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Allow &encryptseed() to take an optional argument - a courseID, and to retrieve the course's internal.encseed when it is not currently available in %env.  Used to perform decryption on encrypted URLs included in the baseurl of feedback messages, if the message is read when the corresponding course role is unselected.

    1: # The LearningOnline Network
    2: # URL translation for encrypted filenames
    3: #
    4: # $Id: lonenc.pm,v 1.19 2006/12/24 21:22:33 raeburn 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:             my %seedhash = 
   51:                &Apache::lonnet::get('environment',['internal.encseed'],
   52:                                     $course{'domain'},$course{'num'});
   53:             $seed = $seedhash{'internal.encseed'};
   54:         }
   55:     }
   56:     if (defined($seed)) {
   57:         $seed=~s/[^0-9a-f]/0/g;
   58:         $seed.='0123456789abcdef';
   59:         $seed=substr($seed.$seed,0,32);
   60:         return pack("H32",$seed);
   61:     } else {
   62:         return;
   63:     }
   64: }
   65: 
   66: sub unencrypted {
   67:     my ($uri,$cid) = @_;
   68:     $uri=~s/^\/enc\/(\d+)\///;
   69:     my $cmdlength=$1;
   70:     # strip any added extension
   71:     $uri=~s/\.[^.]*//;
   72:     my $seed=&encryptseed($cid);
   73:     unless ($seed) {
   74: 	return '/'.$uri;
   75:     }
   76:     $uri=&unescape($uri);
   77:     my $cipher=new IDEA $seed;
   78:     my $decuri='';
   79:     for (my $encidx=0;$encidx<length($uri);$encidx+=16) {
   80: 	$decuri.=$cipher->decrypt(
   81: 				  pack("H16",substr($uri,$encidx,16))
   82: 				  );
   83:     }
   84:     $env{'request.enc'}=1;
   85:     $decuri=&remove_noise($decuri);
   86:     return substr($decuri,0,$cmdlength);
   87: }
   88: 
   89: # add a randomish character after every 4th caharacter
   90: sub add_noise {
   91:     my ($uri)=@_;
   92:     my @noise=split(/(.)/,(&gettimeofday())[1]);
   93:     my $noisy;
   94:     my $i;
   95:     foreach my $chunk (split(/(....)/,$uri)) {
   96: 	$noisy.=$chunk;
   97: 	$noisy.=$noise[($i++)%(scalar@noise)];
   98:     }
   99:     return $noisy;
  100: }
  101: 
  102: # remove every fifth character
  103: sub remove_noise {
  104:     my ($uri)=@_;
  105:     my $clean;
  106:     foreach my $chunk (split(/(....)./,$uri)) { $clean.=$chunk; }
  107:     return $clean;
  108: }
  109: 
  110: sub encrypted {
  111:     my ($uri,$force_enc) = @_;
  112:     if (!$force_enc && $env{'request.role.adv'}) { return($uri); }
  113:     my $seed=&encryptseed();
  114:     unless ($seed) {
  115: 	return $uri;
  116:     }
  117:     my $cmdlength=length($uri);
  118:     # add noise before enc so that that same url's look different
  119:     $uri=&add_noise($uri);
  120:     my $noiselength=length($uri);
  121:     $uri.=time;
  122:     my $encuri='';
  123:     my $cipher=new IDEA $seed;
  124:     for (my $encidx=0;$encidx<=$noiselength;$encidx+=8) {
  125: 	$encuri.=unpack("H16",
  126: 			$cipher->encrypt(substr($uri,$encidx,8)));
  127:     }
  128:     return '/enc/'.$cmdlength.'/'.&escape($encuri);
  129: }
  130: 
  131: sub check_encrypt {
  132:     my $str=shift;
  133:     if (ref($str)) {
  134:         if ($env{'request.enc'}) { $$str = &Apache::lonenc::encrypted($$str); }
  135:         return;
  136:     } else {
  137:         if ($env{'request.enc'}) { return &Apache::lonenc::encrypted($str); }
  138:     }
  139:     return $str;
  140: }
  141: 
  142: sub check_decrypt {
  143:     my ($str)=@_;
  144:     if (ref($str)) {
  145: 	if ($$str=~m|^/enc/|) { $$str=&Apache::lonenc::unencrypted($$str); }
  146: 	return;
  147:     }
  148:     if ($str=~m|^/enc/|) { return &Apache::lonenc::unencrypted($str); }
  149:     return $str;
  150: }
  151: 
  152: sub encrypt_ref {
  153:     my ($token,$elements,$force_enc)=@_;
  154:     my $html;
  155:     if ($force_enc || $env{'request.enc'}) {
  156: 	while (my ($name,$value)= each(%{ $elements })) {
  157: 	    if (!$value) { next; }
  158: 	    my $href=&Apache::lonnet::hreflocation($Apache::lonxml::pwd[-1],$value);
  159: 	    if ($href !~ /^http:/) {
  160: 		# IE really wants an extension
  161: 		my ($extension) = ($href =~ m/(\.[^.]*)$/);
  162: 		$href = &Apache::lonenc::encrypted($href,$force_enc);
  163: 		$href .= $extension;
  164: 	    }
  165: 	    $token->[2]->{$name}=$href;
  166: 	}
  167: 	delete($token->[2]->{'encrypturl'});
  168: 	$html = &Apache::edit::rebuild_tag($token);
  169:     } else {
  170: 	$html = $token->[4];
  171:     }
  172:     return $html;
  173: }
  174: 1;
  175: __END__
  176: 
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