--- loncom/lti/ltiauth.pm	2019/07/18 18:28:46	1.19
+++ loncom/lti/ltiauth.pm	2022/04/06 21:44:49	1.36
@@ -1,7 +1,7 @@
 # The LearningOnline Network
 # Basic LTI Authentication Module
 #
-# $Id: ltiauth.pm,v 1.19 2019/07/18 18:28:46 raeburn Exp $
+# $Id: ltiauth.pm,v 1.36 2022/04/06 21:44:49 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -30,8 +30,8 @@ package Apache::ltiauth;
 
 use strict;
 use LONCAPA qw(:DEFAULT :match);
+use Encode;
 use Apache::Constants qw(:common :http);
-use Net::OAuth;
 use Apache::lonlocal;
 use Apache::lonnet;
 use Apache::loncommon;
@@ -42,6 +42,7 @@ use LONCAPA::ltiutils;
 sub handler {
     my $r = shift;
     my $requri = $r->uri;
+    my $hostname = $r->hostname;
 #
 # Check for existing session, and temporarily delete any form items
 # in %env, if session exists
@@ -57,17 +58,17 @@ sub handler {
         }
     }
 #
-# Retrieve data POSTed by LTI Consumer on launch
+# Retrieve data POSTed by LTI launch
 #
     &Apache::lonacc::get_posted_cgi($r);
     my $params = {};
     foreach my $key (sort(keys(%env))) {
         if ($key =~ /^form\.(.+)$/) {
-            $params->{$1} = $env{$key};
+            $params->{$1} = &Encode::decode('UTF-8',$env{$key});
         }
     }
 #
-# Check for existing session, and restored temporarily
+# Check for existing session, and restore temporarily
 # deleted form items to %env, if session exists.
 #
     if ($handle ne '') {
@@ -79,7 +80,7 @@ sub handler {
     }
 
     unless (keys(%{$params})) {
-        &invalid_request($r,1);
+        &invalid_request($r,'No parameters included in launch request');
         return OK;
     }
 
@@ -89,7 +90,7 @@ sub handler {
             $params->{'oauth_version'} &&
             $params->{'oauth_signature'} &&
             $params->{'oauth_signature_method'}) {
-        &invalid_request($r,2);
+        &invalid_request($r,'One or more required parameters missing from launch request');
         return OK;
     }
 
