@extschema:name@ extends the existing @extschema@ feature so that
we can also insert the schema name of some required extension,
thus making cross-extension references robust even if they are in
different schemas.
However, this has the same hazard as @extschema@: if the schema
name is embedded literally in an installed object, rather than being
looked up once during extension script execution, then it's no longer
safe to relocate the other extension to another schema. To deal with
that without restricting things unnecessarily, add a "no_relocate"
option to extension control files. This allows an extension to
specify that it cannot handle relocation of some of its required
extensions, even if in themselves those extensions are relocatable.
We detect "no_relocate" requests of dependent extensions during
ALTER EXTENSION SET SCHEMA.
Regina Obe, reviewed by Sandro Santilli and myself
Discussion: https://postgr.es/m/003001d8f4ae$402282c0$c0678840$@pcorp.us
Previously, if an extension script did CREATE OR REPLACE and there was
an existing object not belonging to the extension, it would overwrite
the object and adopt it into the extension. This is problematic, first
because the overwrite is probably unintentional, and second because we
didn't change the object's ownership. Thus a hostile user could create
an object in advance of an expected CREATE EXTENSION command, and would
then have ownership rights on an extension object, which could be
modified for trojan-horse-type attacks.
Hence, forbid CREATE OR REPLACE of an existing object unless it already
belongs to the extension. (Note that we've always forbidden replacing
an object that belongs to some other extension; only the behavior for
previously-free-standing objects changes here.)
For the same reason, also fail CREATE IF NOT EXISTS when there is
an existing object that doesn't belong to the extension.
Our thanks to Sven Klemm for reporting this problem.
Security: CVE-2022-2625
ALTER TABLE commands in an extension script are added to an event
trigger command list; but starting with commit b5810de3f4 they do so in
a memory context that's too short-lived, so when execution ends and time
comes to use the entries, they've already been freed.
(This would also be a problem with ALTER TABLE commands in a
multi-command query string, but these serendipitously end in
PortalContext -- which probably explains why it took so long for this to
be reported.)
Fix by using the memory context specifically set for that, instead.
Backpatch to 13, where the aforementioned commit appeared.
Reported-by: Philippe Beaudoin
Author: Jehan-Guillaume de Rorthais <jgdr@dalibo.com>
Discussion: https://postgr.es/m/20200902193715.6e0269d4@firost
Attempting to use a temporary table within a two-phase transaction is
forbidden for ages. However, there have been uncovered grounds for
a couple of other object types and commands which work on temporary
objects with two-phase commit. In short, trying to create, lock or drop
an object on a temporary schema should not be authorized within a
two-phase transaction, as it would cause its state to create
dependencies with other sessions, causing all sorts of side effects with
the existing session or other sessions spawned later on trying to use
the same temporary schema name.
Regression tests are added to cover all the grounds found, the original
report mentioned function creation, but monitoring closer there are many
other patterns with LOCK, DROP or CREATE EXTENSION which are involved.
One of the symptoms resulting in combining both is that the session
which used the temporary schema is not able to shut down completely,
waiting for being able to drop the temporary schema, something that it
cannot complete because of the two-phase transaction involved with
temporary objects. In this case the client is able to disconnect but
the session remains alive on the backend-side, potentially blocking
connection backend slots from being used. Other problems reported could
also involve server crashes.
This is back-patched down to v10, which is where 9b013dc has introduced
MyXactFlags, something that this patch relies on.
Reported-by: Alexey Bashtanov
Author: Michael Paquier
Reviewed-by: Masahiko Sawada
Discussion: https://postgr.es/m/5d910e2e-0db8-ec06-dd5f-baec420513c3@imap.cc
Backpatch-through: 10
Must do pg_stat_clear_snapshot() inside test's loop, or our snapshot of
pg_stat_activity will never change :-(. Thinko in b3427dade -- evidently
my workstation never really iterated the loop in testing. Per buildfarm.
deleteWhatDependsOn() had grown an uncomfortably large number of
assumptions about what it's used for. There are actually only two minor
differences between what it does and what a regular performDeletion() call
can do, so let's invent additional bits in performDeletion's existing flags
argument that specify those behaviors, and get rid of deleteWhatDependsOn()
as such. (We'd probably have done it this way from the start, except that
performDeletion didn't originally have a flags argument, IIRC.)
