Multihost.md

CIFS-over-SSH: Access to multiple remote hosts, no Kerberos

(tested Win10 1809,1909,20H2,21H1,21H2,22H2 and Win11 22H2 Home&Enterprise)

Introduction

This tutorial contains screenshots for the English version of Windows 10 and 11.

To be able to mount a Windows share on a single remote host over SSH we will need

• Administrator access to the local computer, including the ability to elevate privileges. If you don't know what I am talking about then stop reading right here.

• One real or virtual network adapter, NOT bound to the Client for Microsoft Networks driver.

• One real or virtual network adapter, bound to the Client for Microsoft Networks driver.

Normally you should already have such an adapter, as otherwise you would not be able to mount any Windows shares.

This part of the tutorial is split into the following steps:

1. As most people do not have a spare real network adapter in their computer, we will add an extra virtual network adapter by installing the Microsoft KM-TEST Loopback Adapter.

2. After that, the network adapter must be properly configured.

3. Starting with Windows 10 update 1903, the Windows 10 feature "SMB 1.0" must be turned off.

4. Furthermore, a few Windows system services need to be tweaked.

5. Next, reboot Windows to verify that we've been able to grab port 445 and to see if the lanmanserver service is up and running.

6. Finally, we launch a special OpenSSH session and mount our remote share.

7. For those wishing to undo the above steps follow the instructions at the bottom of this page.

Windows 10 Upgrade woes

Multiple persons have reported problems after a major Windows 10 upgrade (e.g. from 1803 to 1809). This is due mostly to the disappearance of the Microsoft KM-TEST Loopback Adapter and of the portproxy rule. In order to recover after a Windows 10 upgrade, try

• Redo step 1 and reboot
• If the adapter is still not present, run the devmgmt.msc management console application and choose View->Show Hidden devices to see you can find the adapter again. If not, redo step 2.
• Redo steps 3, 4 and 5.

Installing the Loopback Adapter

To install the Loopback adapter follow these steps:

• Start the Add Hardware Wizard by either going Start->Settings->Control Panel->Add Hardware or by starting a console window with elevated (Administrator) privileges. In the console window type

  hdwwiz.exe

• The Hardware Wizard will come up:

  

  Click Next to continue.

• Select Install the hardware that I manually select from a list:

  

  Click Next to continue.

• Select the entry Network adapters:

  

  Click Next to continue.

• In the next screen

  

  first select Microsoft from the list of Manufacturers and then select Microsoft KM-TEST Loopback Adapter from the list of Network Adapters. Finally, click Next once more.

• Almost finished:

  

  This is your last chance to abort, otherwise, click Next.

• After a while you should see:

  

  Click Finish to exit the Hardware Wizard.

You are now ready to configure your newly installed Loopback adapter. Even though Windows might not ask you to, reboot anyways (heey, it's a Microsoft OS ;-)).

From reports I've seen on the Internet a reboot is sometimes required for the loopback adapter to come up properly.

Configuring the Loopback Adapter

Now that your newly installed loopback adapter is up and running we must configure it properly:

• Go to the Network Connections Center:

  

• Choose the loopback adapter (usually it is named something like "Local Area Connection #3") and right-click on it:

  

• Choose Properties, after which a new window will appear

  

  Make sure that

  • the entry Client for Microsoft Networks is NOT enabled, i.e. does not have a checkmark in front of it.
  • the entry File and Printer sharing for Microsoft Networks is NOT enabled, i.e. does not have a checkmark in front of it.
  • the entry Internet Protocol (TCP/IP) is enabled.

• Select the entry Internet Protocol (TCP/IP), then click on Properties.

• A new window will appear:

  

  Select Use the following IP address and fill in for the 'IP address' 10.255.255.1 and for the 'Subnet mask' 255.255.255.0. This IP address will be used to mount shares from the first remote host.

  It is not necessary to fill in the 'Default gateway' or a 'DNS server'.

• Click on Advanced to make the following window appear:

  

  Deselect Automatic metric and fill in the value of 9999 as the 'Interface metric' as shown above.

• In the same window, click on the button Add in the block labeled IP addresses. A new window will pop up:

  

  Add an IP address for each of the extra remote hosts that you want to mount shares from.

  For example, if you need to mount shares from 3 different servers, repeat this step twice, filling in 'IP Address' = 10.255.255.2, 'Subnet mask' = 255.255.255.0 and 'IP Address' = 10.255.255.3, 'Subnet mask' = 255.255.255.0.

