In order to keep this blog post a bit more relevant, there have been some improvements since that post was written. Squid v3.2 has been released earlier this year, making ssl interception more seamless and easier. The new features for HTTPS interception can be found while reading through the man page for http_port:
1. The “transparent” keyword has been changed to “intercept“:
intercept Rename of old 'transparent' option to indicate proper functionality.
INTERCEPT is now better described as:
intercept Support for IP-Layer interception of outgoing requests without browser settings. NP: disables authentication and IPv6 on the port.
2. In order to avoid more certificate errors when intercepting HTTPS sites, squid now can dynamically generate SSL certificates, using generate-host-certificates. This means the CN of the certificate should now match that of the origin server, though the certificate will still be generated using SQUID’s private key:
SSL Bump Mode Options: In addition to these options ssl-bump requires TLS/SSL options. generate-host-certificates[=<on|off>] Dynamically create SSL server certificates for the destination hosts of bumped CONNECT requests.When enabled, the cert and key options are used to sign generated certificates. Otherwise generated certificate will be selfsigned. If there is a CA certificate lifetime of the generated certificate equals lifetime of the CA certificate. If generated certificate is selfsigned lifetime is three years. This option is enabled by default when ssl-bump is used. See the ssl-bump option above for more information.
Looks like the above is an offshoot of the excellent work here: http://wiki.squid-cache.org/Features/DynamicSslCert
Make sure to use the above two features for smoother HTTPS interception – though remember, always warn users that SSL traffic is being decrypted, privacy is a highly-valued right…