On 11/08/2024 12:41, Pavel Stehule wrote:
ne 11. 8. 2024 v 9:23 odesílatel Ayush Vatsa <ayushvatsa1...@gmail.com
<mailto:ayushvatsa1...@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.
--
Heikki Linnakangas
Neon (https://neon.tech)
