1: # The LearningOnline Network
2: # URL translation for encrypted filenames
3: #
4: # $Id: lonenc.pm,v 1.16 2006/05/30 19:47:28 www 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 $seed=$env{'course.'.$env{'request.course.id'}.'.internal.encseed'};
39: $seed=~s/[^0-9a-f]/0/g;
40: $seed.='0123456789abcdef';
41: $seed=substr($seed.$seed,0,32);
42: return pack("H32",$seed);
43: }
44:
45: sub unencrypted {
46: my $uri=shift;
47: $uri=~s/^\/enc\/(\d+)\///;
48: my $cmdlength=$1;
49: my $seed=&encryptseed();
50: unless ($seed) {
51: return '/'.$uri;
52: }
53: $uri=&unescape($uri);
54: my $cipher=new IDEA $seed;
55: my $decuri='';
56: for (my $encidx=0;$encidx<length($uri);$encidx+=16) {
57: $decuri.=$cipher->decrypt(
58: pack("H16",substr($uri,$encidx,16))
59: );
60: }
61: $env{'request.enc'}=1;
62: $decuri=&remove_noise($decuri);
63: return substr($decuri,0,$cmdlength);
64: }
65:
66: # add a randomish character after every 4th caharacter
67: sub add_noise {
68: my ($uri)=@_;
69: my @noise=split(/(.)/,(&gettimeofday())[1]);
70: my $noisy;
71: my $i;
72: foreach my $chunk (split(/(....)/,$uri)) {
73: $noisy.=$chunk;
74: $noisy.=$noise[($i++)%(scalar@noise)];
75: }
76: return $noisy;
77: }
78:
79: # remove every fifth character
80: sub remove_noise {
81: my ($uri)=@_;
82: my $clean;
83: foreach my $chunk (split(/(....)./,$uri)) { $clean.=$chunk; }
84: return $clean;
85: }
86:
87: sub encrypted {
88: my ($uri,$force_enc) = @_;
89: if (!$force_enc && $env{'request.role.adv'}) { return($uri); }
90: my $seed=&encryptseed();
91: unless ($seed) {
92: return $uri;
93: }
94: my $cmdlength=length($uri);
95: # add noise before enc so that that same url's look different
96: $uri=&add_noise($uri);
97: my $noiselength=length($uri);
98: $uri.=time;
99: my $encuri='';
100: my $cipher=new IDEA $seed;
101: for (my $encidx=0;$encidx<=$noiselength;$encidx+=8) {
102: $encuri.=unpack("H16",
103: $cipher->encrypt(substr($uri,$encidx,8)));
104: }
105: return '/enc/'.$cmdlength.'/'.&escape($encuri);
106: }
107:
108: sub check_encrypt {
109: my $str=shift;
110: if ($env{'request.enc'}) { return &Apache::lonenc::encrypted($str); }
111: return $str;
112: }
113:
114: sub check_decrypt {
115: my ($str)=@_;
116: if (ref($str)) {
117: if ($$str=~m|^/enc/|) { $$str=&Apache::lonenc::unencrypted($$str); }
118: return;
119: }
120: if ($str=~m|^/enc/|) { return &Apache::lonenc::unencrypted($str); }
121: return $str;
122: }
123:
124: sub encrypt_ref {
125: my ($token,$elements,$force_enc)=@_;
126: my $html;
127: if ($force_enc || $env{'request.enc'}) {
128: while (my ($name,$value)= each(%{ $elements })) {
129: if (!$value) { next; }
130: my $href=&Apache::lonnet::hreflocation($Apache::lonxml::pwd[-1],$value);
131: if ($href !~ /^http:/) {
132: $href = &Apache::lonenc::encrypted($href,$force_enc);
133: }
134: $token->[2]->{$name}=$href;
135: }
136: delete($token->[2]->{'encrypturl'});
137: $html = &Apache::edit::rebuild_tag($token);
138: } else {
139: $html = $token->[4];
140: }
141: return $html;
142: }
143: 1;
144: __END__
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