t=# create table sd(i int);
CREATE TABLE
t=# insert into sd select 1;
INSERT 0 1
t=# create user nr;
CREATE ROLE
t=# create function s() returns table (i int) as $$
begin
return query select * from sd;
end;
$$ language plpgsql security definer;
CREATE FUNCTION

-bash-4.2$ psql -U nr t
psql (9.3.14)
Type "help" for help.

t=> select * from sd;
ERROR:  permission denied for relation sd
t=> select * from s();
 i
---
 1
(1 row)