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

Firefox 37.0 - Fast, safe Web browser. (...
Firefox offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals and casual... Read more
Arq 4.11 - Online backup to Google Drive...
Arq is super-easy online backup for the Mac. Back up to your own Google Drive storage (15GB free storage), your own Amazon Glacier ($.01/GB per month storage) or S3, or any SFTP server. Arq backs up... Read more
MacFamilyTree 7.3.4 - Create and explore...
MacFamilyTree gives genealogy a facelift: it's modern, interactive, incredibly fast, and easy to use. We're convinced that generations of chroniclers would have loved to trade in their genealogy... Read more
Yummy FTP 1.10.2 - FTP/SFTP/FTPS client...
Yummy FTP is an FTP + SFTP + FTPS file transfer client which focuses on speed, reliability and productivity. Whether you need to transfer a few files or a few thousand, schedule automatic backups, or... Read more
VueScan 9.5.08 - 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
Iridient Developer 3.0.1 - Powerful imag...
Iridient Developer (was RAW Developer) is a powerful image conversion application designed specifically for OS X. Iridient Developer gives advanced photographers total control over every aspect of... Read more
Air Video Server HD 2.1.0 - Stream video...
Air Video Server HD streams videos instantly from your computer on your iPhone, iPad, iPod touch or Apple TV. No need to worry about converting or transferring files. We took everything that was... Read more
Duplicate Annihilator 5.7.5 - Find and d...
Duplicate Annihilator takes on the time-consuming task of comparing the images in your iPhoto library using effective algorithms to make sure that no duplicate escapes. Duplicate Annihilator... Read more
BusyContacts 1.0.2 - Fast, efficient con...
BusyContacts is a contact manager for OS X that makes creating, finding, and managing contacts faster and more efficient. It brings to contact management the same power, flexibility, and sharing... Read more
Capture One Pro 8.2.0.82 - RAW workflow...
Capture One Pro 8 is a professional RAW converter offering you ultimate image quality with accurate colors and incredible detail from more than 300 high-end cameras -- straight out of the box. It... Read more

2K Announces WWE 2K, Mobile's First...
It seems like this month has been pretty big for wrestling. First Wrestlemania, then 2K has announces that they're releasing  WWE 2K for iOS. It's a simulation-based WWE game where you'll get to play with several WWE superstars such as John Cena, ... | Read more »
How the Apple Watch Could Change the Fac...
The Apple Watch is still a ways out, but my previous musings on the wearable’s various features got me thinking: what might it be like a year after launch? Two years? Five years? What if it becomes a symbiotic part of the iOS framework to the point... | Read more »
Pie In The Sky: A Pizza Odyssey (Games)
Pie In The Sky: A Pizza Odyssey 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: A game about delivering pizza. In space. | Read more »
Chosen Gives Hopeful Singers, Songwriter...
If YouTube videos and reality TV shows like The Voice have taught us one thing, it’s that there are a lot of people out there who are anxious to show the world their talents. And if they’ve taught us a second thing, it’s that there’s an almost... | Read more »
Android's Popular OfficeSuite Now A...
Once only available for Android devices, OfficeSuite has finally landed on the app store. The Mobile Systems app lets you view, edit, create, and share Word, Excel, and PowerPoint documents as well as convert them to/from PDFs. It's touted as being... | Read more »
Warhammer: Arcane Magic is Coming Soon,...
Turbo Tape Games has announced that they're joining forces with Games Workshop to bring the turn-based strategy board game, Warhammer: Arcane Magic, to life on the iOS. | Read more »
Fast & Furious: Legacy's Creati...
| Read more »
N-Fusion and 505's Ember is Totally...
| Read more »
These are All the Apple Watch Apps and G...
The Apple Watch is less than a month from hitting store shelves, and once you get your hands on it you're probably going to want some apps and games to install. Fear not! We've compiled a list of all the Apple Watch apps and games we've been able to... | Read more »
Appy to Have Known You - Lee Hamlet Look...
Being at 148Apps these past 2 years has been an awesome experience that has taught me a great deal, and working with such a great team has been a privilege. Thank you to Rob Rich, and to both Rob LeFebvre and Jeff Scott before him, for helping me... | Read more »

Price Scanner via MacPrices.net

Adobe Brings Powerful Layout-Design Capabilit...
Adobe today announced the availability of Adobe Comp CC, a free iPad app that enables rapid creation of layout concepts for mobile, Web and print projects. With Comp CC, designers can rough out and... Read more
Apple offering refurbished 27-inch 5K iMacs f...
The Apple Store is offering Apple Certified Refurbished 27″ 3.5GHz 5K iMacs for $2119 including free shipping. Their price is $380 off the price of new models, and it’s the lowest price available for... Read more
16GB iPad mini on sale for $199, save $50
Walmart has 16GB iPad minis (1st generation) available for $199.99 on their online store, including free shipping. Their price is $50 off MSRP. Online orders only. Read more
New 128GB MacBook Airs on sale for $50 off MS...
 B&H Photo has 128GB 11″ and 13″ 2015 MacBook Airs on sale today for $50 off MSRP including free shipping plus NY sales tax only: - 11″ 1.6GHz/128GB MacBook Air (Model #MJVM2LL/A): $849 $50 off... Read more
13-inch 2.6GHz Retina MacBook Pro (refurbishe...
The Apple Store has Apple Certified Refurbished 13″ 2.6GHz/128GB Retina MacBook Pros available for $979 including free shipping. Original MSRP for this model was $1299. 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
Samsung Galaxy S 6 and Galaxy S 6 edge U.S. P...
Samsung Electronics America, Inc. has announced the Galaxy S 6 and Galaxy S 6 edge will be available in the U.S. beginning April 10, with pre-orders being accepted now. “We have completely reimagined... Read more
13-inch 2.5GHz MacBook Pro (refurbished) avai...
The Apple Store has Apple Certified Refurbished 13″ 2.5GHz MacBook Pros available for $829, or $270 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.... Read more
Save up to $80 on iPad Air 2s, NY tax only, f...
 B&H Photo has iPad Air 2s on sale for $80 off MSRP including free shipping plus NY sales tax only: - 16GB iPad Air 2 WiFi: $469.99 $30 off - 64GB iPad Air 2 WiFi: $549.99 $50 off - 128GB iPad... Read more
iMacs on sale for up to $205 off MSRP
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: $1019 $80 off - 21″ 2.7GHz iMac: $1189 $110 off - 21″ 2.9GHz... Read more

Jobs Board

DevOps Software Engineer - *Apple* Pay, iOS...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
*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
Sr. Technical Services Consultant, *Apple*...
**Job Summary** Apple Professional Services (APS) has an opening for a senior technical position that contributes to Apple 's efforts for strategic and transactional Read more
Lead *Apple* Solutions Consultant - Retail...
**Job Summary** Job Summary The Lead ASC is an Apple employee who serves as the Apple business manager and influencer in a hyper-business critical Reseller's store Read more
*Apple* Pay - Site Reliability Engineer - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.