#!/usr/local/bin/perl -w
#
# $Revision: 1.1 $
#

use strict;
use POSIX qw(:termios_h);

use Sys::Hostname;

local $main::Timeout = 15;
my $Password = 0;

for ( my $i = 0 ; $i <= $#ARGV ; ++ $i )
{
  if ( $ARGV[$i] eq "-n" )
  {
    $main::Timeout = 0; # zero means infinitity
  }
  elsif ( $ARGV[ $i ] eq "-p" )
  {
    $Password = 1;
  }
  elsif ( $ARGV[ $i ] eq "-t" )
  {
    my $j = $i;
    ++$i;
    if ( $i > $#ARGV )
    {
      print STDERR "lock: option requires an argument -- $ARGV[$j]\n";
      usage ();
      exit 1;
    }
    elsif ( $ARGV[$i] !~ /^[1-9]\d*$/ )	# don't let the user specify 0.
    {
      print STDERR "lock: illegal timeout value\n";
      usage();
      exit 1;
    }
    $main::Timeout = $ARGV[$i];
  }
  else
  {
    print STDERR "lock: illegal option -- $ARGV[$i]\n";
    usage();
    exit 1;
  }
}

local $main::fd_stdin = fileno(STDIN);
local $main::term = new POSIX::Termios;
$main::term->getattr($main::fd_stdin);
local $main::oterm = $main::term->getlflag();
local $main::echo = &POSIX::ECHO;
local $main::noecho = $main::oterm & ~$main::echo;
$| = 1; # Make our pipes piping hot!

my $key;
my $again;

if ( $Password )
{
  $key = (getpwuid($<))[1];
}
else
{
  print "Key: ";
  noecho();
  $key = <STDIN>;
  echo();
  print "\n";
  chomp $key;

  print "Again: ";
  noecho();
  $again = <STDIN>;
  echo();
  print "\n";
  chomp $again;

  if ( $key ne $again )
  {
    print "lock: passwords didn't match.\n";
    exit 1;
  }
}

my $Tty = tty();
my $Host = hostname();
my $Date = localtime(time);

# lock: /dev/ttyq8 on myhost.mydomain. timeout in 15 minutes
# time now is Fri Aug  6 17:47:26 EDT 1999
print "lock: $Tty on $Host. ";
if ( $main::Timeout > 0 )
  {
    print "timeout in $main::Timeout minutes\n";
  }
else
  {
    print "no timeout\n";
  }
print "time is now $Date";

foreach my $sig ( keys (%SIG) )
  {
    $SIG{$sig} = 'handler';
  }

if ( $main::Timeout > 0 )
{ 
  alarm ( 60*$main::Timeout );
}

noecho();
do
{
  print "\nKey: ";
  $again = <STDIN>;
  chomp $again;
  $again = code($again) if ( $Password );
} while ( ! defined($again) or ( $key ne $again ) );
echo();
print "\n";

sub noecho
{
  $main::term->setlflag($main::noecho);
  $main::term->setattr($main::fd_stdin, TCSANOW);
}

sub echo
{
  $main::term->setlflag($main::oterm);
  $main::term->setattr($main::fd_stdin, TCSANOW);
}

sub usage
{
  print STDERR "usage: lock [-n] [-p] [-t timeout]\n";
}

sub code
  {
    my $word = shift;
    my $pwd = (getpwuid($<))[1];
    my $salt = substr($pwd,0,2);
    return crypt($word,$salt);
  }

# upon interupt
# lock: type in the unlock key. 

sub handler
  {
    my $sig = shift;
    if ( $sig eq 'ALRM' )
      {
	print "lock: timeout\n";
	exit 0;
      }
    else
      {
	print "lock: type in the unlock key.";
	if ( $main::Timeout > 0 )
	  {
	    my $timeleft = alarm(0);
	    my $minleft = int($timeleft/60);
	    my $secleft = $timeleft%60;
	    printf " timeout in %d:%s%d minutes", $minleft, 
              $secleft < 10 ? "0" : "", $secleft;
	    alarm($timeleft);
	  }
	print "\n";
      }
  }

sub tty
  {
    "";
  }

__END__

=pod

=head1 NAME

B<lock> -- reserves a terminal

=head1 SYNOPSYS

B<lock> [B<-n>] [B<-p>] [B<-t> I<timeout>]

=head1 DESCRIPTION

B<lock> requests a password from the user, reads it again for verification
and then will normally not relinquish the terminal until the password is
repeated.  There are two other conditions under which it will terminate:
it will timeout after some interval of time and it may be killed by someone
with the appropriate privileges.

=head2 OPTIONS

All of the specified options are optional.

=over 4

=item -n

Don't use a timeout value.  Terminal will be locked forever.

=item -p

A password is not requested, instead the user's current login password is 
used.

=item -t I<timeout>

The time limit (default 15 minutes) is changed to I<timeout> minutes.

=back

=head1 CAVEATS

The BSD version of the B<lock> command supports using an S/Key to
lock the terminal.

=head1 AUTHOR

The Perl implementation of B<lock> was writtem by Aron Atkins, 
I<atkins@gweep.net>.

=head1 COPYRIGHT and LICENSE

This program is copyright by Aron Atkins 1999.

This program is free and open software. You may use, copy, modify, distribute
and sell this program (and any modified variants) in any way you wish,
provided you do not restrict others to do the same.

=cut