My 0.02€ to try to illustrate a possible private session variable based
implementation for this use case:
* Session starts
\c app
* app does SELECT setup_user('user-auth-key-data', 'some-other-blob')
SELECT setup_user('fjshdfjkshfjks', 'jklfsjfklsjfk');
** setup_user is SECURITY DEFINER to 'appadmin'
-- appadmin did:
CREATE FUNCTION setup_user(TEXT, TEXT)
RETURNS BOOLEAN SECURITY DEFINER AS $$
** 'appadmin' owns a variable IS_AUDITOR. Other roles have only read
access to it.
not sure how it is used afterwards... is it the same as USER_IS_AUDITOR?
** setup_user(...) does whatever expensive/slow work it has to do
... checks, updates, whatever
** setup_user sets USER_IS_AUDITOR var
-- declare a private session variable
DECLARE @user_is_auditor BOOLEAN PRIVATE;
-- set its value to whatever appropriate
SET @user_is_auditor = ???;
--- returns its value
RETURN @user_is_auditor;
$$ LANGUAGE xxx;
* Later RLS policies simply reference USER_IS_AUDITOR var. They don't
need to know the 'user-auth-key-data', or do whatever expensive
processing that it does.
-- appadmin did:
CREATE FUNCTION isUserAuditor()
RETURNS BOOLEAN SECURITY DEFINER AS $$
-- say variable is just confirmed if it exists already in session?
DECLARE @user_is_auditor BOOLEAN PRIVATE;
RETURN @user_is_auditor;
$$ LANGUAGE xxx;
* Other later triggers, etc, also reference USER_IS_AUDITOR
The variable is not directly referenced, one would have to call
isUserAuditor() to access the private session value, but then you can
GRANT/REVOKE whatever you want on the access function.
* User cannot make themselves an auditor by SETting USER_IS_AUDITOR
Indeed, the user cannot access the private variable, only appadmin can,
and probably root could.
The user could create its own private session variable @user_is_auditor,
or a public session variable of the same name. That would be distinct
variables which would not influence isUserAuditor which would use its own.
--
Fabien.
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