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- Include verification of common name when creating SSL tunnel unless
  connecting to/from pre-2.12 node.
- $IO::Socket::SSL::DEBUG is set to current $DEBUG value so debugging
  from IO/Socket/SSL.pm is written to lond_errors or lonc_errors.

#   This module defines and implements a class that represents
#   a connection to a lond daemon.
#
# $Id: LondConnection.pm,v 1.62 2018/12/14 02:05:38 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 LondConnection;

use strict;
use IO::Socket;
use IO::Socket::INET;
use IO::Handle;
use IO::File;
use Fcntl;
use POSIX;
use Crypt::IDEA;
use LONCAPA::lonlocal;
use LONCAPA::lonssl;


my $DebugLevel=0;
my %perlvar;
my %secureconf;
my %badcerts;
my %hosttypes;
my %crlchecked;
my $InsecureOk;

#
#  Set debugging level
#
sub SetDebug {
    $DebugLevel = shift;
}

#
#   The config read is done in this way to support the read of
#   the non-default configuration file in the
#   event we are being used outside of loncapa.
#

my $ConfigRead = 0;

#   Read the configuration file for apache to get the perl
#   variables set.

sub ReadConfig {
    Debug(8, "ReadConfig called");

    my $perlvarref = read_conf('loncapa.conf');
    %perlvar    = %{$perlvarref};
    $ConfigRead = 1;

    $InsecureOk = $perlvar{loncAllowInsecure};

    unless (lonssl::Read_Connect_Config(\%secureconf,\%perlvar) eq 'ok') {
        Debug(1,"Failed to retrieve secureconf hash.\n");
    }
    unless (lonssl::Read_Host_Types(\%hosttypes,\%perlvar) eq 'ok') {
        Debug(1,"Failed to retrieve hosttypes hash.\n");
    }
    %badcerts = ();
    %crlchecked = ();
}

sub ResetReadConfig {
    $ConfigRead = 0;
}

sub Debug {

    my ($level, $message) = @_;

    if ($level < $DebugLevel) {
	print STDERR ($message."\n");
    }
}

=pod

=head2 Dump

Dump the internal state of the object: For debugging purposes, to stderr.

=cut

sub Dump {
    my $self   = shift;
    my $level  = shift;
    my $now    = time;
    my $local  = localtime($now);
    
    if ($level >= $DebugLevel) {
	return;
    }

    
    my $key;
    my $value;
    print STDERR "[ $local ] Dumping LondConnectionObject:\n";
    print STDERR join(':',caller(1))."\n";
    while(($key, $value) = each %$self) {
	print STDERR "$key -> $value\n";
    }
    print STDERR "-------------------------------\n";
}

=pod

Local function to do a state transition.  If the state transition
callback is defined it is called with two parameters: the self and the
old state.

=cut

sub Transition {

    my ($self, $newstate) = @_;

    my $oldstate = $self->{State};
    $self->{State} = $newstate;
    $self->{TimeoutRemaining} = $self->{TimeoutValue};
    if($self->{TransitionCallback}) {
	($self->{TransitionCallback})->($self, $oldstate); 
    }
}



=pod

=head2 new

Construct a new lond connection.

Parameters (besides the class name) include:

=item hostname

host the remote lond is on. This host is a host in the hosts.tab file

=item port

 port number the remote lond is listening on.

=item lonid

 lonid of the remote lond is listening on.

=item deflonid

 default lonhostID of the remote lond is listening on.

=cut

sub new {
    my ($class, $DnsName, $Port, $lonid, $deflonid, $loncaparev) = @_;

    if (!$ConfigRead) {
	ReadConfig();
	$ConfigRead = 1;
    }
    &Debug(4,$class."::new( ".$DnsName.",".$Port.",".$lonid.",".$deflonid.",".$loncaparev.")\n");

    my ($conntype,$gotconninfo,$allowinsecure);
    if ((ref($secureconf{'connto'}) eq 'HASH') &&
        (exists($hosttypes{$lonid}))) {
        $conntype = $secureconf{'connto'}{$hosttypes{$lonid}};
        if ($conntype ne '') {
            if ($conntype ne 'req') {
                $allowinsecure = 1;
            }
            $gotconninfo = 1;
        }
    }
    unless ($gotconninfo) {
        $allowinsecure = $InsecureOk;
    }

