How to decode Rijndael in ruby (encoded in VB.net)

Question

Hello,

I am using Rinjael to encode in VB.NET and need to decode in Ruby. My VB.NET encryption class looks like this:

Private Class Encryptor
        Private symmetricKey As System.Security.Cryptography.RijndaelManaged
        Private iVector As Byte()
        Private Key As Byte()
        Public Function encrypt(ByVal data As String) As String
            Try
                Dim plainTextBytes As Byte() = System.Text.Encoding.ASCII.GetBytes(data)
                Dim encryptor As System.Security.Cryptography.ICryptoTransform = symmetricKey.CreateEncryptor(Key, iVector)
                Dim memoryStream As New System.IO.MemoryStream
                Dim cryptoStream As System.Security.Cryptography.CryptoStream = New System.Security.Cryptography.CryptoStream(memoryStream, encryptor, System.Security.Cryptography.CryptoStreamMode.Write)
                cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length)
                cryptoStream.FlushFinalBlock()
                Dim cipherTextBytes As Byte() = memoryStream.ToArray()
                memoryStream.Close()
                cryptoStream.Close()
                Return Convert.ToBase64String(cipherTextBytes)
            Catch
                Return ""
            End Try
        End Function
        Public Function decrypt(ByVal data As String) As String
            Try
                Dim crypted As Byte() = Convert.FromBase64String(data)
                Dim decryptor As System.Security.Cryptography.ICryptoTransform = symmetricKey.CreateDecryptor(Key, iVector)
                Dim memoryStream As New System.IO.MemoryStream(crypted)
                Dim cryptoStream As System.Security.Cryptography.CryptoStream = New System.Security.Cryptography.CryptoStream(memoryStream, decryptor, System.Security.Cryptography.CryptoStreamMode.Read)
                Dim plain(crypted.Length) As Byte
                Dim count As Integer = cryptoStream.Read(plain, 0, plain.Length)
                memoryStream.Close()
                cryptoStream.Close()
                Return System.Text.Encoding.UTF8.GetString(plain, 0, count)
            Catch
                Return ""
            End Try
        End Function

        Public Sub New(ByVal clientkey As String)
            iVector = System.Text.Encoding.ASCII.GetBytes("1234567890123456")
            Key = System.Text.Encoding.ASCII.GetBytes(clientkey)
            symmetricKey = New System.Security.Cryptography.RijndaelManaged
            symmetricKey.Mode = System.Security.Cryptography.CipherMode.CBC
        End Sub
    End Class

this works ok and I am able to decrypt in java using the AES/CBC/PKCS5Padding. Now, my password and iv are 16 characters long (16*16bit = 256). When I try to decrypt in Ruby, it complains that my password is to short... I assume that it is using 8bit chars. I use this class for decryption in ruby:

    require 'openssl'

module Crypt
  # Decrypts a block of data (encrypted_data) given an encryption key
  # and an initialization vector (iv).  Keys, iv's, and the data 
  # returned are all binary strings.  Cipher_type should be
  # "AES-256-CBC", "AES-256-ECB", or any of the cipher types
  # supported by OpenSSL.  Pass nil for the iv if the encryption type
  # doesn't use iv's (like ECB).
  #:return: => String
  #:arg: encrypted_data => String 
  #:arg: key => String
  #:arg: iv => String
  #:arg: cipher_type => String
  def Crypt.decrypt(encrypted_data, key, iv, cipher_type)
    aes = OpenSSL::Cipher::Cipher.new(cipher_type)
    aes.decrypt
    aes.key = key
    aes.iv = iv if iv != nil
    aes.update(encrypted_data) + aes.final  
  end

  # Encrypts a block of data given an encryption key and an 
  # initialization vector (iv).  Keys, iv's, and the data returned 
  # are all binary strings.  Cipher_type should be "AES-256-CBC",
  # "AES-256-ECB", or any of the cipher types supported by OpenSSL.  
  # Pass nil for the iv if the encryption type doesn't use iv's (like
  # ECB).
  #:return: => String
  #:arg: data => String 
  #:arg: key => String
  #:arg: iv => String
  #:arg: cipher_type => String  
  def Crypt.encrypt(data, key, iv, cipher_type)
    aes = OpenSSL::Cipher::Cipher.new(cipher_type)
    aes.encrypt
    aes.key = key
    aes.iv = iv if iv != nil
    aes.update(data) + aes.final      
  end
end

Now. By trying to decrypt using Crypt.decrypt(data,key,iv, "AES-CBC-256") i am certain that preliminary string/byte transformations have to be done on my data,key,iv to work correctly.

How shall I call Crypt.decrypt using key = "passwordpassword" and iv="1234567890123456"? Do I need to base64 decode my data?

Here's my decryption call, which doesn't seem to work (trying padding with zeroes):

   text = Base64.decode64(text)
   pass = Digest::SHA1.hexdigest("#{@pass}0000000000000000").unpack('a2'*32).map{|x| x.hex}.pack('c'*32)
   iv = Digest::SHA1.hexdigest("12345678901234560000000000000000").unpack('a2'*32).map{|x| x.hex}.pack('c'*32)
   return Crypt.decrypt(text,pass,iv,"AES-256-CBC")

Answer 1

Because the VB app encodes the result as base64, it does look like the ruby script will need to use the Base64 module to decode it first.

I believe the key given to the Ruby AES key must be 256 bits. So your password would need to be 32 bytes long exactly in that case. It would be better to use a scheme such as this.

Answer 2

Solution. It was a 128bit encryption (wrongly thinking that the default in .NET managed was 256). Hence, this code works (notice "AES-128-CBC"):

   text = Base64.decode64(text)
   pass = "passwordpassword"
   iv = "1234567890123456"
   return Crypt.decrypt(text,pass,iv,"AES-128-CBC")