Annotation of loncom/lti/ltiutils.pm, revision 1.4
1.1 raeburn 1: # The LearningOnline Network with CAPA
2: # Utility functions for managing LON-CAPA LTI interactions
3: #
1.4 ! raeburn 4: # $Id: ltiutils.pm,v 1.3 2017/12/30 14:04:00 raeburn Exp $
1.1 raeburn 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 LONCAPA::ltiutils;
30:
31: use strict;
32: use Net::OAuth;
33: use Digest::SHA;
34: use UUID::Tiny ':std';
35: use Apache::lonnet;
36: use Apache::loncommon;
37: use LONCAPA qw(:DEFAULT :match);
38:
39: #
40: # LON-CAPA as LTI Consumer or LTI Provider
41: #
42: # Determine if a nonce in POSTed data has expired.
43: # If unexpired, confirm it has not already been used.
44: #
45: # When LON-CAPA is operating as a Consumer, nonce checking
46: # occurs when a Tool Provider launched from an instance of
47: # an external tool in a LON-CAPA course makes a request to
48: # (a) /adm/service/roster or (b) /adm/service/passback to,
49: # respectively, retrieve a roster or store the grade for
50: # the original launch by a specific user.
51: #
52: # When LON-CAPA is operating as a Provider, nonce checking
53: # occurs when a user in course context in another LMS (the
1.4 ! raeburn 54: # Consumer) launches an external tool to access a LON-CAPA URL:
1.1 raeburn 55: # /adm/lti/ with LON-CAPA symb, map, or deep-link ID appended.
56: #
57:
58: sub check_nonce {
59: my ($nonce,$timestamp,$lifetime,$domain,$ltidir) = @_;
60: if (($ltidir eq '') || ($timestamp eq '') || ($timestamp =~ /^\D/) ||
61: ($lifetime eq '') || ($lifetime =~ /\D/) || ($domain eq '')) {
62: return;
63: }
64: my $now = time;
65: if (($timestamp) && ($timestamp < ($now - $lifetime))) {
66: return;
67: }
68: if ($nonce eq '') {
69: return;
70: }
71: if (-e "$ltidir/$domain/$nonce") {
72: return;
73: } else {
74: unless (-e "$ltidir/$domain") {
75: unless (mkdir("$ltidir/$domain",0755)) {
76: return;
77: }
78: }
79: if (open(my $fh,'>',"$ltidir/$domain/$nonce")) {
80: print $fh $now;
81: close($fh);
82: return 1;
83: }
84: }
85: return;
86: }
87:
88: #
89: # LON-CAPA as LTI Consumer
90: #
91: # Determine the domain and the courseID of the LON-CAPA course
92: # for which access is needed by a Tool Provider -- either to
93: # retrieve a roster or store the grade for an instance of an
94: # external tool in the course.
95: #
96:
97: sub get_loncapa_course {
98: my ($lonhost,$cid,$errors) = @_;
99: return unless (ref($errors) eq 'HASH');
100: my ($cdom,$cnum);
101: if ($cid =~ /^($match_domain)_($match_courseid)$/) {
102: my ($posscdom,$posscnum) = ($1,$2);
103: my $cprimary_id = &Apache::lonnet::domain($posscdom,'primary');
104: if ($cprimary_id eq '') {
105: $errors->{5} = 1;
106: return;
107: } else {
108: my @intdoms;
109: my $internet_names = &Apache::lonnet::get_internet_names($lonhost);
110: if (ref($internet_names) eq 'ARRAY') {
111: @intdoms = @{$internet_names};
112: }
113: my $cintdom = &Apache::lonnet::internet_dom($cprimary_id);
114: if (($cintdom ne '') && (grep(/^\Q$cintdom\E$/,@intdoms))) {
115: $cdom = $posscdom;
116: } else {
117: $errors->{6} = 1;
118: return;
119: }
120: }
121: my $chome = &Apache::lonnet::homeserver($posscnum,$posscdom);
122: if ($chome =~ /(con_lost|no_host|no_such_host)/) {
123: $errors->{7} = 1;
124: return;
125: } else {
126: $cnum = $posscnum;
127: }
128: } else {
129: $errors->{8} = 1;
130: return;
131: }
132: return ($cdom,$cnum);
133: }
134:
135: #
136: # LON-CAPA as LTI Consumer
137: #
138: # Determine the symb and (optionally) LON-CAPA user for an
139: # instance of an external tool in a course -- either to
140: # to retrieve a roster or store a grade.
