Re: Prevent object capture in CREATE/ALTER EXTENSION scripts

Hi all,

I tested the latest patch series for preventing object capture in
CREATE/ALTER EXTENSION scripts.
First, I was able to reproduce the reported issue. With f(varchar)
owned by the trusted role and an attacker-owned f(text) in the same
schema, the call f('abc') from the extension script resolved to the
attacker-owned function and returned ATTACKER FUNCTION.
I then tested patch 0001 alone. The behavior was unchanged, and the
extension script still resolved the call to ATTACKER FUNCTION.
After applying both patches, I repeated the test with the varchar
function owned by a superuser and the text function owned by a
non-superuser. This time, the extension was created successfully and
the result was:
SELECT * FROM test_ext.capture_result;
TRUSTED FUNCTION
I also checked the normal function calls outside the extension script:
f('abc'::varchar) -> TRUSTED FUNCTION
f('abc'::text) -> ATTACKER FUNCTION
f('abc') ->ATTACKER FUNCTION
So the normal function resolution behavior remains unchanged.
The regression tests added by the patch also passed successfully:
Overall, the patch worked as expected in my testing. The extension
script now selects the trusted candidate instead of the attacker-owned
candidate when both overloads are present.

Regards,
solai