    # The host must map to an entry in the hosts table:
    #  We connect to the dns host that corresponds to that
    #  system and use the hostname for the encryption key 
    #  negotion.  In the objec these become the Host and
    #  LoncapaHim fields of the object respectively.
    #
    # if it is me use loopback for connection
    if ($DnsName eq &main::my_hostname()) { $DnsName="127.0.0.1"; }
    Debug(9, "Connecting to $DnsName");
    # Now create the object...
    my $self     = { Host               => $DnsName,
                     LoncapaHim         => $lonid,
                     LoncapaDefid       => $deflonid,
                     LoncapaRev         => $loncaparev, 
                     Port               => $Port,
                     State              => "Initialized",
		     AuthenticationMode => "",
		     InsecureOK         => $allowinsecure,
                     TransactionRequest => "",
                     TransactionReply   => "",
                     NextRequest        => "",
                     InformReadable     => 0,
                     InformWritable     => 0,
                     TimeoutCallback    => undef,
                     TransitionCallback => undef,
                     Timeoutable        => 0,
                     TimeoutValue       => 30,
                     TimeoutRemaining   => 0,
		     LocalKeyFile       => "",
                     CipherKey          => "",
                     LondVersion        => "Unknown",
                     Cipher             => undef,
		     ClientData         => undef};
    bless($self, $class);
    unless ($self->{Socket} = IO::Socket::INET->new(PeerHost => $self->{Host},
					       PeerPort => $self->{Port},
					       Type     => SOCK_STREAM,
					       Proto    => "tcp",
					       Timeout  => 3)) {
	Debug(8, "Error? \n$@ \n$!");
	return undef;		# Inidicates the socket could not be made.
    }
    my $socket = $self->{Socket}; # For local use only.
    $socket->sockopt(SO_KEEPALIVE, 1); # Turn on keepalive probes when idle.
    #  If we are local, we'll first try local auth mode, otherwise, we'll try
    #  the ssl auth mode:

    my $key;
    my $keyfile;
    if ($DnsName eq '127.0.0.1') {
	$self->{AuthenticationMode} = "local";
	($key, $keyfile)         = lonlocal::CreateKeyFile();
	Debug(8, "Local key: $key, stored in $keyfile");
	   
	#  If I can't make the key file fall back to insecure if 
	#  allowed...else give up right away.

	if(!(defined $key) || !(defined $keyfile)) {
            my $canconnect = 0;
            if (ref($secureconf{'connto'}) eq 'HASH') {
                unless ($secureconf{'connto'}->{'dom'} eq 'req') {
                    $canconnect = 1;
                }
            } else {
                $canconnect = $InsecureOk;
            }
	    if ($canconnect) {
		$self->{AuthenticationMode} = "insecure";
		$self->{TransactionRequest} = "init\n";
	    } 
	    else {
		$socket->close;
		return undef;
	    }
	}
	$self->{TransactionRequest} = "init:local:$keyfile\n";
	Debug(9, "Init string is init:local:$keyfile");
	if(!$self->CreateCipher($key)) { # Nothing's going our way...
	    $socket->close;
	    return undef;
	}

    } else {
	#  Remote peer:  I'd like to do ssl, but if my host key or certificates
	#  are not all installed, my only choice is insecure, if that's 
	#  allowed:

	my ($ca, $cert) = lonssl::CertificateFile;
	my $sslkeyfile  = lonssl::KeyFile;
        my $badcertfile = lonssl::has_badcert_file($self->{LoncapaHim});
        my ($loncaparev) = ($perlvar{'lonVersion'} =~ /^[\'\"]?([\w.\-]+)[\'\"]?$/);

	if (($conntype ne 'no') && (defined($ca)) && (defined($cert)) && (defined($sslkeyfile)) &&
            (!exists($badcerts{$self->{LoncapaHim}})) && !$badcertfile) {
	    $self->{AuthenticationMode} = "ssl";
	    $self->{TransactionRequest} = "init:ssl:$loncaparev\n";
	} elsif ($self->{InsecureOK}) {
	    # Allowed to do insecure:
	    $self->{AuthenticationMode} = "insecure";
	    $self->{TransactionRequest} = "init::$loncaparev\n";
	} else {
	    # Not allowed to do insecure...
	    $socket->close;
	    return undef;
	}
    }

    #
    # We're connected.  Set the state, and the events we'll accept:
    #
    $self->Transition("Connected");
    $self->{InformWritable}     = 1;    # When  socket is writable we send init
    $self->{Timeoutable}        = 1;    # Timeout allowed during startup negotiation. 

    
    #
    # Set socket to nonblocking I/O.
    #
    my $flags    = fcntl($socket, F_GETFL,0);
    if(!$flags) {
	$socket->close;
	return undef;
    }
    if(!fcntl($socket, F_SETFL, $flags | O_NONBLOCK)) {
	$socket->close;
	return undef;
    }

    # return the object :

    Debug(9, "Initial object state: ");
    $self->Dump(9);

    return $self;
}

=pod

=head2 Readable

This member should be called when the Socket becomes readable.  Until
the read completes, action is state independet. Data are accepted into
the TransactionReply until a newline character is received.  At that
time actionis state dependent:

=item Connected

in this case we received challenge, the state changes to
ChallengeReceived, and we initiate a send with the challenge response.

