2 - Raspberry PI Community Projects

11.6. HTTP/FTP Proxy
An HTTP/FTP proxy acts as an intermediary for HTTP and/or FTP connections.
twofold:
Its role is
• Caching: recently downloaded documents are copied locally, which avoids multiple
downloads.
• Filtering server: if use of the proxy is mandated (and outgoing connections are blocked
unless they go through the proxy), then the proxy can determine whether or not the
request is to be granted.
Falcot Corp selected Squid as their proxy server.
11.6.1. Installing
The squid 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.
Prior to installing, care should be taken to check that the system can identify its own complete
name: the hostname -f must return a fully-qualified name (including a domain). If it does
not, then the /etc/hosts file should be edited to contain the full name of the system (for instance,
arrakis.falcot.com). The official computer name should be validated with the network
administrator in order to avoid potential name conflicts.
11.6.2. Configuring a Cache
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:
# INSERT YOUR OWN RULE(S) HERE TO ALLOW ACCESS FROM YOUR CLIENTS
# Example rule allowing access from your local networks. Adapt
# 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
Example 11.30
The /etc/squid/squid.conf file (excerpts)
286 The Debian Administrator's Handbook