141: #
142: # Use the digested symb to lookup the real symb in exttools.db
143: # and the digested userID to lookup the real userID (if needed).
144: # and extract the exttool instance and symb.
145: #
146:
147: sub get_tool_instance {
148: my ($cdom,$cnum,$digsymb,$diguser,$errors) = @_;
149: return unless (ref($errors) eq 'HASH');
150: my ($marker,$symb,$uname,$udom);
151: my @keys = ($digsymb);
152: if ($diguser) {
153: push(@keys,$diguser);
154: }
155: my %digesthash = &Apache::lonnet::get('exttools',\@keys,$cdom,$cnum);
156: if ($digsymb) {
157: $symb = $digesthash{$digsymb};
158: if ($symb) {
159: my ($map,$id,$url) = split(/___/,$symb);
160: $marker = (split(m{/},$url))[3];
161: $marker=~s/\D//g;
162: } else {
163: $errors->{9} = 1;
164: }
165: }
166: if ($diguser) {
167: if ($digesthash{$diguser} =~ /^($match_username):($match_domain)$/) {
168: ($uname,$udom) = ($1,$2);
169: } else {
170: $errors->{10} = 1;
171: }
172: return ($marker,$symb,$uname,$udom);
173: } else {
174: return ($marker,$symb);
175: }
176: }
177:
178: #
179: # LON-CAPA as LTI Consumer
180: #
181: # Retrieve data needed to validate a request from a Tool Provider
182: # for a roster or to store a grade for an instance of an external
183: # tool in a LON-CAPA course.
184: #
185: # Retrieve the Consumer key and Consumer secret from the domain
186: # configuration or the Tool Provider ID stored in the
187: # exttool_$marker db file and compare the Consumer key with the
188: # one in the POSTed data.
189: #
190: # Side effect is to populate the $toolsettings hashref with the
191: # contents of the .db file (instance of tool in course) and the
192: # $ltitools hashref with the configuration for the tool (at
193: # domain level).
194: #
195:
196: sub get_tool_secret {
197: my ($key,$marker,$symb,$cdom,$cnum,$toolsettings,$ltitools,$errors) = @_;
198: return unless ((ref($toolsettings) eq 'HASH') && (ref($ltitools) eq 'HASH') &&
199: (ref($errors) eq 'HASH'));
200: my ($consumer_secret,$nonce_lifetime);
201: if ($marker) {
202: %{$toolsettings}=&Apache::lonnet::dump('exttool_'.$marker,$cdom,$cnum);
203: if ($toolsettings->{'id'}) {
204: my $idx = $toolsettings->{'id'};
205: my %lti = &Apache::lonnet::get_domain_lti($cdom,'consumer');
206: if (ref($lti{$idx}) eq 'HASH') {
207: %{$ltitools} = %{$lti{$idx}};
208: if ($ltitools->{'key'} eq $key) {
209: $consumer_secret = $ltitools->{'secret'};
210: $nonce_lifetime = $ltitools->{'lifetime'};
211: } else {
212: $errors->{11} = 1;
213: return;
214: }
215: } else {
216: $errors->{12} = 1;
217: return;
218: }
219: } else {
220: $errors->{13} = 1;
221: return;
222: }
223: } else {
224: $errors->{14};
225: return;
226: }
227: return ($consumer_secret,$nonce_lifetime);
228: }
229:
230: #
231: # LON-CAPA as LTI Consumer
232: #
233: # Verify a signed request using the consumer_key and
234: # secret for the specific LTI Provider.
235: #
236:
237: sub verify_request {
238: my ($params,$protocol,$hostname,$requri,$reqmethod,$consumer_secret,$errors) = @_;
239: return unless (ref($errors) eq 'HASH');
240: my $request = Net::OAuth->request('request token')->from_hash($params,
241: request_url => $protocol.'://'.$hostname.$requri,
242: request_method => $reqmethod,
243: consumer_secret => $consumer_secret,);
244: unless ($request->verify()) {
245: $errors->{15} = 1;
246: return;
247: }
248: }
249:
250: #
251: # LON-CAPA as LTI Consumer
252: #
253: # Verify that an item identifier (either roster request:
254: # ext_ims_lis_memberships_id, or grade store:
255: # lis_result_sourcedid) has not been tampered with, and
256: # the secret used to create the unique identifier has not
257: # expired.
