# The LearningOnline Network
# User Authentication Module
#
# $Id: lonauth.pm,v 1.162 2020/12/18 15:23:03 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::lonauth;

use strict;
use LONCAPA qw(:DEFAULT :match);
use Apache::Constants qw(:common);
use CGI qw(:standard);
use Apache::loncommon();
use Apache::lonnet;
use Apache::lonmenu();
use Apache::createaccount;
use Apache::ltiauth;
use Fcntl qw(:flock);
use Apache::lonlocal;
use Apache::File();
use HTML::Entities;
use Digest::MD5;
 
# ------------------------------------------------------------ Successful login
sub success {
    my ($r, $username, $domain, $authhost, $lowerurl, $extra_env,
	$form,$skipcritical,$cid) = @_;

# ------------------------------------------------------------ Get cookie ready
    my $cookie =
	&Apache::loncommon::init_user_environment($r, $username, $domain,
						  $authhost, $form,
						  {'extra_env' => $extra_env,});

    my $public=($username eq 'public' && $domain eq 'public');

    if ($public or $lowerurl eq 'noredirect') { return $cookie; }

# -------------------------------------------------------------------- Log this

    my $ip = &Apache::lonnet::get_requestor_ip();
    &Apache::lonnet::log($domain,$username,$authhost,
                         "Login $ip");

# ------------------------------------------------- Check for critical messages

    unless ($skipcritical) {
        my @what=&Apache::lonnet::dump('critical',$domain,$username);
        if ($what[0]) {
	    if (($what[0] ne 'con_lost') && ($what[0]!~/^error\:/)) {
	        $lowerurl='/adm/email?critical=display';
            }
        }
    }

# ----------------------------------------------------------- Get cookies ready
    my ($securecookie,$defaultcookie);
    my $ssl = $r->subprocess_env('https');
    if ($ssl) {
        $securecookie="lonSID=$cookie; path=/; HttpOnly; secure";
        my $lonidsdir=$r->dir_config('lonIDsDir');
        if (($lonidsdir) && (-e "$lonidsdir/$cookie.id")) {
            my $linkname=substr(Digest::MD5::md5_hex(Digest::MD5::md5_hex(time(). {}. rand(). $$)), 0, 32).'_linked';
            if (-e "$lonidsdir/$linkname.id") {
                unlink("$lonidsdir/$linkname.id");
            }
            my $made_symlink = eval { symlink("$lonidsdir/$cookie.id",
                                              "$lonidsdir/$linkname.id"); 1 };
            if ($made_symlink) {
                $defaultcookie = "lonLinkID=$linkname; path=/; HttpOnly;";
                &Apache::lonnet::appenv({'user.linkedenv' => $linkname});
            }
        }
    } else {
        $defaultcookie = "lonID=$cookie; path=/; HttpOnly;";
    }
# -------------------------------------------------------- Menu script and info
    my $destination = $lowerurl;
    if ($env{'request.lti.login'}) {
        if (($env{'request.lti.reqcrs'}) && ($env{'request.lti.reqrole'} eq 'cc')) {
            &Apache::loncommon::content_type($r,'text/html');
            if ($securecookie) {
                $r->headers_out->add('Set-cookie' => $securecookie);
            }
            if ($defaultcookie) {
                $r->headers_out->add('Set-cookie' => $defaultcookie);
            }
            $r->send_http_header;
            if (ref($form) eq 'HASH') {
                $form->{'lti.login'} = $env{'request.lti.login'};
                $form->{'lti.reqcrs'} = $env{'request.lti.reqcrs'};
                $form->{'lti.reqrole'} = $env{'request.lti.reqrole'};
                $form->{'lti.sourcecrs'} = $env{'request.lti.sourcecrs'};
            }
            &Apache::ltiauth::lti_reqcrs($r,$domain,$form,$username,$domain);
            return;
        }
        if ($env{'request.lti.selfenrollrole'}) {
            if (&Apache::ltiauth::lti_enroll($username,$domain,
                                             $env{'request.lti.selfenrollrole'}) eq 'ok') {
                $form->{'role'} = $env{'request.lti.selfenrollrole'};
                &Apache::lonnet::delenv('request.lti.selfenrollrole');
            } else {
                &Apache::ltiauth::invalid_request($r,24);
            }
        }
    }
    if (defined($form->{role})) {
        my $envkey = 'user.role.'.$form->{role};
        my $now=time;
        my $then=$env{'user.login.time'};
        my $refresh=$env{'user.refresh.time'};
        my $update=$env{'user.update.time'};
        if (!$update) {
            $update = $then;
        }
        if (exists($env{$envkey})) {
            my ($role,$where,$trolecode,$tstart,$tend,$tremark,$tstatus);
            &Apache::lonnet::role_status($envkey,$update,$refresh,$now,\$role,\$where,
                                         \$trolecode,\$tstatus,\$tstart,\$tend);
            if ($tstatus eq 'is') {
                $destination  .= ($destination =~ /\?/) ? '&' : '?';
                my $newrole = &HTML::Entities::encode($form->{role},'"<>&');
                $destination .= 'selectrole=1&'.$newrole.'=1';
            }
        }
    }
    if (defined($form->{symb})) {
        my $destsymb = $form->{symb};
        my $encrypted;
        if ($destsymb =~ m{^/enc/}) {
            $encrypted = 1;
            if ($cid) {
                $destsymb = &Apache::lonenc::unencrypted($destsymb,$cid);
            }
        }
        $destination  .= ($destination =~ /\?/) ? '&' : '?';
        if ($destsymb =~ /___/) {
            my ($map,$resid,$desturl)=split(/___/,$destsymb);
            $desturl = &Apache::lonnet::clutter($desturl);
            if ($encrypted) {
                $desturl = &Apache::lonenc::encrypted($desturl,1,$cid);
                $destsymb = $form->{symb};
            }
            $desturl = &HTML::Entities::encode($desturl,'"<>&');
            $destsymb = &HTML::Entities::encode($destsymb,'"<>&');
            $destination .= 'destinationurl='.$desturl.
                            '&destsymb='.$destsymb;
        } elsif (!$encrypted) {
            $destsymb = &HTML::Entities::encode($destsymb,'"<>&');
            $destination .= 'destinationurl='.$destsymb;
        }
    }
    if ($destination =~ m{^/adm/roles}) {
        $destination  .= ($destination =~ /\?/) ? '&' : '?';
        $destination .= 'source=login';
    }

