Linux as a Proxy Server
The TIS fwtk builds fairly easily. I had to apply the http-gw patch in order to get the HTTP proxy to build. If you are building this toolkit on a system other than Linux, make sure you use gmake instead of make. I ran into this problem when I tried to build this package on an SGI. Doing this may require you to first acquire and build GNU make, which is available at ftp://prep.ai.mit.edu/pub/gnu/.
There is no configure script available with the TIS fwtk. Instead, there are several versions of the Makefile.config. Simply apply the http-gw patch, move Makefile.config.linux to Makefile.config, run make and then run make install. Note that in order to build the x-gw X proxy, you need the Motif libraries. The easiest way to get them is to download lesstif, a Motif clone available at http://www.hungry.com/products/. The following are the steps required to build and install the fwtk software:
tar xvzf fwtk-2.0.tar.gz cd fwtk chmod -R 755 * tar xvf ../http-gw.patch.tar mv Makefile.config Makefile.config.orig ln -s Makefile.config.linux Makefile.config makea su make install
The binaries are placed in the /usr/local/etc directory, a location not likely to be affected by system upgrades. The proxies can be configured to run as daemons or by inetd. Take careful note of the man pages. There are specific command-line arguments that must be invoked in order to get the proxy to run as a daemon. As I mentioned above, you can configure as many or as few of the proxies provided. The configuration is much more complicated than for the Socks5 server. The configuration file is called /usr/local/etc/netparam and is parsed based on the proxies. Each line starts with the name of the proxy followed by a colon and then by the options (see Listing 4).
The client configuration is different from the Socks5 configuration. For the two browsers mentioned above, simply leave the Socks5 entry blank and fill in the HTTP proxy and port, as well as FTP and TELNET entries, if you have set these services up on the firewall. Good news for those using a browser other than Navigator and Explorer—you can use the TIS fwtk http-gw proxy with any browser. Simply prefix all web addresses with http://IP-or-name-of-firewall-host/. For FTP, you first FTP to the proxy-server host. When prompted for the user name, enter email@example.com; the proxy then goes out and makes the appropriate connection. For News, you must configure the plug-gw as illustrated in the configuration file (see Listing 4). Accessing news is as simple as configuring your news client to point to the proxy server instead of the real news server.
When I first set out to construct a firewall/proxy server solution where I work, I initially chose the Socks5 server. (I had downloaded them both, but the Socks5 server compiled without errors, thus sealing my choice.) Within a day, I had figured out which settings I needed for my network and had the server running as a daemon.
Getting users excited about using the proxy server as opposed to direct Internet access is not easy. Recently, a user approached me ranting about how he could not stream video in from the Internet. After he calmed down, I asked him which URL he was trying to access. Then I quickly found a FAQ for the particular plug-in he was using with an entry similar to “How do I stream video through a firewall.” After reading the FAQ and looking at the available options, I found that this particular plug-in did not have Socks5 support. It did, however, have support for general HTTP proxying. So, I turned my attention back to the TIS fwtk I had abandoned 10 months before. I found a newer version, applied the http-gw patch, executed gmake and had the toolkit running later that day. The video streaming worked beautifully.
This story illustrates the fact that you do not have to make an either/or decision about Socks5 or the TIS firewall toolkit. The two packages can be used together to give your users a wide variety of Internet access.
Setting up a proxy server is a great way to give your users Internet access while still protecting your network from Internet attacks. Between both the Socks5 server and the TIS firewall toolkit, you can give your users as much or as little Internet access as you want.
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