Fix mishandling of column-level SELECT privileges for join aliases.

scanNSItemForColumn, expandNSItemAttrs, and ExpandSingleTable would
pass the wrong RTE to markVarForSelectPriv when dealing with a join
ParseNamespaceItem: they'd pass the join RTE, when what we need to
mark is the base table that the join column came from.  The end
result was to not fill the base table's selectedCols bitmap correctly,
resulting in an understatement of the set of columns that are read
by the query.  The executor would still insist on there being at
least one selectable column; but with a correctly crafted query,
a user having SELECT privilege on just one column of a table would
nonetheless be allowed to read all its columns.

To fix, make markRTEForSelectPriv fetch the correct RTE for itself,
ignoring the possibly-mismatched RTE passed by the caller.  Later,
we'll get rid of some now-unused RTE arguments, but that risks
API breaks so we won't do it in released branches.

This problem was introduced by commit 9ce77d75c, so back-patch
to v13 where that came in.  Thanks to Sven Klemm for reporting
the problem.

Security: CVE-2021-20229

diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index b875a506463f813def8fc1227fb80731b675bb3f..af43a62cb2562b6b716daa99ae2b92ddc5210ce7 100644 (file)
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -68,7 +68,7 @@ static int    scanRTEForColumn(ParseState *pstate, RangeTblEntry *rte,
                             const char *colname, int location,
                             int fuzzy_rte_penalty,
                             FuzzyAttrMatchState *fuzzystate);
-static void markRTEForSelectPriv(ParseState *pstate, RangeTblEntry *rte,
+static void markRTEForSelectPriv(ParseState *pstate,
                                 int rtindex, AttrNumber col);
 static void expandRelation(Oid relid, Alias *eref,
                           int rtindex, int sublevels_up,
@@ -660,8 +660,8 @@ updateFuzzyAttrMatchState(int fuzzy_rte_penalty,
  *   If found, return an appropriate Var node, else return NULL.
  *   If the name proves ambiguous within this nsitem, raise error.
  *
- * Side effect: if we find a match, mark the item's RTE as requiring read
- * access for the column.
+ * Side effect: if we find a match, mark the corresponding RTE as requiring
+ * read access for the column.
  */
 Node *
 scanNSItemForColumn(ParseState *pstate, ParseNamespaceItem *nsitem,
@@ -990,21 +990,15 @@ searchRangeTableForCol(ParseState *pstate, const char *alias, const char *colnam
 
 /*
  * markRTEForSelectPriv
- *    Mark the specified column of an RTE as requiring SELECT privilege
+ *    Mark the specified column of the RTE with index rtindex
+ *    as requiring SELECT privilege
  *
  * col == InvalidAttrNumber means a "whole row" reference
- *
- * External callers should always pass the Var's RTE.  Internally, we
- * allow NULL to be passed for the RTE and then look it up if needed;
- * this takes less code than requiring each internal recursion site
- * to perform a lookup.
  */
 static void
-markRTEForSelectPriv(ParseState *pstate, RangeTblEntry *rte,
-                    int rtindex, AttrNumber col)
+markRTEForSelectPriv(ParseState *pstate, int rtindex, AttrNumber col)
 {
-   if (rte == NULL)
-       rte = rt_fetch(rtindex, pstate->p_rtable);
+   RangeTblEntry *rte = rt_fetch(rtindex, pstate->p_rtable);
 
    if (rte->rtekind == RTE_RELATION)
    {
@@ -1036,13 +1030,13 @@ markRTEForSelectPriv(ParseState *pstate, RangeTblEntry *rte,
            {
                int         varno = ((RangeTblRef *) j->larg)->rtindex;
 
-               markRTEForSelectPriv(pstate, NULL, varno, InvalidAttrNumber);
+               markRTEForSelectPriv(pstate, varno, InvalidAttrNumber);
            }
            else if (IsA(j->larg, JoinExpr))
            {
                int         varno = ((JoinExpr *) j->larg)->rtindex;
 
-               markRTEForSelectPriv(pstate, NULL, varno, InvalidAttrNumber);
+               markRTEForSelectPriv(pstate, varno, InvalidAttrNumber);
            }
            else
                elog(ERROR, "unrecognized node type: %d",
@@ -1051,13 +1045,13 @@ markRTEForSelectPriv(ParseState *pstate, RangeTblEntry *rte,
            {
                int         varno = ((RangeTblRef *) j->rarg)->rtindex;
 
