OpenSSH from Linux to Windows 7 via tunneled RDP

I recently acquired a new second hand Asus laptop from my work,
that will be performing a handful of responsibilities on one of my networks.

This is the process I took to set up OpenSSH on Cygwin running on the Windows 7 box.

I won’t be going over the steps to tunnel RDP as I’ve already done this in another post

Make sure your LAN Manager Authentication Level is set as high as practical.
Keeping in mind, that some networked printers using SMB may struggle with these permissions set to high.

  1. Windows Firewall -> Allowed Programs -> checked Remote Desktop.
  2. System Properties -> Remote tab -> turn radio button on to at least “Allow connections from computers running any version of Remote Desktop”
    If you like, this can be turned off once SSH is set-up, or you can just turn the firewall rule off that lets RDP in.

CopSSH which I used on my last set of Linux to Windows RDP via SSH set-ups is no longer free.
So I’m not paying for something I can get for free, but with a little extra work involved.

So I looked at some other Windows SSH offerings

  1. freeSSHd which looked like a simple set-up, but it didn’t appear to be currently maintained.
  2. OpenSSH the current latest version of 5.9 released September 6, 2011
    A while back OpenSSH wasn’t being maintained. Looks like that’s changed.

OpenSSH is part of Cygwin, so you need to create a
c:\cygwin directory and download setup.exe into it.

    1. Right click on c:\cygwin\setup.exe and select “Run as Administrator”.
      Click Next.
    2. If Install from Internet is not checked, check it. Then click Next.
    3. Accept the default “Root Directory” of C:\cygwin. Accept the default for “Install For” as All Users.
    4. Accept the default “Local Package Directory” of C:\cygwin.
    5. Accept the default “Select Your Internet Connection” of “Direct Connection”. Click Next.
    6. Select the closest mirror to you. Click Next.
    7. You can expand the list by clicking the View button, or just expand the Net node.
    8. Find openssh and click the Skip text, so that the Bin check box for the item is on.
    9. Find tcp_wrappers and click the Skip text, so that the Bin check box for the item is on.

If you selected tcp_wrappers and get the “ssh-exchange-identification: Connection closed by remote host” error,
you’ll need to edit /etc/hosts.allow and add the following two lines before the PARANOID line.

ALL: 127.0.0.1/32 : allow
 ALL: [::1]/128: allow

These lines were already in the /etc/hosts.allow

(optional) find the package “diffutils”, click on the word “skip” so that an x appears in Column B,
find the package “zlib”, click on the word “skip” (it should be already selected) so that an x appears in Column B.

Click Next to start the install.
Click Next again to… Resolving Dependencies, keep default “Select required packages…” checked.
At the end of the install, I got the “Program compatibility Assistant” stating… This program might not have installed correctly.
I clicked This program installed correctly.

Add an environment variable to your Systems Path variable.
Edit the Path and append ;c:\cygwin\bin

Right click the new Cygwin Terminal shortcut and Run as administrator.
Make sure the following files have the correct permissions.

/etc/passwd -rw-r–r–
/etc/group -rw-r–r–
/var drwxr-xr-x

Create a sshd.log file in /var/log/

touch /var/log/sshd.log
chmod 664 /var/log/sshd.log

Run ssh-host-config

  1. Cygwin will then ask Should privilege separation be used? Answer Yes
  2. Cygwin will then ask Should this script create a local user ‘sshd’ on this machine? Answer Yes
  3. Cygwin will then ask Do you want to install sshd as service? Answer Yes
  4. Cygwin will then ask for the value of CYGWIN for the daemon: []? Answer ntsec tty
  5. Cygwin will then ask Do you want to use a different name? Answer no
  6. Cygwin will then ask Please enter a password for new user cyg_server? Enter a password twice and remember it.

replicate your Windows user credentials with cygwin

mkpasswd -cl > /etc/passwd
mkgroup --local > /etc/group

I think (although I haven’t tried it yet) when you change your user password, which you should do regularly,
you should be able to run the above 2 commands again to update your password.
As I haven’t done this yet, I would take a backup of these files before I ran the commands.

to start the service, type the following:

net start sshd

Test SSH

ssh localhost

When you make changes to the /etc/sshd_config,
because it’s owned by cyg_server, you’ll need to make any changes as the owner.
I added the following line to the end of the file:

Ciphers blowfish-cbc,aes128-cbc,3des-cbc

As it sounds like Blowfish runs faster than the default AES-128

There are also a collection of changes to be made to the /etc/sshd_config

for example:

  • Change the LoginGraceTime to as small as possible number.
  • PermitRootLogin no
  • Set PasswordAuthentication to no once you get key pair auth set-up.
  • PermitEmptyPasswords no
  • You can also setup AllowUsers and DenyUsers.

The options available are here in the man page (link updated 2013-10-06).
This is also helpful, I used this for my CopSSH setup.

Open firewalls TCP port 22 and close the RDP port once SSH is working.

As my blog post says:
ssh-copy-id MyUserName@MyWindows7Box

I already had a key pair with pass phrase, so I used that.
Now we should be able to ssh without being prompted for a password, but instead using key pair auth.

http://pigtail.net/LRP/printsrv/cygwin-sshd.html
http://www.petri.co.il/setup-ssh-server-vista.htm
http://www.scottmurphy.info/open-ssh-server-sshd-cygwin-windows

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2 Responses to “OpenSSH from Linux to Windows 7 via tunneled RDP”

  1. Ewan Says:

    I rarely comment, but after reading through a few of the responses on
    OpenSSH from Linux to Windows 7 via tunneled RDP Binarymist.
    I actually do have a couple of questions for you if you do not mind.
    Could it be simply me or does it look like some of these comments appear like they are written
    by brain dead individuals? 😛 And, if you are posting at other social sites,
    I’d like to follow you. Would you make a list of all of all your social networking sites like your linkedin profile, Facebook page or twitter feed?

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