# The LearningOnline Network
# Basic LTI Authentication Module
#
# $Id: ltiauth.pm,v 1.2 2017/12/07 15:36:25 raeburn Exp $
#
# Copyright Michigan State University Board of Trustees
#
# This file is part of the LearningOnline Network with CAPA (LON-CAPA).
#
# LON-CAPA is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# LON-CAPA is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with LON-CAPA; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#
# /home/httpd/html/adm/gpl.txt
#
# http://www.lon-capa.org/
#

package Apache::ltiauth;

use strict;
use LONCAPA qw(:DEFAULT :match);
use Apache::Constants qw(:common :http);
use Net::OAuth;
use Apache::lonlocal;
use Apache::lonnet;
use Apache::loncommon;
use Apache::lonacc;
use LONCAPA::ltiutils;

sub handler {
    my $r = shift;
    my $requri = $r->uri;
#
# Retrieve data POSTed by LTI Consumer on launch  
#
    &Apache::lonacc::get_posted_cgi($r);
    my $params = {};
    foreach my $key (sort(keys(%env))) {
        if ($key =~ /^form\.(.+)$/) {
            $params->{$1} = $env{$key};
        }
    }

    unless (keys(%{$params})) {
        &invalid_request($r,1);
        return OK;
    }

    unless ($params->{'oauth_consumer_key'} &&
            $params->{'oauth_nonce'} &&
            $params->{'oauth_timestamp'} &&
            $params->{'oauth_version'} &&
            $params->{'oauth_signature'} &&
            $params->{'oauth_signature_method'}) {
        &invalid_request($r,2);
        return OK;
    }

#
# Retrieve "internet domains" for all this institution's LON-CAPA
# nodes.
#
    my ($udom,$uname,$uhome,$cdom,$cnum,$symb,$mapurl,@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};
    }

#
# For user who launched LTI in Consumer, determine user's domain in 
# LON-CAPA.
#
# Order is:
#
# (a) from custom_userdomain item in POSTed data
# (b) from lis_person_sourcedid in POSTed data
# (c) from default "log-in" domain for node
#     (can support multidomain servers, where specific domain is 
#      first part of hostname).
#
# Note: "internet domain" for user's domain must be one of the
# "internet domain(s)" for the institution's LON-CAPA servers.
#
    if (exists($params->{'custom_userdomain'})) {
        if ($params->{'custom_userdomain'} =~ /^$match_domain$/) {
            my $uprimary_id = &Apache::lonnet::domain($params->{'custom_userdomain'},'primary');
            if ($uprimary_id ne '') {
                my $uintdom = &Apache::lonnet::internet_dom($uprimary_id);
                if (($uintdom ne '') && (grep(/^\Q$uintdom\E$/,@intdoms))) {
                    $udom = $params->{'custom_userdomain'};
                }
            }
        }
    }
    my $defdom = &Apache::lonnet::default_login_domain();
    my ($domain,$possuname,$possudom,$possmapuser);
    if ($env{'form.lis_person_sourcedid'} =~ /^($match_username)\:($match_domain)$/) {
        ($possuname,$possudom) = ($1,$2);
        if ($udom eq '') {
            my $uintdom = &Apache::lonnet::domain($possudom,'primary');
            if (($uintdom ne '') && (grep(/^\Q$uintdom\E$/,@intdoms))) {
                $udom = $possudom;
                $possmapuser = 'lis_person_sourcedid';
            } else {
                $udom = $defdom;
            }
        } elsif ($udom eq $possudom) {
            $possmapuser = 'lis_person_sourcedid';
        }
    }
    unless ($possuname) {
        if ($env{'form.lis_person_sourcedid'} =~ /^$match_username$/) {
            $possuname = $env{'form.lis_person_sourcedid'};
            $possmapuser = 'lis_person_sourcedid';
        } elsif ($env{'form.lis_person_contact_email_primary'} =~ /^$match_username$/) {
            $possuname = $env{'form.lis_person_contact_email_primary'};
            $possmapuser = 'lis_person_contact_email_primary';
        }
        unless ($udom) {
            $udom = $defdom;
        }
    }

