# The LearningOnline Network
# URL translation for encrypted filenames
#
# $Id: lonenc.pm,v 1.13 2006/03/22 19:55:39 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/
#
package Apache::lonenc;
use strict;
use Apache::Constants qw(:common :remotehost);
use Apache::lonnet;
use Apache::File();
use Apache::loncommon;
use Crypt::IDEA;
use Time::HiRes qw(gettimeofday);
sub handler {
my $r = shift;
my %cookies=CGI::Cookie->parse($r->header_in('Cookie'));
my $lonid=$cookies{'lonID'};
my $cookie;
if ($lonid) {
my $handle=$lonid->value;
$handle=~s/\W//g;
my $lonidsdir=$r->dir_config('lonIDsDir');
$env{'request.enc'}=1;
if ((-e "$lonidsdir/$handle.id") && ($handle ne '')) {
# Initialize Environment
&Apache::lonnet::transfer_profile_to_env($lonidsdir,$handle);
# Decrypt URL and redirect
my $redirect=&unencrypted($r->uri);
if ($r->args) { $redirect.='?'.$r->args; }
$r->internal_redirect($redirect);
return OK;
}
}
return FORBIDDEN;
}
sub encryptseed {
my $seed=$env{'course.'.$env{'request.course.id'}.'.internal.encseed'};
$seed=~s/[^0-9a-f]/0/g;
$seed.='0123456789abcdef';
$seed=substr($seed.$seed,0,32);
return pack("H32",$seed);
}
sub unencrypted {
my $uri=shift;
$uri=~s/^\/enc\/(\d+)\///;
my $cmdlength=$1;
my $seed=&encryptseed();
unless ($seed) {
return '/'.$uri;
}
$uri=&Apache::lonnet::unescape($uri);
my $cipher=new IDEA $seed;
my $decuri='';
for (my $encidx=0;$encidx<length($uri);$encidx+=16) {
$decuri.=$cipher->decrypt(
pack("H16",substr($uri,$encidx,16))
);
}
$env{'request.enc'}=1;
$decuri=&remove_noise($decuri);
return substr($decuri,0,$cmdlength);
}
# add a randomish character after every 4th caharacter
sub add_noise {
my ($uri)=@_;
my @noise=split(/(.)/,(&gettimeofday())[1]);
my $noisy;
my $i;
foreach my $chunk (split(/(....)/,$uri)) {
$noisy.=$chunk;
$noisy.=$noise[($i++)%(scalar@noise)];
}
return $noisy;
}
# remove every fifth character
sub remove_noise {
my ($uri)=@_;
my $clean;
foreach my $chunk (split(/(....)./,$uri)) { $clean.=$chunk; }
return $clean;
}
sub encrypted {
my ($uri,$force_enc) = @_;
if (!$force_enc && $env{'request.role.adv'}) { return($uri); }
my $seed=&encryptseed();
unless ($seed) {
return $uri;
}
my $cmdlength=length($uri);
# add noise before enc so that that same url's look different
$uri=&add_noise($uri);
my $noiselength=length($uri);
$uri.=time;
my $encuri='';
my $cipher=new IDEA $seed;
for (my $encidx=0;$encidx<=$noiselength;$encidx+=8) {
$encuri.=unpack("H16",
$cipher->encrypt(substr($uri,$encidx,8)));
}
return '/enc/'.$cmdlength.'/'.&Apache::lonnet::escape($encuri);
}
sub check_encrypt {
my $str=shift;
if ($env{'request.enc'}) { return &Apache::lonenc::encrypted($str); }
return $str;
}
sub check_decrypt {
my ($str)=@_;
if (ref($str)) {
if ($$str=~m|^/enc/|) { $$str=&Apache::lonenc::unencrypted($$str); }
return;
}
if ($str=~m|^/enc/|) { return &Apache::lonenc::unencrypted($str); }
return $str;
}
sub encrypt_ref {
my ($token,$elements,$force_enc)=@_;
my $html;
if ($force_enc || $env{'request.enc'}) {
while (my ($name,$value)= each(%{ $elements })) {
if (!$value) { next; }
my $href=&Apache::lonnet::hreflocation($Apache::lonxml::pwd[-1],$value);
if ($href !~ /^http:/) {
$href = &Apache::lonenc::encrypted($href,$force_enc);
}
$token->[2]->{$name}=$href;
}
delete($token->[2]->{'encrypturl'});
$html = &Apache::edit::rebuild_tag($token);
} else {
$html = $token->[4];
}
return $html;
}
1;
__END__
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