@@ -97,12 +98,176 @@ sub handler {
 # Retrieve "internet domains" for all this institution's LON-CAPA
 # nodes.
 #
-    my ($udom,$uname,$uhome,$cdom,$cnum,$symb,$mapurl,@intdoms);
+    my @intdoms;
     my $lonhost = $r->dir_config('lonHostID');
     my $internet_names = &Apache::lonnet::get_internet_names($lonhost);
     if (ref($internet_names) eq 'ARRAY') {
         @intdoms = @{$internet_names};
     }
+#
+# Determine course's domain in LON-CAPA
+# for basic launch using key and secret managed
+# in LON-CAPA course (i.e., uri begins /adm/launch)
+#
+
+   my ($cdom,$cnum);
+
+# Note: "internet domain" for course's domain must be one of the
+# internet domains for the institution's LON-CAPA servers.
+#
+    if ($requri =~ m{^/adm/launch(|/.*)$}) {
+        my $tail = $1;
+        if ($tail =~ m{^/tiny/($match_domain)/(\w+)$}) {
+            my ($urlcdom,$urlcnum) = &course_from_tinyurl($tail);
+            if (($urlcdom ne '') && ($urlcnum ne '')) {
+                $cdom = $urlcdom;
+                $cnum = $urlcnum;
+                my $primary_id = &Apache::lonnet::domain($cdom,'primary');
+                if ($primary_id ne '') {
+                    my $intdom = &Apache::lonnet::internet_dom($primary_id);
+                    if (($intdom ne '') && (grep(/^\Q$intdom\E$/,@intdoms))) {
+#
+# Verify the signed request using the secret for LTI link
+# protectors for which the key in the POSTed data matches
+# keys in the course configuration.
+#
+# Request is invalid if the signed request could not be verified
+# for the key and secret from LON-CAPA course configuration for
+# LTI link protectors or from LON-CAPA configuration for the
+# course's domain if there are LTI Providers which may be used.
+#
+# Determine if nonce in POSTed data has expired.
+# If unexpired, confirm it has not already been used.
+#
+# Retrieve information for LTI link protectors in course
+# where url was /adm/launch/tiny/$cdom/$uniqueid
+#
+
+                        my ($itemid,$ltitype,%crslti,%lti_in_use);
+                        $itemid = &get_lti_itemid($requri,$hostname,$params,$cdom,$cnum,'linkprot');
+                        if ($itemid) {
+                            %crslti = &Apache::lonnet::get_course_lti($cnum,$cdom);
+                        }
+                        if (($itemid) && (ref($crslti{$itemid}) eq 'HASH')) {
+                            $ltitype = 'c';
+                            if (&LONCAPA::ltiutils::check_nonce($params->{'oauth_nonce'},$params->{'oauth_timestamp'},
+                                                                $crslti{$itemid}{'lifetime'},$cdom,$r->dir_config('lonLTIDir'))) {
+                                %lti_in_use = %{$crslti{$itemid}};
+                            } else {
+                                &invalid_request($r,'Time limit exceeded for launch request credentials');
+                                return OK;
+                            }
+                        } else {
+                            $itemid = &get_lti_itemid($requri,$hostname,$params,$cdom,'','linkprot');
+                            my %lti;
+                            if ($itemid) {
+                                %lti = &Apache::lonnet::get_domain_lti($cdom,'linkprot');
+                            }
+                            if (($itemid) && (ref($lti{$itemid}) eq 'HASH')) {
+                                $ltitype = 'd';
+                                if (&LONCAPA::ltiutils::check_nonce($params->{'oauth_nonce'},$params->{'oauth_timestamp'},
+                                                                        $lti{$itemid}{'lifetime'},$cdom,
+                                                                        $r->dir_config('lonLTIDir'))) {
+                                    %lti_in_use = %{$lti{$itemid}};
+                                } else {
+                                    &invalid_request($r,'Time limit exceeded for launch request credentials');
+                                    return OK;
+                                }
+                            }
+                        }
+                        if (($itemid) && ($lti_in_use{'requser'})) {
+                            my %courseinfo = &Apache::lonnet::coursedescription($cdom.'_'.$cnum);
+                            my $ltiauth;
+                            if (exists($courseinfo{'internal.ltiauth'})) {
+                                $ltiauth = $courseinfo{'internal.ltiauth'};
+                            } else {
+                                my %domdefs = &Apache::lonnet::get_domain_defaults($cdom);
+                                $ltiauth = $domdefs{'crsltiauth'};
+                            }
+                            if ($ltiauth) {
+                                my $possuname;
+                                my $mapuser = $lti_in_use{'mapuser'};
+                                if ($mapuser eq 'sourcedid') {
+                                    if ($params->{'lis_person_sourcedid'} =~ /^$match_username$/) {
+                                        $possuname = $params->{'lis_person_sourcedid'};
+                                    }
+                                } elsif ($mapuser eq 'email') {
+                                    if ($params->{'lis_person_contact_email_primary'} =~ /^$match_username$/) {
+                                        $possuname = $params->{'lis_person_contact_email_primary'};
+                                    }
+                                } elsif (exists($params->{$mapuser})) {
+                                    if ($params->{$mapuser} =~ /^$match_username$/) {
+                                        $possuname = $params->{$mapuser};
+                                    }
+                                }
+                                if ($possuname ne '') {
+                                    my $uhome = &Apache::lonnet::homeserver($possuname,$cdom);
+                                    unless ($uhome eq 'no_host') {
+                                        my $uname = $possuname;
+                                        my ($is_student,$is_nonstudent);
+                                        my %course_roles =
+                                            &Apache::lonnet::get_my_roles($uname,$cdom,,'userroles',['active'],
+                                                                          ['cc','co','in','ta','ep','ad','st','cr'],
+                                                                          [$cdom]);
+                                        foreach my $key (keys(%course_roles)) {
+                                            my ($trest,$tdomain,$trole,$sec) = split(/:/,$key);
+                                            if (($trest eq $cnum) && ($tdomain eq $cdom)) {
+                                                if ($trole eq 'st') {
+                                                    $is_student = 1;
+                                                } else {
+                                                    $is_nonstudent = 1;
+                                                    last;
+                                                }
+                                            }
+                                        }
+                                        if (($is_student) && (!$is_nonstudent)) {
+                                            unless (&Apache::lonnet::is_advanced_user($uname,$cdom)) {
+                                                foreach my $key (%{$params}) {
+                                                    delete($env{'form.'.$key});
+                                                }
+                                                &linkprot_session($r,$uname,$cnum,$cdom,$uhome,$itemid,$ltitype,$tail,$lonhost);
+                                                return OK;
+                                            }
+                                        }
+                                    }
+                                }
+                                if ($lti_in_use{'notstudent'} eq 'reject') {
+                                    &invalid_request($r,'Information for valid user missing from launch request');
+                                    return OK;
+                                }
+                            }
+                        }
+                        if ($itemid) {
+                            foreach my $key (%{$params}) {
+                                delete($env{'form.'.$key});
+                            }
+                            my $ltoken = &Apache::lonnet::tmpput({'linkprot' => $itemid.$ltitype.':'.$tail},
+                                                                 $lonhost,'link');
+                            if ($ltoken) {
+                                $r->internal_redirect($tail.'?ltoken='.$ltoken);
+                                $r->set_handlers('PerlHandler'=> undef);
+                            } else {
+                                &invalid_request($r,'Failed to store information from launch request');
+                            }
+                        } else {
+                            &invalid_request($r,'Launch request could not be validated');
+                        }
+                    } else {
+                        &invalid_request($r,'Launch unavailable on this LON-CAPA server');
+                    }
+                } else {
+                    &invalid_request($r,'Launch unavailable for this domain');
+                }
+            } else {
+                &invalid_request($r,'Invalid launch URL');
+            }
+        } else {
+            &invalid_request($r,'Invalid launch URL');
+        }
+        return OK;
+    }
+
+    my ($udom,$uname,$uhome,$symb,$mapurl);
 
