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connect-tunnel

NAME

connect-tunnel - Create CONNECT tunnels through HTTP proxies

SYNOPSIS

connect-tunnel [ -Lv ] [ -A user:pass ] [ -P proxy:port ]
               [ -C controlport ] [ -T port:host:hostport ]

DESCRIPTION

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

connect-tunnel makes use of the HTTP "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).

OPTIONS

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

-A, --proxy-authentication user:password

Proxy authentication information.

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

-C, --control-port controlport

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

See ``CONTROL CONNECTIONS'' for more details about the available commands.

-L, --local-only

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

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

-P, --proxy proxy[:port]

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

See also ``ENVIRONMENT VARIABLES''.

-T, --tunnel port:host:hostport

Specifies that the given port on the local host is to be forwarded to the given host and hostport on the remote side. This works by allocating a socket to listen to port on the local side, and whenever a connection is made to this port, 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 connect-tunnel.

On Unix systems, only root can forward privileged ports.

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

-U, --user-agent string

Specify User-Agent value to send in HTTP requests. The default is to send "connect-tunnel/version".

-v, --verbose

Verbose output.

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

EXAMPLES

To connect to a SSH server running on "ssh.example.com", on port 443, through the proxy "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 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
 
 

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 your credentials, use the --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 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 .BAT file. ";-)"

ENVIRONMENT VARIABLES

The environment variable "HTTP_PROXY" can be used to provide a proxy definition.

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

AUTHOR

Philippe ``BooK'' Bruhat, "<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.

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. ":-("

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

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

* HTTP Tunnels Through Proxies, Daniel Alman

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

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

COPYRIGHT

Copyright 2003-2007, Philippe Bruhat. All rights reserved.

LICENSE

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