whoami on a CIFS session

[Moshe Yosevshvili]

hi all, 
 I'd like to get the username of the user that opened a CIFS session.
in NTLM the username is in plain text and can be retrieved during session 
setup.
in Kerberos, on the other hand, it's encrypted in the ticket (assume i can't 
read the ticket).
is there an MS-RPC call that i can send to the file-server in the context of 
this session that will
return the username. this is kind of a "whoami" utility for a CIFS session.
 thanks for your time,
 Moshe.