-               markRTEForSelectPriv(pstate, NULL, varno, InvalidAttrNumber);
+               markRTEForSelectPriv(pstate, varno, InvalidAttrNumber);
            }
            else if (IsA(j->rarg, JoinExpr))
            {
                int         varno = ((JoinExpr *) j->rarg)->rtindex;
 
-               markRTEForSelectPriv(pstate, NULL, varno, InvalidAttrNumber);
+               markRTEForSelectPriv(pstate, varno, InvalidAttrNumber);
            }
            else
                elog(ERROR, "unrecognized node type: %d",
@@ -1078,7 +1072,10 @@ markRTEForSelectPriv(ParseState *pstate, RangeTblEntry *rte,
 
 /*
  * markVarForSelectPriv
- *    Mark the RTE referenced by a Var as requiring SELECT privilege
+ *    Mark the RTE referenced by the Var as requiring SELECT privilege
+ *    for the Var's column (the Var could be a whole-row Var, too)
+ *
+ * The rte argument is unused and will be removed later.
  */
 void
 markVarForSelectPriv(ParseState *pstate, Var *var, RangeTblEntry *rte)
@@ -1089,7 +1086,7 @@ markVarForSelectPriv(ParseState *pstate, Var *var, RangeTblEntry *rte)
    /* Find the appropriate pstate if it's an uplevel Var */
    for (lv = 0; lv < var->varlevelsup; lv++)
        pstate = pstate->parentParseState;
-   markRTEForSelectPriv(pstate, rte, var->varno, var->varattno);
+   markRTEForSelectPriv(pstate, var->varno, var->varattno);
 }
 
 /*
@@ -3031,9 +3028,13 @@ expandNSItemAttrs(ParseState *pstate, ParseNamespaceItem *nsitem,
    /*
     * Require read access to the table.  This is normally redundant with the
     * markVarForSelectPriv calls below, but not if the table has zero
-    * columns.
+    * columns.  We need not do anything if the nsitem is for a join: its
+    * component tables will have been marked ACL_SELECT when they were added
+    * to the rangetable.  (This step changes things only for the target
+    * relation of UPDATE/DELETE, which cannot be under a join.)
     */
-   rte->requiredPerms |= ACL_SELECT;
+   if (rte->rtekind == RTE_RELATION)
+       rte->requiredPerms |= ACL_SELECT;
 
    forboth(name, names, var, vars)
    {

diff --git a/src/backend/parser/parse_target.c b/src/backend/parser/parse_target.c
index 566c5178373e5ebb015758315d54ca3a7c051fb3..5503f8d1c929a28460fe1fe6c136a055e8c27779 100644 (file)
--- a/src/backend/parser/parse_target.c
+++ b/src/backend/parser/parse_target.c
@@ -1356,9 +1356,13 @@ ExpandSingleTable(ParseState *pstate, ParseNamespaceItem *nsitem,
        /*
         * Require read access to the table.  This is normally redundant with
         * the markVarForSelectPriv calls below, but not if the table has zero
-        * columns.
+        * columns.  We need not do anything if the nsitem is for a join: its
+        * component tables will have been marked ACL_SELECT when they were
+        * added to the rangetable.  (This step changes things only for the
+        * target relation of UPDATE/DELETE, which cannot be under a join.)
         */
-       rte->requiredPerms |= ACL_SELECT;
+       if (rte->rtekind == RTE_RELATION)
+           rte->requiredPerms |= ACL_SELECT;
 
        /* Require read access to each column */
        foreach(l, vars)