=item ReceivingReply

In this case a reply has been received for a transaction, the state
goes to Idle and we disable write and read notification.

=item ChallengeReeived

we just got what should be an ok\n and the connection can now handle
transactions.

=cut

sub Readable {
    my $self    = shift;
    my $socket  = $self->{Socket};
    my $data    = '';
    my $rv;
    my $ConnectionMode = $self->{AuthenticationMode};

    if ($socket) {
	eval {
	    $rv = $socket->recv($data, POSIX::BUFSIZ, 0);
	}
    } else {
	$self->Transition("Disconnected");
	return -1;
    }
    my $errno   = $! + 0;	             # Force numeric context.

    unless (defined($rv) && length $data) {# Read failed,
	if(($errno == POSIX::EWOULDBLOCK)   ||
	   ($errno == POSIX::EAGAIN)        ||
	   ($errno == POSIX::EINTR)) {
	    return 0;
	}

	# Connection likely lost.
	&Debug(4, "Connection lost");
	$self->{TransactionRequest} = '';
	$socket->close();
	$self->Transition("Disconnected");
	return -1;
    }
    # If we actually got data, reset the timeout.

    if (length $data) {
	$self->{TimeoutRemaining}   = $self->{TimeoutValue}; # getting data resets the timeout period.
    }
    #  Append the data to the buffer.  And figure out if the read is done:

    &Debug(9,"Received from host: ".$data);
    $self->{TransactionReply} .= $data;
    if($self->{TransactionReply} =~ m/\n$/) {
	&Debug(8,"Readable End of line detected");
	

	if ($self->{State}  eq "Initialized") { # We received the challenge:
	    #   Our init was replied to. What happens next depends both on
	    #  the actual init we sent (AuthenticationMode member data)
	    #  and the response:
	    #     AuthenticationMode == local:
	    #       Response ok:   The key has been exchanged and
	    #                      the key file destroyed. We can jump
	    #                      into setting the host and requesting the
	    #                      Later we'll also bypass key exchange.
	    #       Response digits: 
	    #                      Old style lond. Delete the keyfile.
	    #                      If allowed fall back to insecure mode.
	    #                      else close connection and fail.
	    #       Response other:
	    #                      Failed local auth 
	    #                      Close connection and fail.
	    #
	    #    AuthenticationMode == ssl:
	    #        Response ok:ssl
	    #        Response digits:
	    #        Response other:
	    #    Authentication mode == insecure
	    #        Response digits
	    #        Response other:
	    
	    my $Response = $self->{TransactionReply};
	    if($ConnectionMode eq "local") {
		if($Response =~ /^ok:local/) { #  Good local auth.
		    $self->ToVersionRequest();
		    return 0;
		}
		elsif ($Response =~/^[0-9]+/) {	# Old style lond.
		    return $self->CompleteInsecure();

		}
		else {		                # Complete flop
		    &Debug(3, "init:local : unrecognized reply");
		    $self->Transition("Disconnected");
		    $socket->close;
		    return -1;
		}
	    }
	    elsif ($ConnectionMode eq "ssl") {
		if($Response =~ /^ok:ssl/) {     # Good ssl...
		    my $sslresult = $self->ExchangeKeysViaSSL();
                    if ($sslresult == 1) { # Success skip to vsn stuff
			# Need to reset to non blocking:

			my $flags = fcntl($socket, F_GETFL, 0);
			fcntl($socket, F_SETFL, $flags | O_NONBLOCK);
			$self->ToVersionRequest();
			return 0;
		    } 
		    else { # Failed in ssl exchange.
		        if (($sslresult == -1) && (lonssl::LastError == -1) && ($self->{InsecureOK})) {
                            my $badcertdir = &lonssl::BadCertDir();
                            if (($badcertdir) && $self->{LoncapaHim}) {
                                if (open(my $fh,'>',"$badcertdir/".$self->{LoncapaHim})) {
                                    close($fh);
                                }
                            }
			    $badcerts{$self->{LoncapaHim}} = 1;
                            &Debug(3,"SSL verification failed: close socket and initiate insecure connection");
                            $self->Transition("ReInitNoSSL");
                            $socket->close;
                            return -1;
			}
			&Debug(3,"init:ssl failed key negotiation!");
			$self->Transition("Disconnected");
			$socket->close;
			return -1;
                    }
		} 
		elsif ($Response =~ /^[0-9]+/) { # Old style lond.
		    return $self->CompleteInsecure();
		}
		else {		                 # Complete flop
		}
	    }
	    elsif ($ConnectionMode eq "insecure") {
		if($self->{TransactionReply} eq "refused\n") {	# Remote doesn't have
		    
