On Wed, 2022-06-08 at 19:06 +0900, Etsuro Fujita wrote: > On Wed, Jun 8, 2022 at 2:51 PM Kyotaro Horiguchi <horikyota....@gmail.com> > wrote: > > At Wed, 08 Jun 2022 07:05:09 +0200, Laurenz Albe <laurenz.a...@cybertec.at> > > wrote in > > > diff --git a/doc/src/sgml/postgres-fdw.sgml > > > b/doc/src/sgml/postgres-fdw.sgml > > > index b43d0aecba..b4b7e36d28 100644 > > > --- a/doc/src/sgml/postgres-fdw.sgml > > > +++ b/doc/src/sgml/postgres-fdw.sgml > > > @@ -274,6 +274,14 @@ OPTIONS (ADD password_required 'false'); > > > but only for that table. > > > The default is <literal>false</literal>. > > > </para> > > > + > > > + <para> > > > + Note that <command>EXPLAIN</command> will be run on the remote > > > server > > > + at query planning time, <emphasis>before</emphasis> permissions > > > on the > > > + foreign table are checked. This is not a security problem, since > > > the > > > + subsequent error from the permission check will prevent the user > > > from > > > + seeing any of the resulting data. > > > + </para> > > > </listitem> > > > </varlistentry> > > > > Looks fine. I'd like to add something like "If needed, depriving > > unprivileged users of relevant user mappings will prevent such remote > > executions that happen at planning-time." > > I agree on that point; if the EXPLAIN done on the remote side is > really a problem, I think the user should revoke privileges from the > remote user specified in the user mapping, to prevent it. I’d rather > recommend granting to the remote user privileges consistent with those > granted to the local user.
I don't think that is better. Even if the local and remote privileges are consistent, you will get an error from the *remote* table access when trying to use a foreign table on which you don't have permissions. The above paragraph describes why. Note that the original complaint against oracle_fdw that led to this thread was just such a case. Yours, Laurenz Albe
