WSLSSHSetup.ps1

##########################################################################
# Automated OpenSSH Server configuration for Windows through the Windows #
# Subsystem for Linux (WSL).                                             #
##########################################################################

#
# Before this script can be run successfully, please make sure WSL is
# installed and enabled by running the following command in the PowerShell:
#
# wsl --install
#
# If you get the wsl command's manual page, wither wsl is already installed
# on your system, or you need to run:
#
# wsl.exe --install -d Ubuntu
# (See https://github.com/MicrosoftDocs/WSL/issues/1054#issuecomment-756981917)
#
# After installation, you must reboot your computer:
# shutdown -r
# 
# Wait for Ubuntu to finish its setup process. Once completed, this script should install
# and configure OpenSSH Server using a new user (by default wslssh) and
# the provided password.

$wslUsername = "wslssh"
$wslPassword = "wslsshPass"
$createUserCommand = "sudo useradd $wslUsername"
$changePasswordCommand = "echo `"${wslUsername}:${wslPassword}`" | chpasswd"


# Create new user in WSL.
wsl /bin/bash -c "$createUserCommand || $changePasswordCommand"

# Install OpenSSH Server within WSL.
$removeSSH = "sudo apt remove -y openssh-server"
$installSSH = "sudo apt install -y openssh-server"

# Edit the OpenSSH Server service configuration to allow remote access for
# the current user using password authentication.
$sshdConfigPath = "/etc/ssh/sshd_config"
$sedPatten = "s/PasswordAuthentication no/PasswordAuthentication yes/g"
$enablePasswordAuth = "sudo sed -i -e '${sedPatten}' ${sshdConfigPath}"
$allowUser = "echo 'AllowUsers ${wslUsername}' | `
              sudo tee -a /etc/ssh/sshd_config"
$restartSSH = "sudo service ssh --full-restart"

# Allow the SSH service to be started using an external trigger from Windows.
$startSSHTask = "echo '%sudo ALL=NOPASSWD: /usr/sbin/sshd' | `
                 sudo tee /etc/sudoers.d/ssh"

# Execute WSL SSH setup.
wsl -u root /bin/bash -c `
    "$removeSSH && `
     $installSSH && `
     $enablePasswordAuth && `
     $allowUser && `
     $restartSSH && `
     $startSSHTask"

# Create a new task on Windows to start the SSH service on system startup.
$taskName = "Start SSH Server"
$taskDescription = "Starts the OpenBSD Secure Shell server service on WSL."
$taskExecutable = "%windir%\System32\bash.exe"
$taskArgument = '-c "sudo /etc/init.d/ssh start"'
$taskAction = New-ScheduledTaskAction `
    -Execute $taskExecutable `
    -Argument $taskArgument
$taskTrigger = New-ScheduledTaskTrigger -AtStartup
Register-ScheduledTask `
    -TaskName $taskName `
    -Action $taskAction `
    -Trigger $taskTrigger `
    -Description $taskDescription 

# Create a new firewall rule to allow inbound TCP traffic on local port 22.
New-NetFirewallRule `
    -DisplayName "SSH Server" `
    -Direction Inbound `
    -LocalPort 22 `
    -Protocol TCP `
    -Profile Domain,Private `
    -Action Allow