 #
 # For user who launched LTI in Consumer, determine user's domain in 
@@ -198,7 +363,7 @@ sub handler {
         if ($tail =~ m{^/uploaded/($match_domain)/($match_courseid)/(?:default|supplemental)(?:|_\d+)\.(?:sequence|page)(|___\d+___.+)$}) {
             ($urlcdom,$urlcnum,my $rest) = ($1,$2,$3);
             if (($cdom ne '') && ($cdom ne $urlcdom)) {
-                &invalid_request($r,3);
+                &invalid_request($r,'Incorrect domain in requested URL');
                 return OK;
             }
             if ($rest eq '') {
@@ -217,30 +382,15 @@ sub handler {
         } elsif ($tail =~ m{^/($match_domain)/($match_courseid)$}) {
             ($urlcdom,$urlcnum) = ($1,$2);
             if (($cdom ne '') && ($cdom ne $urlcdom)) {
-                &invalid_request($r,4);
+                &invalid_request($r,'Incorrect domain in requested URL');
                 return OK;
             }
         } elsif ($tail =~ m{^/tiny/($match_domain)/(\w+)$}) {
-            ($urlcdom,my $key) = ($1,$2);
-            if (($cdom ne '') && ($cdom ne $urlcdom)) {
-                &invalid_request($r,5);
+            ($urlcdom,$urlcnum) = &course_from_tinyurl($tail);
+            if (($urlcdom eq '') || ($urlcnum eq '')) {
+                &invalid_request($r,'Invalid URL shortcut');
                 return OK;
             }
-            my $tinyurl;
-            my ($result,$cached)=&Apache::lonnet::is_cached_new('tiny',$urlcdom."\0".$key);
-            if (defined($cached)) {
-                $tinyurl = $result;
-            } else {
-                my $configuname = &Apache::lonnet::get_domainconfiguser($urlcdom);
-                my %currtiny = &Apache::lonnet::get('tiny',[$key],$urlcdom,$configuname);
-                if ($currtiny{$key} ne '') {
-                    $tinyurl = $currtiny{$key};
-                    &Apache::lonnet::do_cache_new('tiny',$urlcdom."\0".$key,$currtiny{$key},600);
-                }
-            }
-            if ($tinyurl ne '') {
-                $urlcnum = (split(/\&/,$tinyurl))[0];
-            }
         }
         if (($cdom eq '') && ($urlcdom ne '')) { 
             my $cprimary_id = &Apache::lonnet::domain($urlcdom,'primary');
@@ -263,59 +413,19 @@ sub handler {
     }
 
