slight improvement to fetch ssh keys from github

enable_ssh_on_windows.ps1

Param( 
    [parameter(Mandatory=$true)]
    [string]$SSHPublicKey
)

$ErrorActionPreference = "Stop"


function Get-SSHKeyFromGithub {
    Param(
        [Parameter(Mandatory=$true)]
        [string]$SSHKeyString
    )

    if ($SSHKeyString.StartsWith("gh:")) {
        $user = $SSHKeyString.Substring(3)
        if (!$user) {
            Throw("Invalid SSH key string {0}" -f @($SSHPublicKey))
        }
        $baseURL = "https://github.com/{0}.keys" -f @($user)
        $keys = wget -UseBasicParsing $baseURL
        return $keys.Content
    } else if ($SSHKeyString.StartsWith("ssh")) {
        return $SSHKeyString
    }
    Throw("Invalid ssh key string")
}

function Set-SSHPublicKey {
        Param(
                [Parameter(Mandatory=$true)]
                [string]$SSHKeyString
        )
    if(!$SSHKeyString) {
        return
    }
    $authorizedKeysFile = Join-Path $env:ProgramData "ssh\administrators_authorized_keys"
    Set-Content -Path $authorizedKeysFile -Value $SSHKeyString -Encoding ascii
    $acl = Get-Acl $authorizedKeysFile
    $acl.SetAccessRuleProtection($true, $false)
    $administratorsRule = New-Object system.security.accesscontrol.filesystemaccessrule("Administrator
s", "FullControl", "Allow")
    $systemRule = New-Object system.security.accesscontrol.filesystemaccessrule("SYSTEM", "FullControl
", "Allow")
    $acl.SetAccessRule($administratorsRule)
    $acl.SetAccessRule($systemRule)
    $acl | Set-Acl 
}

# Install OpenSSH

$(

Get-WindowsCapability -Online -Name OpenSSH* | Add-WindowsCapability -Online
$sshd = Get-Service sshd -ErrorAction SilentlyContinue
if (!$sshd) {
    Throw("SSH service is missing. Reboot may be required after capability install.")
}

Set-Service -Name sshd -StartupType Automatic
Start-Service sshd


# Fetch SSH Keys from github if called with a github ID
# eg: gh:gabriel-samfira
# Return string as is otherwise
$keys = Get-SSHKeyFromGithub -SSHKeyString $SSHPublicKey

# Authorize SSH key
Set-SSHPublicKey -SSHKeyString $keys

# Set PowerShell as default shell
New-ItemProperty -Force -Path "HKLM:\SOFTWARE\OpenSSH" -PropertyType String `
                 -Name DefaultShell -Value "C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe"

) *>$1 > C:\output.txt