		    $self->Transition("Disconnected"); # in host tables.
		    $socket->close();
		    return -1;

		}
		return $self->CompleteInsecure();
	    }
	    else {
		&Debug(1,"Authentication mode incorrect");
		die "BUG!!! LondConnection::Readable invalid authmode";
	    }


	}  elsif ($self->{State} eq "ChallengeReplied") {
	    if($self->{TransactionReply} ne "ok\n") {
		$self->Transition("Disconnected");
		$socket->close();
		return -1;
	    }
	    $self->ToVersionRequest();
	    return 0;

	} elsif ($self->{State} eq "ReadingVersionString") {
	    chomp($self->{TransactionReply});
	    $self->{LondVersion}       = $self->{TransactionReply};
	    $self->Transition("SetHost");
	    $self->{InformReadable}    = 0;
	    $self->{InformWritable}    = 1;
	    my $peer = $self->{LoncapaHim};
	    $self->{TransactionRequest}= "sethost:$peer\n";
	    return 0;
	} elsif ($self->{State} eq "HostSet") { # should be ok.
	    if($self->{TransactionReply} ne "ok\n") {
		$self->Transition("Disconnected");
		$socket->close();
		return -1;
	    }
	    #  If the auth mode is insecure we must still
	    #  exchange session keys. Otherwise,
	    #  we can just transition to idle.

	    if($ConnectionMode eq "insecure") {
		$self->Transition("RequestingKey");
		$self->{InformReadable}  = 0;
		$self->{InformWritable}  = 1;
		$self->{TransactionRequest} = "ekey\n";
		return 0;
	    }
	    else {
		$self->ToIdle();
		return 0;
	    }
	} elsif ($self->{State}  eq "ReceivingKey") {
	    my $buildkey = $self->{TransactionReply};
            chomp($buildkey);
	    my $key = $self->{LoncapaHim}.$perlvar{'lonHostID'};
	    $key=~tr/a-z/A-Z/;
	    $key=~tr/G-P/0-9/;
	    $key=~tr/Q-Z/0-9/;
	    $key =$key.$buildkey.$key.$buildkey.$key.$buildkey;
	    $key               = substr($key,0,32);
	    if(!$self->CreateCipher($key)) {
		$self->Transition("Disconnected");
		$socket->close();
		return -1;
	    } else {
		$self->ToIdle();
		return 0;
	    }
	} elsif ($self->{State}  eq "ReceivingReply") {

	    # If the data are encrypted, decrypt first.

	    my $answer = $self->{TransactionReply};
	    if($answer =~ /^enc\:/) {
		$answer = $self->Decrypt($answer);
		$self->{TransactionReply} = "$answer\n";
	    }
	    # if we have a NextRequest do it immeadiately
	    if ($self->{NextRequest}) {
		$self->{TransactionRequest} = $self->{NextRequest};
		undef( $self->{NextRequest} );
		$self->{TransactionReply}   = "";
		$self->{InformWritable}     = 1;
		$self->{InformReadable}     = 0;
		$self->{Timeoutable}        = 1;
		$self->Transition("SendingRequest");
		return 0;
	    } else {
	    # finish the transaction

		$self->ToIdle();
		return 0;
	    }
	} elsif ($self->{State} eq "Disconnected") { # No connection.
	    return -1;
	} else {			# Internal error: Invalid state.
	    $self->Transition("Disconnected");
	    $socket->close();
	    return -1;
	}
    }

    return 0;
    
}


=pod

This member should be called when the Socket becomes writable.

The action is state independent. An attempt is made to drain the
contents of the TransactionRequest member.  Once this is drained, we
mark the object as waiting for readability.

Returns  0 if successful, or -1 if not.

=cut
sub Writable {
    my $self     = shift;		# Get reference to the object.
    my $socket   = $self->{Socket};
    my $nwritten;
    if ($socket) {
	eval {
	    $nwritten = $socket->send($self->{TransactionRequest}, 0);
	}
    } else {
	# For whatever reason, there's no longer a socket left.


