Product SiteDocumentation Site

11.6. HTTP/FTP-mellomtjener

En HTTP/FTP-mellomtjener fungerer som et mellomledd for HTTP- og/eller FTP-tilkoblinger. Dens rolle er todelt:
Falcot Corp valgte Squid som sin mellomtjener.

11.6.1. Å installere

The squid[2] Debian package only contains the modular (caching) proxy. Turning it into a filtering server requires installing the additional squidguard package. In addition, squid-cgi provides a querying and administration interface for a Squid proxy.
Før du installerer, er det viktig å ta hensyn til at systemet kan identifisere sitt eget fullstendige navn: hostname -f må returnere et fullt kvalifisert navn (inkludert et domene). Hvis den ikke gjør det, så skal /etc/hosts-filen redigeres til å inneholde fullt navn på systemet (for eksempel arrakis.falcot.com). Det offisielle navnet på datamaskinen skal godkjennes av nettverksadministratoren for å unngå potensielle navnekonflikter.

11.6.2. Oppsett av et hurtiglager

Enabling the caching server feature is a simple matter of editing the /etc/squid/squid.conf configuration file and allowing machines from the local network to run queries through the proxy. The following example shows the modifications made by the Falcot Corp administrators:

Eksempel 11.22. The /etc/squid/squid.conf file (excerpts)

# INSERT YOUR OWN RULE(S) HERE TO ALLOW ACCESS FROM YOUR CLIENTS
#
include /etc/squid/conf.d/*

# Example rule allowing access from your local networks.
# Adapt localnet in the ACL section to list your (internal) IP networks
# from where browsing should be allowed

acl our_networks src 192.168.1.0/24 192.168.2.0/24
http_access allow our_networks
http_access allow localhost
# And finally deny all other access to this proxy
http_access deny all

11.6.3. Oppsett av et filter

squid itself does not perform the filtering; this action is delegated to squidGuard. The former must then be configured to interact with the latter. This involves adding the following directive to the /etc/squid/squid.conf file:
url_rewrite_program /usr/bin/squidGuard -c /etc/squid/squidGuard.conf
The /usr/lib/cgi-bin/squidGuard.cgi CGI program also needs to be installed, using /usr/share/doc/squidguard/examples/squidGuard.cgi.gz as a starting point. Required modifications to this script are the $proxy and $proxymaster variables (the name of the proxy and the administrator's contact email, respectively). The $image and $redirect variables should point to existing images representing the rejection of a query.
The filter is enabled with the service squid reload command. However, since the squidguard package does no filtering by default, it is the administrator's task to define the policy. This can be done by creating the /etc/squid/squidGuard.conf file (using /etc/squidguard/squidGuard.conf.default as template if required).
Den gjeldende databasen må regenereres med update-squidguard etter hver forandring i squidGuard-oppsettsfilen (eller en av de lister over domener eller nettadresser den nevner). Oppsettsfil-syntaksen er dokumentert på den følgende nettsiden:


[2] The squid3 package, providing Squid until Debian Jessie, is now a transitional package and will automatically install squid.
[3] PICS has been superseded by the Protocol for Web Description Resources (POWDER system: https://www.w3.org/2009/08/pics_superseded.html.