desproxy

desproxy(1)                      User Commands                     desproxy(1)



NAME
       desproxy - a TCP tunnel for HTTP proxies

SYNOPSIS
         desproxy remote_host remote_port proxy_host proxy_port local_port

OPTIONS
       None.

DESCRIPTION
       HTTP proxies are network servers that are used to give HTTP (web)
       access to computers that are not connected to the Internet. This is a
       typical scenario in corporate networks and recently in home networks
       too. HTTP proxies connect to the Internet either directly or via a
       parent proxy (which in fact connects to the Internet directly or via
       another parent proxy, and so on...)

       HTTP clients (web browsers) use HTTP proxies to request web pages; the
       HTTP server just forwards those request to the destination server. All
       the negotiation is done via the HTTP protocol, which is designed just
       to carry HTTP requests and no generic (TCP/IP) traffic. That is why you
       can't (normally) use Internet applications beside your web server if
       you are behind a HTTP proxy.

       That is what desproxy is good for. Desproxy is a TCP tunnel, which
       means desproxy can forward TCP/IP traffic via a HTTP proxy. Desproxy
       uses a HTTP/1.1 method (CONNECT) to establish TCP/IP connections on
       demand. CONNECT is used for SSL connections when accessing to secure
       sites, so if you can access sites that support SSL (www.hotmail.com for
       example) you can use desproxy.

       Not all IP (Internet) traffic is just TCP/IP. In fact there are two
       more protocols widely used in the Internet not supported by desproxy:
       UDP and ICMP:

       ·   ICMP is used to manage large IP networks. The only application
           using ICMP you may miss is ping.

       ·   UDP is an unreliable connection-less fast transport protocol,
           mostly used in network games and other applications that need low
           latency network traffic. Notably DNS uses UDP packets for fast
           delivery.

   Will desproxy work with my HTTP proxy?
       Short answer: just give it a try

       Long answer: desproxy should work with every HTTP proxy, with the
       following exceptions:

       ·   MS Proxies with NTLM authentication. NTLM is a proprietary
           authentication method from Microsoft, not a standard authentication
           method. Maybe in the future desproxy will support NTLM
           authentication, but currently it doesn't.

       ·   HTTP/1.0 Proxies. Desproxy needs the CONNECT method, which is only
           available from HTTP/1.1 protocol version. It's very unlikely your
           proxy doesn't accept HTTP/1.1 requests.

       ·   HTTP/1.1 Proxies without the CONNECT method. Maybe your network
           administrator deactivated CONNECT support in the proxy, or maybe
           CONNECT is restricted to the HTTPS port (443).

   Assumptions
       Let's assume the following:

       ·   your HTTP proxy host name is "proxy" and its address is "192.0.0.1"

       ·   your HTTP proxy port is "8080"

       ·   your HTTP proxy doesn't need authentication. It case you need HTTP
           authentication, please read [2]this.

       ·   your system console will be a terminal (xterm, the console or a
           virtual terminal) if you are running Linux, *BSD or other UN*X

   About connections
       Imagine you need a network application that uses only one TCP/IP
       connection with just one server. That's the case of IRC in which you
       connect to an IRC server or ssh where you tipically connect just to one
       UNIX computer at a time. That's what I called a "static connection".

       Of course that's not the case of a web browser or a file sharing
       program, both of them doing several connections at a time to different
       computers. That's what I call "dynamic connections".

STATIC CONNECTIONS EXAMPLES
   item How to use desproxy to connect to IRC
       Suppose you want to connect to IRC using irc.undernet.org port 6667 as
       your IRC server. First you have to start a system console (see
       Assumptions above for details) and type

           desproxy irc.undernet.org 6667 proxy 8080 1080

       That should start desproxy, giving you the copyright notice along with
       some information. The following is a screen capture from desproxy
       0.0.23

           -----------------------------------
           desproxy                     0.0.23

           (c) Miguelanxo Otero Salgueiro 2001

           This release brought to you patched
           by Rutger Nijlunsig.

           See RutgerWork.txt in documentation
           for details about new features.

           Great work guy!
           -----------------------------------
           TCP port 1080 Binded & Listening
           Press ENTER to Quit

       Desproxy reports it is listening in local port 1080 ready for a
       connection.

       Open your favourite IRC client (install it first ;D) and connect to
       127.0.0.1 port 1080 as your irc server (127.0.0.1 is a virtual IP,
       always referencing to your local machine). Then, your IRC client should
       connect to desproxy. It looks like

           Connection request from 127.0.0.1, port 1220
           Connecting to http proxy (proxy:8080)
           Bidirectional connection established

       Then you should be able to use your IRC client as if you were directly
       connected to irc.undernet.org.

