Fix privilege checks in pg_stats_ext and pg_stats_ext_exprs.

The catalog view pg_stats_ext fails to consider privileges for
expression statistics.  The catalog view pg_stats_ext_exprs fails
to consider privileges and row-level security policies.  To fix,
restrict the data in these views to table owners or roles that
inherit privileges of the table owner.  It may be possible to apply
less restrictive privilege checks in some cases, but that is left
as a future exercise.  Furthermore, for pg_stats_ext_exprs, do not
return data for tables with row-level security enabled, as is
already done for pg_stats_ext.

On the back-branches, a fix-CVE-2024-4317.sql script is provided
that will install into the "share" directory.  This file can be
used to apply the fix to existing clusters.

Bumps catversion on 'master' branch only.

Reported-by: Lukas Fittl
Reviewed-by: Noah Misch, Tomas Vondra, Tom Lane
Security: CVE-2024-4317
Backpatch-through: 14

1 files changed, 4 insertions, 7 deletions

diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 2e61f6d74e7..53047cab5fc 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -305,12 +305,7 @@ CREATE VIEW pg_stats_ext WITH (security_barrier) AS
                             array_agg(base_frequency) AS most_common_base_freqs
                      FROM pg_mcv_list_items(sd.stxdmcv)
                    ) m ON sd.stxdmcv IS NOT NULL
-    WHERE NOT EXISTS
-              ( SELECT 1
-                FROM unnest(stxkeys) k
-                     JOIN pg_attribute a
-                          ON (a.attrelid = s.stxrelid AND a.attnum = k)
-                WHERE NOT has_column_privilege(c.oid, a.attnum, 'select') )
+    WHERE pg_has_role(c.relowner, 'USAGE')
     AND (c.relrowsecurity = false OR NOT row_security_active(c.oid));
 
 CREATE VIEW pg_stats_ext_exprs WITH (security_barrier) AS
@@ -380,7 +375,9 @@ CREATE VIEW pg_stats_ext_exprs WITH (security_barrier) AS
          JOIN LATERAL (
              SELECT unnest(pg_get_statisticsobjdef_expressions(s.oid)) AS expr,
                     unnest(sd.stxdexpr)::pg_statistic AS a
-         ) stat ON (stat.expr IS NOT NULL);
+         ) stat ON (stat.expr IS NOT NULL)
+    WHERE pg_has_role(c.relowner, 'USAGE')
+    AND (c.relrowsecurity = false OR NOT row_security_active(c.oid));
 
 -- unprivileged users may read pg_statistic_ext but not pg_statistic_ext_data
 REVOKE ALL ON pg_statistic_ext_data FROM public;