• Click on the WINS tab:

  

  and select Disable NetBIOS over TCP/IP.

• Click on OK.

• You are now back in the main 'TCP/IP Properties' screen. Click OK again.

• You are now back in the main 'Loopback Properties' screen. Click Close.

Disabling the 'SMB 1.0' Windows feature

Starting with Windows 10 update 1903 we need to disable the Windows feature SMB 1.0:

• Go to the Control Panel->Programs->Programs and Features and select Turn Windows features on or off

• A list of features pops up:

  

  Scroll down and deselect the feature SMB 1.0/CIFS File Sharing support

• Now close this control panel item.

(Thanks to Michael Uhlenberg for pointing this out)

Tweaking the 'LanmanServer' service

First, we need to tweak a Windows system service to overcome the thing that Microsoft broke. The root cause of the problem is that we need to access the file share using TCP port 445. However, when Windows boots, this port is grabbed by the system lanmanserver service for all interfaces.

If we can insert a portproxy rule to grab port 445 for the loopback interface before the lanmanserver service starts, we can circumvent this. Be aware that portproxy rules are executed by the iphlpsvc service.

By adding a dependency to the lanmanserver service we ensure that the iphlpsvc service is always launched before the lanmanserver service. This section explains how to do this:

• Start a console window with elevated (Administrator) privileges.
• Get the list of service dependencies by typing:

  sc qc lanmanserver

You should see output similar to this:

[SC] QueryServiceConfig SUCCESS

SERVICE_NAME: lanmanserver
        TYPE               : 20  WIN32_SHARE_PROCESS 
        START_TYPE         : 2   AUTO_START
        ERROR_CONTROL      : 1   NORMAL
        BINARY_PATH_NAME   : C:\WINDOWS\system32\svchost.exe -k netsvcs -p
        LOAD_ORDER_GROUP   : 
        TAG                : 0
        DISPLAY_NAME       : Server
        DEPENDENCIES       : SamSS
                           : Srv2
        SERVICE_START_NAME : LocalSystem

Alternatively, you can use the Powershell command

  Get-Service -DisplayName server -RequiredServices

• Note down the names of the services on which the Server service (also known as lanmanserver) depends. In this case, these services are samss and srv2 (the service names are case independent).

• Change the list of services on which the lanmanserver services depends by adding the iphlpsvc service to the list of required services found in the previous step:

  sc config lanmanserver depend= samss/srv2/iphlpsvc

NOTES:

• The space after the "depend= " is required!

• Dependencies are separated using slashes ("/").

• Next we add a portproxy rule to reroute TCP port 445 to a port of our choosing. For this tutorial, I choose 44445. We need to do this for each of the IP addresses that we set up in the previous section:

  netsh interface portproxy add v4tov4 listenaddress=10.255.255.1 listenport=445 connectaddress=10.255.255.1 connectport=44445
  netsh interface portproxy add v4tov4 listenaddress=10.255.255.2 listenport=445 connectaddress=10.255.255.2 connectport=44445
  netsh interface portproxy add v4tov4 listenaddress=10.255.255.3 listenport=445 connectaddress=10.255.255.3 connectport=44445

NOTE: The connectaddress must be identical to the listenaddress

If all went well you should see something like

The portproxy rule is persistent, so there should be no need to repeat this step after a reboot.

Reboot and verify

Of course, now that we have made modifications to the 'Required Services' dependency of the 'LanmanServer' service we have to reboot Windows before proceeding.

• Reboot Windows.
• Verify that the portproxy was applied successfully by checking the open ports on the system. Type in a command console

  netstat -an | find ":445"

You should see something like:

C:\WINDOWS\system32>netstat -an | find ":445"
  TCP    0.0.0.0:445            0.0.0.0:0              LISTENING
  TCP    10.255.255.1:445       0.0.0.0:0              LISTENING
  TCP    10.255.255.2:445       0.0.0.0:0              LISTENING
  TCP    10.255.255.3:445       0.0.0.0:0              LISTENING
  TCP    [::]:445               [::]:0                 LISTENING

If you see only '0.0.0.0:445' instead then the 'portproxy' rule was not applied correctly. Verify that the right 'portproxy' rule was used

   netsh interface portproxy show v4tov4

and verify that the IpHlpSvc service is running at Windows startup using

  sc query iphlpsvc

Another reason for the 'port grabbing' to fail could be the LanmanWorkstation service running at Windows startup. If so, try giving it the same treatment as LanmanServer. However, on the Windows 10 installations I tested this service was running at system startup without causing any problems.

