User Interface: Identities and Visibility

The user interface is intended for direct communication with the user, for example through a graphical interface. The two kinds of interactions needed at least are a PIN entry exchange, and the selection of a local identity and to which remotes it may be revealed.

An assumption that is (currently) made by the TLS Pool is that servers are always revealing their identities to any clients; but that clients may want to hold back on what part of them they reveal to servers: To a music site I might want to be a Kate Bush fan, while towards the tax office I might want to show another side of me.

To facilitate this, the user interface implements an interaction known as the local identity service, through the library call tlspool_localid_service(3). This is a registration that will evoke callbacks when a choice of a user identity is to be made. There is a great variety of situations in which this is desired, and flags can be used to control just that.

When a local identity callback is made, the principal concerns of the TLS Pool are:

• What local identity can I reveal to the remote identity of the current session?
• Can I reveal the identity to a more general selector than just the remote end point?

The user is presented with a popup to ask precisely that.

A very, very mundane implementation of this facility is included with the TLS Pool as lidsel.c — but any sane person would prefer a nicer interface, like the default TLS Pool GUI.

The other aspect presenting interactions to the user is the PIN entry. For this, a simplistic implementation is provided in pinentry.c, but again most users will prefer the default GUI instead.

The mechanism for PIN entry is similar to that for local identity selection, namely a registration for callbacks, this time through library call tlspool_pin_service(3).