   How to use desproxy to log in a computer using ssh
       Suppose you have a shell account in a computer that supports secure
       connections via ssh. Let's assume it's called shell.corporate.com. SSH
       uses port number 22 by default. So start a new system console and type:

          desproxy shell.corporate.com 22 proxy 8080 1080

       Then, tell your ssh client to connect to localhost (127.0.0.1) port
       1080 and you should get a ssh password prompt!

   How to use desproxy to use other static clients
       Let's assume you want to use network application X, which doesn't
       support HTTP proxies but use one TCP/IP connection (like IRC and SSH).
       To make X work with desproxy, you just have to 1) Search for the
       default port of that application 2) Search for the default server of
       that application and 3) Start desproxy, passing that info as command
       line parameters. Format is

           desproxy remote_host remote_port proxy_host proxy_port local_port

       Just give a local_port of your desire, but always over 1023, cause
       lower ports may need administrator privileges.

   About HTTP Authentication
       Some HTTP proxies need for security reasons a method of checking
       client's identity. That's called HTTP authentication (or HTTP
       authorization).

       Despoxy now supports Basic HTTP authentication. If your proxy needs
       other kind of authentication (either Digest or NTLM) desproxy won't
       work.

       For desproxy to work with a HTTP proxy that needs authentication, you
       have to tell desproxy which username and password to use. Desproxy
       reads the environment variable PROXY_USER to get that info.

       Suppose your proxy username is "mayka" and your proxy password is
       "007sgotLTK". Then, before using any of the desproxy programs you
       should type this in your system console:

           set PROXY_USER=mayka:007sgotLTK

       Beware passwords can include some characters that should be escaped
       from the system console. For example, if your password is "moon!=sun",
       and you are running Linux, you should type

           export PROXY_USER=yourusername:moon\!\=sun

       Note characters "!" and "=" are escaped using the backslash "\". If you
       are running MS Windows, as long as I know, you don't have to escape any
       valid password character.

       head1 Troubleshooting

       A normal desproxy session looks like this:

           $ desproxy 127.0.0.1 21 127.0.0.1 4480 2222

           -----------------------------------
           desproxy                  <version>

           HTTP/1.1
           (c) Miguelanxo Otero Salgueiro 2001
           -----------------------------------

           Listening on port 2222
           Connection request from 127.0.0.1, port 1227
           Connecting to http proxy (127.0.0.1:4480)
           Bidirectional connection stablished
           (127.0.0.1:21) <-> (localhost)
           End of connection.

       Here, a connection to local ftp server (127.0.0.1:21) is made by using
       local proxy (127.0.0.1:4480). You can see how, after the connection is
       accepted, desproxy connected to the proxy, interchanged some bytes (a
       FTP session) and terminates the connection.

       Desproxy is quite self explanatory about errors. Desproxy-inetd is far
       more obscure, because the way inetd uses it (can't print error
       messages) to the console.

       Basically there are two kind of errors:

       ·   Errors reported when connecting to the proxy: the http page showing
           the error is displayed.

       ·   Every other error: a short error message is displayed.

       Some common HTTP errors (as reported by the proxy)

            * HTTP 400 Bad Request - Some versions of desproxy (0.0.21) cause
              this error (FATAL)
            * HTTP 403 Forbidden - Forbidden to do that (FATAL)
            * HTTP 404 Not Found - Page not found, or resource not found (MINOR)
            * HTTP 405 Method not Allowed - Can't do CONNECT method (FATAL)
            * HTTP 500 Internal Server Error - Maybe you're trying to connect to
              a remote closed port (remote site reported connection refused)
              (MINOR)
            * HTTP 503 Service Unavailable -> The proxy can't reach the site
              (MINOR)
            * HTTP 505 HTTP Version Not Supported - CONNECT method not available
              (FATAL)
            * HTTP 502 Bad Gateway - Stands for "DNS lookup error" (MINOR)

       (FATAL) - Forget about using desproxy, you can't surpass the proxy.
       (TODO) - To do, not yet implemented.  (MINOR) - Temporary fault or
       maybe your fault.

ENVIRONMENT
       PROXY_USER
           An example:

              PROXY_USER=mayka:007sgotLTK

           Beware passwords can include some characters that should be escaped
           from the system console. For example, if your password is
           "moon!=sun", and you are running Linux, you should type

       PROXY_USER
           An example:

               PROXY_USER=yourusername:moon\!\=sun

           Note characters "!" and "=" are escaped using the backslash "\".

FILES
       None.

SEE ALSO
       dnsproxy-dns(1), dnsproxy-inetd(1), dnsproxy-socksserver(1), connect(1)

AUTHORS
       This manual page was written by Jari Aalto <jari.aalto@cante.net>, for
       the Debian GNU system (but may be used by others). Released under
       license GPL v2 or, at your option, any later version.



desproxy                          2012-05-01                       desproxy(1)