• After Windows comes up and you have logged in, check the status of the 'lanmanserver' service. Open a command console (no privilege elevation is required) and type

  sc query lanmanserver

The 'LanmanServer' service should be in the state Running. If it is not, then follow these steps to create a task using the Task Schedule to start it at system startup.

If the port is not grabbed correctly (i.e. no 10.255.255.1:445 in the netstat output) then try the Old driver tweak instructions to see if that works better for you.

Putting it all together

Now that we have configured both our loopback adapter we can put it all together by launching a special OpenSSH connection and mounting the shares from the remote servers fs1.example.org, fs2.example.org and fs3.example.org as Windows shares:

• Launch an OpenSSH session with some special port-forwarding rules and login on login.example.org as normal. Open a Command console or terminal and type:

  ssh -v -N -n -L 10.255.255.1:44445:fs1.example.org:445 \
               -L 10.255.255.2:44445:fs2.example.org:445 \
               -L 10.255.255.3:44445:fs3.example.org:445 \
                <Your-userid>@login.example.org

Yes, there are lots of colons in that -L option but you need them all.

• The first time you start the command with the special port forwarding rules, you will be (probably) be prompted by the Windows Defender Firewall that it has blocked some features:

  

  Allow access to at least Public networks by ticking the checkbox, then click on Allow access as otherwise the port-forwarding will not work.

• Make sure port-forwarding is working properly by checking the (verbose) log:

  

  Make sure the line

  debug1: Local connections to 10.255.255.1:44445 forwarded to remote address fs.example.org:445

is present before continuing.

• Go to Start->Run and type \\10.255.255.1\
• In the Console window you should now see a line

  debug1: Connection to port 44445 forwarding to fs.example.org:445 requested.

as in the following screenshot:

If this is present then you can decrease the debug logging of the OpenSSH session by removing the -v option from the command line:

  ssh -N -n -L 10.255.255.1:44445:fs1.example.org:445 \
            -L 10.255.255.2:44445:fs2.example.org:445 \
            -L 10.255.255.3:44445:fs3.example.org:445 \
            <Your-userid>@login.example.org

Note If you carefully inspect the above screenshot then you will notice that I am using the (built-in) OpenSSH Authentication Agent in combination with an SSH public/private keypair to avoid having to type in my password every time.

• You will be prompted to authenticate yourself:

  

  For the Username, fill in the domain DOMAIN\ followed by your userid.

• You should now see your remote share in Windows Explorer!

Mapping a network drive

To make life even easier it might be handy to map a network drive to your remote share:

• Start Windows Explorer and choose Tools->Map Network Drive.

• In the next screen, fill in:

  

• Choose an available drive letter.

• Do NOT click on Browse but type in as the Folder name: \\10.255.255.1\<directory>

• Enable the checkbox in front of Connect using different credentials.

• Now click on Finish.

• In the next screen, fill in your Windows userid:

  

  For the Username, fill in the domain DOMAIN\ followed by your userid.

• In the next screen, click on Finish to complete the network drive mapping.

• You should now see a new drive letter appear in the Folders tree-list in Windows Explorer. Click on it to verify that you are indeed viewing the remote shares from each server.

Control+Z! Undo! Undo!

For those wishing to undo the CIFS-over-SSH trick follow these steps:

• Start a console window with elevated (Administrator) privileges.
• Restore the dependencies of the lanmanserver service by typing

  sc config lanmanserver depend= samss/srv2

NOTES

• the list of required services may be slightly different on your system. Use the PowerShell command from this section to obtain a list.
• the space after the depend= !
• Remove the portproxy rules by typing

  netsh interface portproxy delete v4tov4 listenaddress=10.255.255.1 listenport=445
  netsh interface portproxy delete v4tov4 listenaddress=10.255.255.2 listenport=445
  netsh interface portproxy delete v4tov4 listenaddress=10.255.255.3 listenport=445
  ....

• Remove the firewall rule to allow SSH to do portforwarding from 10.255.255.1:

  • Go to the Windows Control Panel

  • Select System and Security, then Windows Defender Firewall

  • Select Allowed apps, and scroll down in the list to SSH Telnet and Rlogin client and deselect the permissions

    

    Then press OK

• Start a Device Manager by typing

  devmgmt.msc

• Expand the 'Network Adapters', right-click on Loopback adapter and select Uninstall.
• If necessary, use the 'Task Scheduler' from the 'Administrative Tasks' menu to delete the task 'Start LanmanServer driver'.