 #
-# Retrieve information for LTI Consumers in course domain
-# and populate hash --  %lti_by_key -- for which keys
-# are those defined in domain configuration for LTI.
-#
- 
-    my %lti = &Apache::lonnet::get_domain_lti($cdom,'provider');
-    unless (keys(%lti) > 0) {
-        &invalid_request($r,6);
-        return OK;
-    }
-    my %lti_by_key;
-    if (keys(%lti)) {
-        foreach my $id (keys(%lti)) {
-            if (ref($lti{$id}) eq 'HASH') {
-                my $key = $lti{$id}{'key'};
-                push(@{$lti_by_key{$key}},$id);
-            }
-        }
-    }
-
+# Retrieve information for LTI Consumers in course's domain
+# defined in domain configuration for LTI.
 #
 # Verify the signed request using the secret for those
-# Consumers for which the key in the POSTed data matches 
-# keys in the domain configuration for LTI.
+# Consumers for which the key in the POSTed data matches
+# keys in the course configuration or the domain configuration
+# for LTI.
 #
-    my $hostname = $r->hostname;
-    my $protocol = 'http';
-    if ($ENV{'SERVER_PORT'} == 443) {
-        $protocol = 'https';
-    }
 
-    if (exists($params->{'oauth_callback'})) {
-        $Net::OAuth::PROTOCOL_VERSION = Net::OAuth::PROTOCOL_VERSION_1_0A;
-    } else {
-        $Net::OAuth::PROTOCOL_VERSION = Net::OAuth::PROTOCOL_VERSION_1_0;
-    }
-
-    my ($itemid,$consumer_key,$secret);
-    $consumer_key = $params->{'oauth_consumer_key'};
-    if (ref($lti_by_key{$consumer_key}) eq 'ARRAY') {
-        foreach my $id (@{$lti_by_key{$consumer_key}}) {
-            if (ref($lti{$id}) eq 'HASH') {
-                $secret = $lti{$id}{'secret'};
-                my $request = Net::OAuth->request('request token')->from_hash($params,
-                                                   request_url => $protocol.'://'.$hostname.$requri,
-                                                   request_method => $env{'request.method'},
-                                                   consumer_secret => $secret,);
-                if ($request->verify()) {
-                    $itemid = $id;
-                    last;
-                }
-            }
-        }
+    my %lti;
+    my $itemid = &get_lti_itemid($requri,$hostname,$params,$cdom);
+    if ($itemid) {
+        %lti = &Apache::lonnet::get_domain_lti($cdom,'provider');
     }
 
 #
@@ -324,7 +434,7 @@ sub handler {
 # configuration in LON-CAPA for that LTI Consumer.
 #
     unless (($itemid) && (ref($lti{$itemid}) eq 'HASH')) {
-        &invalid_request($r,7);
+        &invalid_request($r,'Launch request could not be validated');
         return OK;
     }
 
@@ -334,7 +444,7 @@ sub handler {
 #
     unless (&LONCAPA::ltiutils::check_nonce($params->{'oauth_nonce'},$params->{'oauth_timestamp'},
                                             $lti{$itemid}{'lifetime'},$cdom,$r->dir_config('lonLTIDir'))) {
-        &invalid_request($r,8);
+        &invalid_request($r,'Time limit exceeded for launch request credentials');
         return OK;
     }
 
