#!/usr/bin/perl -w
use strict;
use warnings;
use Net::Proxy;
use LWP::UserAgent;
use Getopt::Long;

our $VERSION = '0.06';

# default configuration
our %CONF = (
    'proxy-authentication' => '',
    'proxy'                => $ENV{HTTP_PROXY},
    'user-agent'           => "connect-tunnel/$VERSION",
    'verbose'              => 0,
);

#
# get and check the options
#
GetOptions( \%CONF, "verbose|v+", "tunnel|T=s@", "proxy|P=s",
    "proxy-authentication|A=s", "local-only|L", "user-agent|U=s" );

# set up the verbosity level
Net::Proxy->set_verbosity( $CONF{verbose} );

# check for a proxy
if ( $CONF{proxy} ) {
    $CONF{proxy} .= ":8080" if not $CONF{proxy} =~ /:/;
}

die "--proxy <proxy:port> option required$/" if !$CONF{proxy};

# create the tunnels entrances
die "--tunnel <port:host:hostport> option required$/"
  unless exists $CONF{tunnel};

# split proxy-authentication
{
    my ( $user, $pass ) = split ':', $CONF{'proxy-authentication'}, 2;
    $CONF{'proxy-authentication'} = $CONF{'proxy-authentication'}
        ? [ proxy_user => $user, proxy_pass => $pass ]
        : [];
}

for my $tunnel ( @{ $CONF{tunnel} } ) {
    die "--tunnel <port:host:hostport> format required$/"
      if $tunnel !~ /^\d+:[\w.]+:\d+$/;
    my ( $port, $host, $hostport ) = split ':', $tunnel;
    my ( $proxy_host, $proxy_port) = split ':', $CONF{proxy};

    my $proxy = Net::Proxy->new(
        {   in => {
                type  => 'tcp',
                port  => $port,
                host  => $CONF{'local-only'} ? 'localhost' : '0.0.0.0',
            },
            out => {
                type        => 'connect',
                host        => $host,
                port        => $hostport,
                proxy_host  => $proxy_host,
                proxy_port  => $proxy_port,
                proxy_agent => $CONF{'user-agent'},
                @{ $CONF{'proxy-authentication'} },
            },
        }
    );

    $proxy->register();
}

# the main loop
Net::Proxy->mainloop();

__END__

=head1 NAME

connect-tunnel - Create CONNECT tunnels through HTTP proxies

=head1 SYNOPSIS

B<connect-tunnel> S<[ B<-Lv> ]> S<[ B<-A> I<user:pass> ]> S<[ B<-P> I<proxy:port> ]>
               S<[ B<-C> I<controlport> ]> S<[ B<-T> I<port:host:hostport> ]>

=head1 DESCRIPTION

B<connect-tunnel> sets up tunneled connections to external hosts
by redirecting connections to local ports towards thoses hosts/ports
through a HTTP proxy.

B<connect-tunnel> makes use of the HTTP C<CONNECT> method to ask the
proxy to create a tunnel to an outside server. Be aware that some
proxies are set up to deny outside tunnels (either to ports other
than 443 or outside a specified set of outside hosts).

=head1 OPTIONS

The program follows the usual GNU command line syntax, with long
options starting with two dashes.

=over 4

=item B<-A>, B<--proxy-authentication> I<user:password>

Proxy authentication information.

Please note that all the authentication schemes supported by
C<LWP::UserAgent> are supported (we use an C<LWP::UserAgent> internally
to contact the proxy).

=item B<-C>, B<--control-port> I<controlport>

The port to which one can connect to issue control commands to
B<connect-tunnel>.

See L<CONTROL CONNECTIONS> for more details about the available commands.

=item B<-L>, B<--local-only>

Create the tunnels so that they will only listen on C<localhost>.
Thus, only connections originating from the machine that runs
B<connect-tunnel> will be accepted.

That was the default behaviour in B<connect-tunnel> version 0.02.

=item B<-P>, B<--proxy> I<proxy>[I<:port>]

The proxy is required to connect the tunnels.
If no port is given, 8080 is used by default.

See also L<ENVIRONMENT VARIABLES>.

