Programming Microsoft Visual Basic .NET/Programming Microsoft Visual Basic .NET (Microsoft Press)(X08-78517)(2002).bin/setup/vbnet/19 advanced win32 techniques/encryptorservice/encryptor.vb

Text File | 2002-03-16 | 7.8 KB | 216 lines

Imports System.ServiceProcess

Public Class Encryptor
    Inherits System.ServiceProcess.ServiceBase

#Region " Component Designer generated code "

    Public Sub New()
        MyBase.New()

        ' This call is required by the Component Designer.
        InitializeComponent()

        ' Add any initialization after the InitializeComponent() call

    End Sub

    ' The main entry point for the process
    Shared Sub Main()
        Dim ServicesToRun() As System.ServiceProcess.ServiceBase

        ' More than one NT Service may run within the same process. To add
        ' another service to this process, change the following line to
        ' create a second service object. For example,
        '
        '   ServicesToRun = New System.ServiceProcess.ServiceBase () {New Service1, New MySecondUserService}
        '
        ServicesToRun = New System.ServiceProcess.ServiceBase() {New Encryptor()}

        System.ServiceProcess.ServiceBase.Run(ServicesToRun)
    End Sub
    Friend WithEvents FileSystemWatcher1 As System.IO.FileSystemWatcher

    'Required by the Component Designer
    Private components As System.ComponentModel.Container

    ' NOTE: The following procedure is required by the Component Designer
    ' It can be modified using the Component Designer.
    ' Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.FileSystemWatcher1 = New System.IO.FileSystemWatcher()
        CType(Me.FileSystemWatcher1, System.ComponentModel.ISupportInitialize).BeginInit()
        '
        'FileSystemWatcher1
        '
        Me.FileSystemWatcher1.NotifyFilter = ((System.IO.NotifyFilters.FileName Or System.IO.NotifyFilters.DirectoryName) _
                    Or System.IO.NotifyFilters.LastWrite)
        '
        'Encryptor
        '
        Me.CanPauseAndContinue = True
        Me.ServiceName = "Encryptor"
        CType(Me.FileSystemWatcher1, System.ComponentModel.ISupportInitialize).EndInit()

    End Sub

#End Region

    ' The path of the watched directory.
    ' IMPORTANT: create this directory if it doesn't exist

    Dim Path As String = "C:\Encrypt"

    ' the service has been started

    Protected Overrides Sub OnStart(ByVal args() As String)
        If args.Length > 0 Then
            Path = args(0)
            Me.EventLog.WriteEntry(Path)
        End If
        ' Ensure that the directory exists.
        If Not System.IO.Directory.Exists(Path) Then
            System.IO.Directory.CreateDirectory(Path)
        End If
        ' Start receiving file events.
        FileSystemWatcher1.Path = Path
        FileSystemWatcher1.EnableRaisingEvents = True
    End Sub

    ' the service has been stopped, paused, or resumed

    Protected Overrides Sub OnStop()
        ' Stop receiving file events.
        FileSystemWatcher1.EnableRaisingEvents = False
    End Sub

    Protected Overrides Sub OnPause()
        ' Stop receiving file events.
        FileSystemWatcher1.EnableRaisingEvents = False
    End Sub

    Protected Overrides Sub OnContinue()
        ' Start receiving file events.
        FileSystemWatcher1.EnableRaisingEvents = True
    End Sub


    ' This is the binary password.
    Dim pwBytes() As Byte = {123, 234, 12, 9, 78, 89, 212}
    ' This is the extension used for temporary files.
    Dim tempExt As String = ".$$$"

    Private Sub FileSystemWatcher1_Created(ByVal sender As Object, ByVal e As System.IO.FileSystemEventArgs) Handles FileSystemWatcher1.Created
        ' Ignore temporary files created by the encryption process.
        If System.IO.Path.GetExtension(e.FullPath) = tempExt Then Exit Sub

        Do
            Try
                ' Encrypt the file being created.
                EncryptFile(e.FullPath, pwBytes)
                ' Exit if successful
                Exit Do
            Catch ex As Exception
                Dim attempts As Integer
                attempts += 1
                ' Make up to 10 attempts.
                If attempts > 10 Then Exit Sub
                ' Wait for a while and retry the operation.
                System.Threading.Thread.Sleep(1000)
            End Try
        Loop

    End Sub

    ' This is the encryption/decryption routine

    Private Sub EncryptFile(ByVal Filename As String, ByVal pwBytes() As Byte)
        ' This the the size of each input block.
        ' (Files must be decrypted using the same block size.)
        Const BLOCKSIZE = 8192

        ' Determine the name of the temporary file.
        Dim tempFile As String = Filename & tempExt

        ' Open the source file as a binary input stream.
        Dim inStream As New System.IO.FileStream(Filename, IO.FileMode.Open)
        ' Open the output temporary file as a binary input stream.
        Dim outStream As New System.IO.FileStream(tempFile, IO.FileMode.Create)
        ' Determine the number of bytes to read.
        Dim bytesLeft As Long = inStream.Length
        ' Prepare an input buffer.
        Dim buffer(BLOCKSIZE - 1) As Byte

        ' Loop until there are bytes to read.
        Do While bytesLeft > 0
            ' Read max 8K bytes at a time
            Dim bytesToRead As Long = Math.Min(BLOCKSIZE, bytesLeft)
            ' Read into the input buffer.
            inStream.Read(buffer, 0, bytesToRead)
            ' Encrypt this buffer.
            EncryptArray(buffer, pwBytes)
            ' Output to the temporary file.
            outStream.Write(buffer, 0, bytesToRead)
            ' We have fewer bytes to read now
            bytesLeft -= bytesToRead
        Loop

        ' Close the two streams.
        inStream.Close()
        outStream.Close()
        ' Delete the source file.
        System.IO.File.Delete(Filename)
        ' Rename the temporary file as the original file.
        System.IO.File.Move(tempFile, Filename)
    End Sub

    ' This routine encrypts an array of bytes.
    Sub EncryptArray(ByVal buffer() As Byte, ByVal pwBytes() As Byte)
        ' This index points to the buffer.
        Dim index As Integer
        ' This index points to the password array.
        Dim i As Integer
        ' The max value for i.
        Dim maxval As Integer = pwBytes.Length

        For index = 0 To buffer.Length - 1
            ' XOR each element in the buffer with the corresponding p
            buffer(index) = buffer(index) Xor pwBytes(i)
            ' ensure that the index is always in the valid range.
            i = (i + 1) Mod maxval
        Next
    End Sub

    ' This method is called only if the CanShutdown property is True.

    Protected Overrides Sub OnShutdown()
        ' Add here the code to execute when the system shuts down
    End Sub

    ' This method is called only if the CanHandlePowerEvent property is True.

    Protected Overrides Function OnPowerEvent(ByVal powerStatus As System.ServiceProcess.PowerBroadcastStatus) As Boolean
        Select Case powerStatus
            Case PowerBroadcastStatus.Suspend
                ' Add here the code to execute when the system enters suspend mode.
            Case PowerBroadcastStatus.ResumeSuspend
                ' Add here the code to execute when the system exits suspend mode.
            Case PowerBroadcastStatus.BatteryLow
                ' Add here the code to execute when batteries are low.
        End Select
        ' This method must return True.
        Return True
    End Function

    ' This method is called when a custom command is sent to the service.

    Protected Overrides Sub OnCustomCommand(ByVal command As Integer)
        Select Case command
            Case 1
                ' React to custom command #1
            Case 2
                ' React to custom command #1
        End Select
    End Sub
End Class