparkle is the intuitive site builder that lets you create sites for your online portfolio, team or band pages, or... Read more
Spotify 1.0.57.474. - Stream music, crea...
Spotify is a streaming music service that gives you on-demand access to millions of songs. Whether you like driving rock, silky R&B, or grandiose classical music, Spotify's massive catalogue puts... Read more
beaTunes 5.0.1 - Organize your music col...
beaTunes is a full-featured music player and organizational tool for music collections. How well organized is your music library? Are your artists always spelled the same way? Any R.E.M. vs REM?... Read more
LibreOffice 5.3.4.2 - Free, open-source...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
VOX 2.8.26 - Music player that supports...
VOX just sounds better! The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all audio formats you should ever need.... Read more
iFFmpeg 6.4.0 - Convert multimedia files...
iFFmpeg is a comprehensive media tool to convert movie, audio and media files between formats. The FFmpeg command line instructions can be very hard to master/understand, so iFFmpeg does all the hard... Read more
Beamer 3.3 - Stream any movie file from...
Beamer streams to your Apple TV.... Plays any movie file - Just like the popular desktop movie players, Beamer accepts all common formats, codecs and resolutions. AVI, MKV, MOV, MP4, WMV, FLV. To... Read more
jAlbum Pro 14.0 - Organize your digital...
jAlbum Pro has all the features you love in jAlbum, but comes with a commercial license. You can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly... Read more
Apple Remote Desktop Client 3.9.3 - Clie...
Apple Remote Desktop Client is the best way to manage the Mac computers on your network. Distribute software, provide real-time online help to end users, create detailed software and hardware reports... Read more

Latest Forum Discussions

See All

This War of Mine gets a new ending and m...
This War of Mine just got a big new update, featuring free DLC that adds a new ending to the game, among other exciting changes. The update is celebrating the game's two-year release anniversary. Apart from the new ending, which will be quite... | Read more »
Summon eight new heroes in Fire Emblem H...
Nintendo keeps coming at us with Fire Emblem Heroes updates, and it doesn't look like that trend is stopping anytime soon. The folks behind the game have just announced the new War of the Clerics Voting Gauntlet, expected to start next Tuesday. [... | Read more »
The best deals on the App Store this wee...
iOS publishers are pulling out all the stops this week -- there's a huge number of seriously great games at discounted prices this week. Let's not waste any time and get right down to business. [Read more] | Read more »
The House of da Vinci (Games)
The House of da Vinci 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: Enter The House of Da Vinci, a new must-try 3D puzzle adventure game. Solve mechanical puzzles, discover hidden... | Read more »
Solve the disappearance of history’s gre...
Blue Brain Games invites you to indulge in an immersive hands-on 3D puzzle adventure in similar vein to The Room series, with its debut release The House of Da Vinci. Set during the historic period of the Italian Renaissance (when Leonardo himself... | Read more »
Age of Rivals (Games)
Age of Rivals 3.3 Device: iOS Universal Category: Games Price: $.99, Version: 3.3 (iTunes) Description: Deep civilization-building strategy in a fast-paced card game! | Read more »
Panthera Frontier (Games)
Panthera Frontier 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: | Read more »
Angry Birds Evolution beginner's gu...
Angry Birds changes things up a fair bit in its latest iteration, Angry Birds Evolution. The familiar sling-shot physics mechanics are still there, but the game now features team-based gameplay, RPG elements, and a new top-down view. With all of... | Read more »
Sega Forever is for the retro game fans
Sega is launching a new retro games service titled Sega Forever, in a move that's sure to delight games enthusiasts with a bit of nostalgia. Sega's releasing five classic games for free. The titles include Sonic the Hedgehog, Phantasy Star II,... | Read more »
The Little Acre (Games)
The Little Acre 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: | Read more »

Price Scanner via MacPrices.net

ABBYY TextGrabber 6 for iOS Implements Instan...
ABBYY has announced the release of TextGrabber 6.0.0, an important feature update to the company’s productivity app developed for iOS and Android devices. TextGrabber 6.0 now offers Real-Time... Read more
vPhone, First Smartphone That Can’t Be Lost,...
Austin, Texas based Hypori has introduced the vPhone, a virtual smartphone that affords every business user the benefits of separate work and personal phones, conveniently delivered on a single... Read more
Save this weekend with 2016 refurbished MacBo...
Apple has dropped prices on Certified Refurbished 2016 15″ and 13″ MacBook Pros by as much as $590 off original MSRP. An Apple one-year warranty is included with each model, and shipping is free: -... Read more
New 27-inch 3.4GHz iMac on sale for $1699, sa...
MacMall has the new 2017 27″ 3.4GHz iMac (MNE92LL/A) in stock and on sale for $1699 including free shipping. Their price is $100 off MSRP. Read more
Clearance 2016 MacBook Pros available for up...
B&H Photo has clearance 2016 13″ and 15″ MacBook Pros in stock today and on sale for up to $400 off original MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: - 15″ 2.7GHz... Read more
Apple Ranks 9th In comScore Top 50 U.S. Digit...
comScore, Inc. has released its monthly ranking of U.S. online activity at the top digital media properties for May 2017 based on data from comScore Media Metrix Multi-Platform. * Entity has... Read more
10.5-inch iPad Pros available for up to $20 o...
B&H Photo has the new 2017 10.5″ iPad Pros available for up to $20 off MSRP including free shipping plus NY & NJ sales tax only: - 64GB iPad Pro WiFi: $649 - 256GB iPad Pro WiFi: $749 - 512GB... Read more
Three Off-The-Beaten-Track iOS Apps That Dese...
One of the great things about using iPads and iPhones is the vast selection of apps available for most anything you want or need to do. The three outlined in this article have been in my core app... Read more
Apple No. 1 Spot In Gartner Top 100 Vendors i...
Gartner, Inc. has unveiled the top global 100 vendors in IT in 2016 based on their revenue across IT (excluding communication services) and component market segments. In the Gartner Global Top 100:... Read more
Clearance iMacs available for up to $300 off...
B&H Photo has clearance 21″ and 27″ Apple iMacs available starting at $949, each including free shipping plus NY & NJ sales tax only: - 27″ 3.3GHz iMac 5K: $1999 $300 off original MSRP - 27″... Read more

Jobs Board

*Apple* News Product Marketing Mgr., Publish...
…organizational consensus on strategy and vision for publisher tools, authoring, and Apple News Format.Carries this strategy and vision across the organization to Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Security Data Analyst - *Apple* Information...
…data sources need to be collected to allow Information Security to better protect Apple employees and customers from a wide range of threats.Act as the subject matter Read more
Lead *Apple* Solutions Consultant - Apple I...
…integrity, and trust.Success Metrics/Key Performance Indicators:Quantitative* Year over Year growth in Apple Product and Beyond the Box sales in the assigned Point of Read more
*Apple* Solutions Consultant till v%u00E5r...
…ethics, integrity, and trust.Success Metrics/Key Performance Indicators:QuantitativeYear over Year growth in Apple Product and Beyond the Box sales in the assigned Point Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.