how to successfully test for a valid admin password in leopard?

[WoodenBrain]

I want to test to see if an admin password entered by a user is valid. In theory something like this should work:

set user_pass to "ii"
try
	do shell script "sudo -k"
	set test_password to do shell script ("ls /private/var/root/") password user_pass with administrator privileges
on error myerr
	log "the password is invalid"
end try

However, instead of being trapped by try, Leopard puts up an authentication dialog. I believe this did not happen on Tiger, but could be mistaken.

Is there some better way?

[WoodenBrain]

got the answer on the mailing lists from Alex Luttgents:

It looks like that starting with Leopard, do shell script expects an
explicit user name instead of assuming the current user.

So, this one seems to emulate the behavior as observed under Tiger:

set user_pass to "ii"
try
 set user_name to do shell script "id -un"
 set test_password to do shell script ("ls /private/var/root/") user  
name user_name password user_pass with administrator privileges
on error myerr
 log myerr
end try

and should be working equally well under both Tiger and Leopard.

HTH,
Axel