	$self->Transition("Disconnected");
	return -1;
    }
    my $errno    = $! + 0;
    unless (defined $nwritten) {
	if($errno != POSIX::EINTR) {
	    $self->Transition("Disconnected");
	    return -1;
	}
      
    }
    if (($nwritten >= 0)                        ||
        ($errno == POSIX::EWOULDBLOCK)    ||
	($errno == POSIX::EAGAIN)         ||
	($errno == POSIX::EINTR)          ||
	($errno ==  0)) {
	$self->{TimeoutRemaining} = $self->{TimeoutValue};
	substr($self->{TransactionRequest}, 0, $nwritten) = ""; # rmv written part
	if(length $self->{TransactionRequest} == 0) {
	    $self->{InformWritable} = 0;
	    $self->{InformReadable} = 1;
	    $self->{TransactionReply} = '';
	    #
	    # Figure out the next state:
	    #
	    if($self->{State} eq "Connected") {
		$self->Transition("Initialized");
	    } elsif($self->{State} eq "ChallengeReceived") {
		$self->Transition("ChallengeReplied");
	    } elsif($self->{State} eq "RequestingVersion") {
		$self->Transition("ReadingVersionString");
	    } elsif ($self->{State} eq "SetHost") {
		$self->Transition("HostSet");
	    } elsif($self->{State} eq "RequestingKey") {
		$self->Transition("ReceivingKey");
#            $self->{InformWritable} = 0;
#            $self->{InformReadable} = 1;
#            $self->{TransactionReply} = '';
	    } elsif ($self->{State} eq "SendingRequest") {
		$self->Transition("ReceivingReply");
		$self->{TimeoutRemaining} = $self->{TimeoutValue};
	    } elsif ($self->{State} eq "Disconnected") {
		return -1;
	    }
	    return 0;
	}
    } else {			# The write failed (e.g. partner disconnected).
	$self->Transition("Disconnected");
	$socket->close();
	return -1;
    }
    
}
=pod

=head2 Tick

   Tick is called every time unit by the event framework.  It

=item 1 decrements the remaining timeout.

=item 2 If the timeout is zero, calls TimedOut indicating that the current operation timed out.

=cut
    
sub Tick {
    my $self = shift;
    $self->{TimeoutRemaining}--;
    if ($self->{TimeoutRemaining} < 0) {
	$self->TimedOut();
    }
}

=pod

=head2 TimedOut

called on a timeout.  If the timeout callback is defined, it is called
with $self as its parameters.

=cut

sub TimedOut  {

    my $self = shift;
    if($self->{TimeoutCallback}) {
	my $callback = $self->{TimeoutCallback};
	my @args = ( $self);
	&$callback(@args);
    }
}

=pod

=head2 InitiateTransaction

Called to initiate a transaction.  A transaction can only be initiated
when the object is idle... otherwise an error is returned.  A
transaction consists of a request to the server that will have a
reply.  This member sets the request data in the TransactionRequest
member, makes the state SendingRequest and sets the data to allow a
timout, and to request writability notification.

=cut

sub InitiateTransaction {

    my ($self, $data) = @_;

    Debug(1, "initiating transaction: ".$data);
    if($self->{State} ne "Idle") {
	Debug(0," .. but not idle here\n");
	return -1;		# Error indicator.
    }
    # if the transaction is to be encrypted encrypt the data:
    (my $sethost, my $server,$data)=split(/:/,$data,3);

    if($data =~ /^encrypt\:/) {
	$data = $self->Encrypt($data);
    }

    # Setup the trasaction
    # currently no version of lond supports inlining the sethost
    if ($self->PeerVersion() <= 321) {
	if ($server ne $self->{LoncapaHim}) {
	    $self->{NextRequest}        = $data;
	    $self->{TransactionRequest} = "$sethost:$server\n";
	    $self->{LoncapaHim}         = $server;
	} else {
	    $self->{TransactionRequest}        = $data;
	}
    } else {
	$self->{LoncapaHim}         = $server;
	$self->{TransactionRequest} = "$sethost:$server:$data";
    }
    $self->{TransactionReply}   = "";
    $self->{InformWritable}     = 1;
    $self->{InformReadable}     = 0;
    $self->{Timeoutable}        = 1;
    $self->{TimeoutRemaining}   = $self->{TimeoutValue};
    $self->Transition("SendingRequest");
}


=pod

=head2 SetStateTransitionCallback

Sets a callback for state transitions.  Returns a reference to any
prior established callback, or undef if there was none:

=cut

sub SetStateTransitionCallback {
    my $self        = shift;
    my $oldCallback = $self->{TransitionCallback};
    $self->{TransitionCallback} = shift;
    return $oldCallback;
}

=pod

=head2 SetTimeoutCallback

Sets the timeout callback.  Returns a reference to any prior
established callback or undef if there was none.

=cut

sub SetTimeoutCallback {

    my ($self, $callback) = @_;

    my $oldCallback          = $self->{TimeoutCallback};
    $self->{TimeoutCallback} = $callback;
    return $oldCallback;
}

=pod

=head2 Shutdown:

Shuts down the socket.

