Database Auditing

I'm evaluating of use postgresql but for local law requirements is
needed for the access of some kind of data (sensitive) a log of the
accesses (Auditing) is a feature available in many databases but i've
seen that lacks in PostgreSQL, there are already plans to implement it
or patches already submitted ?
If not both could someone give me some hints on how do it and where
"attach" the code like open the file in postmaster.c intercept the query
in that function etc.

Thank you in advance :)