Passing parameters to an executable

Question

I have an application that is divided into two different executables.

The first executable is the brain of my application, in this executable, in which I named it STUB, will be all the main logic of the application with some additional and optional methods (some mandatory, however, variables), as hosts, ports, pop-ups, etc.

The second executable is exactly the part of the optional and the mandatory, in which I call it the UI, IE, the user will choose the options you want and from this UI, create the new executable.

Using my STUB as a *.exe base, I want my UI to re-write my STUB by setting user-defined options, thus creating a new executable that will work according to the options the user has chosen.

The only type of application I can remember to have such functionality are the Rats (Remote Administration Tools) and some Keyloggers, in which you can create a remote connection server to control a computer, and in this creation you can define several options (your ip, installation location, etc.). Connection servers are also generated from a *.exe base.

I took a random image from google to illustrate, in it, there is a customization window of a RAT (Note that the last tab is precisely the construction of *.exe with preset settings):

@UPDATE: I don’t know if it helps but, by going through prehistoric codes I found a code on VB6 that does something similar. It takes one the STD.exe file that initially does nothing and on top of it creates another (RWSTD.exe) adding a Msgbox() when it starts. I have tried to research the function of these lines of code and try to replicate in C#, but without success. Look at the codes:

Customer UI:

Private Sub Command1_Click()

    Dim STD As String, RWSTD As String, MID As String, DEL As String
    DEL = "DELIMITADOR"

    Open App.Path & "\STD.exe" For Binary As #1
    STD = Space(LOF(1))
    Get #1, , STD
    Close #1

    If FileExists(App.Path & "\RWSTD.exe") Then
        Kill App.Path & "\RWSTD.exe"
    End If

    Open App.Path & "\RWSTD.exe" For Binary As #1
    RWSTD = Space(LOF(1))
    Get #1, , RWSTD
    Put #1, , STD & DEL & txtMsgBox.Text
    Close #1

End Sub

Private Sub Form_Load()
    If Not FileExists("STD.exe") Then
        Unload Me
    End If
End Sub

STB.exe:

Sub Starter()
    Dim DATA As String, DEL() As String, i As Long

    Open App.Path & "\" & App.EXEName & ".exe" For Binary As #1
    DATA = Space(LOF(1))
    Get #1, , DATA
    Close #1

    DEL() = Split(DATA, "DELIMITADOR")

    For i = 1 To UBound(DEL)
        If Not (DEL(i) = "MZ") Then
            MsgBox (DEL(i))
        End If
    Next
End Sub

Answer 1

If you want to change string values that are inside the executable, you can do the following:

1) Convert the executable to an IL file (Intermediate language);
2) Search/replace the IL file.
3) Recompile the IL to generate the new executable.

The . NET SDK has the tool Ildasm.exe to make that conversion.