# The LearningOnline Network
# Redirect Single Sign On authentication to designated URL: 
# /adm/sso, by default.
#
# $Id: lonshibauth.pm,v 1.14 2021/12/12 20:49:26 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/
#

=head1 NAME

Apache::lonshibauth - Redirect Single Sign On authentication

=head1 SYNOPSIS

Invoked when an Apache config file includes:
PerlAuthenHandler Apache::lonshibauth

If server is configured as a Shibboleth SP, the main Apache 
configuration file, e.g., /etc/httpd/conf/httpd.conf
(for RHEL/CentOS/Scentific Linux/Fedora) should contain:

LoadModule mod_shib /usr/lib/shibboleth/mod_shib_22.so

or equivalent (depending on Apache version) 
before the line to include conf/loncapa_apache.conf

If some other Apache module is in use for Single Sign On
authentication e.g., mod_auth_cas or mod_sentinel,
then a separate config file should be created which
includes settings for the authentication module.
 
=head1 INTRODUCTION

Redirects a user requiring Single Sign On to a URL on the server  
which is configured to use that service. The default URL is:
/adm/sso. 

If this is to be used with a Single Sign On service other Shibboleth
then an Apache config file needs to be loaded which: 

(a) loads the corresponding Apache module, and 
(b) sets appropriate values for perl vars in 
an <IfModule mod_***></IfModule> block, and
(c) sets an appropriate value for AuthType in a
<Location /adm/sso><IfModule mod_***>
</IfModule></Location> block, which also contains

require valid-user

PerlAuthzHandler       Apache::lonshibacc

PerlAuthzHandler       Apache::lonacc 

In the case of Shibboleth no additional file is needed
because loncapa_apache.conf already contains:

<IfModule mod_shib>
    PerlAuthenHandler Apache::lonshibauth
    PerlSetVar lonOtherAuthen yes
    PerlSetVar lonOtherAuthenType Shibboleth

</IfModule>

and

<Location /adm/sso>
  Header set Cache-Control "private,no-store,no-cache,max-age=0"
  <IfModule mod_shib>
    AuthType shibboleth
    ShibUseEnvironment On
    ShibRequestSetting requireSession 1
    ShibRequestSetting redirectToSSL 443
    require valid-user
    PerlAuthzHandler       Apache::lonshibacc
    PerlAuthzHandler       Apache::lonacc
    ErrorDocument     403 /adm/login
    ErrorDocument     500 /adm/errorhandler
  </IfModule>
  <IfModule !mod_shib>
    PerlTypeHandler        Apache::lonnoshib
  </IfModule>

</Location>

If the service is not Shibboleth, then (optionally) a URL that is 
not /adm/sso can be used as the URL for the service, e.g., /adm/cas
or /adm/sentinel, by setting a lonOtherAuthenUrl perl var
in an Apache config file containing (for example):

PerlSetVar lonOtherAuthenUrl /adm/sentinel

<IfModule mod_sentinel>
    PerlAuthenHandler Apache::lonshibauth
    PerlSetVar lonOtherAuthen yes
    PerlSetVar lonOtherAuthenType Sentinel

</IfModule>

<Location /adm/sentinel>
  Header set Cache-Control "private,no-store,no-cache,max-age=0"
  <IfModule mod_sentinel>
    AuthType Sentinel
    require valid-user
    PerlAuthzHandler  Apache::lonshibacc
    PerlAuthzHandler  Apache::lonacc
    ErrorDocument     403 /adm/login
    ErrorDocument     500 /adm/errorhandler
  </IfModule>
  <IfModule !mod_sentinel>
    PerlTypeHandler        Apache::lonnoshib
  </IfModule>

</Location>

In the example above for Sentinel SSO, it would also be possible to 
use /adm/sso instead of /adm/sentinel, in which case (i) there would be 
no need to define lonOtherAuthenUrl, (ii) there would be <Location /adm/sso> 
and (iii) the <IfModule !></IfModule> block would not be needed as 
it is already present in /etc/httpd/conf/loncapa_apache.conf.

=head1 HANDLER SUBROUTINE

This routine is called by Apache and mod_perl.

=over 4

If $r->user is defined and requested URL is not /adm/sso or
other specific URL as set by a lonOtherAuthenUrl perlvar,
then redirect to /adm/sso (or to the specific URL).

Otherwise return DECLINED.

In the case of redirection a query string is appended,
which will contain either (a) the originally requested URL,
if not /adm/sso (or lonOtherAuthenUrl URL), and 
any existing query string in the original request, or
(b) if original request was for /tiny/domain/uniqueID,
or if redirect is to /adm/login to support dual SSO and
non-SSO, a query string which contains sso=tokenID, where the
token contains information for deep-linking to course/resource. 

Support is included for use of LON-CAPA's standard log-in
page -- /adm/login -- to support dual SSO and non-SSO 
authentication from that "landing" page.

To enable dual SSO and non-SSO access from /adm/login
a Domain Coordinator will use the web GUI:
Main Menu > Set domain configuration > Display
("Log-in page options" checked) 
and for any of the LON-CAPA domain's servers which
will offer dual login will check "Yes" and then set:
(a) SSO Text, Image, Alt Text, URL, Tool Tip
(b) non-SSO: Text

The value in the URL field should be /adm/sso,
or the same URL as set for the lonOtherAuthenUrl
perl var, e.g., /adm/sentinel.

