Chapter 16. Configuring the Squid Caching Proxy Server

# yum install squid

1. Adapt the localnet access control lists (ACL) to match the IP ranges that should be allowed to use the proxy:

   acl localnet src 192.0.2.0/24
   acl localnet 2001:db8::/32

   By default, the /etc/squid/squid.conf file contains the http_access allow localnet rule that allows using the proxy from all IP ranges specified in localnet ACLs. Note that you must specify all localnet ACLs before the http_access allow localnet rule.

   Important

   Remove all existing acl localnet entries that do not match your environment.
2. The following ACL exists in the default configuration and defines 443 as a port that uses the HTTPS protocol:

   acl SSL_ports port 443

   If users should be able to use the HTTPS protocol also on other ports, add an ACL for each of these port:

   acl SSL_ports port port_number

3. Update the list of acl Safe_ports rules to configure to which ports Squid can establish a connection. For example, to configure that clients using the proxy can only access resources on port 21 (FTP), 80 (HTTP), and 443 (HTTPS), keep only the following acl Safe_ports statements in the configuration:

   acl Safe_ports port 21
   acl Safe_ports port 80
   acl Safe_ports port 443

   By default, the configuration contains the http_access deny !Safe_ports rule that defines access denial to ports that are not defined in Safe_ports ACLs.
4. Configure the cache type, the path to the cache directory, the cache size, and further cache type-specific settings in the cache_dir parameter:

   cache_dir ufs /var/spool/squid 10000 16 256

   With these settings:
   • Squid uses the ufs cache type.
   • Squid stores its cache in the /var/spool/squid/ directory.
   • The cache grows up to 10000 MB.
   • Squid creates 16 level-1 sub-directories in the /var/spool/squid/ directory.
   • Squid creates 256 sub-directories in each level-1 directory.
   If you do not set a cache_dir directive, Squid stores the cache in memory.

1. Create the cache directory:

   # mkdir -p path_to_cache_directory

2. Configure the permissions for the cache directory:

   # chown squid:squid path_to_cache_directory

3. If you run SELinux in enforcing mode, set the squid_cache_t context for the cache directory:

   # semanage fcontext -a -t squid_cache_t "path_to_cache_directory(/.*)?"
   # restorecon -Rv path_to_cache_directory

   If the semanage utility is not available on your system, install the policycoreutils-python-utils package.

# firewall-cmd --permanent --add-port=3128/tcp
# firewall-cmd --reload

# systemctl start squid

# systemctl enable squid