Author image Patrick LeBoutillier


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


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

  # 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.


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


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


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.


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.


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.


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.


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, 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.


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

  Ex: HTTunnelMaxReadLength     16384

The default value is 131072 bytes.


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.


I'm sure there are some in there :)


File::FDkeeper, File::FDpasser, LWP


Patrick LeBoutillier, <>


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.

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