Creating Dynamic SSH Tunnel on Windows with Plink – Scriptable SSH Tunnels on Windows

creating-ssh-tunnel-on-windows-with-plink-ssh-tunnel-diagram-tunnel-email-traffic

In my earlier articles I've explained about Creating SSH Tunnels on Linux and BSD and how to create SSH Tunnels with Putty Terminal client on Windows.

Creating SSH Tunnels is a precious knowledge every advanced computer user, a system administrator or security expert should be well aware of.

Probably still there are plenty of people for which the SSH Tunnelling is something never heard of or even if heard it is a mythical term covered by ancient shadows 🙂

So What is an SSH Tunnel? – SSH Tunnels shortly explained.

A SSH tunnel consists of an encrypted tunnel created through a SSH protocol
connection
.

An SSH tunnel can be used to transfer unencrypted traffic over a
network through an encrypted channel
between two hosts (host A and Host B) usually using remote and local port.

Requirements for SSH tunnel

Where Host B has to be running a version of OpenSSH server on some reachable port from Host B, (lets say 22).
Host B OpenSSH server has to be with (enabled X11Forwarding X11Forwarding yes in /etc/ssh/sshd_config) and Host A needs to have some SSH client supporting port forwarding (ssh command on Linux – part of (openssh-client package) and on Windows – Putty / Plink or any other of the many available ssh tunneling clients).

Probably most common SSH Tunnel use is to bypass firewalls that prohibits or filter certain internet services.
In other words SSH Tunnels can be used to get around firewall filtering. If you never heard of Bypassing firewalls with port forwarding I recommend to check this article

We can use a ssh tunnel to securely transfer files between a FTP server and a client even though the FTP
protocol itself is not encrypted
, Tnnel traffic to an SQL server, Tunnel traffic from your Desktop PC to a Proxy
SSH tunnels can be used to tunnel outbound E-mail traffic back to your work PC to avoid having to change SMTP servers etc.

A very common SSH Tunnel use is by office workers who don't want their Custom Web browsing habbits and Web history be tracked,

For people who has to travel a lot tunneling SSH traffic from notebook to your home based SMTP is mandatory, otherwise your e-mail passwords, might end up captured by someone who manages the Free WI-FI used by you somewhere on the road or cafeteria. Another good case use of SSH Tunnel is to tunnel VNC traffic.

SSH Tunneling was historically very famous in days where IRC (Internet Relay Chat) and used to be common way (for people who want to prevent their real IP address from publicly visible) on the Internet.
SSH Tunneling is great way to maintain high communication security, however because it requires some basic technical knowledge most people neglect it or never heard of it, so I hope this article will give at least basic ideas to people new to tunneling.

How to create SSH Tunnels on Microsoft Windows

SSH Tunneling has been originally invented on UNIX / Linux platform, luckily nowdays it is easily possible to create SSH tunnels on almost any moden OS (including Mac OS X and M$ Windows).

Using Plink it is possible to create easily (batch) scriptable SSH tunnels on Windows

Generally here is example of basic plink use syntax:
 

plink.exe {remote-host} -P 22 -C -D 10080 -l username -pw password
 

To make a Tunnel with Plink to remote SSH Server (remote-ssh-server.com) listening for connections on port 22 on localhost 10022

"C:Program Files (x86)PuTTYplink.exe" -ssh remote-username@tunnel-to-ssh-server-host.com -pw PASSWORD123 -C -T -D 127.0.0.1:10022 -N

-D – option instructs Plink to make "Dynamic SOCKS-based port forwarding"
Dynamic Socks-based port forwarding will make your ssh client a simple socks server which listen to port 10022 for incoming connections.
-Ttells plink not to open interactive shell on remote server (disable pty allocation)
-Cenables traffic compression

Using the -D option you can prepare tunnel to traffic all your outgoing server traffic via the SSH tunneling host.

E. g. -D allows you to use the remote ssh server as a proxy server with no need for remote server to run anything except SSH service and have Internet connection.