#
# Determine course's domain in LON-CAPA
#
# Order is:
#
# (a) from custom_coursedomain item in POSTed data
# (b) from tail of requested URL (after /adm/lti) if it has format of a symb  
# (c) from tail of requested URL (after /adm/lti) if it has format of a map 
# (d) from tail of requested URL (after /adm/lti) if it has format /domain/courseID
# (e) from tail of requested URL (after /adm/lti) if it has format /tiny/domain/...
# i.e., a shortened URL (see bug #6400) -- not implemented yet.   
# (f) same as user's domain 
#
# Request invalid if custom_coursedomain is defined and is inconsistent with
# domain contained in requested URL.
#
# Note: "internet domain" for course's domain must be one of the
# internet domains for the institution's LON-CAPA servers.
#

    if (exists($params->{'custom_coursedomain'})) {
        if ($params->{'custom_coursedomain'} =~ /^$match_domain$/) {
            my $cprimary_id = &Apache::lonnet::domain($params->{'custom_coursedomain'},'primary');
            if ($cprimary_id ne '') {
                my $cintdom = &Apache::lonnet::internet_dom($cprimary_id);
                if (($cintdom ne '') && (grep(/^\Q$cintdom\E$/,@intdoms))) {
                    $cdom = $params->{'custom_coursedomain'};
                }
            }
        }
    }

    my ($tail) = ($requri =~ m{^/adm/lti(|/.*)$});
    my $urlcnum;
    if ($tail ne '') {
        my $urlcdom;
        if ($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);
                return OK;
            }
            if ($rest eq '') {
                $mapurl = $tail;
            } else {
                $symb = $tail;
                $symb =~ s{^/+}{};
            }
#FIXME Need to handle encrypted URLs 
        } elsif ($tail =~ m{^/($match_domain)/($match_courseid)$}) {
            ($urlcdom,$urlcnum) = ($1,$2);
            if (($cdom ne '') && ($cdom ne $urlcdom)) {
                &invalid_request($r,4);
                return OK;
            }
        }
        if (($cdom eq '') && ($urlcdom ne '')) { 
            my $cprimary_id = &Apache::lonnet::domain($urlcdom,'primary');
            if ($cprimary_id ne '') {
                my $cintdom = &Apache::lonnet::internet_dom($cprimary_id);
                if (($cintdom ne '') && (grep(/^\Q$cintdom\E$/,@intdoms))) {
                    $cdom = $urlcdom;
                }
            } else {
                $urlcnum = '';
            }
        }
    }
    if ($cdom eq '') {
        if ($udom ne '') {
            $cdom = $udom;
        } else {
            $cdom = $defdom;
        }
    }

#
# 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,5);
        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);
            }
        }
    }

#
# 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.
#
    my $hostname = $r->hostname;
    my $protocol = 'http';
    if ($ENV{'SERVER_PORT'} == 443) {
        $protocol = 'https';
    }

    my ($itemid,$key,$secret,@ltiroles);
    $key = $params->{'oauth_consumer_key'};
    if (ref($lti_by_key{$key}) eq 'ARRAY') {
        foreach my $id (@{$lti_by_key{$key}}) {
            if (ref($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;
                }
            }
        }
    }

#
# Request is invalid if the signed request could not be verified
# for the Consumer key and Consumer secret from the domain
# configuration in LON-CAPA for that LTI Consumer.
#
    unless (($itemid) && (ref($lti{$itemid}) eq 'HASH')) {
        &invalid_request($r,6);
        return OK;
    }

