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- BUG#5315, need an enc seed when not in course context,
  doesn't really matter what it is though

    1: # The LearningOnline Network
    2: # URL translation for encrypted filenames
    3: #
    4: # $Id: lonenc.pm,v 1.21 2007/07/20 19:07:25 albertel Exp $
    5: #
    6: # Copyright Michigan State University Board of Trustees
    7: #
    8: # This file is part of the LearningOnline Network with CAPA (LON-CAPA).
    9: #
   10: # LON-CAPA is free software; you can redistribute it and/or modify
   11: # it under the terms of the GNU General Public License as published by
   12: # the Free Software Foundation; either version 2 of the License, or
   13: # (at your option) any later version.
   14: #
   15: # LON-CAPA is distributed in the hope that it will be useful,
   16: # but WITHOUT ANY WARRANTY; without even the implied warranty of
   17: # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   18: # GNU General Public License for more details.
   19: #
   20: # You should have received a copy of the GNU General Public License
   21: # along with LON-CAPA; if not, write to the Free Software
   22: # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   23: #
   24: # /home/httpd/html/adm/gpl.txt
   25: #
   26: # http://www.lon-capa.org/
   27: #
   28: 
   29: package Apache::lonenc;
   30: 
   31: use strict;
   32: use Apache::lonnet;
   33: use Crypt::IDEA;
   34: use Time::HiRes qw(gettimeofday);
   35: use LONCAPA;
   36:  
   37: sub encryptseed {
   38:     my ($cid) = @_;
   39:     if (!defined($cid)) {
   40:         $cid = $env{'request.course.id'};
   41:     }
   42:     my $seed;
   43:     if (defined($cid)) {
   44:         if (defined$env{'course.'.$cid.'.internal.encseed'}) {
   45:             $seed = $env{'course.'.$cid.'.internal.encseed'};
   46:         } else {
   47:             my %descargs = ( 'one_time' => 1);
   48:             my %course = 
   49:                &Apache::lonnet::coursedescription($cid,\%descargs);
   50:             $seed = $course{'internal.encseed'};
   51:         }
   52:     }
   53:     if (defined($seed)) {
   54:         $seed=~s/[^0-9a-f]/0/g;
   55:         $seed.='0123456789abcdef';
   56:         $seed=substr($seed.$seed,0,32);
   57:         return pack("H32",$seed);
   58:     } else {
   59:         return pack("H32",1);
   60:     }
   61: }
   62: 
   63: sub unencrypted {
   64:     my ($uri,$cid) = @_;
   65:     $uri=~s/^\/enc\/(\d+)\///;
   66:     my $cmdlength=$1;
   67:     # strip any added extension
   68:     $uri=~s/\.[^.]*//;
   69:     my $seed=&encryptseed($cid);
   70:     unless ($seed) {
   71: 	return '/'.$uri;
   72:     }
   73:     $uri=&unescape($uri);
   74:     my $cipher=new IDEA $seed;
   75:     my $decuri='';
   76:     for (my $encidx=0;$encidx<length($uri);$encidx+=16) {
   77: 	$decuri.=$cipher->decrypt(
   78: 				  pack("H16",substr($uri,$encidx,16))
   79: 				  );
   80:     }
   81:     $env{'request.enc'}=1;
   82:     $decuri=&remove_noise($decuri);
   83:     return substr($decuri,0,$cmdlength);
   84: }
   85: 
   86: # add a randomish character after every 4th caharacter
   87: sub add_noise {
   88:     my ($uri)=@_;
   89:     my @noise=split(/(.)/,(&gettimeofday())[1]);
   90:     my $noisy;
   91:     my $i;
   92:     foreach my $chunk (split(/(....)/,$uri)) {
   93: 	$noisy.=$chunk;
   94: 	$noisy.=$noise[($i++)%(scalar@noise)];
   95:     }
   96:     return $noisy;
   97: }
   98: 
   99: # remove every fifth character
  100: sub remove_noise {
  101:     my ($uri)=@_;
  102:     my $clean;
  103:     foreach my $chunk (split(/(....)./,$uri)) { $clean.=$chunk; }
  104:     return $clean;
  105: }
  106: 
  107: sub encrypted {
  108:     my ($uri,$force_enc) = @_;
  109:     if (!$force_enc && $env{'request.role.adv'}) { return($uri); }
  110:     my $seed=&encryptseed();
  111:     unless ($seed) {
  112: 	return $uri;
  113:     }
  114:     my $cmdlength=length($uri);
  115:     # add noise before enc so that that same url's look different
  116:     $uri=&add_noise($uri);
  117:     my $noiselength=length($uri);
  118:     $uri.=time;
  119:     my $encuri='';
  120:     my $cipher=new IDEA $seed;
  121:     for (my $encidx=0;$encidx<=$noiselength;$encidx+=8) {
  122: 	$encuri.=unpack("H16",
  123: 			$cipher->encrypt(substr($uri,$encidx,8)));
  124:     }
  125:     return '/enc/'.$cmdlength.'/'.&escape($encuri);
  126: }
  127: 
  128: sub check_encrypt {
  129:     my $str=shift;
  130:     if (ref($str)) {
  131:         if ($env{'request.enc'}) { $$str = &Apache::lonenc::encrypted($$str); }
  132:         return;
  133:     } else {
  134:         if ($env{'request.enc'}) { return &Apache::lonenc::encrypted($str); }
  135:     }
  136:     return $str;
  137: }
  138: 
  139: sub check_decrypt {
  140:     my ($str)=@_;
  141:     if (ref($str)) {
  142: 	if ($$str=~m|^/enc/|) { $$str=&Apache::lonenc::unencrypted($$str); }
  143: 	return;
  144:     }
  145:     if ($str=~m|^/enc/|) { return &Apache::lonenc::unencrypted($str); }
  146:     return $str;
  147: }
  148: 
  149: sub encrypt_ref {
  150:     my ($token,$elements,$force_enc)=@_;
  151:     my $html;
  152:     if ($force_enc || $env{'request.enc'}) {
  153: 	while (my ($name,$value)= each(%{ $elements })) {
  154: 	    if (!$value) { next; }
  155: 	    my $href=&Apache::lonnet::hreflocation($Apache::lonxml::pwd[-1],$value);
  156: 	    if ($href !~ /^http:/) {
  157: 		# IE really wants an extension
  158: 		my ($extension) = ($href =~ m/(\.[^.]*)$/);
  159: 		$href = &Apache::lonenc::encrypted($href,$force_enc);
  160: 		$href .= $extension;
  161: 	    }
  162: 	    $token->[2]->{$name}=$href;
  163: 	}
  164: 	delete($token->[2]->{'encrypturl'});
  165: 	$html = &Apache::edit::rebuild_tag($token);
  166:     } else {
  167: 	$html = $token->[4];
  168:     }
  169:     return $html;
  170: }
  171: 1;
  172: __END__
  173: 
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