Thread: Preventing non-superusers from altering session authorization
Hi all,
I briefly mentioned this issue in another mailing thread [0].
Currently, a user is allowed to execute SET SESSION AUTHORIZATION [1]
if the role they connected to PostgreSQL with was a superuser at the
time of connection. Even if the role is later altered to no longer be a
superuser, the session can still execute SET SESSION AUTHORIZATION, as
long as the session isn't disconnected. As a consequence, if that role
is altered to no longer be a superuser, then the user can use SET
SESSION AUTHORIZATION to switch to another role that is a superuser and
regain superuser privileges. They can even re-grant themselves the
superuser attribute.
It is possible that the user had already run SET SESSION AUTHORIZATION
to set their session to a superuser before their connecting role lost
the superuser attribute. In this case there's not much we can do.
Also, from looking at the code and documentation, it looks like SET
SESSION AUTHORIZATION works this way intentionally. However, I'm unable
to figure out why we'd want it to work this way.
I've attached a patch that would fix this issue by checking the catalog
to see if the connecting role is currently a superuser every time SET
SESSION AUTHORIZATION is run. However, according to the comment I
deleted there's something invalid about reading the catalog from that
function, though I wasn't able to understand it fully.
One downside is that if a user switches their session authorization to
some role, then loses the superuser attribute on their connecting role,
they may be stuck in a that role with no way to reset their session
authorization without disconnecting and reconnecting.
Thanks,
Joe Koshakow
[0] https://www.postgresql.org/message-id/CAAvxfHco7iGw4NarymhfLWN6PjzYRrbYFt2BnSFeSD5sFzqEJQ%40mail.gmail.com
[1] https://www.postgresql.org/docs/15/sql-set-session-authorization.html
Currently, a user is allowed to execute SET SESSION AUTHORIZATION [1]
if the role they connected to PostgreSQL with was a superuser at the
time of connection. Even if the role is later altered to no longer be a
superuser, the session can still execute SET SESSION AUTHORIZATION, as
long as the session isn't disconnected. As a consequence, if that role
is altered to no longer be a superuser, then the user can use SET
SESSION AUTHORIZATION to switch to another role that is a superuser and
regain superuser privileges. They can even re-grant themselves the
superuser attribute.
It is possible that the user had already run SET SESSION AUTHORIZATION
to set their session to a superuser before their connecting role lost
the superuser attribute. In this case there's not much we can do.
Also, from looking at the code and documentation, it looks like SET
SESSION AUTHORIZATION works this way intentionally. However, I'm unable
to figure out why we'd want it to work this way.
I've attached a patch that would fix this issue by checking the catalog
to see if the connecting role is currently a superuser every time SET
SESSION AUTHORIZATION is run. However, according to the comment I
deleted there's something invalid about reading the catalog from that
function, though I wasn't able to understand it fully.
One downside is that if a user switches their session authorization to
some role, then loses the superuser attribute on their connecting role,
they may be stuck in a that role with no way to reset their session
authorization without disconnecting and reconnecting.
Thanks,
Joe Koshakow
[0] https://www.postgresql.org/message-id/CAAvxfHco7iGw4NarymhfLWN6PjzYRrbYFt2BnSFeSD5sFzqEJQ%40mail.gmail.com
[1] https://www.postgresql.org/docs/15/sql-set-session-authorization.html
Attachment
On Wed, Jun 21, 2023 at 04:28:43PM -0400, Joseph Koshakow wrote: > Currently, a user is allowed to execute SET SESSION AUTHORIZATION [1] > if the role they connected to PostgreSQL with was a superuser at the > time of connection. Even if the role is later altered to no longer be a > superuser, the session can still execute SET SESSION AUTHORIZATION, as > long as the session isn't disconnected. As a consequence, if that role > is altered to no longer be a superuser, then the user can use SET > SESSION AUTHORIZATION to switch to another role that is a superuser and > regain superuser privileges. They can even re-grant themselves the > superuser attribute. I suspect most users aren't changing the superuser attribute on roles very often, so it's unlikely to be a problem. But it might still be worth revisiting. > It is possible that the user had already run SET SESSION AUTHORIZATION > to set their session to a superuser before their