#
# Determine if nonce in POSTed data has expired.
# If unexpired, confirm it has not already been used.
#
    unless (&LONCAPA::ltiutils::check_nonce($params->{'oauth_nonce'},$params->{'oauth_timestamp'},
                                            $lti{$itemid}{'lifetime'},$cdom,$r->dir_config('lonLTIDir'))) {
        &invalid_request($r,7);
        return OK;
    }

#
# Determinine if source of username matches requirement from the 
# domain configuration for the specific LTI Consumer.
# 

    if ($lti{$itemid}{'mapuser'} eq $possmapuser) {
        $uname = $possuname;
    } elsif ($lti{$itemid}{'mapuser'} eq 'lis_person_sourcedid') {
        if ($params->{'lis_person_sourcedid'} =~ /^$match_username$/) {
            $uname = $possuname;
        }
    } elsif ($lti{$itemid}{'mapuser'} eq 'lis_person_contact_email_primary') {
        if ($params->{'lis_person_contact_email_primary'} =~ /^$match_username$/) {
            $uname = $params->{'lis_person_contact_email_primary'};
        }
    } elsif (exists($params->{$lti{$itemid}{'mapuser'}})) {
        if ($params->{$lti{$itemid}{'mapuser'}} =~ /^$match_username$/) {
            $uname = $params->{$lti{$itemid}{'mapuser'}};
        }
    }

#
# Determine the courseID of the LON-CAPA course to which the
# launch of LON-CAPA should provide access.
#
# Order is:
#
# (a) from course mapping (if the link between Consumer "course" and 
# Provider "course" has been established previously).
# (b) from tail of requested URL (after /adm/lti) if it has format of a symb
# (c) from tail of requested URL (after /adm/lti) if it has format of a map
# (d) from tail of requested URL (after /adm/lti) if it has format /domain/courseID
# (e) from tail of requested URL (after /adm/lti) if it has format /tiny/domain/...
# i.e., a shortened URL (see bug #6400) -- not implemented yet.
#
# If Consumer course included in POSTed data points as a target course which
# has a format which matches a LON-CAPA courseID, but the course does not
# exist, the request is invalid.
# 

    my ($sourcecrs,%consumers);
    if ($lti{$itemid}{'mapcrs'} eq 'course_offering_sourcedid') {
        $sourcecrs = $params->{'course_offering_sourcedid'};
    } elsif ($lti{$itemid}{'mapcrs'} eq 'context_id') {
        $sourcecrs = $params->{'context_id'};
    } elsif ($lti{$itemid}{'mapcrs'} ne '') {
        $sourcecrs = $params->{$lti{$itemid}{'mapcrs'}};
    }

    my $posscnum;
    if ($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 ($crshome =~ /(con_lost|no_host|no_such_host)/) {
                    &invalid_request($r,8);
                    return OK;
                } else {
                    $posscnum = $consumers{$sourcecrs};
                }
            }
        }
    }

    if ($urlcnum ne '') {
        if ($posscnum ne '') {
            if ($posscnum ne $urlcnum) {
                &invalid_request($r,9);
                return OK;
            } else {
                $cnum = $posscnum;
            }
        } else {
            my $crshome = &Apache::lonnet::homeserver($urlcnum,$cdom);
            if ($crshome =~ /(con_lost|no_host|no_such_host)/) {
                &invalid_request($r,10);
                return OK;
            } else {
                $cnum = $urlcnum;
            }
        }
    } elsif ($posscnum ne '') {
        $cnum = $posscnum;
    }

#
# Get LON-CAPA role to use from role-mapping of Consumer roles
# defined in domain configuration for the appropriate LTI
# Consumer.
#
# If multiple LON-CAPA roles are indicated, choose based
# on the order: cc, in, ta, ep, st
#

    my $reqrole;

    my @roleorder = ('cc','in','ta','ep','st');
    if ($params->{'roles'} =~ /,/) {
        @ltiroles = split(/\s*,\s*/,$params->{'role'});
    } else {
        my $singlerole = $params->{'roles'};
        $singlerole =~ s/^\s|\s+$//g;
        @ltiroles = ($singlerole);
    }
    if (@ltiroles) {
        if (ref($lti{$itemid}{maproles}) eq 'HASH') {
            my %possroles;
            map { $possroles{$lti{$itemid}{maproles}{$_}} = 1; } @ltiroles;
            my @possibles = keys(%possroles);
            if (@possibles == 1) {
                if (grep(/^\Q$possibles[0]\E$/,@roleorder)) {
                    $reqrole = $possibles[0];

