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Configuring WSL as a ControlMaster relay server (view source)

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Disclaimer: This is still and experimental procedure (work in progress). Your feedback is welcome.
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=== How to install Linux on Windows with WSL ===
<translate>
Please follow this link for more detailed instructions
 
<!--T:1-->
{{Warning|title=Disclaimer |content=This is still an experimental procedure (work in progress).<br><br>
If you have suggestions, please write to [[technical support]].}}
 
<!--T:21-->
With this procedure you can leverage ControlMaster under WSL so you may log into the clusters with several apps under native Windows for a certain period without having to use multifactor authentication for every session.
 
=== Install Linux on Windows with WSL === <!--T:2-->
Please follow this link for more detailed instructions:
  https://docs.alliancecan.ca/wiki/Windows_Subsystem_for_Linux_(WSL)
  https://docs.alliancecan.ca/wiki/Windows_Subsystem_for_Linux_(WSL)


<!--T:3-->
This setup assumes the following on the sample config files:
This setup assumes the following on the sample config files:
* you selected Ubuntu as your distro of choice
* you selected Ubuntu as your distribution
* the hostname for the WSL instance is 'ubuntu'. Edit /etc/hostname (ubuntu) and /etc/hosts (127.0.0.1 localhost ubuntu)
* the hostname for the WSL instance is <i>ubuntu</i>: <i>/etc/hostname</i> contains <i>ubuntu</i> and <i>/etc/hosts</i> contains <i>127.0.0.1 localhost ubuntu</i>
* the Windows system is named 'smart' and my login name is 'jaime'
* the Windows system is named <i>smart</i> and the login name is <i>jaime</i>
* the user name on the ubuntu VM is also 'jaime'
* the user name on the Ubuntu VM is also <i>jaime</i>
* the Alliance user name is 'pinto' and I want to connect to 'cedar'
* the Alliance user name is <i>pinto</i> and we want to connect to Cedar


=== Install additional packages ===
=== Install additional packages === <!--T:4-->
<pre>
<pre>
  sudo apt update && sudo apt upgrade -y
  sudo apt update && sudo apt upgrade -y
  sudo apt install openssh-server -y
  sudo apt install openssh-server -y
</pre>
You may log in from Windows to Ubuntu with <code>ssh localhost</code>.


NOTE: you may login from Windows to Ubuntu with: ssh localhost
=== General idea of the setup === <!--T:5-->
</pre>
=== General idea of the setup ===
<pre>
<pre>
[ssh client] ----> [ssh relay server] ----> [ssh target server]
[ssh client] ----> [ssh relay server] ----> [ssh target server]
your Windows    modified authorized_keys    using cedar for
your Windows    modified authorized_keys    using cedar for
   machine          in your Ubuntu VM          this exercise
   machine          in your Ubuntu VM          this exercise
  'smart'              'ubuntu'                  'cedar'
<i>smart</i>        <i>ubuntu</i>                Cedar
</pre>
</pre>


=== Login to the ubuntu VM and create a custom_ssh folder ===
=== Log into the Ubuntu VM and create a <i>custom_ssh</i> folder === <!--T:6-->
<pre>
<pre>
jaime@ubuntu:~$ cat custom_ssh/sshd_config
jaime@ubuntu:~$ cat custom_ssh/sshd_config
Line 38: Line 48:
Subsystem sftp /usr/lib/openssh/sftp-server
Subsystem sftp /usr/lib/openssh/sftp-server
PidFile /home/jaime/custom_ssh/sshd.pid
PidFile /home/jaime/custom_ssh/sshd.pid
NOTE: you may copy the ssh_host keys from /etc/ssh
</pre>
</pre>
You may copy the ''ssh_host'' keys from ''/etc/ssh'' with:
<pre>sudo cp /etc/ssh/ssh_host_ed25519_key /home/jaime/custom_ssh/</pre>


=== Customize .ssh/config on ubuntu ===
=== Customize <i>.ssh/config</i> on Ubuntu === <!--T:7-->
<pre>
<pre>
jaime@ubuntu:~$ cat .ssh/config
jaime@ubuntu:~$ cat ~/.ssh/config
Host cedar
Host cedar
     ControlPath ~/.ssh/cm-%r@%h:%p
     ControlPath ~/.ssh/cm-%r@%h:%p
Line 53: Line 63:
</pre>
</pre>


=== Customize the authorized_keys ===
=== Customize the authorized keys === <!--T:8-->
<pre>
<pre>
jaime@ubuntu:~/custom_ssh$ cat /home/jaime/custom_ssh/authorized_keys
jaime@ubuntu:~/custom_ssh$ cat /home/jaime/custom_ssh/authorized_keys
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIHSRvqzlffkzcjRAaMQoTBrPe5FxlSA6cQ0v3yVzN+A+
ssh-ed25519 AAAZDINzaC1lZDI1NTE5AAC1lZDIvqzlffkzcjRAaMQoTBrPe5FxlSAjRAaMQyVzN+A+
</pre>


NOTE: use the same public ssh key that you uploaded to CCDB
<!--T:9-->
</pre>
Use the same public SSH key that you uploaded to CCDB.


=== Now start the sshd server on 'ubuntu' ===
=== Now start the sshd server on Ubuntu === <!--T:10-->
<pre>
<pre>
jaime@ubuntu:~/custom_ssh$ /usr/sbin/sshd -f ${HOME}/custom_ssh/sshd_config
jaime@ubuntu:~/custom_ssh$ /usr/sbin/sshd -f ${HOME}/custom_ssh/sshd_config
</pre>


NOTE: make sure your start the server as yourself, now as root.
<!--T:11-->
</pre>
Make sure you start the server as yourself, not as root.
You will also need to start the sshd server every time you restart your computer, or after closing or restarting WSL.