@@ -345,19 +455,20 @@ sub handler {
 
     if (!$lti{$itemid}{'requser'}) {
         if ($tail =~ m{^/tiny/($match_domain)/(\w+)$}) {
+            my $ltitype = 'd';
             foreach my $key (%{$params}) {
                 delete($env{'form.'.$key});
             }
-            my $ltoken = &Apache::lonnet::tmpput({'linkprot' => $itemid.':'.$tail},
+            my $ltoken = &Apache::lonnet::tmpput({'linkprot' => $itemid.$ltitype.':'.$tail},
                                                    $lonhost);
             if ($ltoken) {
                 $r->internal_redirect($tail.'?ltoken='.$ltoken);
                 $r->set_handlers('PerlHandler'=> undef);
             } else {
-                &invalid_request($r,9);    
+                &invalid_request($r,'Failed to store information from launch request');
             }
         } else {
-            &invalid_request($r,10);
+            &invalid_request($r,'Launch URL invalid for matched launch credentials');
         }
         return OK;
     }
@@ -415,13 +526,14 @@ sub handler {
     if ($sourcecrs ne '') {
         %consumers = &Apache::lonnet::get_dom('lticonsumers',[$sourcecrs],$cdom);
         if (exists($consumers{$sourcecrs})) {
-            if ($consumers{$sourcecrs} =~ /^$match_courseid$/) {
-                my $crshome = &Apache::lonnet::homeserver($consumers{$sourcecrs},$cdom);
+            if ($consumers{$sourcecrs} =~ /^\Q$itemid:\E($match_courseid)$/) {
+                my $storedcnum = $1;
+                my $crshome = &Apache::lonnet::homeserver($storedcnum,$cdom);
                 if ($crshome =~ /(con_lost|no_host|no_such_host)/) {
-                    &invalid_request($r,11);
+                    &invalid_request($r,'Invalid courseID included in launch data');
                     return OK;
                 } else {
-                    $posscnum = $consumers{$sourcecrs};
+                    $posscnum = $storedcnum;
                 }
             }
         }
@@ -430,7 +542,7 @@ sub handler {
     if ($urlcnum ne '') {
         if ($posscnum ne '') {
             if ($posscnum ne $urlcnum) {
-                &invalid_request($r,12);
+                &invalid_request($r,'Course ID included in launch data incompatible with URL');
                 return OK;
             } else {
                 $cnum = $posscnum;
@@ -438,7 +550,7 @@ sub handler {
         } else {
             my $crshome = &Apache::lonnet::homeserver($urlcnum,$cdom);
             if ($crshome =~ /(con_lost|no_host|no_such_host)/) {
-                &invalid_request($r,13);
+                &invalid_request($r,'Valid course ID could not be extracted from requested URL');
                 return OK;
             } else {
                 $cnum = $urlcnum;
@@ -503,7 +615,7 @@ sub handler {
                                                     $domdesc,\%data,\%alerts,\%rulematch,
                                                     \%inst_results,\%curr_rules,%got_rules);
                 if ($result eq 'notallowed') {
-                    &invalid_request($r,14);
+                    &invalid_request($r,'Account creation not permitted for this user');
                 } elsif ($result eq 'ok') {
                     if (($ltiroles[0] eq 'Instructor') && ($lcroles[0] eq 'cc') && ($lti{$itemid}{'mapcrs'}) &&
                         ($lti{$itemid}{'makecrs'})) {
@@ -512,16 +624,16 @@ sub handler {
                         }
                     }
                 } else {
-                    &invalid_request($r,15);
+                    &invalid_request($r,'An error occurred during account creation');
                     return OK;
                 }
             } else {
-                &invalid_request($r,16);
+                &invalid_request($r,'Account creation not permitted');
                 return OK;
             }
         }
     } else {
-        &invalid_request($r,17);
+        &invalid_request($r,'Could not determine username and/or domain for user');
         return OK;
     }
 
@@ -533,20 +645,26 @@ sub handler {
 
     my $reqcrs;
     if ($cnum eq '') {
-        if ((@ltiroles) && ($lti{$itemid}{'mapcrs'}) &&
-            ($ltiroles[0] eq 'Instructor') && ($lcroles[0] eq 'cc') && ($lti{$itemid}{'makecrs'})) {
-            my (%can_request,%request_domains);
-            &Apache::lonnet::check_can_request($cdom,\%can_request,\%request_domains,$uname,$udom);
-            if ($can_request{'lti'}) {
-                $reqcrs = 1;
-                &lti_session($r,$itemid,$uname,$udom,$uhome,$lonhost,undef,$mapurl,$tail,
-                             $symb,$cdom,$cnum,$params,\@ltiroles,$lti{$itemid},\@lcroles,
-                             $reqcrs,$sourcecrs);
+        if ($lti{$itemid}{'crsinc'}) {
+            if ((@ltiroles) && ($lti{$itemid}{'mapcrs'}) &&
+                ($ltiroles[0] eq 'Instructor') && ($lcroles[0] eq 'cc') && ($lti{$itemid}{'makecrs'})) {
+                my (%can_request,%request_domains);
+                &Apache::lonnet::check_can_request($cdom,\%can_request,\%request_domains,$uname,$udom);
+                if ($can_request{'lti'}) {
+                    $reqcrs = 1;
+                    &lti_session($r,$itemid,$uname,$udom,$uhome,$lonhost,undef,$mapurl,$tail,
+                                 $symb,$cdom,$cnum,$params,\@ltiroles,$lti{$itemid},\@lcroles,
+                                 $reqcrs,$sourcecrs);
+                } else {
+                    &invalid_request($r,'No LON-CAPA course available, and creation is not permitted for this user');
+                }
             } else {
-                &invalid_request($r,18);
+                &invalid_request($r,'No LON-CAPA course available, and creation is not permitted');
             }
         } else {
-            &invalid_request($r,19);
+            &lti_session($r,$itemid,$uname,$udom,$uhome,$lonhost,undef,$mapurl,$tail,
+                         $symb,$cdom,$cnum,$params,\@ltiroles,$lti{$itemid},\@lcroles,
+                         $reqcrs,$sourcecrs);
         }
         return OK;
     }
@@ -554,7 +672,7 @@ sub handler {
 #
 # If LON-CAPA course is a Community, and LON-CAPA role
 # indicated is cc, change role indicated to co.
-# 
+#
 