                }
            } elsif (@possibles > 1) {
                foreach my $item (@roleorder) {
                    if ($possroles{$item}) {
                        $reqrole = $item;
                        last;
                    }
                }
            }
        }
    }

#
# If no LON-CAPA username  -- is user allowed to create one?
#

    my $selfcreate;
    if (($uname ne '') && ($udom ne '')) {
        $uhome = &Apache::lonnet::homeserver($uname,$udom);
        if ($uhome =~ /(con_lost|no_host|no_such_host)/) {
            &Apache::lonnet::logthis(" LTI authorized unknown user $uname:$udom ");
            if (ref($lti{$itemid}{'makeuser'}) eq 'ARRAY') {
                if (@{$lti{$itemid}{'makeuser'}} > 0) {
                    foreach my $ltirole (@ltiroles) {
                        if (grep(/^\Q$ltirole\E$/,@{$lti{$itemid}{'makeuser'}})) {
                            $selfcreate = 1;
                        }
                    }
                }
            }
            if ($selfcreate) {
#FIXME Do user creation here.
                return OK
            } else {
                &invalid_request($r,11);
                return OK;
            } 
        } 
    } else {
        &invalid_request($r,12);
        return OK;
    }

#
# If no LON-CAPA course available, check if domain's configuration
# for the specific LTI Consumer allows a new course to be created 
# (requires role in Consumer to be: Instructor).
#

    if ($cnum eq '') {
        if ((@ltiroles) && (grep(/^Instructor$/,@ltiroles)) &&
            ($lti{$itemid}{'mapcrs'})) {
#FIXME Create a new LON-CAPA course here.
            return OK;
        } else {
            &invalid_request($r,13);
            return OK; 
        }
    }

#
# If LON-CAPA course is a Community, and LON-CAPA role
# indicated is cc, change role indicated to co.
# 

    if ($reqrole eq 'cc') {
        if (($cdom ne '') && ($cnum ne '')) {
            my %crsenv = &Apache::lonnet::coursedescription($cnum.'_'.$cdom,{ 'one_time' => 1,});
            if ($crsenv{'type'} eq 'Community') {
                $reqrole = 'co'; 
            }
        }
    }

#
# Determine if user has required LON-CAPA role
# in the mapped LON-CAPA course.
#

    my $role;
    my %crsroles = &Apache::lonnet::get_my_roles($uname,$udom,'userroles',undef,[$reqrole],[$cdom]);
    if (exists($crsroles{$cnum.':'.$cdom.':'.$reqrole})) {
        $role = $reqrole.'./'.$cdom.'/'.$cnum;
#FIXME Need to accommodate sections
    } elsif (ref($lti{$itemid}{'selfenroll'}) eq 'ARRAY') {
        if (grep(/^\Q$reqrole\E$/,@{$lti{$itemid}{'selfenroll'}})) {
#FIXME Do self-enrollment here
            return OK;
        } else {
            &invalid_request($r,14);
        }
    }

#
# Store consumer-to-LON-CAPA course mapping
#
    if (($sourcecrs ne '')  && ($consumers{$sourcecrs} eq '') && ($cnum ne '')) {
        &Apache::lonnet::put_dom('lticonsumers',{ $sourcecrs => $cnum },$cdom);
    }