connecting role lost > the superuser attribute. In this case there's not much we can do. Right. > Also, from looking at the code and documentation, it looks like SET > SESSION AUTHORIZATION works this way intentionally. However, I'm unable > to figure out why we'd want it to work this way. I found a brief mention in the archives about this implementation decision [0], but I don't think it explains the reasoning. > I've attached a patch that would fix this issue by checking the catalog > to see if the connecting role is currently a superuser every time SET > SESSION AUTHORIZATION is run. However, according to the comment I > deleted there's something invalid about reading the catalog from that > function, though I wasn't able to understand it fully. This comment was added in e5d6b91. I see that RESET SESSION AUTHORIZATION with a concurrently dropped role will FATAL with your patch but succeed without it, which could be part of the reason. > One downside is that if a user switches their session authorization to > some role, then loses the superuser attribute on their connecting role, > they may be stuck in a that role with no way to reset their session > authorization without disconnecting and reconnecting. It looks like SetSessionAuthorization() skips the privilege checks if the target role is the authenticated role, so I don't think they'll get stuck. [0] https://postgr.es/m/Pine.LNX.4.30.0104182119290.762-100000%40peter.localdomain -- Nathan Bossart Amazon Web Services: https://aws.amazon.com
On Wed, Jun 21, 2023 at 04:28:43PM -0400, Joseph Koshakow wrote:
> + roleTup = SearchSysCache1(AUTHOID, ObjectIdGetDatum(AuthenticatedUserId));
> + if (!HeapTupleIsValid(roleTup))
> + ereport(FATAL,
> + (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
> + errmsg("role with OID %u does not exist", AuthenticatedUserId)));
> + rform = (Form_pg_authid) GETSTRUCT(roleTup);
I think "superuser_arg(AuthenticatedUserId)" would work here.
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
On Wed, Jun 21, 2023 at 11:48 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
>
> On Wed, Jun 21, 2023 at 04:28:43PM -0400, Joseph Koshakow wrote:
> > + roleTup = SearchSysCache1(AUTHOID, ObjectIdGetDatum(AuthenticatedUserId));
> > + if (!HeapTupleIsValid(roleTup))
> > + ereport(FATAL,
> > + (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
> > + errmsg("role with OID %u does not exist", AuthenticatedUserId)));
> > + rform = (Form_pg_authid) GETSTRUCT(roleTup);
>
> I think "superuser_arg(AuthenticatedUserId)" would work here.
Yep, that worked. I've attached a patch with this change.
> I see that RESET SESSION AUTHORIZATION
> with a concurrently dropped role will FATAL with your patch but succeed
> without it, which could be part of the reason.
That might be a good change? If the original authenticated role ID no
longer exists then we may want to return an error when trying to set
your session authorization to that role.
Thanks,
Joe Koshakow
Attachment
Hi,
I’ve just stumbled upon this patch and thread and thought I could share an idea of adding an optional temporary secret to SET SESSION AUTHORIZATION so that it is only possible to RESET SESSION AUTHORIZATION by providing the same secret ,like:
SET SESSION AUTHORIZATION [role] GUARDED BY ‘[secret]’;
...
RESET SESSION AUTHORIZATION WITH ‘[secret]’;
The use case is: I have a set of Liquibase scripts I would like to execute as a different role each and make sure they cannot escape the sandbox.
As I am not a Postgres hacker I wonder how difficult to implement it might be…
Thanks,
Michal
On 23 Jun 2023, at 00:39, Joseph Koshakow <koshy44@gmail.com> wrote:<v2-0001-Prevent-non-superusers-from-altering-session-auth.patch>
On Wed, Jun 21, 2023 at 11:48 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
>
> On Wed, Jun 21, 2023 at 04:28:43PM -0400, Joseph Koshakow wrote:
> > + roleTup = SearchSysCache1(AUTHOID, ObjectIdGetDatum(AuthenticatedUserId));
> > + if (!HeapTupleIsValid(roleTup))
> > + ereport(FATAL,
> > + (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
> > + errmsg("role with OID %u does not exist", AuthenticatedUserId)));
> > + rform = (Form_pg_authid) GETSTRUCT(roleTup);
>
> I think "superuser_arg(AuthenticatedUserId)" would work here.
Yep, that worked. I've attached a patch with this change.
> I see that RESET SESSION AUTHORIZATION
> with a concurrently dropped role will FATAL with your patch but succeed
> without it, which could be part of the reason.
That might be a good change? If the original authenticated role ID no
longer exists then we may want to return an error when trying to set
your session authorization to that role.
