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Perl module Term::ReadPassword

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Octocat-spinner-32 README
README
This module is in alpha-testing. Build in the usual way; send bug reports
and patches to me at the address below. From the documentation:

NAME
    Term::ReadPassword - Asking the user for a password

SYNOPSIS
      use Term::ReadPassword;
      while (1) {
        my $password = read_password('password: ');
        redo unless defined $password;
        if ($password eq 'flubber') {
          print "Access granted.\n";
          last;
        } else {
          print "Access denied.\n";
          redo;
        }
      }

DESCRIPTION
    This module lets you ask the user for a password in the
    traditional way, from the keyboard, without echoing.

    This is not intended for use over the web; user authentication
    over the web is another matter entirely. Also, this module
    should generally be used in conjunction with Perl's crypt()
    function, sold separately.

    The read_password function prompts for input, reads a line of
    text from the keyboard, then returns that line to the caller.
    The line of text doesn't include the newline character, so
    there's no need to use chomp.

    While the user is entering the text, a few special characters
    are processed. The character delete (or the character backspace)
    will back up one character, removing the last character in the
    input buffer (if any). The character CR (or the character LF)
    will signal the end of input, causing the accumulated input
    buffer to be returned. And, optionally, the character Control-C
    may be used to terminate the input operation. (See details
    below.) All other characters, even ones which would normally
    have special purposes, will be added to the input buffer.

    It is not recommended, though, that you use the as-yet-
    unspecified control characters in your passwords, as those
    characters may become meaningful in a future version of this
    module. Applications which allow the user to set their own
    passwords may wish to enforce this rule, perhaps with code
    something like this:

        {
          # Naked block for scoping and redo
          my $new_pw = read_password("Enter your new password: ");
          if ($new_pw =~ /([^\x20-\x7E])/) {
            my $bad = unpack "H*", $1;
            print "Your password may not contain the ";
            print "character with hex code $bad.\n";
            redo;
          } elsif (length($new_pw) < 5) {
            print "Your password must be longer than that!\n";
            redo;
          } elsif ($new_pw ne read_password("Enter it again: ")) {
            print "Passwords don't match.\n";
            redo;
          } else {
            &change_password($new_pw);
            print "Your password is now changed.\n";
          }
        }

    The second parameter to read_password is the optional
    `idle_timeout' value. If it is a non-zero number and there is no
    keyboard input for that many seconds, the input operation will
    terminate. Notice that this is not an overall time limit, as the
    timer is restarted with each new character.

    The third parameter will optionally allow the input operation to
    be terminated by the user with Control-C. If this is not
    supplied, or is false, a typed Control-C will be entered into
    the input buffer just as any other character. In that case,
    there is no way from the keyboard to terminate the program while
    it is waiting for input. (That is to say, the normal ability to
    generate signals from the keyboard is suspended during the call
    to read_password.)

    If the input operation terminates early (either because the
    idle_timeout was exceeded, or because a Control-C was enabled
    and typed), the return value will be `undef'. In either case,
    there is no way provided to discover what (if anything) was
    typed before the early termination, or why the input operation
    was terminated.

    So as to discourage users from typing their passwords anywhere
    except at the prompt, any input which has been "typed ahead"
    before the prompt appears will be discarded. And whether the
    input operation terminates normally or not, a newline character
    will be printed, so that the cursor will not remain on the line
    after the prompt.

SECURITY
    You would think that a module dealing with passwords would be
    full of security features. You'd think that, but you'd be wrong.
    For example, perl provides no way to erase a piece of data from
    memory. (It's easy to erase it so that it can't be accessed from
    perl, but that's not the same thing as expunging it from the
    actual memory.) If you've entered a password, even if the
    variable that contained that password has been erased, it may be
    possible for someone to find that password, in plaintext, in a
    core dump. And that's just one potential security hole.

    In short, if serious security is an issue, don't use this
    module.

AUTHOR
    Tom Phoenix <rootbeer@redcat.com>

SEE ALSO
    Term::ReadLine, the "crypt" entry in the perlfunc manpage, and
    your system's manpages for the low-level I/O operations used
    here.

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