    my $windowname = 'loncapaclient';
    if ($env{'request.lti.login'}) {
        $windowname .= 'lti';
    }
    my $windowinfo = Apache::lonhtmlcommon::scripttag('self.name="'.$windowname.'";');
    my $brcrum = [{'href' => '',
                   'text' => 'Successful Login'},];
    my $args = {'bread_crumbs' => $brcrum,};
    unless ((defined($form->{role})) || (defined($form->{symb}))) {
        my $update=$env{'user.update.time'};
        if (!$update) {
            $update = $env{'user.login.time'};
        }
        my %roles_in_env;
        my $showcount = &Apache::lonroles::roles_from_env(\%roles_in_env,$update);
        if ($showcount == 1) {
            foreach my $rolecode (keys(%roles_in_env)) {
                my ($cid) = ($rolecode =~ m{^\Quser.role.st./\E($match_domain/$match_courseid)(?:/|$)});
                if ($cid) {
                    my %coursedescription =
                        &Apache::lonnet::coursedescription($cid,{'one_time' => '1'});
                    if ($coursedescription{'type'} eq 'Placement') {
                        $args->{'crstype'} = 'Placement';
                    }
                    last;
                }
            }
        }
    }

# ------------------------------------------------- Output for successful login

    &Apache::loncommon::content_type($r,'text/html');
    if ($securecookie) {
        $r->headers_out->add('Set-cookie' => $securecookie);
    }
    if ($defaultcookie) {
        $r->headers_out->add('Set-cookie' => $defaultcookie);
    }
    $r->send_http_header;

    my ($start_page,$js,$pagebody,$end_page);
    if ($env{'request.lti.login'}) {
        $args = {'only_body' => 1};
        if ($env{'request.lti.target'} eq '') {
            my $ltitarget = (($destination =~ /\?/) ? '&' : '?').
                            'ltitarget=iframe';
            $js = <<"ENDJS";

<script type="text/javascript">
// <![CDATA[
function setLTItarget() {
    var newloc = '$destination';
    if (parent !== window) {
        newloc += '$ltitarget';
    }
    window.location.href=newloc;
}
// ]]>
</script>