Thanks,
Joe Koshakow
On Thu, Jun 22, 2023 at 06:39:45PM -0400, Joseph Koshakow wrote:
> On Wed, Jun 21, 2023 at 11:48 PM Nathan Bossart <nathandbossart@gmail.com>
> wrote:
>> I see that RESET SESSION AUTHORIZATION
>> with a concurrently dropped role will FATAL with your patch but succeed
>> without it, which could be part of the reason.
>
> That might be a good change? If the original authenticated role ID no
> longer exists then we may want to return an error when trying to set
> your session authorization to that role.
I was curious why we don't block DROP ROLE if there are active sessions for
the role or terminate any such sessions as part of the command, and I found
this discussion from 2016:
https://postgr.es/m/flat/56E87CD8.60007%40ohmu.fi
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
>> That might be a good change? If the original authenticated role ID no
>> longer exists then we may want to return an error when trying to set
>> your session authorization to that role.
>
> I was curious why we don't block DROP ROLE if there are active sessions for
> the role or terminate any such sessions as part of the command, and I found
> this discussion from 2016:
>
> https://postgr.es/m/flat/56E87CD8.60007%40ohmu.fi
Ah, that makes sense that we don't prevent DROP ROLE on active roles.
Though, we do error when you try and set your role or session
authorization to a dropped role. So erroring on RESET SESSION
AUTHORIZATION when the original role is dropped makes it consistent
with SET SESSION AUTHORIZATION TO <dropped-original-role>. On the other
hand it makes it inconsistent with RESET ROLE, which does not error on
a dropped role.
- Joe Koshakow
>> longer exists then we may want to return an error when trying to set
>> your session authorization to that role.
>
> I was curious why we don't block DROP ROLE if there are active sessions for
> the role or terminate any such sessions as part of the command, and I found
> this discussion from 2016:
>
> https://postgr.es/m/flat/56E87CD8.60007%40ohmu.fi
Ah, that makes sense that we don't prevent DROP ROLE on active roles.
Though, we do error when you try and set your role or session
authorization to a dropped role. So erroring on RESET SESSION
AUTHORIZATION when the original role is dropped makes it consistent
with SET SESSION AUTHORIZATION TO <dropped-original-role>. On the other
hand it makes it inconsistent with RESET ROLE, which does not error on
a dropped role.
- Joe Koshakow
On Fri, Jun 23, 2023 at 1:54 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
On Thu, Jun 22, 2023 at 06:39:45PM -0400, Joseph Koshakow wrote:
> On Wed, Jun 21, 2023 at 11:48 PM Nathan Bossart <nathandbossart@gmail.com>
> wrote:
>> I see that RESET SESSION AUTHORIZATION
>> with a concurrently dropped role will FATAL with your patch but succeed
>> without it, which could be part of the reason.
>
> That might be a good change? If the original authenticated role ID no
> longer exists then we may want to return an error when trying to set
> your session authorization to that role.
I was curious why we don't block DROP ROLE if there are active sessions for
the role or terminate any such sessions as part of the command, and I found
this discussion from 2016:
https://postgr.es/m/flat/56E87CD8.60007%40ohmu.fi
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
Nathan Bossart <nathandbossart@gmail.com> wrote:
> I see that RESET SESSION AUTHORIZATION
> with a concurrently dropped role will FATAL with your patch but succeed
> without it, which could be part of the reason.
I didn't even realize it, but the change to superuser_arg() in v2 fixed
this issue. The catalog lookup is only done if
userid != AuthenticatedUserId. So RESET SESSION AUTHORIZATION with a
concurrently dropped role will no longer FATAL.
Thanks,
Joe
> I see that RESET SESSION AUTHORIZATION
> with a concurrently dropped role will FATAL with your patch but succeed
> without it, which could be part of the reason.
I didn't even realize it, but the change to superuser_arg() in v2 fixed
this issue. The catalog lookup is only done if
userid != AuthenticatedUserId. So RESET SESSION AUTHORIZATION with a
concurrently dropped role will no longer FATAL.
Thanks,
Joe
On Sat, Jul 1, 2023 at 11:33 AM Joseph Koshakow <koshy44@gmail.com> wrote:
>> That might be a good change? If the original authenticated role ID no
>> longer exists then we may want to return an error when trying to set
>> your session authorization to that role.
