Imports System.Threading
Imports System.Security.Policy
Imports System.Security.Cryptography
Imports System.Reflection
Imports System.IO
Imports System.Collections.Generic
Imports System

Namespace SecStarter

	<Serializable> _
	Friend Class SecureLoader
		Private dllList As New Dictionary(Of String, Byte())()

		Private executableBinary() As Byte

		Friend Sub LoadAssembies(ByVal password As String)
			Dim fileList() As String = Directory.GetFiles(Environment.CurrentDirectory)

			For Each fileName As String In fileList
				If fileName.EndsWith(".exee") Then
					Me.executableBinary = LoadAndDecrypt(fileName, password)
				End If

				If fileName.EndsWith(".dlle") Then
					Dim startIndex As Integer = fileName.LastIndexOf("\") + 1
					Dim nameOnly As String = fileName.Substring(startIndex, fileName.Length - (startIndex + 5))
					Me.dllList.Add(nameOnly, LoadAndDecrypt(fileName, password))
				End If
			Next fileName
		End Sub

		Friend Sub StartTheApp()
			Dim theThread As New Thread(AddressOf MainWorkerThread)
			theThread.Start()
		End Sub

		Public Sub MainWorkerThread()
			Dim adevidence As Evidence = AppDomain.CurrentDomain.Evidence
			Dim domain As AppDomain = AppDomain.CreateDomain("Debug", adevidence)

			AddHandler domain.AssemblyResolve, AddressOf Domain_AssemblyResolve

			domain.ExecuteAssemblyByName("TestingDebug.exe")
		End Sub

		Private Function Domain_AssemblyResolve(ByVal sender As Object, ByVal args As ResolveEventArgs) As System.Reflection.Assembly
			If args.Name.EndsWith(".exe") Then
				Dim assembly As System.Reflection.Assembly = System.Reflection.Assembly.Load(Me.executableBinary)
				Return assembly
			Else
				Dim assemblyData() As String = args.Name.Split(","c)
				Dim assembly As System.Reflection.Assembly = System.Reflection.Assembly.Load(dllList(assemblyData(0)))
				Return assembly
			End If
		End Function

		Private Function LoadAndDecrypt(ByVal filename As String, ByVal password As String) As Byte()
			Dim theAssemblyBytes() As Byte = Nothing

			If File.Exists(filename) Then
				Dim fileBlob() As Byte = File.ReadAllBytes(filename)
				Dim saltData(7) As Byte
				Dim fileData((fileBlob.Length - 8) - 1) As Byte

				' extract the salt that we need for proper key derivation from pwd (added as 8 byte header by the cryptor)
				For i As Integer = 0 To 7
					saltData(i) = fileBlob(i)
				Next i

				' binary dll data follows after the salt
				For i As Integer = 8 To fileBlob.Length - 1
					fileData(i - 8) = fileBlob(i)
				Next i

				' password + salt -> key
				Dim deriveBytes As New Rfc2898DeriveBytes(password, saltData)
				Dim memoryStream As New MemoryStream()

				Dim aesCipher As Aes = New AesManaged()
				aesCipher.Key = deriveBytes.GetBytes(aesCipher.KeySize \ 8)
				aesCipher.IV = deriveBytes.GetBytes(aesCipher.BlockSize \ 8)
				aesCipher.Mode = CipherMode.CBC
				aesCipher.Padding = PaddingMode.None

				' decrypt the assembly
				Dim cryptoStream As New CryptoStream(memoryStream, aesCipher.CreateDecryptor(), CryptoStreamMode.Write)
				cryptoStream.Write(fileData, 0, fileData.Length)
				cryptoStream.Close()

				theAssemblyBytes = memoryStream.ToArray()
			End If

			Return theAssemblyBytes
		End Function
	End Class
End Namespace