[Interest] QLineEdit - clearing the password from memory

[Atlant Schmidt]

Marcus:

> I need to make sure that the password is not kept in memory when
> QLineEdit is destroyed. I tried to use QLineEdit::clear() or
> QLineEdit::setText() but the password string stays in memory. I
> basically want to zeroise the private member string that holds the
> text, I believe QLineEditPrivate::text is the one. How can I access
> this member without changing Qt sources?

  Object-oriented programming gives and object-oriented
  programming takes away. This is one of those cases
  where it takes away. Unless you're willing to go to
  hacky lengths to get around the C++ object system,
  then by design, you *CAN'T* get to private members.

  But what you're proposing would be a very nice, very
  sensible feature for QLineEdit when it's running in
  QLineEdit::Password or QLineEdit::PasswordEchoOnEdit
  or even QLineEdit::NoEcho mode: securely clean up the
  private data upon destruction. So why not modify the
  sources and pass your change back to the community?
  This sounds like a pretty simple change.

                               Atlant


-----Original Message-----
From: interest-bounces+aschmidt=dekaresearch.com at qt-project.org [mailto:interest-bounces+aschmidt=dekaresearch.com at qt-project.org] On Behalf Of Marcus Frenkel
Sent: Wednesday, April 04, 2012 06:24
To: interest at qt-project.org
Subject: [Interest] QLineEdit - clearing the password from memory

Hi

I need to make sure that the password is not kept in memory when
QLineEdit is destroyed. I tried to use QLineEdit::clear() or
QLineEdit::setText() but the password string stays in memory. I
basically want to zeroise the private member string that holds the
text, I believe QLineEditPrivate::text is the one. How can I access
this member without changing Qt sources?

The alternative is to catch key events and store the text in a string
I can control, but there is too much to implement considering the
usage of selection, delete, backspace, arrow keys etc.

Thank you!
Marcus
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