>
> I was curious why we don't block DROP ROLE if there are active sessions for
> the role or terminate any such sessions as part of the command, and I found
> this discussion from 2016:
>
> https://postgr.es/m/flat/56E87CD8.60007%40ohmu.fi
Ah, that makes sense that we don't prevent DROP ROLE on active roles.
Though, we do error when you try and set your role or session
authorization to a dropped role. So erroring on RESET SESSION
AUTHORIZATION when the original role is dropped makes it consistent
with SET SESSION AUTHORIZATION TO <dropped-original-role>. On the other
hand it makes it inconsistent with RESET ROLE, which does not error on
a dropped role.
- Joe KoshakowOn Fri, Jun 23, 2023 at 1:54 PM Nathan Bossart <nathandbossart@gmail.com> wrote:On Thu, Jun 22, 2023 at 06:39:45PM -0400, Joseph Koshakow wrote:
> On Wed, Jun 21, 2023 at 11:48 PM Nathan Bossart <nathandbossart@gmail.com>
> wrote:
>> I see that RESET SESSION AUTHORIZATION
>> with a concurrently dropped role will FATAL with your patch but succeed
>> without it, which could be part of the reason.
>
> That might be a good change? If the original authenticated role ID no
> longer exists then we may want to return an error when trying to set
> your session authorization to that role.
I was curious why we don't block DROP ROLE if there are active sessions for
the role or terminate any such sessions as part of the command, and I found
this discussion from 2016:
https://postgr.es/m/flat/56E87CD8.60007%40ohmu.fi
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
I've discovered an issue with this approach. Let's say you have some
session open that is connected as a superuser and you run the following commands:
- CREATE ROLE r1 LOGIN SUPERUSER;
- CREATE ROLE r2;
- CREATE ROLE r3;
Then you open another session connected with user r1 and run the
following commands:
- SET SESSION AUTHROIZATION r2;
- BEGIN;
- SET SESSION AUTHORIZATION r3;
Then in your original session run:
- ALTER ROLE r1 NOSUPERUSER;
Finally in the r1 session run:
- CREATE TABLE t ();
Postgres will then panic with the following logs:
2023-07-08 16:33:27.787 EDT [157141] ERROR: permission denied for schema public at character 14
2023-07-08 16:33:27.787 EDT [157141] STATEMENT: CREATE TABLE t ();
2023-07-08 16:33:27.787 EDT [157141] ERROR: permission denied to set session authorization
2023-07-08 16:33:27.787 EDT [157141] WARNING: AbortTransaction while in ABORT state
2023-07-08 16:33:27.787 EDT [157141] ERROR: permission denied to set session authorization
2023-07-08 16:33:27.787 EDT [157141] WARNING: AbortTransaction while in ABORT state
2023-07-08 16:33:27.787 EDT [157141] ERROR: permission denied to set session authorization
2023-07-08 16:33:27.787 EDT [157141] WARNING: AbortTransaction while in ABORT state
2023-07-08 16:33:27.787 EDT [157141] ERROR: permission denied to set session authorization
2023-07-08 16:33:27.787 EDT [157141] PANIC: ERRORDATA_STACK_SIZE exceeded
2023-07-08 16:33:27.882 EDT [156878] LOG: server process (PID 157141) was terminated by signal 6: Aborted
2023-07-08 16:33:27.882 EDT [156878] DETAIL: Failed process was running: CREATE TABLE t ();
I think the issue here is that if a session loses the ability to set
their session authorization in the middle of a transaction, then
rolling back the transaction may fail and cause the server to panic.