Also, add a SKIP_EXTENSIONS flag bit that prevents ever recursing to an
extension, and use that when dropping temporary objects at session end.
This provides a more general solution to the problem addressed in a hacky
way in commit 08dd23cec: if an extension script creates temp objects and
forgets to remove them again, the whole extension went away when its
contained temp objects were deleted. The previous solution only covered
temp relations, but this solves it for all object types.
These changes require minor additions in dependency.c to pass the flags
to subroutines that previously didn't get them, but it's still a net
savings of code, and it seems cleaner than before.
Having done this, revert the special-case code added in 08dd23cec that
prevented addition of pg_depend records for temp table extension
membership, because that caused its own oddities: dropping an extension
that had created such a table didn't automatically remove the table,
leading to a failure if the table had another dependency on the extension
(such as use of an extension data type), or to a duplicate-name failure if
you then tried to recreate the extension. But we keep the part that
prevents the pg_temp_nnn schema from becoming an extension member; we never
want that to happen. Add a regression test case covering these behaviors.
Although this fixes some arguable bugs, we've heard few field complaints,
and any such problems are easily worked around by explicitly dropping temp
objects at the end of extension scripts (which seems like good practice
anyway). So I won't risk a back-patch.
Discussion: https://postgr.es/m/e51f4311-f483-4dd0-1ccc-abec3c405110@BlueTreble.com
Commit 08dd23cec introduced an exception to the rule that extension member
objects can only be dropped as part of dropping the whole extension,
intending to allow such drops while running the extension's own creation or
update scripts. However, the exception was only applied at the outermost
recursion level, because it was modeled on a pre-existing check to ignore
dependencies on objects listed in pendingObjects. Bug #14434 from Philippe
Beaudoin shows that this is inadequate: in some cases we can reach an
extension member object by recursion from another one. (The bug concerns
the serial-sequence case; I'm not sure if there are other cases, but there
might well be.)
To fix, revert 08dd23cec's changes to findDependentObjects() and instead
apply the creating_extension exception regardless of stack level.
Having seen this example, I'm a bit suspicious that the pendingObjects
logic is also wrong and such cases should likewise be allowed at any
recursion level. However, changing that would interact in subtle ways
with the recursion logic (at least it would need to be moved to after the
recursing-from check). Given that the code's been like that a long time,
I'll refrain from touching it without a clear example showing it's wrong.
Back-patch to all active branches. In HEAD and 9.6, where suitable
test infrastructure exists, add a regression test case based on the
bug report.
Report: <20161125151448.6529.33039@wrigleys.postgresql.org>
Discussion: <13224.1480177514@sss.pgh.pa.us>
For reasons of sheer brain fade, we (I) was calling systable_endscan()
immediately after systable_getnext() and expecting the tuple returned
by systable_getnext() to still be valid.
That's clearly wrong. Move the systable_endscan() down below the tuple
usage.
Discovered initially by Pavel Stehule and then also by Alvaro.
Add a regression test based on Alvaro's testing.
Without CASCADE, if an extension has an unfullfilled dependency on
another extension, CREATE EXTENSION ERRORs out with "required extension
... is not installed". That is annoying, especially when that dependency
is an implementation detail of the extension, rather than something the
extension's user can make sense of.
In addition to CASCADE this also includes a small set of regression
tests around CREATE EXTENSION.
Author: Petr Jelinek, editorialized by Michael Paquier, Andres Freund
Reviewed-By: Michael Paquier, Andres Freund, Jeff Janes
Discussion: 557E0520.3040800@2ndquadrant.com