ENDJS
            $args->{'add_entries'} = {'onload' => "javascript:setLTItarget();"};
            $pagebody =  '<noscript><span class="LC_warning">'
                        .&mt('Use of LON-CAPA requires Javascript to be enabled in your web browser.')
                        .'</span></noscript>';
        } else {
            $args->{'redirect'} = [0,$destination,1];
        }
        $start_page=&Apache::loncommon::start_page('',$js,$args);
    } else {
        $args->{'redirect'} = [0,$destination];
        $start_page=&Apache::loncommon::start_page('Successful Login',
                                                   $js,$args);

        my %lt=&Apache::lonlocal::texthash(
				           'wel' => 'Welcome',
				           'pro' => 'Login problems?',
				          );
        $pagebody = "<h1>$lt{'wel'}</h1>\n".
                    &mt('Welcome to the Learning[_1]Online[_2] Network with CAPA. Please wait while your session is being set up.','<i>','</i>');
        my $loginhelp = &loginhelpdisplay($domain);
        if ($loginhelp) {
            $pagebody .= '<p><a href="'.$loginhelp.'">'.$lt{'pro'}.'</a></p>';
        }
    }
    $end_page = &Apache::loncommon::end_page();
    $r->print(<<ENDSUCCESS);
$start_page
$windowinfo
$pagebody
$end_page
ENDSUCCESS
    return;
}

# --------------------------------------------------------------- Failed login!

sub failed {
    my ($r,$message,$form) = @_;
    (undef,undef,undef,my $clientmathml,my $clientunicode) =
        &Apache::loncommon::decode_user_agent();
    my $args = {};
    if ($clientunicode && !$clientmathml) {
        $args = {'browser.unicode' => 1};
    }

    my $start_page = &Apache::loncommon::start_page('Unsuccessful Login',undef,$args);
    my $uname = &Apache::loncommon::cleanup_html($form->{'uname'});
    my $udom = &Apache::loncommon::cleanup_html($form->{'udom'});
    if (&Apache::lonnet::domain($udom,'description') eq '') {
        undef($udom);
    }
    my $retry = '/adm/login';
    if ($uname eq $form->{'uname'}) {
        $retry .= '?username='.$uname;
    }
    if ($udom) {
        $retry .= (($retry=~/\?/)?'&amp;':'?').'domain='.$udom;
    }
    if (exists($form->{role})) {
        my $role = &Apache::loncommon::cleanup_html($form->{role});
        if ($role ne '') {
            $retry .= (($retry=~/\?/)?'&amp;':'?').'role='.$role;
        }
    }
    if (exists($form->{symb})) {
        my $symb = &Apache::loncommon::cleanup_html($form->{symb});
        if ($symb ne '') {
            $retry .= (($retry=~/\?/)?'&amp;':'?').'symb='.$symb;
        }
    }
    if (exists($form->{firsturl})) {
        my $firsturl = &Apache::loncommon::cleanup_html($form->{firsturl});
        if ($firsturl ne '') {
            $retry .= (($retry=~/\?/)?'&amp;':'?').'firsturl='.$firsturl;
            if ($firsturl =~ m{^/tiny/$match_domain/\w+$}) {
                unless (exists($form->{linkprot})) {
                    if (exists($form->{linkkey})) {
                        $retry .= 'linkkey='.$form->{linkkey};
                    }
                }
            }
        }
    }
    if (exists($form->{linkprot})) {
        my $ltoken = &Apache::lonnet::tmpput({linkprot => $form->{'linkprot'}},
                                             $r->dir_config('lonHostID'));
        if ($ltoken) {
            $retry .= (($retry =~ /\?/) ? '&' : '?').'ltoken='.$ltoken;
        }
    }
    my $end_page = &Apache::loncommon::end_page();
    &Apache::loncommon::content_type($r,'text/html');
    $r->send_http_header;
    my @actions =
         (&mt('Please [_1]log in again[_2].','<a href="'.$retry.'">','</a>'));
    my $loginhelp = &loginhelpdisplay($udom);
    if ($loginhelp) {
        push(@actions, '<a href="'.$loginhelp.'">'.&mt('Login problems?').'</a>');
    }
    #FIXME: link to helpdesk might be added here

    $r->print(
       $start_page
      .'<h2>'.&mt('Sorry ...').'</h2>'
      .&Apache::lonhtmlcommon::confirm_success(&mt($message),1).'<br /><br />'
      .&Apache::lonhtmlcommon::actionbox(\@actions)
      .$end_page
    );
 }

# ------------------------------------------------------------------ Rerouting!

sub reroute {
    my ($r) = @_;
    &Apache::loncommon::content_type($r,'text/html');
    $r->send_http_header;
    my $msg='<b>'.&mt('Sorry ...').'</b><br />'
           .&mt('Please [_1]log in again[_2].');
    &Apache::loncommon::simple_error_page($r,'Rerouting',$msg,{'no_auto_mt_msg' => 1});
}

# ---------------------------------------------------------------- Main handler

sub handler {
    my $r = shift;
    my $londocroot = $r->dir_config('lonDocRoot');
# Are we re-routing?
    if (-e "$londocroot/lon-status/reroute.txt") {
	&reroute($r);
	return OK;
    }

    &Apache::lonlocal::get_language_handle($r);

