Without any rationale as to why CREATE TEMP TABLEs checks the session
user in the archives, could we open this up for discussion again?


Well, let me put it this way: if you want to change the behavior you're going to have to work much harder than just reverting the prior patch.

IIRC the fundamental reason the code works that way is that
InitTempTableNamespace is done only once per session.  If it checks
against current_user rather than session_user then (a) the results will
be inconsistent, and (b) you create a different sort of security hole,
which is that if a setuid function is the first to try to create a temp
table in a particular session, then not-so-privileged functions will
still be able to create temp tables later in the session.

Hrm, I didn't realize that: points taken. Since temp schemas are always owned by the superuser, why aren't the ACL checks done when the temp relation is created as opposed to when the schema is created? I see what you're saying about things currently needing to use GetSessionuserId() instead of GetUserId(), but if a check for istemp is pushed down into DefineRelation(), then (from what I can tell) GetUserId() can be used in InitTempTableNamespace(). Object owners can only delete their objects, the temp schema can't be deleted as is because its owner is the superuser.


I think the attached patch addresses both of your concerns. Things are consistent in that SECURITY DEFINER/TEMP TABLEs will now work as expected. The security hole isn't an issue because security checks are applied both in InitTempTableNamespace() and DefineRelation().

At the moment, this behavior cripples the usefulness
of having a TEMP table be used as a trusted cache for data.

What exactly do you think makes a temp table suitable as a trusted cache? Or more suitable than non-temp tables?

Revoke all privs on temp tables except from the DBA, then setup functions to use the temp table as a way of maintaining state information across transactions (within the same session). It's a hack to get around the lack of server side variables. In many ways, actually, it works out better because I can wrap functions or PostgreSQL's permissions around the temp relations and get exactly the access that I need... far more fine grained than anything I could do with a GUC or some other server side MIB/variable implementation.


I don't really believe in the notion of restricting temp table creation
to setuid functions.  AFAICS the only reason for forbidding temp table
creation is to prevent a session from using any on-disk resources, and
that hardly works if it can still do so via calling setuid functions.

It can't populate or read data out of the temp relation though, which is ideal for my situation.


-sc
Index: catalog/namespace.c
===================================================================
RCS file: /projects/cvsroot/pgsql-server/src/backend/catalog/namespace.c,v
retrieving revision 1.63
diff -u -r1.63 namespace.c
--- catalog/namespace.c 13 Feb 2004 01:08:20 -0000      1.63
+++ catalog/namespace.c 29 Apr 2004 07:33:49 -0000
@@ -1639,12 +1639,8 @@
         * First, do permission check to see if we are authorized to make temp
         * tables.      We use a nonstandard error message here since
         * "databasename: permission denied" might be a tad cryptic.
-        *
-        * Note we apply the check to the session user, not the currently active
-        * userid, since we are not going to change our minds about temp table
-        * availability during the session.
         */
-       if (pg_database_aclcheck(MyDatabaseId, GetSessionUserId(),
+       if (pg_database_aclcheck(MyDatabaseId, GetUserId(),
                                                         ACL_CREATE_TEMP) != 
ACLCHECK_OK)
                ereport(ERROR,
                                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
Index: commands/tablecmds.c
===================================================================
RCS file: /projects/cvsroot/pgsql-server/src/backend/commands/tablecmds.c,v
retrieving revision 1.102
diff -u -r1.102 tablecmds.c
--- commands/tablecmds.c        1 Apr 2004 21:28:44 -0000       1.102
+++ commands/tablecmds.c        29 Apr 2004 07:33:49 -0000
@@ -165,8 +165,12 @@
        {
                AclResult       aclresult;
 
-               aclresult = pg_namespace_aclcheck(namespaceId, GetUserId(),
-                                                                                 
ACL_CREATE);
+               if (stmt->relation->istemp)
+                 aclresult = pg_namespace_aclcheck(MyDatabaseId, GetUserId(),
+                                                   ACL_CREATE_TEMP);
+               else
+                 aclresult = pg_namespace_aclcheck(namespaceId, GetUserId(),
+                                                   ACL_CREATE);
                if (aclresult != ACLCHECK_OK)
                        aclcheck_error(aclresult, ACL_KIND_NAMESPACE,
                                                   get_namespace_name(namespaceId));


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Sean Chittenden
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