@dobey I have filtered https connections for years without breaking the encryption, this is easy when the proxy is declared in the browser (non transparent proxy).
What I want to do now is the same thing inside a smartphone running UT, to be able to filter Internet connections. So this is really an UT question because the proxy will be running inside the phone, I cannot have any control of connections running through 3G or 4G.
I have already installed UT on my Nexus 5. I have already set up the filter with an internal DNS server (Unbound) and it works. But filtering with squid is slightly better and I would like to test it.
@arubislander : thanks for the suggestion. But it is not a possible solution because if the proxy is not declared in the browser, the browser will encrypt itself the connection, and filtering is no longer possible. If the proxy is declared, the browser communicates with it without encryption (otherwise the proxy would be unable to do its job) and the proxy encrypts the connection if it does not have the page in cache and must forward the request.