# -------------------------------- Prevent users from attempting to login twice
    my $handle = &Apache::lonnet::check_for_valid_session($r);
    if ($handle ne '') {
        my $lonidsdir=$r->dir_config('lonIDsDir');
        if ($handle=~/^publicuser\_/) {
# For "public user" - remove it, we apparently really want to login
            unlink($r->dir_config('lonIDsDir')."/$handle.id");
        } else {
# Indeed, a valid token is found
            &Apache::lonnet::transfer_profile_to_env($lonidsdir,$handle);
	    &Apache::loncommon::content_type($r,'text/html');
	    $r->send_http_header;
	    my $start_page = 
	        &Apache::loncommon::start_page('Already logged in');
	    my $end_page = 
	        &Apache::loncommon::end_page();
            my $dest = '/adm/roles';
            if ($env{'form.firsturl'} ne '') {
                $dest = $env{'form.firsturl'};
                if ($env{'form.firsturl'} =~ m{^/tiny/$match_domain/\w+$}) {
                    &Apache::lonnet::appenv({'request.deeplink.login' => $env{'form.firsturl'}}); 
                }
            }
            $r->print(
               $start_page
              .'<p class="LC_warning">'.&mt('You are already logged in!').'</p>'
              .'<p>'.&mt('Please either [_1]continue the current session[_2] or [_3]log out[_4].'
                    ,'<a href="'.$dest.'">','</a>','<a href="/adm/logout">','</a>')
              .'</p>'
              .$end_page
            );
            return OK;
        }
    }

# ---------------------------------------------------- No valid token, continue


    my $buffer;
    if ($r->header_in('Content-length') > 0) {
	$r->read($buffer,$r->header_in('Content-length'),0);
    }
    my %form;
    foreach my $pair (split(/&/,$buffer)) {
       my ($name,$value) = split(/=/,$pair);
       $value =~ tr/+/ /;
       $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C",hex($1))/eg;
       $form{$name}=$value;
    }

    if ((!$form{'uname'}) || (!$form{'upass0'}) || (!$form{'udom'})) {
	&failed($r,'Username, password and domain need to be specified.',
		\%form);
        return OK;
    }

# split user logging in and "su"-user

    ($form{'uname'},$form{'suname'},$form{'sudom'})=split(/\:/,$form{'uname'});
    $form{'uname'} = &LONCAPA::clean_username($form{'uname'});
    $form{'suname'}= &LONCAPA::clean_username($form{'suname'});
    $form{'udom'}  = &LONCAPA::clean_domain($form{'udom'});
    $form{'sudom'} = &LONCAPA::clean_domain($form{'sudom'});

    my $role   = $r->dir_config('lonRole');
    my $domain = $r->dir_config('lonDefDomain');
    my $prodir = $r->dir_config('lonUsersDir');
    my $contact_name = &mt('LON-CAPA helpdesk');

# ---------------------------------------- Get the information from login token

    my $tmpinfo=Apache::lonnet::reply('tmpget:'.$form{'logtoken'},
                                      $form{'serverid'});

    if (($tmpinfo=~/^error/) || ($tmpinfo eq 'con_lost') || 
        ($tmpinfo eq 'no_such_host')) {
	&failed($r,'Information needed to verify your login information is missing, inaccessible or expired.',\%form);
        return OK;
    } else {
	my $reply = &Apache::lonnet::reply('tmpdel:'.$form{'logtoken'},
					   $form{'serverid'});
        if ( $reply ne 'ok' ) {
            &failed($r,'Session could not be opened.',\%form);
	    &Apache::lonnet::logthis("ERROR got a reply of $reply when trying to contact ". $form{'serverid'}." to get login token");
	    return OK;
	}
    }

    if (!&Apache::lonnet::domain($form{'udom'})) {
        &failed($r,'The domain you provided is not a valid LON-CAPA domain.',\%form);
        return OK;
    }

    my ($key,$firsturl,$rolestr,$symbstr,$iptokenstr,$linkstr)=split(/&/,$tmpinfo);
    if ($rolestr) {
        $rolestr = &unescape($rolestr);
    }
    if ($symbstr) {
        $symbstr= &unescape($symbstr);
    }
    if ($iptokenstr) {
        $iptokenstr = &unescape($iptokenstr);
    }
    if ($linkstr) {
        $linkstr = &unescape($linkstr);
    }
    if ($firsturl =~ m{^/tiny/$match_domain/\w+$}) {
        $form{'firsturl'} = $firsturl;
    }
    if ($rolestr =~ /^role=/) {
        (undef,$form{'role'}) = split('=',$rolestr);
    }
    if ($symbstr =~ /^symb=/) { 
        (undef,$form{'symb'}) = split('=',$symbstr);
    }
    if ($iptokenstr =~ /^iptoken=/) {
        (undef,$form{'iptoken'}) = split('=',$iptokenstr);
    }
    if ($linkstr =~ /^linkprot=/) {
        (undef,$form{'linkprot'}) = split('=',$linkstr);
    } elsif ($linkstr =~ /^linkkey=/) {
        (undef,$form{'linkkey'}) = split('=',$linkstr);
    }

    my $upass = $ENV{HTTPS} ? $form{'upass0'} 
        : &Apache::loncommon::des_decrypt($key,$form{'upass0'});

