无法使用LockBox3解密XXTEA加密的字符串

有两个问题。首先,XXTEA解密程序中存在缺陷。如果您迫不及待地想发布修复程序,我已经发布了一个代码增量,您可以应用它并重新编译以获得即时解决方案。我有点惊讶,XXTEA没有单元测试。这个库中的其他所有内容都有大量的单元测试,所以我也将致力于此。

ChainModeId 不 ChainMode ). 这种差异是为了使设计时属性配置更容易。

http://lockbox.seanbdurkin.id.au/HomePage 源代码来自 https://github.com/SeanBDurkin/tplockbox .我用Delphi 10.2 Tokyo进行了测试;目标=Win32。

此外,如果有人想通过贡献已知答案测试(KAT)来帮助解决问题,这对所有人都有好处。

program TestLockBox;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.SysUtils,
  TPLB3.CryptographicLibrary,
  TPLB3.Codec,
  TPLB3.Random,
  TPLB3.Constants;

var
  sMessage: string;
  sCipher: string;
  sRecon: string;

const
      CipherId    = XXTEA_Large_ProgId;  IsBlockMode = False;
  //  CipherId    = Twofish_ProgId;      IsBlockMode = True;
  ChainMode   = 'native.CBC';
  Password    = 'password';
  Seed        = 1;

function TForm1_btnEncryptClick( const sPlainText: string): string;
var
    PlainText : string;
   CipherText : string;
    CryptoLib : TCryptographicLibrary;
        Codec : TCodec;
begin
    try
      CryptoLib := TCryptographicLibrary.Create(nil);
      Codec := TCodec.Create(nil);
      Codec.CryptoLibrary := CryptoLib;
      if IsBlockMode then
          begin
          Codec.StreamCipherId := BlockCipher_ProgId;
          Codec.BlockCipherId  := CipherId
          end
        else
          Codec.StreamCipherId := CipherId;
      Codec.ChainModeId    := ChainMode;
      Codec.Password := Password;
      PlainText := sPlainText;
      Codec.EncryptString( PlainText, CipherText, Tencoding.UTF8 );
      Codec.Burn;
    finally
      Codec.Free;
      CryptoLib.Free;
      result := CipherText;
    end;
end;

function TForm1_btnDecryptClick( const sCipherText: string): string;
var
     PlainText : string;
    CipherText : string;
     CryptoLib : TCryptographicLibrary;
         Codec : TCodec;
begin
    try
      CryptoLib := TCryptographicLibrary.Create(nil);
      Codec := TCodec.Create(nil);
      Codec.CryptoLibrary := CryptoLib;
      if IsBlockMode then
          begin
          Codec.StreamCipherId := BlockCipher_ProgId;
          Codec.BlockCipherId  := CipherId
          end
        else
          Codec.StreamCipherId := CipherId;
      Codec.ChainModeId    := ChainMode;
      Codec.Password := Password;
      CipherText := sCipherText;
      Codec.DecryptString( PlainText, CipherText, Tencoding.UTF8 );
      Codec.Burn;
    finally
      Codec.Free;
      CryptoLib.Free;
      result := PlainText;
    end;
end;

begin
  if Seed = -1 then
      TRandomStream.Instance.Randomize
    else
      TRandomStream.Instance.Seed := Seed;
  try
    sMessage := 'Your lips are smoother than vasoline.';
    WriteLn( 'Plaintext="' + sMessage + '"');
    sCipher  := TForm1_btnEncryptClick( sMessage);
    WriteLn( 'Base64 representation of ciphertext=' + sCipher);
    sRecon := TForm1_btnDecryptClick( sCipher);
    WriteLn( 'The reconstructed plaintext = "' + sRecon + '"');
    if sMessage = sRecon then
        WriteLn( 'Test result = PASS')
      else
        WriteLn( 'Test result = FAIL')
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
  WriteLn('Press Enter to close the program.');
  ReadLn;
end.

清单二:修复

procedure TXXTEA_LargeBlock_LE_Decryptor.End_Decrypt;
var
  RequiredSizeDecrease: integer;
  L: integer;
  PlaintextArray, CiphertextArray: TLongWordDynArray;
begin
if FisBuffering then
    begin
    if FBufLen = 0 then exit;
//    c <= 211 ==>
//      2.2.1 Decrypt the message as one XXTEA block.
//      2.2.2 De-salt the decrypted plaintext. That is to say discard the last
//        8 bytes at the head of the decrypted plaintext.
//      2.2.3 De-pad the message out at the tail. The number of pad bytes to
//        remove is the value of the last byte.
    L := FBufLen div 4;
    SetLength( CiphertextArray, L); // Setup longword array.
    SetLength( PlaintextArray , L);
      begin
      // XXTEA only valid if blocksize is at least 2 longwords.
      // With the padding, this should ALWAYS be the case.
      // Otherwise the ciphertext message is invalid.
      Move( FBuffer[0], CiphertextArray[0], FBufLen); // Convert padded message to longwords.
      XXTEA_Decrypt( FKey.FNativeKey, CiphertextArray, PlaintextArray); // One-block encryption.
      end;
    FBufLen := L * 4;
    if FBufLen >= 8 then
        Dec( FBufLen, 8) // de-salt
      else
        FBufLen := 0;
    if FBufLen > 0 then  // Calculate pad.
        begin
        if Length( FBuffer) < FBufLen then
          SetLength( FBuffer, FBufLen);
        Move( PlaintextArray[0], FBuffer[0], FBufLen);
        RequiredSizeDecrease := FBuffer[FBufLen-1]
        end
      else
        RequiredSizeDecrease := 0;
    if FBufLen >= RequiredSizeDecrease then
        Dec( FBufLen, RequiredSizeDecrease) // de-pad
      else
        FBufLen := 0;
    if FBufLen > 0 then
      FPlainText.Write( FBuffer[0], FBufLen)
    end
  else
    begin
    FFixedDec.End_Decrypt;
    FOutputBuffer.EndStreaming; // Discard last 12 bytes
    FreeAndNil( FOutputBuffer)
    end;
FFixedDec := nil;
FFixedCipher := nil
end;