diff --git a/src/test/regress/expected/privileges.out b/src/test/regress/expected/privileges.out
index dac1d07e92b977226228db674fa7c46a2f284347..4ddd723377c979fc8f0e9137628e7313e09b66e2 100644 (file)
--- a/src/test/regress/expected/privileges.out
+++ b/src/test/regress/expected/privileges.out
@@ -474,8 +474,54 @@ SELECT 1 FROM atest5 a JOIN atest5 b USING (two); -- fail
 ERROR:  permission denied for table atest5
 SELECT 1 FROM atest5 a NATURAL JOIN atest5 b; -- fail
 ERROR:  permission denied for table atest5
+SELECT * FROM (atest5 a JOIN atest5 b USING (one)) j; -- fail
+ERROR:  permission denied for table atest5
+SELECT j.* FROM (atest5 a JOIN atest5 b USING (one)) j; -- fail
+ERROR:  permission denied for table atest5
 SELECT (j.*) IS NULL FROM (atest5 a JOIN atest5 b USING (one)) j; -- fail
 ERROR:  permission denied for table atest5
+SELECT one FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)) j; -- ok
+ one 
+-----
+   1
+(1 row)
+
+SELECT j.one FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)) j; -- ok
+ one 
+-----
+   1
+(1 row)
+
+SELECT two FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)) j; -- fail
+ERROR:  permission denied for table atest5
+SELECT j.two FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)) j; -- fail
+ERROR:  permission denied for table atest5
+SELECT y FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)) j; -- fail
+ERROR:  permission denied for table atest5
+SELECT j.y FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)) j; -- fail
+ERROR:  permission denied for table atest5
+SELECT * FROM (atest5 a JOIN atest5 b USING (one)); -- fail
+ERROR:  permission denied for table atest5
+SELECT a.* FROM (atest5 a JOIN atest5 b USING (one)); -- fail
+ERROR:  permission denied for table atest5
+SELECT (a.*) IS NULL FROM (atest5 a JOIN atest5 b USING (one)); -- fail
+ERROR:  permission denied for table atest5
+SELECT two FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+ERROR:  permission denied for table atest5
+SELECT a.two FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+ERROR:  permission denied for table atest5
+SELECT y FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+ERROR:  permission denied for table atest5
+SELECT b.y FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+ERROR:  permission denied for table atest5
+SELECT y FROM (atest5 a LEFT JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+ERROR:  permission denied for table atest5
+SELECT b.y FROM (atest5 a LEFT JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+ERROR:  permission denied for table atest5
+SELECT y FROM (atest5 a FULL JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+ERROR:  permission denied for table atest5
+SELECT b.y FROM (atest5 a FULL JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+ERROR:  permission denied for table atest5
 SELECT 1 FROM atest5 WHERE two = 2; -- fail
 ERROR:  permission denied for table atest5
 SELECT * FROM atest1, atest5; -- fail

diff --git a/src/test/regress/sql/privileges.sql b/src/test/regress/sql/privileges.sql
index 407150baf3a41f8b14f118e77ae1ff5ae98a8e64..80581757a2f8db7a6aa078fe9f2a3734ab53a226 100644 (file)
--- a/src/test/regress/sql/privileges.sql
+++ b/src/test/regress/sql/privileges.sql
@@ -301,7 +301,26 @@ SELECT 1 FROM atest5; -- ok
 SELECT 1 FROM atest5 a JOIN atest5 b USING (one); -- ok
 SELECT 1 FROM atest5 a JOIN atest5 b USING (two); -- fail
 SELECT 1 FROM atest5 a NATURAL JOIN atest5 b; -- fail
+SELECT * FROM (atest5 a JOIN atest5 b USING (one)) j; -- fail
+SELECT j.* FROM (atest5 a JOIN atest5 b USING (one)) j; -- fail
 SELECT (j.*) IS NULL FROM (atest5 a JOIN atest5 b USING (one)) j; -- fail
+SELECT one FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)) j; -- ok
+SELECT j.one FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)) j; -- ok
+SELECT two FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)) j; -- fail
+SELECT j.two FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)) j; -- fail
+SELECT y FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)) j; -- fail
+SELECT j.y FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)) j; -- fail
+SELECT * FROM (atest5 a JOIN atest5 b USING (one)); -- fail
+SELECT a.* FROM (atest5 a JOIN atest5 b USING (one)); -- fail
+SELECT (a.*) IS NULL FROM (atest5 a JOIN atest5 b USING (one)); -- fail
+SELECT two FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+SELECT a.two FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+SELECT y FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+SELECT b.y FROM (atest5 a JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+SELECT y FROM (atest5 a LEFT JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+SELECT b.y FROM (atest5 a LEFT JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+SELECT y FROM (atest5 a FULL JOIN atest5 b(one,x,y,z) USING (one)); -- fail
+SELECT b.y FROM (atest5 a FULL JOIN atest5 b(one,x,y,z) USING (one)); -- fail
 SELECT 1 FROM atest5 WHERE two = 2; -- fail
 SELECT * FROM atest1, atest5; -- fail
 SELECT atest1.* FROM atest1, atest5; -- ok