# ---------------------------------------------------------------- Authenticate

    my %domconfig = &Apache::lonnet::get_dom('configuration',['usercreation'],$form{'udom'});
    my ($cancreate,$statustocreate) =
        &Apache::createaccount::get_creation_controls($form{'udom'},$domconfig{'usercreation'});
    my $defaultauth;
    if (ref($cancreate) eq 'ARRAY') {
        if (grep(/^login$/,@{$cancreate})) {
            $defaultauth = 1;
        }
    }
    my $clientcancheckhost = 1;
    my $authhost=Apache::lonnet::authenticate($form{'uname'},$upass,
                                              $form{'udom'},$defaultauth,
                                              $clientcancheckhost);

# --------------------------------------------------------------------- Failed?

    if ($authhost eq 'no_host') {
	&failed($r,'Username and/or password could not be authenticated.',
		\%form);
        return OK;
    } elsif ($authhost eq 'no_account_on_host') {
        if ($defaultauth) {
            my $domdesc = &Apache::lonnet::domain($form{'udom'},'description');
            unless (&check_can_host($r,\%form,'no_account_on_host',$domdesc)) {
                return OK;
            }
            my $start_page = 
                &Apache::loncommon::start_page('Create a user account in LON-CAPA');
            my $lonhost = $r->dir_config('lonHostID');
            my $origmail = $Apache::lonnet::perlvar{'lonSupportEMail'};
            my $contacts = 
                &Apache::loncommon::build_recipient_list(undef,'helpdeskmail',
                                                        $form{'udom'},$origmail);
            my ($contact_email) = split(',',$contacts); 
            my $output = 
                &Apache::createaccount::username_check($form{'uname'},$form{'udom'},
                                                       $domdesc,'',$lonhost,
                                                       $contact_email,$contact_name,
                                                       undef,$statustocreate);
            &Apache::loncommon::content_type($r,'text/html');
            $r->send_http_header;
            &Apache::createaccount::print_header($r,$start_page);
            $r->print('<h3>'.&mt('Account creation').'</h3>'.
                      &mt('Although your username and password were authenticated, you do not currently have a LON-CAPA account at this institution.').'<br />'.
                      $output.&Apache::loncommon::end_page());
            return OK;
        } else {
            &failed($r,'Although your username and password were authenticated, you do not currently have a LON-CAPA account in this domain, and you are not permitted to create one.',\%form);
            return OK;
        }
    }

    if (($firsturl eq '') || 
	($firsturl=~/^\/adm\/(logout|remote)/)) {
	$firsturl='/adm/roles';
    }

    my $hosthere;
    if ($form{'iptoken'}) {
        my %sessiondata = &Apache::lonnet::tmpget($form{'iptoken'});
        my $delete = &Apache::lonnet::tmpdel($form{'iptoken'});
        if (($sessiondata{'domain'} eq $form{'udom'}) &&
            ($sessiondata{'username'} eq $form{'uname'})) {
            $hosthere = 1;
        }
    }

# --------------------------------- Are we attempting to login as somebody else?
    if ($form{'suname'}) {
        my ($suname,$sudom,$sudomref);
        $suname = $form{'suname'};
        $sudom = $form{'udom'};
        if ($form{'sudom'}) {
            unless ($sudom eq $form{'sudom'}) {
                if (&Apache::lonnet::domain($form{'sudom'})) {
                    $sudomref = [$form{'sudom'}];
                    $sudom = $form{'sudom'};
                }
            }
        }
# ------------ see if the original user has enough privileges to pull this stunt
	if (&Apache::lonnet::privileged($form{'uname'},$form{'udom'},$sudomref)) {
# ---------------------------------------------------- see if the su-user exists
	    unless (&Apache::lonnet::homeserver($suname,$sudom) eq 'no_host') {
# ------------------------------ see if the su-user is not too highly privileged
		if (&Apache::lonnet::privileged($suname,$sudom)) {
                    &Apache::lonnet::logthis('Attempted switch user to privileged user');
                } else {
                    my $noprivswitch;
#
# su-user's home server and user's home server must have one of:
# (a) same domain
# (b) same primary library server for the two domains
# (c) same "internet domain" for primary library server(s) for home servers' domains
#
                    my $suprim = &Apache::lonnet::domain($sudom,'primary');
                    my $suintdom = &Apache::lonnet::internet_dom($suprim);
                    unless ($sudom eq $form{'udom'}) {
                        my $uprim = &Apache::lonnet::domain($form{'udom'},'primary');
                        my $uintdom = &Apache::lonnet::internet_dom($uprim);
                        unless ($suprim eq $uprim) {
                            unless ($suintdom eq $uintdom) {
                                &Apache::lonnet::logthis('Attempted switch user '
                                   .'to user with different "internet domain".');                        
                                $noprivswitch = 1;
                            }
                        }
                    }