That's probably what the deleted comment mean when it said:
> * It's OK because the check does not require catalog access and can't
session open that is connected as a superuser and you run the following commands:
- CREATE ROLE r1 LOGIN SUPERUSER;
- CREATE ROLE r2;
- CREATE ROLE r3;
Then you open another session connected with user r1 and run the
following commands:
- SET SESSION AUTHROIZATION r2;
- BEGIN;
- SET SESSION AUTHORIZATION r3;
Then in your original session run:
- ALTER ROLE r1 NOSUPERUSER;
Finally in the r1 session run:
- CREATE TABLE t ();
Postgres will then panic with the following logs:
2023-07-08 16:33:27.787 EDT [157141] ERROR: permission denied for schema public at character 14
2023-07-08 16:33:27.787 EDT [157141] STATEMENT: CREATE TABLE t ();
2023-07-08 16:33:27.787 EDT [157141] ERROR: permission denied to set session authorization
2023-07-08 16:33:27.787 EDT [157141] WARNING: AbortTransaction while in ABORT state
2023-07-08 16:33:27.787 EDT [157141] ERROR: permission denied to set session authorization
2023-07-08 16:33:27.787 EDT [157141] WARNING: AbortTransaction while in ABORT state
2023-07-08 16:33:27.787 EDT [157141] ERROR: permission denied to set session authorization
2023-07-08 16:33:27.787 EDT [157141] WARNING: AbortTransaction while in ABORT state
2023-07-08 16:33:27.787 EDT [157141] ERROR: permission denied to set session authorization
2023-07-08 16:33:27.787 EDT [157141] PANIC: ERRORDATA_STACK_SIZE exceeded
2023-07-08 16:33:27.882 EDT [156878] LOG: server process (PID 157141) was terminated by signal 6: Aborted
2023-07-08 16:33:27.882 EDT [156878] DETAIL: Failed process was running: CREATE TABLE t ();
I think the issue here is that if a session loses the ability to set
their session authorization in the middle of a transaction, then
rolling back the transaction may fail and cause the server to panic.
That's probably what the deleted comment mean when it said:
> * It's OK because the check does not require catalog access and can't
> * fail during an end-of-transaction GUC reversion
Interestingly, if the r1 session manually types `ROLLBACK` instead of
executing a command that fails, then everything is fine and there's no
panic. I'm not familiar enough with transaction handling to know why
there would be a difference there.
executing a command that fails, then everything is fine and there's no
panic. I'm not familiar enough with transaction handling to know why
there would be a difference there.
Thanks,
Joe Koshakow
On Sat, Jul 08, 2023 at 04:44:06PM -0400, Joseph Koshakow wrote: > 2023-07-08 16:33:27.787 EDT [157141] PANIC: ERRORDATA_STACK_SIZE exceeded > 2023-07-08 16:33:27.882 EDT [156878] LOG: server process (PID 157141) was > terminated by signal 6: Aborted > 2023-07-08 16:33:27.882 EDT [156878] DETAIL: Failed process was running: > CREATE TABLE t (); > > I think the issue here is that if a session loses the ability to set > their session authorization in the middle of a transaction, then > rolling back the transaction may fail and cause the server to panic. > That's probably what the deleted comment mean when it said: > >> * It's OK because the check does not require catalog access and can't >> * fail during an end-of-transaction GUC reversion Yeah. IIUC the ERROR longjmps to a block that calls AbortTransaction(), which ERRORs again when resetting the session authorization, which causes us to call AbortTransaction() again, etc., etc. > Interestingly, if the r1 session manually types `ROLLBACK` instead of > executing a command that fails, then everything is fine and there's no > panic. I'm not familiar enough with transaction handling to know why > there would be a difference there. I haven't had a chance to dig into this one yet, but that is indeed interesting. -- Nathan Bossart Amazon Web Services: https://aws.amazon.com
On Sat, Jul 8, 2023 at 6:09 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
>> I think the issue here is that if a session loses the ability to set
>> their session authorization in the middle of a transaction, then
>> rolling back the transaction may fail and cause the server to panic.
>> That's probably what the deleted comment mean when it said:
>>
>>> * It's OK because the check does not require catalog access and can't
>>> * fail during an end-of-transaction GUC reversion
>
> Yeah. IIUC the ERROR longjmps to a block that calls AbortTransaction(),
> which ERRORs again when resetting the session authorization, which causes
> us to call AbortTransaction() again, etc., etc.
Everything seems to work fine if the privilege check is moved to
check_session_authorization. Which is maybe what the comment meant
instead of assign_session_authorization.
I've attached a patch with this change.
Thanks,
Joe Koshakow
Attachment
On Sat, Jul 08, 2023 at 07:08:35PM -0400, Joseph Koshakow wrote:
> On Sat, Jul 8, 2023 at 6:09 PM Nathan Bossart <nathandbossart@gmail.com>
> wrote:
>
>>> I think the issue here is that if a session loses the ability to set
>>> their session authorization in the middle of a transaction, then
>>> rolling back the transaction may fail and cause the server to panic.
