log *** instead of actual User-Password in postauth_query

Dear List! I am wondering if there is a way to convert a password to a number of asterisk symbols (*) matching the length of the actual password using unlang. For obvious reasons i do not want to log the cleartext password in radpostauth. But i don't want to completely omit the field either. Changing the postauth_query in dialup.conf is pretty straightforward, but i could not figure out how to replace the password with the exact same number of * symbols. The best i could come up with so far is: %{%{#User-Password}:-0} Which outputs the length of the password as a number. Is there a straightforward way to achieve what i want? tia, Michael