Hacktoberfest 2026: as issues que os mantenedores marcaram para outubro, abertas e boas para iniciantes. Ver issues do Hacktoberfest

Access violation if GCM mode is set after cipher is initialized

Aberta
  • Algo errado?
#74 3 comentários 0 reações 1 responsável Ver no GitHub

@MHumm já está trabalhando nisso.

Desde 8/5/2024.

Avaliação

Esta issue ainda não foi avaliada.

Descrição

bug

To Reproduce

  1. Open demo project Cipher_Console
  2. Change Cipher.Mode to cmGCM
  3. Run the code. You receive EAccessViolation

Usually, if you change the cipher mode after the cipher has been initialized, then TDECCipher.SetMode should call Done on the cipher and re-initialize it.

GCM Encode requires that TGCM.Init is called and has set FEncryptionMethod := EncryptionMethod. However, if Ciper.Mode is set after the cipher has been initialized, then TGCM is created but TGCM.Init has not been called.

procedure TDECCipherModes.InitMode;
begin
  if FMode = TCipherMode.cmGCM then
  begin
    if Context.BlockSize = 16 then
      FGCM := TGCM.Create
    else
      // GCM requires a cipher with 128 bit block size
      raise EDECCipherException.CreateResFmt(@sInvalidBlockSize,
                                             [128, GetEnumName(TypeInfo(TCipherMode),
                                             Integer(FMode))]);
  end
  else
    if Assigned(FGCM) then
      FreeAndNil(FGCM);
end;

The program flow if Mode has been set before init:

  1. TDECCipher.Init()
  2. TDECCipher.Init()
  3. TDECCipherModes.OnAfterInitVectorInitialized ( calls FGCM.Init(self.DoEncode, OriginalInitVector) )
  4. TGCM.Init

The program flow if Mode has been set after init:

  1. TDECCipher.SetMode
  2. TDECCipherModes.InitMode
  3. TGCM.Create, but not TGCM.Init ( I am not sure where I get OriginalInitVector from )

So... what do we do? We probably need to preserve the InitVector, so we can call TGCM.Init with the correct parameters.

The other solution is to forbid to change the mode after the cipher has been initialized. But this is a code breaking change.

Linguagem predominante
HTML
Estrelas
286
Forks
78
Merge médio
1d 4h
PRs com merge (30d)
4

Preparar o ambiente

Primeiros passos

  1. Leia a issue inteira e depois o guia de contribuição do projeto.
  2. Comente na issue dizendo que vai assumir — evita que duas pessoas façam o mesmo trabalho.
  3. Faça um fork do repositório e trabalhe em uma branch.
  4. Abra um pull request que referencie o número da issue.

Mais de MHumm/DelphiEncryptionCompendium

Todas as issues de MHumm/DelphiEncryptionCompendium

Receba novas issues na sua caixa de entrada

Um resumo curto de issues do GitHub para quem está começando.