# -*- perl -*-

# This is part of CGI::Auth::Hybrid, a perl CGI authentication module.
# Copyright (C) 2012 Ian Jackson.
# 
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# 
# This program 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 Affero General Public License for more details.
# 
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

BEGIN {
    use Exporter   ();
    our ($VERSION, @ISA, @EXPORT, @EXPORT_OK, %EXPORT_TAGS);

    $VERSION     = 1.00;
    @ISA         = qw(Exporter);
    @EXPORT      = qw();
    %EXPORT_TAGS = ( );     # eg: TAG => [ qw!name1 name2! ],

    @EXPORT_OK   = qw(setup);
}
our @EXPORT_OK;

use DBI;
use CGI;

#---------- default callbacks ----------

sub has_a_param ($$) {
    my ($c,$cn) = @_;
    foreach my $pn (@{ $r->{S}{$cn} }) {
	return 1 if $r->_cm('get_param')($pn);
    }
    return 0;
}

#---------- verifier object methods ----------

sub new_verifier {
    my $class = shift;
    my $s = {
	S => {
	    assocdb_path => 'cah-assocs.db';
	    assocdb_dsn => undef,
	    assocdb_user => '',
	    assocdb_password => '',
	    assocdb_table => 'assocs',
	    random_source => '/dev/urandom',
	    associdlen => 128, # bits
	    login_timeout => 86400, # seconds
	    assoc_param_name => 'cah_associd',
	    password_param_name => 'password',
	    logout_param_names => [qw(cah_logout)],
	    loggedout_param_names => [qw(cah_loggedout)],
	    promise_check_mutate => 0,
	    get_param => sub { $_[0]->param($_[2]) },
	    get_cah_cookie => sub { $_[0]->cookie($s->{S}{cookie_name}) },
	    get_method => sub { $_[0]->request_method() },
            is_login => sub { defined $_[1]->_rp('password_param_name') },
            login_ok => sub { die },
	    is_logout => sub { $_[1]->has_a_param('logout_param_names') },
	    is_loggedout => sub { $_[1]->has_a_param('loggedout_param_names') },
	    is_page => sub { return 1 },
	},
	Dbh => undef,
    };
    my ($k,$v);
    while (($k,$v,@_) = @_) {
	die "unknown setting $k" unless exists $s->{S}{$k};
	$s->{S}{$k} = $v;
    }
    bless $s, $class;
    $s->_dbopen();
    return $s;
}

sub _dbopen ($) {
    my ($s) = @_;
    my $dbh = $s->{Dbh};
    return $dbh if $dbh; 

    $s->{S}{assocdb_dsn} ||= "dbi:SQLite:dbname=$s->{S}{assocdb_path}";

    my $u = umask 077;
    $dbh = DBI->open($s->{S}{assocdb_dsn}, $s->{S}{assocdb_user}, 
		     $s->{S}{assocdb_password}, { 
			 AutoCommit => 0, RaiseError => 1,
		     });
    die "${assocdb_dsn} $! ?" unless $dbh;
    $s->{Dbh} = $dbh;

    $dbh->do("BEGIN");

    eval {
	$dbh->do("CREATE TABLE $s->{S}{assocdb_table} (".
		 " associdh VARCHAR PRIMARY KEY,".
                 " username VARCHAR,".
		 " last INTEGER NOT NULL"
		 ")");
    };
    return $dbh;
}

#---------- request object methods ----------

sub new_request {
    my ($classbase, $cgi, @extra) = @_;
    if (!ref $classbase) {
	$classbase = $classbase->new_verifier(@extra);
    } else {
	die if @extra;
    }
    my $r = {
	S => $classbase->{S},
	Dbh => $classbase->{Dbh},
	Cgi => $cgi,
    };
    bless $r, ref $classbase;
}

sub _ch ($$@) { # calls an application hook
    my ($r,$methname, @args) = @_;
    my $methfunc = $r->{S}{$methname};
    return $methfunc->($r->{Cgi}, $r, @args);
}

sub _rp ($$@) {
    my ($r,$pnvb) = @_;
    my $pn = $r->{S}{$pnvb};
    my $p = $r->_ch('get_param',$pn)
}