>>> That's probably what the deleted comment mean when it said:
>>>
>>>> * It's OK because the check does not require catalog access and can't
>>>> * fail during an end-of-transaction GUC reversion
>>
>> Yeah. IIUC the ERROR longjmps to a block that calls AbortTransaction(),
>> which ERRORs again when resetting the session authorization, which causes
>> us to call AbortTransaction() again, etc., etc.
src/backend/utils/misc/README has the following relevant text:
Note that there is no provision for a failure result code. assign_hooks
should never fail except under the most dire circumstances, since a failure
may for example result in GUC settings not being rolled back properly during
transaction abort. In general, try to do anything that could conceivably
fail in a check_hook instead, and pass along the results in an "extra"
struct, so that the assign hook has little to do beyond copying the data to
someplace. This applies particularly to catalog lookups: any required
lookups must be done in the check_hook, since the assign_hook may be
executed during transaction rollback when lookups will be unsafe.
> Everything seems to work fine if the privilege check is moved to
> check_session_authorization. Which is maybe what the comment meant
> instead of assign_session_authorization.
Ah, that does make more sense.
I think we should split this into two patches: one to move the permission
check to check_session_authorization() and another for the behavior change.
I've attached an attempt at the first one (that borrows heavily from your
latest patch). AFAICT the only reason that the permission check lives in
SetSessionAuthorization() is because AuthenticatedUserIsSuperuser is static
to miscinit.c and doesn't have an accessor function. I added one, but it
would probably just be removed by the following patch. WDYT?
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
Attachment
On Sun, Jul 9, 2023 at 12:47 AM Nathan Bossart <nathandbossart@gmail.com> wrote:
> I think we should split this into two patches: one to move the permission
> check to check_session_authorization() and another for the behavior change.
> I've attached an attempt at the first one (that borrows heavily from your
> latest patch). AFAICT the only reason that the permission check lives in
> SetSessionAuthorization() is because AuthenticatedUserIsSuperuser is static
> to miscinit.c and doesn't have an accessor function. I added one, but it
> would probably just be removed by the following patch. WDYT?
I think that's a good idea. We could even keep around the accessor
function as a good place to bundle the calls to
Assert(OidIsValid(AuthenticatedUserId))
and
superuser_arg(AuthenticatedUserId)
> * Only a superuser may set auth ID to something other than himself
Is "auth ID" the right term here? Maybe something like "Only a
superuser may set their session authorization/ID to something other
than their authenticated ID."
> But we set the GUC variable
> * is_superuser to indicate whether the *current* session userid is a
> * superuser.
Just a small correction here, I believe the is_superuser GUC is meant
to indicate whether the current user id is a superuser, not the current
session user id. We only update is_superuser in SetSessionAuthorization
because we are also updating the current user id in SetSessionUserId.
For example,
test=# CREATE ROLE r1 SUPERUSER;
CREATE ROLE
test=# CREATE ROLE r2;
CREATE ROLE
test=# SET SESSION AUTHORIZATION r1;
SET
test=# SET ROLE r2;
SET
test=> SELECT session_user, current_user;
session_user | current_user
--------------+--------------
r1 | r2
(1 row)
test=> SHOW is_superuser;
is_superuser
--------------
off
(1 row)
Which has also made me realize that the comment on is_superuser in
guc_tables.c is incorrect:
> /* Not for general use --- used by SET SESSION AUTHORIZATION */
Additionally the C variable name for is_superuser is fairly misleading:
> session_auth_is_superuser
The documentation for this GUC in show.sgml is correct:
> True if the current role has superuser privileges.
As an aside, I'm starting to think we should consider removing this
GUC. It sometimes reports an incorrect value [0], and potentially is
not used internally for anything.
I've rebased my changes over your patch and attached them both.
[0] https://www.postgresql.org/message-id/CAAvxfHcxH-hLndty6CRThGXL1hLsgCn%2BE3QuG_4Qi7GxrHmgKg%40mail.gmail.com
Attachment
On Sun, Jul 9, 2023 at 1:03 PM Joseph Koshakow <koshy44@gmail.com> wrote:
>> * Only a superuser may set auth ID to something other than himself
> Is "auth ID" the right term here? Maybe something like "Only a
> superuser may set their session authorization/ID to something other
> than their authenticated ID."
>> But we set the GUC variable
>> * is_superuser to indicate whether the *current* session userid is a
>> * superuser.
