Different output form AES 256 PHP and Delphi FMX

[Morrismx]

I have to encrypt/decrypt a string on AES 256 CBC, and I'm getting a shorter string compared wit PHP.

PHP Example: https://gist.github.com/ezegg/8d54c98b8fbdce263409eabaf8afabe6

    PHP Output
   DB8BRqb2q6BW/HLQYN2pr2n9DTL1Q8kp2lvZi3rogbxjEasiMbgU4q5/vDav+p0O0KWlfMm
   NekXN+UkbUiB+s/LNf1MF2EgOQEZoivxgp+UJxsuT5vDIMmQXUkuwkyUE+a7hH5FwaDDY8D
   NwW2kowFXeE69AcOMaWnyZ+YplKNEUOzQzLstBxWnJE+aSr0+vQN3knkIIjbT10yfSTV/OQA==
  
  FMX Output.
   DB8BRqb2q6BW/HLQYN2pr2n9DTL1Q8kp2lvZi3rogbxjEasiMbgU4q5/vDav+p0O0KWlfMm
   NekXN+UkbUiB+s/LNf1MF2EgOQEZoivxgp+UJxsuT5vDIMmQXUkuwkyUE+a7hH5FwaDDY8D
   NwW2kowFXeE69AcOMaWnyZ+YplKNEUOzQzLstBxWnJE+aSr0+v9Q21xA==

As you can see, string is "shorter" in Delphi.

here is the test string, Secret key and init vector SECRET_KEY = "HPo7OLqB4Fkk4E2yGOtwqw8H5fHR9kNx67OR4g4UdlA="; IV = "p5ldmBPdd/9pjC0bDC/nSg==";

Input String: {"idServicio":79, "idProducto":209 , "referencia": "40425475190118187271", "montoPago": 9999, "telefono":"1111111111", "horaLocal":"20200401222821"}

Thank you

[MHumm]

That should not differ. I have some suspicion...

1. Could you please provide your Delphi source code?

2. Did you call the Done method at the end before looking at the output? The Done method processes the last block (including padding where necessary) and could thus make the difference!

[Morrismx]

Hi,

Im using Cipher_FMX demo proyect.

procedure TFormMain.ButtonEncryptClick(Sender: TObject); var Cipher : TDECCipher; InputFormatting : TDECFormatClass; OutputFormatting : TDECFormatClass; InputBuffer : TBytes; OutputBuffer : TBytes; begin

if not GetSettings(InputFormatting, OutputFormatting) then exit;

if ComboBoxCipherAlgorithm.ItemIndex >= 0 then begin if not GetCipherAlgorithm(Cipher) then exit;

try
  InputBuffer  := System.SysUtils.BytesOf(EditPlainText.Text);

  if InputFormatting.IsValid(InputBuffer) then
  begin
    OutputBuffer := (Cipher as TDECFormattedCipher).EncodeBytes(InputFormatting.Decode(InputBuffer));
    EditCipherText.Text := string(DECUtil.BytesToRawString(OutputFormatting.Encode(OutputBuffer)));
  end
  else
    ShowErrorMessage('Input has wrong format');
finally
  Cipher.Free;
end;

end else ShowErrorMessage('No cipher algorithm selected'); end;

I not sure where should i call Done Method, i guess this method does the encryption: OutputBuffer := (Cipher as TDECFormattedCipher).EncodeBytes(InputFormatting.Decode(InputBuffer));

[MHumm]

Ok, done plays no role here as it seems. The answer was out of my head. But if I take the data you specify I get a key too long failure, the IV is not in hexadecimal etc. Is it possible to deliver the input data (include the filler byte used) in a form I can directly enter into the demo without any conversions etc.?

[Morrismx]

what i did for simplicity, was to convert IV to HEX and put the hex value on (a7995d9813dd77ff698c2d1b0c2fe74a ) on EditInitVector.text edit, and on GetCipherAlgorithm function I modified a bit. so I can decode the base64 secret key, as follows:

function TFormMain.GetCipherAlgorithm(var Cipher : TDECCipher):Boolean; begin var SKey:RawByteString ; var i:integer;

result := false;

// Find the class type of the selected cipher class and create an instance of it Cipher := TDECCipher.ClassByName( ComboBoxCipherAlgorithm.Items[ComboBoxCipherAlgorithm.ItemIndex]).Create;

if TFormat_HEX.IsValid(RawByteString(EditInitVector.Text)) and TFormat_HEX.IsValid(RawByteString(EditFiller.Text)) then begin if CheckBoxBase46.IsChecked then {Add this checkBox to decode Base64 secret key} begin SKey:=TFormat_Base64.Decode(EditKey.Text); Cipher.Init(Skey, TFormat_HEX.Decode(RawByteString(EditInitVector.Text)), StrToInt('0x' + EditFiller.Text)); end else begin Cipher.Init(RawByteString(EditKey.Text), TFormat_HEX.Decode(RawByteString(EditInitVector.Text)), StrToInt('0x' + EditFiller.Text));

end;
Cipher.Mode := GetSelectedCipherMode;

end else begin ShowErrorMessage('Init vector or filler byte not given in hexadecimal representation'); exit; end;

result := true; end;

[Morrismx]

here is the modified project. Cipher_FMX.zip

[MHumm]

Thanks for providing the modified project. I try to look at it as soon as I can, but currently there's too much going on, like finalizing the new release and preparing my talk on EKON (https://entwickler-konferenz.de/tips-tricks-and-technics/kryptographiegrundlagen-am-beispiel-der-dec-delphi-encryption-compendium/).

The problem most likely has to do with the way DEC handles padding, which I'm not really familiar with yet. That was designed by the original creator of the library, which I do not know personally. I know his successor though, but I doubt he did much on that part.

[MHumm]

Somebody (not me due to lack of time) tried to run yet test program provided but got an exception. The key length is too long. Is the key base 64 coded?

[fastbike]

The implementation of TNetEncoding Base64 in Delphi has a built in limit at which point it splits with a CRLF sequence - not sure if this is helpful ? We had an issue with a truncated encrypted value due to this.

[MHumm]

Thanks for adding the idea it might be related to line break handling in Delphi's Base64 implementation. @Morrismx can you check that one? DEC contains its own Base64 implementation in DECFormat.pas unit, if I'm not mistaken that one has a property to set the line width. But I'm right now a bit in a hurry, so I cannot check the code :-(

[geoffsmith82]

@fastbike FYI If you manually create a TBase64Encoding instead of of using TNetEncoding.Base64... you can specify line length, including not splitting it up on a line at all.

Also I have noticed in my 11.2 that there actually is a TNetEncoding.Base64String that doesn't split the base64 up into lines at all.

[MHumm]

Can somebody of you check if that splitting is the culprit?