     my %crsenv;
     if ($lcroles[0] eq 'cc') {
@@ -632,7 +750,7 @@ sub handler {
             }
         }
         if ($reqrole eq '') {
-            &invalid_request($r,20);
+            &invalid_request($r,'No matching role available in LON-CAPA course, and not permitted to self-enroll');
             return OK;
         } else {
             unless (%crsenv) {
@@ -642,10 +760,10 @@ sub handler {
             my $default_enrollment_end_date   = $crsenv{'default_enrollment_end_date'};
             my $now = time;
             if ($default_enrollment_end_date && $default_enrollment_end_date <= $now) {
-                &invalid_request($r,21);
+                &invalid_request($r,'No active role available in LON-CAPA course, and past end date for self-enrollment');
                 return OK;
             } elsif ($default_enrollment_start_date && $default_enrollment_start_date >$now) {
-                &invalid_request($r,22);
+                &invalid_request($r,'No active role available in LON-CAPA course, and brefor start date for self-enrollment');
                 return OK;
             } else {
                 $selfenrollrole = $reqrole.'./'.$cdom.'/'.$cnum;
@@ -659,11 +777,41 @@ sub handler {
     }
 
 #
-# Store consumer-to-LON-CAPA course mapping
+# Retrieve course type of LON-CAPA course to check if mapping from a Consumer
+# course identifier permitted for this type of course (one of: official,
+# unofficial, community, textbook, placement or lti.
+#
+
+    unless (%crsenv) {
+        %crsenv = &Apache::lonnet::coursedescription($cdom.'_'.$cnum);
+    }
+    my $crstype = lc($crsenv{'type'});
+    if ($crstype eq '') {
+        $crstype = 'course';
+    }
+    if ($crstype eq 'course') {
+        if ($crsenv{'internal.coursecode'}) {
+            $crstype = 'official';
+        } elsif ($crsenv{'internal.textbook'}) {
+            $crstype = 'textbook';
+        } elsif ($crsenv{'internal.lti'}) {
+            $crstype = 'lti';
+        } else {
+            $crstype = 'unofficial';
+        }
+    }
+
+#
+# Store consumer-to-LON-CAPA course mapping if permitted
 #
 
-    if (($sourcecrs ne '')  && ($consumers{$sourcecrs} eq '') && ($cnum ne '')) {
-        &Apache::lonnet::put_dom('lticonsumers',{ $sourcecrs => $cnum },$cdom);
+    if (($lti{$itemid}{'storecrs'}) && ($sourcecrs ne '') && 
+        ($consumers{$sourcecrs} eq '') && ($cnum ne '')) {
+        if (ref($lti{$itemid}{'mapcrstype'}) eq 'ARRAY') {
+            if (grep(/^$crstype$/,@{$lti{$itemid}{'mapcrstype'}})) {
+                &Apache::lonnet::put_dom('lticonsumers',{ $sourcecrs => $itemid.':'.$cnum },$cdom);
+            }
+        }
     }
 