> Just a small correction here, I believe the is_superuser GUC is meant
> to indicate whether the current user id is a superuser, not the current
> session user id. We only update is_superuser in SetSessionAuthorization
> because we are also updating the current user id in SetSessionUserId.
I just realized that you moved this comment from
SetSessionAuthorization. I think we should leave the part about setting
the GUC variable is_superuser on top of SetSessionAuthorization since
that's where we actually set the GUC.
Thanks,
Joe Koshakow
>> * Only a superuser may set auth ID to something other than himself
> Is "auth ID" the right term here? Maybe something like "Only a
> superuser may set their session authorization/ID to something other
> than their authenticated ID."
>> But we set the GUC variable
>> * is_superuser to indicate whether the *current* session userid is a
>> * superuser.
> Just a small correction here, I believe the is_superuser GUC is meant
> to indicate whether the current user id is a superuser, not the current
> session user id. We only update is_superuser in SetSessionAuthorization
> because we are also updating the current user id in SetSessionUserId.
I just realized that you moved this comment from
SetSessionAuthorization. I think we should leave the part about setting
the GUC variable is_superuser on top of SetSessionAuthorization since
that's where we actually set the GUC.
Thanks,
Joe Koshakow
On Sun, Jul 09, 2023 at 08:54:30PM -0400, Joseph Koshakow wrote: > I just realized that you moved this comment from > SetSessionAuthorization. I think we should leave the part about setting > the GUC variable is_superuser on top of SetSessionAuthorization since > that's where we actually set the GUC. Okay. Here's a new patch set in which I believe I've addressed all feedback. I didn't keep the GetAuthenticatedUserIsSuperuser() helper function around, as I didn't see a strong need for it. And I haven't touched the "is_superuser" GUC, either. I figured we can take up any changes for it in the other thread. -- Nathan Bossart Amazon Web Services: https://aws.amazon.com
Attachment
On Mon, Jul 10, 2023 at 4:32 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
> Okay. Here's a new patch set in which I believe I've addressed all
> feedback. I didn't keep the GetAuthenticatedUserIsSuperuser() helper
> function around, as I didn't see a strong need for it.
Thanks, I think the patch set looks good to go!
> And I haven't
> touched the "is_superuser" GUC, either. I figured we can take up any
> changes for it in the other thread.
Yeah, I think that makes sense.
Thanks,
Joe Koshakow
> Okay. Here's a new patch set in which I believe I've addressed all
> feedback. I didn't keep the GetAuthenticatedUserIsSuperuser() helper
> function around, as I didn't see a strong need for it.
Thanks, I think the patch set looks good to go!
> And I haven't
> touched the "is_superuser" GUC, either. I figured we can take up any
> changes for it in the other thread.
Yeah, I think that makes sense.
Thanks,
Joe Koshakow
On Mon, Jul 10, 2023 at 04:46:07PM -0400, Joseph Koshakow wrote: > Thanks, I think the patch set looks good to go! Great. I'm going to wait a few more days in case anyone has additional feedback, but otherwise I intend to commit this shortly. -- Nathan Bossart Amazon Web Services: https://aws.amazon.com
On Mon, Jul 10, 2023 at 01:49:55PM -0700, Nathan Bossart wrote: > Great. I'm going to wait a few more days in case anyone has additional > feedback, but otherwise I intend to commit this shortly. I've committed 0001 for now. I'm hoping to commit the other two patches within the next couple of days. -- Nathan Bossart Amazon Web Services: https://aws.amazon.com
On Wed, Jul 12, 2023 at 09:37:57PM -0700, Nathan Bossart wrote: > On Mon, Jul 10, 2023 at 01:49:55PM -0700, Nathan Bossart wrote: >> Great. I'm going to wait a few more days in case anyone has additional >> feedback, but otherwise I intend to commit this shortly. > > I've committed 0001 for now. I'm hoping to commit the other two patches > within the next couple of days. Committed. I dwelled on whether to proceed with this change because it doesn't completely solve the originally-stated problem; i.e., a role that has changed its session authorization before losing superuser can still take advantage of the privileges of the target role, which might include reaquiring superuser. However, I think SET ROLE is subject to basically the same problem, and I'd argue that this change is strictly an improvement, if for no other reason than it makes SET SESSION AUTHORIZATION more consistent with SET ROLE. -- Nathan Bossart Amazon Web Services: https://aws.amazon.com