=head1 NAME

Apache::HTTunnel - Universal HTTP tunnel using Apache + mod_perl


=head1 SYNOPSIS

  # on the server: in /etc/httpd/conf.d/perl_httunnel.conf
    PerlSetVar              HTTunnelFifo          /var/lib/httunnel/httunnel.sock
    PerlPostConfigRequire   Apache/HTTunnel.pm
    <Location "/httunnel">
      SetHandler      perl-script
      PerlResponseHandler   Apache::HTTunnel
    </Location>

  # on the client: in /etc/httunnel.d/server_ssh.cfg
    [server ssh]
    local_port = 9876
    url = http://server/httunnel
    remote_host = localhost
    remote_port = 22

  # on the client
    % /usr/bin/httunnel -f /etc/httunnel.d/ssh.cfg &
    % ssh localhost -p 9876 

    # You will now have a ssh connection to server where the packets
    # are actually being transported over many HTTP requests.
       
 
=head1 DESCRIPTION

C<Apache::HTTunnel> allows the creation of HTTP tunnels using Apache and 
mod_perl. The C<HTTunnel::Client> class (or the C<httunnel> daemon) can be
used to configure the tunnels.


=head1 CONFIGURATION

The following configuration directives can be used inside httpd.conf (or
some other file in the conf.d directory) to control the behaviour of 
C<Apache::HTTunnel>. 

Please note that HTTunnelFifo and HTTunnelConnectionTimeout must be used
before the PerlPostConfigRequire directive since they are used at startup 
time. The other directives can be specified at the Location level.

=over 4

=item HTTunnelFifo

Specifies the path to be used for the fifo that allows communication
between the keeper process and the Apache workers.

  Ex: HTTunnelFifo              /var/lib/httunnel/httunnel.sock

There is no default value. This directive is mandatory.

=item HTTunnelConnectionTimeout

Specifies the number of seconds after which inactive connections
will be closed. The connection table is checked at least every 15 
seconds.

  Ex: HTTunnelConectionTimeout  900

The default value is 900, meaning connections idle for more than
15 minutes will be closed.

=item HTTunnelAllowedTunnels

Specifies towards which host/port combinations this server allows tunnels
to be established. The format is as such:

  Ex: HTTunnelAllowedTunnels    "\
        *              => 22, \
        myhost         => 3389 | 5800, \
        host1 | host2  => * "

You can specify many sections by separating them by commas (,). Within each 
section, multiple hosts/ports may be specified by separating them with pipes 
(|). The asterisk (*) can be used as a wildcard, allowing any host/port.
There is no default value. This directive is mandatory.

=item HTTunnelMaxConnectTimeout

When a client sends a connection request, it may specify a timeout
value for the connection. In order to prevent blocking in the Apache child
in cases when the connection blocks, this directive limits the 
connection timeout that may be specified by the client.

  Ex: HTTunnelMaxConnectTimeout 10

The default value is 15 seconds. It is best to keep the value relatively
low to prevent blocking in the Apache child.

=item HTTunnelMaxReadTimeout

C<HTTunnel::Client> needs to poll to check if there is some data to be 
read from the remote socket. In order to not be troubled by proxies or 
other intermediaries that may terminate long lasting connections 
prematurely, C<Apache::HTTunnel> will purposely time-out read requests 
that take longer than HTTunnelReadTimeout seconds. A special response 
is sent to the client telling it to retry the read request.

  Ex: HTTunnelMaxReadTimeout    10

The default value is 15 seconds. It is best to keep the value relatively
low to prevent blocking in the Apache child.

=item HTTunnelMaxReadLength

The maximum number of bytes that a client may request for a read.

  Ex: HTTunnelMaxReadLength     16384

The default value is 131072 bytes.


=head1 SECURITY

Please keep in mind that HTTP is not, by default, encrypted. Further more, 
you will most certainly want to control which users are permitted to use 
the /httunnel URL since it can provide an entry point into your network. 

For these reasons, the use of SSL and Basic Authentication is strongly 
recommended. See the Apache documentation (mod_ssl, mod_allow, mod_auth) 
for more information on how to configure these features.

Also, be sure to keep a tight HTTunnelAllowedTunnels that allows only access
to the hosts/ports that are necessary.


=head1 BUGS

I'm sure there are some in there :)


=head1 SEE ALSO

L<File::FDkeeper>, L<File::FDpasser>, L<LWP>


=head1 AUTHOR

Patrick LeBoutillier, E<lt>patl@cpan.orgE<gt>


=head1 COPYRIGHT AND LICENSE

Copyright 2005 by Patrick LeBoutillier

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself. 

=cut