=== Customize .ssh/config on 'smart' with RemoteCommand ===
=== Customize <i>.ssh/config</i> on <i>smart</i> with <code>RemoteCommand</code> === <!--T:12-->
<pre>
<pre>
jaime@smart ~/.ssh cat config
jaime@smart ~/.ssh cat config
Line 76: Line 89:
</pre>
</pre>


=== You are now ready to try to login to cedar ===
=== You are now ready to try to log into Cedar === <!--T:13-->
<pre>
<pre>
jaime@smart ~
jaime@smart ~
Line 90: Line 103:
</pre>
</pre>


=== Alternative setup ===
=== Alternative setup === <!--T:14-->
There is another way in which you could customize the authorized_keys on Ubuntu and the ~/.ssh/config on Windows such that it may work better for some Windows GUI apps that don't let you explicitly set the RemoteCommand (such as WinSCP). In this case you set the RemoteCommand on the pub key:
There is another way in which you could customize the authorized keys on Ubuntu and the <i>~/.ssh/config</i> on Windows such that it may work better for some Windows GUI apps that don't let you explicitly set the <code>RemoteCommand</code> (such as WinSCP). In this case you set the <code>RemoteCommand</code> on the public key:
<pre>
<pre>
jaime@ubuntu:~/custom_ssh$ cat /home/jaime/custom_ssh/authorized_keys
jaime@ubuntu:~/custom_ssh$ cat /home/jaime/custom_ssh/authorized_keys
command="ssh cedar" ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIHSRvqzlffkzcjRAaMQoTBrPe5FxlSA6cQ0v3yVzN+A+
command="ssh cedar" ssh-ed25519 AAAZDINzaC1lZDI1NTE5AAC1lZDIvqzlffkzcjRAaMQoTBrPe5FxlSAjRAaMQyVzN+A+


<!--T:15-->
jaime@smart ~/.ssh cat config
jaime@smart ~/.ssh cat config
Host ubuntu
Host ubuntu
Line 102: Line 116:
</pre>
</pre>


You may still "ssh ubuntu -p 2222" after that from a shell on Windows.
<!--T:16-->
You may still use <code>ssh ubuntu -p 2222</code> after that from a shell on Windows.


=== Setup with MobaXterm ===
=== Setup with MobaXterm === <!--T:17-->


<!--T:18-->
[[File:MobaXterm-setup.jpg]]
[[File:MobaXterm-setup.jpg]]


<!--T:19-->
[[File:MobaXterm-VSL-localdriveC.jpg]]
[[File:MobaXterm-VSL-localdriveC.jpg]]
</translate>
<!--
=== Outstanding challenges ===
With this setup you may be prompt for MFA duo authentication only on the first session. Subsequently multiple SSH sessions can be started on Cedar without MFA. This also works fine to get remote shells on Cedar from several apps running natively on Windows. We already tried for WinSCP, but we can assume it will work for other apps with some tweaks.


=== Outstanding Challenges ===
However, what I'm realizing now is that on those very same Windows apps I'm not able to list/display the contents of the local Windows drives. Instead they all show the contents of the ubuntu relay server, which may not be what users want. I imagine in the most generic case they would like to transfer files directly between Windows and cedar, and not between Ubuntu and cedar. In any case, users may still see the contents of the Windows host mounted as the /mnt file system on Ubuntu [[Windows_Subsystem_for_Linux_(WSL)#File_access_between_Windows_and_Linux|as explained here]].
With this setup you may be prompt for MFA-duo authentication only on the first session. Subsequently multiple ssh sessions can be started on cedar without MFA. This also works fine to get remote shells on cedar from several apps running natively on Windows. I already tried for WinSCP, but we can assume if will work for other apps with some tweaks.
 
However, what I'm realizing now is that on those very same Windows apps I'm not able to list/display the contents of the local Windows drives. Instead they all show the contents of the ubuntu relay server, which may not be what users want. In the most generic case they would like to transfer files directly between Windows and cedar, and not between Ubuntu and cedar. In any case, users may still see the contents of the Windows host mounted as the /mnt file system on Ubuntu [[Windows_Subsystem_for_Linux_(WSL)#File_access_between_Windows_and_Linux|as explained here]].


I'm also trying to understand how to setup scp directly from Windows to cedar.
I'm also trying to understand how to setup scp and sftp directly from Windows to cedar. To that effect, we might want explore the possibility of having a "generic command script", similar to the setup with automation under MFA, in which we could capture several commands with the pub key in the authorized_keys file.


Ultimately we can conceive multiple stanzas in the .ssh/config, one for each site (cedar, graham, beluga, ...) on different ports (2222, 2223, 2224, ...)  
Ultimately we can conceive multiple stanzas in the .ssh/config, one for each site (cedar, graham, beluga, ...) on different ports (2222, 2223, 2224, ...)  


Therefore, I probably need a hand from some of you to figure this out. Alliance staff members could post suggestions in the security-mfa channel. Users in general please send email to support with the subject "WSL, ControlMaster/MFA suggestion". Thanks
Therefore, I probably need a hand from some of you to figure this out. Alliance staff members could post suggestions in the security-mfa channel. Users in general please send email to support with the subject "WSL, ControlMaster/MFA suggestion". Thanks
-->
Mboisson
Bureaucrats, cc_docs_admin, cc_staff, rsnt_translations
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