Fix column-privilege leak in error-message paths

While building error messages to return to the user,
BuildIndexValueDescription and ri_ReportViolation would happily include
the entire key or entire row in the result returned to the user, even if
the user didn't have access to view all of the columns being included.

Instead, include only those columns which the user is providing or which
the user has select rights on.  If the user does not have any rights
to view the table or any of the columns involved then no detail is
provided and a NULL value is returned from BuildIndexValueDescription.
Note that, for key cases, the user must have access to all of the
columns for the key to be shown; a partial key will not be returned.

Back-patch all the way, as column-level privileges are now in all
supported versions.

This has been assigned CVE-2014-8161, but since the issue and the patch
have already been publicized on pgsql-hackers, there's no point in trying
to hide this commit.

1 files changed, 63 insertions, 22 deletions

diff --git a/src/backend/utils/adt/ri_triggers.c b/src/backend/utils/adt/ri_triggers.c
index 32621e0fc26..0c1d67e4934 100644
--- a/src/backend/utils/adt/ri_triggers.c
+++ b/src/backend/utils/adt/ri_triggers.c
@@ -3495,6 +3495,9 @@ ri_ReportViolation(RI_QueryKey *qkey, const char *constrname,
 	bool		onfk;
 	int			idx,
 				key_idx;
+	Oid			rel_oid;
+	AclResult	aclresult;
+	bool		has_perm = true;
 
 	if (spi_err)
 		ereport(ERROR,
@@ -3513,12 +3516,14 @@ ri_ReportViolation(RI_QueryKey *qkey, const char *constrname,
 	if (onfk)
 	{
 		key_idx = RI_KEYPAIR_FK_IDX;
+		rel_oid = fk_rel->rd_id;
 		if (tupdesc == NULL)
 			tupdesc = fk_rel->rd_att;
 	}
 	else
 	{
 		key_idx = RI_KEYPAIR_PK_IDX;
+		rel_oid = pk_rel->rd_id;
 		if (tupdesc == NULL)
 			tupdesc = pk_rel->rd_att;
 	}
@@ -3538,45 +3543,81 @@ ri_ReportViolation(RI_QueryKey *qkey, const char *constrname,
 						   RelationGetRelationName(pk_rel))));
 	}
 
-	/* Get printable versions of the keys involved */
-	initStringInfo(&key_names);
-	initStringInfo(&key_values);
-	for (idx = 0; idx < qkey->nkeypairs; idx++)
+	/*
+	 * Check permissions- if the user does not have access to view the data in
+	 * any of the key columns then we don't include the errdetail() below.
+	 *
+	 * Check table-level permissions first and, failing that, column-level
+	 * privileges.
+	 */
+	aclresult = pg_class_aclcheck(rel_oid, GetUserId(), ACL_SELECT);
+	if (aclresult != ACLCHECK_OK)
 	{
-		int			fnum = qkey->keypair[idx][key_idx];
-		char	   *name,
-				   *val;
-
-		name = SPI_fname(tupdesc, fnum);
-		val = SPI_getvalue(violator, tupdesc, fnum);
-		if (!val)
-			val = "null";
+		/* Try for column-level permissions */
+		for (idx = 0; idx < qkey->nkeypairs; idx++)
+		{
+			aclresult = pg_attribute_aclcheck(rel_oid, qkey->keypair[idx][key_idx],
+											  GetUserId(),
+											  ACL_SELECT);
+			/* No access to the key */
+			if (aclresult != ACLCHECK_OK)
+			{
+				has_perm = false;
+				break;
+			}
+		}
+	}
 
-		if (idx > 0)
+	if (has_perm)
+	{
+		/* Get printable versions of the keys involved */
+		initStringInfo(&key_names);
+		initStringInfo(&key_values);
+		for (idx = 0; idx < qkey->nkeypairs; idx++)
 		{
-			appendStringInfoString(&key_names, ", ");
-			appendStringInfoString(&key_values, ", ");
+			int			fnum = qkey->keypair[idx][key_idx];
+			char	   *name,
+					   *val;
+
+			name = SPI_fname(tupdesc, fnum);
+			val = SPI_getvalue(violator, tupdesc, fnum);
+			if (!val)
+				val = "null";
+
+			if (idx > 0)
+			{
+				appendStringInfoString(&key_names, ", ");
+				appendStringInfoString(&key_values, ", ");
+			}
+			appendStringInfoString(&key_names, name);
+			appendStringInfoString(&key_values, val);
 		}
-		appendStringInfoString(&key_names, name);
-		appendStringInfoString(&key_values, val);
 	}
 
 	if (onfk)
 		ereport(ERROR,
 				(errcode(ERRCODE_FOREIGN_KEY_VIOLATION),
 				 errmsg("insert or update on table \"%s\" violates foreign key constraint \"%s\"",
-						RelationGetRelationName(fk_rel), constrname),
-				 errdetail("Key (%s)=(%s) is not present in table \"%s\".",
-						   key_names.data, key_values.data,
-						   RelationGetRelationName(pk_rel))));
+						RelationGetRelationName(fk_rel),
+						constrname),
+				 has_perm ?
+					 errdetail("Key (%s)=(%s) is not present in table \"%s\".",
+							   key_names.data, key_values.data,
+							   RelationGetRelationName(pk_rel)) :
+					 errdetail("Key is not present in table \"%s\".",
+							   RelationGetRelationName(pk_rel))));
 	else
 		ereport(ERROR,
 				(errcode(ERRCODE_FOREIGN_KEY_VIOLATION),
 				 errmsg("update or delete on table \"%s\" violates foreign key constraint \"%s\" on table \"%s\"",
 						RelationGetRelationName(pk_rel),
-						constrname, RelationGetRelationName(fk_rel)),
+						constrname,
+						RelationGetRelationName(fk_rel)),
+				 has_perm ?
 			errdetail("Key (%s)=(%s) is still referenced from table \"%s\".",
 					  key_names.data, key_values.data,
+					  RelationGetRelationName(fk_rel)) :
+					errdetail("Key is still referenced from table \"%s\".",
 					  RelationGetRelationName(fk_rel))));
 }