=back

=head1 NOTABLE SUBROUTINES

=over 4

=item set_token()

Inputs: 2
$r - request object
$lonhost - hostID of current server

Output: 1
$querystring - query string to append to URL
when redirecting.

If any of the following items are present in the original query string:
role, symb, and linkkey, then they will be stored in the token file
on the server, for access later to support deep-linking.  If the ltoken
item is available, from successful launch from an LTI Consumer where
LON-CAPA is the LTI Provider, but not configured to accept user 
information, and the destination is a deep-link URL /tiny/domain/uniqueiD,
then the LTI number, type (c or d), and tiny URL will be saved as the
linkprot item in a token file.

=back

=cut

package Apache::lonshibauth;

use strict;
use lib '/home/httpd/lib/perl/';
use Apache::lonnet;
use Apache::loncommon;
use Apache::lonacc;
use Apache::Constants qw(:common REDIRECT);
use LONCAPA qw(:DEFAULT :match);

sub handler {
    my $r = shift;
    my $ssourl = '/adm/sso';
    if ($r->dir_config('lonOtherAuthenUrl') ne '') {
        $ssourl = $r->dir_config('lonOtherAuthenUrl');
    }
    my $target = $ssourl;
    if (&Apache::lonnet::get_saml_landing()) {
        $target = '/adm/login';
    }
    if (($r->user eq '') && ($r->uri ne $target) && ($r->uri ne $ssourl)) {
        my $lonhost = $Apache::lonnet::perlvar{'lonHostID'};
        my $hostname = &Apache::lonnet::hostname($lonhost);
        if (!$hostname) { $hostname = $r->hostname(); }
        my $protocol = $Apache::lonnet::protocol{$lonhost};
        unless ($protocol eq 'https') { $protocol = 'http'; }
        my $alias = &Apache::lonnet::use_proxy_alias($r,$lonhost);
        if (($alias ne '') &&
            (&Apache::lonnet::alias_sso($lonhost))) {
            $hostname = $alias;
        }
        my $dest = $protocol.'://'.$hostname.$target;
        if ($target eq '/adm/login') {
             my $querystring = &set_token($r,$lonhost);
             if ($querystring ne '') {
                 $dest .= '?'.$querystring;
             }
        } else {
            my $uri = $r->uri;
            if ($uri =~ m{^/tiny/$match_domain/\w+$}) {
                my $querystring = &set_token($r,$lonhost);
                if ($querystring ne '') {
                    $dest .= '?'.$querystring;
                }
            } else {
                if ($r->args ne '') {
                    $dest .= (($dest=~/\?/)?'&':'?').$r->args;
                }
                unless (($uri eq '/adm/roles') || ($uri eq '/adm/logout')) {
                    unless ($r->args =~ /origurl=/) {
                        $dest.=(($dest=~/\?/)?'&':'?').'origurl='.$uri;
                    }
                }
            }
        }
        $r->header_out(Location => $dest);
        return REDIRECT;
    } else {
        return DECLINED;
    }
}

sub set_token {
    my ($r,$lonhost) = @_;
    my ($firsturl,$querystring,$ssotoken,@names,%token);
    @names = ('role','symb','ltoken','linkkey');
    map { $token{$_} = 1; } @names;
    unless (($r->uri eq '/adm/roles') || ($r->uri eq '/adm/logout')) {
        $firsturl = $r->uri;
    }
    if ($r->args ne '') {
        &Apache::loncommon::get_unprocessed_cgi($r->args);
    }
    if ($r->uri =~ m{^/tiny/$match_domain/\w+$}) {
        if ($env{'form.ttoken'}) {
            my %info = &Apache::lonnet::tmpget($env{'form.ttoken'});
            &Apache::lonnet::tmpdel($env{'form.ttoken'});
            if ($info{'ltoken'}) {
                $env{'form.ltoken'} = $info{'ltoken'};
            } elsif ($info{'linkkey'} ne '') {
                $env{'form.linkkey'} = $info{'linkkey'};
            }
        } else {
            unless (($env{'form.ltoken'}) || ($env{'form.linkkey'})) {
                &Apache::lonacc::get_posted_cgi($r,['linkkey']);
            }
        }
    }
    my $extras;
    foreach my $name (@names) {
        if ($env{'form.'.$name} ne '') {
            if ($name eq 'ltoken') {
                my %info = &Apache::lonnet::tmpget($env{'form.ltoken'});
                &Apache::lonnet::tmpdel($env{'form.ltoken'});
                if ($info{'linkprot'}) {
                    $extras .= '&linkprot='.&escape($info{'linkprot'});
                    last;
                }
            } else {
                $extras .= '&'.$name.'='.&escape($env{'form.'.$name});
            }
        }
    }
    if (($firsturl ne '') || ($extras ne '')) {
        $extras .= ':sso';
        $ssotoken = &Apache::lonnet::reply('tmpput:'.&escape($firsturl).
                                           $extras,$lonhost);
        $querystring = 'sso='.$ssotoken;
    }
    if ($r->args ne '') {
        foreach my $key (sort(keys(%env))) {
            if ($key =~ /^form\.(.+)$/) {
                my $name = $1;
                next if (($token{$name}) || ($name eq 'ttoken'));
                $querystring .= '&'.$name.'='.$env{$key};
            }
        }
    }
    return $querystring;
}

1;
__END__