# pages/param-sets are
#   n normal non-mutating page
#   r retrieval of information for JS, non-mutating
#   m mutating page
#   u update of information by JS, mutating
#   i login
#   o logout
#   O "you have just logged out" page load

# in cook and par,
#    a, aN     anything including -
#    t, tN     temporary value (in our db, no logged in user yet)
#    y, yN     value corresponds to logged-in user
#    n, nN     value not in our db
#    x, xN     t or y
#    -         no value supplied
# if N differs the case applies only when the two values differ
# (eg,   a1 y2   does not apply when the logged-in value is supplied twice)

# "stale session" means request originates from a page from a login
# session which has been revoked (eg by logout); "cleared session"
# means request originates from a browser which has a different (or
# no) cookie.

    # Case analysis, cookie mode, app promises re mutate:
    # cook parm meth form
    #                      
    #  any -   POST  nrmuoi   bug or attack, fail
    #  any -   GET    rmuoi   bug or attack, fail
    #  any any GET     muoi   bug or attack, fail
    #  any t   any   nrmu     bug or attack, fail
    #
    #  -   -   GET         O  "just logged out" page
    #  (any other)         O  bug or attack, fail
    #
    #  a1  a2  POST      o    logout
    #                           if a1 is valid, revoke it
    #                           if a2 is valid, revoke it
    #                           delete cookie
    #                           redirect to "just logged out" page
    #                             (which contains link to login form)
    #
    #  -   t   POST       i   complain about cookies being disabled
    #                           (with link to login form)
    #
    #  any n   POST       i   complain about stale login form
    #                           show new login form
    #
    #  x1  t2  POST       i   login (or switch user)
    #                           if bad
    #                             show new login form
    #                           if good
    #                             revoke x1 if it was valid and !=t2
    #                             upgrade t2 to y2 in our db (setting username)
    #                             set cookie to t2
    #                             redirect to GET of remaining params
    #
    #  t1  a2  ANY   nrmu     treat as  - a2 ANY
    #
    #  y   -   GET   n        cross-site link
    #                           show data
    #
    #  y   y   GET   nr       fine, show page or send data
    #  y   y   POST  nrmu     mutation is OK, do operation
    #
    #  y1  y2  GET   nr       request from stale page
    #                           do not revoke y2 as not RESTful
    #                           treat as   y1 n GET
    #
    #  y1  y2  POST  nrmu     request from stale page
    #                           revoke y2
    #                           treat as   y1 n POST
    #
    #  y   n   GET   n        intra-site link from stale page,
    #                           treat as cross-site link, show data
    #
    #  y   n   POST  n m      intra-site form submission from stale page
    #                           show "session interrupted"
    #                           with link to main data page
    #
    #  y   n   GET    r       intra-site request from stale page
    #                           fail
    #
    #  y   n   POST   r u     intra-site request from stale page
    #                           fail
    #
    #  -/n y2  GET   nr       intra-site link from cleared session
    #                           do not revoke y2 as not RESTful
    #                           treat as   -/n n GET
    #
    #  -/n y2  POST  nrmu     request from cleared session
    #                           revoke y2
    #                           treat as   -/n n POST
    #
    #  -/n n   GET   n        cross-site link but user not logged in
    #                           show login form with redirect to orig params
    #
    #  -/n n   GET    rmu     user not logged in
    #                           fail
    #
    #  -/n n   POST  n m      user not logged in
    #                           show login form
    #
    #  -/n n   POST   r u     user not logged in
    #                           fail

sub check_divert ($) {
    my ($r) = @_;

