[zeromq-dev] ZAP / Security refactoring

[Jeremy Rossi]

I have been spending sometime with zeromq and zap.  With this I am thinking about refactoring the libzmq zap / security code a little to add some features and solve a problem I have.  

I think we should be able to stack mechanisms.  So that you are are able to use ZMQ_CURVE and ZMQ_PLAIN  on the same socket.  This would allow secure transport of the username/password with out having to manage the keys.  Also in my use case would allow the zap provider to learn the public key of a client while still providing authentication for that learning process.  

To achieve this I think the ZAP frame generation and processing should be moved to stream_engine.cpp and make calls into the mechanisms to gather the needed information to send to zap endpoint.  

Figured I would start the chat before working on code and get some feedback.