=cut

sub Shutdown {
    my $self = shift;
    my $socket = $self->GetSocket();
    Debug(5,"socket is -$socket-");
    if ($socket) {
	# Ask lond to exit too.  Non blocking so
	# there is no cost for failure.
	eval {
	    $socket->send("exit\n", 0);
	    $socket->shutdown(2);
	}
    }
    $self->{Timeoutable}   = 0;	# Shutdown sockets can't timeout.
}

=pod

=head2 GetState

selector for the object state.

=cut

sub GetState {
    my $self = shift;
    return $self->{State};
}

=pod

=head2 GetSocket

selector for the object socket.

=cut

sub GetSocket {
    my $self  = shift;
    return $self->{Socket};
}


=pod

=head2 WantReadable

Return the state of the flag that indicates the object wants to be
called when readable.

=cut

sub WantReadable {
    my   $self = shift;

    return $self->{InformReadable};
}

=pod

=head2 WantWritable

Return the state of the flag that indicates the object wants write
notification.

=cut

sub WantWritable {
    my $self = shift;
    return $self->{InformWritable};
}

=pod

=head2 WantTimeout

return the state of the flag that indicates the object wants to be
informed of timeouts.

=cut

sub WantTimeout {
    my $self = shift;
    return $self->{Timeoutable};
}

=pod

=head2 GetReply

Returns the reply from the last transaction.

=cut

sub GetReply {
    my $self = shift;
    return $self->{TransactionReply};
}

=pod

=head2 Encrypt

Returns the encrypted version of the command string.

The command input string is of the form:

  encrypt:command

The output string can be directly sent to lond as it is of the form:

  enc:length:<encodedrequest>

=cut

sub Encrypt {
    
    my ($self, $request) = @_;

   
    # Split the encrypt: off the request and figure out it's length.
    # the cipher works in blocks of 8 bytes.

    my $cmd = $request;
    $cmd    =~ s/^encrypt\://;	# strip off encrypt:
    chomp($cmd);		# strip off trailing \n
    my     $length=length($cmd);	# Get the string length.
    $cmd .= "         ";	# Pad with blanks so we can fill out a block.

    # encrypt the request in 8 byte chunks to create the encrypted
    # output request.

    my $Encoded = '';
    for(my $index = 0; $index <= $length; $index += 8) {
	$Encoded .= 
	    unpack("H16", 
		   $self->{Cipher}->encrypt(substr($cmd, 
						   $index, 8)));
    }

    # Build up the answer as enc:length:$encrequest.

    $request = "enc:$length:$Encoded\n";
    return $request;
    
    
}

=pod

=head2 Decrypt

Decrypt a response from the server.  The response is in the form:

 enc:<length>:<encrypted data>

=cut

sub Decrypt {

    my ($self, $encrypted) = @_;

    #  Bust up the response into length, and encryptedstring:

    my ($enc, $length, $EncryptedString) = split(/:/,$encrypted);
    chomp($EncryptedString);

    # Decode the data in 8 byte blocks.  The string is encoded
    # as hex digits so there are two characters per byte:

    my $decrypted = "";
    for(my $index = 0; $index < length($EncryptedString);
	$index += 16) {
	$decrypted .= $self->{Cipher}->decrypt(
				    pack("H16",
					 substr($EncryptedString,
						$index, 
						16)));
    }
    #  the answer may have trailing pads to fill out a block.
    #  $length tells us the actual length of the decrypted string:

    $decrypted = substr($decrypted, 0, $length);
    Debug(9, "Decrypted $EncryptedString to $decrypted");

    return $decrypted;

}
# ToIdle
#     Called to transition to idle... done enough it's worth subbing
#     off to ensure it's always done right!!
#
sub ToIdle {
    my $self   = shift;

    $self->Transition("Idle");
    $self->{InformWritiable} = 0;
    $self->{InformReadable}  = 0;
    $self->{Timeoutable}     = 0;
}

#  ToVersionRequest
#    Called to transition to "RequestVersion"  also done a few times
#    so worth subbing out.
#
sub ToVersionRequest {
    my $self   = shift;
    
    $self->Transition("RequestingVersion");
    $self->{InformReadable}   = 0;
    $self->{InformWritable}   = 1;
    $self->{TransactionRequest} = "version\n";
    
}
#
#  CreateCipher
#    Given a cipher key stores the key in the object context,
#    creates the cipher object, (stores that in object context),
#    This is done a couple of places, so it's worth factoring it out.
#
# Parameters:
#    (self)
#    key - The Cipher key.
#
# Returns:
#    0   - Failure to create IDEA cipher.
#    1   - Success.
#
sub CreateCipher {
    my ($self, $key)   = @_;	# According to coding std.