    my $meth = $r->_ch('get_method');
    my $cookv = $r->_ch('get_cah_cookie');
    my $parmv = $r->_rp('assoc_param_name');

    my $cookt = $r->_db_lookup($cookv);
    my $parmt = $r->_db_lookup($parmv);

    if ($r->_ch('is_logout')) {
	$r->_must_be_post();
	die unless $parmt;
	$r->_db_perhaps_revoke($cookv);
	$r->_db_perhaps_revoke($parmv);
	$r->_queue_set_cookie('');
	return 'REDIRECT-LOGGEDOUT'
    }
    if ($r->_ch('is_loggedout')) {
	die unless $meth eq 'GET';
	die unless $cookt;
	die unless $parmt;
	return ('SMALLPAGE-LOGGEDOUT', "You have been logged out.");
    }
    if ($r->_ch('is_login')) {
	$r->_must_be_post();
	return ('LOGIN-STALE',
		"This session was stale and you need to log in again.")
	    if $parmt eq 'n';
	die unless $parmt eq 't' || $parmt eq 'y';
	$r->_queue_preserve_params();
	return ('SMALLPAGE-NOCOOKIE',
		"You do not seem to have cookies enabled.  ".
		"You must enable cookies as we use them for login.")
	    if !$cookt && $parmt eq 't';
	return ('LOGIN-BAD',
		"Incorrect username/password.")
	    unless defined $username && length $username;
	$r->_db_perhaps_revoke($cookv) 
	    if defined $cookv && !(defined $parmv && $cookv eq $parmv);
	$r->_queue_set_cookie($parmv);
	my $username = $r->_ch('login_ok');
	$r->_db_record_login_ok($parmv,$username);
	return 'REDIRECT-LOGGEDIN';
    }
    if (!$r->{S}{promise_check_mutate}) {
	if ($meth ne 'POST') {
	    return 'MAINPAGEONLY';
	    # NB caller must then ignore params & path!
	    # if this is too hard they can spit out a small form
	    # with a "click to continue"
	}
    }
    if ($cookt eq 't') {
	$cookt = undef;
    }
    die if $parmt eq 't';

    if ($cookt eq 'y' && $parmt eq 'y' && $cookv ne $parmv) {
	$r->_db_perhaps_revoke($parmv) if $meth eq 'POST';
	$parmt = 'n';
    }

    if ($cookt ne 'y') {
	die unless !$cookt || $cookt eq 'n';
	die unless !$parmt || $parmt eq 'n' || $parmt eq 'y';
	if ($meth eq 'GET') {
	    $r->_queue_preserve_params();
	    return ('LOGIN-INCOMINGLINK',
		    "You need to log in again.");
	} else {
	    return ('LOGIN-FRESH',
		    "You need to log in again.");
	}
    }

    die unless $cookt eq 'y';
    die unless $parmt eq 'y';
    die unless $cookv eq $parmv;
    return '';
}

UP TO HERE

sub _check_core ($) {
    my ($r) = @_;
    my $qassoc = $r->_ch('get_param');
    my ($nassoc,$nmutate);
    if (!defined $r->{S}{cookie_name}) {
	# authentication is by hidden form parameter only
	return undef unless defined $qassoc;
	$nassoc = $qassoc;
	$nmutate = 1;
    } else {
	# authentication is by cookie
	# the cookie suffices for read-only GET requests
	# for mutating and non-GET requests we require hidden param too
	my $cassoc = $r->_ch('get_cookie');
	return undef unless defined $cassoc;
	$nassoc = $cassoc;
	if (defined $qassoc && $qassoc eq $cassoc) {
	    $nmutate = 1;
	} else {
	    return undef unless $r->{S}{promise_check_mutate};
	    return undef unless $r->_ch('get_method') eq 'GET';
	    $nmutate = 0;
	}
    }

    my $dbh = $r->{Dbh};
    my ($nusername, $nlast) =
	$dbh->selectrow_array("SELECT username, last".
			      " FROM $r->{S}{assocdb_table}".
			      " WHERE associd = ?", {}, $nassoc);
    return undef unless defined $nusername;
    my $timeout = $r->{S}{login_timeout};
    return undef unless !defined $timeout || time <= $nlast + $timeout;