                    unless ($noprivswitch) {
#
# server where log-in occurs must have same "internet domain" as su-user's home
# server
#
                        my $lonhost = $r->dir_config('lonHostID');
                        my $hostintdom = &Apache::lonnet::internet_dom($lonhost);
                        if ($hostintdom ne $suintdom) {
                            &Apache::lonnet::logthis('Attempted switch user on a '
                                .'server with a different "internet domain".'); 
                        } else {

# -------------------------------------------------------- actually switch users

		            &Apache::lonnet::logperm('User '.$form{'uname'}.' at '.
                              $form{'udom'}.' logging in as '.$suname.':'.$sudom);
		            $form{'uname'}=$suname;
                            if ($form{'udom'} ne $sudom) {
                                $form{'udom'}=$sudom;
                            }
                        }
                    }
		}
	    }
	} else {
	    &Apache::lonnet::logthis('Non-privileged user attempting switch user');
	}
    }

    my ($is_balancer,$otherserver);

    unless ($hosthere) {
        ($is_balancer,$otherserver) =
            &Apache::lonnet::check_loadbalancing($form{'uname'},$form{'udom'},'login');
        if ($is_balancer) {
            # Check if browser sent a LON-CAPA load balancer cookie (and this is a balancer)
            my ($found_server,$balancer_cookie) = &Apache::lonnet::check_for_balancer_cookie($r);
            if (($found_server) && ($balancer_cookie =~ /^\Q$env{'user.domain'}\E_\Q$env{'user.name'}\E_/)) {
                $otherserver = $found_server;
            }
            if ($otherserver eq '') {
                my $lowest_load;
                ($otherserver,undef,undef,undef,$lowest_load) = &Apache::lonnet::choose_server($form{'udom'});
                if ($lowest_load > 100) {
                    $otherserver = &Apache::lonnet::spareserver($lowest_load,$lowest_load,1,$form{'udom'});
                }
            }
            if ($otherserver ne '') {
                my @hosts = &Apache::lonnet::current_machine_ids();
                if (grep(/^\Q$otherserver\E$/,@hosts)) {
                    $hosthere = $otherserver;
                }
            }
        }
    }

    if (($is_balancer) && (!$hosthere)) {
        if ($otherserver) {
            &success($r,$form{'uname'},$form{'udom'},$authhost,'noredirect',undef,
                     \%form);
            my $switchto = '/adm/switchserver?otherserver='.$otherserver;
            if (($firsturl) && ($firsturl ne '/adm/switchserver') && ($firsturl ne '/adm/roles')) {
                $switchto .= '&origurl='.$firsturl; #should escape
            }
            if ($form{'role'}) {
                $switchto .= '&role='.$form{'role'};
            }
            if ($form{'symb'}) {
                $switchto .= '&symb='.$form{'symb'};
            }
            if ($form{'linkprot'}) {
                $env{'request.linkprot'} = $form{'linkprot'};
            } elsif ($form{'firsturl'} =~ m{^/tiny/$match_domain/\w+$}) {
                if ($form{'linkkey'}) {
                    $env{'request.linkkey'} = $form{'linkkey'};
                }
                $env{'request.deeplink.login'} = $form{'firsturl'};
            }
            $r->internal_redirect($switchto);
        } else {
            &Apache::loncommon::content_type($r,'text/html');
            $r->send_http_header;
            $r->print(&noswitch());
        }
        return OK;
    } else {
        if (!&check_can_host($r,\%form,$authhost)) {
            my ($otherserver) = &Apache::lonnet::choose_server($form{'udom'});
            if ($otherserver) {
                &success($r,$form{'uname'},$form{'udom'},$authhost,'noredirect',undef,
                         \%form);
                my $switchto = '/adm/switchserver?otherserver='.$otherserver;
                if (($firsturl) && ($firsturl ne '/adm/switchserver') && ($firsturl ne '/adm/roles')) {
                    $switchto .= '&origurl='.$firsturl; #should escape
                }
                if ($form{'role'}) {
                    $switchto .= '&role='.$form{'role'};
                }
                if ($form{'symb'}) {
                    $switchto .= '&symb='.$form{'symb'};
                }
                if ($form{'linkprot'}) {
                    $env{'request.linkprot'} = $form{'linkprot'};
                } elsif ($form{'firsturl'} =~ m{^/tiny/$match_domain/\w+$}) {
                    if ($form{'linkkey'}) {
                        $env{'request.linkkey'} = $form{'linkkey'};
                    }
                    $env{'request.deeplink.login'} = $form{'firsturl'};

