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#!/usr/bin/perl
# The Learning Online Network with CAPA
#
# apachereload - setuid script that reloads the apache daemon.
#
# $Id: apachereload,v 1.6 2006/01/28 00:52:27 albertel Exp $
#
# Copyright Michigan State University Board of Trustees
#
# This file is part of the LearningOnline Network with CAPA (LON-CAPA).
#
# LON-CAPA 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.
#
# LON-CAPA 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 LON-CAPA; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#
# /home/httpd/html/adm/gpl.txt
#
# http://www.lon-capa.org/
#


use strict;
#
#  This script is a setuid script that must be run as user www
#  it effectively just executes /etc/init.d/httpd reload.
#  causing the apache daemon to get HUP'd.  The script is
#  run by lond after re-initing it's host information.

$ENV{'PATH'}='/bin:/usr/bin:/usr/local/sbin:/home/httpd/perl'; # Nullify path
                                                               # information
delete @ENV{qw(IFS CDPATH ENV BASH_ENV)}; # nullify potential taints

my $command = "/etc/init.d/httpd reload";

use lib '/home/httpd/lib/perl/';
use LONCAPA::Configuration;
my %perlvar= %{&LONCAPA::Configuration::read_conf('loncapa.conf')};

my ($execdir) = ($perlvar{'lonDaemons'} =~/(.*)/);
my $dist=`$execdir/distprobe`;
if ($dist =~ /^(suse|sles)/) {
    $command = "/etc/init.d/apache reload";
}
# Do not print error messages
my $noprint=1;

print "In apachereload" unless $noprint;

# ----------------------------- Make sure this process is running from user=www
my $wwwid=getpwnam('www');
&disable_root_capability;
if ($wwwid!=$>) {
    print("User ID mismatch.  This program must be run as user 'www'\n")
	unless $noprint;
    exit 1;
}

# ----------------------------------- Start running script with www permissions
&disable_root_capability;

# --------------------------- Handle case of another apachereload process (locking)
unless (&try_to_lock('/tmp/lock_apachereload')) {
    print "Error. Too many other simultaneous password change requests being ".
	"made.\n" unless $noprint;
    exit 4;
}


&enable_root_capability;
($>,$<)=(0,0);


#  Now run the reload:
#

system($command);

#  Remove the lock file.



&disable_root_capability;
unlink('/tmp/lock_apachereload');
exit 0;

# ---------------------------------------------- have setuid script run as root
sub enable_root_capability {
    if ($wwwid==$>) {
	($<,$>)=($>,0);
	($(,$))=($),0);
    }
    else {
	# root capability is already enabled
    }
    return $>;
}

# ----------------------------------------------- have setuid script run as www
sub disable_root_capability {
    if ($wwwid==$<) {
	($<,$>)=($>,$<);
	($(,$))=($),$();
    }
    else {
	# root capability is already disabled
    }
}

# ----------------------- make sure that another apachereload process isn't running
sub try_to_lock {
    my ($lockfile)=@_;
    my $currentpid;
    my $lastpid;
    # Do not manipulate lock file as root
    if ($>==0) {
	return 0;
    }
    # Try to generate lock file.
    # Wait 3 seconds.  If same process id is in
    # lock file, then assume lock file is stale, and
    # go ahead.  If process id's fluctuate, try
    # for a maximum of 10 times.
    for (0..10) {
	if (-e $lockfile) {
	    open(LOCK,"<$lockfile");
	    $currentpid=<LOCK>;
	    close LOCK;
	    if ($currentpid==$lastpid) {
		last;
	    }
	    sleep 3;
	    $lastpid=$currentpid;
	}
	else {
	    last;
	}
	if ($_==10) {
	    return 0;
	}
    }
    open(LOCK,">$lockfile");
    print LOCK $$;
    close LOCK;
    return 1;
}

=head1 NAME

apachereload -setuid script to reload the apache web server.

=head1 DESCRIPTION

LON-CAPA - setuid script to reload the apache web server.

=head1 README

LON-CAPA  setuid script to reload the apache web server.

=head1 PREREQUISITES

=head1 COREQUISITES

=pod OSNAMES

linux

=pod SCRIPT CATEGORIES

LONCAPA/Administrative

=cut

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Please contact the server administrator at root@localhost to inform them of the time this error occurred, and the actions you performed just before this error.

More information about this error may be available in the server error log.