258: #
259: # Prepending the current secret (if still valid),
260: # or the previous secret (if current one is no longer valid),
261: # to a string composed of the :::-separated components
262: # must generate the result signature in the lis item ID
263: # sent by the Tool Provider.
264: #
265:
266: sub verify_lis_item {
267: my ($sigrec,$context,$digsymb,$diguser,$cdom,$cnum,$toolsettings,$ltitools,$errors) = @_;
268: return unless ((ref($toolsettings) eq 'HASH') && (ref($ltitools) eq 'HASH') &&
269: (ref($errors) eq 'HASH'));
270: my ($has_action, $valid_for);
271: if ($context eq 'grade') {
272: $has_action = $ltitools->{'passback'};
273: $valid_for = $ltitools->{'passbackvalid'}
274: } elsif ($context eq 'roster') {
275: $has_action = $ltitools->{'roster'};
276: $valid_for = $ltitools->{'rostervalid'};
277: }
278: if ($has_action) {
279: my $secret;
280: if (($toolsettings->{$context.'secretdate'} + $valid_for) > time) {
281: $secret = $toolsettings->{$context.'secret'};
282: } else {
283: $secret = $toolsettings->{'old'.$context.'secret'};
284: }
285: if ($secret) {
286: my $expected_sig;
287: if ($context eq 'grade') {
288: my $uniqid = $digsymb.':::'.$diguser.':::'.$cdom.'_'.$cnum;
289: $expected_sig = &get_service_id($secret,$uniqid);
290: if ($expected_sig eq $sigrec) {
291: return 1;
292: } else {
1.2 raeburn 293: $errors->{17} = 1;
1.1 raeburn 294: }
295: } elsif ($context eq 'roster') {
296: my $uniqid = $digsymb.':::'.$cdom.'_'.$cnum;
297: $expected_sig = &get_service_id($secret,$uniqid);
298: if ($expected_sig eq $sigrec) {
299: return 1;
300: } else {
1.2 raeburn 301: $errors->{18} = 1;
1.1 raeburn 302: }
303: }
304: } else {
1.2 raeburn 305: $errors->{19} = 1;
1.1 raeburn 306: }
307: } else {
1.2 raeburn 308: $errors->{20} = 1;
1.1 raeburn 309: }
310: return;
311: }
312:
313: #
314: # LON-CAPA as LTI Consumer
315: #
316: # Sign a request used to launch an instance of an external
1.4 ! raeburn 317: # tool in a LON-CAPA course, using the key and secret supplied
1.1 raeburn 318: # by the Tool Provider.
319: #
320:
321: sub sign_params {
1.3 raeburn 322: my ($url,$key,$secret,$sigmethod,$paramsref) = @_;
1.1 raeburn 323: return unless (ref($paramsref) eq 'HASH');
1.3 raeburn 324: if ($sigmethod eq '') {
325: $sigmethod = 'HMAC-SHA1';
326: }
1.1 raeburn 327: my $nonce = Digest::SHA::sha1_hex(sprintf("%06x%06x",rand(0xfffff0),rand(0xfffff0)));
328: my $request = Net::OAuth->request("request token")->new(
329: consumer_key => $key,
330: consumer_secret => $secret,
331: request_url => $url,
332: request_method => 'POST',
1.3 raeburn 333: signature_method => $sigmethod,
1.1 raeburn 334: timestamp => time,
335: nonce => $nonce,
336: callback => 'about:blank',
337: extra_params => $paramsref,
338: version => '1.0',
339: );
340: $request->sign;
341: return $request->to_hash();
342: }
343:
344: #
345: # LON-CAPA as LTI Consumer
346: #
347: # Generate a signature for a unique identifier (roster request:
348: # ext_ims_lis_memberships_id, or grade store: lis_result_sourcedid)
349: #
350:
351: sub get_service_id {
352: my ($secret,$id) = @_;
353: my $sig = Digest::SHA::sha1_hex($secret.':::'.$id);
354: return $sig.':::'.$id;
355: }
356:
357: #
358: # LON-CAPA as LTI Consumer
359: #
360: # Generate and store the time-limited secret used to create the
361: # signature in a service request identifier (roster request or
362: # grade store). An existing secret past its expiration date
363: # will be stored as old<service name>secret, and a new secret
364: # <service name>secret will be stored.
