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Getting Through Fire Walls

Question

My company (organisation, etc) has an internal internet but general access to the external internet is not allowed. How can I run a www client to access offf-site things?

TCP tunneling through firewalls

There are two ways. If you are simply a user with no sympathy from the guys running the gateway, then you have to use an existing gateway. Typically, there will be a telnet gateway to which you can telnet which then allows you to ask politely to be connected to a given remote machine.

It is possible to change way that www clients to a TCP connect to do all of this for every connection. The code in in HTTP.c and HTTCP.c in the libwww library. This has been done successfully at for example Xerox PARC ands other places.

Running a WWW Gateway

You can do it this way if you can run a new gateway on the firewall machine. You will need to persuade your management that this is safe and necessary. (Try showing them a good www client and then see what they say! )

WWW clients can be set to redirect requests to a gateway using 

		setenv WWW_http_GATEWAY  http://gw.here.com/
		setenv WWW_wais_GATEWAY  http://gw.here.com/
		setenv WWW_gopher_GATEWAY http://gw.here.com/
setting it separately for each type of URL. They then use HTTP protocol to go to the gateway, which returns whatever document/search it was they wanted. See also: running a WWW gateway.

The client can in fact run with a rule file instead of the environment variables, which allows more complicated selections to be set up.

The CERN WWW server (httpd) will run as a gateway just by being configured correctly. The rule file needs lines like for example 

		pass	http:*
		pass	wais:*
		pass	gopher:*
		fail	news:alt.*
		pass	news:*
The gateway can at the same time be a server for files, by putting in lines like 
		pass	http://gw.here.com/*	file:/pub/*
		pass	/*			file:/pub/*
There are lots of alternatives. Clearly you can be quite specific about what you do and do not want to allow through. But censorship may only get you into trouble with your users.
Tim BL 1992