There is a line in squid default configuration:
# Deny CONNECT to other than secure SSL ports
http_access deny CONNECT !SSL_ports
acls are applied from top down, so CONNECT acl will deny access to all non SSL and SSL ports. I mean it never reaches the second access rule.
CONNECT
here means the HTTPS CONNECT method, i.e., the standardized way a browser talks to a proxy server, asking for a connection to an HTTPS-serving sitehttp_access deny CONNECT !SSL_ports
means 'deny all HTTPS CONNECT that asks to be connected to a port other than SSL_ports'. If the browser sends a CONNECT method asking to be connected to an SSL_port, the rule doesn't fire.Whether or not the CONNECT actually gets through depends on the successive
http_access
rules.