How do I encrypt a string to be compatible with a drupal V 7 password

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VB

PHP

Drupal

Hi, hopefully someone can help.

I have to update a user's details in a MySQL Drupal environment from a VB.NET application/ASP.

So the user changes their password using classic ASP, this calls a .COM compliant DLL Class written in VB.NET

The instructions I have found are:

Here is an example hash from Drupal 7:

"pass" : "$S$Dxl65W9p07LfQU7jvy5CnsyDpMoLujiAgzy123khcg1OJi/P9pKS"

The characters 0-2 are the type ( $S$ is Drupal 7 )

The character 3 is the number of log2 rounds (X) based on the position of the char in this list: './0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz' So in our example 'D' would map to 15
The characters 4-11 are the SALT
The rest is a SHA512 hash using 2^X rounds.
The binary result is then converted to a string using base64.

$count = 1 << $count_log2;
$hash = hash($algo, $salt . $password, TRUE);
do { $hash = hash($algo, $hash . $password, TRUE);
} while (--$count);

Not being a cryptographer of any sort, I found to encrypt a string into SHA512 using VB.NET I can use this code:

Private Function EncryptSHA512Managed(ByVal ClearString As String) As String
      Dim uEncode As New UnicodeEncoding()
      Dim bytClearString() As Byte = uEncode.GetBytes(ClearString)
      Dim sha As New System.Security.Cryptography.SHA512Managed()
      Dim hash() As Byte = sha.ComputeHash(bytClearString)
      Dim Z as Integer = 0

       For Z = 1 To HowManyTimes - 1
          hash2 = sha.ComputeHash(hash)
          hash = hash2
      Next

      Return Convert.ToBase64String(hash2)
  End Function

So from what I understand about the PHP explanation (and I have never used PHP) I would do something like this:

  Private Function EncryptionStringForDrupal() As String
        Dim EncStr As String = "apassword"
      
' Going to use TestSale as my salt test.

        Return "$S$DTestSalt" & EncryptSHA512Managed("TestSalt" & EncStr)

    End Function

With The "D" in the example PHP text, thats 15^2 and it comes out as 32,768 encryption loops and the resulting drupal encrypted password comes out as

$S$DTestSaltTjmIXDexvVOnQDA4ojamH2PFxVrfIKJLJBKNtclZaxs/LHiF8Wxx2kMb03qeo+FUK7prxEiKfToY50ZG0SQ3QA==

But its still wrong -

What I have tried:

Banging head against wall, but it did not solve it.