    $self->{CipherKey} = $key; # Save the text key...
    my $packedkey = pack ("H32", $key);
    my $cipher            = new IDEA $packedkey;
    if($cipher) {
	$self->{Cipher} = $cipher;
	Debug("Cipher created  dumping socket: ");
	$self->Dump(9);
	return 1;
    }
    else {
	return 0;
    }
}
# ExchangeKeysViaSSL
#     Called to do cipher key exchange via SSL.
#     The socket is promoted to an SSL socket. If that's successful,
#     we read out cipher key through the socket and create an IDEA
#     cipher object.
# Parameters:
#    (self)
# Returns:
#      true    - Success.
#      false   - Failure.
#
# Assumptions:
#  1.   The ssl session setup has timeout logic built in so we don't
#     have to worry about DOS attacks at that stage.
#  2.   If the ssl session gets set up we are talking to a legitimate
#     lond so again we don't have to worry about DOS attacks.
#  All this allows us just to call 
sub ExchangeKeysViaSSL {
    my $self   = shift;
    my $socket = $self->{Socket};
    my $peer = $self->{LoncapaHim};
    my $peerdef = $self->{LoncapaDefid};
    my $loncaparev = $self->{LoncapaRev};

    #  Get our signed certificate, the certificate authority's 
    #  certificate and our private key file.  All of these
    #  are needed to create the ssl connection.

    my ($SSLCACertificate,
	$SSLCertificate) = lonssl::CertificateFile();
    my $SSLKey             = lonssl::KeyFile();
    my $CRLFile;
    unless ($crlchecked{$peerdef}) {
        $CRLFile = lonssl::CRLFile();
        $crlchecked{$peerdef} = 1;
    }
    #  Promote our connection to ssl and read the key from lond.

    my $SSLSocket = lonssl::PromoteClientSocket($socket,
						$SSLCACertificate,
						$SSLCertificate,
						$SSLKey,
                                                $peer,
                                                $peerdef,
                                                $CRLFile,
                                                $loncaparev);
    if(defined $SSLSocket) {
	my $key  = <$SSLSocket>;
	lonssl::Close($SSLSocket);
	if($key) {
	    chomp($key);	# \n is not part of the key.
	    return $self->CreateCipher($key);
	} 
	else {
	    Debug(3, "Failed to read ssl key");
	    return 0;
	}
    }
    else {
	# Failed!!
	Debug(3, "Failed to negotiate SSL connection!");
	return -1;
    }
    # should not get here
    return 0;

}



#
#  CompleteInsecure:
#      This function is called to initiate the completion of
#      insecure challenge response negotiation.
#      To do this, we copy the challenge string to the transaction
#      request, flip to writability and state transition to 
#      ChallengeReceived..
#      All this is only possible if InsecureOk is true.
# Parameters:
#      (self)    - This object's context hash.
#  Return:
#      0   - Ok to transition.
#     -1   - Not ok to transition (InsecureOk not ok).
#
sub CompleteInsecure {
    my $self = shift;
    if ($self->{InsecureOK}) {
	$self->{AuthenticationMode} = "insecure";
	&Debug(8," Transition out of Initialized:insecure");
	$self->{TransactionRequest} = $self->{TransactionReply};
	$self->{InformWritable}     = 1;
	$self->{InformReadable}     = 0;
	$self->Transition("ChallengeReceived");
	$self->{TimeoutRemaining}   = $self->{TimeoutValue};
	return 0;
	
	
    }
    else {
	&Debug(3, "Insecure key negotiation disabled!");
	my $socket = $self->{Socket};
	$socket->close;
	return -1;
    }
}

###########################################################
#
#  The following is an unashamed kludge that is here to
# allow LondConnection to be used outside of the
# loncapa environment (e.g. by lonManage).
# 
#   This is a textual inclusion of pieces of the
#   Configuration.pm module.
#


my @confdirs=('/etc/httpd/conf/','/etc/apache2/');

# ------------------- Subroutine read_conf: read LON-CAPA server configuration.
# This subroutine reads PerlSetVar values out of specified web server
# configuration files.
sub read_conf
  {
    my (@conf_files)=@_;
    my (%perlvar,%configdirs);
    foreach my $filename (@conf_files,'loncapa_apache.conf') {
        my $configdir = '';
        $configdirs{$filename} = [@confdirs];
        while ($configdir eq '' && @{$configdirs{$filename}} > 0) {
            my $testdir = shift(@{$configdirs{$filename}});
            if (-e $testdir.$filename) {
                $configdir = $testdir;
            }
        }
        if ($configdir eq '') {
            die("Couldn't find a directory containing $filename");
        }
	if($DebugLevel > 3) {
	    print STDERR ("Going to read $configdir.$filename\n");
	}
	open(CONFIG,'<'.$configdir.$filename) or
	    die("Can't read $configdir$filename");
	while (my $configline=<CONFIG>) {
	    if ($configline =~ /^[^\#]*PerlSetVar/) {
	        my ($unused,$varname,$varvalue)=split(/\s+/,$configline);
		chomp($varvalue);
		$perlvar{$varname}=$varvalue;
	    }
	}
	close(CONFIG);
    }
    if($DebugLevel > 3) {
	print STDERR "Dumping perlvar:\n";
	foreach my $var (keys %perlvar) {
	    print STDERR "$var = $perlvar{$var}\n";
	}
    }
    my $perlvarref=\%perlvar;
    return $perlvarref;
}