    # hooray
    return ($nusername, $nassoc, $nmutate);
}

sub record_login ($$) {
    my ($r,$nusername) = @_;
    my $rsp = $r->{S}{random_source};
    my $rsf = new IO::File $rsp, '<' or die "$rsp $!";
    my $bytes = ($r->{S}{associdlen} + 7) >> 3;
    my $nassocbin;
    $!=0;
    read($rsf,$nassocbin,$bytes) == $bytes or die "$rsp $!";
    close $rsf;
    my $nassoc = unpack "H*", $nassocbin;
    my $dbh = $r->{Dbh};
    $dbh->do("INSERT INTO $r->{S}{assocdb_table}".
	     " (associd, username, last) VALUES (?,?,?)", {},
	     $nassoc, $nusername, time);
    $dbh->do("COMMIT");
    $r->{U} = $nusername;
    $r->{A} = $nassoc;
}

sub _check ($) {
    my ($r) = @_;

    return if exists $r->{Username};
    ($r->{Username}, $r->{Assoc}, $r->{Mutate}) = $r->_check();

    if (defined $r->{Assoc}) {
	$dbh->do("UPDATE $r->{S}{assocdb_table}".
		 " SET last = ?".
		 " WHERE associd = ?", {}, time, $nassoc);
	$dbh->do("COMMIT");
    }
}

sub logout ($) {
    my ($r) = @_;

    my ($nusername, $nassoc, $nmutate) = $r->_check();
    return undef unless $nmutate;
    $dbh->do("DELETE FROM $r->{S}{assocdb_table}".
	     " WHERE associd = ?", {}, $nassoc);
    $dbh->do("COMMIT");
    return $nusername;
}

sub check ($) {
    my ($r) = @_;
    $r->_check();
    return !!defined $r->{Username};
}

sub check_mutate ($) {
    my ($r) = @_;
    $r->check();
    return $r->{Mutate};
}

sub username ($) {
    my ($r) = @_;
    $r->check();
    return $r->{Username};

sub hidden_val ($) {
    my ($r) = @_;
    $r->check();
    return defined $r->{Assoc} ? $r->{Assoc} : '';
}

#---------- simple wrappers ----------

sub hidden_hargs ($) {
    my ($r) = @_;
    return (-name => $r->{S}{param_name},
	    -default => $r->hidden_val());
}

sub hidden_html ($) {
    my ($r) = @_;
    return hidden($r->hidden_hargs());
}

sub cookiea_cargs ($) {
    my ($r) = @_;
    return (-name => $r->{S}{cookie_name},
	    -value => hidden_val());
}

__END__

=head1 NAME

CGI::Auth::Hybrid - web authentication optionally using cookies

=head1 SYNOPSYS

 my $verifier = CGI::Auth::Hybrid->new_verifier(setting => value,...);
 my $authreq = $verifier->new_request($cgi_request_object);

 my $authreq = CGI::Auth::Hybrid->new_request($cgi_request_object,
                                              setting => value,...);

=head1 USAGE PATTERN FOR SIMPLE APPLICATIONS

 $authreq->check_ok() or return;

 blah blah blah
 $authreq->mutating();
 blah blah blah

=head1 USAGE PATTERN FOR FANCY APPLICATIONS

 my $divert_kind = $authreq->check_divert();
 if ($divert_kind) {
     if ($divert_kind eq 'LOGGEDOUT') {
	 print "goodbye you are now logged out" and quit
     } elsif ($divert_kind eq 'NOCOOKIES') {
	 print "you need cookies" and quit
     ... etc.
     }
 }

