Time for action – enforcing proxy authentication

If we want to enforce proxy authentication, we can add the following lines to our configuration file:

acl authenticated proxy_auth REQUIRED
http_access allow authenticated
http_access deny all

With the previous configuration, only authenticated users will be able to access the proxy server. If we want to specifically identify individual clients with usernames, we can pass a list of users as well. This may be needed if we want to give extra privileges to some users. For example:

acl authenticated proxy_auth REQUIRED
acl admins proxy_auth john sarah
acl special_website dstdomain admin.example.com
http_access allow admins special_website
http_access deny special_website
http_access allow authenticated
http_access deny all

Therefore, if we have the preceding lines in our configuration file, only the users john and sarah will be able to access admin.example.com, but other authenticated users will be able to access all websites except admin.example...