Re: getpass alternative [Re: getpass documentation]

[Micah Cowan]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Simon Josefsson wrote:
> Another problem that I discovered is that gnulib's getpass.c inhibits
> signals, so the user cannot press ^C/^Z.  This is even more of a problem
> when the user needs to type the same password twice: the process may be
> stuck in a loop that can't be canceled waiting for the user to type two
> identical strings.

Yes, I would have preferred to let ^C gracefully terminate the program,
as well (and ^Z could perhaps result in a newline being output before
suspension, with the prompt re-issued upon SIGCONT). Ideally, it would
add an extra newline to its output for that condition as well. The
problem with that, of course, is that a program may well wish to do
other things as well, in response to a signal, and so it may not be wise
to have the getpass-like facility install its own temporary signal handles.

However, letting the application use its own signal handlers still
leaves the problem of the app not knowing where it might want to send an
extra newline (and, the bother of having to reopen /dev/tty, when it had
potentially just been opened a moment ago by getpass). It seems to me
then that the "find appropriate interactive file streams" logic should
be split off separately, so that the app has full knowledge of what
streams are being used for communication (or can even specify
alternatives). This would also eliminate the need for a separate
getpassword_confirmed function; it could also potentially be used for a
gnupg-agent-style mechanism (I don't know: I'm not clear on how that
usually works).

Usage something like:

  FILE *in, *out;
  get_interactive_device (&in, &out, GID_DISABLE_SIGNALS);
  for (;;)
    {
      char *pass1, *pass2;
      pass1 = getpassword ("Password: ", in, out);
      /* Check pass1 against NULL here */
      pass2 = getpassword ("Re-enter password: ", in, out);
      /* And here for pass2 */
      if (! strcmp (pass1, pass2)) break;
      fputs ("Passwords don't match, plase try again.\n", out);
    }

Note that, the above only works if getpassword returns newly allocated
space, intended for deallocation by the app (which is IMO preferable
anyway). Some folks would probably also want a version that gives them
direct control over allocation/reallocation.

- --
Micah J. Cowan
Programmer, musician, typesetting enthusiast, gamer,
and GNU Wget Project Maintainer.
http://micah.cowan.name/
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFIMUCe7M8hyUobTrERAlldAJ9OiImZBtM70rP4SdCrLUSNi2tfVgCeK20t
4RBZcgqn5FnauTqg/q2uEgc=
=LTF0
-----END PGP SIGNATURE-----