#
# Check if user should be hosted here or switched to another server.
#

    &Apache::lonnet::logthis(" LTI authorized user: $uname:$udom role: $role course: $cnum:$cdom");
    $r->user($uname);
    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 = $otherserver;
            }
        }
    }
    if (($is_balancer) && (!$hosthere)) {
        # login but immediately go to switch server.
        &Apache::lonauth::success($r,$uname,$udom,$uhome,'noredirect');
        if ($symb) {
            $env{'form.symb'} = $symb;
        }
        if ($role) {
            $env{'form.role'} = $role;
        }
        if ($lti{$itemid}{'passback'}) {
            if ($params->{'lis_result_sourcedid'}) {
                $env{'request.lti.passbackid'} = $params->{'lis_result_sourcedid'};
            }
            if ($params->{'lis_outcome_service_url'}) {
                $env{'request.lti.passbackurl'} = $params->{'lis_outcome_service_url'};
            }
        }
        if (($lti{$itemid}{'roster'}) && (grep(/^Instructor$/,@ltiroles))) {
            if ($params->{'ext_ims_lis_memberships_id'}) {
                $env{'request.lti.rosterid'} = $params->{'ext_ims_lis_memberships_id'}; 
            }
            if ($params->{'ext_ims_lis_memberships_url'}) {
                $env{'request.lti.rosterurl'} = $params->{'ext_ims_lis_memberships_url'};
            }
        }
        $env{'request.lti.login'} = 1;
        foreach my $key (%{$params}) {
            delete($env{'form.'.$key});
        }
        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 need data that
        # migrate expects to do login
        foreach my $key (%{$params}) {
            delete($env{'form.'.$key});
        }
        my $ip = $r->get_remote_host();
        my %info=('ip'        => $ip,
                  'domain'    => $udom,
                  'username'  => $uname,
                  'server'    => $lonhost,
                  'lti.login' => 1,
                 );
        if ($role) {
            $info{'role'} = $role;
        }
        if ($symb) {
            $info{'symb'} = $symb; 
        }
        if ($lti{$itemid}{'passback'}) {
            if ($params->{'lis_result_sourcedid'}) {
                $info{'lti.passbackid'} = $params->{'lis_result_sourcedid'}
            }
            if ($params->{'lis_outcome_service_url'}) {
                $info{'lti.passbackurl'} = $params->{'lis_outcome_service_url'}
            }
        }
        if (($lti{$itemid}{'roster'}) && (grep(/^Instructor$/,@ltiroles))) {
            if ($params->{'ext_ims_lis_memberships_id'}) {
                $info{'lti.rosterid'} = $params->{'ext_ims_lis_memberships_id'};
            }
            if ($params->{'ext_ims_lis_memberships_url'}) {
                $info{'lti.rosterurl'} = $params->{'ext_ims_lis_memberships_url'};
            }
        }
        unless ($info{'symb'}) {
            if ($mapurl) {
                $info{'origurl'} = $mapurl;
                if ($mapurl =~ m{/default_\d+\.sequence$}) {
                    $info{'origurl'} .=  (($mapurl =~/\?/)?'&':'?').'navmap=1';
                }
            } else {
                unless ($tail eq '/adm/roles') {
                    $info{'origurl'} = '/adm/navmaps';
                }
            }
        }
        if (($is_balancer) && ($hosthere)) {
            $info{'noloadbalance'} = $hosthere;
        }
        my $token = &Apache::lonnet::tmpput(\%info,$lonhost);
        $env{'form.token'} = $token;
        $r->internal_redirect('/adm/migrateuser');
        $r->set_handlers('PerlHandler'=> undef);
    }
    return OK;
}

sub invalid_request {
    my ($r,$num) = @_;
    &Apache::loncommon::content_type($r,'text/html');
    $r->send_http_header;
    if ($r->header_only) {
        return;
    }
    &Apache::lonlocal::get_language_handle($r);
    $r->print(
        &Apache::loncommon::start_page('Invalid LTI call').
        &mt('Invalid LTI call [_1]',$num).
        &Apache::loncommon::end_page());
    return;
}

1;