[krbdev.mit.edu #7743] kadmin cannot add principal and extract random key in one step

[Greg Hudson via RT]

If a kadmin client has only "add" privileges, it cannot add a principal 
with a random key and get the key in a single step.  If the client gives 
addprinc the -randkey option, then nobody except the KDC will know the 
key, and the won't be able to act on the created principal.

The workaround is to create the principal with a password and then use 
self-service to change the key to a random key.  But this is awkward at 
best: the client must make up a temporary but secure password, the 
kadmin server must perform unnecessary string-to-key operations, the 
password could fail password quality rules, etc..

A possible design to allow addition and key extraction as a single step 
would be:

* Create a new create_principal4 RPC which accepts the same argument as 
create_principal3 but returns the keys, either using a chrand_ret or a 
substantially identical structure.  create_principal3 can be implemented 
in terms of create_principal4 in the server library, just as 
create_principal is implemented in terms of create_principal3.

* Add a -keytab argument to the addprinc command.  If it is used, kadmin 
uses create_principal4 (and therefore only works with a new kadmin 
server); otherwise it uses create_principal3 or create_principal as 
appropriate.