Hello I confirmed, that setting search_path is indeed sometimes needed in case of SECURITY DEFINER routines that have SQL-standard bodies. See an example at the end of the letter.
I suggest the following paragraph to the documentation: Starting from PostgreSQL 14 SQL-standard bodies can be used in SQL-language functions. This form tracks dependencies between the function and objects used in the function body. However, there is still a possibility that such function calls other code that reacts to search path. Thus, as a best practice, SECURITY DEFINER functions with SQL-standard bodies should also override search_path. Best regards Erki Eessaar ************************* /*Table in the schema public.*/ CREATE TABLE public.A(a INTEGER PRIMARY KEY); /*Table in the schema pg_temp.*/ CREATE TABLE pg_temp.A(a INTEGER PRIMARY KEY); /*SECURITY DEFINER function without SQL-standard function body.*/ CREATE OR REPLACE FUNCTION f1 () RETURNS VOID AS $$ INSERT INTO A(a) VALUES (1); $$ LANGUAGE sql SECURITY DEFINER; /*SECURITY DEFINER function with SQL-standard function body that invokes the function without SQL-standard function body. It does not explicitly set the search path.*/ CREATE OR REPLACE FUNCTION f2 () RETURNS VOID LANGUAGE sql SECURITY DEFINER BEGIN ATOMIC SELECT f1(); END; /*SECURITY DEFINER function with SQL-standard function body that invokes the function without SQL-standard function body. It does explicitly set the search path.*/ CREATE OR REPLACE FUNCTION f2_secure () RETURNS VOID LANGUAGE sql SECURITY DEFINER SET search_path = public, pg_temp BEGIN ATOMIC SELECT f1(); END; SELECT f2(); SELECT * FROM public.A; /*Result 0 rows.*/ SELECT * FROM pg_temp.A; /*Result 1 row.*/ DELETE FROM pg_temp.A; SELECT f2_secure(); SELECT * FROM public.A; /*Result 1 row. SET search_path in the invoking function had an effect to the invoked function*/ SELECT * FROM pg_temp.A; /*Result 0 rows.*/ ________________________________ From: Bruce Momjian <br...@momjian.us> Sent: Wednesday, September 28, 2022 8:07 PM To: Erki Eessaar <erki.eess...@taltech.ee> Cc: pgsql-docs@lists.postgresql.org <pgsql-docs@lists.postgresql.org> Subject: Re: SQL-standard function bodies and creating SECURITY DEFINER routines securely On Tue, Aug 16, 2022 at 03:32:36PM -0400, Bruce Momjian wrote: > On Sat, Dec 25, 2021 at 02:36:27PM +0000, Erki Eessaar wrote: > > > > Hello > > > > PostgreSQL 14 added the feature: "Allow SQL-language functions and > > procedures > > to use SQL-standard function bodies." > > > > If I understand correctly, then in this case the system will track > > dependencies between tables and routines that use the tables. Thus, the > > SECURITY DEFINER routines that use the new approach do not require the > > following mitigation, i.e., SET search_path= is not needed. The following > > part > > of documentation does not mention this. > > > > https://www.postgresql.org/docs/current/sql-createfunction.html# > > SQL-CREATEFUNCTION-SECURITY > > > > [elephant] PostgreSQL: Documentation: 14: CREATE FUNCTION > > Overloading. PostgreSQL allows function overloading; that is, the > > same name can be used for several different functions so long as > > they have distinct input argument types.Whether or not you use > > it, > > this capability entails security precautions when calling > > functions > > in databases where some users mistrust other users; see Section > > 10.3.. Two functions are considered the same if they have the > > same > > ... > > www.postgresql.org<http://www.postgresql.org> > > I have written the attached patch to mention this issue about sql_body > functions. The doc patch was reverted based on feedback in this email thread: https://www.postgresql.org/message-id/flat/AM9PR01MB8268BF5E74E119828251FD34FE409%40AM9PR01MB8268.eurprd01.prod.exchangelabs.com If you think we should add new wording, please suggest it, thanks. -- Bruce Momjian <br...@momjian.us> https://momjian.us EDB https://enterprisedb.com Indecision is a decision. Inaction is an action. Mark Batterson
