function working

grants_to_grant.sql

@@ -0,0 +1,9 @@
+-- grant execution on the function
+grant execute on function dba.passchanger(_password text) to dodger;
+
+-- only insert is needed to allow audit trace
+GRANT INSERT ON TABLE dba.pwdhistory TO dodger;
+
+-- the following permissions are necessary to change the 'VALID UNTIL' date
+grant select on pg_catalog.pg_authid to dodger ;
+grant update (rolvaliduntil) on pg_catalog.pg_authid to dodger ;

passchanger.sql

@@ -0,0 +1,54 @@
+
+-- Schema creation
+create schema dba ;
+
+-- password history table
+CREATE TABLE IF NOT EXISTS dba.pwdhistory
+(
+    usename character varying COLLATE pg_catalog."default",
+    password character varying COLLATE pg_catalog."default",
+    changed_on timestamp without time zone
+)
+TABLESPACE pg_default;
+
+ALTER TABLE IF EXISTS dba.pwdhistory
+    OWNER to postgres;
+
+
+-- the function
+CREATE OR REPLACE FUNCTION dba.passchanger(_password text)
+    RETURNS integer
+    LANGUAGE 'plpgsql'
+    COST 100
+    VOLATILE PARALLEL UNSAFE
+AS $BODY$
+declare
+   _min_password_length int := 8;  -- specify min length here
+   _usename text := '';
+begin
+   select user into _usename;
+   if length(_password) >= _min_password_length then
+      EXECUTE format('ALTER USER %I WITH PASSWORD %L', _usename, _password);
+   else  -- also catches NULL
+      -- raise custom error
+      raise exception 'Password too short!'
+      using errcode = '22023'  -- 22023 = "invalid_parameter_value'
+          , detail = 'Please check your password.'
+          , hint = 'Password must be at least ' || _min_password_length || ' characters.';
+   end if;
+   
+   insert into dba.pwdhistory
+          (usename, password, changed_on)
+   values (_usename, md5(_password),now());
+   EXECUTE format('update pg_catalog.pg_authid set rolvaliduntil=now() + interval ''120 days'' where rolname=''%I'' ', _usename);
+--   update pg_catalog.pg_authid 
+--         set rolvaliduntil='2021-12-30 00:00:00+01' where rolname='dodger' ;
+   return 0;
+exception
+   -- trap existing error and re-raise with added detail
+   when unique_violation then  -- = error code 23505   
+      raise unique_violation
+      using detail = 'Password already used earlier. Please try again with a different password.';
+end
+$BODY$;
+