 #
@@ -676,6 +824,22 @@ sub handler {
     return OK;
 }
 
+sub get_lti_itemid {
+    my ($requri,$hostname,$params,$cdom,$cnum,$context) = @_;
+    return unless (ref($params) eq 'HASH');
+    my $protocol = 'http';
+    if ($ENV{'SERVER_PORT'} == 443) {
+        $protocol = 'https';
+    }
+    my $url = $protocol.'://'.$hostname.$requri;
+    my $method = $env{'request.method'};
+    if ($cnum ne '') {
+        return &Apache::lonnet::courselti_itemid($cnum,$cdom,$url,$method,$params,$context);
+    } else {
+        return &Apache::lonnet::domainlti_itemid($cdom,$url,$method,$params,$context);
+    }
+}
+
 sub lti_enroll {
     my ($uname,$udom,$selfenrollrole) = @_;
     my $enrollresult;
@@ -731,24 +895,7 @@ sub lti_session {
     } else {
         &Apache::lonnet::logthis(" LTI authorized user ($itemid): $uname:$udom, course dom: $cdom");
     }
-    my ($is_balancer,$otherserver,$hosthere);
-    ($is_balancer,$otherserver) =
-        &Apache::lonnet::check_loadbalancing($uname,$udom,'login');
-    if ($is_balancer) {
-        if ($otherserver eq '') {
-            my $lowest_load;
-            ($otherserver,undef,undef,undef,$lowest_load) = &Apache::lonnet::choose_server($udom);
-            if ($lowest_load > 100) {
-                $otherserver = &Apache::lonnet::spareserver($lowest_load,$lowest_load,1,$udom);
-            }
-        }
-        if ($otherserver ne '') {
-            my @hosts = &Apache::lonnet::current_machine_ids();
-            if (grep(/^\Q$otherserver\E$/,@hosts)) {
-                $hosthere = $otherserver;
-            }
-        }
-    }
+    my ($is_balancer,$otherserver,$hosthere) = &check_balancer($r,$uname,$udom);
     my $protocol = 'http';
     if ($ENV{'SERVER_PORT'} == 443) {
         $protocol = 'https';
@@ -779,7 +926,9 @@ sub lti_session {
                 $env{'request.lti.uri'} = $tail;
             } else {
                 unless ($tail eq '/adm/roles') {
-                    $env{'form.origurl'} = '/adm/navmaps';
+                    if ($cnum) {
+                        $env{'form.origurl'} = '/adm/navmaps';
+                    }
                 }
             }
         }
@@ -815,7 +964,7 @@ sub lti_session {
         if ($params->{'launch_presentation_document_target'}) {
             $env{'request.lti.target'} = $params->{'launch_presentation_document_target'};
         }
-        foreach my $key (%{$params}) {
+        foreach my $key (keys(%{$params})) {
             delete($env{'form.'.$key});
         }
         my $redirecturl = '/adm/switchserver';
@@ -825,9 +974,8 @@ sub lti_session {
         $r->internal_redirect($redirecturl);
         $r->set_handlers('PerlHandler'=> undef);
     } else {
-        # need to login them in, so generate the need data that
-        # migrate expects to do login
-        foreach my $key (%{$params}) {
+        # need to login them in, so generate the data migrate expects to do login
+        foreach my $key (keys(%{$params})) {
             delete($env{'form.'.$key});
         }
         if (($ltihash->{'callback'}) && ($params->{$ltihash->{'callback'}})) {
@@ -887,7 +1035,9 @@ sub lti_session {
                 $info{'origurl'} = $tail;
             } else {
                 unless ($tail eq '/adm/roles') {
-                    $info{'origurl'} = '/adm/navmaps';
+                    if ($cnum) {
+                        $info{'origurl'} = '/adm/navmaps';
+                    }
                 }
             }
         }
@@ -902,8 +1052,72 @@ sub lti_session {
     return;
 }
 
