ne 11. 8. 2024 v 14:08 odesílatel Heikki Linnakangas <hlinnaka@iki.fi> napsal:
On 11/08/2024 12:41, Pavel Stehule wrote: > ne 11. 8. 2024 v 9:23 odesílatel Ayush Vatsa <ayushvatsa1810@gmail.com > <mailto:ayushvatsa1810@gmail.com>> napsal: > > Hi PostgreSQL Community, > > I have a scenario where I am working with two functions: one in SQL > and another in C, where the SQL function is a wrapper around C > function. Here’s an example: > > |CREATE OR REPLACE FUNCTION my_func(IN input text) RETURNS BIGINT AS > $$ DECLARE result BIGINT; BEGIN SELECT col2 INTO result FROM > my_func_extended(input); RETURN result; END; $$ LANGUAGE plpgsql; > CREATE OR REPLACE FUNCTION my_func_extended( IN input text, OUT col1 > text, OUT col2 BIGINT ) RETURNS SETOF record AS 'MODULE_PATHNAME', > 'my_func_extended' LANGUAGE C STRICT PARALLEL SAFE; | > > I need to prevent direct execution of |my_func_extended| from psql > while still allowing it to be called from within the wrapper > function |my_func|. > > I’m considering the following options: > > 1. Using GRANT/REVOKE in SQL to manage permissions. > 2. Adding a check in the C function to allow execution only if > |my_func| is in the call stack (previous parent or something), > and otherwise throwing an error. > > Is there an existing approach to achieve this, or would you > recommend a specific solution? > > You can use fmgr hook, and hold some variable as gate if your function > my_func_extended can be called > > https://pgpedia.info/f/fmgr_hook.html > <https://pgpedia.info/f/fmgr_hook.html> > > With this option, the execution of my_func_extended will be faster, but > all other execution will be little bit slower (due overhead of hook). > But the code probably will be more simpler than processing callback stack. > > plpgsql_check uses fmgr hook, and it is working well - just there can be > some surprises, when the hook is activated in different order against > function's execution, and then the FHET_END can be executed without > related FHET_START.
Sounds complicated. I would go with the GRANT approach. Make my_func() a SECURITY DEFINER function, and revoke access to my_func_extended() for all other roles.
Another option to consider is to not expose my_func_extended() at the SQL level in the first place, and rewrite my_func() in C. Dunno how complicated the logic in my_func() is, if that makes sense.
+1
The SPI API is not difficult, and this looks like best option
