#!/usr/bin/perl
use strict;

# admof
# Copyright (C) 2006  Jeff Arnold <jbarnold@mit.edu>
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
#
# See /COPYRIGHT in this repository for more information.

$ENV{PATH} = '';

my $targetuser;
unless(($targetuser) = ($ARGV[0] =~ /^([\w._-]+)$/)) {
  error("Invalid locker name: <$ARGV[0]>.");
}
my $curuser;
unless(($curuuser) = ($ARGV[1] =~ /^([\w._-]+)\@ATHENA\.MIT\.EDU$/)) {
  error("An internal error has occurred.\nContact scripts\@mit.edu for assistance.");
}

my $fs = `@fs_path@ 2>/dev/null la /mit/$targetuser/`;
my @fs = split(/\n/, $fs);

#Access list for . is
#Normal rights:
#  system:scripts-root rlidwka
#  system:anyuser rl

unless($fs[0] =~ /^Access list for \/mit\/$targetuser\/ is$/ &&
       $fs[1] =~ /^Normal rights:$/) {
  error("Cannot find locker <$targetuser>.");
}

if($ARGV[2] && !getpwnam($targetuser)) {
  error("Locker <$targetuser> does not have a scripts.mit.edu account.");
}

for(my $i = 2; $i < @fs; $i++) {
  my ($id) = ($fs[$i] =~ /^  ([\w:_-]+) rlidwka$/);
  if($id eq "") { next; }
  my $group;
  if($id eq $curuser) { success(); }
  elsif(($group) = ($id =~ /^(system:.+)/)) {
    my $mems = `@pts_path@ 2>/dev/null membership $group`;
    my @mems = split(/\n/, $mems);

#Members of system:scripts-root (id: -56104) are:
#  hartmans
#  jbarnold
#  presbrey
#  tabbott
#  hartmans.root

    next if($mems[0] !~ /^Members of $group \(id: \S+\) are:$/);
    
    if($mems =~ /\s+$curuser\s+/) {
	success();
    }
  }
}

print <<END;

ERROR:
It appears as though you are not an administrator of locker <$targetuser>.
In order to be able to su to <$targetuser>, you must have full AFS access
to the root directory of locker <$targetuser>.  Try running the command
fs sa /mit/$targetuser $curuser all
on Athena in order to explicitly grant yourself full AFS access.
Contact scripts\@mit.edu if you are unable to solve the problem.

END

exit(1);

sub error {
  print STDERR "\nERROR:\n$_[0]\n\n";
  exit(1);
}

sub success {
  print STDERR "\n== SUCCESS ==\nYou are now logged in as user <$targetuser>.\n";
  print STDERR "To return to being <$curuser>, type \"exit\".\n\n";
  exit(33);
}