Interactivity in SASL mechanisms

[Laurence Lundblade <lgl@xxxxxxxxxxxx>]

Looking at a couple of the newer SASL mechanisms such as DIGEST and 
SecureID I see they presume the possibility of some interaction with the 
user during the SASL negotiation. I believe this can't be avoided in some 
cases, but it is undesirable as for example:

- mail checking and sending are often unattended
- interaction increases connect time which:
    - can cost if you pay by the minute (e.g. wireless data call)
    - can add load to the server (processes hang around)
- mail checks often connect to multiple mail servers. It is better
  to get all the credentials up front before all the mail checks
  start because one often starts a mail check and then goes
  for a cup of coffee or such
- mail checking and sending are often background operations
  and popping up dialogues for authentication can be confusing

One thing I've done already with SMTP AUTH is to remember what the server 
said last time. This may work with things like realms but I haven't tried 
to implement it yet.

So it seems that eliminating interactively would be a good thing for SASL 
mechanisms.

LL