Datasheet

“main” (Installation and Administration) — 2004/6/25 — 13:29 — page 610 — #636

clients. For Linux, install the pidentd package for this purpose. For

Windows, there is free software available for download from the

Internet. To ensure that only clients with a successful ident lookup are

permitted, deﬁne a corresponding ACL here:

acl identhosts ident REQUIRED

http_access allow identhosts

http_access deny all

Here, too, replace REQUIRED with a list of permitted user names.

Using ident can slow down the access time quite a bit, because ident

lookups are repeated for each request.

25.3.6 Conﬁguring a Transparent Proxy

The usual way of working with proxy servers is the following: the web

browser sends requests to a certain port in the proxy server and the proxy

provides these required objects, whether they are in its cache or not. When

working in a network, several situations may arise:

For security reasons, it is recommended that all clients use a proxy to

surf the Internet.

All clients must use a proxy, regardless of whether they are aware of

it.

The proxy in a network is moved, but the existing clients should re-

tain their old conﬁguration.

In all these cases, a transparent proxy may be used. The principle is very

easy: the proxy intercepts and answers the requests of the web browser,

so the web browser receives the requested pages without knowing from

where they are coming. As the name indicates, the entire process is done

transparently.

Kernel Conﬁguration

First, make sure the kernel of the proxy server supports a transparent

proxy. If not, add these options to the kernel and recompile it. For more

details, refer to Section 9 on page 233.

610 25.3. Proxy Server: Squid