From ecb0fd33720fab91df1207e85704f382f55e1eb7 Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nathan@postgresql.org>
Date: Wed, 13 Mar 2024 14:49:26 -0500
Subject: Reintroduce MAINTAIN privilege and pg_maintain predefined role.

Roles with MAINTAIN on a relation may run VACUUM, ANALYZE, REINDEX,
REFRESH MATERIALIZE VIEW, CLUSTER, and LOCK TABLE on the relation.
Roles with privileges of pg_maintain may run those same commands on
all relations.

This was previously committed for v16, but it was reverted in
commit 151c22deee due to concerns about search_path tricks that
could be used to escalate privileges to the table owner.  Commits
2af07e2f74, 59825d1639, and c7ea3f4229 resolved these concerns by
restricting search_path when running maintenance commands.

Bumps catversion.

Reviewed-by: Jeff Davis
Discussion: https://postgr.es/m/20240305161235.GA3478007%40nathanxps13
---
 src/backend/commands/cluster.c | 43 +++++++++++++++++++++++++++++++-----------
 1 file changed, 32 insertions(+), 11 deletions(-)

(limited to 'src/backend/commands/cluster.c')

diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c
index cea7c8ea368..c04886c4090 100644
--- a/src/backend/commands/cluster.c
+++ b/src/backend/commands/cluster.c
@@ -77,6 +77,7 @@ static void copy_table_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex,
 static List *get_tables_to_cluster(MemoryContext cluster_context);
 static List *get_tables_to_cluster_partitioned(MemoryContext cluster_context,
 											   Oid indexOid);
+static bool cluster_is_permitted_for_relation(Oid relid, Oid userid);
 
 
 /*---------------------------------------------------------------------------
@@ -144,7 +145,8 @@ cluster(ParseState *pstate, ClusterStmt *stmt, bool isTopLevel)
 		tableOid = RangeVarGetRelidExtended(stmt->relation,
 											AccessExclusiveLock,
 											0,
-											RangeVarCallbackOwnsTable, NULL);
+											RangeVarCallbackMaintainsTable,
+											NULL);
 		rel = table_open(tableOid, NoLock);
 
 		/*
@@ -362,8 +364,8 @@ cluster_rel(Oid tableOid, Oid indexOid, ClusterParams *params)
 	 */
 	if (recheck)
 	{
-		/* Check that the user still owns the relation */
-		if (!object_ownercheck(RelationRelationId, tableOid, save_userid))
+		/* Check that the user still has privileges for the relation */
+		if (!cluster_is_permitted_for_relation(tableOid, save_userid))
 		{
 			relation_close(OldHeap, AccessExclusiveLock);
 			goto out;
@@ -1619,7 +1621,7 @@ finish_heap_swap(Oid OIDOldHeap, Oid OIDNewHeap,
 
 
 /*
- * Get a list of tables that the current user owns and
+ * Get a list of tables that the current user has privileges on and
  * have indisclustered set.  Return the list in a List * of RelToCluster
  * (stored in the specified memory context), each one giving the tableOid
  * and the indexOid on which the table is already clustered.
@@ -1636,8 +1638,8 @@ get_tables_to_cluster(MemoryContext cluster_context)
 	List	   *rtcs = NIL;
 
 	/*
-	 * Get all indexes that have indisclustered set and are owned by
-	 * appropriate user.
+	 * Get all indexes that have indisclustered set and that the current user
+	 * has the appropriate privileges for.
 	 */
 	indRelation = table_open(IndexRelationId, AccessShareLock);
 	ScanKeyInit(&entry,
@@ -1651,7 +1653,7 @@ get_tables_to_cluster(MemoryContext cluster_context)
 
 		index = (Form_pg_index) GETSTRUCT(indexTuple);
 
-		if (!object_ownercheck(RelationRelationId, index->indrelid, GetUserId()))
+		if (!cluster_is_permitted_for_relation(index->indrelid, GetUserId()))
 			continue;
 
 		/* Use a permanent memory context for the result list */
@@ -1699,10 +1701,13 @@ get_tables_to_cluster_partitioned(MemoryContext cluster_context, Oid indexOid)
 		if (get_rel_relkind(indexrelid) != RELKIND_INDEX)
 			continue;
 
-		/* Silently skip partitions which the user has no access to. */
-		if (!object_ownercheck(RelationRelationId, relid, GetUserId()) &&
-			(!object_ownercheck(DatabaseRelationId, MyDatabaseId, GetUserId()) ||
-			 IsSharedRelation(relid)))
+		/*
+		 * It's possible that the user does not have privileges to CLUSTER the
+		 * leaf partition despite having such privileges on the partitioned
+		 * table.  We skip any partitions which the user is not permitted to
+		 * CLUSTER.
+		 */
+		if (!cluster_is_permitted_for_relation(relid, GetUserId()))
 			continue;
 
 		/* Use a permanent memory context for the result list */
@@ -1718,3 +1723,19 @@ get_tables_to_cluster_partitioned(MemoryContext cluster_context, Oid indexOid)
 
 	return rtcs;
 }
+
+/*
+ * Return whether userid has privileges to CLUSTER relid.  If not, this
+ * function emits a WARNING.
+ */
+static bool
+cluster_is_permitted_for_relation(Oid relid, Oid userid)
+{
+	if (pg_class_aclcheck(relid, userid, ACL_MAINTAIN) == ACLCHECK_OK)
+		return true;
+
+	ereport(WARNING,
+			(errmsg("permission denied to cluster \"%s\", skipping it",
+					get_rel_name(relid))));
+	return false;
+}
-- 
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