Отличная статья - http://www.cyberciti.biz/tips/linux-unix-squid-proxy-server-authentication.html

закончил тем, что использовал следующее: используйте на свой страх и риск ... поскольку я не знаю, что он делает.

#proxy auth
auth_param basic program /usr/local/libexec/ncsa_auth /usr/local/etc/passwd
auth_param basic children 5
auth_param basic realm Squid proxy-caching web server
auth_param basic credentialsttl 2 hours
auth_param basic casesensitive off
#auth_param basic program /usr/local/bin/err

acl ncsa_users proxy_auth REQUIRED
http_access allow ncsa_users

#
# Recommended minimum configuration:
#
acl manager proto cache_object
acl localhost src 127.0.0.1/32 ::1
acl to_localhost dst 127.0.0.0/8 0.0.0.0/32 ::1

# Example rule allowing access from your local networks.
# Adapt to list your (internal) IP networks from where browsing
# should be allowed
acl localnet src 10.0.0.0/8 # RFC1918 possible internal network
acl localnet src 172.16.0.0/12  # RFC1918 possible internal network
acl localnet src 192.168.0.0/16 # RFC1918 possible internal network
acl localnet src fc00::/7       # RFC 4193 local private network range
acl localnet src fe80::/10      # RFC 4291 link-local (directly plugged) machines

acl SSL_ports port 443
acl Safe_ports port 80      # http
acl Safe_ports port 21      # ftp
acl Safe_ports port 443     # https
acl Safe_ports port 70      # gopher
acl Safe_ports port 210     # wais
acl Safe_ports port 1025-65535  # unregistered ports
acl Safe_ports port 280     # http-mgmt
acl Safe_ports port 488     # gss-http
acl Safe_ports port 591     # filemaker
acl Safe_ports port 777     # multiling http
acl CONNECT method CONNECT

#
# Recommended minimum Access Permission configuration:
#
# Only allow cachemgr access from localhost
http_access allow manager localhost
http_access deny manager

# Deny requests to certain unsafe ports
http_access deny !Safe_ports

# Deny CONNECT to other than secure SSL ports
http_access deny CONNECT !SSL_ports

# We strongly recommend the following be uncommented to protect innocent
# web applications running on the proxy server who think the only
# one who can access services on "localhost" is a local user
#http_access deny to_localhost

#
# INSERT YOUR OWN RULE(S) HERE TO ALLOW ACCESS FROM YOUR CLIENTS
#

# 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
http_access allow localnet
http_access allow localhost

# And finally deny all other access to this proxy
http_access deny all


# Squid normally listens to port 3128
http_port 3128

# Uncomment and adjust the following to add a disk cache directory.
#cache_dir ufs /usr/local/var/cache 100 16 256

# Leave coredumps in the first cache dir
coredump_dir /usr/local/var/cache

# Add any of your own refresh_pattern entries above these.
refresh_pattern ^ftp:       1440    20% 10080
refresh_pattern ^gopher:    1440    0%  1440
refresh_pattern -i (/cgi-bin/|\?) 0 0%  0
refresh_pattern .       0   20% 4320

Примерно так должно работать:

acl example proxy_auth REQUIRED
http_access allow example

Для единообразия это конфигурация, которую вы можете использовать с LDAP:

auth_param basic program /usr/lib/squid/ldap_auth -ZZ -b "dc=example,dc=com" -f "(&(uid=%s)(!(gn=noaccess))(!(cn=noaccess)))" -h ldap.example.org -v 3
acl ldap proxy_auth REQUIRED
http_access allow ldap
http_access deny all

Что он делает, так это пытается аутентифицировать пользователя с uid на сервере LDAP ldap.example.org (предпочтительно использовать IP-адрес) и не разрешает доступ, когда gn равно «noaccess» ИЛИ cn равно «noaccess».

Это запретит доступ ко всему остальному.