I started down this path and learned some things, although
maybe not enough to be 100% accurate here.
A proxy by default cannot explicitly see SSL data or the
security model is compromised. The
request
is a request to a proxy to open a connection to a server.
The idea (I think) is that the proxy can see that request,
can then open a socket to the named host/port, and pass data
back and forth between the client. I've seen this done by
having the proxy take a CONNECT and turn it into a socket
open to the server. So you can't just pass the CONNECT on
as you can for other HTTP requests. Once the connection is
established I'd think the proxy could dig into the data if
it knows enough about the client's encryption settings to do
so. Never gone that far though ...