MSTSC Username/Password

Imports System
Imports System.Text
Imports System.Runtime.InteropServices
Imports System.ComponentModel
Imports Microsoft.VisualBasic

Public Class DPAPI
<DllImport("Crypt32.dll", SetLastError:=True, CharSet:=System.Runtime.InteropServices.CharSet.Auto)> Private Shared Function CryptProtectData( _
ByRef pPlainText As DATA_BLOB, _
ByVal szDescription As String, _
ByRef pEntropy As DATA_BLOB, _
ByVal pReserved As IntPtr, _
ByRef pPrompt As CRYPTPROTECT_PROMPTSTRUCT, _
ByVal dwFlags As Integer, _
ByRef pCipherText As DATA_BLOB _
) As Boolean
End Function

<DllImport("Crypt32.dll", SetLastError:=True, CharSet:=System.Runtime.InteropServices.CharSet.Auto)> _
Private Shared Function CryptUnprotectData( _
ByRef pCipherText As DATA_BLOB, _
ByRef pszDescription As String, _
ByRef pEntropy As DATA_BLOB, _
ByVal pReserved As IntPtr, _
ByRef pPrompt As CRYPTPROTECT_PROMPTSTRUCT, _
ByVal dwFlags As Integer, _
ByRef pPlainText As DATA_BLOB _
) As Boolean
End Function

<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Unicode)> _
Friend Structure DATA_BLOB
Public cbData As Integer
Public pbData As IntPtr
End Structure

<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Unicode)> _
Friend Structure CRYPTPROTECT_PROMPTSTRUCT
Public cbSize As Integer
Public dwPromptFlags As Integer
Public hwndApp As IntPtr
Public szPrompt As String
End Structure

Private Const CRYPTPROTECT_UI_FORBIDDEN As Integer = 1
Private Const CRYPTPROTECT_LOCAL_MACHINE As Integer = 4

Private Shared Sub InitPrompt _
( _
ByRef ps As CRYPTPROTECT_PROMPTSTRUCT _
)
ps.cbSize = Marshal.SizeOf(GetType(CRYPTPROTECT_PROMPTSTRUCT))
ps.dwPromptFlags = 0
ps.hwndApp = IntPtr.Zero
ps.szPrompt = Nothing
End Sub

Private Shared Sub InitBLOB _
( _
ByVal data As Byte(), _
ByRef blob As DATA_BLOB _
)
' Use empty array for null parameter.
If data Is Nothing Then
data = New Byte(0) {}
End If

' Allocate memory for the BLOB data.
blob.pbData = Marshal.AllocHGlobal(data.Length)

' Make sure that memory allocation was successful.
If blob.pbData.Equals(IntPtr.Zero) Then
Throw New Exception( _
"Unable to allocate data buffer for BLOB structure.")
End If

' Specify number of bytes in the BLOB.
blob.cbData = data.Length
Marshal.Copy(data, 0, blob.pbData, data.Length)
End Sub

Public Enum KeyType
UserKey = 1
MachineKey
End Enum

Private Shared defaultKeyType As KeyType = KeyType.UserKey

Public Shared Function Encrypt _
( _
ByVal keyType As KeyType, _
ByVal plainText As String, _
ByVal entropy As String, _
ByVal description As String _
) As String
If plainText Is Nothing Then
plainText = String.Empty
End If
If entropy Is Nothing Then
entropy = String.Empty
End If

Dim result As Byte()
Dim encrypted As String = ""
Dim i As Integer
result = Encrypt(keyType, _
Encoding.Unicode.GetBytes(plainText), _
Encoding.Unicode.GetBytes(entropy), _
description)
For i = 0 To result.Length - 1
encrypted = encrypted & Convert.ToString(result(i), 16).PadLeft(2, "0").ToUpper()
Next
Return encrypted.ToString()
End Function

Public Shared Function Encrypt _
( _
ByVal keyType As KeyType, _
ByVal plainTextBytes As Byte(), _
ByVal entropyBytes As Byte(), _
ByVal description As String _
) As Byte()
If plainTextBytes Is Nothing Then
plainTextBytes = New Byte(0) {}
End If

If entropyBytes Is Nothing Then
entropyBytes = New Byte(0) {}
End If

If description Is Nothing Then
description = String.Empty
End If

Dim plainTextBlob As DATA_BLOB = New DATA_BLOB
Dim cipherTextBlob As DATA_BLOB = New DATA_BLOB
Dim entropyBlob As DATA_BLOB = New DATA_BLOB

Dim prompt As _
CRYPTPROTECT_PROMPTSTRUCT = New CRYPTPROTECT_PROMPTSTRUCT
InitPrompt(prompt)

Try
Try
InitBLOB(plainTextBytes, plainTextBlob)
Catch ex As Exception
Throw New Exception("Cannot initialize plaintext BLOB.", ex)
End Try

Try
InitBLOB(entropyBytes, entropyBlob)
Catch ex As Exception
Throw New Exception("Cannot initialize entropy BLOB.", ex)
End Try

Dim flags As Integer = CRYPTPROTECT_UI_FORBIDDEN

If keyType = keyType.MachineKey Then
flags = flags Or (CRYPTPROTECT_LOCAL_MACHINE)
End If

Dim success As Boolean = CryptProtectData( _
plainTextBlob, _
description, _
entropyBlob, _
IntPtr.Zero, _
prompt, _
flags, _
cipherTextBlob)

If Not success Then
Dim errCode As Integer = Marshal.GetLastWin32Error()

Throw New Exception("CryptProtectData failed.", _
New Win32Exception(errCode))
End If

Dim cipherTextBytes(cipherTextBlob.cbData) As Byte

Marshal.Copy(cipherTextBlob.pbData, cipherTextBytes, 0, _
cipherTextBlob.cbData)

Return cipherTextBytes
Catch ex As Exception
Throw New Exception("DPAPI was unable to encrypt data.", ex)
Finally
If Not (plainTextBlob.pbData.Equals(IntPtr.Zero)) Then
Marshal.FreeHGlobal(plainTextBlob.pbData)
End If

If Not (cipherTextBlob.pbData.Equals(IntPtr.Zero)) Then
Marshal.FreeHGlobal(cipherTextBlob.pbData)
End If

If Not (entropyBlob.pbData.Equals(IntPtr.Zero)) Then
Marshal.FreeHGlobal(entropyBlob.pbData)
End If
End Try
End Function

End Class