                }
                $r->internal_redirect($switchto);
            } else {
                &Apache::loncommon::content_type($r,'text/html');
                $r->send_http_header;
                $r->print(&noswitch());
            }
            return OK;
        }

# ------------------------------------------------------- Do the load balancing

# ---------------------------------------------------------- Determine own load
        my $loadlim = $r->dir_config('lonLoadLim');
        my $loadavg;
        {
            my $loadfile=Apache::File->new('/proc/loadavg');
            $loadavg=<$loadfile>;
        }
        $loadavg =~ s/\s.*//g;
        my $loadpercent=sprintf("%.1f",100*$loadavg/$loadlim);
        my $userloadpercent=&Apache::lonnet::userload();

# ---------------------------------------------------------- Are we overloaded?
        if ((($userloadpercent>100.0)||($loadpercent>100.0))) {
            my $unloaded=Apache::lonnet::spareserver($loadpercent,$userloadpercent,1,$form{'udom'});
            if (!$unloaded) {
                ($unloaded) = &Apache::lonnet::choose_server($form{'udom'});
            }
            if ($unloaded) {
                &success($r,$form{'uname'},$form{'udom'},$authhost,'noredirect',
                         undef,\%form);
                if ($form{'linkprot'}) {
                    $env{'request.linkprot'} = $form{'linkprot'};
                } elsif ($form{'firsturl'} =~ m{^/tiny/$match_domain/\w+$}) {
                    if ($form{'linkkey'}) {
                        $env{'request.linkkey'} = $form{'linkkey'};
                    }
                    $env{'request.deeplink.login'} = $form{'firsturl'};
                }
                $r->internal_redirect('/adm/switchserver?otherserver='.$unloaded.'&origurl='.$firsturl);
                return OK;
            }
        }
        if (($is_balancer) && ($hosthere)) {
            $form{'noloadbalance'} = $hosthere;
        }
        my $extra_env;
        if ($form{'linkprot'}) {
            my ($linkprotector,$uri) = split(/:/,$form{'linkprot'},2);
            if ($linkprotector) {
                $extra_env = {'user.linkprotector' => $linkprotector,
                              'user.linkproturi'   => $uri,};
            }
        } elsif ($form{'firsturl'} =~ m{^/tiny/$match_domain/\w+$}) {
            if ($form{'linkkey'}) {
                $extra_env = {'user.deeplinkkey' => $form{'linkkey'},
                              'user.keyedlinkuri' => $form{'firsturl'},
                              'request.deeplink.login' => $form{'firsturl'}};
            } else {
                $extra_env = {'request.deeplink.login' => $form{'firsturl'}};
            }
        }
        &success($r,$form{'uname'},$form{'udom'},$authhost,$firsturl,$extra_env,
                 \%form);
        return OK;
    }
}

