[krbdev.mit.edu #6336] enctype negotiation - etype list

[Ken Raeburn via RT]

The current enctype negotiation code on the trunk has a funny way of  
coming up with the enctype list to send.

The RFC says that if the session key is in the list, it should be at  
the end.

The current code looks up the enctype list, which is ordered by  
preference, and scans it for the session key type.  If it finds it, it  
*swaps* it with the entry at the end of the list. So if the session  
key type was first on the list, it's now last, and you're telling the  
application server that the enctype you'd really like to use is the  
one that was originally last in your preference order.

It probably should truncate the list after the session key type, if  
it's found.  And, just for kicks, check and see if the session key  
type is first on the list and skip enctype negotiation altogether if  
it is, since we can't get a more-preferred enctype in that case.

Ken