#
#   Get the version of our peer.  Note that this is only well
#   defined if the state machine has hit the idle state at least
#   once (well actually if it has transitioned out of 
#   ReadingVersionString   The member data LondVersion is returned.
#
sub PeerVersion {
   my $self = shift;
   my ($version) = ($self->{LondVersion} =~ /Revision: 1\.(\d+)/);
   return $version;
}

#
#  Manipulate the client data field
#
sub SetClientData {
    my ($self, $newData) = @_;
    $self->{ClientData} = $newData;
}
#
#  Get the current client data field.
#
sub GetClientData {
    my $self = shift;
    return $self->{ClientData};
}

#
# Get the HostID of our peer 
#

sub PeerLoncapaHim {
    my $self = shift;
    return $self->{LoncapaHim};
}

#
# Get the Authentication mode
#

sub GetKeyMode {
    my $self = shift;
    return $self->{AuthenticationMode};
}

1;

=pod

=head1 Theory

The lond object is a state machine.  It lives through the following states:

=item Connected:

a TCP connection has been formed, but the passkey has not yet been
negotiated.

=item Initialized:

"init" sent.

=item ChallengeReceived:

lond sent its challenge to us.

=item ChallengeReplied:

We replied to lond's challenge waiting for lond's ok.

=item RequestingKey:

We are requesting an encryption key.

=item ReceivingKey:

We are receiving an encryption key.

=item Idle:

Connection was negotiated but no requests are active.

=item SendingRequest:

A request is being sent to the peer.

=item ReceivingReply:

Waiting for an entire reply from the peer.

=item Disconnected:

For whatever reason, the connection was dropped.

When we need to be writing data, we have a writable event. When we
need to be reading data, a readable event established.  Events
dispatch through the class functions Readable and Writable, and the
watcher contains a reference to the associated object to allow object
context to be reached.

=head2 Member data.

=item Host

Host socket is connected to.

=item Port

The port the remote lond is listening on.

=item Socket

Socket open on the connection.

=item State

The current state.

=item AuthenticationMode

How authentication is being done. This can be any of:

    o local - Authenticate via a key exchanged in a file.
    o ssl   - Authenticate via a key exchaned through a temporary ssl tunnel.
    o insecure - Exchange keys in an insecure manner.

insecure is only allowed if the configuration parameter loncAllowInsecure 
is nonzero.

=item TransactionRequest

The request being transmitted.

=item TransactionReply

The reply being received from the transaction.

=item InformReadable

True if we want to be called when socket is readable.

=item InformWritable

True if we want to be informed if the socket is writable.

=item Timeoutable

True if the current operation is allowed to timeout.

=item TimeoutValue

Number of seconds in the timeout.

=item TimeoutRemaining

Number of seconds left in the timeout.

=item CipherKey

The key that was negotiated with the peer.

=item Cipher

The cipher obtained via the key.


=head2 The following are callback like members:

=item Tick:

Called in response to a timer tick. Used to managed timeouts etc.

=item Readable:

Called when the socket becomes readable.

=item Writable:

Called when the socket becomes writable.

=item TimedOut:

Called when a timed operation timed out.


=head2 The following are operational member functions.

=item InitiateTransaction:

Called to initiate a new transaction

=item SetStateTransitionCallback:

Called to establish a function that is called whenever the object goes
through a state transition.  This is used by The client to manage the
work flow for the object.

=item SetTimeoutCallback:

Set a function to be called when a transaction times out.  The
function will be called with the object as its sole parameter.

=item Encrypt:

Encrypts a block of text according to the cipher negotiated with the
peer (assumes the text is a command).

=item Decrypt:

Decrypts a block of text according to the cipher negotiated with the
peer (assumes the block was a reply.

=item Shutdown:

Shuts off the socket.

=head2 The following are selector member functions:

=item GetState:

Returns the current state

=item GetSocket:

Gets the socekt open on the connection to lond.

=item WantReadable:

true if the current state requires a readable event.

=item WantWritable:

true if the current state requires a writable event.

=item WantTimeout:

true if the current state requires timeout support.

=cut