-N – stands for "don't start shell/command SSH-2 only"

On success of SSH Tunnel establishing you will get a pop-up window similar to below screenshot (note that some of the messages in cmd line are from a batch script – if no batch script is used you wil only get a window with "Using Username":

plink_establishing_ssh_tunnel-on-microsoft-windows-screenshot

Note: That if you're about to be using Plink command frequently add it to your Windows SYSTEM PATH (check my previous article – how to add Putty to System PATH) to enable it invokable without writting the full command path location.

Once this Window is open if you still have doubt, where the tunnel is established, the quickest way to test whether tunnel is working is to open telnet to localhost port 10022.

In Windows command prompt type:
 

C:> telnet localhost 10022

 

You will get a remote server SSH version printed, like on below shot:

windows-testing-whether-ssh-tunnel-is-working-with-telnet-screenshot-black-screen

Now lets say now you would like to access the internet via just created SSH tunnel.
You can do it by simply setting Socks Proxy in your Firefox / Opera (or whatever browser you use).

Whether you want to run the SSH Tunnel permanent and periodically check whether tunnel is allve and respawn it in case plink quit, you can use a very simple batch script like one below:
 

@ECHO OFF
tasklist /FI "IMAGENAME eq plink.exe" 2>NUL | find /I /N "plink.exe">NUL

if "%ERRORLEVEL%"=="0"  ( echo Programm is running exiting
exit
)
echo "Not Running"
start /b "C:Program Files (x86)PuTTYplink.exe" -ssh remote-username@tunnel-to-ssh-server-host.com -pw Password123 -T -C -D 127.0.0.1:10022 -N"


If you're a Linux guy and you don't want to mess around with Plink but still want to create your SSH tunnels following SSH client UNIX command line syntax, setup the Cygwin port of OpenSSH for Windows.

Or if you're unsure whether remote server is always reachable (you're moving with your notebook from (Country) network to network), you can use also portqry – windows port scanner to check whether remote ssh server port is opened:
 

@ECHO OFF
tasklist /FI "IMAGENAME eq plink.exe" 2>NUL | find /I /N "plink.exe">NUL
if "%ERRORLEVEL%"=="0"  ( echo Programm is running exiting
pause
exit
)
portqry -n tunnel-to-ssh-server-host.com -p tcp -e 22
if %ERRORLEVEL%==0 echo tunnel-to-ssh-server-host.com Reachable Connecting ..
if NOT %ERRORLEVEL%==0 (echo tunnel-to-ssh-server-host.com.com Unreachable
exit)
echo "Not Running. Starting"
"C:Program Files (x86)PuTTYplink.exe" -ssh remote-username@tunnel-to-ssh-server-host.com -pw Password123 -T -C -D 127.0.0.1:10080 –N


Here is another sample use of Plink to create tunnel via SSH host tunnel-to-ssh-server-host.com  to listen for connections on localhost port 1234 and forward all incoming traffic to squid proxy server on 192.168.1.5 on port 3128.
 

C:Usersgeorgi>plink.exe -v -x -a -T -C -noagent -ssh -L 127.0.0.1:1234:192.168.1.5:3128 remote-username@tunnel-to-ssh-server-host.com

Setting then 127.0.0.1:1234 in  Firefox Proxy browser settings will make all traffic from your browser to flow securily to your own proxy server (letting you hide your "custom traffic" from company Web sniffers (Proxying) and Web filtering.
A remark to make here is 192.168.1.5 is (a internal server with Squid Proxy, configured to pass traffic to the internet ).

Here is a way to make tunnel between your remote SSH server and local Desktop PC to make Google queries without being logged by your ISP or company where you're working:

plink.exe "-v -x -a -T -C -noagent -ssh -L 127.
0.0.1:1234:95.158.130.242:443 -pw SecretPassword123 -l hipo pc-freak.net"

95.158.130.242 – is one of the IPs www.google.com resolves to
pc-freak.net – is name of my home router.

To make tunneled queries to Google then open in browser https://127.0.0.1:1234

using_localhost_ssh_tunnel_to_anonymously-search-in-google-plink-tunnel-for-security

 

If you're a lazy windows user and don't want to bother to make your tunnels from command line and you want need nice gui way to manage multiple tunnels – check out putty-tunnel-manager.