365: #
366: # Secrets are specific to service name and to the tool instance
367: # (and are stored in the exttool_$marker db file).
368: # The time period a secret remains valid is determined by the
369: # domain configuration for the specific tool and the service.
370: #
371:
372: sub set_service_secret {
373: my ($cdom,$cnum,$marker,$name,$now,$toolsettings,$ltitools) = @_;
374: return unless ((ref($toolsettings) eq 'HASH') && (ref($ltitools) eq 'HASH'));
375: my $warning;
376: my ($needsnew,$oldsecret,$lifetime);
377: if ($name eq 'grade') {
378: $lifetime = $ltitools->{'passbackvalid'}
379: } elsif ($name eq 'roster') {
380: $lifetime = $ltitools->{'rostervalid'};
381: }
382: if ($toolsettings->{$name} eq '') {
383: $needsnew = 1;
384: } elsif (($toolsettings->{$name.'date'} + $lifetime) < $now) {
385: $oldsecret = $toolsettings->{$name.'secret'};
386: $needsnew = 1;
387: }
388: if ($needsnew) {
389: if (&get_tool_lock($cdom,$cnum,$marker,$name,$now) eq 'ok') {
390: my $secret = UUID::Tiny::create_uuid_as_string(UUID_V4);
391: $toolsettings->{$name.'secret'} = $secret;
392: my %secrethash = (
393: $name.'secret' => $secret,
394: $name.'secretdate' => $now,
395: );
396: if ($oldsecret ne '') {
397: $secrethash{'old'.$name.'secret'} = $oldsecret;
398: }
399: my $putres = &Apache::lonnet::put('exttool_'.$marker,
400: \%secrethash,$cdom,$cnum);
401: my $delresult = &release_tool_lock($cdom,$cnum,$marker,$name);
402: if ($delresult ne 'ok') {
403: $warning = $delresult ;
404: }
405: if ($putres eq 'ok') {
406: return 'ok';
407: }
408: } else {
409: $warning = 'Could not obtain exclusive lock';
410: }
411: } else {
412: return 'ok';
413: }
414: return;
415: }
416:
417: #
418: # LON-CAPA as LTI Consumer
419: #
420: # Add a lock key to exttools.db for the instance of an external tool
421: # when generating and storing a service secret.
422: #
423:
424: sub get_tool_lock {
425: my ($cdom,$cnum,$marker,$name,$now) = @_;
426: # get lock for tool for which secret is being set
427: my $lockhash = {
428: $name."\0".$marker."\0".'lock' => $now.':'.$env{'user.name'}.
429: ':'.$env{'user.domain'},
430: };
431: my $tries = 0;
432: my $gotlock = &Apache::lonnet::newput('exttools',$lockhash,$cdom,$cnum);
433:
434: while (($gotlock ne 'ok') && $tries <3) {
435: $tries ++;
436: sleep(1);
437: $gotlock = &Apache::lonnet::newput('exttools',$lockhash,$cdom,$cnum);
438: }
439: return $gotlock;
440: }
441:
442: #
443: # LON-CAPA as LTI Consumer
444: #
445: # Remove a lock key from exttools.db for the instance of an external
446: # tool created when generating and storing a service secret.
447: #
448:
449: sub release_tool_lock {
1.3 raeburn 450: my ($cdom,$cnum,$marker,$name) = @_;
1.1 raeburn 451: # remove lock
452: my @del_lock = ($name."\0".$marker."\0".'lock');
453: my $dellockoutcome=&Apache::lonnet::del('exttools',\@del_lock,$cdom,$cnum);
454: if ($dellockoutcome ne 'ok') {
455: return 'Warning: failed to release lock for exttool';
456: } else {
457: return 'ok';
458: }
459: }
460:
461: 1;
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