+sub linkprot_session {
+    my ($r,$uname,$cnum,$cdom,$uhome,$itemid,$ltitype,$dest,$lonhost) = @_;
+    $r->user($uname);
+    if ($ltitype eq 'c') {
+        &Apache::lonnet::logthis("Course Link Protector ($itemid) authorized student: $uname:$cdom, course: $cdom\_$cnum");
+    } elsif ($ltitype eq 'd') {
+        &Apache::lonnet::logthis("Domain LTI for link protection ($itemid) authorized student: $uname:$cdom, course: $cdom\_$cnum");
+    }
+    my ($is_balancer,$otherserver,$hosthere) = &check_balancer($r,$uname,$cdom);
+    if (($is_balancer) && (!$hosthere)) {
+        # login but immediately go to switch server
+        &Apache::lonauth::success($r,$uname,$cdom,$uhome,'noredirect');
+        $env{'form.origurl'} = $dest;
+        $env{'request.linkprot'} = $itemid.$ltitype.':'.$dest;
+        $env{'request.deeplink.login'} = $dest;
+        my $redirecturl = '/adm/switchserver';
+        if ($otherserver ne '') {
+            $redirecturl .= '?otherserver='.$otherserver;
+        }
+        $r->internal_redirect($redirecturl);
+        $r->set_handlers('PerlHandler'=> undef);
+    } else {
+        # need to login them in, so generate the data migrate expects to do login
+        my $ip = $r->get_remote_host();
+        my %info=('ip'             => $ip,
+                  'domain'         => $cdom,
+                  'username'       => $uname,
+                  'server'         => $lonhost,
+                  'linkprot'       => $itemid.$ltitype.':'.$dest,
+                  'home'           => $uhome,
+                  'origurl'        => $dest,
+                  'deeplink.login' => $dest,
+                 );
+        my $token = &Apache::lonnet::tmpput(\%info,$lonhost);
+        $env{'form.token'} = $token;
+        $r->internal_redirect('/adm/migrateuser');
+        $r->set_handlers('PerlHandler'=> undef);
+    }
+    return;
+}
+
+sub check_balancer {
+    my ($r,$uname,$udom) = @_;
+    my ($is_balancer,$otherserver,$hosthere);
+    ($is_balancer,$otherserver) =
+        &Apache::lonnet::check_loadbalancing($uname,$udom,'login');
+    if ($is_balancer) {
+        if ($otherserver eq '') {
+            my $lowest_load;
+            ($otherserver,undef,undef,undef,$lowest_load) = &Apache::lonnet::choose_server($udom);
+            if ($lowest_load > 100) {
+                $otherserver = &Apache::lonnet::spareserver($r,$lowest_load,$lowest_load,1,$udom);
+            }
+        }
+        if ($otherserver ne '') {
+            my @hosts = &Apache::lonnet::current_machine_ids();
+            if (grep(/^\Q$otherserver\E$/,@hosts)) {
+                $hosthere = $otherserver;
+            }
+        }
+    }
+    return ($is_balancer,$otherserver,$hosthere);
+}
+
 sub invalid_request {
-    my ($r,$num) = @_;
+    my ($r,$msg) = @_;
     &Apache::loncommon::content_type($r,'text/html');
     $r->send_http_header;
     if ($r->header_only) {
@@ -912,9 +1126,38 @@ sub invalid_request {
     &Apache::lonlocal::get_language_handle($r);
     $r->print(
         &Apache::loncommon::start_page('Invalid LTI call','',{ 'only_body' => 1,}).
-        &mt('Invalid LTI call [_1]',$num).
+        '<h3>'.&mt('Invalid LTI launch request').'</h3>'.
+        '<p class="LC_warning">'.
+        &mt('Launch of LON-CAPA is unavailable from the "external tool" link you had followed in another web application.').
+        ' '.&mt('Launch failed for the following reason:').
+        '</p>'.
+        '<p class="LC_error">'.$msg.'</p>'.
         &Apache::loncommon::end_page());
     return;
 }
 
+sub course_from_tinyurl {
+    my ($tail) = @_;
+    my ($urlcdom,$urlcnum);
+    if ($tail =~ m{^/tiny/($match_domain)/(\w+)$}) {
+        ($urlcdom,my $key) = ($1,$2);
+        my $tinyurl;
+        my ($result,$cached)=&Apache::lonnet::is_cached_new('tiny',$urlcdom."\0".$key);
+        if (defined($cached)) {
+            $tinyurl = $result;
+        } else {
+            my $configuname = &Apache::lonnet::get_domainconfiguser($urlcdom);
+            my %currtiny = &Apache::lonnet::get('tiny',[$key],$urlcdom,$configuname);
+            if ($currtiny{$key} ne '') {
+                $tinyurl = $currtiny{$key};
+                &Apache::lonnet::do_cache_new('tiny',$urlcdom."\0".$key,$currtiny{$key},600);
+            }
+        }
+        if ($tinyurl ne '') {
+            $urlcnum = (split(/\&/,$tinyurl))[0];
+        }
+    }
+    return ($urlcdom,$urlcnum);
+}
+
 1;