I myself am not a SSH Tunnel expert and thus Iwould be happy to learn further from people for some interesting cases and custom ways to do  SSH Tunnels. If you know of better advantageous ways to tunnel traffic, please share.

Happy tunneling ! 🙂

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6 Responses to “Creating Dynamic SSH Tunnel on Windows with Plink – Scriptable SSH Tunnels on Windows”

  1. admin says:
    Firefox 30.0 Firefox 30.0 Windows 7 x64 Edition Windows 7 x64 Edition
    Mozilla/5.0 (Windows NT 6.1; WOW64; rv:30.0) Gecko/20100101 Firefox/30.0

    If you want to make sure your SSH Tunnel is always active and respawned if it dies you can create a Neverending Batch Loop and start it as a Windows service.

    :: This is a batch file. Save with file name: plink_forever.bat
      :restart
      plink saved_session_name
      goto restart
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  2. Doppiamunnezza says:
    Firefox 30.0 Firefox 30.0 Windows 7 x64 Edition Windows 7 x64 Edition
    Mozilla/5.0 (Windows NT 6.1; WOW64; rv:30.0) Gecko/20100101 Firefox/30.0

    Hi, the scenario you depicted can work trough a proxy that requires authentication? This is the situation:
    My work pc (windows 7) connects to the internet through a proxy server that requires a username/password and i would like to RDP into it from my home pc but i can’t modify proxy configuration so i was thinking that making an ssh tunnel (reverse tunnel really) could work to reach my goal.
    Do you think your example can be adapted to my scenario?
    If not do you know of any product i can use?
    Thanks in advance

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    • admin says:
      Firefox 30.0 Firefox 30.0 Windows 7 x64 Edition Windows 7 x64 Edition
      Mozilla/5.0 (Windows NT 6.1; WOW64; rv:30.0) Gecko/20100101 Firefox/30.0

      Hi Doppiamunnezza,

      If you have already running SSH server (Linux host) and this host could connect to your Windows remote desktop port (3389) you can use plink to forward SSH tunnelled traffic via the Linux host like so:

      plink.exe -P 22 -L 13389:windows-rdp-host.com:3389 server-username@remote-linux-server.com
      pw secretpassword -N -C

      SSH tunnel will be be available via localhost:13389. From windows command line to connect with
      Remote Desktop Client:

      mstsc.exe -v localhost:13389

      Note that connection will be a bit slow but this depends also on your internet connection between linux-server and windows host and yourself within the net where you’re.

      To do the same SSH Tunnel to foward traffic via 13389 (if you’re using a Linux desktop) issue:

      ssh -p 22 -L 13389:rdp.hec.bg:3389 hipo@pc-freak.net -v

      Hope this helps
       

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      • Doppiamunnezza says:
        Firefox 30.0 Firefox 30.0 Windows 7 x64 Edition Windows 7 x64 Edition
        Mozilla/5.0 (Windows NT 6.1; WOW64; rv:30.0) Gecko/20100101 Firefox/30.0

        Hi, thanks for your answer but i’m not really sure i’ve understood …
        In your hypothesis the linux box (SSH Server) is in the same lan with the windows box i want to rdp into ??

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  3. File Transfer Protocol Linux Command says:
    Firefox 35.0 Firefox 35.0 Windows 7 x64 Edition Windows 7 x64 Edition
    Mozilla/5.0 (Windows NT 6.1; WOW64; rv:35.0) Gecko/20100101 Firefox/35.0 AlexaToolbar/alxf-2.21

    What a material of un-ambiguity and preserveness of precious knowledge regarding unpredicted emotions.

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  4. visitor says:
    Firefox 33.0 Firefox 33.0 Windows 7 x64 Edition Windows 7 x64 Edition
    Mozilla/5.0 (Windows NT 6.1; WOW64; rv:33.0) Gecko/20120101 Firefox/33.0

    your formatting blog, and content, are shit!

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