sub check_can_host {
    my ($r,$form,$authhost,$domdesc) = @_;
    return unless (ref($form) eq 'HASH');
    my $canhost = 1;
    my $lonhost = $r->dir_config('lonHostID');
    my $udom = $form->{'udom'};
    my @intdoms;
    my $internet_names = &Apache::lonnet::get_internet_names($lonhost);
    if (ref($internet_names) eq 'ARRAY') {
        @intdoms = @{$internet_names};
    }
    my $uprimary_id = &Apache::lonnet::domain($udom,'primary');
    my $uint_dom = &Apache::lonnet::internet_dom($uprimary_id);
    unless ($uint_dom ne '' && grep(/^\Q$uint_dom\E$/,@intdoms)) {
        my $machine_dom = &Apache::lonnet::host_domain($lonhost);
        my $hostname = &Apache::lonnet::hostname($lonhost);
        my $serverhomeID = &Apache::lonnet::get_server_homeID($hostname);
        my $serverhomedom = &Apache::lonnet::host_domain($serverhomeID);
        my %defdomdefaults = &Apache::lonnet::get_domain_defaults($serverhomedom);
        my %udomdefaults = &Apache::lonnet::get_domain_defaults($udom);
        my $loncaparev;
        if ($authhost eq 'no_account_on_host') {
            $loncaparev = &Apache::lonnet::get_server_loncaparev($machine_dom);
        } else {
            $loncaparev = &Apache::lonnet::get_server_loncaparev($machine_dom,$lonhost);
        }
        $canhost = &Apache::lonnet::can_host_session($udom,$lonhost,$loncaparev,
                                                     $udomdefaults{'remotesessions'},
                                                     $defdomdefaults{'hostedsessions'});
    }
    unless ($canhost) {
        if ($authhost eq 'no_account_on_host') {
            my $checkloginvia = 1;
            my ($login_host,$hostname) = 
                &Apache::lonnet::choose_server($udom,$checkloginvia);
            &Apache::loncommon::content_type($r,'text/html');
            $r->send_http_header;
            if ($login_host ne '') {
                my $protocol = $Apache::lonnet::protocol{$login_host};
                $protocol = 'http' if ($protocol ne 'https');
                my $newurl = $protocol.'://'.$hostname.'/adm/createaccount';
#FIXME Should preserve where user was going and linkprot by setting ltoken at $login_host
                $r->print(&Apache::loncommon::start_page('Create a user account in LON-CAPA').
                          '<h3>'.&mt('Account creation').'</h3>'.
                          &mt('You do not currently have a LON-CAPA account at this institution.').'<br />'.
                          '<p>'.&mt('You will be able to create one by logging into a LON-CAPA server within the [_1] domain.',$domdesc).'</p>'.
                          '<p>'.&mt('[_1]Log in[_2]','<a href="'.$newurl.'">','</a>').
                          &Apache::loncommon::end_page());
            } else {
                $r->print(&Apache::loncommon::start_page('Access to LON-CAPA unavailable').
                          '<h3>'.&mt('Account creation unavailable').'</h3>'.
                          &mt('You do not currently have a LON-CAPA account at this institution.').'<br />'.
                          '<p>'.&mt('Currently a LON-CAPA server is not available within the [_1] domain for you to log-in to, to create an account.',$domdesc).'</p>'.
                          &Apache::loncommon::end_page());
            }
        } else {
            &success($r,$form->{'uname'},$udom,$authhost,'noredirect',undef,
                     $form);
            if ($form->{'linkprot'}) {
                $env{'request.linkprot'} = $form->{'linkprot'};
            } elsif ($form->{'firsturl'} =~ m{^/tiny/$match_domain/\w+$}) {
                if ($form->{'linkkey'}) {
                    $env{'request.linkkey'} = $form->{'linkkey'};
                }
                $env{'request.deeplink.login'} = $form->{'firsturl'};
            }
            my ($otherserver) = &Apache::lonnet::choose_server($udom);
            $r->internal_redirect('/adm/switchserver?otherserver='.$otherserver);
        }
    }
    return $canhost;
}

sub noswitch {
    my $result = &Apache::loncommon::start_page('Access to LON-CAPA unavailable').
                 '<h3>'.&mt('Session unavailable').'</h3>'.
                 &mt('This LON-CAPA server is unable to host your session.').'<br />'.
                 '<p>'.&mt('Currently no other LON-CAPA server is available to host your session either.').'</p>'.
                 &Apache::loncommon::end_page();
    return $result;
}

sub loginhelpdisplay {
    my ($authdomain) = @_;
    my $login_help = 1;
    my $lang = &Apache::lonlocal::current_language();
    if ($login_help) {
        my $dom = $authdomain;
        if ($dom eq '') {
            $dom = &Apache::lonnet::default_login_domain();
        }
        my %domconfhash = &Apache::loncommon::get_domainconf($dom);
        my $loginhelp_url;
        if ($lang) {
            $loginhelp_url = $domconfhash{$dom.'.login.helpurl_'.$lang};
            if ($loginhelp_url ne '') {
                return $loginhelp_url;
            }
        }
        $loginhelp_url = $domconfhash{$dom.'.login.helpurl_nolang'};
        if ($loginhelp_url ne '') {
            return $loginhelp_url;
        } else {
            return '/adm/loginproblems.html';
        }
    }
    return;
}

1;
__END__


<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>500 Internal Server Error</title>
</head><body>
<h1>Internal Server Error</h1>
<p>The server encountered an internal error or
misconfiguration and was unable to complete
your request.</p>
<p>Please contact the server administrator at 
 root@localhost to inform them of the time this error occurred,
 and the actions you performed just before this error.</p>
<p>More information about this error may be available
in the server error log.</p>
</body></html>