=item B<-T>, B<--tunnel> I<port:host:hostport>

Specifies that the given I<port> on the local host is to be forwarded
to the given I<host> and I<hostport> on the remote side. This works by
allocating a socket to listen to I<port> on the local side, and whenever
a connection is made to this I<port>, B<connect-tunnel> forwards it to
the proxy (with the credentials, if required), which in turn forwards
it to the final destination.

Note that this does not imply the use of any cryptographic system
(SSL or any other). This is a simple TCP redirection. The security
if any, is the one provided by the protocol used to connect to the
destination through B<connect-tunnel>.

On Unix systems, only root can forward privileged ports.

Note that you can setup tunnels to multiple destinations, by using
the B<--tunnel> option several times.

=item B<-U>, B<--user-agent> I<string>

Specify User-Agent value to send in HTTP requests.
The default is to send C<connect-tunnel/I<version>>.

=item B<-v>, B<--verbose>

Verbose output.

This option can be used several times for more verbose output.

=back

=head1 EXAMPLES

To connect to a SSH server running on C<ssh.example.com>, on port 443,
through the proxy C<proxy.company.com>, running on port 8080, use the
following command:

    connect-tunnel -P proxy.company.com:8080 -T 22:ssh.example.com:443

And now point your favorite ssh client to the machine running
B<connect-tunnel>.

You can also emulate a "standard" user-agent:

    connect-tunnel -U "Mozilla/4.03 [en] (X11; I; Linux 2.1.89 i586)"
                   -P proxy.company.com:8080 -T 22:ssh.example.com:443

B<connect-tunnel> can easily use your proxy credentials to connect
outside:

    connect-tunnel -U "Mozilla/4.03 [en] (X11; I; Linux 2.1.89 i586)"
                   -P proxy.company.com:8080 -T 22:ssh.example.com:443
                   -A book:s3kr3t

But if you don't want anybody else to connect to your tunnels
and through the proxy with I<your> credentials, use the
B<--local-only> option:

 connect-tunnel -U "Mozilla/4.03 [en] (X11; I; Linux 2.1.89 i586)"
                -P proxy.company.com:8080 -T 22:ssh.example.com:443
                -A book:s3kr3t -L

If you have several destinations, there is no need to run several
instances of B<connect-tunnel>:

 connect-tunnel -U "Mozilla/4.03 [en] (X11; I; Linux 2.1.89 i586)"
                -P proxy.company.com:8080 -A book:s3kr3t -L
                -T 22:ssh.example.com:443
                -T 222:ssh2.example.com:443

But naturally, you will need to correctly set up the ports in your clients.

Mmm, such a long command line would perfectly fit in an alias or a F<.BAT>
file. C<;-)>

=head1 ENVIRONMENT VARIABLES

The environment variable C<HTTP_PROXY> can be used to provide
a proxy definition.

The environment variable is overriden by the B<--proxy> option,
if passed to B<connect-tunnel>.

=head1 AUTHOR

Philippe "BooK" Bruhat, C<< <book@cpan.org> >>.

I seem to have re-invented a well-known wheel with that script, but at
least, I hope I have added a few interesting options to it.

=head1 SCRIPT HISTORY

The first version of the script was a quick hack that let me go through
a corporate proxy.

Version 0.02 and version 0.03 were released on CPAN in 2003.

Version 0.04 sits half-finished in a CVS repository at home: I couldn't
decypher the spaghetti of my data structures any more. C<:-(>

Version 0.05 (and higher) are based on C<Net::Proxy>, and included with
the C<Net::Proxy> distribution.

=head1 

Even though it's not rocket science, B<connect-tunnel> has been cited
in at least one academic works:

=over 4

=item * I<HTTP Tunnels Through Proxies>, Daniel Alman

Available at SANS InfoSec Reading Room: Covert Channels
L<http://www.sans.org/rr/whitepapers/covert/>

Direct link: L<http://www.sans.org/rr/whitepapers/covert/1202.php>

=back

=head1 COPYRIGHT

Copyright 2003-2006, Philippe Bruhat. All rights reserved.

=head1 LICENSE

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

=cut