Question

I need to automate an command line application. It asks the user to enter a password. All my approches to send the password via STDIN failed. Now I am trying to do this with an wrapper-programm using .NET.

I am starting the application creating a new process, setting the StartInfo-properties and then start the process:

Dim app_path As String
Dim app_args As String
Dim myProcess As Process = New Process()
myProcess.StartInfo.FileName = app_path
myProcess.StartInfo.Arguments = app_args
myProcess.StartInfo.UseShellExecute = False
myProcess.Start()

I did try to use the StartInfo.RedirectStandardInput Property but with no success.

Now I came accross the WriteConsoleInput function from the kernel32.dll that I included like this:

Declare Function WriteConsoleInput Lib "kernel32.dll" Alias "WriteConsoleInputA" (ByVal hConsoleInput As Integer, ByVal lpBuffer As String, ByVal nNumberOfCharsToWrite As Integer, ByRef lpNumberOfCharsWritten As Integer) As Boolean

I can get the handle of the process via the myProcess.Handle property. But sending input to the input-buffer using this way was also not possible.

I found those questions but they did not help:

• How do I write ‘PAGE DOWN’ into the console input buffer? (1475353)

• Java – passing input into external C/C++ application (1421273)

• Controlling a Windows Console App w/ stdin pipe (723424)

Using StraceNtX.exe I got this output for the moment the app is waiting for input:

[T4024] GetConsoleMode(f, 12d35c, 12d3af, 77bff894, ...) = 1
[T4024] SetConsoleMode(f, 0, 12d3af, 77bff894, ...) = 1
[T4024] ReadConsoleInputA(f, 12d348, 1, 12d360, ...) = 1

Can anyone tell me, what else to try or how to do the above the right way?
Thanks!

---

Based on Tim Robinsons answere I’ve got this code now, but it does not work:

myProcess = New Process()
myProcess.StartInfo.FileName = app_path
myProcess.StartInfo.Arguments = app_args
myProcess.StartInfo.WindowStyle = ProcessWindowStyle.Normal
myProcess.StartInfo.UseShellExecute = False
myProcess.Start()
' Wait for process requesting passwort input
System.Threading.Thread.Sleep(3000)
Dim len As Integer
len = 0
Dim handle As Integer
handle = GetStdHandle(STD_INPUT_HANDLE)
WriteConsoleInput(handle, "Test", 4, len)

My programm is an commandline application that should act as an wrapper.

The input is send but in a way that it is not typed into the password field but that below the password field a new promt is shown (without even showing the input).

Tim, can you give me an example?

Answer 1

Sorry for my late reply, been very busy.

Here is an full code example, stripped down from my code. I hope I did not delete something crucial.

Private Sub runWaitInput(ByVal exe As String, ByVal parameter As String, ByVal trigger As String, ByVal input As String)
    ' runs an process, waits for a certain string in stdout and then enters text '
    Dim proc As Process
    Dim stdOut As StreamReader
    Dim ch As Int32
    Dim buffer As String = ""
    Dim InputRecords(0) As KeyEventStruct

    ' create process '
    proc = New Process()
    proc.StartInfo.FileName = exe
    proc.StartInfo.Arguments = parameter
    proc.StartInfo.UseShellExecute = False
    proc.StartInfo.RedirectStandardOutput = True
    proc.Start()

    ' redirect stdOut '
    stdOut = proc.StandardOutput
    While Not proc.HasExited
        ' read character '
        ch = stdOut.Read()
        Console.Write(Convert.ToChar(ch))
        buffer = buffer & Convert.ToChar(ch)
        ' read output and check for trigger-text '
        If buffer.LastIndexOf(trigger) <> -1 Then
            buffer = ""
            InputRecords(0) = New KeyEventStruct
            InputRecords = generateInputRecord(input & Convert.ToChar(13))
            WriteConsoleInput(STD_INPUT_HANDLE, InputRecords, InputRecords.Count(), New Integer)
        End If
    End While
    Console.Write(stdOut.ReadToEnd())
End Sub

Function generateInputRecord(ByVal str As String) As KeyEventStruct()
    Dim ret(str.Count() - 1) As KeyEventStruct
    For i = 0 To str.Count - 1 Step 1
        With ret(i)
            .EventType = 1
            .bKeyDown = True
            .uChar.AsciiChar = Convert.ToInt32(str(i))
            .dwControlKeyState = 0
            .wRepeatCount = 1
            .wVirtualKeyCode = 0
            .wVirtualScanCode = 0
        End With
    Next
    Return ret
End Function

It uses the following module:

Imports System.Runtime.InteropServices

Module ConsoleUtils

    <Flags()> Public Enum ControlKeyState As Integer
        RightAltPressed = &H1
        LeftAltPressed = &H2
        RightCtrlPressed = &H4
        LeftCtrlPressed = &H8
        ShiftPressed = &H10
        NumLockOn = &H20
        ScrollLockOn = &H40
        CapsLockOn = &H80
        EnhancedKey = &H100
    End Enum

    <StructLayout(LayoutKind.Explicit)> Public Structure CHAR_UNION
        <FieldOffset(0)> Public UnicodeChar As Short
        <FieldOffset(0)> Public AsciiChar As Byte
    End Structure

    <DllImport("kernel32", EntryPoint:="WriteConsoleInputA", CharSet:=CharSet.Auto, SetLastError:=True, ThrowOnUnmappablechar:=True)> _
        Public Function WriteConsoleInput( _
            ByVal hConsoleInput As IntPtr, _
            ByVal lpBuffer() As KeyEventStruct, _
            ByVal nLength As Integer, _
            ByRef lpNumberOfEventsWritten As Integer _
        ) As Boolean
    End Function

    <DllImport("KERNEL32.DLL", EntryPoint:="GetStdHandle", SetLastError:=False, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
        Public Function GetStdHandle( _
            ByVal nStdHandle As Integer _
        ) As Integer
    End Function

    <StructLayout(LayoutKind.Sequential)> Public Structure KeyEventStruct
        Public EventType As Short
        <MarshalAs(UnmanagedType.Bool)> Public bKeyDown As Boolean
        Public wRepeatCount As Short
        Public wVirtualKeyCode As Short
        Public wVirtualScanCode As Short
        Public uChar As CHAR_UNION
        Public dwControlKeyState As ControlKeyState
    End Structure

    Public ReadOnly STD_OUTPUT_HANDLE As IntPtr = New IntPtr(GetStdHandle(-11))
    Public ReadOnly STD_INPUT_HANDLE As IntPtr = New IntPtr(GetStdHandle(-10))
    Public ReadOnly STD_ERROR_HANDLE As IntPtr = New IntPtr(GetStdHandle(-12))

End Module

With this function you can start the process and wait for a line of output (i.e. “password:”). Then the function will enter the provided text followed by an return.

I hope this helps!

Regards
sc911